All-inorganic Cs2AgBiBr6/CuSCN-based photodetectors for weak light imaging

Weak light imaging has drawn more and more attention because of its promising potential for practical applications in security monitoring and space exploration. In this work, all-inorganic Cs2AgBiBr6 double perovskite-based self-powered photodetectors containing inorganic copper thiocyanate (CuSCN) as hole-transport layers (HTLs) are successfully fabricated and applied for weak light imaging, which is the first report on the weak light imaging application of all-inorganic lead-free perovskite photodetectors. CuSCN films with favorable optical property and hole extraction capability are prepared via a cost efficient and fast solvent removal method, demonstrating the potential for high-performance perovskite-based devices as transparent components. It is revealed that the band alignment of the device is effectively optimized with the presence of CuSCN HTLs, which can availably transport holes while block electrons at the Cs2AgBiBr6/CuSCN interface, resulting in remarkable improvement of photoresponse performance. The responsivity and detectivity are 0.34 A W−1 and 1.03×1013 Jones, respectively. In particular, the light current has a boost of almost 10 times. Furthermore, the photodetectors are integrated into a self built light detection imaging system uti lizing the focused laser scanning imaging mode. With illumination of as low as 5 nW cm−2 (405 nm), the image involving graphics and words with a size of 5 cm×5 cm can still be distinctly recognized. These results suggest the promising potential of all-inorganic perovskite-based devices for weak light detection and imaging applications.