First-Principles Investigation of the Structural and Photoelectronic Properties of Ch3nh3pbi3 Perovskites

In this paper, four phases of CH3NH3PbI3 have been successfully established, including C-phase, T-phase, O-phase and 2H-phase. We calculated the equilibrium lattice parameters of the four phases using DFT +Â U and then calculated the energy band and density of states of the four phases based on this. Among the four phases, only the 2H-phase has an indirect band gap and the others have a direct band gap. Meanwhile, to analyze the changing trend of electronic properties of CH3NH3PbI3 under pressure, we obtained the effective masses of carriers and carrier concentration for four phases by fitting the band-edge structures. The T-phase has the smallest effective mass of carriers and the highest carrier concentration, which means that it is best suited to be a photovoltaic material. The optical absorption of CH3NH3PbI3 is mainly concentrated in the visible region and ultraviolet region. Furthermore, we found that the changing pressure is an effective strategy to regulate the photoelectric properties of CH3NH3PbI3. As the pressure increases, the electronic and optical properties of CH3NH3PbI3 are further improved. This work confirms that the T-phase is the most suitable structure for photovoltaic materials and also provides a theoretical basis for improving the photoelectric conversion efficiency of CH3NH3PbI3 by changing the pressure.