Complete Energy Transfer Research Articles

Quadratic Cascading in Quasi-Phase-Matching: An Alternative Route to Efficient Third-Harmonic Generation

We report on the theoretical/numerical investigation of simultaneous second- and third-harmonic generation from a single wavelength input in quasi-phase-matched crystals. The presented technique consists of a quadratic crystal with two first-order quasi-phase-matched sections: one designed for quasi-phase-matching to second-harmonic generation and the other for quasi-phase-matching to third-harmonic generation via sum-frequency generation. We identify an optimal length ratio (optimal number of domains) for these sections in order to enhance the conversion to the third harmonic, achieving nearly complete energy transfer. The advantages of the method are demonstrated both numerically and analytically, with a specific example using periodically poled lithium niobate. Quadratic cascading with quasi-phase-matching proves to be an effective approach for achieving cubic-like effects with high conversion efficiencies.

Novel isocyanobenzene carbazole-based thermally activated delayed fluorophors towards solution-processed blue emitting OLED devices with high efficiency

Achieving efficient blue emission is an exigent challenge for the application of thermally activated delayed fluorescent organic light-emitting diodes (TADF-OLEDs). Carbazole benzonitrile-based TADF molecules exhibit promising performance in achieving the goal. Here, by replacing the cyano group in the sensitizer with the isocyano group, a 9 nm hypochromatic shift in photoluminescence spectra of the sensitizer and an enhanced efficiency of the Förster energy transfer (FET) in TADF-sensitized fluorescence (TSF) is found. By using the isocyano-based compounds as sensitizers, a maximum external quantum efficiency of 24.5% is obtained in solution-processed OLEDs, surpassing the cyano-based counterparts with similar structures. Moreover, the full width at half maximum (FWHM) of the emitter in the electroluminescence spectrum is also decreased from 47 nm to 38 nm, indicating a more complete energy transfer.

Full Picture of Energy Transfer in a Trivalent Europium Complex with Bidentate β-Diketonate Ligand.

Trivalent europium (Eu(III)) complexes emit narrow-band luminescence as a result of energy transfer following the photoexcitation of antenna ligands. Bidentate β-diketonates are typically used as antenna ligands; however, their entire energy transfer mechanism to Eu(III) remains unknown. We used time-resolved photoluminescence spectroscopy and femtosecond transient absorption spectroscopy to map the complete intramolecular energy transfer process in the [Eu(hfa)3(TPPO)2] (hfa = hexafluoroacetylacetonate, TPPO = triphenylphosphine oxide) complex; hfa is a β-diketonate antenna ligand. Our analysis provides a "full picture" of energy transfer, tracing each step from initial photoexcitation to final relaxation: intersystem crossing in the ligands, energy transfer from the ligands to the metal center, and multiple internal conversion of Eu(III). We demonstrated that the direct bonds of the bidentate ligands enabled a quick and near-unity-efficiency energy transfer from the triplet state of the ligand to the 5D2 state of Eu(III). We also revealed that the loss of the ligand-centered intersystem crossing process reduces the overall sensitization efficiency. Our findings provide a foundation for the rational design of advanced luminescent materials, paving the way for advances in lanthanide-based luminescence research.

A coupled plasma-thermal model for hollow cathode power decomposition and parametric analysis

Abstract A 2D axisymmetric transient coupled plasma-thermal model is developed to simulate the plasma behavior during the self-sustained discharge of hollow cathodes, which presents a complete hollow cathode structure and energy transfer processes in multiphysics fields. The model has been validated by quantitative agreement between the simulation results and experimental data on the plasma and emitter temperature at the NSTAR cathode. The effects of thermal protection design, operating conditions, and geometric design on the cathode performance are analysed through electric and thermal power decomposition. The parametric analysis shows that the optimal thermal protection design is to use a 1/3 thickness cathode tube with 4 layers of radiation shielding close to the tube, which reduces 43.7% conductive and 61.1% radiative heat dissipation, respectively. Increasing the inlet flow rate counter-intuitively reduces the emitter temperature due to the potential reversal in the diffusion electric field dominated region, revealing that the flow rate can be traded for the dual optimisation of lifetime and power consumption. Under high current conditions, the IAT effect dominates the plume resistance to increase the discharge voltage after an inflexion point, which is the main factor limiting the cathode performance. A large internal radius gives a uniform low emission and helps to prolong life, while the orifice length should be avoided to be longer than 4 times the orifice radius due to the significantly enhanced Joule heating in the narrow orifice. The orifice radius determines the power deposition due to electron and ion bombardment through potential penetration. For high-current discharger cathodes dominated by electron bombardment, large or through-orifice designs are preferred, while for low-current neutralizer cathodes dominated by electron bombardment, small-orifice designs are recommended.

Terpyridyl-Imidazole Based Ligand Coordinated to Ln(Hexafluoroacetyl acetonate)3 Core: Synthesis, Structural Characterization, Luminescence Properties, and Thermosensing Behaviors in Solution and PMMA Film.

A new array of ternary lanthanide complexes of the form [Ln(hfa)3(tpy-HImzphen)] have been synthesized and thoroughly characterized wherein Ln = LaIII (1), EuIII (2), SmIII (3), and TbIII (4); hfa = hexafluoroacetylacetonate; and tpy-HImzphen = 2-(4-[2,2':6',2″]terpyridin-4'-yl-phenyl)-1H-phenanthro[9,10-d]imidazole. Incorporation of tpy-HImzphen onto the Ln-hfa moiety induced a bathochromic shift of the absorption window of the complexes into the visible region. Extensive investigations of the luminescence characteristics have been conducted both at RT and at 77 K to understand the deactivation pathways of the complexes. Both steady-state and time-resolved emission spectral behaviors indicate four distinctive behaviors upon incorporation of tpy-HImzphen onto the lanthanide core, viz., a huge red-shift of the ligand-centered peak for LaIII; almost complete energy transfer for EuIII; very little energy transfer for SmIII, while reverse energy transfer in the case of TbIII. In addition, the EuIII-complex exhibits its excellence in luminescence thermometry in the solution state as well as in poly(methyl methacrylate) (PMMA) thin films. The thermosensitive luminescence response in solution was further utilized to mimic set-reset flip-flop logic operation. A plausible energy transfer scheme has been devised to explain dissimilar luminescence behaviors in the complexes. The role of LMCT was also considered for the observed thermosensing property of the Eu(III) complex.

Tuning exciton dynamics by the dielectric confinement effect in quasi-two-dimensional perovskites

The dielectric confinement effect plays an essential role in optoelectronic devices. Existing studies on the relationship between the dielectric confinement and the photoelectric properties are inadequate. Herein, three organic spacers with different dielectric constants are employed to tune the exciton dynamics of quasi-two-dimensional (quasi-2D) Ruddlesden–Popper perovskite films. Femtosecond transient absorption spectroscopy reveals that the small dielectric constant ligand enables a weak dynamic disorder and a large modulation depth of the coherent phonons, resulting in a more complete energy transfer and the inhibition of a trap-mediated nonradiative recombination. Additionally, the increase in the bulk-ligand dielectric constant reduces the corresponding exciton binding energy and then suppresses the Auger recombination, which is beneficial for high-luminance light-emitting diodes. This work emphasizes the importance of dielectric confinement for regulating the exciton dynamics of layered perovskites.

Comprehensive Photophysical and Nonlinear Spectroscopic Study of Thioanisolyl‐Picolinate Triazacyclononane Lanthanide Complexes

AbstractDetailed photophysical studies of luminescent lanthanide complexes are presented and elaborated using a newly developed thioanisolyl‐picolinate antenna and the related tacn macrocyclic ligand. The new ligand proved to sensitise Nd(III), Sm(III), Eu(III) and Yb(III) emission. Eu(III) complex showed complete energy transfer, yielding high quantum yield (44 %) and brightness, while the Tb(III) analogue underwent a thermally activated back‐energy transfer, resulting in a strong oxygen quenching of the triplet excited state. Transient absorption spectroscopy measurements of Gd(III), Tb(III) and Eu(III) compounds confirmed the sensitization processes upon the charge‐transfer antenna excitation. The triplet excited state lifetime of the Tb(III) complex was 5‐times longer than that of the Gd(III) analogue. In contrast, the triplet state was totally quenched by the energy transfer to the 4f‐metal ion in the Eu(III) species. Nonlinear two‐photon absorption highlighted efficient biphotonic sensitization in Eu(III) and Sm(III) complexes. In case of the Nd(III) compound, one‐photon absorption in 4f–4f transitions was predominant, despite the excitation at the antenna two‐photon band. This phenomenon was due to the Nd(III) 4f–4f transitions overlapping with the wavelength‐doubled absorption of the complex.

Robust temporal adiabatic passage with perfect frequency conversion between detuned acoustic cavities

For classical waves, phase matching is vital for enabling efficient energy transfer in many scenarios, such as waveguide coupling and nonlinear optical frequency conversion. Here, we propose a temporal quasi-phase matching method and realize robust and complete acoustical energy transfer between arbitrarily detuned cavities. In a set of three cavities, A, B, and C, the time-varying coupling is established between adjacent elements. Analogy to the concept of stimulated Raman adiabatic passage, amplitudes of the two couplings are modulated as time-delayed Gaussian functions, and the couplings’ signs are periodically flipped to eliminate temporal phase mismatching. As a result, robust and complete acoustic energy transfer from A to C is achieved. The non-reciprocal frequency conversion properties of our design are demonstrated. Our research takes a pivotal step towards expanding wave steering through time-dependent modulations and is promising to extend the frequency conversion based on state evolution in various linear Hermitian systems to nonlinear and non-Hermitian regimes.

Integration Challenges and Solutions for Solar-Powered Electric Vehicle Charging Infrastructure: From Panel to Battery

The integration of solar power with electric vehicle (EV) charging infrastructure presents a promising avenue to foster sustainable transportation. This study delves into the multifaceted challenges encountered in the synthesis of solar-powered EV charging stations and proffers solutions that span the complete energy transfer chain from photovoltaic panels to EV batteries. Initial concerns address the intermittent nature of solar energy and its impact on the reliability of power delivery. Advanced energy management strategies are explored, incorporating predictive analytics and real-time adjustment mechanisms to enhance the consistency and efficiency of power flow. The second part of the investigation scrutinizes the power electronics interface, emphasizing the need for high-efficiency converters that can operate effectively over varied solar insolation levels. Novel circuit topologies are presented, alongside adaptive control algorithms designed to optimize the power conversion process. Collectively, the findings underscore the potential of solar-powered EV charging infrastructure to not only support the decarbonization of transportation but also to contribute to the stability and efficiency of the power grid. The intersection of power electronics, energy management, and grid integration forms the cornerstone of this endeavor, with each domain providing critical components to the holistic solution. It culminates in a set of recommendations for policy, design, and operation that can accelerate the adoption of this technology.

Formation of binary magnon polaron in a two-dimensional artificial magneto-elastic crystal

We observed strong tripartite magnon-phonon-magnon coupling in a two-dimensional periodic array of magnetostrictive nanomagnets deposited on a piezoelectric substrate, forming a 2D magnetoelastic “crystal”; the coupling occurred between two Kittel-type spin wave (magnon) modes and a (non-Kittel) magnetoelastic spin wave mode caused by a surface acoustic wave (SAW) (phonons). The strongest coupling occurred when the frequencies and wavevectors of the three modes matched, leading to perfect phase matching. We achieved this condition by carefully engineering the frequency of the SAW, the nanomagnet dimensions and the bias magnetic field that determined the frequencies of the two Kittel-type modes. The strong coupling (cooperativity factor exceeding unity) led to the formation of a new quasi-particle, called a binary magnon-polaron, accompanied by nearly complete (~100%) transfer of energy from the magnetoelastic mode to the two Kittel-type modes. This coupling phenomenon exhibited significant anisotropy since the array did not have rotational symmetry in space. The experimental observations were in good agreement with the theoretical simulations.

Environment-mediated entropic uncertainty in charging quantum batteries.

We studied the dynamics of entropic uncertainty in Markovian and non-Markovian systems during the charging of open quantum batteries (QBs) mediated by a common dissipation environment. In the non-Markovian regime, the battery is almost fully charged efficiently, and the strong non-Markovian property is beneficial for improving the charging power. In addition, the results show that the energy storage is closely related to the couplings of the charger-reservoir and battery-reservoir; that is, the stronger coupling of a charger reservoir improves energy storage. In particular, entanglement is required to obtain the most stored energy and is accompanied by the least tight entropic bound. Interestingly, it was found that the tightness of the entropic bound can be considered as a good indicator of the energy transfer in different charging processes, and the complete energy transfer always corresponds to the tightest entropic bound. Our results provide insight into the optimal charging efficiency of QBs during practical charging.

Efficient bubble energy harvesting by promoting pressure potential energy release using helix flow channel

The bubble energy harvesting system can provide in-situ energy supply for the subsea observation equipment through two stages of energy conversion. However, the conversion efficiency of bubble potential energy to fluid energy in the first stage is much lower than that of fluid energy to electrical energy in the second stage, limiting the output capability of the bubble energy harvesting system. Here, a complete energy transfer and conversion model for the subsea bubble energy harvesting is established for the first time. Regardless of the type of transducer used in the system, increasing the released pressure potential energy can substantially improve the efficiency of bubble energy harvesting. Based on this mechanism, we proposed a method to improve the released pressure potential energy and verified the results using a bubble energy harvesting system with a 3D streamline. The flow velocity and fluid volume of the system can be controlled by adjusting the helix angle and cylindrical diameter. Compared with the original system, the fluid pressure potential energy released of a 3D-system with a helix angle of 50 degrees can increase by at least 26%. The output energy density of the 3D-system with a height of 1.6 m can reach 6.6 J/m3, which is 59 times higher than that of the existing technology. This technology can efficiently harvest energy from subsea gas sources, and has the potential to become a long-term in-situ power supply solution for subsea observation networks.

Sub-optical-cycle light-matter energy transfer in molecular vibrational spectroscopy

The evolution of ultrafast-laser technology has steadily advanced the level of detail in studies of light-matter interactions. Here, we employ electric-field-resolved spectroscopy and quantum-chemical modelling to precisely measure and describe the complete coherent energy transfer between octave-spanning mid-infrared waveforms and vibrating molecules in aqueous solution. The sub-optical-cycle temporal resolution of our technique reveals alternating absorption and (stimulated) emission on a few-femtosecond time scale. This behaviour can only be captured when effects beyond the rotating wave approximation are considered. At a femtosecond-to-picosecond timescale, optical-phase-dependent coherent transients and the dephasing of the vibrations of resonantly excited methylsulfonylmethane (DMSO2) are observed. Ab initio modelling using density functional theory traces these dynamics back to molecular-scale sample properties, in particular vibrational frequencies and transition dipoles, as well as their fluctuation due to the motion of DMSO2 through varying solvent environments. Future extension of our study to nonlinear interrogation of higher-order susceptibilities is fathomable with state-of-the-art lasers.

Generation of red light with intense photoluminescence assisted by Forster resonance energy transfer from Znq2 and DCM thin films

In this work, a novel experimental investigation of photoluminescence properties of Znq2 thin films co-doped with different concentrations of DCM were performed. The thin films were successfully deposited on glass substrates with different compositions, under high vacuum, by using the vacuum evaporation technique. For all compositions, the photoluminescence was measured at room temperature and also at low temperature in a wide range from 77 to 300 K with a step of 25 K in a high vacuum. The lifetime of the sample studied in real time was also measured using the decay time technique. The results obtained confirm that the doping influences the intensity of the DCM photoluminescence and also shows a complete energy transfer occurred from Znq2 to DCM which may have shifted the photoluminescence peak from Znq2 to the orange wavelength region which is related to DCM. The lifetime of the sample studied in real time was about 4.47 ns for Znq2 and while all the other samples showed two decay time components. As a result, the doping influences the optical properties of Znq2 and makes it a potential candidate for optoelectronic applications.Graphical abstract

Physicochemical properties of Li3Ba2La3(MoO4)8:Eu,Tb red-emitting phosphor for solid state white lamps

In this work, combustion synthesis was used for the first time to fabricate a phosphor material with red emission for applications in solid-state white-light lamps. We synthesized a material with emission wavelength at λem = 617 nm, excited under long UV-blue wavelength based on Eu3+, Tb3+-activated molybdates Li3Ba2(La1–x–yEuxTby)3(MoO4)8 with 0 ≤ x ≤ 1 and 0 ≤ y ≤ 1. A series of powder samples were produced by the combustion method and post-annealed at 800 °C in air. The crystalline phase formation was investigated by X-ray diffraction, which reveals the monoclinic C2/c (15) space group. It is observed that crystalline structure and morphology are preserved when the host lattice is doped with Eu3+ or Tb3+ single ions and co-doped with both ions at different doping concentrations. A detailed characterization by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) shows a similar morphology in all samples: rather large (1–7 μm) agglomerate particles with irregular shapes and surrounded by smaller nanoparticles of 50 nm in size. UV–visible absorption spectra confirm the presence of Eu3+ and Tb3+ ions. The luminescent properties of the obtained phosphors were studied in detail. Cathodoluminescence measurements indicate that the best emission intensity is for Eu3+:Tb3+ doping ratios of 80:0, 90:0 and 20:80. On the other hand, samples with 80:0, 60:40, and 20:80 doping ratios show the highest intensity in a detailed photoluminescence analysis and they exhibit the highest quantum yield values. A complete and efficient energy transfer from the sensitizer Tb3+ to the activator Eu3+ is observed in all co-doped phosphors post-annealed at 800 °C for 4 h. Thus, the Li3Ba2La3(MoO4)8:Eu3+,Tb3+ materials fabricated by combustion synthesis are excellent phosphors for being applied as red-emitting component in solid-state white-light lamps due to an improved color rendering index (CRI) that can be obtained under long UV-blue excitation wavelengths.

Simple Double Hetero[5]helicenes Realize Highly Efficient and Narrowband Circularly Polarized Organic Light-Emitting Diodes

Simple Double Hetero[5]helicenes Realize Highly Efficient and Narrowband Circularly Polarized Organic Light-Emitting Diodes

Quasinormal modes of a semi-holographic black brane and thermalization

We study the quasinormal modes and non-linear dynamics of a simplified model of semi-holography, which consistently integrates mutually interacting perturbative and strongly coupled holographic degrees of freedom such that the full system has a total conserved energy. We show that the thermalization of the full system can be parametrically slow when the mutual coupling is weak. For typical homogeneous initial states, we find that initially energy is transferred from the black brane to the perturbative sector, later giving way to complete transfer of energy to the black brane at a slow and constant rate, while the entropy grows monotonically for all time. Larger mutual coupling between the two sectors leads to larger extraction of energy from the black brane by the boundary perturbative system, but also quicker irreversible transfer of energy back to the black brane. The quasinormal modes replicate features of a dissipative system with a softly broken symmetry including the so-called k-gap. Furthermore, when the mutual coupling is below a critical value, there exists a hybrid zero mode with finite momentum which becomes unstable at higher values of momentum, indicating a Gregory-Laflamme type instability. This could imply turbulent equipartitioning of energy between the boundary and the holographic degrees of freedom in the presence of inhomogeneities.

Polar Lanthanide Anthracene Complexes Exhibiting Magnetic, Luminescent and Dielectric Properties

AbstractMultifunctional molecular materials combining magnetic, luminescent and dielectric properties are attractive for potential applications in spintronics and molecular devices. Herein we report three isostructural mononuclear lanthanide phosphonates, namely, Ln(NO3)3(2‐deap)3 [Ln=Dy (1Dy), Er (2Er), Yb (3Yb), 2‐deap=diethyl anthrancen‐2‐ylphosphonate] which crystallize in polar space group Pna21. Magnetic studies revealed field‐induced slow magnetization relaxation for 1Dy and 3Yb, but not for 2Er down to 1.8 K. Theoretical calculations were conducted to rationalize the magneto‐structural relationship. The photoluminescent properties are also dependent on the lanthanide ion. For 1Dy, luminescence was observed only in the visible region mainly originating from the ligand. For 2Er, luminescence was observed only in the near‐infrared (NIR) region due to a complete energy transfer from the ligand to the ErIII ion. Regarding to 3Yb, luminescence was observed in both visible and NIR regions suggesting a partial energy transfer from the ligand to YbIII ion. Dielectric and piezoelectric measurements were performed on single crystals of 3Yb, which confirmed the presence of high dielectric anisotropy and weak piezoelectric response.

Extreme spectral asymmetry of Akhmediev breathers and Fermi-Pasta-Ulam recurrence in a Manakov system.

The dynamics of Fermi-Pasta-Ulam (FPU) recurrence in a Manakov system is studied analytically. Exact Akhmediev breather (AB) solutions for this system are found that cannot be reduced to the ABs of a single-component nonlinear Schrödinger equation. Expansion-contraction cycle of the corresponding spectra with an infinite number of sidebands is calculated analytically using a residue theorem. A distinctive feature of these spectra is the asymmetry between positive and negative spectral modes. A practically important consequence of the spectral asymmetry is a nearly complete energy transfer from the central mode to one of the lowest-order (left or right) sidebands. Numerical simulations started with modulation instability of plane waves confirm the findings based on the exact solutions. It is also shown that the full growth-decay cycle of the AB leads to the nonlinear phase shift between the initial and final states in both components of the Manakov system. This finding shows that the final state of the FPU recurrence described by the vector ABs is not quite the same as the initial state. Our results are applicable and can be observed in a wide range of two-component physical systems such as two-component waves in optical fibers, two-directional waves in crossing seas, and two-component Bose-Einstein condensates.

The role of Yb2+ as a scintillation sensitiser in the near-infrared scintillator CsBa2I5:Sm2+

The feasiblity of using Yb2+ as a scintillation sensitiser for CsBa2I5:Sm2+ near-infrared scintillators has been assessed. CsBa2I5 samples with concentrations ranging from 0.3% to 2% Yb2+ and 0–1% Sm2+ have been studied. The scintillation properties have been determined and the dynamics of the scintillation mechanism have been studied through photoluminescence measurements. Radiationless energy transfer between Yb2+ ions plays a key role in increasing the ratio between the spin-forbidden and spin-allowed emission with increasing Yb2+ concentration in samples where Yb2+ is the only dopant. In samples co-doped with Sm2+, the Yb2+ 4f13[F27/2]5d1[LS] and 4f13[F27/2]5d1[HS] states both serve as donor states for radiationless energy transfer to Sm2+ with a rate of energy transfer that is inversely proportional to the luminescence lifetime the respective donor states. At a Sm2+ concentration of 1%, 85% of the Yb2+ excitations are transferred to Sm2+ through radiationless energy transfer. Almost all of the remaining Yb2+ emission is reabsorbed by Sm2+, resulting in nearly complete energy transfer.