Solid Emission Research Articles

First-principles investigation of near-field energy transfer between localized quantum emitters in solids

We present a predictive and general approach to investigate near-field energy transfer processes between localized defects in semiconductors, which couples first-principles electronic structure calculations and a nonrelativistic quantum electrodynamics description of photons in the weak-coupling regime. The approach is general and can be readily applied to investigate broad classes of defects in solids. We apply our approach to investigate an exemplar point defect in an oxide, the F center in MgO, and we show that the energy transfer from a magnetic source, e.g., a rare-earth impurity, to the vacancy can lead to spin nonconserving long-lived excitations that are dominant processes in the near field, at distances relevant to the design of photonic devices and ultrahigh dense memories. We also define a descriptor for coherent energy transfer to predict geometrical configurations of emitters to enable long-lived excitations, that are useful to design optical memories in semiconductor and insulators. Published by the American Physical Society 2024

Difluoro Dipyridomethene Boron Complexes: Synthesis, Characterization, and Ab Initio Calculations.

Molecular engineering studies on the meso-cyano difluoro dipyridomethene boron complexes are presented and two series (a and b) of novel fluorophores are extensively studied. Halogenated derivatives were reacted under Suzuki-Miyaura or Sonogashira cross coupling reactions to introduce electron-donating or electron-withdrawing functional groups on positions 1 and 2 of the aromatic ligand. All derivatives were obtained in 14-90% yields and studied in detail by structural, photophysical, and computational analyses. Both series display excellent emissive properties in solution with blue to orange fluorescence emission upon blue light absorption and promising features as solid emitters. All the spectroscopic measurements are supported and confirmed by first-principles theoretical calculations combining TD-DFT and CC2. Series b, featuring an aryl substituent onto position 1 of the aromatic core, showed significantly large Stokes shifts values.

Polymer-Surface-Mediated Mechanochemical Reaction for Rapid and Scalable Manufacture of Perovskite QD Phosphors.

Perovskite quantum dots (QDs) have been considered new-generation emitters for lighting and displays due to their high photoluminescence (PL) efficiency, and pure color. However, their commercialization process is currently hindered by the challenge of mass production in a quick and environmentally friendly manner. In this study, a polymer-surface-mediated mechanochemical reaction (PMR) is proposed to prepare perovskite QDs using a high-speed multifunction grinder for the first time. PMR possesses two distinctive features: i) The ultra-high rotating speed (>15 000rpm) of the grinder facilitates the rapid conversion of the precursor to perovskite; ii) The surface-rich polymer particulate ensures QDs with high dispersity, avoiding QD aggregation-induced PL quenching. Therefore, PMR can successfully manufacture green perovskite QDs with a high PL quantum yield (PLQY) exceeding 90% in a highly material- (100% yield), time- (1kgmin-1), and effort- (solvent-free) efficient manner. Moreover, the PMR demonstrates remarkable versatility, including synthesizing by various polymers and producing diverse colored and Pb-free phosphors. Importantly, these phosphors featuring a combination of polymer and perovskite, are facilely processed into various solid emitters. The proposed rapid, green, and scalable approach has great potential to accelerate the commercialization of perovskite QDs.

Polycrystalline monophenyl solid emitters with amplified spontaneous emission

There are many reports of small molecules exhibiting amplification spontaneous emission laser properties, but there are few reports of single benzene rings exhibiting laser properties while achieving high solid state emission from polycrystalline states. This work takes two very simple organic molecules and constructs an efficient single benzene ring solid state emitter. The crystal laser properties are based on aggregation‐induced emissions (AIE) generated through an excited‐state intramolecular proton transfer reaction (ESIPT).

Modeling of Radiative Emission from Shallow Color Centers in Single Crystalline Diamond

AbstractOptically active defects in diamond are widely used as bright single‐photon sources for quantum sensing, computing, and communication. For many applications, it is useful to place the emitter close to the diamond surface, where the radiative properties of the emitter are strongly modified by its dielectric environment. It is well‐known that the radiative power from an electric dipole decreases as the emitter approaches an interface with a lower‐index dielectric, leading to an increase in the radiative lifetime. For emitters in crystalline solids, modeling of this effect needs to take into account the crystal orientation and direction of the surface cut, which can greatly impact the emission characteristics. In this paper, a framework for analyzing the emission rates of shallow (<100 nm) defects is provided, in which optical transitions are derived from electric dipoles in a plane perpendicular to their spin axis. The calculations for the depth‐dependent radiative lifetime for color centers in (100)‐, (110)‐, and (111)‐cut diamond are presented, which can be extended to other vacancy defects in diamond.

Facile Construction of New Hybrid Conjugation via Boron Cage Extension.

Aromatic polycyclic systems have been extensively utilized as structural subunits for the preparation of various functional molecules. Currently, aromatics-based polycyclic systems are predominantly generated from the extension of two-dimensional (2D) aromatic rings. In contrast, polycyclic compounds based on the extension of three-dimensional (3D) aromatics such as boron clusters are less studied. Here, we report three types of boron cluster-cored tricyclic molecular systems, which are constructed from a 2D aromatic ring, a 3D aromatic nido-carborane, and an alkyne. These new tricyclic compounds can be facilely accessed by Pd-catalyzed B-H activation and the subsequent cascade heteroannulation of carborane and pyridine with an alkyne in an isolated yield of up to 85% under mild conditions without any additives. Computational results indicate that the newly generated ring from the fusion of the 3D carborane, the 2D pyridyl ring, and an alkyne is non-aromatic. However, such fusion not only leads to a 1H chemical shift considerably downfield shifted owing to the strong diatropic ring current of the embedded carborane but also devotes to new/improved physicochemical properties including increased thermal stability, the emergence of a new absorption band, and a largely red-shifted emission band and enhanced emission efficiency. Besides, a number of bright, color-tunable solid emitters spanning over all visible light are obtained with absolute luminescence efficiency of up to 61%, in contrast to aggregation-caused emission quenching of, e.g., Rhodamine B containing a 2D-aromatics-fused structure. This work demonstrates that the new hybrid conjugated tricyclic systems might be promising structural scaffolds for the construction of functional molecules.

Unprecedented intact radical anions, closed shell anions, cluster ions, and traditional cations and radical cations by LIFDI-MS.

Liquid injection field desorption ionization (LIFDI) proves the extraordinary softness of the ionization process combined with a convenient sample supply under the exclusion of moisture and air. LIFDI-mass spectrometry (MS) is used for organometallic and other seriously air-sensitive compounds forming intact ions without substantial fragmentation. Unprecedented molecular radical anions M-• are presented along with well-known intact M+• radical cations. Furthermore closed shell cations [C]+ and adduct ions like [M + H]+ or [M + Alkali]+ are gently transferred from the solid emitter surface into the gas phase. Anions [A]- or [M - H]- are accessible by LIFDI-MS at medium field strengths. Ion pairs [C]+[A]- are separately detected by positive and negative mode LIFDI-MS, respectively. Here we give an overview of the different ion types accessible by LIFDI-MS. For the first time the field ionization/desorption of solar cell electron acceptor compounds is shown to deliver M-• and M2-• radical ions.

Intramolecular C-H⋅⋅⋅O Hydrogen-Bonded Solid Emitter as Colorimetric and Fluorometric Cyanide-Selective Chemodosimeter.

An indole-indanedione-based small molecule, compound 1Me, comprising an intramolecular C-H⋅⋅⋅O hydrogen-bond (H-bond) and with an intramolecular charge transfer (ICT) characteristic was prepared for the colorimetric and fluorometric detection of CN- . Compound 1Me is virtually nonfluorescent in solution but emits a strong yellow fluorescence in the solid state because of the intramolecular C-H⋅⋅⋅O H-bond, which inhibits the free rotation of the exocyclic C-C single bond of 1Me. The nucleophilic addition of CN- to the β-conjugated carbon of the indanedione group of 1Me, which breaks the intramolecular C-H⋅⋅⋅O H-bond and blocks ICT, causes the colorimetric and fluorometric responses of 1Me to CN- . Furthermore, inexpensive and portable paper-based test kits containing 1Me could be used to rapidly and conveniently sense CN- using the naked eye in real time. The results provide a new strategy for designing colorimetric and fluorometric cyanide-selective sensors based on an intramolecular C-H⋅⋅⋅O hydrogen bonded solid emitter.

Methylated Barbituric Acid-Functionalized Tetraphenylethylene: Aggregation- Induced Emission, Mechanochromism, and Optical Wave-Guiding Properties

Background: Restrained by the aggregation-causing quenching of conventional fluorophores, the design and synthesis of solid-state emissive materials is a persistent pursuit for scientists. The discovery of aggregation-induced emission provides an efficient strategy for preparing solidstate emissive luminogens. Objectives: A multifunctional solid-state emissive material DMBTPE was prepared from tetraphenylethylene and N-methylated barbituric acid through the construction of donor-acceptor structure. Method: DMBTPE showed typical aggregation–induced emission characteristics: non–emissive when molecularly dissolved in solution while strongly emissive in the aggregated state or as solid. Owing to the strong donor–acceptor interaction, the maximum absorption of DMBTPE shifted to the visible light region. DMBTPE also exhibited reversible mechanochromic fluorescence with 30– 40 nm emission wavelength change. Results: DSC and XRD results indicated the transition between the amorphous state and crystalline state was accounted for the mechanochromic fluorescence behavior. The microcrystalline rods of DMBTPE grown from hot ethanol solution exhibited good optical waveguiding effect and the optical loss was as low as 0.018 dB/μm. Conclusions: DMBTPE was an efficient solid emitter. Such attributes enable this kind of materials to find wide applications in many areas, such as biological imaging and optoelectronic devices.

Nanofiber-Induced Losses Inside an Optical Cavity

Optical high-finesse cavities are a well-known means to enhance light-matter interactions. Despite much progress in the realization of strongly coupled light-matter systems, the controlled positioning of single solid emitters in cavity modes remains a challenge. We pursue the idea of using nanofibers with subwavelength diameter as a substrate for such emitters. This paper addresses the question of how strongly optical nanofibers influence the cavity modes. We analyze the influence of the fiber position for various fiber diameters on the finesse of the cavity and on the shape of the modes.

A defect-induced emission material with turn-on mechanoresponsive luminescence serving as a data storage

Most of the mechanoresponsive luminescent (MRL) materials function based on phase transition (crystalline-to-amorphous or crystalline-to-crystalline) or solid-state chemical reaction of the organic solid emitters. However, it is difficult to enable a turn-on type mechanoresponsive luminescence using such strategy. In this work, the defect-induced emission (DIE) of (E)-(4-((2-hydroxy-4-methoxybenzylidene)amino)phenyl)(phenyl) methanone (HMPM) was disclosed, which endows the resulting material with reversible turn-on MRL. The crystalline powder of HMPM is non-emissive, but the emission intensity can be greatly enhanced by external mechanical stimuli, showing high contrast. In the semiquantitative experiment, pressure up to 1.78 N would generate crystal defects, and further induces DIE. Crystallographic data demonstrate that the dark-state stems from the closely-connected plane-style aggregation of neighboring molecules, which allows the intermolecular orbital-overlapping to the disadvantage of radiative transition. Mechanical stimuli would destroy the plane-style aggregation to block intermolecular orbital overlap and the possible energy transfer, resulting in emission-enhancement. Taking advantage of the DIE nature, an information storage film is fabricated, capable of data-writing via mechanical force and data-erasing by fumigation treatment, showing rewritability as well as high signal contrast.

Combined effects of ion-pairing on multi-emissive properties of benzimidazolium salts

Strong ion-pairing in a benzimidazolium-based solid emitter impacts its photophysical properties by promoting fluorescence quenching, enhancing phosphorescence and boosting phosphorescence quantum efficiency under direct triplet-state population.

Color-Tunable and ESIPT-Inspired Solid Fluorophores Based on Benzothiazole Derivatives: Aggregation-Induced Emission, Strong Solvatochromic Effect, and White Light Emission.

Organic solid materials with color-tunable emissions have been extensively applied in various fields. However, a rational design and facile synthesis of an ideal fluorophore are still challenging due to the undesirable aggregation-caused quenching effect in concentrated solution and solid form. Herein, we have developed a series of 2-(2'-hydroxyphenyl)benzothiazole (HBT)-derived color-tunable solid emitters by switching functional groups at the ortho-position of a hydroxyl group via formylation and an aldol condensation reaction. By tuning the electron-withdrawing ability and the π-conjugated framework introduced by the functional groups, fluorophores emit light covering the full-color range from blue to near-infrared regions with high quantum yields in their solid form and show a significant solvatochromic effect in polar solvents. The aggregation-induced emission (AIE) or aggregation-induced emission enhancement (AIEE) and excited-state intramolecular proton transfer (ESIPT) involving fluorescence mechanism, along with their inter/intramolecular interactions in crystals, are elucidated to depict the key factors for tunable emissions and high emitting efficiency. Furthermore, high-quality white-light-emitting materials are obtained in various solvents and polydimethylsiloxane (PDMS) films with combined fluorophores. Overall, these studies report a promising strategy for the construction of organic solid materials with color-tunable emission and shed light on methods for obtaining desirable emission efficiency.

Material platforms for defect qubits and single-photon emitters

Quantum technology has grown out of quantum information theory and now provides a valuable tool that researchers from numerous fields can add to their toolbox of research methods. To date, various systems have been exploited to promote the application of quantum information processing. The systems that can be used for quantum technology include superconducting circuits, ultracold atoms, trapped ions, semiconductor quantum dots, and solid-state spins and emitters. In this review, we will discuss the state-of-the-art of material platforms for spin-based quantum technology, with a focus on the progress in solid-state spins and emitters in several leading host materials, including diamond, silicon carbide, boron nitride, silicon, two-dimensional semiconductors, and other materials. We will highlight how first-principles calculations can serve as an exceptionally robust tool for finding novel defect qubits and single-photon emitters in solids, through detailed predictions of electronic, magnetic, and optical properties.

Theoretical insights into photochemical ESITP process for novel DMP-HBT-py compound**Project supported by the Science and Technology Research Project of Henan Province, China (Grant No. 172102210391) and the Higher Vocational School Program for Key Teachers from Department of Education of Henan Province, China (Grant No. 2019GZGG042).

We execute the density functional theory (DFT) and time-dependent density functional theory (TDDFT) approaches to make a detailed exploration about excited state luminescent properties as well as excited state intramolecular proton transfer (ESIPT) mechanism for the novel 2,6-dimethyl phenyl (DMP-HBT-py) system. Firstly, we check and confirm the formation and stabilization of hydrogen bonding interaction for DMP-HBT-py. Via optimized geometrical parameters of primary chemical bond and infrared (IR) spectra, we find O–H⋯N hydrogen bond of DMP-HBT-py should be strengthened in S1 state. Insights into frontier molecular orbitals (MOs) analyses, we infer charge redistribution and charge transfer (ICT) phenomena motivate ESIPT trend. Via probing into potential energy curves (PECs) in related electronic states, we come up with the ultrafast ESIPT behavior due to low potential barrier. Furthermore, we search the reaction transition state (TS) structure, the ultrafast ESIPT behavior and mechanism of DMP-HBT-py compound can be re-confirmed. We sincerely wish this work could play roles in further developing novel applications based on DMP-HBT-py compound and in promoting efficient solid emitters in OLEDs in future.

Effect of π-conjugation on solid-state fluorescence in highly planar dyes bearing an intramolecular H-bond

Efficient solid emitters with planar architectures are desirable for some practical applications. However, molecules with coplanar structures and conformational rigidity generally exhibit small Stokes shifts, thus resulting in self-absorption. Multi-aromatic hydrocarbons are one typical example that easily undergoes aggregation-caused quenching (ACQ) due to intermolecular π-π interactions. Herein, a highly planar seven-ringed dye containing benzothiazole- and triphenyl-fused moieties (HTpT) without any bulky or propeller-shaped substituent at its periphery was facilely synthesized from a Cu+-catalyzed Scholl reaction. By extending the phenyl in excited-state intramolecular proton transfer (ESIPT)-active dye (HBT) to naphthyl (HNT) and to triphenyl (HTpT), HNT shows hypsochromic emission and small Stokes shift (20 nm) in comparison with parent HBT, and suffers from ACQ. Contrarily, HTpT exhibits bright red solid-state fluorescence (λem: 600 nm, Φf: 22.7%) with a 200 nm Stokes shift. Steady-state fluorescence spectra, theoretical calculations, and X-ray diffraction analysis are performed to elucidate these different photo-physical properties. In addition, unlike most lysosomal targeting probes containing proton-binding amino or morpholine moieties, which can cause an “alkalinizing effect” that interferes with the activity of normal cells, HTpT without a basic amino group can specifically light up cellular lysosomes.

Tunable bandgap renormalization by nonlocal ultra-strong coupling in nanophotonics

In quantum optics, great effort is being invested in enhancing the interaction of quantum emitters with light. The different approaches include increasing the number of emitters, the laser intensity or the local photonic density of states at the location of an atom-like localized emitter. In contrast, solid-state extended emitters hold an unappreciated promise of vastly greater enhancements through their large number of vacant electronic valence states. However, the majority of valence states are considered optically inaccessible by a conduction electron. We show that, by interfacing three-dimensional (3D) solids with 2D materials, we can unlock the unoccupied valence states by nonlocal optical interactions that lead to ultra-strong coupling for each conduction electron. Consequently, nonlocal optical interactions fundamentally alter the role of the quantum vacuum in solids and create a new type of tunable mass renormalization and bandgap renormalization, which reach tens of millielectronvolts in the example we show. To present quantitative predictions, we develop a non-perturbative macroscopic quantum electrodynamic formalism that we demonstrate on a graphene–semiconductor–metal nanostructure. We find new effects, such as nonlocal Rabi oscillations and femtosecond-scale optical relaxation, overcoming all other solid relaxation mechanisms and fundamentally altering the role of optical interactions in solids. When interfacing a graphene layer with a thin solid emitter, the quantum plasmonic vacuum allows each solid electron to access all unoccupied valence states through the nonlocality of their light-matter interaction, creating ultra-strong coupling alongside mass and bandgap renormalization.

Enhanced DNA Sensing and Chiroptical Performance by Restriction of Double-Bond Rotation of AIE cis-Tetraphenylethylene Macrocycle Diammoniums.

The aggregation-induced emission (AIE) mechanism of restriction of double-bond rotation (RDBR) was utilized to design an excellent solid emitter and sensor for the first time. Thus, cis-tetraphenylethylene (TPE) macrocycle diammoniums were synthesized and bound to a DNA chain by its two ammonium arms. The formed TPE dicycle at the cis position restricted the rotation of the double bond in both the ground and excited states, resulting in AIE enhancement, chiroptical performance enhancement, and sensing enhancement.

Pyrene-based aggregation-induced emission luminogens and their applications

Pyrene shows very weak or quenched fluorescence in the solid state, but it is possible to turn it to a bright solid emitter by using aggregation-induced emission (AIE) strategies.

Multi-responsive red solid emitter: Detection of trace water and sense of relative humidity

A multi-responsive D-A type compound ( CYQ ) based on pyrone and triphenylamine was designed and successfully synthesized. The target compound exhibited distinct aggregation-enhanced emission (AEE) effect. Solvatochromic experiment and density functional theory (DFT) indicated CYQ possessed excellent intramolecular charge transfer (ICT) ability. Besides, its mechanofluorochromic property (MFC) was found with a 37 nm red-shift. Powder wide-angle X-ray diffraction (PXRD) and differential scanning calorimetry (DSC) measurements were performed to demonstrate the transformation from the crystalline to amorphous states upon grinding. Surprisingly, CYQ displayed a hypersensitive response to trace water in organic solvents with an excellent detection limit as low as 0.0096% in tetrahydrofuran (THF). Furthermore, it was found that the fluorescent intensity of CYQ declined progressively upon humidity rise, and its color change can be witnessed by naked eyes. Therefore, the relative humidity (RH) sensing strategy guarantees the AIEgen to become a colorimetric sensor under various conditions.