化学学报 ›› 2016, Vol. 74 ›› Issue (8): 689-693.DOI: 10.6023/A16050245 上一篇    下一篇

研究论文

甲脒基铅卤钙钛矿结构及光电特性的第一性原理研究

赵兹罡, 牛永强, 赵洋, 宋清华, 忻灵, 鲁效庆   

  1. 中国石油大学华东理学院 青岛 266580
  • 收稿日期:2016-05-17 出版日期:2016-08-15 发布日期:2016-08-10
  • 通讯作者: 鲁效庆 E-mail:luxq@upc.edu.cn
  • 基金资助:

    项目受国家自然科学基金(21303266),研究生创新工程项目(No. YCXJ2016084)和大学生创新创业训练项目(No. 20151342)资助.

First-Principles Theory Investigation on Structural and Photoelectronic Properties of Formamidinium Lead Halide Perovskites

Zhao Zigang, Niu Yongqiang, Zhao Yang, Song Qinghua, Xin Ling, Lu Xiaoqing   

  1. College of Science, China University of Petroleum, Qingdao 266580, China
  • Received:2016-05-17 Online:2016-08-15 Published:2016-08-10
  • Supported by:

    Project supported by the National Natural Science Foundation of China (21303266), Postgraduate's Innovation Project (YCXJ2016084) and Student's Platform for Innovation and Entrepreneurship Training Program (No. 20151342)

甲脒基铅卤钙钛矿作为光电转换材料,引起了人们的广泛关注. 采用第一性原理对甲脒基铅卤钙钛矿FAPbIxCl3-x(FA=NH2CH=NH2+x=0~3)的结构及光电特性进行了理论研究. 计算结果表明,FA在三方晶系的FAPbX3X=Cl,Br,I)中沿[001]方向排布,而在混合FAPbIxCl3-x中,八面体PbX6X=Cl,I)的扭转导致FA朝向发生了微小的偏移. FA对于平衡晶体结构起着重要的作用,并作为电荷供体为PbI3骨架贡献约0.76 e的电荷. FAPbIxCl3-x属于直接带隙半导体,其价带顶(VBM)主要由I 5p(Cl 3p)和少量Pb 6s轨道杂化的反键轨道组成,而导带底主要由Pb 6p轨道组成. 随着I/Cl比例的增大,FAPbIxCl3-x的晶格常数和体积逐渐增大,禁带宽度逐渐减小,吸收光谱发生红移. FAPbI3的禁带宽度为1.53 eV,表现出最佳的吸收光谱特性,是一类极具潜力的光电转换材料.

关键词: 钙钛矿, 第一性原理, 光电特性, 能带结构, 吸收光谱

Formamidinium lead halide perovskites have attracted wide attention as photoelectronic conversion materials due to the high photoelectronic conversion efficiency (PCE), low cost and simple synthetic process. The structural, electronic and optical properties of mixed formamidinium lead halide perovskites FAPbIxCl3-x (FA=NH2CH=NH2+, x=0~3) have been investigated by the first-principles theory. Our results show that FA cations lie along [001] direction in the trigonal FAPbX3 (X=Cl, Br, I). However, the direction is slightly shifted owing to the distortion of PbX6 (X=Cl, I) octahedrons in the mixed FAPbIxCl3-x. The Pb-I bond distances (0.315~0.334 nm) are larger than Pb-Cl bond distances (0.282~0.302 nm). With the increase of I/Cl ratio, the lattice parameters and volumes of FAPbIxCl3-x increase. The FA cations play a crucial role in balancing the crystal structure, but they do not participate into the process of frontier orbital transition directly. They just play the role of charge donors to contribute ca. 0.76 e to PbI3 framework. FAPbIxCl3-x are direct band-gap semiconductors, with the direct bandgap nature at Z (0, 0, 0.5) symmetry point. The valence band maximum (VBM) is composed of antibonding orbitals of I 5p (Cl 3p) and a few Pb 6s orbitals, and the conduction band minimum (CBM) is composed of Pb 6p orbital. There exists a combined covalent and ionic bonding mechanism between Pb and I (Cl) ions. As the I/Cl ratio increases, the band gaps decrease and the absorption spectra are red shifted. FAPbI3 has an ideal band gap of 1.53 eV. It exhibits the superior absorption spectrum especially in the range of 300 nm to 500 nm, which elucidates that FAPbI3 has great potential as the photoelectronic conversion material. Our results could provide theoretical guidance for the experimental design and synthesis of perovskite solar cells.

Key words: perovskite, first-principles theory, photoelectronic property, band structure, absorption spectrum