Anisotropic In Situ Strain-Engineered Halide Perovskites for High Mechanical Flexibility

Even though halide perovskite materials have been increasingly investigated as flexible devices, mechanical properties under flexible environments have rarely been reported on. Herein, a nonconventional deposition technique that can generate extra compressive or tensile stress in representative inorganic CsPbBr(3)and hybrid MAPbI(3)(methylammonium lead iodide) halide perovskites is proposed for higher mechanical flexibility. As an impressive result of bending fracture evaluation, fracture energy is substantially improved by approximate to 260% for CsPbBr(3)and approximate to 161% for MAPbI(3)with the maximum compressive strain of -1.33%. Origin of the flexibility enhancements by the in situ strain is verified with structural simulation where the anisotropic lattice distortion, that is, contraction in theabplane and elongation along thec-axis, is evident with changes in atomic bond lengths and angles in the halide perovskites. Other mechanical properties such as hardness, film strength, and fracture toughness are also discussed with direct comparisons between the inorganic and hybrid halides. Beyond the successful adjustment of this in situ deposition technique, the strain-dependent mechanical properties are expected to be extensively useful for designing halides-based flexible devices.