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Circularly polarized light (CPL) detection has wide applications in many fields, where the anisotropy factor (gIph) is an important indicator to characterize the CPL detection performance. So far, many materials with high gIph have been reported, however, the exploration of the regulation of gIph is still in its infancy. Herein, two novel alternating chiral‐achiral cations intercalation‐type chiral hybrid perovskites (CHPs), named (R/S‐1‐phenylpropylamine)(propylamine)PbBr4 (1‐R/S), exhibit above room‐temperature (RT) polar‐phase transition, which greatly regulates the gIph value. The gIph of 1‐R is 0.04 in high‐temperature phase chiral non‐polar (P212121) by applying 5 V bias, interestingly, with the temperature decrease, the gIph value in low‐temperature phase chiral polar (P21) gradually increases (0.22@360K, 0.40@340K, 0.47@320K), and finally reaches a maximum of 0.5 at RT. Such value is not only the highest among 2D CHPs to date, but presents a 12.5‐fold amplification compared with 0.04. Further, this rare phenomenon should be attributed to the built‐in electric field induced by the polar photovoltaic effect, which sheds light on further obtaining CHPs with large gIph. [ABSTRACT FROM AUTHOR]

2D chiral hybrid perovskites have recently emerged as outstanding semiconductor materials. However, most of the reported 2D chiral perovskites have limited structural types and contain high levels of toxic lead, which severely hinders their further applications. Herein, by using a mixed‐cation strategy, an unprecedented type of lead‐free cluster‐based 2D chiral hybrid double perovskite derivatives are successfully obtained, [(R/S‐PPA)4(IPA)6Ag2Bi4I24]·2H2O (1‐R and 1‐S), and [(R/S‐PPA)4(n‐BA)6Ag2Bi4I24]·2H2O (2‐R and 2‐S) (R/S‐PPA=R/S–1‐phenylpropylamine; IPA=isopentylamine; n‐BA=n‐butylamine). Their inorganic skeletons are linked by binuclear {Bi2I10} and infinite chain {Ag2Bi2I14}∞, in which bismuth clusters and multiple coordination modes (e.g., tetrahedral AgI4 and octahedral AgI6) are introduced into the double perovskite system for the first time. This introduction induces distortion of the inorganic layer, which may facilitate the transfer of chirality from the chiral cations into achiral double perovskite skeletons. Further, circular dichroism measurements and circularly polarized light detection confirm their inherent chiral optical activities. In addition, 1‐S exhibits an ultralow X‐ray detection limit of 129.5 nGy s−1, which is 42‐fold lower than that of demands in regular medical diagnosis (5.5 µGy s−1). This study provides a pathway to construct novel type of lead‐free cluster‐based double perovskite derivatives. [ABSTRACT FROM AUTHOR]

Hybrid organic–inorganic perovskite (HOIP) ferroelectrics with high Curie temperature (Tc), typified by the lead halide hybrid perovskite ferroelectrics, are developing rapidly owing to their maneuverable ferroelectricity at high temperatures. However, acquiring high‐Tc lead‐free HOIP ferroelectrics via rational strategy still needs development. In this study, a brand‐new program by modulating the steric confinement in a cuplike cavity to design high‐Tc bismuth‐halide ferroelectrics [H2mdap]BiX5 (H2mdap = N‐Methyl‐1,3‐Propanediamine, X = Cl (1), Br (2), I(3)) is proposed. Emphatically, the Tc enhanced dramatically from 264 K of 3 to 318 K of 2 and 377 K of 1, induced by the substitution of Br and Cl to I, accompanied with an interesting transition from second‐order phase transition (for 3) to the first‐order one (for 1 and 2). The extent of Tc increase is up to 113 K, which far outweighs that of reported Pb‐halide hybrid ferroelectrics. Structural and computational analyses elucidate that this unprecedented improvement of Tc is due to the higher phase transition energy barriers induced by modulating the steric confinement of cuplike cavity via halogen substitution. These results will provide new inspiration for designing high‐Tc lead‐free HOIP ferroelectrics. [ABSTRACT FROM AUTHOR]

The exceptional photophysical properties of 3D organic–inorganic lead halide hybrids (OILHs) endow their significant potential for usage in optoelectronics, which has sparked intense research on novel 3D OILHs and associated applications. However, constructing new 3D OILHs based on large organic cations suffers from tough challenges due to the limitation of the Goldschmidt tolerance factor rule, let alone further explorations of their practical applications. Herein, a brand‐new 3D lead chloride hybrid, (1MPZ)Pb4Cl10·H2O (1, 1MPZ = 1‐methylpiperazine) is reported, featuring a dense 3D lead chloride framework made of the corner‐, edge‐, and face‐shared lead chloride polyhedra. 1 presents a broadband white light emission with a large Stokes shift and a nanosecond photoluminescence lifetime, which originates from radiative recombination of self‐trapped excitons (STEs) induced by the highly distorted structure. Such a reabsorption‐free and fast‐decayed STEs emission coupling with the dense 3D architecture further enables 1 with effective X‐ray scintillation with good sensitivity. Impressively, 1 also shows superior environmental and radiation stability. This study provides a new 3D OILH with appealing luminescence, not only expanding the 3D OILH family but also inspiring the exploitation of their optoelectronic applications. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) lead-based hybrid perovskites with highly intrinsic anisotropy and entertaining semiconductor properties are well suited for polarization-sensitive photodetection. Nonetheless, their chemical instability and environmental hazards hinder their further application. Recenly, 2D double perovskites have received much attention as excellent green alternatives to lead-based perovskites. However, the application of 2D double perovskite in broad-spectrum polarization-sensitive detection has not been explored. In this work, we first grew centimeter-sized crystals (11 × 3 × 1 mm3) of 2D hybrid double perovskite (IPA)4AgBiI8 (IPA is iodopropylamine) with narrow bandgap of Eg = 1.87 eV. Remarkably, the single-crystal photodetectors of (IPA)4AgBiI8 show broad-spectrum polarization-sensitive response, even at 660 nm, with a large dichroism ratio (Iphc/Iphb ≈ 1.23), a large detectivity up to ∼1010 Jones, and a relatively rapid response time (∼450 μs). All these outstanding features combine to produce (IPA)4AgBiI8, an excellent polarized photodetector material. This work introduces a novel 2D hybrid double perovskite material for broad-spectrum polarization-sensitive photodetection. [ABSTRACT FROM AUTHOR]

A mixed‐cation 3D lead bromide hybrid perovskite (NMDAP)2FAPb4Br13 (1, NMDAP2+ = N‐methyl‐1,3‐diaminopropanium, FA+ = formamidinium) is tailored by incorporating the large NMDAP2+ cation with the small FA+ ion into 3D FAPbBr3. Structurally, the small FA+ ions occupy the prototypical cavities formed by distorted corner‐sharing PbBr6 octahedra as in FAPbBr3, while the bulky NMDAP2+ ions are confined to the expanded lattice which is defined by a new structural motif composed of eight corner‐sharing PbBr6 octahedra and four edge‐sharing octahedra. This localized lattice expansion from FAPbBr3 creates a new branch of the intriguing 3D hybrid perovskite family, breaking the limits of the conventional Goldschmidt tolerance factor rule. Moreover, a high two‐photon absorption (2AP) coefficient of 60.8 cm MW−1 was demonstrated to near‐infrared (NIR) 800 nm illumination, enabling sensitive NIR photoresponses with large on/off ratio (≈104) as well as favorable stability. [ABSTRACT FROM AUTHOR]

Electrocaloric effect driven by electric fields displays great potential in realizing highly efficient solid-state refrigeration. Nevertheless, most known electrocaloric materials exhibit relatively poor cooling performance near room temperature, which hinders their further applications. The emerging family of hybrid perovskite ferroelectrics, which exhibits superior structural diversity, large heat exchange and broad property tenability, offers an ideal platform. Herein, we report an exceptionally large electrocaloric effect near room temperature in a designed hybrid perovskite ferroelectric [(CH3)2CHCH2NH3]2PbCl4, which exhibits a sharp first-order phase transition at 302 K, superior spontaneous polarization (>4.8 μC/cm2) and relatively small coercive field (<15 kV/cm). Strikingly, a large isothermal entropy change ΔS of 25.64 J/kg/K and adiabatic temperature change ΔT of 11.06 K under a small electric field ΔE of 29.7 kV/cm at room temperature are achieved, with giant electrocaloric strengths of isothermal ΔS/ΔE of 0.86 J·cm/kg/K/kV and adiabatic ΔT/ΔE of 370 mK·cm/kV, which is larger than those of traditional ferroelectrics. This work presents a general approach to the design of hybrid perovskite ferroelectrics, as well as provides a family of candidate materials with potentially prominent electrocaloric performance for room temperature solid-state refrigeration. Most known electrocaloric materials show relatively poor cooling performance near room temperature, hindering their applications. Here, the authors achieve large electrocaloric effect near room temperature in a hybrid perovskite ferroelectric, useful for high-performance solid-state refrigeration. [ABSTRACT FROM AUTHOR]