Novel functional materials based on triarylamines-synthesis and application in electroluminescent devices and photorefractive systems

A variety of new functional materials based on triarylamines, such as low m olecular weight glasses which possess hole conducting/photoconductive prope rties as well as amorphous bifunctional materials which combine photoconduc tive and non-linear optical (NLO) properties in one compound, have been syn thesized. The new hole transporting glasses belong to the class of 1,3,5-tr is(triaryldiamino)benzenes (TTADB). The hyperbranched structure and the lar ge aryl groups attached as substituents lead to high glass transition tempe ratures (T-g) of up to 141 degrees C in these compounds. The TTADBs do not recrystallize upon cooling from the melt, but form stable glasses. Cyclic v oltammetry studies reveal multi-oxidation stages for these compounds of whi ch the first oxidation is reversible. The HOMO energy values determined fro m CV for TTADB-1 and TTADB-2 are -4.82 and -4.94 eV, respectively. Light em itting diodes with the structure ITO/TTADB-2/Alq3/Al (where ITO = indium ti n oxide) show high efficiency and large current carrying capacity. Further, bifunctional compounds have been synthesized in which a photoconductive mo iety such as bis(carbazolyl)triphenylamine or bis(diphenylamino)triphenylam ine is covalently bound to different NLO chromophores. Some of these compou nds are thermally and morphologically stable amorphous materials, possessin g T-g in the range from 85 to 122 degrees C. Cyclic voltammetry measurement s reveal that the HOMO energy values are between -4.81 and - 5.45 eV. In ph otorefractive measurements using 40 mu m thick samples, a diffraction effic iency of 27%, which corresponds to a refractive index modulation Delta n) o f 3.5 x 10(-3), a maximum two beam coupling gain coefficient (Gamma) of 90 cm(-1) and a response time of 40 ms were obtained.