物理化学学报 >> 2016, Vol. 32 >> Issue (6): 1439-1445.doi: 10.3866/PKU.WHXB201603154

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第一性原理研究混合钙钛矿CH3NH3PbxSn1-xI3结构及光电特性

鲁效庆*(),赵兹罡,李可,魏淑贤,瞿媛媛,牛永强,刘学锋*()   

  • 收稿日期:2016-01-06 发布日期:2016-06-03
  • 通讯作者: 鲁效庆,刘学锋 E-mail:luxq@upc.edu.cn;liuxf@upc.edu.cn
  • 基金资助:
    国家自然科学基金(21303266);中央高校自主创新项目(15CX05050A, 14CX02214A)

First-Principles Investigation of the Structural and Photoelectronic Properties of CH3NH3PbxSn1-xI3 Mixed Perovskites

Xiao-Qing LU*(),Zi-Gang ZHAO,Ke LI,Shu-Xian WEI,Yuan-Yuan QU,Yong-Qiang NIU,Xue-Feng LIU*()   

  • Received:2016-01-06 Published:2016-06-03
  • Contact: Xiao-Qing LU,Xue-Feng LIU E-mail:luxq@upc.edu.cn;liuxf@upc.edu.cn
  • Supported by:
    The project was supported by the National Natural Science Foundation of China(21303266);Fundamental Research Funds for the Central Universities, China(15CX05050A, 14CX02214A)

摘要:

有机/无机钙钛矿是一类极具潜质的光电材料,目前已实现超过20%的光电转化效率。本文采用第一性原理对有机/无机混合钙钛矿CH3NH3PbxSn1-xI3 (x = 0-1)的结构及光电特性进行了理论研究。结果表明,范德华力(VDW)在优化钙钛矿结构中起着重要的作用,考虑范德华力可减小Pb/Sn―I键长,从而减小体系体积。通过分析甲胺离子CH3NH3+的态密度和Bader电荷,我们发现其对前线轨道没有贡献,仅仅扮演电荷供体的角色。Pb/Sn与I之间同时存在共价键和离子键相互作用。价带顶(VBM)主要是由I 5p以及Pb 6s (Sn 5s)杂化组成,而导带底(CBM)主要由Pb 6p (Sn 5p)轨道组成。在可见光区,随着波长的增加,体系吸收强度呈现整体下降趋势;随着Sn/Pb比值逐渐增大,吸收强度呈现增大趋势。CH3NH3SnI3在可见光区表现出较佳的吸收光谱特性。

关键词: 钙钛矿, 光电特性, 能带结构, 态密度, 介电函数, 第一性原理

Abstract:

Organic/inorganic perovskites have exhibited great potential as photoelectronic materials, achieving remarkable photoelectric conversion efficiency, currently over 20%. The structural, electronic, and optical properties of organic/inorganic hybrid CH3NH3PbxSn1-xI3 perovskites (x = 0-1) have been investigated by the first-principles theory. Our results indicate that the van der Waals (VDW) interaction plays a crucial role in the structure optimization. Accounting for VDW force correction, both the Pb/Sn―I bond lengths and volumes are decreased. By analyzing the density of states and the Bader charge of CH3NH3+ cations, we find that cations contribute only slightly to the band edge, but play the role of charge donors. There exists a combined covalent and ionic interaction between Pb/Sn and I ions. The valence band maximum (VBM) is mainly contributed by the I 5p orbitals with the overlapping of Pb 6s (Sn 5s) orbitals, while the conduction band minimum (CBM) is dominated by Pb 6p (Sn 5p) orbitals. In the visible light region, with increasing wavelength, the absorption intensity demonstrates a decreasing trend; as the Sn/Pb ratio increases, the absorption intensity shows an increasing trend. CH3NH3SnI3 perovskites demonstrate great potential to absorb light in the visible region.

Key words: Perovskite, Photoelectric property, Band structure, Density of states, Dielectric function, First-principles theory

MSC2000: 

  • O641