Work Function Research Articles

Insights into bismuthene and antimonene as cisplatin drug carriers: A theoretical comparative investigation

While effective targeted delivery is a challenge in nanomedicine for the delivery of anti-cancer drugs, this work focuses on the potential use of Bismuthene and antimonene nanosheets as nanocarriers for cisplatin anti-cancer using DFT methods. The results indicate that, compared to antimonene, bismuthene demonstrates significantly better physical stability, drug release rate, solubility, and biocompatibility, making it an excellent candidate for drug delivery systems. The parallel and perpendicular orientations of the anticancer drug were adsorbed on both nanosheets; the parallel configuration was the most energetically favored with an adsorption energy of −0.79 eV at the parallel site. A charge transfer from the drug to the bismuthene sheet is also revealed by the electronic charge analysis and DOS calculation, thus confirming efficient drug adsorption. Modeling a proton attack on the drug and the carrier surface near the adsorption sites was performed to model drug release, showing the stability and potential of bismuthene in this aspect of drug release mechanisms. Further, with an approach to studying its interactions with biomolecules, interactions of the drug molecule have been analyzed with amino acids, showing that drugs interact efficiently. Further assessments concerning work function, recovery time, electron localization function, and frontier molecular orbital analyses leave no doubt that bismuthene has beneficial features over antimonene. These thorough assessments present bismuthene as a more promising nanocarrier for the delivery of anti-cancer drugs and open a potential pathway to enhance the efficacy of strategies against cancer treatment.

Non‐Ionic Perylene‐Diimide Polymer as Universal Cathode Interlayer for Conventional, Inverted, and Blade‐Coated Organic Solar Cells

AbstractAs a class of predominantly used cathode interlayers (CILs) in organic solar cells (OSCs), perylene‐diimide (PDI)‐based polymers exhibit intriguing characteristics of excellent charge transporting capacity and suitable energy levels. Despite that, PDI‐based CILs with satisfied film‐forming ability and adequate solvent resistance are rather rare, which not only limits the further advance of OSC performances but also hinders the practical use of PDI CILs. Herein, we designed and synthesized two non‐conjugated PDI polymers for achieving high power conversion efficiency (PCE) in diverse types of OSCs. The utilization of oligo (ethylene glycol) (OEG) linkage enhanced the n‐doping effect of PDI polymers, leading to an improved ability of the CIL to reduce work function and improve electron transporting capability. Moreover, the introduction of the non‐ionic OEG chain effectively improve the wetting property and solvent resistance of PDI polymers, so the PPDINN CIL can withstand diverse processing conditions in fabricating different OSCs, including conventional, inverted and blade‐coated devices. The binary OSC with conventional structure using PPDINN CIL showed a PCE of 18.6 %, along with an improved device stability. Besides, PPDINN is compatible with the large‐area blade‐coating technique, and a PCE of 16.6 % was achieved in the 1‐cm2 OSC where a blade‐coated PPDINN was used.

Unveiling the potential of newly synthesized 2D TMCC monolayer for H2S gas sensing: A DFT study

The 2D monolayer of transition metal carbo-dichalcogenide (TMCC) has been recently synthesized from its bulk form. It is a unique blend of MXenes and transition metal dichalcogenides (TMDCs), offering superior properties compared to its individual parent components. TMCC has not yet been explored for its potential in gas sensing applications, motivating us to investigate its performance for detecting H2S gas molecule. The pristine monolayer of TMCC (Nb2S2C) exhibited weak H2S adsorption energy (-0.18 eV), leading to low sensitivity, poor selectivity, underscoring surface modification. The decoration strategy was incorporated by considering transition metal (TM) atoms like Ti, Co, Cu, Pd and Ag. Ti and Co decorated TMCC showed superior H2S gas sensing performance. Ti showed maximum binding energy (-5.44 eV) followed by Co (-4.91 eV). The adsorption energy of H2S on Ti and Co decorated TMCC were comparable having values of -1.08 eV and -1.09 eV respectively while showing respective practical recovery time of 6 s and 8.5 s at 350 K, respectively. The improved adsorption mechanism is due to orbital interaction and charge transfer. Work function sensitivity and thermal stability upto 400 K was assessed. The study shows Ti and Co decorated TMCC monolayer as a suitable candidate for H2S sensing, inspiring experimentalists to fabricate TMCC-based H2S sensors.

Non-Ionic Perylene-Diimide Polymer as Universal Cathode Interlayer for Conventional, Inverted, and Blade-Coated Organic Solar Cells.

As a class of predominantly used cathode interlayers (CILs) in organic solar cells (OSCs), perylene-diimide (PDI)-based polymers exhibit intriguing characteristics of excellent charge transporting capacity and suitable energy levels. Despite that, PDI-based CILs with satisfied film-forming ability and adequate solvent resistance are rather rare, which not only limits the further advance of OSC performances but also hinders the practical use of PDI CILs. Herein, we designed and synthesized two non-conjugated PDI polymers for achieving high power conversion efficiency (PCE) in diverse types of OSCs. The utilization of oligo (ethylene glycol) (OEG) linkage enhanced the n-doping effect of PDI polymers, leading to an improved ability of the CIL to reduce work function and improve electron transporting capability. Moreover, the introduction of the non-ionic OEG chain effectively improve the wetting property and solvent resistance of PDI polymers, so the PPDINN CIL can withstand diverse processing conditions in fabricating different OSCs, including conventional, inverted and blade-coated devices. The binary OSC with conventional structure using PPDINN CIL showed a PCE of 18.6 %, along with an improved device stability. Besides, PPDINN is compatible with the large-area blade-coating technique, and a PCE of 16.6 % was achieved in the 1-cm2 OSC where a blade-coated PPDINN was used.

Comment on “Tunneling-tip-induced collapse of the charge gap in the excitonic insulator Ta2NiSe5 ”

In this study, we investigate the discrepancy between the estimate of Q. He [], who observed a remarkable collapse of the exciton gap in Ta2NiSe5 due to the electrostatic field between the scanning tunneling microscope (STM) tip and the sample, and that of a recent angle-resolved photoemission spectroscopy investigation [C. Chen , ]. It is proposed that a critical factor contributing to this discrepancy is due to He 's assumption of a constant work function of the STM tip. This assumption led to an underestimation of the tip-induced electric field. Using a literature value for the sample work function, a more substantial electric field strength is obtained, which resolves the apparent conflict between the doping estimates of these two techniques. Furthermore, our findings highlight the importance of the STM tip condition, which can significantly impact the tip work function and, consequently, influence the doping estimation in experiments involving tip-induced electric fields. Published by the American Physical Society 2024

Low turn-on voltage AlGaN/GaN Schottky barrier diode with a low work function anode and high work function field plate

AlGaN/GaN Schottky barrier diodes (SBDs) with a low work function W anode and a high work function Ni field plate on sapphire substrates are investigated in this Letter. The low work function metal W leads to the low turn-on voltage, while the high work function metal Ni maintains the leakage current and increases the breakdown voltage. An ultralow turn-on voltage of 0.23 V determined by the positive fixed charge at the AlGaN/Si3N4 interface is achieved in this W/Ni SBD. More importantly, benefitting from the dual-metal anode/field plate structure, the on-resistance decreases from 7.99 to 5.53 Ω mm, and the breakdown voltage increases from 493 to 1219 V. In addition, the turn-on voltage decreases less than 57%, and the on-resistance increases less than 186% at a high temperature up to 120 °C. The W/Ni SBD with a cathode–anode length of 18 μm and a field plate length of 4 μm shows a low turn-on voltage of 0.23 V, a low on-resistance of 5.53 Ω mm, a leakage current of 0.65 mA/mm, and a high breakdown voltage of 1.21 kV, indicating a great potential for power electronic applications.

Performance Enhancement of SnS Solar Cell with Tungsten Disulfide Electron Transport Layer and Molybdenum Trioxide Hole Transport Layer

Herein, a new heterojunction photovoltaic (PV) device is designed by incorporating molybdenum trioxide (MoO3) as a hole transport layer (HTL), tin sulfide (SnS) as an absorber, and tungsten disulfide (WS2) as an electron transport layer (ETL). The PV outputs of the proposed thin‐film solar cell (TFSC) of Ni/MoO3/SnS/WS2/FTO/Al are investigated using the widely used solar cell simulator (SCAPS‐1D). It is found that the SnS TFSC with suitable band alignments at both the SnS/WS2 and MoO3/SnS interfaces gives better photoconversion efficiency than the conventional one. To optimize the material properties, the performance parameters, including open‐circuit voltage (Voc), short‐circuit current density (Jsc), fill factor (FF), and efficiency, have been calculated by varying the influences of the material's thickness, doping concentration, bulk and interface defect densities, operational temperature, and work function of back‐contact. At optimized thicknesses of 0.1 μm for MoO3 HTL and 1.0 μm for SnS absorber, the efficiency is estimated to be 30.42% with Voc of 1.02 V, Jsc of 34.38 mA cm−2, and FF of 87.04% for the suggested TFSC. These outcomes imply that the nontoxic MoO3 and WS2 materials can be applied as HTL and ETL into the inexpensive, highly efficient, and environmentally friendly SnS‐based PV cell.

Electronic regulation of Ce,F-Ni2P/CoP catalyst for efficient water splitting

Designing efficient non-precious-metal bifunctional electrocatalysts is still challenging at present. Herein, the efficient Ce,F-Ni2P/CoP electrocatalyst for water splitting was successfully fabricated. As shown from the present investigation, the codoping of Ce and F in Ni2P/CoP induced the f-p-d gradient orbital coupling in the Ce-F-metal structural unit of the catalyst, significantly reducing the work function of the catalyst, which accelerated the reaction kinetics and improved the intrinsic catalytic activity. The catalyst exhibited the outstanding hydrogen evolution reaction (HER) activity in the full pH range and, especially in alkaline electrolyte, an ultra-low oxygen evolution reaction (OER) overpotential of 243 mV at 50 mA·cm−2 and an excellent HER overpotential of 88 mV at 10 mA·cm−2 were achieved. Moreover, Ce,F-Ni2P/CoP displayed an excellent overall water splitting (OWS) performance with η10 = 1.52 V. DFT theoretical calculations also showed that the gradient orbital coupling resulted in the reduction of the work function of the catalyst. Our work provides a new understanding of designing and constructing high-performance catalysts.

Heat-Excitation-Based Triboelectric Charge Promotion Strategy.

The surface charge decay is observed at high temperatures due to thermionic emission, which, however, may not be the only mechanism contributing to the surface charge variation. Here, a triboelectric charge promotion strategy due to the heat-excitation effect of hot electrons near the fermi level is demonstrated, while the final charge is determined by the balance between thermionic emission and the heat-excitation effect. It is demonstrated that metals with lower work function exhibit a better heat excitation capability, and polymers with lower fluorine content in molecule chains further boost the charge output, where metal/Kapton pairs demonstrated a charge promotion of over 2 times at the temperature of 383K with good durability during 90min measurement. The heat-excitation effect and charge durability in sliding freestanding-triboelectric-layer (SFT) mode triboelectric nanogenerator (TENG) is demonstrated as well, where the energy is promoted by over 3 times and the capacitor charging speed is doubled as well, with an energy promotion from 109.34 to 373µJ per cycle to successfully trigger a discharger. This work suggests a promising future of the heat-excitation effect as a new charge promotion strategy for TENG toward different applications in high-temperature environments.

Application of a Standard Simulation Module as a Tool for Professional Development of Higher Education Teachers

The cycle of advanced training of the faculty on the basis of the Federal Accreditation Center of Perm State Medical University was created to form the professional competencies of students and the work functions of teachers. To introduce practical classes into the programs of clinical disciplines, a standard simulation module (SIM) was used, which is becoming a mandatory basis for the educational process at the University. The analysis of 106 SIM showed the use of simulation equipment and identified problems that are the basis for further development of the course.

A novel dual functional gradient Zn(O,S)/Mg electron-selective contact for dopant‐free silicon solar cells with efficiencies approaching 21 %

Dopant-free carrier-selective contacts have the potential to mitigate or eliminate parasitic absorption, auger recombination losses, etc. Therefore, the vigorous development of dopant-free carrier-selective contact materials is an important way to enhance the performance of crystalline silicon (c-Si) photovoltaics. This study presents the concept of magnetron sputtering gradient deposited zinc oxide (Gd-Zn(O,S)) combined with a low work function magnesium metal layer. Subsequently, the Gd-Zn(O,S)/Mg bifunctional layer was further investigated and optimised to determine its suitability as a contact layer for electron transfer in c-Si solar cells. This strategy simultaneously enables a good passivation and a low contact resistance. The c-Si(n)/a-Si:H(i)/Gd-Zn(O,S)/Mg devices are constructed and achieved an optimal contact recombination current density (J0) of approximately 1.51 fA cm−2, along with a minimum ρc of approximately 35.89 mΩ.cm2. As a consequence, the power conversion efficiency of a prototype silicon heterojunction solar cell is 20.92 %. This study demonstrates that the strategy of replacing the a-Si:H(n) electron transport layer with Gd-Zn(O,S) is an effective approach for improving the SHJ cell. This study also provides new perspectives for designing novel dopant-free carrier-selective contact structures.

A new attempt to further reduce the work function of the cesiated surface: The strongest electronegative element fluorine co-adsorption with cesium on Mo (001) surface

The efficiency of hydrogen negative ion production in negative ion sources depends on the work function of the molybdenum surface. Deposition of cesium (Cs) atoms on the Mo surface reduces the work function from over 4.0 eV to about 1.50–1.80 eV. However, the Fermi level remains below the affinity level (−0.75 eV) of hydrogen negative ions. To explore further reduction methods, the work function of Cs co-adsorbed with fluorine on the Mo (001) surface was studied using DFT calculations. The results show that at 4/16 θ Cs coverage, adding fluorine can reduce the work function, achieving the lowest value of 1.40 eV at 8/16 θ F coverage. Analysis reveals a significant vacuum-inward dipole moment with fluorine-Cs co-adsorption, favorably reducing the work function. However, fluorine’s strong electronegativity also creates a surface-directed dipole moment, increasing the work function. Introducing fluorine is beneficial only at 4/16 θ Cs coverage, indicating that precise control of Cs coverage is necessary to achieve lower work functions.

Deciphering the work function induced local charge regulation towards activating an octamolybdate cluster-based solid for acidic water oxidation.

The advancement of highly robust and efficient electrocatalysts for the oxygen evolution reaction (OER) under acidic conditions is imperative for the sustainable production of green hydrogen. In accomplishing sustainable and sturdy electrocatalysts for oxygen evolution at low pH, the challenge is tough for non-iridium/ruthenium-based electrocatalysts. This study elaborates on the intrinsic alterations in electronic arrangements and structural disorder upon the precise activation of an octamolybdate cluster-based solid [{Cu(pz)4}2Mo8O26]·2H2O through room temperature grinding with rGO (reduced graphene oxide), resulting in enhanced conductivity, stability, and activity of the electrocatalyst towards the acidic OER without employing any benchmark metal ion (Ru or Ir). Additionally, the work function of the composites was found to be low compared to that of pristine polyoxometalates (POMs), indicative of the improved conducive behavior, which is lacking in the POM structure. The catalyst displays a notably reduced overpotential of 185 mV to achieve a current density of 10 mA cm-2, coupled with significant stability lasting 24 hours at a higher current density of 100 mA cm-2. These findings propose the manipulation of crystalline POMs with highly conductive non-metallic elements to facilitate superior water oxidation at lower pH levels which can help in the production of green hydrogen.

Through thickness anisotropy in all inorganic perovskite thin films via two-step synthesis: implications for voltaic devices.

Cesium-lead-bromide (CsPbBr3) has shown promise in thin film photovoltaics due to its desirable energy band gap, charge mobility and chemical and thermal stability. The low solubility of its single crystal in organic solvents has driven development of the two-step spin-coating technique. In this work, precursor solutions of different PbBr2 and CsBr concentrations were spin-coated and investigated via Photoelectron Spectroscopy. The properties of the CsxPbyBrz film in cross-section demonstrate this method leads to varying stoichiometries, work functions and band gaps through the thickness. This anisotropy of the perovskite thickness has ramifications for design of photovoltaic devices.

Simulation study of cadmium-free CIGS solar cell for efficiency enhancement by minimizing recombination losses through back surface field mechanism

Thin-film photovoltaic cells provide benefits over conventional first-generation technology, including lighter weight, greater flexibility, and lower power generation costs. Chalcogenide solar cells offer good efficiency and technological maturity among thin-film technology. In this work, a solar cell device structure, Al/FTO/SnS2/CIGS/CuO/Ni, is examined using SCAPS-1D. Further, by incorporating the back surface field (BSF) layer, the conversion efficiency increased from 18.93 % to 29.88 %, followed by VOC of 0.96 V, JSC of 37.07 mA cm−2, and FF of 83.71 %. This increment in device performance is owing to the lowering back surface recombination velocity and the additional hole tunnelling activity offered by the BSF layer by forming a quasi-ohmic contact, i.e. metal-semiconductor contact with negligible junction resistance relative to the total resistance of the device. Throughout this research work, the authors studied several factors such as surface recombination velocity, temperature impact, front and back contact metal work functions, parasitic resistance impact, gallium proportion, and doping density impact on CIGS solar cells. The work also included a calibration with experimental data from published sources to validate the simulation results.This paper presents a new approach for producing high-efficiency, eco-friendly CIGS solar cells with CuO back surface field mechanism.

Energy Level Tuning in CsPbBr3 Perovskite Solar Cells through In Situ-Polymerized PEDOT Hole Transport Layer.

The all-inorganic CsPbBr3 perovskite solar cells exhibit excellent stability against humidity and thermal conditions as well as relatively low production cost, rendering them a gradually emerging research hot spot in the field of photovoltaics. However, the absence of a hole transport layer (HTL) in its common structure and the substantial energy level difference of up to 0.6 eV between the highest occupied molecular orbital (HOMO) level of CsPbBr3 and the work function of the carbon electrode have emerged as the primary factor limiting the improvement of its power conversion efficiency (PCE). In this work, the monomer 2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT) is spin-coated onto the surface of the CsPbBr3 film directly and then subjected to annealing; DBEDOT undergoes in situ polymerization to form poly(3,4-ethylenedioxythiophene) (PEDOT), which aims to ameliorate the issue of excessive energy level difference between CsPbBr3 and the carbon electrode, and to facilitate the extraction and transport efficiency of holes between the CsPbBr3 perovskite and the carbon electrode. Compared to the pristine device, the PCE of the device based on in situ polymerization is enhanced and achieves a maximum efficiency of 9.81%. Furthermore, the unencapsulated devices based on in situ polymerization maintain 95.9% of their original efficiency after 40 days of stability testing.

Novel Two-Terminal Synapse/Neuron Based on an Antiferroelectric Hafnium Zirconium Oxide Device for Neuromorphic Computing.

Functionally diverse devices with artificial neuron and synapse properties are critical for neuromorphic systems. We present a two-terminal artificial leaky-integrate-fire (LIF) neuron based on 6 nm Hf0.1Zr0.9O2 (HZO) antiferroelectric (AFE) thin films and develop a synaptic device through work function (WF) engineering. LIF neuron characteristics, including integration, firing, and leakage, are achieved in W/HZO/W devices due to the accumulated polarization and spontaneous depolarization of AFE HZO films. By engineering the top electrode with asymmetric WFs, we found that Au/Ti/HZO/W devices exhibit synaptic weight plasticity, such as paired-pulse facilitation and long-term potentiation/depression, achieving >90% accuracy in digit recognition within constructed artificial neural network systems. These findings suggest that AFE HZO capacitor-based neurons and WF-engineered artificial synapses hold promise for constructing efficient spiking neuron networks and artificial neural networks, thereby advancing neuromorphic computing applications based on emerging AFE HZO devices.

Design and Optimization of Iron-Based Superionic-Like Conductor Anode for High-Performance Lithium/Sodium-Ion Batteries.

Metal selenides have received extensive research attention as anode materials for batteries due to their high theoretical capacity. However, their significant volume expansion and slow ion migration rate result in poor cycling stability and suboptimal rate performance. To address these issues, the present work utilized multivalent iron ions to construct fast pathways similar to superionic conductors (Fe-SSC) and introduced corresponding selenium vacancies to enhance its performance. Based on first-principles calculations and molecular dynamics simulations, it is demonstrated that the addition of iron ions and the presence of selenium vacancies reduced the material's work function and adsorption energy, lowered migration barriers, and enhances the migration rate of Li+ and Na+. In Li-ion half batteries, this composite material exhibites reversible capacity of 1048.3 mAh g-1 at 0.1 A g-1 after 100 cycles and 483.6 mAh g-1 at 5.0 A g-1 after 1000 cycles. In Na-ion half batteries, it is 687.7 mAh g-1 at 0.1 A g-1 after 200 cycles and 325.9 mAh g-1 at 5.0 A g-1 after 1000 cycles. It is proven that materials based on Fe-SSC and selenium vacancies have great applications in both Li-ion batteries and Na-ion batteries.

Atom layer deposited TiO2 electron transport layer for silicon heterojunction solar cells to achieve high performance

Silicon/compound heterojunction (SCH) solar cells based on p-type and n-type c-Si wafers using atom layer deposition-TiO2 and low work function metal as the electron transport layer and rear electrode are fabricated. Efficiencies of 20.6 % and 21.6 % are achieved on p-type and n-type silicon solar cells, respectively. High Voc exceeding 700 mV have been realized on both kinds of Si wafers. Special attention has been paid to the SCH solar cells based on p-type c-Si wafers in which the TiO2 electron transport layer serves as the emitter. Carrier transport mechanisms and junction characteristics of the SCH solar cells are analyzed based on dark J-V measurement. The formation of a strong inversion layer at the Si surface region is determined, which implies the high Voc potential of the SCH solar cells based on p-type Si. An optical loss analysis is performed along with a possible solution to further improve the Jsc. The feasibility of TiO2 applied as an efficient electron transport layer (emitter) in p-type SCH solar cells with high performance has been showed.

Designed bimetallic layer-encapsulated tungsten powders for reinforcing tungsten-silver matrix composite electrical contact materials

Electrical contact materials (ECMs) play a pivotal role in maintaining the stability and efficiency of electrical instruments and electronic devices by regulating the current flow. As an essential member of ECMs, W-Ag matrix composite ECMs (W-Ag-MC-ECMs) are integral, demonstrating commendable resistance to welding and arc erosion. However, the limited wettability between the two phases curtails their broader applications. Herein, Ag-Cu and Ag-Ni bimetallic layer-encapsulated tungsten powders were designed and successfully synthesized through a two-step electroless plating process. Subsequently, the W-Ag-MC-ECMs were fabricated following the powder metallurgy route, including the solution ball milling process and the spark plasma sintering technique. The results indicated that Cu-Ag solid solution and Ni with a metal binder effect could strengthen the interface bonding, which can dramatically improve the microhardness (up to 182HV), strength (up to 600 MPa), ductility (up to 24 %) and resistance to arc erosion (nearly two times longer service life). In addition, during the arc erosion, attributed to the Cu-Ag solid solution effect of W@Ag@Cu/Ag-MC-ECMs and solution-strengthening effect of W@Ag@Ni/Ag-MC-ECMs, the work function increases and the arc energy decreases, which reduces mass loss and extends the service life of the contacts.