Solution-processable functionalized graphene in donor/acceptor-type organic photovoltaic cells

An organic photovoltaic device based on an acceptor of solution-processable functionalized graphene (SPFGraphene) was designed. The devices were based on heterostructure polymer-graphene composite layers. The structural configuration of devices is ITO/PEDOT:PSS/P3HT:SPFGraphene/LiF/Al. Due to the functional groups of the graphene, a homogeneous blend of graphene–polymer composite could be obtained. In the graphene–polymer composite, the graphene acted as exciton dissociation sites and provided the transport pathway of LUMO-graphene-Al. Doping of graphene into P3HT resulted in appropriate energetic distance between HOMO and LUMO of the donor/acceptor for a high open circuit voltage and provided higher exciton dissociation volume mobility of carrier transport for a large short-circuit current density. The device containing only 10 wt% of graphene shows the best performance with a power conversion efficiency of 0.88%, an open-circuit voltage of 0.77 V, and a short-circuit current density of 3.72 mA/cm2.