Effects of TiO2 blocking layer formation by SolGel method on conversion efficiency of dye-sensitized solar cell

A layer of TiO₂ thin film less than ~ 500 nm in thickness, as a blocking layer, was coated by sol-gel method directly onto the anode electrode to be isolated from the electrolyte in dye-sensitized solar cells (DSCs). This is to prevent the back-transferring of electron from the electrode to the electrolyte (I^-/I₃^-). The effects of gel processing as well as heat treatment condition of the as-coated film on the thickness and consolidation to substrate were studied. The flexible DSCs were fabricated with working electrode of Ti thin foil coated with a blocking TiO₂ layer, dye-attached mesoporous TiO₂ film, gel electrolyte and counter electrode of Pt-deposited indium doped tin oxide/polyethylene naphthalate (ITO/PEN). The photo-current conversion efficiency of the cell was 5.3% (V_oc = 0.678 V, J_sc = 12.181 mA/cm², ff=0.634) under AM1.5, 100 mW/cm² illumination.