Unexpected effect of dye's molar extinction coefficient on performance of back contact dye-sensitized solar cells

The effect of dyes' molar extinction coefficients (epsilon) on the performance of back contact dye-sensitized cells (BCDSCs) was studied. Unexpected behavior, which contrasted with that expected for conventional DSCs, was observed. Specifically, a dye with lower epsilon improved the performance of BCDSCs, whereas a dye with higher e did not improve the BCDSCs' efficiency, even with increasing TiO2 thickness. Our analysis revealed that BCDSCs with lower epsilon dye were capable to obtain a more efficient electron collection due to its higher electron generation rate closer to the collecting electrode and shorter electron transport distance, leading to an improved efficiency. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4769897]