High-Efficiency Red Perovskite Light-Emitting Diodes by Designing the Landscapes of MoO(x).

Perovskite quantum dot light-emitting diodes (Pe QLEDs) hold significant application potential in next-generation displays, but the device performance remains compromised by the acidity and hygroscopicity of the widely adopted hole injection layer (HIL), poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Molybdenum oxide (MoO) has garnered significant attention due to its excellent environmental stability; however, there is still a lack of research on the influence of different molybdenum ion contents on the physicochemical properties of molybdenum oxide itself and its application as a hole injection layer (HIL) in red Pe QLEDs. In this work, three MoO solutions with the conduction band level from -4.70 to -5.15 eV were prepared by modulating the HO ratio to regulate the Mo and Mo content, and different MoO were adopted as HIL to systematically investigate the influence of energy landscapes on device performance. A gradient conduction band energy was realized, and optimal hole injection was obtained when the ratio of Mo is 48.1%, with an external quantum efficiency (EQE) of 28.6% realized. This efficiency is comparable to that of PEDOT:PSS-based devices and represents the highest value reported for MoO-based red Pe QLEDs. Besides, the operational stability was enhanced from 3.0 to 10.6 h, and after being stored for 48 h in a high-humidity environment, the half-life (T) remained above 3.0 h, far exceeding that of PEDOT:PSS-based devices, which nearly lost their operational stability. The proposed MoO-based Pe QLEDs exhibited significantly improved operational and storage stabilities.