To overcome the lack of electron type polymer which can be used in polymer electroluminescent(EL) devices,using n-type semiconducting inorganic material ZnO:Zn as electron transport layer and p-type semiconducting polymer poly(2,5-bis (dodecyloxy)-phenylenevinylene)(PDDOPV) as hole transport layer,the device covered the organic/inorganic composite film with the structure ITO/PDDOPV/ZnO:Zn/Al is successfully fabricated.The highest ratio of the luminescent efficiency of heterojunction device to that of single layer device of PDDOPV is 38.6 at 8 V,and brightness and current of heterojunction device are 19.4 times and 0.5 time of that of single layer device respectively.The results demonstrate that the insertion of ZnO:Zn layer can transport electrons and block holes that lead to the decrease of current and the increase of luminescent brightness and efficiency.A very interesting phenomenon is that the EL spectra blue-shift with the increase of applied voltage and the different PL spectra are obtained at different excitation wavelength,we attribute this phenomenon to the conformation of new light-emitting unit.