Element Diffusion Induced Carrier Transport Enhancement in High‐Performance CZTSSe Self‐Powered Photodetector

Abstract

AbstractCu2ZnSn(S,Se)4 (CZTSSe) has attracted great interest in thin‐film solar cells due to its excellent photoelectric performance in past decades, and recently is gradually expanding to the field of photodetectors. Here, the CZTSSe self‐powered photodetector is prepared by using traditional photovoltaic device structure. Under zero bias, it exhibits the excellent performance with a maximum responsivity of 0.77 A W−1, a high detectivity of 8.78 × 1012 Jones, and a wide linear dynamic range of 103 dB. Very fast response speed with the rise/decay times of 0.576/1.792 µs, and ultra‐high switching ratio of 3.54 × 105 are obtained. Comprehensive electrical and microstructure characterizations confirm that element diffusion among ITO, CdS, and CZTSSe layers not only optimizes band alignment of CdS/CZTSSe, but also suppresses the formation of interface defects. Such a suppression of interface defects and spike‐like band alignment significantly inhibit carrier nonradiative recombination at interface and promote carrier transport capability. The low trap density in CZTSSe and low back contact barrier of CZTSSe/Mo could be responsible for the very fast response time of photodetector. This work definitely provides guidance for designing a high performance self‐powered photodetector with high photoresponse, high switching ratio, fast response speed, and broad linear dynamic range.