Electron injection behavior of lithium quinolate (Liq)/Ca/Al cathode was investigated by using X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy (UPS). Interfacial energy barrier lowering of Liq/Ca/Al cathode was dependent on Ca thickness and maximum energy level shift was observed at a Ca thickness of 1 nm. Maximum current density could be obtained in Liq/Ca/Al device at a Ca thickness of 1 nm and it was well correlated with energy level shift from UPS measurement. Power efficiency of Liq/Al device could be improved by more than 70% by inserting Ca layer between Liq and Al. (C) 2008 Elsevier B. V. All rights reserved.