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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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Langmuir−Blodgett (LB) films of an amphiphilic long-chain derivative of anthracene, of which the molecular packing shows a strong resemblance with the ab-plane of anthracene crystals, were investigated with respect to their photoconductive properties. Efficient photoinduced charge carrier generation and in-plane charge transport have been observed in LB-films of (2A7), using a gap configuration. The wavelength and intensity dependence of the quantum yield of the photocurrent in absence of a photosensitizer suggest an intrinsic bulkcharge generation mechanism. The intensity dependence of the photocurrent suggests a combination of nongeminate and alien recombination of charge carriers. The increase of the quantum yield in the presence of air is an indication that, upon photoexcitation, mobile holes are formed. By covering the multilayer assembly with a rhodamine containing monolayer, a significant increase of the quantum yield is obtained upon excitation of both the anthracene chromophore and the dye. In the case of dye excitation, the values and the field dependence of the photocurrents due to the photosensitized injection of holes from the layer of excited dye molecules into the 2A7 multilayer resemble those obtained for anthracene crystals covered by adsorbed dyes.

Using X-ray reflectivity, we have investigated the vertical ordering of multilayers of an asymmetrically substituted triphenylene derivative. A value of 1.37 nm is found for the thickness of an individual monolayer. Detailed fits for the reflectivity data have been performed. The corresponding electron density profiles suggest that very smooth, regular Y-type films are formed. The absence of clear Bragg peaks in the X-ray reflection curve and the small electron density fluctuations in the multilayer can be explained by an interdigitating packing of edge-on oriented disks in adjacent layers.