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Solution-Processed Warm White Organic Light-Emitting Diodes Based on a Blue Thermally Activated Delayed Fluorescence Dendrimer

Solution-Processed Warm White Organic Light-Emitting Diodes Based on a Blue Thermally Activated Delayed Fluorescence Dendrimer

Xiaoqing Liao, Xin Yang, Jiang Cheng, Ying Li, Xiang Meng, Jie Li, Qibing Pei, Lu Li

Chempluschem. 2018 Apr;83(4):274-278.

PMID: 31957278

Abstract:

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 .

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP337526882	Ir(BT)2(acac)		337526-88-2	Price

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