Co-sensitization effect of chlorophyll and anthocyanin on optical absorption properties and power conversion efficiency of dye-sensitized solar cells

Abstract

In this article, the chemical structure, optical absorption and photoluminescence properties of un/adsorbed dyes of hibiscus flower (H), pumpkin leaf (P), sweet potato leaf (S) and their composites (H: P & H: S) have been studied. The chemical structural properties revealed the O–H, C–C and C = O as the main anchoring functional groups. The optical absorption properties revealed two definite bands in between 450–500 nm and 600–680 nm wavelength for chlorophyll-based dyes and a peak at 526 nm for anthocyanin based dye extract. The composite dye extracts revealed optical absorption bands corresponding to chlorophyll and anthocyanin pigments with enhanced absorption of light. Five different solar cells based on H, P, S, H:P-3:1 and H:S-3:1 were developed and revealed an efficiency of ~ 0.08, 0.3, 0.5, 0.7 and ~ 1% respectively. The efficiency was reduced by half after 30 days. The composites had the highest power conversion efficiency due to more O–H, C–C and C = O binding sites on TiO2 nanoparticles, reduced rate of electron–hole pair recombination and a wide range of optical absorption. These studies suggest that co-pigmentation can be an alternative strategy to increasing the power conversion efficiency in DSSCs.