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Three-dimensional (3D) organic-inorganic hybrid perovskites (OIHPs) have achieved tremendous success in direct X-ray detection due to their high absorption coefficient and excellent carrier transport. However, owing to the centrosymmetry of classic 3D structures, these reported X-ray detectors mostly require external electrical fields to run, resulting in bulky overall circuitry, high energy consumption, and operational instability. Herein, we first report the unprecedented radiation photovoltage in 3D OIHP for efficient self-driven X-ray detection. Specifically, the 3D polar OIHP MhyPbBr 3 (1, Mhy=methylhydrazine) shows an intrinsic radiation photovoltage (0.47 V) and large mobility-lifetime product (1.1×10 -3  cm 2  V -1 ) under X-ray irradiation. Strikingly, these excellent physical characteristics endow 1 with sensitive self-driven X-ray detection performance, showing a considerable sensitivity of 220 μC Gy -1  cm -2 , which surpasses those of most self-driven X-ray detectors. This work first explores highly sensitive self-driven X-ray detection in 3D polar OIHPs, shedding light on future practical applications., (© 2024 Wiley-VCH GmbH.)

A mixed-cation 3D lead bromide hybrid perovskite (NMDAP) 2 FAPb 4 Br 13 (1, NMDAP 2+ = N-methyl-1,3-diaminopropanium, FA + = formamidinium) is tailored by incorporating the large NMDAP 2+ cation with the small FA + ion into 3D FAPbBr 3 . Structurally, the small FA + ions occupy the prototypical cavities formed by distorted corner-sharing PbBr 6 octahedra as in FAPbBr 3 , while the bulky NMDAP 2+ ions are confined to the expanded lattice which is defined by a new structural motif composed of eight corner-sharing PbBr 6 octahedra and four edge-sharing octahedra. This localized lattice expansion from FAPbBr 3 creates a new branch of the intriguing 3D hybrid perovskite family, breaking the limits of the conventional Goldschmidt tolerance factor rule. Moreover, a high two-photon absorption (2AP) coefficient of 60.8 cm MW -1 was demonstrated to near-infrared (NIR) 800 nm illumination, enabling sensitive NIR photoresponses with large on/off ratio (≈10 4 ) as well as favorable stability., (© 2022 Wiley-VCH GmbH.)

Halide hybrid perovskites are attracting considerable attention as highly promising candidates for directly sensing X-ray radiation, but it is challenging to realize passive X-ray detection without an external power supply. However, the bulk photovoltaic effect (BPVE) in ferroelectrics promotes the independent separation of photoexcited carriers. Herein, by dimensionality reconstruction of a pure-two-dimensional (P-2D) monolayered perovskite (CH 3 OC 3 H 9 N) 2 PbBr 4 , we obtained a quasi-two-dimensional (Q-2D) ferroelectric (CH 3 OC 3 H 9 N) 2 CsPb 2 Br 7 . Converting P-2D into Q-2D perovskite stimulates a significant BPVE associated with robust ferroelectricity, as well as an enhanced mobility lifetime product. These features show the potential of the first passive X-ray detector based on ferroelectrics with an impressive sensitivity up to 410 μC Gy -1  cm -2 at zero bias, which is even superior to the value of the state-of-the-art α-Se detector operated at relatively high bias., (© 2021 Wiley-VCH GmbH.)

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) 2 PbBr 4 (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 GeS 2 )., (© 2020 Wiley-VCH GmbH.)

Polarized light detection is attracting increasing attention for its wide applications ranging from optical switches to high-resolution photodetectors. Two-dimensional (2D) hybrid perovskite-type ferroelectrics combining inherent light polarization dependence of bulk photovoltaic effect (BPVE) with excellent semiconducting performance present significant possibilities. Now, the BPVE-driven highly sensitive polarized light detection in a 2D trilayered hybrid perovskite ferroelectric, (allyammonium) 2 (ethylammonium) 2 Pb 3 Br 10 (1), is presented. It shows a superior BPVE with near-band gap photovoltage of ca. 2.5 V and high on/off switching ratio of current (ca. 10 4 ). Driven by the superior BPVE, 1 exhibits highly sensitive polarized light detection with a polarization ratio as high as ca. 15, which is far more beyond than those of structural anisotropy-based monocomponent devices. This is the first realization of BPVE-driven polarized light detection in hybrid perovskite ferroelectrics., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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 CsAgBiBr 7 (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  cm 2  V -1 . This figure-of-merit realized in 2D hybrid double perovskites is unprecedented and comparable with that of CH 3 NH 3 PbI 3 wafers. (BA) 2 CsAgBiBr 7 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 Gy air -1  cm -2 ., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Photosensitive organic-inorganic hybrid ferroelectrics are emerging as a new class of promising materials with a broad spectral response (e.g., visible light, UV light, and IR light) for optoelectronic applications. However, spectrally customized photoresponses in ferroelectrics have not been achieved. Herein, we report a photosensitive organic-inorganic hybrid ferroelectric, (diisobutylammonium) 3 ClCoCl 4 (1), with a notable spontaneous polarization of approximately 4.6 μC cm -2 and high Curie temperature (T c =372.5 K). More interestingly, it features spectrally selective absorption at specific wave bands ranging from 550 to 700 nm with a large absorption coefficient, which was assigned to the d-d transition of Co 2+ from the 4 A 2 to the 4 T 1 (P) state. It is emphasized that 1 shows spectrally customized photosensitivity with distinct photocurrent generation under light illumination at 550-700 nm. This is the first hybrid photosensitive ferroelectric with a spectrally customized photoresponse. This finding should lead to innovative applications of hybrid photosensitive ferroelectrics, especially towards spectrally selective optoelectronic devices., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Fast switching of spontaneous polarization (P s ) is one of the most essential requirements for ferroelectrics used in the field of data storage. However, in contrast to inorganic counterparts, the low operating frequency (<500 Hz) for molecular ferroelectrics severely hinders their large-scale applications. Herein, for the first time, we achieved the room-temperature fastest switching of the P s in a new molecular ferroelectric, N-methylmorpholinium trinitrophenolate (1), which displays notable ferroelectricity (P s =3.2 μc cm -2 ). Strikingly, electric polarizations of 1 have been switched under a record-high frequency of 263 kHz, and this performance remains stable without any obvious fatigue after ca. 2×10 5 switching cycles. To our knowledge, 1 is the first organic ferroelectric to switch polarization at such a high operating frequency, exceeding the majority of organic ferroelectrics, which opens up new possibilities for its potential in the field of non-volatile memory., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Cesium-lead halide perovskites (e.g. CsPbBr 3 ) have gained attention because of their rich physical properties, but their bulk ferroelectricity remains unexplored. Herein, by alloying flexible organic cations into the cubic CsPbBr 3 , we design the first cesium-based two-dimensional (2D) perovskite ferroelectric material with both inorganic alkali metal and organic cations, (C 4 H 9 NH 3 ) 2 CsPb 2 Br 7 (1). Strikingly, 1 shows a high Curie temperature (T c =412 K) above that of BaTiO 3 (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 (>10 3 )., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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, (C 4 H 9 NH 3 ) 2 (CH 3 NH 3 ) 2 Pb 3 Br 10 (1), has been constructed by tailored alloying of the mixed organic cations into 3D prototype of CH 3 NH 3 PbBr 3 . 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. 2.5×10 3 ), 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 CH 3 NH 3 PbI 3 ., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Nitrates have long been ignored for practical uses as nonlinear optical (NLO) materials because they are usually very easy to dissolve in water; despite this, the π-conjugated [NO 3 ] - is among the most desirable NLO-active structural units. The cooperation of three structural chromophores, namely, Bi 3 O 6 OH short chains with 6s 2 lone pair electrons, distorted TeO 6 octahedra with d 10 electrons, and π-conjugated [NO 3 ] - triangles, generates a new nitrate NLO material, Bi 3 TeO 6 OH(NO 3 ) 2 , which exhibits an enhanced phase-matchable NLO response of three times that of KH 2 PO 4 (3×KH 2 PO 4 ), exceeding those of most nitrate NLO materials. Remarkably, the new material did not show obvious weight loss and degeneration of NLO response after being dipped in de-ionized water for 24 h, indicating that it is highly resistant to water. Theoretical calculations reveal that foreign water molecules cannot stably stay in the crystal lattice of Bi 3 TeO 6 OH(NO 3 ) 2 . These findings highlight the introduction of diverse chromophores into the nitrate systems as an effective approach for developing practical nitrate NLO materials that are of high water-resistance and good optical performance., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Perovskite lead halides (CH3 NH3 PbI3 ) 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)3 Sb2 Br9 (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., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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 (>10(4) ), which compete with the most active photovoltaic material CH3 NH3 PbI3 . 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., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)