Emission characteristics of Tb(o-MBA)3phen doped in PVK system

A rare-earth complex Tb (o-MBA)3phen has been synthesized and used as an emitting material in electroluminescence. By doping it into the conjugated polymer PVK, devices with different structures were fabricated: Device A: Glass/ITO/PVK: Tb(o-MBA)3phen /LiF/Al; Device B: Glass/ITO/PVK: Tb(o-MBA)3phen/AlQ/LiF/Al; Device C: Glass/ITO/PVK: Tb(o-MBA)3phen/BCP/AlQ/LiF/Al. The characteristics of these devices were investigated. For single-layer and double-layer devices, the emission of PVK was completely restrained, and only the green emission from Tb3+ can be observed in electroluminescence. It is because of the different mechanism of electroluminescence and photoluminescence. In photoluminescence process, the energy of Tb complex may come from PVK through Förster energy transfer process, and in electroluminescence process direct sequential charge trapping appeared to be the main operating mechanism. From the optimized device B, bright green emission can be obtained, and the highest EL brightness of the device reached 180 cd/m2 at 15 V.