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Frontiers of Optoelectronics

, Volume 11, Issue 4, pp 375–384 | Cite as

Efficient deep red phosphorescent OLEDs using 1,2,4-thiadiazole core-based novel bipolar host with low efficiency roll-off

  • Runda Guo
  • Wenzhi Zhang
  • Qing Zhang
  • Xialei Lv
  • Lei WangEmail author
Research Article
  • 9 Downloads

Abstract

A series of 1,2,4-thiadiazole core-based bipolar materials, 2,2′-(1,2,4-thiadiazole-3,5-diyl)bis(N,N-diphenylaniline) (o-TPATHZ), 3,3′-(1,2,4-thiadiazole-3,5-diyl)bis(N,N-diphenylaniline) (m-TPATHZ) and 4,4′-(1,2,4-thiadiazole-3,5-diyl)bis(N,N-diphenylaniline) (p-TPATHZ) were developed as the host matrixes for the deep red phosphorescent emitters tris(1-phenylisoqiunoline) iridium (Ir(piq)3) and [bis(2-methyldibenzo-[f,h]-quinoxaline) Ir(III)(acetylacetonate)] (Ir(MDQ)2(acac)). By systematic studying, we demonstrated that there are two types of charge-trapping effect within the emissive layers through adjusting the host-guest compatibility. And, it is revealed that a symmetric charge-trapping effect can contribute to realizing a stable charge-balance, which led to a mitigating efficiency roll-off at high current density. Consequently, a maximum external quantum efficiency (EQE) of 16.2% was achieved by an optimized device with p-TPATHZ-Ir(piq)3 emissive layer. Remarkably, the EQE still remained as high as 15.7% at the high luminance of 1000 cd/m2.

Keywords

1, 2, 4-thiadiazole core low efficiency roll-off deep red phosphorescent devices symmetrical charge-trapping effect 

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Notes

Acknowledgements

This research work was supported by the National Natural Science Foundation of China (Grant Nos. 51573065 and 51727809), China Postdoctoral Science Foundation (No. 2017M620321), the science and technology support program of Hubei Province (No. 2015BAA075), the Fundamental Research Funds for the Central Universities, HUST (No. 2018KFYXKJC043). Thanks to SCTS/CGCL HPCC of HUST for providing computing resources and technical support. The Analytical and Testing Center at Huazhong University of Science and Technology is acknowledged for characterization of new compounds.

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Copyright information

© Higher Education Press and Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  • Runda Guo
    • 1
  • Wenzhi Zhang
    • 1
  • Qing Zhang
    • 1
  • Xialei Lv
    • 1
  • Lei Wang
    • 1
    Email author
  1. 1.Wuhan National Laboratory for OptoelectronicsHuazhong University of Science and TechnologyWuhanChina

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