Dye-Sensitized solar cell with Al₂O₃ /TiO₂ or MgO/TiO₂ electrode layer

This research investigated the performance of dye-sensitized solar cells with composite Al2O3/TiO2 and MgO/TiO2 electrode layer. The amount of Al2O3 or MgO added was in the range of 0 to 2 % (w/w). The composite mixture was synthesized by sol-gel methods and sprayed onto the conducting glass by an ultrasonic spray coater. The thickness of the film was approximately 10 µm. Dye sensitized solar cells with an electrode of 1 % (w/w) Al2O3 and TiO2 that was sintered at 400°C yielded the highest efficiency of 5.04%. The addition of alumina increased an isoelectric point of the mixture, resulting in greater amount of dye molecules being adsorbed on the surface. This increase led to improved short circuit current density and higher efficiency of the cells when compared to cells with pure TiO2 electrode. On the other hand, the addition of magnesium oxide lowered an isoelectric point of the mixture, thereby decreasing the amount of dye adsorbed. This decrease led to smaller short circuit current density and lower efficiency of the cell. When the sintering temperature of composite Al2O3/TiO2 electrode increased, the efficiency dropped because anatase phase was converted to the rutile phase and surface area was decreased. When a double-layered Al2O3/TiO2 electrode was employed, the efficiency of the solar cell increased to 5.50% when compared to a single-layered Al2O3/TiO2 electrode with similar specific surface area. Double-layered TiO2 electrode increased the light scattering, resulting in more light reflected back to dye layer, as evident in diffused reflectance spectrum.