New polyurethanes with carbazole and OXD derivate as hole-transporting layer for organic light emitting diodes

PMSE 6

Cheng-Hsiu Ku, kutonyku@yahoo.com.tw, Institute of Polymer Science and Engineering, National Taiwan University, Taipei, 106, Taiwan
A novel study in hole-transport polyurethanes (PU's) has been developed. The PU's materials were prepared from condensation polymerization of isophorone diisocyanate (IPDI) and 3,6-diphenol-9-butylcarbazole 4, with various amounts of 2,5-bis(4-hydroxyphenyl)-1,3,4-oxadiazole 5, and with 4-tert-butyl phenol as the end group when terminating the reaction.. The PU's materials show increased hole-injection properties that were concluded on the basis of the improved current injection in the corresponding hole-only device. The Cz-PU interfacial layer has been inserted in ITO/PEDOT-PSS(30nm)/PU(30nm)/NPB(40nm)/Alq3(40nm)/LiF(1nm) /Al(150nm) when fabricating the OLED device has a dramatic voltage reduction of 3.0V. The performance of luminance efficiency in the OLED device was improved up to 4.40 cd/A. The maximum brightness increases up to 17120 cd/m2 with the Cz: OXD ratio of 1: 1 compared with that of 9223 cd/m2 for the standard device in device configuration ITO/PEDOT-PSS(30nm)/ƒ{NPB(40nm)/Alq3(40nm)/LiF(1nm)/Al(150 nm).