Electro-optical model of photonic crystal bulk heterojunction organic solar cells

In this work, we present a two-dimensional electro-optical model for the operation of bulk heterojunction (BHJ) organic solar cells with photonic crystal (PC) geometries. The model is applied to the test case of a one-dimensional (1-D) periodic PC device and a conventional planar control cell with poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-p-phenylene vinylene]:[6,6]-phenyl C61-butyric acid methyl ester (MDMO-PPV:PCBM) as the photoactive BHJ material. From the optical model we demonstrate absorption enhancements of 16% for the PC device compared to the planar control cell. In terms of the electrical model, the non-planar geometry of the PC significantly alters the internal electric field in the photoactive region, which causes a 5% reduction in the exciton dissociation probability and a significant 8.4-fold increase in the bimolecular recombination rate. Investigations are also discussed which are currently being conducted to resolve these predictions with experiment.