Laser-induced photoconductivity in organic compounds and its application to a photochromic switch.

Photoconductivity in thin organic films is studied using light from a high power pulsed dye laser. Photoconduction is investigated in polycyclic aromatic hydrocarbons, carotenoids, organic dyes, and poly (N-vinyl carbazole). Spectral sensitization of photoconduction in $\beta$-carotene glass and poly (N-vinyl carbazole) by organic dyes is observed. The light intensity dependence of the photocurrent in anthracene and several dyes is linear. A two-photon dependence is observed in other PAHs and carotenoids. Phthalocyanine displays a one-photon dependence at low intensity and a two-photon dependence at high intensity. A resonant two-photon ionization process is proposed as the charge carrier generation mechanism in these compounds. An optical memory switch is devised which utilizes photoconductivity and photochemical reactions as the basis of the switching mechanism. The concentration of a photoconducting dye, methylene blue, in a poly (ethylene oxide)/water matrix is modulated by a reversible photoreduction of the dye by ascorbic acid. The memory state is read by monitoring photoconduction in the cell. Both the photoconduction of the polymer/dye system and the various photoreactions in the polymer matrix are studied, and the relationships of the experimental parameters on the operation of the switch are observed. Sensitized photoemission of the semiconductor electrodes and photo-oxidation of the polymer matrix are experimental problems to be overcome.Ph.D.Analytical chemistryPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/128291/2/8907157.pd