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Lone-Pair Delocalization Effects within Electron Donor Molecules: The Case of Triphenylamine and Its Thiophene-Analog
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.ORCID iD: 0000-0001-8739-7773
KTH Royal Institute of Technology, Department of Theoretical Chemistry and Biology & Korea Advanced Institute of Science and Technology (KAIST), Department of Chemistry.ORCID iD: 0000-0003-1671-8298
ISM-CNR, Trieste LD2 Unit, Italy.
ISM-CNR, Tito Scalo (Pz), Italy.
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2018 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 31, p. 17706-17717Article in journal (Refereed) Published
Abstract [en]

Triphenylamine (TPA) and its thiophene-analog, N,N-diphenyl-2-thiophenamine (DPTA), are both well-known as electron-donating molecules implemented in optoelectronic devices such as organic solar cells and LEDs. Comprehensive valence and core level photoelectron spectroscopy, as well as near edge X-ray absorption spectroscopy (NEXAFS), measurements have been performed on gas phase TPA and DPTA. The experimental results have been compared to density functional theory calculations, providing a detailed description of the molecular electronic structure. Specifically, the C 1s photoelectron lines of both TPA and DPTA were resolved in the different C atom contributions and their binding energies explained as the result of two counter-acting effects: (1) the electronegativity of the nitrogen atom (and sulfur atom in DPTA) and (2) the the N (and S in DPTA) lone-pair electrons. In addition, the C K-edge NEXAFS spectrum of DPTA reveals that the lowest unoccupied molecular orbital (LUMO) energy position is affected differently if the core hole site is on the phenyl compared to the thiophene ring. The electron-donating properties of these two molecules are largely explained by the significant contribution of the N lone-pair electrons (p(z)) to the highest occupied molecular orbital. The contribution to the LUMO and to the empty density of states of the sulfur of the thiophene ring in DPTA explains the better performance of donor-pi-acceptor molecules containing this moiety and implemented in photoenergy conversion devices.

Place, publisher, year, edition, pages
2018. Vol. 122, no 31, p. 17706-17717
National Category
Physical Sciences Theoretical Chemistry Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-355118DOI: 10.1021/acs.jpcc.8b06475ISI: 000441484600014OAI: oai:DiVA.org:uu-355118DiVA, id: diva2:1228912
Funder
Swedish Research Council, VR 2014-3776Carl Tryggers foundation
Note

Title in thesis list of papers: Lone Pair Delocalization Effect within Electron Donor Molecules:The Case of Triphenylamine (TPA) and Its Thiophene-Analog(DPTA)

Available from: 2018-06-29 Created: 2018-06-29 Last updated: 2018-10-15Bibliographically approved
In thesis
1. Synchrotron Radiation Studies of Molecular Building Blocks for Functional Materials
Open this publication in new window or tab >>Synchrotron Radiation Studies of Molecular Building Blocks for Functional Materials
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The research on new materials is a primary driving force for progress in human society. One of the most significant research topic nowadays is the development of new functional materials for technological applications, like perovskite implemented in solar cells, and graphene as a representative for the new 2D materials family. It is then crucial to fully understand the functionality of such materials from a fundamental point of view, as a complementary and useful guide to develop/design new devices of improved performance and energy efficiency.

In the thesis, comprehensive characterizations of molecular building blocks used in i) novel energy conversion devices (CoPc, TPA, DPTA and m-MTDATA), and ii) in 2D materials (biphenylene and melamine) have been performed by PhotoElectron Spectroscopy (PES), and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy carried out at synchrotron radiation facilities, representing effective, powerful light source dedicated to the front-line materials research of great value in both science and industry. PES and NEXAFS spectroscopy, in combination with Density Functional Theory (DFT) calculations have provided a deep understanding of the electronic structure of the investigated systems in relation to their functionality. The investigations always included the combination and comparison between experimental and theoretical results. The studied molecules were characterized as free and adsorbed on surfaces, from the simple building blocks to more complex molecular systems. The characterizations allowed us to identify the electronic structure modifications due to substitutions (Paper III), increasing complexity of the molecules (Paper V), molecule-substrate interactions (Paper I, II, IV, V) and intra-molecular H-bonding interactions (Paper VI).

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 97
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1693
Keywords
Synchrotron radiation study, Functional materials, Molecular building blocks, Electron donor, 2D material, Gas-phase, Organic thin film, Electronic structure, Molecule-molecule interaction, Molecule-substrate interaction, Photoelectron spectroscopy, PES, XPS, Near edge X-ray absorption fine structure, NEXAFS, X-ray Absorption Spectroscopy, XAS, Au(111), Cu(111), Surface, Interface, Electronic structure, H-bonding, Cobalt phthalocyanine, CoPc, Triphenylamine, TPA, DPTA, m-MTDATA, Melamine, Biphenylene, Carbon nitride, Graphenylene, Density functional theory, DFT
National Category
Atom and Molecular Physics and Optics Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-354766 (URN)978-91-513-0383-3 (ISBN)
Public defence
2018-09-07, Häggsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
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Available from: 2018-08-14 Created: 2018-06-29 Last updated: 2018-08-28

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Zhang, TengBrumboiu, Iulia E.Rensmo, HåkanBrena, BarbaraLanzilotto, ValeriaPuglia, Carla

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