The Use of Rutile‐ and Anatase‐Titania Layers towards Back Light Scattering in Dye‐Sensitized Solar Cells

Dye‐sensitized solar cells (DSCs) with nanocrystalline TiO 2 (NCT) particles (ca. 20 nm) as foundation layer and mesoporous anatase phase microspheres (AMT) or rutile phase microspheres (RMT), as the back light‐scattering layer, were fabricated. The phase‐pure AMT, 0.42 μm or RMT particles, 0.50 μm were obtained at 500 o C and 900 o C, respectively. The DSCs employing NCT/AMT and NCT/RMT bi‐layered films depicted power conversion efficiencies of 5.9% and 6.3%, respectively, compared to 4.0% of DSCs with only NCT films. The efficiencies were improved up to 9.0% after depositing compact nano‐TiO 2 layers beneath the NCT film. The optical and electrochemical investigations of the DSCs quantitatively elucidated, through longer electron life time and enhanced back light scattering, the substantial improvement in power conversion efficiency to the texture tuning of titania films, in particular by the rutile phase.