Regensburg 2025 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 16: Organic Semiconductors
HL 16.6: Vortrag
Dienstag, 18. März 2025, 10:45–11:00, H14
Modifying the density of states in dipolar organic semiconductors — •Andrei Stankevich1, Prakhar Sahay3, Heinz Bässler1, Wolfgang Brütting3, Fabian Eller2, Eva M. Herzig2, Andrey Kadashchuk1, and Anna Köhler1 — 1Soft Matter Optoelectronics, University of Bayreuth — 2Dynamics and Structure Formation, University of Bayreuth — 3Institute of Physics, University of Augsburg,
Charge transport properties of amorphous organic semiconductors are controlled by energetic disorder. Certain device properties, such as the energies of charge transfer states in organic light-emitting diodes, can be improved by using dipolar molecules as host. Such molecules, however, also introduce interactions between charge carriers and randomly aligned dipoles. A key consequence of this is that increases the energetic disorder, hence causing a broad distribution of localized states, which hinders charge transport. We combined thermally stimulated luminescence studies with grazing incidence wide angle X-ray scattering, to demonstrate how the density of states in dipolar materials can be tailored. We demonstrate that the DOS is highly sensitive to the deposition technique and, consequently, the resulting film morphology. Furthermore, we show that the energetic disorder is not only determined by the static dipole moment, but also by the polarizability of charged molecules. Through this insight we derive design rules for common OLED materials that exhibit a with high dipole moments while maintaining charge transport properties comparable to those of non-polar counterparts.
Keywords: charge transport; thermally stimulated luminescence; density of states