LC13086B- Due to the growing global demand for energy, the development of efficient ways of harnessing solar power has become a key scientific challenge. Among promising low-cost alternatives to silicon photovoltaics, dye-sensitized solar cells based on mesoporous TiO2 films sensitized with the dye Ru(dcbpyH2)2(NCS)2 (N3 dye) have gained prominence due to their relatively high energy conversion efficiencies. In dye-sensitized cells the photocurrent is generated via ultrafast electron transfer from the photoexcited dye sensitizer to the semiconductor. As a result the atomistic nature of the semiconductor/dye interface plays a critical role in the performance of these solar cells. Substantial efforts have been devoted to elucidating the structure of this interface, and yet its atomistic nature remains highly controversial. Here we perform a systematic comparison between measured core-level photoemission spectra at the TiO2/N3 interface and the spectra calculated by us from first principles for a variety of atomistic interface models. This analysis suggests that systematic
hydrogen-bonding between dyes occurs on the TiO2 surface, leading to a supramolecular assembly. The present finding hails a paradigm shift in our understanding of dye-sensitized solar cells and bears on the design of more efficient nanoscale photovoltaics.
