Universität zu Köln

Fazzi, Daniele ORCID: 0000-0002-8515-4214 and Negri, Fabrizia . Addressing the Elusive Polaronic Nature of Multiple Redox States in a pi-Conjugated Ladder-Type Polymer. Adv. Electron. Mater.. HOBOKEN: WILEY. ISSN 2199-160X

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Abstract

Poly(benzimidazole-benzophenanthroline) (BBL) is a ladder-type conjugated polymer showing remarkable charge transport properties. Upon doping it displays various conductive regimes, leading to two insulator-to-conductor transitions. Such transitions are never fully characterized, limiting understanding of its charged states. Open issues are: i) the electron/hole polaron relaxations, ii) the structure-function relationships of multiple redox states and their connection with the conductive regimes, and iii) the role of protonation. Such knowledge-gaps are tackled via a comprehensive computational investigation of multiple redox species. Polarons show polyradicaloid character, as revealed by combining broken-symmetry density functional theory, fragment orbital density, and multireference analysis. Electron/hole polaron relaxations occur on the polymer chain, the former localizing on the benzophenanthroline moieties, the latter on the benzimidazole units. Modeling of multiple charged species, up to one electron per repeat unit (1 eru), reveals a complex scenario of quasidegenerate states each featuring different spin multiplicity. Four redox states are responsible for the BBL insulator-to-conductor transitions. The two high conductive states refer to the electron polaron (0.25 eru) and the redox species with 0.75 eru. The insulating regimes refer to the bipolaron (0.50 eru) and the redox state with 1 eru. Protonation is modeled, revealing polaron-like features in the spectroscopic properties.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Fazzi, Daniele UNSPECIFIED orcid.org/0000-0002-8515-4214 UNSPECIFIED Negri, Fabrizia UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-308710
DOI:	10.1002/aelm.202000786
Journal or Publication Title:	Adv. Electron. Mater.
Publisher:	WILEY
Place of Publication:	HOBOKEN
ISSN:	2199-160X
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Chemistry > Institute of Physical Chemistry
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language ELECTRONIC-STRUCTURES; CONDUCTING POLYMERS; DIRADICAL CHARACTER; DENSITY; TRANSITION; POLARIZATION; TRANSISTORS; ABSORPTION; PREDICTION; BIPOLARONS Multiple languages Nanoscience & Nanotechnology; Materials Science, Multidisciplinary; Physics, Applied Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/30871