Solution-Processed Tin-Antimony Quaternary Chalcohalides for Self-Powered Broadband Photodetectors

Abstract

The mixed-metal quaternary chalcohalides of group IV and V elements are a promising class of low-toxicity perovskite-inspired materials with tunable bandgaps and desirable defect tolerance. Sn₂SbS₂I₃ is known for its broadband absorption, low exciton binding energy, ambient stability, and solution processability in thin films. However, its use in optoelectronic devices has so far been only limited to solar cells. In this work, the first self-powered photodetectors based on Sn₂SbS₂I₃ thin films, sandwiched in an n–i–p device configuration are reported. The insertion of an interlayer at the hole-transport layer/gold top-electrode interface reduces the dark current and improves the device performance. The high external quantum efficiency of the devices in the range of 350−900 nm hints to a broadband spectral photoresponsivity. The devices indeed exhibit promising photodetection properties, namely a photoresponsivity of 0.33 A W⁻¹, a specific detectivity of 1.55 × 10¹² Jones, and photoresponse/decay times of 0.52 and 0.45 s at zero bias voltage. These results, combined with the excellent operational stability of the photodetectors, encourage the exploration of a wide range of practical light-sensing applications for quaternary chalcohalides and stimulate device and material engineering to further enhance photodetection across the UV-Visible-NIR spectrum.