Persistent non-equilibrium interface dipoles at quasi-2D organic/inorganic semiconductor interfaces: The effect of gap states

We investigate the role of gap states in the quasi-2D van der Waals crystal SnS2 and their influence on the electronic structure formed at the hybrid interface between SnS2 and several different organic semiconductors. We demonstrate that this density of states creates trapped carriers, generating an interfacial electric field that transiently alters the energy level alignment at the hybrid interface. The trapped carriers are extremely long-lived due to the weak interlayer coupling that is characteristic of quasi-2D materials. We suggest that these effects, observed here by photoemission spectroscopy, likely play a role for many different van der Waals materials with moderate screening lengths, with direct impact on optoelectronic and transport properties in the (quasi-)2D limit.