In this letter, I/V curves, output luminance of the organic light emitting diodes (OLEDs) with N-2 doped electron transport layer (ETL) have been studied in detail. Experimental results show that the turn on voltage and driving voltage of OLEDs with ETL evaporated in the optimum N-2 gas ambient pressure of 1 x 10(-4) Torr are reduced from 3.5 to 1 V and 7.7 to 5.7 V, respectively. The significant improving mechanism has been illustrated comprehensively with a schematic energy diagram model. (C) 2002 Elsevier Science Ltd. All rights reserved.