Showing papers on "Silicon published in 2022"

Efficient and stable perovskite-silicon tandem solar cells through contact displacement by MgFx

Abstract: The performance of perovskite solar cells with inverted polarity (p-i-n) is still limited by recombination at their electron extraction interface, which also lowers the power conversion efficiency (PCE) of p-i-n perovskite-silicon tandem solar cells. A MgFx interlayer with thickness of ~1 nanometer at the perovskite/C60 interface favorably adjusts the surface energy of the perovskite layer through thermal evaporation, which facilitates efficient electron extraction and displaces C60 from the perovskite surface to mitigate nonradiative recombination. These effects enable a champion open-circuit voltage of 1.92 volts, an improved fill factor of 80.7%, and an independently certified stabilized PCE of 29.3% for a monolithic perovskite-silicon tandem solar cell ~1 square centimeter in area. The tandem retained ~95% of its initial performance after damp-heat testing (85°C at 85% relative humidity) for >1000 hours. Description A fluoride boost The wide-bandgap perovskite layer in perovskite-silicon tandem solar cells is still limited by high interface recombination at the electron extraction interface. Liu et al. show that adding an ultrathin magnesium fluoride interlayer between the perovskite and C60 electron transport layer during growth facilitates mitigated nonradiative recombination. An analysis of electronic structural data showed that conduction band bending of the perovskite and C60 facilitated electron extraction. A monolithic perovskite-silicon tandem solar cell with a certified power conversion efficiency of 29.3% retained about 95% of its initial performance for 1000 hours. —PDS The surface energy of the perovskite layer at the C60 interface is favorably adjusted with a magnesium fluoride interlayer.

Carrier control in Sn–Pb perovskites via 2D cation engineering for all-perovskite tandem solar cells with improved efficiency and stability

Abstract: All-perovskite tandem solar cells are promising for achieving photovoltaics with power conversion efficiencies above the detailed balance limit of single-junction cells, while retaining the low cost, light weight and other advantages associated with metal halide perovskite photovoltaics. However, the efficiency and stability of all-perovskite tandem cells are limited by the Sn–Pb-based narrow-bandgap perovskite cells. Here we show that the formation of quasi-two-dimensional (quasi-2D) structure (PEA)2GAPb2I7 from additives based on mixed bulky organic cations phenethylammonium (PEA+) and guanidinium (GA+) provides critical defect control to substantially improve the structural and optoelectronic properties of the narrow-bandgap (1.25 eV) Sn–Pb perovskite thin films. This 2D additive engineering results in Sn–Pb-based absorbers with low dark carrier density (~1.3 × 1014 cm−3), long bulk carrier lifetime (~9.2 μs) and low surface recombination velocity (~1.4 cm s−1), leading to 22.1%-efficient single-junction Sn–Pb perovskite cells and 25.5%-efficient all-perovskite two-terminal tandems with high photovoltage and long operational stability. Tong et al. form a 2D perovskite layer with two large organic cations to improve the structural and optoelectronic properties of Sn–Pb perovskites, and eventually the performance of single-junction and tandem solar cells.

Status and perspectives of crystalline silicon photovoltaics in research and industry

Abstract: Crystalline silicon (c-Si) photovoltaics has long been considered energy intensive and costly. Over the past decades, spectacular improvements along the manufacturing chain have made c-Si a low-cost source of electricity that can no longer be ignored. Over 125 GW of c-Si modules have been installed in 2020, 95% of the overall photovoltaic (PV) market, and over 700 GW has been cumulatively installed. There are some strong indications that c-Si photovoltaics could become the most important world electricity source by 2040–2050. In this Review, we survey the key changes related to materials and industrial processing of silicon PV components. At the wafer level, a strong reduction in polysilicon cost and the general implementation of diamond wire sawing has reduced the cost of monocrystalline wafers. In parallel, the concentration of impurities and electronic defects in the various types of wafers has been reduced, allowing for high efficiency in industrial devices. Improved cleanliness in production lines, increased tool automation and improved production technology and cell architectures all helped to increase the efficiency of mainstream modules. Efficiency gains at the cell level were accompanied by an increase in wafer size and by the introduction of advanced assembly techniques. These improvements have allowed a reduction of cell-to-module efficiency losses and will accelerate the yearly efficiency gain of mainstream modules. To conclude, we discuss what it will take for other PV technologies to compete with silicon on the mass market. Crystalline silicon solar cells are today’s main photovoltaic technology, enabling the production of electricity with minimal carbon emissions and at an unprecedented low cost. This Review discusses the recent evolution of this technology, the present status of research and industrial development, and the near-future perspectives.

Understanding Performance Limiting Interfacial Recombination in pin Perovskite Solar Cells

Abstract: Perovskite semiconductors are an attractive option to overcome the limitations of established silicon based photovoltaic (PV) technologies due to their exceptional opto‐electronic properties and their successful integration into multijunction cells. However, the performance of single‐ and multijunction cells is largely limited by significant nonradiative recombination at the perovskite/organic electron transport layer junctions. In this work, the cause of interfacial recombination at the perovskite/C60 interface is revealed via a combination of photoluminescence, photoelectron spectroscopy, and first‐principle numerical simulations. It is found that the most significant contribution to the total C60‐induced recombination loss occurs within the first monolayer of C60, rather than in the bulk of C60 or at the perovskite surface. The experiments show that the C60 molecules act as deep trap states when in direct contact with the perovskite. It is further demonstrated that by reducing the surface coverage of C60, the radiative efficiency of the bare perovskite layer can be retained. The findings of this work pave the way toward overcoming one of the most critical remaining performance losses in perovskite solar cells.

A Silicon Monoxide Lithium-Ion Battery Anode with Ultrahigh Areal Capacity

Abstract: Abstract Silicon monoxide (SiO) is an attractive anode material for next-generation lithium-ion batteries for its ultra-high theoretical capacity of 2680 mAh g −1 . The studies to date have been limited to electrodes with a relatively low mass loading (< 3.5 mg cm −2 ), which has seriously restricted the areal capacity and its potential in practical devices. Maximizing areal capacity with such high-capacity materials is critical for capitalizing their potential in practical technologies. Herein, we report a monolithic three-dimensional (3D) large-sheet holey graphene framework/SiO (LHGF/SiO) composite for high-mass-loading electrode. By specifically using large-sheet holey graphene building blocks, we construct LHGF with super-elasticity and exceptional mechanical robustness, which is essential for accommodating the large volume change of SiO and ensuring the structure integrity even at ultrahigh mass loading. Additionally, the 3D porous graphene network structure in LHGF ensures excellent electron and ion transport. By systematically tailoring microstructure design, we show the LHGF/SiO anode with a mass loading of 44 mg cm −2 delivers a high areal capacity of 35.4 mAh cm −2 at a current of 8.8 mA cm −2 and retains a capacity of 10.6 mAh cm −2 at 17.6 mA cm −2 , greatly exceeding those of the state-of-the-art commercial or research devices. Furthermore, we show an LHGF/SiO anode with an ultra-high mass loading of 94 mg cm −2 delivers an unprecedented areal capacity up to 140.8 mAh cm −2 . The achievement of such high areal capacities marks a critical step toward realizing the full potential of high-capacity alloy-type electrode materials in practical lithium-ion batteries.

One-Step, Vacuum-Assisted Construction of Micrometer-Sized Nanoporous Silicon Confined by Uniform Two-Dimensional N-Doped Carbon toward Advanced Li Ion and MXene-Based Li Metal Batteries.

Abstract: With the advantages of a high theoretical capacity, proper working voltage, and abundant reserves, silicon (Si) is regarded as a promising anode for lithium-ion batteries. However, huge volume expansion and low electronic conductivity impede the commercialization of Si anodes. We devised a one-step, vacuum-assisted reactive carbon coating technique to controllably produce micrometer-sized nanoporous silicon confined by homogeneous N-doped carbon nanosheet frameworks (NPSi@NCNFs), achieved by the solid state reaction of a commercial bulk precursor and the subsequent evaporation of byproducts. The graphitization degree, C and N contents of the carbon shell, as well as the porosity of Si can be regulated by adjusting the synthetic conditions. A rational structure can mitigate volume expansion to maintain structural integrity, enhance electronic conductivity to facilitate charge transport, and serve as a protected layer to stabilize the solid electrolyte interphase. The NPSi@NCNF anode enables a stable cycling performance with 95.68% capacity retention for 4000 cycles at 5 A g-1. Furthermore, a flexible 2D/3D architecture is designed by conjugating NPSi@NCNFs with MXene. Lithiophilic NPSi@NCNFs homogenize Li nucleation and growth, evidenced by structural evolutions of MXene@NPSi@NCNF deposited Li. The application potential of NPSi@NCNFs and MXene@NPSi@NCNFs is estimated via assembling full cells with LiNi0.8Co0.1Mn0.1O2 and LiNi0.5Mn1.5O4 cathodes. This work offers a method for the rational design of alloy-based materials for advanced energy storage.

High-density switchable skyrmion-like polar nanodomains integrated on silicon

Abstract: Topological domains in ferroelectrics1-5 have received much attention recently owing to their novel functionalities and potential applications6,7 in electronic devices. So far, however, such topological polar structures have been observed only in superlattices grown on oxide substrates, which limits their applications in silicon-based electronics. Here we report the realization of room-temperature skyrmion-like polar nanodomains in lead titanate/strontium titanate bilayers transferred onto silicon. Moreover, an external electric field can reversibly switch these nanodomains into the other type of polar texture, which substantially modifies their resistive behaviours. The polar-configuration-modulated resistance is ascribed to the distinct band bending and charge carrier distribution in the core of the two types of polar texture. The integration of high-density (more than 200 gigabits per square inch) switchable skyrmion-like polar nanodomains on silicon may enable non-volatile memory applications using topological polar structures in oxides.

Heteroatoms (Si, B, N, and P) doped 2D monolayer MoS2 for NH3 gas detection

Abstract: 2D transition metal dichalcogenide MoS2 monolayer quantum dots (MoS2-QD) and their doped boron (B@MoS2-QD), nitrogen (N@MoS2-QD), phosphorus (P@MoS2-QD), and silicon (Si@MoS2-QD) surfaces have been theoretically investigated using density functional theory (DFT) computation to understand their mechanistic sensing ability, such as conductivity, selectivity, and sensitivity toward NH3 gas. The results from electronic properties showed that P@MoS2-QD had the lowest energy gap, which indicated an increase in electrical conductivity and better adsorption behavior. By carrying out comparative adsorption studies using m062-X, ωB97XD, B3LYP, and PBE0 methods at the 6-311G++(d,p) level of theory, the most negative values were observed from ωB97XD for the P@MoS2-QD surface, signifying the preferred chemisorption surface for NH3 detection. The mechanistic studies provided in this study also indicate that the P@MoS2-QD dopant is a promising sensing material for monitoring ammonia gas in the real world. We hope this research work will provide informative knowledge for experimental researchers to realize the potential of MoS2 dopants, specifically the P@MoS2-QD surface, as a promising candidate for sensors to detect gas.

Nano-optical designs for high-efficiency monolithic perovskite–silicon tandem solar cells

Abstract: Abstract Perovskite–silicon tandem solar cells offer the possibility of overcoming the power conversion efficiency limit of conventional silicon solar cells. Various textured tandem devices have been presented aiming at improved optical performance, but optimizing film growth on surface-textured wafers remains challenging. Here we present perovskite–silicon tandem solar cells with periodic nanotextures that offer various advantages without compromising the material quality of solution-processed perovskite layers. We show a reduction in reflection losses in comparison to planar tandems, with the new devices being less sensitive to deviations from optimum layer thicknesses. The nanotextures also enable a greatly increased fabrication yield from 50% to 95%. Moreover, the open-circuit voltage is improved by 15 mV due to the enhanced optoelectronic properties of the perovskite top cell. Our optically advanced rear reflector with a dielectric buffer layer results in reduced parasitic absorption at near-infrared wavelengths. As a result, we demonstrate a certified power conversion efficiency of 29.80%.

A Silicon Monoxide Lithium-Ion Battery Anode with Ultrahigh Areal Capacity

Abstract: Abstract Silicon monoxide (SiO) is an attractive anode material for next-generation lithium-ion batteries for its ultra-high theoretical capacity of 2680 mAh g −1 . The studies to date have been limited to electrodes with a relatively low mass loading (< 3.5 mg cm −2 ), which has seriously restricted the areal capacity and its potential in practical devices. Maximizing areal capacity with such high-capacity materials is critical for capitalizing their potential in practical technologies. Herein, we report a monolithic three-dimensional (3D) large-sheet holey graphene framework/SiO (LHGF/SiO) composite for high-mass-loading electrode. By specifically using large-sheet holey graphene building blocks, we construct LHGF with super-elasticity and exceptional mechanical robustness, which is essential for accommodating the large volume change of SiO and ensuring the structure integrity even at ultrahigh mass loading. Additionally, the 3D porous graphene network structure in LHGF ensures excellent electron and ion transport. By systematically tailoring microstructure design, we show the LHGF/SiO anode with a mass loading of 44 mg cm −2 delivers a high areal capacity of 35.4 mAh cm −2 at a current of 8.8 mA cm −2 and retains a capacity of 10.6 mAh cm −2 at 17.6 mA cm −2 , greatly exceeding those of the state-of-the-art commercial or research devices. Furthermore, we show an LHGF/SiO anode with an ultra-high mass loading of 94 mg cm −2 delivers an unprecedented areal capacity up to 140.8 mAh cm −2 . The achievement of such high areal capacities marks a critical step toward realizing the full potential of high-capacity alloy-type electrode materials in practical lithium-ion batteries.

Monolithic Perovskite‐Silicon Tandem Solar Cells: From the Lab to Fab?

Abstract: This review focuses on monolithic 2‐terminal perovskite‐silicon tandem solar cells and discusses key scientific and technological challenges to address in view of an industrial implementation of this technology. The authors start by examining the different crystalline silicon (c‐Si) technologies suitable for pairing with perovskites, followed by reviewing recent developments in the field of monolithic 2‐terminal perovskite‐silicon tandems. Factors limiting the power conversion efficiency of these tandem devices are then evaluated, before discussing pathways to achieve an efficiency of >32%, a value that small‐scale devices will likely need to achieve to make tandems competitive. Aspects related to the upscaling of these device active areas to industry‐relevant ones are reviewed, followed by a short discussion on module integration aspects. The review then focuses on stability issues, likely the most challenging task that will eventually determine the economic viability of this technology. The final part of this review discusses alternative monolithic perovskite‐silicon tandem designs. Finally, key areas of research that should be addressed to bring this technology from the lab to the fab are highlighted.

Microstructure and oxidation resistance of Si-MoSi2 ceramic coating on TZM (Mo-0.5Ti-0.1Zr-0.02C) alloy at 1500 °C

Abstract: The Si-MoSi2 ceramic coatings were prepared on TZM alloy through a hot dip silicon-plating (HDS) process. The hot dip experiments results showed that Si-MoSi2 ceramic coatings have a very dense surface morphology and low roughness (0.258 ± 0.009 to 0.347 ± 0.019 μm). The Si-MoSi2 ceramic coatings presents a typical layered structure with the outermost silicon-rich MoSi2 layer, the intermediate layer is the pure MoSi2 layer, and the Mo5Si3/Mo5Si3C diffusion layer between the MoSi2 layer and the TZM substrate. The oxidation tests showed that MoSi2 ceramic coating maintained a complete appearance after high temperature oxidation at 1500 °C for 4 h. The self-healing SiO2 protective film effectively inhibits the diffusion of oxygen and reduces the consumption rate of MoSi2 layer. HDS Si-MoSi2 ceramic coating presents a very excellent oxidation resistance at high temperature, which is mainly attributed to the uniform and dense coating structure and high surface silicon concentration.

An Ion‐Conductive Grafted Polymeric Binder with Practical Loading for Silicon Anode with High Interfacial Stability in Lithium‐Ion Batteries

Abstract: Binders are required to dissipate huge mechanical stress and enhance the lithium‐ion diffusion kinetics of silicon anodes during cycling. Herein, a stress‐distribution binder with high ionic conductivity (GG‐g‐PAM) is constructed by grating polyacrylamide (PAM) onto ion‐conductive guar gum (GG) backbone. The mechanical stress distribution toward the grafted PAM chain enables the effective stress dissipation of the GG‐g‐PAM binder, and thus maintains a stable electrode‐electrolyte interface during cycling. The stress dissipation ability of the GG‐g‐PAM binder is confirmed by PeakForce atomic force microscopy experiments and finite element simulations. In addition, lithium complexation sites provided by oxygen heteroatoms in GG of the GG‐g‐PAM binder construct the Li‐ion pathways for facilitating Li ionic diffusion in the Si anodes. The good cyclabilities of Ah‐level pouch cells based on Si nanoparticle anodes strongly confirm GG‐g‐PAM as a desirable binder for practical Si anodes.

Emergent ferroelectricity in subnanometer binary oxide films on silicon

Abstract: The critical size limit of voltage-switchable electric dipoles has extensive implications for energy-efficient electronics, underlying the importance of ferroelectric order stabilized at reduced dimensionality. We report on the thickness-dependent antiferroelectric-to-ferroelectric phase transition in zirconium dioxide (ZrO2) thin films on silicon. The emergent ferroelectricity and hysteretic polarization switching in ultrathin ZrO2, conventionally a paraelectric material, notably persists down to a film thickness of 5 angstroms, the fluorite-structure unit-cell size. This approach to exploit three-dimensional centrosymmetric materials deposited down to the two-dimensional thickness limit, particularly within this model fluorite-structure system that possesses unconventional ferroelectric size effects, offers substantial promise for electronics, demonstrated by proof-of-principle atomic-scale nonvolatile ferroelectric memory on silicon. Additionally, it is also indicative of hidden electronic phenomena that are achievable across a wide class of simple binary materials. Description Ultrathin ferroelectric films The electrical properties of ferroelectrics can be changed with an electric field, making them attractive materials for computer hardware applications. Cheema et al. show that extremely thin films of zirconium dioxide on a silica substrate have ferroelectric order down to the unit cell scale. Whereas in many other materials the ferroelectric behavior is suppressed at the few-nanometer scale, a ferroelectric phase transition occurs if zirconium dioxide is thinner than two nanometers. This property might be true for any fluorite-structured binary oxide, making these types of thin films attractive for next-generation electronics. —BG Decreasing the thickness of zirconium dioxide on a silicon substrate creates ferroelectric ordering.

Multi-component ZnO alloys: Bandgap engineering, hetero-structures, and optoelectronic devices

Abstract: The desire for developing ultraviolet optoelectronic devices has prompted extensive studies toward wide-bandgap semiconductor ZnO and its related alloys. Bandgap engineering as well as p-type doping is the key toward practical applications of ZnO. As yet, stable and reproducible p-type doping of ZnO remains a formidable challenge. To circumvent p-type conductivity, ZnO-based optoelectronic devices have been developed with hetero-structures of ZnO alloys. In past decades, substantial efforts have been made to engineer the band structure of ZnO via isovalent cation- or anion-substitution for obtaining desired material properties, and considerable progresses have been achieved. The purpose of this review is to summarize recent advances in the experimental and theoretical studies on bandgap engineering of ZnO by formation of multi-component alloys, and the development of related hetero-structures and optoelectronic devices. First, we briefly introduce the general properties, epitaxial growth techniques, and bandgap engineering of ZnO. Then, we focus on presenting the current status of researches on ZnO ternary and quaternary alloys for bandgap engineering. The issues about substituent solubility limit and phase separation, as well as variations of lattice parameters and bandgap with the substituent content in the alloys are discussed in detail. Further, ZnO alloys based hetero-structures including hetero-junctions, quantum wells, and superlattices are reviewed, and recent achievements in the area of optoelectronic devices based on ZnO multi-component alloys are summarized. The review closes with outlooking the likely developing trend of multi-component alloys for the bandgap engineering of ZnO and related hetero-structures, and the potential and pathway of multi-component alloys in settling the p-type doping of ZnO.

FeNiP/MoOx integrated electrode grown on monocrystalline NiMoO4 nanorods with multi-interface for accelerating alkaline hydrogen evolution reaction

Abstract: Transition metal phosphides are promising candidates for alkaline hydrogen evolution reaction (HER), but the activation of H2O molecule is deficient. We adopt an interface engineering strategy to synthesize a hierarchical FeNiP/MoOx integrated electrode with multi-interface grown on monocrystalline NiMoO4 nanorods. Such catalyst exhibits remarkable alkaline HER performance with a low overpotential of 97 mV at the current density of 100 mA cm−2 and sustainable durability over 20 h. Experimental and theoretical results reveal that interfaces among Fe2P, Ni5P4, and MoOx can efficiently activate H2O molecules and facilitate H desorption. Moreover, employing FeNiP/MoOx/NiMoO4/NF as a cathode, the cell voltage as low as 1.62 V to achieve a current density of 100 mA cm−2, with admirable durability over 20 h for alkaline water splitting (1.0 M NaOH + 0.5 M NaCl). This work offers a new avenue to rationally design a 3D robust, cost-effective catalyst with multi-interface for large-scale practical hydrogen production.

Emergent ferroelectricity in subnanometer binary oxide films on silicon.

Abstract: The critical size limit of voltage-switchable electric dipoles has extensive implications for energy-efficient electronics, underlying the importance of ferroelectric order stabilized at reduced dimensionality. We report on the thickness-dependent antiferroelectric-to-ferroelectric phase transition in zirconium dioxide (ZrO2) thin films on silicon. The emergent ferroelectricity and hysteretic polarization switching in ultrathin ZrO2, conventionally a paraelectric material, notably persists down to a film thickness of 5 angstroms, the fluorite-structure unit-cell size. This approach to exploit three-dimensional centrosymmetric materials deposited down to the two-dimensional thickness limit, particularly within this model fluorite-structure system that possesses unconventional ferroelectric size effects, offers substantial promise for electronics, demonstrated by proof-of-principle atomic-scale nonvolatile ferroelectric memory on silicon. Additionally, it is also indicative of hidden electronic phenomena that are achievable across a wide class of simple binary materials.

Non-Volatile Reconfigurable Silicon Photonics Based on Phase-Change Materials

Abstract: The traditional ways of tuning a silicon photonic network are mainly based on the thermo-optic effect or the free carrier dispersion. The drawbacks of these methods are the volatile nature and the extremely small change in the complex refractive index (Δn<0.001). In order to achieve low energy consumption and smaller footprint for applications such as photonic memories, optical computing, programmable gate array, and optical neural network, it is essential that the two optical states of the system exhibit high optical contrast and remain non-volatile. Phase change materials (PCMs) such as Ge2Sb2Te5 provide an excellent solution, thanks to the drastic contrast in refractive index between two states which can be switched reversibly and in a non-volatile fashion. Here, we review the recent progress in the field of non-volatile reconfigurable silicon photonics based on PCMs. We start with a general introduction to the material properties of PCMs that have been exploited in integrated photonics and discuss their operating wavelengths. The various photonic switches that are built upon these PCMs are reviewed. Lastly, we review the recent applications of PCM-based photonic integrated circuits and discuss the potential future directions of this field.

Fully Textured, Production‐Line Compatible Monolithic Perovskite/Silicon Tandem Solar Cells Approaching 29% Efficiency

Abstract: Perovskite/silicon tandem solar cells are promising avenues for achieving high‐performance photovoltaics with low costs. However, the highest certified efficiency of perovskite/silicon tandem devices based on economically matured silicon heterojunction technology (SHJ) with fully textured wafer is only 25.2% due to incompatibility between the limitation of fabrication technology which is not compatible with the production‐line silicon wafer. Here, a molecular‐level nanotechnology is developed by designing NiOx/2PACz ([2‐(9H‐carbazol‐9‐yl) ethyl]phosphonic acid) as an ultrathin hybrid hole transport layer (HTL) above indium tin oxide (ITO) recombination junction, to serve as a vital pivot for achieving a conformal deposition of high‐quality perovskite layer on top. The NiOx interlayer facilitates a uniform self‐assembly of 2PACz molecules onto the fully textured surface, thus avoiding direct contact between ITO and perovskite top‐cell for a minimal shunt loss. As a result of such interfacial engineering, the fully textured perovskite/silicon tandem cells obtain a certified efficiency of 28.84% on a 1.2‐cm2 masked area, which is the highest performance to date based on the fully textured, production‐line compatible SHJ. This work advances commercially promising photovoltaics with high performance and low costs by adopting a meticulously designed HTL/perovskite interface.