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

Abstract

A new series of organic sensitizers LJB-H, LJB-F_o and LJB-F_m 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-F_m 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-F_o). Conversely, due to the resonance effect with respect to cyanoacrylic acid, the ortho-F-substituted LJB-F_o has a larger energy gap but stronger TiO₂ affinity. As a result, LJB-F_o shows better DSSC performance with J_sc = 15.58 mA cm⁻², V_oc = 787 mV, FF = 0.67 and η = 8.22%.