Solution processed nickel oxide anodes for organic photovoltaic devices

Abstract

Nickel oxide thin films have been prepared from a nickel acetylacetonate (Ni(acac)) precursor for use in bulk heterojunction organic photovoltaic devices. The conversion of Ni(acac) to NiOx has been investigated. Oxygen plasma treatment of the NiO layer after annealing at 400°C affords solar cell efficiencies of 5.2%. Photoelectron spectroscopy shows that high temperature annealing converts the Ni(acac) to a reduced form of nickel oxide. Additional oxygen plasma treatment further oxidizes the surface layers and deepens the NiO work function from 4.7eV for the annealed film, to 5.0eV allowing for efficient hole extraction at the organic interface.