Huoy-Jen Yuh

Charge Transport Processes in Molecularly Doped Polymers: Interaction Effect Between Charge Transporting Molecules and Polymers

Abstract Hole transport has been investigated in films of solid solutions of N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine (TPD) and a structural variant of TPD in bisphenol A polycarbonate, polystyrene and phenoxy. Rather than being ‘inert’ as previously assumed, the binder plays a major role in influencing the rate of charge exchange between molecules. It is found that the absolute values of the drift mobilities, their electric field dependence and the activation energies are strong functions of the binder polymer employed to cast the film. At equivalent molecular concentrations but with two different binder polymers, the mobilities can vary by as much as two orders of magnitude. In some instances mobility decreases as the electric field is increased. The role that binder plays is related to the dispersibility of the diamine molecules in the polymeric binders. It is concluded that the the best molecular dispersion is observed when polystyrene is employed.

Charge-transport processes in molecularly doped polymers : binder effect

Abstract Hole transport has been investigated in films of solid solutions of N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine (TPD) in bisphenol A polycarbonate and polystyrene. Rather than being ‘inert’ as previously assumed, the binder plays a major role in influencing the rate of charge exchange between molecules. It is found that the absolute values of the drift mobilities, their electric-field dependence and the activation energies are strong functions of the binder polymer employed to cast the films. At equivalent low molecular concentrations, the hole mobility in films of molecular dispersions in polystyrene is two orders of magnitude higher than that observed in dispersions in polycarbonate, on which most investigations reported in the literature have been carried out. The increased mobility of dispersions in polystyrene is directly related to the reduction in the activation energies.

Charge injection through Langmuir–Blodgett films into organic polymers

The steady‐state current‐voltage characteristics resulting from charge injection from a metal into an organic charge transporting polymer are found to deviate significantly from the space‐charge‐limited values when a Langmuir–Blodgett film of cadmium stearate is interposed between the metal and the organic polymer. A phenomenological model of charge injection is proposed to account for the observed features, and to quantify the injection level of a non‐Ohmic contact.