First-Principles Theory Investigation on Structural and Photoelectronic Properties of Perovskites: Trigonal versus Hexagonal HC(NH2)(2)PbI3

作者：Zhao Zigang; Lu Xiaoqing^*; Li Ke; Wei Shuxian; Liu Xuefeng^*; Niu Kai; Guo Wenyue

来源：Acta Chimica Sinica, 2016, 74(12): 1003-1008.

DOI：10.6023/A16080437

• HC(NH2)(2)PbI3 perovskite
• first-principles theory
• crystal deformation
• photoelectronic property
• bonding energy

Formamidinium lead halide perovskite FAPbI(3) (FA= HC(NH2)(2)(+)) has drawn wide attention as efficient photo-electronic conversion material. First-principles calculations were performed by using the Vienna ab initio simulation package (VASP) based on density functional theory. The structure configuration, electronic property, absorption spectrum, and bonding energy were analyzed to elucidate the structural and photoelectronic properties of trigonal and hexagonal FAPbI(3) perovskites. Results showed that the crystal deformation from trigonal to hexagonal crystal would distort the PbI3 framework, change the covalent/ionic Pb-I bonds, and eventually alter the semiconductor bandgaps. The trigonal and hexagonal FAPbI(3) perovskites are both direct-bandgap semiconductors. The direct-bandgap nature of trigonal crystal locates at Z (0, 0, 0.5) symmetry point with the ideal bandgap of ca. 1.50 eV; the direct-bandgap nature of hexagonal crystal locates at G (0, 0, 0) symmetry point with the wide bandgap of ca. 2.50 eV. For the both crystals, the main contributions to VBM (valence band maximum) are I 5p orbitals with a little overlapping of Pb 6s orbitals, and the main components of CBM (conduction band minimum) are Pb 6p orbitals. The FA cations do not directly participate into the electron transition process, just acting as charge donors to supply PbI3 framework with more than 0.7 e. There exists both covalent and ionic interactions between Pb and I ions. Compared with the hexagonal crystal, the trigonal FAPbI(3) possesses smaller electron and hole effective masses. It exhibits dramatic red shifted absorption spectrum and a better absorption efficiency than hexagonal FAPbI(3) and tetragonal MAPbI(3) (MA=CH3NH3+) perovskites. Bonding energy analyses showed that the hexagonal FAPbI(3) was more stable than the trigonal crystal, and interaction between FA and PbI3 framework was stronger than that between MA and PbI3 framework. Our results could provide theoretical guidance for the experimental design and synthesis of FAPbI(3) perovskite solar cells.

• 出版日期2016-12-15
• 单位中国石油大学（北京）