Stabilisation of the electrical and optical properties of dielectric/Cu/dielectric structures through the use of efficient dielectric and Cu:Ni alloy

Abstract

Dielectric/Metal/Dielectric structures can be used as substituent to transparent conductive electrodes. The dielectric used is often a transition metal oxide such as MoO3-x and the metal is Ag. In the present work we propose to substitute Cu to Ag. The difficulty with Cu is its high diffusion rate into MoO3-x. In order to prevent this negative effect we used Cu:Ni alloy as metal layer. If using such alloy is efficient to reduce Cu diffusion, it works well only with WO3-x and not with MoO3-x. We show that after deposition of the alloy only 0.5 at% of Ni is present in Cu films. This small atomic concentration makes it possible to preserve the electrical and optical properties of the metal films but limits its control of Cu diffusion in time. Therefore it is necessary to use an oxide, here WO3-x, which also limits the diffusion of metals. By adding these two effects due to the alloy and the oxide it is possible to form Dielectric/Metal/Dielectric structures with quite stable properties. These WO3-x/Cu:Ni/WO3-x structures can be used as anodes in organic photovoltaic cells. The different behaviors of the structures according to whether they use WO3-x or MoO3-x are discussed in terms of thin film porosity.