Cross-linkable fluorenyl-substituted aromatic amines for polymeric hole transporting networks

Fluorenyl-substituted aromatic amines containing reactive oxetanyl groups have been synthesized. Full characterization of their structure by NMR-, IR- and mass spectrometry is presented. The synthesized materials were examined by various techniques including differential scanning calorimetry, thermogravimetry, electron photoemission spectrometry and xerographic time of flight technique. The electron photoemission spectra of the layers of the derivatives showed ionization potentials of 5.4-5.65 eV. These derivatives have been tested as hole transporting materials in bilayer OLEDs with Alq3 as the emitter. The device with derivative containing benzidine core exhibited the best overall performance with turn-on voltage of ∼2.5 V, a maximum luminance efficiency of 4 cd/A and maximum brightness of about 6000 cd/m2. The derivative was also used for the preparation of cross-linked hole transporting layers by photoinduced polymerization. The layers obtained were also tested in light emitting diodes. The devices demonstrated maximum photometric efficiency of 1.65 cd/A and maximum brightness of about 3000 cd/m2.