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Proceedings Paper

Highly efficient and stable phosphorescent organic light-emitting diodes employing TADF materials as host (Conference Presentation)
Author(s): Hirohiko Fukagawa; Yukiko Iwasaki; Takahisa Shimizu
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Paper Abstract

The OLED is one of the key devices for realizing next-generation displays and lighting. The efficiency of OLEDs has been improved markedly by employing phosphorescent emitters. However, there are two main issues in the practical application of phosphorescent OLEDs (PHOLEDs): the relatively short operational lifetime of green/blue devices and the relatively high cost owing to the use of a costly emitter with a concentration of about 10% in the emitting layer. Here, we report on our success in resolving these issues by the utilization of thermally activated delayed fluorescent (TADF) materials as the host materials for phosphorescent emitters. Operationally stable green PHOLEDs are demonstrated by employing a TADF material as the host since the triplet excitons of the host, which are key elements in operational degradation, are transferred rapidly to the emitter following the Förster process via reverse intersystem crossing from the triplet to singlet states. In this case, the concentration of the emitter can be reduced to 1–3 wt%, similar to that in fluorescent OLEDs. Although an external quantum efficiency (EQE) of about 20% is obtained in many PHOLEDs regardless of the TADF host, the operational lifetime strongly depends on the host. Our optimized green PHOLED employing only 1 wt% phosphorescent emitter exhibits an EQE of over 20%, a small efficiency roll-off, and a long operational lifetime on the order of 10,000 h with an initial luminance of 1,000 cd/m2.

Paper Details

Date Published: 4 November 2016
PDF: 1 pages
Proc. SPIE 9941, Organic Light Emitting Materials and Devices XX, 99410I (4 November 2016); doi: 10.1117/12.2236751
Show Author Affiliations
Hirohiko Fukagawa, NHK Japan Broadcasting Corp. (Japan)
Yukiko Iwasaki, NHK Japan Broadcasting Corp. (Japan)
Takahisa Shimizu, NHK Japan Broadcasting Corp. (Japan)


Published in SPIE Proceedings Vol. 9941:
Organic Light Emitting Materials and Devices XX
Franky So; Chihaya Adachi; Jang-Joo Kim, Editor(s)

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