Molecular dynamics in an organic semiconductor glass

TPD (N,N-Diphenyl-N,N’bis(methylphenyl)-1,1′-biphenyl-4,4′-diamines) is a molecular glass and organic semiconductor used in OLEDs and other industrial applications. Packing and motion of the molecules will affect the overlap of pi molecular orbitals, which will affect the charge carrier efficiency and device performance. Muoniated radicals formed by Mu addition to TPD will be used as local probes of the dynamics. We have three goals in this proposal: (1) Studying how the phenyl ring dynamics, which will affect the charge transfer in devices, change with temperature. (2) Confirming there is no change in phenyl ring dynamics at Tg in the molecular glass TPD, which is unlike the polymer glass PS. (3) Understanding the temperature hysteresis in phenyl ring dynamics observed with betaNMR. This is the first step towards studying thin film ultrastable TPD glasses with low-energy muSR.