Abstract
Dye-Sensitized Solar Cells (DSSCs), based on TiO2 and assembled using a dye from Beta vulgaris extract (BVE) with Tetraethylorthosilicate (TEOS), are reported. The dye BVE/TEOS increased its UV resistance, rendering an increase in the cell lifetime; the performance of these solar cells was compared to those prepared with BVE without TEOS. The efficiency η for the solar energy conversion was, for BVE and BVE/TEOS, of 0.89% ± 0.006% and 0.68% ± 0.006% with a current density Jsc of 2.71 ± 0.003 mA/cm2 and 2.08 ± 0.003 mA/cm2, respectively, using in both cases an irradiation of 100 mW/cm2 at 25 °C. The efficiency of the BVE solar cell dropped from 0.9 ± 0.006 to 0.85 ± 0.006 after 72 h of operation, whereas for the BVE/TEOS, the efficiency remained practically constant in the same period of time.
Highlights
The use of natural pigments as sensitizing dyes for the conversion of solar energy in electricity represents a very attractive alternative, due to significant benefits such as low cost, easy processing, environmental friendliness, low human toxicity [1,2], etc
Absorption spectra of the Beta vulgaris extract (BVE) and BVE/TEOS were analyzed, both diluted in water at pH = 3.5, with the spectrophotometer at wavelengths between 260 and 800 nm, but only showing the area of interest, between 300 and 700 nm
The BVE/TEOS was prepared from the lyophilized powder to be used in the solar cell: 79.1 mg of modified-dye sensitizer powder was dissolved in 25 mL of distilled water; the pH was adjusted to 3.5 by the addition of an aqueous solution 1N of HCl
Summary
The use of natural pigments as sensitizing dyes for the conversion of solar energy in electricity represents a very attractive alternative, due to significant benefits such as low cost, easy processing, environmental friendliness, low human toxicity [1,2], etc. The efficiencies of solar energy conversion by betalains are 0.67% from beetroot (Beta vulgaris), compared to anthocyanins as dye sensitizers, slightly higher efficiencies (η) [6] This is rather low compared with efficiencies of 10 to 11% for a dye-sensitized based on ruthenium [2,16,17,18,19,20], one of the key of this disadvantage is the ratio of the rates of injection and recombination electron transfer [9,16,21], other parameter key is the rate at which the oxidized dye reacts with the reduced form of the redox mediator, which is typically I−/I3− [6]. To overcome the solvent evaporation problem, some authors have been working to improve the electrolyte and cell encapsulation [1,2]; for the second problem and by betalains, this present work proposed the use of Tetraethylorthosilicate as photodegradation inhibiting agent to decrease the UV degradation with a concomitant increment in the lifetime of the cell
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