Effect of Stepwise Doping on Lifetime and Efficiency of Blue and White Phosphorescent Organic Light Emitting Diodes.
We investigated a light emission mechanism of blue phosphorescent organic light emitting diodes (PHOLEDs), using a stepwise doping profile of 2, 8, and 14 wt.% within the emitting layer (EML). We fabricated several blue PHOLEDs with phosphorescent blue emitter iridium(III) bis[(4,6-difluorophenyl)-pyridinato-N,C2]picolinate doped in N,N'-dicarbazolyl-3,5-benzene as a p-type host material. A blue PHOLED with the highest doping concentration as part of the EML close to an electron transporting layer showed a maximum luminous efficiency of 20.74 cd/A, and a maximum external quantum efficiency of 10.52%. This can be explained by effective electron injection through a highly doped EML side. Additionally, a white OLED based on the doping profile was fabricated with two thin red EMLs within a blue EML maintaining a thickness of 30 nm for the entire EML. Keywords: Blue Phosphorescent Organic Light Emitting Diodes, Stepwise Doping Structure, Charge Trapping Effect.
Song Eun
SE
Lee
Ho Won
HW
Lee
Seok Jae
SJ
Lee
Ja-ryong
JR
Koo
Dong Hyung
DH
Lee
Hyung Jin
HJ
Yang
Hye Jeong
HJ
Kim
Seung Soo
SS
Yoon
Young Kwan
YK
Kim
D003116:Color; D004735:Energy Transfer; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008029:Lighting / Q000295:instrumentation*; D008422:Materials Testing; D053761:Nanocomposites / Q000737:chemistry* / Q000648:ultrastructure; D009930:Organic Chemicals / Q000737:chemistry*; D012666:Semiconductors
D009930:Organic Chemicals