Fabrication of dye-sensitized solar cells using chlorophylls c1 and c2 and their oxidized forms and from Undaria pinnatifida (Wakame)

Two different types of chlorophyll c (c1 and c2) and their oxidized forms ( c 1 ′ and c 2 ′ ) were isolated from a brown seaweed, Undaria pinnatifida, and their structures were determined by mass spectrometry and 1H NMR spectroscopy. The order of conversion efficiencies in titania-based solar cells using these chlorophyll sensitizers, i.e., c 2 ( 4.6 % ) > c 1 ( 3.4 % ) > c 2 ′ ( 2.6 % ) ≧ c 1 ′ ( 2.5 % ) , were explained in terms of a more extended conjugated system and the resultant higher electron densities in Chl c2 than Chl c1 as well as the different configurations and electron densities of the vinyl carboxyl group in Chls c 2 ′ and c 1 ′ .