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Graphene has potential for applications in solar cells. We show that the short circuit current density of P3HT (Poly(3-hexylthiophene-2,5-diyl):PCBM((6,6)-Phenyl C61 butyric acid methyl ester) solar cells is enhanced by 10% upon the addition of graphene, with a 15% increase in the photon to electric conversion efficiency. We discuss the performance enhancement by studying the crystallization of P3HT, as well as the electrical transport properties. We show that graphene improves the balance between electron and hole mobilities with respect to a standard P3HT:PCBM solar cell.

Lately, research efforts in photovoltaics towards hybrid solar cells based on nanostructured metal oxides and conjugated polymers have been intensifying. However, very limited effort has been spent so far to investigate their recombination kinetics in comparison with their fully organic counterpart. In this work, impedance spectroscopy under different illumination intensities is used to probe the recombination kinetics of hybrid solar cells based on ZnO nanorod arrays and poly(3-hexylthiophene). A recombination-based model developed for fully organic solar cells is effectively applied in our hybrid solar cells, demonstrating their similarity in device physics and establishing the nanorod array/polymer compound as true bulk heterojunction.