Donor–acceptor dyes with fluorine substituted phenylene spacer for dye-sensitized solar cells

A new series of organic sensitizers LJB-H, LJB-Fo and LJB-Fm with triphenylamine, 3,4-ethylenedioxythiophene plus various functionalized phenylenes, and cyanoacrylic acid as the donor, π-spacer, and anchoring group, respectively. These organic sensitizers exhibit much higher molar extinction coefficients than the parent LJ1 dye as well as reveal a remarkable fluorine substituent effect. LJB-Fm with fluoro substitution at the meta position relative to cyanoacrylic acid possesses a lower S0–S1 gap and weaker coupling with the TiO2 electrode (cf.LJB-H and LJB-Fo). Conversely, due to the resonance effect with respect to cyanoacrylic acid, the ortho-F-substituted LJB-Fo has a larger energy gap but stronger TiO2 affinity. As a result, LJB-Fo shows better DSSC performance with Jsc = 15.58 mA cm−2, Voc = 787 mV, FF = 0.67 and η = 8.22%.