The orbital angular momentum of electrons presents exciting opportunities for developing energy-efficient, low-power magnetic devices. Typically, the generation of orbital currents is driven by the transfer of orbital angular momentum from 3d transition metal magnets, either through the application of an electric field using the orbital Hall effect or through magnetization dynamics. Chiral phonons are quantized lattice vibrations that carry non-zero angular momentum due to the circular motion of atoms. An interplay of chiral phonon dynamics and electrons would enable the direct generation of orbital angular momentum, even without the need for magnetic elements. Here we experimentally demonstrate the generation of orbital currents from chiral phonons activated in the chiral insulator α-quartz under an applied magnetic field and a temperature gradient. We refer to this phenomenon as the orbital Seebeck effect. The generated orbital current is selectively detected in tungsten and titanium films deposited on quartz through the inverse orbital Hall effect. Our findings hold promise for orbitronics based on chiral phonons in non-magnetic insulators and shed light on the fundamental understanding of chiral phonons and their interaction with electron orbitals. Generation of orbital currents in a non-magnetic material can be useful to build efficient orbitronic devices. Now, the interplay of chiral phonons and electrons is shown to produce orbital currents in α-quartz.

Organic light-emitting diodes (OLEDs) have been established as a premium display technology for consumer electronics and offer much promise for flexible, large-screen electronics and wearable devices. Despite their commercial success, OLED displays still face major bottlenecks in performance, including limited efficiency, operational lifetime (stability), and efficiency roll-off at high brightness. Deuteration of OLED hosts and emitters is an effective means to address these limitations for fluorescent and phosphorescent systems. Here we describe recent advancements in the development of deuterated organic and organometallic compounds for OLEDs, with a particular focus on their performance benefits, the underlying working mechanisms, and practical challenges associated with their large-scale adoption. This Review surveys recent advances in deuterated compounds for light-emitting devices, addressing the advantages of deuteration, its working mechanisms, and prospects for wider implementation.

Chiral materials are important tools for transducing circularly polarized light within many emerging opto-electronic and spin-based technologies. Here, we demonstrate that thin films of a bismuth iodide-based 0D chiral hybrid organic-inorganic semiconductor (HOIS) exhibit large anisotropy values in circularly polarized light emission (CPLE) that approach 50%, with mirror-image responses from front-and back-side measurements. A comprehensive analysis of light-wave propagation, absorption, emission, and scattering is constructed on the basis of a symmetry-derived exciton fine structure model, which accurately describes the direction and polarization dependence of the observed excitonic circular dichroism and CPLE, including contributions from both photoluminescence and resonant Raman scattering. Our analysis indicates that molecular chirality drives preferential film alignment with respect to the out-of-plane lattice vector direction, producing the observed anisotropies. This first demonstration in an HOIS system provides a unique route for enhancing polarization-dependent emission, and circularly polarized light transduction more broadly, in self-assembled HOIS.

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.

Two-dimensional (2D) hybrid organic/inorganic perovskites are an emerging materials class for optoelectronic and spintronic applications due to strong excitonic absorption and emission, large spin-orbit coupling, and Rashba spin-splitting effects. For many of the envisioned applications, tuning the majority charge carrier (electron or hole) concentration is desirable, but electronic doping of metal-halide perovskites has proven to be challenging. Here, we demonstrate electron injection into the lower-energy branch of the Rashba-split conduction band of 2D phenethylammonium lead iodide by means of n-type molecular doping at room temperature. The molecular dopant, benzyl viologen (BV), is shown to compensate adventitious p-type impurities and can lead to a tunable Fermi level above the conduction band minimum and increased conductivity in intrinsic samples. The doping-induced carrier concentration is monitored by the observation of free-carrier absorption and intraband optical transitions in the infrared spectral range. These optical measurements allow for an estimation of the Rashba splitting energy E R approximate to 38 +/- 4 meV. Photoinduced quantum beating measurements demonstrate that the excess electron density reduces the electron spin g-factor by ca. 6%. This work demonstrates controllable carrier concentrations in hybrid organic/inorganic perovskites and yields potential for room temperature spin control through the Rashba effect.

Two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs) with enhanced stability, high tunability, and strong spin-orbit coupling have shown great potential in vast applications. Here, we extend the already rich functionality of 2D HOIPs to a new territory, realizing topological superconductivity and Majorana modes for fault-tolerant quantum computation. Especially, we predict that room-temperature ferroelectric BA2PbCl4 (BA for benzylammonium) exhibits topological nodal-point superconductivity (NSC) and gapless Majorana modes on selected edges and ferroelectric domain walls when proximity-coupled to an s-wave superconductor and an in-plane Zeeman field, attractive for experimental verification and application. Since NSC is protected by spatial symmetry of 2D HOIPs, we envision more exotic topological superconducting states to be found in this class of materials due to their diverse noncentrosymmetric space groups, which may open a new avenue in the fields of HOIPs and topological superconductivity.

In thermally activated delayed -fluorescence (TADF) materials, the fluorescence efficiency is enhanced through reverse intersystem crossing (RISC) from triplet to singlet excitons. The performance of organic light -emitting devices (OLEDs) based on TADF materials highly depends on the thermal conversion efficiency of the lowest triplet exciton T1 into the lowest singlet exciton S1, which relates to the energy difference AES1-T1. Here we investigate the RISC process in two TADF compounds with vastly different AES1-T1 using magneto -optical spectroscopies that include magnetophotoinduced absorption (MPA) in films and magnetoelectroluminescence (MEL) in OLEDs. The photoinduced absorption spectrum of the fast RISC material clearly shows that both singlet and triplet excitons coexist under steady-state conditions. Since the MPA response of the singlet and triplet excitons are similar and have the same polarity, we conclude that the magnetic field does not influence the RISC process in the studied compounds. We also find that the MEL response in OLEDs based on these compounds originates from the injected polaron pair species before they decay into S1 and T1 excitonic states in the emissive TADF layer.

We present time-resolved Kerr rotation (TRKR) spectra in thin films of CH3NH3PbI3 (MAPI) hybrid perovskite using a unique picosecond microscopy technique at 4 K having a spatial resolution of 2 mu m and temporal resolution of 1 ps, subjected to both an in-plane applied magnetic field up to 700 mT and an electric field up to 10(4) V/cm. We demonstrate that the obtained TRKR dynamics and spectra are substantially inhomogeneous across the MAPI films with prominent resonances at the exciton energy and interband transition of this compound. From the obtained quantum beating response as a function of magnetic field in the Voigt configuration, we also extract the inhomogeneity of the electron and hole Lande g-values and spin coherence time, T-2*. We also report the TRKR dependence on both the applied magnetic field and electric field. From the change in the quantum beating dynamics, we found that T-2* substantially decreases upon the application of an electric field. At the same time, from the induced spatial TRKR changes, we show that the electric field induced effects are caused by ion migration in the MAPI films.

Picosecond time-resolved and cw magneto-optical methods have been used for studying the spin-related properties of excitons and photocarriers in methyl-ammonium lead bromide (MAPbBr(3)) thin film, single crystal, and light-emitting diodes (LED), focusing on the Lande g values of these species. Using the transient circularly polarized photoinduced quantum beatings (QB) under an applied magnetic field, B in MAPbBr(3) single crystal, we obtained the anisotropic g values of electrons for B field along [010] and [001]: |g([001])(e)| = 2.15 and |g([010])(e)| = 1.75, and for holes |g([001])(h)| = 0.42 and |g([010])(h)| = 0.60. We also used the magnetic circular dichroism method for measuring the bright excitons' g value, g(ex) = g(e) + g(h) = 2.5. From these two types of measurements we conclude that g(h) > 0 in MAPbBr(3). This conclusion was corroborated by measuring the magnetoelectroluminescence response of LED based on MAPbBr(3) active layer. The g values in single crystal and their average in films are in excellent agreement with a k center dot p model that shows similarity and difference to those of MAPbI3. We also observed the influence of the Overhauser field on the QB frequencies that is induced by the dynamic nuclear polarization generated by the spin-aligned electrons using circularly polarized pump or probe beams.

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. Hybrid metal halide semiconductors typically rely on chiral A-site ammonium cations for chiral induction in the lattice. Now it has been shown that chirality in low-dimensional achiral metal halide semiconductors can be induced by non-ammonium, non-A-site chiral molecules through remote stereocontrol of the inorganic framework.

Spintronics in halide perovskites has drawn significant attention in recent years, due to their highly tunable spin-orbit fields and intriguing interplay with lattice symmetry. Here, we perform first-principles calculations to determine the spin relaxation time (T-1) and ensemble spin dephasing time (T-2(*)) in a prototype halide perovskite, CsPbBr3. To accurately capture spin dephasing in external magnetic fields we determine the Lande g-factor from first principles and take it into account in our calculations. These allow us to predict intrinsic spin lifetimes as an upper bound for experiments, identify the dominant spin relaxation pathways, and evaluate the dependence on temperature, external fields, carrier density, and impurities. We find that the Frohlich interaction that dominates carrier relaxation contributes negligibly to spin relaxation, consistent with the spin-conserving nature of this interaction. Our theoretical approach may lead to new strategies to optimize spin and carrier transport properties.

This study revisits the electroabsorption (EA) spectrum of polyacetylene, (CH)(x) thin films, for both the cis- and trans-isomers, as functions of the electric field strength, isomerization degree, and light polarization states. The EA spectrum of cis-(CH)(x) reveals an oscillatory feature that follows the Stark shift-related first derivative of the material's absorption spectrum that contains v(0-1) and v(0-2) sidebands of the excited C=C stretching vibration that agrees well with the Raman scattering (RS) spectrum. In contrast, the EA spectrum of trans-(CH)(x) does not match the first derivative of the material's absorption spectrum, and the phonon sideband frequency does not agree with the RS spectrum. In addition, the EA spectrum of trans-(CH)(x) reveals a band below the first allowed 1B(u) exciton. We interpret this feature as due to the electric field activated even-parity dark (forbidden) exciton, namely mA(g) (m > 2), showing that the "nonluminescent" trans-(CH)(x) is due to the reverse order of the excited states, where a series of dark mA(g) excitons lies below the allowed 1B(u) exciton. This agrees with the unusual phonon sideband in trans-(CH)(x) absorption, since the excited state attenuation caused by the fast internal conversion from 1B(u) to mA(g) influences the apparent frequency that determines the phonon sideband. Consequently, from the EA and RS spectra we estimate the 1B(u) lifetime in trans-(CH)(x) to be similar to 30 fs. Moreover, the integrated EA spectrum of trans-(CH)(x) shows a traditional Huang-Rhys type series with a relaxation parameter, S similar to 0.5. This indicates that the EA spectrum of the trans isomer is also determined by a Stark shift related to the first derivative of the absorption spectrum, but preferentially for the longest chains in the film's chain lengths distribution. This is due to the N-3 response of the nonlinear susceptibility, chi((3)) (similar to EA), dependence on the chain length having N monomers.

Overcoming the constraints of single-cation phases and further enhancing structural asymmetry represent critical objectives for optimizing emergent optoelectronic and spin-related properties in two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs). Here, we demonstrate homochiral (S/S) and heterochiral (R/S) cation mixing in 2D HOIPs via a 1:1 mixing of S- and R-4-bromo-alpha-methylbenzylammonium with S-1-methylhexyammonium. The R/S system achieves an enhanced structural asymmetry, marked by a significant Pb-I-Pb bond angle disparity (Delta beta = 9.24 degrees), attributed to the distinctive asymmetric templating effects from mixed cations with distinct molecular structures and opposite absolute configurations. Consequently, spin-orbit-coupled hybrid density functional theory (DFT) calculations indicate a substantial spin splitting (Delta E = 78.5 meV), among the largest reported for PbI42--based 2D HOIPs. Nonequivalent chiral information from homo- and heterochiral mixing further modulates the Cotton effect for the same elemental composition. Our study demonstrates an important materials design strategy for enhancing structural asymmetry and advancing symmetry-breaking-reliant properties in organic-inorganic hybrids.

We have studied the spin properties of localized photocarriers in the band tails (BT) of polycrystalline MAPbBr(3) films having a nanometer crystal size using circularly polarized photoluminescence (PL) induced by a magnetic field up to 17.5 T at cryogenic temperatures as well as time-of-flight (TOF) transient photocurrent. The absorption spectrum of these films reveals BT states caused by structural and energetic disorders, having a broadly distributed Urbach edge ranging from 28 to 120 meV. This is corroborated by dispersive transport of photogenerated electrons and holes observed via TOF, where the photocarriers thermalize with time deeply in the BT, giving rise to time-dependent mobility. Consequently, the PL emission spectrum in these films originates from radiative recombination of the localized electron and hole pairs in the BT states. Upon applying a magnetic field in the Faraday configuration, field-induced circular polarized PL has been observed, from which an effective Lande g-factor of the localized e-h pairs, g(e-h), was extracted to be 2.5 +/- 0.2, in good agreement with the g-factor of free excitons measured using magnetic circular dichroism spectroscopy. In addition, we also found that the spin relaxation time for the e-h pairs in the BT states is similar to 26 ns at 5 K and similar to 10 ns at 80 K, indicating that nanocrystalline MAPbBr(3) could be a good candidate for applications in spintronics and quantum computing.

A comprehensive study of the exciton fine structure (EFS) is presented in 2D‐phenethylammonium lead iodide films using magnetic field‐induced polarization of photoluminescence (PL) in both Faraday and Voigt configurations at fields up to 25 Tesla. Three exciton bands are identified in the PL spectrum associated with bound, dark, and bright excitons, respectively. Under a high magnetic field in Faraday/Voigt configuration, large field‐induced circular/linear polarization is observed in the PL band related to the dark exciton, which is magnetically activated. Furthermore, it is found that the dark exciton has an anomalous field‐induced circular polarization, which cannot be explained by the classical Boltzmann distribution of spin‐polarized species. These findings are well explained by an effective mass model that includes exchange terms unique to the monoclinic symmetry as a perturbation of the EFS in the approximate tetragonal symmetry. It is also confirmed that the field‐induced linear polarization is sensitive to the monoclinic exchange term, whereas the field‐induced circular polarization is immune to such term.

Spin accumulation in semiconductor structures at room temperature and without magnetic fields is key to enable a broader range of opto-electronic functionality. Current efforts are limited due to inherent inefficiencies associated with spin injection into semiconductor structures. Here, we demonstrate spin injection across chiral halide perovskite/III-V interfaces achieving spin accumulation in a standard semiconductor III-V (AlxGa1-x)0.5In0.5P multiple quantum well (MQW) light emitting diode (LED). The spin accumulation in the MQW is detected via emission of circularly polarized light with a degree of polarization of up to ~15%. The chiral perovskite/III-V interface was characterized with X-ray photoemission spectroscopy (XPS), cross sectional scanning Kelvin probe force microscopy, and cross section transmission electron microscopy (TEM) imaging, showing a clean semiconductor/semiconductor interface where the fermi-level can equilibrate. These findings demonstrate chiral perovskite semiconductors can transform well-developed semiconductor platforms to ones that can also control spin.

Chiral materials exhibit many interesting physical properties including circular dichroism, circularly polarized photoluminescence, and spin selectivity. Since its discovery, chirality-induced spin selectivity (CISS) has been demonstrated in many chiral material systems, which indicates promising applications in spintronic devices. Thus, searching for compounds that possess both sizable chirality and excellent spin transport properties is in order. Hybrid organic-inorganic perovskites have attracted intensive research interest due to their long carrier lifetime, high carrier mobility, chemically tunable electronic properties, and long spin lifetime, which make this emerging class of semiconductors promising candidate for spintronics. Moreover, hybrid perovskites integrate inorganic octahedral framework and organic ligands, which may introduce chirality into the materials, especially in quasi-two-dimensional structures. Recently, CISS has been observed in 2D chiral hybrid perovskites, showing the spin filtering effect. Studies of CISS in chiral hybrid perovskites not only help deepen our understanding of CISS mechanism but also shed new light on designing novel spintronic devices. In this review, we summarize the state-of-the-art studies of CISS effect in 2D chiral hybrid organic-inorganic perovskites system. We also discuss the remaining challenges and research opportunities of employing CISS in next-generation spintronic devices.

The relationship between the structural asymmetry and optoelectronic properties of functional materials is an active area of research. The movement of charges through an oriented chiral medium depends on the spin configuration of the charges, and such systems can be used to control spin populations without magnetic components - termed the chiral-induced spin selectivity (CISS) effect. CISS has mainly been studied in chiral organic molecules and their assemblies. Semiconductors are non-magnetic extended systems that allow for the control of charge transport, as well as the absorption and emission of light. Therefore, introducing chirality into semiconductors would enable control over charge, spin and light without magnetic components. Chiral metal halide semiconductors (MHSs) are hybrid organic-inorganic materials that combine the properties of small chiral organic molecules with those of extended inorganic semiconductors. Reports of CISS in chiral MHSs have resulted in breakthroughs in our understanding of CISS and in the realization of spin-dependent optoelectronic properties. This Review examines the fundamentals and applications of CISS in chiral MHSs. The structural diversity and key structure-property relationships, such as chiral transfer from the organic to the inorganic components, are summarized. With a focus on the underlying chemistry and physics, the control of spin, light and charge in these semiconductors is explored.

High-Tc molecular magnets have amassed much promise; however, the long-standing obstacle for its practical applications is the inaccessibility of high-temperature molecular magnets showing dynamic and nonvolatile magnetization control. In addition, its functional durability is prone to degradation in oxygen and heat. Here, we introduce a rapid prototyping and stabilizing strategy for high Tc (360 K) molecular magnets with precise spatial control in geometry. The printed molecular magnets are thermally stable up to 400 K and air-stable for over 300 days, a significant improvement in its lifetime and durability. X-ray magnetic circular dichroism and computational modeling reveal the water ligands controlling magnetic exchange interaction of molecular magnets. The molecular magnets also show dynamical and reversible tunability of magnetic exchange interactions, enabling a colossal working temperature window of 86 K (from 258 to 344 K). This study provides a pathway to flexible, lightweight, and durable molecular magnetic devices through additive manufacturing.