Md Fahim Al Fattah, Asif Abdullah Khan, Saikiran Khamgaonkar, Majid Haji Bagheri, Danyah Khan, Md Rasidul Islam, Mahmoud Almadoun, Aixi Pan, Alexander Li, Marwa Abd‐Ellah, Vivek Maheshwari, D. Ban
ABSTRACT With the continuous drive for miniaturizing optoelectronic devices, 2D layered halide perovskites have been intensively studied in photo‐electric conversion for their superior stability and remarkable performance even at their atomically thin structure. Although UV sensing is reported, its deployment in visible light detection is yet to be realized. We use a rational halogen mixing strategy to first report an experimental visible light photodetector of Cs 2 PbBr 2 I 2 with a bandgap of 1.96 eV. Through a rigorous experimental investigation in conjunction with computational modeling, we achieve a high‐quality active layer with large grains and small trap density yielding extraordinary performance. We observe a high quantum efficiency in our vertical photodetector (VPD) owing to trap‐mediated persistent photoconductivity (PPC). Our optoelectronic analysis reveals that bulk trap states are responsible for the observed EQE gain, which retard electrons transit time by trap/de‐trap process while multiple holes are extracted to the external circuit. The device exhibits an external quantum efficiency exceeding 200%, a responsivity of 830 mA W −1 at 488 nm, and an on/off ratio approaching 10 5 . This gain strategy exploiting the trap‐assisted carrier delay coupled with the light‐induced electric field could be a potential approach for next‐generation, energy‐efficient, self‐powered photodetectors.