Two-dimensional (2D) materials have been well developed for polarization-sensitive photodetection, while new 2D members used in shortwave region (>2.5 eV) still remain scarce. The family of 2D hybrid perovskite ferroelectrics, in which the coupling of spontaneous polarization (P s ) and light benefits dissociation of photoinduced carriers, has shown great potential in this portfolio. Here, we report a new 2D hybrid perovskite ferroelectric, [CH 3 (CH 2 ) 3 NH 3 ] 2 (CH 3 NH 3 )Pb 2 Br 7 (1), which exhibits a superior P s of 3.6 μC/cm 2 and a relatively wide bandgap (∼2.55 eV). The unique 2D perovskite motif results in an intrinsic anisotropy of optical absorption (the ratio α c /α a ≈ 1.9 at 405 nm), involving its polarizationsensitive activity. As expected, the strongest photoresponses were observed along the c-axis (i.e., parallel to P s ), along with a large dichroism ratio (I ph c /I ph a ≈ 2.0) and highly sensitive detectivity up to ∼10 9 Jones. Further, crystal-device of 1 shows a fast responding rate (∼20 μs) and excellent antifatigued merits. As pioneering work, 1 is the first polarization-sensitive ferroelectric in the new branch of 2D hybrid perovskites. Such intriguing behaviors make 1 a potential candidate for the shortwave polarized-light detection, which also sheds light on new functionalities for future optoelectronic application of hybrid perovskites.

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Single crystals of lead halide hybrid perovskites (e. g., CH3NH3PbI3 and CsPbBr3) have been developed as promising candidates for X-ray detection, owing to their excellent attributes including low trap density, high X-ray absorption cross section, and high carrier mobility. The toxicity of lead, however, is a potential bottleneck that hinders their device application toward green and sustainable competitors. Herein, we reported a new lead-free bismuth-iodide hybrid of (H2MDAP)­BiI5 (1, H2MDAP = N-methyl-1,3-diaminopropanium), adopting one-dimensional (1D) metal-halogen frameworks, which behaves as a potential alternative for X-ray detection. Large-size single crystals of 1 with sizes up to 9 × 7 × 4 mm3 were successfully grown via top-seeded solution growth method. The as-grown crystal exhibits notable semiconducting properties, including a narrow bandgap of 1.83 eV, trap density of 3.6 × 1011 cm–3, carrier mobility of 1.42 cm2 V–1 s–1, and high X-ray absorption coefficient. Consequently, the fabricated crystal-based X-ray photoconductor enables the conversion of X-ray to electrical signals with a sensitivity of ∼1.0 μC Gyair –1 cm–2. These results throw light on further exploration on X-ray-sensitive materials based on the lead-free metal halogen hybrids.

Antiferroelectric materials have been regarded as a promising candidate for electronic energy storage devices, due to their natural double polarization versus electric field (P–E) hysteresis loops. Currently, two-dimensional organic–inorganic hybrid perovskites with structural diversity and tunability, have received blooming interests, whereas above-room-temperature antiferroelectrics are still unreported in this perovskite system. Herein, for the first time, we successfully acquire a two-dimensional Ruddlesden–Popper hybrid perovskite antiferroelectric, ((CH3)2CHCH2NH3)2CsPb2Br7 (1), which shows an above-room-temperature Curie temperature at 353 K, trigging by the synergistic dynamic motion of inorganic Cs atoms and organic isobutylammonium cations. Intriguingly, the antiferroelectricity of 1 existing over a wide temperature range of 298–353 K are revealed by the distinct double P–E hysteresis loops. Besides, 1 possesses remarkable energy storage efficiency up to 69%, comparable to those of some reported inorganic antiferroelectric ceramics, promoting 1 potential application in energy storage devices. This work provides an avenue to construct novel antiferroelectric materials for high-performance electronic device applications.