Abstract
Eight vegetable dyes extracted from flowers, fruits and leaves abundant in the wide biodiversity of the Andes region of South America were extracted with ethanol without purification to explore as vegetable photosensitizers in dye-sensitized solar cells (DSSCs). The absorbance spectra were measured by UV–visible spectroscopy and the photoelectrical performance of the DSSCs based on these dyes with a homemade solar simulator, constructed only for educational purposes under 1 sun of illumination. The open-circuit voltages (Voc) and the short-circuit photocurrent densities (Jsc) varied from 0.39 to 0.48 V and from 0.04 to 0.56 mA cm−2, and the power conversion efficiency (PCE) ranged from 0.01 to 0.18%. Particularly, the highest Voc and PCE values of the DSSCs sensitized by the ethanol extracts of Mortiño fruit (Vaccinium floribundum) and Jamaica flowers (Hibiscus sabdariffa) without purification were presumably associated with anthocyanin, the most effective component present in both vegetable photosensitizers. Hence, various components of the ethanol extracts obtained from these two vegetable dyes were purified by liquid–liquid extraction using different organic solvents of different polarity, namely petroleum ether, chloroform, ethyl acetate, n-butanol, and distilled water. Ethyl acetate resulted as the most favorable solvent for purification of ethanol extracts from Mortiño fruit and Jamaica flowers to use as vegetable photosensitizers in DSSCs. The PCE of the DSSC fabricated with the dye extracted in ethyl acetate from Mortiño fruit achieved 0.33%, with Voc of 0.520 V and Jsc of 1.014 mA cm−2, whereas the corresponding values obtained from the dye extracted from Jamaica flowers reached 0.22% with Voc of 0.541 V and Jsc of 0.678 mA cm−2. Thus, the purification of vegetable dyes used as photosensitizer impacts the photoelectrochemical performance of DSSCs.
Highlights
dye-sensitized solar cells (DSSCs), regarded as one of the most hopeful category of photovoltaic devices for the conversion of solar energy to electricity, have been widely investigated because of their high theoretical power conversion efficiency (PCE), simple fabrication process, low cost, a great potential for large-scale applications (Cherepy et al 1997; Vekariya et al 2016)
The fill factors of the DSSC sensitized by Mortiño fruit dye extracts and the DSSC sensitized by N719 are comparable 58.2%, and both are lower than the DSSC sensitized by Jamaica flowers dye extract (60.5%). These results suggest that the interaction between the photosensitizer and the active sites onto nanoporous TiO2 film is significant in enhancing the energy conversion efficiency of DSSC sensitized by Mortiño fruit rather than Jamaica flowers
The photoelectrochemical performance of the DSSCs photosensitized with the extracts of these vegetable dyes showed that Jsc varied from 0.04 to 0.56 mA, the Voc was in the range of 0.39-0.48 V, and the PCE fluctuated from 0.01 to 0.18%
Summary
DSSCs, regarded as one of the most hopeful category of photovoltaic devices for the conversion of solar energy to electricity, have been widely investigated because of their high theoretical PCE, simple fabrication process, low cost, a great potential for large-scale applications (Cherepy et al 1997; Vekariya et al 2016). The major components of DSSCs are photo-electrodes, photosensitizers, electrolytes, and counter electrodes (Scheme 1). Among these four major components, photosensitizers categorically play an important role, as they are the origin of light harvesting in DSSCs (Vekariya et al 2016). DSSCs reach a maximum PCE around 13% by using a porphyrin photosensitizer and graphene nanoplatelets (GNPs) as a counter electrode (CE) (Calogero et al 2015; Salam et al 2015). Metal organic dyes (ruthenium polypyridil complex) have been used as efficient photosensitizers for DSSCs. In laboratory scale, a PCE of 11.1% has already been achieved by exploring ruthenium (Ru-based complex dye) N-719 attached to the TiO2 under 1 sun illumination (Calogero et al 2015). The preparation routes for metal complexes are often based on multi-step reactions involving long, tedious and Ramirez‐Perez et al Renewables (2019) 6:1
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