Bandgap tunability by synergistic mixture of plant-derived as photo-absorber candidates

The application of natural plant-derived dyes to replace ruthenium-based material as photo-absorber in solar cells application, have been extensively studied and proven. Several advantages such as low cost, abundant in supply, sustain and environmentally-safe make the natural materials as current choice photo-absorber candidates. Natural plant-derived dyes are known containing natural compounds (e.g. carotenoids, chlorophyll, anthocyanin) that have the characteristics of electronic delocalization in extended π-orbital system involving in electronic transfer mechanism. To date, massive investigations were performed to exploit this π-electronic system for further potential application of photo-absorber in solar cells. Hence, the hybrid dyes from the mixture of Pandanus amaryilifolius (pandan, P) and Curcuma longs (turmeric, T) were successfully prepared and several physical characterizations were carried out to analyse the photo-absorber (sensitizer) properties. From the results obtained, by adjusting the ratios of P:T into 1:2, 1:4, 4:1, and 8:1, the wavelength of photo-absorbers were slightly shifted and the indirect bandgap (Eg) values were significantly changed from 2.54 eV and 2.35 eV in P and T to 2.32 eV, 2.30 eV, 2.40 eV and 2.45 eV of P, T, 1 P: 2 T, 1 P: 2 T, 4 P: 1 T, and 8 P: 1 T, respectively. With this new approach, the bandgap of the hybrid dyes as core point in modulating electrical conductivity of photo-absorber can be simply tuned. By implying two different extract dyes to form hybrid dyes, the bandgap was found decreased and much lower with higher ratio of T used. With the smaller bandgap 2.30 eV, the conductivity values of 1 P: 4T increasing from 0.47 mV in P and 0.56 mV in T to 204.26 mV in 1P: 4T. Overall results suggesting that by adjusting the ratio mixture of hybrid dyes solution, the photo-absorber properties and the Eg values were differed and with slight modification method, better electrical conductivity can be expected for solar cells application.