Hydrothermal synthesis of TiO2 nanocrystals in different basic pHs and their applications in dye sensitized solar cells

In this research TiO2 nanocrystals with sizes about 11-70 nm were grown by hydrothermal method. The process was performed in basic autoclaving pH in the range of 8.0-12.0. The synthesized anatase phase TiO2 nanocrystals were then applied in the phtoanode of the (lye sensitized solar cells It was shown that the final average size of the nanocrystals was larger when the growth was carried out in higher autoclaving pHs. The photoanodes made of TiO2 nanocrystals prepared in the pHs of 8.0 and 9.0 represented low amounts of dye adsorption and light scattering. The performance of the corresponding dye sensitized solar cells was also not acceptable. Nevertheless, the energy conversion efficiency was better for the state of pH of 9.0. For the photoanodes made of TiO2 nanocrystals prepared at autoclaving pH of 10.0, the dye adsorption and light scattering were quite higher. The photovoltaic characteristics of the best cell in this state were 15.25 mA/cm(2), 740 mV, 0.6 and 6.8% for the short-circuit current density, open circuit voltage, fill factor and efficiency, respectively. The photoanodes composed of TiO2 nanocrystals prepared in autoclaving pHs of 11.0 and 12.0 demonstrated lower amount of dye adsorption and higher light scattering. This was quite considerable for the state of pH of 12.0. The energy conversion efficiencies were consequently decreased compared to that of the p1-1 of 10.0. The optimum situation was finally discussed based on the nanocrystals size and its influence on the sensitization and light harvesting efficiency. (C) 2015 Elsevier B.V. All rights reserved.