We report a material screening study for phase transitions of multication hybrid halide perovskite films. Two hundred sixty-six films processed with flash infrared annealing were optically and structurally characterized. This data was compiled into a database to use as a reliable guide for fundamental studies of halide perovskites. We determine the optimum conditions for the formation of the mixed-cations halide perovskite active phase. We subjected the films to different stress conditions (light, temperature, humidity) resulting in five compositions that were thermodynamically stable. From these, the photoinduced phase instability process of the hybrid perovskite films was explored. These intrinsic stability tests showed that the correct multication combination plays a fundamental role in the crystal growth and thermodynamic stability of the films.