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Abstract Chiral hybrid organic‐inorganic perovskites (HOIPs) are widely investigated due to their superior chiroptical and chiral spintronic properties. Research on the enhancement of chiroptical performance is highly important for the real application of chiral HOIPs. This work employed a rare earth doping strategy to increase the magnetic transition dipole moment of chiral 2D HOIPs R‐/S‐NPB (NPB = 1‐(1‐naphthyl) ethylammonium lead bromide). Doping with Eu3+ does not change the original layered NPB microstructure, and R‐/S‐NPB‐Eu exhibited the magnetic dipole‐allowed transition luminescence of Eu3+ at 594 nm (5D0→7F1). Circular polarized luminescence (CPL) spectra combined with theoretical calculations and transient photoluminescence measurements indicated that the introduction of Eu3+ can enhance the magnetic transition dipole moment of R‐/S‐NPB, thus resulting in an unprecedented glum of 0.05. To the best of our knowledge, this is the highest value for chiral perovskite films. This work combines the unique and superior optoelectronic properties of rare‐earth ions with chiral perovskite and develops an efficient strategy to increase its anisotropy factor, which can accelerate the development of chiral optoelectronics and spintronics towards real application.

The spin degree of freedom in hybrid organic–inorganic perovskites (HOIPs) has become a rapidly growing research topic in both HOIPs and spintronics fields due to its fundamental scientific significance and tight relevance with optoelectronics. The flourishing achievements of HOIP spintronics call for a timely review to summarize the key progress and guide future developments. In this review, classical spintronic phenomena based on spin‐orbit coupling (SOC) are discussed, especially Rashba splitting and related applications such as spin‐charge conversion. Owing to the unique chirality‐spin coupling, spintronics in chiral HOIPs are particularly focused on, including chirality‐induced spin selectivity (CISS). Based on the complex band structure and carrier/exciton, spin dynamics is also widely investigated and constitutes an indispensable part of HOIP spintronics. Aside from the three main threads, other spintronic phenomena such as magneto‐optical coupling and device exploration are involved as promising opportunities. Despite the continuous breakthroughs in HOIP spintronics, more efforts are required to expand material systems, explore new physics, and optimize device configurations for enhanced performance and high integration. A deep understanding of spin behaviors in HOIPs will create a new platform beyond conventional optoelectronic and photovoltaic applications. [ABSTRACT FROM AUTHOR]

Colorless‐to‐black switching has attracted widespread attention for smart windows and multifunctional displays because they are more useful to control solar energy. However, it still remains a challenge owing to the tremendous difficulties in the design of completely reverse absorptions in transmissive and colored states. Herein, we report on an electrochemical device that can switch between colorless and black by using the electrochemical process of hybrid organic–inorganic perovskite MAPbBr3, which shows a high integrated contrast ratio of up to 73% from 400 to 800 nm. The perovskite solution can be used as the active layer to assemble the device, showing superior transmittance over the entire visible region in neutral states. By applying an appropriate voltage, the device undergoes reversible switching between colorless and black, which is attributed to the formation of lead and Br2 in the redox reaction induced by the electron transfer process in MAPbBr3. In addition, the contrast ratio can be modulated over the entire visible region by changing the concentration and the applied voltage. These results contribute toward gaining an insightful understanding of the electrochemical process of perovskites and greatly promoting the development of switchable devices. [ABSTRACT FROM AUTHOR]

Abstract Colorless‐to‐black switching has attracted widespread attention for smart windows and multifunctional displays because they are more useful to control solar energy. However, it still remains a challenge owing to the tremendous difficulties in the design of completely reverse absorptions in transmissive and colored states. Herein, we report on an electrochemical device that can switch between colorless and black by using the electrochemical process of hybrid organic–inorganic perovskite MAPbBr3, which shows a high integrated contrast ratio of up to 73% from 400 to 800 nm. The perovskite solution can be used as the active layer to assemble the device, showing superior transmittance over the entire visible region in neutral states. By applying an appropriate voltage, the device undergoes reversible switching between colorless and black, which is attributed to the formation of lead and Br2 in the redox reaction induced by the electron transfer process in MAPbBr3. In addition, the contrast ratio can be modulated over the entire visible region by changing the concentration and the applied voltage. These results contribute toward gaining an insightful understanding of the electrochemical process of perovskites and greatly promoting the development of switchable devices.

Crystalline materials have governed the development of hybrid organic‐inorganic perovskites (HOIPs), giving rise to a variety of fascinating applications such as solar cells and optoelectronic devices. With increasing interest in non‐crystalline systems, the glassy state of HOIPs has recently been identified. Here, the basic building blocks of crystalline HOIPs appear to be retained, though their glasses lack long‐range periodic order. The emerging family of glasses formed from HOIPs exhibits diverse properties, complementary to their crystalline state. This mini review describes the chemical diversity of both three‐dimensional and two‐dimensional crystalline HOIPs and demonstrates how glasses are produced from these materials. Specifically, current achievements in melt‐quenched glasses formed from HOIPs are highlighted. We conclude with our perspective on the future of this new family of materials. [ABSTRACT FROM AUTHOR]

The development of digital technology has made our lives more advanced as a society familiar with the Internet of Things (IoT). Solar cells are among the most promising candidates for power supply in IoT sensors. Perovskite photovoltaics (PPVs), which have already attained 25% and 40% power conversion efficiencies for outdoor and indoor light, respectively, are the best candidates for self-powered IoT system integration. In this review, we discuss recent research progress on PPVs under indoor light conditions, with a focus on device engineering to achieve high-performance indoor PPVs (Id-PPVs), including bandgap optimization and defect management. Finally, we discuss the challenges of Id-PPVs development and its interpretation as a potential research direction in the field. [ABSTRACT FROM AUTHOR]

This article describes a machine learning guided framework for screening the potential toxicity impact of amine chemistries used in the synthesis of hybrid organic–inorganic perovskites. Using a combination of a probabilistic molecular fingerprint technique that encodes bond connectivity (MinHash) coupled to non‐linear data dimensionality reduction methods (Uniform Manifold Approximation and Projection), we develop an "Amine Atlas." We show how the Amine Atlas can be used to rapidly screen the relative toxicity levels of amine molecules used in the synthesis of 2D and 3D perovskites and help identify safer alternatives. Our work also serves as a framework for rapidly identifying molecular similarity guided, structure–function relationships for safer materials chemistries that also incorporate sustainability/toxicity concerns. [ABSTRACT FROM AUTHOR]

MAPbBr3 (MA = CH3NH3+) doping with bismuth increases electric conductivity, charge carrier density and photostability, reduces toxicity, and expands light absorption. However, Bi doping shortens excited-state lifetimes due to formation of DY− charge recombination centers. Using nonadiabatic molecular dynamics and time-domain density functional theory, we demonstrate that the DY− center forms a deep, highly localized hole trap, which accelerates nonradiative relaxation ten-fold and is responsible for 90% of carrier losses. Hole trapping occurs by coupling between the valence band and the trap state, facilitated by the Br atoms surrounding the Bi dopant. Passivation of the DY− center with chlorines heals the local geometry distortion, eliminates the trap state, and makes the carrier lifetimes longer than even in pristine MAPbBr3. The decreased charge recombination arises from reduced nonadiabatic coupling and shortened coherence time, due to diminished electron-hole overlap around the passivated defect. Our study demonstrates accelerated nonradiative recombination in Bi-doped MAPbBr3, suggests a strategy for defect passivation and reduction of nonradiative energy losses, and provides atomistic insights into unusual defect properties of metal halide perovskites needed for rational design of high-performance perovskite solar cells and optoelectronic devices. [ABSTRACT FROM AUTHOR]

The development of digital technology has made our lives more advanced as a society familiar with the Internet of Things (IoT). Solar cells are among the most promising candidates for power supply in IoT sensors. Perovskite photovoltaics (PPVs), which have already attained 25% and 40% power conversion efficiencies for outdoor and indoor light, respectively, are the best candidates for self-powered IoT system integration. In this review, we discuss recent research progress on PPVs under indoor light conditions, with a focus on device engineering to achieve high-performance indoor PPVs (Id-PPVs), including bandgap optimization and defect management. Finally, we discuss the challenges of Id-PPVs development and its interpretation as a potential research direction in the field.

Two-dimensional semiconductors are considered intriguing materials for photonic applications, thanks to their stunning optical properties and the possibility to manipulate them at the nanoscale. In this review, we focus on transition metal dichalcogenides and low-dimensional hybrid organic-inorganic perovskites, which possess the same characteristics related to planar confinement of their excitons: large binding energies, wide exciton extension, and high oscillator strength. We describe their optoelectronic properties and their capability to achieve strong coupling with light, with particular attention to polariton-polariton interactions. These aspects make them very attractive for polaritonic devices working at room temperature, in view of the realization of all-optical logic circuits in low-cost and easy-to-synthesize innovative materials.

Perovskites are among the most famous materials due to their exceptional properties: they present nearly all existing types of interesting properties, in particular as ferroics or multiferroics, they may be insulators, (super)conductors, or semiconductors, magnetoresistant, they are used in numerous devices, they present hundreds of variants and different crystalline phases and phase transitions, and recently appeared as probably the most promising materials for photovoltaics. With a crystal structure characterized by octahedra that share their corners, these materials belong to the wider category of « Framework Structure (FWS) materials » the structure of which is based on units (octahedra, tetrahedra, …) that share some of their corners (or edges) with their neighbours. This particular feature of FWS materials confers to them unique properties. This review volume is constituted of 26 chapters on different aspects, and is divided in two parts, « Fundamental aspects and general properties », and « Elaborated materials and applied properties ». Its main purpose is to attempt to identify the properties common to all members of the vast family of FWS materials, and understand their differences. Besides perovskites, derived compounds as 2D perovskites, Dion-Jacobson, Ruddlesden-Popper, Aurivillius, tungsten-bronzes, and others, are presented, and their preparation and/or properties as single crystals, ceramics, thin films, multilayers, nanomaterials, nanofibers, nanorods, etc, are discussed. We focus on new trends and important recent developments by leaving somewhat aside more classical aspects which can be easily found in older textbooks or review articles. Among most recent applications, this volume focuses on applications related with interactions with other molecules, on photovoltaics, and on memories, with a special attention to perovskite solar cells that have certainly attracted the most attention of researchers in recent years, opening extremely promising routes in photovoltaics. In conclusion, this book presents a collection of texts elucidating various aspects of the relation between structural organization (including dynamical aspects) and singular properties of framework crystals; it proposes a reasonable balance between experimental and theoretical results, and between fundamental aspects and applied properties. This volume can be approached on several levels (each chapter initially assumes that the reader is not a specialist in the subject, and is presented in a pedagogical way) : it is accessible to master or doctoral students, as well as to researchers who want to have informations on recent developments, who will find excellent detailed introductions up to hotsubjects. It may also be used by undergraduate students who should approach given subjects. The volume contains 800 pages written by about 70 authors from different countries, it has an index, and is completed by numerous figures to illustrate the text.

Recent experiments report the rotation of FA (FA=HC[NH2]2+) cations significantly influence the excited-state lifetime of FAPbI3. However, the underlying mechanism remains unclear. Using ab initio nonadiabatic (NA) molecular dynamics combined with time-domain density functional simulations, we have demonstrated that reorientation of partial FA cations significantly inhibits nonradiative electron-hole recombination with respect to the pristine FAPbI3 due to the decreased NA coupling by localizing electron and hole in different positions and the suppressed atomic motions. Slow nuclear motions simultaneously increase the decoherence time, which is overcome by the reduced NA coupling, extending electron-hole recombination time scales to several nanoseconds and being about 3.9 times longer than that in pristine FAPbI3, which occurs within sub-nanosecond and agrees with experiment. Our study established the mechanism for the experimentally reported prolonged excited-state lifetime, providing a rational strategy for design of high performance of perovskite solar cells and optoelectronic devices. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • MAIBi was synthesized and applied as new visible-light effective photocatalyst. • Photocatalytic efficiency was in agreement with structural and optical properties. • Possible mechanisms of photodegradation were proposed. • Visible-light irradiation sources were compared. Abstract In this work, the photocatalytic activity of a new visible light-responsive (CH 3 NH 3) 3 Bi 2 I 9 hybrid organic-inorganic perovskite (HOIP) was addressed for the very first time in the treatment of aqueous solutions of model organic dyes. The photocatalyst was successfully prepared by a low temperature solvo-termal method, easily reproducible. The catalyst was characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction spectrometer (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDS), X-ray photoelectron spectroscopy (XPS) techniques and UV diffuse reflectance spectrum. The efficiency of photocatalyst was tested for the removal of different type of dyes: fluorone dye (rhodamine B), thiazine dye (methylene blue) and azo dye (reactive Blue 4). Moreover, a multi-contaminated solution, with methylene blue and crystal violet (triarylmethane dye), was used to simulate a real industrial wastewater effluent. The results highlighted an increase of the photocatalytic activity respect the pristine precursor, bismuth iodide. The experiments showed that the values of removal was higher for rhodamine B respect the other dyes, with a removal of 98% after three hours under visible light irradiation. The efficiency of the photocatalyst was also confirmed under optimal conditions with high pressure liquid chromatography (HPLC). The gradual disappearance of rhodamine B peak accompanied by the appearance of by-products peaks was investigated. The stability of the photocatalyst was tested for three consecutive re-cycles. Analysis on different visible light sources was performed: halogen provided higher efficiency respect LED lamp. The outcomes of the present work aim to open the possibility of considering HOIP as a new potential photocatalyst for contaminants treatment. [ABSTRACT FROM AUTHOR]

Hybrid organic–inorganic perovskites, while well examined for photovoltaic applications, remain almost completely unexplored in the terahertz (THz) range. These low-cost hybrid materials are extremely attractive for THz applications because their optoelectronic properties can be chemically engineered with relative ease. Here, we experimentally demonstrate the first attempt to apply solution-processed polycrystalline films of hybrid perovskites for the development of photoconductive terahertz emitters. By using the widely studied methylammonium-based perovskites MAPbI3 and MAPbBr3, we fabricate and characterize large-aperture photoconductive antennas. The work presented here examines polycrystalline perovskite films excited both above and below the bandgap, as well as the scaling of THz emission with the applied bias field and the optical excitation fluence. The combination of ultrafast time-resolved spectroscopy and terahertz emission experiments allows us to determine the still-debated room temperature carrier lifetime and mobility of charge carriers in halide perovskites using an alternative noninvasive method. Our results demonstrate the applicability of hybrid perovskites for the development of scalable THz photoconductive devices, making these materials competitive with conventional semiconductors for THz emission.

Abstract A procedure for the physical vapor deposition (PVD), in high-vacuum conditions, for high purity and crystalline methylammonium lead halide perovskite thin films is described. This procedure and methodology can be used to fabricate high-performance hybrid organic-inorganic materials that have recently emerged as the next-generation photovoltaic technology. PVD of methylammonium iodide and lead iodide to produce lead halide perovskite thin films was optimized according to the equilibrium vapor pressures of corresponding precursors evaporated from Knudsen effusion cells. Optical properties of perovskite thin films were characterized by UV-Vis-NIR and fluorescence spectroscopy. The high crystallinity of vapor-deposited thin films on glass, indium tin oxide, fluorine-doped tin oxide, and TiO 2 surfaces was proved by scanning electron microscopy and X-ray diffraction. This vapor deposition approach leads to the production of very pure, crystalline and high stable perovskite thin films. Highlights • High-purity perovskite films can be prepared by a vapor deposition approach. • Thin film deposition is controlled by the molar flow rate of perovskite sources. • Stoichiometric flow rates of both reactants are achieved by using Knudsen cells. • Compact, uniform, stable and crystalline perovskite thin films were produced. [ABSTRACT FROM AUTHOR]

[Display omitted] • Application of molecular spectroscopy in studies of hybrid organic–inorganic perovskites. • Review of recent studies on formates, hypophosphites, azides, cyanides, dicyanamides and halides. • NMR, EPR, IR, Raman, dielectric and optical spectroscopy as a probe of phase transition mechanisms. Hybrid organic–inorganic perovskites (HOIPs) constitute unique coordination polymers with a huge potential of transforming modern materials chemistry due to their wide applications, mainly in electronics, optoelectronics and photovoltaics. Yearly, thousands of works on HOIPs are published in various fields of science, technology and industry. Many of these studies are devoted to structural and structure-related properties. Molecular spectroscopy methods (optical and broadband dielectric spectroscopy, IR, Raman, EPR, NMR) are often used to understand their magnetic, optical and luminescent properties; energy conversion; basic molecular dynamics; hydrogen bond-associated guest molecule-framework interactions; stability; flexibility; mechanisms of temperature- and pressure induced phase transitions; and other more sophisticated physical phenomena, such as polar properties, ferroelectricity, multiferroicity, etc. The goal of this review is to create a comprehensive and versatile phase-related guide for researchers working in the field of HOIPs using a wide range of molecular spectroscopy techniques. This review presents a systematical description of very recent achievements obtained using modern molecular spectroscopy methods. It also summarizes the current state of knowledge on HOIPs, including metal formates, hypophosphites, azides, cyanides, dicyanamides, and halides templated by protonated amines and phosphines that adopt a perovskite architecture. [ABSTRACT FROM AUTHOR]

Hybrid organic–inorganic perovskites, while well examined for photovoltaic applications, remain almost completely unexplored in the terahertz (THz) range. These low-cost hybrid materials are extremely attractive for THz applications because their optoelectronic properties can be chemically engineered with relative ease. Here, we experimentally demonstrate the first attempt to apply solution-processed polycrystalline films of hybrid perovskites for the development of photoconductive terahertz emitters. By using the widely studied methylammonium-based perovskites MAPbI3 and MAPbBr3, we fabricate and characterize large-aperture photoconductive antennas. The work presented here examines polycrystalline perovskite films excited both above and below the bandgap, as well as the scaling of THz emission with the applied bias field and the optical excitation fluence. The combination of ultrafast time-resolved spectroscopy and terahertz emission experiments allows us to determine the still-debated room temperature carrier lifetime and mobility of charge carriers in halide perovskites using an alternative noninvasive method. Our results demonstrate the applicability of hybrid perovskites for the development of scalable THz photoconductive devices, making these materials competitive with conventional semiconductors for THz emission. [ABSTRACT FROM AUTHOR]

The astonishing progress achieved in perovskite solar cells in recent years has coincided with the growing interest in machine learning (ML) for material discovery, and the number of papers reporting the use of ML in perovskite solar research has been increased significantly in last two years. ML has been used for various purposes such as discovering new perovskites by screening the large computational or experimental datasets, analyzing the spectroscopic data augmented by data extracted from databases, determining conditions for higher efficiency or stability using experimental data and identifying the basic trends in perovskite solar cell technology by analyzing the published papers and patents. This communication aims to review the research articles as well as the perspectives, comments and opinions, to assess the current directions and summarize the challenges and opportunities for the future works in the field. ga1 • Machine learning (ML) works on organolead perovskite solar cells are reviewed. • Both experimental and computational data are used to develop ML models. • Data created in house or extracted from papers and databases are utilized. • Screening perovskites for band gap, structure and stability are common applications. • Machine learning models for cell efficiency and stability were also studied. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid perovskite (CH 3 NH 3)PbX 3 [X = I−, Cl−, and Br− materials were evaluated with memristors for resistive switching (RS) and synaptic functionalities. Analog or multilevel memory behaviors, as well as digital RS characteristics of the Ag/MAPbI 3 /FTO device structure, were observed in the case of CH 3 NH 3 PbI 3 , whereas (CH 3 NH 3)PbCl 3 and (CH 3 NH 3)PbBr 3 showed no switching characteristics. The conduction mechanism of RS was dominated by ohmic conduction, space-charge-limited conduction (SCLC), and trap-filled SCLC in both the low-resistance state and the high-resistance state. It is considered that the formation of the β -AgI phase at the interface between Ag and MAPbI 3 thin films resulted in different RS and synaptic function behaviors. We successfully emulated the fundamental synaptic characteristics with only a Ag/MAPbI 3 /FTO memristor, such as the spike-rate-dependent plasticity, paired-pulse facilitation, post-tetanic potentiation, transition from short-term memory to long-term memory, and spike-timing dependent plasticity. The energy consumption of the MAPbI 3 -based memristor was estimated to be as low as 47 fJ/μm2. Our results indicate that organic–inorganic hybrid perovskite (CH 3 NH 3)PbI 3 can be adopted in brain-inspired synaptic devices for hardware-based neuromorphic system applications. Image 1 • Organic-Inorganic hybrid perovskite (CH 3 NH 3)PbX 3 [X = I−, Cl−, Br− is explored as synapse material. • CH 3 NH 3 PbI 3 shows better multi-level switching behavior due to β -AgI formation in Ag/perovskite/FTO device.. • Various synaptic functions are attained with CH 3 NH 3 PbI 3 synaptic device. [ABSTRACT FROM AUTHOR]

There is a common phenomenon in the preparation of perovskite quantum dots (QDs) by reprecipitation method that large particles were always produced with desired QDs. Understanding the fabrication mechanism can contribute to improve this phenomenon. Herein, we demonstrate a two-step strategy for synthesis of perovskite QDs and large nanoparticles (LNPs), where the growth of QDs and LNPs involves two possible pathways, the quick intercalation reaction process and the dissolution-recrystallization process. Following two pathways, we have created QDs with high photoluminescence quantum yields (ca. 46–71%), tunable size (ca. 3.2–5.4 nm) and LNPs with tunable size from 25 to 300 nm, where their emission wavelength can be tuned from 500 nm to 534 nm. Importantly, based on the comprehensive insight into the formation mechanism, we have achieved the conversion from LNPs to QDs partly through adding surfactants properly, which is expected to pave the way for the development of pure production of perovskite QDs. Image 1 • We demonstrate a two-step strategy for synthesis of perovskite QDs and large nanoparticles. • The perovskite QDs with tunable size (ca. 2.3–5.4 nm) manifest high photoluminescence quantum yields. • We have achieved the conversion from perovskite large nanoparticles to QDs partly through adding surfactants properly. • The possible mechanism was reported to make clear the function of surfactants on the formation of perovskite QDs and LNPs. [ABSTRACT FROM AUTHOR]