Ruthenium(II) Photosensitizers with Electron‐Rich Diarylamino‐Functionalized 2,2′‐Bipyridines and Their Application in Dye‐Sensitized Solar Cells

New ruthenium(II) photosensitizers [Ru(dcbpy)(L)(NCS) 2 ] (dcbpy = 4,4′‐dicarboxylic acid‐2,2′‐bipyridine; L = 4,4′‐bis{di[4‐( N , N′ ‐dimethylamino)phenyl]amino}‐2,2′‐bipyridine ( 1 ), 4,4′‐bis[di(4‐methoxyphenyl)amino]‐2,2′‐bipyridine ( 2 ), and 4,4′‐bis[di(4‐tolyl)amino]‐2,2′‐bipyridine ( 3 )) were prepared and characterized and their application in dye‐sensitized solar cells is presented. The optical absorption of these photosensitizers gives a peak at around 540 nm, which is very similar to that of the standard N719. The maximum incident photon‐to‐current conversion efficiency (IPCE) of 80.6 % was obtained for 3 , which corresponded to a power conversion efficiency ( η ) of 5.68 % under standard air mass (AM) 1.5 sunlight (versus N719 at 6.76 %). Molecular cosensitization of 3 with an organic dye, QS‐DPP‐I, yielded higher η values up to 6 % relative to the cells based on individual photosensitizers, and the corresponding IPCE can reach 93.6 % at 549 nm. A preliminary stability test of the devices was also conducted.