This letter reports on the effect of the triplet energy (ET) of the hole-blocking layer (HBL) on triplet exciton quenching between the emissive layer (EML) host and the HBL of phosphorescent organic light-emitting diodes (PHOLEDs). Using different EML hosts and HBLs having different ET's and electron mobilities, the effects of the ET's of the HBL have been analyzed. When the ETof the HBL is lower than that of the EML host, the PHOLEDs show significant dependence of reduced device performances. PHOLEDs having a 3-(4-biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole HBL show 65% improved external quantum efficiency (EQE) at 500 cd/m2with a 4, 4'4,-tris(N-carbazolyl)-triphenyl-amine host than that with an N,N-dicarbazolyl-4-4-biphenyl host, while PHOLEDs having a 2,9-dimethyl-4,7- diphenyl-1,10-phenanthroline HBL show 41% reduced EQE. To solve the remaining key issue of developing highly efficient PHOLEDs, the ETof matching the EML and the HBL is extremely desirable and is also explored.
Bibliographical noteFunding Information:
Manuscript received October 6, 2009; revised January 19, 2010. Date of publication March 15, 2010; date of current version April 23, 2010. This work was supported in part by the Korean Science and Engineering Foundation under Grant R11-2007-045-01003-0 funded by the Korean Ministry of Education, Science and Technology (MEST), by World Class University Project R32-2008-000-10082-0 of MEST, and by the IT R&D program of MKE/IITA (2009-F-017-01, Development of Fundamental Technologies for Flexible Combined-Function Organic Electronic Device). The review of this letter was arranged by Editor C. Jagadish.
- Phosphorescent organic light-emitting diodes (PHOLEDs)
- Triplet energy of hole-blocking layer (HBL)
- Triplet quenching
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering