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C: Energy Conversion and Storage; Energy and Charge Transport
Assessment of BODIPY-Oxasmaragdyrin Dyads for Dye Sensitized Solar Cells: Aromaticity, Photosensitization Capability and Charge Transport Merlys Borges-Martinez, Daniel Álvarez, Nicolas Montenegro-Pohlhammer, M. Isabel Menendez, Ramón Lopez, and Gloria Ines Cardenas-Jiron J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.9b05136 • Publication Date (Web): 22 Jul 2019 Downloaded from pubs.acs.org on July 26, 2019
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The Journal of Physical Chemistry
Assessment of BODIPY-Oxasmaragdyrin Dyads for Dye Sensitized Solar Cells: Aromaticity, Photosensitization Capability and Charge Transport
Merlys Borges-Martínez,a Daniel Alvarez,b Nicolas Montenegro-Pohlhammer,a M. Isabel Menéndez,b Ramón López,*b Gloria Cárdenas-Jirón*a
aLaboratory
of Theoretical Chemistry, Faculty of Chemistry and Biology, University of Santiago de Chile (USACH), 9170022, Santiago, Chile.
bDepartamento
de Química Física y Analítica, Facultad de Química, Universidad de Oviedo, C/Julián Clavería 8, 33006 Oviedo, Asturias, Spain.
*Author to whom the correspondence should be addressed *Email:
[email protected] *Email:
[email protected] 1 ACS Paragon Plus Environment
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ABSTRACT Dye-sensitized solar cells (DSSC) are presented as an alternative among renewable energies where the dye plays an important role to obtain an effective device. Our goal in this work is to examine the influence of several bridging functional groups between the BODIPY and oxasmaragdyrin systems forming dyads (D), as potential components of DSSC, on the aromatic, photophysical and charge transport properties of these ones. A set of 11 dyads made of the oxasmaragdyrin with 2,6dimethoxyphenyl and methylamine groups in two of their meso carbons (S) and the 4,4-difluoro-4bora-3a,4a-diaza-s-indacene (BODIPY, B) moieties that differ in the binding bridge between them has been analyzed with density functional theory (DFT). The geometries were optimized with the B3LYP/6-311G(d,p) level of theory employing D3 Grimme´s correction, and a set of six functionals (B3LYP, BHandHLYP, CAM-B3LYP, PBE0, wB97X, TPSSh) were evaluated for reference systems in time dependent-DFT calculations. We found that TPSSh presents the best agreement with the available data of UV-vis spectra, so it was used for the calculation of the electronic absorption spectra of the 11 oxasmaragdyrins and 11 dyads. When the bridge between S and B consists of one (D3), two (D5), or three acetylene units (D6), a strong absorption band in the infrared region around 1000 nm can be achieved. These bands correspond to charge-separated excited states that favor a panchromatic absorption in that region. The aromaticity index NICS(0) computed at the macrocycle center ring critical point using the GIAO/B3LYP/6-311G(d,p) level of theory show in all these systems an aromatic character for the oxasmaragdyrin macrocycle (-10.7 to -12.4 ppm). We also found that all dyads present a favorable electron injection toward the semiconductor TiO2 because the LUMO energy of the dyad is higher than the conduction band of the semiconductor (-4.3 eV) used in a solar cell. Besides, the HOMO energy of the dyads D3, D5 and D6 is lower than the redox potential (-4.8 eV) of a mediator as the I-/I3- system used to recover it after the circulation of electrons. Nonequilibrium Green`s function-based calculations performed for a couple of dyads; with (D6) and without (D4) a significant charge transfer band, connected to Au-electrodes show that D6 resulted to be a better conductor in agreement with the charge transfer results obtained from the photophysical properties. Finally, the Gibbs free energy for the formation of the dyads here investigated is calculated. All of them show to be exergonic reactions (Gsolution
