Hybrid polymer solar cells from highly reactive diethylzinc: MDMO-PPV versus P3HT

The degradation of poly[2-methoxy-5-(3',7'-dimethyloetyloxy)-p-phenylene vinylene] (MDMO-PPV) during the processing of hybrid organic/inorganic bulk-heterojunction solar cells with zinc oxide (ZnO) from a molecular precursor as acceptor is reported. Upon addition of diethylzinc, the absorption spectrum of MDMO-PPV shifts to the blue, and hole transport through the polymer deteriorates dramatically, indicating a reduction of the conjugation length of the polymer backbone. To prevent polymer degradation through the breaking of trans vinyl bonds, regioregular poly (3-hexylthiophene) (P3HT) is introduced as the electron donor. This system of P3HT and precursor ZnO reveals an unchanged UV-vis absorption profile and zero-field hole mobility with respect to the pristine polymer as well as an improved photovoltaic performance with an estimated power conversion efficiency of 1.4% (AM1.5 global reference spectrum, 1 kW/m(2)).