Hole transporting properties of cyclic pentamer of 4-butyltriphenylamine

Abstract

The cyclic pentamer of 4-butyltriphenylamine (CBTPA [5]) was prepared by the Pd-catalyzed C-N coupling reaction followed by purification with a combination of chromatographic techniques. Due to the rigid cyclic structure, the glass-transition temperature of CBTPA [5] was 215 °C. The space-charge-limited current mobility in its amorphous film was determined to be 1.3 × 10-4 cm2 V-1 s-1 which was higher than that of poly(4-butyltriphenylamine) (PBTPA) by a factor of 100. The higher mobility is ascribed to the higher purity of CBTPA [5], monodispersed nature, and homogeneous electron distribution of the highest occupied molecular orbital.