Field-enhanced photodegradation of pyrromethene dye films

The photodegradation of pyrromethene films, neat and polymer-dispersed, is investigated by measuring the relative photocarrier yield as a function of accumulated 532 mm laser pulses. The rate of reduction in photocarrier prod uction is compared for samples irradiated in the absence and presence of an electric field by utilizing a delayed-photocurrent collection method. High er bias resulted in higher photocarrier reduction rates: field-enhanced pho todegradation. We report the result for polymer-dispersed pyrromethene mixe d with dimethylbenzoquinone (electron acceptor) or triphenylamine (electron donor) and vacuum deposited samples. The photocarrier reduction is correla ted with the appearance of dark spots, as confirmed by optical microscopy. For these samples, the photocarrier reduction is attributed to intrinsic de grading reaction of dye ions resulting from the optical excitation in the p resence of strong electric fields. (C) 1999 Elsevier Science S.A. All right s reserved.