Synthesis, Crystal Structure, UV-Vis Adsorption Properties, Photoelectric Behavior, and DFT Computational Study of All-Inorganic and Lead-Free Copper Halide Salt K2Cu2Cl6

Exploring the Influence of Cation and Halide Substitution in the Structure and Optical Properties of CH3NH3NiCl3 Perovskite

This manuscript details a comprehensive investigation into the synthesis, structural characterization, thermal stability, and optical properties of nickel-containing hybrid perovskites, namely CH3NH3NiCl3, CsNiCl3, and CH3NH3NiBrCl2. The focal point of this study is to unravel the intricate crystal structures, thermal behaviors, and optical characteristics of these materials, thereby elucidating their potential application in energy conversion and storage technologies. X-ray powder diffraction measurements confirm that CH3NH3NiCl3 adopts a crystal structure within the Cmcm space group, while CsNiCl3 is organized in the P63/mmc space group, as reported previously. Such structural diversity underscores the complex nature of these perovskites and their potential for tailored applications. Thermal analysis further reveals the stability of CH3NH3NiCl3 and CH3NH3NiBrCl2, which begin to decompose at 260 °C and 295 °C, respectively. The optical absorption properties of these perovskites studied by UV-VIS-NIR spectroscopy revealed the bands characteristic of Ni2+ ions in an octahedral environment. Notably, these absorption bands exhibit subtle shifts upon bromide substitution, suggesting that optical properties can be finely tuned through halide modification. Such tunability is paramount for the design and development of materials with specific optical requirements. By offering a detailed examination of these properties, the study lays the groundwork for future advancements in material science, particularly in the development of innovative materials for sustainable energy technologies.

Synthesis, Characterization, and Photoelectric and Electrochemical Behavior of (CH3NH3)2Zn1-xCoxBr4 Perovskites

We report the synthesis, characterization, and photoelectric and electrochemical properties of (CH3NH3)2Zn1-xCoxBr4 (x = 0.0, 0.3, 0.5, 0.7, and 1.0) samples. X-ray powder and single-crystal diffraction confirm the formation of solid solution across the entire range. Additionally, as the cobalt concentration increases, the crystallinity of the samples decreases, as indicated by the powder diffraction patterns. All samples remain stable up to 560 K, beyond which they decompose into CH3NH3Br and the respective bromide. The semiconductor behavior of the compounds is confirmed through optical absorption measurements, and band gap values are determined by using the Tauc method from diffuse reflectance spectra. Raman spectroscopy reveals a slight redshift in all vibration modes with increasing cobalt content. Finally, photovoltaic measurements on solar cells constructed with (MA)2CoBr4 perovskite exhibit modest performance, and electrochemical measurements indicate that the compound with the composition (MA)2Zn0.3Co0.7Br4 exhibits the highest current for electrochemical water reduction during oxygen evolution.

Growth optimization of single-phase novel colloidal perovskite Cs3Bi2I9 nanocrystals and Cs3Bi2I9@SiO2 core-shell nanocomposites for bio-medical application

Lead-free halide perovskites have gained attention in recent years as viable materials with more distinctive characteristics than conventional semiconductor materials. Lead-free Cs₃Bi₂I₉ colloidal perovskite nanocrystal is chosen to eliminate its single-phase synthesis difficulty and implement the material in bioimaging applications. Nanostructured Cs₃Bi₂I₉ perovskite composites were coated with a thin coating of SiO₂ by an in situ tetraethyl orthosilicate/(3-aminopropyl)trimethoxysilane injection growth method to enhance their stability in aqueous medium and biocompatibility. Single-phase novel Cs₃Bi₂I₉ colloidal perovskite nanocrystal synthesis was successfully developed and optimized by adopting different synthetic conditions with varied experimental parameters. Characterization studies, including X-ray diffractometry and transmission electron microscopy, confirm the hexagonal structure of Cs₃Bi₂I₉ crystals and their cubic morphology. A broad emission peak in the red region was captured for pure and composite perovskite under different excitation wavelengths and was observed using a UV-visible spectrophotometer. Bioimaging of Cs₃Bi₂I₉@SiO₂ composites incorporated with L929 cells was conducted using an inverted fluorescence microscope under blue and green excitation. The results obtained from bioimaging studies indicated that the Cs₃Bi₂I₉@SiO₂ nanocomposites entered the cell field and exhibited an emission under excitation. The non-toxic behavior of the synthesized Cs₃Bi₂I₉@SiO₂ composites was demonstrated using MTT cytotoxicity assay in L929 fibroblast mouse cells, showing better cell compatibility.

Ultrathin covalent and cuprophilic interaction-assembled copper-sulfur monolayer in organic metal chalcogenide for oriented photoconductivity

We report the thinnest copper sulfur atomic monolayer in an organic copper chalcogenide [Cu(CMP)]_n (CMP = 5-chloro-2-mercaptopyridine). The layer features a new type of copper sulfur structure woven by both covalent bond and cuprophilic interaction and shows an intriguing oriented photoconductivity.

A halogen bonding assembled hybrid copper halide framework as a promising hypotoxicity photodetector

The first halogen bonding assembled three-dimensional hybrid copper iodide was obtained by a facile and sustainable “All-in-One” synthesis strategy and shows great application potential as a hypotoxicity photodetector.

All-Inorganic Lead-Free Perovskite(-Like) Single Crystals: Synthesis, Properties, and Applications

Due to their nontoxicity, stability, and unique optoelectronic properties, all-inorganic lead-free halide semiconductors with perovskite and perovskite-like structures have successfully emerged as promising optoelectronic materials for various applications, such as solar cells, light-emitting diodes (LEDs), photodetectors, and X-ray detectors. To further explore their practical potentials, researchers have paid more attention in all-inorganic lead-free perovskite (-like) (ILFP) single crystals. For these single crystals, the advantages of large sizes, uniform surface morphology, and few defects can facilitate their excellent performances and practical applications. Besides, compared with the low dimensional and polycrystalline ILFP materials, the ILFP single crystals feature enhanced performances, including a longer carrier diffusion length and a larger light absorption coefficient, which attract a great deal of attention. Therefore, focus is on the researching progress of ILFP single crystals and the development of their preparation methods, as well as the novel properties of ILFP single crystals. In addition, the reported applications of ILFP single crystals are proposed to highlight their practical importance. With the perspective of the evolution and challenges, the current limitations of the materials and devices are discussed, followed by an inspirational outlook on their future development directions.

Recent advances toward environment-friendly photodetectors based on lead-free metal halide perovskites and perovskite derivatives

Recently, metal-halide perovskites have emerged as promising materials for photodetector (PD) applications owing to their superior optoelectronic properties, such as ambipolar charge transport characteristics, high carrier mobility, and so on. In the past few years, rapid progress in lead-based perovskite PDs has been witnessed. However, the critical environmental instability and lead-toxicity seriously hinder their further applications and commercialization. Therefore, searching for environmentally stable and lead-free halide perovskites (LFHPs) to address the above hurdles is certainly a worthwhile subject. In this review, we present a comprehensive overview of currently explored LFHPs with an emphasis on their crystal structures, optoelectronic properties, synthesis and modification methods, as well as the PD applications. LFHPs are classified into four categories according to the replacement strategies of Pb²⁺, including AB(ii)X₃, A₃B(iii)₂X₉, A₂B(i)B(iii)'X₆, and newly-emerging perovskite derivatives. Then, we give a demonstration of the preliminary achievements and limitations in environment-friendly PDs based on such LFHPs and perovskite derivatives, and also discuss their applications in biological synapses, imaging, and X-ray detection. With the perspective of their properties and current challenges, we provide an outlook for future directions in this rapidly evolving field to achieve high-quality LFHPs and perovskite derivatives for a broader range of fundamental research and practical applications.

Synthesis, crystal structure and photoresponse of tetragonal phase single crystal CH3NH3PbCl3

The performance of lead halogen perovskite is often closely related to its crystal structure. However, the chemical and optoelectronic properties of tetragonal phase single crystal MAPbCl3 (SC T-MAPbCl3) are rarely reported. In this study, we synthesized SC T-MAPbCl3 with the P4/mcc (124) space group by a modified inverse temperature crystallization (M-ITC) method. The twist angle of the Cl anion on the equatorial plane of the PbCl64- octahedron around the c-axis is 8.4°. The resistance (62 MΩ) of SC T-MAPbCl3 obviously decreased to 3 MΩ under 395 and 404 nm ultraviolet light. The photodetector based on SC T-MAPbCl3 under 3 V bias voltage exhibits high sensitivity (2.60 μA cm-2 under 1 W m-2 light intensity). The high selectivity of the device is in the ultraviolet region, rather than the visible region.

Organic–inorganic hybrid (CH3NH3)2FeCuI4Cl2 and (CH3NH3)2InCuI6 for ultraviolet light photodetectors

In this study, we fabricate photodetector device based on organic–inorganic hybrid (CH₃NH₃)₂FeCuI₄Cl₂ (MA₂FeCuI₄Cl₂) and (CH₃NH₃)₂InCuI₆ (MA₂InCuI₆) for the first time.

Green Solution-Processed Tin-Based Perovskite Films for Lead-Free Planar Photovoltaic Devices

The eco-friendly Sn-based perovskites have attracted more and more attention in lead-free perovskite photovoltaic field. However, the device performance and reproducibility are greatly challenged in preparing high-quality perovskite films. Here, we fabricated uniform and dense Sn-based perovskite films via a green gas pump treatment technology. Remarkably, we successfully fabricated a large-area (>20 cm²) Sn-based perovskite film with a mirror-like surface, which is the largest Sn-based perovskite film ever reported. Besides, we found that the phase separation phenomenon induced by excess SnF₂ was eliminated when the pressure is 1500 Pa. Finally, we fabricated highly reproducible Sn-based solar cells and obtained an inspiring efficiency of 1.85%, which is the highest reported efficiency for Sn-based devices with a configuration of fluorine-doped tin oxide/compact TiO₂/perovskite/hole transport material/electrode. Our results demonstrate the feasibility of using gas pump treatment technique to prepare high-quality Sn-based perovskite films, which paves a way for large-scale green manufacturing of Sn-based perovskite solar cells in the future.