Cyanobacterial Pigments as Natural Photosensitizers for Dye-Sensitized Solar Cells

Three filamentous freshwater cyanobacterial strains were grown at high light intensity to produce lipidic dyes composed of xanthophylls, carotenes and chlorophyll a. The properties of the pigments were evaluated as suitable natural compounds to be applied in dye-sensitized solar cells (DSSC). The assembled DSSC were characterized using the density current vs. potential profiles and electrochemical impedance spectroscopy. With an efficiency of 0.127 %, our results are higher than those previously reported using similar structured compounds from natural sources as algae and cyanobacteria, among others. The best efficiencies were probably related to the strains with high content in pigments probably related to myxoxanthophyll-like derivates and aphanizophyll, carotenoids with many hydroxyl groups able to interact with the semiconductor surface. The stability of the bonding between the dyes and the titanium oxide of the photoelectrode is crucial to ensuring acceptable performance of the DSSC, which was successfully achieved in our experiments with carotenoids with many hydroxyl groups. Our results point to cyanobacterial pigments as a promising source of natural dyes for use in solar cells.