Excellent Transport Properties Research Articles

Chalcogenide perovskites: enticing prospects across a wide range of compositions and optoelectronic properties for stable photodetector devices

Abstract Photodetectors are indispensable components of many modern light sensing and imaging devices, converting photon energy into processable electrical signal through absorption, carrier generation and extraction using semiconducting thin films with appropriate optoelectronic properties. Recently, metal halide perovskites have demonstrated groundbreaking photodetector performance due to their exceptional properties originating from their perovskite structure. However, toxicity and stability remain challenges for their large-scale applications. Inspired by the perovskite structure, intense investigation in search of highly stable, non-toxic and earth abundant materials with superior optoelectronic features has led to the discovery of chalcogenide perovskites (CPs). These are unconventional semiconductors with the formula ABX3, where A and B are cations and X is a chalcogen, which covers the compounds with the corner sharing perovskite structures of type II-IV- VI3 compounds (II = Ba, Sr, Ca, Eu; IV = Zr, Hf; VI = S, Se) and III1-III2-VI3 compounds (III1 and III2 = Lanthanides, Y, Sc; VI = S, Se). The increased coordination and ionicity in these compounds contribute to their excellent charge transport properties and exceptionally high optical absorption coefficient (> 105 cm−1). The present review encompasses theoretical analysis that provides electronic band structures and the orbital contributions that support the excellent optoelectronic properties. Furthermore, the challenging thin film deposition, characterizations, and their application in photodetection focusing on BaZrS3-which is the most studied one, are ascribed. Additionally, we suggest prospects that can bring out the true potential of these materials in photodetection and photovoltaics.

Phenanthrene Treatment for O‐xylene‐Processed PM6:Y6‐Based Organic Solar Cells Enables Over 19% Efficiency

AbstractAchieving excellent charge transport properties in high‐performance organic solar cells (OSCs) generally requires photovoltaic materials to have strong crystallinity. Meanwhile, non‐halogenated solvent processing is very important for future application of the OSCs. However, highly crystalline materials will pose challenges for the control of molecular aggregation behavior in donor/acceptor blend films processed with high boiling point non‐halogenated solvents. Herein, a new approach to effectively regulate the aggregation of represented strong crystallinity material Y6 in high boiling point processing solvents is developed by employing phenanthrene (PAT) with unique crystallinity and relatively loose molecular stacking as volatile solid additive. It is elucidated that PAT treatment shows a significant effect in inhibiting the excessive self‐aggregation of Y6 in high boiling point solvent during the film formation process and reducing the crystallization rate of Y6 molecules under thermal annealing, resulting in highly ordered molecular packing and favorable phase‐separated morphology. As a result, the PM6:Y6‐based device processed with chlorobenzene, toluene, and o‐xylene achieve excellent power conversion efficiencies (PCEs) of 17.71%, 17.99%, and 19.04%, respectively. The efficiency of 19.04% represents the highest value so far for the PM6:Y6‐based binary OSCs processed with high boiling point non‐halogenated solvents.

Antibacterial cellulose-based membrane with heat dissipation and liquid transportation for food packaging applications

Food spoilage, caused by fungi and bacteria, has drawn increasing attention due to the lack of suitable temperature and humidity control, resulting in food waste and health risks. It is still a great challenge to develop green packaging materials with excellent antibacterial activities and effective temperature/humidity control for food preservation. Herein, a new strategy is proposed to obtain food packaging material with antibacterial ability, heat dissipation, and liquid transportation functions. In this strategy, Zn-Al layered double hydroxide (LDH)@cellulose was obtained by extracting cellulose from sugarcane husks, followed by in-situ growth of LDH nanosheets on the surface of cellulose. Then, asymmetric structured packaging material, namely cellulose acetate/LDH@cellulose (CALC) membrane, was prepared by the combination of electrospinning and hydrophobic modification. The characterization results confirmed that the CALC membrane exhibits asymmetric surface structure and wettability properties, endowing heat dissipation and liquid transportation for food packaging applications. Due to the asymmetric reflectivity and infrared emissivity, the CALC membrane exhibited excellent heat dissipation properties with a surface temperature of 10.3℃, which is lower than that of commercial food packaging material. Furthermore, the excellent liquid transport properties of the CALC membrane are demonstrated by the fact that water can penetrate from the hydrophobic side to the hydrophilic side within 32s, providing the appropriate storage temperature and dry environment for foods. In addition, compared with PE film, the CALC membrane also has antibacterial properties and UV resistance, which is beneficial to improving the storage conditions for foods. This study shows that the developed CALC membrane and corresponding design strategy can be extended for the preparation of other packaging materials for applications in research and food industrial fields.

Unlocking the mechanical, thermodynamic and thermoelectric properties of NaSbS2: A DFT scheme.

The present study focuses on the ground state mechanical, acoustic, thermodynamic and electronic transport properties of NaSbS2 polymorphs using the density functional theory (DFT) and semi-classical Boltzmann transport theory. The mechanical stability of the polymorphs is affirmed by the calculated elastic tensor. The calculated elastic properties asserted that all the polymorphs exhibit soft, brittle, anisotropic nature containing dominant covalent bonding. The 2D polar graphs are used to describe the anisotropic characteristic of the elastic parameters. The estimated value of Young's modulus and lattice thermal conductivity suggested that the polymorphs could be suitable for thermal barrier coating. Heat capacity, melting temperature, thermal conductivities, Grüneisen parameter, and thermal expansion coefficient of the polymorphs have also been studied to demonstrate thermodynamic behavior. The predicted lower values of lattice thermal conductivity declared that NaSbS2 polymorphs exhibit excellent electrical conductivity and transport properties. The estimated Seebeck coefficient (S), power factor (PF) and figure of merit (ZT) suggested that n-type triclinic and monoclinic, as well as p-type trigonal NaSbS2, are better for thermoelectric applications. The optimal carrier concentration for monoclinic structure is 1021cm-3 for T<750K, while it becomes 1020cm-3 for T>750K. It is also found that the optimal carrier concentration of the trigonal is 1021cm-3, whereas it is 1020cm-3 for triclinic structures. Therefore, it can be stated that NaSbS2 polymorphs possess excellent thermoelectric features, making them a promising choice for thermoelectric (TE) applications.

A sandwich-type electrochemiluminescence biosensor based on Ni3(HAB)2/Au@ZnNiAl-LDH/Ru@MIL-53(Al)-NH2 for ultra-sensitive detection of microRNA-155.

Anovel electrochemiluminescence (ECL) biosensor was developed for the ultrasensitive detection of miRNA-155, based on the synergistic combination of multifunctional nanomaterials. The biosensor employed a conductive metal-organic framework (MOF), Ni3(HAB)2 (HAB = hexaaminobenzene), as the substrate material. The unique π-electron conjugated structure of Ni3(HAB)2 endowed the biosensor with excellent electron transport properties, significantly enhancing its sensitivity. Furthermore, the innovative preparation ofAu@ZnNiAl-LDH nanocomposites, characterized by a high specific surface area was employed to synergistically enhance the catalytic performance of the biosensor in conjunction with Ni3(HAB)2.The Au@ZnNiAl-LDH also provided stable anchoring sites for the capture unit, comprised of a DNA tetrahedron hairpin composite structure (DT-HP). Additionally, a porous aluminum-based metal-organic framework (MIL-53(Al)-NH2) was utilized to encapsulate Ru(bpy)32+, constructing a Ru@MIL-53(Al)-NH2 signal unit that effectively improved the stability of the ECL signal. Under optimal conditions, the ECL intensity of the biosensor exhibited a robust linear relationship with the logarithm of miRNA-155 concentration over a range 3 fM to 1nM, achieving a detection limit as low as 0.9 fM. Moreover, the biosensor demonstrated exceptional specificity, selectivity, and stability, highlighting its significant potential for applications in bioanalysis and clinical diagnosis, particularly for the early diagnosis of tumor.

Entropy Manipulation of SrTiO3 Perovskite for Enhanced Thermoelectric and Mechanical Properties.

Reducing the thermal conductivity while maintaining excellent electrical transport properties is crucial for enhancing the thermoelectric performance of SrTiO3-based perovskites. Here, we successfully achieved this goal through precisely manipulating the configurational entropy. A series of Ca0.25Nd0.25Sr0.5-x BaxTiO3 (x = 0, 0.05, 0.15, 0.25) ceramics were successfully synthesized using the solid-state reaction combined with graphite burial sintering. It was discovered that structural defects from competing elements in the A-site not only slowed diffusion and hindered grain growth but also increased oxygen vacancies by creating additional gas transmission channels. The gradual decrease in carrier mobility with increasing entropy resulted in the degradation of electrical conductivity, while the Seebeck coefficient experienced a large enhancement due to band modification and increased carrier scattering. Meanwhile, multiscale defects, including point defects, local strain fields, dislocations, and grain boundaries, effectively scatter phonons, leading to a low lattice thermal conductivity of 1.73 W·m-1·K-1. Consequently, the sample with x = 0.15 exhibited a peak ZT of 0.15 at 900 K, reflecting a 148% enhancement compared to that of the matrix. In addition, the hardness increases with configurational entropy because of the chemical disorder, grain refinement, and increased defect concentration. The work emphasizes the importance of precise manipulation of configurational entropy, offering valuable insights for optimizing thermoelectric materials through entropy engineering strategy.

Electron Donor‐Functionalized Pyrenes with Amplified Spontaneous Emission for Violet–Blue Electroluminescent Devices Beyond the Spin Statistical Limit

AbstractDirect electrically pumped organic lasers remain inaccessible to date, due to an interplay of different adverse effects. The most important of these effects are insufficient charge carrier mobility in the organic material, accumulation of triplet excitons upon charge injection, and absorption from the electrodes in the device. While triplet state management can be achieved using molecules that recycle triplet states into emissive singlet states, these molecules rarely support amplified emission. Pyrene derivatives not only show excellent charge transport properties, but their rigid π‐conjugated structure also entails excellent electro‐ and photoluminescence efficiency. Pyrenes exhibit very low‐lying first excited triplet states, rendering this class of molecules interesting for ultrafast upper‐level reverse intersystem crossing. This process counteracts the triplet accumulation in organic lasers. Here, pyrenes are functionalized with electron‐rich moieties of different donor strengths. Through comprehensive spectroscopic and quantum chemical analysis, the character of the charge transfer excited state is correlated with optical properties, excited state lifetimes, amplified spontaneous emission, and triplet recycling. Two donor functionalized pyrenes are reported with violet–blue emission that overcome the spin‐statistical limit of conventional organic emitters with spin factors ηST of up to 0.43 and low thresholds for amplified spontaneous emission Eth down to 1.73 µJ cm−2.

Intercalation‐Assisted In Situ Exfoliation of Cu2Se Nanosheets as Anode for Ultralong‐Life Aqueous “Rocking‐Chair” Zinc‐Ion Batteries

AbstractAqueous zinc ion batteries (AZIBs) are a potential energy storage device due to their low cost and environmental friendliness. However, the problems of Zn metal anode lead to low coulombic efficiency and safety problems, thus hindering the practical application of AZIBs. Therefore, developing zinc‐metal free anode materials can effectively avoid the problems. Herein, an intercalation‐assisted in situ exfoliation mechanism is reported to obtain Cu2Se nanosheets (E‐Cu2Se) during the electrochemical reaction. The good conductivity of Cu2Se nanosheets ensures the rapid (de)intercalation of zinc ions and excellent charge transport properties in Cu2Se. Furthermore, Cu2Se not only has strong structural stability itself but also can effectively inhibit zinc dendrite through the conversion of copper between the cathode and anode. The results show that the E‐Cu2Se electrode has a low intercalation potential (≈0.4 V) and a high specific capacity of 284.8 mAh g−1 after 100 cycles at 0.1 A g−1. Meanwhile, a “rocking‐chair” aqueous zinc‐ion battery assembled with ZnxMnO2 as cathode delivers a specific capacity of 40 mAh g−1 after 60 000 cycles. The exfoliation mechanism of E‐Cu2Se is discussed based on various characterization techniques and theoretical calculations. This study is expected to provide a new avenue for the development high‐performance “rocking‐chair” AZIBs.

Gate-tunable high tunneling magnetoresistance induced by hybrid interface states in Ni-electrode single-molecule junctions

Based on the density functional theory and non-equilibrium Green's function method, the modulation effects of gate voltage on the spin transport properties of Ni/triphenylene/Ni single-molecule junctions are investigated. The plane-, platform-, and tip-shaped electrode configurations are considered in the calculations. The numerical results show that the electrode configuration and gate voltage significantly influence the hybrid interface states (HIS) and further the spin transport properties of the molecular junctions. The molecular junctions with plane- and platform-shaped electrode configurations show weak spin polarization (SP) and tunneling magnetoresistance (TMR). Still, they exhibit excellent field effect transistor behaviors with the modulation of the gate voltage. Due to the delocalized spin-down HIS located at the Fermi level, the molecular junction with tip-shaped electrode configuration presents high and controllable SP and TMR behaviors through the gate voltage modulation. The calculations demonstrate that high spin-polarized HIS located at the Fermi level are extremely significant for the generation of excellent spin transport properties in molecular junctions composed of non-magnetic molecule and magnetic electrodes.

(Digital Presentation) Screening Analysis of Hydrogen Absorption in Metal-Modified Carbon Supports

Hydrogen fuel is rapidly gaining recognition as a promising alternative energy source with the potential to help address the global energy crisis. As the demand for sustainable and environmentally friendly energy solutions increases, hydrogen stands out due to its abundance and clean combustion, producing only water as a byproduct. Carbon-based materials, known for their large surface area and excellent mass transport properties, play a critical role in enhancing hydrogen fuel applications. These materials are particularly effective in catalysis, adsorption, and energy storage, making them invaluable in the pursuit of more efficient and sustainable energy systems [1-19].This study evaluated the hydrogen uptake of five different activated carbon materials, each modified with a distinct metal ion (Ni, Co, Ag, Cu, Zn), to assess the impact of metal modification on hydrogen storage capacity. The structural and compositional changes resulting from the metal modifications were thoroughly characterized using various analytical techniques. Powder X-ray Diffraction (PXRD) was employed to analyze the crystalline structures of the modified carbons, providing insight into potential alterations in their lattice arrangements. Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy was used to detect changes in functional groups, highlighting any chemical modifications caused by the metal incorporation. Scanning Electron Microscopy (SEM) offered detailed surface morphology images, enabling a close examination of the physical alterations to the carbon materials. Together, these techniques provided a comprehensive understanding of how metal modifications influence the hydrogen storage capabilities of activated carbon materials.Nitrogen adsorption isotherms were measured at 77 K (liquid nitrogen temperature) to evaluate the surface area and pore size distribution of the samples. Brunauer-Emmett-Teller (BET) surface area analysis was conducted to obtain precise data on the specific surface area, offering insights into the extent of the available surface for adsorption. Additionally, the pore size distribution was carefully assessed to characterize the porosity of the metal-modified carbons, providing a deeper understanding of their structural properties and potential influence on hydrogen storage performance.The hydrogen uptake capacity of the metal-modified activated carbon samples was evaluated at 77 K across a pressure range from ambient to 1 bar. The results revealed significant differences in hydrogen storage capacities based on the type of metal ion used for modification. Notably, the activated carbon samples modified with nickel (Ni) and cobalt (Co) ions demonstrated the highest hydrogen storage capacities, with uptakes approaching 5%. In contrast, the copper (Cu) modified carbon showed the lowest hydrogen uptake capacity.These findings emphasize the substantial impact that metal ion modification has on the hydrogen storage performance of activated carbon. The superior performance of the Ni- and Co-modified carbons suggests their strong potential for practical applications in hydrogen storage technologies. Furthermore, this study underscores the broader significance of metal ion modifications in enhancing the properties of activated carbon, positioning it as a promising material for a wide range of advanced technological applications. References Biehler, E.; Quach, Q.; Abdel-Fattah, T.M. ECS J. Solid State Sci. Technol. 2023, 12, 081002.Quach, Q.; Biehler, E.; Elzamzami, A.; Huff, C.; Long, J.M.; Abdel-Fattah, T.M. Catalysts. 2021, 11, 118.Huff, C.; Dushatinski, T.; Barzanji, A.; Abdel-Fattah, N.; Barzanji, K.; Abdel-Fattah, T.M. ECS J. Solid State Sci. Technol. 2017, 6, M69.Huff, C.; Long, J.M.; Aboulatta, A.; Heyman, A.; Abdel-Fattah, T.M. ECS J. Solid State Sci. Technol. 2017, 6, 115–118.Huff, C.; Quach, Q.; Long, J.M.; Abdel-Fattah, T.M. ECS J. Solid State Sci. Technol. 2020, 9, 101008.Huff, C.; Long, J.M.; Heyman, A.; Abdel-Fattah, T.M. ACS Appl. Energy Mater. 2018, 1, 4635–4640.Huff, C.; Dushatinski, T.; Abdel-Fattah, T.M. International Journal of Hydrogen Energy 2017, 42 (30), 18985-18990.Dushatinski, T., Huff, C.; Abdel-Fattah, T.M. Applied Surface Science 2016, 385, 282-288Huff, C.; Long, J.M.; Abdel-Fattah, F.M. 2020, 10, 1014.Huff, C.; Biehler, E.; Quach, Q.; Long, J.M.; Abdel-Fattah, T.M. Colloid Surf. A 2021, 610, 125734Biehler, E.; Quach, Q.; Abdel-Fattah, T.M. 2024, 14, 423.Biehler, E.; Quach, Q.; Abdel-Fattah, T.M. 2024, 17, 3327.Biehler, E.; Quach, Q.; Abdel-Fattah, T.M. J. Compos. Sci. 2024, 8, 270.Abdel-Fattah, T.M.; Biehler, E. Adv. Carbon J. 2024, 1, 1–19.Quach, Qui, Erik Biehler, and Tarek M. Abdel-Fattah. Journal of Composites Science, 7, 279 (2023).Biehler, Erik, Qui Quach, and Tarek M. Abdel-Fattah Materials 16, 4779 (2023). Quach, Qui, Erik Biehler, and Tarek M. Abdel-Fattah Catalysts 13, 1117 (2023).Biehler, Erik, Qui Quach, and Tarek M. Abdel-Fattah Nanomaterials 13, 1994 (2023).Biehler, Erik, Qui Quach, and Tarek M. Abdel-Fattah Energies 16, 5053 (2023).

Effect of Sr2+ doping on the structure and electrical properties of hexagonal perovskite Ba7-xSrxNb4MoO20-δ electrolyte: Experimental and DFT modeling studies

Ba7Nb4MoO20 exhibits excellent oxygen ion transport properties and is a promising electrolyte material for solid oxide fuel cell (SOFC). To further enhance its oxygen ionic conductivity, element doping is an effective strategy. However, few studies have delved into the impact mechanism of doping strategies on the electrolyte's conductivity properties from the perspective of electronic structure. Here, the enhancement mechanism of oxygen ionic conductivity in Ba7Nb4MoO20 was analyzed using the the methods of density of states (DOS) and Crystal Orbital Hamilton Populations (COHP). Since the electronic conductivities of the electrolytes are negligible, their total conductivies can essentially be regarded as the conductivies of oxygen ions. As the Sr doping amount increases, the oxygen ionic conductivities of the electrolytes also increase. The bulk conductivity shows a negative correlation with the Sr doping amount, which is due to the higher bond energy of Sr-O compared to Ba-O. On the other hand, Sr promotes grain growth and reduces the number of grain boundaries, thereby decreasing the resistance to oxygen diffusion at the grain boundaries and thus enhancing the grain boundary conductivity. In the Ba7-xSrxNb4MoO20-δ (x=0, 0.1, 0.2, 0.3, and 0.4) perovskite oxides, Ba6.6Sr0.4Nb4MoO20-δ has the highest conductivity, reaching 1.12 × 10-4S cm-1 at 500°C. This work not only develops a SOFC electrolyte material with promising application prospects, but also provides theoretical guidance for its doping modification.

Steady-State Inverse-Temperature Crystallization Enabling Low Defect Perovskite Single Crystal and Efficient X-Ray Detectors.

Organic-inorganic halide perovskite single crystals (SCs) have shown great potential in radiation detection applications due to their large radiation stopping power and excellent carrier transport properties. The spatial-confined inverse-temperature crystallization (ITC) method has been widely adopted to obtain large-sized SCs. However, they usually face the problems of uneven stress distribution and high defect density due to the limited crystal growth space and varied growth rate with the increase in temperature, making it difficult to fabricate highly sensitive and stable radiation detectors. In this study, the steady-state inverse-temperature crystallization method (SS-ITC) is developed to regulate the growth process of SCs by controlling the growth speed precisely to achieve a constant rate of growth as the temperature increases. Compared with the conventional ITC-grown samples, the lattice spacing of SCs prepared by the SS-ITC method is reduced by 1.2% due to tensile stress relaxation, resulting in a lower defect density of 7.93×109cm-3 and a remarkable uniformity over a large area. As a result, the co-planar X-ray detectors based on these high-quality SCs exhibit a high sensitivity of 1.67×105 µC Gyair -1cm-2, representing the best performing MAPbBr3-based X-ray detectors reported to date.

Lateral Mn5Ge3 spin-valve in contact with a high-mobility Ge two-dimensional hole gas

Abstract Ge two-dimensional hole gases (2DHG) in strained modulation-doped quantum-wells represent a promising material platform for future spintronic applications due to their excellent spin transport properties and the theoretical possibility of efficient spin manipulation. Due to the continuous development of epitaxial growth recipes extreme high hole mobilities and low effective masses can be achieved, promising an efficient spin transport. Furthermore, the Ge 2DHG can be integrated in the well-established industrial complementary metal-oxide-semiconductor (CMOS) devices technology. However, efficient electrical spin injection into a Ge 2DHG—an essential prerequisite for the realization of spintronic devices—has not yet been demonstrated. In this work, we report the fabrication and low-temperature magnetoresistance (MR) measurements of a laterally structured Mn5Ge3/Ge 2DHG/ Mn5Ge3 device. The ferromagnetic Mn5Ge3 contacts are grown directly into the Ge quantum well by means of an interdiffusion process with a spacing of approximately 130 nm, forming a direct electrical contact between the ferromagnetic metal and the Ge 2DHG. Here, we report for the first time a clear MR signal for temperatures below 13 K possibly arising from successful spin injection into the high mobility Ge 2DHG. The results represent a step forward toward the realization of CMOS compatible spintronic devices based on a 2DHG.

High Performance and Colorful Polymer Thermoelectrics with Imprinted Porous Film.

The rapid development of the Internet of Things and wearable electronics has generated growing interest in creating high-performance and visually striking polymer thermoelectric (TE) devices. However, existing polymer TE materials have yet to fully meet these diverse demands. In this study, imprinted porous polymer films are introduced that exhibit both high TE performance and a spectrum of structural colors. The porous architecture not only preserves excellent charge transport properties but also significantly enhances phonon-like scattering, resulting in a more than 50% reduction in thermal conductivity for the PDPPSe-12 film. This leads to a 170% increase in the figure of merit (ZT), achieving a peak value of 0.52 at 363K. Furthermore, the highly ordered porous structure imparts the PDPPSe-12 films with both a wide range of structural colors and remarkable stretchability, making them ideal for wearable TE generators. This approach is widely applicable to various polymeric systems, offering a novel strategy for advancing state-of-the-art plastic TE materials through microstructural engineering.

Engineering of aqueous binder mediated organic/inorganic artificial interfacial layers for enhancing silicon anode performance

The expansion of silicon volume significantly impacts the degradation of silicon anodes. The current binder-formed interface fails to effectively suppress this expansion due to the absence of rigid inorganic components. Therefore, we develop an aqueous binder-mediated interfacial engineering strategy to construct an organic/inorganic artificial interfacial layer in situ during the electrode preparation process. This artificial interfacial layer, consisting of an organic alginate–lithium citric acid–tannin derivative (LiACT) binder and inorganic Li2SiO3, is generated by a combination of chemical reactions and hydrogen bonding between tannic acid, citric acid, sodium alginate, silicon, and lithium hydroxide. The three-dimensional structure provides the LiACT binder with a strong binding force. The elasticity of LiACT, the high Young's modulus of Li2SiO3, and their fast ionic conductivity enable this artificial interfacial layer to exhibit robust rigidity-flexibility and excellent ionic-electronic transport properties. Therefore, the Si electrode coated with this artificial interfacial layer (Si@LiACT) exhibits high coulombic efficiency (99.2 % in the 5th cycle), excellent cycling stability (89.2 % capacity retention after 200 cycles), and superior rate performance (1044 mAh g−1 at 4C). These enhancements are attributed to the unique organic/inorganic artificial interfacial layer, which effectively inhibits silicon volume expansion, alleviates interfacial side reactions, and promotes interfacial charge transfer.

Experimental comparison of cycle modifications and ejector control methods using variable geometry and CO2 pump in a multi-evaporator transcritical CO2 refrigeration system

To reduce the direct global warming impact of refrigerants in HVAC&R applications, low-global warming potential (GWP) refrigerants, including natural refrigerants, have been extensively investigated as alternatives to hydrofluorocarbon (HFC) refrigerants. Among the natural refrigerants, Carbon Dioxide (CO2) offers several advantages, such as excellent transport and thermo-physical properties, being neither toxic nor flammable, and having a low price and high availability around the world. However, the high critical pressure and low critical temperature of CO2 often lead to transcritical operation, resulting in lower efficiency due to the additional compressor power necessary to achieve transcritical operation relative to subcritical HFC cycles. Therefore, a number of cycle modifications are used to enhance the coefficient of performance (COP) of transcritical CO2 cycles to meet or surpass those of HFC cycles. This paper provides a systematic experimental investigation of four such cycle architectures by employing the same multi-stage, two-evaporator CO2 refrigeration cycle test stand, 3 of these configurations in transcritical and 1 in subcritical conditions. The four cycles architectures included intercooling, open economization, an internal heat exchanger and two different ejector control approaches. Specifically, a variable-diameter motive nozzle and a variable-speed liquid CO2 pump located directly upstream of the ejector motive nozzle inlet were analyzed. Based on the experimental data, the maximum COP improvements are 4.64 % and 9.47 % when the ejector and the internal heat exchanger are used, respectively. The CO2 pump, once successfully stabilized, can control the ejector, increase its efficiency by up to 15 % and increase the cooling capacity to a maximum of 6.2 %. Nevertheless, a reduction in COP is measured when the pump is in use; however, unlike the other three different configurations, it was only analyzed under subcritical conditions.

Topological valley waveguide state transport based on the nesting difference

Acoustic topological waveguide states are characterized by topologically protected transport. Existing acoustic topological valley-locked waveguide state transport structures can only realize single-scene acoustic field modulation due to the limitation of structural tunability, and it is difficult to realize width degree of freedom and reconfigurable transport paths of acoustic waves by adjusting the transport structure for complex acoustic field. Therefore, the transport structures become a conceptualized idea in terms of tunability. Our study introduces a nesting method in the design of the sonic crystal scatterer, which splits the scatterer structure into a removable outer shell and a core, and three topological phase transitions can be realized by only changing the nesting method of the sonic crystal shell, this approach constructs a fully reconfigurable topological waveguide. The results demonstrate that changing the nesting of the sonic crystals induces effective spatial inversion symmetry breaking, which leads to the valley topological phase transitionSimulations and experiments demonstrate that this transport structure has excellent robust transport properties with large inflection corners, and it is capable of realizing acoustic focusing, acoustic channeling, and acoustic logic gates. This fully reconfigurable sonic crystal design method can provide implications for the modulation of other classical waves.

Numerical optimization of cesium tin-germanium triiodide/antimony selenide perovskite solar cell with fullerene nanolayer

SCAPS-1D platform was used to simulate a solar cell with FTO/CdS/Sb2Se3/CuInSe2/Au structure which was recently fabricated by Liu et al. (2022) [1] [Journal of Energy Chemistry68 521–528 (2022)] and a very similar result was obtained. Reported parameters were Fill Factor (FF) = 53.60 %, short circuit current density (JSC) = 26.18 mA/cm2, open circuit voltage (VOC) = 0.37 V, and power conversion efficiency (PCE) = 5.19 %, while simulated parameters were FF of 54.68 %, JSC of 27.54 mA/cm2, VOC of 0.36 V, and PCE = 5.55 %. The advancements have been evaluated by analyzing FTO/CdS/Sb2Se3/CuInSe2/Au and FTO/C60/Sb2Se3/CuInSe2/Au configurations, serving as the reference cells. To improve the cell performance, the CdS layer was replaced with another layer (C60) which shows excellent electron transport properties. Replacing the CdS layer with C60 led to an increase in the power conversion efficiency by 65 % (from 5.55 % up to 9.20 %). In photovoltaic systems, the PCE constitutes a pivotal parameter that can be enhanced through the absorption of a broad spectrum of incident photons. Consequently, the implementation of two absorber layers within a solar cell, each characterized by a graded band gap energy, enables the capture of solar photons over a more extensive spectral range. Therefore, a perovskite containing a band gap of 1.5 eV, lead-free, and Sn-based was used as the second absorber layer in the device. Therefore, a solar cell with FTO/C60/CsSn0.5Ge0.5I3/Sb2Se3/CuInSe2/Au structure was simulated, and significant results were achieved. Results showed that inserting the CsSn0.5Ge0.5I3 layer led to an increase in PCE up to 11.42 %.

Construction of black phosphorus/metal-organic framework composites for electrochemical detection of uric acid

The detection of uric acid (UA) concentration is of great significance for the prevention and treatment of related diseases. In this work, we used a static precipitation strategy to prepare a surface carbonized cobalt-based metal-organic frameworks (MOFs) composite black phosphorus nanosheets (BPNS) electrode material for electrochemical detection of UA. The results showed that the sensor had a linear detection range of UA concentration from 1 to 2000 μM in acetate buffer with pH=5.6. In addition, the sensor still maintains a peak current response of 91.9 % after one month, indicating its good stability and anti-interference performance. The enhancement of sensing performance is attributed to the fact that the composite material retains the excellent electronic transport properties of BPNS. At the same time, the composite of MOFs makes the specific surface area and porosity of the material increase, so that the stability of BPNS is significantly improved. This work will provide new ideas for the construction of stable and efficient UA electrochemical sensors.

Evaluating diffusivity for efficient electrocatalytic conversion of carbon dioxide into multicarbon products using dealloyed hierarchically nanoporous copper

Hierarchical nanoporous copper (Hi-NPC) is a promising catalyst for carbon dioxide reduction reaction (CO2RR) due to its high surface area and excellent mass transport properties. To evaluate the effect of its architecture, eutectic-phased Cu18Al82 and single-phased Cu33Al67 were potentiostatically dealloyed to produce Hi-NPC and homogeneous nanoporous copper (Ho-NPC), respectively. At a comparable overpotential, the Hi-NPC electrocatalyst exhibited a significantly higher C2+ partial current density (jC2+) in CO2RR, reaching 510 mA/cm2, compared to both Ho-NPC (72 mA/cm2) and Cu electrodes (23 mA/cm2). When the current density was normalized by the electrochemically active surface area, the CO production among three electrodes demonstrated similar electrochemical behavior. However, notable differences were observed in the formation of C2H4 and C2H5OH, which can be attributed to the hierarchical structure of Hi-NPC facilitating C–C coupling to form C2 products. Although the Tafel plot indicated the CO2RR kinetics were identical for all three electrodes, linear sweep voltammetry experiments revealed that Hi-NPC exhibited the steepest current variation slope. Furthermore, the improved diffusivity was further confirmed by conducting oxygen reduction reactions with varying partial O2/N2 flow rates and electrochemical impedance spectroscopies. The hydrophobic properties of the electrode under various CO2RR current densities were also evaluated by water contact angle test.