Interfacial engineering to modulate surface dipoles, work functions and dielectric confinement of halide perovskites.

The interfacial properties between perovskite photoactive and charge transport layers are critical for device performance and operational stability. Therefore, an accurate theoretical description of the link between surface dipoles and work functions is of scientific and practical interest. We show that for a CsPbBr perovskite surface functionalized by dipolar ligand molecules, the interplay between surface dipoles, charge transfers, and local strain effects leads to upward or downward shifts of the valence level. We further demonstrate that the contribution of individual molecular entities to the surface dipoles and electric susceptibilities are essentially additive. Finally, we compare our results to those predicted from conventional classical approaches based on a capacitor model that links the induced vacuum level shift and the molecular dipole moment. Our findings identify recipes to fine-tune materials work functions that provide valuable insights into the interfacial engineering of this family of semiconductors.