Wide band gap triarylamine derivative doped with organosulfonic acid and its application for organic light-emitting devices

Abstract

We report a bis-type wide band gap triarylamine derivative, N, N′-diphenyl-N, N-bis(3-methylphenyl)-[1,1′-diphenyl]-4,4′-diamine (TPD), that was chemically doped with camphorsulfonic acid (CSA) in chloroform. Optical measurements showed that new optical absorption peak, leading to a broadband (480–620 nm) photoluminescence, was created in the TPD–CSA after doping, while the redox peak of TPD was shifted by the CSA doping. A tuneable (from green to red) electroluminescence (EL) was measured from organic light-emitting devices with the TPD–CSA-dispersed polymer layer and a green emission layer (tris(8-hydroxyquinolinato)aluminium – Alq3). The red EL, which is actually impossible from the Alq3 layer that intrinsically emits typical green light, has been ascribed to the contribution from both newly generated gap state in the TPD–CSA molecules and shifted charge recombination zone owing to hole mobility changes in the TPD–CSA-dispersed polymer layers.