Design of novel efficient sensitizing dye for nanocrystalline TiO2 solar cell; tripyridine-thiolato (4,4′,4″-tricarboxy-2,2′:6′,2″-terpyridine)ruthenium(II)

We have designed tripyridine-thiolato (4,4′,4″-tricarboxy-2,2′:6′,2″-terpyridine)ruthenium(II) [complex 1], a novel efficient sensitizing dye for dye sensitized TiO2 solar cells, based on the DFT MO calculations with PBE0 functional. Complex 1 is a modified BD (black dye: trithiocyanato (4,4′,4″-tricarboxy-2,2′:6′,2″-terpyridine)ruthenium(II) complex) molecule where NCS ligands of BD are replaced by C5H4NS ligands. Molecular and electronic structures of complex 1 have been theoretically characterized. Complex 1 is expected to have the following two advantages over BD, in addition to the advantage of high electron transfer rate from the photoexcited dye to TiO2 realized in BD: (1) higher electron transfer rate from redox systems to oxidized dyes; (2) higher absorption efficiency to solar spectrum. We propose complex 1 as a novel efficient sensitizing dye which provides the higher efficiency than does BD for dye sensitized solar cells.