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What is the role of planarity and torsional freedom for aggregation in a π-conjugated donor–acceptor model oligomer?

Title data

Wedler, Stefan ; Bourdick, Axel ; Athanasopoulos, Stavros ; Gekle, Stephan ; Panzer, Fabian ; McDowell, Caitlin ; Nguyen, Thuc-Quyen ; Bazan, Guillermo C. ; Köhler, Anna:
What is the role of planarity and torsional freedom for aggregation in a π-conjugated donor–acceptor model oligomer?
In: Journal of Materials Chemistry C. (2020) .
ISSN 2050-7534
DOI: https://doi.org/10.1039/D0TC00217H

Abstract in another language

Ordered domains play a central role in determining the properties of organic semiconductors, and thereby the performance of their devices. The molecules in these ordered domains are often characterized by planar backbone conformations. We investigate the influence of backbone planarity on the propensity to form ordered structures using a pair of model oligomers with electron poor benzothiadiazole moieties and electron rich thiophene units. The two oligomers differ by their central unit, where a bithiophene unit either allows for flexible twists (“TT”), or where it is bridged as a cyclopentadithiophene to provide a rigid planar connection (“CT”). Temperature dependent absorption and luminescence spectroscopy in solution along with atomistic simulations show that the more flexible TT readily forms aggregates upon cooling, while CT instead first forms non-emissive excimers and only forms aggregates below 200 K. Molecular dynamics simulations reveal that aggregation in TT can only be accounted for if TT takes on a planar conformation in the course of the aggregation process. The stronger intermolecular interaction in TT compared to the banana-shaped CT can then be related to the larger number of attractive intermolecular interactions between the various subunits. Thus, molecular flexibility is an important design parameter, as it determines the accessibility of ordered intermolecular structures and ultimately device performance.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics
Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Chair Experimental Physics II - Optoelectronics of Soft Matter
Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Chair Experimental Physics II - Optoelectronics of Soft Matter > Chair Experimental Physics II - Optoelectronics of Soft Matter - Univ.-Prof. Dr. Anna Köhler
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 530 Physics
Date Deposited: 17 Mar 2020 10:29
Last Modified: 17 Mar 2020 10:29
URI: https://eref.uni-bayreuth.de/id/eprint/54637