Highly Efficient Phosphorescent Blue Organic Light-Emitting Diodes Based on Double-Emitting Layer

Abstract

In this paper, We have demonstrated lower driving voltage and efficient Blue phosphorescent organic light emitting diodes (PHOLEDs) using iridium (III) bis[(4,6-di-fluoropheny)-pyridinato-N,C²] picolinate doped in N,N′-dicarbazolyl-3,5-benzene (mCP) and 2,2′,2″-(1,3,5-benzenetryl)tris(1-phenyl)-1H-benzimidazol (TPBi) as double-emitting layer system. D-EML layers were employed to have good exciton confinement. We also demonstrated that mCP as electron blocking layer inserted EML and HTL for higher efficiency. The optimized device of double EML of mCP:TPBi(1:1) exhibited a maximum external quantum efficiency of 9.22% at 0.21 mA/cm², a maximum Current efficiency of 18.89 cd/A at 0.21 mA/cm², and Commission Internationale de I'Eclairage coordinates of (0.17, 0.35) at 1000 cd/m², respectively.

Keywords:

• Blue phosphorescent organic light emitting diodes
• double-emitting layer
• energy transfer
• exciton confinement

Acknowledgments

This work was supported by the ERC program of the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea Ministry of Education, Science and Technology (MEST) (No. R11-2007-045-03001-0).