Explanation of Light-Intensity Dependence of Photoconductivity in Zinc Phthalocyanine

Abstract
Photoconductivity of zinc phthalocyanine single crystals was studied over a temperature range from 0 to 120 °C. The photocurrent increased exponentially with an increase of light intensity. The power p in the relation I ∝ Lp (I, photocurrent; L, light intensity) varied with temperature and became smaller than ½ above 320 °K. This value of p less than ½ could not be explained by Rose's theory, in which it was shown that p could vary only between 1 and ½, but an advanced explanation was given in this paper by assuming the diffusion effect of photoexcited carriers and the exponential trap distribution.