π-π Interaction-Driven Charge Separation and Interlayer Transfer in Polymeric Carbon Nitride

Polymeric carbon nitride (PCN), also called melon, is a well-studied nonmetal catalyst in the field of photocatalysis, while the nature of charge transport in PCN has not been thoroughly unveiled at the microscopic level. In this work, we have combined density functional theory (DFT) and nonadiabatic dynamics (NAMD) simulations to investigate the effect of interlayer interactions on the dynamic properties of photogenerated carriers of melon. Overall, the interlayer pi-pi interaction has a greater effect on hot electrons than on holes, which accelerates the relaxation of electrons in bulk melon. In both monolayer and bulk melon, electrons and holes have the same antibonding pi bond characteristics, which drives the separation of charges. However, due to the strong pi-pi stacking, carriers in bulk melon can transfer and separate between layers, causing the much longer nonradiative recombination of charge carriers in bulk than that in monolayer, which makes melon have a long carrier lifetime and exhibit photoelectric performance similar to that of inorganic semiconductors.