Synthesis of novel fluorene-based poly(iminoarylene)s and their application to buffer layer in organic light-emitting diodes

The fluorene-based poly(iminoarylene)s with triarylamine unit were simply synthesized from palladium-catalyzed polycondensation of 2,7-dibromo-9,9-di-n-alkyllfluorene with primary amines such as aniline and p-toluidine. The polymers with high molecular weight were obtained and were thermally stable. The HOMO levels of the polymers (similar to-5.1 eV) were close to the work function of ITO. Organic light-emitting diodes (OLEDs) of the form ITO/polymer/TPD/Alq(3)/LiF/Al showed lower turn-on voltage (V-T = 2.2 V), the enhanced efficiency, and the higher maximum luminance at the higher current density (PFA1: 12 370 cd/m(2) at 427 mA/cm(2)) than those of the device without polymer (V-T = 3.6 V, 5790 cd/m(2) at 233 mA/cm(2)). It is expected that these polymers can be used as a buffer layer in OLEDs.