Cu-Doped nickel oxide prepared using a low-temperature combustion method as a hole-injection layer for high-performance OLEDs

Abstract

Solution-processed Cu doped nickel oxide (Cu-NiO_x) is used as a hole injection layer (HIL) in phosphorescent green organic light-emitting diodes (OLEDs). Hole injection materials are very important for achieving high performance OLEDs. Herein, solution-processed Cu doped NiO_x prepared using a combustion method is demonstrated as the HIL in OLEDs. Nickel oxide (NiO_x) thin films incorporated with p-type Cu dopants resulted in a significantly improved conductivity and hole-injection capability. The UV-ozone treated NiO_x shows significantly better hole injection than that without being treated by UV-ozone. Our results show that phosphorescent green OLEDs with UV-ozone treated Cu:NiO_x show a maximum current efficiency of 85.3 cd A⁻¹, which is remarkably higher than the conventional device based on poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) which has a maximum current efficiency of 68.3 cd A⁻¹.