•Knoevenagel condensation of OMPA with dimethylformamide dimethyl acetal (DMF-DMA).•The chemical modification induce a high changes on the photophysical properties of the prepared oligomer.•The ...chemical modification induce a change on the electronic properties improved by DFT computations.
The synthesized oligo 4-(methoxyphenyl) acetonitrile (OMPA) was chemically modified by Knoevenagel condensation of OMPA with dimethylformamide dimethyl acetal (DMF-DMA). The obtained oligomer is composed of short chains of poly 3-(dimethylamino)-2-(4-methoxyphenyl)acrylonitrile and denoted OMFA. Experimental measurements: ultraviolet-visible (UV-vis), steady-state and time-resolved photoluminescence spectroscopies, infrared spectroscopy, and thermogravimetric analysis (TGA), were combined with theoretical calculations, based on density functional theory (DFT) methodologies, to highlight the effect of the grafting of the dimethyl-amine group on the photo-physical and electronic properties of the as-synthesized oligomer. Thus, a redshift of the absorption and photoluminescence spectra is observed upon the chemical grafting of the functional group. Added to that, a decrease of the optical bandgap (Egopt) and the energy gap EH-L=EHOMO-ELUMO occurs upon the chemical modification. DFT computations show that the chemical insertion of the dimethyl-amine group into the monomer and the oligomer induces a drastic change on their frontier orbitals HOMO and LUMO.
Experimental measurement on oligomeric 4-(methoxyphenyl)acetonitrile (OMPA) synthesized via an electrochemical method indicated that the average chain length for OMPA was around 5 units (5-MPA)
J ...Mol Struct 1031:186 (2013)
, but did not provide enough information to completely characterize the chemical structure of the molecule. Nevertheless a possible structure was proposed on the basis of
13
C NMR and the spin density hypothesis for radical polymerization. A more complete validation of the resultant structure is needed to show the extent to which the structure is consistent with a variety of measured properties. This is done here for the infrared (IR), ultraviolet–visible (UV–vis), and photoluminescence (PL) spectra of 5-MPA which are found to agree reasonably well with the experimentally measured spectra of OMPA. Electronic structure information regarding the highest-occupied molecular orbital (HOMO) and the lowest-unoccupied molecular orbital (LUMO) energies, ionization potentials and electron affinities, as well as optical properties (UV–vis, PL) is also provided.
Graphical Abstract
Comparison of theoretical and experimental UV-visible absorption and photoluminescence spectra of oligomeric 4-(methoxyphenyl)acetonitrile
A very interesting challenge concerns the elaboration of nanowires from organic polymers with the aim to design novel nanoelectronic devices. The new VK-Stilbene copolymer based on organic nanowires ...was developed and characterized in this context. The VK-Stilbene nanowires were made with a template method by filling nanopores of AOO membranes. The prepared nanowires wereinvestigated by morphological spectroscopy and micro-Raman Rinshaw analysis. The modifications of photoemissive properties from microscopy film to nanowires were described by steady-state optical techniques combinedwith time-resolved photoluminescence spectroscopy. A blue shift of the luminescence are observed in the case of nanowires proceed from structural order and shortening of effective conjugation lengths. Therefore, VK-Stilbene nanowires exhibit a remarkably quasi-exponential long-lived and blue-shifted ascribed to a confinement-effect of intra-chain singlet excitons. Additionally, these nano-objects show an increase in the quantum yield with respect to bulk samples. The acquired optical data confirm that VK-Stilbene nanomaterials may be suitable for nanotechnologies.
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•Engineering of the VK-Stilbene in nanowires through hard template method for tuning the photoluminescence.•Photoluminescence properties of the nanowires can be explained by the new arrangement of chains copolymer by confinement.•A high quantum yields of photoluminescence and good luminescence efficiency in VK-Stilbene nanowires.
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•DFT and TD-DFT theoretical methods.•Narrow band-gap small molecules.•Intramolecular charge transfer.•Calculated results give a direction to design novel donor small molecules for ...high-performance organic photovoltaic device.
In search of novel high-performance materials for use in organic solar cells, we used density-functional theory and time-dependent density functional theory to design a series of organic small molecules derived from the recently synthesized BT(-2T-DCV-Hex)2 donor molecule. In this work, we replaced the BT unit by different acceptors in order to improve their electronic properties, optical absorption and performance in organic solar cell applications. We found that the hybrid functional B3PW91 with the 6-31G(d) basis set gave highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the BT(-2T-DCV-Hex)2 in better agreement with the experimental oxidation and reduction potentials. However, the range-separated hybrid functional WB97XD was the most appropriate functional for describing the maximum absorption wavelength. Our calculation indicate that the designed small molecules donor proposed here are expected to offer better performances compared to the BT(-2T-DCV-Hex)2, such as a lower HOMO energy, a narrower HOMO-LUMO energy gap, a larger absorption range and may lead to power conversion efficiencies reaching the (7–9)% range.
As emphasized in a recent review article Chem. Rev. 122, 14180 (2022), organic solar cell (OSC) photoconversion efficiency has been rapidly evolving with results increasingly comparable to those of ...traditional inorganic solar cells. Historically, OSC performance improvement focused first on the morphology of P3HT:PC61BM solar cells then went through different stages to shift lately interest towards nonfullerene acceptors (NFAs) as a replacement of PC61BM acceptor (ACC) molecule. Here, we use density-functional theory (DFT) and time-dependent (TD) DFT to investigate four novel NFAs of A-D-A (acceptor-donor-acceptor) form derived from the recently synthesized IDIC-4Cl Dyes and Pigments 166, 196 (2019). Our level of theory is carefully evaluted for IDIC-4Cl and then applied to the four novel NFAs in order to understand how chemical modifications lead to physical changes in cyclic voltammetry (CV) frontier molecular orbital (FMO) energies and absorption spectra in solution.Finally we design and apply a new type of Scharber plot for NFAs based upon some simple but we think reasonable assumptions. Unlike the original Scharber plots where a larger DON band gap favors a larger PCE, our modified Scharber plot reflects the fact that a smaller ACC band gap may favor PCE by filling in gaps in the DON acceptor spectrum. We predict that only the candidate molecule with the least good acceptor A, with the highest frontier molecular orbital energies, and one of the larger CV lowest unoccupied molecular orbital (LUMO) highest unoccupied molecular orbital (HOMO) gaps, will yield a PM6:ACC PCE exceeding that of the parent IDIC-4Cl ACC. This candidate also shows the largest oscillator strength for the primary 1 (HOMO,LUMO) charge-transfer transition and the largest degree of delocalization of charge transfer of any of the ACC molecules investigated here.
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