Fruit extracts and ruthenium polypyridinic dyes for sensitization of TiO2 in photoelectrochemical solar cells

Dye-sensitization of nanocrystalline n-type TiO2 was achieved by using fruit extracts as a natural source of sensitizers. Fresh extracts of chaste tree fruit ("maria-preta", Solanum americanum, Mill.), mulberry ("amora", Morus alba, L.) and cabbage-palm fruit ("acai", Euterpe oleracea, Mart) were employed as TiO2 sensitizers in thin-layer sandwich-type photoelectrochemical solar cells. Conversion of visible light into electricity was accomplished with natural sensitizers resulting in I-sc and V-oc, values similar to those obtained employing traditional synthesized dyes. Fill-factor values from 0.40 to 0.61 were obtained with the fruit extracts. The photoelectrochemical performance of such cells and the use of natural sensitizers, as an alternative to commonly used synthetic dyes based on cis- [(debH(2))(2)RuLL'], dcbH(2) = 4,4'-(CO2H)(2)-2,2'-bipyridine and L/L' = SCN-, X-, etc., are discussed. (C) 2003 Elsevier Science B.V. All rights reserved.