Diffusion-Induced Enhanced Photoresponsivity, Detectivity in Ag2S and In2Se3 Heterostructure for UV-Visible Photodetector: An Experimental and Computational Analysis

Abstract

For recent optical communication and imaging systems, photodetectors are playing a pivotal role. Metal chalcogenide-based photodetectors are widely used for visible light photodetection. In this regard, the In2Se3 and Ag2S combined heterostructure is a promising candidate for Visible light photodetection. The annealing-induced Ag2S diffusion into the In2Se3 layer resulted in a high-performance photo detectivity of 7.32 × 109 Jones. It shows the highest photocurrent during both the rise (62.35 nA) and decay (67.74 nA) phases, coupled with a strong Ion/Ioff ratio of 3.96 (rise) and 3.18 (decay). Its rise and fall times (τr = 7.15 s, τd = 6.35 s) are moderate and well-balanced, suggesting efficient charge separation and recombination kinetics. The bandgap of the annealed film increased with the reduction of structural disorder as probed from the UV-Visible spectroscopy and well supported by the DFT result. The amorphous to polycrystalline phase transformation induced surface morphology change, reduced the contact angle, thus decreasing the hydrophobicity. The refractive index decreased with an increase in optical transmission and skin depth, while optical density reduced upon annealing. The X-ray photoelectron spectroscopy revealed the oxidation states of the elements, while energy dispersive X-ray analysis presented the elemental composition in the films. The heterostructure formation and its mixing upon annealing are viewed from the cross-sectional FESEM images, and the presence of the planes was noticed through HRTEM images. The observed optical properties, along with the enhanced photodetection, pave the way toward the construction of novel III-VI metal chalcogenide-based heterojunctions for high-performance and broadband photodetectors.