Growth behavior of titanium dioxide thin films at different precursor temperatures

The hydrophilic TiO2 films were successfully deposited on slide glass substrates using titanium tetraisopropoxide as a single precursor without carriers or bubbling gases by a metal-organic chemical vapor deposition method. The TiO2 films were employed by scanning electron microscopy, Fourier transform infrared spectrometry, UV-Visible [UV-Vis] spectroscopy, X-ray diffraction, contact angle measurement, and atomic force microscopy. The temperature of the substrate was 500°C, and the temperatures of the precursor were kept at 75°C (sample A) and 60°C (sample B) during the TiO2 film growth. The TiO2 films were characterized by contact angle measurement and UV-Vis spectroscopy. Sample B has a very low contact angle of almost zero due to a superhydrophilic TiO2 surface, and transmittance is 76.85% at the range of 400 to 700 nm, so this condition is very optimal for hydrophilic TiO2 film deposition. However, when the temperature of the precursor is lower than 50°C or higher than 75°C, TiO2 could not be deposited on the substrate and a cloudy TiO2 film was formed due to the increase of surface roughness, respectively

CdSe quantum dot-sensitized solar cells exceeding efficiency 1% at full-sun intensity

Colloidal cadmium selenide (CdSe) quantum dots QDs) have been prepared and exploited as inorganic dyes to sensitize a large-band-gap TiO2 layer for QD-sensitized solar cells. The optimized QD-sensitized solar cells exhibited an unprecedented incident photon-to-charge carrier generation efficiency of 36% and an overall conversion efficiency of over 1.7% at 0.1 sun and 1% at full sun intensity with a cobalt(II/III)-based redox system. The photovoltaic characteristics of CdSe QD-sensitized cells are compared with standard dye-sensitized solar cells, in which the former exhibited about half of the efficiency of the latter. From the kinetics of charge transfer monitored using transient spectroscopic and voltage decay measurements in the CdSe QD-sensitized cell, the regeneration yield of oxidized QDs was found to be close to almost unity, and the electron lifetime was longer in the CdSe QD-sensitized cell than in the dye-sensitized solar cellclose26