Investigation of 35 Elements as Single Metal Oxides, Mixed Metal Oxides, or Dopants for Titanium Dioxide for Dye-Sensitized Solar Cells

A total of 35 elements were investigated as single component metal oxides and as dopants for TiO2 for use in dye-sensitized solar cells (DSCs). An array dispenser and scanner system was utilized for high-throughput testing of the single component metal oxides and hundreds of doped TiO2 compositions. The optimal dopant concentrations were identified and summarized according to their effect on short circuit current (I-sc) and open circuit voltage (V-oc). New dopant candidates were discovered, including several post-transition metals, which showed improvements in DSC performance when incorporated at compositions of 6% In TiO2, 6% Sn TiO2, and 6% Sb TiO2 (metals basis). These compositions were used to synthesize scaled-up DSC devices for detailed characterization. Incorporation of 6% In into TiO2 enhanced V-oc substantially and increased I-sc slightly, 6% Sn improved I-sc while preserving V-oc, and 6% Sb increased I-sc significantly but decreased V-oc. When coincorporated, Cr and Sb showed a complementary interaction, which reduced resistance to charge transport in the DSC device. The 2% Cr, 6% Sb TiO2, showed higher I-sc and V-oc values than 6% Sb TiO2 and considerably higher I-sc than 2% Cr TiO2. The fill-factor for 2% Cr, 6% Sb TiO2 was relatively low, but the maximum power was higher than the other compositions due to the higher currents. The V-oc values for DSC devices with different compositions correlated linearly with the measured flat-band potentials (E-FB).