How the surface energy of ultra-thin CuF2 film as anode buffer layer affect the organic light-emitting devices?

The effect of surface energy on organic light-emitting device performance was demonstrated by depositing an ultra-thin CuF2 buffer layer on indium tin oxide (ITO) substrates, followed by ultraviolet (UV)-ozone treatment. An optimal thickness UV-ozone treated CuF2 (4 nm)/ITO anode significantly improved device performance. Work function estimates from X-ray photoelectron measurements suggested that both pristine and UV-ozone treated CuF2/ITO anodes had no hole injection barrier. Measurements of energy band, surface energy and surface polarity indicated device improvement came from the simultaneous increase in work function and surface energy of ITO by adding treated CuF2 film between ITO and the hole-transporting layer.