Exploring the effect of mono- and di-fluorinated triphenylamine-based molecules as electron donors for dye-sensitised solar cells

Dye that is consisting of donor-π-π-linkers-acceptor (D-π-π-A) is characterised by enhancement of light-harvesting capability in dye-sensitised solar cell (DSSC) applications. In this work, the DFT and TDDFT using the CAM-B3LYP XC-functional with 6-31G+(d) basis set and were used to study the geometrical, electronic, and photovoltaic properties of four dyes. Two of the investigated dyes are previously reported as successful photosensitisers with power conversion efficiencies of 8.22 and 7.0%, and two are novel designed ones. The investigated dyes are based on triphenylamine (TPA) as electron-donor and cyanoacrylic acid (CA) as electron-acceptor groups, and two π-linkers, i.e. dihydrothieno-dioxine (DHO) and fluorophenylene (FP). The four dyes are different in the FP unit which has Fluorine (F) atom/s in different position and with a different number. The study aims to: (1) justify the reported superiority performance of T2FC (with one F atom at the ortho-position with respect to the CA unit) over the T3FC (with one F atom at the meta-position), and (2) explore the effect of incorporating another F atom at the second ortho-position (T26FC) or at the meta-position (T35FC). The results are supported by the data obtained from calculations of adsorption parameters of dyes adsorbed on (TiO₂)₂₄ anatase (1 0 1).