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We prove Strichartz estimates (both regular and reversed) for a scattering state to the wave equation with a charge transfer Hamiltonian in

Recently, a bulk nickelate superconductor La 3 Ni 2 O 7 is discovered at pressures with a remarkable high transition temperature T c ∼ 80 K. Here, we study a Hubbard model with tight-binding parameters derived from ab initio calculations of La 3 Ni 2 O 7 , by employing large scale determinant quantum Monte Carlo and cellular dynamical mean-field theory. Our result suggests that the superexchange couplings in this system are comparable to that of cuprates. The system is a charge transfer insulator as the hole concentration becomes four per site at large Hubbard U . Upon hole doping, two low-energy spin-singlet bands emerge in the system exhibiting distinct correlation properties: while the one composed of the out-of-plane Ni- d 3 z 2 − r 2 and O- p z orbitals demonstrates strong antiferromagnetic correlations and narrow effective bandwidth, the in-plane singlet band consisting of the Ni- d x 2 − y 2 and O- p x / p y orbitals is in general more itinerant. Over a broad range of hole doping, the doped holes occupy primarily the d x 2 − y 2 and p x / p y orbitals, whereas the d 3 z 2 − r 2 and p z orbitals retain underdoped. We propose an effective t - J model to capture the relevant physics and discuss the implications of our result for comprehending the La 3 Ni 2 O 7 superconductivity.

Multiresonant thermally activated delayed fluorescence (MR‐TADF) emitters have been the focus of extensive design efforts as they are recognized to show bright, narrowband emission, which makes them very appealing for display applications. However, the planar geometry and relatively large singlet–triplet energy gap lead to, respectively, severe aggregation‐caused quenching (ACQ) and slow reverse intersystem crossing (RISC). Here, a design strategy is proposed to address both issues. Two MR‐TADF emitters triphenylphosphine oxide (TPPO)‐tBu‐DiKTa and triphenylamine (TPA)‐tBu‐DiKTa have been synthesized. Twisted ortho‐substituted groups help increase the intermolecular distance and largely suppress the ACQ. In addition, the contributions from intermolecular charge transfer states in the case of TPA‐tBu‐DiKTa help to accelerate RISC. The organic light‐emitting diodes (OLEDs) with TPPO‐tBu‐DiKTa and TPA‐tBu‐DiKTa exhibit high maximum external quantum efficiencies (EQEmax) of 24.4% and 31.0%, respectively. Notably, the device with 25 wt% TPA‐tBu‐DiKTa showed both high EQEmax of 28.0% and reduced efficiency roll‐off (19.9% EQE at 1000 cd m−2) compared to the device with 5 wt% emitter (31.0% EQEmax and 11.0% EQE at 1000 cd m−2). The new emitters were also introduced into single‐layer light‐emitting electrochemical cells (LECs), equipped with air‐stable electrodes. The LEC containing TPA‐tBu‐DiKTa dispersed at 0.5 wt% in a matrix comprising a mobility‐balanced blend‐host and an ionic liquid electrolyte delivered blue luminance with an EQEmax of 2.6% at 425 cd m−2. The high efficiencies of the OLEDs and LECs with TPA‐tBu‐DiKTa illustrate the potential for improving device performance when the DiKTa core is decorated with twisted bulky donors. DiKTa cores decorated with twisted ortho‐disposed groups show high photoluminescence quantum yield (PLQY) and suppression of aggregation‐caused quenching (ACQ). triphenylamine (TPA)‐tBu‐DiKTa with ortho‐disposed donors also shows improved reverse intersystem crossing (RISC) process, which contributes to outstanding performance in both organic light‐emitting diodes (OLEDs) and light‐emitting electrochemical cells (LECs).

The existence of bound charge transfer (CT) excitons at the interface of monolayer lateral heterojunctions has been debated in literature, but contrary to the case of interlayer excitons in vertical heterostructure their observation still has to be confirmed. Here, we present a microscopic study investigating signatures of bound CT excitons in photoluminescence spectra at the interface of hBN-encapsulated lateral MoSe 2 -WSe 2 heterostructures. Based on a fully microscopic and material-specific theory, we reveal the many-particle processes behind the formation of CT excitons and how they can be tuned via interface- and dielectric engineering. For junction widths smaller than the Coulomb-induced Bohr radius we predict the appearance of a low-energy CT exciton. The theoretical prediction is compared with experimental low-temperature photoluminescence measurements showing emission in the bound CT excitons energy range. We show that for hBN-encapsulated heterostructures, CT excitons exhibit small binding energies of just a few tens meV and at the same time large dipole moments, making them promising materials for optoelectronic applications (benefiting from an efficient exciton dissociation and fast dipole-driven exciton propagation). Our joint theory-experiment study presents a significant step towards a microscopic understanding of optical properties of technologically promising 2D lateral heterostructures. The authors unveil the many-particle processes underpinning the formation of bound charge transfer excitons at the interface of hBN-encapsulated lateral MoSe 2 -WSe 2 heterostructures. The excitons can be tuned via interface (i.e. high quality lateral junction) and dielectric (i.e. hBN encapsulation) engineering.

Doping of organic semiconductors is crucial for the operation of organic (opto)electronic and electrochemical devices. Typically, this is achieved by adding heterogeneous dopant molecules to the polymer bulk, often resulting in poor stability and performance due to dopant sublimation or aggregation. In small-molecule donor–acceptor systems, charge transfer can yield high and stable electrical conductivities, an approach not yet explored in all-conjugated polymer systems. Here, we report ground-state electron transfer in all-polymer donor–acceptor heterojunctions. Combining low-ionization-energy polymers with high-electron-affinity counterparts yields conducting interfaces with resistivity values five to six orders of magnitude lower than the separate single-layer polymers. The large decrease in resistivity originates from two parallel quasi-two-dimensional electron and hole distributions reaching a concentration of ∼10 13  cm –2 . Furthermore, we transfer the concept to three-dimensional bulk heterojunctions, displaying exceptional thermal stability due to the absence of molecular dopants. Our findings hold promise for electro-active composites of potential use in, for example, thermoelectrics and wearable electronics. Doping through spontaneous electron transfer between donor and acceptor polymers is obtained by selecting organic semiconductors with suitable electron affinity and ionization energy, achieving high conductivity in blends and bilayer configuration.

Doping of semiconductors, i.e., accurately modulating the charge carrier type and concentration in a controllable manner, is a key technology foundation for modern electronics and optoelectronics. However, the conventional doping technologies widely utilized in silicon industry, such as ion implantation and thermal diffusion, always fail when applied to two-dimensional (2D) materials with atomically-thin nature. Surface charge transfer doping (SCTD) is emerging as an effective and non-destructive doping technique to provide reliable doping capability for 2D materials, in particular 2D semiconductors. Herein, we summarize the recent advances and developments on the SCTD of 2D semiconductors and its application in electronic and optoelectronic devices. The underlying mechanism of STCD processes on 2D semiconductors is briefly introduced. Its impact on tuning the fundamental properties of various 2D systems is highlighted. We particularly emphasize on the SCTD-enabled high-performance 2D functional devices. Finally, the challenges and opportunities for the future development of SCTD are discussed.

To satisfy the requirements of substantial green development, it is urgent to explore an innovative eco‐friendly semiconductor photocatalyst to efficiently achieve visible‐light‐driven photocatalytic H2 evolution (PHE). The strategy of promoting the spatial separation efficiency of photoinduced carriers can essentially enhance the PHE performance of a photocatalyst. Herein, a graphitic carbon nitride (g‐C3N4)‐based donor–acceptor (D‐A) copolymer (CNDMx) is constructed by simple one‐pot thermal polycondensation, using urea and 5,8‐DibroMoquinoxaline (as an electron donor) as precursors. The electron D‐A modulation consequently creates an internal electric field to facilitate the intramolecular charge transfer within the copolymer. A series of experimental characterizations and density functional theory calculations are applied to elucidate the variation and correlation of the structure and PHE performance of the as‐prepared catalysts. It is found that the best average PHE rate of 3012.5 μmol g−1 h−1 can be achieved over the optimal D‐A copolymer under visible‐light (400 < λ < 800 nm) irradiation, which is ~3.3 times that of pure urea‐derived g‐C3N4. The corresponding apparent quantum efficiency is 1.3% at 420 nm. This study provides a protocol for designing effective visible‐light photocatalysts via D‐A modulation of polymeric semiconductors. A critical factor during semiconductor‐based photocatalytic H2 evolution (PHE) is the effective separation of photoinduced carriers. In this study, the internal electric field is built for intramolecular charge transfer of carbon nitride after donor–acceptor modulation, ensuring efficient PHE.

We investigate SrIrO₃/LaNiO₃ superlattices in which we observe a full electron transfer at the interface from Ir to Ni, triggering a massive structural and electronic reconstruction. Through experimental characterization and first-principles calculations, we determine that a large crystal field splitting from the distorted interfacial IrO₆ octahedra surprisingly dominates over the spin–orbit coupling and together with the Hund’s coupling results in the high-spin (S = 1) configurations on both the Ir and Ni sites. This demonstrates the power of interfacial charge transfer in coupling lattice, charge, orbital, and spin degrees of freedom, opening fresh avenues of investigation of quantum states in oxide superlattices.

A general mechanism is presented by which topological physics arises in strongly correlated systems without flat bands. Starting from a charge transfer insulator, topology emerges when the charge transfer energy between the cation and anion is reduced to invert the lower Hubbard band and the spin-degenerate charge transfer band. A universal low-energy theory is developed for the inversion of the charge transfer gap in a quantum antiferromagnet. The inverted state is found to be a quantum anomalous Hall (QAH) insulator with noncoplanar magnetism. Interactions play two essential roles in this mechanism: producing the insulating gap and quasiparticle bands prior to the band inversion, and causing the change of magnetic order necessary for the QAH effect after inversion. Our theory explains the electric-field-induced transition from a correlated insulator to a QAH state inAB-stacked transition-metal-dichalcogenides bilayerMoTe2/WSe2.

Although numerous thermally activated delayed fluorescence (TADF) organic light‐emitting diodes (OLEDs) have been demonstrated, efficient blue or even sky‐blue TADF‐based nondoped solution‐processed devices are still very rare. Herein, through‐space charge transfer (TSCT) and through‐bond charge transfer (TBCT) effects are skillfully incorporated, as well as the multi‐(donor/acceptor) characteristic, into one molecule. The former allows this material to show small singlet–triplet energy splitting (ΔEST) and a high transition dipole moment. The latter, on the one hand, further lights up multichannel reverse intersystem crossing (RISC) to increase triplet exciton utilization via degenerating molecular orbitals. On the other hand, the nature of the molecular twisted structure effectively suppresses intermolecular packing to obtain high photoluminescence quantum yield (PLQY) in neat flims. Consequently, using this design strategy, T‐CNDF‐T‐tCz containing three donor and three acceptor units, successfully realizes a small ΔEST (≈0.03 eV) and a high PLQY (≈0.76) at the same time; hence the nondoped solution‐processed sky‐blue TADF‐OLED displays record‐breaking efficiency among the solution process‐based nondoped sky‐blue OLEDs, with high brightness over 5200 cd m−2 and external quantum efficiency up to 21.0%. A novel multi‐(donor/acceptor) thermally activated delayed fluorescence (TADF) molecule with through‐space/‐bond charge transfer is developed. Its nondoped solution‐processed sky‐blue organic light‐emitting diode (OLED) displays high performance with an external quantum efficiency (EQEmax) up to 21.0%, which represents the record‐breaking efficiency among the solution process‐based nondoped sky‐blue OLEDs.