Spontaneous Silver Doping and Surface Passivation of CsPbI Perovskite Active Layer Enable Light-Emitting Devices with an External Quantum Efficiency of 11.2.

Lead halide perovskite nanocrystals are currently under intense investigation as components of solution-processed light-emitting devices (LEDs). We demonstrate LEDs based on Ag doped-passivated CsPbI perovskite nanocrystals with external quantum efficiency of 11.2% and an improved stability. Ag and trilayer MoO/Au/MoO structure were used as cathode and anode, respectively, which reduce the electron injection barrier and ensure the high transparency and low resistance of the anode. Silver ions diffuse into perovskite film from the Ag electrode, as confirmed by the elemental mapping, the presence of Ag 3d peaks in the X-ray photoelectron spectrum, and the peak shift in the X-ray diffraction patterns of CsPbI. In addition to doping, silver ions play the beneficial role of passivating surface defect states of CsPbI nanocrystals, which results in increased photoluminescence quantum yield, elongated emission lifetime, and improved stability of perovskite films.