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.
Highlights
Taking advantage of high photoluminescence quantum yield (PLQY), excellent color purity, high carrier mobility and low-temperature solution-processing, organometal halide perovskites have been studied extensively for their applications in solution-processed light-emitting diodes (LEDs) [1,2]
Since Friend’s group reported the first demonstration about room-temperature infrared and green light emission observed in LEDs with CH3NH3PbX3 (X is I−, Br- or Cl−) perovskite emission layers (EML) in 2014 [3], organic-inorganic perovskite light-emitting diodes (PeLEDs) have attracted much attention and their external quantum efficiency (EQE) of PeLEDs increased rapidly from 0.1% to exceeding 20% [3,4,5,6,7]
The results indicate that all PeLEDs have an EL peak at ~528 nm, suggesting the color stability of our devices
Summary
Taking advantage of high photoluminescence quantum yield (PLQY), excellent color purity, high carrier mobility and low-temperature solution-processing, organometal halide perovskites have been studied extensively for their applications in solution-processed light-emitting diodes (LEDs) [1,2]. It is noted that the MoO3 concentration in the composite is small, and the electron transport material (SPW-111) is not usually used in PeLEDs. Besides, Zheng et al developed a composite hole injection layer (HIL) of MoOx-doped GO in tris(8-hydroxy-quinolinato)aluminum (Alq3)-based OLEDs [24], and Meng et al modified the PEDOT:PSS HTL by doping a MoO3 ammonia solution with largely adjusted volume ratio of (0~0.8): in all inorganic CsPbBr3 PeLEDs [26]. Zheng et al developed a composite hole injection layer (HIL) of MoOx-doped GO in tris(8-hydroxy-quinolinato)aluminum (Alq3)-based OLEDs [24], and Meng et al modified the PEDOT:PSS HTL by doping a MoO3 ammonia solution with largely adjusted volume ratio of (0~0.8): in all inorganic CsPbBr3 PeLEDs [26] According to these results, the doping of MoO3 in HTLs is promising to reduce the contact barrier and luminescent quenching at PEDOT:PSS/EML interface. Three-step spin coating method was employed 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
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