Fig. 1. Dye molecular structures and their optical and electronic properties.
a Molecular structures of dyes (NT35, MS4, MS5, and XY1b) and copper complex ([Cu(I)(tmby)2][TFSI] and [Cu(II)(tmby)2][TFSI]2, tmby = 4,4′,6,6′-tetramethyl-2,2′-bipyridine; TFSI = bis(trifluoromethylsulfonyl)imide). b UV–Vis absorption spectra of NT35, MS4, MS5, and XY1b adsorbed on 2.2 μm thick transparent TiO2 films. c Energy levels diagram of TiO2, dyes, and [Cu(I)tmby)2][TFSI].