Hole barrier height reduction in inverted quantum-dot light-emitting diodes with vanadium(V) oxide/poly N-vinylcarbazole hole transport layer

Abstract

This study demonstrates superior electrical and electroluminescence performance of inverted quantum-dot light-emitting diodes (QD-LEDs) with a V2O5/poly(N-vinylcarbazole) (PVK) hole conduction layer. Hole- and electron-only device measurements reveal a more balanced charge carrier injection as well as the higher hole conduction capability in the inverted QD-LED than the standard one. Smooth stepwise hole conduction energy levels with a remarkably reduced hole barrier height (Delta h) from 1.74 to 0.89 eV at QD/PVK are found to be responsible for high hole conduction and high luminous efficiency in the inverted QD-LED, which is validated by ultraviolet photoelectron spectroscopy measurements. The down-shifted electronic energy levels of PVK for reducing the Delta h are discussed from the point of view of molecular orientation of PVK governed by interfacial atomic interaction with underlayers of V2O5 and QD for standard and inverted device structures, respectively. Published by AIP Publishing.