Solution-processed vanadium oxide as an efficient hole injection layer for quantum-dot light-emitting diodes

Abstract

PEDOT:PSS (polyethylene dioxythiophene:polystyrenesulfonate) is widely used as a hole injection layer (HIL) for various optoelectronic devices because of its high conductivity and high work-function. However, the acidic and hygroscopic nature of PEDOT:PSS are detrimental to the long-term stability of the devices. In this work, we develop a solution processed vanadium pentoxide (V₂O₅) as an alternative to the PEDOT:PSS. The sol–gel derived V₂O₅ is easily obtained by spin-coating the vanadium oxytriisopropoxide solution, followed by thermal annealing at 120 °C for 1 min. With the proposed V₂O₅ HIL, quantum dot light-emitting diodes (QLEDs) exhibit a maximum current efficiency of 10.91 cd A⁻¹ and a peak EQE of 7.25%, which are very close to those of devices with a conventional PEDOT:PSS HIL. Moreover, by substituting the problematic PEDOT:PSS with the inorganic V₂O₅, the stability/lifetime of the QLEDs is substantially improved. Our results demonstrate that the sol–gel derived V₂O₅ is an effective alternative to PEDOT:PSS for efficient, low cost and stable QLED devices.