Computational and experimental study of betalains, natural dyes to be used in dye-sensitized solar cells (DSSC)

Aware that the world's energy supply is in danger due to the reduction of fossil fuel reserves, in particular oil, and its detrimental effects on the environment, as the main cause of global warming, it is urgent to focus efforts on the development of renewable energy generated from natural resources such as sunlight, wind, rain, tides and geothermal heat. The search for these alternative sources is one of the most important challenges that humanity currently faces. Among these alternative sources, the sun has the potential to make the greatest energy contribution, since only one hour of solar radiation (3.8 × 1023 kW) is enough to satisfy the human energy demand for one year (1.6 × 1010 kW in 2005). Plants are the ones that make best use of solar energy, through photosynthesis, while man can take advantage of it by using solar cells to generate electricity, these solar cells work with certain materials capable of absorbing more or less solar energy. In this work we will focus on third generation solar cells, specifically those of the DSSC type (or dye-sensitized solar cell) that use a photosensitive compound as a solar energy collector, this compound can be an organic, natural or synthetic dye. With this research, it is intended to carry out a computational and experimental study that allows a better understanding of the relationship between the molecular structure of the dye of interest, its electronic and photo-physical properties and its efficiency in DSSC cells. The computational study will be developed using the Theory of Functional Density (DFT) and the TDDFT (time-dependent DFT) approach, to calculate the electronic and optical properties of some of the compounds belonging to the Betalain family, which are a group of natural dyes that are found predominantly in fruits and flowers, of which about seventy derivatives have been described so far, in order to determine their possible use as sensitizing dyes in DSSC cells. For each colorant, computational data will be obtained, such as HOMO-LUMO gap, wavelength of maximum absorption (max), light harvesting efficiency (LHE), open circuit voltage (Voc), among others, which will be They will be compared with the experimental data obtained by measuring the photovoltaic parameters of the cell made with the use of the chosen dye. Experimentally, the main parameters that characterize the photovoltaic performance of DSSC-type cells will be established, that is: IPCE (efficiency in the conversion of incident photons to generated electrons); Voc (Open Circuit Voltage), Isc (Short Circuit Current); FF (Fill Factor) General conversion efficiency (η) and IV curves with which the photovoltaic performance of a DSSC can be evaluated based on the parameters Voc, Isc, FF and η. This study will allow expanding the knowledge associated with the generation of clean energies and in a novel way, it seeks to combine scientific research with the SDGs (Sustainable Development Goals) and with the challenge proposed by the Faculty of Basic Sciences of the University of Medellín, when addressing the subject in Science of Materials, specifically compounds that can be used to benefit the environment.

Objectives-General: Computationally determine which natural dyes, belonging to the Betalain family, can be used as sensitizers in DSSC cells and corroborate them experimentally by studying the main associated photovoltaic parameters. -Specific1. Computational study of dyes belonging to the Betalain family with potential use as dyes for DSSC.2 type cells. Calculate the photovoltaic parameters of the dyes and determine which of these have the best photovoltaic properties for use in DSSC-type cells.3. To experimentally validate some of the dyes studied computationally, through their use in DSSC cell models.

This research aims to carry out a computational and experimental study of the dyes belonging to the Betalain family, natural compounds that can be used in DSSC cells and of which around seventeen derivatives have been described so far, which allows a better understanding of the relationship between the molecular structure of the dye of interest, its electronic and photo-physical properties and its efficiency in DSSC cells. For the vast majority of Betalains, no research has been reported in which they have been studied using the DFT computational tool and DFDFT. Except for betanidin, isobetanidin, indicaxanthin and portulaxanthin, these, like betanin, contain functional groups that are very good electron donors, an important property in dyes to be used in DSSCs. Among the compounds to be studied from the betalain family are: Betanin , Isobetanin, probetanin, neobetanin, vulgaxanthin, miraxanthin, portulaxanthin, indicaxanthin, dopaxanthin, muscaurin, portulacaxanthin, alanine-Bx, methionine-Bx, phenylalanine-Bx, phenelethylamine-Bx. “-decarboxyBetanin, among others