Revealing the Atomic-Scale Mechanism of Performance Enhancement in Organically Passivated Perovskite Light-Emitting Diodes

Thermally evaporated perovskite light-emitting diodes (PeLEDs) are attractive for scalable display manufacturing but remain limited by grain-boundary defects and residual strain. Here, we identify how a Lewis base passivator, PPF, reconstructs grain boundaries in evaporated CsPbBr 3 through coordination between P═O groups and undercoordinated Pb 2+ sites. PPF relaxes grain-boundary tensile strain from 3.25 to 0.18% and reshapes the local projected electric field, leading to reduced defect-assisted nonradiative recombination and improved carrier injection. As a result, the PeLEDs deliver an external quantum efficiency of 17.6% and a T 50 of 66.7 min at an initial luminance of 1000 cd m −2, compared with 8.8% and 16.2 min for control devices. These results establish a direct structure-field-performance correlation for vapor-deposited perovskites and provide guidance for evaporated perovskite optoelectronics.