Abstract
The time delay (τ d ) in the transient electroluminescence(EL) signal of a bilayer organic light-emitting diode with a structure of indium-tin oxide /N,N ′ -diphenyl- N,N ′ -bis(3methylphenyl)- (1,1 ′ -biphenyl)- 4,4 ′ -diamine /tris(8-hydroxyquinoline) aluminum ( Alq 3 )/ Al has been measured and analyzed as a function of the thickness (D) of the Alq 3 layer. For a thin layer of Alq 3 (D200 nm ), τ d approaches the intrinsic electron transit time through Alq 3 . Electron mobility of Alq 3 can be evaluated for the thick-film devices and the results are in excellent agreement with independent time-of-flightmeasurements. The application of transient EL in mobilitymeasurement for C540-doped Alq 3 is discussed.