Laser-Induced Photoconductivity in Thin Organic Films

Abstract

Photoconductivity in polynuclear aromatic hydrocarbons has been shown to be wavelength dependent and related to the electronic absorption spectrum. Photoconductivity is studied in several PNAHs with the use of light from a pulsed dye laser. The voltage dependence, light intensity dependence, and temperature dependence and the effect of ambient gases on the photocurrent are investigated in thin-film samples on a surface-type cell. The majority charge carriers are holes which flow across the surface of the sample. Photocurrents on the order of microamperes are observed. A preliminary investigation of the effect of temperature on the spectral dependence of the photocurrent shows that the peaks narrow when the sample is cooled to 80 K. This technique may prove useful as a method of obtaining sharp spectra of some organic thin films.