Journal Article

PUBDB-2021-00219

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Electrostatic Interactions Shape Molecular Organization and Electronic Structure of Organic Semiconductor Blends

D’Avino, G. (Corresponding author) ; Duhm, S.Extern* ; Della Valle, R. G. ; Heimel, G. ; Oehzelt, M.Extern* ; Kera, S. ; Ueno, N. ; Beljonne, D. ; Salzmann, I.Extern*

2020
American Chemical Society Washington, DC

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Please use a persistent id in citations: doi:10.1021/acs.chemmater.9b04763  doi:10.3204/PUBDB-2021-00219

Abstract: Halogenation of conjugated molecules represents a powerful approach to tune the electronic structure of molecular thin films through inductive effects and long-range intermolecular electrostatic interactions. The mixing of halogenated molecules with their pristine counterparts has recently proven successful in altering the blend’s energy levels to adjust the open-circuit voltage of organic solar cells by the mixing ratio. Here, we show that the prevailing rationale for this effect is not equally valid for different molecular orientations. We provide a comprehensive experimental and theoretical analysis of the prototypical blend formed by pentacene and perfluoropentacene to relate structure with electronic properties. We find a mixed-stack structural motif in standing and lying orientations depending on the substrate nature. In the standing orientation, the ionization potential lies in between the values of the pure components, in line with the established picture of averaged molecular quadrupole moments. For the lying orientation, however, we experimentally observe an ionization potential lower than both pristine values, which seems at odds with this simple rationale. Electrostatic simulations based on the knowledge of the atomistic structure of the films capture the complex experimental scenario for both orientations. In particular, the ultralow ionization potential of films formed by lying molecules is identified as a signature of the monolayer structure, where quadrupolar interactions are responsible for a difference of ca. 0.4 eV in the highest occupied molecular orbital energy as compared to thicker films with the same molecular orientation.

Note: We thank Wolfgang Caliebe (HASYLAB, DESY) for experimental support and Roland Resel (TU-Graz) for fruitful discussions.

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Contributing Institute(s):

1. DOOR-User (DOOR ; HAS-User)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

Experiment(s):

1. DORIS Beamline W1 (DORIS III)

Appears in the scientific report 2020

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Database coverage:
; ; Clarivate Analytics Master Journal List ; Current Contents - Engineering, Computing and Technology ; Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; Essential Science Indicators ; IF >= 10 ; JCR ; Nationallizenz ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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