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Inelastic n-changing collisions play an important role in the evolution of Rydberg atoms into ultracold plasmas. However, for the initially intermediate n (n ∼ 40) Rydberg states, these collisions can hardly be observed due to the low electron temperature in ultracold plasmas. In this work, we designed an experimental scheme to facilitate collisions between free electrons at 1.5 eV and intermediate n Rydberg atoms. Using the field ionization technique, we measured the state distributions resulting from the evolution of initially cold rubidium atoms in the 45P3/2 Rydberg state. The experimentally obtained probability of inelastic collisions excitation agrees well with the Monte Carlo simulation results. In addition, our experimental results indicate that the n-changing population induced by hot electrons is significant for lower nP Rydberg states. Our work plays a significant role in calculating the rates of electron–ion three-body recombination in ultracold plasmas. [ABSTRACT FROM AUTHOR]

In this paper, we present a methodology of laser ablation simulation including electronic entropy effects. Ablation by ultrashort laser pulses is suitable for micromachining because of its small thermal damage. To further enhance its effectiveness, it is crucial to explore both theoretically and experimentally the desirable conditions for processing. The density functional theory calculations predict that hot electrons make crystalline lattice thermodynamically unstable at electronic temperature roughly above 20 000 K due to the electronic entropy-driven mechanism. In our simulations, equations combining hydrodynamic equations and the two-temperature model are modeled and are numerically solved, where the electronic entropy effects are included as the electronic temperature-dependent latent heat, boiling point, and melting point. For metal targets, Al and Cu, the calculated ablation rates for 100 fs laser pulses agree with the experimental one at laser fluences up to 10 J/cm 2. The heat-affected zone (HAZ) is numerically evaluated from the thickness of the molten layer. Short pulses produce a high ablation rate and small HAZ because of the suppression of diffusion of the deposited pulse energy. Electronic entropy effects make a clear difference between 100 fs and 10 ps pulses. The calculation method presented in this paper serves as a useful tool for exploring nonequilibrium between electrons and ions in the equation of states for metals such as Al and Cu. [ABSTRACT FROM AUTHOR]

We present a multiscale method coupling the theory of open quantum systems with real-time ab initio treatment of electronic structure to study hot-carrier dynamics in photoexcited plasmonic systems. We combine the Markovian Stochastic Schrödinger equation with an ab initio GW coupled to the Bethe–Salpeter (BSE) equation description of the electronic degrees of freedom, interacting with a metallic nanoparticle modeled classically according to the polarizable continuum model. We apply this methodology to study the effect of relaxation (T1) and pure dephasing (T2) times on the hot-carrier dynamics in a system composed of a quantum portion described at GW/BSE level, i.e., a CHO fragment adsorbed on a vertex of a rhodium nanocube, and of the rest of the nanocube, treated classically, when irradiated with a 2.7 eV light pulse, inspired by the experimental results on plasmon-driven CO2 photoreduction. A net hole injection from rhodium to CHO is observed, with and without the classical portion of the nanocube. The nanocube effect is to enhance the generated charge population by two orders of magnitude. The nonradiative decay, via a relaxation time T1 based on the energy-gap law, produces a rapid decrease of the charge population. Results with T2 only show that a charge injection retarded with respect to the pulse, which is present in the coherent dynamics, disappears when coherence is erased. [ABSTRACT FROM AUTHOR]

Physical processes involving hot electrons, including their generation, transport, injection, and relaxation, have been an extensive area of research. The most widely utilized method for actuating the creation of hot electrons involves the excitation of plasmonic modes followed by their non-radiative decay, channeling the energy into these energetic carriers. Since plasmonics has already evolved into a mature field of scientific exploration, active plasmonic devices serve as an ideal platform to study hot-electron physics. In this Perspective article, we will provide the reader with a comprehensive outline of the physics underlying hot-electron dynamics. Emphasis will be placed on the characteristic timescales involved with the lifecycle of hot electrons, the generation and decay mechanisms of surface plasmon-induced hot electrons, and the material platforms suitable for such a study. Then, we will move on to discuss different temperature models used to explain the evolution of hot electrons and the changes in the optical properties of the materials they are generated in or injected into. Finally, we will focus on some of the interesting optical phenomena occurring at ultrafast timescales mediated by hot-carrier dynamics. Such a discussion is expected to incorporate valuable insights into our understanding of the synergistic relationship between hot-electron dynamics and active plasmonics, thereby paving the way for novel applications involving optoelectronics and energy conversion. [ABSTRACT FROM AUTHOR]

In the continuity of a previous jet-cooled rovibrational study of trans and cis conformers of 2-furfural in the mid-infrared region (700–1750 cm−1) [Chawananon et al., Molecules 28 (10), 4165 (2023)], the present work investigates the far-infrared spectroscopy of 2-furfural using a long path absorption cell coupled to a high-resolution Fourier transform spectrometer and synchrotron radiation at the AILES beamline of the SOLEIL synchrotron. Guided by anharmonic calculations, vibrational energy levels and excited-state rotational constants are sufficiently predictive for a complete assignment of all fundamental and combination bands up to 700 cm−1, as well as the rovibrational analysis of 4 (1) low-frequency modes of trans-(cis-)2-furfural. A global rovibrational simulation, including far-infrared rovibrational lines and microwave and millimeter-wave rotational lines assigned in a previous study [Motiyenko et al., J. Mol. Spectrosc., 244, 9 (2007)] provides a reliable set of ground- and excited-state rotational parameters involving ring torsion, bending, and ring puckering modes of 2-furfural. In a second step, a rovibrational analysis of several hot band sequences, mainly involving the lowest frequency ring CHO torsion mode, is carried out. Reliable values of some anharmonic coefficients are obtained experimentally and could serve as a benchmark for validating advanced anharmonic calculations related to these large amplitude motions of flexible molecules. [ABSTRACT FROM AUTHOR]

Lead halide perovskites (LHPs) have gained prominence for their exceptional photophysical properties, holding promise for applications in high-end optoelectronic devices. However, the presence of lead is one of the major obstacles to the commercialization of LHPs in the field of photovoltaics. To address this, researchers have explored environment friendly lead-free perovskite solar cells by investigating non-toxic perovskite materials. This study explores the enhancement of photophysical properties through chemical engineering, specifically cation exchange, focusing on the crucial photophysical process of hot carrier cooling. Employing femtosecond transient absorption spectroscopy and optical pump terahertz probe spectroscopy, we have probed the carrier relaxation dynamics in A3Sb2I9 with cesium and rubidium cations. This study unravels that the carrier relaxation is found to be slower in Rb3Sb2I9; along with this, the transient mobility decay is found to be retarded. Overall, this study suggests that an antimony-based Rb3Sb2I9 perovskite could be a substantial lead-free perovskite in photovoltaics. These findings provide valuable insights into cation engineering strategies, aiming to improve the overall performance of lead-free-based photovoltaic devices. [ABSTRACT FROM AUTHOR]

Metals exhibit nonequilibrium electron and lattice subsystems at transient times following femtosecond laser excitation. In the past four decades, various optical spectroscopy and time-resolved diffraction methods have been used to study electron–phonon coupling and the effects of underlying dynamical processes. Here, we take advantage of the surface specificity of reflection ultrafast electron diffraction (UED) to examine the structural dynamics of photoexcited metal surfaces, which are apparently slower in recovery than predicted by thermal diffusion from the profile of absorbed energy. Fast diffusion of hot electrons is found to critically reduce surface excitation and affect the temporal dependence of the increased atomic motions on not only the ultrashort but also sub-nanosecond times. Whereas the two-temperature model with the accepted physical constants of platinum can reproduce the observed surface lattice dynamics, gold is found to exhibit appreciably larger-than-expected dynamic vibrational amplitudes of surface atoms while keeping the commonly used electron–phonon coupling constant. Such surface behavioral difference at transient times can be understood in the context of the different strengths of binding to surface atoms for the two metals. In addition, with the quantitative agreements between diffraction and theoretical results, we provide convincing evidence that surface structural dynamics can be reliably obtained by reflection UED even in the presence of laser-induced transient electric fields. [ABSTRACT FROM AUTHOR]

Irradiation of semiconductors by energetic beams generates excess electrons and holes and may cause device degradation or failure. Both gradual degradation by total ionizing radiation (TID) and sudden degradation/failure (soft/hard breakdown) by a combination of energetic heavy ions and high voltages (typically single-event effects or SEEs) are mediated by excess carriers. The role of defect dynamics in TID degradation has been adequately understood by a combination of experiments and density-functional-theory (DFT) quantum calculations, but little has been done so far to document a role for ion-induced defects in SEE. Here, we report proof-of-principle DFT calculations in a model cubic GaN system for two defect-related excess-carrier phenomena that can play a role in various forms of device degradation and failure. The first phenomenon is the existence, dynamics, and potential roles of defect-induced quasi-localized "resonant states" in the energy-band continua. These states can enhance TID-excess-carrier and hot-carrier degradation. Furthermore, they evolve and multiply during energetic-ion-induced atom recoils and defect creation (displacement damage) and can potentially serve as excess-carrier conduction paths in SEE. The second phenomenon is the conversion of isolated vacancies into nanovoids that can participate in the formation of conducting defect "nanowires" dressed by resonances or in explosive SEE hard breakdowns. [ABSTRACT FROM AUTHOR]

We analyze the operation of the hot-electron FET bolometers with the graphene channels (GCs) and the gate barrier layers. Such bolometers use the thermionic emission of the hot electrons heated by incident-modulated THz radiation. The hot electrons transfer from the GC into the metal gate. As the THz detectors, these bolometers can operate at room temperature. We show that the response and ultimate modulation frequency of the GC-FET bolometers are determined by the efficiency of the hot-electron energy transfer to the lattice and the GC side contacts due to the 2DEG lateral thermal conductance. The dependences of these mechanisms on the band structure and geometrical parameters open the way for the GC-FET bolometers optimization, in particular, for the enhancement of the maximum modulation frequency. [ABSTRACT FROM AUTHOR]

In recent years, all-inorganic perovskite materials have become an ideal choice for new thin film solar cells due to their excellent photophysical properties and have become a research hotspot. Studying the ultrafast dynamics of photo-generated carriers is of great significance for further improving the performance of such devices. In this work, we focus on the transient dynamic process of CsPbBr3/TiO2 composite systems with different Mn2+ doping contents using femtosecond transient absorption spectroscopy technology. We used singular value decomposition and global fitting to analyze the transient absorption spectra and obtained three components, which are classified as hot carrier cooling, charge transfer, and charge recombination processes, respectively. We found that the doping concentration of Mn2+ has an impact on all three processes. We think that the following two factors are responsible: one is the density of defect states and the other is the bandgap width of perovskite. As the concentration of doped Mn2+ increases, the charge transfer time constant shows a trend of initially increasing, followed by a subsequent decrease, reaching a turning point. This indicates that an appropriate amount of Mn2+ doping can effectively improve the photoelectric performance of solar cell systems. We proposed a possible charge transfer mechanism model and further elucidated the microscopic mechanism of the effect of Mn2+ doping on the interface charge transfer process of the CsPbBr3/TiO2 solar cell system. [ABSTRACT FROM AUTHOR]

In order to develop an efficient metal-free solar energy harvester, we herein performed the electronic structure calculation, followed by the hot carrier relaxation dynamics of two dimensional (2D) aza-covalent organic framework by time domain density functional calculations in conjunction with non-adiabatic molecular dynamics (NAMD) simulation. The electronic structure calculation shows that the aza-covalent organic framework (COF) is a direct bandgap semiconductor with acute charge separation and effective optical absorption in the UV-visible region. Our study of non-adiabatic molecular dynamics simulation predicts the sufficiently prolonged electron–hole recombination process (6.8 nanoseconds) and the comparatively faster electron (22.48 ps) and hole relaxation (0.51 ps) dynamics in this two-dimensional aza-COF. According to our theoretical analysis, strong electron–phonon coupling is responsible for the rapid charge relaxation, whereas the electron–hole recombination process is slowed down by relatively weak electron–phonon coupling, relatively lower non-adiabatic coupling, and quick decoherence time. We do hope that our results of NAMD simulation on exciton relaxation dynamics will be helpful for designing photovoltaic devices based on this two dimensional aza-COF. [ABSTRACT FROM AUTHOR]

While SnF2 is reported as an effective additive for improving the efficiency of lead-free tin-based perovskite solar cells, the mechanism is still unclear and requires further studies. Upon incorporating SnF2 into MASnI3, SnF2 reduces the intrinsic carrier density from 1018 to 1012 cm–3 and produces a longer carrier diffusion length as confirmed by the Hall measurements. The femtosecond transient absorption spectroscopy shows that SnF2 doping enhances the hot-phonon bottleneck effect of MASnI3. The slow cooling process of hot carriers may help to reduce non-radiative recombination, increase the fluorescence lifetime, and, therefore, improve the utilization rate of carriers. Finally, lead-free low bandgap perovskite MASnI3 is utilized as a light absorbing layer in solar cells, achieving high optical current and high voltage in tin-based perovskite solar cells. The final power conversion efficiency is 10.2%, while the power conversion efficiency for the control unit is 6.69%. [ABSTRACT FROM AUTHOR]

As typical representatives of group III chalcogenides, InSe, α-In2Se3, and β′-In2Se3 have drawn considerable interest in the domain of photoelectrochemistry. However, the microscopic mechanisms of carrier dynamics in these systems remain largely unexplored. In this work, we first reveal that hot electrons in the three systems have different cooling rate stages and long-lived hot electrons, through the utilization of density functional theory calculations and nonadiabatic molecular dynamics simulations. Furthermore, the ferroelectric polarization of α-In2Se3 weakens the nonadiabatic coupling of the nonradioactive recombination, successfully competing with the narrow bandgap and slow dephasing process, and achieving both high optical absorption efficiency and long carrier lifetime. In addition, we demonstrate that the ferroelectric polarization of α-In2Se3 not only enables the formation of the double type-II band alignment in the InSe/α-In2Se3/InSe heterostructure, with the top and bottom InSe sublayers acting as acceptors and donors, respectively, but also eliminates the hindrance of the built-in electric field at the interface, facilitating an ultrafast interlayer carrier transfer in the heterojunction. This work establishes an atomic mechanism of carrier dynamics in InSe, α-In2Se3, and β′-In2Se3 and the regulatory role of the ferroelectric polarization on the charge carrier dynamics, providing a guideline for the design of photoelectronic materials. [ABSTRACT FROM AUTHOR]

Revived attention in black phosphorus (bP) has been tremendous in the past decade. While many photoinitiated experiments have been conducted, a cross-examination of bP's photocarrier and structural dynamics is still lacking. In this article, we provide such analysis by examining time-resolved data acquired using optical transient reflectivity and reflection ultrafast electron diffraction, two complementary methods under the same experimental conditions. At elevated excitation fluences, we find that more than 90% of the photoinjected carriers are annihilated within the first picosecond (ps) and transfer their energy to phonons in a nonthermal, anisotropic fashion. Electronically, the remaining carrier density around the band edges induces a significant interaction that leads to an interlayer lattice contraction in a few ps but soon diminishes as a result of the continuing loss of carriers. Structurally, phonon–phonon scattering redistributes the energy in the lattice and results in the generation of out-of-plane coherent acoustic phonons and thermal lattice expansion. Their onset times at ∼6 ps are found to be in good agreement. Later, a thermalized quasi-equilibrium state is reached following a period of about 40–50 ps. Hence, we propose a picture with five temporal regimes for bP's photodynamics. [ABSTRACT FROM AUTHOR]

The electron–phonon scattering plays a crucial role in determining the electronic, transport, optical, and thermal properties of materials. Here, we employ a non-Markovian stochastic Schrödinger equation (NMSSE) in momentum space, together with ab initio calculations for energy bands and electron–phonon interactions, to reveal the phonon-mediated ultrafast hole relaxation dynamics in the valence bands of monolayer black phosphorus. Our numerical simulations show that the hole can initially remain in the high-energy valence bands for more than 100 fs due to the weak interband scatterings, and its energy relaxation follows single-exponential decay toward the valence band maximum after scattering into low-energy valence bands. The total relaxation time of holes is much longer than that of electrons in the conduction band. This suggests that harnessing the excess energy of holes may be more effective than that of electrons. Compared to the semiclassical Boltzmann equation based on a hopping model, the NMSSE highlights the persistence of quantum coherence for a long time, which significantly impacts the relaxation dynamics. These findings complement the understanding of hot carrier relaxation dynamics in two-dimensional materials and may offer novel insights into harnessing hole energy in photocatalysis. [ABSTRACT FROM AUTHOR]

Hot carrier solar cells could offer a solution to achieve high efficiency solar cells. Due to the hot-phonon bottleneck in perovskites, the hot carrier lifetime could reach hundreds of ps. Such that exploring perovskites could be a good way to promote hot carrier technology. With the incorporation of large organic cations, the hot carrier lifetime can be improved. By using ultrafast transient spectroscopy, the hot carrier relaxation and extraction kinetics are measured. From the transient kinetics, 2-phenyl-acetamidine cation based perovskites exhibit the highest initial carrier temperature, longest carrier relaxation, and slowest hot carrier relaxation. Such superior behavior could be attributed to reduced electron–phonon coupling induced by lattice strain, which is a result of the large organic cation and also a possible surface electronic state change. Our discovery exhibits the potential to use large organic cations for the use of hot carrier perovskite solar cells. [ABSTRACT FROM AUTHOR]

Modulation doping of silicon has great potential for miniaturization, surface passivation, and third generation photovoltaics (PV). At a modulation-doped silicon surface, we observe the formation of a 2D hole layer at the silicon surface at low temperatures by means of photoluminescence (PL) measurements. A line shape analysis of band–band and hot luminescence reveals the hole density (which is equal to the modulation-doped acceptor density). A high excitation intensity leads to a Fermi edge singularity of the band–band and hot PL emission. While the 2D layer can be characterized by the observed luminescence, the spectral region of twice the bandgap is fully dominated by emission from this surface layer, impeding the measurement of bulk hot luminescence, e.g., from Auger electrons or from nonthermalized carriers in a hot carrier PV device. [ABSTRACT FROM AUTHOR]

Energy transfer has been proven to be an effective method to optimize optoelectronic conversion efficiency by improving light absorption and mitigating nonradiative losses. We prepared 2D/3D CsPbBr3 hybrid assemblies at different reaction temperatures using the hot injection method and found that the photoluminescence quantum yields (PLQYs) of these hybrids were greatly enhanced from 53.4% to 72.57% compared with 3D nanocrystals (NCs). Femtosecond transient absorption measurements were used to study the PLQY enhancement mechanisms, and it was found that the hot carrier lifetime improved from 0.36 to 1.88 ps for 2D/3D CsPbBr3 hybrid assemblies owing to the energy transfer from 2D nanoplates to 3D NCs. The energy transfer benefits the excited carrier accumulation and prolonged hot carrier lifetime in 3D NCs in hybrid assemblies, as well as PLQY enhancement in materials. [ABSTRACT FROM AUTHOR]

We report temperature-dependent hot carrier dynamics in liquid-phase epitaxy-grown GaSb1−xBix epilayers with dilute amounts of Bi (x ≾ 0.4%). Degenerate pump–probe (λ = 800 nm) transient reflectivity (PPTR) was used to investigate the carrier dynamics in the epilayers. The PPTR signal consists of two transient processes (fast and slow) at all temperatures for all epilayers. The fast, hot carrier relaxation time, which is attributed to the combined effect of intervalley scattering and thermalization of carriers below cryogenic temperatures (<100 K), is observed to increase with an increase in temperature (≈0.8–2 ps at 6.6 K and ≈4–5 ps at 300 K). However, at higher temperatures (>100 K), the interband CHSH-Auger recombination process affects the band-to-band recombination, leading to an increase in the slower decay time. The findings offer crucial insights for optimizing GaSbBi for hot carrier solar cell applications. [ABSTRACT FROM AUTHOR]

Modeling light–matter interactions in hybrid plasmonic materials is vital to their widening relevance from optoelectronics to photocatalysis. Here, we explore photoluminescence (PL) from ZnO nanorods (ZNRs) embedded with gold nanoparticles (Au NPs). A progressive increase in Au NP concentration introduces significant structural disorder and defects in ZNRs, which paradoxically quenches defect related visible PL while intensifying the near band edge (NBE) emission. Under UV excitation, the simulated semi-classical model realizes PL from ZnO with sub-bandgap defect states, eliciting visible emissions that are absorbed by Au NPs to generate a non-equilibrium hot carrier distribution. The photo-stimulated hot carriers, transferred to ZnO, substantially modify its steady-state luminescence, reducing NBE emission lifetime and altering the abundance of ionized defect states, finally reducing visible emission. The simulations show that the change in the interfacial band bending at the Au–ZnO interface under optical illumination facilitates charge transfer between the components. This work provides a general foundation to observe and model the hot carrier dynamics and strong light–matter interactions in hybrid plasmonic systems. [ABSTRACT FROM AUTHOR]

The development of robust and efficient photocatalytic constructs for boosting the water oxidation reaction (WOR) is needed for establishing a sunlight-driven renewable energy infrastructure. Here, we synthesized plasmonic core–shell nanoconstructs consisting of triangular gold nanoprism (AuTNP) core with mixed manganese oxide (MnOx) shell for photoelectrocatalytic WOR. These constructs show electrocatalytic WOR with a low onset overpotential requirement of 270 mV at pH 10. Photoexcitation showed further enhancement of their catalytic activity resulting in ∼15% decrease of the onset overpotential requirement along with the generation of photocurrent density of up to 300 μA/cm2. We showed that such light-driven enhancement of AuTNP@MnOx dyad's catalytic activity toward the WOR process includes contributions from both photocatalytic (hot carriers driven) and photothermal effects with photothermal effect playing the major role for wavelength between 532 and 808 nm. The contribution from the photocatalytic effect is appreciable only for high-energy excitations near the interband region, while the photothermal effect largely dominates for lower energy excitations near the LSPR wavelengths of the dyad. [ABSTRACT FROM AUTHOR]

Prolonging the lifetime of photoinduced hot carriers in lead–halide perovskite quantum dots (QDs) is highly desirable because it can help improve the photovoltaic conversion efficiency. Ligand engineering has recently become a promising strategy to achieve this; nevertheless, mechanistic studies in this field remain limited. Herein, we propose a new scenario of ligand engineering featuring Pb2+/Br− site-selective capping on the surface of CsPbBr3 QDs. Through joint observations of temperature-dependent photoluminescence, ultrafast transient absorption, and Raman spectroscopy of the two contrasting model systems of CsPbBr3 QDs (i.e., capping with organic ligand only vs hybrid organic/inorganic ligands), we reveal that the phononic regulation of Pb–Br stretching at the Br-site (relative to Pb-site) leads to a larger suppression of charge–phonon coupling due to a stronger polaronic screening effect, thereby more effectively retarding the hot-carrier cooling process. This work opens a new route for the manipulation of hot-carrier cooling dynamics in perovskite systems via site-selective ligand engineering. [ABSTRACT FROM AUTHOR]

Two-dimensional molybdenum disulfide (MoS2) has been proved to be a good candidate in photodetectors, and MoS2/graphene (MoS2/G) heterostructure has been widely used to expand the optical response wavelength of MoS2. To clarify the carrier transfer dynamics in the MoS2/G heterostructure, time-resolved transient absorption and two-color pump–probe measurements are performed. By comparing the carrier dynamics in MoS2 and MoS2/G under different pump wavelengths, we find that interfacial excitons are formed in the heterostructure, and fast hot carriers transfer (<200 fs) from graphene to MoS2 are observed. The results indicate that the formed heterostructure with graphene can not only expand the optical response wavelength of MoS2 but also improve the response time of the device in the near-infrared region. [ABSTRACT FROM AUTHOR]

The lattice mismatch, defect, and weak interlayer coupling severely constrain the practical application of van der Waals heterojunctions (vdWHs) in the field of optoelectronic devices. Here, we introduced the 2D ferroelectric (FE) material AgBiP2Se6 to construct defect-free, low lattice-mismatched AgBiP2Se6/MoSe2 heterojunctions with different polariton directions (I, II, III). The AgBiP2Se6 layer can provide an excellent FE electric field to enhance the interlayer coupling and stiffness. The larger interlay stiffness reduces the probability of electron–phonon scattering and then results in significant carrier mobility (∼0.5 × 104 cm2 V−1 s−1) for configurations I and II. Phase transition of FE to paraelectric AgBiP2Se6 in the AgBiP2Se6/MoSe2 heterojunctions can be achieved under specific biaxial strain, which can effectively regulate the electronic structure. Applying the strain and electric field can regulate the bandgap and band alignment of configurations I and II. The photoelectric conversion efficiency of configuration I can reach as high as 20.54% under 2% biaxial strain. Furthermore, configuration II holds a nearly free electron state near the Fermi level under an electric field, which can act as a favorable electron transport channel. A design to strengthen interlayer coupling in the FE-based AgBiP2Se6/MoSe2 heterojunction has been proposed, and it can provide a new way to break through the traditional bottleneck in the development of optoelectronic devices. [ABSTRACT FROM AUTHOR]

We report a study on the electronic structure and chemical bonding of the BiB molecule using high-resolution photoelectron imaging of cryogenically cooled BiB− anion. By eliminating all the vibrational hot bands, we can resolve the complicated detachment transitions due to the open-shell nature of BiB and the strong spin–orbit coupling. The electron affinity of BiB is measured to be 2.010(1) eV. The ground state of BiB− is determined to be 2Π(3/2) with a σ2π3 valence electron configuration, while the ground state of BiB is found to be 3Σ−(0+) with a σ2π2 electron configuration. Eight low-lying spin–orbit excited states [3Σ−(1), 1Δ(2), 1Σ+(0+), 3Π(2), 3Π(1), 1Π(1)], including two forbidden transitions, [3Π(0−) and 3Π(0+)], are observed for BiB as a result of electron detachment from the σ and π orbitals of BiB−. The angular distribution information from the photoelectron imaging is found to be critical to distinguish detachment transitions from the σ or π orbital for the spectral assignment. This study provides a wealth of information about the low-lying electronic states and spin–orbit coupling of BiB, demonstrating the importance of cryogenic cooling for obtaining well-resolved photoelectron spectra for size-selected clusters produced from a laser vaporization cluster source. [ABSTRACT FROM AUTHOR]

Optical phonons serve as the fast and efficient carriers of energy across periodic polymers due to their delocalization, large group velocity because of covalent bonding, and large energy quantum compared to that for acoustic phonons as it was observed in a number of recent measurements in different oligomers. However, this transport is dramatically sensitive to anharmonic interactions, including the unavoidable interaction with acoustic phonons responsible for transport decoherence, suppressing ballistic transport at long distances. Here, we show that this decoherence is substantially suppressed if the group velocity of optical phonons is less than the sound velocity of acoustic phonons; otherwise, ballistic transport is substantially suppressed by a Cherenkov-like emission of acoustic phonons. This conclusion is justified considering energy and momentum conservation during phonon absorption or emission and supported by the numerical evaluation of the lifetimes of the optical phonons. It is also consistent with the recent experimental investigations of ballistic optical phonon transport in oligomers with the minor exception of relatively short oligophenylenes. [ABSTRACT FROM AUTHOR]

In this work, we investigated the effect of hole transporting poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) interfacing with Mn-doped CdS/ZnS quantum dots (QDs) deposited on an indium tin oxide (ITO) substrate on the photoemission of upconverted hot electrons under weak continuous wave photoexcitation in a vacuum. Among the various factors that can influence the photoemission of the upconverted hot electrons, we studied the role of PEDOT:PSS in facilitating the hole transfer from QDs and altering the energy of photoemitted hot electrons. Compared to hot electrons emitted from QDs deposited directly on the ITO substrate, the addition of the PEDOT:PSS layer between the QD and ITO layers increased the energy of the photoemitted hot electrons. The increased energy of the photoemitted hot electrons is attributed in part to the reduced steady-state positive charge on the QDs under continuous photoexcitation, which reduces the energy required to eject the electron from the conduction band. [ABSTRACT FROM AUTHOR]

Advancing the energy‐intensive Haber–Bosch process faces significant challenges due to the intrinsic constraints of scaling relations in heterogeneous catalysis. Herein, we reported an approach of bending the "seesaw effect" to regulate the scaling relations over a tailored α‐Fe metallic material (α‐Fe‐110s), realizing highly efficient light‐driven thermal catalytic ammonia synthesis with a rate of 1260 μmol gcatalyst−1 h−1 without additional heating. Specifically, the thermal catalytic activity of α‐Fe‐110s was significantly enhanced by the novel stepped {110} surface, exhibiting a 3.8‐fold increase compared to the commercial fused‐iron catalyst with promoters at 350 °C. The photo‐induced hot electron transfer further accelerates the dinitrogen dissociation and hydrogenation simultaneously, effectively overcoming the limitation of scaling relation over identical sites. Consequently, the ammonia production rate of α‐Fe‐110s was further enhanced by 30 times at the same temperature with irradiation. This work designs an efficient and sustainable system for ammonia synthesis and provides a novel approach for regulating the scaling relations in heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

Electron–ion coupling is a fundamental process in nonequilibrium Warm Dense Matter. It also plays a central role in governing the states resulting from the interaction of high-intensity ultrafast lasers and free-electron-lasers with matter, an area that is of growing interest. Our inadequate understanding of the process was revealed in 1992 by the discovery of much weaker than expected electron–ion coupling in the nonequilibrium state at a shock front in Si where energy was transferred from hot ions to cold electrons. This necessarily raised questions about the behavior of electron–ion coupling in states with hot electrons and cold ions. It became a new focus of the field with the discovery of apparently constant electron–ion coupling in f s -laser heated Au, prompting a wide range of experimental and theoretical investigations of non-equilibrium warm dense Au as well as Cu for almost two decades. Fueling the pursuit were the findings of both constant and temperature-dependent coupling from subsequent experiments while the results of theoretical models were revealing reduced electron temperature dependence of electron–ion coupling. The goal of this review is to provide a concise historical account of the reported investigations, focussing on the salient characteristics of the experiments and models and how the diverse findings may be reconciled. Surprisingly, with alternative interpretations of some of the experimental results, a consistent behavior of weak electron–ion coupling has now emerged for f s -laser heated Au and Cu for electron temperature up to 20,000 K, corroborated by the evolution of theoretical predictions towards weak coupling. This is a significant progress. It will incentivize new research to gain further understanding of electron–ion coupling in nonequilibrium Warm Dense Matter. [ABSTRACT FROM AUTHOR]

Plasmon-induced photocatalysis showed great potential to improve the photocatalytic nitrogen fixation efficiency, due to the localized surface plasmon resonance effect. The performances of the photocatalytic nitrogen fixation were evaluated by ammonia production rate, apparent quantum efficiency, solar-to-ammonia efficiency, and turnover frequency. The ammonia production rate was compared with three kinds of catalyst, i.e. nano-metals, nano-metal modified semiconductors and highly doped semiconductors. The outstanding contributions of hot electron injection effect, near-field enhancement effect, photothermal effect to nitrogen fixation efficiency were described. The creation of active sites, construct vacancies, and doping regulation were effective methods to prepare high performance catalysts for photocatalytic nitrogen fixation. • Nano-metal-modified semiconductor catalysts achieve ammonia production rate of 785 μmol g−1 h−1. • Highiy doped semiconductors re-define the landscape of photocatalytic NH 3 generation. • The ammonia production rate, apparent quantum efficiency and Solar-to-Ammonia can be used to evaluate the performance ofphotocatalyst. • Hot electron injection effect as a guide for the synthesis of plasma-induced photocatalysts. [ABSTRACT FROM AUTHOR]

The emergence of global warming issues has triggered the interest in producing carbon-neutral energy sources and fossil-based chemicals from affordable and renewable feedstocks (e.g., bio-ethanol). Herein, the synthesis of highly dispersed CuS/TiO 2 photothermal catalysts is reported for simultaneously converting ethanol into hydrogen and acetaldehyde under simulated sunlight. The catalyst achieved a hydrogen evolution rate of 51.61 mmol g−1 h−1 and an acetaldehyde production rate of 48.63 mmol g−1 h−1, with a maximal acetaldehyde selectivity of 97% among carbon-containing products. Compared to pristine TiO 2 , the introduction of plasmonic CuS largely extended the light adsorption range and enhanced the photothermal performance, whilst the formation of heterojunction structure improved the charge transfer and separation efficiency. The density functional theory calculation results demonstrate that CuS/TiO 2 composite interfaces could significantly lower the activation energy of ethanol dehydrogenation reaction and improve hydrogen evolution reaction ability. This study provides deep insight into understanding and optimizing hot carrier dynamics in photothermal catalytic systems. • Novel CuS/TiO 2 catalyst for efficient ethanol dehydrogenation to co-produce hydrogen and acetaldehyde under mild conditions. • 0.05 CuS/TiO 2 achieved a H 2 evolution rate of 51.61 mmol g−1 h−1 and an acetaldehyde production rate of 48.63 mmol g−1 h−1. • Synergistic effects of heterojunction and significant photothermal effect induced by CuS enhanced catalytic performance. • Reduced activation energy for ethanol dehydrogenation and improved H 2 evolution were achieved by CuS/TiO2 interface. [ABSTRACT FROM AUTHOR]

Electrochemical reactivity is known to be dictated by the structure and composition of the electrocatalyst-electrolyte interface. Here, we show that optically generated electric fields at this interface can influence electrochemical reactivity insofar as to completely switch reaction selectivity. We study an electrocatalyst composed of gold-copper alloy nanoparticles known to be active toward the reduction of CO2 to CO. However, under the action of highly localized electric fields generated by plasmonic excitation of the gold-copper alloy nanoparticles, water splitting becomes favored at the expense of CO2 reduction. Real-time time-dependent density functional tight binding calculations indicate that optically generated electric fields promote transient-hole-transfer-driven dissociation of the O-H bond of water preferentially over transient-electron-driven dissociation of the C-O bond of CO2. These results highlight the potential of optically generated electric fields for modulating pathways, switching reactivity on/off, and even directing outcomes. [ABSTRACT FROM AUTHOR]

The development of photocatalysts that maximize the utilization of the solar spectrum is crucial to achieving efficient photocatalysis. Herein, the synthesized W 18 O 49 @ZnIn 2 S 4 hollow hierarchical structure exhibits superior photothermal-assisted hydrogen (H 2) photocatalytic performance under full solar spectrum irradiation. Within this photocatalyst design framework, the use of hollow spherical W 18 O 49 exploits the Localized Surface Plasmon Resonance (LSPR) effect, resulting in increased light absorption. This imparts additional energy to photogenerate carriers through ZnIn 2 S 4 , expediting charge migration and elevating the temperature of the reaction system, consequently facilitating the separation of carriers. Notably, the optimized WO(16h)@ZIS-10 sample shows impressive hydrogen evolution rates of 3.11 mmol g−1 under sunlight exposure and 4.98 mmol g−1 h−1 under composite illumination of AM 1.5G and near-infrared (NIR). Additionally, the study explores the impact of different heating methods on photocatalytic activity in solid-liquid reactions, providing valuable insights into effective solar energy conversion through high-activity solar-assisted photocatalysts. The W 18 O 49 @ZnIn 2 S 4 photothermal catalysts with suitable core-shell thickness was developed, which can efficiently utilize the hot electrons from LSPR effect, thus display a superior hydrogen evolution performance with photothermal synergistic effect. [Display omitted] • Successful construction of a hollow layered structure of core-shell W 18 O 49 @ZnIn 2 S 4. • High hydrogen production activity and stability. • Good practical application prospect. [ABSTRACT FROM AUTHOR]

Hot-carrier solar cells offer the potential for enhanced power conversion efficiency by tapping into the kinetic energy of hot carriers generated upon sunlight absorption. This involves using specially designed materials capable of efficiently extracting and utilizing the energy of these hot carriers to produce electrical power. Here, we observed such a hot carrier effect in hexamine doped methylammonium lead triiodide perovskite solar cells when exposed to 100 mW/cm2 of 5000 K white LED light. We discovered that these perovskite solar cells exhibited remarkable power conversion efficiency, reaching up to 54.22% with the Voc (open-circuit voltage) and Jsc (short-circuit current density) values were measured at 1.10 V and 54 mA/cm2, respectively. In comparison, under similar conditions but using a solar simulator, the power conversion efficiency remained below 20%. Our results suggest that the high PCE under white LED irradiation is due to the fine resonance between the light energy and perovskite band gap energy, enabling long carrier lifetime and then allowing massive photovoltaics process. These findings highlight the alternative to achieve hot carrier's perovskite solar cells and efficient energy generation by converting light energy into the wavelength match with the perovskite materials absorber energy band gap. [ABSTRACT FROM AUTHOR]

Electron transport characteristics were measured at room temperature applying nanosecond duration electrical pulses on two-dimensional electron gas (2DEG) channel in AlGaN/GaN heterostructures grown on SiC substrate. Crystal lattice self-heating effects were minimised by usage of nanosecond duration pulses being as short as 2 ns. We were able to reach highest current densities of 1.24 A/mm and 1.80 A/mm for different type of AlGaN/AlN/GaN and AlGaN/GaN heterostructures under the electric field of 57 kV/cm and 69 kV/cm, respectively. Even stronger electric field usage was allowed by the pulse source employed (up to 75 kV/cm for channel length of 12.5 μ m), however, that was not needed as the electric current near saturation was observed. The three-dimensional (3D) electron channels in GaN epilayer on GaN substrate were also investigated under pulsed electric field reaching up to 216 kV/cm. The electron drift velocity was found from experimental charge current density characteristics assuming that Hall electron density does not change in the sample under high electric fields. Maximum drift velocities for the 2DEG channels in AlGaN/GaN and AlGaN/AlN/GaN samples were found to be up to 1.2 × 10 7 cm/s at 69 kV/cm and 1.1 × 10 7 cm/s at 57 kV/cm, respectively, while, the highest value of ∼ 2.6 × 10 7 cm/s at 216 kV/cm was obtained for the 3D GaN channels. In the region of high electric fields the electron drift velocity in 2DEG channel was smaller than that in 3D channel as the result of stronger hot-phonon effect. [ABSTRACT FROM AUTHOR]

Recently, planar and broadband hot-electron photodetectors (HE PDs) were established but exhibited degraded performances due to the adoptions of the single-junction configurations and the utilizations of absorbable films with thicknesses larger than the electronic mean free path. In this work, we present a five-layer design for planar HE PDs assisted by triple junctions in which an ultrathin Pt layer dominates the broadband and displays strong optical absorption (>0.9 from 900 nm to 1700 nm). Optical studies reveal that the optical admittance matching between optical admittances of designed device and air at all interested wavelengths is responsible for broadband light-trapping that induces prominent energy depositions in Pt layers. Electrical investigations show that, benefitting from suppressed hot-electron transport losses and increased hot-electron harvesting junctions, the predicted responsivity of the designed HE PD is up to 8.51 mA/W at 900 nm. Moreover, the high average absorption (responsivity) of 0.96 (3.66 mA/W) is substantially sustained over a broad incidence angle regardless of the polarizations of incident light. The comparison studies between five-layer and three-layer devices emphasize the superiority of five-layer design in strong optical absorption in Pt layers and efficient hot-electron extraction. [ABSTRACT FROM AUTHOR]

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Intraband carrier relaxation in quantum dots (QDs) has been a subject of extensive spectroscopic investigation for several decades, and have been used to optimize the efficiency of opto‐electronic processes. In the past few years, metal halide perovskites‐based QDs have been shown to exhibit slow hot‐carrier cooling characteristics that are desirable for photo‐energy harvesting technologies. While several mechanisms are proposed to rationalize the retardation of the cooling dynamics, including hot‐phonon bottleneck and polaronic effects, the role of inter‐particle connectivity in these dynamics is largely ignored. Here, an in‐depth study of photo‐excitation dynamics and carrier cooling on perovskite QD solids with varying degrees of inter‐dot coupling is presented. It is observed that inter‐particle connectivity has deterministic effects on the many‐body interactions that are relevant for carrier cooling. These include carrier–carrier interactions that result in Auger‐reheating of the carriers, and lattice characteristics that subsequently affect the phonon‐assisted cooling dynamics. This spectroscopic study of ultrafast carrier dynamics in perovskite QD solids establishes inter‐dot separation as a critical material design parameter for the optimization of photo‐generated carrier temperature, which fundamentally determines the luminescence characteristics and thus the opto‐electronic quality of the material. [ABSTRACT FROM AUTHOR]

Halogen‐mixed CsPb(Br/I)3 perovskite quantum dots (PeQDs) embedded glass can address the issue of stability, but suffers from low photoluminescence quantum yields (PLQYs) for the hindered in situ nucleation/growth inside the robust glass network. Uncovering the exact mechanism is highly desirable to develop high‐performance CsPb(Br/I)3@glass for commercial applications, but the topic remains unexplored. Here, based on femtosecond transient (fs‐TA) absorption, temperature‐dependent PL spectra, and theoretical calculations, a comprehensive understanding on heat‐treatment (HT) temperature‐induced modification of microstructures and carrier dynamics in the CsPb(Br/I)3@glass is build. It is evidenced that high‐temperature HT will promote more I− ions diffusion from glass matrix into CsPb(Br/I)3 lattice, leading to the retarded hot carrier (HC) cooling, and improved exciton recombination. This is attributed to the synergistic effect of the reduced effect carrier mass, the weakened carrier‐phonon coupling, the inhibited Klemens channel, and the eliminated defect states. Revealing these underlying mechanisms will empower to exert precise control and optimize PLQY of CsPb(Br/I)3@glass up to near unity. [ABSTRACT FROM AUTHOR]

Strongly correlated manganites can be considered as model systems for the study of photovoltaic harvesting of hot polarons that can be excited from the electronically ordered ground state. In order to gain basic understanding of hot polaron harvesting, the deviations of the photovoltaic response of a heterojunction with polaronic absorber from a conventional semiconductor are analyzed. Specifically, the spectral and photon power density dependence of the open circuit voltage Uoc and the short circuit current density Jsc in heterojunctions consisting of orbital ordered Pr1‐xCaxMnO3 (x = 0.1, PCMO) thin films epitaxially grown on single crystalline (100) SrTiO3 (STO) and Nb‐doped (100) SrTiO3 (STNO) substrates are investigated. The observed behavior is fundamentally different from conventional solar cells, in which Uoc is limited by fast carrier relaxation to the band edges. Whereas the spectral and photon power dependence of Uoc of conventional semiconductor junctions is well described by the Shockley‐Queisser (SQ) theory, the hot polaron junctions surprisingly show a scaling law behavior of Uoc. Such scaling laws otherwise apply to equilibrium order parameters in second‐order phase transitions. It is concluded that its physical origin is the unique dependence of the quasi‐Fermi level splitting on temperature, photon energy, and power density in a hot polaron system. [ABSTRACT FROM AUTHOR]

The viability of double perovskite Cs2AgBiBr6 in low‐light environments is studied for CO2 photoreduction. It is observed that light intensity significantly influences product formation with I0.56 depending on the overall product formation rate. The photodetection measurement reveals that photocurrent as a function of incident power follows a power law ∝ I0α with α = 0.80, which is attributed to the carrier trapping at higher light power. Furthermore, power‐dependent transient absorption spectroscopy is studied and observed that at higher fluence, carrier scattering can be dominating. Interestingly, it is found that at higher power, hot carrier relaxation dynamics are altered, and electron‐phonon coupling is enhanced, resulting in a lower carrier concentration participating in the photocatalytic reaction, which can limit charge carrier extraction and CO2 reduction. This study highlights the potential of perovskite semiconductors as promising candidates for photocatalytic reactions in low‐light conditions, broadening their applicability in real‐world scenarios. [ABSTRACT FROM AUTHOR]

Photocatalytic oxygen reduction to H2O2 based on g‐C3N4 has presented promising potential for sustainable solar‐fuel production. Yet tuning the timescale of hot electron's lifetime to effectively participate in the surface reactions remains challenging. Here, an electron‐deficient engineering strategy is developed by incorporating an electron‐deficient structure (EDS) with different conjugate regions into large conjugate‐heptazine framework (LCHF) of g‐C3N4 to steer hot electrons of the different timescales to effectively activate O2 for efficient photocatalytic H2O2 production. Femtosecond transientabsorption spectroscopy reveals that introducing EDS into LCHF can steer hot electron rapid transfer to the trapping sites of EDS and notably eliminate the deeply trapped electrons as well as enhance the shallow capture. It is demonstrated that pyromellitic dianhydride not only can tune the lifetime scale of hot electrons but also provide nonpolarized active sites to effectively activate O2 forming H2O2 with lower energy barrier via direct or stepwise 2e− pathways. This photocatalyst achieves an H2O2 yield rate of 25.40 mmol g−1 h−1, enabling an apparentquantumyield of 45.7% at 400 nm and a solar‐to‐chemical efficiency of 2.63%, outperforming the other reported photocatalysts. This work will shed light on the design of organic photocatalysts to tune hot electrons to effectively engage in the surface reaction. [ABSTRACT FROM AUTHOR]

Photocatalytic CO2 reduction is gaining more interest as a sustainable route to produce methanol, a key starting material in the synthesis of many chemicals and a potential energy carrier. Here, metal‐organic frameworks (MOFs) are used as platforms to integrate plasmonic Au nanospheres and Cu active centers in joint bifunctional hybrid photocatalysts. The methodology followed in obtaining stable Au@UiO‐67‐bpy‐Cu MOFs is based on synthesizing Au@UiO‐67‐bypiridine (bpy) MOFs through a core‐shell procedure, and then modifying them with Cu ions after their coordination with the bpy ligands. This gains the final structure regular coverage of active metal centers that can be excited by the interaction with the plasmonic nanospheres. In the absence of Au, the system demonstrates selectivity toward the formation of methanol under hole scavenger‐free conditions owing to the excitation of the bpy‐Cu complex with visible light. The obtained yield duplicates upon Au nanospheres incorporation as a result of the injection of hot electrons, excited by surface‐mediated intraband processes, to the bpy‐Cu states, thus increasing their CO2 reduction efficiency. Additionally, the catalytic activity remains stable during four consecutive cycles. [ABSTRACT FROM AUTHOR]

In this paper, we study a three-dimensional full hydrodynamic model in a bounded domain with insulating and adiabatic boundary. The model takes the form of nonisentropic Euler-Poisson system and incorporates recombination/generation terms, describing the bipolar transport of hot carriers in semiconductor optoelectronic devices. Of particular concern are the existence, uniqueness and exponential stability of thermal equilibrium states to the model, since these mathematical results are rendered useful in numerical simulation and physical theory of semiconductors. They are rigorously proved by the perturbation argument and energy method. [ABSTRACT FROM AUTHOR]

Defect tolerance is a critical enabling factor for efficient lead-halide perovskite materials, but the current understanding is primarily on band-edge (cold) carriers, with significant debate over whether hot carriers can also exhibit defect tolerance. Here, this important gap in the field is addressed by investigating how intentionally-introduced traps affect hot carrier relaxation in CsPbX3 nanocrystals (X = Br, I, or mixture). Using femtosecond interband and intraband spectroscopy, along with energy-dependent photoluminescence measurements and kinetic modelling, it is found that hot carriers are not universally defect tolerant in CsPbX3, but are strongly correlated to the defect tolerance of cold carriers, requiring shallow traps to be present (as in CsPbI3). It is found that hot carriers are directly captured by traps, instead of going through an intermediate cold carrier, and deeper traps cause faster hot carrier cooling, reducing the effects of the hot phonon bottleneck and Auger reheating. This work provides important insights into how defects influence hot carriers, which will be important for designing materials for hot carrier solar cells, multiexciton generation, and optical gain media. The efficiency of lead-halide perovskite photovoltaics is related to the tolerance of their band-edge charge-carriers to point defects. Here, the authors show that this tolerance can be extended to hot carriers depending on the defect energy level. [ABSTRACT FROM AUTHOR]

Quasi‐2D lead‐halide perovskites consist of conducting inorganic layers with tunable thickness (n) separated by large organic spacer cations. Typically, domains with different n and bandgaps are formed within a single film. Here, the crystallization of the films is tuned by mixing Dion‐Jacobson (DJ) with Ruddlesden‐Popper (RP) spacer cations. Compared to the quasi‐2D perovskite film based on solely the DJ type spacer 1,4‐phenylenedimethylammonium (PDMA), a film with less defects and more vertically aligned crystallization is achieved by addition of the RP type spacer propylammonium (PA). As the film structure plays an important role in the photophysics, time‐resolved photoluminescence (TRPL) and femtosecond transient absorption (TA) are used to investigate the impact of mixing these spacer cations on the dynamics of hot carrier cooling, the occurrence and directionality of energy or electron transfer between the different domains, and the exciton and charge carrier dynamics. Exciton transfer from low‐n to high‐n domains occurs at a favorable faster rate for the PDMA‐based film (0.0640 ps−1) compared to the PA‐based film (0.0365 ps−1), while the mixed spacer film demonstrates intermediate behavior (0.0473 ps−1). This study facilitates the design of advanced materials with optimized photophysical characteristics for a next generation of optoelectronic devices. [ABSTRACT FROM AUTHOR]

The possibility of coherent manipulation of optical and thermal energies in noble metal nanostructures has given birth to an enduring research arena coined by thermoplasmonics. Upon interaction with electromagnetic radiation, the energy of the produced hot electrons in metallic nanostructures is converted into heat and is transferred to the medium as a consequence of numerous relaxation processes. Gold nanorods have, often, been adopted as the classical anisotropic nanostructures owing to excellent shape-selective plasmonic tunability in the vis–NIR region. When a pair of metallic nanostructures are sufficiently close to each other to imbue electromagnetic interaction, there occurs evolution of collective plasmon modes, substantial enhancement of near field and strong squeezing of electromagnetic energy at the interparticle spatial region of the dimeric nanostructures. Recent advances in the 'tips and tricks' guide to assembling, even, anisotropic nanostructures in colloidal dispersions have offered the opportunity to interplay with the phenomenological plasmonic and thermal characteristics. The photothermal attributes emerging due to electromagnetic coupling of fringing fields have been explored considering parallel and perpendicular configurations of gold nanorod dimers as the prototypical systems from theoretical and experimental perspectives and their biomedical consequences have been realised in a mice model towards the photothermal apoptosis of cancerous cells. [ABSTRACT FROM AUTHOR]

One of the most promising approaches to addressing the current global energy and environmental crisis is the development and utilization of hydrogen energy. Photoelectrochemical (PEC) water splitting represents a clean and sustainable method for converting solar energy into hydrogen. In this article, we employed a hydrothermal-photodeposition method to fabricate Au@Pt decorated polyaniline (PANI)/TiO 2 (TNAP), which realized the synergy of p-n heterojunction and surface plasmon resonance (SPR). Experimental results revealed that p-n heterojunction can be formed between PANI and TiO 2 , whereas PANI can utilize visible light and the strong interaction between Au and PANI can realize the rapid transfer of hot electrons. Meanwhile, the outer layer Pt nanoparticles can accelerate water oxidation reaction kinetics. Therefore, the as-prepared TNAP exhibited the synergy promotion of p-n heterojunction and SPR effect, which is benefit for promoted light utilization and efficient charge transfer and separation. The optimized TNAP structure achieved hydrogen evolution rate of 19.26 μmol/cm2·h and photocurrent density of 1.20 mA/cm2 at a bias of 1.23 V vs. RHE, which is significantly higher than that of single semiconductor. This article suggests that the synergy promotion of SPR effect and p-n heterojunction is an efficient strategy to promote the efficiency of PEC water splitting. [Display omitted] • PANI/TiO 2 p-n heterojunction realizes the spatial separation of charge carriers. • Au NPs induced strong SPR effect and improve light utilization efficiency. • Strong interaction between PANI and Au promotes the transfer of hot electrons. • Surface Pt act as active sites and accelerate water oxidation reaction. • TNAP exhibited the synergy promotion of p-n heterojunction and SPR effect. [ABSTRACT FROM AUTHOR]

Direct bandgap group IV semiconductors, like strained Ge, GeSn, or hexagonal SiGe, are considered promising for photonic integration on silicon. For group IV semiconductor lasers, it is crucial to understand the carrier cooling efficiency toward the band edges. From a fundamental perspective, a study of carrier cooling within the Γ-valley of direct bandgap group IV semiconductors is particularly interesting since the Fröhlich interaction is expected to be very weak or even absent in these materials due to the nonpolar lattice. Intravalley carrier relaxation within the Γ-valley of a nonpolar semiconductor has not been experimentally accessible before since it has always been overshadowed by intervalley processes between energetically close indirect conduction band minima. Here, we study carrier cooling in direct bandgap hexagonal silicon-germanium (hex-SiGe) nanowires, allowing us to study carrier cooling in an isolated Γ-valley that is sufficiently separated from the indirect minima. We obtain a hot carrier cooling time of 180 ps in the Γ-valley of hex-SiGe. Although the cooling is much slower than in bulk polar group III/V materials due to the absence of Fröhlich interaction, it is comparable to the cooling time in an InGaAs MQW laser structure. We conclude that carrier cooling does not inherently limit hex-SiGe to serve as a laser gain material. This result is an important insight into the field of group IV semiconductor lasers. [ABSTRACT FROM AUTHOR]

Nanoscale subsurface characterization technologies based on the scanning electron microscope platform offer incomparable advantages of nondestructiveness and penetration depths up to the micrometer scale. However, the electron beam can serve not just as a mechanical/electrical excitation source but also as an excellent nanoscale thermal excitation source, which can facilitate the development of nanoscale subsurface imaging methods based on the Seebeck effect in semiconducting materials. In this work, a subsurface nondestructive imaging technology, scanning thermoelectric capacitance microscopy (STeCM), was developed based on the interaction between a non-steady-state electron beam and semiconducting materials, exploiting the Seebeck effect. In STeCM, a square wave-modulated hot electron beam with huge kinetic energy excites a "thermal wave" in the subsurface local region of the semiconducting sample. The heated local region, acting as a thermoelectric capacitor, undergoes cyclic charging and discharging, leading to the generation of periodic current due to non-equilibrium carrier migration. The second-order harmonic component of this current is demodulated to visualize embedded local thermal/thermoelectric inhomogeneities. Amazingly, for STeCM sample, only a smooth or polished surface is required, eliminating the need for any microfabrication, which will effectively decrease the configuration difficulty in the experiment. STeCM offers an alternative subsurface nondestructive imaging technology for more efficient, simple, and robust characterization. [ABSTRACT FROM AUTHOR]