Search

This study introduces a strategic buffer layer approach to mitigate thermal‐induced pixel shrinkage in top‐emission organic light‐emitting diodes (TEOLEDs), enhancing both thermal stability and efficiency. A new cathode composed of binary alloy from silver (Ag) and copper (Cu) is developed for their moderately high binding energy, improving film uniformity and boosting optical and electrical performance. High surface energy metals, aluminum (Al) and Cu are employed as buffer layers to regulate the growth mechanism, resulting in an exceptionally smooth cathode film. The optimal device is designed by incorporating a bilayer electron injection layer consisting of lithium fluoride (LiF) and ytterbium (Yb) along with the buffer layer. The TEOLEDs achieved an impressive efficiency of 178 cd A−1 and luminance of 247,000 cd m−2 while demonstrating superior thermal stability, with the absence of cathode shrinkage after 240 h at 85 °C. This stability is attributed to the suppression of thermal diffusion and aggregation, facilitated by the high surface energy buffer layer and innovative cathode compositions employed. [ABSTRACT FROM AUTHOR]

Miniaturizing van der Waals (vdW) ferroelectric materials to atomic scales is essential for modern devices like nonvolatile memory and sensors. To unlock their full potential, their growth mechanisms, interface effects, and stabilization are preferably investigated, particularly for ultrathin 2D nanosheets with single‐unit cell thickness. This study focuses on Bi2TeO5 (BTO) and utilizes precise control over growth kinetics at the nucleation temperature to create specific interfacial reconfiguration layers. Ultrathin BTO nanosheets with planar ferroelectricity at a single‐unit cell thickness are successfully grown. Atomic‐scale characterization reveals a disordered distribution of elements in the interfacial layer, which buffers strain from lattice mismatch. The theoretical calculations support these observations. Furthermore, this strategy also can be extended to the growth of a variety of 2D ternary oxide nanosheets. This work contributes to a better understanding of growth and stability mechanisms in 2D ultrathin nanosheets. [ABSTRACT FROM AUTHOR]

Interface strain significantly affects polarization in ferroelectric devices. In this paper, an innovative strategy is proposed to substantially enhance ferroelectric polarization using an ultra‐thin “soft‐buffer‐layer” (SBL), which reduces dislocation density and increases the tetragonality of ferroelectric thin films because of small elastic constants of Ti3Al along x and y axes. And in this work, it is demonstrated that PbZr0.4Ti0.6O3 (PZT) thin films are perfect c‐axis‐oriented epitaxial structures on (001) SrTiO3 (STO) substrates. The PZT capacitor with Ti3Al buffer layer exhibits a remarkable remnant polarization, reaching up to 131.93 µC cm−2 at an applied voltage of 5.00 V. Surprisingly, under the clamping effect of SrRuO3 and STO, Ti3Al films exhibit cubic structure and facilitate matching to the PZT film. It is proposed that the introduction of the Ti3Al buffer layer notably improves the tetragonality (c/a) ratio from 1.002 to 1.024, and significantly enhancing the polarization. There is no doubt that this adjustment reduces dislocation density and decreases stress influence from STO substrate. Given these advantages, the SBL method presents a compelling option for epitaxial PZT films, and also for enhancing the physical properties of other functional thin film materials. [ABSTRACT FROM AUTHOR]

Freestanding semiconductor membranes hold significant potential for heterogeneous integration technology and flexible electronics. Remote epitaxy, which leverages electrostatic interactions between epilayers and substrates through two-dimensional (2D) materials such as graphene, offers a promising solution for fabricating freestanding single-crystal membranes. Although the thinness, uniformity, and cleanness of 2D materials need to be meticulously controlled to enable the remote epitaxy of high-quality thin films, attaining such ideal growth templates has been challenging thus far. In this study, we demonstrate a controlled graphitization method to form a pristine graphene buffer layer (GBL) directly on SiC substrates and utilize this GBL template for GaN remote epitaxy. The quasi-two-dimensional GBL layer obtained by the method is completely free of damage or contamination, facilitating strong epitaxial interaction between the GaN epilayer and the SiC substrate. Furthermore, we reveal that a two-step growth of GaN on this GBL template enables the formation of single-crystal GaN epilayers and their exfoliation. Thus, this study represents an important step toward developing high-quality, freestanding semiconductor membranes. [ABSTRACT FROM AUTHOR]

Utilizing rare earth doped ceria in solid oxide cells (SOCs) engineering is indeed a strategy aimed at enhancing the electrochemical devices' durability and activity. Particularly, Gd‐doped ceria (GDC) is actively used for barrier layer and catalytic additives in solid oxide fuel cells (SOFCs). In this study, experiments are conducted with La‐doped CeO2 (LDC), in which the Ce sites are predominantly occupied by La, to prevent the formation of the Ce‐Zr solid solution. This LDC is comparably used as a functional interlayer between the electrolyte and cathode if sintered at lower temperatures to avoid La2Zr2O7 impurity. In addition, the high substitution of La3+ into the ceria lattice improves the oxygen non‐stoichiometry of LDC, leading to accelerated electrochemical high performance by the additional role of LDC for oxygen supplier capacitance at high current operation. Thus, it is confirmed that the improved SOFC high performance is achieved at the maximum power density (MPD) of ≈2.15 W cm−2 at 800 °C when the optimized LDC buffer layer is hired at the anode‐supported typed‐Samsung's SOFC by lowering the sintering temperature to prevent LDC's impurity reaction. [ABSTRACT FROM AUTHOR]

This study investigates the effect of using low-purity oxides in synthesizing lanthanum strontium titanate ferrite (LSTF) on its electrochemical performance as a solid oxide fuel cell (SOFC) cathode material. Lanthanum oxide at 30% and 60% purity is extracted from monazite, and iron oxide at 70% and 90% purity is extracted from ilmenite as the LSTF precursor. Symmetrical pellets are fabricated from yttria-stabilized zirconia (YSZ) as the electrolyte, samarium-doped ceria (SDC) as the buffer layer, and silver paste as the current-collecting layer (CCL). Results from electrochemical impedance spectroscopy (EIS) demonstrate that LSTF made from extracted lanthanum with low purity shows comparable electrical performance with a polarity resistance (Rp) of below 0.2 Ω at operational temperature of 800 °C compared to LSTF made from commercial ingredients, while LSTF made from extracted iron shows equal performance only with high-purity ingredients. LSTF made with extracted lanthanum and iron exhibits an Rp of 0.5 Ω and does not show comparable performance with LSTF made with commercial ingredients, likely due to a high variety of impurities. Based on this study, LSTFLa30 and LSTFFe90 show high potential for SOFC cathode applications at operating temperatures in the range of 700–800 °C. • Demonstrate examples of lanthanum and iron extraction at various purities. • Providing more data for LSTF as SOFC cathode materials. • Usage of low purity ingredients can cut down the cost of cathode materials. • Low purity lanthanum has potential as cathode materials ingredients. • Low purity iron can inhibit the performance of LSTF. [ABSTRACT FROM AUTHOR]

The interfacial incompatibility between lithium phosphorus oxynitride (LiPON) and anode greatly deteriorates the performance of thin‐film all‐solid‐state supercapacitors (ASSSCs). This article investigates oxygen plasma treatment to improve the interface. Through appropriate plasma treatment, a Li2O/Li3PO4 composite layer is formed by replacing nitrogen with oxygen at the LiPON surface owing to strong reactivity of oxygen plasma. This composite layer inherits the merits of both Li2O (including good mechanical strength and ultralow electrical conductivity) and Li3PO4 (including good chemical stability and relatively high ionic conductivity), and thus is quite desirable for service as a LiPON/anode buffer layer with excellent chemical and mechanical stability, high ionic conductivity and low electrical conductivity. Consequently, the corresponding plasma‐treated ASSSC displays much better electrochemical performance than the no‐treated one in terms of its higher specific capacitance (≈15.4 mF cm−2 at 0.5 µA cm−2), better cycling stability (≈95.1% of the retained capacity after 15 000 cycles) and lower self‐discharge rate (66.4% of the retained voltage after 20 h). The plasma‐treated one also shows both excellent flexible and electrochromic characteristics and demonstrates the ability of self‐adaptive temperature adjustment for smart window applications. [ABSTRACT FROM AUTHOR]

Future carbon management strategies require storage in elemental form, achievable through a sequence of CO2 hydrogenation reactions. Hydrogen is recycled from molecular intermediates by dehydrogenation, and side product acetylene selectively hydrogenated to ethylene. Existing Pd alloy catalysts for gas purification underperform in concentrated feeds, necessitating novel concepts. Atomistic simulations unveil superior selectivity of Pd:C solid solutions that optimize chemisorption energies and preclude sub-surface hydrides, verified here with model thin films. Multiple design criteria deduced from conventional catalysts facilitate synthesizing a self-repairing Pd:C system of a laterally condensed catalyst (LCC). A Pd layer prepared on a designated SiO2 buffer layer enables control of reactive interface, sub-surface volume and extended functional interface towards the buffer. Function and metric are supervised by operando micro-spectroscopy. This catalyst design shows, ethylene productivity >1 kmolC2H4/gPd/hour is reproducibly achieved and benchmarked against known catalysts. Photovoltaics deposition technologies enable scalability on real-world substrates saving active metal. A design-of-experiment approach demonstrates the improvement potential of the LCC approach. The selective hydrogenation of trace acetylene to ethylene is a well-established process for purifying fossil-derived ethylene streams. Here, the authors present a self-repairing Pd-C laterally condensed catalyst that improves selectivity, prevents sub-surface hydride formation, and achieves high ethylene productivity, effectively bridging the gap between powder catalysts and single-crystal model catalysts. [ABSTRACT FROM AUTHOR]

ABSTRACT The mechanism of the In‐catalyzed reaction of GaAs with In metal to form InxGa1−xAs was explained by comparing the interfacial reactions of metallic In and GaAs at high and low temperatures. Specifically, GaAs dissolved in In metal at the defects under the catalysis of In, and then In diffused into the GaAs crystals to replace Ga in the lattices. Based on this mechanism, a new method was developed for preparing an InxGa1−xAs buffer layer on GaAs by combining the ion‐sputtering method and annealing. The buffer layer and its effect on the quality of the epitaxial layer grown on GaAs were verified and analyzed by transmission electron microscopy, X‐ray diffraction, Hall effect measurements, and Raman scattering. The buffer layer was found to adopt the original dislocations on the GaAs surface, which prevented substrate dislocations from entering the epitaxial layer and reduced the dislocations generated due to the mismatch between the substrate and buffer layer. When the composition of the epitaxial layer is similar to that of the buffer layer, the quality of the epitaxial layer is significantly improved. [ABSTRACT FROM AUTHOR]

The MBE-method with plasma activation of nitrogen is used to obtain III-nitride HEMT heterostructures containing an ultrathin AlN barrier. The influence of the nucleation and buffer layer growth modes on the crystalline quality, surface morphology, and electrophysical properties of experimental HS samples is studied. The sheet resistance of the optimized HS is less than 230 Ω/□. Test microwave transistors with Schottky gate are manufactured. The parametric model of the HEMT based on an AlN/GaN HS is proposed. [ABSTRACT FROM AUTHOR]

Understanding the nature of grain boundaries is a prerequisite for fabricating high-performance superconducting bulks and wires. For iron-based superconductors [e.g. Ba(Fe,Co)2As2, Fe(Se,Te), and NdFeAs(O,F)], the dependence of the critical current density ${J_{\rm{c}}}$ J c on misorientation angle (${\theta _{{\rm{GB}}}}$ θ GB ) has been explored on [001]-tilt grain boundaries, but no data for other types of orientations have been reported. Here, we report on the structural and transport properties of Fe(Se,Te) grown on CeO2-buffered symmetric [010]-tilt roof-type SrTiO3 bicrystal substrates by pulsed laser deposition. X-ray diffraction and transmission electron microscopy revealed that ${\theta _{{\rm{GB}}}}$ θ GB of Fe(Se,Te) was smaller whereas ${\theta _{{\rm{GB}}}}$ θ GB of CeO2 was larger than that of the substrate. The difference in ${\theta _{{\rm{GB}}}}$ θ GB between the CeO2 buffer layer and the substrate is getting larger with increasing ${\theta _{{\rm{GB}}}}$ θ GB . For ${\theta _{{\rm{GB}}}} \ge {24^ \circ }$ θ GB ≥ 24 ∘ of the substrates, ${\theta _{{\rm{GB}}}}$ θ GB of Fe(Se,Te) was zero, whereas ${\theta _{{\rm{GB}}}}$ θ GB of CeO2 was continuously increasing. The inclined growth of CeO2 can be explained by the geometrical coherency model. The $c$ c -axis growth of Fe(Se,Te) for ${\theta _{{\rm{GB}}}} \ge {24^ \circ }$ θ GB ≥ 24 ∘ of the substrates is due to the domain matching epitaxy on (221) planes of CeO2. Electrical transport measurements confirmed no reduction of inter-grain ${J_{\rm{c}}}$ J c for ${\theta _{{\rm{GB}}}} \le {9^ \circ }$ θ GB ≤ 9 ∘ , indicative of strong coupling between the grains. IMPACT STATEMENT: The issue of weak-links inherent in iron-based superconductors, Fe(Se,Te), can be avoided by employing CeO2-buffer layer containing the Σ9[110]/{221} grain boundary. [ABSTRACT FROM AUTHOR]

Photovoltaic-thermoelectric (PV-TE) tandem system has been considered as an effective way to fully utilize the solar spectrum, and has been demonstrated in a perovskite solar cell (PSC)-thermoelectric (TE) configuration. However, the conventional PSC-TE tandem architecture cannot convert infrared light transmitted through the upper PSC into heat effectively, impeding the heat-electricity conversion of TE devices. Herein, a semi-transparent PSC-photothermal-TE tandem system is designed for improved photothermal utilization. Through optimizing the buffer layer of the back transparent electrode, semi-transparent PSC with a power conversion efficiency (PCE) of 13% and an average transmittance of 53% in the range of 800–1500 nm was obtained. On this basis, a photothermal thin film was introduced between the semi-transparent PSC and the TE device, which increased the efficiency contribution ratio of the TE device from 14% to 19%, showing enhanced utilization of AM 1.5 G solar spectrum and improved photo-thermal-electric conversion efficiency. IMPACT STATEMENT: We have constructed a semi-transparent perovskite solar cell-photothermal-thermoelectric tandem system through the optimization of transparent back electrode and the introduction of photothermal thin-film, realizing enhanced utilization of solar energy. [ABSTRACT FROM AUTHOR]

The novel, high electron mobility material ZnOxNy${\rm ZnO}_x{\rm N}_y$ has been investigated theoretically as an absorber in a two‐terminal tandem solar cell. In addition to its high mobility, ZnOxNy${\rm ZnO}_x{\rm N}_y$ can attain sufficiently low carrier concentration to enable pn$pn$‐junctions, and has a tunable bandgap around the 1.7 eV range. It is therefore suitable for pairing with a Si‐based bottom cell. In addition to the ZnOxNy${\rm ZnO}_x{\rm N}_y$ layer, the tandem cell consists of a Cu2O${\rm Cu}_2{\rm O}$ emitter and a Si heterojunction bottom cell. A buffer layer is introduced between the emitter and absorber in the top cell to mediate a large valence band offset that resulted in a poor fill factor, FF$FF$. A ZnOxNy${\rm ZnO}_x{\rm N}_y$ buffer layer bandgap of 1.5 eV gave the highest power conversion efficiency (PCE). The objective is to estimate the optimal performance of ZnOxNy${\rm ZnO}_x{\rm N}_y$ in a tandem solar cell. The dependence of current–voltage (J$J$–V$V$) characteristics on thickness, mobility and carrier concentration in the ZnOxNy${\rm ZnO}_x{\rm N}_y$ layer is evaluated, and found to yield maximum performance with 0.35 μm$\umu {\rm m}$, 250 cm2${\rm cm}^2$ Vs–1 and 1016$10^{16}$cm−3${\rm cm}^{-3}$, respectively. Using these conditions, the J$J$–V$V$ parameters of the device under AM1.5 illumination are short circuit current density, JSC=17.76$J_{SC}=17.76$ mA cm−2${\mathrm{cm}}^{-2}$, open circuit voltage, VOC=1.74$V_{OC}=1.74$ V, FF=83.8%$FF=83.8\%$ and PCE=25.9%${\rm PCE}\,=25.9\%$. With this, it is reported on, to the best of the knowledge, the first device simulation based on ZnOxNy${\rm ZnO}_x{\rm N}_y$. [ABSTRACT FROM AUTHOR]

Photovoltaic technology has gained wide acceptance because of its potential to mitigate climate change while offering pathways to reduce carbon footprint and inspiring renewable energy access and uptake. Herein, we investigate the performance of a solar cell configuration, FTO/TiO2/CH3NH3SnI3/CuI/Pd, by device simulation using solar cell capacitance device simulator (SCAPS-1D). The study analyses the impact of temperature, absorber layer thickness and buffer layers on the electrical and optoelectronic outcomes of the model cell. The simulation reveals optimal power conversion efficiency (PCE) of 23.98%, Voc of 0.8762, modest fill factor (FF) of 75.27% and remarkable photocurrent density (Jsc) of 34.33 mA/cm2. The selection of palladium as the preferred metal back contact is supported by its high work function, stability in ambient conditions, affordability compared to gold and low resistivity. CdS, distinguished by its remarkable PCE of 24.04%, emerges as the most promising buffer material for the model cell. Increased temperature from 260 to 500 K did not affect the electrical parameters significantly indicating that the model cell with CuI as the hole transport layer (HTL) has a robust temperature tolerance and hence stable in the design of perovskite cell modules based on CuI. The optimal density of defects for the material was generally found to be 1015 cm−3 whereas the optimal density for the acceptor was 1016 cm−3. These findings highlight the feasibility of the model cell design, characterized by use of eco-friendly materials, relatively affordable materials, low toxicity, and impressive PCE, thus inspiring potential fabrication and commercialization. [ABSTRACT FROM AUTHOR]

Organic and quantum dot (QD) light-emitting diodes (OLEDs and QLEDs, respectively) have been known for their practical application in full-color displays. Each primary color-emitting layer (EML) needs to be patterned via fine metal shadow masks (FMMs) or inkjet printing. However, the FMM method suffers from a shadow effect, misalignment, and size limitation, while inkjet printing hinders fine patterning, which disrupts high-resolution, large-scale fabrication. Here, we show a novel organic–QD hybrid device architecture by introducing a red QD common layer (QDCL). Since the QDCL is deposited onto all sub-pixels in a solution process without patterning, one patterning step for the red sub-pixel is reduced for full-color display fabrication. The green and blue OLEDs incorporating a red-emitting QDCL emitted their own color, owing to the effective exciton confinement within the EML by adopting a buffer layer, while the QDs in the QDCL emitted saturated red light. As a result, we could demonstrate a full-color organic–QD hybrid light-emitting device fabricated on a single substrate using the QDCL. We believe our strategy would help fabricate full-color and high-resolution displays with reduced manufacturing costs and time. [ABSTRACT FROM AUTHOR]

The chemical and electronic structure of the front contact i‐ZnO/InxSy:Na interface for Cu(In,Ga)(S,Se)2‐based thin‐film solar cells is investigated using a combination of x‐ray and electron spectroscopies. Upon i‐ZnO sputter deposition on the InxSy:Na buffer layer, we find an intermixed heterojunction and the formation of InOx and Na2SO4. The window layer is shown to consist of a mixture of Zn(OH)2 and ZnO, with decreasing relative Zn(OH)2 content for thicker window layers. Moreover, we observe diffusion of sodium to the surface of the window layer. We derive electronic surface band gaps of the i‐ZnO and InxSy:Na layers of 3.86 ± 0.18 eV and 2.60 ± 0.18 eV, respectively, and find a largely flat conduction band alignment at the i‐ZnO/InxSy:Na interface. [ABSTRACT FROM AUTHOR]

In organic light-emitting diodes (OLEDs), hole transport is typically about two orders of magnitude faster than electron transport. This leads to carrier complexation near the cathode and exciton bursting on the cathode metal surface, greatly reducing the luminescence efficiency of the device. To solve this problem, we constructed a composite buffer layer of poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonate) (PEDOT:PSS) synergized with silver nanoparticles (Ag NPs) and introduced it between the anode and the organic layer, which allows the holes to diffuse laterally under the influence of the concentration gradient, so that the luminescent region extended beyond the overlap of the cathode–anode. The lateral diffusion of holes can reduce the accumulation of holes in the device and improve the device stability. More importantly, adding the material C70 with a high highest occupied molecular orbital (HOMO) energy level to form a heterojunction in this buffer layer can further control the lateral diffusion distance and the longitudinal injection rate of holes; when the ratio of the two is 1:1, the carrier balance of the OLED is optimal, and the optical performance is excellent. This work provides a new strategy for OLED current balancing and opens up a new avenue for fabricating high-efficiency OLEDs. [ABSTRACT FROM AUTHOR]

The design of a Cd‐free and wider‐bandgap buffer layer is stringent for future Cu(In,Ga)Se2 (CIGSe) thin‐film solar cell applications. For that, an In2S3 buffer layer alloyed with a limited amount of O (well below 25 mol%) has been proposed as a pertinent alternative solution to CdS or Zn(O,S) buffers. However, the chemical stability of the In2S3/CIGSe heterointerface when O is added is not completely clear. Therefore, in this work, the buffer/absorber interface for a series of sputter‐deposited In2S3 buffers with and without O is investigated. It is found that the solar cell with the highest open‐circuit voltage is obtained for the O‐free In2S3 buffer sputtered at 220 °C. This improved open‐circuit voltage could be explained by the presence of a 20 nm‐thick ordered vacancy compound (OVC) at the absorber surface. A much thinner OVC layer (5 nm) or even the absence of this layer is found for the cell with In2(O0.25S0.75)3 buffer layer where O is inserted. The volume fraction of the OVC layer is directly linked with the magnitude of Cu diffusion from the CIGSe surface into the In2(OxS1−x)3 buffer layer. The O addition strongly reduces the Cu diffusion inside the buffer layer up to complete suppression for very high O contents in the buffer. Finally, it is discussed that the presence of the OVC layer may lower the valence band maximum, thereby forming a hole barrier, suppressing charge carrier recombination at the In2(OxS1−x)3/CIGSe interface, which could result in an increased open‐circuit voltage. [ABSTRACT FROM AUTHOR]

The effect of the MnxGey buffer layer on the morphology, transport and magnetic properties of Mn5Ge3 thin films grown on substrates Si(111) has been studied. Using X-ray diffraction analysis and atomic force microscopy, it has been found that changing the thickness and structure of the buffer layer with a gradient MnxGey composition has made it possible to control the crystalline quality and smoothness of epitaxial films. Changes in the microstructure and surface roughness has not affected the temperature of the phase transitions revealed from the temperature dependences of the resistivity and magnetization at 75 and 300 K. It has been shown that the features of the magnetization curve shape for films with different buffer layers have been closely related to the inhomogeneity of the films in thickness and surface roughness while maintaining the micromagnetic constants and orientation of the easy magnetization axis. The value of the change in the magnetic part of entropy ΔS has been calculated to be 2.1 J kg–1 K–1 at 1 T, which is comparable with the value for gadolinium and exceeds that for Mn5Ge3(001) films grown on GaAs substrates. [ABSTRACT FROM AUTHOR]

The velocity gradient tensor can be decomposed into normal straining, pure shearing and rigid rotation tensors, each with distinct symmetry and normality properties. We partition the strength of turbulent velocity gradients based on the relative contributions of these constituents in several canonical flows. These flows include forced isotropic turbulence, turbulent channels and turbulent boundary layers. For forced isotropic turbulence, the partitioning is in excellent agreement with previous results. For wall-bounded turbulence, the partitioning collapses onto the isotropic partitioning far from the wall, where the mean shearing is relatively weak. By contrast, the near-wall partitioning is dominated by shearing. Between these two regimes, the partitioning collapses well at sufficiently high friction Reynolds numbers and its variations in the buffer layer and the log-law region can be reasonably modelled as a function of the mean shearing strength. Altogether, our results highlight the expressivity and broad applicability of the velocity gradient partitioning as advantages for turbulence modelling. [ABSTRACT FROM AUTHOR]

This study investigates the band alignment of the Zn0.8Mg0.2O/Sb2Se3 interface structure to improve solar cell performance. Sb2Se3 is a promising absorber material. However, Sb2Se3 solar cells exhibit a lower conversion efficiency than CuInGaSe2 and CdTe solar cells. The lower efficiency of Sb2Se3 solar cells is attributed to the severe open‐circuit voltage loss caused by the band structure at the buffer/Sb2Se3 interface. Sb2Se3 solar cells typically employ CdS as the buffer layer, and the CdS/Sb2Se3 interface exhibits a cliff structure, which results in interfacial recombination. By contrast, a ZnMgO buffer layer can form a spike structure with Sb2Se3 at their interface, which reduces recombination and, as a result, enhances conversion efficiency. Therefore, this study employs the ZnMgO buffer layer and analyzes their material properties with various Mg contents and band structure at buffer/absorber layer interface. A ZnMgO buffer layer is sputter‐deposited on Sb2Se3. The optical bandgap of ZnMgO is 3.3–3.72 eV, corresponding to an Mg content of 0–0.35 at%. The carrier concentration indicates an appropriate doping level ranging from 1014 to 1016 cm−3. The Zn0.8Mg0.2O/Sb2Se3 interface is characterized via interface‐induced band bending. The Zn0.8Mg0.2O/Sb2Se3 interface exhibits a spike structure with a positive delta conduction band offset of +0.193 eV. [ABSTRACT FROM AUTHOR]

The performance of aqueous zinc‐ion batteries (AZIBs) at high temperatures (HT) is severely compromised by active water corrosion, parasitic reactions, and dendrite growth. Herein, zinc trifluoroacetate is introduced at a low concentration (0.2 m), dissolved in triethyl phosphate (TEP)and H2O. The active water is suppressed due to the reconstructed original hydrogen bond network, which helps inhibit parasitic reactions and severe corrosion. Meanwhile, a solid electrolyte interphase (SEI) formed on the zinc anode due to the decomposition of the introduced zinc salt. The high‐tolerance SEI physically separates the electrolyte and anode, reducing the corrosion caused by active water. Moreover, TEP, as a prevalent fire‐retardant cosolvent, can preferentially anchor on the zinc sheet, serving as a shielding buffer layer. TEP is not only reconstructing the structure of the electric double layer (EDL), decreasing the content of active water, but also accelerating the prompt formation of SEI further. As proof of this synergistic effect, the assembled symmetric Zn. [ABSTRACT FROM AUTHOR]

In this study, we developed a metal–semiconductor field-effect transistor (MESFET) using a Ge-doped α-Ga2O3 channel layer grown via mist chemical vapor deposition (CVD). As a buffer layer, Fe-doped α-Ga2O3 was deposited between the Ge-doped α-Ga2O3 channel layer and the m-plane sapphire substrate to reduce the influence of threading dislocations and suppress current leakage. Furthermore, an n+ contact layer heavily doped with Ge was deposited on the channel layer to reduce the contact resistance. The carrier concentration and Hall mobility of the channel layer were 2.1 × 1017 cm−3 and 44 cm2 V−1 s−1, respectively. The transfer length method indicates that the contact between the metal and the n+ layer exhibits Ohmic behavior with a resistance as low as 16 Ω mm. The MESFET exhibited a maximum current of 24 mA/mm and an on-resistance of 587 Ω mm at VGS = 2 V. The Ion/Ioff ratio exceeded 109. The breakdown voltage was 364 V, the leakage current between the drain and the source was below 10−5 mA/mm, and the power figure of merit was 1.2 MW/cm2. These results demonstrate that the mist CVD-derived Ge-doped α-Ga2O3 can give rise to a MESFET with good performance. [ABSTRACT FROM AUTHOR]

A new scintillation material composed of InAs quantum dots (QDs) hosted within a GaAs matrix was developed, and its performance with different types of radiation is evaluated. A methodology for designing an integrated photodetector (PD) with a low defect density and that is optically matched to the QD's emission spectrum is introduced, utilizing an engineered epitaxial InAlGaAs metamorphic buffer layer. The photoluminescence (PL) collection efficiency of the integrated PD is examined using two-dimensional scanning laser excitation. The detector response to 5.5 MeV α-particles and 122 keV photons is presented. Yields of 13 electrons/keV for α-particles and 30–60 electrons/keV for photons were observed. The energy resolution of 12% observed with α-particles was mainly limited by noise- and geometry-related optical losses. The radiation hardness of an InAs QDs hosted within GaAs and a wider band gap AlGaAs ternary alloy was studied under a 1 MeV proton implantation up to a 1014 cm−2 dose. The integrated PL responses were compared to evaluate PL quenching due to non-radiative defects. The QDs embedded in the AlGaAs demonstrated improved radiation hardness compared to QDs in the GaAs matrix and in the InGaAs quantum wells. [ABSTRACT FROM AUTHOR]

The merits of a low‐cost fabrication process, suitable band structure, excellent wettability to perovskite precursor, and outstanding stability ensure NiOx as a hole transport material with beneficial characteristics to construct high‐performance perovskite solar cells (PSCs). However, direct contact between perovskite and NiOx causes delamination and chemical instability and thus results in poor carrier transport and short device lifespan. Here, we propose a solution for this issue by introducing an organic salt additive 4‐(trifluoromethyl) benzylammonium formate (TFMBAFa) in the perovskite precursor to passivate perovskite film and NiOx@(2‐(3,6‐dimethyl‐9H‐carbazol‐9‐yl) ethyl) phosphonic acid (Me‐2PACz) composited hole transport layer (HTL), and thus construct a buffer layer between perovskite‐HTL interface. The effective diminishing of NiOx/perovskite interfacial reactions and defects results in enhanced carrier transport. Consequently, the target device achieves simultaneous improvements in power conversion efficiency (24.2%), storage stability (T100 > 1400 h), thermal stability (T80 > 1000 h), and operational stability (T70 > 850 h), where T100, T80, and T70 refer to the retention of 100%, 80%, and 70% of initial PCE, respectively. This work provides an effective strategy to advance the performance of NiOx‐based inverted PSCs. [ABSTRACT FROM AUTHOR]

Along with the growing popularity of the p‐i‐n structure, bathocuproine (BCP) is increasingly recognized as a crucial buffer layer between the electron transport layer and electrode with the role of mitigating Schottky contact and enhancing performance. However, the chemical structure and role of its functional groups have not been thoroughly elucidated. This study introduces a novel modification of BCP in perovskite solar cells (PSCs) by altering functional groups to optimize their geometrical molecular structures and electronic properties. The substitution of aromatic phenyl and p‐tolyl groups to 2,9‐position on the BCP is highly effective in increasing the planarity of the conjugated backbone and protecting the reactive nitrogen atoms of the phenanthroline core, thereby improving charge transport and device stability. Experimental analyses, including electrostatic force microscopy, impedance spectroscopy, and photoluminescence, reveal that the modified BCP significantly enhances charge transport, reduces recombination losses, and markedly improves the structural stability of PSCs, leading to prolonged device lifetimes. The findings highlight the potential of structurally optimized BCP derivatives as a critical component in advancing high‐efficiency and durable PSCs. [ABSTRACT FROM AUTHOR]

The goal of achieving batteries with high energy density and high safety profile has been a driving force in developing all‐solid‐state lithium metal batteries (ASSLMBs). However, the complex issues arising from the interfacial interaction between lithium anode/cathode and solid‐state electrolytes (SSE) have hindered the progress of ASSLMBs. This study presents a strategy for constructing an organic/inorganic buffer layer via employing Li‐ion exchanging chemistry of H1.6Mn1.6O4 (HMO) with a flexible matrix of polyethylene oxide (PEO). The buffer layer shows a remarkable ion conductivity of 3.21 × 10−4 S cm−1 at 25 °C originating from the exceptional Li+‐H+ ion exchange capability of HMO. This PEO/HMO buffer layer not only establishes an intimate physical contact between the Li anode/cathode and the SSE but also functions as a dynamic Li+ transfer station to facilitate Li+ movement through the interfaces improving interfacial stability. By pairing with cathodes of LiFePO4 (LFP) and LiNi0.8Co0.1Mn0.1O2 (NCM811), the ASSLMBs feature high‐rate capability and stable cycling performance with low polarization. This marks the utilization of HMO as a superior interfacial material to replace conventional lithium salts, with improved ion transport, decreased polarization, and enhanced overall performances. This constitutes a significant advancement toward the next‐generation energy storage solutions for ASSLMBs. [ABSTRACT FROM AUTHOR]

In GaN‐on‐Si nanowire integration schemes, where the nanowires are contacted through the substrate, the interfaces between silicon substrate, AlN buffer layer, and GaN nanowire are of high interest. Herein, analysis by scanning transmission electron microscopy (STEM) of GaN nanowires grown on Si(111) by metal–organic vapor phase epitaxy using a polarity‐ and site‐controlled growth method is presented. This method is based on prestructuring the substrate, ex situ oxidation of the surface, and in situ oxide layer desorption. First, an AlN layer is grown to prevent melt‐back etching. Samples are prepared for STEM by focused ion beam cutting. STEM measurements in three different regions reveal that the AlN buffer material is polycrystalline. The degree of polycrystallinity is found to depend on the observed region: the highest degree exists at the field area between nanowires and the lowest at the sidewall of the Si‐pillars. On the sidewall, the c→$$ \overrightarrow{c} $$‐direction of the AlN grain is tilted by 30.1° with regard to the Si{111} sidewall plane, leading to reduced lattice mismatch at this location. The growth of GaN is competing with diffusion of Ga atoms through grain boundaries. The dominant mechanism is dependent on the region, leading to site‐controlled growth of nanowires. [ABSTRACT FROM AUTHOR]

ABSTRACT Two‐dimensional grazing‐incidence wide‐angle X‐ray diffraction data were acquired from CeO2 thin films serving as buffer layers on r‐cut sapphire substrates to investigate the depth profiles of crystallinity and preferential orientation as well as surface conditions. The thin film samples were sputter‐deposited under different conditions. Data were obtained at an X‐ray wavelength of 0.100 nm at 0.02° intervals from 0.06° to 0.30° at the grazing‐incidence angle. A 60‐nm‐thick CeO2 thin film sputter‐deposited under Ar (Ar‐60) and a 100‐nm‐thick CeO2 thin film sputter deposited using 10 vol.% O2 in Ar (O+Ar‐100) were found to have partially oriented three‐dimensional bulk crystal structures with preferential orientation in the (100) direction near the surface. The lattice constant for the Ar‐60 film was found to be approximately 0.30% smaller than that for a CeO2 standard, whereas the lattice constant for the O+Ar‐100 film was approximately 0.50% larger. Lattice mismatch between the CeO and CeO2 on the substrate surface is evidently not an issue based on the lattice constants near the surface. Hence, both films could be considered to represent optimal buffer layers for YBa2Cu3O6+δ thin film growth. However, even in the case of a CeO2 thin film suitable for use as a buffer layer, the difference in lattice constants between the interior and surface of an Ar‐60 film was found to be relatively small, whereas that for an O+Ar‐100 film was relatively large. These results show that it is important to analyze the film surface in detail by reducing the incidence angle to less than 0.1°. [ABSTRACT FROM AUTHOR]

This paper presents a systematic investigation of the structural, elastic, electronic, and optical properties of two semiconductor materials: the tetragonal chalcopyrite, MgSnP2 and the cubic perovskite SrTiO3. These materials were chosen for their distinct characteristics, including optimal band gaps conducive to photovoltaic (PV) conversion and strong absorption, particularly within the visible solar spectrum. Structural optimization and property calculations were performed using the CASTEP (CAmbridge Serial Total Energy Package) code within Density Functional Theory (DFT), utilizing the Generalized Gradient Approximation (GGA) with the Perdew–Burke–Erzenhof (PBE) exchange-correlation function. The calculated lattice parameters align excellently with previously reported theoretical values. Analysis of the electronic band structure provides compelling evidence of semiconductor behavior in the compounds. Electronic properties reveal band gaps of Eg = 1.255 eV for MgSnP2 and Eg = 1.83 eV for SrTiO3, respectively, from G-G and R-G high symmetry points, enabling them to absorb a wide range of the solar spectrum. The obtained B/G ratio for MgSnP2 is 2.6, surpassing the critical value of 1.75 according to Pugh's criterion, indicating its ductile or malleable nature with significant deformation capacity before failure. Conversely, the B/G ratio for MgSnP2 is 1.49, below the threshold of 1.75, classifying it as a brittle material with limited plastic deformation and a tendency for sudden fracture. Finally, the calculated solar cell efficiency of MgSnP2 is found to be 25.5%, comparable to conventional silicon-based cells, while SrTiO3 exhibits an efficiency of 20.6%, making it a promising candidate for use as a transparent conductive oxide (TCO) or buffer layer in PV devices. These results highlight the potential of both materials in advancing next-generation PV technologies. [ABSTRACT FROM AUTHOR]

Fluorescence emission of a typical poly(9,9‐dialkylfluorene) derivative (PF Green B)‐based polymer light‐emitting diodes (PLEDs) clearly demonstrates that it partially involves the contribution of triplet excitons by the triplet–triplet fusion (TTF) process through measuring the magneto‐electroluminescence (MEL) responses of devices at different bias conditions and temperatures. The TTF process to fluorescence intrinsically correlates with the concentration, lifetime, and polaron quenching of triplet excitons, as modulated by different bias regimes and conditions. Varying the cathode configurations of PLEDs by an additional exciton blocking layer and cathode buffer layers in PLEDs, such as a thin layer of bathocuproine, tetractylammonium bromide, or poly(ethylene glycol) dimethyl ether with metal cathodes, changes the carrier dynamics and regulates the magnitude of TTF process to fluorescence. The performance of the devices has increased due to the enhanced TTF process in fluorescence, as characterized by the measurement of MEL responses. The results in this work unveil the “hidden” component of fluorescence emission, which originates from the fusion of triplet excitons to singlet excitons in typical PLEDs. The results elucidate that TTF of triplet excitons to fluorescence emission can be a practicable mechanism that contributes to enhancing the performance of devices. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to detect the bolt loosening under conditions of impact loading with a low-cost self-powered triboelectric nanogenerator sensor. Design/methodology/approach: In this work, an Al/PTFE-based triboelectric nanogenerator (AP-TENG) is used as a sensor. A pendulum impact device and a force hammer were used to apply the impact loads. The bolt status and the applied torque can be monitored under impact loading conditions by using the output voltage results of the AP-TENGs. Findings: The output voltage results of the current AP-TENG sensor under five different bolt torques, i.e. from 0.5 to 2.5 N m, were measured. The measurements revealed that a thicker buffer layer significantly contributed to the generation of higher voltages. Besides, the AP-TENG was also used to light ten commercial green LEDs in series, and the brightness of the LEDs was high enough even for the daytime, which showed that it can be used as the alarm device. In addition, a sudden loose test was also carried out, and the obvious voltage spikes can be seen without the external impact. The force hammer impact tests have expanded the application scope of the AP-TENG in the bolt loosening detection. Originality/value: The bolt loosening monitoring is important and useful for the safe operation. The application of TENG technology for detecting bolt loosening remains relatively unexplored. In addition, ten commercial green LEDs can be driven by the AP-TENG sensor, which can be used for the early warning of the bolted loosening status. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-06-2024-0216/ [ABSTRACT FROM AUTHOR]

AlGaN is attractive for fabricating deep ultraviolet (DUV) optoelectronic and electronic devices of light-emitting diodes (LEDs), photodetectors, high-electron-mobility field-effect transistors (HEMTs), etc. We investigated the quality and optical properties of AlxGa1−xN films with high Al fractions (60–87%) grown on sapphire substrates, including AlN nucleation and buffer layers, by metal–organic chemical vapor deposition (MOCVD). They were initially investigated by high-resolution X-ray diffraction (HR-XRD) and Raman scattering (RS). A set of formulas was deduced to precisely determine x(Al) from HR-XRD data. Screw dislocation densities in AlGaN and AlN layers were deduced. DUV (266 nm) excitation RS clearly exhibits AlGaN Raman features far superior to visible RS. The simulation on the AlGaN longitudinal optical (LO) phonon modes determined the carrier concentrations in the AlGaN layers. The spatial correlation model (SCM) analyses on E2(high) modes examined the AlGaN and AlN layer properties. These high-x(Al) AlxGa1−xN films possess large energy gaps Eg in the range of 5.0–5.6 eV and are excited by a DUV 213 nm (5.8 eV) laser for room temperature (RT) photoluminescence (PL) and temperature-dependent photoluminescence (TDPL) studies. The obtained RTPL bands were deconvoluted with two Gaussian bands, indicating cross-bandgap emission, phonon replicas, and variation with x(Al). TDPL spectra at 20–300 K of Al0.87Ga0.13N exhibit the T-dependences of the band-edge luminescence near 5.6 eV and the phonon replicas. According to the Arrhenius fitting diagram of the TDPL spectra, the activation energy (19.6 meV) associated with the luminescence process is acquired. In addition, the combined PL and time-resolved photoluminescence (TRPL) spectroscopic system with DUV 213 nm pulse excitation was applied to measure a typical AlGaN multiple-quantum well (MQW). The RT TRPL decay spectra were obtained at four wavelengths and fitted by two exponentials with fast and slow decay times of ~0.2 ns and 1–2 ns, respectively. Comprehensive studies on these Al-rich AlGaN epi-films and a typical AlGaN MQW are achieved with unique and significant results, which are useful to researchers in the field. [ABSTRACT FROM AUTHOR]

Tandem solar cells have the potential to be more efficient than the Shockley–Queisser limit imposed on single junction cells. In this study, optical and electrical modeling based on experimental data were used to investigate the possibility of boosting the performance of kesterite/c-Si tandem solar cells by inserting an alternative nontoxic TiO2 buffer layer into the kesterite top subcell. First, with SCAPS-1D simulation, we determined the data reported for the best kesterite (CZTS (Eg = 1.5 eV)) device in the experiments to be used as a simulation baseline. After obtaining metric parameters close to those reported, the influence on the optoelectronic characteristics of replacing CdS with a TiO2 buffer layer was studied and analyzed. Different top subcell absorbers (CZTS0.8Se0.2 (Eg = 1.4 eV), CZTS (Eg = 1.5 eV), CZTS (Eg = 1.6 eV), and CZT0.6Ge0.4S (Eg = 1.7 eV)) with different thicknesses were investigated under AM1.5 illumination. Then, to achieve current matching conditions, the c-Si bottom subcell, with an efficiency at the level of commercially available subcells (19%), was simulated using various top subcells transmitting light calculated using the transfer matrix method (TMM) for optical modeling. Adding TiO2 significantly enhanced the electrical and optical performance of the kesterite top subcell due to the decrease in parasitic light absorption and heterojunction interface recombination. The best tandem device with a TiO2 buffer layer for the top subcell with an optimum bandgap equal to 1.7 eV (CZT0.6Ge0.4S4) and a thickness of 0.8 µm achieved an efficiency of approximately 20%. These findings revealed that using a TiO2 buffer layer is a promising way to improve the performance of kesterite/Si tandem solar cells in the future. However, important optical and electrical breakthroughs are needed to make kesterite materials viable for tandem applications. [ABSTRACT FROM AUTHOR]

Heterostructures with InAs/InGaAs quantum dots grown by molecular beam epitaxy on the surface of InGaAs metamorphic buffer layers with a linearly graded composition profile on GaAs(001) substrates have been studied by X-ray diffraction, transmission electron microscopy, and, upon the growth of an additional quantum-dot layer on the surface of the structure, by atomic force microscopy. The tendency to the formation of quantum objects elongated along the [1–10] direction (so-called quantum dashes), caused by asymmetry in the surface migration of In along different crystallographic directions, is confirmed. It is established that the surface density of both quantum dots and quantum dashes is as high as (2‒4) × 1010 cm–2. At the same time, narrow lines associated with emission from individual quantum dots are observed in the spectra of low-temperature (T = 10 K) microphotoluminescence in a wide wavelength range (1.30–1.55 µm). The size and shape of quantum dots have been estimated from atomic-force microscopy and transmission electron microscopy data and good agreement with the previously reported parameters is demonstrated. [ABSTRACT FROM AUTHOR]

Herein, triangular‐lattice nanopillar templates are fabricated on sputter‐deposited AlN/Si (111) substrates. Nanotemplate selective‐area growth via radiofrequency‐plasma‐assisted molecular beam epitaxy is employed to grow GaN nanocolumns on the nanopillars. Well‐ordered uniform GaN nanocolumn arrays are obtained by inserting a migration‐enhanced‐epitaxy grown AlN/AlGaN buffer layer, thereby aligning the polarity of GaN to Ga‐polar. Subsequently, bulk InGaN active layers are grown on top of the GaN nanocolumns with increasing growth time (tg = 10–20 min). In the initial stage of growth (tg = 10 min), low‐In‐content InGaN grows on the edges of the six‐sided pyramidal top of the GaN nanocolumns. As the growth progresses, low‐In‐composition InGaN fills the sides between InGaN on the edges, while high‐In‐composition InGaN rapidly grows on the top of the c‐plane nanocolumns. High‐angle annular dark‐field scanning transmission electron microscopy reveals the formation of an InGaN core, covered with a low‐In‐composition InGaN shell, on the top of the nanocolumns. At tg = 20 min, the photoluminescence spectrum exhibits a peak at 669 nm with a full width at half maximum value of 51.7 nm. Thus, the proposed method is suitable for growing red‐light‐emitting well‐ordered InGaN/GaN nanocolumn arrays on Si. [ABSTRACT FROM AUTHOR]

Metal–organic vapor phase epitaxy of GaN on sapphire (0001) substrates without using low‐temperature (LT) buffer layers is demonstrated. The growth of GaN is achieved by pretreatment of sapphire with trimethylaluminum (TMA) at a high temperature (1050 °C) in a H2 + N2 gas mixture. The TMA pretreatment forms AlN, which acts as nucleation seeds for the subsequent growth of GaN at the same temperature. When AlN created by the TMA pretreatment is three‐dimensional, similar to conventional LT buffer layers, the GaN layers exhibit good structural properties such as atomically smooth surfaces and narrow X‐ray diffraction line widths, comparable to those of GaN on LT buffer layers. In addition, the growth evolution of GaN on TMA‐pretreated sapphire is similar to that on GaN or AlN LT buffer layers. These similarities between the TMA pretreatment and conventional LT buffer‐layer technologies might offer an opportunity to further generalize the heteroepitaxy growth model of GaN. [ABSTRACT FROM AUTHOR]

The strain relaxation, surface morphology, and reflectivity of AlGaN‐distributed Bragg reflectors (DBRs) grown via metal–organic chemical vapor deposition on AlN/Al2O3 templates are investigated. Strain relaxation begins in a 10‐period Al0.50Ga0.50N (27 nm)/Al0.75Ga0.25N (29 nm) DBR, and the degree of strain relaxation (DSR) increases with the number of DBR periods. The 30‐period DBR exhibits a peak reflectivity of 0.82 at 279 nm, with a stopband of 12 nm. The DSR of n‐Al0.62Ga0.38N on the 30‐period DBR increases from 70% to 100% as the n‐Al0.62Ga0.38N thickness increases from 0.4 to 2.5 μm. Although the surface of a DBR comprises numerous spiral hillocks, n‐Al0.62Ga0.38N grown on an AlGaN DBR exhibits a step‐flow growth. A DSR of 100% with threading screw dislocations of 2.0 × 108 cm−2 and threading edge dislocations of 1.2 × 109 cm−2 is obtained for a 2.5 μm‐thick n‐Al0.62Ga0.38N on a 30‐period AlGaN DBR. [ABSTRACT FROM AUTHOR]

The buffer leakage phenomena have a large effect on high‐power and fast‐switching GaN high electron mobility transistor devices. Herein, the buffer leakage mechanism in a GaN‐on‐Si substrate with AlGaN buffer layers is investigated by using samples with various carbon concentrations. Comparing the leakage current with crystallinity and impurity concentration, it is found that the vertical leakage current is dominated by both threading dislocations and bulk impurities. Increasing the carbon concentration of buffer layers suppresses leakage current in the bulk conducting regime in high electric fields but increases it in the dislocation conducting regime in low electric fields. These results indicate that the optimal carbon concentration of buffer layers depends on the target electric field. [ABSTRACT FROM AUTHOR]

AlGaN/GaN high electron mobility transistors (HEMTs) with different GaN channel layers grown on AlN buffer layer are fabricated and investigated in order to optimize the device performances and to study the noise properties. To investigate the strain effect of the GaN channel layer grown on the AlN buffer layer, the positive shift of Raman peak is observed as the GaN channel becomes thinner. The threshold voltages (Vth) of the fabricated devices shift to positive direction according to the decreased GaN channel layer due to the decreased 2‐dimensional electron gas (2DEG) and deteriorated crystal quality of GaN channel layer. All devices demonstrated 1/f noise properties and the dominance of the carrier number fluctuations (CNF) noise mechanism. The largest trap density (Nt) value in the narrowest GaN channel device is because of the degraded crystal quality and the enhanced strain effect of the GaN channel layer. However, the lowest noise levels at the drain current (Id) > 10−6 A for the device with the GaN channel thickness of 30 nm grown on AlN buffer layer are observed to be due to the fully depleted GaN channel layer although its poor crystal quality. [ABSTRACT FROM AUTHOR]

As‐grown GaN buffer layers have a significant electron concentration, which causes an increase in leakage current and a decrease in the breakdown voltage, VBR, of GaN High Electron Mobility Transistors (HEMTs). To prevent this, deep acceptor traps of density, NAT, are added to the GaN layer during growth. While a study on the effect of NAT on VBR is available in the literature, that on the effect of NAT on contact resistance, Rc, of source/drain contacts is lacking. Herein, the following is established using technology computer‐aided design simulations calibrated with measured current–voltage characteristics of ungated AlGaN/GaN structures: 1) Rc increases significantly with NAT and with the depth of the trap level from the conduction band. For trap level 2.5 eV below the conduction band, Rc doubles for an increase in NAT from 1 × 1016 to 5 × 1017 cm−3. 2) The variation of Rc with temperature is non‐monotonic. Over a temperature range of 300–450 K, Rc is nearly constant with temperature for NAT = 1 × 1016 cm−3 and decreases by 20% for NAT = 5 × 1017 cm−3, when traps are 2.5 eV below the conduction band. Also, the degradation of the transfer and output characteristics of GaN HEMTs due to a notable increase in Rc due to NAT is investigated. [ABSTRACT FROM AUTHOR]

N-polar GaN film was obtained by using a high-temperature AlN buffer layer. It was found that the polarity could be inverted by a thin low-temperature AlN interlayer with the same V/III ratio as that of the high-temperature AlN layer. Continuing to increase the V/III ratio of the low-temperature AlN interlayer, the Ga-polarity of GaN film was inverted to N-polarity again but the crystal quality and surface roughness of GaN film greatly deteriorated. Finally, we analyzed the chemical environment of the AlN layer by x-ray photoelectron spectroscopy (XPS), which provides a new direction for the control of GaN polarity. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The plasma immersion nitriding system was utilized to make massive nitrogen supersaturation (MNS) to CoCrMo disc and die substrates at 723 K for 21.6 ks. The top layer thickness in the multi-layered MNSed layer was 20 μm. Its nitrogen solute content reached 5 mass% on average after SEM-EDX analysis. The surface hardness was 1300 HV1N (HV0.1), which was much higher than the bare CoCrMo with 450 HV1N. The original polycrystalline structure was modified to be a multi-layered microstructure, which consisted of the nanograined MNSed top layer, the buffer layer with a thickness of 5 μm, and the column–granular structured layer with their textured crystallographic orientations. The BOD (ball-on-disc) testing was employed to describe the frictional sliding behavior under the applied loads of 5 N and 10 N and the sliding velocity of 0.1 m/s against the AISI316 ball. The friction coefficient was held constant by 0.68 on average. The CNC (Computer Numerical Control) stamping system was employed to upset the fine-grained 1.0 mm thick AISI316 wire up to 70% in reduction in thickness. The friction coefficient at RT was estimated to be 0.05. A round, fine-grained AISI316 wire was shaped into a thin plate with a thickness of 0.3 mm in cold and dry. [ABSTRACT FROM AUTHOR]

In recent years, ablation of the buffer layer in high-voltage cables has become a prevalent issue compromising the reliability of power transmission systems. Given the internal location of these faults, direct monitoring and assessment are challenging, resulting in numerous undetected ablation hazards. Previous practice has demonstrated that detecting buffer layer ablation through surface temperature distribution changes is feasible, offering a convenient, efficient, and non-destructive approach. However, the variability in heat generation and the subtle temperature differences in thermal infrared images, compounded by noise interference, can impair the accuracy and timeliness of fault detection. To overcome these challenges, this paper introduces an adaptive enhancement method for the thermal infrared imaging of high-voltage cable buffer layer ablation. The method involves an Average Gradient Weighted Guided Filtering (AGWGF) technique to decompose the image into background and detail layers, preventing noise amplification during enhancement. The background layer, containing the primary information, is enhanced using an improved Contrast Limited Adaptive Histogram Equalization (CLAHE) to accentuate temperature differences. The detail layer, rich in high-frequency content, undergoes improved Adaptive Bilateral Filtering (ABF) for noise reduction. The enhanced background and detail layers are then fused and stretched to produce the final enhanced thermal image. To vividly depict temperature variations in the buffer layer, pseudo-color processing is applied to generate color-infrared thermal images. The results indicate that the proposed method's enhanced images and pseudo-colored infrared thermal images provide a clearer and more intuitive representation of temperature differences compared to the original images, with an average increase of 2.17 in information entropy and 8.38 in average gradient. This enhancement facilitates the detection and assessment of buffer layer ablation faults, enabling the prompt identification of faults. [ABSTRACT FROM AUTHOR]

Aqueous Zn-based batteries (AZBs) are hindered by issues associated with the Zn electrodeposition process (ZEDP) on electrode surfaces, including passivation, dendrite formation, and hydrogen evolution. One of the important reasons is the drastic fluctuation in the concentration of Zn2+ ions on the electrode surface during the charging and discharging process. In this work, an electrolyte with Zn2+ ion buffer layer (EZIBL) is proposed to regulate the ZEDP. First, numerical simulations and corresponding experiments are conducted to assess the impact of different thicknesses of the Zn2+ ion buffer layer (ZIBL) on the variation in Zn2+ ion concentration, from which the optimal thickness of the ZIBL is determined. Then, the regulation role of EZIBL in the cycling process is demonstrated by a Zn-Cu half cell. Further, combined with the potential profile of the symmetric cell and the experimental phenomena, the regulation role of EZIBL in ZEDP is systematically explained at the mechanistic level through the analysis of key parameters. Finally, a full battery composed of Zn-LiMn2O4 is assembled to evaluate the practical applicability of the EZIBL in real battery cycles, which shows great enhancement in capacity retention and coulombic efficiency. This work proposes the design of the EZIBL used to regulate the ZEDP and provides a simple, low-cost regulation method for the development of high-performance AZBs. [ABSTRACT FROM AUTHOR]

Hysteresis window observed in ferroelectric negative capacitance field-effect transistors (NCFETs) have been a persistent challenge in the development of reliable logic circuits, often leading to abnormal operational conditions. Despite its significance, the underlying factors driving this hysteresis phenomenon remain elusive. In this study, we employ the quasi-static L–K equation in conjunction with the Mott–Gurney law to study the impact of VO++ migration on the hysteresis behavior of NCFETs, based on a surface potential-based physical model. Compared with pristine NCFET, the difference of peak voltages in value of 1.3 V was achieved in VO++-involved sample upon reverse and forwards scanning. This result clearly suggests that the relaxation of charged oxygen vacancies significantly affects the threshold voltage under applied sweeping voltages, providing a plausible explanation for the emergence of hysteresis windows in NCFETs. A replacement of the conventional oxide layer with a buffer layer containing high-mobility ions is proposed to adjust the hysteresis window. Importantly, in accordance with the theoretical predictions, the increased ion mobility results in a substantial reduction in the hysteresis window observed in NCFETs. Our proposed physical mechanism, elucidating the space-charge-induced hysteresis behavior, provides fresh insights for mitigating hysteresis effects, thereby advancing the potential applications of NCFETs in logic circuits. [ABSTRACT FROM AUTHOR]

All‐solid‐state batteries (ASSBs), configured with solid electrolytes, have received considerable attention as a future energy solution across diverse sectors of modern society. Unlike conventional liquid electrolytes in particular, sulfide solid electrolytes have various advantages, such as high ionic conductivity (>10−3 S cm−1), good ductile properties, and thermal stability. Despite these advantages, the practical application of sulfide solid electrolytes in ASSBs is still limited due to their interfacial instability with commercial cathode materials. Unfortunately, the spontaneous formation of a space charge layer (SCL) at the interface between the cathode material and the solid electrolyte leads to heightened interfacial resistance, obstructing Li+ transport. To address this issue, proper interfacial engineering is still required to facilitate smooth Li+ migration across the interfaces. In this respect, various functional materials have been under exploration as buffer layers, which are intended to suppress the formation of the SCL at these interfaces. Herein, focus is given on the critical significance of these buffer layers between cathode materials and sulfide solid electrolytes in the development of ASSBs. Considering the present limitations, future research directions for next‐generation ASSBs are discussed. These insights are poised to offer valuable guidance for the strategic design and development of highly reliable ASSBs. [ABSTRACT FROM AUTHOR]

Nickel‐doped cobalt bi‐metal nanoparticles (Ni/Co BMNPs) are employed in the transport buffer layer of thin‐film polymer solar cell to assist in the collection of photons generated current. P3HT:PCBM blend‐based polymer solar cells are successfully fabricated with modified hole transport layer (HTL)‐containing BMNPs at different concentrations. The performance of the devices has generally improved compared to the reference cell by the presence of BMNPs in the transport buffer layer, and shows sign of dependence on concentration level. Significant improvements in device performance are recorded at optimum level of 0.05% BMNPs by weight, which resulted in a high current density of 15.31 mA cm−2, and recorded 5.05% power conversion efficiency (PCE). This is 67.8% growth in PCE is compared to the reference cell. Moreover, another investigation is conducted using device simulation program to check the reproducibility of the experiments. The device that is made to mimic the best performance at 0.05% BNMP concentration produced an efficiency of 5.76%. Such reproducibility of data is an important development toward better understanding of the charge transport process in polymer solar cell. This study further provides new evidences about factors that influence device performance due to the inclusion of the BMNPs. [ABSTRACT FROM AUTHOR]

The photomultiplication type organic photodetectors (PM‐OPDs) are prepared with structure of ITO/PNDIT‐F3N/F8BT/Y6‐1O:P3HT (100:3, wt/wt)/Al, containing hole traps formed with P3HT surrounded by Y6‐1O in active layers. The PM‐OPDs exhibit external quantum efficiency (EQE)>100% in the spectral response range from 310 to 910 nm, resulting from electron tunneling injection assisted by trapped hole near ITO electrode. The incorporation of F8BT buffer layers can induce the markedly decreased dark current density (JD) due to the large electron injection barrier. The light current density (JL) of PM‐OPDs exhibits slightly decreased by inserting F8BT buffer layers due to the enhanced electron tunneling injection assisted by the more trapped holes near ITO electrode. The signal‐to‐noise ratio (SNR) of PM‐OPDs achieves over 40‐fold increment by inserting appropriate thickness of F8BT buffer layers, resulting from the markedly decreased JD and reasonably high JL. The optimal PM‐OPDs exhibit excellent photodetection capability with EQE of 4200% at 360 nm and 6600% at 850 nm, associated with the specific detectivity of 3.9 × 1011 Jones at 360 nm and 9.7 × 1011 Jones at 850 nm. [ABSTRACT FROM AUTHOR]