Preparation and Periodic Emission of Superlattice CdS/CdS:SnS₂ Microwires

Semiconductor superlattice micro-/nanowires could greatly increase the versatility and power of modulating electronic (or excitonic, photonic) transport, optical properties. In this communication, we report growth of a semiconductor CdS/CdS:SnS2 superlattice microwire through a coevaporation technique with microenvironmental control. Such a novel superlattice microwire can modulate the exciton and photons to show multipeak emissions with periods in a wide spectral range, which arise in the 1-d photon crystal and confined exciton emission. This system can be widely used in producing multicolor emissions, low-threshold lasing, study light-matter interaction, slow light engineering, and weak nonlinear optical devices

Magnetic Exciton Relaxation and Spin–Spin Interaction by the Time-Delayed Photoluminescence Spectra of ZnO:Mn Nanowires

ZnO:Mn nanostructures are important diluted magnetic materials, but their electronic structure and magnetic origin are still not well understood. Here we studied the time-delayed and power-dependent photoluminescence spectra of Mn­(II) doped ZnO nanowires with very low Mn concentration. From the time-delayed emission spectra, we obtained their electronic levels of single Mn ion replacement of Zn ions in ZnO nanowire. The high d-level emissions show up unusually because of the stronger p–d hybridization than that in ZnS, as well as the spin–spin coupling. After increasing Mn doping concentration, the ferromagentic cluster of the Mn–O–Mn with varied configurations can form and give individual emission peaks, which are in good agreement with the ab initio calculations. The presence of clustered Mn ions originates from their ferromagnetic coupling. The lifetimes of these d levels show strong excitation power-dependent behavior, indication of strong spin-dependent coherent emission. One-dimensional structure is critical for this coherent emission behavior. These results indicate that the d state is not within Mn ion only, but a localized exciton magnetic polaron, Mn–O–Mn coupling should be one source of ferromagnetism in ZnO:Mn lattice, the latter also can combine with free exciton for EMP and produce coherent EMP condensation and emission from a nanowire. This kind of nanowires can be expected to work for both spintronic and spin-photonic devices if we tune the transition metal ion doping concentration in it

Temperature-Dependent Double Exciton Competition Emission in One Dimensional Copper-Based Organic–Inorganic Hybrid Perovskites

Organic–inorganic hybrid perovskites with temperature-dependent dual emission are attracting more attention due to their promising application in fluorescence intensity ratio technology. Herein, we report a Cu-based organic–inorganic hybrid perovskite (BDA)Cu2Br4 (BDA = C4H12N22+) with dimeric clusters ([Cu2Br6]4–) and organic cations (BDA) periodically arranged in a one-dimensional structure. This structure enables lattice self-trapping and strong coupling between electrons and phonons. The difference in the degree of lattice distortion affected by the temperature decrease leads to the mutual competition between two different self-trapped excitons, thus causing the two self-trapped emissions, resulting in the emission changes from the blue light to the orange-red light. Furthermore, these change in emission color can reverse while the temperature increases. This property potentially enables applications in temperature sensing, blue LEDs, and solid-state lighting

Statistics of tens-of-photon states scattered by optical cavity, two-level atom and Jaynes-Cummings emitter

Manipulating photon states serves as a primary requirement for various optical devices and is of high relevance for quantum information technology. Nevertheless, the fundamental theoretical framework for tens-of-photon states has not been established. This study successfully establishes the matrix-product-state theory to explore the statistics of the tens-of-photon states scattered by optical cavities (OCs), two-level atoms (TLAs), and Jaynes-Cummings emitters (JCEs) in waveguide-QED systems. Taking the incident 10-photon states as an example, we reveal some novel physical results that differ from those for few-photon cases. We verify that OCs do not change the statistics of the incident photon states, being independent of the photon number. However, for the TLAs and JCEs, the photon number strongly impacts the photon bunching and anti-bunching behaviors. As the photon number increases, there exists a maximum value for the photon-photon correlation induced by the JCE. Especially, the scattered waves by the TLA (or JCE) exhibit extremely different statistics behaviors for the 10-photon cases from those for the bi-photon. These distinguishable conclusions for the tens-of-photon states and the developed matrix-product-state theory pave the way for the multi-photon manipulation

Highly Emissive, Color-Tunable, Phosphine-Free Mn:ZnSe/ZnS Core/Shell and Mn:ZnSeS Shell-Alloyed Doped Nanocrystals

High-quality Mn:ZnSe/ZnS core/shell and Mn:ZnSeS shell-alloyed doped nanocrystals (d-dots) with up to 50% photoluminescence (PL) quantum yield (QY) have been synthesized based on nucleation-doping strategy through a phosphine-free approach. The formation of MnSe nanoclusters was achieved by adjusting the ratio of stearic acid to manganese stearate and using a highly reactive Se precursor. Mn: ZnSe/ZnS core/shell d-dots were prepared by an epitaxial ZnS growth on the Mn:ZnSe core. The PL QY of Mn:ZnSe/ZnS core/shell d-dots decreased dramatically after injections of S precursor but was completely recovered through an UV irradiation. After annealing at 240 °C for 30 min, the core/shell Mn:ZnSe/ZnS d-dots evolved to the Mn:ZnSeS shell-alloyed d-dots with high PL QY. The PL peak position of the d-dots could be tuned within a relatively large optical window, from 584 to 605 nm

Excited State Regulated Emission in Hybrid Indium Halides via Crystal Structure Switch

Organic–inorganic metal halides have become one of the most promising materials in the next generation of optoelectronic applications due to their high charge carrier mobility and tunable band gaps. In this study, Sb:PA6InCl9 and Sb:PA4NaInCl8 single crystals were prepared through evaporation crystallization, respectively. Due to the different degrees of lattice distortions, the highly efficient yellow emission in Sb:PA6InCl9 at 610 nm and the green emission in Sb:PA4NaInCl8 at 545 nm were achieved by regulation of the excited state, respectively. By introducing additional sodium ions in the post-treatment, we found that the zero-dimensional Sb:PA6InCl9 could rapidly convert into a two-dimensional layered structure of Sb:PA4NaInCl8, thus resulting in a novel green/yellow emission switch. This work guides the structural and performance control of organic–inorganic hybrid In-based metal halides and offers broad prospects for luminescent switching in anticounterfeiting applications

Topologically protected Fano resonance in photonic valley Hall insulators

Rapidly developing photonics brings many interesting resonant optical phenomena, in which the Fano resonance (FR) always intrigues researchers because of its applications in optical switching and sensing. However, its sensitive dependence on environmental conditions makes it hard to implement in experiments. We in this work suggest a topologically-protected FR based on the photonic valley Hall insulators, immune to the system impurities. The topologically-protected FR is achieved by coupling the valley-dependent topological edge states (TESs) with one double-degenerate cavity. The $\delta$-type photonic transport theory we build reveals that this topological FR dates from the interference of the two transmissions that are attributed to the parity-odd cavity mode and the parity-even one. We confirm that the induced Fano line shape of the transmission spectra is robust against the bending domain walls and disorders. Our work may provoke exciting frontiers for manipulating the valley transport and pave a way for the topologically protected photonic devices such as optical switches, low-threshold lasers, and ultra-sensitive sensors

Efficient Yellow Emission and Near-Unified Photoluminescence Quantum Yield of Sb³⁺ in a One-Dimensional Confinement Cadmium Chloride Lattice

Sb3+, with a 5s2 electron configuration, has been widely studied as a dopant for its efficient self-trapped exciton (STE) broadband emission. However, the efficient emission of Sb3+-doped one-dimensional (1D) structures and the energy/charge transfer between the host and dopant are rarely reported. In this paper, a series of Sb3+-doped 1D (TDMP)­CdCl4 (TDMP = trans-2,5-dimethylpiperazine) powder crystals were prepared by the solvothermal method. The 1D quantum confinement effect and Jahn–Teller distortion in this organic–inorganic hybrid with a soft lattice generate strong electron–phonon coupling. In addition, we also found a fast energy transfer process between the host ([CdCl6]2–) and the dopant ([SbCl6]3–). The synergy of strong electron–phonon coupling and fast energy transfer enables 8.8% Sb3+:(TDMP)­CdCl4 to exhibit efficient broadband yellow emission under UV excitation with a photoluminescence quantum yield (PLQY) of 99.69%. DFT calculations indicate that the emission comes from the triplet self-trapped excitons (STEs) emission of the [SbCl6]3– octahedron. This work provides a deeper understanding of the emission of Sb3+ in doped systems and provides a strategy to guide the design of future efficient luminescent materials

Modified Charge Injection in Green InP Quantum Dot Light-Emitting Diodes Utilizing a Plasma-Enhanced NiO Buffer Layer

With the growing concern for green and environmentally friendly quantum dots (QDs), the investigation of low-toxicity heavy-metal-free light-emitting materials and devices has become a research hotspot. Due to their high quantum yield, tunable emission, and environmentally friendly properties, the low-toxicity III–V InP quantum dot light-emitting devices (QLEDs) have great application potential in next-generation full-color displays and lighting. In this work, charge injection in high-performance green InP QLEDs was modified by using a low-temperature atomic layer-deposited (ALD) nickel oxide (NiO) buffer layer. The device with the NiO buffer layer effectively suppressed the nonradiative recombination process and enhanced the hole injection, exhibiting a 1.35-fold enhanced external quantum efficiency (EQE). Moreover, different oxygen plasma-enhanced conditions were applied to the deposition of the NiO film. As the ambient oxygen flux increased (50–200 sccm), Ni2+ and interstitial oxygen vacancies were generated within the NiO film, which effectively improved the hole injection and promoted the carrier balance injection. The best-performing device with a 100 sccm O2–NiO film realized a 2.36 times higher EQE (6.75%) than the device without the NiO buffer layer, with a maximum current efficiency (CE) of 12.73 cd/A. The experimental results provide an effective strategy to further improve the charge balance and performance of InP-based QLED

Synthesis of Highly Emissive Mn-Doped ZnSe Nanocrystals without Pyrophoric Reagents

Manganese-doped zinc selenide quantum dots (Mn:ZnSe d-dots) with high optical quality, pure dopant emission with 40−60% photoluminescence quantum yield, were synthesized with air-stable and generic starting materials, namely zinc (manganese) fatty acid salts with corresponding free fatty acids, Se powder, fatty amine, and octadecene. The pyrophoric, highly toxic, and expensive organo-phospines were eliminated from the existing synthetic protocols for high quality Mn:ZnSe d-dots, which changed the reaction profile substantially mainly because of the enhanced reactivity of elemental Se with the presence of fatty amines. The reaction temperatures for two key processes involved in “nucleation-doping”, namely, formation of MnSe nanoclusters and their overcoating by the host, were both reduced. Multiple injection techniques were employed to realize balanced diffusion of the Mn ions in the d-dots. The resulting d-dots were found to be in zinc-blende crystal structure, with optimal spherical shape, nearly monodispersed, and controlled in their Mn:Zn ratio