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Dynamically Steered Maser Action of Rydberg Excitons in Cu <sub/>2</sub> O
摘要： The Rydberg excitons in Cu2O are a promising candidate for realization of solid state maser. The highly excited states, unique to this crystal, provide the necessary energy level transitions for emission of microwaves. The achievement of population inversion is facilitated by exceptionally long lifetimes of excitons and their strong coupling to external field. Moreover, due to the strong Stark shift of excitonic energy levels, one can tune the emission wavelength on demand.
关键词： Rydberg excitons,microwaves,maser
更新于2025-09-23 15:22:29
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Efficient and stable emission of warm-white light from lead-free halide double perovskites
摘要： Lighting accounts for one-fifth of global electricity consumption1. Single materials with efficient and stable white-light emission are ideal for lighting applications, but photon emission covering the entire visible spectrum is difficult to achieve using a single material. Metal halide perovskites have outstanding emission properties2,3; however, the best-performing materials of this type contain lead and have unsatisfactory stability. Here we report a lead-free double perovskite that exhibits efficient and stable white-light emission via self-trapped excitons that originate from the Jahn–Teller distortion of the AgCl6 octahedron in the excited state. By alloying sodium cations into Cs2AgInCl6, we break the dark transition (the inversion-symmetry-induced parity-forbidden transition) by manipulating the parity of the wavefunction of the self-trapped exciton and reduce the electronic dimensionality of the semiconductor4. This leads to an increase in photoluminescence efficiency by three orders of magnitude compared to pure Cs2AgInCl6. The optimally alloyed Cs2(Ag0.60Na0.40)InCl6 with 0.04 per cent bismuth doping emits warm-white light with 86 ± 5 per cent quantum efficiency and works for over 1,000 hours. We anticipate that these results will stimulate research on single-emitter-based white-light-emitting phosphors and diodes for next-generation lighting and display technologies.
关键词： lead-free halide double perovskites,self-trapped excitons,white-light emission,photoluminescence efficiency,Jahn–Teller distortion
更新于2025-09-23 15:21:21
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Moire intralayer excitons in a MoSe <sub/>2</sub> /MoS <sub/>2</sub> heterostructure
摘要： Spatially periodic structures with a long range period, referred to as moir′e pattern, can be obtained in van der Waals bilayers in the presence of a small stacking angle or of lattice mismatch between the monolayers. Theoretical predictions suggest that the resulting spatially periodic variation of the band structure modifies the optical properties of both intra and interlayer excitons of transition metal dichalcogenides heterostructures. Here, we report on the impact of the moir′e pattern formed in a MoSe2/MoS2 heterobilayer encapsulated in hexagonal boron nitride. The periodic in-plane potential results in a splitting of the MoSe2 exciton and trion in both emission and absorption spectra. The observed energy difference between the split peaks is fully consistent with theoretical predictions.
关键词： valley polarization,van der Waals heterostructures,moir′e pattern,moir′e excitons,Transition metal dichalcogenides
更新于2025-09-23 15:21:21
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Electron–hole correlations govern Auger recombination in nanostructures
摘要： The fast nonradiative decay of multiexcitonic states via Auger recombination is a fundamental process affecting a variety of applications based on semiconductor nanostructures. From a theoretical perspective, the description of Auger recombination in confined semiconductor nanostructures is a challenging task due to the large number of valance electrons and exponentially growing number of excited excitonic and biexcitonic states that are coupled by the Coulomb interaction. These challenges have restricted the treatment of Auger recombination to simple, noninteracting electron–hole models. Herein we present a novel approach for calculating Auger recombination lifetimes in confined nanostructures having thousands to tens of thousands of electrons, explicitly including electron–hole interactions. We demonstrate that the inclusion of electron–hole correlations are imperative to capture the correct scaling of the Auger recombination lifetime with the size and shape of the nanostructure. In addition, correlation effects are required to obtain quantitatively accurate lifetimes even for systems smaller than the exciton Bohr radius. Neglecting such correlations can result in lifetimes that are 2 orders of magnitude too long. We establish the utility of the new approach for CdSe quantum dots of varying sizes and for CdSe nanorods of varying diameters and lengths. Our new approach is the first theoretical method to postdict the experimentally known “universal volume scaling law” for quantum dots and makes novel predictions for the scaling of the Auger recombination lifetimes in nanorods.
关键词： semiconductor nanocrystals,quantum dots,excitons,auger recombination,biexcitons,nanorods
更新于2025-09-23 15:21:21
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Vibrational fingerprint of localized excitons in a two-dimensional metal-organic crystal
摘要： Long-lived excitons formed upon visible light absorption play an essential role in photovoltaics, photocatalysis, and even in high-density information storage. Here, we describe a self-assembled two-dimensional metal-organic crystal, composed of graphene-supported macrocycles, each hosting a single FeN4 center, where a single carbon monoxide molecule can adsorb. In this heme-like biomimetic model system, excitons are generated by visible laser light upon a spin transition associated with the layer 2D crystallinity, and are simultaneously detected via the carbon monoxide ligand stretching mode at room temperature and near-ambient pressure. The proposed mechanism is supported by the results of infrared and time-resolved pump-probe spectroscopies, and by ab initio theoretical methods, opening a path towards the handling of exciton dynamics on 2D biomimetic crystals.
关键词： FeN4 center,spin transition,ab initio theoretical methods,excitons,carbon monoxide,infrared spectroscopy,graphene,time-resolved pump-probe spectroscopy,two-dimensional metal-organic crystal
更新于2025-09-23 15:21:21
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Strong Exciton-Plasmon Coupling and Hybridization of Organic-Inorganic Exciton-Polaritons in Plasmonic Nanocavity <sup>*</sup>
摘要： We investigate strong exciton-plasmon coupling and plasmon-mediated hybridization between the Frenkel (F) and Wannier–Mott (WM) excitons of an organic-inorganic hybrid system consisting of a silver ring separated from a monolayer WS2 by J-aggregates. The extinction spectra of the hybrid system calculated by employing the coupled oscillator model are consistent with the results simulated by the finite-difference time-domain method. The calculation results show that strong couplings among F excitons, WM excitons, and localized surface plasmon resonances (LSPRs) lead to the appearance of three plexciton branches in the extinction spectra. The weighting efficiencies of the F exciton, WM exciton and LSPR modes in three plexciton branches are used to analyze the exciton-polaritons in the system. Furthermore, the strong coupling between two different excitons and LSPRs is manipulated by tuning F or WM exciton resonances.
关键词： coupled oscillator model,finite-difference time-domain method,localized surface plasmon resonances,plasmonic nanocavity,exciton-plasmon coupling,Frenkel excitons,organic-inorganic hybrid system,Wannier–Mott excitons
更新于2025-09-23 15:21:01
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Excitation that lasts
摘要： The atomic-scale Legoland of two-dimensional (2D) materials has become a much-frequented scientific playground, with building blocks aplenty to create and explore virtually unlimited stacking configurations. When two or more individual monolayers are placed together to form an artificial homo- or heterostructure with weakly interacting constituent layers, that is where the real van der Waals (vdW) architecture begins. Such creations offer electronic, optical and magnetic phenomena that are often utterly unlike the monolayer case. One notable example is the emergence of a new type of exciton in which the electron and the hole are spatially located in different layers. While the formation of these ‘interlayer’ or ‘indirect’ excitons is not exclusive to vdW structures, such as transition metal dichalcogenide (TMD) bilayers in which these species have been observed so far, the unique properties of the constituent 2D materials stemming from the intrinsic valley physics and the enhanced Coulomb interactions at the 2D limit make for an exciting research journey. Likewise, the much-discussed idea of high-temperature exciton condensation using long-lived interlayer excitons remains a possibility that is yet to be experimentally explored. In contrast to monolayers, vdW layered structures possess an additional degree of freedom: the twist angle that stems from the sensitive dependence of the exciton properties on the interlayer interaction and the structural alignment of the constituent monolayers. This unique feature is of particular importance from the perspective of practical applications as it offers a new means of engineering and manipulation of interlayer excitons.
关键词： TMD heterobilayers,excitons,2D materials,van der Waals structures,interlayer excitons
更新于2025-09-23 15:21:01
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Colloidal Synthesis of Ternary Copper Halides Nanocrystals for High-Efficiency Deep-Blue Light-Emitting Diodes with a Half-Lifetime Above 100 Hours
摘要： Currently, the blue perovskite light-emitting diodes (PeLEDs) suffer from a compromise in lead-toxicity and poor operation stability, and most previous studies have struggled to meet the crucial blue NTSC standard. In this study, electrically-driven deep-blue LEDs (~445 nm) based on zero-dimensional (0D) Cs3Cu2I5 nanocrystals (NCs) were demonstrated with the color coordinates of (0.16, 0.07) and a high external quantum efficiency of ~1.12%, comparable with the best-performing blue LEDs based on lead-halide perovskites. Encouraged by the remarkable stability of Cs3Cu2I5 NCs against heat and environmental oxygen/moisture, the proposed device was operated in a continuous current mode for 170 h, producing a record half-lifetime of ~108 h. The device stability was further verified by an aggressive thermal cycling test (300?360?300 K) and a 35-day storage test. Together with the eco-friendly features and facile colloidal synthesis technique, the 0D Cs3Cu2I5 NCs can be therefore regarded as a promising candidate for deep-blue LEDs applications.
关键词： self-trapped excitons,light-emitting diodes,stability,Cs3Cu2I5 nanocrystals,deep-blue
更新于2025-09-23 15:21:01
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: From quantum dots to bulk crystals and additional boundary conditions for Rydberg exciton-polaritons
摘要： We propose schemes for calculation of optical functions of a semiconductor with Rydberg excitons for a wide interval of dimensions. We have started with a zero-dimensional structure (quantum dot), then going to one-dimensional (quantum wire), two-dimensional (quantum wells and wide quantum wells), and ?nally three-dimensional bulk crystals; our analytical ?ndings are illustrated numerically, showing an agreement with available experimental data. Calculations including exciton-polaritons are performed; the case of a large number of polariton branches is discussed, and obtained theoretical absorption spectra show good agreement with experimental data.
关键词： quantum wells,bulk crystals,exciton-polaritons,quantum wires,Rydberg excitons,quantum dots
更新于2025-09-23 15:21:01
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Coupled 3D master equation and 1D drifta??diffusion approach for advanced OLED modeling
摘要： A novel simulation approach for excitonic organic light-emitting diodes (OLEDs) is established by combining a continuous one-dimensional (1D) drift-diffusion (DD) model for the charge carrier dynamics with a three-dimensional (3D) master equation (ME) model describing the exciton dynamics in a multi-layer OLED stack with an additional coupling to a thin-film optics solver. This approach effectively combines the computational efficiency of the 1D DD solver with the physical accuracy of a discrete 3D ME model, where excitonic long-range interactions for energy transfer can be taken into account. The coupling is established through different possible charge recombination types as well as the carrier densities themselves. We show that such a hybrid approach can efficiently and accurately describe steady-state and transient behavior of optoelectronic devices reported in literature. Such a tool will facilitate the optimization and characterization of multilayer OLEDs and other organic semiconductor devices.
关键词： drift-diffusion,excitons,master equation,OLED
更新于2025-09-23 15:21:01