Solvent‐Regulated Electronic Structure and Morphology of Inorganic Hole Injection Layers for Efficient Quantum Dot Light‐Emitting Diodes

Abstract

Inorganic charge transport layers (CTLs) have been proved to be effective for improving the stability of electroluminescent devices. However, the effective regulation of electronic structure for solution‐processed inorganic CTLs is still challenging by doping or interface engineering, and the film morphology is usually poor due to the surface aggregation. In this work, we precisely regulated the energy level and mobility of inorganic phosphomolybdic acid (PMA) hole injection layers (HILs) by adjusting the polarity of solvents and the resulting inorganic HILs with proper electronic structure acts as an energy ladder to better promote hole injection, thereby achieving balanced carrier transport in quantum dot light‐emitting diodes (QLEDs). Meanwhile, the surface morphology of the inorganic PMA film is also improved by employing solvents with high boiling point which minimizes the surface tension and is conducive to the formation of smooth and pinhole‐free films. As a result, the devices using PMA dissolved in n‐butanol with a lower polarity exhibits a peak EQE of 19.2%, which is 3.6 times higher than that of QLED using PMA obtained from acetone solvent with a higher polarity. This work provides a general method for the deposition of high‐quality HILs for fabrication of solution‐processed inorganic functional layers and optoelectronic devices. This article is protected by copyright. All rights reserved.