Improved Efficiency of Perovskite Light-Emitting Diodes Using a Three-Step Spin-Coated CH3NH3PbBr3 Emitter and a PEDOT:PSS/MoO3-Ammonia Composite Hole Transport Layer

Abstract

High efficiency perovskite light-emitting diodes (PeLEDs) using PEDOT:PSS/MoO₃-ammonia composite hole transport layers (HTLs) with different MoO₃-ammonia ratios were prepared and characterized. For PeLEDs with one-step spin-coated CH₃NH₃PbBr₃ emitter, an optimal MoO₃-ammonia volume ratio (0.02) in PEDOT:PSS/MoO₃-ammonia composite HTL presented a maximum luminance of 1082 cd/m² and maximum current efficiency of 0.7 cd/A, which are 82% and 94% higher than those of the control device using pure PEDOT:PSS HTL respectively. It can be explained by that the optimized amount of MoO₃-ammonia in the composite HTLs cannot only facilitate hole injection into CH₃NH₃PbBr₃ through reducing the contact barrier, but also suppress the exciton quenching at the HTL/CH₃NH₃PbBr₃ interface. Three-step spin coating method was further used to obtain uniform and dense CH₃NH₃PbBr₃ films, which lead to a maximum luminance of 5044 cd/m² and maximum current efficiency of 3.12 cd/A, showing enhancement of 750% and 767% compared with the control device respectively. The significantly improved efficiency of PeLEDs using three-step spin-coated CH₃NH₃PbBr₃ film and an optimum PEDOT:PSS/MoO₃-ammonia composite HTL can be explained by the enhanced carrier recombination through better hole injection and film morphology optimization, as well as the reduced exciton quenching at HTL/CH₃NH₃PbBr₃ interface. These results present a promising strategy for the device engineering of high efficiency PeLEDs.