Quasi-solid-state dye-sensitized solar cells employing nanocrystalline TiO2 films made at low temperature

Quasi-solid-state dye-sensitized solar cells with enhanced performance were made by using nanocrystalline TiO2 films without any template deposited on plastic or glass substrates at low temperature. A simple and benign procedure was developed to synthesize the low-temperature TiO2 nanostructured films. According to this method, a small quantity of titanium isopropoxide (TTIP) was added in an ethanolic dispersion of TiO2 powder consisting of nanoparticles at room temperature, which after alkoxide's hydrolysis helps to the connection between TiO2 particles and to the formation of mechanically stable thick films on plastic or glass substrates. Pure TiO2 films without any organic residuals consisting of nanoparticles were formed with surface area of 56 m2/g and pore volume of 0.383 cm3/g similar to that obtained for Degussa-P25 powder. The structural properties of the films were characterized by microscopy techniques, X-ray diffractometry, and porosimetry. Overall solar to electric energy conversion efficiencies of 5.3% and 3.2% (under 1sun) were achieved for quasi-solid-state dye-sensitized solar cells employing such TiO2 films on F:SnO2 glass and ITO plastic substrates, respectively. Thus, the quasi-solid-state device based on low-temperature TiO2 attains a conversion efficiency which is very close to that obtained for cells consisting of TiO2 nanoparticles sintered at high temperature.