Charge Carrier Generation Mechanism for Titanyl Phthalocyanine by the Analysis of Time-resolved Fluorescence Emission

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Time-resolved fluorescence spectra and lifetimes of phthalocyanine pigments were measured by using the single photon counting technique. The single photon counting system were consisting of dye laser, photomultiplier, monochrometer, signal processor and personal computer system. alpha-, x-type Metal-free phthalocyanine pigments, alpha-, beta-, epsilon-type copper-phthalocyanine pigments and alpha-type titanyl phthalocyanine pigment dispersed in a binder polymer were coated on the glass substrate. Copper phthalocyanine pigments were used after purification process by the train sublimation technique.The fluorescence spectra for the samples exposed to He-Ne laser light were obtained by this system. Phthalocyanine pigments emitted fluorescence in the near infrared wavelength range from 800nm to 900nm. The intensity of fluorescence for x-type metal-free phthalocyanine pigment was larger than that of other pigments. The relation between the intensity of fluorescence and photocarrier generation efficiency was not obtained from this experimental results.The transient of fluorescence emission for x-type metal-free phthalocyanine pigment was measured by using the singly photon counting technique. The life time of fluorescence for the sample exposed to 610nm wavelength of dye laser light was about 2 mu seconds. This life time is larger than that of phthalocyanine molecules dissolved in the organic solution. It is considered that this life time of fluorescence corresponds to the diffusion of exciton in phthalocyanine pigment.