Dual-biowaste-based dye-sensitized solar cells using natural chlorophyll dye and natural counter electrode derived from fallen leaves

For facing the environmental challenge induced by the arbitrary release of biowaste, numerous renewable biowastes have served as raw materials for valuable biomaterials, including biowaste-derived natural dyes (BND) and biowaste-derived carbon materials (BCM). The emergence of dye-sensitized solar cells (DSSCs) has paved the way for the application of the BND and BCM in energy conversion field. We investigated the configuration and photovoltaic performance of a dual-biowaste-based DSSCs using the BND as a natural photosensitizer and the BCM as a natural counter electrode catalyst, with emphasis on understanding the influence of the molecular structure of chlorophyll in the BND and the porous structure of the BCM upon the device performance. The BND and BCM were fabricated employing both fallen leaves as the raw materials through facile technique. The chlorophyll with keto C=O in the mulberry leaf extracted BND displays more integrated porphyrin structure than that without keto C=O in the plantain leaf extracted BND, giving the device higher photocurrent density. In contrast, compared with the mulberry leaf pyrolyzed BCM, the plantain leaf pyrolyzed BCM possesses better electrochemical performances owing to its own larger surface areas, more developed mesopore and ordered tubular macropores, which brings about higher fill factor for the device. Consequently, the conversion efficiency (η) of the dual-biowaste-based DSSCs employing the mulberry leaf-derived BND and plantain leaf-derived BCM is 0.28%. Moreover, the BCM used as the catalyst in a typical N719 sensitized cells has higher η in comparison with the graphite, thanks to its own unique porous structure and dual-doped amorphous carbon skeleton with oxygen-containing groups. The η of 1.28% and 1.51% are, respectively, obtained for the mulberry and plantain leaves-based device, whereas that of 0.77% is achieved for the graphite-based one. These results obviously exhibit a facile biowaste valorization into valuable BND and BCM used in energy conversion field.