Carbazole–oxadiazole containing polyurethanes as phosphorescent host for organic light emitting diodes

New types of polyurethanes (PUs) were prepared from condensation polymerization of isophorone diisocyanate (IPDI) with various combination of 9-butyl-3,6-bis(4-hydroxyphenyl)carbazole (Cz) and 2,5-bis(4-hydroxyphenyl)-1,3,4-oxadiazole (OXD), and end-capped with 4-tert-butyl phenol. The Cz-OXD PUs can also be used as host for phosphorescent dye. Red EL emission was obtained when Ir(btp)2(acac) or Ir(2-phq)2(acac) was used as the phosphorescent dyes in Cz-OXD (3:1) PU. Maximum brightness of 394 cd/m2 and EL efficiency of 1 cd/A were achieved for the Ir(2-phq)2(acac) base device. In addition, white light PLED was demonstrated when co-dopant of Ir(btp)2(acac) and Firpic were used.