Composition-Property Relations for GA_x FA_y MA_{1- x - y} PbI₃ Perovskites

Halide perovskites are materials for diverse optoelectronic applications owing to a combination of factors, including their compositional flexibility. A major source of this diversity of compositions comes from the use of mixed organic cations in the A-site of such compounds to form solid solutions. Many organic cations are possible for this purpose. Although significant progress is made over years of intensive research, the determination of systematic relationships between the compositions and properties of halide perovskites is not exploited accordingly. Using the MAPbI₃ prototype, a wide range of compositions substituted by formamidinium (FA⁺ ) and guanidinium (GA⁺ ) cations are studied. From a detailed collection of experimental data and results reported in the literature, heat maps correlating the composition of GA_x FA_y MA_{1- x - y} PbI₃ solid solutions with phase transition temperatures, dielectric permittivity, and activation energies are constructed. Considering the characteristics of organic cations, namely their sizes, dipole moments, and the number of N─H bonds, it is possible to interpret the heat maps as consequences of these characteristics. This work brings a systematization of how obtaining specific properties of halide perovskites might be possible by customizing the characteristics of the A-site organic cations.