Enhanced photocurrent generation by folding-driven H-aggregate formation

A novel bis(merocyanine) dye has been synthesized and its folding and aggregation behavior has been elucidated in dependence on the solvent polarity. Extended cofacially pi-stacked H-aggregates could be prepared in nonpolar solvents based on the preorganized folded dimer structure of the dye exhibiting a more than 120 nm hypsochromic shift of the absorption band. Furthermore, incorporation of such H-aggregate domains in bulk heterojunction (BHJ) solar cells by careful adjustment of processing conditions afforded a nearly twofold increase in the photocurrent generation. Our detailed investigations on the external quantum efficiencies of these blends reveal that the increase of the short-circuit current density J(SC) stems from the H-aggregated dye manifold in the photoactive layer of the solar cell devices.