Density functional theory study on the electronic structures and related properties of Ag-doped CH3NH3PbI3 perovskite

Abstract

In order to improve power conversion efficiency and stability, doping is commonly adopted strategy to tune and modify the structures and properties of CH3NH3PbI3 materials in organic-inorganic hybrid perovskite emerging solar cells. Here, to understand the photovoltaic performance of Ag-doped perovskite CH3NH3PbI3 at high dopant concentration, based upon density functional theory calculations for crystal structures, dopant formation energies, energy bands, density of states, optical absorptions, effective masses and exciton binding energies, we studied the effects of Pb replacement by Ag on electronic structures, optical and charge transport properties of perovskite CH3NH3PbI3 with cubic, tetragonal and orthorhombic phases at Ag concentration of 12.5%. It was found that, introducing Ag dopant induces more significant distortion of AgI6 octahedral. Also, introducing Ag dopant is possible to change the order of phase stability, and to improve the optical absorption properties of tetragonal phase. Furthermore, the Ag dopant shifts Fermi level to deep energy and slightly increases band gap without introducing extra dopant states. Whereas, the increased electron/hole effective masses by introducing Ag-dopant at this dopant concentration lead to the reduced charge carrier mobilities and imbalanced charge transport properties, and also result into more difficult exciton dissociation.