Graphene oxide as an effective hole transport material for low-cost carbon-based mesoscopic perovskite solar cells

Carbon-based perovskite solar cells (PSCs) are fast developing toward large-scale production. In this study, graphene oxide (GO) was applied as a hole transport material (HTM) for carbon-based mesoscopic PSCs with n-i-p structure. The GO was prepared using a simple Hummer's method, while the carbon counter electrode was deposited using a doctor blade and heated at a temperature of 120 degrees C. The mesoscopic carbon-based PSCs with various GO dispersion (1.0, 1.5, and 2.0 mg.ml(-1)) are fabricated and characterised for optimised photovoltaic performance. Consequently, the use of GO as HTM improved the quality of perovskite film by providing perovskite crystals with larger grain size and fewer pinholes. The power conversion efficiency (PCE) of 10.01% was obtained with GO dispersion concentration of 1.0 mg.ml(-1), which was significantly higher than a similar device without HTM with a PCE of 8.32%. These results show that GO effectively serves as a promising HTM. Combined with the use of carbon as a replacement for metals as a back-contact electrode, this work demonstrates that the overall material cost for perovskite solar cells could be reduced while maintaining excellent photovoltaic performance.