(NH₄)₂AgX₃ (X = Br, I): 1D Silver Halides with Broadband White Light Emission and Improved Stability

Recently, ternary copper(I) halides have emerged as alternatives to lead halide perovskites for light emission applications. Despite their high-efficiency photoluminescence (PL) properties, most copper(I) halides are blue emitters with unusually poor tunability of their PL properties. Here, we report the impact of substitution of copper with silver in the high-efficiency blue-emitting Cu(I) halides through hydrothermal synthesis and characterization of (NH₄)₂AgX₃ (X = Br, I). (NH₄)₂AgX₃ are found to exhibit contrasting light emission properties compared to the blue-emitting Cu(I) analogues. Thus, (NH₄)₂AgBr₃ and (NH₄)₂AgI₃ exhibit broadband whitish light emission at room temperature with PL maxima at 394 and 534 nm and full width at half-maximum values of 142 and 114 nm, respectively. Based on our combined experimental and computational results, the broadband emission in (NH₄)₂AgX₃ is attributed to the presence of high-stability self-trapped excitons and defect-bound excitons. (NH₄)₂AgBr₃ and (NH₄)₂AgI₃ both have significantly improved air and moisture stability as compared to the related copper(I) halides, which are prone to degradation via oxidation. Our results suggest that silver halides should be considered alongside their copper analogues for high-efficiency light emission applications.