ZnBr2 mediated transformation from nonluminescent Cs4PbBr6 to green-emitting Zn-doped CsPbBr3/Cs4PbBr6 nanocrystals for electroluminescent light-emitting diodes

Zero-dimensional (0D) perovskites have attracted a great deal of attention over the last few years due to their fascinating properties. However, their application in electroluminescent (EL) Light-emitting diodes (LEDs) is limited and suffering from extremely low device performance. Herein, the nonluminescent Cs4PbBr6 nanocrystals (NCs) were successfully transformed to highly luminescent Zn-doped CsPbBr3/Cs4PbBr6 NCs via an insertion reaction with ZnBr2, which changed the atomic molar ratios of NCs and promoted the formation of CsPbBr3. In this reaction, the Zn2+ ions provided by ZnBr2 together with the Pb2+ ions can occupy the B-site due to the similar ion radius. The extra Br- ions not only can facilitate the transformation process, but also can passivate the surface defects of the NCs, resulting in high photoluminescence quantum yield (PL QY) of 77.5%. Furthermore, as-synthesized Zn-doped CsPbBr3/Cs4PbBr6 NCs were used as emitters to fabricate EL LEDs. The device achieved the maximum current efficiency of 9.8 cd/A and a peak external quantum efficiency of 3.2%, which is the best performance of the CsPbBr3/Cs4PbBr6 based LEDs. This reveals the great application potential of CsPbBr3/Cs4PbBr6 NCs as EL emitters in LEDs.