The metal cation mixing in hybrid perovskite has been suggested as an effective strategy not only to promote the performance and stability but also to reduce the content of toxic lead element for environmental and health concerns. However, such a strategy has yet been well demonstrated in two-dimensional (2D) hybrid perovskites with multilayered thickness (n > 1). Here, we theoretically investigated the lead-less and lead-free 2D hybrid perovskites with tin-lead (Sn–Pb) and germanium-tin (Ge–Sn) mixed metal cations, namely, the BA₂MA_n-1Sn_n/2Pb_n/2I_3n+1 and BA₂MA_n-1Ge_n/2Sn_n/2I_3n+1 (BA: C₄H₉NH₃⁺; n = 1–4), by means of first-principle calculations. It is found that the electronic structure and light absorption properties of the 2D hybrid perovskites can be efficiently tuned to the optimal range for solar cells by combining the metal cations mixing and the layer thickness (n) adjustment. Markedly, due to the enhanced in-plane elastic modulus but greatly reduced deformation potential constant, both the Ge–Sn and Sn–Pb mixed 2D perovskites show high carrier mobility (∼10³−10⁴ cm²V^–1S⁻¹), which are superior to that of their 3D analogues. Moreover, the Sn–Pb mixed 2D perovskites expose much stronger visible light absorption than the non-mixed Sn- or Pb-based 2D perovskites. In addition, the in-air stability of metal-cation-mixed 2D hybrid perovskites are greatly improved compared to the 3D halide perovskites. This work suggests the great potential of the metal-cation-mixed 2D hybrid perovskite for photovoltaic and optoelectronic applications with largely reduced lead content.

混合钙钛矿中的金属阳离子混合被认为是一种有效的策略，不仅可以提高性能和稳定性，还可以降低有毒铅元素的含量，以解决环境和健康问题。然而，这种策略尚未在具有多层厚度（ n  > 1）的二维（2D）混合钙钛矿中得到很好的证明。在这里，我们从理论上研究了具有锡铅 (Sn-Pb) 和锗锡 (Ge-Sn) 混合金属阳离子的无铅和无铅二维混合钙钛矿，即 BA ₂ MA _n-1 Sn _{n/ 2} Pb _n/2 I _3n+1和 BA ₂ MA _n-1 Gen _/2 Sn _n/2 I_3n+1 (BA: C ₄ H ₉ NH ₃ ⁺ ; n  = 1-4)，通过第一性原理计算。研究发现，通过结合金属阳离子混合和层厚（n）调整，可以有效地将二维杂化钙钛矿的电子结构和光吸收特性调整到太阳能电池的最佳范围。值得注意的是，由于面内弹性模量提高但变形势常数大大降低，Ge-Sn 和 Sn-Pb 混合二维钙钛矿均显示出高载流子迁移率（ ~10 ³ -10 ⁴ cm ² V ^{- 1} S ^-1)，它们优于它们的 3D 类似物。此外，Sn-Pb 混合的二维钙钛矿比非混合的 Sn 或 Pb 基二维钙钛矿具有更强的可见光吸收。此外，与 3D 卤化物钙钛矿相比，金属阳离子混合的 2D 杂化钙钛矿的空气稳定性大大提高。这项工作表明金属阳离子混合二维混合钙钛矿在铅含量大大降低的光伏和光电应用中具有巨大潜力。