Results are presented of a study on luminescence quenching, by an applied electric field, of x-form metal-free phthalocyanine and type II chlorogallium phthalocyanine, both of which are highly efficient photocarrier generating material. Experimental results, especially the time dependence, indicate that the quenching of the fluorescence seems to be the effect of photogenerated charges, rather than induced by an electric field. An irreversible decrease of the fluorescence intensity occurs under prolonged illumination with electric field applied.