Performance enhancement of dye-sensitized solar cells based on anthocyanin by carbohydrates

Dye-sensitized solar cells (DSSCs) were fabricated using anthocyanin extracted from red cabbage (Brassica oleracea var. capitata f. rubra). Carbohydrates were found to be excellent performance enhancers that functioned in a dose-dependent manner. Different types of carbohydrates generally had different enhancement capabilities in the order of oligosaccharide > disaccharide > monosaccharide > polysaccharide. The enhancement capability was also highly dependent on the constituents of carbohydrates. Two oligosaccharides, Isomalto-oligosaccharide (IMO) and xylooligosaccharide (XOS), showed the highest capability. The DSSCs sensitized with them as additives to anthocyanin exhibited a power conversion efficiency (η) over 1.6% (an improvement of 60%) with a short-circuit current (JSC) of about 4 mA/cm2, and open-circuit voltage (VOC) around 630 mV. The mode of interaction of anthocyanin with extrinsic carbohydrates was proposed and discussed. The use of carbohydrates and a common coadsorbent deoxycholic acid (DCA) together could induce an additional enhancement, which boosted the efficiency up to 1.87% (an accumulative improvement of 90%). This study provided a choice of a promising and powerful enhancer for the DSSCs based on natural anthocyanins.