Megan Smith with Ken Singer

Trap Spectroscopy in Photo-refractive Polymers

The mechanisms of photoconduction are of great interest due to the role of photoconduction in xerography and photorefractive holography. Photoconduction involves the excitation of electrons in response to light, leading, in the case of the materials of interest here, to the transport of electron holes. Some of the holes move to locations classified as traps because of the location of their energy levels. Hence a space-charge field develops in response to the electromagnetic field, which can act as a record of the light intensity pattern incident on the material.

     Thus, hole traps are essential to the photorefractive process. An understanding of the nature of these sites is therefore useful in the study of photorefractive materials.  This project will study the energy spectrum of trapping sites in photorefractive polymers using temperature dependent measurements of the time-of-flight mobility and xerographic discharge. The material investigated consists of a polymer called polyvinylcarbazole (PVK) which acts as the charge transporting agent, 4,4′-n-pentylcyanobiphenyl (5BC) as the nonlinear optical element and C60 as a sensitizer. Other materials may also be investigated in order to examine structure-property relationships.