TY  - JOUR
AU  - D’Avino, Gabriele
AU  - Duhm, Steffen
AU  - Della Valle, Raffaele Guido
AU  - Heimel, Georg
AU  - Oehzelt, Martin
AU  - Kera, Satoshi
AU  - Ueno, Nobuo
AU  - Beljonne, David
AU  - Salzmann, Ingo
TI  - Electrostatic Interactions Shape Molecular Organization and Electronic Structure of Organic Semiconductor Blends
JO  - Chemistry of materials
VL  - 32
IS  - 3
SN  - 1520-5002
CY  - Washington, DC
PB  - American Chemical Society
M1  - PUBDB-2021-00219
SP  - 1261 - 1271
PY  - 2020
N1  - We thank Wolfgang Caliebe (HASYLAB, DESY) for experimental support and Roland Resel (TU-Graz) for fruitful discussions.
AB  - 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.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000513299400031
DO  - DOI:10.1021/acs.chemmater.9b04763
UR  - https://bib-pubdb1.desy.de/record/453855
ER  -