Preparation of high gain NIR photodetectors based on gradient AgInS2(Se) thin films with A W−1 level responsivity†

Abstract

High-performance near-infrared (NIR) thin-film photodetectors hold great promise for biological detection applications. Techniques based on two-dimensional materials, while well-studied, face challenges in achieving large-area detection with a response current that is readable by a multimeter. In this study, we introduce a high-performance NIR photodetector based on gradient AgInS₂(Se) thin films. To fabricate a AgInS₂(Se) film with a high selenization rate and minimal stress, we prepared a loosely structured AgInS₂ precursor using an ultrasonic spray pyrolysis (USP) method. The photodetectors, based on an AgInS₂(Se)/CdS heterojunction, exhibited remarkably high responsivity, achieving 51.58 A W⁻¹ and 0.315 A W⁻¹ at 660 nm and 1050 nm, respectively, under a 2 V reverse bias. Concurrently, they demonstrated exceptionally high external quantum efficiency (EQE) values of 9709.3% and 37.3% at the respective wavelengths. To demonstrate practical applications, we successfully fabricated a large-scale (5 × 4 cm², with an active area of 12 cm²) photodetector capable of generating milliamp-level photocurrents under low light conditions. This photodetector was employed for pulse monitoring and assessing the ripeness of kiwifruits, showcasing the potential of this large-scale technology for biological applications.