The Role of M3+ Substitutional Doping (M = In, Sb, Bi) in the Passivation of the α-CsPbI3(100) Surface

Abstract

Photovoltaic applications based on perovskite materials still face several challenges to deliver high power conversion efficiency, in particular the chemical passivation of surfaces, which is required to remove surface electronic states. In this work, we propose a surface passivation route for the α-CsPbI3(100) surface through substitutional doping at the Pb sites by trivalent cations such as In, Sb, or Bi. Our ab initio investigation was based on density functional theory calculations. We found a preferential doping position at surface octahedrons by more than 0.35 eV/dopant in comparison with inner layers as well as a bandgap decrease due to surface states and optical bandgaps wider than fundamental ones as a result of dark transitions. The surface passivation with Bi atoms demonstrates to be the most effective one, with enhanced sunlight absorption when compared to the 3D bulk α-CsPbI3. Furthermore, we changed the doping concentration and demonstrate the possibility to combine trivalent cations with other passivating mechanisms. Therefore, our computational results disclose a promising route for saturating perovskite surfaces.