Organic solar cells using a ZnO/Cu/ZnO anode deposited by ion beam sputtering at room temperature for flexible devices.

The development of indium-free transparent conductive oxides (TCOs) on polymer substrates for flexible devices requires deposition at low temperatures and a limited thermal treatment. In this paper, we investigated the optical and electrical properties of ZnO/Cu/ZnO multi-layer electrodes obtained by ion beam sputtering at room temperature for flexible optoelectronic devices. This multilayer structure has the advantage of adjusting the layer thickness to favor antireflection and surface plasmon resonance of the metallic layer. We found that the optimal electrode is made up of a 10 nm-thick Cu layer between two 40 nm-thick ZnO layers, which results in a sheet resistance of 12 omega/(see symbol), a high transmittance of 85% in the visible range, and the highest figure of merit of 5.4 x 10(-3) (see symbol)/omega. A P3HT:PCBM-based solar cell showed a power conversion efficiency (PCE) of 2.26% using the optimized ZnO (40 nm)/Cu (10 nm)/ZnO (40 nm) anode.