Photoconversion Efficiency of Titania Solar Cells Co-Sensitized with Natural Pigments from Cochineal, Papaya Peel and Microalga Scenedesmus Obliquus

Three natural pigments obtained from cochineal, papaya peel, and the microalga Scenedesmus obliquus were tested as sensitizers in dye sensitized Titania solar cells. The absorption characteristics of the pigments and the photoelectrochemical parameters were studied to determine the photoconversion efficiency of the cells. The interfacial charge transport processes present in the individually sensitized and the co-sensitized cells were determined by electrochemical impedance spectroscopy (EIS). The highest efficiencies achieved for individual pigments after testing a set of different concentrations were 0.228, 0.093 and 0.064% using cochineal, papaya peel extract and Scenedesmus obliquus extract respectively. 0.36% conversion efficiency was reached in the sensitized cell using a combination of the three pigments. The efficiency reached is in the range of those reported for natural pigments. Papaya peel extract and chlorophylls from Scenedesmus obliquus were examined for the first time as possible sensitizers in DSSC.