In this study, the structural stability, electronic and optical properties of all-inorganic mixed-metal double perovskites Cs₂Sn_1-xB_xI₆ (B = Si, Ge; x = 0, 0.25, 0.50, 0.75, 1) have been explored by using first-principles calculations. Our calculated results show that Cs₂SnI₆ shows excellent stability, while Cs₂SiI₆ and Cs₂GeI₆ are unstable. Moreover, the structural stability of Cs₂SnI₆ is reduced by doping Si or Ge. The predicted band gaps of the Cs₂Sn_1-xSi_xI₆ systems are in the range of 1.1−1.3 eV. The band gaps of the Cs₂Sn_1-xGe_xI₆ systems decrease gradually with the increasing concentration of Ge doping. Cs₂SnI₆ exhibits the highest optical absorption coefficient in the visible light region among the Cs₂Sn_1-xSi_xI₆ systems. The Cs₂Sn_1-xGe_xI₆ systems show stronger absorption coefficients in the range of 500−1000 nm compared to the pure Cs₂SnI₆ perovskite. Based on our calculated results, Cs₂SnI₆ is expected to become the most promising candidate material for perovskite solar cells.

在这项研究中，全无机混合金属双钙钛矿Cs ₂ Sn _{1- x} B _x I ₆（B = Si，Ge; x = 0，0.25，0.50，0.75，1）的结构稳定性，电子和光学性质已经通过使用第一性原理计算进行了探索。我们的计算结果表明，Cs ₂ SnI ₆具有出色的稳定性，而Cs ₂ SiI ₆和Cs ₂ GeI ₆不稳定。此外，通过掺杂Si或Ge降低了Cs ₂ SnI ₆的结构稳定性。Cs ₂ Sn的预测带隙_{1- x} Si _x I ₆系统的范围为1.1-1.3 eV。Cs ₂ Sn _{1- x} Ge _x I ₆系统的带隙随着Ge掺杂浓度的增加而逐渐减小。在Cs ₂ Sn _{1- x} Si _x I ₆系统中，Cs ₂ SnI ₆在可见光区域显示最高的光吸收系数。Cs ₂ Sn _{1- x} Ge _x I ₆与纯Cs ₂ SnI ₆钙钛矿相比，该系统在500-1000 nm范围内显示出更强的吸收系数。根据我们的计算结果，Cs ₂ SnI ₆有望成为钙钛矿太阳能电池最有希望的候选材料。