Toward Next‐Generation High‐Speed Communication and Imaging: Solution‐Processed Sb ₂ (S,Se) ₃ /CdS Heterojunction for Ultrafast Self‐Powered Photodetector

The pursuit of multifunctional photodetectors (PDs) that combine broadband responsivity, high specific detectivity under low‐light conditions, and robust operation across extreme temperatures is a cornerstone for advancing next‐generation optical communication and imaging systems. Herein, we report a self‐powered PD FTO/CdS/Sb 2 (S,Se) 3 /Au via a low‐cost solution‐processed method. At zero bias, the Sb 2 (S,Se) 3 ‐based PD exhibits a responsivity of 0.6 A/W, a specific detectivity of 7.68 × 10 12 Jones, ultrafast response/recovery times of 1.13/1.90 µs, and a 3 dB bandwidth of 175 kHz under 785 nm illumination (4.09 µW/cm 2 ). Most strikingly, the unencapsulated device exhibits excellent stability from 10 to 575 K, which is rarely reported for Sb 2 (S,Se) 3 ‐based PDs. The practical multifunctional applicability of this single PD is further validated by its successful integration as a high‐speed receiver in a visible light communication system and a sensing pixel for high‐resolution imaging. Compared with the reference Sb 2 (S,Se) 3 sample, the performance enhancement of the Sb 2 (S,Se) 3 /CdS heterojunction PD arises from the built‐in electric field ( E bi ) that enables the effective carrier separation/extraction, and the heterojunction structure that reduces the interface/bulk trap densities of the Sb 2 (S,Se) 3 film. This work opens a promising avenue in near‐infrared imaging, light communication and extreme‐environment sensing.