Study on combination of natural red and green dyes to improve the power conversion efficiency of dye sensitized solar cells

In this paper, natural red dye extracted from beetroot (Beta vulgaris) and green dye extracted from spinach (Spinacia oleracea) was used as a sensitizer source for natural dye-based dye-sensitized solar cells (DSSC). DSSC, sensitized with natural red and green dyes yields low cell performance, i.e, for red dye efficiency obtained was, eta = 0.56% and for green dye, eta = 0.49%. Here to improve the cell performance, these two dyes (red and green) were combined at different volume ratios in order to get the maximum cell efficiency and the optimum dye combination ratio. From the UV absorption spectrum, the combination of dyes showed a wide absorption spectra and higher absorbance in the visible solar spectrum than both the single individual red or green dye. By the optimized combination of dyes (80% red + 20% green) co-sensitized DSSC, the observed cell parameters were, Isc = 4.65 mA, Voc = 386.7mA and FF = 0.55. DSSC co-sensitized with the optimum combination of red and green dyes, the maximum cell efficiency obtained was 0.99%, which is almost 2 and 1.77 times higher than that of the single individual red and green dyes.