Optimizing a Simple Natural Dye Production Method for Dye-Sensitized Solar Cells: Examples for Betalain (Bougainvillea and Beetroot Extracts) and Anthocyanin Dyes

Abstract

We present a study about the sensitizers extracted from natural resources. This paper focuses on how to select, extract and characterize natural dyes, giving some guides to establish a protocol for the whole process of fabricating and using these dyes. The influence of the extraction solvent and method, and of parameters such as pH are analyzed. Also, dye precursor and dye extract stability have been studied, as well as how the dye adsorbs onto substrates and the effect of mixing or concentrating the extracts. Results concerning betalain pigments present in bougainvillea and beetroot extracts, and anthocyanins in eggplant extracts, analyzed by using UV-Vis spectrometry, are included. As an example of application, we report procedures intended to test and enhance the dye potential as a main component of dye-sensitized solar cells (DSSCs). DSSCs mimic nature’s photosynthesis and have some advantages like an easy and low-cost fabrication procedure. Their efficiency depends on its design and fabrication process and also on the different components involved. Hence, optimizing each component is essential to achieve the best performance, and thus the dye used as a sensitizer is crucial. We fabricate cells by using a simple procedure: As the interest is focused on the sensitizer, the same consecutive steps are followed, varying only the dye extract. Among all the natural-dyes tested, beetroot extract reaches up to 0.47% cell efficiency, which is near the highest values found in literature for this pigment.

Effect of using betalain, anthocyanin and chlorophyll dyes together as a sensitizer on enhancing the efficiency of dye‐sensitized solar cell

“…If these solar cells are to be considered as a green energy originator, the more "natural" the dye, the more "green" the cell. 13 Therefore, several researchers are pondering over natural dyes to sensitize titania to be eco-friendly and cheaper than metal complex dyes. [14][15][16][17] This study intended to use three natural dyes (anthocyanin, betalain, and chlorophyll) extracted from various hibiscuses (Roselle) originating from different parts of India (Manipur and Assam), spinach (Spinacia oleracea), coriander (Coriandrum sativum), black rice (Oryza sativa L.) and beetroot (Beta vulgaris).…”

“Paper Dye-Sensitized Solar Cell” Based on Carbon-Nanotube-Composite Papers

“…However, as compared with other flexible DSCs that use CNTs and anthocyanin dye [17], the value was not so high, although there are differences between our DSC and others, e.g., other studies used a TiO 2 -based semiconducting electrode. The efficiency of the other DSCs was from about 0.1% to about 3.2% [3]. For detailed evaluation, theoretical analysis and additional measurement, e.g., for mobility, must be conducted.…”

“…In this study, the maximum value of the FF of our modified DSC was 0.22 (from Equation (2)). Since the FF of general DSCs is from 0.35 to 0.7 [3,39], this needs to be improved. We feel that the maximum power obtained from a DSC can be improved by lowering its series resistance or increasing its parallel resistance.…”

“…A DSC generates electricity by using dyes that absorb light and emit electrons. Since a DSC can generate electricity without using rare metals and can use various natural dyes [3][4][5][6], it can be fabricated at a low cost and is easy to use [7]. Previously, we developed a unique DSC by using carbon nanotube (CNT) paint [8], i.e., a paint-type DSC.…”

Insight into incident photon to current conversion efficiency in chlorophylls

“…[21] Chlorophylls belong to the natural photosynthetic dye, which efficiently harvests the light and the photosynthesis. [22,23] Chlorophyll derivatives are applied as the photosensitizers in the DSSCs because of their ability to absorb blue and red light.…”