An organic p-n bilayer photocatalyst, comprising a perylene derivative (PTCBI, n-type) and cobalt phthalocyanine (CoPc, n-type), is utilized for the oxidative formation of molecular hydrogen (H-2) from a borane-ammonia complex (NH3BH3, AB). The formation of H-2 occurs photocatalytically at the surface of CoPc in the organo-bilayer, along with the reduction of O-2 by a reducing power generated at PTCBI. The mechanism to illustrate the H-2-formation from AB by the organo-photocatalyst may be different from that of the conventional photocatalysis by inorganic semiconductors. To further understand the mechanism of H-2-formation, photoelectrochemistry is further investigated using the PTCBI/CoPc bilayer as a photoanode. Considering the resulting faradaic efficiency for H-2-formation, at least two possible equations have to be suggested: BH3OH- (intermediate) + 3OH(-) -> BO2- + 3/2H(2) + 2H(2)O + 3e(-) and BH3OH- (intermediate) + 2OH(-) -> BO2- + 2H(2) + H2O + 2e(-).