Passivation of PEA⁺ to MAPbI₃ (110) surface states by first-principles calculations*

Abstract

The MAPbI3 (110) surface with low indices of crystal face is a stable and highly compatible photosensitive surface. Since the electronic states on the surface can be detrimental to the photovoltaic efficiency of the device, they should be passivated. Phenylethylamine (PEA+), as a molecular ligand, has been widely used in continuous degradation and interfacial charge recombination experiments, and has satisfactory performance in improving surface defects. Therefore, we construct an adsorption model of MAPbI3 with small molecules, calculating the lattice structure and electronic properties of PEA+-adsorbed MAPbI3 (110) surface. It is found that PEA+ as a passivator can effectively weaken the electronic states and regulate the band gap of the MAPbI3 (110) surface. Before and after adding the passivator, the peak value of electronic state densities at MAPbI3 (110) surface is reduced by about 50%, and the band gap is apparently reduced. Moreover, by comparing the Bader atomic charge and spatial charge distributions before and after PEA+’s adsorption on the surface of MAPbI3, we observe a substantial change of PEA+ charges, which suggests the surface states have been passivated by PEA+.