Effects of HNO3 treatment of TiO2 nanoparticles on the photovoltaic properties of dye-sensitized solar cells

The effects of the nitric acid (HNO3) treatment of TiO2 nanoparticles on the photovoltaic properties of the dye-sensitized solar cell (DSSC) were investigated. The HNO3 treatment enhanced the dispersion of TiO2 particles, increased the surface area and porosity of the sintered TiO2 films, increased the relative proportion of the Ti3+ state in the Ti 2p X-ray photoelectron spectroscopy spectrum, significantly increased the amount of adsorbed dye molecules on the TiO2 electrode, and reduced the charge-transfer resistance at the TiO2/dye/electrolyte interface. The short circuit photocurrent density (Isc) was increased due to the increased amount of adsorbed dye molecules and the reduced charge-transfer resistance. The HNO3 pre-treatment of TiO2 particles improved the overall conversion efficiency of the DSSC by about 14%.