New Cu-based Dyes for application in Dye Sensitized Solar Cells (DSSC), Organic Light Emitting Diodes (OLEDs) and water splitting : an experimental and computational study

Casademont Reig, Irene
Nowadays, one of the most prolific chemical research lines is the one which analyzes the molecules used in solar cells based on dyes, called Dye-Sensitized Solar Cells (DSSC). These solar cells are a promising alternative to the silicon photovoltaic cells because they are easier to build and very cheap. The challenge today is to improve the yield of DSSC to increase its use in the transformation of sunlight into electricity and promote one of the most abundant sources of renewable energy. The dyes used in DSSC also have other applications such as in organic LEDs (Light Emetin Diodes) devices and in the water splitting process, particularly in the reduction of water in H2. For this reason, in this project, it has been studied computationally a family of sixteen copper photosensitizers, which three of them have been synthetized and characterized in the laboratory. In the computational study, we have simulated the UV-Vis absorption spectra using several functionals based on time-dependent density functional theory. Among the methods used, we found LC-ωPBE functional, which separates the electron repulsion terms into two different terms which are treated using different methods. The function that allows this separations depends on the attenuating parameter. The optimization of this parameter is a key procedure to reproduce the experimental values of UV-Vis absorption spectra. We realized this optimization in gas phase and using several descriptors based on Koopmans theory. The comparison between simulated spectras with the experimental ones, shows that the spectra made with B3LYP functional is the one which fits most with the experimental absorption spectra of this dye family with a not very large charge-transfer character. However LC-ωPBE functional with the attenuating parameter optimized also gives acceptable results. In catalytic studies, the photosensitizer that shows more efficiency in the water reduction process is the one which has sulfur trioxide in its structure, PS11, in an acetonitrile and water solution (4:6). This will allow us to continue with this research to improve the adjustment of the computationally simulated absorption spectra and find new molecules that present a wider range of absorption ​
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