Electrophoretic deposition of reduced graphene oxide nanosheets on TiO2 nanotube arrays for dye-sensitized solar cells

In the present work, electrophoretic deposition (EPD) is used to deposit reduced graphene oxide (RGO) nanosheets onto a TiO2 nanotube array for application as photoelectrode in dye-sensitized solar cells (DSSCs). The as-deposited RGO nanosheets are very uniform and can be obtained with controllable thickness. Due to the enhanced electronic conductivity caused by RGO, the short-circuit current of DSSCs based on RGO-modified TiO2 nanotube arrays is much higher than that of DSSCs based on unmodified TiO2 nanotube arrays. In addition, the short-circuit current (Jsc) increases with longer EPD time for RGO deposition but decreases with increased EPD time later; a peak value of 8.87 mA cm−2 is reached for Jsc at an EPD time of 30 s. Therefore, DSSC based on TiO2 nanotubes (6.8 μm long) modified using EPD time 30 s delivers the highest energy conversion efficiency of 4.10%, while DSSC consisting of bare nanotubes exhibits efficiency of 2.97% and short-circuit current of 6.24 mA cm−2, which represents a 38.0% enhancement of energy conversion efficiency in DSSC consisting of TiO2 nanotubes modified with RGO compared to that of DSSC based on bare nanotubes. Moreover, RGO-deposition on longer bamboo-type TiO2 nanotube arrays (16.8 μm long) can further increase the energy conversion efficiencies to 6.01% by utilizing higher surface area of bamboo-type nanotubes for dye loading.