Quasi solid state dye sensitized solar cells employing a polymer electrolyte and xanthene dyes

A series of organic dyes in the xanthene class namely Rose Bengal (RB), Eosin Y (EY) and Fluorescein sodium (FLU) were used as photo-sensitizer for nano-crystalline TiO2, for the application of quasi solid state dye sensitized solar cells. These dyes have same backbone with different number of electron acceptor groups. The dye with the highest number of electron acceptor group, i.e. 8 namely RB shows highest power conversion efficiency due the lower band gap and higher light harvesting efficiency (LHE). The ionic conductivity of polymer electrolyte used in quasi solid state DSSC was examined in terms of polymer content and redox couple concentration. The dependence of photovoltaic performance of the solar cell on the polymer content in the electrolyte used in DSSC, was studied by current–voltage characteristics under illumination and electrochemical impedance spectroscopy (EIS). The result indicates the charge transfer behavior occurred at nano-crystalline TiO2/electrolyte and PEDOT:PSS/electrolyte interface plays an important role in influencing the photovoltaic performance of the device. The quasi solid state dye sensitized solar cell posseses a good long-term stability and power conversion efficiency is almost equal to that of DSSCs with liquid electrolyte.