First-Principles Investigation on the Electronic and Mechanical Properties of Cs-Doped CH3NH3PbI3

Methylammonium lead iodide, CH3NH3PbI3, is currently a front-runner as light absorber in hybrid solar cells. Despite the high conversion efficiency, the stability of CH3NH3PbI3 is still a major obstacle for commercialization application. In this work, the geometry, electronic structure, thermodynamic, and mechanical property of pure and Cs-doped CH3NH3PbI3 have been systematically studied by first-principles calculations within the framework of the density functional theory (DFT). Our studies suggest that the (CH3NH3)+ organic group takes a random orientation in perovskite lattice due to the minor difference of orientation energy. However, the local ordered arrangement of CH3NH3+ is energetic favorable, which causes the formation of electronic dipole domain. The band edge states of pure and Cs-doped CH3NH3PbI3 are determined by (PbI6)− group, while A-site (CH3NH3)+ or Cs+ influences the structural stability and electronic level through Jahn–Teller effect. It has been demonstrated that a suitable concentration of Cs can enhance both thermodynamic and mechanical stability of CH3NH3PbI3 without deteriorating the conversion efficiency. Accordingly, this work clarifies the nature of electronic and mechanical properties of Cs-doped CH3NH3PbI3, and is conducive to the future design of high efficiency and stable hybrid perovskite photovoltaic materials