A series of polymer light emitting devices (PLEDs) based on the composite films of N-arylbenzimidazoles trimer (TPBI), poly (n-vinylcarbazole) (PVK), and a triarylaminooxadiazole-containing tetraphenylsilane light emitting polymer (PTOA) were investigated. Electroluminescence (EL) performance is enhanced with doped TPBI into the light-emitting layer for the PTOA-based devices. A deep blue emission (Commission Internationale de L'Eclairage (CIEx,y) corodinates (0.16,0.06)) is obtained for the TPBI-PTOA-based device. Brightness and current efficiency of the TPBI-PTOA-based device can be as high as 961 cd/m(2) and 1.85 cd/A, respectively. The EL performances of TPBI-PTOA composite film-based devices are further enhanced by inserting a TPBI layer into the light emitting layer and cathode interface for a better electron and hole charge balance. Doping TPBI into the light-emitting layer of PVK-PTOA is not favorable for enhanced EL performances. Brightness and current efficiency reduced with increasing TPBI content for the TPBI-PVK-PTOA-based devices. Similar results are obtained for devices based on the TPBI-PVK-PTOA/TPBI bi-layer composite solid film. Morphology and charge balance effects on EL performances of TPBI-PTOA and TPBI-PVK-PTOA composite films based PLEDs are discussed in detail. (C) 2008 Wiley Periodicals, Inc.