3D-to-2D Dimensional Reduction for Exploiting a Multilayered Perovskite Ferroelectric toward Polarized-Light Detection in the Solar-Blind Ultraviolet Region

Polarized-light detection in solar-blind ultraviolet region is indispensable for optoelectronic applications, whereas new 2D candidates targeted at solar-blind UV range remain extremely scarce. 2D hybrid perovskite ferroelectrics that combine polarization and semiconducting properties are of increasing interest. Here, using the 3D-to-2D dimensional reduction of CH₃NH₃PbCl₃, we designed a multilayered hybrid perovskite ferroelectric, (CH₃CH₂NH₃)₂(CH₃NH₃)₂Pb₃Cl₁₀, which shows spontaneous polarization and a high Curie temperature (390 K) comparable with that of BaTiO₃ (393 K). The wide band gap (ca. 3.35 eV) and anisotropic absorbance stemming from its intrinsic 2D motif, greatly favor its polarization-sensitive activity in UV region. The device displays excellent polarization-sensitive behavior under 266 nm, along with a large dichroic ratio (ca. 1.38) and high on/off current ratio (ca. 2.3×10³).     

Ferroelectricity-Driven Self-Powered Ultraviolet Photodetection with Strong Polarization Sensitivity in a Two-Dimensional Halide Hybrid Perovskite

Polarization-sensitive ultraviolet (UV) photodetection is highly indispensable in military and civilian applications and has been demonstrated with various wide-band photodetectors. However, it still remains elusive to achieve the self-powered devices, which can be operated in the absence of external bias. Herein, for the first time, ferroelectricity-driven self-powered photodetection towards polarized UV light was successfully demonstrated in a 2D wide-band gap hybrid ferroelectric (BPA)₂PbBr₄ (BPA=3-bromopropylammonium) ( 1 ). We found that the prominent spontaneous polarization in 1 results in a bulk photovoltaic effect (BPVE) of 0.85 V, that independently drives photoexcited carriers separation and transport and thus supports self-powered ability. This self-powered detector shows strong polarization sensitivity to linearly polarized UV illumination with a polarization ratio up to 6.8, which is superior to that of previously reported UV-polarized photodetectors (ZnO, GaN, and GeS₂).     

Polarization‐Driven Self‐Powered Photodetection in a Single‐Phase Biaxial Hybrid Perovskite Ferroelectric

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)₂Pb₃Br₁₀ ( 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.     

Dimensional Reduction of Cs2AgBiBr6: A 2D Hybrid Double Perovskite with Strong Polarization Sensitivity

By dimensional reduction of the 3D motif of Cs₂AgBiBr₆, a lead‐free 2D hybrid double perovskite, (i‐PA)₂CsAgBiBr₇ ( 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 α_b/α_c=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.     

A Chiral Reduced‐Dimension Perovskite for an Efficient Flexible Circularly Polarized Light Photodetector

Chiral quasi‐2D perovskite single crystals (SCs) were investigated for their circular polarized light (CPL) detecting capability. Quasi‐2D chiral perovskites, [(R)‐β‐MPA]₂MAPb₂I₇ ((R)‐β‐MPA=(R)‐(+)‐β‐methylphenethylamine, MA=methylammonium), have intrinsic chirality and the capability to distinguish different polarization states of CPL photons. Corresponding quasi‐2D SCs CPL photodetector exhibit excellent detection performance. In particular, our device responsivity is almost one order of magnitude higher than the reported 2D perovskite CPL detectors to date. The crystallization dynamics of the film were modulated to facilitate its carrier transport. Parallel oriented perovskite films with a homogeneous energy landscape is crucial to maximize the carrier collection efficiency. The photodetector also exhibits superior mechanical flexibility and durability, representing a promising candidate for sensitive and robust CPL photodetectors.     

A Butterfly‐Inspired Hierarchical Light‐Trapping Structure towards a High‐Performance Polarization‐Sensitive Perovskite Photodetector

Extensive applications for photodetectors have led to demand for high‐responsivity polarization‐sensitive light detection. Inspired by the elaborate architecture of butterfly Papilio paris, a 1D nanograting bonded porous 2D photonic crystal perovskite photodetector (G‐PC‐PD) using a commercial DVD master and 2D crystalline colloidal arrays template was fabricated. The coupling effect from grating diffraction and reflection of the PC stopband renders the enhanced light harvesting of G‐PC‐PD. The porous scaffold and nanoimprinting process afford a highly crystalline perovskite film. White light responsivity and detectivity of G‐PC‐PD are up to 12.67 A W^?1 and 3.22×10¹³ Jones (6～7 times that of a pristine perovskite photodetector). The highly ordered nanograting arrays of G‐PC‐PD enable polarization‐sensitive light detection with a rate of ?0.72 nA deg^?1. This hierarchical perovskite integrated nanograting and 2D PC architecture opens a new avenue to high‐performance optoelectronic devices.     

Exploring a Lead‐free Semiconducting Hybrid Ferroelectric with a Zero‐Dimensional Perovskite‐like Structure

Perovskite lead halides (CH₃NH₃PbI₃) have recently taken a promising position in photovoltaics and optoelectronics because of remarkable semiconducting properties and possible ferroelectricity. However, the potential toxicity of lead arouses great environmental concern for widespread application. A new chemically tailored lead‐free semiconducting hybrid ferroelectric is reported, N‐methylpyrrolidinium)₃Sb₂Br₉ ( 1 ), which consists of a zero‐dimensional (0‐D) perovskite‐like anionic framework connected by corner‐ sharing SbBr₆ coordinated octahedra. It presents a large ferroelectric spontaneous polarization of approximately 7.6 μC cm^?2, as well as notable semiconducting properties, including positive temperature‐dependent conductivity and ultraviolet‐sensitive photoconductivity. Theoretical analysis of electronic structure and energy gap discloses a dominant contribution of the 0‐D perovskite‐like structure to the semiconducting properties of the material. This finding throws light on the rational design of new perovskite‐like hybrids, especially lead‐free semiconducting ferroelectrics.     

Tailored Engineering of an Unusual (C4H9NH3)2(CH3NH3)2Pb3Br10 Two‐Dimensional Multilayered Perovskite Ferroelectric for a High‐Performance Photodetector

Two‐dimensional (2D) layered hybrid perovskites have shown great potential in optoelectronics, owing to their unique physical attributes. However, 2D hybrid perovskite ferroelectrics remain rare. The first hybrid ferroelectric with unusual 2D multilayered perovskite framework, (C₄H₉NH₃)₂(CH₃NH₃)₂Pb₃Br₁₀ ( 1 ), has been constructed by tailored alloying of the mixed organic cations into 3D prototype of CH₃NH₃PbBr₃. Ferroelectricity is created through molecular reorientation and synergic ordering of organic moieties, which are unprecedented for the known 2D multilayered hybrid perovskites. Single‐crystal photodetectors of 1 exhibit fascinating performances, including extremely low dark currents (ca. 10⁻¹² A), large on/off current ratios (ca. 2.5×10³), and very fast response rate (ca. 150 μs). These merits are superior to integrated detectors of other 2D perovskites, and compete with the most active CH₃NH₃PbI₃.     

A Photoferroelectric Perovskite‐Type Organometallic Halide with Exceptional Anisotropy of Bulk Photovoltaic Effects

Perovskite‐type ferroelectrics composed of organometallic halides are emerging as a promising alternative to conventional photovoltaic devices because of their unique photovoltaic effects (PVEs). A new layered perovskite‐type photoferroelectric, bis(cyclohexylaminium) tetrabromo lead ( 1 ), is presented. The material exhibits an exceptional anisotropy of bulk PVEs. Upon photoexcitation, superior photovoltaic behaviors are created along its inorganic layers, which are composed of corner‐sharing PbBr₆ octahedra. Semiconducting activity with remarkable photoconductivity is achieved in the vertical direction, showing sizeable on/off current ratios (>10⁴), which compete with the most active photovoltaic material CH₃NH₃PbI₃. In 1 the temperature‐dependence of photovoltage coincides fairly well with that of polarization, confirming the dominant role of ferroelectricity in such highly anisotropic PVEs. This finding sheds light on bulk PVEs in ferroelectric materials, and promotes their application in optoelectronic devices.     

A Chiral Reduced-Dimension Perovskite for an Efficient Flexible Circularly Polarized Light Photodetector

Chiral quasi-2D perovskite single crystals (SCs) were investigated for their circular polarized light (CPL) detecting capability. Quasi-2D chiral perovskites, [(R)-β-MPA]₂MAPb₂I₇ ((R)-β-MPA=(R)-(+)-β-methylphenethylamine, MA=methylammonium), have intrinsic chirality and the capability to distinguish different polarization states of CPL photons. Corresponding quasi-2D SCs CPL photodetector exhibit excellent detection performance. In particular, our device responsivity is almost one order of magnitude higher than the reported 2D perovskite CPL detectors to date. The crystallization dynamics of the film were modulated to facilitate its carrier transport. Parallel oriented perovskite films with a homogeneous energy landscape is crucial to maximize the carrier collection efficiency. The photodetector also exhibits superior mechanical flexibility and durability, representing a promising candidate for sensitive and robust CPL photodetectors.     

A Three-Dimensional M3AB-Type Hybrid Organic–Inorganic Antiperovskite Ferroelectric: [C3H7FN]3[SnCl6]Cl

Since the first perovskite CaTiO₃ was discovered in 1839, the development of perovskite has a history of 180 years. The emergence of solar cells (CH₃NH₃)PbI₃ has set off the trend of hybrid organic–inorganic perovskite (HOIP) materials. Since then, various HOIPs have sprung up and been widely used in various material devices. Among them, HOIP ferroelectrics have gained widespread attention. However, antiperovskite, as a twin brother of perovskite, has been neglected although it has similar structure with perovskite. Here, we successfully found that [C₃H₇FN]₃[SnCl₆]Cl has a three-dimensional (3D) antiperovskite structure with the formula M₃AB. Importantly, the compound exhibits obvious ferroelectric properties with an Aizu notation of 622F6 at 391 K. To the best of our knowledge, this is the first 3D hybrid organic–inorganic antiperovskite ferroelectric, which will greatly promote the development of antiperovskite families with more superior physical properties.     

A Visible‐Light Driven Photoelectrochemical Aptasensor for Endocrine Disrupting Chemicals Bisphenol A with High Sensitivity and Specificity

A visible‐light driven photoelectrochemical (PEC) sensor based on aptamer immobilized TiO₂‐Fe₂O₃ nanotubes was proposed for the first time and highly sensitive and selective bisphenol A determination was realized. Taking advantage of the alloy oxide nanotube structure, high surface area, good biocompatibility, superior photoelectrocatalytic performance, a limit of detection toward BPA as low as 1.8×10^?11 M with linearity in the range from 1.8×10^?11 to 3.2×10^?9 M could be achieved. Specificity was greatly exhibited for this aptasensor under 100‐fold excess concentration of estriol, resorcinol, nonylphenol, 2,4‐D, acetamiprid, chlorpyrifos and omethoate. Simultaneously, satisfactory results were obtained in real water sample investigation from industrial plastics and drinking water. A novel visible‐light driven PEC method for highly sensitive and selective detection of BPA was thus established.     

Alloying n‐Butylamine into CsPbBr3 To Give a Two‐Dimensional Bilayered Perovskite Ferroelectric Material

Cesium‐lead halide perovskites (e.g. CsPbBr₃) have gained attention because of their rich physical properties, but their bulk ferroelectricity remains unexplored. Herein, by alloying flexible organic cations into the cubic CsPbBr₃, we design the first cesium‐based two‐dimensional (2D) perovskite ferroelectric material with both inorganic alkali metal and organic cations, (C₄H₉NH₃)₂CsPb₂Br₇ ( 1 ). Strikingly, 1 shows a high Curie temperature (T_c=412 K) above that of BaTiO₃ (ca. 393 K) and notable spontaneous polarization (ca. 4.2 μC cm^?2), triggered by not only the ordering of organic cations but also atomic displacement of inorganic Cs⁺ ions. To our knowledge, such a 2D bilayered Cs⁺‐based metal–halide perovskite ferroelectric material with inorganic and organic cations is unprecedented. 1 also shows photoelectric semiconducting behavior with large “on/off” ratios of photoconductivity (>10³).     

二维有机-无机杂化钙钛矿铁电材料的研究进展

铁电性通常是指电介质材料的自发极化取向随着外加电场发生变化的性能.以自发极化为核心,铁电材料表现出优异的介电响应、热释电性、压电性、电光效应和非线性光学效应等,是一类具有广阔应用前景的功能材料.近年来,二维有机-无机杂化钙钛矿化合物在铁电研究领域崭露头角,逐渐发展为铁电材料的重要组成部分.此类材料具有独特的结构兼容性与...     

Multilayered 2D Cesium-Based Hybrid Perovskite with Strong Polarization Sensitivity: Dimensional Reduction of CsPbBr3

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)₂CsPb₂Br₇ ( 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 (I_pc/I_pa) of ≈2.1, being much higher than that of the isotropic CsPbBr₃ crystal and reported CH₃NH₃PbI₃ 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.     

Centimeter-Size Single Crystals of Halide Perovskite Photoferroelectric Solid Solution with Ultrahigh Pyroelectricity Boosted Photodetection

Photoferroelectrics, especially emerging halide perovskite ferroelectrics, have motivated tremendous interests owing to their fascinating bulk photovoltaic effect (BPVE) and cross-coupled functionalities. However, solid solutions of halide perovskite photoferroelectrics with controllable structure and enhanced performance are scarcely explored. Herein, through mixing cage cation, a homogeneous halide perovskite photoferroelectric PA₂FA_xMA_1−xPb₂Br₇ solid solution (PA, FA and MA are CH₃CH₂CH₂NH₃⁺, NH₂CHNH₂⁺ and CH₃NH₃⁺, 0≤x≤1) has been developed, which demonstrates tunable Curie temperature in a wide range of 263–323 K and excellent optoelectrical features. As the component adjusted to x=0.7, the bulk crystal demonstrates ultrahigh pyroelectric coefficient up to 1.48 μC cm⁻² K⁻¹ around room temperature. Strikingly, benefiting from the light-induced pyroelectricity and remarkable BPVE, a self-powered and sensitive photodetector based solid solution crystals with boosted responsivity and detectivity over than 1300 % has been achieved. This pioneering work sheds light on the exploration of photoferroelectric solid solutions towards high-performance photoelectronic devices.     

Ultrathin Two‐Dimensional Organic–Inorganic Hybrid Perovskite Nanosheets with Bright,Tunable Photoluminescence and High Stability

Two‐dimensional (2D) organic–inorganic hybrid perovskite nanosheets (NSs) are attracting increasing research interest due to their unique properties and promising applications. Here, for the first time, we report the facile synthesis of single‐ and few‐layer free‐standing phenylethylammonium lead halide perovskite NSs, that is, (PEA)₂PbX₄ (PEA=C₈H₉NH₃, X=Cl, Br, I). Importantly, their lateral size can be tuned by changing solvents. Moreover, these ultrathin 2D perovskite NSs exhibit highly efficient and tunable photoluminescence, as well as superior stability. Our study provides a simple and general method for the controlled synthesis of 2D perovskite NSs, which may offer a new avenue for their fundamental studies and optoelectronic applications.     

Ultrathin Two‐Dimensional Organic–Inorganic Hybrid Perovskite Nanosheets with Bright,Tunable Photoluminescence and High Stability

Two‐dimensional (2D) organic–inorganic hybrid perovskite nanosheets (NSs) are attracting increasing research interest due to their unique properties and promising applications. Here, for the first time, we report the facile synthesis of single‐ and few‐layer free‐standing phenylethylammonium lead halide perovskite NSs, that is, (PEA)₂PbX₄ (PEA=C₈H₉NH₃, X=Cl, Br, I). Importantly, their lateral size can be tuned by changing solvents. Moreover, these ultrathin 2D perovskite NSs exhibit highly efficient and tunable photoluminescence, as well as superior stability. Our study provides a simple and general method for the controlled synthesis of 2D perovskite NSs, which may offer a new avenue for their fundamental studies and optoelectronic applications.     

A reduced-dimensional polar hybrid perovskite for self-powered broad-spectrum 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.     

Benign‐by‐Design Solventless Mechanochemical Synthesis of Three‐, Two‐, and One‐Dimensional Hybrid Perovskites

Organic–inorganic hybrid perovskites have attracted significant attention owing to their extraordinary optoelectronic properties with applications in the fields of solar energy, lighting, photodetectors, and lasers. The rational design of these hybrid materials is a key factor in the optimization of their performance in perovskite‐based devices. Herein, a mechanochemical approach is proposed as a highly efficient, simple, and reproducible method for the preparation of four types of hybrid perovskites, which were obtained in large amounts as polycrystalline powders with high purity and excellent optoelectronics properties. Two archetypal three‐dimensional (3D) perovskites (MAPbI₃ and FAPbI₃) were synthesized, together with a bidimensional (2D) perovskite (Gua₂PbI₄) and a “double‐chain” one‐dimensional (1D) perovskite (GuaPbI₃), whose structure was elucidated by X‐ray diffraction.