Natural dye extracts from fruit peels as sensitizer in ZnO-based dye-sensitized solar cells

As a result of twin problems of environmental pollution and continuous depletion of fossil fuels, a search for renewable and clean energy sources is necessary. This paper discusses the simple extraction techniques without any further purification of natural dyes from some fruit peels and their performance in DSSCs. Natural dyes extracted from fruit peels of Carica papaya, Citrus lanatus, Persea americana and Solanum melongena were used as sensitizers to fabricate ZnO-based dye-sensitized solar cells (DSSCs). The extracts of the natural dyes were characterized and studied using UV-Vis absorption spectroscopy, Fourier transforms infra-red (FTIR) and Photoluminescence (PL) spectroscopy. The photo-anode semiconductor material was prepared and characterized. The photo-voltaic characteristics of the fabricated DSSCs were measured under simulated solar light (power of incident light 100 mWcm^-2 from Air Mass 1.5G). These studies indicated the presence of pheophytin 'a' in most of the extracts studied as the main pigments with other accessory pigments. The solar to electric conversion efficiencies for the pheophytin 'a' dye based solar cells are estimated as 0.017%, 0.013%, 0.010% and 0.011% for Carica papaya, Citrus lanatus, Persea americana and Solanum melongena, respectively. The dye extracts from Carica papaya exhibits higher photo-sensitized performance compared to the other extracts and this is due to the better charge transfer between the dyes of Carica papaya and ZnO photo-anode surface. Conversion of visible light into electricity was accomplished with natural dyes and ZnO-based DSSCs, resulting in excellent photo-electric properties compared to those in literature.