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Nature
Feb, 2024;626 (7998): 300-305.

Stable blue phosphorescent organic LEDs that use polariton-enhanced Purcell effects.

Haonan Zhao, Claire E Arneson, Dejiu Fan, Stephen R Forrest
Author Information
  1. Haonan Zhao: Department of Physics, University of Michigan, Ann Arbor, MI, USA.
  2. Claire E Arneson: Department of Physics, University of Michigan, Ann Arbor, MI, USA. ORCID
  3. Dejiu Fan: Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, USA. ORCID
  4. Stephen R Forrest: Department of Physics, University of Michigan, Ann Arbor, MI, USA. stevefor@umich.edu. ORCID
PMID: 38122821 DOI: 10.1038/s41586-023-06976-8

Abstract

Phosphorescent organic light-emitting diodes (PHOLEDs) feature high efficiency, brightness and colour tunability suitable for both display and lighting applications. However, overcoming the short operational lifetime of blue PHOLEDs remains one of the most challenging high-value problems in the field of organic electronics. Their short lifetimes originate from the annihilation of high-energy, long-lived blue triplets that leads to molecular dissociation. The Purcell effect, the enhancement of the radiative decay rate in a microcavity, can reduce the triplet density and, hence, the probability of destructive high-energy triplet-polaron annihilation (TPA) and triplet-triplet annihilation (TTA) events. Here we introduce the polariton-enhanced Purcell effect in blue PHOLEDs. We find that plasmon-exciton polaritons (PEPs) substantially increase the strength of the Purcell effect and achieve an average Purcell factor (PF) of 2.4 ± 0.2 over a 50-nm-thick emission layer (EML) in a blue PHOLED. A 5.3-fold improvement in LT90 (the time for the PHOLED luminance to decay to 90% of its initial value) of a cyan-emitting Ir-complex device is achieved compared with its use in a conventional PHOLED. Shifting the chromaticity coordinates to (0.14, 0.14) and (0.15, 0.20) into the deep blue, the Purcell-enhanced devices achieve 10-14 times improvement over similarly deep-blue PHOLEDs, with one structure reaching the longest Ir-complex device lifetime of LT90 = 140 ± 20 h reported so far. The polariton-enhanced Purcell effect and microcavity engineering provide new possibilities for extending deep-blue PHOLED lifetimes.

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