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Dark-triplet-induced instability and efficiency roll-off in blue phosphorescent organic light-emitting devices

Jan Tiepelt1, Jaekang Song1, Aden Seeglitz2, Christopher Picart2, Rebecca Hanscam3, Oliver Nix3, Alexandra Raeber3, Ting-An Lin1, Weikun Zhu1 et al.

Peter F. Satterthwaite1, Jong Woong Park1, Farnaz Niroui1, Troy Van Voorhis3, Jian Li2,*, and Marc Baldo1,†

  • *Contact author: jian.li.1@asu.edu
  • †Contact author: baldo@mit.edu
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Phys. Rev. Applied 25, 024049 – Published 17 February, 2026

DOI: https://doi.org/10.1103/cdwt-lh3j

Abstract

The relative instability of high-efficiency blue phosphorescent organic light-emitting devices (OLEDs) is an important and longstanding challenge. Conventional models of degradation emphasize the dynamics of emissive triplet excitons on phosphorescent molecules, neglecting the potential role of nonemissive, “dark,” triplet excitons on host and charge blocking molecules. Bright and dark triplet dynamics are probed in situ using surface plasmon polariton-coupled modulation and magnetic exciton annihilation modulation, respectively. It is observed that dark triplet excitons dominate both the instability and efficiency roll-off of a high-performance blue phosphorescent OLED. Dissociating dark triplets both improves device stability and reduces efficiency losses at high brightness by a factor of 2. The combined benefit to stability of Purcell engineering and dark triplet management is a factor of 3.5. The results demonstrate that dark triplet excitons reduce the potential benefit of Purcell engineering, emphasizing the importance of in-situ characterization and control of dark triplets to realize the goal of stable blue phosphorescent OLEDs.

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Phys. Rev. Applied 25, 024049– Published 17 February, 2026
  • Received 10 February 2025
  • Revised 25 June 2025
  • Accepted 7 January 2026
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