Polarization-Induced Exciton–Polaron Quenching in Organic Light-Emitting Devices and Its Control by Dipolar Doping

Evgeny Pakhomenko, Siliang He, Russell J. Holmes

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Many electron transport layer (ETL) materials employed in organic light-emitting devices (OLEDs) show a preferred orientation of the molecular permanent dipole moments. This phenomenon is known as spontaneous orientation polarization (SOP) and results in the formation of bound polarization charge. In an OLED, this leads to the accumulation of polarons (typically holes) at the ETL/emissive layer interface to balance this charge. Previous work on phosphorescent OLEDs has found that exciton–polaron quenching due to SOP-induced hole accumulation can reduce peak efficiency by ≈20%. In this work, the generality of this phenomenon is systematically established by probing polaron accumulation and quenching in phosphorescent OLEDs with varying degrees of SOP. Exciton quenching is quantified by optically probing the photoluminescence of the device emissive layer during operation. It is found that the degree of SOP-induced luminescence quenching and reduction in device efficiency scale directly with ETL SOP. It is further demonstrated that the degree of polarization and amount of quenching can be tuned by mixing the polar ETL with a nonpolar host (dipolar doping). This work establishes a ubiquitous role for SOP in determining OLED efficiency and demonstrates dipolar doping as a means to tune the underlying exciton–polaron quenching.

Original languageEnglish (US)
Article number2201348
JournalAdvanced Optical Materials
Volume10
Issue number23
DOIs
StatePublished - Dec 5 2022

Bibliographical note

Funding Information:
R.J.H. and E.P. acknowledge support from Ronald L. and Janet A. Christenson, the Robert and Beverly Sundahl Fellowship, and Prof. C. D. Frisbie for the use of a potentiostat.

Publisher Copyright:
© 2022 Wiley-VCH GmbH.

Keywords

  • dipolar doping
  • exciton–polaron quenching
  • organic light-emitting devices
  • spontaneous orientation polarization

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