Hole-Transporting Side-Chain Polymer Bearing a Thermally Crosslinkable Bicyclo[4.2.0]octa-1,3,5-trien-3-yl Group for High-Performing Thermally Activated Delayed Fluorescence OLED

Cheol Hun Jeong, Mallesham Godumala, Jiwon Yoon, Suna Choi, Yong Woo Kim, Dae Hyuk Choi, Min Ju Cho, Dong Hoon Choi

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

A new side-chain polymer (X-TPACz) bearing hole-transporting pendant groups accompanying a thermally crosslinkable entity was synthesized using N-([1,1′-biphenyl]-4-yl)-N-(4-(9-(4-vinylbenzyl)-9H-carbazol-3-yl)phenyl)bicyclo[4.2.0]octa-1(6),2,4-trien-3-amine (6) via addition polymerization. The X-TPACz could be spontaneously crosslinked without using any further reagents and showed a good film-forming property upon low-temperature thermal treatment. The thermal curing temperature for the X-TPACz film was optimized to be 180 °C based on a differential scanning calorimetry thermogram. Moreover, the thermal degradation temperature of X-TPACz measured to be over 467 °C using thermogravimetric analysis demonstrated that it shows excellent thermal stability. In particular, X-TPACz exhibits the highest occupied molecular orbital (HOMO) energy level to be -5.26 eV, which is beneficial for facile hole injection and transportation. Consequently, the thermally activated delayed fluorescence organic light-emitting diodes fabricated using X-TPACz as the hole-transporting material showed state-of-the-art performances with a low turn-on voltage (V on ) of only 2.7 V and a high external quantum efficiency (EQE) of 19.18% with a high current efficiency (CE) of 66.88 cd/A and a high power efficiency (PE) of 60.03 lm/W, which are highly superior to those of the familiar poly(9-vinylcarbazole) (PVK)-based devices (V on = 3.9 V, EQE of 17.42%, with CE of 58.33 cd/A and PE of 33.32 lm/W). The extremely low turn-on voltage and high EQE were found to be due to the higher-lying highest occupied molecular orbital energy level (E HOMO = -5.23 eV) and better hole-transporting property of X-TPACz than those of PVK.

Original languageEnglish
Pages (from-to)17602-17609
Number of pages8
JournalACS Applied Materials and Interfaces
Volume11
Issue number19
DOIs
Publication statusPublished - 2019 May 15

Keywords

  • hole-transport material
  • organic light-emitting diode
  • solution process
  • thermal crosslinking
  • thermally activated delayed fluorescence

ASJC Scopus subject areas

  • Materials Science(all)

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