Highly efficient bipolar host materials towards solution-processable blue and green thermally activated delayed fluorescence organic light emitting diodes

New versatile host materials with good solubility in common organic solvents are greatly desired to promote solution-processable thermally activated delayed fluorescence organic light-emitting diodes. This paper describes the design and synthesis of two new host materials, namely 3′-(9 H -carbazol-9...

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Veröffentlicht in:Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2018, Vol.6 (37), p.10000-10009
Hauptverfasser: Godumala, Mallesham, Choi, Suna, Kim, Seong Keun, Kim, Si Woo, Kwon, Jang Hyuk, Cho, Min Ju, Choi, Dong Hoon
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Sprache:eng
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Zusammenfassung:New versatile host materials with good solubility in common organic solvents are greatly desired to promote solution-processable thermally activated delayed fluorescence organic light-emitting diodes. This paper describes the design and synthesis of two new host materials, namely 3′-(9 H -carbazol-9-yl)-[1,1′-biphenyl]-3,5-diylbis(diphenylphosphine oxide) ( CDPO ) and 3′,5′-di-(9 H -carbazol-9-yl)-[1,1′-biphenyl]-3,5-diylbis (diphenylphosphine oxide) ( mCPDPO ), featuring hole-transporting carbazole and electron-transporting diphenylphosphine oxide (DPO) entities. The donor strength was varied to a constant n-type DPO core to tune the functional properties. The detailed studies proved that the resulting two new materials exhibit excellent solubility in common organic solvents, high triplet energy (>2.80 eV), high glass transition temperature (up to 133 °C), and good bipolar electronic nature. Consequently, both compounds were used as hosts in solution-processable blue and green thermally activated delayed fluorescence (TADF) OLEDs. In particular, the devices using mCPDPO as a host in the emissive layer showed outstanding performance with a maximum current efficiency, power efficiency, and external quantum efficiency of 35.3 cd A −1 , 17.0 lm W −1 and 15.4% in the blue-emitting diode, and 61.5 cd A −1 , 29.7 lm W −1 and 18.8% in the green-emitting diode, respectively. These results corroborated the potential of carbazole-phosphine oxide derivatives as host materials in solution-processable blue and green TADF OLEDs.
ISSN:2050-7526
2050-7534
DOI:10.1039/C8TC02649A