Theoretical investigation effects of anchor groups on photovoltaic properties for the C217-based dye sensitizer

Designing and synthesizing high-performable dye sensitizers has kept an important and hot issue in dye-sensitized solar cells (DSSCs). In this work, with the (TiO2)16 cluster, we theoretically investigated the effects of five different anchor groups (–CONHOH, –CSSH, –OH, –PO3H2, and –SO2H) on the photovoltaic properties of the C217 dye by means of density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations coupled with the incoherent charge-hopping model. Results showed that the –CSSH can remarkably narrow the HOMO-LUMO gap, and enhance the dye absorption for the solar radiation. Inversely, the –OH enlarges the HOMO-LUMO gap, and induces the weaker harvest for the sun light. Using the bidentate adsorption model, the power conversion efficiency (PCE) for the C217-(TiO2)16 system was predicted to be as high as 9.72%, which was in excellent agreement with its measured value (9.80%). More interestingly, the DSSC based on the 2-(TiO2)16 system was found to possess an high open-circuit voltage of 0.782 V, large short-circuit photocurrent density of 25.08 mA cm−2 and high fill factor of 0.767, corresponding to a higher PCE of 15.04% than the C217-(TiO2)16, denoting the 2-TiO2 system is a very promising DSSC candidate, and is worth further experimental study.