We report the superior stability of the composite Cs2 CO3:Ag/Ag cathode structure, which can be used in efficient organic light-emitting diodes (OLEDs).Devices with the Cs2 CO3: Ag (1:10, 5nm)/Ag (95 nm) cathode show a considerably improved lifetime compared with the control device with the Cs2 CO3 (0.5 nm)/Ag (100 nm) cathode.The composite Cs2 CO3: Ag/Ag film is proved to be stable in the atmosphere.X-ray diffraction (XRD) is applied to analyze the crystalline structure of the Cs2 CO3: Ag film, and it is demonstrated that CsAg alloy is formed,leading to the improved stability of the thin film and the devices.