Quantifying the Effect of Interfacial Dipoles on the Energy Level Alignment of Metal-Halide Perovskites

Surface passivation with suitable organic molecules has emerged as an effective strategy to reduce surface defects and improve the device efficiency. Adsorption of organic molecules on a metal-halide perovskite (MHP) surface, however, implies electrostatic and charge transfer interactions, which may alter the energy levels of the perovskite underneath. Here, we elucidate the effects of differently functionalized anilines, a prototypical passivating molecule, on the electronic levels of methylammonium lead iodide by DFT calculations. While the nature of the surface-passivating molecules undoubtedly affects the dipole moment, we argue that the adsorption geometry and the extent of surface coverage play equally important roles in influencing the energy level alignment of the perovskite interface with charge extraction layers.