Mapping the Room-Temperature Dynamic Stabilities of Inorganic Halide Double Perovskites

The diverse chemistry of halide double perovskites (A2MM′X6) has provided material scientists with exciting opportunities to discover new multifunctional materials. However, similar to their single perovskite counterparts, the presence of strongly anharmonic phonons, which can further couple with the electronic subsystem in halide double perovskites, plays a vital role in determining the finite temperature phase stabilities and the lifetime of the photoexcited states in these materials to be used as solar absorbers. Using the high-throughput computational framework that we have previously established for building the database of room-temperature phase stabilities and vibrational anharmonicities for cubic single perovskites, we further extend this database to cover ∼2000 cubic halide double perovskites extracted from the Materials Project database. It is discovered that the halide double perovskites possess higher dynamic stabilities compared to their single perovskite counterparts. The correlation between the vibrational anharmonicity and the complex chemistry of halide double perovskites is uniquely revealed with unsupervised machine learning, highlighting the important role played by the atomic weight of the M and M′ cations and the halide anions. Further examination on the electronic dynamics for 19 selected direct band gap halide double perovskites reveals significantly strengthened electron–phonon coupling behaviors despite their low vibrational anharmonicity. This illustrates a challenge behind the development of halide double perovskites as efficient materials for solar cells but may be harnessed in other applications such as thermochromic sensing