Enhancing Performance of CsSnBr ₃ Light‐Emitting Diodes via Synergistic Ion Doping and in Situ Interfacial Reaction

Tin-based perovskites are among the most promising lead-free emitters for perovskite light-emitting diodes (PeLEDs), but their performance is severely hindered by the uncontrolled rapid crystallization and facile oxidation. Here, we report a synergistic bulk-interface strategy for enhancing performance of CsSnBr₃ PeLEDs by combining Zn²⁺ bulk doping with an in situ interfacial reaction. Incorporation of ZnBr₂ suppresses Sn vacancies and residual SnBr₂ while regulating crystallization to improve film morphology. Concurrently, sodium citrate-modified PEDOT:PSS promotes deprotonation of 6-phosphonylhexyl acid, forming robust coordination bonds that delay crystallization and passivate defects. Benefiting from these dual effects, the optimized devices achieve a record external quantum efficiency for CsSnBr₃ PeLEDs. This work highlights the effectiveness of synergistic bulk-interface regulation in tuning crystallization kinetics, providing constructive insights for the development of efficient lead-free perovskite optoelectronics.