The utilization of solar integrated thermoelectric technology plays a crucial role in addressing the global energy crisis. Enhancing the performance of the integrated technology can be achieved by introducing a photothermal layer. This layer consists of a photothermal material that exhibits broad solar absorption, including the near-infrared (IR) region. Wide-bandgap 2D semiconductor materials were used as the photothermal material. The integration shows better performance than other conventional techniques. This work includes an evaluation using COMSOL, a computational technique. Simulation models were developed and used to predict performance under various solar irradiance conditions. Results were predicted for electrical parameters and found to be 6.2 V produced by an individual module, whereas when the photothermal layer is introduced between the integrated technology, the device can produce a voltage of approximately 9 V. These findings include the comparison study of different photothermal materials. Thus, the proposed work involves predicting and optimizing the behavior of the integrated device in various environmental conditions and provides a way to maximize its energy conversion efficiency.
Thermally activated delayed fluorescence (TADF) polymers have emerged as a promising class of emissive materials for solution-processed organic light-emitting diodes (SP-OLEDs) due to their ability to utilize both singlet and triplet excitons for efficient light generation. Recent advances in molecular design, including main-chain donor-acceptor architectures, pendant-type systems, through-space charge transfer structures, and copolymer strategies, have enabled significant improvements in their photophysical and electroluminescent properties. These polymers exhibit favourable characteristics such as high photoluminescence quantum yields, small singlet-triplet energy gaps, and efficient delayed fluorescence, leading to encouraging device performances. In addition, their polymeric nature provides important advantages, including reduced aggregation-caused quenching, excellent film-forming ability, and compatibility with low-cost solution-processing techniques. Despite these benefits, TADF polymers still face limitations compared to small-molecule emitters, particularly in achieving higher external quantum efficiencies and superior colour purity with narrow emission bandwidths. Therefore, continued research focused on molecular engineering, structural optimization, and device design is essential to further enhance their performance and fully exploit their potential for next-generation, high-efficiency SP-OLED applications.
Thin film thermoelectric materials have garnered significant attention due to their potential for efficient energy conversion in various applications, ranging from waste heat recovery to wearable electronics to space exploration. This review paper provides a comprehensive overview of recent advancements in thin film thermoelectric materials and devices. The first discusses the fundamental principles governing thermoelectricity and the parameters influencing the thermoelectric performance, such as the Seebeck coefficient, electrical conductivity, and thermal conductivity. Then, it elucidates the unique properties of thin films that make them promising candidates for thermoelectric applications. It then highlights recent developments in novel thermoelectric materials, including conventional inorganic materials such as bismuth telluride, as well as emerging materials like lanthanum (III) telluride. The synthesis methods, including physical vapor deposition, chemical vapor deposition, and solution-based techniques, are further discussed along with their impacts on the structural and electrical properties of thin film thermoelectric materials. The review also highlights recent progress in the fabrication of device and their performances. Finally, future research directions and emerging trends in thin film thermoelectric are outlined to inspire further advancements in this rapidly evolving field.
It is undeniable that novel 2D devices and heterostructures will have a lasting impact on the advancement of future technologies. However, the inherent instability of many exfoliated van der Waals (vdW) materials is a well-known hurdle yet to be overcome. Thus, the sustained interest in exfoliated vdW materials underscores the importance of understanding the mechanisms of sample degradation to establish proactive protective measures. Here, the impact of prolonged synchrotron-based X-ray beam exposure on exfoliated flakes of two contemporary vdW materials, NiPS3 and α - RuCl3 , is explored using resonant inelastic X-ray scattering (RIXS) and total fluorescence yield X-ray absorption spectroscopy (XAS). In NiPS3 , the resulting RIXS and XAS spectra show a suppression, then vanishing, of NiS 6 multiplet excitations coupled with an upward shift of the peak energy of the XAS as a function of X-ray dose. In α - RuCl3 , the signs of beam damage from the RIXS spectra are less evident. However, the post-experiment characterization of both materials using Raman spectroscopy exhibits signals of an amorphous and disordered system compared to pristine flakes; in addition, energy-dispersive X-ray spectroscopy of NiPS3 shows evidence of ligand vacancies. As synchrotron radiation is fast becoming a required probe to study 2D vdW materials, these findings lay the groundwork for the development of future protective measures for synchrotron-based prolonged X-ray beam exposure, as well as for X-ray free electron laser.
We present a contactless determination of the two-dimensional electron gas (2DEG) properties in AlScN/GaN and AlYN/GaN high electron mobility transistor (HEMT) structures using the terahertz optical Hall effect (OHE) over a temperature range of 20 K–360 K. The structures are grown on sapphire or 4H-SiC substrates by metalorganic chemical vapor deposition (MOCVD) and feature ∼10-nm thick barrier layers with Sc and Y contents ranging from 4.6% to 17.3% and 3.3% to 8.2%, respectively. The temperature dependencies of the 2DEG density and mobility parameters are analyzed and discussed in a comparative manner. Additionally, conclusions are drawn regarding the predominant scattering mechanisms at both low and room temperatures. Furthermore, the 2DEG effective mass parameter m* in AlScN/GaN and AlYN/GaN is determined for the first time. At low temperatures m* is found to be in the range 0.20−0.27m0, close to the value of 0.23m0 for bulk GaN. As temperature increases above 100 K, m* gradually rises reaching 0.33−0.39m0 at room temperature, consistent with findings for AlGaN/GaN HEMTs. The underlying causes of this temperature-dependent increase in effective mass are discussed, with a possible explanation linked to polaron effects and deviations from the classical Drude model.
Resonant inelastic x-ray scattering (RIXS) can probe electron-hole excitations in excitonic insulators (EIs) which are realized by Coulomb attractive interaction between electrons and holes in semimetals or narrow gap semiconductors. In the present article, we review the exotic electronic state of an EI candidate Ta2NiSe5 which is probed by Ni 2p-3d RIXS as well as Ni 2p x-ray photoemission/absorption spectroscopy. The RIXS results on the exotic electronic state under the electron-hole and electron-lattice correlations suggest requirement of a new theoretical scheme which can describe itinerant electron-hole excitations and the localized charge-transfer excitations as well as the electron-lattice interaction.
Charge order has been a central focus in the study of cuprate high-temperature superconductors due to its intriguing yet not fully understood connection to superconductivity. Recent advances in resonant inelastic x-ray scattering (RIXS) in the soft x-ray regime have enabled the first momentum-resolved studies of dynamic charge order correlations in the cuprates. This progress has opened a window for a more nuanced investigation into the mechanisms behind the formation of charge order (CO) correlations. This review provides an overview of RIXS-based measurements of dynamic CO correlations in various cuprate materials. It specifically focuses on electron-doped cuprates and Bi-based hole-doped cuprates, where the CO-related RIXS signals may reveal signatures of the effective Coulomb interactions. This aims to explore a connection between two central phenomena in the cuprates: strong Coulomb correlations and CO-forming tendencies. Finally, we discuss current open questions and potential directions for future RIXS studies as the technique continues to improve and mature, along with other probes of dynamic correlations that would provide a more comprehensive picture.
Resonant inelastic X-ray scattering (RIXS) has played a pivotal role in advancing our understanding of spin-orbit physics in 5d transition metal materials. The progress in RIXS techniques has closely paralleled improvements in energy resolution, which have enabled the study of very low-lying excitations and led to the discovery of numerous new phenomena with significant scientific and technological implications. The multi-bend achromat (MBA) lattice upgrade of third-generation synchrotron sources, such as the Advanced Photon Source (APS), heralds a transformative era by introducing enhancements in brilliance and emittance. These advancements provide an opportunity to push the boundaries of RIXS techniques, meeting the challenges at the research frontiers of material science. This article aims to highlight key instrumental and technical advancements that enable the achievement of meV resolution in RIXS and discuss the impact of such high-resolution RIXS on exploring spin-orbit physics in 5d transition metal materials.
Space-charge-limited current (SCLC) measurements are commonly employed to characterize charge-transport properties of semiconductors used in next-generation thin-film optoelectronics, such as organic π-conjugated small molecules and polymers, and metal-halide perovskites. Despite the wide-spread adoption of the method, there is no community-wide consensus around how SCLC measurements should be performed, nor how the data should be analyzed and reported. While it is common to report device characteristics by employing a simplistic analytical model for fitting a single J-V curve obtained from a solitary device at room temperature—sometimes in a very select voltage range—expectedly, such an approach will often not give an accurate picture of the underlying physics. On that account, we here aim to highlight the importance of reporting values extracted from not just a solitary single-carrier device measured at room temperature, but from devices with different thicknesses measured at varying device temperature. We also highlight how the choice of device thickness is especially critical in determining what device and material characteristics can be extracted from SCLC measurements, and how this choice can greatly affect the conclusions drawn about the probed semiconducting material. While other factors could affect the outcome of an SCLC measurement and the subsequent analysis, we hope that the topics covered in this article will result in overall improved charge-transport characterization of thin-film semiconductors and initiate a broader discussion into SCLC metrology at large.
Uniaxial stress has proven to be a powerful experimental tuning parameter for effectively controlling lattice, charge, orbital, and spin degrees of freedom in quantum materials. In addition, its ability to manipulate the symmetry of materials has garnered significant attention. Recent technical progress to combine uniaxial stress cells with quantum oscillation and angle-resolved photoemission techniques allowed to study the electronic structure as function of uniaxial stress. This review provides an overview on experimental advancements in methods and examines studies on diverse quantum materials, encompassing the semimetal WTe2, the unconventional superconductor Sr2RuO4, Fe-based superconductors, and topological materials.
EDITORIAL article Front. Electron. Mater, 17 April 2024Sec. Superconducting Materials Volume 4 - 2024 | https://doi.org/10.3389/femat.2024.1403513
Neuromorphic computing is a promising paradigm for developing energy-efficient and high-performance artificial intelligence systems. The unique properties of lithium niobate-based (LiNbO3)-based memristors, such as low power consumption, non-volatility, and high-speed switching, make them ideal candidates for synaptic emulation in neuromorphic systems. This study investigates the potential of LiNbO3-based memristors to revolutionize neuromorphic computing by exploring their synaptic behavior and optimizing device parameters, as well as harnessing the potential of LiNbO3-based memristors to create efficient and high-performance neuromorphic computing systems. By realizing efficient and high-speed neural networks, this literature review aims to pave the way for innovative artificial intelligence systems capable of addressing complex real-world challenges. The results obtained from this investigation will be crucial for future researchers and engineers working on designing and implementing LiNbO3-based neuromorphic computing architectures.
The performance of superconducting radio-frequency Nb cavities at high radio-frequency (rf) fields in the absence of field emission can be limited by either a sharp decrease of the quality factor Q0(Bp) above peak surface magnetic fields Bp ∼100 mT or by a quench. We have measured Q0(Bp) at 2 K of several 1.3 GHz single-cell Nb cavities with different grain sizes, and with different ambient magnetic fields and cooldown rates below the critical temperature. Temperature mapping and a novel magnetic field mapping systems were used to find the location of “hot-spots” and regions of trapped magnetic flux. The use of a variable input coupler allowed further exploring the dissipative state. The results showed a remarkable thermal stability in some cavities with up to 200 W of rf power dissipation at 2 K, whereas other cavities quenched at much lower rf power. We observed a narrow distributions of the onset fields of hot-spots which were not affected by thermal cycling or by conditions which favor the formation of Nb hydrides. Furthermore, a poor correlation was found between the location of hot-spots and trapped vortices. We suggest that the totality of our experimental data can be explained by a sharp increase of the residual surface resistance above 120–140 mT due to the field-induced breakdown of a proximity-coupled metallic suboxide layer at the surface.
Muon spins precess in transverse magnetic fields and emit a positron preferentially in the spin direction at the instant of decay, enabling muon spin rotation (μSR) as a precise probe of local magnetic fields in matter. μSR has been used to characterize superconducting radio-frequency (SRF) materials since 2010. At TRIUMF, a beam of 4.2 MeV μ+ is implanted at a material-dependent depth of approximately 150 μm. A dedicated spectrometer was developed to measure the field of first vortex penetration and pinning strength in SRF materials in parallel magnetic fields of up to 300 mT. A low-energy beam available at PSI implants μ+ at variable depth in the London layer allowing for direct measurements of the London penetration depth from which other material parameters relevant for SRF applications, such as the lower critical field and the superheating field, can be calculated. Beta-detected nuclear magnetic resonance (β-NMR) is a technique similar to low-energy μSR using beams of low-energy β radioactive ions. With a recent upgrade, it is capable of detecting the penetration of parallel magnetic vortices, depth resolved with nanometer resolution at applied fields of up to 200 mT. In this paper, we review the impact and capabilities of these techniques for SRF research.
We report radio-frequency measurements of quality factors and temperature mapping of a nitrogen doped Nb superconducting RF cavity. Cavity cutouts of hot and cold spots were studied with low temperature scanning tunneling microscopy and spectroscopy, X-ray photoelectron spectroscopy and secondary electron microscopy. Temperature mapping revealed a substantial reduction of the residual resistance upon cooling the cavity with a greater temperature gradient and hysteretic losses at the quench location, pointing to trapped vortices as the dominant source of residual surface resistance. Analysis of the tunneling spectra in the framework of a proximity effect theory shows that hot spots have a reduced pair potential and a wider distribution of the contact resistance between the Nb and the top Nb oxide. Alone, these degraded superconducting properties account for a much weaker excess dissipation as compared with the vortex contribution. Based on the correlation between the quasiparticle density of states and temperature mapping, we suggest that degraded superconducting properties may facilitate vortex nucleation or settling of trapped flux during cooling the cavity through the critical temperature.
Strange metal behavior appears across a variety of condensed matter settings and beyond, and achieving a universal understanding is an exciting prospect. The beyond-Landau quantum criticality of Kondo destruction has had considerable success in describing the behavior of strange metal heavy fermion compounds, and there is some evidence that the associated partial localization-delocalization nature can be generalized to diverse materials classes. Other potential overarching principles at play are also being explored. An intriguing proposal is that Planckian scattering, with a rate of k B T/ℏ, leads to the linear temperature dependence of the (dc) electrical resistivity, which is a hallmark of strange metal behavior. Here we extend a previously introduced analysis scheme based on the Drude description of the dc resistivity to optical conductivity data. When they are well described by a simple (ac) Drude model, the scattering rate can be directly extracted. This avoids the need to determine the ratio of charge carrier concentration to effective mass, which has complicated previous analyses based on the dc resistivity. However, we point out that strange metals typically exhibit strong deviations from Drude behavior, as exemplified by the “extreme” strange metal YbRh2Si2. This calls for alternative approaches, and we point to the power of strange metal dynamical (energy-over-temperature) scaling analyses for the inelastic part of the optical conductivity. If such scaling extends to the low-frequency limit, a strange metal relaxation rate can be estimated, and may ultimately be used to test whether strange metals relax in a Planckian manner.
EDITORIAL article Front. Electron. Mater, 09 January 2023Sec. Superconducting Materials Volume 2 - 2022 | https://doi.org/10.3389/femat.2022.1120381
With piezoelectric small-volume composites gaining importance in smart device applications and nanoindentation being recognized as a versatile method for assessing the properties of layer materials, the present study is focused on the indentation response of the small-volume piezoelectric structures multi-layered composites. In particular, the effects of the nature of the substrate and surrounding materials, on the indentation response of piezoelectric nanocomposites, such as nanoislands, nanowires, and multi-layered composites are investigated. By developing three-dimensional finite element modeling, the complex interaction between the fundamental elastic, piezoelectric and dielectric properties of the piezoelectric materials and the elastic, plastic and electrically conducting or insulating properties of the surrounding materials, on the indentation response of the layered composites is analyzed. It is found that: (i) a substrate material that is elastically stiffer enhances the mechanical indentation stiffness and the electric indentation stiffness while plastic deformation in the substrate causes a reduction in the mechanical and electrical indentation stiffness; (ii) the effective piezoelectric and mechanical indentation stiffnesses of piezoelectric multi-layered composites are bounded by the corresponding characteristics of the bulk material counterparts from which the individual layers are constructed; (iii) electrically conducting surrounding materials produce a softening effect while insulating materials enhance the electrical indentation stiffness resulting in more charges being accumulated during the indentation process.
In recent years, perovskite material-based photovoltaic devices have attracted great attention of researchers because of an expeditious improvement in their efficiency from 3.8% to over 25%. The electron transport layer (ETL), which functions for the extraction and transportation of photogenerated electrons from active perovskite material to the electrodes, is a vital part of these perovskite solar cells (PSCs). The optoelectronic properties of these electron transport layer materials also have an impact on the performance of these perovskite solar cells, and for commercialized flexible perovskite solar cells, low-temperature and solution-processable electron transport layers having high stability and suitable optoelectronic properties are needed. In this regard, the solution-processable films of different metal oxides have been largely investigated by many research groups. So, this review summarizes the optoelectronic properties of the different metal oxide-based electron transport layers and the development in the performance of the perovskite solar cells, which have solution-processable metal oxides as electron transport layers.
We report calculations of a DC superheating field Hsh in superconductors with nanostructured surfaces. Numerical simulations of the Ginzburg–Landau (GL) equations were performed for a superconductor with an inhomogeneous impurity concentration, a thin superconducting layer on top of another superconductor, and superconductor–insulator–superconductor (S-I-S) multilayers. The superheating field was calculated taking into account the instability of the Meissner state with a non-zero wavelength along the surface, which is essential for the realistic values of the GL parameter κ. Simulations were performed for the material parameters of Nb and Nb3Sn at different values of κ and the mean free paths. We show that the impurity concentration profile at the surface and thicknesses of S-I-S multilayers can be optimized to enhance Hsh above the bulk superheating fields of both Nb and Nb3Sn. For example, an S-I-S structure with a 90-nm-thick Nb3Sn layer on Nb can boost the superheating field up to ≈500 mT, while protecting the superconducting radio-frequency (SRF) cavity from dendritic thermomagnetic avalanches caused by local penetration of vortices.
