Synthesis of polymers for hole and electron transport materials in organic electroluminescent devices

Styrene-type polymers having tetraphenylbenzidine (TPD) or tetraphenylphenyldiaminobenzene unit (PDA) and a oxadiazole unit (PBD) on the side chain were prepared as hole and electron transport materials, respectively, of an electroluminescent (EL) device. The device structures employed were [indium-tin-oxide (ITO)/hole transport layer (HTL)/Al] (type I), or [ITO/hole transport layer (HTL)/electron transport layer (ETL)/Al] (type II). Type I devices provided current density higher than 100 mA/cm/sup 2/ but no luminescence was observed. Type II devices emitted luminescence of about 10 cd/m/sup 2/ at the current density of about 170 mA/cm/sup 2/. The emission maximums of these devices were 460 and 530 nm for the device using TPD and PDA, respectively.