Bluephosphorescent organic light emitting devices (PhOLEDs) using 1,3,5-tris(N-phenylbenzimiazole-2-yl) benzene[TPBI] as a host and bis((4,6-difluorophenyl)-pyridinate-N,C2') picolinate [FIrpic] as a dopant in the emitter were fabricated with different treatments of electron transport layer(ETL). The device with an ETL of 4,7diphenyl-1,10-phenanthroline [Bphen] (device A) showed higher current density and luminance under the same applied voltages than the device with an ETL of aluminum-tris-8-hydroxyquinoline [Alq(3)] (device B). On the other hand, the device with an ETL of Alq3 showed better roll-off characteristics in the current efficiency degradation according to the voltage increase than the device with an ETL of Bphen. The device with an ETL of Bphen/Alq(3) double layers (device C) showed a trade-off in the electroluminescence characteristics with higher current density and luminance than the device B and better roll-off characteristics of current efficiency than the device A. Electroluminescent spectra of the fabricated devices showed the double emission peaks at 479 nm and 500 nm. (C) 2010 Elsevier B. V. All rights reserved.