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 production is compared for samples irradiated in the absence and presence of an electric field by utilizing a delayed-photocurrent collection method. Higher bias resulted in higher photocarrier reduction rates: field-enhanced photodegradation. We report the result for polymer-dispersed pyrromethene mixed with dimethylbenzo-quinone (electron acceptor) or triphenylamine (electron donor) and vacuum deposited samples. The photocarrier reduction is correlated with the appearance of dark spots, as confirmed by optical microscopy. For these samples, the photocarrier reduction is attributed to intrinsic degrading reaction of dye ions resulting from the optical excitation in the presence of strong electric fields. # 1999 Elsevier Science S.A. All rights reserved