Interfacial electronic structure between a W-doped In₂O₃ transparent electrode and a V₂O₅ hole injection layer for inorganic quantum-dot light-emitting diodes

Abstract

The interfacial electronic structure between a W-doped In₂O₃ (IWO) transparent electrode and a V₂O₅ hole injection layer (HIL) has been investigated using ultraviolet photoelectron spectroscopy for high-performance and inorganic quantum-dot light-emitting diodes (QLEDs). Based on the interfacial electronic structure measurements, we found gap states in a V₂O₅ HIL at 1.0 eV below the Fermi level. Holes can be efficiently injected from the IWO electrode into poly[(9,9-dioctylfluorenyl-2,7-diyl)-<i>co</i>-(4,4'-(4-<i>sec</i>-butylphenyl)diphenylamine)] (TFB) through the gap states of V₂O₅, which was confirmed by the hole injection characteristics of a hole-only device. Therefore, conventional normal-structured QLEDs were fabricated on a glass substrate with the IWO transparent electrode and V₂O₅ HIL. The maximum luminance of the device was measured as 9443.5 cd m^-2. Our result suggests that the IWO electrode and V₂O₅ HIL are a good combination for developing high-performance and inorganic QLEDs.