DELAY PHOTOCONDUCTIVITY IN POLYANILINE FILMS FROM DIFFERENT SOLVENTS

Decay kinetics of photoconductivity induced by the nanosecond laser pu lses has been studied for films of polyaniline (PANI) in the emeraldin e base form (EB) in the temperature range from 110 to 300 K. The films are prepared by casting solutions of EB in formic acid and N-methyl-2 -pyrrolidinone (NMP) on glass plates covered by conducting layer of Sn O2. Photocurrent signals were registered up to 40 ms and 20 mu s in th e films obtained from formic acid and from NMP, respectively. In both cases the kinetic curves are fitted well by the stretched-exponential function F-1(t) similar to exp[-(t/tau(str))(beta)] with the temperatu re dependent parameters tau(str) and beta. It was found that the quant um yield of photocharge was equal to 10(-4) for the films obtained fro m the formic acid solution and to 2.10(-6) for those obtained from the NMP solution. The possible mechanisms accounting for photocurrent cha racteristics are discussed.