Insight Into the Photoelectric Conversion Mechanism of Broadband Self‐Powered Cu ₂ CdSnSe ₄ Photodetectors

ABSTRACT Cu 2 CdSnSe 4 (CCTSe), a quaternary chalcogenide semiconductor, combines earth‐abundant elements, a high absorption coefficient, and a narrow bandgap, making it an attractive absorber for broadband photodetectors. However, current research on CCTSe photodetectors predominantly relies on vacuum‐based techniques; these methods not only suffer from high costs and complex operation but also face challenges in large‐scale production. To address these limitations, we propose and demonstrate a sulfur‐free precursor one‐step solution process for the fabrication of self‐powered CCTSe thin film photodetectors. By optimizing the selenization process, the resulting CCTSe films exhibit significantly enhanced crystallinity, with effectively suppressed defect states‐key improvements that enable exceptional zero‐bias performance. Specifically, the photodetector achieves a responsivity of 0.52 A/W, a specific detectivity of 5.18 × 10 12 Jones, and a dark current on the order of 10 −9 A. Notably, the device maintains a stable photoresponse under repeated on‐off switching cycles at a typical broadband near‐infrared wavelength 1550 nm, which confirms its excellent photostability and reliable detection capability. These findings validate that the proposed sulfur‐free precursor solution process not only enables high‐performance CCTSe photodetectors but also provides a cost‐effective and scalable pathway for the development of next‐generation broadband visible to near‐infrared optoelectronic devices.