Aggregation of chalcogenoxanthylium-based sensitizers in dye-sensitized solar cells

Efficient solar-to-electrical energy conversion requires a large overlap between the solar spectrum and the absorption spectrum of the photoactive electrode. This presentation will focus on a novel class of dyes which undergo aggregation-induced spectral changes, resulting in enhanced performance of dye-sensitized solar cells. Rhodamine derivatives with heavier chalcogen heteroatoms shift the absorbance maximum to correspond to the maximum in the solar spectrum, thus mimicking the more costly transition metal-based dyes. The intramolecular geometry of the novel dyes has also been tailored to promote aggregation on the titania surface for the purpose of widening the absorption bands and enabling higher surface coverages. Preliminary data show incident photon to current efficiencies of greater than 50% over a 100-nm window, and greater than 20% throughout the visible region.