Dual-functional catalysis indicates that an organic p–n bilayer induces the catalytic oxidation involved in downhill reactions, not only under illumination but also in the dark. When the organo-bilayer is composed of a perylene derivative (3,4,9,10-perylenetetracarboxylic-bis-benzimidazole (PTCBI), n-type) and cobalt phthalocyanine (CoPc, p-type), only the photocatalytic oxidation of hydrazine (N₂H₄) occurs. However, the loading of Ag co-catalyst onto the CoPc surface in the PTCBI/CoPc bilayer successfully led to dual catalysis in terms of the oxidation of N₂H₄ to N₂. To develop the present dual catalysis Ag loading was essential to achieve the catalysis performance particularly without irradiation.