The behavior of bright, efficient, low-driving-voltage blue organic light-emitting diodes based on amino-oxadiazole-fluorenes (AODFs) withAl2O3/Alcathodes is described. It is shown that the thinAl2O3buffer layer sharply enhances current injection, increases the device efficiency, and reduces the driving voltage; the performance of devices with the optimal oxide buffer layer thickness approaches those withMg0.9Ag0.1cathodes. The effects of theAl2O3buffer layer are believed to result from the removal of interface gap states induced by defects and chemical bonds between the AODF and Al, which trap carriers and quench singlet excitons nonradiatively. ©1997 American Institute of Physics.