Solar cells based on lead-free double perovskites as absorber layer is an environment friendly, stable alternative for the conventional lead based hybrid halide perovskites. A comprehensive theoretical study on the optical and electronic properties of all-inorganic double perovskite with A₂BB’X₆ stoichiometry is done using density functional theory. Doping studies on (Rb_xCs_1-x )₂AgBiBr₆ perovskite is done using the virtual crystal approximation method within density functional theory. It is found that as increasing the Rb content (x) from 0.0 to 1.0 in Rb_xCs_1-xAgBiBr₆, the lattice parameter, dielectric constant and band gap are found to be decreasing linearly in accordance with Vegard's law. The lattice constant decreases linearly in x with a function of a(x) = 11.516 - 0.0057 x (Å), while the band gap decreases linearly as a function of x, E_g(x) = 1.472 - 0.0009 x (eV). Opto-electronic properties of substitutional doping of Rb in (Rb_xCs_1-x)₂AgBiBr₆ is compared with Cs₂AgBiX₆ (X=Cl, Br, I) and Br doped Cs₂AgIn(Br_xCl_1-x)₆.

中文翻译：

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用于太阳能电池的全无机无铅卤化物双钙钛矿（RbxCs1-x）2AgBiBr6的光电性能

基于无铅双钙钛矿作为吸收层的太阳能电池是传统铅基混合卤化物钙钛矿的一种环保，稳定的替代品。利用密度泛函理论对A ₂ BB'X ₆ 化学计量的全无机双钙钛矿的光学和电子性质进行了全面的理论研究。（Rb _x Cs _1-x）₂ AgBiBr ₆钙钛矿的掺杂研究是使用密度泛函理论中的虚拟晶体近似方法进行的。发现随着Rb _x Cs _1-x AgBiBr中Rb含量（x）从0.0增加到1.0_{如图6所示}，发现晶格参数，介电常数和带隙根据维加德定律线性减小。晶格常数在x中以a（x）= 11.516-0.0057 x（Å）的函数线性减小，而带隙随x线性地减小，E _g（x）= 1.472-0.0009 x（eV）。比较了（ Rb _x Cs _1-x）₂ AgBiBr ₆与Rs掺杂的Cs ₂ AgBiX ₆（X = Cl，Br，I）和Br掺杂的Cs ₂ AgIn（Br _x）的Rb替代掺杂的光电性能Cl _1-x）₆。