SEMICONDUCTOR PROPERTIES OF ORGANIC DYES. II. TRYPAFLAVINE.
AMERICAN METEOROLOGICAL SOCIETY BOSTON MASS
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When a solid film of trypaflavine is illuminated in vacuum, a photocurrent can be observed which is directly proportional to the light intensity and the applied field strength. The inertia of the photocurrent during illumination and after the light has been extinguished is of the order of one minute. For films several tens of microns thick, photoconductivity can be seen throughout the absorption band. The relative photocurrent yield becomes maximum at 500 millimicrons and drops to zero in the region from 500-600 millimicrons. The photocurrent increases exponentially with increasing temperature. The photoconductivity of the film is greater in oxygen than that in a vacuum. The effect of oxygen on the film is a function of the wavelength of the exciting light for long waves photosorption predominates, accompanied by an increase in the photocurrent, while for short waves, in addition to photosorption, there is a photochemical reaction accompanied by attenuation of the photocurrent and, in the case of prolonged illumination, it is accomplished by irreversible photo-oxidation of the dye. Author