Cyclometalated ruthenium(ii) complexes with bis(benzimidazolyl)benzene for dye-sensitized solar cells†
A series of cyclometalated ruthenium complexes with bis(benzimidazolyl)benzene ligands were prepared and their applications in dye-sensitized solar cells are presented. The Ru(III/II) redox process of these complexes occurs at +0.71 V vs. Ag/AgCl. All complexes show broad absorptions extending into the near-infrared (NIR) region. The length of alkyl chains on the benzimidazole rings were found critical to the device performance. Sensitizer 4b with octyl substituents exhibits the best cell performance under the standard air mass 1.5 sunlight (η = 3.7%, Jsc = 9.85 mA cm−2, Voc = 555 mV, FF = 0.67). The device exhibits appreciable action in the NIR region between 700 and 850 nm.