Effect of Sr substitution on the property and stability of CH3NH3SnI3 perovskite: A first-principles investigation
Effect of Sr substitution on the property and stability of CH3NH3SnI3 perovskite: A first-principles investigation
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DOI：
10.1002/er.5339
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发表时间：
2020-06-10
影响因子：
4.6
通讯作者：
Meng, Lingpeng
中科院分区：
文献类型：
--
作者：
Jia, Yanfeng;Zeng, Yanli;Meng, Lingpeng
有机-无机杂化钙钛矿太阳能电池（PSCs）的功率转换效率已超过25%，但其不稳定性限制了其实际应用。本文采用基于密度泛函理论的第一性原理计算方法，对Sn- Sr混合无铅钙钛矿MASn(1-x)Sr(x)I(3)（x = 0,0.25, 0.5, 0.75, 1）进行了综合研究。分析和讨论了材料的晶体结构、带隙、表面性能以及氧和水分子在材料表面的吸附。结果表明，随着Sr组分的增加，MASn(1-x)Sr(x)I(3)的晶格常数和带隙增大。MASrI(3)的带隙为4.16 eV，太大而不适合作为太阳能电池中的高效光吸收剂，但其中半取代化合物MASrI(0.5)Sr(0.5)I(3)的带隙为1.37 eV。氧和水分子都倾向于吸附在金属位点（Sn和Sr）上，并且Sr原子对氧和水分子的吸引力大于Sn原子。水对金属原子的吸附力比氧分子的吸附力强。在吸附过程中Sn原子向O-2/H2O分子的电荷转移量大于Sr原子向吸附物的电荷转移量，说明在空气条件下Sn原子比Sr原子更容易被氧化。O-2/H2O在清洁表面和H2O/O-2预吸附表面的吸附能相当，表明已吸附的分子不排斥即将吸附的分子。因此，我们预测通过将MASnI(3)中的Sn原子替换为Sr原子，可以得到具有合适带隙的稳定的Sn- Sr混合PSC材料，并且Sr原子的加入可以在一定程度上保护Sn原子不被氧化。本研究为进一步实验寻找新型无铅钙钛矿材料提供了依据。
The power conversion efficiency of organic-inorganic hybrid perovskite solar cells (PSCs) has exceeded 25%, but the instability limited their practical applications. In this paper, we report a comprehensive study on a Sn- and Sr-mixed lead-free perovskites, MASn(1-x)Sr(x)I(3)(x = 0, 0.25, 0.5, 0.75, 1), by using the firstprinciples calculations based on the density functional theory. The crystal structures, band gaps, surface properties, and the adsorptions of oxygen and water molecules on the surfaces of the materials were analyzed and discussed. Our results show that the lattice constants and band gaps of MASn(1-x)Sr(x)I(3) become larger with the increase of Sr components. The band gap of MASrI(3) is 4.16 eV, which is too large to be suitable as an efficient photo absorber in the solar cell, but one of the half substituted compounds, MASn(0.5)Sr(0.5)I(3,) has an adequate band gap of 1.37 eV. Both oxygen and water molecules prefer to adsorb on the metal sites (Sn and Sr), and Sr atom has larger attractive ability to oxygen and water molecules than Sn atom. The adsorptions of water on metal atoms are stronger than that of oxygen molecule. The charge transfer from Sn atom to O-2/H2O molecule is larger than that from Sr to the adsorbate in the adsorption process, meaning that Sn atom is easier to be oxidized than Sr atom in the air condition. The adsorption energies for O-2/H2O adsorbed on clean, and H2O/O-2 preadsorbed surfaces are comparable, indicating that the already adsorbed molecule does not exclude the upcoming molecule. So, we predict that a stable Sn- and Sr-mixed PSC material with a suitable band gap can be obtained through the substitution of Sn atom in MASnI(3) by Sr atom, and the addition of Sr atom would protect Sn atom from the oxidation to a certain extent. This study is expected to be helpful for further experiments to find new kinds of possible lead-free perovskite materials.