Formation and photovoltaic performance of few-layered graphene-decorated TiO2 nanocrystals used in dye-sensitized solar cells

Abstract

Few-layer graphene/TiO₂ nanocrystal composites are successfully in situ synthesized at a low temperature of 400 °C using C₂₈H₁₆Br₂ as the precursor. Raman mapping images show that the TiO₂ nanocrystals are very uniformly dispersed in the composite films, and the in situ coating during the thermal decomposition process will favor the formation of a good interface combination between the few-layered graphene and the TiO₂ nanocrystals. The few-layer graphene/TiO₂ nanocrystal composites are used as photoanodes in dye-sensitized solar cells (DSSCs), and the conversion efficiency of 8.25% is obtained under full sun irradiation (AM 1.5), which increases by 65% compared with that of the pure TiO₂ nanocrystal DSSCs (5.01%). It is found that the good interface combination between few-layered graphene and TiO₂ nanocrystals may improve the electric conductivity and lifetime of photoinduced electrons in DSSCs. Moreover, some carbon atoms are doped into the crystal structure of the TiO₂ nanocrystals during the thermal decomposition process, which will enhance the light absorption by narrowing the band gap and favor the improvement of the photovoltaic efficiency.