Heteroleptic Ruthenium Sensitizers with Hydrophobic Fused‐Thio­phenes for Use in Efficient Dye‐­Sensitized Solar Cells

Abstract

AbstractTwo fused‐thiophene‐containing ruthenium sensitizers, [Ru(Hdcbpy)(ottip)(NCS)2]–·0.5[H]+·0.5[N(C4H9)4]+ [Z1, H2dcbpy = 4,4′‐dicarboxy‐2,2′‐bipyridine, ottip = 2‐(5‐octylthieno[3,2‐b]thiophen‐2‐yl)‐1H‐imidazo[4,5‐f][1,10]phenanthroline] and [Ru(Hdcbpy)(odttip)(NCS)2]–·0.5[H]+·0.5[N(C4H9)4]+ {Z2, odttip = 2‐[6‐octyldithieno(3,2‐b:2′,3′)thiophen‐2‐yl]‐1H‐imidazo[4,5‐f][1,10]phenanthroline}, were designed for use in dye‐sensitized solar cell (DSSC) applications. The fused‐thiophene‐based Z1 and Z2 have stronger light‐harvesting capabilities compared with a non‐fused‐thiophene analog, [Ru(Hdcbpy)(otip)(NCS)2]–·0.5[H]+·0.5[N(C4H9)4]+ [JF‐2t, otip = 2‐(5‐octylthiophen‐2‐yl)‐1H‐imidazo[4,5‐f][1,10]phenanthroline], and a standard N3 dye. The power‐conversion efficiency of the Z1‐ and Z2‐sensitized solar cells were superior (8.70 % and 8.15 %) to JF‐2t‐ and N3‐sensitized solar cells (7.85 and 7.40 %, respectively) under standard AM1.5G full sunlight irradiation. The photovoltaic performance of Z1 was better than Z2, primarily owing to the fact that Z1‐based cells have a higher level of dye loading and less charge recombination, as seen from the electrochemical impedance spectroscopy data. This study not only demonstrates the excellent power‐conversion efficiency of new fused‐thiophene ruthenium sensitizers, but also points to the promise that fused‐thiophene antennas might be a useful molecule in the engineering of ruthenium dyes for DSSCs.