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New 3-Ethynylaryl Coumarin-Based Dyes for DSSC Applications: Synthesis, Spectroscopic Properties, and Theoretical Calculations. | LitMetric

AI Article Synopsis

  • A series of 3-ethynylaryl coumarin dyes were synthesized, incorporating different thiophene units and an alkylated benzotriazole for use in dye-sensitized solar cells (DSSCs).
  • The study compared variations in substitution patterns at the coumarin unit with natural compounds like 6,7-dihydroxycoumarin, and noted significant changes in fluorescence and absorption spectra due to structural modifications.
  • The dye containing the thieno [3,2-] thiophene showed the best performance, achieving a conversion efficiency of 2.00% and a high photocurrent, attributed to its unique molecular structure and charge transfer properties.

Article Abstract

A set of 3-ethynylaryl coumarin dyes with mono, bithiophenes and the fused variant, thieno [3,2-] thiophene, as well as an alkylated benzotriazole unit were prepared and tested for dye-sensitized solar cells (DSSCs). For comparison purposes, the variation of the substitution pattern at the coumarin unit was analyzed with the natural product 6,7-dihydroxycoumarin (Esculetin) as well as 5,7-dihydroxycomarin in the case of the bithiophene dye. Crucial steps for extension of the conjugated system involved Sonogashira reaction yielding highly fluorescent molecules. Spectroscopic characterization showed that the extension of conjugation via the alkynyl bridge resulted in a strong red-shift of absorption and emission spectra (in solution) of approximately 73-79 nm and 52-89 nm, respectively, relative to 6,7-dimethoxy-4-methylcoumarin (λ = 341 nm and λ = 410 nm). Theoretical density functional theory (DFT) calculations show that the Lowest Unoccupied Molecular Orbital (LUMO) is mostly centered in the cyanoacrylic anchor unit, corroborating the high intramolecular charge transfer (ICT) character of the electronic transition. Photovoltaic performance evaluation reveals that the thieno [3,2-] thiophene unit present in dye leads to the best sensitizer of the set, with a conversion efficiency (η = 2.00%), best V (367 mV) and second best J (9.28 mA·cm), surpassed only by dye (J = 10.19 mA·cm). This high photocurrent value can be attributed to increased donor ability of the 5,7-dimethoxy unit when compared to the 6,7 equivalent ().

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8156968PMC
http://dx.doi.org/10.3390/molecules26102934DOI Listing

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