On the mechanism of photogeneration of charge carriers in polydiacetylene crystals

Experimental data are presented which give evidence about the short free path before recombination of free charge carriers in single crystals of polydiacetylene-toluene-sulphonate (PDA TS). The free path is shown to be much shorter than the millimetre-size electrode spacing. The recombination of carriers occurs via traps (of Shockly-Read type) or, at higher intensities, bimolecularly. The results obtained do not allow the authors to consider as substantiated the literature data on high (up to 10 5 cm 2 V -1 s -1 ) mobility of carriers in PDA TS, and on the validity of one-dimensional diffusive theory of charge-pair separation as applied to PDA TS. All these data critically depend on the assumption of the absence of recombination.