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Antiferroelectric materials with an electrocaloric effect (ECE) have been developed as promising candidates for solid-state refrigeration. Despite the great advances in positive ECE, reports on negative ECE remain quite scarce because of its elusive physical mechanism. Here, a giant negative ECE (maximum ΔS∼ −33.3 J kg–1K–1with ΔT∼ −11.7 K) is demonstrated near room temperature in organometallic perovskite, iBA2EA2Pb3I10(1, where iBA = isobutylammonium and EA = ethylammonium), which is comparable to the greatest ECE effects reported so far. Moreover, the ECE efficiency ΔS/ΔE(∼1.85 J cm kg–1K–1kV–1) and ΔT/ΔE(∼0.65 K cm kV–1) are almost 2 orders of magnitude higher than those of classical inorganic ceramic ferroelectrics and organic polymers, such as BaTiO3, SrBi2Ta2O9, Hf1/2Zr1/2O2, and P(VDF-TrFE). As far as we know, this is the first report on negative ECE in organometallic hybrid perovskite ferroelectric. Our experimental measurement combined with the first-principles calculations reveals that electric field-induced antipolar to polar structural transformation results in a large change in dipolar ordering (from 6.5 to 45 μC/cm2under the ΔEof 18 kV/cm) that is closely related to the entropy change, which plays a key role in generating such giant negative ECE. This discovery of field-induced negative ECE is unprecedented in organometallic perovskite, which sheds light on the exploration of next-generation refrigeration devices with high cooling efficiency.

Chemiresistive sensing has been regarded as the key monitoring technique, while classic oxide gas detection devices always need an external power supply. In contrast, the bulk photovoltage of photoferroelectric materials could provide a controllable power source, holding a bright future in self-powered gas sensing. Herein, we present a new photoferroelectric ([n-pentylaminium]2[ethylammonium]2Pb3I10, 1), which possesses large spontaneous polarization (∼4.8 μC/cm2) and prominent visible-photoactive behaviors. Emphatically, driven by the bulk photovoltaic effect, 1enables excellent self-powered sensing responses for NO2at room temperature, including extremely fast response/recovery speeds (0.15/0.16 min) and high sensitivity (0.03 ppm–1). Such figures of merit are superior to those of typical inorganic systems (e.g., ZnO) using an external power supply. Theoretical calculations and in situ diffuse reflectance infrared Fourier transform spectroscopy measurements confirm the great selectivity of 1for NO2. As far as we know, this is the first realization of ferroelectricity-driven self-powered gas detection. Our work sheds light on the self-powered sensing systems and provides a promising way to broaden the functionalities of photoferroelectrics.

Driven by the breakthrough development of lead (Pb)-based halide perovskites, halide double perovskites have also emerged as remarkably multipurpose materials owing to their environmental friendliness, abundant physicochemical properties, and structural tunability. However, despite their recent soaring progress, the realization of switchable dielectrics in this fascinating family remains considerably less explored. In this study, centimeter-sized single crystals of a single-layer halide double perovskite (3-bromopropylaminium)4AgBiBr8(1) with dimensions up to 20 mm × 17 mm × 5 mm have been successfully synthesized by using the solution cooling method. The single crystal undergoes a ferroelastic phase transition of mmmF2/mdefined by the Aizu notation, which is attributed to the synergistic interaction between octahedral distortion and flexible molecular motion according to structural analysis. Noteworthily, it possesses desirable ferroelastic phase transition-triggered switchable dielectric properties near the high temperature of 373 K, which can be switched between two stable dielectric states. Additionally, 1 possesses an indirect-bandgap semiconducting feature and exhibits an X-ray response with a sensitivity of up to 517 µC Gyair−1cm−2at a 40 V bias voltage. We believe that this study provides another efficient application path for Pb-free halide double perovskites with intelligent functions.

Motivated by the high performance of optoelectronic devices, organic–inorganic hybrid perovskites (OIHPs), particularly three-dimensional (3D) OIHPs, have taken a promising position in optoelectronic devices, owing to their high absorption coefficient, long carrier lifetime, and superior conversion efficiency. However, 3D OIHPs inevitably suffer from destruction under moisture operating conditions; it is a great struggle to synchronously realize high performance and long-term stability in optoelectronic devices. Herein, bulk single crystals (6 × 2 × 1.5 mm3) of the 3D hybrid perovskitoid (C6H10N2)Pb2Br6(1, C6H10N22+= N,N′-dimethyl-pyrazinium) have been grown successfully, which exhibit an excellent light absorption capacity (730 nm) and superior stability. Based on the bulk crystals of 1, photodetectors are fabricated with an extremely low dark current (3.5 pA), large current on/off ratio (>103), considerable responsivity (R, 4 mA W–1), and detectivity (D*, 4 × 1010Jones). Strikingly, these devices possess excellent working stability (over 90 days) under ultralong air exposure, which are much better than most of the reported 3D OIHP devices. Furthermore, both experimental and computational investigations reveal that the excellent stability originates from the hydrophobic property of alkyl groups in C6H10N22+cations. All of these results not only provide an efficient avenue to acquire 3D perovskitoid bulk single crystals but also inspire further exploration of ultrastable photoelectric devices.

Circularly polarized light (CPL) detection has sparked overwhelming research interest for its widespread chiroptoelectronic and spintronic applications. Ferroelectric materials, especially emerging layered hybrid perovskite ferroelectrics, exhibiting striking bulk photovoltaic effect (BPVE) present significant possibilities for CPL detection by a distinctive working concept. Herein, for the first time, we demonstrate the realization of robust angular anisotropy of CPL detection in a new layered hybrid perovskite ferroelectric crystal (CPA)2FAPb2Br7(1, CPA is chloropropylammonium, FA is formamidinium), which crystallized in an optically active achiral polar point group. Benefiting from the notable spontaneous polarization (5.1 μC/cm2) and excellent semiconducting characteristics, single crystals of 1exhibit remarkable BPVE under light illumination, with a high current on/off switching ratio (ca. 103). More intriguingly, driven by the angular carrier drift originating from spin-dependent BPVE in optically active ferroelectrics, 1displays highly sensitive self-powered CPL detection performance, showing a robust angular anisotropy factor up to 0.98, which is far more than those achieved by material intrinsic chirality. This work provides an unprecedented approach for realizing highly sensitive CPL detection, which sheds light on the further design of optically active ferroelectrics for chiral photonic applications.

Ferroelectrics with switchable spontaneous polarization have taken a dominant position as the nonlinear optical candidates, of which birefringence is an essential merit to optical devices. Despite the increasing advance of hybrid perovskite ferroelectrics, it remains a great challenge to control and tune their birefringence, thus hindering their practical optical applications. Here, we present a 2D trilayered hybrid perovskite-type ferroelectric obtained by 3D-to-2D dimensional tailoring, [(CH3)2CH(CH2)2NH3]2(CH3NH3)2Pb3Cl10, showing biaxial polarizations of ∼5 μC/cm2and a relatively wide optical band gap. The intrinsic 2D architecture results in highly anisotropic principal refractive indices, namely, the optical birefringence. Interestingly, its birefringence can be reversibly switched through ferroelectric-to-paraelectric symmetry breaking. The birefringence tuning is further established by virtue of pretransitional modulation of ferroelectricity, exhibiting unusual polarization-dependent behaviors. In our judgment, this study on the polarization-dependent birefringence of hybrid perovskite ferroelectrics will provide a new pathway toward modulating nonlinear optical properties for smart devices.

Two-dimensional (2D) ternary materials have sprung up in a broad variety of optoelectronic applications due to their robust degree of freedom to design the physical properties of the materials through adjusting the stoichiometric ratio. However, the controlled growth of high-quality 2D ternary materials with good chemical stoichiometry remains challenging, which severely impedes their further development and future device applications. Herein, we synthesize ternary Bi2Te2Se (BTS) flakes with a thickness down to 4 nm and a lateral dimension about 60 µm by an atmospheric-pressure solid source thermal evaporation method on a mica substrate. The phonon vibration and electrical transportation of 2D BTS are respectively investigated by temperature-dependent Raman spectrum and conductivity measurements. Furthermore, the photodetector based on 2D BTS exhibits excellent performance with a high light on/off ratio of 1300 (365 nm), a wide spectral response range from 365 to 980 nm, and an ultra-fast response speed up to 2 µs. In addition, its electrical and photoelectric properties can be modulated by the gate voltage, offering an improved infrared responsivity to 2.74 A W−1and an on/off ratio of 2266 under 980 nm. This work introduces an effective approach to obtain 2D BTS flakes and demonstrates their excellent prospects in optoelectroni cs.

Due to the breakthrough development of layered hybrid perovskites, the multilayered hybrid double perovskites have emerged as outstanding semiconducting materials owing to their environmental friendliness and superior stability. Despite recent booming advances, the realization of above-room temperature ferroelectricity in this fascinating family remains a huge challenge. Herein, when the molecular design strategy of aromatic cation alloying is applied, an above-room temperature “green” bilayered hybrid double perovskite photoferroelectric, (C6H5CH2NH3)2CsAgBiBr7(BCAB), is successfully developed with a notable saturation polarization of 10.5 μC·cm–2and high-Curie temperature (Tc∼ 483 K). Strikingly, such a Tcachieves a new record in multilayered hybrid perovskite ferroelectrics, which extends the ferroelectric working temperature to a high level. Further computational investigation reveals that the high-Tcoriginated from the high phase-transition energy barrier switched by the rotation of the aromatic cation in the confined environment of the inorganic layers. In addition, benefiting from the attractive polarization and remarkable photoelectric properties, a bulk photovoltaic effect (BPVE) with a prominent zero-bias photocurrent (2.5 μA·cm–2) is achieved. As far as we know, such a high-Tcmultilayered hybrid double perovskite ferroelectric is unprecedented, which sheds light on the rational design of an environmental photoferroelectric for high performance photoelectric devices.

Chiral hybrid perovskites have brought an unprecedented opportunity for circularly polarized light (CPL) detection. However, the circular polarization sensitivity of such a detector remains extremely low because of the high exciton recombination rate in those single-phase hybrid perovskites. Here, a heterostructure construction strategy is proposed to reduce the electron–hole recombination rate in a chiral hybrid perovskite and achieve CPL detectors with greatly amplified circular polarization sensitivity. A heterostructure crystal, namely, [(R)-MPA]2MAPb2I7/MAPbI3((R)-MPA = (R)-methylphenethylamine, MA = methylammonium), has been successfully created by integrating a chiral two-dimensional (2D) perovskite with its three-dimensional counterpart via solution-processed heteroepitaxy. Strikingly, the sharp interface of the as-grown heterostructure crystal facilitates the formation of a built-in electric field, enabling the combined concepts of charge transfer and chirality transfer, which effectively reduces the recombination probability for photogenerated carriers while retaining chiroptical activity of chiral 2D perovskite. Thereby, the resultant CPL detector exhibits significantly amplified circular polarization sensitivity at zero bias with an impressive anisotropy factor up to 0.67, which is about six times higher than that of the single-phase [(R)-MPA]2MAPb2I7(0.1). As a proof-of-concept, the strategy we presented here enables a novel path to modulate circular polarization sensitivity and will be helpful to design chiral hybrid perovskites for advanced chiroptical devices.

High-Curie-temperature (Tc) ferroelectrics have exhibited broad applications in optoelectronic devices. Recently, two-dimensional multilayered perovskite ferroelectrics with excellent photoelectric attributes are attracting increasing interest as new systems of photoferroelectrics. However, the effective tuning of the Tcvalue of a multilayered perovskite photoferroelectric system still remains a huge challenge. Here, by a halogen substitution strategy to introduce bromine atoms on n-propylamine cations, the hybrid perovskite photoferroelectric (3-bromopropylaminium)2(formamidinium)Pb2Br7(BFPB) with a high Tcvalue (348.5 K) was obtained. It is notable that BFPBadopts a two-dimensional bilayered inorganic framework, with tight linking to the organic cation by C–Br···Br–Pb halogen···halogen interactions and N–H···Br hydrogen bonds. Intriguingly, in comparison with the prototypical compound (n-propylaminium)2(formamidinium)Pb2Br7, a remarkable augmentation of 85.2 K in the resulting Tcvalue of BFPBis clearly observed, which further broadens the temperature range of its application. In combination with the remarkable ferroelectric and semiconducting attributes, the reversible bulk photovoltaic effect was realized in single crystals of BFPB. This finding can not only enhance the hybrid perovskite ferroelectric family but also further promote the photoelectric application of ferroelectrics.

Two-dimensional (2D) hybrid perovskites with the Ruddlesden-Popper lattice (A′)2(A)n−1MnX3n+1are emerging as the promising optoelectronic candidates, both the inorganic and organic ingredients of which can be tailored to modulate the physical properties. Nevertheless, there is a scarcity of 2D multilayered motifs with the A-site large-size cations occupying perovskite cavities. Here, by rational mixed-cation alloying, we present a new 2D hybrid perovskite, (4-TFBMA)2(DMA)Pb2I7(1), in which the secondary cation of CH3NH2CH3+(DMA) is located inside the perovskite cage while the aromatic 4-(trifluoromethyl)benzylammonium (4-TFBMA) cation acts as a spacer moiety. Benefiting from the quantum structure of alternating organic spacers and inorganic networks, crystal-array detectors of 1 show fascinating in-plane photodetection responses of large detectivity (−2.95 × 1012Jones) and responsivity (−1.97 A W−1), comparable to those of some inorganic 2D counterparts. In addition, a fast response rate (−264 µs) and a low dark current are also realized, related to the high crystalline quality and suppression of the hopping barrier due to the insulating organic spacing layers. This result sheds light on the further exploration of new 2D hybrid perovskites toward high-performance photodetector applications.

Halide double perovskites have emerged as remarkable semiconductors owing to their nontoxicity and superior optoelectronic features. Despite recent exciting progress, halide double perovskites with bulk ferroelectricity are still sparse. Herein, we report the discovery of a multiaxial layered halide double perovskite ferroelectric, BA2CsAgBiBr7(1, BA = n-butylammonium), which exhibits a fascinating ferroelectric feature with a Curie temperature of ∼273 K and unique semiconducting nature. Particularly, for 1, the dimensional reduction reduced strong coupling of octahedral rotations and cation ordering leads to a notable spontaneous polarization of 5.2 μC/cm2and an extremely high fatigue resistance (over 107switching), which are comparable to those of oxide perovskites. As far as we are aware, this is the first example of a multiaxial ferroelectric in the booming family of halide double perovskites. Another fascinating feature is that 1also possesses a biaxial ferroelastic order with a high Curie temperature of 375 K. Such discovery of a halide double perovskite ferroelectric with multiple ferroic orders signifies an important step toward designing multifunctional ferroelectric materials as well as inspires their further applications in optoelectronic devices.

Benefiting from their structural flexibility and solution processability, organic–inorganic metal halide hybrids with efficient white-light emission present a great promise for solid-state lighting and display applications. However, most of these reported high-performance single-component white-light materials contain lead. Herein, we report a “green” organic zinc halide, [(N-AEPz)ZnCl4]Cl (1; N-AEPz = N-aminoethylpiperazine), exhibiting prominent bluish-white-light emission with a photoluminescence quantum efficiency as high as 11.52%. Such a value is among the highest in the reported metal halide white-light emitters. Mechanism studies disclose that the broad-band emission is ascribed to the synergistic work of organic salts and inorganic clusters. This work would incent research on single-component white-light materials for next-generation display and lighting technologies.

Ferroelectric semiconductors, combining semiconduction, spontaneous polarization, and photoinduced excitation, show great promise to enhance the performance of solar cells, pressure sensors, and photodetectors. Particularly, organic–inorganic lead halide perovskite ferroelectrics have been explored for their prominent carrier transport properties and structural tunability. However, a high concentration of toxic Pb is a stumbling block for their further application. Here, we present a lead-free hybrid perovskite semiconductor, (C4H9NH3)2(NH3CH3)2Sn3Br10(1), which exhibits a large spontaneous polarization of 11.76 μC cm–2at room temperature. Significantly, 1presents a spontaneous polar ordering transition, similar to the better-known perovskite ferroelectrics, and exhibits ferroelectric phase transition behaviors. To our best knowledge, 1is the first example of a Sn-based hybrid perovskite semiconductor featuring ferroelectric performance. Mechanistic studies reveal that such ferroelectricity can be attributable to the synergistic effects of ordering of organic cations and stereochemically active lone-pair electrons inducing distortion of inorganic octahedra. This work provides an effective way to explore “green” ferroelectric semiconductors with potentially enhanced energy conversion efficiency.

Perovskite ferroelectrics, in which the spontaneous polarization (Ps) is conducive to the separation of photoexcited charge carriers, have shown great potential for self-powered photodetection. Nevertheless, such self-powered ferroelectric photodetectors are mostly dominated by traditional inorganic oxides and exhibit relatively small zero-bias photocurrent, which limit their further application. Herein, we present a wide-bandgap 2D trilayered lead chloride hybrid perovskite ferroelectric, EA4Pb3Cl10(1, EA = ethylammonium), which shows a notable Psof ∼4.5 μC/cm2and a high Curie temperature (415 K) beyond that of BaTiO3(393 K). Significantly, benefiting from the wide bandgap of 3.39 eV, a self-powered visible-blind ultraviolet (UV) photodetector has been successfully realized, with a zero-bias photocurrent as high as 18.6 μA/cm2, which is nearly 2 orders of magnitude larger than those of mostly conventional inorganic ferroelectrics. As a pioneering study, this work offers an efficient approach for exploring wide-bandgap perovskite ferroelectrics and will excavate their application in the field of self-powered visible-blind UV photodetection.

Environmental contextThe release of antimony and its compounds to the environment can present a toxic hazard for humans. We evaluated the use of birnessite to dissolve antimony trioxide and found that birnessite accelerated the dissolution process, and ~50% of the oxidised antimony was absorbed. The results can help evaluate the bioavailability of antimony in the environment. AbstractThe most important naturally occurring forms of antimony (Sb) are the ore mineral stibnite (Sb2S3) and its principal weathering product antimony trioxide (Sb2O3). Moreover, most Sb is released into the environment as Sb2O3 from manufacturing, formulations, processing, and the use and disposal of Sb products. In this study, birnessite (δ-MnO2) was employed to promote Sb2O3 dissolution. The Sb2O3 dissolution rate accelerated from ~2% to >99% after 9 days of reaction, and more than 98% of the dissolved SbIII was oxidised into SbV in the presence of birnessite. The birnessite-promoted oxidative dissolution mechanism of Sb2O3 was studied through experiments on the effects of the reaction time and pH. The release rate of Sb in the aqueous phase at the initial stage (335.4 μmol L−1 day−1, pH 6.5) was much higher than that at the late stage (13.28 μmol L−1 day−1, pH 6.5), and when the pH increased from 4.7 to 8.0, the Sb release rate decreased from 351.2 μmol L−1 day−1 to 257.7 μmol L−1 day−1. The dissolution promotion effects of birnessite on Sb2O3 were the most evident under acidic and neutral conditions (the percentages of dissolved Sb2O3 under acidic and neutral conditions were 98.3% and 100.0% after 9 days of reaction). Not all of the produced SbV was released in the reaction solution because ~50% of it was adsorbed by birnessite, and the amount of Sb adsorbed increased with increasing pH. Therefore, alkaline conditions are shown to reduce the release of SbV by inhibiting Sb2O3 dissolution (86.7%) and enhancing SbV adsorption. These results could help clarify the geochemical cycle and fate of Sb in the environment.

Reactive oxygen species (ROS) produced from the oxygenation of reactive Fe(II) species significantly affect the transformation of metalloids such as Sb at anoxic–oxic redox interfaces. However, the main ROS involved in Sb(III) oxidation and Fe (oxyhydr)oxides formation during co-oxidation of Sb(III) and Fe(II) are still poorly understood. Herein, this study comprehensively investigated the Sb(III) oxidation and immobilization process and mechanism during Fe(II) oxygenation. The results indicated that Sb(III) was oxidized to Sb(V) by the ROS produced in the aqueous and solid phases and then immobilized by formed Fe (oxyhydr)oxides via adsorption and coprecipitation. In addition, chemical analysis and extended X-ray absorption fine structure (EXAFS) characterization demonstrated that Sb(V) could be incorporated into the lattice structure of Fe (oxyhydr)oxides via isomorphous substitution, which greatly inhibited the formation of lepidocrocite (γ-FeOOH) and decreased its crystallinity. Notably, goethite (α-FeOOH) formation was favored at pH 6 due to the greater amount of incorporated Sb(V). Moreover, singlet oxygen (1O2) was identified as the dominant ROS responsible for Sb(III) oxidation, followed by surface-adsorbed ·OHads, ·OH, and Fe(IV). Our findings highlight the overlooked roles of 1O2and Fe (oxyhydr)oxide formation in Sb(III) oxidation and immobilization during Fe(II) oxygenation and shed light on understanding the geochemical cycling of Sb coupled with Fe in redox-fluctuating environments.

In recent years, there has been a surge in research enthusiasm on searching for solid-state nonlinear optical (NLO) switching materials in halide perovskites owing to their exceptional structural flexibility, compositional diversity, and broad property tenability. However, the majority of reported halide perovskite NLO switching materials contain toxic elements (e.g., Pb), which raise significant environmental concerns. Herein, we present a novel lead-free multilayered halide perovskite NLO switching material, (BA)2(EA)2Sn3Br10(1, where BA is butylammonium and EA is ethylammonium). Driven by the stereochemically active lone-pair electrons of the Sn2+cation and the cage-confined effect of EA rotators, 1undergoes a phase transition with symmetry breaking from P4/mncto Cmc21, which gives rise to a highly efficient modulation of the quadratic NLO property (0.7 times that of KH2PO4) at a high temperature of 353 K. Furthermore, crystallographic investigation combined with theoretical calculations reveals that the efficient modulation of NLO properties in 1stems from the synergistic effects between stereochemically active lone pair-induced octahedral distortions and order/disorder transformation of organic cations. This study opens up an instructive avenue for designing and advancing environmentally friendly solid-state NLO switches in halide perovskites.

Antimony(V) substitution is common in secondary ferrihydrite, especially in mining areas and tailings. However, its impact on the adsorption behavior of ferrihydrite is still unclear. Therefore, this study investigated the influential mechanisms of Sb(V) substitution on the lattice structure and surface properties of Sb-substituted ferrihydrite (SbFh), and its adsorption of coexisting Sb(OH)6–. Antimony(V) is substituted at Fe1 sites and is primarily distributed on the surface. Substitution has opposing effects on the outer- and inner-sphere complexation of Sb(OH)6–. On one hand, substituted-Sb(V) transfers more positive charges to ≡FeOH, reducing the number of H bonds. Subsequently, the charge saturation of ≡FeOH decreases, surface charge increases, and outer-sphere complexation is promoted. On the other hand, the elevated bond valence of Sb–O increases charge saturation of ≡FeOH, reducing the charge capacity that ≡FeOH can accommodate from inner-sphere complexes. Thus, inner-sphere complexation is inhibited. Inner-sphere complexation plays a more important role, and Sb(OH)6–adsorption is inhibited. Additionally, the primary complexation modes of Sb(OH)6–transform from bidentate to monodentate complexation. This research has important implications for understanding the environmental behavior of ferrihydrite, as well as the fate and bioavailability of antimony in mining areas and tailings.

Antiferroelectrics, characterized by the natural polarization-electric field (P–E) double hysteresis loops, has been developed as a promising branch for energy storage. Here, we present the first antiferroelectric in the booming family of lead iodide hybrid perovskites, (BA)2(EA)2Pb3I10(1, where BA = n-butylammonium and EA = ethylammonium), which exhibits one of the highest Curie temperatures (∼363 K) for the majority of known molecular systems. Strikingly, its high-temperature antiferroelectricity, triggered by an antipolar alignment of adjacent dipoles, is confirmed by the characteristic double P–Ehysteresis loops, thus enabling remarkable energy storage efficiencies in the range of 65%–83%. This merit is almost comparable to those of many inorganic counterparts, suggesting the great potential of 1for energy storage. Another fascinating attribute is that 1also acts as a room-temperature biaxial ferroelectric with spontaneous polarization of 5.6 μC·cm–2. As far as we know, this study on the high-temperature antiferroelectric, along with room-temperature biaxial ferroelectricity, is unprecedented for the versatile lead iodide hybrid perovskites, which sheds light on the design of new electric-ordered materials and facilitates their application of high-performance devices.

Single crystals of lead halide hybrid perovskites (e. g., CH3NH3PbI3and 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 1with sizes up to 9 × 7 × 4 mm3were 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 × 1011cm–3, carrier mobility of 1.42 cm2V–1s–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–1cm–2. These results throw light on further exploration on X-ray-sensitive materials based on the lead-free metal halogen hybrids.

Organic–inorganic lead halide hybrids have attracted extensive interest in solid-state lighting, due to their superior color tunability and low-cost solution processing. However, the relatively low photoluminescence quantum efficiency (PLQE) is a common issue for most bulk lead halide hybrids. Inspired by the intriguing luminescence properties of heterometallic complexes, we rationally developed an unprecedented two-dimensional (2D) Pb–Mn heterometallic halide hybrid, (C5H14N2)2Pb4MnCl14(2), through a precisely tailored synthetic approach based on (C5H14N2)2Pb5Cl14(1). Intriguingly, 2features a unique 2D heterometallic halide layer configuration, in which the strong quantum confinement facilitates efficient energy transfer from bound excitons to d-states of Mn2+, resulting in highly sensitized Mn2+emission. The PLQE of 2is up to 32%, considerably higher than that of pristine 1(less than 1%). Moreover, 2presents significant environmental and thermal stability, benefiting from its cluster feature. To our best knowledge, this is the first example of construction of a Pb–Mn heterometallic halide hybrid with bulk highly efficient red emission. This work provides a way to enhance the PLQE of lead halide hybrids via sensitization in rationally designed heterometallic halide hybrids.

Multiaxial molecular ferroelectrics, in which multiple-directional switching of spontaneous polarization creates diverse properties, have shown many intriguing advantages, making them indispensable complements to conventional inorganic oxides. Despite recent blooming advances, multiaxial molecular ferroelectric with bulk photovoltaic effects still remains a huge blank. Herein, we report a biaxial lead halide ferroelectric, EA4Pb3Br10(1, EA = ethylammonium), which adopts the unique trilayered perovskite motif with a high Curie temperature of ∼384 K. Particularly, for 1, the distinct symmetry breaking with 4/mmmFmm2 species leads to the emergence of four equivalent polarization directions in the ferroelectric phase. Based on its biaxial nature, the bulk photovoltaic effect of 1can be facilely tuned between such multiple directions through electric poling. As far as we know, this is the first report on biaxial hybrid perovskite ferroelectric showing directionally tunable photovoltaic activity. This work provides an avenue to control the bulk physical properties of multiaxial molecular ferroelectrics, and highlights their potential for further applications in the field of smart devices.

Organic–inorganic hybrid perovskites, most markedly CH3NH3PbI3, have attracted extensive interest because of their potential use in optoelectronic and photovoltaic applications. Nevertheless, the toxicity of lead restricts their further application. Here, we successfully synthesized two lead-free heteromorphic hybrids, (C7H18N2O)3Sb4I18·H2O (1) and (C7H18N2O)Sb2I8·H2O (2, C7H18N2O2+is N-aminopropylmorpholinium), both of which belong to the zero-dimensional tetranuclear perovskite-like structure. However, the inorganic [Sb4I18] cluster of 1adopts a tetragonal topology, while 2features the distorted [Sb4I16] motif; this disparity leads to a significant distinction between their electronic structures as well as an optical band gap (Eg). Their absorption cutoffs are measured to be 708 nm (for 1, Eg= 1.71 eV) and 578 nm (for 2, Eg= 2.11 eV), respectively. In particular, 1exhibits a stronger photoelectric response in a wider optical region compared to that of 2, and the “on/off” ratio of conductivity of 1is estimated to ∼300 under sunlight illumination. Density functional theory calculation discloses that different inorganic motifs make greater contributions to their electronic structure and photoelectric response. It is believed that the heteromorphic method allows a potential pathway for construction of new lead-free hybrid materials as light absorbers for photoelectric application.

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 1existing over a wide temperature range of 298–353 K are revealed by the distinct double P–Ehysteresis loops. Besides, 1possesses remarkable energy storage efficiency up to 69%, comparable to those of some reported inorganic antiferroelectric ceramics, promoting 1potential application in energy storage devices. This work provides an avenue to construct novel antiferroelectric materials for high-performance electronic device applications.

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 (Ps) and light benefits dissociation of photoinduced carriers, has shown great potential in this portfolio. Here, we report a new 2D hybrid perovskite ferroelectric, [CH3(CH2)3NH3]2(CH3NH3)Pb2Br7(1), which exhibits a superior Psof 3.6 μC/cm2and a relatively wide bandgap (∼2.55 eV). The unique 2D perovskite motif results in an intrinsic anisotropy of optical absorption (the ratio αc/αa≈ 1.9 at 405 nm), involving its polarization-sensitive activity. As expected, the strongest photoresponses were observed along the c-axis (i.e., parallel to Ps), along with a large dichroism ratio (Iphc/Ipha≈ 2.0) and highly sensitive detectivity up to ∼109Jones. Further, crystal-device of 1 shows a fast responding rate (∼20 μs) and excellent antifatigued merits. As pioneering work, 1is the first polarization-sensitive ferroelectric in the new branch of 2D hybrid perovskites. Such intriguing behaviors make 1a potential candidate for the shortwave polarized-light detection, which also sheds light on new functionalities for future optoelectronic application of hybrid perovskites.

Two new non-centrosymmtric fluoride sulfates nonlinear optical materials with pseudo-KTP structure were successfully obtained by element substitution.