Molecular Design of Anthracene-Bridged Metal-Free Organic Dyes for Efficient Dye-Sensitized Solar Cells

A series of metal-free organic dyes bridged by anthracene-containing pi-conjugations were designed and synthesized as new chromophores for the application of dye-sensitized solar cells (DSCs). Detailed investigations on the relationship between the dye structures, photophysical properties, electrochemical properties, and performances of DSCs are described. With the introduction of the anthracene moiety, together with a triple bond for the fine-tuning of molecular planar configurations and to broaden absorption spectra, the short-circuit photocurrent densities (J(sc)) and open-circuit photovoltages (V-oc) of DSCs were improved to a large extent. The improvement of J(sc) is attributed to much broader absorption spectra of the dyes with the anthracene moiety. Electrochemical impedance spectroscopy (EIS) analysis reveals that the introduction of the anthracene moiety suppresses the charge recombination arising from electrons in TiO2 films with I-3(-) ions in the electrolyte, thus improving V-oc considerably. On the basis of optimized molecular structures and DSC test conditions, the dye TC501 shows a prominent solar energy conversion efficiency (eta) up to 7.03% (J(sc) = 12.96 mA . cm(-2), V-OC = 720 mV, ff = 0.753) under simulated AM 1.5 irradiation (100 mW . cm(-2)).