Abstract
The mixed layer for an emitting layer (EML) consists of two materials 4,4′,4′′-tris(N-carbazolyl)-triphenylamine (TCTA) and 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi) without host material. A series of EML structures were fabricated with three types of single mixed layers (mixing ratio 2:1, 1:2) and double mixed layers (mixing ratio 2:1/1:2), and the EML of using double mixed layer was optimized. The maximum luminous efficiency (LE) and quantum efficiency (QE) were 62.07 cd/A, 18.92%, respectively. Moreover, the roll-off ratio of LE was 20.42% at 20,000 cd/m2. Interestingly, this result shows the roll-off ratio was reduced roughly 50% compared to the reference device.
Acknowledgment
This research was supported by the MSIP (Ministry of Science, ICT & Future Planning), Korea, under the ITRC (Information Technology Research Center) support program NIPA-2013-(H0301-13-1004) supervised by the NIPA (National IT Industry Promotion Agency) and the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP)(CAFDC/Young Kwan Kim/No. 2007-0056090).