Ragi (finger millet) starch-based gel electrolytes for dye-sensitized solar cell application

Starch was isolated from ragi grains using alkali extraction method. Crystallinity of isolated ragi starch (RGS) was studied using X-ray diffraction technique, and thermal properties of RGS were characterized by differential scanning calorimetry. Novel ragi starch (RGS) based gel electrolyte for dye-sensitized solar cells (DSSCs) was prepared and characterized for the first time. In the first part, the effects of additives guanidinium thiocyanate (GSCN) and N-methylbenzimidazole (NMBI) on the photovoltaic performance of DSSC were investigated. Considerable improvement of open circuit voltage was found in the addition of only NMBI to the electrolyte, while only addition of GSCN has an influence on the short circuit current. Synergetic effects were observed when NMBI and GSCN were used together in the gel electrolyte. In the second part, various weight percentages of multiwalled carbon nanotubes (MWCNTs) were added to observe the cell performance. DSSCs fabricated with the optimum weight percentage (1 wt%) of MWCNT achieved a maximum conversion efficiency of 4.34%, an open circuit voltage (Voc) of 0.803 V, short circuit current density (Jsc) of 9.54 mA cm–2 and fill factor (FF) of 56.59%. Here we reported the novel ragi starch-based gel electrolytes for DSSC application along with the effect of different additives, such as GSCN, NMBI, and various weight percentages of MWCNTs incorporated into the gel electrolyte.