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Solution‐Processed Warm White Organic Light‐Emitting Diodes Based on a Blue Thermally Activated Delayed Fluorescence Dendrimer
Author(s) -
Liao Xiaoqing,
Yang Xin,
Cheng Jiang,
Li Ying,
Meng Xiang,
Li Jie,
Pei Qibing,
Li Lu
Publication year - 2018
Publication title -
chempluschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.801
H-Index - 61
ISSN - 2192-6506
DOI - 10.1002/cplu.201700465
Subject(s) - oled , iridium , dopant , electroluminescence , photochemistry , quantum efficiency , exciton , fluorescence , materials science , phosphorescence , singlet state , dendrimer , chemistry , optoelectronics , doping , nanotechnology , polymer chemistry , optics , atomic physics , excited state , organic chemistry , physics , layer (electronics) , quantum mechanics , catalysis
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 17.34 cd A −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 Förster 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 Δ( x , y ) vary only (0.02, 0.02) in the luminance range of 100 to 10 000 cd m −2 .