Highly Efficient Solution-Processed Organic Light-Emitting Diodes Containing a New Cross-linkable Hole Transport Material Blended with Commercial Hole Transport Materials

Hyein Ha, Young Jae Shim, Da Hwan Lee, Eun Young Park, In Ho Lee, Seok Keun Yoon, Min Chul Suh

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)

Abstract

A new small-molecular thermally cross-linkable material {[4-(9-phenyl-9H-carbazol-4-yl)phenyl]-bis-(4′-vinylbiphenyl-4-yl)-amine} (PCP-bis-VBPA, PbV) containing the styrene moiety was synthesized for hole transport layers in wet processed organic light-emitting diodes (OLEDs). It was found that PbV exhibited relatively high glass temperatures above 154 °C and a triplet energy (T1) greater than 2.81 eV. This new synthetic hole transport material (HTM) forms very uniform films after cross-linking reaction with little pin-holes, although it was small-molecule-based cross-linkable HTM. However, to solve the certain minor non-uniformity caused by pinholes with various sizes, a semi-interpenetrating network was formed with well-known polymeric HTM with high mobility [e.g., poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenyl amine), TFB, or poly(N,N′-bis-4-butylphenyl-N,N′-bisphenyl)benzidine, poly-TPD]. As a result, we successfully fabricated red phosphorescent OLED showing an efficiency of about 16.7 cd/A and 12.4% (external quantum efficiency) if we applied PbV blended with 20% of TFB or poly-TPD. In particular, the efficiency and lifetime are significantly improved by 1.5 and 4.5 times, respectively, compared to those of the control device without using blended HTM.

Original languageEnglish
Pages (from-to)21954-21963
Number of pages10
JournalACS applied materials & interfaces
Volume13
Issue number18
DOIs
Publication statusPublished - 12 May 2021

Bibliographical note

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Keywords

  • cross-linkable HTM
  • organic light-emitting diode (OLED)
  • red phosphorescent OLED
  • solution process

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