Preliminary study of performance of dye-sensitized solar cell of nano-TiO₂ coating deposited by vacuum cold spraying

The control of nanoporous microstructure of TiO₂ coating in the dye-sensitized solar cells (DSC) through preparation methods influences significantly the performance of the cells. To investigate the effect of microstructure of TiO₂ deposit on the cell's performance, in present study, vacuum cold spray (VCS) process is employed to deposit nanocrystalline TiO₂ coatings on an ITO conductive glass substrate. TiO₂ deposits were produced using nanosized particles of 25 nm in the diameter and composite powder composed of polyethylene glycol (PEG) and 25 nm TiO₂ particles. The deposition characteristics and the microstructure of the coating are characterized by scanning electron microscopy, x-ray diffraction analysis. The performance of the cell is tested under illumination of a metal halide lamp with a radiation intensity of 600 W·-m^-2. It was found that a dense TiO₂ coating with retention of crystal structure of powder can be deposited by vacuum cold spraying directly using nanosized TiO₂ powder. A cell with TiO₂ coating of 3.8 urn thick deposited directly by 25 nm powders yielded a short current density of 90.0 A·m^-2 and conversion efficiency of 5.1% which was comparable with that of the wet doctor blading TiO₂ coating. Using a composite powder of TiO ₂ with PEG, a porous TiO₂ coating with a thickness up to several tens of micrometers can be deposited by vacuum cold spraying. A DSC cell of TiO₂ coating deposited using a composite powder containing 41.2% PEG presented a higher short current density of 145.0 A·m^-2, and conversion efficiency of 7.1%.