Charge carrier dynamics and degradation phenomena in organic light-emitting diodes doped by a thermally activated delayed fluorescence emitter

Yutaka Noguchi, Hyung Jun Kim, Ryuta Ishino, Kenichi Goushi, Chihaya Adachi, Yasuo Nakayama, Hisao Ishii

研究成果: ジャーナルへの寄稿学術誌査読

34 被引用数 (Scopus)

抄録

We report on the charge carrier dynamics and their degradation phenomena in an organic light-emitting diode (OLED) doped by a thermally activated delayed fluorescence emitter; (4s,6s)-2,4,5,6-tetra(9H-carbazol-9-yl) isophthalonitrile (4CzIPN). Displacement current measurement (DCM) data revealed the presence of negative interface charge originating from the spontaneous orientation polarization of the electron transport layer (ETL), 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl) benzene. The negative interface charge acts as a hole reservoir and thus confines the recombination zone near the emission layer (EML); 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP):4CzIPN (5 wt%)/ETL interface. By keeping the recombination zone far from the hole transport layer, 4,4′-bis[N-(1-naphthyl)-N-phenylamino]-biphenyl (α-NPD), a better electroluminescence efficiency is expected because the Dexter energy transfer from the triplet state of 4CzIPN to that of α-NPD is suppressed. Moreover, we found an excellent linear relation between the accumulated hole amount and luminance losses owing to device aging. The results are consistent with hole traps originating at the degradation products of CBP as the main factor of device degradation. We suggest device architectures based on the charge carrier dynamics for better efficiency and lifetime.

本文言語英語
ページ(範囲)184-191
ページ数8
ジャーナルOrganic Electronics
17
DOI
出版ステータス出版済み - 2月 2015

!!!All Science Journal Classification (ASJC) codes

  • 電子材料、光学材料、および磁性材料
  • 生体材料
  • 化学 (全般)
  • 凝縮系物理学
  • 材料化学
  • 電子工学および電気工学

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