Layer-by-Layer Titanium (IV) Chloride Treatment of TiO 2 Films to Improve Solar Energy Harvesting in Dye-Sensitized Solar Cells

A layer-by-layer titanium (IV) chloride treatment was applied on different layers of TiO 2 in dye-sensitized solar cells (DSSCs). The effects were analysed and compared with standard untreated devices. A significant increase in short-circuit current density ( J SC ) was observed by employing layer-by-layer TiCl 4 treatment of TiO 2 in DSSCs. This increase of J SC is attributed to the increased inter-particle connectivity and increase in TiO 2 nanoparticle size, resulting in better electron transfer and a lower charge carrier recombination rate. The DSSC fabricated with layer-by-layer-treated TiO 2 achieved power conversion efficiency of 8.3%, which is significantly higher than the 6.7% achieved for the DSSC fabricated without TiCl 4 treatment. Electrochemical impedance spectroscopy (EIS) was performed to assess the better performance of the device fabricated with TiCl 4 treatment. Atomic force microscopy and surface roughness were studied to visualize and statistically determine the function of TiCl 4 treatment on different layers of TiO 2 . Transient photocurrent and transient photovoltage measurements were also performed to gain insight into interfacial charge carrier recombination.