Photoconductivity of Solids by Richard H. Bube (Repost)

The concept that photoconductivity, in contrast to photoemission, is normally best regarded as a change in conductivity; that the terms "primary" and "secondary" photocurrents lose their distinction in a "conductivity" analysis; that, to a good approximation, all nonmetals should be photoconductive; and that the enormous range of photosensitivities can easily be resolved in terms of the lifetime of a free carrier-all these concepts are only now gaining wide acceptance.