Molecularly tailored dual-interface passivation via solvent-free rub-on transfer for efficient and stable perovskite LEDs.

Conventional solution-based passivation methods for perovskite light-emitting diodes (PeLEDs) often introduce secondary defects. A molecularly tailored dual-interface passivation strategy is presented using a solvent-free rub-on transfer method, which enables uniform molecular deposition without inducing secondary defects. Specifically, 4-mercaptopyridine (4-MPy) is applied at the buried interface, and 2-mercaptopyridine (2-MPy) is applied on the perovskite surface. At the buried interface, 4-MPy stabilizes Ni3+ states, reduces oxygen vacancies, and improves hole injection. In contrast, surface-deposited 2-MPy coordinates effectively with undercoordinated Pb2+ ions, forming wide-bandgap complexes that suppress trap states and enhance carrier confinement. As a result, the optimized PeLEDs achieve a maximum external quantum efficiency of 24.67% and a current efficiency of 95.01 candela per ampere, the highest values reported for solution-processed polycrystalline CsPbBr3-based PeLEDs. Furthermore, the operational half-life is substantially extended by nearly 10-fold at an initial luminance of 1000 candela per square meter.