| In this thesis we studied the electrical properties of bulk heterojunction organic photovoltaic (OPV) devices fabricated using a variety of conjugated polymers, including regioregular P3HT, regiorandom P3HT, MEH-PPV and Mercedes, and several fullerene derivatives including [C61]PCBM, [C71]PCBM, bis-PCBM, Jalapeno and Habanero.;We first optimized the fabrication recipe for P3HT/PCBM devices to yield a power conversion efficiency ∼3.5%, which is comparable to the reported state-of-the-art P3HT/PCBM device performance.;We then fabricated OPV devices using alternative high LUMO fullerenes and a narrow bandgap/deep HOMO polymer to enhance OPV device performance and studied the electrical properties of these devices. Devices fabricated using P3HT/Jalapeno demonstrate a high efficiency ∼5%.;Finally, we discovered an innovative spin-related method, which can potentially compliment the use of alternative donor/acceptor materials, to enhance OPV device performance. We doped the spin ½ radial Galvinoxyl into P3HT/PCBM devices and improved efficiency from 3.5% to 4%. Our experimental results suggest that the existence of Galvinoxyl at the P3HT/PCBM interface facilitates the exciton/polaron dissociation process, while Galvinoxyl molecules that are sparsely distributed in PCBM domains yield enhanced free charge carrier transport. |
