物理化学学报 >> 2021, Vol. 37 >> Issue (4): 2007015.doi: 10.3866/PKU.WHXB202007015

所属专题: 金属卤化物钙钛矿光电材料和器件

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全无机卤化铅钙钛矿的结构、热力学稳定性和电子性质

李亚文1, 那广仁1, 罗树林1, 贺欣1,2,*(), 张立军1,*()   

  1. 1 集成光电子学国家重点实验室,教育部汽车材料重点实验室,吉林大学材料科学与工程学院,长春 130012
    2 吉林大学物理学院,长春 130012
  • 收稿日期:2020-07-06 录用日期:2020-08-11 发布日期:2020-08-17
  • 通讯作者: 贺欣,张立军 E-mail:xin_he@jlu.edu.cn;lijun_zhang@jlu.edu.cn
  • 基金资助:
    博士后创新人才计划(BX20190143);吉林省科技发展计划(20190201016JC)

Structural, Thermodynamical and Electronic Properties of All-Inorganic Lead Halide Perovskites

Yawen Li1, Guangren Na1, Shulin Luo1, Xin He1,2,*(), Lijun Zhang1,*()   

  1. 1 State Key Laboratory of Integrated Optoelectronics, Key Laboratory of Automobile Materials of MOE, College of Materials Science and Engineering, Jilin University, Changchun 130012, China
    2 College of Physics, Jilin University, Changchun 130012, China
  • Received:2020-07-06 Accepted:2020-08-11 Published:2020-08-17
  • Contact: Xin He,Lijun Zhang E-mail:xin_he@jlu.edu.cn;lijun_zhang@jlu.edu.cn
  • About author:Email:lijun_zhang@jlu.edu.cn (L.Z.)
    Email: xin_he@jlu.edu.cn (X.H.)
  • Supported by:
    the Postdoctoral Innovative Talents Supporting Program, China(BX20190143);the Jilin Province Science and Technology Development Program, China(20190201016JC)

摘要:

有机-无机杂化卤化铅钙钛矿因具有独特的电子和光学特性,已经成为光电领域最有前途的材料。但是,有机-无机钙钛矿材料及器件稳定性差,限制了其实际应用。与杂化钙钛矿相比,全无机卤化物钙钛矿CsPbX3 (X = Cl,Br,I)显示出更强的热稳定性。全无机卤化物钙钛矿CsPbX3具有多个晶型,在不同的温度下呈不同相结构。目前,关于CsPbX3的结构和物理性质仍存在争议。本文我们针对三个晶相α-,β-和γ-CsPbX3的结构,热力学稳定性和电子性质进行了全面的理论研究。第一性原理计算表明,从高温α相到低温β相,然后再到γ相的相变伴随着PbX6八面体的畸变。零温形成能计算表明,γ相最稳定,这与实验中γ相为低温稳定相的结论一致。电子性质计算表明,所有CsPbX3钙钛矿都表现出直接带隙性质,并且带隙值从α相到β相再到γ相逐渐增加。这是由于相变发生时,Pb-X成键强度逐渐减弱,使价带顶能量降低,进而带隙增加。在所有相中,α相结构中较强的Pb-X相互作用,导致了较强的带边色散,使其具有较小的载流子有效质量。

关键词: 无机卤化物钙钛矿, 光电性质, 第一性原理计算, 电子结构

Abstract:

Organic-inorganic hybrid lead halide perovskites have emerged as the most promising materials in the field of optoelectronics due to their unique electronic and optical properties. However, the poor long-term material and device stabilities of these materials have limited their practical application. Compared to organic-inorganic hybrid perovskites, all-inorganic halide perovskites like CsPbX3 (X = Cl, Br, I) show enhanced thermal stability and the potential to resolve the issue of instability. Nevertheless, the structural and physical properties of all-inorganic CsPbX3 halide perovskites with multiple structural polymorphs are still under debate. A recent research article on CsPbI3 reported the wrongly indexed the XRD pattern of γ-CsPbI3 as α-CsPbI3. Consequently, the band gap of γ-CsPbI3 (1.73 eV) was erroneously designated for α-CsPbI3. Therefore, there is a need for systematic research on the relationship between the structural features and electronic properties of CsPbX3. Here, we present a comprehensive theoretical study of the structural, thermodynamical and electronic properties of three polymorphic phases, α-, β-, and γ-CsPbX3. The space group of α-, β-, and γ-CsPbX3 are Pm${\rm{\bar 3}}$m, P4/mbm, and Pnma, respectively. First-principles calculations indicate that the phase transition from the high-temperature α-phase to the low-temperature β-phase and then to the γ phase is accompanied by an increase in the degree of PbX6 octahedral distortion. The zero-temperature energetic calculations reveal that the γ-phase is the most stable. This is consistent with the fact that experimentally, the γ-phase is stabilized at a relatively low temperature. Analysis of the electronic properties indicates that all the CsPbX3 perovskites exhibit a direct-gap nature and the band gap values increase from α to β, and then to the γ phase. From the analysis of the orbital hybridization near the band gap edges, the increase can be explained by the downshift of the valence band edges caused by the gradual weakening of the Pb-X chemical bond. Among all the phases, the strongest Pb-X interaction in the α-phase leads to the most dispersive band-edge states and thus the smallest carrier effective masses, which are beneficial for carrier transport. Additionally, the band gaps decreased by changing the halogen type from Cl to Br and I under the same phase. this is a consequence of the increased X np orbital energies from Cl 3p to Br 4p and then to I 3p that leads to a high valence band edge for CsPbI3 and results in the smallest band gap. Our results provide deep understanding on the relationship between the physical properties and structural features of all-inorganic lead halide perovskites.

Key words: Inorganic halide perovskite, Optoelectronic property, First-principles calculation, Electronic structure

MSC2000: 

  • O649