Amorphous molecular materials: charge transport in the glassy state of N,N'-di(biphenylyl)-N,N '-diphenyl-[1, 1 '-biphenyl]-4,4 '-diamines

Charge transport in the glassy state of a new family of amorphous molecular materials, N,N'-di(biphenyl-2-yl)-N, N'-diphenyl-[1,1'-biphenyl]-4,4'-diam ine (o-BPD), N,N'-di(biphenyl-3-yl)-N, N'-diphenyl-[1,1'-biphenyl]-4,Q-diam ine (m-BPD), and N, N'-di(biphenyl-4-yl)N, N'-diphenyl-[1, 1'-biphenyl]-4,4 '-diamine (p-BPD), has been studied. It was found that the molecular glass of p-BPD exhibits a high hole drift mobility of 1.0 x 10(-3) cm(2)V(-1)s(-1 ) at an electric field of 1.0 X 10(5) Vcm(-1) at 293 K and that the hole dr ift mobility of m-BPD is more than one-order of magnitude smaller than thos e of o- and p-BPD. The analysis of the electric-field and temperature depen dencies of the drift mobilities in terms of the disorder formalism shows th at the difference in energetic disorder is responsible for the difference i n the drift mobilities of these materials. (C) 2000 Elsevier Science S.A. A ll rights reserved.