Fullerene Contribution to Photocurrent Generation in Organic Photovoltaic Cells

Organic photovoltaic devices based on blends of organic donors and acceptors are a promising new energy generation technology. In the case of binary blends based on mixtures of conjugated polymer donors and fullerene acceptors, the conventional view is that light harvesting occurs in the conjugated polymer component, and following primary charge separation at a donor-acceptor interface, the photogenerated charges are then transported by the respective donor and acceptor networks. By comparing the results of detailed optical modeling with device performance, we demonstrate that for 1:1 blends of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) this conventional view is incomplete and that there is a significant fullerene photocurrent contribution. Analysis of the photocurrent generation in these devices yields the result that ca. 13% of device short circuit current under air mass (AM) 1.5 illumination conditions arises from the contribution of the fullerene component.