Fig. 1. Basic structure and properties of perovskite quantum dots. (a) Crystal structure of quantum dots of cesium lead halide perovskite^[30]; (b) high-resolution transmission electron microscopic image of perovskite quantum dots^[7]; (c) defect tolerance characteristics of perovskite quantum dots^[32]; (d) fluorescence spectrum characteristics of perovskite quantum dots^[7]; (e) absorption spectra and fluorescence lifetime of perovskite quantum dots^[7]

Fig. 2. Synthesis method of perovskite quantum dots. (a) Schematic diagram of the synthesis of perovskite quantum dots by hot injection method; (b) effect of ligand chain length on the synthesis of perovskite quantum dots by hot injection method^[49]; (c) reaction equilibrium control of perovskite quantum dot synthesis^[50]; (d) synthesis of perovskite quantum dots with oleic acid and oleylamine solvent^[51]; (e) hot injection method synthesis of perovskite quantum dots with benzoyl halide as a halogen precursor^[53]

Fig. 3. Surface passivation of perovskite quantum dots. (a) Schematic diagram of defects in quantum dots^[66]; (b) types of ligands on the surface of perovskite quantum dots^[30]; (c) sodium ion passivation of perovskite quantum dot surface^[83]; (d) alumina coating passivation of perovskite quantum dots^[84]; (e) ligand exchange and SiO₂ coating passivation of perovskite quantum dots^[85]

Fig. 4. Self-assembly method of quantum dots. (a) Schematic diagram of superlattice preparation by saturated solvent evaporation^[14]; (b) device diagram of a saturated solvent evaporation method^87]; (c) schematic diagram of perovskite quantum dot assembly by ultrasonic method^[94]; (d) template method to control the self-assembly position and size of perovskite quantum dot superlattice^[95]; (e) multicomponent superlattice films prepared at the liquid-liquid interface^[96]

Fig. 5. Structural characterization methods for perovskite quantum dot superlattices. (a) TEM image of a CsPbBr₃ quantum dot superlattices^[102]; (b) HAADF-STEM image of CsPbBr₃ quantum dot superlattices^[14]; (c) schematic diagram of the working principle of GIWAXS and GISAXS^[103]; (d) OA/OLA capped CsPbBr₃ superlattice (left) and zwitterion-capped CsPbBr₃ superlattice (right) with their GISAXS mapping and simulated crystallographic information^[106]; (e) two-dimensional GISAXS pattern (on Si₃N₄ membrane)^[88]; (f) GIWAXS patterns for CsPbBr₃ and CsPbI₃ films with different ligands^[107]; (g) steady-state PL and absorption spectra of colloidal solutions of NPLs used to form superlattices with different face orientations and their corresponding 2D GIWAXS patterns (q_z: out-of-plane scattering vector; q_r: in-plane scattering vector)^[108]

Fig. 6. Optical characteristics of superfluorescence (SF) in metal-halide perovskite quantum dot superlattices. (a) Basic processes and characteristics of SF^[109]; (b) schematic diagram of the formation of SF in perovskite quantum dot superlattices^[14]; (c) PL spectra of quantum dots and coupled quantum dot superlattices (left) and time-resolved PL decay of quantum dots and coupled quantum dot superlattices (right; blue: uncoupled quantum dots; red: coupled quantum dot superlattices)^[14]; (d) time-resolved emission intensity trace under different excitation powers (left) and SF decay ${\tau }_{\mathrm{S}\mathrm{F}}$ (top right), SF emission intensity (middle right), and collective delay time ${\tau }_{\mathrm{D}}$ (bottom right) as functions of laser power^[14]; (e) HAADF-STEM images and SF emission spectrum of binary ABO₃-type superlattices^[88]; (f) schematic diagram of exciton coherence in perovskite quantum dot solids^[113]

Fig. 7. Exciton phase transitions, cavity-enhanced superfluorescence (CESF) characteristics, and their relationship with pump density in quantum dot superlattice microcavities. (a) Phase transitions of exciton ensembles during the self-assembly of quantum dots into superlattice microcavities (“+” and “-” represent holes and electrons, respectively)^[114]; (b) time-resolved PL decay of SF and CESF^[15]; (c) peak intensity I_max of SF/CESF signals vs pumping density^[15]; (d) power dependences of radiative time t_r^[15]; (e)(f) schematic illustrations of the remaining dipoles after conventional laser and CESF processes^[15]

Fig. 8. Development and application of CESF. (a) Experimental demonstration of quantum containers with ultrafast transition of exciton quantum coherence based on CsPbBr₃ superlattice microcavities^[15]; (b) nanosecond laser performance diagram of CsPbBr₃ quantum dot superlattices [left: PL intensity and full width at half maximum (FWHM) vs pumping intensity; right: laser spectrum]^[83]; (c) time dynamics analysis of multi-mode CESF under different pumping densities^[118]; (d) emission spectrum and fitted laser spectrum of typical CsPbBr₂Cl superlattices as functions of power, and the inset shows two-dimensional optical WGM distribution^[119]; (e) schematic diagram of low-threshold CESF process by preparing spherical quantum dot superlattices^[120]

Fig. 9. Novel physical mechanisms in CESF. (a) Physical pictures of the excited states and different radiation effects in QD and superlattice samples^[24]; (b) echo-like SF with radiative energy fluctuations in a superlattice post-excitation pulse disturbance^[24]; (c) physical explanation of the echo-like radiation [red-purple spheres: excitons; brown arrows passing through the spheres: cooperative radiation phase; blue halo: laser field introduced by the disturbance; orange-green background: virtual light field shared by cooperative (thermal) excitons; grid lines: unit quantum dots in the superlattice sample] ^[24]; (d) time-resolved PL image under different pump densities^[114]; (e) schematic diagram of sample structure for generating cooperative exciton polaritons^[25]; (f) angle-resolved PL spectra of a DBR-superlattice thin film excited above twice the pump threshold power^[25]

Fig. 10. Application prospect of superfluorescence and cavity enhanced superfluorescence. (a) Second-order correlation measurement of superradiation in waveguide^[128]; (b) schematic diagram of storage protocol for superradiant quantum memory^[129]; (c) quantum optical properties of superradiant light sources^[130]; (d) schematic diagram of experimental apparatus for free electron triggered superfluorescence^[131]

Table 1. State-of-the-art superfluorescence and cavity-enhanced superfluorescence observations in perovskite quantum dot superlattces with key information