STUDIES OF PHOTOCONDUCTIVITY IN BETA-APO-8' CAROTENAL

The photoconductive properties of a carotenoid polyene, beta-Apo-8' ca rotenal in polycrystalline form has been studied. The growth of the ph otocurrent shows an overshoot in the growth-time curve before steady s tate value is attained. This behaviour of photocurrent is proposed to be due to higher value of recombination coefficient than trapping coef ficient. From the temperature dependence study it is observed that the steady state photocurrent, at first increases with increase of temper ature, attains a maximum at a particular temperature T-max and then de creases with temperature. The T-max value agrees with the temperature above and below which steady state photocurrent is attained differentl y. Monomolecular and bimolecular recombination processes at two temper ature regimes are proposed to account for the observed behaviour. The dependence of photocurrent with excitation light intensity and wavelen gth study provide information on the carrier generation processes. The fast decay of photocurrent have been observed at different temperatur es and from this study the decay constant is calculated and it is foun d to be temperature independent.