Suppressed charge recombination aided co-sensitization in dye-sensitized solar cells-based natural plant extracts

Abstract

The pigments extracted from striga hermontheca, boungainvillea and momordice charantia labeled SH, BG and MC, respectively and their mixed dyes at 1:1 by volume labeled SH:MC, BG:MC and BG:SH were successfully deployed as sensitizers in fabrication of nature-based dye sensitized solar cells (DSSCs). The morphology of TiO2 as the photo anode was studied using scanning electron microscopy (SEM). The absorption, functional group, photovoltaic parameters, electrochemical impedance spectroscopy (EIS) and stability of the dye pigments and cells were studied using UV-Vis spectrophotometer, FTIR spectrometer, Keithley source meter equipped with solar simulator (2400 series), potentiostat and environmental chamber, respectively. A more positive interaction is expected as the derived dyes come from three different natural sources because they work mutually in nature. Co-sensitization of dyes showed synergistic activity with improved cell performance of 12–24-fold higher than that sensitized with any of the single dye. The cells based on mixed dyes retained ca. 18 %, 15 % and 36 % for SH:MC, BG:MC and BG:SH, respectively at 60℃ for 30 min compared with the DSSCs-based single dyes which suffered more severe degradation. Also, EIS measurements show all the cell based on mixed dyes have longer electron lifetime τnthan the cells based on single dyes. Likewise, electron collection efficiency ηcc values of the cells based on mixed dye are higher than the cells based on the single dyes. Among the cells-based mixed dyes, BG:SH has the longest τn and highest ηcc values of 18.16 ms and 0.64, respectively, which suggest better suppression of recombination for efficiency enhancement.