Density functional theory study of the geometric structure and energetics of triphenylamine-based hole-transporting molecules

We compare the geometric and electronic structures of triphenylamine and N,N,′-diphenyl-N,N′-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (TPD), two widely used models for hole-transporting molecules. It is seen that triphenylamine and TPD display significantly different properties, the biphenyl segment playing a major role in the latter. We also evaluate, for the two compounds, the reorganization energy involved in the electron-transfer process from a neutral molecule to a hole-containing molecule (radical-cation).