Metal-Free Benzodithiophene-Containing Organic Dyes for Dye-Sensitized Solar Cells

Two new metal-free organic dyes, CR29 and CR52, with high extinction coefficients in the visible spectral region between 400-650 nm, have been synthesized. The donor-acceptor structure of the dyes feature benzodithiophene moieties BDT1 and BDT as rigid ?-conjugated spacers, which have so far been very little studied for dye-sensitized solar cell (DSSC) applications. DFT/TDDFT calculations have been employed to guide the design of the chromophores as well as to shed light on their electronic and optical properties. Photophysical and electrochemical characterization studies have been carried out to gather information on the charge transfer processes occurring at the dye-semiconductor interfaces. Under standard AM 1.5 conditions, DSSC sensitized with CR29 showed good conversion efficiencies: 5.14 % in the liquid electrolyte cell setup and 2.47 % in the solid-state DSSC.