AIP Advances (Aug 2018)

Vacuum chamber considerations for improved organic light-emitting diode lifetime

  • Hiroshi Fujimoto,
  • Shin-ichiro Kobayashi,
  • Hin Wai Mo,
  • Satoshi Yukiwaki,
  • Kaori Nagayoshi,
  • Mao Yasumatsu,
  • Kentaro Harada,
  • Chihaya Adachi

DOI
https://doi.org/10.1063/1.5047542
Journal volume & issue
Vol. 8, no. 8
pp. 085025 – 085025-7

Abstract

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We investigated the influence of vacuum chamber impurities on the lifetime of highly efficient TADF-based OLEDs. Batch-to-batch lifetime variations are clearly correlated with the results of contact angle measurements, which reflect the amount of impurities present in the chamber. Introduction of ozone gas can clean the impurities out of the vacuum chamber, reducing the contact angle to less than 10°. In the vacuum chamber of a new deposition system designed using resin-free vacuum components, various plasticizers and additive agents were initially detected by WTD-GC-MS analysis, but these impurities vanished after ozone gas cleaning. Devices fabricated in the new chamber exhibited lifetimes that are approximately twice those of OLEDs fabricated in a pre-existing chamber. These results suggest that impurities, particularly from plasticizers, in the vacuum chamber greatly influence the OLED lifetime.