Inorganic Halide Research Articles

All-Inorganic Halide Perovskites Boost High-Ranged Figure-of-Merit in Bi0.4Sb1.6Te3 for Thermoelectric Cooling and Low-Grade Heat Recovery.

The all-inorganic halide perovskite CsPbX3 (X = Cl, Br, or I) offers various advantages, such as tunable electronic structure and high carrier mobility. However, its potential application in thermoelectric materials remains underexplored. In this study, we propose a simple yet effective method to synthesize a CsPbX3/Bi0.4Sb1.6Te3 (BST) nanocomposite by sintering a uniformly mixed raw powder. The intrinsic excitation of the BST system is suppressed by exploiting the rich phase structure and tunable electrical transport properties of CsPbX3, and the thermoelectric properties were synergistically optimized. Notably, for CsPbI3, its phase-transition-induced dislocation arrays together with low group velocities drastically reduce thermal conductivity. As a result, the composite achieves an ultrahigh average figure-of-merit (ZT) of 1.4 from 298 to 523 K. The two-pair TE module demonstrates a superior conversion efficiency of 7.3%. This study expands the potential applications of inorganic halide perovskites, into thermoelectrics.

Circularly Polarized Photoluminescence in Chiral Hybrid Organic–Inorganic Manganese Halide Perovskites: From Bulk Materials to Exfoliated Flakes

AbstractLayered hybrid organic–inorganic metal‐halide perovskites (HOIPs) can acquire chirality from molecules incorporated into their structure showing exciting possibilities in optoelectronics and spintronics. However, researchers have focused their attention on the study of bulk compounds, namely unstable and toxic Pb HOIPs. Herein, the chiroptical properties of R‐ and S‐β‐methylphenethylammonium Mn chloride HOIPs are reported in both the bulk and the few‐layer limit as exfoliated flakes. Red photoluminescence (PL) emission originating from the octahedrally coordinated Mn2+ is observed, with a PL shift to longer wavelengths when passing from bulk to flakes. Circular dichroism and circularly polarized PL mirrored‐signals for enantiomers are found in bulk samples, while in flakes, a degree of circularly polarized emission (P) of up to 17% at 80 K is achieved, comparable to Pb‐based HOIPs. Moreover, angle‐resolved PL measurements on flakes show that the PL emission and P are isotropic. These findings highlight the potential of these HOIPs from bulk to flakes for spin‐optoelectronic applications.

High-quality organic–inorganic lead-free bismuth halide perovskite film for resistive switching memory application

High-quality organic–inorganic lead-free bismuth halide perovskite film for resistive switching memory application

Gram-scale microwave-assisted synthesis of high-quality CsPbBr3 nanocrystals for optoelectronic applications

Fully inorganic halide perovskite nanocrystals (NCs) are promising candidates for optoelectronic applications due to their beneficial properties such as their amenability to solution processing, high absorption coefficients, and high quantum yields. Various methods have been developed to prepare perovskite CsPbX3 (X = Cl, Br, and I) NCs; however, large-scale synthesis with high-quality CsPbX3 NCs remains challenging. In the study, we report an advanced method for the gram-scale synthesis of all-inorganic perovskite NCs via specially designed microwave-assisted synthesis, which offers uniform reaction energy transfer, excellent reproducibility, and flexible parameter tuning. The composition, size and uniformity of the CsPbBr3 NCs have been optimized by controlling the surfactant ratio, precursor ratio, and reaction time. This systematic optimization leads to the production of gram-scale (> 0.165 g per a 100 ml reaction mixture for a single synthesis cycle) high-quality, phase-pure CsPbBr3 NCs with a uniform size of ∼ 10 nm. These optimized NCs exhibit a sharp photoluminescence peak centered at 515 nm with a photoluminescence quantum yield of 94 % and produce excellent radioluminescence under X-ray irradiation. To test the feasibility of these NCs for use in real optoelectronic devices, a photodetector consisting of CsPbBr3 NCs and monolayer MoS2 was fabricated, demonstrating enhanced photosensitivity and a faster response time compared with a pure MoS2-based photodetector. The proposed gram-scale microwave-assisted synthesis method thus has the potential to promote the commercialization of metal halide perovskite NCs through cost-effective mass production for use in many optoelectronic applications.

Ligand engineering for improving the stability and optical properties of CsPbI3 perovskite nanocrystals

Inorganic lead halide perovskite nanocrystals (NCs) have recently become one of the research topics for optoelectronic applications due to their excellent photophysical properties. Despite their notable thermal stability over organic-inorganic halide perovskites, CsPbI3 NCs suffer from the phase instability of α-CsPbI3 phase at room temperature and under ambient conditions. Here, the effects of 4-Hydroxybenzoic acid (4-HBA) as an additive to standard oleic acid – oleylamine pair on the stability and optical properties of CsPbI3 perovskite NCs are discussed. 4-HBA addition into perovskite NC systems causes a compressive strain on perovskite lattice, which leads to the formation of a mixed phase α- and γ-CsPbI3 phases while pristine perovskite has α-CsPbI3 phase. Time-dependent stability of the perovskite NCs was tested under an ethanol (EtOH) medium. After EtOH exposure of the perovskite NCs, CsPbI3 NCs transformed to non-perovskite phase in 1 h while 4-HBA added CsPbI3 NCs still have perovskite phase after 48 h. In addition to the improved optical properties of the perovskite NCs, 4-HBA addition remarkably improves CsPbI3 perovskite stability.

Highly effective hybrid antimony chloride emitter with antithermal quenching phosphorescence emission for Solid-State lighting

Low-dimensional organic–inorganic metal halides, which have exceptional host–guest structures and high radiative recombination have emerged as a primary focus in the exploration of multifaceted optoelectronic materials. Nevertheless, the employment feasibility of these materials in optoelectronic field is significantly hindered by the unavoidable thermal quenching effect. In this paper, zero-dimensional (0D) hybrid metal halide (Ph3S)2SbCl5 exhibited a negative thermal quenching effect (NTQ) between 90 K and 300 K, and the color of the powder gradually changed from pink (670 nm) to orange (645 nm). The origin of the negative thermal quenching effect in (Ph3S)2SbCl5 is attributed to trap states induced by structural defects, as supported by experimental characterization and first-principles calculations. The potential application of this material in light-emitting diodes (LEDs) is explored, showing good color rendering index (95.2) and thermal stability. By uncovering the impact of defects on the photophysical characteristics of materials, this research paves the way for exploring novel approaches to enhance the performance of LEDs based on NTQ mechanism.

Superfluorescence in Metal Halide Perovskites

AbstractSuperfluorescence (SF) is a unique quantum optical phenomenon where an ensemble of atoms or molecules exhibit coherent emission of an intense burst of light of high directionality, with temporal coherence. SF exhibits ultrafast optical characteristics and is considerably explored in diverse inorganic and hybrid semiconductor materials at cryogenic temperatures, including inorganic and hybrid metal halide perovskites. Notably, SF is reported in different perovskites’ nanocrystal superlattices, alongside two examples in thin films, impressively achieving SF at room temperature. The density of quantum emitters, excited state characteristics, interaction strengths, and temperature all affect the SF threshold. Although significant progress is reported in the observance of SF phenomena, a full interpretation of the relationship between the factors that determine the SF threshold and the intrinsic material properties remains unclear. This review addresses the current state‐of‐the‐art observations of SF in perovskite systems, such as nanocrystal superlattices and thin films, elucidating the optical properties, ultrafast dynamics, and the proposed mechanisms for room‐temperature SF. The review concludes with a discussion on the existing challenges, unresolved questions, and future perspectives for advancing perovskite SF research

Strain-induced changes in the electronic, optical and mechanical properties of the inorganic cubic halide perovskite Sr3PBr3 with FP-DFT

In recent years, inorganic perovskite materials have garnered significant attention in solar technology due to their outstanding structural, optical, mechanical, and electronic properties. A comprehensive investigation, employing first-principles density-functional theory, was conducted to assess the impact of compressive and tensile strain on the optical and electrical properties of cubic perovskite Sr3PBr3. The unstrained Sr3PBr3 exhibits a direct bandgap of 1.528 eV/2.32 eV with PBE/HSE functions at the Γ point. Under compressive strain, the bandgap decreases (1.23 eV at −4% strain), leading to a redshift in the absorption coefficient spikes, while tensile strain results in a slight bandgap increase (1.723 eV at +4 % strain) and a blueshift in absorption coefficient spikes. Total density of states was computed as 18.75 and 1.60 electrons/eV at VB and CB without strain. The value of static dielectric constant was measured as 5.24. The initial critical point of dielectric constant, large absorption peak, and maximum loss function were calculated at 1.47, 7.28, and 9.15 eV without strain. The material demonstrates excellent light absorption in the range of visible light, aligning with its electronic properties. The Sr3PBr3 perovskite is therefore thought to be perfect for usage in solar cells for the generation of power and light control.

Effect of organic molecule layer on the interfacial engineering, stability, and conversion efficiency of the perovskite solar cell heterostructure

Stability in the perovskite solar cells (PSCs) is a major concern nowadays, and interfacial engineering is the key to achieving this most important issue. As per the interfacial engineering, the organic molecules may play a vital role in PSCs as we incorporate these as interfacial layers, mainly between perovskite absorber and hole transport layer. The latest reports confirm the usefulness of the organic–inorganic mixed halides perovskites-based PSCs over the purely inorganic or other PSCs with the organic hole transport layers such as spiro-OMeTAD. The focus of this featured letter is to discuss the effect of organic molecule layer on the interfacial engineering, stability and conversion efficiency of the PSC devices. Additionally, the efforts are dedicated to focusing on the importance of evolving new molecules to advance stability as well as the high photovoltaic output issues, including the commercialization issues, new opportunities, and future directions. These properties can be principally interesting for the interface engineering of PSCs.

Solution Processed Hybrid Lead Perovskite Films for White Light Emission and Lasing Applications

Abstract2D organic–inorganic hybrid lead halide perovskite films are fascinating optoelectronic materials for white‐light emission and lasing applications. Here, it is demonstrated that nano‐meter‐thick films of perovskites can be formed at room temperature using Langmuir–Schaefer (LS) deposition technique. In situ X‐ray measurements reveal a self‐assembly process of the 2D perovskite formation at the air–water interface. This formation process requires the presence of stearic acid monolayer on the water subphase having a solution of lead‐perovskite in dimethylformamide. Microscopy and X‐ray measurements of these nanofilms transferred onto substrates show crystalline phase formation that deviates from the known orthorhombic structure of the bulk crystals. The nanofilms exhibit novel broad optical emission with sharp band‐edge transition in temperature‐dependent photoluminescence studies. Also, their band‐edge emission is distinctly blue‐shifted compared to that of thicker 2D perovskite flakes prepared by the slow‐cooling chemical synthesis process. 2D flakes exhibit lasing that cannot be obtained in the LS nanofilms as their thicknesses are lower than the lasing wavelength prohibiting wave‐guide formation. The results show that the 2D single‐crystalline nature of the LS films and flakes are suitable materials to develop broad‐band white light emission across the entire visible range and to obtain lasing without external cavities, respectively.

Wide‐Gap Perovskites for Indoor Photovoltaics

Organic–inorganic halide perovskite semiconductors have revolutionized next‐generation photovoltaics (PV) due to several characteristics such as solution‐processability, gap tunability, and excellent charge generation and transport properties. This has made them very adaptable for various applications in light harvesting and photodetection. One such rapidly growing application is indoor photovoltaics (IPV) which have the potential to power standalone Internet of Things devices. IPV requires wider optimal bandgaps than solar cells (1.8 vs 1.3 eV) due to the differences between the spectra of artificial lights versus solar radiation. For IPV applications, the active layer wide‐gap perovskite must be developed systemically considering all other components of the device, such as interlayers, electrodes, and scaling. This perspective provides an overview of the potential and challenges facing perovskite‐based IPV from a theoretical, material, and experimental perspective. Furthermore, accurate characterization of perovskite IPVs under simulated indoor conditions is discussed and candidate perovskite PV (PPV) systems are presented to provide insight into IPV development. These include IPV‐optimized formamidinium cesium‐based perovskite, wide‐gap p‐i‐n devices, and 2D perovskite devices, tested under spectrophotometrically calibrated LED illumination at various indoor‐relevant illuminances and benchmarked against thermodynamic predictions. Finally, strategies required to create stable, optimized PPV devices for indoor applications are discussed.

Electronic structure and effective mass of pristine and Cl-doped CsPbBr3

Organic–inorganic lead halide perovskites (LHPs) have attracted great interest owing to their outstanding optoelectronic properties. Typically, the underlying electronic structure would determinate the physical properties of materials. But as for now, limited studies have been done to reveal the underlying electronic structure of this material system, comparing to the huge amount of investigations on the material synthesis. The effective mass of the valance band is one of the most important physical parameters which plays a dominant role in charge transport and photovoltaic phenomena. In pristine CsPbBr3, the Fröhlich polarons associated with the Pb–Br stretching modes are proposed to be responsible for the effective mass renormalization. In this regard, it would be very interesting to explore the electronic structure in doped LHPs. Here, we report high-resolution angle-resolved photoemission spectroscopy (ARPES) studies on both pristine and Cl-doped CsPbBr3. The experimental band dispersions are extracted from ARPES spectra along both Γ¯ – M¯ – Γ¯ and X¯ – M¯ – X¯ high symmetry directions. DFT calculations are performed and directly compared with the ARPES data. Our results have revealed the band structure of Cl-doped CsPbBr3 for the first time, which have also unveiled the effective mass renormalization in the Cl-doped CsPbBr3 compound. Doping dependent measurements indicate that the chlorine doping could moderately tune the renormalization strength. These results will help understand the physical properties of LHPs as a function of doping.

Regulating photoluminescence through single-crystal-to-single-crystal transformation of solvent-containing zero-dimensional hybrid metal halide isomers

Regulating photoluminescence (PL) properties induced by single-crystal-to-single-crystal (SCSC) transformation has sparked significant interest in the research of zero-dimensional organic–inorganic metal halides (0-D OIMHs). To best of our knowledge, the SCSC transformation of solvent-containing 0-D OIMH isomers hasn’t been reported yet. In this work, we report the first example of SCSC transformation between two isomers containing lattice solvent molecules, namely α- and β-[EtPPh3]2[SbCl5]·MeCN (α- and β-1·MeCN; EtPPh3 = ethyltriphenylphosphonium; MeCN = acetonitrile). Differential scanning calorimetry (DSC) results show that the SCSC transformation from α- to β-1·MeCN is an exothermic process, implying that β-1·MeCN is a more stable phase than α-1·MeCN. Moreover, α- and β-1·MeCN exhibit bright orange (emission peak: 610 nm) and red (emission peak: 635 nm) emission under 360/365 nm excitation, respectively. DFT calculations suggest that the negligible self-absorption and a strong exciton confinement contribute to their effective PL emission. By analyzing temperature-dependent PL spectra, β-1·MeCN has been found to exhibit stronger electron-phonon coupling under excitation than α-1·MeCN. Thus, the broader emission with full width at half maximum (FWHM: 134 vs. 147 nm) and the higher photoluminescence quantum yield (PLQY: 40.37% vs. 70.50%) have been realized by SCSC transformation from α- to β-1·MeCN by heating at 92 °C. Benefitting from the regulation of PL performances brought by SCSC transformation, the white light-emitting-diode (LED) devices assembled by using β-1·MeCN as red phosphor could be optimized, and the CRI reaches as high as 95.3.

Boosted Second Harmonic Generation of a Chiral Hybrid Lead Halide Resonant to Charge Transfer Exciton from Metal Halide Octahedra to Ligand

AbstractChiral hybrid organic–inorganic metal halides (HOMHs) offer an ideal platform for the advancement of second‐order nonlinear optical (NLO) materials owing to their inherent noncentrosymmetric structures. The enhancement of optical nonlinearity of chiral HOMHs could be achieved by matching the free exciton and/or self‐trapped exciton energy levels with desired NLO frequencies. However, the current scarcity of resonance modes and low resonance ratio hamper the further improvements of NLO performance. Herein, we propose a new resonant channel of charge transfer (CT) excited states from metal halide polyhedra to organic ligand to boost the second‐order optical nonlinearity of chiral HOMHs. The model lead halide (C7H10N)PbBr3 (C7H10N=1‐ethylpyridinium) exhibits a drastically enhanced second harmonic generation in resonance to the deep CT exciton energy, with intensity of up to 111.0 times that of KDP and 10.9 times that of urea. The effective NLO coefficient has been determined to be as high as ~40.2 pm V−1, balanced with a large polarization ratio and high laser damage threshold. This work highlights the contribution of organic ligands in the construction of a resonant channel for enhancing second‐order NLO coefficients of metal halides, and thus provides guidelines for designing new chiral HOMHs materials for advanced nonlinear photonic applications.

Computational study of stability, photovoltaic, and thermoelectric properties of new inorganic lead-free halide perovskites

Abstract Due to their rich and extraordinary properties, halide perovskites have gained attention over time for their applications in thermoelectric and solar cells. Here, several physical properties (stability, photovoltaic, and thermoelectric) of inorganic halide perovskites XZnI3 (X = Na, K, Rb, Cs) are predicted using the density functional theory (DFT) within the Wien2k code. The optimization of structural parameters has been calculated using PBE-GGA approach. The tolerance factor, Born criteria, phonon dispersion, and negative formation energy show the formation and stability of these studied materials in the ideal cubic structure. Additionally, the modified Becke-Johnson method is applied for optoelectronic and transport properties. All compounds exhibit the nature of indirect band gap semiconductors with better absorption in the visible and ultraviolet regions 10^{5} \textrm {cm}^{-1})$ ?> . The transport properties present high electrical conductivity, large Seebeck coefficient, and good (PF, ZT) factors for all these materials. Finally, all these properties of inorganic halide perovskites open up new possibilities for efficient applications in thermoelectric and solar cells.

A novel halide hybrid white light emitter with remarkable structural and emission stability

Addressing the issues of self-absorption effect among different components in traditional white light-emitting diodes (WLEDs) and the high cost associated with rare earth elements, we propose the potential utility of zero-dimensional organic–inorganic metal halide hybrids (0D OIMHs) in white WLEDs fabrication. In this study, we synthesized a novel 0D OIMH, (C5N2H14)ZnCl4, characterized by broadband white light emission. The (C5N2H14)ZnCl4 crystal features a short ultraviolet cutoff situated at 190 nm and emits cold white light with a Color Rendering Index (CRI) of 73 under an excitation wavelength of 260 nm. Furthermore, (C5N2H14)ZnCl4 demonstrates exceptional structural and emission stability in an air atmosphere over a span of three months.

Surface stability and morphological transformations of CsPbI3

Metal-halide perovskites, particularly inorganic cesium-lead halide perovskites, have emerged as exceptional candidates for several technological applications in the 21st century, such as photovoltaic devices, optoelectronic and photocatalysis. This study systematically investigates the CsPbI3 surfaces through density functional theory (DFT) simulations and morphological analyses. The (001), (110), and (111) surfaces were investigated in terms of their possible terminations (here named α, β, γ, δ and ε), where the relations between their outermost coordination polyhedra, bond lengths, charge distribution, electronic and morphological properties were revealed. The results demonstrate that the (001) and (110) surfaces stand out as the most stables, with Esurf001-α=Esurf110-γ=0.08J/m2. Concerning the electronic properties, it is observed that the (110) and (111) present α terminations with acceptor states, while the β with donor states, making it possible to tune the system semiconducting behavior (n or p-type) via surface termination control. The Wulff construction was employed to show that (001), (110) and (111) surface stabilizations can produce cubic, dodecahedral and octahedral nanocrystal morphologies, respectively. By probing the depths of CsPbI3 surfaces, this research advances new concepts about the design and functionalization of perovskite halide, offering a crucial direction for experimental synthesis strategies.

Tuning the physical properties of inorganic novel perovskite materials Ca3PX3 (X=I, Br and Cl): Density function theory

In photovoltaic technology, inorganic perovskite solar cells formed from halide have developed into a noteworthy prospect, primarily attributable to their exceptional efficiency, cost-effectiveness, and straightforward manufacturing techniques. Lead-free A3BX3 inorganic perovskites have generated significant attention within the environmentally friendly solar industry thanks to their extraordinary characteristics encompassing thermoelectricity, optoelectronics, and elasticity. This research focuses on the attributes of the structural, electrical, and optical inorganic halide perovskites Ca3PX3 (X = I, Br, and Cl) using the first-principles density-functional theory (FP-DFT). According to the electronic band structures, Ca3PI3, Ca3PBr3, and Ca3PCl3 show semiconductor characteristics with a straight bandgap of 1.4909 eV, 1.9502 eV, and 2.2058 eV, respectively, at the Γ(gamma)-point. Whenever one takes consideration into account the spin-orbital coupling (SOC) effect, the bandgap of the Ca3PI3, Ca3PBr3, and Ca3PCl3 perovskites is minimized to 1.2382 eV, 1.6456 eV, and 1.9056 eV. All these structures' bandgaps are compressed under compressive strain while they expand with tensile strain. The optical properties indicate that these materials have outstanding visible light consumption capabilities due to their distinct band features, comprising functions of dielectric, consumption coefficient, and function of electron collapse. Observations indicate that the dielectric constant peaks of Ca3PX3 (where X represents I, Br, or Cl) exhibit a redshift, moving towards lower photon energy levels as compressive strain increases. Conversely, they show a blueshift behavior, shifting to a greater amount of photon energy levels by applying tensile strain. Therefore, these characteristics render Ca3PX3 perovskites highly suitable for optimizing light guidance for solar power and energy retention tools.

Three new low-dimensional organic inorganic hybrid metal halides: Syntheses, structures and properties

It is well known that organic inorganic hybrid metal halides have been excellent materials in the field of luminescence. So far, organic-inorganic Pb(Ⅱ) halide hybrids materials have been extensively studied for their excellent optical properties. However, the toxicity of lead may generate additional pollution. It is important to develop new lead-free halide hybrids. In this work, three new organic inorganic hybrid metal halides, namely [(C4H10NO)Ag2I3] (1), [(C4H10NO)2CuI2.5]·0.5I·0.5H2O (2) and [(C4H9NO)2CdI2] (3) were synthesized under mild conditions. Compounds 1 and 2 display different one dimensional inorganic chains surrounded by organic amine cations, while compound 3 shows a zero dimensional structure. Their luminescent and optical properties were investigated in detail. The result suggests that these three compounds are potential optical materials.

Intense-Light Sensing Yarns Achieved by Interfused Inorganic Halide Perovskite Nanofiber Network

Intense-Light Sensing Yarns Achieved by Interfused Inorganic Halide Perovskite Nanofiber Network