Paper
22 May 2018 Effect of matrix anisotropy on the apparent emitter orientation in organic LED
Norbert Danz, Nils Haase, Antonia Morherr, Christof Pflumm, Birk Fritsch, Dirk Michaelis
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Abstract
Spontaneously aligning emitter molecules can improve the external efficiency of OLED devices and have been reported for different types of emitters doped into suitable hosts. Similar to the morphological alignment of the active molecules, a birefringence of the host affects the apparent emitter orientation. In order to investigate this effect experimentally, Ir(ppy)3 is co-evaporated into the emitting layer of OLED using hosts with different birefringence properties. Analyzing the electroluminescence emission patterns quantitatively reveals the apparent orientation distribution of the emitters. The results emphasize that host birefringence can be used to suppress perpendicular emitter contributions while amplifying the impact of the horizontal dipoles, thus leading to an enhanced forward emission.
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Norbert Danz, Nils Haase, Antonia Morherr, Christof Pflumm, Birk Fritsch, and Dirk Michaelis "Effect of matrix anisotropy on the apparent emitter orientation in organic LED", Proc. SPIE 10687, Organic Electronics and Photonics: Fundamentals and Devices, 106870U (22 May 2018); https://doi.org/10.1117/12.2306408
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KEYWORDS
Organic light emitting diodes

Birefringence

Anisotropy

Refractive index

Molecules

Light emitting diodes

Thin films

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