Fabrication and characteristics of hole transporting materials–transition metal nanoparticle composites

Abstract

A new concept of inorganic nanoparticle dopant into organic hole transporting materials (HTM) is proposed for the design of semiconducting composites. Composites consisting of HTM and TiO 2 nanoparticles were prepared using a polymer as a matrix. TiO 2 nanoparticles were prepared by sol–gel method starting from titanium tetraisopropoxide. The particle size of TiO 2 ranged from 2 to 5 nm. It was found that electrons were transferred from HTM to TiO 2, leaving holes in HTM. The composites showed semiconducting characteristics with the conductivity on the order of 10 −8 S/cm. A device consisting of ITO/composite/Al showed rectifying ability. The number of the holes was approximately one per 7×10 5 molecules of N, N, N′, N′-tetraphenylbenzidine (TPD) for the composite consisting of polycarbonate, TPD and TiO 2 with the weight ratio of 100:100:3.