Publications by authors named "Grit Kupgan"

6 Publications

  • Page 1 of 1

Resolving Atomic-Scale Interactions in Non-Fullerene Acceptor Organic Solar Cells with Solid-State NMR Spectroscopy, Crystallographic Modelling, and Molecular Dynamics Simulations.

Adv Mater 2021 Nov 24:e2105943. Epub 2021 Nov 24.

University of Lille, CNRS, Centrale Lille Institut, Univ. Artois, UMR 8181, Unité de Catalyse et Chimie du Solide, Lille, F-59000, France.

Fused-ring core non-fullerene acceptors (NFAs), designated "Y-series", have enabled high-performance organic solar cells (OSCs) achieving over 18% power conversion efficiency (PCE). Since the introduction of these NFAs, much effort has been expended to understand the reasons for their exceptional performance. While several studies have identified key optoelectronic properties that govern high PCEs, little is known about the molecular level origins of large variations in performance, spanning from 5 to 18% PCE, e.g., in the case of PM6:Y6 OSCs. Here, we introduce a combined solid-state NMR, crystallography, and molecular modelling approach to elucidate the atomic-scale interactions in Y6 crystals, thin films, and PM6:Y6 bulk heterojunction (BHJ) blends. We show the Y6 morphologies in BHJ blends are not governed by the morphology in neat films or single crystals. Notably, PM6:Y6 blends processed from different solvents self-assemble into different structures and morphologies, whereby the relative orientations of the sidechains and end groups of the Y6 molecules to their fused-ring cores play a crucial role in determining the resulting morphology and overall performance of the solar cells. The molecular-level understanding of BHJs enabled by this approach will guide the engineering of next-generation NFAs for stable and efficient OSCs. This article is protected by copyright. All rights reserved.
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http://dx.doi.org/10.1002/adma.202105943DOI Listing
November 2021

Delocalization of exciton and electron wavefunction in non-fullerene acceptor molecules enables efficient organic solar cells.

Nat Commun 2020 Aug 7;11(1):3943. Epub 2020 Aug 7.

State Key Laboratory of Luminescent Materials and Devices, Institute of Polymer Optoelectronic Materials and Devices, School of Materials Science and Engineering, South China University of Technology, 381 Wushan Road, 510640, Guangzhou, P. R. China.

A major challenge for organic solar cell (OSC) research is how to minimize the tradeoff between voltage loss and charge generation. In early 2019, we reported a non-fullerene acceptor (named Y6) that can simultaneously achieve high external quantum efficiency and low voltage loss for OSC. Here, we use a combination of experimental and theoretical modeling to reveal the structure-property-performance relationships of this state-of-the-art OSC system. We find that the distinctive π-π molecular packing of Y6 not only exists in molecular single crystals but also in thin films. Importantly, such molecular packing leads to (i) the formation of delocalized and emissive excitons that enable small non-radiative voltage loss, and (ii) delocalization of electron wavefunctions at donor/acceptor interfaces that significantly reduces the Coulomb attraction between interfacial electron-hole pairs. These properties are critical in enabling highly efficient charge generation in OSC systems with negligible donor-acceptor energy offset.
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http://dx.doi.org/10.1038/s41467-020-17867-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7414148PMC
August 2020

Modeling Amorphous Microporous Polymers for CO Capture and Separations.

Chem Rev 2018 06 29;118(11):5488-5538. Epub 2018 May 29.

Department of Materials Science and Engineering , University of Florida , Gainesville , Florida 32611 , United States.

This review concentrates on the advances of atomistic molecular simulations to design and evaluate amorphous microporous polymeric materials for CO capture and separations. A description of atomistic molecular simulations is provided, including simulation techniques, structural generation approaches, relaxation and equilibration methodologies, and considerations needed for validation of simulated samples. The review provides general guidelines and a comprehensive update of the recent literature (since 2007) to promote the acceleration of the discovery and screening of amorphous microporous polymers for CO capture and separation processes.
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http://dx.doi.org/10.1021/acs.chemrev.7b00691DOI Listing
June 2018

NLDFT Pore Size Distribution in Amorphous Microporous Materials.

Langmuir 2017 10 22;33(42):11138-11145. Epub 2017 Aug 22.

Department of Materials Science and Engineering and ‡Department of Chemistry, University of Florida , Gainesville, Florida 32611, United States.

The pore size distribution (PSD) is one of the most important properties when characterizing and designing materials for gas storage and separation applications. Experimentally, one of the current standards for determining microscopic PSD is using indirect molecular adsorption methods such as nonlocal density functional theory (NLDFT) and N isotherms at 77 K. Because determining the PSD from NLDFT is an indirect method, the validation can be a nontrivial task for amorphous microporous materials. This is especially crucial since this method is known to produce artifacts. In this work, the accuracy of NLDFT PSD was compared against the exact geometric PSD for 11 different simulated amorphous microporous materials. The geometric surface area and micropore volumes of these materials were between 5 and 1698 m/g and 0.039 and 0.55 cm/g, respectively. N isotherms at 77 K were constructed using Gibbs ensemble Monte Carlo (GEMC) simulations. Our results show that the discrepancies between NLDFT and geometric PSD are significant. NLDFT PSD produced several artificial gaps and peaks that were further confirmed by the coordinates of inserted particles of a specific size. We found that dominant peaks from NLDFT typically reported in the literature do not necessarily represent the truly dominant pore size within the system. The confirmation provides concrete evidence for artifacts that arise from the NLDFT method. Furthermore, a sensitivity analysis was performed to show the high dependency of PSD as a function of the regularization parameter, λ. A higher value of λ produced a broader and smoother PSD that closely resembles geometric PSD. As an alternative, a new criterion for choosing λ, called here the smooth-shift method (SSNLDFT), is proposed that tuned the NLDFT PSD to better match the true geometric PSD. Using the geometric pore size distribution as our reference, the smooth-shift method reduced the root-mean-square deviation by ∼70% when the geometric surface area of the material is greater than 100 m/g.
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http://dx.doi.org/10.1021/acs.langmuir.7b01961DOI Listing
October 2017

Identification of Excipients for Stabilizing Fiberless Adenovirus as Biopharmaceuticals.

J Pharm Sci 2017 07 18;106(7):1764-1771. Epub 2017 Apr 18.

School of Chemical Engineering, Oklahoma State University, 420 Engineering North, Stillwater, Oklahoma 74078. Electronic address:

Reducing the promiscuous tropism of native adenovirus by using fiberless adenovirus is advantageous toward its use as a gene therapy vector or vaccine component. The removal of the fiber protein on native adenovirus abrogates several undesirable interactions; however, this approach decreases the particle's physical stability. To create stable fiberless adenovirus for pharmaceutical use, the effects of temperature and pH on the particle's stability profile must be addressed. Our results indicate that the stability of fiberless adenovirus is increased when it is stored in mildly acidic conditions around pH 6. The stability of fiberless adenovirus can be further enhanced by using excipients. Excipient screening results indicate that the nonionic surfactant Pluronic F-68 and the amino acid glycine are potential stabilizers because of their ability to increase the thermal transition temperature of the virus particle and promote retention of biological activity after exposure to prolonged thermal stress. Our data indicate that the instability of fiberless adenovirus can be ameliorated by storing the virus in the appropriate environment, and it should be possible to further optimize the virus so that it can be used as a biopharmaceutical.
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http://dx.doi.org/10.1016/j.xphs.2017.04.013DOI Listing
July 2017

The effect of fiber truncations on the stability of adenovirus type 5.

Mol Biotechnol 2014 Nov;56(11):979-91

Department of Chemical Engineering, Oklahoma State University, 423 Engineering North, Stillwater, OK, 74078, USA.

While fiberless adenovirus has the potential for use as a vaccine or gene delivery vector, some groups have observed instability issues associated with the modified virus. To investigate the effect of fiber modification on adenovirus stability, we produced mutant adenovirus particles that contained the tail and a portion of the shaft domain without the knob. The shaft domain was either completely removed (i.e., fiberless) or truncated to 7-, 14-, or 21-repeats. The mutants were evaluated by biophysical characterization techniques to determine their relative stabilities based on temperature-induced changes to the secondary, tertiary, and quaternary structures of the virus and its constituent proteins. Data acquired using circular dichroism, intrinsic/extrinsic fluorescence, and static/dynamic light scattering were compiled into a comprehensive empirical phase diagram, which showed that native adenovirus was the most stable followed by fiberless adenovirus and then the mutants with truncated fiber protein. In summary, the individual biophysical measurements and the empirical phase diagram showed that providing several repeats of shaft protein negatively impacted the structural stability of the virus more so than completely removing the fiber protein.
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http://dx.doi.org/10.1007/s12033-014-9777-6DOI Listing
November 2014
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