Formamidinium lead bromide (FAPbBr₃) perovskite has drawn scientific interest in the field of optoelectronic devices. However, the presence of highly toxic lead restricts its application. We approach this problem by studying the role of Sn substitution and Pb vacancy (Pb-□) in reducing the lead concentration and enhancing the stability and solar cell efficiency by forming a composite CH(NH₂)₂Pb_1−x−ySn_x□_yBr₃ (FAPb_1−x−ySn_x□_yBr₃) perovskite. Using the state-of-the-art hybrid density functional theory, we have discussed the important role of spin orbit coupling (SOC) and an electron's self-interaction error. The co-existence of Sn substitution and Pb-□ have been found to be thermodynamically stable using ab initio atomistic thermodynamics. However, Pb-□ introduces trap states deep inside the forbidden gap, which leads to electron–hole recombination centers to reduce the solar cell efficiency. Therefore, the stable configurations with only Sn substitution (FAPb_1−xSn_xBr₃) are considered for further optical study. As compared to the pristine, the mixed perovskites FAPb_1−xSn_xBr₃ with 0 ≤ x ≤ 0.5 are inferred to be promising candidates for solar cell applications because of their better optical properties, higher absorption coefficient and larger spectroscopic limited maximum efficiency (SLME) values.

中文翻译：

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了解Sn取代和Pb-□在增强CH（NH2）2Pb1-x-ySnx□yBr3的光学性质和太阳能电池效率中的作用

甲钛酸溴化铅（FAPbBr ₃）钙钛矿已在光电器件领域引起了科学兴趣。但是，剧毒的铅的存在限制了其应用。通过研究Sn取代和Pb空位（Pb-□）在降低铅浓度，通过形成复合CH（NH ₂）₂ Pb _{1- x - y} Sn _x来提高稳定性和太阳能电池效率方面的作用，来解决这个问题。□ _y Br ₃（FAPb _{1− x − y} Sn _x □ _y Br ₃）钙钛矿。使用最新的混合密度泛函理论，我们讨论了自旋轨道耦合（SOC）和电子的自相互作用误差的重要作用。利用从头算的原子热力学，发现Sn取代和Pb-□的共存是热力学稳定的。但是，Pb-□在禁带间隙的深处引入了陷阱态，这导致电子-空穴复合中心降低了太阳能电池的效率。因此，考虑将仅具有锡取代的稳定构型（FAPb _{1- x} Sn _x Br ₃）用于进一步的光学研究。与原始相比，混合钙钛矿FAPb _{1- x} Sn _x Br₃ 0≤ X ≤0.5的推断为有前途的，因为它们的更好的光学性能的太阳能电池应用，较高的吸收系数和更大的分光有限的最大效率（SLME）值的候选者。