First-principles investigation of the Lewis acid–base adduct formation at the methylammonium lead iodide surface. Issue 16 (9th April 2018)

• Record Type: Journal Article
• Authors: Giorgi, Giacomo; Yamashita, Koichi; Segawa, Hiroshi
• Is Part Of: Physical chemistry chemical physics. Volume 20:Issue 16(2018)
• Page Start: 11183
• Page End: 11195
• Publication Date: 2018-04-09
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c8cp01019f
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Theoretical insights into the mechanism of Lewis acid–base formation at the surface of methylammonium lead iodide (MAPbI3 ). Abstract : We have here performed a campaign of ab initio calculations focusing on the anchoring mechanism and adduct formation of some Lewis bases, both aliphatic and aromatic, on a PbI2 -rich flat (001) methylammonium lead iodide (MAPI) surface. Our goal is to provide theoretical support to the recently reported experimental techniques of MAPI surface passivation via Lewis acid–base neutralization and similarly of MAI·PbI2 ·(Lewis base) adduct formation. We tested several X-donor bases (X = :N, :O, :S), paying attention to the thermodynamic stability of the final MAPI·base adducts and to their electronic properties. Factors that impact on the passivation mechanism are the directionality of the Lewis base lone pair and its enhanced/reduced overlap with MAPI Pb p orbitals, the dipole moment of the base and, similarly, the electronegativity of the X donor atom. Also non-covalent interactions, both at the surface side (intra, MAPI) and at the very interface (inter, MAPI·Lewis base), seem to contribute to the stability of the final adducts. Here we show that the thermodynamic stability does not necessarily correspond to the most effective base → acid dative bond formation. Starting from a low coverage (12.5% of the undercoordinated Pb atoms available at the surface are passivated) this paper paves the way towards the study of cooperative and steric effects among Lewis bases at higher coverages representing, to the best of our knowledge, one of the very first studies focusing on the molecular anchoring on the surfaces of this very important class of materials.