We report our investigation of the electroluminescent properties of multilayer organic light emitting devices using a series of three-phenyl-ring oligo(phenylenevinylene)s with poly(alkyleneoxy) electron-donors and hexylsulfonyl electron-acceptors as emitting materials. The emission color varies from blue to green depending on the substituted end-groups in the molecules. The insertion of hole blocking and electron injecting layers significantly improves the electroluminescent efficiency and extends the operational life time. The maximum electroluminescence efficiency reached is 1.9 cd/A for the blue diodes, and 2.3 cd/A for the blue-green diodes.