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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]

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]

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]