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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 28: Poster III

CPP 28.4: Poster

Wednesday, March 20, 2024, 11:30–13:30, Poster C

Controlling spontaneous orientation polarization in exciplex-forming OLEDs — •Albin Cakaj, Lea Kolb, Alexander Hofmann, and Wolfgang Brütting — Experimental Physics IV, Institute of Physics, University of Augsburg, 86135 Augsburg, Germany

The resulting internal electrical field, due to spontaneous orientation polarization (SOP), affects the charge injection and accumulation behavior of organic light emitting diodes (OLEDs) significantly. While the community has just recently started to understand the formation process and its active control, it is still not completely clear if this effect is advantageous or detrimental in organic semiconductor devices [1]. In our studies, we investigated an exciplex-forming mixture of the polar species TPBi and the nonpolar molecule TCTA regarding their electrical and optical orientation as well as their properties as an emissive layer in OLEDs. By substrate temperature control the film polarization can be tuned over a broad range from 0 to 125 mV/nm, comparable to recent studies for single-molecule films [2]. But despite of the loose exciton binding, the photoluminescence spectra are not affected by changes in the degree of SOP. Investigations on mixed and bilayer devices hint to the conclusion that exciton quenching is almost not apparent in this material combination. This makes the investigated exciplex system possibly a good candidate as a co-host for efficient OLEDs. [1] A. Hofmann et al. Adv. Optical Mater. DOI:10.1002/adom.202101004 (2021) [2] A. Cakaj et al. ACS Appl. Mater. Interfaces, DOI:10.1021/acsami.3c13049 (2023)

Keywords: OLED; Organic Semiconductors; SOP; Exciplex; Exciton Quenching