Phase transition and doping-induced infrared tunable emission of an AgInS2 luminescence semiconductor

Abstract

The development of environmentally friendly, stable, and biocompatible near-infrared-I (NIR-I, 700–900 nm) semiconductor luminescent materials with continuously tunable wavelengths and narrow emission linewidths remains a critical challenge. While AgInS₂ has emerged as a promising candidate for NIR emission, its practical applications are hindered by multiphase coexistence and excited-state dispersion. Herein, we report an AgInS₂ semiconductor with a continuous and narrow emission linewidth in the red and NIR-I windows via a systematic investigation of its phase transition and doping. The thermodynamic stability, intrinsic emission centers, band gaps, and electronic structures of AgInS₂ tetragonal and orthorhombic phases showed significant differences. Reversible phase transition could be realized via thermal treatment and doping. The lattice distortion limit for the tetragonal and orthorhombic phases was estimated to be in the range of −2.9–7.16% and −2.4–8.25%, respectively. Notably, the tetragonal phase exhibited exceptional stability as a host matrix for high-concentration sulfur site substitution. Consequently, a tunable luminescence from 600 to 960 nm and a linewidth below 20 nm was achieved. This work not only elucidates the luminescence mechanism dependent on the phase, but also confirms the importance of phase control for luminescence adjustment.