Flexible Self-Powered Photoelectrochemical Photodetectors Based on Cellulose-Based Hydrogel Electrolytes and Bi₂O₂Se Nanosheets

Photoelectrochemical (PEC)-type photodetectors are gaining significant interest as neoteric self-powered devices, owing to their high spectral responsivity and quick photoresponse. However, the underlying leakage issue makes the aqueous electrolyte contained inside PEC-type photodetectors unsuitable for manufacturing flexible optoelectronics. In this study, we report a flexible, self-powered PEC-type photodetector based on a cellulose-based hydrogel. Using a cellulose-based hydrogel electrolyte as the electron-transferring medium and two-dimensional Bi₂O₂Se nanosheet-coated indium tin oxide glass as the working electrode, the photodetector exhibits excellent self-powered capability. The hydrogel-based PEC photodetector exhibits a broadband photoresponse in the range of 365–850 nm. Moreover, under the condition of an illumination wavelength of 365 nm at a bias voltage of 0.6 V, the photodetector exhibits a responsivity of 0.68 mA/W, a detectivity of 2.44 × 10⁸ Jones, and a fast response time of 85/103 ms, which are comparable to those of photodetectors based on traditional aqueous electrolytes. Additionally, the hydrogel-based PEC photodetectors show good flexibility and stability, maintaining more than 70.3% of their photocurrent density even after 100 cycles of bending at 120°, and no obvious photocurrent decay is observed after storage for 1 week. Based on these results, cellulose-based hydrogel electrolytes have significant potential for future applications in self-powered photodetectors.