Engineered Energy Landscape of Hole Transport Layers for Charge-Balanced Quantum Dot Electroluminescent Devices
발표자
()
초록
내용
Quantum dot light-emitting diodes (QLEDs) have made remarkable progress in terms of device efficiency and stability over past decades and finally reached their ceiling efficiency. However, there is no detailed interpretation on non-ideal operation condition exhibiting lowered EQE out of its maximum, and it has simply been explained as “imbalanced charge injection” to quantum dots (QDs). Herein, we attempt to clarify this non-ideal operation for InP QLEDs employing metal oxide electron transport layer (ETLs) and organic hole transport layers (HTLs) and suggest its remedy. While band gap alignment in hybrid QLEDs helps to balance charge injection rates, asymmetric injection barriers and charge accumulation at junctions debase optimal balance under varying bias. We unveiled the charge imbalance behind luminance-current characteristics using spectroscopic probes. Shaping HTL band structure by doping and alloying seems to mitigate the charge imbalance as well as operational instability.