Enhanced photovoltaic performance of dye-sensitized solar cells-based Carica papaya leaf and black cherry fruit co-sensitizers

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 (Delta E-e) among all the fabricated DSSCs while DSSC-based B has the highest Delta E-e. 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.

Automated summary

Co-sensitization of Carica papaya leaf and black cherry fruit dye extracts significantly improves the light-harvesting ability of the device, thereby increasing the power conversion efficiency of the dye-sensitized solar cells.