Fig. 1. (a) Schematic illustration of the fabrication process of paper-based WS₂ photodetectors via abrading WS₂ crystals and penciling graphite electrodes on paper substrates. (b) Photograph of the 3 × 3 WS₂ photodetector array. Inset shows the magnified view of a WS₂ photodetector. (c) Optical micrograph of a WS₂ photodetector showing the WS₂ channel and graphite electrode regions.

Fig. 2. Comparison of the photoresponse performance of the paper-based WS₂ photodetector (device A) tested in air and vacuum conditions under illumination. (a) Current vs. time across the device under a periodic ON/OFF switching of illumination with a power intensity of 35 mW cm⁻². (b) Zoomed in on three consecutive ON/OFF cycles from (a). (c) Photocurrent vs. time for the WS₂ device as the illumination is switched ON/OFF with increasing incident power intensity from 1.1 mW cm⁻² to 35 mW cm⁻². (d) Photocurrent as a function of the power intensity. Note: Measurements are carried out at a bias voltage of 10 V and with a selected wavelength of 617 nm. The channel length and width of the device A are ~300 μm and 2 mm, respectively.

Fig. 3. Voltage-dependent photoresponse of the paper-based WS₂ photodetector (device B) under the illumination of 617 nm. (a) Photocurrent as a function of time for the WS₂ photodetector while the light is switched ON/OFF under various power intensities at a fixed bias voltage of 35 V. (b) The measured photocurrent and (c) corresponding responsivity as a function of power intensity collected at various bias voltages from 1 to 35 V. (d) The measured photocurrent and responsivity as a function of bias voltage at a fixed power intensity of 35 mW cm⁻².

Fig. 4. Spectral response of the paper-based WS₂ photodetector (device B). (a) Photocurrent vs. time when the device is subjected to cycles of ON/OFF illumination with different wavelengths. (b) Spectrum response of the WS₂ photodetector under various wavelengths of illumination in the range of 365 nm (ultraviolet) to 940 nm (near-infrared). Note: The device is measured at a fixed voltage of 10 V and an incident power intensity of 13 mW cm⁻².

Fig. 5. Integration of the paper-based WS₂ photodetector as detection element in an optical spectrometer. (a) Schematic diagram of the spectrometer system consist of a light source, a light-scattering optical element (reflective diffraction grating), and a detection element. (b) The measured power profiles using a commercial silicon photodiode and (c) photocurrent profiles using the paper-based WS₂ photodetector (device C). Note: As light source we have used a supercontinuum laser with different spectral filters.

Table 1. Comparison of typical device characteristics of the present WS₂ in this work and other TMDCs-based and paper-supported photodetection devices. Response time values highlighted with ^r or ^f represent the rise time and fall time values, respectively.