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We reported a lead-free phase transition compound that enables reversible switching of quadratic nonlinear optical properties.

Molecular ferroelectric films (MFFs) offer a good platform for miniaturized electronic devices, which are inseparable from their multiaxial nature. Despite great studies, soft MFFs with broadband photo-electroactivity still remain a huge blank as the photoexcited leakage current will severely deteriorate ferroelectricity, hindering their optoelectronic applications. Here, we constructed the multiaxial MFF of HA

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults. The insulin-like growth factor-binding protein (IGFBP) family is involved in tumorigenesis and the development of multiple cancers. However, little is known about the prognostic value and regulatory mechanisms of IGFBPs in GBM. Oncomine, Gene Expression Profiling Interactive Analysis, PrognoScan, cBioPortal, LinkedOmics, TIMER, and TISIDB were used to analyze the differential expression, prognostic value, genetic alteration, biological function, and immune cell infiltration of IGFBPs in GBM. We observed that IGFBP1, IGFBP2, IGFBP3, IGFBP4, and IGFBP5 mRNA expression was significantly upregulated in patients with GBM, whereas IGFBP6 was downregulated; this difference in mRNA expression was statistically insignificant. Subsequent investigations showed that IGFBP4 and IGFBP6 mRNA levels were significantly associated with overall survival in patients with GBM. Functional Gene Ontology Annotation and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis revealed that genes coexpressed with IGFBP4 and IGFBP6 were mainly enriched in immune-related pathways. These results were validated using the TIMER and TSMIDB databases. This study demonstrated that the IGFBP family has prognostic value in patients with GBM. IGFBP4 and IGFBP6 are two members of the IGFBP family that had the highest prognostic value; thus, they have the potential to serve as survival predictors and immunotherapeutic targets in GBM.

A novel two-dimensional hybrid perovskite (IA)2(DMA)Pb2Br7 was obtained by introducing a large secondary cation DMA+ into the PbBr6 framework. A highly efficient array photodetector has been assembled using its crystal.

By confining the secondary dimethylammonium (DMA) cation in the distorted perovskite cavity, we assembled a new 2D Ruddlesden-Popper metal halide perovskite of (i-BA)2(DMA)Pb2Br7 (i-BA = n-isobutylammonium), in which DMA cation templates its inorganic perovskite frameworks and its quantum-well motif renders fascinating photoresponse. Crystal-based planar arrays exhibit effective photodetection behaviors, including notable detectivity (~5.6×10^12 Jones), high responsivity (~1.25 A W-1) and large switching ratio (~ 1.5×10^3). Such properties result from its low dark current restricted to the hopping barrier of insulated organic bilayer and strong in-plane photoresponse correlated with the perovskite network. This work throws light on the targeted exploration of photosensitive candidates in the family of organic-inorganic hybrid perovskites, as well as high-performance devices.

Molecular antiferroelectrics (AFEs) have taken a booming position in the miniaturization of energy storage devices due to their low critical electric fields. However, regarding intrinsic competitions between dipolar interaction and steric hindrance, it is a challenge to exploit room-temperature molecular AFEs with high energy storage efficiency. Here, we present a new 2D hybrid perovskite-type AFE, (i-BA)

Summary 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/cm2 and 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.

Antiferroelectric (AFE) materials, featuring an antiparallel alignment of electric dipoles in the adjacent sublattices, are keeping a great promise toward solid-state refrigeration applications on account of their electrocaloric (EC) effects. Although extensive studies have been performed on inorganic oxide counterparts (e.g., PbZrO3 and AgNbO3), metal-free molecular AFE alternatives with the above-room-temperature EC activities are quite scarce but urgently demanded in terms of environmental issues. Herein, we present a new metal-free molecular AFE, cyclohexylmethylammonium bromide (CMB), which exhibits the unusual antiferroelectric-ferroelectric-paraelectric phase transitions around 364 and 368 K upon heating. The phase transition temperatures are much higher than the majority of known molecular AFE materials. The practical utilization level of electric polarization (∼6 μC/cm2) is clearly evidenced by the typical double polarization-electric field hysteresis loops. Strikingly, large positive and negative EC responses with the temperature changes (ΔT) of 4.2 and -3 K are achieved under an electric field of 20 kV/cm. The origin of its antiferroelectricity and EC properties is elucidated by the antipolar reorientation of cations along with displacement of bromine anions, being distinct from the known mechanism of inorganic oxides. Such intriguing AFE behaviors, including large polarization and EC effects, reveal great potentials of CMB for the solid-state refrigeration. This study sheds light on further exploration of new AFE candidates toward environmentally friendly solid-state cooling devices.

Two-dimensional (2D) hybrid perovskites with the Ruddlesden-Popper lattice (A′)2(A)n−1MnX3n+1 are 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 × 1012 Jones) 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.

Metal-free antiferroelectric materials are holding a promise for energy storage application, owing to their unique merits of wearability, environmental friendliness, and structure tunability. Despite receiving great interests, metal-free antiferroelectrics are quite limited and it is a challenge to acquire new soft antiferroelectric candidates. Here, we have successfully exploited binary CMBrxI1-x and CMBrxCl1-x solid solution as single crystals (0 ≤ x ≤ 1, where CM is cyclohexylmethylammonium). A molecule-level modification can effectively enhance Curie temperature. Emphatically, the binary CM-chloride salt shows the highest antiferroelectric-to-paraelectric Curie temperature of ~453 K among the known molecular antiferroelectrics. Its characteristic double electrical hysteresis loops provide a large electric polarization up to ~11.4 μC/cm2, which endows notable energy storage behaviors. To our best knowledge, this work provides an effective solid-solution methodology to the targeted design of new metal-free antiferroelectric candidates toward biocompatible energy storage devices.

Two-dimensional (2D) hybrid perovskites are recently emerging as a potential family of semiconductors for versatile optoelectronic applications. Currently, the "perovskitizer" moieties are rigidly limited to small-size cations, while few 2D metal-halides containing guanidinium cations inside perovskite cages have been studied for photodetection. Herein, we present a new 2D hybrid perovskite, (i-BA)2 (G)Pb2 I7 (where G is guanidinium and i-BA is isobutylammonium), which adopts a bilayered framework of {GPb2 I7 }. Single-crystal structure analyses disclose that G cations act as the perovskitizer, confined in the flexible perovskite cages formed by the distorted PbI6 octahedra. Such inorganic sheets are crucial to the superior semiconducting properties and optical bandgap, as verified by the density functional theory calculation. Furthermore, its planar crystal-array photodetector shows fascinating photoelectric performance, including a quite low dark current (∼4.6×10-11 A), a large current switching ratio (∼1.0×103 ), and a notable photo-responsivity of ∼0.72 A W-1 , suggesting great potential of (i-BA)2 (G)Pb2 I7 for photodetection.

Two-dimensional (2D) organic-inorganic hybrid perovskites, benefiting from their natural anisotropy of quantum-well motifs and optical properties, have shown remarkable polarization-dependent responses superior to the 3D counterparts. Here, for the first time, multiwavelength polarization-sensitive detectors were fabricated by using single crystals of a guanidine-based 2D hybrid perovskite, (BA)2 (GA)Pb2 I7 (where BA+ is n-butylammonium and GA+ is guanidium). Its unique 2D quantum-well structure results in strong crystallographic-dependence of optical absorption. Strikingly, our crystal-based photodetector exhibits a prominent photocurrent dichroic ratio (Imax /Imin ) of ∼2.2 at 520 nm, higher than the typical 2D inorganic materials (GeSe, ∼1.09, PdSe2 , ∼1.8). In addition, notable dichroic ratios of 1.29 and 1.23 at 405 nm and 637 nm are also created for the multiwavelength polarized-light detection. The prominent detecting performances, including low dark current (1.6×10-11 A), considerable on/off ratio (∼2×103 ), high photodetectivity (∼3.3×1011 Jones) and responsivity (∼12.01 mA W-1 ), make (BA)2 (GA)Pb2 I7 a promising candidate for polarized-light detection. This work sheds light on the rational engineering of new 2D hybrid perovskites for the high-performance optoelectronic device applications.

Two-dimensional (2D) hybrid perovskites with intrinsic attributes of structural and optical anisotropy are holding a bright promise for polarization-sensitive photodetection. However, studies on self-powered detection to quite weak polarized light remain scarce in this 2D family. By incorporating an aromatic spacer into the 3D cubic prototype, we have successfully assembled a new 2D hybrid perovskite with a polar motif, (FPEA)

Metal-free antiferroelectric materials are holding a promise for energy storage application, owing to their unique merits of wearability, environmental friendliness, and structure tunability. Despite receiving great interests, metal-free antiferroelectrics are quite limited and it is a challenge to acquire new soft antiferroelectric candidates. Here, we have successfully exploited binary CMBr

Polarized-light detection in the deep ultraviolet solar-blind region is indispensable for optoelectronic applications. 2D hybrid perovskite ferroelectrics with inherent anisotropy and bulk photovoltaic effect (BPVE) have become a robust candidate in this portfolio. We here report a wide band-gap 2D perovskite ferroelectric, (isobutylammonium)

Two-dimensional (2D) hybrid perovskites of Ruddlesden–Popper (RP) lattices are recently booming as a vigorous class of ferroelectrics, whereas their intrinsic van der Waals gaps exert weak interact...

White-light emission in lead halide hybrid perovskites has attracted increasing attention due to their significant applications in the field of light-emitting devices. Despite tremendous efforts, two-dimensional (2D) white-light emissive perovskites with high photoluminescence quantum efficiency (PLQE) remain scarce. In this work, by using alkoxyamine organic cations as a template, we successfully synthesized a new 2D layered hybrid perovskite, (γ-methoxy propyl amine)2PbBr4 (γ-MPAPB), which exhibits bright bluish white-light emission with an excellent color rendering index (CRI) of 85 and a high PLQE of 6.85%. Photoluminescence measurements show a correlation between self-trapped excitons and white-light emission. To the best of our knowledge, this is the first demonstration of a 2D hybrid perovskite with efficient white-light emission based on alkoxyamine cations. This work emphasizes the strategy of introducing alkoxyamine cations into 2D layered hybrid perovskites to design efficient white-light emissive perovskite semiconductors.

Ferroelectricity-induced self-powered photodetection has emerged as an indispensable branch of new optoelectronic devices. Organometallic perovskites that combine ferroelectricity and semiconductor merits are promising. However, it remains a challenge to achieve self-powered photodetection with a low detection limit, due to the polarization deterioration caused by the leakage current of photoexcited carriers. Here, we exploit the high performance self-powered photodetection in the 2D perovskite ferroelectric, (C4H9NH3)2(NH2CHNH2)Pb2Br7 (1), driven by the switchable spontaneous polarization. Most strikingly, an extremely low detection limit of 82 nW cm−2 is achieved, far superior to those of many classical p–n junctions. Further studies disclose that such self-powered behaviors of 1 are related to its inherent photovoltaic effects, stemming from inversion symmetry breaking by ferroelectric polarization. This result advances the future potential of hybrid perovskite ferroelectrics as smart photoelectric devices.

Two-dimensional (2D) Ruddlesden–Popper hybrid perovskites (RPHPs) have shown enormous potential for photoelectric applications owing to their advantages of structural diversity and unique physical properties. Despite extensive studies, the cage-incorporation of secondary amines (e.g., dimethylamine, DMA) to explore 2D RPHPs remains a great challenge. Herein, we present a new member of 2D RPHPs, (BA)2(DMA)Pb2Br7 (1, BA+ = n-butylammonium), for which organic DMA+ cations are enclosed in perovskite cavities. The inorganic perovskite sheets and organic BA+ spacing layers are arranged in the alternate packings, resembling a 2D quantum-well motif. This feature is advantageous for the photoconductivity properties. Consequently, the crystal-based array detectors of 1 exhibit strong photodetection performances, including high detectivity (2.0 × 1011 Jones), large responsivity (31.1 mA W−1), and fast response time (∼8 μs). Moreover, its intrinsic 2D quantum-well structure endows significant anisotropy of conductivity and optical absorption, which account for the strong polarization response with a large dichroic ratio of ∼1.43, falling in the range of other 2D RPHPs. These results reveal the potential of 1 for photodetection and simultaneously shed light on the research on new candidates of 2D RPHPs.

Polarized-light photodetectors are the indispensable elements for practical optical and optoelectronic device applications. Two-dimensional (2D) hybrid perovskite ferroelectrics, in which the coupling of spontaneous polarization (Ps) and light favors the dissociation of photo-induced carriers, have taken a booming position within this portfolio. However, polarized-light photodetectors with a low detection-limit remain unexplored in this 2D ferroelectric family. In this work, the high-quality individual crystals of a 2D perovskite ferroelectric, BA2CsPb2Br7 (1, where BA+ is n-butylammonium), were used to fabricate ultrasensitive polarized-light detectors. Its unique bilayered structural motif results in quite strong electric and optical anisotropy with a large absorption ratio of αc/αa ≈ 3.2 (λ = 405 nm). Besides, the presence of ferroelectric Ps also endows high built-in electric field along the polar c-axis that favors photoelectric activities. Under an extremely low detectable limit of 40 nW/cm2, the detector of 1 exhibits a notable dichroism ratio (Iphc/Ipha ≈ 1.5), a large responsivity of ~39.5 mA/W and a specific detectivity of ~1.2 × 1012 Jones. Moreover, crystal-based devices of 1 also exhibit a fast response speed (~300 μs) and excellent anti-fatigue merits. This work highlights great potentials of hybrid perovskite ferroelectrics toward polarized-light photodetection.

Polar hybrid perovskites have been explored for self-powered photodetection benefitting from prominent transport of photo-induced carriers and the bulk photovoltaic effect (BPVE). However, these self-powered photodetection ranges are relatively narrow depending on their intrinsic wide bandgaps (>2.08 eV), and the realization of broad-spectrum self-powered photodetection is still a difficult task. Herein, we successfully obtained a polar multilayered perovskite, (I-BA)2(MA)2Pb3I10 (IMP, MA+ = methylammonium and I-BA+ = 4-iodobutylammonium), via rational dimension reduction of CH3NH3PbI3. It features the narrowest bandgap of 1.71 eV in a BPV material. As a consequence, the integration of narrow bandgap and BPVE causes the self-powered photodetection to extend to 724 nm for IMP, and a repeatable photovoltaic current reaching 1.0 μA cm−2 is acquired with a high “on/off” ratio of ∼103 and photodetectivity (∼109 Jones) at zero bias. This innovative research provides a foothold for adjusting the physical properties of hybrid perovskites and will expand their potential for self-powered broad-spectrum detection., A polar hybrid perovskite with a wide-spectrum absorption extending to 724 nm was obtained . Benefitting from the narrow bandgap and bulk photovoltaic effects, self-powered broad-spectrum photodetection was achieved in hybrid perovskites.

Antiferroelectric materials, characterized by an antiparallel array of adjacent dipoles, are holding a bright future for solid-state refrigeration based on their electrocaloric (EC) effects. Despite great advances of inorganic oxides and some organic soft polymers, their EC effects are achieved under quite high electric fields that result in too low EC strengths for practical application. Currently, it is a challenge to exploit soft antiferroelectric with strong EC strengths. Here, by the mixed-cation alloying, we present a new perovskite-type soft antiferroelectric, (isopentylammonium)

Perovskite hybrids of lead organometal halides, (e. g., CH3 NH3 PbX3 , X=Cl, Br, I) have gained wide attention since their spectacular progress on optoelectronic technologies in recent years. However, it still remains the fundamental problem, namely, the existence of the toxic, bioaccumulative, polluting element Pb and the instability of humidity. In particular, the use of toxic Pb severely limits the broad applications and commercialization of lead-containing optoelectronic devices, and finding an alternative that preserves the unique optoelectronic properties of the lead halide perovskite is highly urgent. Bi3+ exhibits isoelectronic behavior similar to that of Pb2+ in terms of ion radius and electronegativity, which is expected as an environmentally friendly alternative for lead. However, 1D Bi-based hybrid organic-inorganic light-absorbing materials with pyridinium are not numerous. Although great progress has been made, the research on photoresponse behavior are still rarely reported. Here, we present a lead-free organic-inorganic hybrid absorber with photoconductive response, (C5 H7 N2 )BiI4 (1, C5 H7 N2+ is 2-aminopyridinium), which displays a narrow optical bandgap of ∼1.8 eV. Equally importantly, 1 not only features highly applicable properties, but is also able to absorb across most of the UV/Vis region of the solar spectrum. Furthermore, high-quality single crystal with sizes up to 7×6×4 mm3 was successfully grown. In addition, 1 exhibited extremely low dark current (2×10-11 A) at the bias of 10 V, which indicates that the indicator of 1 is an order of magnitude lower than other reported perovskite photodetectors. Moreover, photocurrent on/off switches is faster (∼670 ms), indicating that 1 can be a promising photosensitive switch. These intriguing properties, namely the lead-free composition, a small band gap, and the fast photoconductive response, suggest promising applications in the field of optoelectronics.

Although two-dimensional (2D) metal-halide double perovskites display versatile physical properties due to their huge structural compatibility, room-temperature ferroelectric behavior has not yet been reported for this fascinating family. Here, we designed a room-temperature ferroelectric material composed of 2D halide double perovskites, (chloropropylammonium)4 AgBiBr8 , using an organic asymmetric dipolar ligand. It exhibits concrete ferroelectricity, including a Curie temperature of 305 K and a notable spontaneous polarization of ≈3.2 μC cm-2 , triggered by dynamic ordering of the organic cation and the tilting motion of heterometallic AgBr6 /BiBr6 octahedra. Besides, the alternating array of inorganic perovskite sheets and organic cations endows large mobility-lifetime product (μτ=1.0×10-3 cm2 V-1 ) for detecting X-ray photons, which is almost tenfold higher than that of CH3 NH3 PbI3 wafers. As far as we know, this is the first study on an X-ray-sensitive ferroelectric material composed of 2D halide double perovskites. Our findings afford a promising platform for exploring new ferroelectric materials toward further device applications.

3D perovskite CsPbBr3 has recently taken a blooming position for optoelectronic applications. However, due to the lack of natural anisotropy of optical attributes, it is a great challenge to fulfil polarization-sensitive photodetection. Here, for the first time, we exploited dimensionality reduction of CsPbBr3 to tailor a 2D-multilayered hybrid perovskite, (TRA)2 CsPb2 Br7 (1, in which TRA is (carboxy)cyclohexylmethylammonium), serving as a potential polarized-light detecting candidate. Its unique quantum-confined 2D structure results in intrinsic anisotropy of electrical conductivity, optical absorbance, and polarization-dependent responses. Particularly, it exhibits remarkable dichroism with the photocurrent ratio (Ipc /Ipa ) of ≈2.1, being much higher than that of the isotropic CsPbBr3 crystal and reported CH3 NH3 PbI3 nanowire (≈1.3), which reveals its great potentials for polarization-sensitive photodetection. Further, crystal-based detectors of 1 show fascinating responses to the polarized light, including high detectivity (>1010 Jones), fast responding time (≈300 μs), and sizeable on/off current ratios (>104 ). To our best knowledge, this is the first study on 2D Cs-based hybrid perovskite exhibiting strong polarization-sensitivity. The work highlights an effective pathway to explore new polarization sensitive candidates for hybrid perovskites and promotes their future electronic applications.

By dimensional reduction of the 3D motif of Cs2 AgBiBr6 , a lead-free 2D hybrid double perovskite, (i-PA)2 CsAgBiBr7 (1, i-PA=isopentylammonium), was successfully designed. It adopts a quantum-confined bilayered structure with alternating organic and inorganic sheets. Strikingly, the unique 2D architecture endows it highly anisotropic nature of physical properties, including electric conductivity and optical absorption (the ratio αb /αc =1.9 at 405 nm). Such anisotropy attributes result in the strong polarization-sensitive responses with large dichroic ratios up to 1.35, being comparable to some 2D inorganic materials. This is the first study on the hybrid double perovskites with strong polarization sensitivity. A crystal device of 1 also exhibits rapid response speed (ca. 200 μs) and excellent stabilities. The family of 2D hybrid double perovskites are promising optoelectronic candidates, and this work paves a new pathway for exploring new green polarization-sensitive materials.

Two-dimensional (2D) multilayered hybrid perovskites have emerged as a promising class of candidates for photovoltaic and photoelectric applications. Currently, most of the 2D multilayered motifs consist of primary amines, while the candidates that accommodate large-size organic cations inside the perovskite cavity as the “perovskiter” component are still scarce. Herein, we exploit a new 2D Ruddlesden–Popper hybrid perovskite, (C5H11NH3)2(CH3NH2CH3)Pb2I7 (1), in which the secondary dimethylammonium cation (i.e., CH3NH2CH3+) acts as the “perovskiter” inside the inorganic {Pb2I7}n perovskite framework. Its quantum-well like structure, formed by alternating the organic spacer (C5H11NH3+) and inorganic sheets, would facilitate the dissociation of photoexcited electron–hole pairs and improve the performance of the optoelectronic device. Consequently, the planar array detector based on high-quality crystals of 1 exhibits fascinating photoresponses, including high responsivity (∼0.67 A W−1), notable detectivity (∼1.65 × 1012 Jones), large photocurrent ratio (∼1.1 × 104) and fast responding rate (∼270 μs). These behaviors are closely associated with its strong in-plane photoactivities related to the perovskite sheets, and extremely low dark current (∼10−11 A) inhibited by the hopping barriers of organic spacer cations. This study paves the potential way to build high-performance optoelectronic devices based on the emerging 2D single-crystal hybrid perovskite materials.

Organic–inorganic hybrid perovskites, most remarkably CH3NH3PbI3, have drawn a worldwide range of attention due to their great potential in optoelectronic and photovoltaic applications. Nevertheless, the concern on the toxicity of the lead (Pb) element in chemical composition deserves to be addressed before it is further commercialized. In the present study, a new lead-free hybrid perovskite-like compound, namely (C5H11N3)SbI5 (1, where C5H11N32+ is histaminium), has been synthesized and belongs to the chiral space group, P212121. Structurally, 1 features a distinct perovskite-type architecture of one-dimensional (1D) zigzag chains formed by the corner-sharing SbI6 octahedra with organic histaminium cations linked to the 1D chain framework via strong N–H⋯I hydrogen bonds. It is noteworthy to mention that 1 enables a wide absorption cutoff at 693 nm, corresponding to the narrow optical bandgap (Eg) of ∼1.79 eV. Consequently, the distinct semiconducting behaviors and notable photoresponses in the visible-light range have been observed in 1, of which the photocurrent on/off ratio reaches up to ∼100 under light illumination at 650 nm. Density functional theory calculation reveals that the 1D zigzag chains formed by inorganic SbI6 octahedra determine its electronic structure and photoelectric activities. In addition to the excellent repeatability of photo-induced currents, 1 also demonstrates superior phase stability and thermal stability. We believe that this study throws light on the further exploration of new lead-free hybrid perovskites for optoelectronic applications.

Recently, organic–inorganic hybrid lead halide perovskites have attracted great attention for optoelectronic applications, such as light-emitting diodes, photovoltaics and optoelectronics. Meanwhile, the flexible organic components of these compounds give rise to a large variety of important functions, such as dielectric phase transitions. However, those containing Pb are harmful to the environment in vast quantities. Herein, a lead-free organic–inorganic hybrid, (C6H14N)2BiCl5 (CHA; C6H14N+ is cyclohexylaminium), has been successfully developed. As expected, CHA exhibits an above-room-temperature solid phase transition at 325 K (Tc), which was confirmed by the differential scanning calorimetry measurement and variable temperature single crystal X-ray diffraction analyses. Further analyses indicate the phase transition is mainly governed by the order–disorder transformation of organic cyclohexylaminium cations. Interestingly, during the process of phase transition, the dielectric constant (e′) of CHA shows an obvious step-like anomaly, which displays a low dielectric constant state below Tc and a high dielectric constant state above Tc. Furthermore, variable temperature conductivity combined with theoretical calculations demonstrate the notable semiconducting feature of CHA. It is believed that our work will provide useful strategies for exploring lead-free organic–inorganic semiconducting hybrid materials with above room temperature dielectric phase transitions.

Ferro-pyro-phototronic (FPP) effect is a triple coupling of ferroelectricity, light-induced pyroelectricity, and photo-excitation, which holds a bright promise for next-generation modern optoelectronic devices. However, except for few oxides (e.g., BaTiO

Halide double perovskites have recently bloomed as the green candidates for optoelectronic applications, such as X-ray detection. Despite great efforts, the exploration of promising organic-inorganic hybrid double perovskites toward X-ray detection remains unsuccessful. Now, single crystals of the lead-free hybrid double perovskite, (BA)2 CsAgBiBr7 (BA+ is n-butylammonium), featuring the unique 2D multilayered quantum-confined motif, enable quite large μτ (mobility-lifetime) product up to 1.21×10-3 cm2 V-1 . This figure-of-merit realized in 2D hybrid double perovskites is unprecedented and comparable with that of CH3 NH3 PbI3 wafers. (BA)2 CsAgBiBr7 crystals also exhibit other intriguing attributes for X-ray detection, including high bulk resistivity, low density of defects and traps, and large X-ray attenuation coefficient. Consequently, a vertical-structure crystal device under X-ray source yields a superior sensitivity of 4.2 μC Gyair-1 cm-2 .

Self-powered photodetection driven by ferroelectric polarization has shown great potential in next-generation optoelectronic devices. Hybrid perovskite ferroelectrics that combine polarization and semiconducting properties have a promising position within this portfolio. Herein, we demonstrate the realization of self-powered photodetection in a new developed biaxial ferroelectric, (EA)2 (MA)2 Pb3 Br10 (1, EA is ethylammonium and MA is methylammonium), which displays high Curie temperature (375 K), superior spontaneous polarization (3.7 μC cm-2 ), and unique semiconducting nature. Strikingly, without an external energy supply, 1 exhibits an direction-selectable photocurrent with fascinating attributes including high photocurrent density (≈4.1 μA cm-2 ), high on/off switching ratio (over 106 ), and ultrafast response time (96/123 μs); such merits are superior to those of the most active ferroelectric oxide BiFeO3 . Further studies reveal that strong inversion symmetry breaking in 1 provides a desirable driving force for carrier separation, accounting for such electrically tunable self-powered photoactive behaviors. This work sheds light on exploring new multifunctional hybrid perovskites and advancing the design of intelligent photoelectric devices.

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 ...

Organic–inorganic hybrid perovskites, most markedly CH3NH3PbI3, have attracted extensive interest because of their potential use in optoelectronic and photovoltaic applications. Nevertheless, the t...

Inorganic-organic hybrid perovskites, especially two-dimensional (2D) layered halide perovskites, have attracted significant attention due to their unique structures and attractive optoelectronic properties, which open up a great opportunity for next-generation photosensitive devices. Herein, we report a new 2D bilayered inorganic-organic hybrid perovskite, (C6 H13 NH3 )2 (NH2 CHNH2 )Pb2 I7 (HFA, where C6 H13 NH3 + is hexylaminium and NH2 CHNH2 + is formamidinium), which exhibits a remarkable photoresponse under broadband light illumination. Structural characterizations demonstrate that the 2D perovskite structure of HFA is constructed by alternant stacking of inorganic lead iodide bilayered sheets and organic hexylaminium layers. Optical absorbance measurements combined with density functional theory (DFT) calculations suggest that HFA is a direct band gap semiconductor with a narrow band gap (Eg ) of ≈2.02 eV. Based on these findings, photodetectors based on HFA crystal wafer are fabricated, which exhibit fascinating optoelectronic properties including large on/off current ratios (over 103 ), fast response speeds (τrise =310 μs and τdecay =520 μs) and high responsivity (≈0.95 mA W-1 ). This work will contribute to the design and development of new two-dimensional bilayer inorganic-organic hybrid perovskites for high-performance photosensitive devices.

Nonlinear optical (NLO) switches driven by a solid-state structural phase transition have attracted extensive attention; however, above-room-temperature solid-state NLO switch materials are still sparse. Herein, we report an above-room-temperature tin halide organic-inorganic hybrid quadratic NLO switchable material, N-methylpyrrolidinium trichloride stannite ([C5 H12 N]SnCl3 , MPSC). The MPSC crystal exhibits a phase-matchable NLO property that is 1.1 times that of KH2 PO4 (KDP) and NLO switching behavior, changing from a high second harmonic generation (SHG) response to a low SHG response at 383 K, thereby demonstrating its prospective applications in the field of nonlinear optics. Variable-temperature crystal structural analysis combined with theoretical calculations revealed that the large NLO response stems from the inorganic SnCl3 moiety, whereas the high-performance NLO switching properties mainly originate from the order/disorder transformation of the N-methylpyrrolidinium. This work provides a new approach to designing and exploring new high-performance quadratic NLO switches involving tin halide organic-inorganic hybrids.

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 Ps of 3.6 μC/cm2 and 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 ∼109 Jones. Further, crystal-device of 1 shows a fast responding rate (∼20 μs) and excellent antif...

Solid–solid phase transition materials have attracted increasing attention because of their variety of applications in optoelectronic devices, data storage, and ferroelectric field-effect transistors. Hybrid organic–inorganic perovskite materials combine the characteristics of organic and inorganic components and thus might be promising candidates to obtain phase-transition materials. Here, we report a lead-free organic–inorganic hybrid (hexamethyleneimine)2BiBr5 (1), which displays successive phase transitions at 268 K, 304 K and 311 K upon heating; these phase transitions are induced by the distorted configurational change in organic cations and slight reorientational displacement of [BiBr5]n2− polyanionic zigzag chains. In addition, the UV/Vis optical spectrum indicates that 1 has an indirect bandgap of 2.70 eV. Furthermore, computational analyses disclose that the inorganic perovskite-like building blocks of 1 contribute significantly to its semiconducting properties. This study offers a pathway to explore new lead-free organic–inorganic hybrids with phase transition.

Organic–inorganic hybrids have shown great potential for assembling dielectric phase transition materials, due to their unique characteristics and structural diversities. Here, we construct a new organic–organic hybrid, (cyclopropylaminium)3BiBr6 (1), which consists of a zero-dimensional inorganic framework of BiBr6 octahedra and ternary cyclic organic cations. It is noteworthy that 1 undergoes a reversible phase transition around Tc = 288 K upon heating, as certified by dielectric and DSC measurements. Variable-temperature structure analyses disclose that the dynamic order–disorder behavior of ternary cyclic organic cations accounts for the phase transition. That is, the frozen ordering of highly-disordered organic cations affords the driving force. Dielectric constants of 1 also exhibit two distinct states in the vicinity of Tc associated with its phase transition, corresponding to the high- and low-dielectric states. Particularly, an obvious dielectric anisotropy is observed along its different crystallographic axis directions; in detail, dielectric anomalies along the c-axis are larger than those along the a- and b-axis. Besides, 1 possesses an optical energy bandgap of ∼2.8 eV determined by its inorganic framework. Such dielectric activities induced by order–disorder transformation may highlight a pathway for the design of new electric-ordered materials.