Tailoring titanium dioxide thin films for photocatalysis and energy efficient glazing via dye-sensitised solar cells

Abstract

This thesis focuses on the synthesis and characterisation of titanium dioxide (TiO2) thin films for photocatalytic applications and use in semi-transparent dye-sensitised solar cells for energy efficient glazing. Several synthetic methods for the production of TiO2 thin films are explored including sol-gel, aerosol-assisted chemical vapour deposition (CVD) and hybrid combinatorial CVD. For sol-gel processing two different precursors were studied; titanium tetra-isopropoxide (TTIP) and titanium bis-ammonium lactato dihydroxide (TiBALD). Non-ionic surfactants (Tween 20, 40, 60 and Brij 58 and 98) were successfully incorporated into all three methods for the production of TiO2 thin films modified morphology, microstructure and enhanced functional properties in some cases. All films are fully characterised using scanning electron microscopy, X-ray diffraction, atomic force microscopy, Raman spectroscopy, UV-Vis spectroscopy, contact angle analysis, as well as assessment for photocatalytic performance with resazurin ‘intelligent’ ink. Photocatalytic performance has been used as an indicator for performance in dye-sensitised solar cells (DSSCs). The best photocatalytic performances with half-lives of up to 2 minutes were obtained for thin films produced with the addition of Brij surfactants. A selection of thin films were tested in semi-transparent DSSC devices with up to 70% transparency, to determine their overall potential for use as energy-efficient glazing. Three DSSC device configurations were tested, whereby the optimum configuration used N3 “black” dye with a dye loading time of 42 hours in combination with a high performance iodine electrolyte and a platinum counter electrode. The highest power conversion efficiencies (PCE) obtained were within the region of 0.1 – 0.3 %, with the highest PCE of 0.3814 % obtained with a 3-layer TTIP sol-gel derived Brij 58 thin film (0.0006 mol dm3) which exhibited an short-circuit current of 0.857 mA/cm2, an open-circuit voltage of 0.71 V and a fill factor of 0.60.