The electroluminescence and photoluminescence of poly (m-phenylenevinylene)-alt- (p-phenylenevinylene) green light emitting copolymers have been studied. The effect of alkoxy substitutions (-OC4H9 and -OC6H13) in single and double layer device configurations was also investigated. In double layer devices, poly (p-phenylene vinylene), PPV (60 nm) was used as a hole transport layer and substantial increase in the longevity, stability and electroluminescence efficiency of the devices was observed. Blending of green light emitting copolymers with poly(N-vinylcarbazole), PVK and [2-(4-biphenylyl)-5-(4-tert-butylphenyl)1,3,4-oxadiazole (butyl-PBD)] gives further promising results, namely an increase in brightness and EL efficiency of the LEDs.