Simultaneous enhancement of efficiency and stability of OLEDs with thermally activated delayed fluorescence materials by modifying carbazoles with peripheral groups

  • Yunge Zhang
  • Dongdong Zhang
  • Taiju Tsuboi
  • Yong Qiu
  • Lian DuanEmail author


Albeit their high efficiencies, the operational stability of the organic light emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) emitters is still far from satisfaction, and few strategies have been proposed to improve their stability. Here, we show that by modifying the carbazole unit, one of the most commonly used donors in TADF emitters, with peripheral groups, both the device efficiency and operational stability can be greatly improved. A well-known TADF molecule— 4,5-di(9H-carbazol-9-yl)phthalonitrile (2CzPN) was chosen as the prototype and modified by introducing peripheral tert-butyl and phenyl groups to the 3,6-positions of the carbazole (named 2tBuCzPN and 2PhCzPN, respectively). The introduced groups not only improve the compounds’ electrochemical stabilities referred to the cyclic voltammetry multi-sweep results, but also promote their photoluminescence quantum yields. Furthermore, reduced singlet-triplet energy gaps are observed, leading to the shortened exciton lifetimes which are benefit to suppress the exciton annihilations. Besides, the steric hindrance of introduced phenyl groups can partly restrain the concentration quenching of the TADF emitter. Consequently, OLEDs based on 2tBuCzPN and 2PhCzPN achieved improved maximum external quantum efficiencies (EQEs) of 17.0% and 14.0%, respectively (compared to 8.5% for 2CzPN). Meanwhile, 2PhCzPN based OLED showed reduced roll-off characteristics and a longer lifetime of 7.8 times higher than that of 2CzPN, testifying the effectiveness of subtle modification of the unstable moieties in simultaneous enhancement of efficiency and stability of OLEDs based on TADF emitters.


TADF OLED stability carbazole peripheral group 


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This work was supported by the National Key Research and Development Program of China (2017YFA0204501), and the National Science Fund of China (51525304, 61890942, U1601651).

Supplementary material

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  1. 1.
    Adachi C. Jpn J Appl Phys, 2014, 53: 060101CrossRefGoogle Scholar
  2. 2.
    Tao Y, Yuan K, Chen T, Xu P, Li H, Chen R, Zheng C, Zhang L, Huang W. Adv Mater, 2014, 26: 7931–7958CrossRefGoogle Scholar
  3. 3.
    Jou JH, Kumar S, Agrawal A, Li TH, Sahoo S. J Mater Chem C, 2015, 3: 2974–3002CrossRefGoogle Scholar
  4. 4.
    Yang Z, Mao Z, Xie Z, Zhang Y, Liu S, Zhao J, Xu J, Chi Z, Aldred MP. Chem Soc Rev, 2017, 46: 915–1016CrossRefGoogle Scholar
  5. 5.
    Su SJ. Chin Sci Bull, 2016, 61: 3448–3452 (in Chinese)Google Scholar
  6. 6.
    Endo A, Sato K, Yoshimura K, Kai T, Kawada A, Miyazaki H, Adachi C. Appl Phys Lett, 2011, 98: 083302CrossRefGoogle Scholar
  7. 7.
    Uoyama H, Goushi K, Shizu K, Nomura H, Adachi C. Nature, 2012, 492: 234–238CrossRefGoogle Scholar
  8. 8.
    Rizzo F, Cucinotta F. Isr J Chem, 2018, 58: 874–888CrossRefGoogle Scholar
  9. 9.
    Dias FB, Bourdakos KN, Jankus V, Moss KC, Kamtekar KT, Bhalla V, Santos J, Bryce MR, Monkman AP. Adv Mater, 2013, 25: 3707–3714CrossRefGoogle Scholar
  10. 10.
    Nishimoto T, Yasuda T, Lee SY, Kondo R, Adachi C. Mater Horiz, 2014, 1: 264–269CrossRefGoogle Scholar
  11. 11.
    Kawasumi K, Wu T, Zhu T, Chae HS, van Voorhis T, Baldo MA, Swager TM. J Am Chem Soc, 2015, 137: 11908–11911CrossRefGoogle Scholar
  12. 12.
    Cho YJ, Yook KS, Lee JY. Adv Mater, 2014, 26: 6642–6646CrossRefGoogle Scholar
  13. 13.
    Hatakeyama T, Shiren K, Nakajima K, Nomura S, Nakatsuka S, Kinoshita K, Ni J, Ono Y, Ikuta T. Adv Mater, 2016, 28: 2777–2781CrossRefGoogle Scholar
  14. 14.
    Nishide J, Nakanotani H, Hiraga Y, Adachi C. Appl Phys Lett, 2014, 104: 233304CrossRefGoogle Scholar
  15. 15.
    Cho YJ, Jeon SK, Chin BD, Yu E, Lee JY. Angew Chem Int Ed, 2015, 54: 5201–5204CrossRefGoogle Scholar
  16. 16.
    Lee SY, Adachi C, Yasuda T. Adv Mater, 2016, 28: 4626–4631CrossRefGoogle Scholar
  17. 17.
    Lee SY, Yasuda T, Komiyama H, Lee J, Adachi C. Adv Mater, 2016, 28: 4019–4024CrossRefGoogle Scholar
  18. 18.
    Zhang Y, Zhang D, Cai M, Li Y, Zhang D, Qiu Y, Duan L. Nanotechnology, 2016, 27: 094001CrossRefGoogle Scholar
  19. 19.
    Sun JW, Lee JH, Moon CK, Kim KH, Shin H, Kim JJ. Adv Mater, 2014, 26: 5684–5688CrossRefGoogle Scholar
  20. 20.
    Kaji H, Suzuki H, Fukushima T, Shizu K, Suzuki K, Kubo S, Komino T, Oiwa H, Suzuki F, Wakamiya A, Murata Y, Adachi C. Nat Commun, 2015, 6: 8476CrossRefGoogle Scholar
  21. 21.
    Lin TA, Chatterjee T, Tsai WL, Lee WK, Wu MJ, Jiao M, Pan KC, Yi CL, Chung CL, Wong KT, Wu CC. Adv Mater, 2016, 28: 6976–6983CrossRefGoogle Scholar
  22. 22.
    Cui LS, Nomura H, Geng Y, Kim JU, Nakanotani H, Adachi C. Angew Chem Int Ed, 2017, 56: 1571–1575CrossRefGoogle Scholar
  23. 23.
    Kuei CY, Tsai WL, Tong B, Jiao M, Lee WK, Chi Y, Wu CC, Liu SH, Lee GH, Chou PT. Adv Mater, 2016, 28: 2795–2800CrossRefGoogle Scholar
  24. 24.
    Shin H, Lee JH, Moon CK, Huh JS, Sim B, Kim JJ. Adv Mater, 2016, 28: 4920–4925CrossRefGoogle Scholar
  25. 25.
    Shizu K, Noda H, Tanaka H, Taneda M, Uejima M, Sato T, Tanaka K, Kaji H, Adachi C. J Phys Chem C, 2015, 119: 26283–26289CrossRefGoogle Scholar
  26. 26.
    Lee SY, Yasuda T, Park IS, Adachi C. Dalton Trans, 2015, 44: 8356–8359CrossRefGoogle Scholar
  27. 27.
    Tsang DPK, Matsushima T, Adachi C. Sci Rep, 2016, 6: 22463CrossRefGoogle Scholar
  28. 28.
    Kim M, Jeon SK, Hwang SH, Lee JY. Adv Mater, 2015, 27: 2515–2520CrossRefGoogle Scholar
  29. 29.
    Lee J, Aizawa N, Numata M, Adachi C, Yasuda T. Adv Mater, 2017, 29: 1604856CrossRefGoogle Scholar
  30. 30.
    Zhang D, Cai M, Zhang Y, Zhang D, Duan L. Mater Horiz, 2016, 3: 145–151CrossRefGoogle Scholar
  31. 31.
    Noda H, Nakanotani H, Adachi C. Sci Adv, 2018, 4: eaao6910Google Scholar
  32. 32.
    Masui K, Nakanotani H, Adachi C. Org Electron, 2013, 14: 2721–2726CrossRefGoogle Scholar
  33. 33.
    Kondakov DY. J Appl Phys, 2008, 104: 084520CrossRefGoogle Scholar
  34. 34.
    Schmidbauer S, Hohenleutner A, König B. Adv Mater, 2013, 25: 2114–2129CrossRefGoogle Scholar
  35. 35.
    So F, Kondakov D. Adv Mater, 2010, 22: 3762–3777CrossRefGoogle Scholar
  36. 36.
    Lin N, Qiao J, Duan L, Wang L, Qiu Y. J Phys Chem C, 2014, 118: 7569–7578CrossRefGoogle Scholar
  37. 37.
    Hong M, Ravva MK, Winget P, Brédas JL. Chem Mater, 2016, 28: 5791–5798CrossRefGoogle Scholar
  38. 38.
    Xiang C, Fu X, Wei W, Liu R, Zhang Y, Balema V, Nelson B, So F. Adv Funct Mater, 2016, 26: 1463–1469CrossRefGoogle Scholar
  39. 39.
    Karon K, Lapkowski M. J Solid State Electrochem, 2015, 19: 2601–2610CrossRefGoogle Scholar
  40. 40.
    Carlier R, Raoult E, Tallec A, Andre V, Gauduchon P, Lancelot JC. Electroanalysis, 1997, 9: 79–84CrossRefGoogle Scholar
  41. 41.
    Majeed SA, Ghazal B, Nevonen DE, Goff PC, Blank DA, Nemykin VN, Makhseed S. Inorg Chem, 2017, 56: 11640–11653CrossRefGoogle Scholar
  42. 42.
    Tuong Ly K, Chen-Cheng RW, Lin HW, Shiau YJ, Liu SH, Chou PT, Tsao CS, Huang YC, Chi Y. Nat Photon, 2017, 11: 63–68CrossRefGoogle Scholar
  43. 43.
    Chan CY, Tanaka M, Nakanotani H, Adachi C. Nat Commun, 2018, 9: 5036CrossRefGoogle Scholar

Copyright information

© Science China Press and Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • Yunge Zhang
    • 1
  • Dongdong Zhang
    • 1
  • Taiju Tsuboi
    • 2
  • Yong Qiu
    • 1
  • Lian Duan
    • 1
    Email author
  1. 1.Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of ChemistryTsinghua UniversityBeijingChina
  2. 2.Department of Polymer Science and EngineeringZhejiang UniversityHangzhouChina

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