Chiral-induced spin selectivity enables a room-temperature spin light-emitting diode

Chiral organic-inorganic hybrid perovskites synthesized using an acoustofluidic closed system

Chiral organic-inorganic hybrid perovskite films hold significant promise for optoelectronic applications due to their unique optical activity and excellent optoelectronic properties. However, their air and moisture sensitivity necessitate inert atmosphere processing, hindering practical application. In this work, we present a closed acoustofluidic system utilizing surface acoustic wave-based microcentrifugation for the synthesis of high-quality (S-MBA)2PbI4 films. By confining both synthesis and film deposition within a sealed chamber, this approach eliminates air exposure, enabling the fabrication of films with enhanced crystallinity and a reduced band gap of 2.37 eV. The resulting chiral perovskite films exhibit significant circular dichroism, with an asymmetry factor of 9.3 × 10-4. Furthermore, control over film surface roughness (achieving <0.6 μm) is demonstrated through modulation of acoustic operation parameters. The cost-effectiveness and versatility of this acoustic microcentrifugation system highlight its potential for advanced film material fabrication.

Measurement Platform to Probe the Mechanism of Chiral-Induced Spin Selectivity through Direction-Dependent Magnetic Conductive Atomic Force Microscopy

This work introduces a magnetic conductive atomic force microscopy (mc-AFM) measurement platform for determining spin polarizations, arising from the chiral-induced spin selectivity (CISS) effect along different directions in helical conducting fibers. By using the principle that the spin preference for electron transport in a chiral material changes with the momentum of the electron, this method quantifies the spin polarization of chiral materials, which straddle a ferromagnetic electrode, i.e., by taking measurements in regions to the right and left of the electrode while it is magnetized in-plane. The working mechanism of the measurement is shown using chiral polyaniline (PANI) fibers, and they reveal that the longitudinal, along the fiber's helical axis, and transverse, perpendicular to the fiber axis, magnetoresistance differ by about a factor of 2. The observations imply that the spin polarization in PANI fibers is not consistent with models that attribute the spin selectivity (or magnetoresistance) solely to the spinterface or to spin-dependent charge injection barriers. In aggregate, this new platform offers a simplified approach for extending the mc-AFM method to resolving the spin-filtered charge currents along different directions in oriented samples.

Elucidating Interfacial Carrier Transfer Dynamics for Circularly Polarized Emission in Self-Assembled Perovskite Heterostructures

By integrating carrier transfer with spin-selectivity in mixed-dimensional perovskites heterostructures (HSs), exceptional chiroptical behaviors can be activated, offering avenues for advanced applications in spintronics and quantum information technologies. However, the critical role of interface effects in this photophysical process remains insufficiently explored. We demonstrate the fabrication of self-assembled chiral 2D/achiral nanocrystal (NC) HSs with different morphologies and chiroptical activities. Using femtosecond transient reflection spectroscopy, the underlying interface-dependent carrier transfer was unraveled. Spin-polarized holes generated in the chiral 2D component can transfer within an ultrafast time scale of ∼362 fs across the coherent heterointerface, inducing circularly polarized luminescence (CPL) in the intrinsically achiral NCs with a high Pc of ∼10.3%. Furthermore, interfacial halide exchange can be utilized to extend the CPL wavelength from green to near-infrared. Our findings reveal the correlation between interfacial properties, charge transfer, and CPL activity, providing insights for the development of high-quality HSs with optimized optical properties.

Spin effects in metal halide perovskite semiconductors

Metal halide perovskite semiconductors (MHSs) are emerging as potential candidates for opto-spintronic applications due to their strong spin-orbit coupling, favorable light emission characteristics and highly tunable structural symmetry. Compared to the significant advancements in the optoelectronic applications of MHSs, the exploration and control of spin-related phenomena remain in their early stages. In this minireview, we provide an overview of the various spin effects observed both in achiral and chiral MHSs, emphasizing their potential for controlling interconversion between spin, charge and light. We specifically highlight the spin selective properties of chiral MHSs through the chirality-induced spin selectivity (CISS) phenomena, which enable innovative functionalities in devices such as spin-valves, spin-polarized light-emitting diodes, and polarized photodetectors. Furthermore, we discuss the prospects of MHSs as spintronic semiconductors and their future development in terms of material design, device architecture and stability.

Chiral nanographenes exhibiting circularly polarized luminescence

Chiral nanographenes constitute an unconventional material class that deviates from planar graphene cutouts. They have gained considerable attention for their ability to exhibit circularly polarized luminescence (CPL), which offers new opportunities in chiral optoelectronics. Their unique π-conjugated architectures, coupled with the ability to introduce chirality at the molecular level, have made them powerful contenders in developing next-generation optoelectronic devices. This review thoroughly explores recent advances in the synthesis, structural design, and CPL performance of chiral nanographenes. We delve into diverse strategies for inducing chirality, including covalent functionalization, helically twisted frameworks, and heteroatom doping, each of which unlocks distinct CPL behaviors. In addition, we discuss the mechanistic principles governing CPL and future directions in chiral nanographenes to achieve high dissymmetry factors (glum) and tunable emission properties. We also discuss the key challenges in this evolving field, including designing robust chiral frameworks, optimizing CPL efficiency, and scaling up real-world applications. Through this review, we aim to shed light on recent developments in the bottom-up synthesis of structurally precise chiral nanographenes and evaluate their impact on the growing domain of circularly polarized luminescent materials.

Chiral All-Inorganic Perovskite Subnanowires

The phenomenon of chiral symmetry breaking during the crystallization of achiral molecules or ions, which leads to the formation of controllable enantiomerically pure crystals, has garnered significant interest but remains a challenge to fully overcome. This presents a particularly formidable obstacle in the creation of three-dimensional (3D) structured chiral all-inorganic perovskites, further complicated by their achiral crystalline space groups. In this report, we successfully synthesized right- or left-handed (P/M) chiral 3D P/M-CsPbX3 (X = Cl, Cl-Br, Br, Br-I) perovskite subnanowires (SNWs), in which Pb(II) can be partially substituted by hetero ions, such as Cu(II), Sn(II), and Mn(II). The selective control of the SNW handedness was achieved through the strategic incorporation of trace chiral amine enantiomers. The chiroptical activity arises from the helical structure of the SNWs. The mechanisms underlying the formation of this chiral structure were systematically investigated and interpreted by using a thermodynamic model. We utilized the chiral P/M-CsPbBr3 SNWs to fabricate circularly polarized light (CPL) photodetectors, which exhibited an impressive photocurrent dissymmetry factor (gIph) of 0.75. In the field of spin light-emitting diodes (spin-LEDs), circularly polarized electroluminescence (CPEL) was accomplished by employing the SNWs as a dual-functional material that provides both chiral-induced spin selectivity (CISS) and CPL emission capabilities.

Dimensionality-Controlled Confinement Effects for Tunable Optoelectronic Properties in Quasi-1D Hybrid Perovskites

Hybrid perovskite dimensional engineering enables the creation of one- to three-dimensional (1D to 3D) networks of corner-sharing metal halide octahedra interspersed by organic cations, offering opportunities to tailor semiconducting properties through quantum- and dielectric-confinement effects. Beyond the discrete options, intermediate dimensionality has been introduced in the form of quasi-2D phases with inorganic layers of varying thickness. The current study extends this approach to quasi-1D lead-iodide systems with variable ribbon widths from 2 to 6 octahedra, stabilized by flexible molecular configurations, cation mixing of organic cations, or guest molecule selection. This family of quasi-1D structures adopts characteristic well-like configurations, with intraoctahedral distortion increasing from the core to the edges. First-principles density-functional theory (DFT) calculations and optical characterizations─i.e., temperature-dependent UV-visible absorption, electro-absorption, photoluminescence, and circular dichroism─collectively demonstrate lower bandgap and exciton binding energy with increased ribbon width due to tailorable quantum confinement and structural distortions. Access to two ribbon widths within a single well-ordered structure yields distinguishable bandgaps and excitonic properties, demonstrating a class of dual-quantum confinement materials within the perovskite family. Our study serves as a starting point, showcasing a paradigm to stabilize increased ribbon widths through further tuning of organic templating effects. This continuum between 2D and 1D structures offers promise for fine-tuning the dimensionality and optoelectronic properties of hybrid perovskites.

Electrical Control of Spin Polarization in a Multiferroic Heterojunction Based on One-Dimensional Chiral Hybrid Metal Halide

Hybrid metal halide materials have been demonstrated to show potential in spintronic applications. In the field of spintronics, controlling the spin degree of freedom by electrical means represents a significant advancement. In this work, we present a spintronic device with a ferromagnet/ferroelectric/ferromagnet heterostructure, in which a one-dimensional (1D) chiral hybrid metal halide serves as an interlayer. The ferroelectricity of the material has been confirmed through both experimental and theoretical approaches. Unlike conventional magnetic tunnel junctions, this multiferroic device exhibits four distinct resistance states, which can be tuned by magnetic and electric fields. Notably, the sign of magnetoresistance can be modulated by an applied bias voltage, demonstrating that the spin polarization of carriers injected from ferromagnetic electrodes can be controlled by an external electric field. Our study not only provides a feasible pathway for electrically controlled spin but also highlights the potential of chiral hybrid metal halides in spintronic applications.

Effect of Crystal Symmetry of Lead Halide Perovskites on the Optical Orientation of Excitons

The great variety of lead halide perovskite semiconductors represents an outstanding platform for studying crystal symmetry effects on the spin-dependent properties. Access to them is granted through the optical orientation of exciton and carrier spins by circularly polarized photons. Here, the exciton spin polarization is investigated at 1.6 K cryogenic temperature in four lead halide perovskite crystals with different symmetries: (almost) cubic in FA0.9Cs0.1PbI2.8Br0.2 and FAPbBr3, and orthorhombic in MAPbI3 and CsPbBr3. Giant optical orientation of 85% is found for the excitons in FA0.9Cs0.1PbI2.8Br0.2, MAPbI3, and CsPbBr3, while it amounts to 20% in FAPbBr3. For all studied crystals, the optical orientation is robust to detuning of the laser photon energy from the exciton resonance, remaining constant for high energy detunings up to 0.3 eV, above which it continuously decreases to zero for detunings exceeding 1 eV. No acceleration of the spin relaxation for excitons with large kinetic energy is found in the cubic and orthorhombic crystals. This evidences the absence of the Dyakonov-Perel spin relaxation mechanism, which is based on the Rashba-Dresselhaus splitting of spin states at finite k-vectors. This indicates that the spatial inversion symmetry is maintained in perovskite crystals, independent of the cubic or orthorhombic phase.

Chiral light-matter interactions in solution-processable semiconductors

Chirality is a fundamental property widely observed in nature, arising in objects without a proper rotation axis, therefore existing as forms with distinct handedness. This characteristic can profoundly impact the properties of materials and can enable new functionality, especially for spin-optoelectronics. Chirality enables asymmetric light and spin interactions in materials, with widespread potential applications ranging from energy-efficient displays, holography, imaging, and spin-selective and enantio-selective chemistry to quantum information technologies. This Review focuses on the emerging material class of solution-processable chiral semiconductors, a broad material class comprising organic, inorganic and hybrid materials. These exciting materials offer the opportunity to design desirable light-matter interactions based on symmetry rules, potentially enabling the simultaneous control of light, charge and spin. We briefly discuss the various types of solution-processible chiral semiconductors, including small molecules, polymers, supramolecular self-assemblies and halide perovskites. We then examine the interplay between chirality and spin in these materials, the various mechanisms of chiral light-matter interactions, and techniques utilized to characterize them. We conclude with current and future applications of chiral semiconductors that take advantage of their chiral light-matter interactions.

Chirality-Induced Spin Selectivity in Hybrid Organic-Inorganic Perovskite Semiconductors

The movement of charges through a chiral medium results in a spin-polarized charge current. This phenomenon, known as the chirality-induced spin selectivity (CISS) effect, enables control over spin populations without the need for magnetic components and operates at room temperature. CISS has been discovered in a range of chiral media and most prominently studied in chiral organic molecular species. Chiral hybrid organic-inorganic perovskite semiconductors combine the unique and functional aspects of inorganic semiconductors with chiral molecules. The inorganic component borrows the homochirality of the organic component to yield a unique family of highly tunable chiral semiconductors, where the enantiomeric purity is defined by the organic component. Semiconductors already form the backbone of modern-day technologies. Adding chirality and control over spin through CISS provides new avenues for creative technological development. This review is intended to be an introduction to these unique systems and the demonstrations of CISS and spin control.

Organic light-emitting transistors with high efficiency and narrow emission originating from intrinsic multiple-order microcavities

Narrow electroluminescence is in high demand for high-resolution displays, optical communication and medical phototherapy. Organic light-emitting transistors, as three-terminal electroluminescent devices, offer advantages in simplifying device architecture and achieving high efficiency under gate regulation. However, achieving high efficiency and narrow emission remains a challenge. Here we demonstrate that laterally integrated organic light-emitting transistors with intrinsic multiple-order microcavities can enhance efficiency and narrow emission with a universal capability for different emitters. Full-width at half-maximum values of 18 nm for red, 14 nm for green and 13 nm for blue were achieved with a maximum narrowed degree of 68%. This resulted in an impressive BT.2020 colour gamut of 97%. The peak current efficiency or blue index values for red, green and blue organic light-emitting transistors reached 26.3 cd A-1, 37.3 cd A-1 and 72.6, respectively. Moreover, organic light-emitting transistors exhibit much narrower emission and higher efficiency than equivalent, comparable devices due to their unique gate regulation capability. Our work could enable smart display technologies with high colour purity and enhanced efficiency.

Pressure-Driven Circularly Polarized Luminescence Enhancement and Chirality Amplification

Achieving ultrahigh-color-purity circularly polarized luminescence (CPL) in low-dimensional chiral perovskites is challenging due to strong electron-phonon coupling caused by lead halide octahedral distortion. Herein, the circularly polarized piezoluminescence behaviors of six novel chiral perovskites, (S/R-3-XPEA)2PbBr4 (PEA = phenethylamine; X = F, Cl, Br), were systematically investigated. Upon compression, (S/R-3-ClPEA)2PbBr4 exhibits significant piezofluorochromic behaviors, transforming from yellow CPL to ultrahigh-color-purity deep-blue CPL. At 2.5 GPa, the deep-blue CPL intensity increases by an order of magnitude and its luminescence asymmetry factors (glum) are amplified from the initial ±0.03 to ±0.1. (S/R-3-BrPEA)2PbBr4 presents a similar piezochromic response, realizing deep-blue CPL at 1.7 GPa, while (S/R-3-FPEA)2PbBr4 retains a yellow CPL under high pressure. High-pressure structural characterization and theoretical calculations confirm that pressure-enhanced halogen bonds reduce the penetration depth of S/R-3-BrPEA+ and S/R-3-ClPEA+ into the [PbBr6]4- frameworks, significantly suppressing electron-phonon coupling and increasing magnetic transition dipole moment in (S/R-3-BrPEA)2PbBr4 and (S/R-3-ClPEA)2PbBr4, which are responsible for the ultrahigh-purity deep-blue CPL and chirality amplification, respectively.

Molecular dynamics simulation to predict assembly structures of bowl-shaped π-conjugated molecules

The proposed computational method using molecular dynamics simulation investigating the structural stability and dynamics of the molecular assembly could predict bulk crystal structures for the rationally designed bowl-shaped π-conjugated molecules. In addition, the process of the formation of the columnar assemblies was reproduced by our simulated annealing simulation.

Synthesis and Chiroptical Properties of Chiral Lead Halide Molecular Clusters

Chiral lead halide molecular clusters (MCs) consisting of PbBr2, neutral achiral butylamine (BTYA), and chiral methylbenzylamine [(R/S)-MBA] with unique chiral optical properties in both the solution and solid states have been synthesized using ligand-assisted reprecipitation and depositing, separately. Ultraviolet-visible (UV-vis) electronic absorption and photoluminescence (PL) spectra show the first electronic absorption band and sharp blue emission band of the chiral MCs that peaked at 404 and 412 nm, respectively, in both solution and films. The emission asymmetry factor |glum| of the chiral MCs is 1.04 × 10-3 in solution and 2.01 × 10-3 in the film state at room temperature, indicating excellent circularly polarized luminescence (CPL) properties. This pronounced asymmetry is attributed to the chiral transfer from the chiral ligand to the BTYA-capped PbBr2 framework due to the chiral MBA ligand coordination with Pb2+. The samples exhibited excellent ambient stability for over 1 month, primarily due to strong BTYA-PbBr2 coordination. The MCs maintained their structure and CPL properties in the solid state, which is important for photonic applications.

Strategies for Stabilizing Metal Halide Perovskite Light-Emitting Diodes: Bulk and Surface Reconstruction of Perovskite Nanocrystals

Light-emitting colloidal lead halide perovskite nanocrystals (PeNCs) are considered promising candidates for next-generation vivid displays. However, the operational stability of light-emitting diodes (LEDs) based on PeNCs is still lower than those based on polycrystalline perovskite films, which requires an understanding of defect formation in PeNCs, both inside the crystal lattice ("bulk") and at the surface. Meanwhile, uncontrollable ion redistribution and electrochemical reactions under LED operation can be severe, which is also related to the bulk and surface quality of PeNCs, and a well-designed device architecture can boost carrier injection and balance radiative recombination. In this review, we consider bulk and surface reconstruction of PeNCs by enhancing the crystal lattice rigidity and rationally selecting the surface ligands. Degradation pathways of PeNCs under applied voltage are discussed, and strategies are considered to avoid both undesirable ion migration and electrochemical reactions in the PeNC films. Subsequently, other critical issues hindering the commercial application of PeNC LEDs are discussed, including the toxicity of Pb in lead halide perovskites, scale-up deposition of PeNC films, and design of active-matrix prototypes for high-resolution LED modules.

Conformer-Mediated Helical Chirality in 2D Layered Hybrid Perovskites

Two-dimensional (2D) chiral hybrid perovskites A2PbI4 (A: chiral organic ion) enable chirality controlled optoelectronic and spin-based properties. A+ organic sublattice induces chirality into the semiconducting [PbI4]2- inorganic sublattice through non-covalent interactions at organic-inorganic interface. Often, the A+ cations in the lattice have different orientations, leading to asymmetry in the non-covalent interactions. In a novel approach, we use different conformers of A+ cations to create asymmetry in the non-covalent interactions, thereby, achieving chiral perovskites with rare helical enantiomorphic structures. We prepared (R-IdPA)2PbI4 and (S-IdPA)2PbI4 (IdPA: 1-iodopropan-2-ammonium) which crystallize in the helical enantiomorphic space groups P43212 and P41212, respectively. The gauche- and anti-conformers of IdPA+ are arranged alternatively in the hybrid structure. Importantly, the anti-conformer of IdPA+ ion have significantly stronger electrostatic, N-H⋅⋅⋅I hydrogen bonding, and I⋅⋅⋅I halogen bonding interactions with the [PbI4]2- sublattice, compared to the gauche-conformer. This periodic asymmetry in non-covalent interactions caused by the alternative arrangement of gauche- and anti-conformers induces chirality in the inorganic sublattice with four-fold screw axes (43 and 41). The enantiomers (R-/S-IdPA)2PbI4 show mirror-image like circular dichroism from excitonic absorption of the inorganic sublattice. This conformer-based design of chiral hybrid perovskites in helical space groups broadens material choices for advanced optoelectronic applications.

Solution-processed spin organic light-emitting diodes based on antisolvent-treated 2D chiral perovskites with strong spin-dependent carrier transport

Chiral perovskites, which are applied to spin organic light-emitting diodes as a spin-induced spin selectivity (CISS) layer, have attracted increasing amounts of attention. A device based on a thicker perovskite CISS layer leads to strongly spin-polarized EL emission. However, chiral perovskite films suffer from poor device performance due to difficulties in carrier injection and film quality. The effects of antisolvent dripping on the chiroptical properties of chiral perovskite films were investigated. The rapid crystallization of chlorobenzene (CB)-treated films generated a high-quality film with fewer halide vacancies and a much greater strength of asymmetric hydrogen bonding. Accordingly, the inorganic structural distortion is greater, resulting in greater chiroptical activity. The chiral perovskite thickness affects the circularly polarized electroluminescence (CP-EL) of spin-OLEDs. The statistics relating device performance and thickness are presented. The spin current polarization degree of chiral perovskites reaches approximately 86%. The maximum CP-EL asymmetry factor (g CP-EL) is 2.6 × 10-2 and maximum external quantum efficiency (EQE) of the spin-OLED device is 3.68%. Spin OLED devices based on chiral perovskites can be manipulated and controlled by thickness and antisolvent treatment. gCPEL intensities for devices based on CB-treated chiral perovskite films can be increased by about 1.75 times compared with devices based on untreated films.

Mn2+-Doped CsPbBr2I Quantum Dots Photosensitive Films for High-Performance Photodetectors

The variable bandgap and high absorption coefficient of all-inorganic halide perovskite quantum dots (QDs), particularly CsPbBr2I make them highly promising for photodetector applications. However, their high defect density and poor stability limit their performance. To overcome these problems, Mn2+-doped CsPbBr2I QDs with varying concentrations were synthesized via the one-pot method in this work. By replacing Pb2+ ions, moderate Mn2+ doping caused lattice contraction and improved crystallinity. At the same time, Mn2+-doping effectively passivated surface defects, reducing the defect density by 33%, and suppressed non-radiative recombination, thereby improving photoluminescence (PL) intensity and carrier mobility. The optimized Mn:CsPbBr2I QDs-based photodetector exhibited superior performance, with a dark current of 1.19 × 10-10 A, a photocurrent of 1.29 × 10-5 A, a responsivity (R) of 0.83 A/W, a specific detectivity (D*) of 3.91 × 1012 Jones, an on/off ratio up to 105, and the response time reduced to less than 10 ms, all outperforming undoped CsPbBr2I QDs devices. Stability tests demonstrated enhanced durability, retaining 80% of the initial photocurrent after 200 s of cycling (compared to 50% for undoped devices) and stable operation over 20 days. This work offers a workable strategy for rational doping and structural optimization in the construction of high-performance perovskite optoelectronic devices.

Circularly polarized electroluminescence from chiral supramolecular semiconductor thin films

Current organic light-emitting diode (OLED) technology uses light-emitting molecules in a molecular host. We report green circularly polarized luminescence (CPL) in a chirally ordered supramolecular assembly, with 24% dissymmetry in a triazatruxene (TAT) system. We found that TAT assembled into helices with a pitch of six molecules, associating angular momentum to the valence and conduction bands and obtaining the observed CPL. Cosublimation of TAT as the "guest" in a structurally mismatched "host" enabled fabrication of thin films in which chiral crystallization was achieved in situ by thermally triggered nanophase segregation of dopant and host while preserving film integrity. The OLEDs showed external quantum efficiencies of up to 16% and electroluminescence dissymmetries ≥10%. Vacuum deposition of chiral superstructures opens new opportunities to explore chiral-driven optical and transport phenomena.

Optimizing the white light emission in the solid state isatin and thiazole based molecular hybrids by introduction of variety of substituents on isatin and thiazole ring systems

An efficient and practical 3-component reaction strategy has been developed for the synthesis of a series of multi-colour emissive isatin-thiazole based fluorophores, thiazolylhydrazonoindolin-2-ones (4) from readily available isatins (1), thiosemicarbazide (2) and α-bromoketones (3) in the presence of biodegradable citric acid (0.1 N) in ethanol at reflux temperature for 40-60 min. The reaction proceeds via condensation (C[double bond, length as m-dash]N) and subsequent heterocyclization (C-S & C-N) in one-pot. Nature-friendly reaction profile, easy to perform, wide substrate scope, use of non-hazardous solvents/catalysts, good functional group tolerance, excellent yields (91-98%) in short reaction times, scalability and products do not require column chromatography purification are the attractive features of the present MCR strategy. The photophysical properties of the titled compounds (4) in both solid and solution states have been evaluated. The study reveals that the prepared isatin-thiazole based molecular hybrids exhibited tunable photophysical properties by varying the substituents on both isatin and thiazole motifs. To our delight, the titled compounds, 4k, 4l, 4m, 4u and 4y displayed white light emission with mega Stokes shifts in the solid state.

Perovskite spin light-emitting diodes with simultaneously high electroluminescence dissymmetry and high external quantum efficiency

Realizing high electroluminescence dissymmetric factor and high external quantum efficiency at the same time is challenging in light-emitting diodes with direct circularly polarized emission. Here, we show that high electroluminescence dissymmetric factor and high external quantum efficiency can be simultaneously achieved in light-emitting diodes based on chiral perovskite quantum dots. Specifically, chiral perovskite quantum dots with chiral-induced spin selectivity can concurrently serve as localized radiative recombination centers of spin-polarized carriers for circularly polarized emission, thereby suppressing the relaxation of spins, Meanwhile, improving the chiral ligand exchange efficiency is found to synergistically promote their spin selectivity and optoelectronic properties so that chiroptoelectronic performance of resulting devices can be facilitated. Our device simultaneously exhibits high electroluminescence dissymmetric factor (R: 0.285 and S: 0.251) and high external quantum efficiency (R: 16.8% and S: 16%), demonstrating their potential in constructing high-performance chiral light sources.

Direct control of electron spin at an intrinsically chiral surface for highly efficient oxygen reduction reaction

The oxygen reduction reaction (ORR) in acidic media suffers from sluggish kinetics, primarily due to the spin-dependent electron transfer involved. The direct generation of spin-polarized electrons at catalytic surfaces remains elusive, and the underlying mechanisms are still controversial due to the lack of intrinsically chiral catalysts. To address this challenge, we investigate topological homochiral PdGa (TH PdGa) crystals with intrinsically chiral catalytic surfaces for ORR. Through spin-resolved photoemission spectroscopy and theoretical simulations, we show that both structural chirality and spin-orbit coupling are critical for inducing spin polarization at the surface of TH PdGa. As a result, TH PdGa achieves a kinetic current density over 100 times higher than the achiral PdGa (AC PdGa) at 0.85 V versus the reversible hydrogen electrode. This work underscores the pivotal role of spin polarization in enhancing acidic ORR activity and lays the groundwork for the rational design of chiral catalysts for spin-dependent catalysis.

Efficient Spin-Light-Emitting Diodes With Tunable Red to Near-Infrared Emission at Room Temperature

Spin light-emitting diodes (spin-LEDs) are important for spin-based electronic circuits as they convert the carrier spin information to optical polarization. Recently, chiral-induced spin selectivity (CISS) has emerged as a new paradigm to enable spin-LED as it does not require any magnetic components and operates at room temperature. However, CISS-enabled spin-LED with tunable wavelengths ranging from red to near-infrared (NIR) has yet to be demonstrated. Here, chiral quasi-2D perovskites are developed to fabricate efficient spin-LEDs with tunable wavelengths from red to NIR region by tuning the halide composition. The optimized chiral perovskite films exhibit efficient circularly polarized luminescence from 675 to 788 nm, with a photoluminescence quantum yield (PLQY) exceeding 86% and a dissymmetry factor (glum) ranging from 8.5 × 10-3 to 2.6 × 10-2. More importantly, direct circularly polarized electroluminescence (CPEL) is achieved at room temperature in spin-LEDs. This work demonstrated efficient red and NIR spin-LEDs with the highest external quantum efficiency (EQE) reaching 12.4% and the electroluminescence (EL) dissymmetry factors (gEL) ranging from 3.7 × 10-3 to 1.48 × 10-2 at room temperature. The composition-dependent CPEL performance is further attributed to the prolonged spin lifetime as revealed by ultrafast transient absorption spectroscopy.

Graphene rolls with tunable chirality

Creating chirality in achiral graphene and other two-dimensional materials has attracted broad scientific interest due to their potential application in advanced optics, electronics and spintronics. However, investigations into their optical activities and related chiro-electronic properties are constrained by experimental challenges, particularly in the precise control over the chirality of these materials. Here a universal wax-aided immersion method is developed to yield graphene rolls with controllable chiral angles, and the method can be generalized in other two-dimensional materials for high-yield fabrication. The left-handed and right-handed rolls exhibit optical activity and excellent spin selectivity effects with a spin polarization over 90% at room temperature. The discovery of tunable chirality-induced spin selectivity in tailored roll-shaped allotropes, achievable only through precise control of chirality, distinguishes itself from other carbon materials or existing chiral materials. Our Dirac fermion model shows that the electrons moving predominately along one side of the chiral roll develop a preferred spin polarization, and the rolling-chirality-induced spin selectivity is a result of this finite spin selectivity effect. Our method opens up opportunities for endowing achiral two-dimensional materials with tunable chirality, and may enable the emergence of quantum behaviours and room-temperature spintronic technologies.

Proximity Effect of Optically Active h-BCN Nanoflakes Deposited on Different Substrates to Tailor Electronic, Spintronic, and Optoelectronic Properties

Hexagonal BCN (h-BCN), an isoelectronic counterpart to graphene, exhibits chirality and offers the distinct advantage of optical activity in the vacuum ultraviolet (VUV) region, characterized by significantly higher wavelengths compared to graphene nanoflakes. h-BCN possesses a wide bandgap and demonstrates desirable semiconducting properties. In this study, we employ Density Functional Theory (DFT) calculations to investigate the proximity effects of adsorbed h-BCN flakes on two-dimensional (2D) substrates. The chosen substrates encompass monolayers of 3D transition metals and WSe2, as well as a bilayer consisting of WSe2/Ni. Notably, the hydrogen-terminated h-BCN nanoflakes retain their planar configuration following adsorption. We observe a strong interaction between h-BCN and fcc-based monolayers such as Ni(111), resulting in the closure of the optical bandgap, while the adsorption energy on WSe2 is significantly weaker, preserving an approximate 1.1 eV bandgap. Furthermore, we demonstrate the magnetism induced by the proximity of adsorbed chiral h-BCN molecules, and the chiral-induced spin selectivity within the proposed systems.

Quantification of Chirality Induced Spin-Orbit Coupling for Long Spin Polarized Lifetime in Hybrid Perovskite

Long spin lifetimes are crucial for maintaining robust spin states during propagation in spintronic devices. Spin-orbit coupling (SOC) in chiral hybrid perovskites can induce chirality-dependent spin splitting, facilitating the manipulation of spin polarization. In this study, we introduce a chiral organic molecule, (R/S)-4-(aminoethyl)piperidinium (4AEP), into iodide-lead-based structures to synthesize chiral [(R/S)-4AEP]PbI4 crystals and thin films. Using circularly polarized pump-probe techniques, we examine the carrier spin dynamics in [(R/S)-4AEP]PbI4. Our results demonstrate that chirality-induced spin splitting significantly enhances the spin-polarization lifetime, achieving a spin splitting of approximately 130 meV at the valence band maximum and spin lifetimes exceeding 1 ns. Density functional theory (DFT) calculations reveal that opposite spin states exist in the R- and S-chiral samples with substantial spin splitting. These findings highlight the potential of chiral hybrid perovskites for spintronics applications.

Single-molecule junctions map the interplay between electrons and chirality

The interplay of electrons with a chiral medium has a diverse impact across science and technology, influencing drug separation, chemical reactions, and electronic transport1-30. In particular, electron-chirality interactions can significantly affect charge and spin transport in chiral conductors, making them highly appealing for spintronics. However, an atomistic mapping of different electron-chirality interactions remains elusive. Here, we find that helicene-based single-molecule junctions behave as a combined magnetic-diode and spin-valve device. This dual-functionality enables the identification of an atomic-scale coexistence of different electron-chirality interactions: the magnetic-diode behavior is attributed to an interaction between electron's angular momentum in a chiral medium and magnetic fields, whereas the spin-valve functionality is ascribed to an interaction between the electron's spin and a chiral medium. This work uncovers the coexistence of electron-chirality interactions at the atomic-scale, identifies their distinct properties, and demonstrates how integrating their functionalities can broaden of the available methods for spintronics.

Hyperfluorescence circularly polarized OLEDs consisting of chiral TADF sensitizers and achiral multi-resonance emitters

Developing circularly polarized organic light-emitting diodes (CP-OLEDs) that simultaneously achieve narrow-spectrum emission and high electroluminescence (EL) efficiency remains a formidable challenge. This work prepares two pairs of efficient circularly polarized thermally activated delayed fluorescence (CP-TADF) materials, featuring high photoluminescence quantum yields, short delayed fluorescence lifetimes, good luminescence dissymmetry factors and large horizontal dipole ratios. They can function as emitters for efficient sky-blue CP-OLEDs, providing high maximum external quantum efficiencies (ηext,maxs) (33.8%) and good EL dissymmetry factors (gELs) (-2.64 × 10-3). More importantly, they can work as sensitizers for achiral multi-resonance (MR) TADF emitters, furnishing high-performance blue and green hyperfluorescence (HF) CP-OLEDs with intense narrow-spectrum CP-EL and good ηext,maxs (31.4%). Moreover, tandem HF CP-OLEDs are fabricated for the first time by employing CP-TADF sensitizers and achiral MR-TADF emitters, which radiate narrow-spectrum CP-EL with an extraordinary ηext,maxs (51.3%) and good gELs (4.87 × 10-3). The circularly polarized energy transfer as well as chirality-induced spin selectivity effect of CP-TADF sensitizers are considered to contribute greatly to the generation of efficient CP-EL from achiral MR-TADF emitters. This work not only explores efficient CP-TADF materials but also provides a facile approach to construct HF CP-OLEDs with achiral MR-TADF emitters.

Emerging devices based on chiral nanomaterials

As advanced materials, chiral nanomaterials have recently gained vast attention due to their special geometry-based physical and chemical properties. The fast development of the related science and technology means that various devices involving polarization-based information encryption, photoelectronic and spintronic devices, 3D displays, biomedical sensors and measurement, photonic engineering, electronic engineering, solar devices, etc., been explored extensively. These fields are at their beginning, and much effort needs to be made, including improving the optical, electronic, and magnetic properties of advanced chiral nanomaterials, precisely designing materials, and developing more efficient construction methods. This review tries to offer a whole picture of these state-of-the-art conditions in these fields and offers perspectives on future development.

Supramolecular Assembly Enhanced Linear and Nonlinear Chiroptical Properties of Chiral Manganese Halides

Chiral hybrid organic-inorganic metal halides (HOMHs) hold great promise in broad applications ranging from ferroelectrics, spintronics to nonlinear optics, owing to their broken inversion symmetry and tunable chiroptoelectronic properties. Typically, chiral HOMHs are constructed by chiral organic cations and metal anion polyhedra, with the latter regarded as optoelectronic active units. However, the primary design approaches are largely constrained to regulation of general components within structural formula. Herein, supramolecular approaches have been taken for the functionalization of chiral enantiomers by anchoring chiral cations with crown ether hosting molecules. Chiral HOMHs of R-/S-(18-crown-6@ClMBA)2MnBr4 have been thus obtained with boosted linear and nonlinear chiroptical properties. The self-assembled cations lead to enhanced structural rigidity, which promote near-unity green light emission and strong circularly polarized luminescence with a high asymmetry factor, along with high efficiency second-order nonlinear optical responses. In particular, these chiral HOMH single crystals demonstrate a sensitive discrimination for circularly polarized laser in the near-infrared region with the nonlinear optical asymmetry factor (gSHG-CD) as high as 1.8. This work highlights the contribution of supramolecular assembly in improving chiroptical performances, offering valuable insights for the design of new chiral HOMH materials with promising application potentials as linear and nonlinear CPL emitters and detectors.

Toward Rhenium-Based Circularly Polarized OLEDs Using Tailored Chiral Re(CO)3 Emitters

Chiral rhenium(I) emitters exhibiting circularly polarized phosphorescence (CPP) are an attractive mainstay for CP organic light-emitting diodes (CP-OLEDs). However, the efficiency of such emitters is not ideal, and they have never been explored for circularly polarized electroluminescence (CPEL) applications. Here, we have tailored robust chiral Re(I) complexes with improved CPP properties, and demonstrated CPEL from rhenium emitters for the first time. Two pairs of enantiomeric Re(I) complexes have been synthesized by introducing of one or two chiral menthol groups into 1,10-phenanthroline unit (phen) of archetypical emitters [ReBr(CO)3(phen)]. The designed complexes exhibit a yellow CPP with enhanced |glum| factors (up to 2.5×10-2) and a good quantum efficiency. The pioneering Re(I)-based CP-OLEDs (based on the obtained emitters) exhibit yellow CPEL with |gEL| factors of up to 6.2×10-3 and a maximal external quantum efficiency of 13.2 %. This work highlights the good potential of chiral Re(I) emitters for CPEL applications, and opens up a new shortcut to CPP-active Re(I) complexes.

Strong Magneto-Chiroptical Effects through Introducing Chiral Transition-Metal Complex Cations to Lead Halide

The interplay between chirality with magnetism can break both the space and time inversion symmetry and have wide applications in information storage, photodetectors, multiferroics and spintronics. Herein, we report the chiral transition-metal complex cation-based lead halide, R-CDPB and S-CDPB. In contrast with the traditional chiral metal halides with organic cations, a novel strategy for chirality transfer from the transition-metal complex cation to the lead halide framework is developed. The chiral complex cations directly participate the band structure and introduce the d-d transitions and tunable magneto-chiroptical effects in both the ultraviolet and full visible range into R-CDPB and S-CDPB. Most importantly, the coupling between magnetic moment of the complex cation and chiroptical properties is confirmed by the magneto-chiral dichroism. For the band-edge transition, the unprecedented modulation of +514 % for S-CDPB and -474 % for R-CDPB was achieved at -1.3 Tesla. Our findings demonstrate a novel strategy to combine chirality with magnetic moment, and provide a versatile material platform towards magneto-chiroptical and chiro-spintronic applications.

Electrically Modulated Multilevel Optical Chirality in GdFeCo Thin Films

This study introduces a simple approach to dynamically control multilevel optical ellipticity in ferrimagnetic GdFeCo alloys by switching the spin orientation through Joule heating induced by electrical current, with the assistance of a low magnetic field of 3.5 mT. It is demonstrated that selecting specific compositions of Gd x (FeCo)100-x alloys, with magnetic compensation temperatures near or above room temperature, allows for significant manipulation of the circular dichroism (CD) effect. This control enables the transformation of transmitted light from linearly polarized to elliptically polarized or the reversal of the rotation direction of elliptically polarized light across the photon energy range from visible (vis) to ultraviolet (UV). The efficacy of this method is rooted in the dominant contributions of FeCo to the CD effect in the vis-to-UV energy range. Because the magnetization of FeCo remains relatively independent of the temperature, substantial optical ellipticity is maintained for optical device applications, regardless of whether the compensation temperature is approached or crossed. Our results highlight the potential of GdFeCo thin films in chiral optics and demonstrate the selective contributions of rare-earth transition-metal elements to the CD effects, facilitating the design of advanced optical devices leveraging energy-resolved CD phenomena.

Chirality induced spin selectivity in electron transport investigated by scanning probe microscopy

Chirality induced spin selectivity (CISS) effect implies the relationship between chirality and magnetism, attracting extensive attention in the fields of physics, chemistry and biology. Since it was first discovered with photoemission method in 1999, the CISS effect has been investigated and measured by a variety of methods. Among different means of measurements, scanning probe microscopy (SPM) as a powerful tool to explore the CISS effect, can directly measure and present the spin filtering property of chiral molecules in electron transport. In this paper, we summarize the recent experiments on the CISS effect studied with scanning tunneling microscopy and atomic force microscopy, analyzing the experimental setups and results, and delving into the underlying mechanisms. The present review offers a concise introduction to several chiral molecules which are investigated by SPM for the CISS effect, and a detailed exploration of various experimental techniques tailored to the unique adsorption structures of these molecules. The impact of molecular structure on spin selectivity and the profound implications of CISS are also demonstrated together with a concise overview of CISS theory. A conclusive synopsis and forward-looking perspectives on the investigation of the CISS effect in electron transport utilizing SPM techniques are presented.

Responsive Chirality: Tailoring Supramolecular Assemblies with External Stimuli as Future Platforms for Electronic/Spintronic Materials

Supramolecular chirality is the major branch of supramolecular chemistry, which not only plays important roles in biological processes but also in synthetically designed aggregated systems. To understand the complex processing of biological systems, the only way is to design supramolecular chiral ensembles that mimic natural biomolecules such as Deoxyribonucleic acid (DNA), Ribonucleic acid (RNA), amino acids, etc. In addition, chiral systems and self-assemblies as molecular motifs with breaking spatial inversion symmetry have been regarded as key substances in electronics and spintronics as well as in fundamental chemistry and physics. Here, in this review, our major concern is understanding modulation in spatial arrangements and packing modes under the impact of any external stimuli, which results in tailoring the handedness of resulted supramolecular chiral superstructures. We, in this review, highlighted the role of external stimuli such as solvent, chemical additives, photo exposure, etc. in altering the supramolecular chirality for their future utility as "active switches" in optoelectronic and spintronic devices and applications.

Magnetochiral charge pumping due to charge trapping and skin effect in chirality-induced spin selectivity

Chirality-induced spin selectivity (CISS) generates giant spin polarization in transport through chiral molecules, paving the way for novel spintronic devices and enantiomer separation. Unlike conventional transport, CISS magnetoresistance (MR) violates Onsager's reciprocal relation, exhibiting significant resistance changes when reversing electrode magnetization at zero bias. However, its underlying mechanism remains unresolved. In this work, we propose that CISS MR originates from charge trapping that modifies the electron tunneling barrier and circumvents Onsager's relation, distinct from previous spin polarization-based models. Charge trapping is governed by the non-Hermitian skin effect, where dissipation leads to exponential wavefunction localization at the ferromagnet-chiral molecule interface. Reversing magnetization or chirality alters the localization direction, changing the occupation of impurity/defect states in the molecule (i.e., charge trapping) - a phenomenon we term magnetochiral charge pumping. Our theory explains why CISS MR can far exceed the ferromagnet spin polarization and why chiral molecules violate the reciprocal relation but chiral metals do not. Furthermore, it predicts exotic phenomena beyond the conventional CISS framework, including asymmetric MR induced by magnetic fields alone (without ferromagnetic electrodes), as confirmed by recent experiments. This work offers a deeper understanding of CISS and opens avenues for controlling electrostatic interactions in chemical and biological systems through the magnetochiral charge pumping.

Why Mixed Halides in 2D Chiral Perovskites Weaken Chirality-Induced Spin Selectivity

2D Ruddlesden-Popper (RP) perovskites, upon inclusion of a chiral amine, exhibit chirality-induced spin selectivity (CISS). Although alloying at the halogen site in MBA-based RPs (MBA: methylbenzylammonium) is one of the suitable routes to tune the CISS effect, the mixed-halide RP perovskites exhibited complete suppression of chirality when probed through circular dichroism (CD). Here, we present the CISS effect in a series of mixed-halide RP perovskites. We show that photoinduced halide segregation is the origin for the apparent chirality suppression. The spin-dependent charge transport was evidenced through magnetic-conducting atomic force microscopy (mc-AFM) studies and magnetoresistance (MR) measurements. The mc-AFM results show that in (R/S-MBA)2PbI4(1-x)Br4x, the CISS effect decreases with bromide inclusion, nonmonotonically; the microstrain developed in the lattice and the spin-polarized charge transport are found to be correlated. Such a behavior has been explained through an inhomogeneity in the strength of the hydrogen bond between the organic moieties and halogens in the inorganic framework of the compounds. Our results further inferred that the hydrogen-bond-induced coupling transfers the chirality from the amine to the inorganic sublattice. The work explains the weakened CISS effect in mixed-halide chiral RP perovskites and provides a strategy to tune the spin-polarized charge transport as well.

Efficient Circularly Polarized Electroluminescence Enabled by Low-Dimensional Bichiral Perovskite Nanocrystals

Chiral organic-inorganic hybrid perovskite nanocrystals have gained attention as promising materials for circularly polarized luminescence emission, owing to their high photoluminescence efficiency and superior charge-carrier mobility. However, achieving circularly polarized electroluminescence (CPEL) from mixed-phase perovskite nanocrystals remains a significant challenge. We present bichiral formamidinium lead bromide (FAPbBr3) nanocrystals that achieve room-temperature circularly polarized light-emitting diodes (LEDs) via a synergistic effect between a chiral interior spacer (methylbenzylamine cation, MBA+) and a chiral surface ligand (camphorsulfonic acid, CSA). The incorporation of MBA+ induces chiral crystal lattices, while CSA ligands, featuring sulfonate groups, effectively passivate defects, suppress exciton spin-flip, and enhance conductivity. The resulting circularly polarized LEDs exhibit an enhanced electroluminescence asymmetry factor (gEL) of ∼2 × 10-3, along with an external quantum efficiency (EQE) of 3.1%. These bichiral nanocrystals represent a significant advancement in luminescence efficiency and enantioselectivity, indicating their potential for next-generation chiroptoelectronic applications.

Metal Halide Perovskite LEDs for Visible Light Communication and Lasing Applications

Metal halide perovskites, known for their pure and tunable light emission, near-unity photoluminescence quantum yields, favorable charge transport properties, and excellent solution processability, have emerged as promising materials for large-area, high-performance light-emitting diodes (LEDs). Over the past decade, significant advancements have been made in enhancing the efficiency, response speed, and operational stability of perovskite LEDs. These promising developments pave the way for a broad spectrum of applications extending beyond traditional solid-state lighting and displays to include visible light communication (VLC) and lasing applications. This perspective evaluates the current state of perovskite LEDs in those emerging areas, addresses the primary challenges currently impeding the development of perovskite-based VLC systems and laser diodes, and provides an optimistic outlook on the future realization of perovskite-based VLC and electrically pumped perovskite lasers.

Spin Dynamics in Hybrid Halide Perovskites - Effect of Dynamical and Permanent Symmetry Breaking

The hybrid organic-inorganic halide perovskite (HOIP), for example, MAPbBr3, exhibits extended spin lifetime and apparent spin lifetime anisotropy in experiments. The underlying mechanisms of these phenomena remain illusive. By utilizing our first-principles density-matrix dynamics approach with quantum scatterings including electron-phonon and electron-electron interactions and self-consistent spin-orbit coupling, we present temperature- and magnetic field-dependent spin lifetimes in hybrid perovskites, in agreement with experimental observations. For centrosymmetric hybrid perovskite MAPbBr3, the experimentally observed spin lifetime anisotropy is mainly attributed to the dynamic Rashba effect arising from the interaction between organic and inorganic components and the rotation of the organic cation. For noncentrosymmetric perovskites, such as MPSnBr3, we found persistent spin helix texture at the conduction band minimum, which significantly enhances the spin lifetime anisotropy. Our study provides theoretical insight into spin dynamics in HOIP and strategies for controlling and optimizing spin transport.

Factors influencing the chiral imprinting in perovskite nanoparticles

Chiral perovskites have emerged as a new class of nanomaterials for manipulation and control of spin polarized current and circularly polarized light for applications in spintronics, chiro-optoelectronics, and chiral photonics. While significant effort has been made in discovering and optimizing strategies to synthesize different forms of chiral perovskites, the mechanism through which chirality is imbued onto the perovskites by chiral surface ligands remains unclear. In this minireview, we provide a detailed discussion of one of the proposed mechanisms, electronic imprinting from a chiral ligand.

Spin-Orbital Ordering Effects of Light Emission in Organic-Inorganic Hybrid Metal Halide Perovskites

Organic-inorganic hybrid metal halide perovskites carrying strong spin-orbital coupling (SOC) have demonstrated remarkable light-emitting properties in spontaneous emission, amplified spontaneous emission (ASE), and circularly-polarized luminescence (CPL). Experimental studies have shown that SOC plays an important role in controlling the light-emitting properties in such hybrid perovskites. Here, the SOC consists of both orbital (L) and spin (S) momentum, leading to the formation of J (= L + S) excitons intrinsically involving orbital and spin momentum. In general, there are three issues in determining the effects of SOC on the light-emitting properties of J excitons. First, when the J excitons function as individual quasi-particles, the configurations of orbital and spin momentum directly decide the formation of bright and dark J excitons. Second, when the J excitons are mutually interacting as collective quasi-particles, the exciton-exciton interactions can occur through orbital and spin momentum. The exciton-exciton interactions through orbital and spin momentum give rise to different light-emitting properties, presenting SOC ordering effects. Third, the J excitons can develop ASE through coherent exciton-exciton interaction and CPL through exciton-helical ordering effect. This review article discusses the SOC effects in spontaneous emission, ASE, and CPL in organic-inorganic hybrid metal halide perovskites.

Intense Circular Dichroism and Spin Selectivity in AgBiS2 Nanocrystals by Chiral Ligand Exchange

Chiral semiconducting nanomaterials offer many potential applications in photodetection, light emission, quantum information, and so on. However, it is difficult to achieve a strong circular dichroism (CD) signal in semiconducting nanocrystals (NCs) due to the complexity of chiral ligand surface engineering and multiple, uncertain mechanisms of chiroptical behavior. Here, a chiral ligand exchange strategy with cysteine on the ternary metal chalcogenide AgBiS2 NCs is developed, and a strong, long-lasting CD signal in the near-UV region is achieved. By carefully optimizing the ligand concentration, the CD peaks are observed at 260 and 320 nm, respectively, giving insight into the different ligand binding mechanisms influencing the CD signal of AgBiS2 NCs. Using density-functional theory, a large degree of crystal distortion by the bidentate mode of ligand chelation, and efficient ligand-NC electron transfer, synergistically resulting in the strongest CD signal (g-factor over 10-2) observed in chiral ligand-exchanged semiconductor NCs to date, is demonstrated. To demonstrate the effective chiral properties of these AgBiS2 NCs, a spin-filter device with over 86% efficiency is fabricated. This work represents a considerable leap in the field of chiral semiconductor NCs and points toward their future applications.

Optical resolution via chiral auxiliaries of curved subphthalocyanine aromatics

Chiral conjugated materials with curved topologies hold significant promise for advanced optoelectronic applications. Among these, bowl-shaped subphthalocyanine (SubPc) aromatics are particularly noteworthy due to their superb optoelectronic properties and synthetic versatility. Despite their potential, the development and application of inherently chiral SubPcs as functional materials have been hampered by the scalability and feasibility limitations of current high-performance liquid chromatography methods. In this work, we employ axial derivatization with BINOL-based chiral auxiliaries to achieve the optical resolution of C 3-symmetric SubPcs. This approach allows us to obtain optically active meta and ortho-substituted SubPc derivatives in high yields and enantiomeric excess through straightforward organic chemistry protocols. In addition, we serendipitously observe unprecedented bowl-to-bowl inversion of the SubPc macrocycle upon removal of the derivatizing ligand under specific experimental conditions. These findings represent a significant milestone in the study of chirality in curved aromatics.

The chirality-induced spin selectivity effect in asymmetric spin transport: from solution to device applications

The chirality-induced spin selectivity (CISS) effect has garnered significant interest in the field of molecular spintronics due to its potential to create spin-polarized electrons without the need for a magnet. Recent studies devoted to CISS effects in various chiral materials demonstrate exciting prospects for spintronics, chiral recognition, and quantum information applications. Several experimental studies have confirmed the applicability of chiral molecules in spin-filtering properties, influencing spin-polarized electron transport and photoemission. Researchers aim to predict CISS phenomena and apply this concept to practical applications by compiling experimental results. To expand the possibilities of spin manipulation and create new opportunities for spin-based technologies, researchers are diligently exploring different chiral organic and inorganic materials for probing the CISS effect. This ongoing research holds promise for developing novel spin-based technologies and advancing the understanding of the intricate relationship between chirality and electron spin. The review highlights the remarkable experimental and theoretical frameworks related to the CISS effect, its impact on spintronics, and its relevance in other scientific areas.

Halogen-Dependent Circular Dichroism and Magneto-Photoluminescence Effects in Chiral 2D Lead Halide Perovskites

Chiral lead halide perovskites (chiral LHPs) have emerged as one of the best candidates for opto-spintronics due to their large spin-orbit coupling (SOC) and unique chirality-induced spin selectivity (CISS) even in the absence of a magnetic field. Here, we report the impact of halide composition on circular dichroism (CD) and magneto-photoluminescence (PL) effects of chiral 2D LHPs (R/S-MBA)2PbBrxI4-x (MBA = C6H5CH2(CH3)NH3). By tuning the mixing ratio of Br/I halide anions, we find that (R/S-MBA)2PbBrxI4-x thin films exhibit tunable and wide wavelength range CD signals. Simultaneously, the main CD signals near the exciton absorption band gradually blue shift until they disappear. Moreover, the halogen-dependent negative magneto-PL effects of (R/S-MBA)2PbBrxI4-x thin films excited by left/right circularly polarized light can be detected at room temperature. We demonstrated that the halide composition can effectively modulate exciton splitting and chirality transfer in (R/S-MBA)2PbBrxI4-x owing to the chirality-induced SOC and crystalline structure transition, which lead to the adjustable CD signals. The interplay of Rashba-type band spin splitting and spin mixing among bright triplet exciton states is responsible for the halogen-dependent magneto-PL effect of chiral 2D LHPs. This study enables chiral 2D LHPs with CISS to be a new class of promising opto-spintronics materials for exploring high-performance spin-light-emitting diodes by halide engineering.

Layered hybrid superlattices as designable quantum solids

Crystalline solids typically show robust long-range structural ordering, vital for their remarkable electronic properties and use in functional electronics, albeit with limited customization space. By contrast, synthetic molecular systems provide highly tunable structural topologies and versatile functionalities but are often too delicate for scalable electronic integration. Combining these two systems could harness the strengths of both, yet realizing this integration is challenging owing to distinct chemical bonding structures and processing conditions. Two-dimensional atomic crystals comprise crystalline atomic layers separated by non-bonding van der Waals gaps, allowing diverse atomic or molecular intercalants to be inserted without disrupting existing covalent bonds. This enables the creation of a diverse set of layered hybrid superlattices (LHSLs) composed of alternating crystalline atomic layers of variable electronic properties and self-assembled atomic or molecular interlayers featuring customizable chemical compositions and structural motifs. Here we outline strategies to prepare LHSLs and discuss emergent properties. With the versatile molecular design strategies and modular assembly processes, LHSLs offer vast flexibility for weaving distinct chemical constituents and quantum properties into monolithic artificial solids with a designable three-dimensional potential landscape. This opens unprecedented opportunities to tailor charge correlations, quantum properties and topological phases, thereby defining a rich material platform for advancing quantum information science.

A Family of Twisted Chiral Engineered Inorganic Nanoarchitectures

Chiral inorganic materials possess unique asymmetric properties that could significantly impact various fields. However, their practical application has been hindered by challenges in creating structurally robust chiral materials. We report the synthesis of well-defined chiral-shaped hollow cobalt oxide nanostructures, extendable to a family of chalcogenides including sulfide, selenide, and telluride through topological transformations. Taking chiral cobalt oxide nanostructures as a representative material, we demonstrate precise control over their chiral architectures, enabling fine-tuning of parameters, such as twist degrees, handedness, and compositions. These chiral nanostructures exhibit high spin selectivity effects that influence the electron transfer processes in catalytic reactions. Leveraging this spin-selective behavior, the chiral cobalt oxide nanoarchitectures demonstrate enhanced electrocatalytic performance in the oxygen evolution reaction compared to their achiral counterparts. Our findings not only expand the library of chiral inorganic materials but also advance the application of chiral effects in fields such as catalysis, spintronics, and beyond.

Remote chirality transfer in low-dimensional hybrid metal halide semiconductors

In hybrid metal halide perovskites, chiroptical properties typically arise from structural symmetry breaking by incorporating a chiral A-site organic cation within the structure, which may limit the compositional space. Here we demonstrate highly efficient remote chirality transfer where chirality is imposed on an otherwise achiral hybrid metal halide semiconductor by a proximal chiral molecule that is not interspersed as part of the structure yet leads to large circular dichroism dissymmetry factors (gCD) of up to 10-2. Density functional theory calculations reveal that the transfer of stereochemical information from the chiral proximal molecule to the inorganic framework is mediated by selective interaction with divalent metal cations. Anchoring of the chiral molecule induces a centro-asymmetric distortion, which is discernible up to four inorganic layers into the metal halide lattice. This concept is broadly applicable to low-dimensional hybrid metal halides with various dimensionalities (1D and 2D) allowing independent control of the composition and degree of chirality.