Derivatives of carbazole and truxene for organic light-emitting diodes

Abstract

Two new derivatives of carbazole and truxene (compound 1 and 2) weredesigned and synthesized for application as hole-transporting material in Organic Light-Emitting Diodes (OLEDs). The synthesis involved the alkylation at the methylene groups in truxene in order to facilitate the solubility in organic solvent and prevent the aggregation of compound by pi-pi stacking. The iodination of truxene core and Cu-catalyzed C-N coupling with carbazole or 3,6-di(9-carbazolyl) carbazole then gave rise to the target compounds in moderate yields.In solution phase, the compounds displayed maximum absorption and emission wavelengths at 330-331 and 367-391 nm, respectively, while they showed absorption at 315-333 and emission at 379-418 nm as thin film state. Both compounds possess excellent thermal stabilities with high glass transition temperatures (Tg) of above 240 ºC. These compounds were fabricated as hole-transporting materials in organic light-emitting devices. The device having the structure of ITO/PEDOT:PSS/2/Alq3/LiF:Alexhibited bright green emissionwith a maximum luminescence of 9,658 cd/m2 at 9.2 V and a turn-on voltage of 3.6 V.