Reducing Spontaneous Orientational Polarization via Semiconductor Dilution Improves OLED Efficiency and Lifetime

Emmanuel O. Afolayan, Ibrahim Dursun, Chao Lang, Evgeny Pakhomenko, Marina Kondakova, Michael Boroson, Michael Hickner, Russell J. Holmes, Noel C. Giebink

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Spontaneous orientational polarization (SOP) in the electron-transport layer (ETL) of organic light-emitting diodes (OLEDs) is increasingly recognized as a key factor influencing their performance. Here, we show that SOP is dramatically reduced in the common electron-transport material 2,2′,2′′-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) by coevaporating it together with medium-density polyethylene. Eliminating SOP from the ETL of blue fluorescent OLEDs in this manner reduces their operating voltage by 0.5 V, increases their external quantum efficiency (EQE) by 30%, and leads to a threefold increase in device lifetime. We show that the EQE and lifetime improvements both originate from reduced exciton-polaron annihilation in the emissive layer, and that this leads to a functional relationship between the two quantities that can be used to quantify the rate of annihilation-induced degradation in the device. These results highlight a substantial opportunity to improve OLED performance by controlling SOP through semiconductor dilution and suggest that this capability can be used to systematically isolate and understand exciton-polaron degradation in the pursuit of stable blue OLEDs.

Original languageEnglish (US)
Article numberL051002
JournalPhysical Review Applied
Issue number5
StatePublished - May 2022

Bibliographical note

Funding Information:
Acknowledgments.—This work is supported by the US Department of Energy (DOE) EERE SSL program under Award No. DE-EE0008717. R.J.H. and E.P. acknowledge support from Ronald L. and Janet A. Christenson and the Robert and Beverly Sundahl Fellowship.

Publisher Copyright:
© 2022 American Physical Society.


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