Aggregation control of organic sensitizers for panchromatic dye co-sensitized solar cells

The photovoltaic properties of dye co-sensitized solar cells were compared with those of mono-sensitized devices. Co-sensitized TiO2 photoelectrodes were prepared from a phenothiazine chromophore for the RED dye and a squaraine chromophore for the BLUE dye to achieve panchromatic light absorption in dye co-sensitized solar cells (DSSCs). Co-sensitization on the TiO2 photo-electrode could reduce the aggregation of the BLUE dye adsorbed on the TiO2 surface, which led to an enhancement of the short circuit current (J(SC)) of the co-sensitized solar cells. The dye co-sensitized solar cells with the RED and BLUE dyes optimized according to the dipping time showed an increase in the photon-to-current efficiency compared to that of the solar cell with a mono-sensitized photo-electrode. The photovoltaic and aggregation properties of the DSSCs were examined by measuring the current-voltage curve, incident photon-to-current efficiency, and electrochemical impedance spectra. (C) 2014 The Japan Society of Applied Physics