The structure–property relationship of organic dyes in mesoscopic titania solar cells: only one double-bond difference

A photosensitizer plays a crucial role in the conversion of solar light to electricity in dye-sensitized solar cells (DSCs). Thereby an all-sided apprehension on its structure–property relationship should to a large extent expedite rational material design. In this paper, we investigate some general impacts of one double-bond variation upon the optoelectronic features of three pairs of cyanoacrylic acid dyes. One double-bond insertion between a triphenylamine electron donor and π-conjugated heterocycles such as thiophene, 3,4-ethylenedioxythiophene and 4,4-dihexyl-4H-cyclopenta[2,1-b:3,4-b]dithiophene endows a bathochromic effect in terms of electronic absorption of a dye-coated titania film, but leads to a relatively lower electron injection yield as indicated by transient emission measurements. Moreover, this style of one more double-bond incorporation brings forth a lower open-circuit photovoltage, owing to the occurrences of a downwards shifted titania conduction band edge and an augmented rate constant of charge recombination at the titania/electrolyte interface as revealed by electrical impedance analyses.