Manipulating Electron-Phonon Coupling for Efficient Tin Halide Perovskite Blue LEDs

Low-dimensional perovskites have opened up a new frontier in light-emitting diodes (LED) due to their excellent properties. However, concerns regarding the potential toxicity of Pb limited their commercial development. Sn-based perovskites are regarded as a promising candidate to replace Pb-based counterparts, while they generally exhibit strong electron-phonon coupling and consequently blue emission quenching at room temperature (RT), thus the Sn-based perovskite blue LED devices have not yet been reported. Herein, the luminescence properties are regulated by assembling a rigid organic skeleton within perovskite structure, and the protonated 4-bromobenzylamine (BrPMA⁺ = C₇H₉BrN⁺) is employed as A site cation to synthesize a 100-oriented 2D perovskite (BrPMA)₂SnBr₄, which exhibits a strong lattice rigidity via strong intermolecular interaction and consequently weak electron-phonon coupling, achieving the excellent blue PL emission at RT. The high quality (BrPMA)₂SnBr₄ perovskite thin films are obtained by further inhibiting oxidation and promoting crystallization. Finally, the Sn-based perovskite blue emission LED is successfully fabricated for the first time at 467 nm with a champion EQE of 1.3% and a maximum brightness of 800 cd m^-2. This work gives insights into the luminescence mechanism of Sn-based perovskites and provides a new theoretical basis for the development of lead-free blue LEDs.