DUAL ELECTROLUMINESCENCE OF AN AMINO-SUBSTITUTED 1,3,5-TRIPHENYLBENZENE

The electroluminescent properties of enyl]-N,N,N',N'-tetrakis(4-ethylp henyl)-[1,1':3',1 ''-terphenyl]-4,4 ''-diamine (pEFTP) were investigat ed in a vapor deposited layer and dispersed in a polymer matrix. Blue- violet electroluminescence was observed, after applying voltages beyon d 12 V for the single layer devices and 22 V for the double layer devi ces. The electroluminescence (EL) spectrum shows two maxima, of which one corresponds to that of the photoluminescence spectrum. Either dire ct radiative recombination of the hole and the electron residing at tw o neighboring molecules or phosphorescence is causing this red shifted electroluminescence maximum. Transient electroluminescence measuremen ts allow us to estimate the mobilities of the charge carriers in the d ifferent transport layers. The occurrence of an EL overshoot after swi tching off a voltage pulse, confirms the importance of detrapping and interfacial phenomena in the radiative recombination in pEFTP. (C) 199 8 American Institute of Physics. [S0021-8979(98)02020-9].