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    Journals >Photonics Research >Volume 9 >Issue 6 >Page 968 > Article
    • Photonics Research
    • Vol. 9, Issue 6, 968 (2021)
    Lead–halide perovskites for next-generation self-powered photodetectors: a comprehensive review
    Chandrasekar Perumal Veeramalai1, Shuai Feng1, Xiaoming Zhang1、5、*, S. V. N. Pammi2, Vincenzo Pecunia3, and Chuanbo Li1、4、6、*
    Author Affiliations
  • 1School of Science, Minzu University of China, Beijing 100081, China
  • 2Department of Materials Science and Engineering, Chungnam National University, 34134 Daejeon, Republic of Korea
  • 3Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, China
  • 4Optoelectronics Research Center, Minzu University of China, Beijing 100081, China
  • 5e-mail: xmzhang@muc.edu.cn
  • 6e-mail: cbli@muc.edu.cn
    • show less
    DOI: 10.1364/PRJ.418450 Cite this Article Set citation alerts
    Chandrasekar Perumal Veeramalai, Shuai Feng, Xiaoming Zhang, S. V. N. Pammi, Vincenzo Pecunia, Chuanbo Li, "Lead–halide perovskites for next-generation self-powered photodetectors: a comprehensive review," Photonics Res. 9, 968 (2021) Copy Citation Text show less

    Abstract

    Metal halide perovskites have aroused tremendous interest in optoelectronics due to their attractive properties, encouraging the development of high-performance devices for emerging application domains such as wearable electronics and the Internet of Things. Specifically, the development of high-performance perovskite-based photodetectors (PDs) as an ultimate substitute for conventional PDs made of inorganic semiconductors such as silicon, InGaAs, GaN, and germanium-based commercial PDs, attracts great attention by virtue of its solution processing, film deposition technique, and tunable optical properties. Importantly, perovskite PDs can also deliver high performance without an external power source; so-called self-powered perovskite photodetectors (SPPDs) have found eminent application in next-generation nanodevices operating independently, wirelessly, and remotely. Earlier research reports indicate that perovskite-based SPPDs have excellent photoresponsive behavior and wideband spectral response ranges. Despite the high-performance perovskite PDs, their commercialization is hindered by long-term material instability under ambient conditions. This review aims to provide a comprehensive compilation of the research results on self-powered, lead–halide perovskite PDs. In addition, a brief introduction is given to flexible SPPDs. Finally, we put forward some perspectives on the further development of perovskite-based self-powered PDs. We believe that this review can provide state-of-the-art current research on SPPDs and serve as a guide to improvising a path for enhancing the performance to meet the versatility of practical device applications.

    1. INTRODUCTION

    The innovation of functional materials with tunable optoelectronic properties will take essential positions in the development of fundamental and applied research fields. Metal halide perovskite materials with a typical crystal structure such as CaTiO3 would evolve into an outstanding semiconductor counterpart to surpass all traditional materials in the optoelectronic field [1,2]. The general chemical formula of perovskites is ABX3, where “A” and “B” are two cations of very different sizes and “X” is an anion that bonds to both “A” and “B.” Progress has been achieved in synthesis, structural characterization, and investigations of physical properties of perovskite compounds in the form of three-dimensional (3D) bulk crystals, two-dimensional (2D) nanosheets, one-dimensional (1D) nanorods or nanowires, and zero-dimensional (0D) quantum dots (QDs) or nanocrystals [3]. Perovskite materials exhibit fascinating and unique physical properties that have been extensively studied for both practical applications and theoretical modeling [4]. In this sense, perovskite materials’ potential applications are varied and include uses in sensors, fuel cells, solar cells, photodetectors (PDs), memory devices, lasers, and spintronic applications [5,6]. Among the above, PDs are an essential optoelectronic component found to have a wide range of applications, both in industry and daily life, including astronomy, surveillance, robotics, smartphones, and environmental monitoring [7,8]. Until recent years, PDs have been made up of inorganic semiconductors such as Si, InGaAs, and GaN, which are used to detect light in the visible range (450–800 nm), infrared (900–1700 nm) range, and UV range (250–400 nm), respectively [4]. Despite the fact that these PD technologies possess mature and authentic fabrication processes, their widespread application and commercialization are impeded by complex and expensive manufacturing processes, mechanical inflexibility to current smart systems, and the requirement of high driving voltage. For example, the photoresponsivities of commercially available Si-, Ge-, and InGaAs-based PDs are usually around few A/W under high bias voltages (5–200 V). Therefore, an alternative is needed to overcome the existing problems; searching for novel material is a motivation.

    Meanwhile, in the near future, the era of the Internet of Things (IoT) will integrate sensors and objects with networks and solely play an eminent role in world economic development [9]. With the predictable trending, the smart sensor network, as an inevitable component of the IoT, will become a key field in deciding the future development of information technology [10]. Understandably, the smart sensor network requires a great amount of electric energy for sustainable and maintenance-free operation. However, such a huge power cannot be provided due to the huge number of sensor networks and the complexity of replacing batteries every time. Therefore, wireless devices should be self-powered without using batteries.

    In general, a conventional PD needs to be operated by an external power source; typically, it is the battery. However, such independent power supplies are not compatible with a future intelligent sensor system in the following ways: (1) the material used for the battery construction is likely to be highly hazardous to the ecosystem; and (2) the requirement of battery recycling has to be considered in terms of cost for an integrated PD network. Therefore, independent, sustainable, and maintenance-free PDs can be operated by an built-in power source or by extracting power from the surrounding environment. So, a PD operated under self-biasing mode is called a self-powered PD.

    In recent years, self-powered electronic devices (in other words, PDs) have received extensive attention along with the rapid development of smart systems and wearable electronics in daily life, for example, smart homes, bioimaging, health monitoring, and optical communications [11]. Generally, self-powered PDs are classified as Schottky diodes, p-n junction diodes, and metal–semiconductor–metal (MSM) diodes based on device structure and junction formation [7,11–16]. By now, there have been numerous reports on SPPDs, which can sense from the deep ultraviolet (DUV) to far infrared regions (FIRs). Though the performance metrics are very adequate, currently all the proposed self-powered perovskite photodetectors (SPPDs) are not suitable for commercial applications due to the complexity of device fabrication, the cost factor, and the mechanical rigidity, which make them difficult to integrate with electronic components. With the benefit of longer carrier diffusion length and high charge carrier mobility, high absorption coefficient (α≈105 cm−1), and high defect tolerance, perovskite materials could be the best choice for self-powered PDs. These excellent optoelectronic properties allow detection of light to be realized within the perovskite layers, even with 100–200 nm thin films, which is ideal for high-resolution imaging applications, whereas conventional technologies such as silicon-based imaging devices require micrometer-range thick layers. Furthermore, the solution processed manufacturing and the ease of fabrication process of perovskite layers at low temperatures compared with conventional complementary metal–oxide–semiconductor (CMOS) technology make it attractive for future development of electronics field. Therefore, these additional advantages of perovskite materials are potentially attractive for large-area manufacturing at low-cost production, which provides fabrication of self-powered PDs on flexible polymer substrates.

    There have been a considerable number of review papers that separately covered perovskite-based PDs, nanoscale self-powered PDs, and self-powered UV PDs [17–19]. However, a comprehensive review focused mainly on self-powered perovskite-based-PDs, specifically on fabrication technique, device performance in-terms of photoresponsivity, specific detectivity, response speed is lacking in the literature. This review is mainly focused on self-powered perovskite-based PDs. First, we introduce the working principle and basic mechanism of self-powered PD systems in two types of modes: the photovoltaic (PV) mode and the integrated-self powered system. Then, we summarize the recent progress on self-powered perovskite-based PDs by sectioning the structure of perovskites such as bulk crystal structure (3D), nanosheets (2D), nanowires or microwires (1D), and QDs or nanocrystals (0D). Besides, we introduce flexible self-powered perovskite photodetectors (SPPDs). Despite the considerable advancement in the field, there are several key challenges ahead to face in the further development of SPPDs. Therefore, we have provided a survey of challenges and opportunities in the last section.

    2. GENERAL PROPERTIES OF ORGANIC-INORGANIC PEROVSKITE AND ALL-INORGANIC PEROVSKITE MATERIALS

    (a), (b) Schematic crystal structure of representative perovskite materials CH3NH3PbI3 and CsPbBr3, simulated from Vesta.3 Software; (c) comparative optical absorption behavior of semiconducting materials. Reproduced from Ref. [6] with permission. Copyright 2014, Springer Nature.

    Figure 1.(a), (b) Schematic crystal structure of representative perovskite materials CH3NH3PbI3 and CsPbBr3, simulated from Vesta.3 Software; (c) comparative optical absorption behavior of semiconducting materials. Reproduced from Ref. [6] with permission. Copyright 2014, Springer Nature.

    Despite the remarkable device performance offered, organic-inorganic perovskites suffer from degradation by air, moisture, temperature, electric field, and light exposure (detailed analysis is provided in challenges and perspectives section later) [30,31]. Particularly, the organic cation clusters [CH3NH3+, FA+, CH(NH2)2+, etc.] in the organic-inorganic hybrid lead halide perovskite are extremely sensitive to the environmental humidity and oxygen content, leading to problems such as poor environmental stability and poor thermal stability [32,33]. Furthermore, the perovskite material intrinsically suffers from issues such as migration of ions and the appearance of hysteresis in the electrical characteristics [34,35]. The making of stable functional devices is greatly restricted by these issues. Therefore, a stable perovskite requires a partial replacement organic counterpart with more stable cations such as long-chain organic cations or inorganic elements such as cesium (Cs) and rubidium (Rb) [36–38]. A representative all-inorganic perovskite CsPbBr3 is a direct band-gap semiconductor with low trap state density, high carrier mobility, long electron-hole diffusion length, etc., and it also has some excellent optical characteristics such as high quantum yield, strong light absorption, high luminous efficiency, and adjustable luminous wavelength (see Table 1) [1].

    3. PERFORMANCE PARAMETERS OF PHOTODETECTORS

    Here, some very important performance parameters to describe the characteristics of a PD can be summarized as follows.

    Responsivity: The responsivity is given as the ratio of the output current or voltage to the power of the input light signal, and the unit is A/W or V/W. R=IpPA,where Ip=Ilight−Idark, P is the incident power density, and A is the effective device area.

    Specific detectivity: D* is a key figure of merit to reflect the sensitivity of a device. In general, the specific detectivity of the PD is related to the noise inversely. It is defined in terms of responsivity R as D*=(AΔf)1/2inR=RA2qId,where R is the responsivity in A W−1, A is the effective device area, Id is the dark current, and q is the coulombic charge of the electron (1.6×10−19  C).

    External quantum efficiency (EQE): EQE is the ratio of the output number of electrons/holes to the number of incident photons, indicating the conversion efficiency of PDs from photons to charges. It is given as follows: EQE=Rhcqλ,where h, c, q, and λ denote Planck’s constant, the speed of light, elementary electron charge, and wavelength, respectively.

    Noise equivalent power (NEP): NEP is the signal power that produces a signal-to-noise ratio (SNR) to be equal to 1, representing the minimum impinging optical power that a PD can distinguish from the noise. It can be written as NEP=(AΔf)1/2D*=inR,where A is the effective device area, Δf is the electrical bandwidth, and in is the noise current.

    Linear dynamic range (LDR): It describes a light intensity range in which the current response of the PD is linearly proportional to the light intensity, and it can be calculated by LDR=20 logJmax−JdJmin−Jd,where Jmax is the upper photocurrent, Jmin is the lower photocurrent, and Jd is the dark current. Detecting both the weak and strong light is required for a high LDR PD.

    Response speed: Rise time (tr) and decay time (td) are defined as the time within which photocurrent increases from 10% to 90% and drops from 90% to 10% of its maximum value.

    4. BRIEF INTRODUCTION ON SPPDS: CLASSIFICATION BY WORKING MECHANISM

    Energy consumption is one of the important aspects considered for modern electronic devices which needs further development to achieve a better sustainable future. This is equally true for commercially available PDs. In recent years, there have been numerous reports on SPPDs operated from the DUV to the near-infrared (NIR) under zero bias voltage. The SPPDs are categorized into two types based on energy source feeding as follows: (1) PV effect-based PDs (Schottky junction and heterojunction) and (2) PDs with integrated self-powered systems.

    A. PV Effect-Based Self-Powered PDs

    Schematic diagrams of working principle of SPPDs in PV mode: heterojunction type (left side) and Schottky type (right side).

    Figure 2.Schematic diagrams of working principle of SPPDs in PV mode: heterojunction type (left side) and Schottky type (right side).

    Apart from SPPDs based on the p-n heterojunction, PDs based on the Schottky junction can also operate without external power sources owing to the PV effect. Furthermore, compared to p-n heterojunction PDs, Schottky-type PDs exhibit ultrarapid response time, high photosensitivity, and low-cost fabrication, which is highly preferable for future applications. Generally, a built-in electric field, which separates the photogenerated electron–hole pairs and gives rise to circuit current, is formed due to the electron’s spontaneous diffusion caused by the work function difference between contact metal and semiconductor. Unfortunately, the surface state of semiconductors could seriously affect the diffusion process. Therefore, to achieve high performance, a great endeavor is required to optimize the stability and quality of the Schottky contact. Up to the present, several investigations of self-powered Schottky-type PDs made from different semiconductors have been reported [18,40–45].

    B. Integrated Nanopower Source-Based Self-Powered PDs

    For the realization of self-powered PDs in PV mode, the following aspects should be considered: (1) SPPDs can not only detect the signals but also must be powered by the detected signals; (2) the photogenerated electron–hole pairs are usually separated by the built-in potential difference provided by the junction-based multilayer structures, which often involve complicated, time-consuming, and uneconomic device fabrication processes [46]; (3) more importantly, the material choice of this kind of device is limited due to issues such as lattice mismatch, surface states, and band alignment [47–49]. These issues not only increase the system size but also greatly limit mobility and independence [50]. In this regard, a miniaturized, uninterruptible energy source is necessary to power up the PD.

    The nanogenerator (NG) is a new technique, first proposed by Wang in 2007, that utilizes mechanical and thermal energies produced by human body motion and then converts into electrical energy [51]. Generally, NGs can be classified into three types based on electricity generation modes: the triboelectric generator (TENG), the piezoelectric NG (PENG), and the pyroelectric NG (PYENG). A TENG is an energy-harvesting device that converts mechanical energy into electrical energy by a combination of triboelectric effect and electrostatic induction. A PENG is a device capable of converting external kinetic energy into electrical energy via motion by piezoelectric materials. The conversion of external thermal energy into electrical energy is adopted for designing PYENGs. Among the above, TENG is a compatible nanoenergy source that is frequently used to back up the electronic devices and has drawn more attention. These NGs are widely used as the micronanoenergy sources for self-powered sensors. However, integration of NGs with sensor devices is always challenging, but further development of NG-based self-powered sensors is extremely attractive.

    5. PEROVSKITE-BASED-SELF-POWERED PDs

    A. Single-Crystal Perovskite PDs

    The single-crystal perovskites possess many unique advantages over polycrystalline thin-film structures, such as high purity, fewer grain boundaries, and enhanced thermal and moisture stabilities. Notably, in a single crystal, low trap density contributes to high carrier mobility and long carrier diffusion lengths, resulting in highly sensitive PDs. High-purity perovskite single crystals have been prepared by several methods reported earlier such as inverse temperature crystallization (ITC) [52], antisolvent vapor-assisted crystallization [26], top-seed solution growth [53], bottom-seeded solution growth [54], and solvent acidolysis crystallization [55].

    (a) Preparation process of the MAPbBr3/MAPbIxBr3−x heterojunction; (b) responsivity of APbBr3/MAPbIxBr3−x and single crystal MAPbBr3 PDs at zero bias under the incident light with wavelengths of 350–800 nm and 400–800 nm, respectively; (c) schematic energy level diagram at the MAPbBr3/MAPbIxBr3−x junction under irradiation. Reproduced with permission from Ref. [56]. Copyright 2016, American Institute of Physics. (d) Photographic image of the as-grown heterostructure single crystal (top); SEM image of the heterostructure interface (bottom). (e) Band diagram of the (4-AMP)(MA)2Pb3Br10/MAPbBr3 heterostructure detector; (f) plots of the R and D* as a function of light intensity; (g) response speed of (4-AMP)(MA)2Pb3Br10/MAPbBr3 heterostructure device at rise edges and fall edges. Reproduced with permission from Ref. [57]. Copyright 2020, Wiley-VCH. (h) Schematic illustration of the Au–Al electrodes separated by 30 μm on MAPbI3 single crystal; (i) schematic illustration of the working mechanism for Schottky junction based on asymmetric electrodes; (j) photocurrent response of Au/MAPbI3/Al device at different wavelengths; (k) spectral photoresponsivity of MAPbI3 single crystal PD. Reproduced with permission from Ref. [58]. Copyright 2016, Royal Society of Chemistry.

    Figure 3.(a) Preparation process of the MAPbBr3/MAPbIxBr3−x heterojunction; (b) responsivity of APbBr3/MAPbIxBr3−x and single crystal MAPbBr3 PDs at zero bias under the incident light with wavelengths of 350–800 nm and 400–800 nm, respectively; (c) schematic energy level diagram at the MAPbBr3/MAPbIxBr3−x junction under irradiation. Reproduced with permission from Ref. [56]. Copyright 2016, American Institute of Physics. (d) Photographic image of the as-grown heterostructure single crystal (top); SEM image of the heterostructure interface (bottom). (e) Band diagram of the (4-AMP)(MA)2Pb3Br10/MAPbBr3 heterostructure detector; (f) plots of the R and D* as a function of light intensity; (g) response speed of (4-AMP)(MA)2Pb3Br10/MAPbBr3 heterostructure device at rise edges and fall edges. Reproduced with permission from Ref. [57]. Copyright 2020, Wiley-VCH. (h) Schematic illustration of the Au–Al electrodes separated by 30 μm on MAPbI3 single crystal; (i) schematic illustration of the working mechanism for Schottky junction based on asymmetric electrodes; (j) photocurrent response of Au/MAPbI3/Al device at different wavelengths; (k) spectral photoresponsivity of MAPbI3 single crystal PD. Reproduced with permission from Ref. [58]. Copyright 2016, Royal Society of Chemistry.

    Similarly, Zhang et al. have reported on a vertical 2D/3D perovskite heterostructure (4-AMP) (MA)2Pb3Br10/MAPbBr3 [4-AMP-4-(aminomethyl) piperidinium], featuring a well-defined interface and high crystalline quality [57]. The photographic image of single-crystal heterostructure and corresponding cross-sectional field emission scanning electron microscopy (FESEM) image are shown in Fig. 3(d). Electrical transport measurements demonstrate that the (4-AMP) (MA)2Pb3Br10/MAPbBr3 heterostructure can form a vertical diode with obvious current rectification behavior and photocurrent generation characteristics. Benefiting from the built-in electrical field at the junction [Fig. 3(e)], PDs based on those millimeter-thickness heterostructure crystals exhibit high performance in self-driven operation mode, including fast response time (600/600 μs), and high detectivity (≈1012  Jones) [Figs. 3(f) and 3(g)].

    (a) Photographic image of CsPbBr3 single crystal; (b) I-V curve of device Au/CsPbBr3/Pt in dark and under illumination; (c) photoresponse of device Au/CsPbBr3/Pt under light pulses measured under zero bias. Reproduced with permission from Ref. [28]. Copyright 2017, Wiley-VCH. (d) Carrier separation transmission diagram of the device based on CH3NH3PbI3 single crystal PD; (e) variation of light responsivity of devices with different channel widths; (f) dependence of responsivity and on–off ratio on the light intensity. Reproduced with permission from Ref. [60]. Copyright 2021, Elsevier.

    Figure 4.(a) Photographic image of CsPbBr3 single crystal; (b) I-V curve of device Au/CsPbBr3/Pt in dark and under illumination; (c) photoresponse of device Au/CsPbBr3/Pt under light pulses measured under zero bias. Reproduced with permission from Ref. [28]. Copyright 2017, Wiley-VCH. (d) Carrier separation transmission diagram of the device based on CH3NH3PbI3 single crystal PD; (e) variation of light responsivity of devices with different channel widths; (f) dependence of responsivity and on–off ratio on the light intensity. Reproduced with permission from Ref. [60]. Copyright 2021, Elsevier.

    In the CH3NH3PbI3 crystal, a [PbI6] octahedral structure is constituted by Pb and I atoms, and CH3NH3+ is located in an octahedron cavity. The distortion of the [PbI6] octahedron results in the Pb2+ not occupying the center of the octahedron, and so the crystal symmetry is destroyed, inducing a spontaneous polarization in the perovskite. The spontaneous polarization of the CH3NH3PbI3 unit cell and the ordered arrangement of the unit cell in the single crystal provide the possibility of the single crystal achieving self-powered PDs. For instance, a self-powered PD in a MAPbI3 single crystal was reported by Zhang et al., where the symmetric electrode is fabricated in Au/MAPbI3/Au [60]. However, from the device structure of Au/MAPbI3/Au, if the MAPbI3 crystal is nonpolar, two Schottky junctions with the same barrier height will be formed at both ends of the device. Such a device has no built-in electric field and cannot realize the self-powered characteristic, which is contrary to the experimentally observed self-powered phenomenon. Therefore, the ferroelectric spontaneous polarization exists in the MAPbI3 single crystal, which is responsible for the self-powered mechanism of PDs. Briefly, the photogenerated carriers in ferroelectric materials are separated by the depolarization field associated with spontaneous polarization and collected by the Au electrodes at both ends of the device to generate the potential difference. The process of carrier movement is shown in Fig. 4(d). Moreover, Fig. 4(e) shows that the photoresponsivity of the device greatly depends on the channel size, i.e., increased channel size could effectively increase the illumination area of the device and enhance the photocurrent, while the carrier collection efficiency is simultaneously reduced, and then the responsivity of the device is decreased. Without external bias, the device exhibited the maximum responsivity of 0.16  A W−1 and the specific detectivity of 5.86×1011 Jones with a fast response time.

    B. Nanostructured Perovskite PDs

    Recently, low-dimensional nanostructures have been extensively studied as a potential building block to construct efficient PDs. Compared with bulk materials, low-dimensional nanoscale materials, with their large surface areas and possible quantum confinement effect, exhibit distinct electronic, optical, chemical, and thermal properties [61]. One should consider that poor structural stability and chemical stability remain major concerns for the practical application of halide perovskites. So, the high surface-area-to-volume ratio of nanostructured perovskite can increase the impact of surface properties on the chemical properties and phase stability. However, nanostructures of halide perovskites can exhibit enhanced structural and chemical stability owing to a surface energy effect and surface ligand functionalization [62]. Therefore, a large variety of perovskite nanostructures, such as QDs/nanocrystals, nanowires/nanorods, and nanosheets, were successfully synthesized, which could be effectively applicable in PDs [3,63].

    (a) Schematic illustration of MAPbI3 NC synthesis; (b) TEM image of MAPbI3 NCs (the inset shows MAPbI3 nanocrystal size distribution plot); (c) schematic diagram of the MAPbI3 NC based self-powered PD; (d) J-V curves of the MAPbI3 NC-based self-powered PD under 808 nm illumination; (e) photocurrent versus time for the PD under light on/off cycles at 0 V under 808 nm illumination. Reproduced with permission from Ref. [50]. Copyright 2020, Wiley-VCH. (f) Cross-sectional SEM image of ITO/ZnO(70 nm)/CdS(150 nm) /CsPbBr3(200 nm)/Au trilayer PDs; (g) I-V curve of trilayer PD device in dark and under 85 μW cm−2 405 nm illumination; (h) potential charges generation and transportation process under 85 μW cm−2 405 nm illumination illustrated by band diagram. Reproduced with permission from Ref. [67]. Copyright 2020, Institute of Physics.

    Figure 5.(a) Schematic illustration of MAPbI3 NC synthesis; (b) TEM image of MAPbI3 NCs (the inset shows MAPbI3 nanocrystal size distribution plot); (c) schematic diagram of the MAPbI3 NC based self-powered PD; (d) J-V curves of the MAPbI3 NC-based self-powered PD under 808 nm illumination; (e) photocurrent versus time for the PD under light on/off cycles at 0 V under 808 nm illumination. Reproduced with permission from Ref. [50]. Copyright 2020, Wiley-VCH. (f) Cross-sectional SEM image of ITO/ZnO(70 nm)/CdS(150 nm) /CsPbBr3(200  nm)/Au trilayer PDs; (g) I-V curve of trilayer PD device in dark and under 85  μW cm−2 405 nm illumination; (h) potential charges generation and transportation process under 85  μW cm−2 405 nm illumination illustrated by band diagram. Reproduced with permission from Ref. [67]. Copyright 2020, Institute of Physics.

    Apart from the Schottky junction PD, perovskite QDs are used as a photosensitive layer in multilayer junctions to realize heterojunction-based self-powered PDs. For example, Imran et al. proposed a trilayer PD with device structure ITO/ZnO/CdS/CsPbBr3/Au [67]. To reduce the interfacial charge carriers’ recombination and the charge transport resistance, CdS nanorods are sandwiched between a ZnO/CsPbBr3 interface. The cross-sectional FESEM image of the device is shown in Fig. 5(f). The typical I-V curve of the device represents the PV effect by the formation of an open-circuit voltage of 0.13 V, as shown in Fig. 5(g). The device performance could be explained based on the band diagram, as illustrated in Fig. 5(h). In the trilayer device, built-in potentials are induced at both the CdS/CsPbBr3 and ZnO/CdS interfaces, and both CsPbBr3 and CdS nanorod layers can absorb the incident light. This doubly formed built-in potential in the trilayer device results in more efficient separation of photogenerated carriers and then more efficient drift to electrodes at zero bias. Overall, the self-powered trilayer PD shows photoresponsivity of 86  mA W−1 and specific detectivity of 6.2×1011 Jones with the rise and decay time of 0.3 s and 0.25 s, respectively.

    Similar to 0D perovskite QDs, 1D perovskite materials also found potential application in PDs owing to their high sensitivity, reduced recombination rate, and quick charge transfer characteristics. Until now, a great number of the studies carried out by researchers on the fabrication of PDs used various perovskite nanowires/nanorods, microwires, microtubes, etc. [68–73]. However, nanowire/nanorod-based self-powered PDs have seldom been reported in the literature. The reasons can be summarized as follows: (i) complicated fabrication process of nanowires (NWs) as a device structure and poor reproducibility; (ii) the photocurrents of the PDs based on aligned NWs or a single NW with MSM structure are very low due to the limited light absorption cross section or the large channel length between the metal electrodes; (iii) a phenomenon of the p-n junction and the Schottky junction required for achieving self-powered PDs is very complicated in individual NW PDs or aligned NW PDs due to difficulties of p or n doping in perovskites and tedious nanowire manipulation [68,74].

    (a) Schematic illustration of the synthesis process of the CsPbBr3 NWs and CsPbBr3 micro- and nanostructures; (b) schematic illustration of the perovskite NW PD; (c) energy band diagram of the perovskite NW PD. (d) J-t curve at the light intensity of 6.4×10−4 mW cm−2; (e) responsivity and detectivity of the device under various optical power. Reproduced with permission from Ref. [68]. Copyright 2018, Elsevier. (f) Schematic illustration of the fabrication process of the P3PCS PD; (g) CsPbBr3 nanowire array; (h) schematic of device structure; (i) responsivity and detectivity curves of P3PCS device; (j) long-term photoresponse curves of P3PCS device under 100 mW cm−2 white light at 0 V. Reproduced with permission from Ref. [69]. Copyright 2019, Wiley-VCH.

    Figure 6.(a) Schematic illustration of the synthesis process of the CsPbBr3 NWs and CsPbBr3 micro- and nanostructures; (b) schematic illustration of the perovskite NW PD; (c) energy band diagram of the perovskite NW PD. (d) J-t curve at the light intensity of 6.4×10−4  mW cm−2; (e) responsivity and detectivity of the device under various optical power. Reproduced with permission from Ref. [68]. Copyright 2018, Elsevier. (f) Schematic illustration of the fabrication process of the P3PCS PD; (g) CsPbBr3 nanowire array; (h) schematic of device structure; (i) responsivity and detectivity curves of P3PCS device; (j) long-term photoresponse curves of P3PCS device under 100  mW cm−2 white light at 0 V. Reproduced with permission from Ref. [69]. Copyright 2019, Wiley-VCH.

    (a) SEM image of CsPbBr3 microplatelets shows sharp edge and smooth surface morphology. (b) Schematic layout of the perovskite CsPbBr3 microplatelets PD based on vertical Schottky junction structure; (c) I-V characteristics of the CsPbBr3 microplatelets PD under 405 nm light illumination with different density; (d) normalized I-t curves of CsPbBr3 microplatelets PD with long-term storage without encapsulation. Reproduced with permission from Ref. [75]. Copyright 2020, Royal Society of Chemistry. (e) Schematic of fabricating process of the CsPbBr3 microcrystal-based PD; (f) room temperature spectral responsivity curves of the CsPbBr3 microcrystal-based PD at 0 V bias. Reproduced with permission from Ref. [76]. Copyright 2019, American Chemical Society. (g) SEM image of CsPbBr3 microcrystal perovskite film. The inset is a digital photograph of the perovskite film under 365 nm purple flashlight. (h) Schematic illustration of the CsPbBr3 microcrystal perovskite PD; (i) power-dependent R and D*CsPbBr3 microcrystal perovskite PD under 0 V bias. Reproduced with permission from Ref. [77]. Copyright 2019, American Chemical Society.

    Figure 7.(a) SEM image of CsPbBr3 microplatelets shows sharp edge and smooth surface morphology. (b) Schematic layout of the perovskite CsPbBr3 microplatelets PD based on vertical Schottky junction structure; (c) I-V characteristics of the CsPbBr3 microplatelets PD under 405 nm light illumination with different density; (d) normalized I-t curves of CsPbBr3 microplatelets PD with long-term storage without encapsulation. Reproduced with permission from Ref. [75]. Copyright 2020, Royal Society of Chemistry. (e) Schematic of fabricating process of the CsPbBr3 microcrystal-based PD; (f) room temperature spectral responsivity curves of the CsPbBr3 microcrystal-based PD at 0 V bias. Reproduced with permission from Ref. [76]. Copyright 2019, American Chemical Society. (g) SEM image of CsPbBr3 microcrystal perovskite film. The inset is a digital photograph of the perovskite film under 365 nm purple flashlight. (h) Schematic illustration of the CsPbBr3 microcrystal perovskite PD; (i) power-dependent R and D*CsPbBr3 microcrystal perovskite PD under 0 V bias. Reproduced with permission from Ref. [77]. Copyright 2019, American Chemical Society.

    C. Polycrystalline Thin-Film Perovskite PDs

    (a) Device structure of the hybrid perovskite PD; (b) LDR of the PD with the device structure ITO/PEDOT:PSS/CH3NH3PbI3−xClx/PCBM/PFN/Al. The PD has a large LDR of 4100 dB. Reproduced with permission from Ref. [85]. Copyright 2014, Springer Nature. (c) SEM image of MAPbI3−xClx thin films on glass substrate; (d) schematic representation of a photodetector device configuration; (e) transient photocurrent properties of device under illumination at 632 nm; (f) long-term photo stability illuminated under 1000 μW/cm2 with different intervals up to 500 h. Reproduced with permission from Ref. [86]. Copyright 2020, Elsevier. (g) SEM image of PMMA-modified CsPbBr3 film; (h) schematic and cross-sectional SEM image of the as-fabricated PD with a structure of ITO/CsPbBr3/PMMA/Ag. Reproduced with permission from Ref. [87]. Copyright 2020, Royal Society of Chemistry. (i) Schematic structure of PD based on all-inorganic perovskite CsPbIxBr3−x; (j) current density-voltage (J-V) curves of CsPbIBr2-based PDs under dark and illumination of 450 nm monochrome light with intensity of 1 μm cm−2 to 1 mW cm−2; (k) photoresponsivity evolution of PDs based on inorganic perovskite CsPbIxBr3−x and hybrid perovskite MAPbI3 in air ambient condition without encapsulation. Reproduced with permission from Ref. [88]. Copyright 2018, Wiley-VCH. (l) Schematic illustration of as-fabricated self-powered PD based on CsxDMA1−xPbI3 perovskite films; (m) responsivity spectrum of the self-powered PD based on the film with CsI/DMAPbI3 molar ratio of 1:2 in the precursor at 0 V; (n) variation of spectral responsivity with time of the self-powered PD in air (10%–20% RH) at a bias voltage of 0 V under 532 nm illumination. Reproduced with permission from Ref. [89]. Copyright 2020, Elsevier. (o) Disordered state of ions under dark (upper) and mobile ions accumulated at the opposite interfaces under illumination due to the light-induced self-poling effect (lower), resulting in the built-in electric field; (p) energy band schematics of the MOS structure under dark before contact. Reproduced with permission from Ref. [90]. Copyright 2019, Royal Society of Chemistry.

    Figure 8.(a) Device structure of the hybrid perovskite PD; (b) LDR of the PD with the device structure ITO/PEDOT:PSS/CH3NH3PbI3−xClx/PCBM/PFN/Al. The PD has a large LDR of 4100 dB. Reproduced with permission from Ref. [85]. Copyright 2014, Springer Nature. (c) SEM image of MAPbI3−xClx thin films on glass substrate; (d) schematic representation of a photodetector device configuration; (e) transient photocurrent properties of device under illumination at 632 nm; (f) long-term photo stability illuminated under 1000  μW/cm2 with different intervals up to 500 h. Reproduced with permission from Ref. [86]. Copyright 2020, Elsevier. (g) SEM image of PMMA-modified CsPbBr3 film; (h) schematic and cross-sectional SEM image of the as-fabricated PD with a structure of ITO/CsPbBr3/PMMA/Ag. Reproduced with permission from Ref. [87]. Copyright 2020, Royal Society of Chemistry. (i) Schematic structure of PD based on all-inorganic perovskite CsPbIxBr3−x; (j) current density-voltage (J-V) curves of CsPbIBr2-based PDs under dark and illumination of 450 nm monochrome light with intensity of 1  μm cm−2 to 1  mW cm−2; (k) photoresponsivity evolution of PDs based on inorganic perovskite CsPbIxBr3−x and hybrid perovskite MAPbI3 in air ambient condition without encapsulation. Reproduced with permission from Ref. [88]. Copyright 2018, Wiley-VCH. (l) Schematic illustration of as-fabricated self-powered PD based on CsxDMA1−xPbI3 perovskite films; (m) responsivity spectrum of the self-powered PD based on the film with CsI/DMAPbI3 molar ratio of 1:2 in the precursor at 0 V; (n) variation of spectral responsivity with time of the self-powered PD in air (10%–20% RH) at a bias voltage of 0 V under 532 nm illumination. Reproduced with permission from Ref. [89]. Copyright 2020, Elsevier. (o) Disordered state of ions under dark (upper) and mobile ions accumulated at the opposite interfaces under illumination due to the light-induced self-poling effect (lower), resulting in the built-in electric field; (p) energy band schematics of the MOS structure under dark before contact. Reproduced with permission from Ref. [90]. Copyright 2019, Royal Society of Chemistry.

    The stability of perovskite PDs, as well as the selection of photoactive material, is the most important issue taken into consideration while designing the structure of PDs. Li et al. demonstrated the fabrication of CsxDMA1−xPbI3 thin films by the solution-processing technique [89]. Instead of PbI2, DMAPbI3 [DMA+=dimethylammonium, (CH3)2NH2+] is chosen to react with CsI, which can enhance the room-temperature phase stability of resultant Cs-based perovskite films. A self-powered PD has been designed, as indicated in Fig. 8(l), which shows broad photoresponse from 300 to 750 nm, with high specific detectivity (>1×1013 Jones) [Fig. 8(m)]. Above all, the device shows excellent long-term stability in the air due to an increased tolerance factor by the introduction of DMA+; in other words, DMA+ prevents the spontaneous transformation of CsPbI3 at room temperature [Fig. 8(n)].

    In perovskite-based optoelectronic devices, ion migration is one of the interesting concepts to be investigated to understand unusual phenomena such as current-voltage hysteresis, switchable PV effect, and light-induced self-poling effect [35,91,92]. Pang and coworkers investigated the self-poling effect in perovskite thin films by designing the PD in a metal–oxide–semiconductor (MOS) structure [90]. The device with structure Si/SiO2/CH3NH3PbI3 showed excellent self-powered photoresponse characteristics and exhibited an excellent on/off ratio of 105 with a bias of 0 V and a fast response time of 25.8 ms. The authors explained the “self-biasing” by the concept of self-poling effect as follows. When no bias is applied, the mobile ions within the perovskite layer show electrical disorder in the dark, and the perovskite has a uniform Fermi level, as shown in Fig. 8(o) (upper side). Under illumination, the built-in electric field is formed when the positive ions/vacancies accumulate at the perovskite/SiO2 interface and the negative ions/vacancies accumulate at the perovskite/Pt interface due to the preset built-in potential caused by band bending in the asymmetrical device [Fig. 8(o) (lower side)]. The typical band diagram elucidated from XPS spectra is shown in Fig. 8(p) and clearly explains the charge transport properties across the device.

    D. Integrated Nanopower System-Based PDs

    (a) Device structure of self-powered PD with MAPbI3 as the photosensitive and triboelectric layer; (b) change of Voc upon repeated illumination that varies in intensity at 100 mW cm−2. Reproduced with permission from Ref. [93]. Copyright 2015, American Chemical Society. (c) Schematic of a triboelectric-assisted perovskite PD showing charge carrier separation assisted by the triboelectric charges created by the TENG; (d) schematic diagram and the working principle of the (+) triboelectric-assisted perovskite PD; (e) transient photoresponse of the triboelectric-actuated perovskite PD (blue) and perovskite PD without assistance of triboelectricity (red) under alternating on–off laser light (50 mW) illumination with a 3 Hz chopping frequency. Reproduced with permission from Ref. [94]. Copyright 2019, Elsevier.

    Figure 9.(a) Device structure of self-powered PD with MAPbI3 as the photosensitive and triboelectric layer; (b) change of Voc upon repeated illumination that varies in intensity at 100  mW cm−2. Reproduced with permission from Ref. [93]. Copyright 2015, American Chemical Society. (c) Schematic of a triboelectric-assisted perovskite PD showing charge carrier separation assisted by the triboelectric charges created by the TENG; (d) schematic diagram and the working principle of the (+) triboelectric-assisted perovskite PD; (e) transient photoresponse of the triboelectric-actuated perovskite PD (blue) and perovskite PD without assistance of triboelectricity (red) under alternating on–off laser light (50 mW) illumination with a 3 Hz chopping frequency. Reproduced with permission from Ref. [94]. Copyright 2019, Elsevier.

    6. FLEXIBLE SELF-POWERED PEROVSKITE-BASED PDs

    The ultra-flexible, ultrafast (<20  ms), wearable, and flexible PDs are the highly studied research field due to their compatibility with a variety of emerging areas such as flexible, stretchable, wearable, portable, and printed optoelectronics. Combined with transparent features, flexible devices can be employed in touch screens and interactive electronics [114]. There are so many novel functional materials including QDs, inorganic nanostructures, 2D layered semiconductors, organic semiconductors, etc., which have been extensively studied as the active layers in flexible optoelectronic devices. Particularly, metal halide perovskites exhibit excellent electrical and optical properties, as well as outstanding mechanical stability, and they have been used as cost-effective flexible PDs [8,115,116]. For high-sensitivity flexible PDs, both high photoresponsivity and mechanical flexibility should be implemented simultaneously in a single device, which sets a great challenge for fabrication techniques and selection of materials [117]. High-temperature processing is also another important factor in order to improve the crystallinity of photosensing material in some cases; there are great obstacles to fabricating devices on flexible substrates such as plastic. Cost-effective perovskite material, which exhibits advantages of solution processing and low-temperature fabrication is the promising light-harvesting material for fabrication of high-performance flexible PDs. The majority of flexible devices fabricated to date have been on ITO transparent conducting electrodes and are fabricated by a solution-processing technique at low temperatures, but ITO is also not the best choice owing to its fragility. Therefore, some other alternatives have also been used, such as carbon nanotubes, graphene, metal nanowires, and conducting polymers [118–122]. Overall, flexible PDs must be fabricated at low temperatures and have specific advantages such as a simple processing technique, low cost, shock resistance, light weight, durability, and portability.

    (a) Plane-view SEM image of CsPbBr3 perovskite thin films Al2O3-modified FTO substrates; (b) photoresponse curves of CsPbBr3 perovskite PDs, Al2O3/CsPbBr3 perovskite PDs, and Al2O3/CsPbBr3/TiO2 perovskite PDs, respectively; (c) energy band diagram of heterojunctions; (d) current–voltage (I-V) curves of PDs under dark and illumination of 405 nm laser with intensity of 6.2 μW cm−2 to 114 mW cm−2; (e) photoresponse curves of ACT PDs under modulated 405 nm laser with various light intensity (0 V); (f) light current and dark current stability at different days for hard substrate device; (g) light current and dark current of flexible device after different bending cycles. Reproduced with permission from Ref. [123]. Copyright 2019, Wiley-VCH.

    Figure 10.(a) Plane-view SEM image of CsPbBr3 perovskite thin films Al2O3-modified FTO substrates; (b) photoresponse curves of CsPbBr3 perovskite PDs, Al2O3/CsPbBr3 perovskite PDs, and Al2O3/CsPbBr3/TiO2 perovskite PDs, respectively; (c) energy band diagram of heterojunctions; (d) current–voltage (I-V) curves of PDs under dark and illumination of 405 nm laser with intensity of 6.2  μW cm−2 to 114  mW cm−2; (e) photoresponse curves of ACT PDs under modulated 405 nm laser with various light intensity (0 V); (f) light current and dark current stability at different days for hard substrate device; (g) light current and dark current of flexible device after different bending cycles. Reproduced with permission from Ref. [123]. Copyright 2019, Wiley-VCH.

    (a) FESEM image of a typical PD with Au/Ag electrode pair; (b) I-V curves of the CH3NH3PbI3 MWs array-based PDs with asymmetric contact electrodes (Au/Ag, Au/Al); (c) histogram of Voc and Isc for devices with different asymmetric electrode pairs; (d) dark current and photocurrent of the flexible PD being bent to various radii. Reproduced with permission from Ref. [71]. Copyright 2019, Wiley-VCH. (e) Device structure and (f) cross-sectional SEM image of MAPbI3:graphene QD based PD. (g) NEP/spectral detectivity of PD. The inset shows excellent flexibility of the PD. (h) Evolution of responsivity during repeated 1000 bending cycles at λ=600 nm and d=4 mm. Reproduced with permission from Ref. [124]. Copyright 2019, American Chemical Society.

    Figure 11.(a) FESEM image of a typical PD with Au/Ag electrode pair; (b) I-V curves of the CH3NH3PbI3 MWs array-based PDs with asymmetric contact electrodes (Au/Ag, Au/Al); (c) histogram of Voc and Isc for devices with different asymmetric electrode pairs; (d) dark current and photocurrent of the flexible PD being bent to various radii. Reproduced with permission from Ref. [71]. Copyright 2019, Wiley-VCH. (e) Device structure and (f) cross-sectional SEM image of MAPbI3:graphene QD based PD. (g) NEP/spectral detectivity of PD. The inset shows excellent flexibility of the PD. (h) Evolution of responsivity during repeated 1000 bending cycles at λ=600  nm and d=4  mm. Reproduced with permission from Ref. [124]. Copyright 2019, American Chemical Society.

    In another approach, the appropriate doping of the photoactive layer would enhance the PD performance and ensure flexible compatibility. Toward that direction, Shin et al. reported the photodiode structure using graphene QDs (GQDs): CH3NH3PbI3 as the photoactive layer and PEDOT:GQDs as the hole transport layer (HTL) [124]. By incorporating GQDs, along with the increase of perovskite layer crystallinity, the work function of PEDOT: GQD HTL is also increased due to modification of PEDOT from benzodide to quinoid by adding carbon-based material, which leads to the efficient generation of charge carriers and reduced recombination at the interface. The typical device structure and its corresponding cross-sectional scanning electron microscopy (SEM) image are presented in Fig. 11(e). The consecutively enhanced photoresponsivity of 0.354  A W−1 and specific detectivity D* of 8.42×1012 Jones were observed, as shown in Fig. 11(f). Furthermore, the flexible PDs also show excellent stability by maintaining 80% of the initial responsivity even after repeated bending for 1000 cycles at a bending radius of 4 mm [Fig. 11(g)].

    (a) Schematic illustration of ferroelectric polarization-induced formation of internal electric field in the nanowire array device; (b) schematic illustration of the fabrication process of flexible P(VDF-TrFE)/perovskite hybrid nanowire arrays-based PD; (c) 650 nm wavelength light illumination of flexible P(VDF-TrFE)/perovskite PDs with various power intensities at 0 V; (d) I-t curves of the poled perovskite-0.6 device under 650 nm light illumination at bending angles with the intersection angle between bending direction and nanowire direction of 0°. Reproduced with permission from Ref. [125]. Copyright 2019, Wiley-VCH. (e) I-t curve of flexible P(VDF-TrFE)/perovskite PDs at different bending cycles. Reproduced with permission from Ref. [126]. Copyright 2019, Wiley-VCH.

    Figure 12.(a) Schematic illustration of ferroelectric polarization-induced formation of internal electric field in the nanowire array device; (b) schematic illustration of the fabrication process of flexible P(VDF-TrFE)/perovskite hybrid nanowire arrays-based PD; (c) 650 nm wavelength light illumination of flexible P(VDF-TrFE)/perovskite PDs with various power intensities at 0 V; (d) I-t curves of the poled perovskite-0.6 device under 650 nm light illumination at bending angles with the intersection angle between bending direction and nanowire direction of 0°. Reproduced with permission from Ref. [125]. Copyright 2019, Wiley-VCH. (e) I-t curve of flexible P(VDF-TrFE)/perovskite PDs at different bending cycles. Reproduced with permission from Ref. [126]. Copyright 2019, Wiley-VCH.

    (a) Schematic diagram of the SFPDs with integrated TENG; (b) change in the measured voltage (ΔV) and voltage responsivity of the device at different light intensities; (c) ΔV at various angles of incident light. Reproduced with permission from Ref. [129]. Copyright 2018, Wiley-VCH. (d) Schematic illustration of the integrated nanosystem, consisting of an energy conversion unit, a light sensing unit, and a current measurement system. (e) J-V curves of the as-fabricated integrated perovskite solar cell; (f) photoresponse curves after 100 and 200 bending cycles. Reproduced with permission from Ref. [130]. Copyright 2016, Wiley-VCH.

    Figure 13.(a) Schematic diagram of the SFPDs with integrated TENG; (b) change in the measured voltage (ΔV) and voltage responsivity of the device at different light intensities; (c) ΔV at various angles of incident light. Reproduced with permission from Ref. [129]. Copyright 2018, Wiley-VCH. (d) Schematic illustration of the integrated nanosystem, consisting of an energy conversion unit, a light sensing unit, and a current measurement system. (e) J-V curves of the as-fabricated integrated perovskite solar cell; (f) photoresponse curves after 100 and 200 bending cycles. Reproduced with permission from Ref. [130]. Copyright 2016, Wiley-VCH.

    Instead of mechanically actuated NGs, the in-built solar cell system can also be an excellent choice for SPPDs. For example, an all-perovskite self-powered nanosystem was demonstrated by Li et al., who assembled the perovskite solar cell with a perovskite PD, as shown in Fig. 13(d) [130]. The authors fabricated planar configuration perovskite solar cell using TiO2 as an electron transport layer, CH3NH3PbI3 as the light-absorbing layer, and P3HT as the hole transport layer. The as-fabricated solar cell was connected to ITO/CH3NH3PbI3/ITO configured planar PD on a flexible PET substrate through Cu wire, and another side of the PD was connected with the amplifier to measure photocurrent. As an energy conversion unit in the nanosystem, the perovskite solar cell with a high efficiency of 10.5% drives the light-sensing unit to achieve the detection of various lights. Under AM1.5 irradiation (100  mW cm−2), the perovskite solar cell can provide a 0.93 V voltage for the PD [Fig. 13(e)]. Furthermore, the mechanical stability and durability of the PD were examined by multiple bending exercises and no obvious degradation of photoresponse behavior was observed, even after 200 bending cycles, implying good mechanical endurance, as shown in Fig. 13(f).

    In addition to the aforementioned SFPD structures, numerous reports have appeared in the literature, as summarized in Table 3. As an example, nanowire array-based PDs show poor photoresponse performance due to the existence of multiple microinterfaces between randomly oriented nanowires, which has been systematically studied by Zeng et al. [131]. The authors fabricated nanowire network (NWN) PDs with a welding strategy that showed ultrahigh performance with an on–off ratio and detectivity of 2.8×104 and 4.16×1013 Jones, respectively. More importantly, the unpackaged NWN PDs show ultrahigh storage stability in the air with a humidity of 55%–65%, and the flexible NWN PDs can withstand 250 bending cycles at different bending radii and 1000 bending cycles at fixed bending radii with no performance degradation being observed. Also, a self-powered flexible fiber-shaped PD based on double-twisted perovskite-TiO2-carbon fiber and CuO-Cu2O-Cu wire was designed by Li et al. and achieved an ultrahigh detectivity of 2.15×1013 Jones and response time of less than 200 ms [136]. Recently, Ogale et al. demonstrated the flexible self-powered PD by forming a heterojunction of SnO3 and cubic phase α-CsPbI3 [101]. The cubic phase of CsPbI3 was stabilized by polyvinylpyrrolidone (PVP) wrapping, by which the device performance and environmental stability of the device have been notably enhanced.

    Summary of Flexible Self-Powered Perovskite-Based PDs

    Primary Component of the PD Device StructurePhysical Mechanism for Self-Mode (Junction)R (mA W−1) (Response Wavelength)D* (Jones)τr/τfBending CycleReference
    ITO/CH3NH3PbI3/AuIntegrated TENG418 (sunlight)1.22×101380/80 ms1000[132]
    Au/CH3NH3PbI3NRs/AuPV (Schottky junction)2.2 (300 nm)1.76×101127.2/26.2 ms–[132]
    Gr/PEDOT:PSS:GQDs/CH3NH3PbI3:GQDs/PCPM/BCP/AlPV (heterojunction)420 (600 nm)8.42×10120.96 μs/–1000[127]
    Au/CH3NH3PbI3 MWs/AgPV (Schottky junction)161.1 (520 nm)1.3×101213.8/16.1 μs–[73]
    Ag/Spiro/CH3NH3PbI3/In2O3/ITOPV (heterojunction)451 (720 nm)1.1×1011<200/<200  ms500[133]
    FTO/Al2O3/CsPbBr3/TiO2/AuPV (heterojunction)440 (405 nm)1.88×101328/270 μs3000[126]
    Al/BCP/PCBM/CH3NH3PbI3/PEDOT:PSS/AuCl3-graphenePV (heterojunction)400 (600 nm)5.3×1013–1000[134]
    Au/PTAA/MAPbI3/ZnO/n-type GRPV (heterojunction)343 (700 nm)5.82×1091/1 μs1000[135]
    C/TiO2/perovskite/CuO/Cu2O/CuPV (heterojunction)563 (800 nm)2.15×1013<200/<200  ms60[136]
    ITO/CH3NH3PbI3/ITOSolar cell110 (730 nm)–2200/300 ms200[133]
    Au/P(VDF-rFE)/CH3NH3PbI3/AuPV (heterojunction)20 (650 nm)1.4×101392/193 μs200[129]
    Au/P(VDF-TrFE)/CH3NH3PbI3 nanowires/AuPV (heterojunction)12 (650 nm)7.3×101288/184 μs200[128]
    Au NWs/PEDOT:PSS/CH3NH3PbI3/PCPM/AlPV (heterojunction)321 (670 nm)–4/3.3 μs–[123]
    C/TiO2/perovskite/SpiroOMeTAD/AuPV (heterojunction)182 (750 nm)1.24×1011<200/<200  ms80[130]
    Ni/CH3NH3PbI3/AlPV (Schottky junction)227 (532 nm)1.36×101161/42 ms1500[72]
    ITO/TiO2/CsPbBr3/SpiroOMeTAD/AuPV (heterojunction)10.1×103 (405 nm)9.35×10138.0/2.3 s1600[136]

    7. CHALLENGES AND FUTURE PERSPECTIVE

    The perovskite-based SPPD operable at various subbands from DUV to the NIR has been achieved. However, the significant advantages and disadvantages regarding perovskite-based PDs are applicable to perovskite-based self-powered PDs too. Despite significant development in perovskite PDs, there are still formidable issues and challenges to be resolved to shift from laboratory to industrial mass production and application. The performance can be further improved by optimizing the intrinsic properties of perovskite material and device fabrication schemes. Apart from key parameters such as photosensitivity, photoresponsivity, detectivity, and response speed, the important criteria for practical device application are that the device has to maintain a stable photocurrent and dark current for the long term under standard conditions. This criterion has mainly been affected by issues such as moisture, thermal condition, and photoinstability [137,138].

    A. Stability against Moisture

    Mostly, perovskite-based optoelectronic devices are based on hybrid organic-inorganic perovskite materials, which have noncoordinated ions such as Pb2+, I−, and MA+ that were responsible for the perovskites to be highly sensitive to moisture and polar solvent and subsequently affect the stability of the perovskite [139,140]. It was found that large-sized cations (i.e., long-chain organic cations) can enhance the stability of perovskite materials [89,141]. The perovskite materials with long-chain cations showed negligible degradation after exposure to moisture for 46 days. It was also reported that the Pb-containing perovskites are stabler in air than their Sn-containing counterparts because Sn2+ is easy to be oxidized to Sn4+. Specifically, the Pb-containing perovskites show only surface degradation in the dark with the bulk properties of the materials retained for a couple of weeks in air. Moreover, it was observed that the metal luster in MAPbI3 single crystals can even keep for more than half a year in air. In contrast, the Sn-containing materials are air- and moisture-sensitive and partially decompose within 2 h before total decomposition after 1 day [142]. Apart from the crystal structure of perovskite, the defect structure of perovskites plays an important role in the deterioration of device performance [143]. The presence of defects in light-sensitive material has commonly been recognized as fatal, such that charge mobility, carrier lifetime, and conductivity are decreased, which are inevitable properties for optoelectronic devices. A stability study on polycrystalline thin film performed by Wang et al. reported that deterioration of perovskite occurs due to the large number of grain boundaries and surface defects. On the other hand, single-crystal perovskites with no grain boundary and diminished surface defects show better stability in the air for a longer time [144]. It has been concluded that the hybrid perovskites tend to decompose due to the hygroscopic nature of amine salts, and degeneration mainly starts at the structural defects of crystal as well as at grain boundaries [145].

    B. Stability against Temperature

    (a) Photoresponsivity evolution of PDs based on inorganic perovskite CsPbIxBr3−x and hybrid perovskite MAPbI3 at 100°C in N2 ambient condition. XRD spectra and digital photographs of (b) CsPbIBr2 and (c) MAPbI3 devices before and after heated at 100°C in N2-filled glove box for 244 h. The obvious PbI2 peak in XRD spectrum of MAPbI3 devices after being heated indicates the decomposition of MAPbI3. Reproduced with permission from Ref. [88]. Copyright 2018, Wiley-VCH. (d) Thermal stability of MAPbI3 NCs; photographic image of samples under 365 nm illumination. The samples are annealed at 40°C, 50°C, 60°C, 70°C, and 80°C for 10 min in open air. Reproduced with permission from Ref. [50]. Copyright 2020, Wiley-VCH.

    Figure 14.(a) Photoresponsivity evolution of PDs based on inorganic perovskite CsPbIxBr3−x and hybrid perovskite MAPbI3 at 100°C in N2 ambient condition. XRD spectra and digital photographs of (b) CsPbIBr2 and (c) MAPbI3 devices before and after heated at 100°C in N2-filled glove box for 244 h. The obvious PbI2 peak in XRD spectrum of MAPbI3 devices after being heated indicates the decomposition of MAPbI3. Reproduced with permission from Ref. [88]. Copyright 2018, Wiley-VCH. (d) Thermal stability of MAPbI3 NCs; photographic image of samples under 365 nm illumination. The samples are annealed at 40°C, 50°C, 60°C, 70°C, and 80°C for 10 min in open air. Reproduced with permission from Ref. [50]. Copyright 2020, Wiley-VCH.

    C. Stability against Light Exposure

    Perovskite semiconductors demand deep investigation with respect to their stability in terms of moisture and temperature. However, the encapsulation technique could give the solution to enhance the stability to some extent. Stability under light exposure is another challenge to be faced while dealing with perovskite-based PDs [137]. The deep insight into the mechanism of light-induced degradation will be valuable for designing highly stable perovskite materials [147]. There are many reports on the degradation of perovskites under light illumination. The hypotheses include electronic trap states [148], photochemical reactions [149,150], activate transport of halide ions and/or organic cations [151], etc. Bag et al. studied the stability of perovskite under light exposure by replacing an MA+ (methylammonium) ion with an FA+ (formamidinium) ion; stability was enhanced by optimizing the balance between MA+ and FA+ ions [151]. Hence, it can be concluded that the controlling of vacancy defects and ion migration deficiency can considerably enhance the stability of perovskite-based devices under long-term exposure to light illumination.

    D. Issue of Toxicity

    Several issues and open questions regarding the commercialization of perovskite-based PDs remain to be confronted. The toxicity caused by lead is always a problem, threatening human health, poisoning organisms, polluting the environment, and causing difficulty in discharging lead from the body. Research indicates that the contamination of lead ions to soil and water sources is permanent and generates a very serious negative impact on human, animal, and plant survival [152–155]. Therefore, to assure human safety and a pollution-free natural environment, it is very essential to develop some non- or low-toxic metal ions to replace lead as perovskite materials. For example, there have been multiple previous attempts to replace Pb2+ ions by less toxic ions such as Sn2+, Bi3+, Ge2+, Sb3+, Mn2+, and Cu2+ ions [156–160]. These efforts not only increase the variety of perovskite materials but also enhance the environmentally friendly features. Although the toxicity has been weakened by lead-free perovskites, the performance of the device needs to be further improved. Among the perovskite components, lead acts as a core skeleton that plays an important role in the generation and transport of charges. The carriers transfer along with the Pb–halogen bond, resulting in poor performance and lower stability after replacing Pb with Sn or Bi. Many researchers have proved that the role of lead is irreplaceable; thus the toxicity treatment of perovskite needs to be further considered. Overall, to facilitate a profound understanding of perovskite characteristics and device physics, the focus should be sharpened to their crystal growth process, defect engineering, device fabrication technique, and more importantly, the stability of devices under ambient conditions.

    8. CONCLUSION

    In summary, by virtue of their superior optoelectronic properties, perovskite materials have made a giant step in the PDs research field. Although significant advances in the development of perovskite-based self-powered PDs have been made in past years, there are still some challenges remaining before moving forward with practical applications. There are two ways to bring the perovskite-based PDs to practical or commercial application: either by optimization of material synthesis with high crystal quality and enhancement of stability issues in perovskite material or advancement in device fabrication strategy. Moreover, PD arrays are less explored for real applications in imaging and biomedical sensing, which should be a focus in the future. Specifically, the fabricated self-powered perovskite PDs should be intelligent, multifunctional, supersmall, extremely sensitive, and energy-efficient. This requires the rational synthesis of materials, fabrication of devices, and integration of various devices into a system with multifunctional characteristics and operation without external power sources. We strongly believe that the reader can acquire more comprehensive knowledge in this field while reading this review and motivate young researchers to undertake the tasks to solve the issues raised in this review.

    References

    [1] J. Yu, G. Liu, C. Chen, Y. Li, M. Xu, T. Wang, G. Zhao, L. Zhang. Perovskite CsPbBr3 crystals: growth and applications. J. Mater. Chem. C, 8, 6326-6341(2020).

    [2] B. Murali, H. K. Kolli, J. Yin, R. Ketavath, O. M. Bakr, O. F. Mohammed. Single crystals: the next big wave of perovskite optoelectronics. ACS Mater. Lett., 2, 184-214(2020).

    [3] F. Mei, D. Sun, S. Mei, J. Feng, Y. Zhou, J. Xu, X. Xiao. Recent progress in perovskite-based photodetectors: the design of materials and structures. Adv. Phys. X, 4, 1592709(2019).

    [4] H. Wang, D. H. Kim. Perovskite-based photodetectors: materials and devices. Chem. Soc. Rev., 46, 5204-5236(2017).

    [5] B. Saparov, D. B. Mitzi. Organic-inorganic perovskites: structural versatility for functional materials design. Chem. Rev., 116, 4558-4596(2016).

    [6] M. A. Green, A. Ho-Baillie, H. J. Snaith. The emergence of perovskite solar cells. Nat. Photonics, 8, 506-514(2014).

    [7] G. Konstantatos, E. H. Sargent. Nanostructured materials for photon detection. Nat. Nanotechnol., 5, 391-400(2010).

    [8] F. H. L. Koppens, T. Mueller, P. Avouris, A. C. Ferrari, M. S. Vitiello, M. Polini. Photodetectors based on graphene, other two-dimensional materials and hybrid systems. Nat. Nanotechnol., 9, 780-793(2014).

    [9] Z. L. Wang. Self-powered nanosensors and nanosystems. Adv. Mater., 24, 280-285(2012).

    [10] J. Gubbi, R. Buyya, S. Marusic, M. Palaniswami. Internet of things (IoT): a vision, architectural elements, and future directions. Future Gener. Comput. Syst., 29, 1645-1660(2013).

    [11] Y. Yang, W. Guo, J. Qi, J. Zhao, Y. Zhang. Self-powered ultraviolet photodetector based on a single Sb-doped ZnO nanobelt. Appl. Phys. Lett., 97, 223113(2010).

    [12] Y.-Q. Bie, Z.-M. Liao, H.-Z. Zhang, G.-R. Li, Y. Ye, Y. B. Zhou, J. Xu, Z.-X. Qin, L. Dai, D.-P. Yu. Self-powered, ultrafast, visible-blind UV detection and optical logical operation based on ZnO/GaN nanoscale p-n junctions. Adv. Mater., 23, 649-653(2011).

    [13] X. Li, L. Tao, Z. Chen, H. Fang, X. Li, X. Wang, J.-B. Xu, H. Zhu. Graphene and related two-dimensional materials: structure-property relationships for electronics and optoelectronics. Appl. Phys. Rev., 4, 021306(2017).

    [14] C. Li, Q. Cao, F. Wang, Y. Xiao, Y. Li, J.-J. Delaunay, H. Zhu. Engineering graphene and TMDs based van der Waals heterostructures for photovoltaic and photoelectrochemical solar energy conversion. Chem. Soc. Rev., 47, 4981-5037(2018).

    [15] M. Dai, H. Chen, R. Feng, W. Feng, Y. Hu, H. Yang, G. Liu, X. Chen, J. Zhang, C.-Y. Xu, P. Hu. A dual-band multilayer InSe self-powered photodetector with high performance induced by surface plasmon resonance and asymmetric Schottky junction. ACS Nano, 12, 8739-8747(2018).

    [16] X. Zhou, X. Hu, J. Yu, S. Liu, Z. Shu, Q. Zhang, H. Li, Y. Ma, H. Xu, T. Zhai. 2D layered material-based van der Waals heterostructures for optoelectronics. Adv. Funct. Mater., 28, 1706587(2018).

    [17] J. Miao, F. Zhang. Recent progress on highly sensitive perovskite photodetectors. J. Mater. Chem. C, 7, 1741-1791(2019).

    [18] L. Su, W. Yang, J. Cai, H. Chen, X. Fang. Self-powered ultraviolet photodetectors driven by built-in electric field. Small, 13, 1701687(2017).

    [19] W. Tian, Y. Wang, L. Chen, L. Li. Self-powered nanoscale photodetectors. Small, 13, 1701848(2017).

    [20] M. Liu, M. B. Johnston, H. J. Snaith. Efficient planar heterojunction perovskite solar cells by vapour deposition. Nature, 501, 395-398(2013).

    [21] J. Huang, Y. Yuan, Y. Shao, Y. Yan. Understanding the physical properties of hybrid perovskites for photovoltaic applications. Nat. Rev. Mater., 2, 17042(2017).

    [22] L. Etgar, P. Gao, Z. Xue, Q. Peng, A. K. Chandiran, B. Liu, M. K. Nazeeruddin, M. Grätzel. Mesoscopic CH3NH3PbI3/TiO2 heterojunction solar cells. J. Am. Chem. Soc., 134, 17396-17399(2012).

    [23] A. Miyata, A. Mitioglu, P. Plochocka, O. Portugall, J. T.-W. Wang, S. D. Stranks, H. J. Snaith, R. J. Nicholas. Direct measurement of the exciton binding energy and effective masses for charge carriers in organic-inorganic tri-halide perovskites. Nat. Phys., 11, 582-587(2015).

    [24] S. Torabi, F. Jahani, V. I. Severen, C. Kanimozhi, S. Patil, R. W. A. Havenith, R. C. Chiechi, L. Lutsen, D. J. M. Vanderzande, T. J. Cleij, J. C. Hummelen, J. A. Koster. Strategy for enhancing the dielectric constant of organic semiconductors without sacrificing charge carrier mobility and solubility. Adv. Funct. Mater., 25, 150-157(2015).

    [25] T. M. Brenner, D. A. Egger, L. Kronik, G. Hodes, D. Cahen. Hybrid organic—inorganic perovskites: low-cost semiconductors with intriguing charge-transport properties. Nat. Rev. Mater., 1, 15007(2016).

    [26] D. Shi, V. Adinolfi, R. Comin, M. Yuan, E. Alarousu, A. Buin, Y. Chen, S. Hoogland, A. Rothenberger, K. Katsiev, Y. Losovyj, X. Zhang, P. A. Dowben, O. F. Mohammed, E. H. Sargent, O. M. Bakr. Low trap-state density and long carrier diffusion in organolead trihalide perovskite single crystals. Science, 347, 519-522(2015).

    [27] G. R. Yettapu, D. Talukdar, S. Sarkar, A. Swarnkar, A. Nag, P. Ghosh, P. Mandal. Terahertz conductivity within colloidal CsPbBr3 perovskite nanocrystals: remarkably high carrier mobilities and large diffusion lengths. Nano Lett., 16, 4838-4848(2016).

    [28] M. I. Saidaminov, M. A. Haque, J. Almutlaq, S. Sarmah, X.-H. Miao, R. Begum, A. A. Zhumekenov, I. Dursun, N. Cho, B. Murali, O. F. Mohammed, T. Wu, O. M. Bakr. Inorganic lead halide perovskite single crystals: phase-selective low-temperature growth, carrier transport properties, and self-powered photodetection. Adv. Opt. Mater., 5, 1600704(2017).

    [29] Y. He, L. Matei, H. J. Jung, K. M. McCall, M. Chen, C. C. Stoumpos, Z. Liu, J. A. Peters, D. Y. Chung, B. W. Wessels, M. R. Wasielewski, V. P. Dravid, A. Burger, M. G. Kanatzidis. High spectral resolution of gamma-rays at room temperature by perovskite CsPbBr3 single crystals. Nat. Commun., 9, 1609(2018).

    [30] A. Fakharuddin, L. Schmidt-Mende, G. Garcia-Belmonte, R. Jose, I. Mora-Sero. Interfaces in perovskite solar cells. Adv. Energy Mater., 7, 1700623(2017).

    [31] T. Leijtens, G. E. Eperon, N. K. Noel, S. N. Habisreutinger, A. Petrozza, H. J. Snaith. Stability of metal halide perovskite solar cells. Adv. Energy Mater., 5, 1500963(2015).

    [32] A. K. Jena, A. Kulkarni, T. Miyasaka. Halide perovskite photovoltaics: background, status, and future prospects. Chem. Rev., 119, 3036-3103(2019).

    [33] Y. Zhou, Y. Zhao. Chemical stability and instability of inorganic halide perovskites. Energy Environ. Sci., 12, 1495-1511(2019).

    [34] Y. Lin, Y. Bai, Y. Fang, Q. Wang, Y. Deng, J. Huang. Suppressed ion migration in low-dimensional perovskites. ACS Energy Lett., 2, 1571-1572(2017).

    [35] H. J. Snaith, A. Abate, J. M. Ball, G. E. Eperon, T. Leijtens, N. K. Noel, S. D. Stranks, J. T.-W. Wang, K. Wojciechowski, W. Zhang. Anomalous hysteresis in perovskite solar cells. J. Phys. Chem. Lett., 5, 1511-1515(2014).

    [36] A. Fakharuddin, U. Shabbir, W. Qiu, T. Iqbal, M. Sultan, P. Heremans, L. Schmidt-Mende. Inorganic and layered perovskites for optoelectronic devices. Adv. Mater., 31, 1807095(2019).

    [37] M. Saliba, T. Matsui, J.-Y. Seo, K. Domanski, J.-P. Correa-Baena, M. K. Nazeeruddin, S. M. Zakeeruddin, W. Tress, A. Abate, A. Hagfeldt, M. Grätzel. Cesium-containing triple cation perovskite solar cells: improved stability, reproducibility and high efficiency. Energy Environ. Sci., 9, 1989-1997(2016).

    [38] J.-W. Lee, D.-H. Kim, H.-S. Kim, S.-W. Seo, S. M. Cho, N.-G. Park. Formamidinium and cesium hybridization for photo- and moisture-stable perovskite solar cell. Adv. Energy Mater., 5, 1501310(2015).

    [39] F. Zhuge, Z. Zheng, P. Luo, L. Lv, Y. Huang, H. Li, T. Zhai. Nanostructured materials and architectures for advanced infrared photodetection. Adv. Mater. Technol., 2, 1700005(2017).

    [40] Z. Bai, X. Chen, X. Yan, X. Zheng, Z. Kang, Y. Zhang. Self-powered ultraviolet photodetectors based on selectively grown ZnO nanowire arrays with thermal tuning performance. Phys. Chem. Chem. Phys., 16, 9525-9529(2014).

    [41] X. Chen, K. Liu, Z. Zhang, C. Wang, B. Li, H. Zhao, D. Zhao, D. Shen. Self-powered solar-blind photodetector with fast response based on Au/β-Ga2O3 nanowires array film Schottky junction. ACS Appl. Mater. Interfaces, 8, 4185-4191(2016).

    [42] L. Duan, F. He, Y. Tian, B. Sun, J. Fan, X. Yu, L. Ni, Y. Zhang, Y. Chen, W. Zhang. Fabrication of self-powered fast-response ultraviolet photodetectors based on graphene/ZnO:Al nanorod-array-film structure with stable Schottky barrier. ACS Appl. Mater. Interfaces, 9, 8161-8168(2017).

    [43] M. Hussain, S. Aftab, S. H. A. Jaffery, A. Ali, S. Hussain, D. N. Cong, R. Akhtar, Y. Seo, J. Eom, P. Gautam, H. Noh, J. Jung. Asymmetric electrode incorporated 2D GeSe for self-biased and efficient photodetection. Sci. Rep., 10, 9374(2020).

    [44] L. Mi, H. Wang, Y. Zhang, X. Yao, Y. Chang, G. Li, G. Li, Y. Jiang. High performance visible–near-infrared PbS-quantum-dots/indium Schottky diodes for photodetectors. Nanotechnology, 28, 055202(2016).

    [45] D. Wu, Y. Jiang, Y. Zhang, Y. Yu, Z. Zhu, X. Lan, F. Li, C. Wu, L. Wang, L. Luo. Self-powered and fast-speed photodetectors based on CdS:Ga nanoribbon/Au Schottky diodes. J. Mater. Chem., 22, 23272-23276(2012).

    [46] D. Li, G. Dong, W. Li, L. Wang. High performance organic-inorganic perovskite-optocoupler based on low-voltage and fast response perovskite compound photodetector. Sci. Rep., 5, 7902(2015).

    [47] P. V. Chandrasekar, S. Yang, J. Hu, M. Sulaman, M. I. Saleem, Y. Tang, Y. Jiang, B. Zou. A one-step method to synthesize CH3NH3PbI3:MoS2 nanohybrids for high-performance solution-processed photodetectors in the visible region. Nanotechnology, 30, 085707(2019).

    [48] R. Zhi, J. Hu, S. Yang, C. Perumal Veeramalai, Z. Zhang, M. I. Saleem, M. Sulaman, Y. Tang, B. Zou. A facile method to synthesize two-dimensional CsPb2Br5 nano-/micro-sheets for high-performance solution-processed photodetectors. J. Alloys. Compd., 824, 153970(2020).

    [49] C. Perumal Veeramalai, S. Yang, R. Zhi, M. Sulaman, M. I. Saleem, Y. Cui, Y. Tang, Y. Jiang, L. Tang, B. Zou. Solution-processed. Adv. Opt. Mater., 8, 2000215(2020).

    [50] L. Peng, L. Hu, X. Fang. Energy harvesting for nanostructured self-powered photodetectors. Adv. Funct. Mater., 24, 2591-2610(2014).

    [51] Z. L. Wang. The new field of photopiezotronics. Mater. Today, 10, 20-28(2007).

    [52] G. Maculan, A. D. Sheikh, A. L. Abdelhady, M. I. Saidaminov, M. A. Haque, B. Murali, E. Alarousu, O. F. Mohammed, T. Wu, O. M. Bakr. CH3NH3PbCl3 single crystals: inverse temperature crystallization and visible-blind UV-photodetector. J. Phys. Chem. Lett., 6, 3781-3786(2015).

    [53] Q. Dong, Y. Fang, Y. Shao, P. Mulligan, J. Qiu, L. Cao, J. Huang. Electron-hole diffusion lengths >175 μm in solution-grown CH3NH3PbI3 single crystals. Science, 347, 967-970(2015).

    [54] Z. Lian, Q. Yan, Q. Lv, Y. Wang, L. Liu, L. Zhang, S. Pan, Q. Li, L. Wang, J.-L. Sun. High-performance planar-type photodetector on (100) facet of MAPbI3 single crystal. Sci. Rep., 5, 16563(2015).

    [55] J. Shamsi, A. L. Abdelhady, S. Accornero, M. Arciniegas, L. Goldoni, A. R. S. Kandada, A. Petrozza, L. Manna. N-methylformamide as a source of methylammonium ions in the synthesis of lead halide perovskite nanocrystals and bulk crystals. ACS Energy Lett., 1, 1042-1048(2016).

    [56] M. Cao, J. Tian, Z. Cai, L. Peng, L. Yang, D. Wei. Perovskite heterojunction based on CH3NH3PbBr3 single crystal for high-sensitive self-powered photodetector. Appl. Phys. Lett., 109, 233303(2016).

    [57] X. Zhang, C. Ji, X. Liu, S. Wang, L. Li, Y. Peng, Y. Yao, M. Hong, J. Luo. Solution-grown large-sized single-crystalline 2D/3D perovskite heterostructure for self-powered photodetection. Adv. Opt. Mater., 8, 2000311(2020).

    [58] J. Ding, H. Fang, Z. Lian, J. Li, Q. Lv, L. Wang, J.-L. Sun, Q. Yan. A self-powered photodetector based on a CH3NH3PbI3 single crystal with asymmetric electrodes. CrystEngComm, 18, 4405-4411(2016).

    [59] P. A. Shaikh, D. Shi, J. R. D. Retamal, A. D. Sheikh, M. A. Haque, C.-F. Kang, J.-H. He, O. M. Bakr, T. Wu. Schottky junctions on perovskite single crystals: light-modulated dielectric constant and self-biased photodetection. J. Mater. Chem. C, 4, 8304-8312(2016).

    [60] X. Zhang, X. Dong, S. Wang, H. Liu, W. Hu, X. Li. A self-powered photodetector based on polarization-driven in CH3NH3PbI3 single crystal (100) plane. Chem. Eng. J., 404, 125957(2020).

    [61] R. Yan, D. Gargas, P. Yang. Nanowire photonics. Nat. Photonics, 3, 569-576(2009).

    [62] Y. Fu, H. Zhu, J. Chen, M. P. Hautzinger, X. Y. Zhu, S. Jin. Metal halide perovskite nanostructures for optoelectronic applications and the study of physical properties. Nat. Rev. Mater., 4, 169-188(2019).

    [63] D. Chen, X. Chen. Luminescent perovskite quantum dots: synthesis, microstructures, optical properties and applications. J. Mater. Chem. C, 7, 1413-1446(2019).

    [64] F. Zhang, H. Zhong, C. Chen, X.-G. Wu, X. Hu, H. Huang, J. Han, B. Zou, Y. Dong. Brightly luminescent and color-tunable colloidal CH3NH3PbX3 (X = Br, I, Cl) quantum dots: potential alternatives for display technology. ACS Nano, 9, 4533-4542(2015).

    [65] L. Protesescu, S. Yakunin, M. I. Bodnarchuk, F. Krieg, R. Caputo, C. H. Hendon, R. X. Yang, A. Walsh, M. V. Kovalenko. Nanocrystals of cesium lead halide perovskites (CsPbX3, X = Cl, Br, and I): novel optoelectronic materials showing bright emission with wide color gamut. Nano Lett., 15, 3692-3696(2015).

    [66] Y. Wang, L. Song, Y. Chen, W. Huang. Emerging new-generation photodetectors based on low-dimensional halide perovskites. ACS Photon., 7, 10-28(2020).

    [67] M. S. Imran, Y. Shengyi, Z. Ruonan, L. Hailong, S. Muhammad, V. Perumal, Z. Zhenheng, B. Attia, Z. Bingsuo. Self-powered, all-solution processed, trilayer heterojunction perovskite-based photodetectors. Nanotechnology, 31, 254001(2020).

    [68] H. Zhou, Z. Song, C. R. Grice, C. Chen, J. Zhang, Y. Zhu, R. Liu, H. Wang, Y. Yan. Self-powered CsPbBr3 nanowire photodetector with a vertical structure. Nano Energy, 53, 880-886(2018).

    [69] F. Cao, W. Tian, K. Deng, M. Wang, L. Li. Self-powered UV–Vis–NIR photodetector based on conjugated-polymer/CsPbBr3 nanowire array. Adv. Funct. Mater., 29, 1906756(2019).

    [70] J. Tao, Z. Xiao, J. Wang, C. Li, X. Sun, F. Li, X. Zou, G. Liao, Z. Zou. A self-powered, flexible photodetector based on perovskite nanowires with Ni-Al electrodes. J. Alloys. Compd., 845, 155311(2020).

    [71] C.-Y. Wu, W. Peng, T. Fang, B. Wang, C. Xie, L. Wang, W.-H. Yang, L.-B. Luo. Asymmetric contact-induced self-driven perovskite-microwire-array photodetectors. Adv. Electron. Mater., 5, 1900135(2019).

    [72] P. V. Chandrasekar, S. Yang, J. Hu, M. Sulaman, Y. Shi, M. I. Saleem, Y. Tang, Y. Jiang, B. Zou. Solution-phase, template-free synthesis of PbI2 and MAPbI3 nano/microtubes for high-sensitivity photodetectors. Nanoscale, 11, 5188-5196(2019).

    [73] Y. Liu, F. Li, C. Perumal Veeramalai, W. Chen, T. Guo, C. Wu, T. W. Kim. Inkjet-printed photodetector arrays based on hybrid perovskite CH3NH3PbI3 microwires. ACS Appl. Mater. Interfaces, 9, 11662-11668(2017).

    [74] Q. Ou, Y. Zhang, Z. Wang, J. A. Yuwono, R. Wang, Z. Dai, W. Li, C. Zheng, Z.-Q. Xu, X. Qi, S. Duhm, N. V. Medhekar, H. Zhang, Q. Bao. Strong depletion in hybrid perovskite p–n junctions induced by local electronic doping. Adv. Mater., 30, 1705792(2018).

    [75] P. Gui, J. Li, X. Zheng, H. Wang, F. Yao, X. Hu, Y. Liu, G. Fang. Self-driven all-inorganic perovskite microplatelet vertical Schottky junction photodetectors with a tunable spectral response. J. Mater. Chem. C, 8, 6804-6812(2020).

    [76] C. Tian, F. Wang, Y. Wang, Z. Yang, X. Chen, J. Mei, H. Liu, D. Zhao. Chemical vapor deposition method grown all-inorganic perovskite microcrystals for self-powered photodetectors. ACS Appl. Mater. Interfaces, 11, 15804-15812(2019).

    [77] H. Zhou, J. Zeng, Z. Song, C. R. Grice, C. Chen, Z. Song, D. Zhao, H. Wang, Y. Yan. Self-powered all-inorganic perovskite microcrystal photodetectors with high detectivity. J. Phys. Chem. Lett., 9, 2043-2048(2018).

    [78] H. Zhou, Z. Song, C. R. Grice, C. Chen, X. Yang, H. Wang, Y. Yan. Pressure-assisted annealing strategy for high-performance self-powered all-inorganic perovskite microcrystal photodetectors. J. Phys. Chem. Lett., 9, 4714-4719(2018).

    [79] W. Nie, H. Tsai, R. Asadpour, J.-C. Blancon, A. J. Neukirch, G. Gupta, J. J. Crochet, M. Chhowalla, S. Tretiak, M. A. Alam, H.-L. Wang, A. D. Mohite. High-efficiency solution-processed perovskite solar cells with millimeter-scale grains. Science, 347, 522-525(2015).

    [80] X. Li, D. Bi, C. Yi, J.-D. Décoppet, J. Luo, S. M. Zakeeruddin, A. Hagfeldt, M. Grätzel. A vacuum flash–assisted solution process for high-efficiency large-area perovskite solar cells. Science, 353, 58-62(2016).

    [81] J.-W. Lee, H.-S. Kim, N.-G. Park. Lewis acid–base adduct approach for high efficiency perovskite solar cells. Acc. Chem. Res., 49, 311-319(2016).

    [82] N. J. Jeon, J. H. Noh, Y. C. Kim, W. S. Yang, S. Ryu, S. I. Seok. Solvent engineering for high-performance inorganic–organic hybrid perovskite solar cells. Nat. Mater., 13, 897-903(2014).

    [83] Q. Chen, H. Zhou, Z. Hong, S. Luo, H.-S. Duan, H.-H. Wang, Y. Liu, G. Li, Y. Yang. Planar heterojunction perovskite solar cells via vapor-assisted solution process. J. Am. Chem. Soc., 136, 622-625(2014).

    [84] D. Bi, C. Yi, J. Luo, J.-D. Décoppet, F. Zhang, S. M. Zakeeruddin, X. Li, A. Hagfeldt, M. Grätzel. Polymer-templated nucleation and crystal growth of perovskite films for solar cells with efficiency greater than 21%. Nat. Energy, 1, 16142(2016).

    [85] L. Dou, Y. Yang, J. You, Z. Hong, W.-H. Chang, G. Li, Y. Yang. Solution-processed hybrid perovskite photodetectors with high detectivity. Nat. Commun., 5, 5404(2014).

    [86] S. V. N. Pammi, R. Maddaka, V.-D. Tran, J.-H. Eom, V. Pecunia, S. Majumder, M.-D. Kim, S. G. Yoon. CVD-deposited hybrid lead halide perovskite films for high-responsivity, self-powered photodetectors with enhanced photo stability under ambient conditions. Nano Energy, 74, 104872(2020).

    [87] X. Liu, Z. Liu, J. Li, X. Tan, B. Sun, H. Fang, S. Xi, T. Shi, Z. Tang, G. Liao. Ultrafast, self-powered and charge-transport-layer-free photodetectors based on high-quality evaporated CsPbBr3 perovskites for applications in optical communication. J. Mater. Chem. C, 8, 3337-3350(2020).

    [88] C. Bao, J. Yang, S. Bai, W. Xu, Z. Yan, Q. Xu, J. Liu, W. Zhang, F. Gao. High performance and stable all-inorganic metal halide perovskite-based photodetectors for optical communication applications. Adv. Mater., 30, 1803422(2018).

    [89] L. Li, F. Zhang, S. Ye, X. Peng, Z. Sun, J. Lian, L. Liu, J. Qu, J. Song. Self-powered photodetectors based on CsxDMA1-xPbI3 perovskite films with high detectivity and stability. Nano Energy, 71, 104611(2020).

    [90] T. Pang, R. Jia, Y. Wang, K. Sun, Z. Hu, Y. Zhu, S. Luan, Y. Zhang. Self-powered behavior based on the light-induced self-poling effect in perovskite-based transport layer-free photodetectors. J. Mater. Chem. C, 7, 609-616(2019).

    [91] Y. Deng, Z. Xiao, J. Huang. Light-induced self-poling effect on organometal trihalide perovskite solar cells for increased device efficiency and stability. Adv. Energy Mater., 5, 1500721(2015).

    [92] Y. Yuan, J. Chae, Y. Shao, Q. Wang, Z. Xiao, A. Centrone, J. Huang. Photovoltaic switching mechanism in lateral structure hybrid perovskite solar cells. Adv. Energy Mater., 5, 1500615(2015).

    [93] L. Su, Z. X. Zhao, H. Y. Li, J. Yuan, Z. L. Wang, G. Z. Cao, G. Zhu. High-performance organolead halide perovskite-based self-powered triboelectric photodetector. ACS Nano, 9, 11310-11316(2015).

    [94] V. K. S. Hsiao, S.-F. Leung, Y.-C. Hsiao, P.-K. Kung, Y.-C. Lai, Z.-H. Lin, K. N. Salama, H. N. Alshareef, Z. L. Wang, J.-H. He. Photo-carrier extraction by triboelectricity for carrier transport layer-free photodetectors. Nano Energy, 65, 103958(2019).

    [95] O. Game, U. Singh, T. Kumari, A. Banpurkar, S. Ogale. ZnO(N)–Spiro-MeOTAD hybrid photodiode: an efficient self-powered fast-response UV (visible) photosensor. Nanoscale, 6, 503-513(2014).

    [96] C. Li, C. Han, Y. Zhang, Z. Zang, M. Wang, X. Tang, J. Du. Enhanced photoresponse of self-powered perovskite photodetector based on ZnO nanoparticles decorated CsPbBr3 films. Sol. Energy Mater. Sol. Cells, 172, 341-346(2017).

    [97] F. Bai, J. Qi, F. Li, Y. Fang, W. Han, H. Wu, Y. Zhang. A high-performance self-powered photodetector based on monolayer MoS2/perovskite heterostructures. Adv. Mater. Interfaces, 5, 1701275(2018).

    [98] R. Saraf, V. Maheshwari. Self-powered photodetector based on electric-field-induced effects in MAPbI3 perovskite with improved stability. ACS Appl. Mater. Interfaces, 10, 21066-21072(2018).

    [99] M. Xue, H. Zhou, G. Ma, L. Yang, Z. Song, J. Zhang, H. Wang. Investigation of the stability for self-powered CsPbBr3 perovskite photodetector with an all-inorganic structure. Sol. Energy Mater. Sol. Cells, 187, 69-75(2018).

    [100] Z.-X. Zhang, Z. Long-Hui, X.-W. Tong, Y. Gao, C. Xie, Y. H. Tsang, L.-B. Luo, Y.-C. Wu. Ultrafast, self-driven, and air-stable photodetectors based on multilayer PtSe2/perovskite heterojunctions. J. Phys. Chem. Lett., 9, 1185-1194(2018).

    [101] U. Bansode, A. Rahman, S. Ogale. Low-temperature processing of optimally polymer-wrapped α-CsPbI3 for self-powered flexible photo-detector application. J. Mater. Chem. C, 7, 6986-6996(2019).

    [102] J. Ghosh, G. Natu, P. K. Giri. Plasmonic hole-transport-layer enabled self-powered hybrid perovskite photodetector using a modified perovskite deposition method in ambient air. Org. Electron., 71, 175-184(2019).

    [103] S. Murali, S. P. Madhusudanan, A. K. Pathak, P. M. Jayasankar, S. K. Batabyal. Carbon assisted methylammonium lead iodide microcrystalline device for an inexpensive self-powered photodetector. Mater. Lett., 254, 428-432(2019).

    [104] X.-W. Tong, Z.-X. Zhang, D. Wang, L.-B. Luo, C. Xie, Y.-C. Wu. Inorganic CsBi3I10 perovskite/silicon heterojunctions for sensitive, self-driven and air-stable NIR photodetectors. J. Mater. Chem. C, 7, 863-870(2019).

    [105] L.-H. Zeng, Q.-M. Chen, Z.-X. Zhang, D. Wu, H. Yuan, Y.-Y. Li, W. Qarony, S. P. Lau, L.-B. Luo, Y. H. Tsang. Multilayered PdSe2/perovskite Schottky junction for fast, self-powered, polarization-sensitive, broadband photodetectors, and image sensor application. Adv. Sci., 6, 1901134(2019).

    [106] W. Zhu, M. Deng, Z. Zhang, D. Chen, H. Xi, J. Chang, J. Zhang, C. Zhang, Y. Hao. Intermediate phase halide exchange strategy toward a high-quality, thick CsPbBr3 film for optoelectronic applications. ACS Appl. Mater. Interfaces, 11, 22543-22549(2019).

    [107] G. R. Adams, V. O. Eze, M. A. S. Shohag, R. Simpson, H. Parker, O. I. Okoli. Fabrication of rapid response self-powered photodetector using solution-processed triple cation lead-halide perovskite. Eng. Res. Express, 2, 015043(2020).

    [108] Z. Liu, X. Liu, B. Sun, X. Tan, H. Ye, J. Zhou, Z. Tang, T. Shi, G. Liao. Cu-doping strategy to enhance photoelectric performance of self-powered hole-conductor-free perovskite photodetector for optical communication applications. Adv. Mater. Technol., 5, 2000260(2020).

    [109] M. I. Saleem, S. Yang, R. Zhi, H. Li, M. Sulaman, P. V. Chandrasekar, Z. Zhang, A. Batool, B. Zou. Self-powered, all-solution processed, trilayer heterojunction perovskite-based photodetectors. Nanotechnology, 31, 254001(2020).

    [110] W. Tian, L. Min, F. Cao, L. Li. Nested inverse opal perovskite toward superior flexible and self-powered photodetection performance. Adv. Mater., 32, 1906974(2020).

    [111] Z. Zhang, W. Zhang, Q. Jiang, Z. Wei, M. Deng, D. Chen, W. Zhu, J. Zhang, H. You. Toward high-performance electron/hole-transporting-layer-free, self-powered CsPbIBr2 photodetectors via interfacial engineering. ACS Appl. Mater. Interfaces, 12, 6607-6614(2020).

    [112] W. Zhu, M. Deng, D. Chen, D. Chen, H. Xi, J. Chang, J. Zhang, C. Zhang, Y. Hao. Sacrificial additive-assisted film growth endows self-powered CsPbBr3 photodetectors with ultra-low dark current and high sensitivity. J. Mater. Chem. C, 8, 209-218(2020).

    [113] H. Fang, Q. Li, J. Ding, N. Li, H. Tian, L. Zhang, T. Ren, J. Dai, L. Wang, Q. Yan. A self-powered organolead halide perovskite single crystal photodetector driven by a DVD-based triboelectric nanogenerator. J. Mater. Chem. C, 4, 630-636(2016).

    [114] S.-T. Han, H. Peng, Q. Sun, S. Venkatesh, K.-S. Chung, S. C. Lau, Y. Zhou, V. A. L. Roy. An overview of the development of flexible sensors. Adv. Mater., 29, 1700375(2017).

    [115] A. Manekkathodi, M.-Y. Lu, C. W. Wang, L.-J. Chen. Direct growth of aligned zinc oxide nanorods on paper substrates for low-cost flexible electronics. Adv. Mater., 22, 4059-4063(2010).

    [116] W. Zheng, R. Lin, Z. Zhang, Q. Liao, J. Liu, F. Huang. An ultrafast-temporally-responsive flexible photodetector with high sensitivity based on high-crystallinity organic–inorganic perovskite nanoflake. Nanoscale, 9, 12718-12726(2017).

    [117] C. Xie, F. Yan. Flexible photodetectors based on novel functional materials. Small, 13, 1701822(2017).

    [118] Z. Liu, K. Parvez, R. Li, R. Dong, X. Feng, K. Müllen. Transparent conductive electrodes from graphene/PEDOT:PSS hybrid inks for ultrathin organic photodetectors. Adv. Mater., 27, 669-675(2015).

    [119] K. Rana, J. Singh, J.-H. Ahn. A graphene-based transparent electrode for use in flexible optoelectronic devices. J. Mater. Chem. C, 2, 2646-2656(2014).

    [120] C. Bao, W. Zhu, J. Yang, F. Li, S. Gu, Y. Wang, T. Yu, J. Zhu, Y. Zhou, Z. Zou. Highly flexible self-powered organolead trihalide perovskite photodetectors with gold nanowire networks as transparent electrodes. ACS Appl. Mater. Interfaces, 8, 23868-23875(2016).

    [121] M. Vosgueritchian, D. J. Lipomi, Z. Bao. Highly conductive and transparent PEDOT:PSS films with a fluorosurfactant for stretchable and flexible transparent electrodes. Adv. Funct. Mater., 22, 421-428(2012).

    [122] C. Perumal Veeramalai, S. Yang, J. Wei, M. Sulaman, R. Zhi, M. I. Saleem, Y. Tang, Y. Jiang, B. Zou. Porous single-wall carbon nanotube templates decorated with all-inorganic perovskite nanocrystals for ultraflexible photodetectors. ACS Appl. Nano Mater., 3, 459-467(2020).

    [123] G. Cen, Y. Liu, C. Zhao, G. Wang, Y. Fu, G. Yan, Y. Yuan, C. Su, Z. Zhao, W. Mai. Atomic-layer deposition-assisted double-side interfacial engineering for high-performance flexible and stable CsPbBr3 perovskite photodetectors toward visible light communication applications. Small, 15, 1902135(2019).

    [124] D. H. Shin, S. H. Shin, S. G. Lee, S. Kim, S.-H. Choi. High-detectivity/-speed flexible and self-powered graphene quantum dots/perovskite photodiodes. ACS Sustain. Chem. Eng., 7, 19961-19968(2019).

    [125] F. Cao, W. Tian, M. Wang, H. Cao, L. Li. Semitransparent, flexible, and self-powered photodetectors based on ferroelectricity-assisted perovskite nanowire arrays. Adv. Funct. Mater., 29, 1901280(2019).

    [126] F. Cao, W. Tian, L. Meng, M. Wang, L. Li. Ultrahigh-performance flexible and self-powered photodetectors with ferroelectric P(VDF-TrFE)/perovskite bulk heterojunction. Adv. Funct. Mater., 29, 1808415(2019).

    [127] H. Sun, T. Lei, W. Tian, F. Cao, J. Xiong, L. Li. Self-powered, flexible, and solution-processable perovskite photodetector based on low-cost carbon cloth. Small, 13, 1701042(2017).

    [128] K. Shen, H. Xu, X. Li, J. Guo, S. Sathasivam, M. Wang, A. Ren, K. L. Choy, I. P. Parkin, Z. Guo, J. Wu. Flexible and self-powered photodetector arrays based on all-inorganic CsPbBr3 quantum dots. Adv. Mater., 32, 2000004(2020).

    [129] S.-F. Leung, K.-T. Ho, P.-K. Kung, V. K. S. Hsiao, H. N. Alshareef, Z. L. Wang, J.-H. He. A self-powered and flexible organometallic halide perovskite photodetector with very high detectivity. Adv. Mater., 30, 1704611(2018).

    [130] H. Lu, W. Tian, F. Cao, Y. Ma, B. Gu, L. Li. A self-powered and stable all-perovskite photodetector–solar cell nanosystem. Adv. Funct. Mater., 26, 1296-1302(2016).

    [131] D. Wu, H. Zhou, Z. Song, M. Zheng, R. Liu, X. Pan, H. Wan, J. Zhang, H. Wang, X. Li, H. Zeng. Welding perovskite nanowires for stable, sensitive, flexible photodetectors. ACS Nano, 14, 2777-2787(2020).

    [132] S. Lim, M. Ha, Y. Lee, H. Ko. Large-area, solution-processed, hierarchical MAPbI3 nanoribbon arrays for self-powered flexible photodetectors. Adv. Opt. Mater., 6, 1800615(2018).

    [133] M. Wang, F. Cao, L. Meng, W. Tian, L. Li. High-performance flexible self-powered photodetector based on perovskite and low-temperature processed In2S3 nanoflake film. Adv. Mater. Interfaces, 6, 1801526(2019).

    [134] J. M. Kim, D. H. Shin, S.-H. Choi. Highly-flexible perovskite photodiodes employing doped multilayer-graphene transparent conductive electrodes. Nanotechnology, 29, 425203(2018).

    [135] J. M. Kim, S. Kim, S.-H. Choi. High-performance n-i-p-type perovskite photodetectors employing graphene-transparent conductive electrodes N-type doped with amine group molecules. ACS Sustain. Chem. Eng., 7, 734-739(2019).

    [136] H. Sun, W. Tian, F. Cao, J. Xiong, L. Li. Ultrahigh-performance self-powered flexible double-twisted fibrous broadband perovskite photodetector. Adv. Mater., 30, 1706986(2018).

    [137] X.-D. Wang, W.-G. Li, J.-F. Liao, D.-B. Kuang. Recent advances in halide perovskite single-crystal thin films: fabrication methods and optoelectronic applications. Sol. RRL, 3, 1800294(2019).

    [138] B. Paci, A. Generosi, J. Wright, C. Ferrero, D. A. Carlo, F. Brunetti. Planar perovskite solar cells: local structure and stability issues. Sol. RRL, 1, 1700066(2017).

    [139] T.-B. Song, Q. Chen, H. Zhou, C. Jiang, H.-H. Wang, Y. Yang, Y. Liu, J. You, Y. Yang. Perovskite solar cells: film formation and properties. J. Mater. Chem. A, 3, 9032-9050(2015).

    [140] Z. Xiao, Y. Yuan, Q. Wang, Y. Shao, Y. Bai, Y. Deng, Q. Dong, M. Hu, C. Bi, J. Huang. Thin-film semiconductor perspective of organometal trihalide perovskite materials for high-efficiency solar cells. Mater. Sci. Eng. R, 101, 1-38(2016).

    [141] I. C. Smith, E. T. Hoke, D. Solis-Ibarra, M. D. McGehee, H. I. Karunadasa. A layered hybrid perovskite solar-cell absorber with enhanced moisture stability. Angew. Chem., 53, 11232-11235(2014).

    [142] C. C. Stoumpos, C. D. Malliakas, M. G. Kanatzidis. Semiconducting tin and lead iodide perovskites with organic cations: phase transitions, high mobilities, and near-infrared photoluminescent properties. Inorg. Chem., 52, 9019-9038(2013).

    [143] C. Ran, J. Xu, W. Gao, C. Huang, S. Dou. Defects in metal triiodide perovskite materials towards high-performance solar cells: origin, impact, characterization, and engineering. Chem. Soc. Rev., 47, 4581-4610(2018).

    [144] Q. Wang, B. Chen, Y. Liu, Y. Deng, Y. Bai, Q. Dong, J. Huang. Scaling behavior of moisture-induced grain degradation in polycrystalline hybrid perovskite thin films. Energy Environ. Sci., 10, 516-522(2017).

    [145] J. H. Noh, S. H. Im, J. H. Heo, T. N. Mandal, S. I. Seok. Chemical management for colorful, efficient, and stable inorganic–organic hybrid nanostructured solar cells. Nano Lett., 13, 1764-1769(2013).

    [146] B. Conings, J. Drijkoningen, N. Gauquelin, A. Babayigit, J. D’Haen, L. D’Olieslaeger, A. Ethirajan, J. Verbeeck, J. Manca, E. Mosconi, F. D. Angelis, H.-G. Boyen. Intrinsic thermal instability of methylammonium lead trihalide perovskite. Adv. Energy Mater., 5, 1500477(2015).

    [147] C. L. C. Ellis, H. Javaid, E. C. Smith, D. Venkataraman. Hybrid perovskites with larger organic cations reveal autocatalytic degradation kinetics and increased stability under light. Inorg. Chem., 59, 12176-12186(2020).

    [148] W. Nie, J.-C. Blancon, A. J. Neukirch, K. Appavoo, H. Tsai, M. Chhowalla, M. A. Alam, M. Y. Sfeir, C. Katan, J. Even, S. Tretiak, J. J. Crochet, G. Gupta, A. D. Mohite. Light-activated photocurrent degradation and self-healing in perovskite solar cells. Nat. Commun., 7, 11574(2016).

    [149] S. Ito, S. Tanaka, K. Manabe, H. Nishino. Effects of surface blocking layer of Sb2S3 on nanocrystalline TiO2 for CH3NH3PbI3 perovskite solar cells. J. Phys. Chem. C, 118, 16995-17000(2014).

    [150] Z. Song, C. Wang, A. B. Phillips, C. R. Grice, D. Zhao, Y. Yu, C. Chen, C. Li, X. Yin, R. J. Ellingson, M. J. Heben, Y. Yan. Probing the origins of photodegradation in organic–inorganic metal halide perovskites with time-resolved mass spectrometry. Sustain. Energy Fuels, 2, 2460-2467(2018).

    [151] M. Bag, L. A. Renna, R. Y. Adhikari, S. Karak, F. Liu, P. M. Lahti, T. P. Russell, M. T. Tuominen, D. Venkataraman. Kinetics of ion transport in perovskite active layers and its implications for active layer stability. J. Am. Chem. Soc., 137, 13130-13137(2015).

    [152] B. Hailegnaw, S. Kirmayer, E. Edri, G. Hodes, D. Cahen. Rain on methylammonium lead iodide based perovskites: possible environmental effects of perovskite solar cells. J. Phys. Chem. Lett., 6, 1543-1547(2015).

    [153] F. Giustino, H. J. Snaith. Toward lead-free perovskite solar cells. ACS Energy Lett., 1, 1233-1240(2016).

    [154] Z. Shi, J. Guo, Y. Chen, Q. Li, Y. Pan, H. Zhang, Y. Xia, W. Huang. Lead-free organic–inorganic hybrid perovskites for photovoltaic applications: recent advances and perspectives. Adv. Mater., 29, 1605005(2017).

    [155] M. Wang, W. Wang, B. Ma, W. Shen, L. Liu, K. Cao, S. Chen, W. Huang. Lead-free perovskite materials for solar cells. Nano-Micro Lett., 13, 62(2021).

    [156] N. K. Noel, S. D. Stranks, A. Abate, C. Wehrenfennig, S. Guarnera, A.-A. Haghighirad, A. Sadhanala, G. E. Eperon, S. K. Pathak, M. B. Johnston, A. Petrozza, L. M. Herz, H. J. Snaith. Lead-free organic–inorganic tin halide perovskites for photovoltaic applications. Energy Environ. Sci., 7, 3061-3068(2014).

    [157] N. Leblanc, N. Mercier, L. Zorina, S. Simonov, P. Auban-Senzier, C. Pasquier. Large spontaneous polarization and clear hysteresis loop of a room-temperature hybrid ferroelectric based on mixed-halide [BiI3Cl2] polar chains and methylviologen dication. J. Am. Chem. Soc., 133, 14924-14927(2011).

    [158] W. Bi, N. Leblanc, N. Mercier, P. Auban-Senzier, C. Pasquier. Thermally induced Bi(III) lone pair stereoactivity: ferroelectric phase transition and semiconducting properties of (MV)BiBr5 (MV = methylviologen). Chem. Mater., 21, 4099-4101(2009).

    [159] B.-W. Park, B. Philippe, X. Zhang, H. Rensmo, G. Boschloo, E. M. J. Johansson. Bismuth based hybrid perovskites A3Bi2I9 (A: methylammonium or cesium) for solar cell application. Adv. Mater., 27, 6806-6813(2015).

    [160] T. Krishnamoorthy, H. Ding, C. Yan, W. L. Leong, T. Baikie, Z. Zhang, M. Sherburne, S. Li, M. Asta, N. Mathews, S. G. Mhaisalkar. Lead-free germanium iodide perovskite materials for photovoltaic applications. J. Mater. Chem. A, 3, 23829-23832(2015).

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    Chandrasekar Perumal Veeramalai, Shuai Feng, Xiaoming Zhang, S. V. N. Pammi, Vincenzo Pecunia, Chuanbo Li, "Lead–halide perovskites for next-generation self-powered photodetectors: a comprehensive review," Photonics Res. 9, 968 (2021)
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