Edge Passivation Research Articles

Structural, electronic, and magnetic properties of binary zigzag antimonene-phosphorene nanoribbons and their mole fractions with different edge passivation: A DFT investigation

The study focuses on binary antimonene-phosphorene, a two-dimensional semiconductor material known for its high carrier mobility, suitable band gap, and strong environmental stability, making it appealing for electronics and spintronics applications. In this study, using density functional theory, we investigated the structural stability and electronic-magnetic properties of zigzag SbP nanoribbons, as well as single Sb and single P nanoribbons. Various edge passivation (H, F, Cl, O, S) are considered, along with different phosphorus mole fractions. The findings show that SbP structures with 25% phosphorus mole fractions, as well as those passivated with various atoms, demonstrate strong conformational stability. SbP nanoribbons passivated with H, F, and Cl exhibit non-magnetic semiconductor behavior, while those passivated with O and S display magnetic metallic properties. Maximal magnetization is observed in SbP nanoribbons passivated with single S atoms, particularly magnetizing both Sb and P atoms at the edges. Additionally, SbP nanoribbons passivated with dual O atoms show negative differential resistivity and a complete spin filtering effect (100%). The study also investigates the variation in magnetization across structures with different phosphorus mole fractions. Overall, the study demonstrates that adjusting phosphorus mole fractions and edge passivation can significantly modify the electronic and magnetic properties of SbP nanoribbons, making them suitable for spintronic nanodevices.

Electronic structure regulation of AlN/SiC nanoribbons through edge passivation with different atoms and doping with various transition metal atoms

Electronic structure regulation of AlN/SiC nanoribbons through edge passivation with different atoms and doping with various transition metal atoms

Optimization of the deposited Al2O3 thin film process by RS-ALD and edge passivation applications for half-solar cells

Optimization of the deposited Al2O3 thin film process by RS-ALD and edge passivation applications for half-solar cells

27.09%-efficiency silicon heterojunction back contact solar cell and going beyond

Crystalline-silicon heterojunction back contact solar cells represent the forefront of photovoltaic technology, but encounter significant challenges in managing charge carrier recombination and transport to achieve high efficiency. In this study, we produced highly efficient heterojunction back contact solar cells with a certified efficiency of 27.09% using a laser patterning technique. Our findings indicate that recombination losses primarily arise from the hole-selective contact region and polarity boundaries. We propose solutions to these issues and establish a clear relationship between contact resistivity, series resistance, and the design of the rear-side pattern. Furthermore, we demonstrate that the wafer edge becomes the main channel for current density loss caused by carrier recombination once electrical shading around the electron-selective contact region is mitigated. With the advanced nanocrystalline passivating contact, wafer edge passivation technologies and meticulous optimization of front anti-reflection coating and rear reflector, achieving efficiencies as high as 27.7% is feasible.

Modification Strategies and Prospects for Enhancing the Stability of Black Phosphorus.

Black phosphorus is a two-dimensional layer material with promising applications due to its many excellent physicochemical properties, including high carrier mobility, ambipolar field effect and unusual in-plane anisotropy. Currently, BP has been widely used in biomedical engineering, photocatalysis, semiconductor devices, and energy storage electrode materials. However, the unique structure of BP makes it highly chemically active, leading to its easy oxidation and degradation in air, which limits its practical applications. Recently, researchers have proposed a number of initiatives that can address the environmental instability of BP, and the application of these physical and chemical passivation techniques can effectively enhance the environmental stability of BP, including four modification methods: covalent functionalization, non-covalent functionalization, surface coordination, physical encapsulation and edge passivation. This review highlights the mechanisms of the above modification techniques in addressing the severe instability of BP in different application scenarios, as well as the advantages and disadvantages of each method. This review can provide guidance for more researchers in studying the marvellous properties of BP and accelerate the practical application of BP in different fields.

Effect of staggered sublattice potential on electronic and transport properties of Bi(111) pristine and hydrogen-passivated nanoribbons

We investigate the impact of staggered sublattice potential (SSP) on the electronic and transport properties of Bi(111) bilayer and nanoribbons through first-principle calculations and the nonequilibrium Green's function method. We find that the topological phase transition of Bi(111) bilayer from topologically nontrivial (Z 2 = 1) to topologically trivial (Z 2 = 0) occurs at Δ = 1.77 eV SSP. Our study also reveals that energy bandgap opens for both pristine zigzag and armchair nanoribbon as the strength of the SSP (Δ > 1.50 eV for armchair nanoribbons and Δ > 1.90 eV for zigzag nanoribbons) increases, transitioning from non-trivial metallic edge states to insulating edge states. Furthermore, we explore the influence of SSP on edge-passivated zigzag nanoribbon. Through edge passivation, the dangling bonds are eliminated. As a result, it requires 0.4 eV less SSP to open an energy gap in edge-passivated nanoribbons compared to pristine nanoribbons. These findings hold promise for the advancement of Bi(111) nanoribbon-based field-effect transistors and spintronic devices.

Spin-filtering properties of topological structures based on stanene and bismuthene nanoribbons with one edge magnetism

The transport properties of spin filters based on two-dimensional magnetic topological insulators (TI) with magnetism at one edge are theoretically studied. The non-equilibrium-Green’s-function (NEGF) formalism based on density functional theory (DFT) derived Hamiltonian is used to study the one-way helical edge states in these structures. We investigated the electronic and magnetic properties of stanene and bismuthene nanoribbons with various metal edge modifications. Our DFT simulations predict the formation of one-way helical edge states in stanene nanoribbons with asymmetric edge passivation. Our results suggest that the spin filtering properties of such structures outperform a comparable spin filter based on spin-polarized quantum-anomalous-Hall effect, as it bypasses a need for a strict interplay of magnetism, topology, and a large electric field (around 2 V gate voltage difference).

Preparation of Al2O3 thin films by RS-ALD and edge passivation application for TOPCon half solar cells

A rotary spatial atomic layer deposition (RS-ALD) method is proposed for the preparation of high-quality Al2O3 thin films and its application to the edge passivation of tunnel-oxide passivated contact (TOPCon) half solar cells. The high- quality Al2O3 thin films were prepared on silicon wafers by optimizing the process conditions with a process pressure of 4 Torr and a trimethylaluminum (TMA, (CH3)3Al) flow rate of 300 sccm. The Al2O3 thin films were annealed to analyse the transformation of the film crystal structure, surface morphology, and passivation properties. Compared to the half solar cells without edge passivation, the efficiency of the cell with only deposited Al2O3 increased by 0.098 %, and the module power increased by 3.08 W. The efficiency of the cell with deposited Al2O3 + annealing increased by a further 0.021–0.119 %, and the module power increased by a further 0.68–3.76 W.

Edge-Passivated Monolayer WSe2 Nanoribbon Transistors.

The ongoing reduction in transistor sizes drives advancements in information technology. However, as transistors shrink to the nanometer scale, surface and edge states begin to constrain their performance. 2Dsemiconductorsliketransition metal dichalcogenides (TMDs)have dangling-bond-free surfaces, hence achieving minimal surface states. Nonetheless, edge state disorder still limits the performance of width-scaled 2D transistors. This work demonstrates a facile edge passivation method to enhance the electrical properties of monolayer WSe2 nanoribbons, by combining scanning transmission electron microscopy, optical spectroscopy, and field-effect transistor (FET) transport measurements. Monolayer WSe2 nanoribbons are passivated with amorphous WOxSey at the edges, which is achievedusing nanolithography and a controlled remote O2 plasma process. The same nanoribbons, with and without edge passivation are sequentially fabricated and measured. The passivated-edge nanoribbon FETs exhibit 10 ± 6 times higher field-effect mobility than the open-edge nanoribbon FETs, which are characterized with dangling bonds at the edges. WOxSey edge passivation minimizes edge disorder and enhances the material quality of WSe2 nanoribbons. Owing to its simplicity and effectiveness, oxidation-based edge passivation could become a turnkey manufacturing solution for TMD nanoribbons in beyond-silicon electronics and optoelectronics.

Contactless edge for edge recombination optimization in solar cell

AbstractAs the conversion efficiency of solar cell approaching its theoretical limits, reducing the power loss during the collection and transmission process is a promising way to improve the performance of solar cell. Cleaved edges create recombination centers, causing up to 0.8%abs (absolute efficiency) of power loss or even more for 156 × 156 mm silicon solar cell. Due to the complexity of edge passivation technique, alternative methods are desired. This article proposes a method to minimize this problem. It is found that most of the recombination current of edge comes from the recombination near the contact and the space charge region (SCR). As a result, keeping the cleaved edge a certain distance away from the contacts and SCR can improve performance effectively. On the other hand, contactless edge can reduce the recombination from the SCR without extra manufacturing difficulty. The results indicate the edge recombination loss can be reduced to less than 0.4%abs after the distance is optimized appropriately.

Theoretical Investigation of Transport Properties of X-doped (X = Cl, P, N) Graphene Quantum Dots Layer Adsorbed with Ammonia Molecule Using Non-Equilibrium Green’s Function

This study investigates the various transport properties, including Density of States (DOS), Transmission Coefficient, Current-Voltage Characteristics (I-V), and HOMO-LUMO energy levels, of X-doped (X = Cl, P, N) graphene quantum dot (GQD) layers with adsorbed ammonia molecules using density functional theory and non-equilibrium Green's function techniques. Our findings revealed the profound influence of different doping and adsorption scenarios on the transport properties of GQD layers. Specifically, chlorine doping leads to notably stronger resonance peaks, resulting in enhanced conductivity of the GQD layer. This effect is less pronounced for P-doped and N-doped GQDs, which exhibit minimal changes in conductance capability. Importantly, we observed a prominent interaction between ammonia molecules and chlorine-doped GQD layers. The HOMO and LUMO energy levels exhibit double degeneracy, significantly impacting edge passivation and the finite dimensions of GQDs, consequently reducing the energy gap. As a result, chlorine-doped GQD layers with adsorbed ammonia molecules exhibit increased energy levels and stronger current characteristics compared to P-GQDs and N-GQDs. HOMO and LUMO are doubly degenerated which has a clear effect on edge passivation as well as the finite size of GQDs and reduces energy gap. Therefore, more energy level and stronger current is available for chlorine doped graphene quantum dots layer with adsorbed ammonia molecule than P-GQDs and N-GQDs. Our theoretical finding highlighted the significant features of edge passivation, doping effect and adsorption of ammonia molecule onto graphene quantum dots layer. Our theoretical analysis highlighted key features encompassing edge passivation, doping effects, and ammonia molecule adsorption on GQD layers. These insights not only develop our fundamental understanding of these systems but also hold promise for novel applications that harness their distinct electronic properties.

Edge passivation: Considerable improvement in photovoltaic performance of perovskite/silicon tandem solar cells

Edge recombination is considered hard to avoid entirely in silicon (Si) solar cells as well as Si-base solar devices, hindering their future commercialization. However, such an important issue in perovskite/silicon (PK/Si) tandem solar cells has not attracted much attention. Herein, a low-temperature, non-vacuum liquid-based edge passivation strategy (LEPS) to improve the power conversion efficiency (PCE) of PK/Si tandem solar cells is proposed. The minority carrier lifetime (τeff) of the PK/Si tandem sample with 495.8 μs significantly enhances to 739.7 μs after passivating the Si sub-cell edge recombination. The open circuit voltage (VOC) of the PK/Si tandem solar cell increases by up to +3.8%abs from the initial state after LEPS treatment due to edge passivation, leading to the PCE of the PK/Si tandem solar cell increases by up to +1.2%abs. Finally, a monolithic PK/Si tandem cell with a PCE of 29.48% was achieved by further utilizing the LEPS, which opened up a simple and effective avenue for enhancing the PCE of PK/Si tandem solar cells and further promoting a higher photovoltaic output power of tandem modules.

Investigating the impact of edge passivation on shingle solar modules

This work deals with solar modules made from rectangular-shaped solar cell strips, so-called shingles, that are interconnected by overlapping one with another. For the fabrication of such modules, host solar cells are cut into several shingles resulting in unpassivated shingle cell edges and relevant recombination losses. As discussed in this work based on simulations, quantifying these losses on module level is not straightforward and is ideally done by referring to the pseudo fill factor pFF. In this context, it is shown that by passivating the cut edges of the shingles by depositing a dielectric layer, a significant pFF increase can be achieved both on shingle as well as on module level. Considering the highest respective pFF value found for modules with and without edge passivation, an increase of ΔpFF = 0.5%abs is reached. At the same time, no significant compromise of the interconnection quality is observed. These results are obtained for monofacial passivated emitter and rear cell (PERC) shingles. In short, this work is the first comprehensive analysis of experimental data on module level in the context of edge passivation. It demonstrates that the deposition of a dielectric passivation layer at the shingle's edges can boost pFF of shingle solar modules, while the current transit between the busbars of jointed shingles is not significantly hindered.

Backscattering-free edge states below all bands in two-dimensional auxetic media

Unidirectional and backscattering-free propagation of sound waves is of fundamental interest in physics and highly sought-after in engineering. Current strategies utilize topologically protected chiral edge modes in bandgaps or complex mechanisms involving active constituents or nonlinearity. Here, we propose a new class of passive, linear, one-way edge states based on spin-momentum locking of Rayleigh waves in two-dimensional media in the limit of vanishing bulk modulus, which provides 100% unidirectional and backscattering-free edge propagation immune to any edge roughness at a broad range of frequencies instead of residing in gaps between bulk bands. We further show that such modes are characterized by a new topological winding number that is analogous to discrete angular momentum eigenvalues in quantum mechanics. These passive and backscattering-free edge waves have the potential to enable a new class of phononic devices in the form of lattices or continua that work in previously inaccessible frequency ranges.

Impact of uniaxial strain on physical properties of zigzag graphene nanoribbons with topological defects

The synergistic regulation mechanism of uniaxial strain, topological defects, edge passivation atom and nanoribbon width on the geometric and electronic structures of zigzag graphene nanoribbons have been studied systematically by first-principles. It is found that the average formation energy and strain energy of X-N 1 N 2-LD-ZGNR (X = H, F and O, as well as, N 1 = N 2 = 3, 4 and 5) increase with the increase of uniaxial strain, and this relationship is also dependent of edge passivation atom species and nanoribbon width. And the edge of 55-LD-ZGNR passivating with O and F atoms is more beneficial than H atom for system stability. The stress–strain curve shows that the limiting strain of zigzag graphene nanoribbon depends on edge passivation atom species and nanoribbon width. The Young’s modulus in the case of ε > 3% and Poisson’s ratio except O-33-LD-ZGNR at ε = 1% of X-N 1 N 2-LD-ZGNR decrease with the increase of the tensile strain, and is dependent of nanoribbon width and edge atom species. And O-55-LD-ZGNR is easier than F-55-LD-ZGNR and H-55-LD-ZGNR to be stretched or compressed. The magnetism is induced in both H-55-LD-ZGNR and F-55-LD-ZGNR, and remains with the increases of uniaxial tension strain. What is more, magnetic property of O-55-LD-ZGNR can be regulated by applying uniaxial strain, and the band gap of the O-N 1 N 2-LD-ZGNR (N 1 = N 2 = 3, 4 and 5) system can be regulated by adjusting the uniaxial tensile strain and nanoribbon width. Our research provides a new method to open the graphene band gap, which can provide some new theoretical guidance for the application of graphene in electronic devices and other fields. The band gap of the O-LD-ZGNDR system is opened as the uniaxial tensile strain increases.

Spin-selective transport in edge-passivated zigzag magnesium dichloride nanoribbons: Towards bipolar spin diode and spin rectification devices

In the present work, we investigate the electronic, magnetic, and spin transport properties of zigzag MgCl2 (ZMgCl2) nanoribbons with different types of edge passivation using first-principles calculations based on density functional theory and non-equilibrium Green’s function techniques. Our findings reveal that the ZMgCl2 nanoribbon with Cl edges (ClαClα) and Mg edges (MgMg) exhibits distinct properties depending on the type of passivation. Passivation with O and F on ClαClα edges transforms the nanoribbon into a magnetic semiconductor. Passivation with H and F on MgMg edges results in a semiconductor behavior, B passivation leads to a half-metal behavior, and O passivation to a magnetic semiconductor. Additionally, our transport simulations demonstrate that the ClαClα-F nanoribbon operates as a single spin filter under bias voltage. For the MgMg-B nanoribbon, the behavior varies depending on the magnetic configuration of the electrodes. In the parallel configuration, MgMg-B also functions as a single spin filter, whereas in the antiparallel configuration, it operates as a dual spin filter device. Overall, our results highlight the remarkable potential of two-dimensional MgCl2 for spintronics applications, emphasizing the influence of edge passivation on the electronic and transport properties of nanoribbons.

Challenges and advantages of cut solar cells for shingling and half-cell modules

Cutting silicon solar cells from their host wafer into smaller cells reduces the output current per cut cell and therefore allows for reduced ohmic losses in series interconnection at module level. This comes with a trade-off of unpassivated cutting edges, which result in power losses. This performance drop can be seen in fill factor FF and open-circuit voltage VOC losses on cut cell level. Based on experimental realization of different solar cell layouts on the same industrial blue wafers (solar cell precursors), a combined simulation method to predict the performance on module level is demonstrated. This method uses Gridmaster+ for cell simulation and SmartCalc. Module for module simulation. The accuracy of the simulations is demonstrated by comparing with experimental results both from host and cut cell level. In addition, significant influence of the current–voltage (I–V) measurement configuration is demonstrated, mainly affecting FF. Using flexible methods like GridTOUCH® for I–V testing gives fast results but can also lead to overestimation of the host cell performance, resulting in overestimated cell-to-module losses or unreasonable comparisons between hosts and cut cells. It is also demonstrated that application of the passivated edge technology (PET) yields I–V characteristics close to those of cells with ideal edges, i.e., without edge recombination. The implications on the module efficiency are also compared between modules built using cells with and without edge passivation, giving the highest efficiency for a shingled module with PET.

Investigating the enhancement of lung cancer sensing: the effect of edge halogenation in armchair stanene nanoribbons.

In this research, we explore the impact of edge passivation using halogen atoms on armchair stanene nanoribbon (ASNR) for the early detection of lung cancer biomarkers. We employ non-equilibrium green function (NEGF) and density functional theory (DFT) methods to evaluate sensing characteristics. The edges of ASNR are passivated with fluorine, chlorine, bromine, and iodine atoms. Our findings indicate a significant enhancement in sensing performance upon halogenation of ASNR. Notable changes in adsorption energy and current for edge-halogenated ASNR configurations demonstrate improved sensing behavior. Moreover, current curves exhibit greater distinctiveness of halogenated ASNR in comparison to hydrogenated ASNR. The calculations indicate a change in adsorption energy (Eads) of -7.59 eV, -7.6 eV, -8.3 eV, and -8.6 eV for the adsorption by styrene on I-ASnNR, Br-ASnNR, toluene on Cl-ASnNR, and styrene on F-ASnNR, respectively. The corresponding sensitivity improves up to 37.33%, 38.09%, 38.35%, and 45.5%, respectively. These findings highlight that the most significant change occurs with the edge fluorination of ASnNR. Our findings underscore the effectiveness of halogen atom edge passivation in ASNR for heightened sensing performance, making it a promising choice for the development of early-detection lung cancer sensors.

New approaches to edge passivation of laser cut PERC solar cells

Recently the development trend in the PV industry is towards much larger wafer formats. With increasing wafer area and the resulting increase in short-circuit current at the cell level, there is also a trend towards sub-cells (solar cell cut into smaller pieces) for module integration. Using sub-cells, the resistance losses through the connection can be reduced. Modules based on sub-cells achieve higher levels of fill factors and thus a higher nominal power. However, the energy yield of such sub-cells is reduced compared to full cells due to the non-passivated laser edge. The laser cut edge causes a high recombination of the charge carriers, which negatively affects the pseudo fill factor as well as open-circuit voltage of the cell. The current work introduces two different approaches for passivating the laser separated PERC solar cells. The experiments were performed on p-type PERC monofacial cells and laser scribe and mechanical cleavage (LSMC) technique was used to obtain sub-cells from the host cells. The method ‘laser scribing and simultaneous Al doping’ increases the pFF of the cleaved cells by +0.2–0.4%abs in comparison to the reference cleaved cells whereas the method ‘laser scribing and subsequent Al doping’ shows an improvement in efficiency of the cleaved cells by + 0.2% abs.

Electron-phonon interactions at the topological edge states in single bilayer Bi(111).

An intriguing feature of two-dimensional topological insulators is the topologically protected electronic edge state, which allows one-way carrier transport without backscattering. Although this feature has strong potential applications in lossless electronics, the ideal behavior of the edge states may be fragile due to electron-phonon (e-ph) interactions at room temperatures. Using density functional perturbation theory calculations for single bilayer Bi(111) as a prototypical 2D topological insulator, we show that e-ph scattering can be a significant source of backscattering at the topological edge states. We also show that e-ph interactions strongly correlate to the dispersions of the electronic edge states. In particular, the e-ph interactions increase significantly with temperature and are much stronger at the nonlinearly dispersed edge states of native edges compared to the linearly dispersed edge states of passivated edges, causing a significant energy dissipation in the temperature range of 200-400 K. Overall, we argue that the e-ph interactions can be a crucial factor at finite temperatures in controlling the electronic transport at the topologically protected edge states.