Impact of Extraction Methods upon Light Absorbance of Natural Organic Dyes for Dye Sensitized Solar Cells Application

Aqueous extraction, cold ethanol, and Soxhlet hot ethanol extraction methods were used to study the general trend in performance of dyes as sensitisers for dye sensitized solar cells (DSSC) from different plants based on optical absorbance, and consequently light harvesting efficiency (LHE). Spathodea campanulata, Thevetia peruviana, Hibiscus sabdariffa, Delonix regia and Acalypha wilkesiana ‘Haleakala’ were used in this study. From the UV/Visible spectrophotometer with the recorded absorption measurements in the range between 300 – 700 nm, the cold ethanol and Soxhlet hot ethanol extracts exhibited LHE between 80 – 100% over 400 ~ 550 nm of visible range, and 40 – 99% for water extracts dyes between 400 – 700 nm. Ethanol extract of Acalypha wilkesiana ‘Haleakala’ had the highest LHE and a widely spread optical spectrum between 400 – 700 nm; it was earmarked as a potential sensitizer candidate for DSSC. The phytochemical screening was applied to detect the presence of anthocyanins, quinones, cuomarines and others in the extracts. Based on the phytochemical screening, there was no appreciable impact of the extraction methods on the presence of the organic compounds relative to individual samples; and also the optical absorption showed that no extraction method was found consistently better than the other in all extracts.