Analysis of device performance and thin-film properties of thermally damaged organic light-emitting diodes

Chang Min Lee, Won Ho Lee, Geon Woo Jeong, Dong Hyun Kim, Dong Hyun Choi, Tae Wook Kim, Amjad Islam, P. Justin Jesuraj, Hassan Hafeez, Hyung Ju Chae, Hyunmin Hong, Kwun Bum Chung, Sanghyuk Park, Myungkwan Song, Chang Su Kim, Seung Yoon Ryu

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

This paper reports the variation in the optical and geometrical properties of individual organic layers to be used for thermally damaged top-emission organic light-emitting diodes (TEOLEDs). The copper deposited on the back of TEOLEDs is employed as a thermal facilitator, and a certain thermal damage occurs to the organic layers and devices. The phosphorescent host material 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) is rapidly damaged to a significant extent owing to the low glass transition temperature (Tg), which also changes its optical and geometrical surface properties. Although the optical properties of the hole transport layer, N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) were changed slightly, the surface morphology was changed significantly. Despite having a higher Tg, the exciton blocking layer, tris(4-carbazoyl-9-ylphenyl)amine (TCTA), shows notable variations in optical properties and surface morphology due to heat exposure. Surprisingly, the electroluminescence spectra and micro-cavity are affected by increasing temperature without any considerable changes in device performance. Hence, this study reveals that besides Tg, the surface morphologies and thicknesses of the organic layers are also important factors in the annealing process and play a vital role in causing thermal damage to TEOLEDs.

Original languageEnglish
Article number106304
JournalOrganic Electronics
Volume99
DOIs
StatePublished - Dec 2021

Keywords

  • Extinction coefficient (k)
  • Glass transition temperature (T)
  • Micro-cavity effect
  • Refractive index (n)
  • Surface morphological degradation
  • Top emission organic light-emitting diodes (TEOLEDs)

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