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Electronic Materials Letters

, Volume 14, Issue 2, pp 89–100 | Cite as

Synthesis, Properties, Calculations and Applications of Small Molecular Host Materials Containing Oxadiazole Units with Different Nitrogen and Oxygen Atom Orientations for Solution-Processable Blue Phosphorescent OLEDs

  • Hua Ye
  • Hongyu Wu
  • Liangyuan Chen
  • Songhua Ma
  • Kaifeng Zhou
  • Guobing Yan
  • Jiazhong Shen
  • Dongcheng Chen
  • Shi-Jian Su
Article
  • 178 Downloads

Abstract

A series of new small molecules based on symmetric electron-acceptor of 1,3,4-oxadiazole moiety or its asymmetric isomer of 1,2,4-oxadiazole unit were successfully synthesized and applied to solution-processable blue phosphorescent organic light-emitting diodes for the first time, and their thermal, photophysical, electrochemical properties and density functional theory calculations were studied thoroughly. Due to the high triplet energy levels (ET, 2.82–2.85 eV), the energy from phosphorescent emitter of iridium(III) bis[(4,6-difluorophenyl)-pyridinate-N,C2′]picolinate (FIrpic) transfer to the host molecules could be effectively suppressed and thus assuring the emission of devices was all from FIrpic. In comparison with the para-mode conjugation in substitution of five-membered 1,3,4-oxadiazole in 134OXD, the meta-linkages of 1,2,4-isomer appending with two phenyl rings cause the worse conjugation degree and the electron delocalization as well as the lower electron-withdrawing ability for the other 1,2,4-oxadiazole-based materials. Noting that the solution-processed device based on 134OXD containing 1,3,4-oxadiazole units without extra vacuum thermal-deposited hole/exciton-blocking layer and electron-transporting layer showed the highest maximum current efficiency (CEmax) of 8.75 cd/A due to the excellent charge transporting ability of 134OXD, which far surpassed the similar devices based on other host materials containing 1,2,4-oxadiazole units. Moreover, the device based on 134OXD presented small efficiency roll-off with current efficiency (CE) of 6.26 cd/A at high brightness up to 100 cd/m2. This work demonstrates different nitrogen and oxygen atom orientations of the oxadiazole-based host materials produce major impact on the optoelectronic characteristics of the solution-processable devices.

Graphical Abstract

Keywords

Oxadiazole OLED Host materials Phosphorescence Electroluminescence Solution-processable 

Notes

Acknowledgements

This work was financially supported by National Natural Science Foundation of China (21572094, 51073057 and 91233116), the Ministry of Science and Technology (2014DFA52030 and 2015CB655003), the Ministry of Education (NCET-11-0159), the Department of Education of Zhejiang Province (Y201533100), and Lishui University (15JZ08). The authors are grateful to Yifan Li and Prof. Chuluo Yang for their help in low temperature phosphorescence measurements.

Supplementary material

13391_2018_11_MOESM1_ESM.doc (1006 kb)
Supplementary material 1 (DOC 1005 kb)

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Copyright information

© The Korean Institute of Metals and Materials 2018

Authors and Affiliations

  1. 1.Institute of Optoelectronic TechnologyLishui UniversityLishuiChina
  2. 2.State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and DevicesSouth China University of TechnologyGuangzhouChina

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