Synergetic impact of natural light harvesting materials to reduce the recombination rate and improve the device performance of dye sensitized solar cells

Natural pigments extracted from Arachis hypogaea flowers and Cassia grandis leaves were used as novel light harvesting materials for the first time in the fabrication of dye-sensitized solar cells (DSSCs). The extracted individual dyes were labelled as AH, CG and the mixture as AC. The absorption spectra confirmed xanthophyll and chlorophyll pigments in AH, CG and AC with the bandgap of 2.64 eV, 2.7 eV, 2.62 eV. Fourier transform infrared spectroscopy (FTIR) was employed to identify the functional groups present in the dyes. The microstructure, homogeneity, porosity, compositional analysis and roughness of bare and dye loaded TiO2 films were examined using field emission scanning electron microscopy (FESEM), Energy Dispersive X-ray spectroscopy (EDAX) and Atomic force microscopy (AFM). The photovoltaic performance was evaluated through Current-voltage characteristics (J-V), Electrochemical impedance spectroscopy analysis (EIS) and Bode phase plot analysis. The findings revealed that DSSC with co-sensitized dye (AC) exhibited V-oc of 533 mV, J(sc) of 0.42 mA cm(-2) and FF of 0.29 with an improved efficiency that was 1.4 and 2.11 times greater than AH and CG dye based devices respectively. The results proved co-sensitization to be an effective approach to increasing the spectral range and device performance of dye sensitized solar cells.