Core/Shell Perovskite Nanocrystals: Synthesis of Highly Efficient and Environmentally Stable FAPbBr3/CsPbBr3 for LED Applications

Abstract Lead halide perovskite nanocrystals (PeNCs) are promising materials for applications in optoelectronics. However, their environmental instability remains to be addressed to enable their advancement into industry. Here the development of a novel synthesis method is reported for monodispersed PeNCs coated with all inorganic shell of cesium lead bromide (CsPbBr 3 ) grown epitaxially on the surface of formamidinium lead bromide (FAPbBr 3 ) NCs. The formed FAPbBr 3 /CsPbBr 3 NCs have photoluminescence in the visible range 460–560 nm with narrow emission linewidth (20 nm) and high optical quantum yield, photoluminescence quantum yield (PLQY) up to 93%. The core/shell perovskites have enhanced optical stability under ambient conditions (70 d) and under ultraviolet radiation (50 h). The enhanced properties are attributed to overgrowth of FAPbBr 3 with all‐inorganic CsPbBr 3 shell, which acts as a protective layer and enables effective passivation of the surface defects. The use of these green‐emitting core/shell FAPbBr 3 /CsPbBr 3 NCs is demonstrated in light‐emitting diodes (LEDs) and significant enhancement of their performance is achieved compared to core only FAPbBr 3 ‐LEDs. The maximum current efficiency observed in core/shell NC LED is 19.75 cd A ‐1 and the external quantum efficiency of 8.1%, which are approximately four times and approximately eight times higher, respectively, compared to core‐only devices.