Centimeter‐Sized Piezoelectric Single Crystal of Chiral Bismuth‐Based Hybrid Halide with Superior Electrostrictive Coefficient

The lead‐free hybrid perovskite piezoelectrics possess advantages of easy processing, light weight, and low‐toxicity over inorganic ceramics. However, the lack of understanding in structure–property relationships hinders exploration of new molecular piezoelectric crystals with excellent performances. Herein, by introducing chiral α‐phenylethylammonium (α‐PEA + ) cations into bismuth‐based hybrid halides, centimeter‐sized ( R ‐α‐PEA) 4 Bi 2 I 10 and ( S ‐α‐PEA) 4 Bi 2 I 10 single crystals with a superior piezoelectric voltage coefficient g 22 of 309 mV m N −1 , are obtained. Structural rigidity in crystals leads to a remarkable electrostrictive coefficient Q 22 of 25.8 m 4 C −2 , nearly 20 times higher than that of poly(vinylidene fluoride) (PVDF), which is beneficial to improve piezoelectricity with the synergistic effect of chirality. Moreover, the as‐grown crystals show outstanding phase stability from 173 K to ≈470 K. This work suggests a design strategy based on rigidity and chirality to exploit novel piezoelectrics among hybrid metal halides.