Work-function-tunable metal-oxide mesh electrode and novel soluble bipolar host for high-performance solution-processed flexible TADF-OLED

Nahyun Kim, Jinhyo Hwang, Ho Jin Lee, Na Yeon Kwon, Jin Young Park, Chang Woo Koh, Min Ju Cho, Sungnam Park, Dong Hoon Choi, Tae Geun Kim

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


Substantial effort has been dedicated to the development of solution-processed flexible organic light-emitting diodes (sf-OLEDs). However, to simultaneously enhance device performance and ensure stable operation under severe mechanical deformation, highly flexible transparent electrodes and efficient soluble organic emitting materials must be optimized together. Here, highly efficient green-emitting thermally activated delayed fluorescence (TADF) sf-OLEDs were developed using a mesh-structured Ni-doped indium zinc oxide (mNIZO) flexible electrode and a novel soluble bipolar host. The mNIZO electrode had excellent optical, electrical, and mechanical properties. The work function of the mNIZO electrode was engineered through surface doping with Ni without optical and electrical losses. 5-(9 H-Carbazol-9-yl)− 3′-(3,6-di-tert-butyl-9 H-carbazol-9-yl)-[1,1′-biphenyl]− 3-carbonitrile (CzCN-tCz) was synthesized as a soluble host material by incorporating a tert-butyl group into 3,3′-di(carbazol-9-yl)− 5-cyano-1,1′-biphenyl (mCBP-CN). Consequently, the mNIZO-based TADF sf-OLED with CzCN-tCz had a maximum external quantum efficiency of 21.0 % on a poly(ethylene 2,6-naphthalate) substrate, and 82 % of the initial luminance was maintained under severe mechanical stress, which is attributable to the high deformability of the mNIZO electrode. The proposed framework is expected to facilitate the design of high-performance cost-effective flexible displays with various forms through a simple process.

Original languageEnglish
Article number108028
JournalNano Energy
Publication statusPublished - 2023 Jan

Bibliographical note

Funding Information:
Ho Jin Lee received his B.S. degree in Electrical Materials Engineering from Kwangwoon University in 2018 and M.S degree in Electrical Engineering from Korea University in 2020. During 2018–2020, he was supported by the National Research Foundation of Korea (NRF). His main research interests focus on flexible & stretchable organic optoelectronic devices.

Funding Information:
This work was supported by the National Research Foundation of Korea ( NRF ) [Grant Numbers 2016R1A3B1908249 , 2019R1A6A1A11044070 ] funded by the Korean Government and LG Display under the LGD-Korea University Incubation Program .

Publisher Copyright:
© 2022 Elsevier Ltd


  • Flexible devices
  • Indium zinc oxide
  • Mesh electrodes
  • Organic light-emitting diodes
  • Thermally activated delayed fluorescence

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • General Materials Science
  • Electrical and Electronic Engineering


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