Modification of nonlinear optical dyes for dye sensitized solar cells: a new use for a familiar acceptor

The chemistry of electron deficient π-acceptors offers unique challenges in the rational design and synthesis of organic dyes for use in solar cells. We have synthesized 2-cyano-2-(3-cyano-4-((E)-4-(dibutylamino)styryl)-5,5-dimethylfuran-2(5H)-ylidene)ethanoic acid (2), a dye containing an carboxylated version of the strongly electron withdrawing TCF group by way of stepwise synthesis and isolation of 2,5-dihydro-2-imino-4,5,5-trimethylfuran-3-carbonitrile (5), previously only available as an intermediate available via microwave chemistry. We use this dye to sensitize nanocrystalline TiO2 in order to examine its efficacy in dye-sensitized solar cells. Crystal structures of an intermediate and the final dye are presented and the isomerization about the terminal alkene is discussed in addition to preliminary solar cell data.