Suppressing series resistance in organic solar cells by oxygen plasma treatment

We demonstrate a low series resistance contact of gold (anode)/zinc-phthalocyznine in a reverse organic photovoltaic device aided by oxygen plasma treatment. The power conversion efficiency appreciated from 0.2% to 2.13%, post O-2 plasma treatment, predominantly due to the reduction in the series resistance of the device. A depth profile of zinc from x-ray photoelectron spectroscopy study revealed a gold layer with graded zinc composition, instead of pure gold, to be an efficient hole-collector from the organic interface. The zinc alloying of the gold layer has clearly been promoted by the oxygen plasma treatment. (C) 2008 American Institute of Physics.