Using light-emitting dyes as a co-host to markedly improve efficiency roll-off in phosphorescent yellow organic light emitting diodes
| Autor: | Szu-Hao Chen, Cheng-Hua Chen, Cheng-I. Chiang, Po-Wei Chen, Chien-Chih Chen, James H. Hong, Ching-Chiun Wang, Chih-Lung Chin, Yi-Shan Wang, Yung-Cheng Jou, Jwo-Huei Jou, Shiang-Hau Peng, Fu-Ching Tung, Jing-Ru Tseng |
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| Rok vydání: | 2013 |
| Předmět: | |
| Zdroj: | J. Mater. Chem. C. 1:394-400 |
| ISSN: | 2050-7534 2050-7526 |
| DOI: | 10.1039/c2tc00067a |
| Popis: | We discovered in this study the feasibility of using regular light-emitting dyes as an effective co-host, rather than a sensitizer, to markedly improve the efficiency of phosphorescent organic light emitting diodes. At 10000 cd m−2, for example, the efficacy of a yellow emitter containing device was increased from 11.7 lm W−1 to 15.4 lm W−1, an increment of 32%, as a sky-blue phosphorescent dye, bis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl)iridium(III) (FIrpic), was blended into a host of 4,4′,4′′-tri(N-carbazolyl)triphenylamine (TCTA). The efficacy at 1000 cd m−2 was 26.7 lm W−1, the highest among all reported yellow OLEDs with a solution-processed emissive layer. The marked efficiency improvement may be attributed to the co-host having an electron trapping character, enabling excitons to generate on itself instead of on the guest, creating an additional efficiency-effective energy transfer route, and having a very efficient co-host to guest energy transfer. The most effective co-host may vary with the variation of the host employed, depending on the energy level pairing of the co-host and host. |
| Databáze: | OpenAIRE |
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