Silicon Layer Research Articles

High-performance compact vertical germanium photodiodes enabled by silicon corner reflectors

High-performance germanium photodiodes are critical components in silicon photonic systems for high-capacity data communications. By reducing the length of the photodiodes, a smaller resistance–capacitance product can be achieved, leading to a larger bandwidth and lower dark current. However, this also leads to diminished responsivity due to insufficient light absorption. Here, we introduce a silicon corner reflector (SCR) to alleviate this issue by reflecting and recycling the unabsorbed light. The process of evanescent coupling between the silicon and germanium layers is elaborately engineered to optimize the efficiency of light absorption. Experimentally, a responsivity of 0.96 A/W, which is a 21% increase compared to the one without SCR, is achieved at 1550 nm with a germanium length of 4.8 μm. Simultaneously, a remarkably low dark current of 0.76 nA and a large bandwidth of 100 GHz are achieved. Open eye diagrams of 140 Gb/s on–off keying and 240 Gb/s four-level pulse amplitude signals are obtained. To the best of our knowledge, this work achieves the lowest dark current density and noise equivalent power to date and offers a promising solution for low-cost, high-performance optical detection.

Low dark current and low voltage germanium avalanche photodetector for a silicon photonic link

Germanium (Ge)-silicon (Si)-based avalanche photodetectors (APDs) featured by a high absorption coefficient in the near-infrared band have gained wide applications in laser ranging, free space communication, quantum communication, and so on. However, the Ge APDs fabricated by the complementary metal oxide semiconductor (CMOS) process suffer from a large dark current and limited responsivity, imposing a critical challenge on integrated silicon photonic links. In this work, we propose a p-i-n-i-n type Ge APD consisting of an intrinsic germanium layer functioning as both avalanche and absorption regions and an intrinsic silicon layer for dark current reduction. Consequently, a Ge APD with a low dark current, low bias voltage, and high responsivity can be obtained via a standard silicon photonics platform. In the experimental measurement, the Ge APD is characterized by a high primary responsivity of 1.1 A/W with a low dark current as low as 7.42 nA and a dark current density of 6.1×10−11 A/μm2 at a bias voltage of −2 V. In addition, the avalanche voltage of the Ge APD is −8.4 V and the measured 3 dB bandwidth of the Ge APD can reach 25 GHz. We have also demonstrated the capability of data reception on 32 Gbps non-return-to-zero (NRZ) optical signal, which has potential application for silicon photonic data links.

Enhanced Drive Current in 10 nm Channel Length Gate-All-Around Field-Effect Transistor Using Ultrathin Strained Si/SiGe Channel

The continuous scaling down of MOSFETs is one of the present trends in semiconductor devices to increase device performance. Nevertheless, with scaling down beyond 22 nm technology, the performance of even the newer nanodevices with multi-gate architecture declines with an increase in short channel effects (SCEs). Consequently, to facilitate further increases in the drain current, the use of strained silicon technology provides a better solution. Thus, the development of a novel Gate-All-Around Field-Effect Transistor (GAAFET) incorporating a strained silicon channel with a 10 nm gate length is initiated and discussed. In this device, strain is incorporated in the channel, where a strained silicon germanium layer is wedged between two strained silicon layers. The GAAFET device has four gates that surround the channel to provide improved control of the gate over the strained channel region and also reduce the short channel effects in the devices. The electrical properties, such as the on current, off current, threshold voltage (VTH), subthreshold slope, drain-induced barrier lowering (DIBL), and Ion/Ioff current ratio, of the 10 nm channel length GAAFET are compared with the 22 nm strained silicon channel GAAFET, the existing SOI FinFET device on 10 nm gate length, and IRDS 2022 specifications device. The developed 10 nm channel length GAAFET, having an ultrathin strained silicon channel, delivers enriched device performance, being augmented in contrast to the IRDS 2022 specifications device, showing improved characteristics along with amended SCEs.

HWCVD growth of hydrogenated nanocrystalline silicon oxide window layers for SHJ solar cells

In recent years, successful development of n-type hydrogenated nanocrystalline silicon oxide (n-nc-SiOx:H) window layers with high conductivity and low parasitic absorption, grown by plasma enhanced chemical vapor deposition (PECVD) technology, has significantly enhanced the power conversion efficiency of silicon heterojunction (SHJ) solar cells. Although SHJ solar cells have significant advantages in efficiency, the high cost of the PECVD equipment presents a significant barrier to their mass production. The utilization of the more cost-effective hot wire chemical vapor deposition (HWCVD) technology presents a promising solution. Nevertheless, HWCVD technology currently lacks an industrially viable methodology for growing high-performance window layers due to a phenomenon of associated severe loss of passivation. In this work, the phenomenon and the solution have been investigated. The results demonstrate that, in HWCVD processes, large amounts of hydrogen and small amounts of oxygen, which are essential for enhancing the crystallinity and conductivity and reducing the parasitic absorption, both induce significant damage to the previously grown intrinsic hydrogenated amorphous silicon layer, leading to poor passivation, and hence much lower cell efficiency. Introduction of a densified amorphous silicon barrier layer was found to be an effective solution to the aforementioned passivation loss, resulting in the successful growth of nc-SiOx:H window layers by HWCVD, with an efficiency enhancement of 0.37%abs. Finally, a commercial-size SHJ solar cell with an efficiency of 24.74 % was fabricated using a home-made HWCVD-based pilot SHJ cell line.

Detection of Low-Density Foreign Objects in Infant Snacks Using a Continuous-Wave Sub-Terahertz Imaging System for Industrial Applications.

Low-density foreign objects (LDFOs) in foods pose significant safety risks to consumers. Existing detection methods, such as metal and X-ray detectors, have limitations in identifying low-density and nonmetallic contaminants. To address these challenges, our research group constructed and optimized a continuous-wave sub-terahertz (THz) imaging system for the real-time, on-site detection of LDFOs in infant snacks. The system was optimized by adjusting the attenuation value from 0 to 9 dB and image processing parameters [White (W), Black (B), and Gamma (G)] from 0 to 100. Its detectability was evaluated across eight LDFOs underneath snacks with scanning at 30 cm/s. The optimal settings for puffed snacks and freeze-dried chips were found to be 3 dB attenuation with W, B, and G values of 100, 50, and 80, respectively, while others required 0 dB attenuation with W, B, and G set to 100, 0, and 100, respectively. Additionally, the moisture content of infant snacks was measured using a modified AOAC-based drying method at 105 °C, ensuring the removal of all free moisture. Using these optimized settings, the system successfully detected a housefly and a cockroach underneath puffed snacks and freeze-dried chips. It also detected LDFOs as small as 3 mm in size in a single layer of snacks, including polyurethane, polyvinyl chloride, ethylene-propylene-diene-monomer, and silicone, while in two layers of infant snacks, they were detected up to 7.5 mm. The constructed system can rapidly and effectively detect LDFOs in foods, offering a promising approach to enhance safety in the food industry.

Au-Doped Black Silicon Photodetector Fabricated by a Femtosecond Laser with Excellent Near-Infrared Response.

Silicon photonic devices are key components in optical imaging and sensing for communication, and the development of silicon-based photodetectors with ideal performance in the visible and infrared spectral ranges can promote the application of silicon photonics in various photoelectronic systems. Here, a Au-doped black silicon photodetector was prepared by a femtosecond laser direct writing technique. The conical micro-/nanostructures with different sizes were produced by different laser fluence irradiation. Ultrafast pump-probe technology revealed that the strong spallation process and phase explosion between Au and silicon facilitate the interfusion of Au atoms into the silicon lattice. EDS analyses, Raman spectra, and XPS spectra show the uniform distribution of Au elements, multiconfiguration amorphous phase transition, and stable chemical valence states of Au elements in Au-doped black silicon layers, respectively. The excellent geometric light trapping performance of the surface conic structure-assisted photodetector achieved a high absorptance of 95% in the 200-1100 nm band. Simultaneously, the introduction of the intermediate band by Au hyperdoping also leads to a strong absorptance of 75% in the 1100-2500 nm band. The photoelectrical response rate of the Au-doped black silicon photodetectors increased by 10 times in the infrared wavelength band by means of the introduced intermediate energy levels through Au element doping. The switching photocurrent ratio is also found to be boosted 10 times, which comes from the reduction of the photon injection barrier. The excellent photoelectronic properties lead to the increased potential of femtosecond laser processing for integration with photonics and electronics, which shows great possibilities in the further progress of energy devices, information technology, and artificial intelligence.

Effects of Geometry and Supporting Silicone Layers on the Performance of Conductive Composite High-Deflection Strain Gauges

Piezoresistive sensors composed of nickel nanostrands, nickel-coated carbon fibers, and silicone can be used to measure large physical deflections but exhibit viscoelastic properties and creep, leading to a complex and nonlinear electrical response that is difficult to interpret. This study considers the impact of modifying the geometry and architecture of the sensors on their mechanical and electrical performance. Varying the sensor thickness leads to potentially significant differences in conductive fiber alignment, while adding external layers of pure silicone provides elastic support for the sensors, potentially reducing their extreme viscoelastic nature. The impact of such modifications on both mechanical and electrical behavior was assessed by analyzing strain to failure, the magnitude of hysteresis with cycling, the repeatability of the electro-mechanical response, the strain level at which resistance begins to monotonically decrease, and the drift in electrical response with cycling. The results indicate that thicker single-layer sensors have less electrical drift. Sensors with a multilayered architecture exhibit several improvements in behavior, such as increasing the range of the monotonic region by approximately 52%. These improvements become more significant as the thickness of the pure silicone layers increases.

Optimizing Myelomeningocele Repair: Assessing the Role of Synthetic Acellular Dermal Regeneration Templates in Complex Closures.

Myelomeningoceles threaten newborns with central nervous system infectious risk. While some myelomeningoceles can be repaired fetally, limited donor tissue in newborns makes covering a substantial defect challenging. This study evaluated the effectiveness of acellular dermal regeneration templates (ADRT) in safely healing refractory myelomeningoceles. Seven myelomeningocele repair cases using ADRT (Integra LifeSciences, Plainsboro, NJ) at an academic children's hospital from April 2020 to June 2023 were reviewed. Patients had unsuccessful closure attempts through fetoscopic, postnatal, or revision surgeries by neurosurgery and plastic surgery, leading to complications that required ADRT to protect the dural repair and promote quicker granulation. The case series included 3 male and 4 female patients, with a median delivery age of 37 weeks (IQR: 33-37). Three underwent fetoscopic repairs, and 4 had postnatal repairs within 48 hours of birth. Six patients required ADRT placement due to failed primary repair. One patient failed fetoscopic closure and required immediate ADRT placement following an emergent cesarean delivery. The median wound size covered was 12cm2 (range, 4-20cm2), and the median hospital stay was 84 days (IQR: 43-105). Three weeks post-ADRT placement, 4 patients showed healthy granulation tissue, and the external silicone layer was removed. Three patients needed additional ADRT for complete wound coverage and successful granulation. After granulation, all wounds eventually epithelialized by secondary intention, with no postoperative infection or wound dehiscence observed. ADRT can aid in wound healing and protect dural repair in myelomeningoceles, offering a viable option for complex or failed primary closures with limited donor tissue.

Spatial‐Dependent Coupling of Electrochemistry, Mass Transport, and Stress in Silicon‐Graphite Composite Electrodes for Lithium‐Ion Batteries

AbstractThe commercialization of high‐capacity silicon materials in lithium‐ion batteries is hindered by significant volume changes. Composite anodes made from silicon and graphite, which increase battery capacity and maintain electrode structural stability, are receiving considerable attention. However, the spatial configuration of the active particles in the electrode is few investigated due to the complexity of experiments at the microscopic scale. Herein, this work focuses on electrochemical, mass transport, and stress coupling mechanisms by considering different spatial configurations of silicon and graphite. In situ electrochemical and stress measurements are first conducted to demonstrate the impact of the active material arrangement. Then, a 2D electrochemical‐mechanical model is developed considering the heterogeneity of electrochemical processes at the particle‐electrolyte interface. The results show that placing silicon in the upper active layer significantly reduces the ion transport resistance, while the graphite layer near the current collector provides a good conductive network for electron transport in the silicon layer, enhancing the performance of the composite electrode structure. By combining electrochemical and mechanical field models with experimental verification, this study deepens the understanding of composite electrode structure design, offering practical guidance for optimizing the spatial configuration of electrode materials to significantly improve battery performance.

Structural Features of Porous Silicon Formed on Heavily Doped Plates of Single-Crystal Silicon with Electron Conductivity

Using scanning electron microscopy, the structures of the surface and internal regions of porous silicon obtained by anodizing heavily doped plates of single-crystal silicon with electron conductivity in a hydrofluoric acid solution at different current densities were studied. It is found that the porous silicon surface has dark gray and light gray pores, which differ in size and surface distribution density. Dark gray pores possess larger sizes, and their density is about 5–10 times less than that of light gray pores. Based on the cross-section imagery, it is shown that light gray pores correspond to underdeveloped channels of small depth, while dark gray pores are the entrance points of deep bottle-shaped channels passing from the surface into the depth of the silicon wafer. The equivalent diameters of light gray pores on the surface of porous silicon are 12–15 nm and are practically independent of the anodic current density. At the same time, the equivalent diameters of dark gray pores and average distances between their centers increase linearly from 15 to 35 nm on the surface and from 35 to 120 nm in the volume of porous silicon when the current density is increased from 30 to 90 mA/cm2. The average thickness of silicon skeleton elements is about 3 nm on the surface and increases to 5–6 nm in the volume. By setting the density of the anode current, it is possible to obtain layers of porous silicon with different structural parameters. The obtained research results have practical significance for the formation of composite materials based on porous silicon, which can be used as a porous matrix for the deposition of metals and semiconductors.

Selective IR wavelengths multichannel filter based on the one-dimensional topological photonic crystals comprising hyperbolic metamaterial

In this research article, we have theoretically introduced a one-dimensional topological photonic crystal (1D TPC) design to provide a better stability due to imperfections and fluctuations in geometry compared to the traditional PC structures. The considered structure is designed by the combination of two different PCs, i.e., PC1 and PC2. PC1 consists of two layers of silicon (Si) and magnesium fluoride (MgF2), while PC2 contains a multilayer stack of MgF2 and hyperbolic metamaterial (HMM). Interestingly, the HMM layer is introduced as a composite of a dielectric material of indium arsenide (InAs), and nanocomposite of Ag nanoparticles inside a hosting medium of Y2O3. The foundations of our theoretical framework are based on Effective Medium Theory (EMT), the Transfer Matrix Method (TMM), and the Maxwell-Garnett model. Our research primarily focuses on utilizing our design as a pass/stop band filter for near-infrared (NIR) applications. Notably, this proposed design exhibits significant stability in the face of imperfections and variations. Our numerical findings highlight the influence of several geometric parameters including the refractive index of hosting medium for Ag nanoparticles, thicknesses, and filling fraction on the characteristics of the resulting filter. Remarkably, the results also reveal the emergence of multiple resonance peaks that maintain high stability against geometric tolerances. We believe our work presents a finite photonic crystal (PC) whose wave localization properties are resilient to random geometric imperfections, making it suitable for NIR filtering applications.

Improved the Sensitivity and Limit of Detection of Surface Alloying SERS Sensors by Controlling Mixing Ratio of Trimetallic (Ag-Au-Pd) Nanoparticles

In this study, three different types of hybrid structures SERS sensors made from different mixing ratio of trimetallic (Ag-Au-Pd) nanoparticles of [Au1: Ag1: Pd1] , [Au1: Ag2: Pd1] , [Au1: Ag2: Pd2] in surface alloying forms deposited on macro porous silicon (macroPsi) layer were created and extensively tested. By using a simple and fast immersion process, trimetallic (Ag-Au-Pd) nanoparticles were created utilizing ion reduction of numerous metallic salts on a macro porous silicon (macroPsi) layer. The macroPsi layers were created using a laser assisted etching (LAE) technique for 15 minutes with a constant density of approximately (28mA/c.m2). At a constant concentration (10-3 M) of HAu.Cl4, Ag.NO3 and Pd.Cl2 to synthesize Au-NPs, Ag-NPs and Pd-NPs, immersion processes with various mixing ratios were performed. The hybrid structures of SERS sensors were examined using XRD, FE-SEM, and Raman microscopes. The sensors were tested at different concentrations from 10-6 to 10-12 of MB target molecules. The SERS trimetallic sensors demonstrated a considerable reliance on hot spot zones among trimetallic nanoparticles. Higher enhancement factor with lower detection limit of Raman signal was obtained from [Au1: Ag2: Pd2] hybrid structures SERS sensor of about 1.5×1010 and 10-14 respectively, due to extra ordinary specific surface area and high surface density forming trimetallic nanoparticles . The variations of mixing ratio of trimetallic (Ag-Au-Pd) provide an effective pathway to develop the sensors performance towards detection of lower concentrations.

FT-IR detection of DMMP on TiO2-Modified porous silicon substrates

In this study, we present a new chemical sensor based on a functionalized porous silicon and sensitive to dimethyl methyl phosphonate (DMMP), a simulant of sarin gas, known as one of the most toxic warfare agents. The porous silicon was prepared by anodising a boron-doped p-Si (100) wafer. A metal oxide TiO2 layer was then deposited by thermal evaporation of Ti and oxidized under atmospheric conditions to form a TiO2 film which was used as a reactive coating. The characterization of the PSi and TiO2/PSi films was investigated using SEM, EDX and XPS spectroscopies. The results indicated that the TiO2 was well incorporated on the surface and slightly inside the porous silicon layer. FT-IR studies were then carried out before and after exposure to DMMP and the detection performance was compared with PSi. The results obtained showed that our surfaces have the ability to detect DMMP down to 0.5 ppm compared to uncoated PSi layer. We have also shown that a TFA pre-treatment of our TiO2 modified PSi, prior the exposure to DMMP, is crucial for increasing its sensitivity and that our sensor can be reused several times with a simple hexane cleaning step, a key criterion for routine applications.

Determination of critical energy release rate at the EVA/Si cell interface of a flexible silicon solar cell

Recently, commercial flexible silicon(Si) solar cells have been available for charging batteries and electronic devices. In this research, we present a methodology for determining the critical energy release rate at the EVA/Si cell interface of a flexible silicon solar cell, which can also be applied to other interfaces in solar cells. The outline of procedure is as follows:•Conduct a peeling test at the EVA/Si cell interface of the solar cell sample•Perform a tensile test on the upper layer of the solar cell sample•Execute IC Peel softwareInputs: Peeling force between EVA and Si layer, Young's modulus (E), Yield stress (σy), and Yield strain (εy) of the upper layerOutput: critical energy release rate (Gc) between EVA and the silicon (Si) layer

Dual-hollow-core anti-resonant fiber with silicon layers and nested resonant tubes for constructing a single-polarization 3 dB coupler.

A novel dual-hollow-core anti-resonant fiber (DHC-ARF) with silicon layers and nested resonant tubes is proposed for constructing a 3 dB single-polarization coupler. High-index silicon layers are deposited inside four cladding tubes along the x-direction and then nested resonant tubes are introduced into these cladding tubes, which is beneficial to promote the mode coupling between the x-polarized fundamental mode and the dielectric mode in the silica/silicon tubes so as to achieve single-polarization characteristics of the DHC-ARF. The properties of the DHC-ARF are optimized using finite element method combined with perfectly matched layer as a boundary condition. By using a 1.51 cm long DHC-ARF, a single-polarization 3 dB coupler is constructed with a relatively wide bandwidth of 29 nm covering the wavelength range from 1530 nm to 1559 nm, in which the polarization extinction ratio (PER) is lower than -20 dB and the coupling ratio can be guaranteed within 50 ± 2%. This bandwidth is more than 2.6 times higher than the bandwidth of currently reported single-polarization coupler. At the wavelength of 1550 nm, the lowest PER reaches -74.8 dB and the loss of the coupler is as low as 0.33 dB.

H‐PME: Development of a Robot Skin Using Halbach Array Permanent Magnet Elastomer

This article presents a novel 3‐axis Halbach permanent magnet elastomer (H‐PME) sensor for the robotic application, which effectively reduces crosstalk along when two sensors are used simultaneously in close proximity, for example, during grasping of thin and delicate objects, needle threading, etc. This sensor integrates a Halbach‐array magnetic elastomer, a 3×3 Hall sensor matrix, and a silicone layer. The magnetic elastomer is produced by combining NdFeB powders with a diameter of 5 μm into silicone, following a weight ratio of 50%, and then magnetized using 2D Halbach‐array magnets. Simulation results reveal the capability to adjust magnetic field strength and distribution by altering the magnet's orientation. The sensor's efficacy in 3‐axis sensing is validated through calibration with a linear model, achieving a good root‐mean‐square error below 0.7 N in force measurement. The H‐PME sensor, with a thickness of merely 4.5 mm, can detect forces up to 50 N. It's simple 3‐layer design allows the thickness to be reduced to as low as 2 mm, while also offering ease of replacement. Crucially, crosstalk evaluation experiments show that the proposed H‐PME sensor can dramatically mitigate crosstalk interference.

Efficient Silicon Solar Cells with Aluminum‐Doped Zinc Oxide‐Based Passivating Contact

AbstractCrystalline silicon (c‐Si) solar cells require passivating contacts to unlock their full efficiency potential. For this doped silicon layers are the materials of choice, as they yield device voltages close to the thermodynamic limit. Yet, replacing such layers with wide‐bandgap metal oxides may be advantageous from a cost perspective and minimize parasitic optical absorption. Here the aluminum‐doped zinc oxide (AZO)‐based passivating contacts with high electron selectivity are presented. The SiO2/AZO/Al2O3 stack is demonstrated to provide excellent surface passivation on c‐Si (implied Voc up to 742 mV) after thermal annealing, and an average contact resistivity of 51 mΩ cm2 is simultaneously obtained after etching off Al2O3 capping layer. By the implementation of AZO‐based electron‐selective contact, a champion power conversion efficiency (PCE) of 24.3% is achieved on c‐Si solar cells, representing the PCE record for metal oxide‐based passivating contacts. Finally, the efficiency potential, cost, and industrial compatibility of the AZO‐based electron‐selective contacts are discussed, paving the way for industrial applications.

First Principle Investigations of Structural, Electronic and Thermal Properties of Pristine, Metal and Non-Metal Doped Silicene for Thermoelectric Applications

Silicene, a two-dimensional hexagonal silicon layer, exhibits exceptional electronic and thermoelectric properties. However, its application in semiconductors is hindered by its zeroband gap, which could be overcome by modifying its electronic properties through doping. In this paper, Density Functional Theory (DFT) calculations were performed to investigate the band gap opening in silicene by studying the effect of magnesium and sulphur doping on its electronic, structural and thermal properties. Pristine silicene has a lattice constant of 3.86 Å and a zero-band gap. Upon doping with 12.5% S and Mg atoms, the lattice constant modifies to 3.45 Å and 3.93 Å, respectively, resulting in a direct band gap opening. For 25% Mg and S doping, the result shows that Mg and S effectively alter the band structure and the band gap of silicene monolayer at various configurations. The maximum band gap was 0.98 eV and 1.22 eV for Mg and S doping into the meta position to the reference point R, respectively. The power factor significantly increases with doping, reaching 1.20 x 1011 WK-2m-1 and 1.40 x 1011 WK- 2 m-1 for 12.5% Mg and S doping compared to 7.4 x 1010 WK-2m-1 for pristine silicene. This substantial enhancement indicates improved thermoelectric performance, making silicene a promising candidate for thermoelectric applications. Results demonstrate that tuning the band gap through doping can simultaneously enhance the power factor, highlighting the potential of Mg/S-doped silicene for efficient energy harvesting and conversion.

Real-time study of the interplay between phase formation and stress evolution at the W1−xSix/a−Si interface

Nanoscale W1−xSix layers with different Si content were deposited by magnetron sputtering on amorphous silicon layers. The structure and stress evolution during deposition were monitored and in real time. Thus, it was possible to disentangle different origins of stress built-up (interface formation, phase formation, grain growth, and texture) on the nanoscale. It was found that the bcc phase with a composition-dependent texture forms at low Si content (less than 10% Si), but only above a critical thickness. At intermediate Si content (13.9% and 16.5% Si), or low Si content and low thicknesses (≲4.5 nm), the β phase with A15 structure and coexisting phases (bcc or amorphous) form, while a single, amorphous phase is observed at high Si content (≳22% Si). An A15 formation driven by impurities (O,C,N) was excluded by combined x-ray photoelectron spectroscopy and x-ray diffraction measurements on a second sample series. calculations of substitutional bcc and A15 W1−xSix alloys support the formation of A15 at higher Si content. The A15-containing interlayer should be taken into account when discussing the superconductivity of W/Si multilayers. The stress evolution during deposition of W1−xSix was correlated with the microstructure evolution, and compared to similar observations for Mo1−xSix. Due to the crystalline phase (bcc/A15) and bcc texture ([111] and [110]) competition, the structure formation of W1−xSix shows a higher complexity. This explains the wide range of stress states (from tensile to compressive) observed after deposition of W1−xSix. Nanoscale W-Si based stress-compensation layers could be employed for tailoring the stress state of nonepitaxial semiconductor devices. Published by the American Physical Society 2024

Silicon heterojunction back-contact solar cells by laser patterning.

Back-contact silicon solar cells, valued for their aesthetic appeal because they have no grid lines on the sunny side, find applications in buildings, vehicles and aircraft and enable self-power generation without compromising appearance1-3. Patterning techniques arrange contacts on the shaded side of the silicon wafer, which offers benefits for light incidence as well. However, the patterning process complicates production and results in power loss. We employed lasers to streamline the fabrication of back-contact solar cells and enhance the power-conversion efficiency. Using this approach, we produced a silicon solar cell that exceeded 27% efficiency. Hydrogenated amorphous silicon layers were deposited onto the wafer for surface passivation and to collect light-generated carriers. A dense passivating contact, which differs from conventional technology practice, was developed. Pulsed picosecond lasers operating at different wavelengths were used to create the back-contact patterns. The approach developed is a streamlined process for producing high-performance back-contact silicon solar cells, with a total effective processing time of about one-third that of the emerging mainstream technology. To meet the terawatt demand, we developed indium-less cells at 26.5% efficiency and precious silver-free cells at 26.2% efficiency. Thus, the integration of solar solutions into buildings and transportation is poised to expand with these technological advances.