We have investigated effect of electron transport material (ETM) on electroluminescence in the PVCz based three-layer polymer light emitting diodes (ITO/HTL/EML/ETL/Mg・Ag). END, PBD, Alq_3, and BCP have been doped as electron transport materials. Device structure was PVCzCz/PVCz:Pe/PVCz:ETM. We have clarified fundamental current transport and luminescent characteristics in the three-layered PVCz polymer LED's that have electron, emission and hole transport layers separately. It was elucidated that a low voltage and high luminance polymer LED's with a luminance higher than 5000cd/m^2 was realized for the first time by the PVCz based 3-layered structure.
