Efficient pure green light-emitting diodes based on formamidinium lead bromide perovskite nanocrystals

Formamidinium (FA) lead bromide (FAPbBr 3 ) perovskite nanocrystals (P-NCs) have ultrapure green emission and high stability, while FAPbBr 3 NCs based light-emitting diodes (FA-NLEDs) still have little report. Here, FAPbBr 3 NCs with a high photoluminescence quantum yield of 85.8% were synthesized. By controlling the concentration of FAPbBr 3 NCs in toluene solution, the exciton recombination region was precisely confined to the emitting layer and the parasitic emission coming from electron transport layer disappeared, resulting in the pure green emissions. The optimized FA-NLED presents a maximum external quantum efficiency (EQE), current efficiency (CE) of 3.84% and 16.08 cd/A respectively, with the EL emission peak of 528 nm, CIE of (0.183, 0.763) and a full width of half-maximum (FWHM) of 24 nm, which is among the best performance of FA-NLEDs.