Highly efficient ruthenium complexes with acetyl electron-acceptor unit for dye sensitized solar cells

Abstract

Two ruthenium complexes sensitizers RC-61 and RC-62 with acetyl electron-acceptor ancillary ligands are reported for highly efficient dye-sensitized solar cells, of which RC-62 obtains a power conversion efficiency of 9.10% compared to 8.23% for the conventional N3 dye. Dye-sensitized solar cells based on RC dyes receive a satisfactory photocurrent density (16.82 and 17.78 mA cm−2 for RC-61 and RC-62, respectively) attributable to the acetyl units ancillary ligands. The electrochemical measurement manifest that the acetyl electron-acceptor group is beneficial to stabilize the highest occupied molecular orbital and the lowest unoccupied molecular orbital levels, which are conducive to the processes of dye regeneration and electron injection. The kinetics of dye recombination and regeneration are investigated by transient absorption spectroscopy. The faster rate of the RC-62 dye cation decay is, the higher efficiency of regeneration process contributing a higher photocurrent. Besides, RC-62 dye exhibits a good long-term stability and maintains more than 92.6% of the initial power conversion efficiency under light soaking for 1000 h. The above conclusions strongly corroborate the superiority of acetyl ancillary ligands at enhancing photocurrent density and power conversion efficiency, propose a strategy to develop ruthenium complexes sensitizers.