[Emitting characteristics and carrier composite regions variety of the blend of terbium complex and poly-n-vinylcarbazole].

A new rare earth complex TbGd(BA)6(bipy)2 was synthesized, which was used as an emitting material in electroluminescence. By doping with poly-N-vinylcarbazole(PVK), the stability and conductivity of terbium complex were improved. The photoluminescence of PVK, terbium complex and their blend indicated that energy transfer from PVK to terbium complex occurred. In the present paper, single-, double- and multi- layer devices were fabricated. In the double-layer devices, holes and electrons were recombined at the interface of emitting layer (EML) and electron transporting layer (ETL). With increasing the thickness of Alq3, especially at highly electric field, carrier composite region transferred closely to ETL. However, in multi-layer devices, carrier composite region was restricted at the interface of emitting layer and holes blocking layer (HBL) due to high HOMO level of BCP. Enhancing electric field, emission from terbium complex was getting saturation gradually and weak emission from PVK was observed. From the optimized multi-layer device, bright and green emission from terbium complex was obtained with the highest EL brightness of the device of 213 cd·m-2 at 13.5 V.