Boosting the performance of quantum dot light-emitting diodes with Mg and PVP Co-doped ZnO as electron transport layer

Zinc oxide (ZnO) nanoparticles (NPs) are extensively adopted material to be used as efficient electron transport layer (ETL) in quantum dot light emitting diodes (QLEDs) due to their suitable properties of high electron mobility, good stability, and easy processability. However, because of the naturally high work function of ZnO NPs, the electrons can be spontaneously transferred at the quantum dot/ZnO interface. In addition, the enormous difference in electron and hole mobility can lead to interfacial exciton quenching and unbalanced charge injection. In this paper, the strategy of replacing the ZnO in QLEDs with Mg and polyvinylpyrrolidone (PVP) inorganic-organic hybrid co-doped ZnO NPs are introduced. The energy band structures of ZnO NPs are tailored by tuning the concentrations of Mg, resulting in a significant suppression of the spontaneous charge transfer at the quantum dot/ETL interface. Furthermore, the surface quenching sites and the electronic mobility of ETL were adjusted via PVP doping. The proposed method significantly enhances the current efficiency and external quantum efficiency to 16.16 cd/A and 15.45%, respectively, an improvement of about 2.5-fold compared to the devices with pure ZnO NPs.