Ag2S Thin Films with Optimized Thickness Fabricated by Thermal Sulfurization for Near-Infrared Photodetectors

Abstract

Silver sulfide (Ag2S) is an emerging chalcogenide compound that has attracted significant attention for photodetector applications due to its excellent optoelectronic properties. However, the performance of Ag2S-based photodetectors is usually subject to the absorber layer design. In this study, Ag2S thin films were fabricated by using a thermal sulfurization technique, and the effect of absorber thickness on Ag2S thin film photodetectors was systematically investigated, aiming to set up a fundamental trade-off between charge separation and light absorption in the device. The optimized self-powered Ag2S photodetector demonstrates a broad detection range from 405 to 980 nm, achieving a high responsivity of 0.24 A W−1 and a specific detectivity of 2.39 × 1012 Jones at 638 nm under zero bias. Notably, the device exhibits ultrafast response times (τrise/τfall = 42.9/32.6 μs). Furthermore, this work explores the defect dynamics in Ag2S photodetectors by using deep-level transient spectroscopy (DLTS), identifying that both hole and electron defects are potentially attributed to silver (VAg) and sulfur vacancies (VS). These insights provide the future optimization strategies for enhancing the performance of Ag2S-based photodetectors.