Polymer Photovoltaic Cells Based on Solution-Processable Graphene and P3HT

A soluble graphene, which has a one‐atom thickness and a two‐dimensional structure, is blended with poly(3‐hexylthiophene) (P3HT) and used as the active layer in bulk heterojunction (BHJ) polymer photovoltaic cells. Adding graphene to the P3HT induces a great quenching of the photoluminescence of the P3HT, indicating a strong electron/energy transfer from the P3HT to the graphene. In the photovoltaic devices with an ITO/PEDOT:PSS/P3HT:graphene/LiF/Al structure, the device efficiency increases first and then decreases with the increase in the graphene content. The device containing only 10 wt % of graphene shows the best performance with a power conversion efficiency of 1.1%, an open‐circuit voltage of 0.72 V, a short‐circuit current density of 4.0 mA cm−2, and a fill factor of 0.38 under simulated AM1.5G conditions at 100 mW cm−2 after an annealing treatment at 160 °C for 10 min. The annealing treatment at the appropriate temperature (160 °C, for example) greatly improves the device performance; however, an annealing at overgenerous conditions such as at 210 °C results in a decrease in the device efficiency (0.57%). The morphology investigation shows that better performance can be obtained with a moderate content of graphene, which keeps good dispersion and interconnection. The functionalized graphene, which is cheap, easily prepared, stable, and inert against the ambient conditions, is expected to be a competitive candidate for the acceptor material in organic photovoltaic applications. Organic photovoltaic cells based on soluble graphene are studied with regard to graphene content, annealing conditions, and morphology. Annealing treatment at an appropriate temperature greatly improves the device performance, and moderate graphene content in the polymer matrix forming an interconnecting network and avoiding aggregation favors the device performance.