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Tunable photostriction of halide perovskites through energy dependent photoexcitation

Bo Peng, Daniel Bennett, Ivona Bravic, Bartomeu Monserrat

Photostriction, the name given to volume changes upon illumination, has recently been observed in halide perovskites. However, the microscopic mechanism remains unclear. In this letter, the authors propose that the orbital character of the electronic bands near the Fermi level determine the photostriction behavior. They find that photoexciting electrons from strong antibonding valence states to weaker antibonding conduction states leads to lattice contraction as a result of weakened antibonding interaction. Interestingly, using higher excitation energies promotes electrons from deeper nonbonding valence states to antibonding conduction states, resulting in giant lattice expansion. These results rationalize the experimentally observed tunable photostriction in halide perovskites.

Tunable photostriction depending on photoexcitation energy
Tunable photostriction depending on excitation energy

Halide perovskites exhibit giant photostriction, that is, volume or shape changes upon illumination. However, the microscopic origin of this phenomenon remains unclear and there are experimental reports of both light-induced lattice expansion and contraction. In this Letter, we establish a general method, based on first-principles calculations and molecular orbital theory, which provides a microscopic picture of photostriction in insulators based on the orbital characters of their electronic bands near the Fermi level. For lead-halide perovskites, we find that different valence states have different bonding characters, leading to opposing strengthening or weakening of bonds depending on the photoexcitation energy. The overall trend is that light induces lattice contraction at low excitation energies, while giant lattice expansion occurs at high excitation energies, rationalizing experimental reports.

Tunable photostriction of halide perovskites through energy dependent photoexcitation
B Peng, D Bennett, I Bravic and B Monserrat
Physical Review Materials 6, L082401 (2022) Editors' Suggestion

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