Effects of oxygen on exciton transport in zinc phthalocyanine layers

The effect of oxygen on the photovoltaic properties of organic solar cells consisting of zinc phthalocyanine and a perylene pigment has been investiga ted. Under solar illumination, it was possible to raise the short-circuit c urrent by a factor of 1.5 when increasing the partial O-2 pressure threefol d from atmospheric pressure in a surrounding gas atmosphere consisting of d ifferent oxygen:nitrogen ratios with a total pressure of 1 bar. On the othe r hand, the exciton diffusion length in ZnPc was observed to decrease at hi gher oxygen pressures, from which we conclude that the range of exciton tra nsport in the ZnPc layer is limited by the presence of ionic impurities suc h as O-2(-). (C) 2000 Elsevier Science B.V. All rights reserved.