Abstract Lead-based perovskite materials are commercially restricted as ideal candidates for solar cell applications due to their toxic nature. Here, we have performed a first-principles investigation of structural, mechanical and optoelectronic properties of the orthorhombic perovskite structures of MAGe1-xSnxI3 (MA = CH3NH3) by using density functional theory (DFT). In this research work, mixed Ge/Sn in different proportion have been considered that allows additional opportunities to find better and improve the practical performance of perovskites for solar cell application. The calculations have revealed that the investigated materials are direct bandgap semiconducting materials and the obtained bandgaps range between 0.569 eV and 1.615 eV. The optical properties have shown that MAGeI3, MAGe0.875Sn0.125I3, MAGe0.375Sn0.625I3 and MASnI3 have an excellent absorption coefficient for visible light that makes them useful as photovoltaic materials. Further mixed materials exhibit higher dielectric performance resulting in higher dispersion of light. These materials also behave as superluminescent semiconducting material at high photon energy. Thus the mixed perovskite structures improve the performance of the solar cells.

中文翻译：

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无铅混合Ge-Sn杂化有机-无机钙钛矿结构、机械和光电性能的第一性原理研究

摘要 铅基钙钛矿材料由于其毒性在商业上被限制为太阳能电池应用的理想候选材料。在这里，我们使用密度泛函理论 (DFT) 对 MAGe1-xSnxI3 (MA = CH3NH3) 的正交钙钛矿结构的结构、机械和光电特性进行了第一性原理研究。在这项研究工作中，已经考虑了不同比例的混合 Ge/Sn，这为寻找更好的钙钛矿和提高太阳能电池应用的实际性能提供了更多机会。计算表明，所研究的材料是直接带隙半导体材料，获得的带隙范围在 0.569 eV 和 1.615 eV 之间。光学性质表明MAGeI3、MAGe0.875Sn0.125I3、MAGe0.375Sn0。625I3 和 MASnI3 对可见光具有出色的吸收系数，这使得它们可用作光伏材料。进一步混合的材料表现出更高的介电性能，导致更高的光色散。这些材料在高光子能量下也表现为超发光半导体材料。因此，混合钙钛矿结构提高了太阳能电池的性能。