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

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,C-2] 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/cm(2), a maximum Current efficiency of 18.89 cd/A at 0.21 mA/cm(2), and Commission Internationale de I'Eclairage coordinates of (0.17, 0.35) at 1000 cd/m(2), respectively.