The effect of co-sensitization methods between N719 and boron dipyrromethene triads on dye-sensitized solar cell performance

A boron dipyrromethene (BODIPY) featuring triphenylamine triad, BD, has been synthesized as a co-sensitizer in dye-sensitized solar cells (DSCs). The optical and electrochemical properties of BD have been characterized using UV-vis spectroscopy and cyclic voltammetry. DSCs containing co-sensitizers, N719 and BD, have been prepared in two procedures using co-deposition and stepwise deposition. The influences of the staining processes, co-deposition and stepwise deposition on dye loading, dye dispersion on a TiO2 photoanode and DSC performance have been investigated using FTIR, SEM-EDS, I-V test and IPCE measurement, respectively. We found that stepwise co-sensitization provided higher solar cell efficiency, compared to those stained with a co-deposition method. N719/5% BD showed the highest power conversion efficiency of 5.14%. Interestingly, the enhanced device efficiency was 66% higher than that of a device containing the single N719 dye.