Hole mobilities in sol-gel materials

New silylated precursors with hole transporting units are prepared by modif ication of different active molecules (carbazole, oxadiazole and tetrapheny lphenylenediamine derivatives) using sol-gel precursors. Absorption and pho toluminescence spectra show that the electronic structures are not signific antly modified by the functionalization, Field dependence of the hole mobil ity of the different sol-gel layers is measured using the time-of-flight te chnique. The highest hole mobility is observed for the layer having tetraph enylphenylenediamine units: 5.7 x 10(-5) cm(2).V-1.s(-1) at a field strengt h of E = 5 x 10(5) V.cm(-1). For the best carbazole compound, the mobility is found to be about twentyfold lower at the same field. Further experiment s are required to test these new materials as hole transporting layers in p hotorefractive and electroluminescent devices. Copyright (C) 2000 John Wile y & Sons, Ltd.