Improved efficiency of red phosphorescent organic light-emitting diodes with combination of heterojunction and mixed host structure.
We report an improvement of efficiency in red phosphorescent organic light-emitting diodes (PHOLEDs) based on a combination of heterojunction (HJ) structure and mixed host (MH) system using a phosphorescent red emitter: bis(2-phenylquinolinato)-acetylacetonate iridium III [Ir(pq)2(acac)] doped in 4,4,N,N'-dicarbazolebiphenyl (CBP) of hole transport type host material and 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi) of electron transport type host material. This combination device resulted in an effective electron and hole balance and distribution of the recombination zone. Therefore, highly efficient red PHOLEDs with maximum luminous efficiency and external quantum efficiency of 21.93 cd/A and 14.09% were achieved. Moreover, the combination device showed a power efficiency of 9.51 lm/W, which is higher than 7.61 lm/W in the control device at a luminance of 1000 cd/m2.
Dong Hwan
DH
Lim
Seok Jae
SJ
Lee
Ja Ryong
JR
Koo
Bo Young
BY
Kim
Hyun Su
HS
Shin
Kum Hee
KH
Lee
Sang Youn
SY
Lee
Woo Young
WY
Kim
Seung Soo
SS
Yoon
Young Kwan
YK
Kim