Hybrid 1D/2D Carbon Nanostructure-Incorporated Titania Photoanodes for Perovskite Solar Cells

The incorporation of carbon nanotubes (CNTs) and graphene, two amazing carbon nanostructures, in photovoltaics has drawn a lot of attention, especially as TiO2–CNT or TiO2–graphene nanocomposite photoanodes. In this study, we prepare a hybrid TiO2–CNT–graphene mesoporous thin film through a mixed-solvent and in situ hydrothermal synthesis, as well as an engineered two-step calcination process, and employ it as a photoanode in perovskite solar cells. The best-performance device (with 0.5 wt % (CNT + graphene)) shows a short-circuit current density of 24.8 mA cm–2, which is 43.4, 39.3, and 19.2% higher than that of bare TiO2-, TiO2–CNT-, and TiO2–graphene-based cells, respectively. Owing to the combination of high electron extraction ability of CNTs and enormously high specific surface area of graphene sheets confirmed by photoluminescence spectroscopy and photovoltage decay measurements, superior charge transport is provided in the photoanode system, resulting in this enhanced photovoltaic performance, with a power conversion efficiency of up to 13.97%. This work demonstrates that the simultaneous presence of graphene and CNT, instead of employing them individually, in a nanocomposite system with TiO2 is able to bring the field of charge collection studies in PSCs up to the mark.