The electronic structures of the 8-hydroxyquinoline-aluminum (Alq3)/Al2O3/Co interfaces were studied by photoelectron spectroscopy. A strong interface dipole was observed, which leads to a reduction in the electron injection barrier. The x-ray photoelectron spectroscopy spectra further indicate that the Al2O3 buffer layer prevents the chemical interaction between Alq3 molecules and Co atoms. X-ray magnetic circular dichroism results demonstrate that a Co layer deposited on an Al2O3 buffered Alq3 layer shows better magnetic ordering in the interface region than directly deposited Co, which suggests a better performance of spin valves with such a buffer layer. This is consistent with the recent results from [ Dediu et al., Phys. Rev. B 78, 115203 (2008) ].