Toward Higher Photovoltage: Effect of Blocking Layer on Cobalt Bipyridine Pyrazole Complexes as Redox Shuttle for Dye-Sensitized Solar Cells

Fluorine-doped tin-oxide (FTO) transparent conducting substrates, for use in cobalt bis(bipyridine pyrazole) complex based dye-sensitized solar cells (DSCs), were compared using the conventional TiCl4 treatment with conformal TiO2 blocking layers formed by atomic layer deposition (ALD). The conformal blocking layer prepared by ALD promotes a decrease in the dark current, owing to retarded recombination between the FTO and the cobalt electrolyte. The thickness for the conformal blocking layer was optimized to attain the best photovoltaic performance. Optimized photovoltaic devices employing a double layer provided the best results, and a peak power conversion efficiency of 10.6% was achieved under full sun light intensity.