压强对有机-无机杂化钙钛矿(MAPbBr 3)电子结构调制的第一性原理研究

First-principles Study on the Modulation of the Electronic Structure of Organic-inorganic Hybrid Perovskite(MAPbBr_3) under Pressure

自2009年以来,有机-无机杂化钙钛矿作为光吸材料的新型太阳能电池受到了广泛关注。在基于密度泛函理论(DFT)的第一性原理计算的基础上,利用VASP软件包,通过改变钙钛矿MAPbBr_3(CH_3NH_3PbBr_3)的晶格常数进行加压模拟计算,系统的研究了压强作用下钙钛矿材料的电子结构的变化。压强作用下带隙值变化的物理机制可以通过MA阳离子和PbBr_6正八面体无机笼之间的氢键作用进行半定量的描述。在压强作用下,Br原子通过靠近氨末端的H原子而响应,会引起了PbBr_6八面体发生不同程度的倾斜和扭曲,导致体系的晶格对称性发生破坏,使得Pb、Br原子之间的电荷密度函数发生变化,进而影响钙钛矿MAPbBr_3在不同压强下的电子结构以及光学性质的变化。

Since 2009,organic-inorganic hybrid perovskites have attracted widespread attention as new light-absorbing solar cells.Based on the first-principles calculations of density functional theory(DFT),VASP software package was uesd to perform the pressure simulation calculation by changing the crystal lattice of the perovskite MAPbBr 3.Changes of the electronic structure of the perovskites under pressure were systematically studied.This can be semiquantitatively described by the effects of the hydrogen bonding between the organic MA cation and the PbBr 6 framework.Under pressure,Br atoms respond by coming closer to the H atoms near the end of the ammonia,causing the rotations and tilts of the PbBr 6 octahedron in different degrees.The lattice symmetry of the system is destroyed,which changes the charge density function between Pb and Br atoms,which in turn affects the changes of electronic structure and optical properties of MAPbBr 3 under different pressures.