Thermally stimulated currents (TSCs) of layered organic photoconductors (OPCs) were measured by excitation of the bisazo pigment to generate carriers. The various TSCs were measured varying the condition of irradiation (temperature, electric field) and methods for current measurement (electric field). The amount of collected carriers was measured with TSC and discussed in terms of carrier generation mechanism. Generation, recombination and separation processes of ion-pairs were analyzed by comparing temperature and/or electric field dependence on carrier generation efficiencies of asymmetrical azo pigment based sample and of an unsymmetrical azo pigment based sample. Observed differences originating from carrier generation materials (CGMs) and carrier transport materials (CTMs) were discussed. The difference in sensitivity among CGMs combined with CTMs is mainly determined by the process of initial ion-pair (or charge transfer state) formation at the interface between CGM and CTM.