Enhanced photovoltaic performance of dye-sensitized solar cells-based Carica papaya leaf and black cherry fruit co-sensitizers
Amarachukwu N. Ossai, Sabastine C. Ezike, P. Timtere, A. D. Ahmed
Abstract
Natural dye sensitizers are attractive as an alternative to expensive and rare organic sensitizers in dye-sensitized solar cells. The partial absorption of solar spectrum by solar cell-based natural dye negates its usefulness as the power conversion efficiency (PCE) is poor. Co-sensitization of two or more natural dyes with variant absorption spectra could be a feasible solution. Herein, Carica papaya leaf (P) and black cherry (B) fruit dye extracts were prepared and used as co-sensitizers at different volume concentration ratios (B:P=1:3, B:P=1:1 and B:P=3:1). The optical performance analysis shows that the light-harvesting ability of the device optimized after the co-sensitization at B:P=3:1 significantly improved. The DSSCs-based B and P show PCEs of 0.25% and 0.29%, respectively. The DSSC-based B:P=3:1 shows the highest PCE of 0.56%. Further investigation using cyclic voltammetry (CV) shows that DSSC-based B:P=3:1 has the smallest electron-injection barrier (ΔEe) among all the fabricated DSSCs while DSSC-based B has the highest ΔEe. Also, electrochemical impedance spectroscopy (EIS) reveals that the DSSC-based B:P=3:1 has the least charge flow resistance, thereby reducing charge recombination in the device. Meanwhile, the radius of the DSSCs-based B arc is the largest depicting presence of high charge flow resistance thereby increasing charge recombination in the device. The co-sensitizer, (B:P=3:1), compensates for absorption defects of single dye ((B or P) and improves the photo-response current. Also, it suppresses the charge recombination in the device and improves the PCE of the device.