Balance Between Energy Migration and Thermal Quenching: Solid Solution Strategy to Highly Boost the Quantum Yield of Copper(I)‐Iodide Cluster

Abstract Cu(I)‐iodide clusters have attracted broad attention due to their outstanding photoluminescence properties. However, their commercial viability is often constrained by moderate quantum yields. In this work, a solid solution strategy is employed to synthesize heterometallic cluster 3·Cu/Ag, achieving nearly 18‐ and 10‐fold enhancements in quantum yield (up to 86.10%) relative to the monometallic clusters 1·Cu and 2·Ag, respectively. Detailed investigations reveal an unprecedented mechanism balancing energy migration and thermal quenching, which underlies the intense emission and distinct thermochromic behavior of 3·Cu/Ag under both cryogenic and ambient conditions. These findings highlight potential applications in luminescent thermometer, multicolor displays, and solid‐state lighting technologies.