Abstract In recent years, all-inorganic lead-free double perovskites have attracted great attention due to their excellent optoelectronic properties. In this work, we have investigated the structural stability, mechanical, electronic and optical properties of Cs2Ti1-xZrxI6 (x = 0, 0.25, 0.5, 0.75, 0.875, 1) based on first-principles calculations for the first time. With the increase of Zr doping concentration, the structural stability of Cs2TiI6 is improved. Moreover, these mixed Cs2Ti1-xZrxI6 systems are predicted to be stable according to the phonon spectrum calculation results. Our calculated results suggest that these Zr-doped double perovskites are brittle materials. When the value of x changes from 0 to 0.875, the band gap variation of Cs2Ti1-xZrxI6 is only 0.26 eV. However, the optical absorption coefficients are apparently decreased after Zr doping. The mixed Cs2Ti1-xZrxI6 systems have suitable band gaps for single-junction solar cells. The band gap of Cs2ZrI6 is predicted to be 1.92 eV, which is an ideal material for tandem solar cell. Our study is expected to explore their future applications in perovskite solar cells.

中文翻译：

---

Zr掺杂对Cs2TiI6稳定性、机械、电子和光学性能的理论研究

摘要 近年来，全无机无铅双钙钛矿因其优异的光电性能而备受关注。在这项工作中，我们首次基于第一性原理计算研究了 Cs2Ti1-xZrxI6 (x = 0, 0.25, 0.5, 0.75, 0.875, 1) 的结构稳定性、机械、电子和光学性质。随着Zr掺杂浓度的增加，Cs2TiI6的结构稳定性得到提高。此外，根据声子谱计算结果，预测这些混合的 Cs2Ti1-xZrxI6 系统是稳定的。我们的计算结果表明这些 Zr 掺杂的双钙钛矿是脆性材料。当 x 值从 0 变为 0.875 时，Cs2Ti1-xZrxI6 的带隙变化仅为 0.26 eV。然而，Zr掺杂后光吸收系数明显降低。混合的 Cs2Ti1-xZrxI6 系统具有适合单结太阳能电池的带隙。Cs2ZrI6 的带隙预计为 1.92 eV，是串联太阳能电池的理想材料。我们的研究有望探索它们在钙钛矿太阳能电池中的未来应用。