Transient electroluminescence (EL) from organic bilayer devices having different N-arylbenzimidazole derivatives as electron-transporting layers (ETLs) was investigated. Using a short voltage pulse as an excitation source, the delay time for the EL was measured and interpreted as the electron transit time across the electron-transporting layer. Electron-mobility can therefore be extracted by considering the luminance mechanism within the devices. The electron-mobilities of the three N-arylbenzimidazole derivatives thus deduced are in the range of 10(-6)-10(-5) cm(2)/V s and are comparable to that of the widely used tris-(8-hydroxyquinoalate) aluminum.