NIR-Absorbing Heptamethine Dyes with Tailor-Made Counterions for Application in Light to Energy Conversion

A method to exchange the counterion of cyanine dyes to Δ-TRISPHAT– and PF6– is presented. The influence of these counterions on the photophysical and electrochemical properties of the cyanine dye in solution is discussed, and tendencies in the solid packing are highlighted by X-ray crystal structures. The compounds were applied in semitransparent bilayer organic solar cells together with C60, and a power conversion efficiency of 2.2% was achieved while maintaining a high transparency level in the visible region of 66%.