Efficient blue organic light-emitting diodes employing thermally activated delayed fluorescence

Qisheng Zhang, Bo Li, Shuping Huang, Hiroko Nomura, Hiroyuki Tanaka, Chihaya Adachi

Research output: Contribution to journalArticlepeer-review

1325 Scopus citations

Abstract

Organic light-emitting diodes (OLEDs) employing thermally activated delayed fluorescence (TADF) have emerged as cheaper alternatives to high-performance phosphorescent OLEDs with noble-metal-based dopants. However, the efficiencies of blue TADF OLEDs are still low at high luminance, limiting full-colour display. Here, we report a blue OLED containing a 9,10-dihydroacridine/ diphenylsulphone derivative that has a comparable performance to today's best phosphorescent OLEDs. The device offers an external quantum efficiency of 19.5% and reduced efficiency roll-off characteristics at high luminance. Through computational simulation, we identified six pretwisted intramolecular charge-transfer (CT) molecules with small singlet-triplet CT state splitting but different energy relationships between 3CT and locally excited triplet (3LE) states. Systematic comparison of their excited-state dynamics revealed that CT molecules with a large twist angle can emit efficient and short-lifetime (a few microseconds) TADF when the emission peak energy is high enough and the 3LE state is higher than the 3CT state.

Original languageEnglish (US)
Pages (from-to)326-332
Number of pages7
JournalNature Photonics
Volume8
Issue number4
DOIs
StatePublished - Apr 2014

Bibliographical note

Funding Information:
This work was supported by a Grant-in-Aid from the Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST) and the International Institute for Carbon Neutral Energy Research (WPI-I2CNER) sponsored by MEXT. The authors thank J.-L. Brédas, M. Kotani and K. Tokumaru for stimulating discussions regarding this work. The authors also thank W. J. Potscavage Jr for assistance with preparation of this manuscript.

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