Abstract
Dye-sensitized solar cells (DSSCs) is a relatively new thin film solar cells. In this study DSSCs were fabricated using anthocyanin as natural dye which was extracted from red cabbage (Brassica oleracea var. capitata f. rubra). Naturally pigments are friendly to environment, abundant in supply, easily accessible and highly absorptive in the visible region, all make them good candidates as alternative photosensitizers. In order to obtain a better performance of dye sensitized solar cells, several means to enhance the efficiency of DSSCs were explored. Activation of electrode was done before assembly. TiO2 electrode was activated at 460oC for 30 mins and platinum electrode at 350 oC for 30 mins. Electrode activation can improve the efficiency by 75.9%. Here the short current density (Jsc in mA/cm2) was raised form 2.56 mA/cm2 to 4.34 mA/cm2, and fill factor was elevated from 0.66 to 0.7. No significant change in open circuit voltage. An optimal soaking conditions for electrode were found to have a duration of 10 min and temperature at 40°C. In addition, carbohydrates have been shown to be performance enhancers. Two oligosacchrides, isomaltooligosaccharide (IMO) and xylooligosaccharides (XOS) were tested. The highest efficiency (2.145%) was reached when 300 mg/mL of XOS was used. Deoxycholic acid (DCA) is a common coadsorbent used along with anthocyanin, for it can act as an effective efficiency enhancer. A combination of 300 mg/mL XOS and 40 mM DCA together could boost the efficiency of DSSCs form 1.034% to 2.366% (an accumulative improvement of 128.8%). Impurity fraction (IPF-1) obtained from anthocyanin extract during purification was concentrated, and added back to anthocyanin extract as enhancer. The efficiency was raised from 1.501 to 1.732% (an improvement of 15.3%), indicating that anthocyanin extract contained unknown substances that can enhance the performance of DSSC. They are most likely some kinds of carbohydrates. It seems that we can effectively promote the efficiency using this natural dye without adding anything else, provided an improved process is employed. With the prevailing demand for being natural, our research may provide a good choice for making solar cells in a more natural way and at lower cost.