Description:
<jats:p>For electric fields up to 2 × 104 V/cm applied normal to the a b plane of virgin anthracene crystals, both the hole and electron photocarrier quantum yields increase linearly with field. Field-dependence plots exhibit a slope to intercept ratio of 3.1 × 10−5 cm/V, a value which is in quantitative agreement with that predicted by Onsager's theory of geminate recombination. In nonvirgin crystals, sharply reduced photocarrier quantum yields at low fields are found to result from recombination of free carriers with oppositely charged trapped carriers left behind in the excitation region from previous experiments. The free carrier-trapped charge recombination rates are found to be diffusion controlled.</jats:p>