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Air-Stable, Lead-Free Zero-Dimensional Mixed Bismuth-Antimony Perovskite Single Crystals with Ultrabroad Band Emission
摘要： Lead-free zero-dimensional (0D) organic-inorganic metal halide perovskites have recently attracted increasing attention for their excellent photoluminescence properties and chemical stability. Here, we report the synthesis and characterization of an air-stable 0D mixed metal halide perovskite (C8NH12)4Bi0.57Sb0.43Br7.H2O, in which individual [BiBr6]3- and [SbBr6]3- octahedral units are completely isolated and surrounded by the large organic cation C8H12N+. Upon photoexcitation, the bulk crystals exhibit ultrabroad band emission ranging from 400 to 850 nm, which originates from both free excitons and self-trapped excitons. This is the first example of 0D perovskites with broadband emission spanning the entire visible spectrum. In addition, (C8NH12)4Bi0.57Sb0.43Br7.H2O exhibits excellent humidity and light stability. These findings present a new direction towards the design of environmentally-friendly, high-performance 0D perovskite light emitters.
关键词： lead-free,bismuth,antimony,photoluminescence,zero-dimensional perovskites
更新于2025-09-19 17:15:36
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DFT study of electronic structure and optical properties of layered two-dimensional CH <sub/>3</sub> NH <sub/>3</sub> PbX <sub/>3</sub> (X=Cl, Br, I)
摘要： Two-dimensional (2D) organic–inorganic hybrid halide perovskites (OIHPs) have been considered by researchers in the field of solar cells due to their high-temperature stability. In this paper, the electronic and optical properties of single-layer (SL) and multilayer (ML) structures of MAPbX3 (X = Cl, Br, I and MA = CH3NH3) have been studied by density functional theory (DFT) in order to predict its photovoltaic capabilities. The results have shown that SL- and ML-MAPbX3 have a direct band gap in the range of 1.76–2.70 eV. The calculation of dielectric constants has depicted that the static dielectric constants (SDCs) of SL-MAPbX3 are smaller than SDCs of ML-MAPbX3. However, as we expected, the reaction of the structures to in-plane (║) and out-of-plane (┴) polarizations was different; therefore, the SL- and ML-MAPbX3 (X = Cl, Br, I) were optically anisotropic. In addition, the intensity of the optical absorption spectrum for ML-MAPbX3 structures is approximately three times higher than that of SL-MAPbX3 structures. By increasing the radius of halogens (RCl<RBr<RI), surface area under the absorption curve increases and absorbs more. Furthermore, our results have shown that the electronic and optical behavior of 2D-MAPbX3 is suitable for photovoltaic applications and makes them useful for OIHP solar cells.
关键词： optical properties,DFT,2D-MAPbX3,organic–inorganic hybrid halide perovskites,solar cell
更新于2025-09-19 17:15:36
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Synthesis of thermally stable and highly luminescent spherical shaped ligand-free Cs4PbBr6 nanospheres with a single polar solvent
摘要： We demonstrate a simple method to synthesis thermally stable and green luminescent ligand-free Cs4PbBr6 nanospheres (NS) with a polar solvent. In this approach, a single polar solvent, N,N-dimethylformamide (DMF) is sufficient enough to convert precursors into cubic shaped ligand-free Cs4PbBr6 crystals. Further, the morphology of cubic shaped Cs4PbBr6 crystals is reformed into spherical shaped Cs4PbBr6 NS by prolonged DMF washing (overnight stirring, 15 h). Besides, the reduction in average particle size of spherical shaped Cs4PbBr6 NS (~70 nm) to one-fourth to the original size of cubic Cs4PbBr6 crystals (~310 nm). The ligand-free spherical shaped Cs4PbBr6 NS showed a high photoluminescence quantum yield of 42.5%, which could compete the conventional ligand mediated Cs4PbBr6 crystals. Moreover, spherical shaped Cs4PbBr6 NS exhibited a high thermal stability even at 200 °C without sacrificing luminescence intensity. Hence, it is foreseen that this approach brings a new strategy to prepare ligand-free Cs4PbBr6 NS as a promising material in optoelectronic devices.
关键词： Perovskites,Single solvent,Nanospheres,Ligand-free,Cs4PbBr6
更新于2025-09-19 17:15:36
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DFT study of SmXO <sub/>3</sub> (X = Al and Co) for elastic, mechanical and optical properties
摘要： The first-principles study of cubic perovskites SmXO3 (X=Al and Co) for elastic, mechanical and optical properties is done in the framework of density functional theory (DFT). Optimized structural parameters are obtained first to find mechanical and optical properties of the materials. These obtained structural parameters are in accordance with the published data. The cubic elastic parameters C11, C12 and C44 are then calculated by using generalized gradient approximation (GGA) as an exchange correlation functional in Kohn–Sham equations. Poisson’s ratio, shear modulus, Young’s modulus and anisotropic factor are deduced from these elastic parameters. These compounds are found to be elastically anisotropic and SmAlO3 is brittle while SmCoO3 is ductile. Their covalent nature is also discussed by using Poisson’s ratio. In addition, optical properties like absorption coefficient, extinction coefficient, energy loss function, dielectric function, refractive index, reflectivity and optical conductivity are studied. This study predicts that SmAlO3 and SmCoO3 are suitable for optoelectronic devices.
关键词： mechanical properties,optical properties,perovskites.,elastic constants,DFT,optical constants
更新于2025-09-19 17:15:36
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Learning-in-Templates Enables Accelerated Discovery and Synthesis of New Stable Double-Perovskites
摘要： In the past three years, Machine Learning (ML) in combination with Density Functional Theory (DFT) has enabled computational screening of compounds with the goal of accelerated materials discovery. Unfortunately, DFT+ML has, until now, either relied on knowledge of the atomic positions at DFT energy minima, which are a priori unknown, or has been limited to chemical spaces of modest size. Here we report a strategy that we term Learning-in-Templates (LiT) wherein we first define a series of space group and stoichiometry templates corresponding to hypothesized compounds and, orthogonally, we allow any list of atoms to take on any template. The LiT approach is deployed in combination with previously-established position-dependent representations and performs best with the representations that rely least on the atomic positions. Since the positions of the atoms in templates are known and do not change, LiT enables us to infer the properties of interest directly; additionally, LiT allows working with increased chemical spaces, since the same elements can take on a large number of templates. Only by using LiT were we able to span a 5x106 double perovskite compounds and achieve an acceleration factor of 700 compared to brute-force DFT, allowing us to predict never-before-screened compounds. Our findings motivated us to synthesize a new BaCuyTa(1-y)S3 perovskite which we show using an Electron Probe Microanalyzer has a 5:3 molar ratio of Cu to Ta, and using powder X-ray Diffraction (XRD) analysis combined with a DFT-based XRD simulation and fitting indicate a new phase having a I4/m space group.
关键词： Atomic Representation,Machine Learning,Density Functional Theory,Double Perovskites
更新于2025-09-19 17:15:36
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Halide perovskites for resistive random-access memories
摘要： Halide perovskite based resistive random-access memory (ReRAM) devices are emerging as a new class of revolutionary data storage devices because their switching material—halide perovskite—has received considerable attention in recent years. Among the electrical characteristics of the material, its current–voltage (I–V) hysteresis, which may occur due to defect formation and migration, means that ReRAM can employ halide perovskites as a resistive switching material. Many studies have been conducted on resistive switching materials; however, the investigation of halide perovskites for ReRAM devices is still in the early research stages; therefore, the application of halide perovskites in ReRAM devices is a topic worth studying. Herein, we introduce halide perovskites and their operating mechanism within a ReRAM device. Moreover, recent notable achievements along with future challenges have been reviewed.
关键词： Halide perovskites,ion migration,hysteresis,resistive random-access memories,switching materials,ReRAM
更新于2025-09-19 17:15:36
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Dynamic Screening and Slow Cooling of Hot Carriers in Lead Halide Perovskites
摘要： Among the exceptional properties of lead halide perovskites (LHPs) is the ultraslow cooling of hot carriers. Carrier densities below the Mott density for large polarons (≤ ≈1018 cm?3) are focused on here. As in other semiconductors, a nascent hot electron distribution initially cools down via emission of longitudinal optical (LO) phonons on the 10?14–10?13 s timescale. What distinguishes LHPs from conventional semiconductors is the exceptionally efficient screening in the former. The dielectric screening in LHPs on the 10?13 s timescale results in an order-of-magnitude reduction in the Coulomb potential upon the formation of a large polaron, likely with ferroelectric-like local ordering. Further LO-phonon emission is inhibited, and this leads to partial retention of hot electron energy on the 10?12 s timescale, more so in hybrid LHPs than in their all-inorganic counterparts. Further cooling of hot polarons occurs on the 10?10 s timescale, and this can be attributed to the slow diffusion of heat out of the large polaron volume due to the low thermal conductivity of LHPs. Like other carrier properties, slow hot carrier cooling in LHPs can be intimately related to efficient screening in a soft, anharmonic, and dynamically disordered lattice.
关键词： dielectric function,lead halide perovskites,screening,hot electrons,large polarons
更新于2025-09-19 17:15:36
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2D/3D Heterostructure for Semitransparent Perovskite Solar Cells with Engineered Bandgap Enables Efficiencies Exceeding 25% in Foura??Terminal Tandems with Silicon and CIGS
摘要： Wide-bandgap perovskite solar cells (PSCs) with optimal bandgap (Eg) and high power conversion efficiency (PCE) are key to high-performance perovskite-based tandem photovoltaics. A 2D/3D perovskite heterostructure passivation is employed for double-cation wide-bandgap PSCs with engineered bandgap (1.65 eV ≤ Eg ≤ 1.85 eV), which results in improved stabilized PCEs and a strong enhancement in open-circuit voltages of around 45 mV compared to reference devices for all investigated bandgaps. Making use of this strategy, semitransparent PSCs with engineered bandgap are developed, which show stabilized PCEs of up to 25.7% and 25.0% in four-terminal perovskite/c-Si and perovskite/CIGS tandem solar cells, respectively. Moreover, comparable tandem PCEs are observed for a broad range of perovskite bandgaps. For the first time, the robustness of the four-terminal tandem configuration with respect to variations in the perovskite bandgap for two state-of-the-art bottom solar cells is experimentally validated.
关键词： tandem solar cells,copper indium gallium diselenide,2D perovskites,3D perovskites
更新于2025-09-19 17:13:59
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Tin and Mixed Leada??Tin Halide Perovskite Solar Cells: Progress and their Application in Tandem Solar Cells
摘要： Metal halide perovskites have recently attracted enormous attention for photovoltaic applications due to their superior optical and electrical properties. Lead (Pb) halide perovskites stand out among this material series, with a power conversion efficiency (PCE) over 25%. According to the Shockley–Queisser (SQ) limit, lead halide perovskites typically exhibit bandgaps that are not within the optimal range for single-junction solar cells. Partial or complete replacement of lead with tin (Sn) is gaining increasing research interest, due to the promise of further narrowing the bandgaps. This enables ideal solar utilization for single-junction solar cells as well as the construction of all-perovskite tandem solar cells. In addition, the usage of Sn provides a path to the fabrication of lead-free or Pb-reduced perovskite solar cells (PSCs). Recent progress in addressing the challenges of fabricating efficient Sn halide and mixed lead–tin (Pb–Sn) halide PSCs is summarized herein. Mixed Pb–Sn halide perovskites hold promise not only for higher efficiency and more stable single-junction solar cells but also for efficient all-perovskite monolithic tandem solar cells.
关键词： tandem solar cells,mixed Pb–Sn halide perovskites,tin halide perovskites,perovskite solar cells
更新于2025-09-19 17:13:59
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Novel Lewis Base Cyclam Self-Passivation of Perovskites without Anti-Solvent Process for Efficient Light-Emitting Diodes
摘要： Metal halide perovskites have been focused as a candidate applied as a promising luminescent material for next-generation high-quality lighting and high-definition display. However, as perovskite film formed, high density of defects would produce in solution processing inevitably, leading to low exciton recombination efficiency in light-emitting diodes (LEDs). Herein, a facile and novel self-passivation strategy to inhibit defects formation in perovskite film for constructing high performance LEDs is developed. For the first time, we introduce 1,4,8,11-tetraazacyclotetradecane (cyclam) in perovskite precursor solution and it spontaneously passivates defect states of CsPbBr3-based perovskite by coaction between amine and uncoordinated lead ions during spin-coating without anti-solvent process. Furthermore, as a delocalized system, cyclam also possesses chemical properties that facilitate exciton transportation. The proposed passivation strategy boosts the external quantum efficiency (EQE) from 1.25% (control device) to 16.24% (cyclam-passivated device). Further, defects passivation is also conductive to reduce LED degradation paths and improve device stability as the extrapolated lifetime (T50) of LEDs at an initial brightness of 100 cd/m2 is increased from 0.9 h to 127 h. These findings indicate the introduction of cyclam is highly effective to enhance the performance of LEDs, and such strategy in effectively reducing the defects could be also applied in other perovskite-based devices, such as lasers, solar cells, and photodetectors.
关键词： perovskites,self-passivation,light-emitting diodes,defect states,Lewis base cyclam
更新于2025-09-19 17:13:59