Tailored Engineering of an Unusual (C4 H9 NH3 )2 (CH3 NH3 )2 Pb3 Br10 Two-Dimensional Multilayered Perovskite Ferroelectric for a High-Performance Photodetector

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, (C₄ H₉ NH₃ )₂ CsPb₂ Br₇ (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 ).

Extra thermo- and water-stable one-dimensional organic-inorganic hybrid perovskite [N-methyldabconium]PbI3 showing switchable dielectric behaviour, conductivity and bright yellow-green emission

Haloplumbate-based perovskites display promising functionalities for advanced photovoltaic, optoelectronic and other applications with high performances and low costs. Herein, we present a study of variable-temperature crystal structures, dielectrics and conductance at 153-513 K, and luminescence at ambient temperature for a one-dimensional organic-inorganic perovskite, [N-methyldabconium]PbI3 (1). Hybrid 1 shows extra thermo- and water-stability (thermal decomposition at ca. 653 K), switchable dielectric behaviour and conductance at around 348 K, owing to symmetry-breaking structure phase transition from the hexagonal space group P63/mmc in the high-temperature phase to the orthogonal space group Pcba in the low-temperature phase, and bright yellow-green emission at room temperature, originating from the electron transition within the semiconducting {PbI3}∞ chains. This study will broaden the scope of lead halide-based hybrid materials for practical application in optical and electrical devices.

Boosting Visible Light Absorption of Metal-Oxide-Based Phototransistors via Heterogeneous In-Ga-Zn-O and CH3NH3PbI3 Films

To broaden the availability and application of metal-oxide (M-O)-based optoelectronic devices, we suggest heterogeneous phototransistors composed of In-Ga-Zn-O (IGZO) and methylammonium lead iodide (CH₃NH₃PbI₃) layers, which act as the amplifier layer (channel layer) and absorption layer, respectively. These heterogeneous phototransistors showed low persistence photocurrent compared with IGZO-only phototransistors and exhibited high photoresponsivity of 61 A/W, photosensitivity of 3.48 × 10⁶, detectivity of 9.42 × 10¹⁰ Jones, external quantum efficiency of 154% in an optimized structure, and high photoresponsivity under water exposure via the deposition of silicon dioxide as a passivation layer. On the basis of these electrical results and various analyses, we determined that CH₃NH₃PbI₃ could be activated as a light absorption layer, current barrier, and plasma damage blocking layer, which would serve to widen the range of applications of M-O-based optoelectronic devices with high photoresponsivity and reliability under visible light illumination.

Guanidinium-Formamidinium Lead Iodide: A Layered Perovskite-Related Compound with Red Luminescence at Room Temperature

Two-dimensional hybrid organic-inorganic lead halides perovskite-type compounds have attracted immense scientific interest due to their remarkable optoelectronic properties and tailorable crystal structures. In this work, we present a new layered hybrid lead halide, namely [CH(NH2)2][C(NH2)3]PbI4, wherein puckered lead-iodide layers are separated by two small and stable organic cations: formamidinium, CH(NH2)2+, and guanidinium, C(NH2)3+. This perovskite is thermally stable up to 255 °C, exhibits room-temperature photoluminescence in the red region with a quantum yield of 3.5%, and is photoconductive. This study highlights a vast structural diversity that exists in the compositional space typically used in perovskite photovoltaics.

Hybrid Dion-Jacobson 2D Lead Iodide Perovskites

The three-dimensional hybrid organic-inorganic perovskites have shown huge potential for use in solar cells and other optoelectronic devices. Although these materials are under intense investigation, derivative materials with lower dimensionality are emerging, offering higher tunability of physical properties and new capabilities. Here, we present two new series of hybrid two-dimensional (2D) perovskites that adopt the Dion-Jacobson (DJ) structure type, which are the first complete homologous series reported in halide perovskite chemistry. Lead iodide DJ perovskites adopt a general formula A'A _n-1Pb _nI_{3 n+1} (A' = 3-(aminomethyl)piperidinium (3AMP) or 4-(aminomethyl)piperidinium (4AMP), A = methylammonium (MA)). These materials have layered structures where the stacking of inorganic layers is unique as they lay exactly on top of another. With a slightly different position of the functional group in the templating cation 3AMP and 4AMP, the as-formed DJ perovskites show different optical properties, with the 3AMP series having smaller band gaps than the 4AMP series. Analysis on the crystal structures and density functional theory (DFT) calculations suggest that the origin of the systematic band gap shift is the strong but indirect influence of the organic cation on the inorganic framework. Fabrication of photovoltaic devices utilizing these materials as light absorbers reveals that (3AMP)(MA)₃Pb₄I₁₃ has the best power conversion efficiency (PCE) of 7.32%, which is much higher than that of the corresponding (4AMP)(MA)₃Pb₄I₁₃.

Highly efficient white-light emission in a polar two-dimensional hybrid perovskite

A polar two-dimensional hybrid perovskite showing efficient white-light emission and a nonlinear optical effect suggests potential application in solid-state optics.

Controllable Synthesis of Two-Dimensional Ruddlesden-Popper-Type Perovskite Heterostructures

Two-dimensional Ruddlesden-Popper type perovskites (2D perovskites) have recently attracted increasing attention. It is expected that 2D perovskite-based heterostructures can significantly improve the efficiency of the optoelectronic devices and extend the material functionalities; however, rational synthesis of such heterostructures has not been realized to date. We report on a general low-temperature synthetic strategy for the synthesis of 2D perovskite-based lateral and vertical (n-CH₃(CH₂)₃NH₃)₂PbI₄/(n-CH₃(CH₂)₃NH₃)₂(CH₃NH₃)Pb₂I₇ heterostructures for the first time. A combination of solution synthesis and gas-solid phase intercalation approach allows us to efficiently synthesize both lateral and vertical heterostructures with great flexibility. X-ray diffraction, photoluminescence, and photoluminescence excitation mapping and electrical transport measurement studies reveal the successful synthesis of lateral and vertical heterostructures with precisely spatial-modulation control and distinguishable interfaces. Our studies not only provide an efficient synthetic strategy with great flexibility, enabling us to create 2D perovskite-based heterostructures, but also offer a platform to investigate the physical processes in those heterostructures.