▎ 摘　　要

The effects of doping graphene into the zinc oxide (ZnO) working electrode of dye-sensitized solar cells (DSSCs) were investigated. The factors investigated in the present study include the type and the amount of graphene in graphene/ZnO composite films. Two different types of graphene were used: a commercial product and one prepared by the Staudenmaier method. The commercial pristine graphene was treated in a mixed acid at 60 degrees C for 2 h to introduce carboxyl and hydroxyl groups to the surface of the carbon material, which improved its dispersion in polar solvents and probably also enhanced its interaction with ZnO nanoparticles, thereby promoting electron transport. The carbon materials were mixed with ZnO nanoparticles (similar to 20 nm) and fabricated into graphene/ZnO composite films by the doctor-blade method using a low-temperature heat-treatment process (150 degrees C for 1 h). Regardless of the type of graphene, an appropriate graphene level boosted the short-circuit current density and thus the overall conversion efficiency of resulting cells. An excessive amount of graphene, in contrast, reduced not only the photocurrent but also the open-circuit voltage, leading to DSSCs of low efficiencies. The best performing device contained 0.01 wt% of the Staudenmaier graphene and reached a power conversion efficiency of 3.67%, corresponding to a 20% improvement compared to the pure ZnO reference cell.