Energy barriers exist at the interfaces between electrodes and organic layers, and interrupt carrier injections. Deteriorated carrier injections result in increasing the driving voltage and lowering the efficiency of organic elecroluminescent devices (OELDs). The assisted double-carrier injections into organic layers can be achieved by lowering these energy barriers. Thin alpha-septithiophene (alpha-7T) layer was inserted for buffer layer and composite cathode composed of OF and Al was formed in order to enhance hole and electron injections, respectively. The orientations of alpha-7T molecules were adjusted by rubbing method and the mass ratio of CsF was varied between 1 and 10 wt%. Upon the investigations, it is believed that the mass ratio of CsF 3 wt% and the horizontal orientation of alpha-7T molecules are the optimized conditions for the performance of OELDs. The characteristics of OELDs with these structures are improved due to the increased carrier injections and the balanced carrier densities in the emission region.