Near‐Zero Segregation on Strongly Exciton Confined Mixed Halide Perovskites Quantum Dots via Octahedron Alloying Reconstruction Engineering

Abstract The state‐of‐the‐art mixed‐halide perovskite (MHP) quantum dots (QDs) open up promising applications in photovoltaic and optoelectronic communities, yet are limited by huge halide segregation. In contrast to the previous A‐site alloy method, customizing other octahedral units for replacing the fundamental optoelectronic unit of [PbX 6 ] 4− (X = Cl, Br, or I), the so‐called B‐site alloying strategy, is expected to inhibit halide segregation fully. Here, a halide octahedron alloying reconstruction engineering is reported to fabricate MHP QDs with near‐zero halide segregation due to their strongly confined excitons. This unprecedented regime is obtained at a water–oil interfacial reaction system using amino‐silane ion exchange accelerator and transition metal hydroxy‐halides salts, introducing abundant [MX 6 ] 4− (M = Zn, Ni, Co, Mn, and Cu) octahedron block and finally fabricating transition metal‐alloyed MAPbX 3 QDs. Photo‐induced excitons in strongly dielectric‐confined Zn‐alloyed perovskite QDs are hardly thermally dissociated and transferred, as featured by ultra‐high exciton binding energy (E b ), fast fluorescence lifetimes (τ avg ), and near 100% photoluminescence quantum yield (PLQY). The fabricated mixed‐halide MAPb 1‐x Zn x X 3 QDs with reduced Pb content over 40% exhibit near‐zero halide segregation, marking the emergence of a practical solution to the detrimental segregation problem, which paves the wave for emerging solar cells and lighting display applications.