Near-Unity Photoluminescence Quantum Yield in Blue-Emitting Cs3Cu2Br5–xIx (0 ≤ x ≤ 5)

Recently, interest in developing efficient, low-cost, nontoxic, and stable metal halide emitters that can be incorporated into solid-state lighting technologies has taken hold. Here we report nontoxic, stable, and highly efficient blue-light-emitting Cs3Cu2Br5–xIx (0 ≤ x ≤ 5). Room-temperature photoluminescence measurements show bright blue emission in the 456 to 443 nm range with near-unity quantum yield for Cs3Cu2I5. Density functional theory calculations and power-dependent PL measurements suggest that the emission results from self-trapped excitons induced by strong charge localization within the zero-dimensional cluster structure of Cs3Cu2Br5–xIx.