Investigation of Tropical Plant‐based Natural Dyes Combination and Adsorption Optimization for Natural Dye‐sensitized Solar Cell

Dye-sensitized solar cells (DSSC) are one low-cost, easy fabrication solar cell with relatively high solar energy conversion efficiency that has been widely studied in the past decades. Environmentally friendly natural dyes are one of the most investigated candidates for the currently using ruthenium dyes; however, the efficiency is still low. In this study, three different tropical plants Calathea veitchiana (C), Begonia maculata (B) leaves, and Delonix regia (D) flowers were selected as dye sensitizers for TiO2 based DSSCs using the visible light absorption intensities and wavelength distributions. All the three plant extracts showed good solar energy conversion efficiency, and the C and D mixtures showed 24% more energy conversion efficiency promotion than that of the highest individual dyes. Our study also indicated that while the blend of natural plant extracts increased the short circuit current (J(sc)) benefited from the broader visible light absorption, the complexity of the mixture could reduce the performance of the solar energy conversion rate by affecting the open-circuit voltage (V-oc). Our specially designed adsorption and desorption process using polarity different solvents significantly improved the conversion efficiency to as high as 1%. The final energy conversion rate is about 40% higher than that of the highest single plant extracts (0.72%). In summary, our study builds relatively high-efficiency natural dye-based DSSC using the combined extracts of two tropical plants with a concise screening process and provides a rapid approach to study the natural dye combinations in DSSCs studies.