Natural Sensitizers and Their Applications in Dye-Sensitized Solar Cell

Abstract

Many organic, inorganic and natural dye sensitizers have been trailed in the past in an attempt to reduce the cost, improve the performance and make the dye-sensitized solar cell (DSSC) technology more environment-friendly. Ruthenium-based complexes are by far the most efficient dye sensitizers and have been commercially used in DSSC technology and achieved approximately 12–14% conversion efficiency. But the problems associated with ruthenium complexes are high cost and toxicity which drive the researchers to identify new metal-free and environment-friendly dye sensitizers such as organic and natural sensitizers. In this regard, natural dye sensitizers due to their low-cost extraction and environment-friendly nature are becoming a new area of research in the field of DSSC technology. These dye sensitizers are naturally occurring dye pigments, such as chlorophyll, betanins, carotenoids, anthocyanins and tannins extracted from flowers, leaves, stems and roots of plants using water, acetone and/or alcohols. At present, the efficiency of natural dye sensitizers is quite low compared to ruthenium-based dye due to selective light absorption. Recently, highest recorded efficiency of 2% has been reported using cocktail of natural dyes extracted from flowers. Attempts have been made to improve the performance of natural dye sensitizers by making cocktails and/or by using a variety of solvents for the extraction of dye molecules.