Spin-assembled nanolayer of a hyperbranched polymer on the anode in organic light-emitting diodes: the mechanism of hole injection and electron blocking.
We introduced a spin-assembled nanolayer of hyperbranched poly(ether sulfone) with sulfonic acid terminal on top of an indium-tin oxide anode in organic light-emitting diodes. This results in great improvement in luminous efficiency, better than that of devices using a commercially available conducting polymer composition as a hole-injection layer. The effect of the nanolayer was investigated by impedance spectroscopy, photovoltaic measurement for built-in-potential, and transient electroluminescence. We concluded that the high luminous efficiency resulted from the efficient electron-blocking by the nanolayer and hole-injection assisted by the accumulation of electrons at the interface. This result implies that, for an efficient hole-injection layer, the electron-blocking capability should be incorporated in addition to the hole-injection and -transport capability.
Lee
Tae-Woo
TW
Samsung Advanced Institute of Technology, Gyeonggi-do, Korea. twlee@postech.ac.kr
Park
Jong-Jin
JJ
Kwon
Young
Y
Hayakawa
Teruaki
T
Choi
Tae-Lim
TL
Park
Jong Hyeok
JH
Das
Rupasree Ragini
RR
Kakimoto
Masa-aki
MA