Blue organic light emitting devices(OLEDs) with Alq, PBD, BBOT or F OXD as the electron transport layer were fabricated by a high vacuum multisource type organic molecular deposition system. The effect of various electron transport layers on the performances of OLED was studied. The result indicates that the performances of devices with electron transport layer added between emitter and cathode are increased greatly. It is found that device: ITO/TPD/PPCP/Alq/Al is optimal in structure compared with other devices. Its turn on voltage is 4 V. Its maximal brightness is 2 000 cd/m 2 and its maximal efficiency is 0.36 lm/W.
