Efficient solution-processed InP quantum-dots light-emitting diodes enabled by suppressing hole injection loss

Solution-processed cadmium-based quantum dots (QDs) light-emitting diodes (QLEDs) have shown promising for high-definition display panels due to their high colour purity and low-cost fabrication, but the toxicity still is a big threat. InP is considered as the most promising cadmium-free material to achieve high performance QLEDs, however, the performance of the InP-based QLEDs is far behind of the cadmium-based counterparts. Here, we report high efficiency InP-based QLEDs with more than 20% of external quantum efficiency (EQE) by suppressing hole injection loss. This suppression is achieved by doping a strong Lewis acid into a Lewis base poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine) to form a Lewis acid-base adduct hole-transport layer (HTL), which improves the hole mobility of the HTL, and reduces the hole transfer barrier between HTL and QDs layer to increase hole transport capability. This eventually leads to a more balanced carrier-injection through accelerating hole-injection to match well with the rate of electron-injection, thus suppressing the hole injection loss in the QLED. The InP-based QLED shows EQE of 20.4%, current efficiency of 25.3 cd·A⁻¹, turn-on voltage of 2.0 V, and luminance of 24,000 cd·m⁻². This strategy would be a constructive approach to reduce hole loss for p-n junction optoelectronics.