Effects of TiCl₄ Post-Treatment on the Efficiency of Dye-Sensitized Solar Cells

The effects of compact TiO₂ overlayers, deposited on TiO₂ photoelectrodes through the hydrolysis of TiCl₄, on the overall performance of dye-sensitized solar cells (DSSCs) were investigated. A thermal treatment at high-enough temperature was required for a more effective and higher dye-loading of the compact TiO₂ overlayers. This led to improvements in the crystallinity and porosity of the layer, which contributed to higher power conversion efficiencies (PCE) of DSSCs compared with the electrodes prepared at relatively lower temperatures. Moreover, the existence of an additional secondary overlayer led to an increase in the net PCE of the cells by increasing the amount of dyeloading, even though this layer itself, in the absence of a first overlayer formed under high thermal treatment, did not enhance cell efficiency, because of the higher charge transport resistance over the layers and an increase in surface states.