Enhancing hole injection by electric dipoles for efficient blue InP QLEDs

Abstract

The unbalanced carrier injection is a key factor that deteriorates the performance of blue InP quantum dot light-emitting diodes (QLEDs). Therefore, to achieve efficient blue InP QLEDs, an effective strategy that balances carrier injection through enhancing the hole injection and transport is in demand. In this study, we introduced an ultrathin MoO3 electric dipole layer between the hole injection layer and the hole transport layer (HTL) to form a pair of dipole-induced built-in electric fields with forward resultant direction to enhance hole injection and facilitate the balance of carrier injection. Meanwhile, the p-doping effect by MoO3 leads to increased carrier concentration and decreased trap density of interfacial HTL, therefore improved its effective hole mobility. Consequently, the maximal external quantum efficiency of blue InP QLEDs was enhanced from 1.0% to 2.1%. This work provides an effective method to balance carrier injection by modulating hole injection and transport, indicating the feasibility to realize high-efficiency QLEDs.

High Quantum Yield Blue InP/ZnS/ZnS Quantum Dots Based on Bromine Passivation for Efficient Blue Light‐Emitting Diodes

“…In our previous work, [30] we had demonstrated that the injection barrier for electron is smaller than that of the hole, leading to excess electron injection in blue InP QLEDs. Thus, this capacitance increasement could be attributed to electron injection, trapping, and accumulation.…”

Highly efficient green InP-based quantum dot light-emitting diodes regulated by inner alloyed shell component

“…The poor performance of green-emitting InP-based QLEDs is also related to Auger recombination as a consequence of unbalanced injection between electrons and holes 29 – 31 . In order to balance the carrier injection in QLED, modifying the energy level position of the charge transport layer or QDs themselves was usually an effective way 30 . For example, Chae’s group tailored the highest occupied molecular orbital and lowest unoccupied molecular orbital level of electron transport layer with magnesium to reduce the electron mobility and thus balanced the injection of holes and electrons.…”

Nanowire-Shaped MoS2@MoO3 Nanocomposites as a Hole Injection Layer for Quantum Dot Light-Emitting Diodes

“…Although their method is straightforward, it needs multiple steps with a longtime reaction process. On the other hand, as MoO 3 is a p-type semiconductor, it can facilitate the mobility of holes via an increase in the concentration of carriers as well as a reduction in the density of traps . From the morphological perspective, almost all reports in this field reported nanosheets/multiple layers or QDs of MoO 3 or MoS 2 structures for the fabrication of LEDs. ,, Indeed, there are only a few reports that assert synthesizing such nanostructures in NW shape but in much bigger sizes relative to what was observed in the present study. − Guo et al designed a two-step-synthesized MoS 2 @MoO 3 core–shell NW with a diameter of 250 ± 30 nm and broad-band absorption as well as good interfacial engineering for stable H 2 evolution characteristics (841.4 μmol.h –1 .g –1 ) .…”

“…On the other hand, as MoO 3 is a p-type semiconductor, it can facilitate the mobility of holes via an increase in the concentration of carriers as well as a reduction in the density of traps. 16 From the morphological perspective, almost all reports in this field reported nanosheets/multiple layers or QDs of MoO 3 or MoS 2 structures for the fabrication of LEDs. 17,20,21 Indeed, there are only a few reports that assert synthesizing such nanostructures in NW shape but in much bigger sizes relative to what was observed in the present study.…”

“…Among such strategies, employing transition-metal dichalcogenides has attracted the attention of the research community. The most promising one is molybdenum-based structures that already demonstrated that they are more active than other materials to promote the charge transport in optoelectronic devices. , Using MoO 3 or MoS 2 nanostructures as a separate layer or additive in the PEDOT/PSS layer has been reported in various LEDs with different light-emitting layers such as perovskite NCs, Cd-based QDs, carbon dots, InP-based QDs, and even organic molecules . Nonetheless, in most cases, minimal attention has been dedicated to the synthesis of such MoO 3 or MoS 2 nanoparticles.…”