We report visible light emission from a diode made from copolymers of 3-alkylthiophenes. These chemically synthesized copolymers exhibit improved electroluminescence and quantum efficiencies compared to poly (3-cyclohexylthiophene). Good solubility of copolymers allows the fabrication of the light emitting diodes by spin-cast polymer film. The devices emit greenish-blue light in wavelength region of 550-580 nm, which is easily visible in poorly lighted room. The quantum efficiencies are in the range of 0.002 to 0.01% (photons per electron) at room temperature; which are significantly higher than corresponding values for poly(3-cyclohexylthiophene) based light emitting diodes. The charge carrier mobility in the device is found to be 5.6 x 10(-4) cm(2)/Vs.