Improved Hole Injection by Enhancing Electron Extraction of Solution-Processed MoO<sub><i>x</i></sub> in Quantum Dot Light-Emitting Diodes
Jing Jiang, Ting Ding, Hui Bao, Yin‐Man Song, Mengwei Wang, Hang Liu, Zhisheng Wu, Zhen Dong Lian, Haizheng Zhong, Hongchao Liu, Shu-Ming Ren, Yang Li, Peili Gao, Kar Wei Ng, Shuangpeng Wang
Abstract
High Resolution Image Download MS PowerPoint Slide Hole injection layers (HILs) are pivotal for the performance of quantum dot light-emitting diodes (QLEDs), with solution-processed inorganic HIL materials being a primary means for the commercial application of QLEDs. Transition metal oxides (TMOs), due to their excellent stability, have been widely employed as inorganic HILs by thermal evaporation in QLEDs; however, the hole injection ability of solution-processed TMO film necessitates further enhancement owing to inferior film quality. In this study, a solution-processed molybdenum oxide (MoO x ) film was used as a HIL, and its hole injection ability in the QLED was improved by tuning the oxygen states. Oxidation treatments on the MoO x layer can effectively mitigate oxygen vacancies, and consequently, the conduction band minimum (CBM) of MoO x is elevated, which enhances the hole injection through easier electron extraction from the highest occupied molecular orbitals (HOMO) of the hole transport layer. The MoO x -based red QLED exhibits significantly longer working lifetimes (T50@100 cd·m –2 of ∼66,892 h) and comparable current efficiencies (13.7 cd·A –1 ) compared to the Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)-based QLEDs. Our research not only proposes a promising approach to high-performance MoO x -based QLEDs but also paves the way for further applications of TMOs in QLEDs.