
1: CARBAZOLE POLYMERS 19
4-oxadiazole groups onto the 9-position of the alter-
nating fluorene unit toform a three-dimensional cardo-
structure (PF-OXD). The polymer has a high glass
transition temperature T
g
of 213
◦
C and a goodthermal
stability. The commonly observed aggregate/excimer
formation in poly(fluorene)s is essentially suppressed
in this polymer.
Usage as the emitting layer shows a bright blue
emission at a turn-on voltage at 5.3 V with a bright-
ness of 2770 cd m
−2
at a drive voltage of 10.8V.
The improved performance of the device in compari-
son to that of poly(9,9-dioctylfluorene) is attributed to
its better electron injection and transport in