Admittance spectroscopy of the electric properties of 1,4-bis[N-(1-naphthyl)-N '-phenylamino]-4,4 ' diamine doped with tungsten oxide

Abstract

We report an efficient p-type doping of NPB layer using WO(3) as a p-dopant. We find that increasing the WO(3) volume percentage can reduce the activation energy of the NPB layer and increase the hole concentration in NPB layer. As a result, the hole-injection can be improved via tunneling through a narrow depletion region due to the increasing band bending which corresponds to the difference of Fermi level position between the ITO and the NPB layer.