Developing two-dimensional (2D) magnets that integrate high thermodynamic stability, high Curie temperature, intrinsic half-metallic properties, and tunability remains a significant challenge. This study, based on density functional theory (DFT), investigates the structural stability, magnetic properties, electronic properties, and mechanical characteristics of the DJ-phase CsMnCl4 perovskite in both 2D and 3D forms. The results show that CsMnCl4 exhibits excellent thermodynamic and dynamic stability: 2D CsMnCl4 has a ferromagnetic (FM) ground state, while 3D CsMnCl4 exhibits in-plane ferromagnetic and interlayer antiferromagnetic (AFM) coupling. The 2D CsMnCl4 is an intrinsic nodal-line half-metal, with metallic properties in the spin-up channel and a large bandgap in the spin-down channel, achieving 100% spin polarization. The spin-up channel of 2D CsMnCl4 exhibits linear dispersion crossing near the Fermi level, with a Fermi velocity as high as 3.52 & times; 105 m/s. Meanwhile, the 2D system has a TC of 206.11 K and a magnetic anisotropy energy (MAE) of 694 mu eV/Mn. Furthermore, structural distortions that introduce symmetry breaking and lift orbital degeneracy, combined with crystal field effects and enhanced p-d hybridization, provide a controllable pathway for CsMnCl4 to evolve from a nodal-line half-metal to a semiconductor. Strain and structural modulation also significantly enhance the magnetic anisotropy of the 2D system, while 3D CsMnCl4 demonstrates excellent mechanical stability and ductility, highlighting the potential of CsMnCl4 in spintronics and multifunctional applications.

Buried interface defects in perovskite solar cells (PSCs) critically limit the device performance and operational stability due to their role in promoting non-radiative recombination and interfacial degradation. Herein, we propose a molecular interface engineering strategy employing a bifunctional small molecule, 3,5-dimethylpyrazole-1-carboxamidin nitrate (DPN), to simultaneously modulate crystallization behavior and passivate undercoordinated Pb2+ ions at the buried interface. Morphological and crystallographic analyses reveal that DPN promotes large grain size, enhanced surface uniformity, and improved vertical crystal orientation. Spectroscopic characterizations confirm a dual-site coordination mechanism, where the pyrazole group acts as the primary coordination site, and the nitrate group provides auxiliary binding to Pb2+, collectively reducing defect densities. As a result, the DPN-modified films exhibit suppressed non-radiative recombination, extended carrier lifetimes, optimized interfacial energy alignment, and improved charge extraction. The corresponding photovoltaic devices deliver a champion power conversion efficiency (PCE) of 25.3%, along with enhanced operational and storage stability. This work demonstrates the efficacy of dual-site molecular passivation at the buried interface, offering a viable strategy for developing highly efficient and stable perovskite photovoltaics.

Combining three-dimensional (3D) perovskites with other two-dimensional materials to form van der Waals (vdW) heterostructures has emerged as an important strategy in the design of electronic and optoelectronic devices. In this study, based on first-principles calculations, we constructed two van der Waals heterostructures composed of three-dimensional HAPbBr3 [HA:(NH2NH3)+] and two-dimensional black phosphorus (BP), namely BP/HAPbBr3 (left-type) and HAPbBr3/BP (right-type) configurations, and systematically investigated their structural, electronic, and optical properties. The results demonstrate that the BP/HAPbBr3 heterostructure exhibits good structural stability at room temperature. This heterostructure presents a type-I band alignment characteristic, with its bandgap approaching the optimal value required for double-junction solar cells, and exhibits high carrier mobility. Furthermore, external electric fields can effectively modulate the band structure and band offset of the heterojunction, inducing a transition from semiconducting to metallic states. The study reveals that when an electric field of -0.2 V/& Aring; is applied to the left-type heterostructure, the bandgap value remains essentially unchanged; meanwhile, its band alignment transforms into Type II. This transition promotes spatial separation of electrons and holes, thereby significantly suppressing carrier recombination. Under electric field effects, significant shifts occur in the band edge positions of both HAPbBr3 and BP. Notably, both heterostructures exhibit a significant enhancement effect on the light absorption performance of the perovskite layer. In summary, van der Waals heterostructures composed of three-dimensional small-molecule perovskites and black phosphorus demonstrate promising application prospects in photovoltaic and optoelectronic devices.

The search for 2D magnetic materials with high spin polarization, elevated Curie temperature, and strong magnetic anisotropy remains a pressing challenge in the field of spintronics. Considering that the magnetic design potential of Dion-Jacobson (DJ) phase 2D perovskites has not yet been fully explored, this study employs first-principles calculations to design and systematically investigate a novel DJ-phase 2D magnetic perovskite, MA2Mn2Cl8 (MA+ =CH3NH3+). The results of AIMD simulations, phonon spectrum, and structural parameter analyses confirm the excellent structural stability of this material. Its ground state is ferromagnetic, exhibiting a typical ferromagnetic half-metallic behavior characterized by 100 % spin polarization at the Fermi surface and a Fermi velocity of 2 x 105 m/s. This feature is verified to be robust across multiple computational approaches, including PBE, GGA + U, PBE + SOC, and HSE06 hybrid functional calculations. The estimated Curie temperature (TC) is approximately 245 K, which is significantly higher than that of conventional 2D ferromagnetic materials, and the magnetic anisotropy energy (MAE) reaches 2.3 meV. Overall, this material overcomes the performance limitations of traditional 2D magnetic systems, providing an ideal candidate for next-generation spintronic devices, and opens up new possibilities for the application of DJ-phase perovskites in the field of magnetic materials.

Flexible supercapacitors have garnered significant attention in the research of flexible energy storage devices in recent years due to their advantages of rapid charging and discharging capabilities, long cycle life, high power density, and outstanding mechanical flexibility. Manganese dioxide (MnO2) has a high theoretical specific capacitance (1370 F g-1) and high crystal phase and morphology tunability, but low conductivity limits performance. Hydrothermal methods can customize nanostructures, but require harsh conditions and a high percentage of conductive agent and binder in the powder electrode, reducing energy density. In this study, MXene nanosheets with excellent conductivity were deposited onto flexible carbon cloth (CC, collector) via a composite fabrication strategy to fabricate MXene/CC. The MXene/CC served as a substrate for further in-situ MnO2 loading through a mild solution immersion process under ambient conditions. After optimization, the MnO2 micro-spheres formed after 8 immersions exhibited the superlative performance. Notably, this method is environmentally benign, easy to operate, and free of conductive agents or binders. The MnO2@MXene@CC-8 (MMC-8, obtained by 8 immersion cycles) positive electrode exhibited a specific capacitance of 234.8 F g-1 at 1 A g-1 in a neutral electrolyte (0.5 M Na2SO4), while the MMC-8//MC asymmetric flexible supercapacitor, employing MXene@CC (MC) as the negative electrode, achieved a capacitance of 21.3 F g-1 at 1 A g-1 with 75 % capacitance retention after 10000 cycles. The device demonstrated an energy density of 9.6 Wh kg-1 at a power density of 902.3 W kg-1. This strategy provides new insights into the scalable fabrication of flexible supercapacitors.

Defect passivation at the surface and grain boundaries of perovskite films is vital for improving both the efficiency and operational stability of perovskite solar cells (PSCs). Here, we report a dual-function nitrogen-rich small molecule, 1H-pyrazole-1-carboxamidine hydrochloride (PCH), as an effective defect passivator for inverted PSCs. PCH is simultaneously employed as a precursor additive for bulk passivation (BP) and as a surface treatment agent for surface passivation (SP), forming a synergistic BP&SP strategy. This combined approach significantly suppresses non-radiative recombination and enhances interfacial energy level alignment. Compared to single-passivation treatments, the BP&SP strategy promotes improved perovskite crystallinity, reduced trap densities, prolonged carrier lifetimes, and more efficient charge transport. As a result, the champion device achieves a power conversion efficiency of 24.75 % with negligible hysteresis and enhanced operational durability. Notably, unencapsulated devices retain over 93 % of their initial efficiency after 1500 h of ambient storage, and over 95 % after 800 h of continuous illumination. This study demonstrates a simple yet powerful molecular engineering route for simultaneously boosting the performance and long-term stability of inverted PSCs through comprehensive defect management.

Despite remarkable progress in the synthesis of rare-earth nanomaterials, achieving precise control over the distribution of lanthanide ion (Ln3+) dopants remains a formidable challenge. Previous studies that utilized NaYF4 with mixed cation occupancy have offered valuable insights into nonuniform elemental doping and its influence on the emission properties of the materials. However, the complex interplay among cation distribution, structural transformation, and luminescent characteristics has not been fully understood and elucidated. This lack of comprehensive knowledge significantly hinders the optimization of the performance of nanomaterials. In this study, the structural transformation of individual beta-NaYF4:Eu3+ nanoparticles under electron beam irradiation was systematically investigated. A discovery was made regarding the transition to a cubic phase. Elemental analysis of the pristine samples revealed that sodium was enriched at the edges of the nanoparticles. This sodium enrichment seemingly initiates the structural transition, which propagates from the surface toward the interior of the particles. Correlated cathodoluminescence electron microscopy (CCLEM) was employed in this research. The results confirmed that the emission intensity is highly correlated with the elemental distribution. Moreover, the structural disorder within the cubic phase leads to a decrease in the site symmetry compared to the theoretical Eu3+ luminescence. Overall, this study provides a more in-depth understanding of how elemental distribution impacts both the structural features and luminescent behavior of these materials. As a result, it makes a significant contribution to the development of optimized nanomaterials with enhanced performance.

Organic-inorganic perovskite solar cells have garnered widespread attention due to their high efficiency, cost-effectiveness, ease of fabrication, and rapid development. Their excellent performance is primarily attributed to high optical absorption, long carrier lifetime, and high electron-hole mobility. To obtain perovskite materials with superior properties, the dynamic stability, electronic properties, transport properties, and optical properties of APbI3 (A=EA, CA, and HA) were investigated using density functional theory (DFT). The formation energy calculations for the three perovskites indicate their ease of preparation. Molecular dynamics simulations and phonon spectrum analyses show that these newly synthesized cationic three-dimensional perovskites possess high stability under ambient conditions. The band structures, effective carrier masses, carrier mobilities, absorption spectra, and power conversion efficiency (PCE) of these novel organic cation perovskites were studied. The tunability of the band structures and band gaps of EAPbI3, CAPbI3, and HAPbI3 were examined under pressures ranging from 0.1 to 1.1GPa. Further band gap tunability from 0.67eV to 3.12eV, suitable for both single-junction and tandem multi-junction solar cells, was achieved by replacing Pb with non-toxic Sn (ASnI3) and substituting I ions with Br ions (APbBr3). In conclusion, the three newly proposed organic cationic three-dimensional perovskite materials exhibit strong structural stability under both pressure and non-pressure conditions, providing significant support for the development of efficient and stable perovskite solar materials.

Lead-halide perovskite (LHP) nanoparticles (NPs), such as CsPbBr3, exhibit exceptional luminescent properties, making them promising candidates for optoelectronic applications. However, maintaining their stability on solid substrates is challenging due to light and heat-induced degradation, even without water and oxygen. Although various post-processing methods aim to enhance stability, achieving this without compromising luminescence is difficult yet critical for practical devices. This study investigates the stability of monolayer CsPbBr3 NPs under simulated light and thermal stress, identifying accelerated post-growth processes as the main instability source. To address this, we evaluated surface ligand post-treatments, including ultraviolet-ozone, plasma, and electron beam (e-beam) irradiation. Among these, low-dose e-beam irradiation proved most effective, significantly enhancing both luminescence and structural stability. Using correlative cathodoluminescence electron microscopy (CCLEM) and transmission electron microscopy (TEM), we established a dose-dependent relationship where optimal e-beam doses suppress nanoparticle growth and boost luminescence, while excessive doses degrade luminescence. Mechanistically, e-beam treatment forms a stable carbonaceous encapsulation layer on nanoparticle surfaces, preventing inter-particle contact and passivating surface impurities without causing significant structural damage. These findings demonstrate that low-dose e-beam irradiation is a versatile tool for tuning CsPbBr3 NPs properties, offering new pathways to optimize the stability and performance of perovskitebased materials in advanced optoelectronic applications.

Lead-halide perovskite nanoparticles (LHP NPs) are highly promising materials for next-generation displays and solid-state lighting due to their exceptional optical properties. However, their inherent instability presents a significant challenge. Recent advances have demonstrated that optoelectronic devices based on monolayer nanoparticle films exhibit both high luminescence efficiency and long-term stability. Our research demonstrates that mobility limitations and anisotropic alignments in CsPbBr3 nanocube monolayer films are key to their stabilization, hindering spontaneous growth through face-to-face fusion and resulting in the formation of connecting necks in a diagonal direction. Introducing laser irradiation confirmed this by significantly accelerating nanocubes growth, increasing mobility, and enhancing local structural ordering, leading to larger and more regularly shaped nanosheets. Fourier transform infrared spectroscopy and energy dispersive spectroscopy line-scan analyses indicated that laser irradiation did not disrupt the ligand structure. Transmission electron microscopy and correlative cathodoluminescence electron microscopy revealed the effects of post-growth and heterogeneous structures, including enhanced luminescence and inhomogeneous intensity in the nanosheets. These findings deepen the understanding of the post-growth mechanism of monolayer nanoparticles and the structure-emission correlation and highlight the unique role of laser irradiation in directing the formation of well-defined and regular nanostructures.

In this study, the theoretical efficiencies of tandem solar cells (TSCs) are investigated through an analysis of various configurations and bandgap combinations. In the results, it is indicated that two‐junction two‐terminal (2J 2T) tandem cells can achieve a maximum efficiency of 45% with subcells exhibiting bandgaps of 1.60 and 0.95 eV, while 2J 4T tandem cells can reach 45.45% efficiency with subcells featuring bandgaps of 1.71 and 0.94 eV. Additionally, 3J 2T TSCs maintain a peak efficiency of 51.19%, utilizing subcells with bandgaps of 1.91, 1.38, and 0.94 eV, while 3J 6T tandem cells exhibit an efficiency peak at 51.49% with subcells showcasing bandgaps of 2.07, 1.39, and 0.93 eV. In this study, a roadmap is offered for optimizing bandgap combinations in TSCs, underscoring the critical role of bandgap engineering in the pursuit of higher solar cell efficiencies. The identified optimal bandgap pairing paves the way for future developments in solar cell technology.

An interface engineering strategy is demonstrated for perovskite solar cells (PSCs) through strategic incorporation of calcium phosphorylcholine chloride (CaPhCl) into self-assembled monolayers (SAMs), achieving remarkable performance enhancement via dual-function interfacial modulation. The large molecular dipole moment of CaPhCl (9.26 D) enables precise energy level alignment at the hole transport interface, while its unique chemical interaction with excess PbI2 promotes stable alpha-phase perovskite formation. This synergistic effect simultaneously addresses two critical challenges in PSC development: interface energetics and stability. The optimized devices achieve a power conversion efficiency of 25.75 % with a high open-circuit voltage of 1.19 V, representing one of the highest efficiencies reported for NiOx-based inverted PSCs. Notably, these devices demonstrate exceptional operational stability, retaining 91 % of their initial efficiency after 1000 h of continuous illumination. Beyond immediate performance gains, this work introduces a new paradigm for interface engineering in perovskite optoelectronics where multifunctional molecular modifiers can simultaneously enhance efficiency and stability, offering a promising pathway toward commercial deployment of highperformance PSCs.

Having a stable interface between perovskite and electron transport layer at p-i-n hybrid halide perovskite solar cells (PSCs), has been considered to be crucial to improve the performance of device. Here, a two-step sulfur-containing molecules surface treatment procedure (TST) was utilized, which involves sequentially coating 2-thiazolamide hydrochloride (SFACl) and methylamine sulfate (MA2SO4) onto the surface of perovskite film to achieve solid interface. Consequently, SFACl induced grains enlarged following a dissolution-crystallization model and formed 2D/3D heterojunction (n = 1); MA2SO4 and residual PbI2 reacted to form PbSO4, which priorly appeared at the grain boundaries. Owing to the interaction between sulfur-containing molecules and perovskite/PbI2, TST film showed improved photoluminescence intensity and prolonged lifetimes. Importantly, TST solar cell (Target 2) achieved a champion efficiency of 21.94 % for CsFA-based device (23.19 % for CsFAMA-based device, certified 23.02 %) compared with that of 20.05 % (Control). The improved device performance was primarily attributed to the larger grain size and defects passivation via multifunctional sulfur-containing molecules. Operational stability results shown that Target 2 device remained 78 % of the initial efficiency while Control remained 57 % of that under continuous illumination after 700 hrs in N2 at room temperature, which can be ascribed to the stable interface inhibiting ion migration. This study offers a comprehensive understanding of sulfur-containing molecules surface modification in PSCs.

Active layers of p–i–n organic–inorganic hybrid perovskite solar cells (PSCs) are passivated by star‐shape, multifunctional triazinane molecules, cyanuric acid (CA), and Tris(dibutylhydroxy‐ benzyl)isocyanuric acid (TPCA). The most interesting is that CA is used as a bulk additive is able to induce a two‐dimensional (2D) structure at grain boundaries (GBs) of the perovskite when excess PbI 2 is present. TPCA is also important to use as a perovskite surface modifier and to reduce the defects in perovskite layer further. The reduced ideality factors, enhanced photoluminescence, and prolonged lifetimes all indicate suppression of non‐radiative recombination. The combination of the two substantially improves fill‐factors and open‐circuit voltages of the devices. This leads to markedly enhanced stabilities of the devices.

In recent years, organic-inorganic metal halide perovskite solar cells have made significant progress in energy conversion efficiency. However, their long-term stability and performance are often affected by the diffusion of halide ions within the perovskite structure. Inhibiting the migration of halide ions is very important to improve the operational stability and efficiency of solar cells. This study proposes a new method to characterize the diffusion of halide ions in perovskite films and demonstrates the effectiveness of incorporation of Rb+ into CsMAFA perovskite compositions. The addition of Rb+ reduces the concentration of mobile ions and the conductivity of ions in the perovskite film, thus eliminating the hysteresis phenomenon of perovskite solar cells. It is found that the efficiency and stability of the device are improved after optimization.

NaYF4 systems have been widely studied as up-conversion host matrices, and their phase transitions are flexible and worth investigating in great detail. Herein, the evolution of morphology and crystal structure of a Eu3+-doped β-NaYF4 single nanoparticle heated in an air atmosphere was investigated using in situ transmission electron microscopy (TEM). The annealing process revealed that the hexagonal β-NaYF4 phase undergoes sequential transformations into high-temperature cubic phases at both 350 °C and 500 °C. The emission characteristics of Eu3+ in the single nanoparticle after heating treatment were also analyzed using Correlative Cathodoluminescence Electron Microscopy (CCLEM). The results of CCLEM suggest a gradual decrease followed by a subsequent increase in structural symmetry. A comprehensive spectroscopic and structural analysis encapsulates the entire transformation process as NaYF4 → YOF → Y2O3. In situ energy dispersive spectroscopy analyses (EDS) support this reaction process. The aforementioned technique yields correlative lattice-resolved TEM images and nanoscale spectroscopic information, which can be employed to assess the structure-function relationships on the nanoscale.

In the field of perovskite solar cells (PSCs), the research on defects in the buried interface has been relatively limited due to its non-exposure; however, this interface significantly impacts the performance enhancement of inverted PSCs. This study employs phenylethylammonium chloride (PEACl) molecules as a buffer layer to modify the buried interface of p-i-n structured PSCs, aiming to enhance the uniformity of self-assembled monolayers (SAMs) and facilitate the uniform nucleation and growth of perovskite films on the substrate. Furthermore, the introduction of the PEACl buffer layer effectively passivates defects at the bottom of the perovskite layer and notably enhances the crystal quality of the perovskite film by mitigating residual stress, thereby reducing nonradiative recombination loss. Following these optimizations, the MA-free PSCs treated with PEACl achieve a power conversion efficiency (PCE) of 24.11%, with significant improvements in storage, thermal stability, and operational stability. Particularly noteworthy is the device's performance in an unencapsulated state, whereas after 1,500 hours of continuous light operation stability testing, it retains 97% of its original efficiency. This study not only enriches the systematic understanding of the characteristics of the buried interface in PSCs but also contributes significantly to advancing the commercial production of perovskite photovoltaic technology.

In recent years, Dion-Jacobson (D-J) perovskite has been extensively studied. In order to further study the application of D-J perovskite materials in spin-optoelectronic multifunctional devices, this paper is based on CsSbCl3Br and CsMnBr4, a zero-band gap semi-metallic material with the same ferromagnetic ground state and the same crystal structure. In this paper, put forward with transverse CsMnBr4/CsSbCl3Br/CsMnBr4 heterojunction optoelectronic devices. The characteristics of photocurrent are discussed using parallel configuration (PC) and anti-parallel configuration (APC) magnetoelectric poles under two conditions: vertical incidence of linearly polarized light and elliptically polarized light utilizing density functional theory and the non-equilibrium Green’s function method. The results reveal that the device can achieve complete spin polarization photocurrent, pure spin current, perfect spin filtering effect, and excellent spin valve effect, with high extinction ratios. Under linearly polarized light, the maximum extinction ratio reaches 2747 for the PC configuration and 5200 for the APC configuration. For elliptically polarized light, the extinction ratio is 739 for the PC configuration and reaches a maximum of 240 for the APC configuration. These results indicate that the lateral CsMnBr4/CsSbCl3Br/CsMnBr4 heterojunction has broad multi-functional application prospects in the field of optoelectronics and spintronics.

The inverted p-i-n PSCs are gradually gaining more attention since they are generally more stable and can employ low-cost transport materials. However, the interfaces between the perovskite and the charge transport layers contribute to major power conversion efficiency (PCE) loss and instability. Here, we use a material of 6-(Trifluoromethyl)pyridine-3-amidinehydrochloride (CF3-PyFACl) to molecularly engineer the interface between the perovskite and electron transport layer. The interface modification results in suppressed nonradiative recombination, and improved interfacial contact. A PCE of 23.17 % is demonstrated, with open-circuit voltage (Voc) and fill factor (FF) of 1.169 V and 84.1 %, respectively. The unencapsulated device retains >80 % of the initial performance after 400 h continuous light soaking.