Branched and bulky substituted ruthenium sensitizers for dye-sensitized solar cells.

We report on the synthesis, and photovoltaic performances of four novel Ru(ii)-bipyridine heteroleptic complexes TT206-209, incorporating branched and bulkier alkyl chains compared to their linear analogues C106 and CYC-B11 previously reported. In both series, we found that dyes containing 2-methyl-hex-2-yl substitution gave better performances than 1,1-dipropylbutyl. The best overall performance over the four dyes was obtained for TT207 (CYC-B11 analogue), which contains 2-methylhex-2-yl type substitution, achieving an overall PCE of 8.5%. Furthermore, the optimization of TT207/DSSCs, with respect to the dye-uptake solvent and electrolyte composition, led to a maximum PCE of 9.1% under AM1.5 G standard conditions.