Light emission from multiple self-trapped excitons in one-dimensional Ag-based ternary halides

Abstract

Ternary metal halides based on Cu(I) and Ag(I) have attracted intensive attention in optoelectronic applications due to their excellent luminescent properties, low toxicity, and robust stability. While the self-trapped excitons (STEs) emission mechanisms of Cu(I) halides are well understood, the STEs in Ag(I) halides remain less thoroughly explored. This study explores the STE emission efficiency within the A2AgX3 (A = Rb, Cs; X = Cl, Br, I) system by identifying three distinct STE states in each material and calculating their configuration coordinate diagrams. We find that the STE emission efficiency in this system is mainly determined by STE stability and influenced by self-trapping and quenching barriers. Moreover, we investigate the impact of structural compactness on emission efficiency and find that the excessive electron-phonon coupling in this system can be reduced by increasing structural compactness. The atomic packing factor is identified as a low-cost and effective descriptor for predicting STE emission efficiency in both Cs2AgX3 and Rb2AgX3 systems. These findings can deepen our understanding of STE behavior in metal halide materials and offer valuable insights for the design of efficient STE luminescent materials.