Regensburg 2019 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 37: Poster Session III

CPP 37.24: Poster

Wednesday, April 3, 2019, 11:00–13:00, Poster B1

Voltage-dependent shift of the emission spectra of exciplex OLEDs — •Thomas Schröther, Thomas Zechel, and Wolfgang Brütting — Institute of Physics, University of Augsburg, 86135 Augsburg, Germany

Exciplexes are excited states between two different molecules in an organic light emitting diode (OLED). After electrical excitation, the hole is located in the highest occupied molecular orbital (HOMO) of the donor material and an electron occupies the lowest unoccupied molecular orbital (LUMO) on the acceptor. These states are recently used to improve the external quantum efficiencies in OLEDs.

In this work we investigated the electroluminescence spectra of the material combination m-MTDATA:BPhen forming exciplex states in OLED devices using two layouts, where the molecules were either mixed or in separate planar layers. After varying the applied voltage, it was possible to discern between two different kinds of spectral shifts that depend on the layout by fitting the data with multiple Gaussian functions. In the mixed OLED the positions of the individual peaks are constant but their contribution to the emission changes. Whereas every single Gaussian shifts with constant height in the planar device resulting in a shift of the whole curve. Based on the theoretical description by Monkman and Al Attar [1] as well as Linderl [2], we present two models to explain this observed difference.

[1] H. A. Al Attar, A. P. Monkman, Adv. Mat. 28 (36), 8014 - 8020 (2016), DOI: 10.1002/adma.201600965

[2] T. Linderl, PhD thesis, University of Augsburg (2017).