Push-pull triphenylamine based chromophores as photosensitizers and electron donors for molecular solar cells

Abstract

A series of pushepull chromophores (1e6) comprising triphenylamine as donor and methylenethiazole, bearing electron-withdrawing groups in the 20 position, as terminal acceptor groups have been developed. The resulting dyes were characterized by UVevis and fluorescence spectroscopies, cyclic and OSWV voltammetries and thermal analysis. The low energy absorption band of these oligomers was located at 583e705 nm in solution. A significant positive solvatochromism, with excellent correlation with the KamleteTaft constant, was found confirming the charge transfer character of this band. Theoretical studies reveal a partial quinoid character in these compounds and a reduced band gap HOMOeLUMO energies of 1e6 derived from electrochemical and optical measurements were found to be suitable for their use as donor materials in combination with PCBM as acceptor in planar heterojunction solar cells. The studied devices, based on stacked cells connected electrically, incorporating these low band gap chromophores exhibited reasonable conversion efficiencies of up to 0.91% under air mass (AM) 1.5G illumination.