Solution-processable vanadium oxide (V2O5) was used as an inorganic hole injection layer (HIL) to improve the performance and stability of quantum-dot light-emitting diodes (QLEDs). Non-acidic and non-hygroscopic V2O5 solution was synthesized and spin-coated onto indium-tin-oxide (ITO)/glass substrate to serve as an HIL for QLEDs. QLEDs with a V2O5 HIL showed efficient hole injection and had improved luminous efficiency and life-time. Maximum luminance and luminous efficiency of QLEDs fabricated under ambient conditions were 12,603 cd/m(2) and 2.96 Cd/A, respectively. Photoelectron spectroscopy measurements were conducted to construct an energy level diagram of the QLEDs, and we found that the gap states of V2O5 enabled efficient hole-injection from ITO into the devices through the V2O5 HIL, resulting in enhanced luminance. These results suggest that solution-processable V2O5 is a feasible alternative to organic HILs for high-performance QLEDs. (C) 2017 Elsevier B.V. All rights reserved.