Photoconductivity in crystals of charge-transfer complex anthracene–tetracyanobenzene

Photoconduction in crystals of a CT complex anthracene–tetracyanobenzene has been studied employing a dc method and pulsed excitation from a dye laser. It has been found that the photogeneration in A–TCNB involves thermal dissociation of the lowest-lying CT state which is also responsible for the crystal fluorescence. The Onsager model of the dissociation of the geminate pair of charges has been found to be inappropriate for the quantitative description of the photogeneration efficiency. The generalized model of Hong and Noolandi is more physically justified, but a description in terms of a simple kinetical scheme is found to be sufficient to explain the general features of the photogeneration in anthracene–TCNB.