Ammonium Thiocyanate-Passivated CsPbI3 Perovskite Nanocrystals for Efficient Red Light-Emitting Diodes

Lead halide perovskite nanocrystals (NCs) as a promising material have been widely applied in optoelectronic devices, but the massive defects reduce their optical properties and consequently limit the device performance. In this work, we developed a method to reduce the surface defects caused by unbonded lead on the surface of NCs by introducing ammonium thiocyanate in the synthesis of CsPbI 3 NCs. Thiocyanate ions can link to the unbonded lead on the surface of perovskite NCs, resulting in a prolonged lifetime and enhanced photoluminescence quantum yield. At the same time, the whole energy level of passivated CsPbI 3 NC films goes down compared to the pristine CsPbI 3 NC films, which contributes to better electron injection. As a result, the passivated NCs based light-emitting diodes (LEDs) realized 10.3% external quantum efficiency and 823 cd m –2 luminance, higher than the LEDs made from the non-passivated NCs.