CARRIER TRANSPORT MECHANISM OF PVCZ-BASED MULTILAYERED ELECTROLUMINESCENT DEVICES

The current-voltage (I-V) dependence of PVCz polymer films has been an alyzed using transport models for insulating material. Space charge li mited current, Schottky current, Poole-Frenkel current and field assis ted tunnelling current have been examined for four types of device wit h different combinations of PVCz and PVCz:perylene layers; the devices with multi-layered structures are: (ITO/PVCz:perylene/ PVCz/Mg-Ag), ( ITO/PVCz/PVCz:perylene/Mg-Ag), (ITO/PVCz/PVCz/Mg-Ag) and (ITO/PVCz:per ylene/PVCz:perylene/Mg-Ag). Below the threshold voltage of electrolumi nescence (EL) operation, the current is mainly limited by space charge in both undoped PVCz and perylene doped PVCz emitting layers. Above t he EL threshold, the I-V characteristic is controlled by field assiste d tunnelling. EL is generated in the polymer layer near the metal (Mg- Ag) interface by carrier injection through the tunnelling limited curr ent. It was made clear that the EL emission in the PVCz multi-layer de vices took place at electric fields higher than 10(6) V/cm. (C) 1997 E lsevier Science S.A.