A Novel Lead‐Free Perovskite Cs ₂ CuBr ₄ /Cs ₃ Bi ₂ Br ₉ Bulk Heterojunction as Self‐Powered Photodetectors: Effect of Precursor Ratios on Photoresponse Behavior

Abstract

In recent years, the demand for efficient and sustainable photodetectors has significantly increased due to their critical role in optical sensing, communication, and imaging applications. As the field of optoelectronics advances, there is an urgent need to develop cost‐effective, environmentally friendly alternatives to conventional lead‐freeperovskite based photodetectors, which pose toxicity concerns. In this work, a novel self‐powered photodetector based on a heterojunction structure formed between Cs 2 CuBr 4 and Cs 3 Bi 2 Br 9 , fabricated via a solution‐processed method has been proposed. This innovative device architecture enables efficient charge separation and transport, leading to enhanced photodetection performance. The developed self‐powered photodetector demonstrates notable performance characteristics, achieving a responsivity of 2.73 × 10 − 5 A W −1 and a specific detectivity of 3.63 × 10 7 Jones under an illumination intensity of 100 mW cm −2 . Additionally, the device exhibits rapid photoresponse dynamics, with a rise time of 0.15 s and a fall time of 0.29 s, highlighting its potential for real‐time photodetection applications. These findings suggest that the Cs 2 CuBr 4 /Cs 3 Bi 2 Br 9 heterostructure is a highly promising material system for the development of cost‐effective, high‐performance, and environmentally friendly self‐powered photodetectors, paving the way for future advancements in sustainable optoelectronics.