Heterojunction Research Articles

Reconfigurable mixed-kernel heterojunction transistors for personalized support vector machine classification

Reconfigurable mixed-kernel heterojunction transistors for personalized support vector machine classification

Effect of biologically synthesized iron-oxide nanoparticles insulating layer on current-voltage characteristics of Ni/Cr/Ni/n-GaN Schottky junction

The microstructural and electrical properties of a prepared Ni/Cr/Ni/FeO/n-GaN metal/oxide/semiconductor (MOS) heterojunction (HJ) (as-deposited and after 600 °C annealing) with biologically synthesized iron oxide (FeO) nanoparticles as an insulating layer are investigated. The formation of FeO films at the junction is confirmed by the measurements of FESEM and XRD analysis. The HJ electrical results are associated with Ni/Cr/Ni/n-GaN metal/semiconductor (MS) Schottky junction (SJ) results. The as-deposited and 600 °C annealed HJs exhibit exceptional rectifying efficiency and incredibly low reverse leakage current compared to the SJ. The 600 °C annealed HJ had a higher Φb than both as-deposited HJ and SJ, indicating that the FeO insulating layer has an impact on the Φb of the devices. The outcomes demonstrate that the Φb values are better for 600 °C annealed junctions. Furthermore, Cheung’s, Norde, and ΨS-V method-based plots are used to analyze the Φb, series resistance (RS), ideality factor (n), and the resultant values are found to be comparable, indicating consistency and validity. Due to the fact that the HJs interface state density (NSS) is lower than that of SJ, the FeO layer is crucial to the decreased NSS. A transition from Poole-Frenkel emission at low voltages to Schottky emission at high voltages was also seen in the SJ. Furthermore, the HJ showed Schottky emission throughout the whole voltage range. Furthermore, trustworthily energy level band diagrams may be used to explain the Φb modulation process, leading to the conclusion that the FeO layer is a suitable material for the design of novel electronic device applications.

Optoelectronic characterization of chemically synthesized CuxIn1-xSe2 nanostructure for suitable application as photoconductive device

CuxIn1-xSe2 nanostructures have been synthesized chemically using Polyvinyl Pyrrolidone (PVP) as capping agent by varying the Cu/In composition ratio. XRD results confirm the formation of cubic CuSe2 and that of wurtzite phase of CuxIn1-xSe2 nanostructure. SEM and TEM images showed spherical shaped particle distribution of CuSe2 and hexagonal sheet/plate shaped CuxIn1-xSe2 nanostructures which are in well agreement with XRD pattern. EDAX spectra for both the structures confirm the presence of Cu, In & Se atomic(%) along with some impurity atoms. Optical band gaps calculated from Tauc plots are found to decrease from 2.5 eV to 1.4 eV from CuSe2 to In-rich CuxIn1-xSe2 samples. The conductivity of the samples shows a significant increase of current with the increase of Indium composition which are co-related with the optical band gap of the samples. A comparative analysis has also been done on Schottky and hetero structure of the CuxIn1-xSe2 samples for suitable application in photovoltaic device. The performance of CuxIn1-xSe2 nanostructures has been analyzed through photo-response studies under illumination of 546 nm monochromatic light for their fruitful application in photoconductive devices. The efficiency of devices is found to increase with % of Indium.

Optoelectronics characteristics of chemically synthesized Cu(In1-xGax)Se2 based Schottky and heterojunctions

CIGS is an important photovoltaic material in recent years. In this work, we have performed a comparative analysis of various conduction mechanism in CIGSe2 based Schottky and hetero junction nanostructures. Cu(In1-xGax)Se2 nanostructure dispersed in PVP matrix has been synthesized through chemical bath deposition method at a compositional variation x = 0-1. The structural and optical characterization are done and correlated with the In/Ga fraction ratio. The conduction mechanism for both Schottky and hetero structures has been analyses and systematically co-related with compositional variation of In/Ga. By using the thermionic theory, the diode parameters ideality factor, saturation current, barrier height is determined in hetero junction device and co related with composition of Cu(In1-xGax)Se2. Richardson-Schottky(RS) mechanism is found to be dominant in Schottky type junction whereas both Pool-Frenkel(PF) and Richardson-Schottky(RS) mechanism is involved in hetero junction at different range of bias. Our findings points to Cu(In1-xGax)Se2 nanostructures synthesized at x = 0, 0.3,0.5 as promising candidate for solar cell because of their optimum diode parameters and band gap for absorption of maximum solar radiation.

Investigation of electrical, photodiode and photovoltaic properties of Au/SiO2/n-Si structures with GO and P3C4MT interface

This study mainly focused on investigating the electrical and photodiode properties of Au/SiO2/n-Si heterostructures with graphene oxide (GO) and poly(3-cyclohexyl-4-methyl-2,5-thiophene) (P3C4MT) interface. For this, GO and P3C4MT thin layer was grown as an interfacial layer between Au and SiO2/n-Si to create this Au/(GO:P3C4MT)/SiO2/n-Si hetero structure. From the current–voltage (I–V) measurements, the values of electrical and photodiode parameters such as ideality factors (n), rectification ratios (RR), saturation currents (I0), barrier heights (Φbo), photocurrent (Iph), photosensivity (RR), photoresponse (R), and detectivity (D*) were examined under dark and variable illuminations (from 20 to 100 mW/cm2 by 20 mW/cm2 steps) at room temperature, respectively. Au/(GO:P3C4MT)/SiO2/n-Si heterostructure exhibited a photoconducting behavior under variable illuminations. Furthermore, the photovoltaic properties such as short circuit current (Isc) and open circuit voltage (Voc) were examined under variable illuminations intensities. The experimental results shows that Au/(GO:P3C4MT)/SiO2/n-Si hetero structure under light illumination exhibits a perfect photodiode behavior, and thus this structure can be used as photodiode in optoelectronic devices.

Unlocking the full potential of monolithic perovskite/biPoly™ Si tandem devices through in-depth analysis and detailed engineering

Perovskite/Si tandem solar cells have emerged as one highly promising tandem configuration of tandem devices for 1-Sun photovoltaic systems. Up to now, heterojunction (HJ) cells have been the dominant silicon bottom cell structure and holds the record efficiency of dual-junction perovskite/Si tandem cells, whereas the investigation on perovskite/Si tandem cells using Si bottom cells that dominate today's mass markets (such as PERC and TOPCon) is still limited. In this work, we delve into the crucial optical and electrical engineering aspects required for perovskite/Si devices based on bifacial TOPCon structures (biPoly™), which has high efficiency potential as a single-junction Si cell, enables TCO-free contacts and is expected to be compatible with current mass production technologies. Simulations predict that such devices can potentially achieve a current density of 20.4 mA/cm2 despite of the parasitic absorption in poly-Si layers, comparable to that of HJ-based perovskite-Si tandem devices. We also demonstrate through simulations that edge and peripheral recombination effects can be mitigated by selecting an appropriate substrate size and employing locally doped poly-Si layers. Such improvements are also preliminarily verified with a prototype device. By carefully designing device structures and advancing fabrication techniques, perovskite/biPoly™ Si tandem cells can come closer to realizing the full potential of biPoly™ cells and achieve efficiencies comparable to those observed in devices utilizing HJ cells.

Theoretical designing of TMDs Janus heterostructures toward efficient photovoltaic and electronic applications

The breakthroughs in designing heterostructures offer advanced frontier to versatile electronic and optoelectronic technology where TMDs based heterojunctions are widely discussed due to fascinating properties. Even, MoSTe/WSTe lateral heterostructure (HS) toward solar cell applications and negative differential resistance (NDR) based devices is yet to be studied. Here, structural, electronic and optical properties of MoSTe and WSTe monolayers along with their lateral and vertical heterostructures have been explored systematically using density functional theory (DFT). The electronic band structures infer semiconducting characters for all considered materials where results declare type-II band alignment for both heterostructures. Remarkably, band gap varies from 1.32 to 0.94 eV for lateral HS due to applied electric field up to 2.5 V/Å. Moreover, the absorption coefficient up to the order of ∼ 7 × 105 is achieved in visible region which validates use of considered materials as best absorber in optoelectronic devices. Dominantly, the SQ efficiency of 33.88 % and 33.75 % are predicted for WSTe monolayer and MoSTe/WSTe lateral HS, respectively which would realize high selectivity of these materials as solar cell device. Through analyzing current-voltage characteristics, significant current (in the range of µA to mA) with NDR behavior is revealed for both monolayers and their vertical HS. In addition, limited threshold voltage (< 1.5 V) and large PVR of 161 and 247 are estimated for MoSTe and WSTe monolayers, respectively. Consequently, present work explores tuning of considered materials in tunneling electronic devices such as oscillators, amplifiers, switching devices and most importantly in solar cell (especially WSTe monolayer and LHS) and other PV devices due to outstanding optical behavior.

Nonlinear optical properties of modified Möbius squared potential well: influence of electric and magnetic fields

ABSTRACT This work presents a numerical study on the electronic and optical properties of modified Möbius squared potential well in the presence of static electric and magnetic fields. The potential well is formed within GaAs/AlGaAs hetero structures. Schrödinger’s equation is solved within the framework of effective mass and envelope wave function approximations to get the wave functions and their corresponding energies of states. The optical absorption coefficients and relative refractive index changes are calculated via the expressions derived from the compact density matrix approach. The numerical results present strong blue shifts on the optical responses of modified Möbius squared potential well when the external electromagnetic fields are strengthening.

Accelerated damp-heat testing at the cell-level of bifacial silicon HJT, PERC and TOPCon solar cells using sodium chloride

Bifacial passivated emitter and rear cells (PERC) currently have the highest share in the photovoltaic market. However, heterojunction (HJT) and tunnel oxide passivated contact (TOPCon) solar cells are expected to gain significant market share shortly. Despite technological advancements, concerns about the reliability of HJT and TOPCon technologies when deployed in the field still need to be addressed. This work investigates the impact of sodium chloride (NaCl) on damp-heat-induced degradation in bifacial HJT, PERC, and TOPCon solar cells by exposing the solar cells to NaCl before damp heat (DH) testing. It is found that among all investigated cell technologies, TOPCon solar cells degrade the most with maximum power (Pmax) loss of up to ∼75%rel, followed by HJT (Pmax drops ∼50%rel), and PERC cells (Pmax drops only ∼10%rel) after 20 h of DH testing, mainly attributed to an increase in Rs on the front side of TOPCon cells, both sides of HJT cells and the rear side of PERC cells. The front of the PERC and the rear of the TOPCon solar cell are found to be stable. The rise in Rs is attributed to the corrosion of the metal contact, which is caused by a high amount of Na+ and Cl− ions penetrating the metal contact. This corrosion leads to increased porosity, detachment of the contact from the silicon interface, and increased recombination loss in some cases. These results are crucial for all cell technologies as they highlight the potential failures that could occur in the field. Na+ and/or Cl− ions are common contaminants present in solar glass, human fingerprints, soldering flux, rainwater, soil/dust, and seawater. During field operation, these ions have the potential to penetrate and directly interact with solar cells. In our view, the preferred solution is for the solar cells to be corrosion-resistant, which can be rapidly assessed using the method presented in this work.

Hierarchical NiCo-LDH@MoS2/CuS composite as efficient trifunctional electrocatalyst for overall water splitting and asymmetric supercapacitor

The development of highly active and long-lived multifunctional electrocatalysts is a key priority to boost clean renewable energy technologies. It is difficult to construct such hierarchically structured materials with an efficient synergistic heterostructure technique to improve electrochemical performance. Here, a novel hierarchical NiCo-LDH@MoS2/CuS heterostructure (HS) was prepared by facile two-step hydrothermal synthesis for water splitting and supercapacitor applications. The hierarchical network of NiCo-LDH is grown on MoS2/CuS and is put forward based on various physio-chemical analysis. The hierarchical structure and heterostructure synergistic effect result in excellent HER (114 mV@10 mA cm−2) and OER (310 mV@10 mA cm−2) activity. Two electrode water-splitting cells (NiCo-LDH@MoS2/CuS||NiCo-LDH@MoS2/CuS) achieved a cell potential of 1.57 V@10 mA cm−2. NiCo-LDH@MoS2/CuS also exhibits the electrochemical charge storage property of 147.16 mAh g−1@0.2 A g−1. NiCo@MoS2/CuS||AC flexible solid-state asymmetric supercapacitor (FSSC) demonstrated charge storage of 226.08 mAh g−1 and energy density of 152.60 W h kg−1@0.2 A g−1 with 90.05 % retention rate, demonstrated the excellent cyclic and structural stability. The acquired knowledge from this study could be a novel strategy for designing hierarchical LDH-based heterostructures as electrode materials for water splitting and energy storage devices.

Interfacial structures evolution at hetero interfaces in SiCf/SiC | Nb | SiCf/SiC sandwich cladding structure

The appropriate hetero interfacial structure between metal and ceramics is a challenging topic in materials science. In this paper, a sandwich hybrid cladding structure made of SiCf/SiC composite and refractory metal niobium (Nb) is designed for application in a lead-cooled fast reactor. A diffusion reactive interfacial layer composed of β-SiC | NbC | Nb5Si4C | α-Nb5Si3 | β-Nb2C | Nb between SiCf/SiC composite and Nb is experimentally validated after heat treatment in a simulating reactor environment. Moreover, Kirkendall voids are found at the interface between Nb5Si4C and Nb5Si3 sublayers when the annealing temperature is higher than 1500 °C. Lastly, the formation mechanisms of interfacial structures are revealed based on thermodynamics and kinetics, meanwhile the diffusion coefficients k at 1500 °C and activation energy are calculated to be 2.81 × 10−14 m2/s and 270 kJ/mol, respectively. This work provides a practical strategy for developing hybrid composites of metal/ceramic matrix composites.

Evidence of charge transfer across the organic-inorganic hetero-junction based visible light driven photo-catalyst

Organic-inorganic hetero-junction based catalysts with efficient charge separation ability for superior photo-catalytic activity have been developed by chemical methods. Titanium dioxide (TiO2) and polypyrrole (PPy) as single photo-catalyst have been investigated and compared with TiO2/PPy hetero-junction composite. TiO2/PPy composite has enhanced efficiency for the degradation of toxic organic dye methylene blue (MB) through the charge transfer route. Broad curves in UV-Vis spectra arise due to polaron and bipolaron in PPy and TiO2/PPy composite. The de-localized polaron (Landé g factor value of 1.99) was further detected by electron spin resonance (ESR). The effect of polaron-bipolaron on the structure of as-synthesized PPy and TiO2/PPy composite has been explored by Raman spectroscopy. The oxidation state of different species and electronic structures below the Fermi level has been investigated by x-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS), which provides molecular orbitals insight and charge transfer state across the hetero-junction TiO2/PPy composite. Collectively, UPS and UV-Vis spectroscopy gives the energy positions (valence/ HOMO band and conduction band (C.B.)/LUMO) for TiO2 and PPy having straggled type band alignment which confirms the hetero junction in the composite.

Reducing Indium Consumption in Silicon Hetero Junction Solar Cells With TCO Stack Systems of ITO and AZO

Reducing Indium Consumption in Silicon Hetero Junction Solar Cells With TCO Stack Systems of ITO and AZO

Assessment of different optimized anti-reflection coatings for ZnO/Si heterojunction solar cells

The heterojunction (HJ) solar cell is one of the superlative alternatives to upgrade traditional single homojunction silicon-based solar cells. The present paper reports on the simulation investigation for examining the high-performance Zinc oxide (ZnO)/Si solar cells with different anti-reflection coatings (ARC), optimizing the absorber, window thickness, and ARC layers. In this study, the parameters were selected, like ZnO as a window layer, Si as an absorber layer, and the thickness of different ARC layers to perform PC1D (personal computer one dimensional) simulation. Aluminum trioxide (Al2O3), Magnesium oxide (MgO), Magnesium fluoride (MgF2), and Titanium nitrate (TIN) were used as a single layer. Without any ARC layer, 18.8% power conversion efficiency (PCE) and 21.3% PCE were recorded for ZnO/Si solar cells at zero reflectance. The MgF2 as a single ARC layer of 110 nm thickness has achieved a PCE of 20.8% compared to other anti-reflection coating materials at an absorber layer of 160 μm and window layer of 0.5 μm. The optimized value of carrier lifetime was found to be 100μs for ARC layers. The values of PCE, Voc and Isc gradually increased with increasing carrier lifetime. The maximum values of Voc = 0.6580, Isc = 0.0386 A and PCE with 20.8% were achieved by MgF2 ARC layer at optimized parameters.

Synthesis and Crystal Structures of Three Thioether Functionalized Lithium Silylamides

AbstractA series of three lithium silylamides Li2Me2Si(NC6H4‐2‐SR)2 (R=Me, Ph, tBu) were prepared from the reaction of the corresponding silylamines Me2Si(NH‐C6H4‐2‐SR)2 with n‐butyl lithium. X‐ray single crystal structure analyses revealed the formation of dimers [Li4{Me2Si(NC6H4‐2‐SR)2}2] with Si2N4Li4 hetero‐adamantane cores. Recrystallisation of [Li4{Me2Si(NC6H4‐2‐SMe)2}2] and [Li4{Me2Si(NC6H4‐2‐SPh)2}2] from diethyl ether led to the formation of the adducts [Li4(Et2O)2{Me2Si(NC6H4‐2‐SMe)2}2] and [Li4(Et2O){Me2Si(NC6H4‐2‐SPh)2}2]. In the case of the SMe derivative the addition of two diethyl ether molecules led to a rearrangement of the Si2N4Li4 core to give a double decker structure and in contrast the hetero adamantane structure is retained in the diethyl ether adduct of the SPh derivative.

Ultrafast Hole Migration at the p-n Heterojunction of One-Dimensional SnS Nanorods and Zero-Dimensional CdS Quantum Dots.

The p-n heterojunctions fabricated from one-dimensional (1D) p-type tin sulfide nanorods (SnS NRs) decorated with n-type zero-dimensional (0D) cadmium sulfide quantum dots (CdS QDs) have gained significant research attention in energy storage devices. Herein, we have successfully synthesized a 1D/0D SnS@CdS heterostructure (HS) using a hot injection method. Structural and morphological studies clearly suggest that CdS QDs are uniformly anchored on the surface of SnS NRs, resulting in intimate contact between two components. The photoluminescence (PL) study revealed the transfer of photoexcited holes from CdS QDs to SnS NRs, which was further confirmed by transient absorption (TA) studies. TA measurements demonstrate the hole transfer from the valence band of CdS QDs to SnS NRs and delocalization of electrons between the conduction band of SnS NRs and CdS QDs in SnS@CdS HS, resulting in efficient charge separation across the p-n heterojunction. These findings will open up a new paradigm for improving the efficiency of optoelectronic devices.

Strain-regulated electronic and optical properties of InSe/WS2 heterostructure from first-principle calculations

InSe/WS2 heterostructure (HS) was constructed in this study to combine the excellent properties of these two monolayer semiconductors. The calculation of enthalpy of formation, phonon spectrum, and elastic constants of heterostructure based on first-principle proves that InSe/WS2 HS has good stability and mechanical property. The study of electronic properties illustrates that InSe/WS2 HS is a type II direct band gap semiconductor with photogenerated electrons (holes) located mainly on the InSe (WS2)-layer, the electron mobility of heterostructure increased a lot (4357.65 cm2V−1s−1), and the hole mobility enhanced a little after the combination of the heterostructure. In addition, the band gap is greatly reduced, providing it with a stronger light absorption capability. Likewise, optical properties (absorption coefficient, reflectivity, loss function, refractive index, dielectric function, and photoconductivity) can be modulated under applied biaxial strain. More importantly, the band gap can be significantly tuned under applied strain (direct ⇆ indirect, 0.02 eV ∼ 1.5eV) to meet the different requirements of devices for semiconductor devices.

Rashba spin-splitting in Janus SnXY/WXY (X, Y = S, Se, Te; X ≠ Y) heterostructures.

Janus transition metal dichalcogenide monolayers have shown a lack of mirror symmetry perpendicular to the 2D plane. The breaking of out-of-plane symmetry, along with the spin-orbit coupling, induces Rashba spin-splitting in these materials. In this work, Rashba spin splitting in Janus tin dichalcogenide monolayers are studied. In addition, the heterostructures of Janus SnXY and WXY (X, Y = S, Se, Te; X 6 = Y) monolayers are discussed. A Rashba spin-splitting energy of about 43 meV, more significant than the room temperature energy, is observed in the Janus SnSSe/WSSe heterostructure. The consequences of vertical strain on the semiconducting heterostructure are examined. Compressive vertical strain enhances the Rashba splitting, and tensile strain reduces the spin-splitting. For the compressive strain of 10.4%, Janus SnSSe/WSSe heterostructure remains semiconductor with only Rashba bands surrounding near the Fermi level. Enhanced Rashba parameter of about 0.96 eVÅ and splitting energy of about 72 meV are observed. These findings confirm that Janus SnSSe/WSSe heterostructure is a productive Rashba material for spintronic device applications.

Enhanced machine learning for nanomaterial identification of photo thermal hydrogen production

Instead of using temperature via an outside source, using energy created inside is the most effective method to improve the efficiency of catalysis. In this research, a novel hollowed TiO2 photothermal nano catalyst (referred to as RuO2/TiO2/Pt/Carbon) for enzymatic production of hydrogen under ultraviolet irradiation is used. It resembles a hedgehog and contains regionally dispersed Pta and RuO2 double co-catalysts. The ultraviolet (UV) thermos kinetic efficacy of the converters that were made was evaluated according to architectural characteristics and the heat influence of the carbon-based surface. There are several inherent benefits for photocatalysis with heterogeneity exist in multi-layered hollowed hetero structures having extremely thin two-dimensional (2D) nanosheet subunits of the including improved sunlight gathering, accelerated separation of charged particles and disposal, and accelerated interface oxidation reactions. The sandwich-like nanotechnology of the charcoal layer, silver tiny particles, and TiO2 surface effectively supports and protects Pt Micro particle against the accumulation and breaking down of Platinum sites that are active. Moreover, the electricity production of the reaction involving hydrogen evolution is nonetheless in its infancy, and there is tonnes of untapped potential for the use of Machine Learning (ML). The following perspective focuses on new developments in the detection of outstanding performance Hydrogen Evolution Reaction (HER) catalysts using Artificial Intelligence (AI) in an effort to stimulate more broad proposals for research. In the course of the research, an Artificial Neural Network (ANN) strategy was created and validated in order to forecast the results of the hydrogen assessment. The analysis of the dataset's test results demonstrates that the ANN technique can reliably and accurately estimate the generation of hydrogen.

Multiple modulation of magnetism in two-dimensional FeCl2/In2Se3 van der Waals heterostructure

The effective modulation of magnetism for two-dimensional (2D) materials not only has potential applications in nanoscale spintronic devices but also has urgent demands in modern industries. In this work, we report the discovery of ferroelectrically (FE) tunable orbital reconstruction in FeCl2/In2Se3 2D van der Waals (vdWs) heterostructures (HSs), which leads to a transition from ferromagnetic (FM) order to ferrimagnetic order (intra-layer magnetic coupling is AFM3 arrangement). The reversible FE polarization not only enables the easy magnetization axis to be tuned from the out-of-plane to in-plane direction but also reduces the net magnetization strength from 31.87 to −0.18 μB/f.u. Based on the charge density differences and the density of states analysis, the preference of FM and AFM3 arrangement can be reasonably explained by the Goodenough–Kanamori–Anderson rule. The ferroelectric switching enables nonvolatile electric control of magnetic order and anisotropy, offering significant potential for high-efficiency nanodevices and nonvolatile information storage. Moreover, modulation of magnetism (magnetic moment from −0.18 to 0.18 μB/f.u.) can also be achieved through interlayer sliding in the −P case, providing a way to control magnetism in 2D vdWs HSs.