Synthesis of novel isophorone-based dyes for dye-sensitized solar cells

Abstract

Four organic dyes containing isophorone as the π-bridge unit were synthesised and their photophysical and electrochemical properties were characterised. They were then used to fabricate dye-sensitised solar cells. Arylamine derivatives and cyanoacrylic acid functioned as electron donors (D) and electron acceptors (A), respectively, to form a D–π–A system without the need for a Pd catalyst. YC-1, with a long chain hexyloxy group and a strong phenothiazine donor moiety, improved both the open-circuit voltage (V_oc) and short-circuit current (J_sc) and reduced charge recombination. The optimum device had a J_sc of 14.86 mA cm⁻², a V_oc of 0.67 V, a fill factor of 0.62 and a photon-to-current conversion efficiency of 60% at 385–605 nm, corresponding to an overall conversion efficiency of 6.18%. The photophysical properties of the dye-sensitised solar cells were analysed using a time-dependent density functional theory model with the B3LYP functional. The electronic nature of the devices was elucidated using electrochemical impedance spectroscopy and controlled intensity modulated photo spectroscopy.