Low-dimensional lead-free organic–inorganic hybrid perovskites have gained increasing attention as having low toxicity, ease of processing, and good optoelectronic properties. Seeking for lead-free and narrow band gap organic–inorganic hybrid perovskites are of great importance for the development and application of photoelectric materials. Here, we reported a Sb-based organic–inorganic hybrid perovskite (MV)­[SbI3Cl2], which has one-dimensional inorganic frameworks of the I-sharing double octahedra. (MV)­[SbI3Cl2] shows a narrow direct band gap of 1.5 eV, and displays obvious photoresponse for the 532 nm light with rapid response speed of t rise = 0.69 s, t decay = 0.28 s. With an illumination power of 5 mW and a 50 V bias, the responsivities (R) and external quantum efficiency (EQE) for (MV)­[SbI3Cl2] photodetector under 532 nm laser are 29.75 mA/W and 6.69% respectively. This Sb-based halide double perovskite material will provide an alternative material for photodetector devices.

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Hybrid improper ferroelectric Ca3Ti2O7 (CTO) and Ca2.99Na0.01Ti2O7 (NaCTO) ceramics were synthesized using the solid‐state reaction method. X‐ray powder diffraction technique was used to determine the phase purity and crystal structure of the prepared ceramics. We investigated their ferroelectric polarization, dynamic switching current, and piezoelectric properties, and confirmed their ferroelectric reversal property with a coercive field of 60‐80 kV/cm. A negative piezoelectric behavior was observed with a maximum strain of −0.01% and −0.007% for CTO and NaCTO, respectively. This abnormal piezoelectric behavior can be used to prepare composites with conventional oxide materials that generally exhibit positive piezoelectricity. Mechanism of the negative piezoelectricity effect was ascribed to its special quasi‐two‐dimensional (quasi‐2D) crystal structure with weak van der Waals (vdW) layers alternating with covalent layers.

Seeking for materials with high dielectric tunability and low coercive field is of great importance for the development and application of microwave tunable devices. In this work, inorganic and organic hybrid crystals (MV)[BiI3Cl2] were synthesized by using a solvothermal reaction method. Higher dielectric tunability (>70%) can be achieved for (MV)[BiI3Cl2] with an ultralow driving electric field (∼40 V/cm). The coercive electric field of (MV)[BiI3Cl2] is around three orders of magnitude lower than that of conventional organic oxides. Moreover, (MV)[BiI3Cl2] exhibits excellent electrical reliability related to the fatigue and the polarization retention property. The ultralow coercive electric field is ascribed to the quasi-one-dimensional structure of the Bi-I-Bi-I inorganic chain in inorganic and organic hybrid (MV)[BiI3Cl2].

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