Abstract Modeling Perovskite materials and tuning their properties by monovalent or divalent cations substitution produce several choice Perovskite compounds, studied extensively to improve the power conversion efficiency, reduce toxicity, and enhance stability. We modeled NH4PbI3 and NH4MgI3 from the parent compound CH3NH3PbI3, by replacing the monovalent CH3 NH 3 + with NH 4 + and the divalent Pb atom with Mg. In this study, the electronic band structure, as well as the electronic bandgaps, were calculated using the Perdew-Burke-Enzenhoff (PBE) and Perdew-Burke-Enzenhoff for solid (PBEsol) exchange-correlation functionals of the Density-functional Theory (DFT) and GW quasiparticle method of the Many-Body Perturbation Theory (MBPT). Similarly, we used Time-Dependent Density Functional Perturbation Theory (TDDFPT) and the solution of the Bethe-Salpeter equation (BSE) of the Many-Body Perturbation Theory to determine the real and imaginary dielectric tensors with and without spin-orbit coupling (SOC). Direct bandgaps at R high symmetry point were reported for NH4PbI3, while NH4MgI3 showed indirect bandgaps at Γ → R high symmetry points with lower bandgaps compared to NH4PbI3. The projected density of state around the Fermi level reveals that the iodine (I) p orbital is most responsible for the valence band in both NH4PbI3 and NH4MgI3, while the Lead (Pb) p orbital and the Magnesium (Mg) s orbitals, show the most prominent contribution to the Conduction bands. Similar Optical spectra were achieved with BSE-SOC, TDDFPT, and TDDFPT-SOC for NH4PbI3 without the absorption onsets, while NH4PbI3 predicts higher values of absorbance and absorption coefficient compared to NH4MgI3 which predict lower reflectivity and higher transmittance. Both compounds show maximum absorption coefficient in the order of 105 in the ultraviolet region like CH3NH3PbI3 and silicon. Therefore, we suggest that NH4PbI3 will be useful as solar cell absorber and UV ray protector, while NH4MgI3 would have more applications in the production of electrochromic materials.

中文翻译：

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用于紫外线防护剂和电致变色材料应用的基于 NH4XI3 (X = Pb, Mg) 的混合钙钛矿的能带结构和吸收光谱

摘要 通过单价或二价阳离子取代对钙钛矿材料进行建模并调整其性质，可以产生多种选择的钙钛矿化合物，这些化合物被广泛研究以提高功率转换效率、降低毒性和增强稳定性。我们从母体化合物 CH3NH3PbI3 模拟了 NH4PbI3 和 NH4MgI3，方法是用 NH 4 + 代替一价 CH3 NH 3 + ，用 Mg 代替二价 Pb 原子。在本研究中，使用密度泛函理论的 Perdew-Burke-Enzenhoff (PBE) 和 Perdew-Burke-Enzenhoff 固体 (PBEsol) 交换相关泛函计算电子能带结构和电子带隙（ DFT) 和多体微扰理论 (MBPT) 的 GW 准粒子方法。相似地，我们使用瞬态密度泛函微扰理论 (TDDFPT) 和多体微扰理论的 Bethe-Salpeter 方程 (BSE) 的解来确定具有和不具有自旋轨道耦合 (SOC) 的实数和虚数介电张量。据报道，NH4PbI3 在 R 高对称点处的直接带隙，而 NH4MgI3 在 Γ → R 高对称点显示出间接带隙，与 NH4PbI3 相比，带隙较低。费米能级周围的投影态密度表明，碘 (I) p 轨道对 NH4PbI3 和 NH4MgI3 中的价带负有最大责任，而铅 (Pb) p 轨道和镁 (Mg) s 轨道表明对传导带的最突出贡献。NH4PbI3 的 BSE-SOC、TDDFPT 和 TDDFPT-SOC 获得了类似的光谱，但没有吸收开始，而与预测较低反射率和较高透射率的 NH4MgI3 相比，NH4PbI3 预测的吸光度和吸收系数值更高。这两种化合物在紫外区显示出最大吸收系数约为 105，如 CH3NH3PbI3 和硅。因此，我们建议 NH4PbI3 将用作太阳能电池吸收剂和紫外线保护剂，而 NH4MgI3 在电致变色材料的生产中将有更多应用。