Energy Level Tuning at the MAPbI₃ Perovskite/Contact Interface Using Chemical Treatment

Metal halide perovskites are rivaling established materials for thin film photovoltaics. Being able to tune interfacial alignment of energy levels may allow a further boost to the efficiency of perovskite optoelectronic devices. By using Density Functional Theory (DFT) modeling and experimental analysis, we show that the band edge energies of the prototypical MAPbI₃ (MA = methylammonium) perovskite can in principle be varied by as much as 1 eV via postsynthetic chemical treatment. In particular, MAI-rich (PbI₂-rich) surfaces induce an energy upshift (downshift) of the perovskite band energies, and this can either inhibit or favor hole transfer at the perovskite/HTL interface.