Journal
CHEMPLUSCHEM
Volume 83, Issue 4, Pages 274-278Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/cplu.201700465
Keywords
dendrimers; electroluminance; fluorescence; FRET; white organic light-emitting diodes
Categories
Funding
- Foundations of National Natural Science Foundation of China (NSFC) [51503022, 61705026, 6160513, U1663229]
- International Science & Technology Cooperation Program of China [2014DFR50830]
- Foundation for Innovation Research Groups of the NSFC [61421002]
- Qualified Personnel Foundation of Taiyuan University of technology (QPFT) [tyutrc201255a]
- Chongqing Municipal Education Commission [KJ1601112]
- Chongqing Science and Technology Commission [cstc2015jcyjA50036, cstc2016jcyjA0148, cstc2016jcyj0367]
- Open Foundation of State Key Laboratory of Electronic Thin Films and Integrated Devices [kfjj201507]
- Natural Science Foundation of Yongchuan District [Ycstc2015nc4001, Ycstc2015nc4002]
- research project for Chongqing University of Arts and Sciences [z2016xc16]
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Thermally activated delayed fluorescence (TADF) emitters have received much attention for the fabrication of white organic light-emitting diodes (WOLEDs); however, challenges remain owing to severe efficiency roll-off, poor color stability, and high cost. In this contribution, solution-processed hybrid WOLEDs were obtained by employing a blue TADF dendrimer, bis{4-[3,6-bis(3,6-di-tert-butylcarbazol-N-yl)carbazol-N-yl]phenyl}sulfone (BPS), combined with an orange iridium complex, bis(2-phenylbenzothiazolato)(acetylacetonate)iridium(III), Ir(bt)(2)(acac), as a co-dopant. The devices achieved a maximum external quantum efficiency of 6.59% and a maximum current efficiency of 17.34cdA(-1). The results suggest that the TADF dendrimer serving as an assistant dopant were helpful in reducing the triplet populations by up-converting the triplet excitons to the singlet state and immediately transferring the singlet excitons to Ir(bt)(2)(acac) (bt=2-phenylbenzothiazolato, acac=acetylacetonato) by virtue of the long-range Forster resonance energy transfer, thus significantly decreasing the triplet-triplet annihilation (TTA). Moreover, the emitters can act as shallow trapping centers to decrease charge and exciton aggregation. The resulting OLEDs exhibit stable electroluminescent spectra and low efficiency roll-off at relatively high current density. The CIE coordinates (x,y) vary only (0.02, 0.02) in the luminance range of 100 to 10000 cdm(-2).
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