High-efficiency green FAPbBr 3 nanosheets light-emitting diodes via a synergistic strategy of temperature control and ligand engineering

Two-dimensional (2-D) formamidinium lead bromide (FAPbBr[Formula: see text] nanosheets (NSs) have great potential for pure green light-emitting diodes (LEDs) because of their high exciton binding energy, narrow emission bandwidth, and good carrier transport properties. However, their device efficiency is still limited by surface defect-induced nonradiative recombination and the charge transport barrier caused by insulating long-chain ligands. In this study, these problems were improved by combining thermal control and surface ligand engineering. By optimizing the hot-injection temperature to [Formula: see text]C, high-quality FAPbBr 3 NSs with lower surface roughness were obtained. In addition, didodecyldimethylammonium bromide (DDAB) was introduced to replace the native long-chain insulating ligands. Time-resolved photoluminescence (TRPL) results show that the optimized 0.2[Formula: see text]mmol DDAB treatment can effectively passivate surface defects and extend the average carrier lifetime to 28.03[Formula: see text]ns. The DDAB treatment also shifts the valence band of FAPbBr 3 NSs upward by 0.3[Formula: see text]eV, leading to better band alignment and enhanced charge injection. As a result, LEDs based on DDAB-treated FAPbBr 3 NSs show an electroluminescence (EL) peak at 523[Formula: see text]nm, a maximum external quantum efficiency (EQE) of 9.76%, which is about 30% higher than that of the untreated device, and a maximum luminance of 13,989[Formula: see text]cd/m 2 , about 80% higher than that of the untreated device.