Bridging TiO₂ nanoparticles using graphene for use in dye-sensitized solar cells

SUMMARY: The use of graphene to bridge TiO₂ particles in the photoanode of dye-sensitized solar cell for reduced electrical resistance has been investigated. The difficulty in dispersing graphene in TiO₂ paste was overcome by first dispersing graphene oxide (GO) into the TiO₂ paste. The GO was then reduced to graphene after the sintering of TiO₂. This is shown through transmission electron microscopy and X-ray photoelectron spectroscopy analysis. Cell performance was evaluated using a solar simulator, incident photon to electron conversion efficiency, intensity modulated photocurrent/photovoltage spectroscopy under blue light, and electrochemical impedance spectroscopy. Depending on the amount of graphene in the photoanode, the cell performance was enhanced to different degrees. A maximum increase of 11.4% in the cell efficiency has been obtained. In particular, the inclusion of graphene has reduced the electron diffusion time by as much as 23.4%, i.e. from 4.74 to 3.63ms and increased the electron lifetime by as much as 42.3%, i.e. from 19.58 to 27.85ms.