Tuning the BODIPY core for its potential use in DSSC: a quantum chemical approach

Boron dipyrromethene (BODIPY) is a highly promising candidate for use in dye-sensitized solar cell (DSSC), because of its attractive absorption characteristics such as strong extinction coefficients in the visible and near-IR ranges (70000–80000 ${\text{M}}^{-1}$ ${\text{cm}}^{-1})$, large quantum yields, longer excited-state lifetime and also high solubility in many organic solvents. Moreover, the absorption peaks can be shifted towards longer wavelengths when functionalized at suitable positions of the BODIPY core. Herein, on the basis of density functional theory (DFT) and time-dependent DFT, we provide the opto-electronic properties of BODIPY core-functionalized dyes to see their applicability in organic DSSC. Our systematic analyses reveal that the 2,6 substituted dyes show better photovoltaic properties compared to the 3,5 substituted ones. On the basis of empirical relationship, we have also calculated the photo-induced electron injection times of some dye-${\text{TiO}}_2$ composites, which seem to be in the ultrafast time scale, thus rendering them a promising candidate for DSSC applications. Our theoretical studies provide that judiciously designed BODIPY core-derived dyes show certain unique spectroscopic and electronic features that make them highly advantageous in DSSC applications as compared to other organic dyes.