We studied the structural stability, electronic and optical properties of CH_3-xF_xNH₃GeI₃ (x = 0, 1, 2, 3) halide perovskites for the first time. The results reveal that CH₃NH₃GeI₃ is the most stable structure among the CH_3-xF_xNH₃GeI₃ compounds. The addition of fluorine in CH₃NH₃ leads to the reduced stability of CH₃NH₃GeI₃. When the H atoms of CH₃NH₃ one by one are replaced by fluorine atom, the CH_3-xF_xNH₃GeI₃ compounds have larger band gaps and show decreased optical absorption coefficients. These results suggest that the effect of fluorine on the organic cation has a significant influence on the material properties of CH₃NH₃GeI₃.

我们首次研究了CH _{3- x} F _x NH ₃ GeI ₃（x  = 0、1、2、3）卤化物钙钛矿的结构稳定性，电子和光学性质。结果表明，CH ₃ NH ₃ GeI ₃是CH _{3- x} F _x NH ₃ GeI ₃化合物中最稳定的结构。在CH ₃ NH _3中添加氟导致CH ₃ NH ₃ GeI _3的稳定性降低。当CH ₃ NH的H原子_3-被氟原子一一取代，CH _{3- x} F _x NH ₃ GeI ₃化合物具有较大的带隙并且显示出降低的光吸收系数。这些结果表明，氟对有机阳离子的影响对CH ₃ NH ₃ GeI ₃的材料性能具有重大影响。