Organic bulk heterojunction photovoltaic devices based on polythiophene-graphene composites.

A solution-processed graphene content was synthesized by treatment of graphite oxide (GO) with phenyl isothiocyanate (PITC) by taking advantage of the functional carboxyl groups of graphene oxide. The GO was prepared by the oxidation of natural graphite powder and was expanded by ultrasonication in order to exfoliate single or/and few-layered graphene oxide sheets. The functionalized graphene oxide, GO-PITC, can be dispersed within poly-(3-hexylthiophene) (P3HT) and can be utilized as the electron acceptor in bulk heterojunction polymer photovoltaic cells. When P3HT is doped with GO-PITC, a great quenching of the photoluminescence of the P3HT occurred, indicating a strong electron transfer from the P3HT to the GO-PITC. The utilization of GO-PITC as the electron acceptor material in poly-(3-hexylthiophene) (P3HT) bulk heterojunction photovoltaic devices was demonstrated, yielding in a power conversion efficiency enhancement of 2 orders of magnitude compared with that of pristine P3HT.