Dipole-Modulated Surface Passivation for High-Efficiency Thermally Evaporated Perovskite Light-Emitting Diodes

Abstract Thermally evaporated CsPbBr3 perovskite light-emitting diodes (PeLEDs) are fundamentally limited by high surface defect densities and severe carrier injection imbalance, which significantly constrain device efficiency and operational stability. Herein, we propose a dipole-modulated surface passivation strategy to address these critical challenges using three phenethylammonium bromide derivatives: phenethylammonium bromide (PEABr), 4-fluorophenethylammonium bromide (p-F-PEABr), and 4-trifluoromethylphenethylammonium bromide (p-CF3-PEABr). The passivation mechanisms, together with the distinct effects of these derivatives on the perovskite films, are systematically investigated, clarifying the critical role of molecular dipole moments in determining passivation efficiency. Among these derivatives, p-CF3-PEABr, which possesses the largest molecular dipole moment, exhibits the most effective defect passivation through strong coordination interactions with undercoordinated lead sites on the perovskite surface. Owing to effective surface defect passivation and the resultant suppression of nonradiative recombination, the optimized PeLED achieves a maximum external quantum efficiency (EQE) of 11.9% and a peak luminance of 40,341 cd m–2, together with significantly enhanced operational stability. These findings demonstrate the promising potential of thermal evaporation for developing high-performance green-emitting CsPbBr3 perovskite light-emitting devices.