The electroluminescent properties of 5′-[4-[bis(4-ethylphenyl)amino]phenyl] -N,N,N′,N′-tetrakis(4-ethylphenyl) -[1,1′:3′,1″-terphenyl]-4,4″-diamine (pEFTP) were investigated in a vapor deposited layer and dispersed in a polymer matrix. Blue–violet electroluminescence was observed, after applying voltages beyond 12 V for the single layer devices and 22 V for the double layer devices. The electroluminescence (EL) spectrum shows two maxima, of which one corresponds to that of the photoluminescence spectrum. Either direct radiative recombination of the hole and the electron residing at two neighboring molecules or phosphorescence is causing this red shifted electroluminescence maximum. Transient electroluminescence measurements allow us to estimate the mobilities of the charge carriers in the different transport layers. The occurrence of an EL overshoot after switching off a voltage pulse, confirms the importance of detrapping and interfacial phenomena in the radiative recombination in pEFTP.

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Upon investigation of the photoconductive properties of polycarbonate doped with 1,3-bis(dicyanomethylene)-indans, a large, temperature independent quantum yield for charge generation was observed. The field and temperature dependence of the charge carrier mobility could be analyzed in the framework of the disorder model, developed by Bässler et al. The prefactor mobility was found to be of the same order of magnitude as that observed for hole transport materials with a comparable dipole moment. In the framework of the used disorder model, this relationship would suggest a dependence of the wave function decay constant on the molecular dipole moment. This would result in a material dependence of the prefactor mobility, which has also been found for other charge transport molecules.

The hole transport properties of 5′-[4-[bis(4-ethylphenyl)amino]phenyl]-N,N,N′,N′-tetrakis(4-ethylphenyl)-[1,1′:3′,1′′-terphenyl]-4,4′′-diamine (pEFTP), an aromatic polyamine, have been studied extensively before. We report on the hole injection processes from metal electrodes, or redox solutions, into polymers molecularly doped with pEFTP. By use of the redox couple Fe 2+ /Fe 3+ at large fields, the injection of charges seems to be limiting the current density. At lower fields, competition between recombination and escape processes could be observed in the presence of the reduced form of the redox couple. The influence of the work function of the metals on the values of the dark currents suggests injection controlled currents characterized by almost exclusive hole transport.

Communications solution of NaHCO,, washed twice with H20. dried over MgSO, and evaporated. A total of 0.11 g (0.33 mmoles) of a white oil was obtained after flash chromathography (silica gel, hexane). Yield: 6%. ',C-NMR (CDCI,, ppm, TMS): 14.0, 22.6, 29.0, 29.1, 30.5. 31.7, 118.7, 124.8, 137.4, 143.9. 'H-NMR: (CDCI,, ppm, TMS): 0.88 (t. 6H), 1.30 (m, 12H), 1.60 (m. 4H), 2.55 (t, 4H), 6.73 (m, ZH), 6.96 (d, 2H. . I = I 4 Hz). i,,,, (CHCI,): 306 nm.Electropolymerization: All compounds were repeatedly chromatographed and used in a highly pure form ( > 99 % from 'H-NMR) for the electropolymerization. It should be stressed that if the compounds used for the electrosynthesis of the polymers were contaminated by even small amounts of another regioisomer, copolymers would result, owing to the fact that regioisomers have very similar oxidation potentials. The polymers from oligomers 11-V were grown by repeated cyclic voltammetric cycles (CVs) at 25 "C and SO mVs-in acetonitrile-0.S M LiCIO, using standard electrochemical equipment; the CVs were performed between 0 and 1.2 V vs. SCE for dimers and between 0 and 1.0 V for trimen. The concentration of the starting molecules in electrosynthesis solution was 1 x 10-M except for methyl-substituted 111. whose concentration was 1 x 10.' M. The polymers from compounds I were galvanostatically prepared at 5 mAcm-2 and 5°C i n nitrobenzene-0.02 M tetrabutylammonium hexafluorophosphate -0.2 M monomer with 50 mCcm-2 polymerization charge. All the polymers were grown on TO (transparent conductive tin oxide electrode). All experimental details and the optical and electrochemical characterization will be published in a rorthcoming paper [14].

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