Crystalline Silicon Research Articles

Growth rate of AL2O3 Thin Film by Liquid Phase Deposition as an Anti-reflection Coating Layer on Crystalline Silicon for Solar Cell Applications

The fabrication of photovoltaic (PV) device requires that surface reflectance of solar cells has to be minimized to achieve higher photo-conversion efficiency (PCE). Antireflection coating layer is deposited on the surface of a p-type crystalline silicon material to reduce the surface reflections of solar radiation and increase its absorption for efficient solar cell application. In this work, aluminum oxide thin film by liquid phase deposition (LPD-Al2O­3) is synthesized from combined solution of aluminum sulfate octadecahydrate (Al2(SO4)3·18H2­O) and sodium carbonate (NaHCO3) with pH of 3.1. Some samples of p-type (100) crystalline silicon (c-Si) wafers of resistivity 1 – 10 mΩ were immersed inside the growth liquid of LPD-Al2O­3 thin film for 1hr – 2.5 hours. This is followed by annealing the samples at a temperature of 450oC, the deposition rate is faster in the range 1 – 1.5 hours is about 35nm/hr. As the growth time increases, the growth rate of the film decreases and remains nearly constant at about 10 nm/hour at 1 – 2 hours. When the growth time exceeds 2 hours, the film thickness remains unchanged showing that the liquid has lost in growth ability. The weighted average reflection (%) of planar c-Si is reduced from 44.9 % to 29.6 % after deposition of the LPD-Al2O­3 for 2.5 hours growth time, indicating a 34.1 % reduction in reflection within wavelength region of 300–1100 nm. While the root means square (RMS) surface roughness of 36.5 nm was also recorded at the highest growth time of 2.5 hours. This shows the effect of thicker LPD-Al2O­3 thin film layer increases the anti-reflecting coating property of the material.

Growth rate of AL2O3 Thin Film by Liquid Phase Deposition as an Anti-reflection Coating Layer on Crystalline Silicon for Solar Cell Applications

The fabrication of photovoltaic (PV) device requires that surface reflectance of solar cells has to be minimized to achieve higher photo-conversion efficiency (PCE). Antireflection coating layer is deposited on the surface of a p-type crystalline silicon material to reduce the surface reflections of solar radiation and increase its absorption for efficient solar cell application. In this work, aluminum oxide thin film by liquid phase deposition (LPD-Al2O­3) is synthesized from combined solution of aluminum sulfate octadecahydrate (Al2(SO4)3·18H2­O) and sodium carbonate (NaHCO3) with pH of 3.1. Some samples of p-type (100) crystalline silicon (c-Si) wafers of resistivity 1 – 10 mΩ were immersed inside the growth liquid of LPD-Al2O­3 thin film for 1hr – 2.5 hours. This is followed by annealing the samples at a temperature of 450oC, the deposition rate is faster in the range 1 – 1.5 hours is about 35nm/hr. As the growth time increases, the growth rate of the film decreases and remains nearly constant at about 10 nm/hour at 1 – 2 hours. When the growth time exceeds 2 hours, the film thickness remains unchanged showing that the liquid has lost in growth ability. The weighted average reflection (%) of planar c-Si is reduced from 44.9 % to 29.6 % after deposition of the LPD-Al2O­3 for 2.5 hours growth time, indicating a 34.1 % reduction in reflection within wavelength region of 300–1100 nm. While the root means square (RMS) surface roughness of 36.5 nm was also recorded at the highest growth time of 2.5 hours. This shows the effect of thicker LPD-Al2O­3 thin film layer increases the anti-reflecting coating property of the material.

A simulation study of irradiation effect on InAs/GaAsSb type II quantum dot structures

Particles in space cause irradiation damage to the solar cells (SCs), resulting in the degradation of their performance. Quantum dot solar cells (QDSCs) have higher theoretical efficiency and better irradiation resistance than the conventional GaAs SCs, which makes them highly promising for application in space. In this paper, we study the proton irradiation effect on InAs/GaAs0.8Sb0.2 QDSCs by SRIM program. The simulation result shows that the InAs/GaAs0.8Sb0.2 QDSCs have fewer vacancies than GaAs SCs when irradiated with low-energy proton, which indicates that the InAs/GaAs0.8Sb0.2 QDSCs have better anti-irradiation characteristics. The study about displacements per atom and proton concentration in two SCs shows that protons with low energy and high irradiation fluences will cause more serious damage in InAs/GaAs0.8Sb0.2 QDSCs. In addition, the proton incident angle affects the vacancy distribution, while the number of QD layers has little effect on it.

High-performance SiOx/MgOx electron-selective contacts for crystalline silicon solar cells

High-performance SiOx/MgOx electron-selective contacts for crystalline silicon solar cells

Investigation of the effect of oxygen flow modulation on ITO film properties to improve the performance of SHJ solar cells

Photovoltaics offer a sustainable solution for the growing energy needs of the world, while reducing environmental impact. Transparent Conductive Oxides (TCOs), which are essential in photovoltaic technology, offer high light transmittance and effective charge carrier extraction. This research focuses on the impact of oxygen (O2) flow rates in the deposition of indium tin oxide (ITO) films on n-type crystalline silicon (c-Si) substrates by DC magnetron sputtering. The structural, optical, and electrical properties were analyzed. Based on the results, the optimal O2 ratio was determined and used in the fabrication of SHJ solar cells, achieving an efficiency of 18.6%.

Double-diode model carrier lifetime-based internal recombination parameter analysis and efficiency prediction of crystalline Si solar cells

With the continuous and significant advancements in the performance of crystalline silicon (c-Si) solar cells, an effective method for a detailed analysis of the efficiency loss factors is increasingly important. Specifically, a detailed analysis of recombination parameter (J0) is crucial for devising strategies to approach the theoretical efficiency limit. In this study, we propose an analysis method that utilizes minority carrier lifetime based on the double-diode model and predicts the performance efficiency of c-Si solar cells. The analysis, conducted through the p-PERC structure, examines the contributions to J0 from different recombination areas. The advantages of this method include: (i) its relative simplicity and reliance on non-destructive analysis techniques; (ii) its capability to extract internal recombination parameters, such as J0,total emitter, J0,rear, and J02, from a fully assembled solar cell with metal contacts. Furthermore, this method serves as a diagnostic tool to identify the sequence in which parameters should be adjusted to enhance solar cell efficiency effectively and to pinpoint areas within the solar cell that significantly limit performance efficiency. Using this method, the diagnosis of the p-PERC cell revealed that the main cause of performance limitation was the emitter in the front region. The carrier lifetime analysis showed that for overcoming cell performance limitations, it is more effective to design process improvements in the following order: i) front emitter region (J0,em), ii) space charge region (J02), iii) rear surface region (J0r).

Comparison of different approaches to texturing monocrystalline silicon wafers for solar cell applications

Texturing the surface of crystalline silicon wafers is a very important step in the production of high-efficiency solar cells. Alkaline texturing creates pyramids on the silicon surface, lowering surface reflectivity and improving light trapping in solar cells. This article provides a comparative evaluation of various wet texturing methods using alkaline solutions with or without additives commonly known as surfactants. One method uses sodium hydroxide (NaOH) and isopropyl alcohol (IPA) to create a surface with a height of about 4.5 μm by texturing for about 30 min, while the other method uses potassium hydroxide (KOH) and other additions known as additives. Texturing was performed using chemicals for only 15 min to create a surface shape with a height of approximately 3.5 μm. Additionally, the two solutions showed reflectance of 8.01 % or 12.1 % in 400–1100 nm, respectively. Both processes used alkaline etching at 80 °C for saw damage removal (SDR) before texturing. These processes have also been investigated in terms of removing potential organic contaminants from surfaces. Characterization techniques used throughout the investigation included optical microscopy, surface reflectance measurements, scanning electron microscopy (SEM), and electron dispersive spectroscopy (EDS). The purpose of this study is to confirm through experiments which texturing techniques are more suitable for mass production and to develop time- and cost-effective texturing techniques for industrial production of high-throughput, high-efficiency solar cells.

Host sensitized down conversion emission in KSrVO4:Yb3+− A potential thermally stable phosphor for solar cell applications

This work reports the successful synthesis of an efficient near infra-red (NIR) emitting KSrVO4:Yb3+ phosphor using the combustion method. The X-ray diffraction technique (XRD) confirmed the orthorhombic phase of a material whereas X-ray photoelectron spectroscopy (XPS) analyzed the elemental makeup and chemical states of the phosphor components. Photoluminescence (PL) analysis revealed that the phosphor exhibit superior thermal stability and emit in the NIR region when activated by near-UV light. An upsurge in emission intensity occurs upon the incorporation of Bi3+ as a co-dopant. Using diffuse reflectance spectra (DRS), optical band gap, metallization constant, and refractive index were computed for all ion concentrations in KSr(1-x)VO4:xYb3+ (0 ≤x ≤ 0.06). For the optimized concentration of Yb3+ into the host, numerical values of these parameters were also estimated. The studies reveal that the produced material may be applied as a solar spectrum converter to improve the efficiency of crystalline silicon (c-Si) solar cells.

Upright Pyramid Surface Textures for Light Trapping and MoOx Layer in Ultrathin Crystalline Silicon Solar Cells

In this work, ray tracing is used to investigate the optical characteristics of various surface structures in ultrathin crystalline silicon (c-Si) for solar cells. Ultrathin c-Si with a thickness of 20 μm is used as the substrate. The light trapping includes front upright pyramids with a molybdenum oxides (MoOx) anti-reflection (AR) layer. Planar ultrathin c-Si (without a MoOx AR layer and upright pyramids) is used as a reference. The wafer ray tracer was developed by a photovoltaic (PV) lighthouse to model the MoOx AR layer to reduce the front surface reflectance and impacts of the AR layer on ultrathin Si solar cells. The optical properties are calculated on the AM1.5 global solar energy spectrum across the 200–1200 nm wavelength region. From the absorbance profile, the photogenerated current density (Jph) in the substrate is also calculated with various surface structures. The front upright pyramids with the MoOx layer result in the largest absorbance enhancement due to the enhanced light scattering by the pyramids and MoOx AR layer. The Jph of 37.41 mA/cm2 is improved when compared to the planar ultrathin c-Si reference. This study is significant as it illustrates the potential of ultrathin c-Si as a promising PV module technology in the future.

Scalable Fabrication Methods of Large‐Area (n‐i‐p) Perovskite Solar Panels

Organometal halide perovskite photovoltaic (PV) cells have achieved power conversion efficiencies (PCEs) comparable to the leading crystalline silicon (c‐Si) PV technology. However, despite their exceptional performance, these perovskite solar cells (PSCs) face technological challenges such as large‐area fabrication complexities and outdoor stability concerns. These challenges need to be addressed to pave the way for the commercialization of PSCs. The key to commercializing PSCs lies in developing stable, large‐area solar modules that offer both high efficiency and reliability. Overcoming the hurdles of large‐area module design and fabrication is a crucial step, and researchers are exploring innovative solutions to tackle these challenges. This review article primarily focuses on the development of large‐area PSCs, recent advancements in this field, and the obstacles related to scaling up this technology. It delves into the techniques used to fabricate perovskite films, with a special emphasis on large‐area and large‐scale PSC manufacturing methods. Moreover, the review highlights stability concerns that perovskite solar modules (PSMs) face and reports on recent progress in addressing these issues. The article concludes by summarizing potential future research directions aimed at realizing the full commercial potential of this innovative and promising solar cell technology.

Comparative analysis of radiation-induced effects on the performance of p-type PERC and TOPCon solar cells for space applications

This work presents a comprehensive numerical evaluation of PERC and TOPCon technologies, focusing on the impact of radiation-induced defects. This assessment is conducted for p-type silicon solar cells as they are intrinsically more resistant to radiation defects. By rigorously calibrating recombination parameters, radiation-induced defect profiles, and other pertinent details, a robust basis is established for an in-depth comparison of the performance characteristics displayed by both architectures under space conditions. The investigation reveals that when utilizing substrates with high doping levels, both PERC and TOPCon cells exhibit nearly identical beginning-of-life (BOL) and end-of-life (EOL) performance. However, with lower substrate doping concentrations, both technologies show improved BOL efficiency. Notably, this enhanced BOL efficiency does not translate into superior EOL efficiency. This distinction in EOL efficiency can be attributed to two primary factors triggered by radiation exposure. Firstly, the emergence of defects leads to a reduction in open-circuit voltage. Secondly, dopant compensation contributes to an increase in series resistance. Specifically, for PERC cells, the challenge of elevated series resistance is further exacerbated by the requirement for majority carriers to traverse both vertically and laterally to reach the rear metal contact. When a robust defect recovery mechanism or resilient cover glass is absent, substrates characterized by lower doping levels display increased susceptibility to the adverse effects of radiation-induced defects and the subsequent dopant compensation. Under these circumstances, the TOPCon technology demonstrates a significant advantage over PERC, particularly for high electron fluence due to its full area contacts for both minority and majority charge carriers.

Level set simulation of focused ion beam sputtering of a multilayer substrate.

The evolution of a multilayer sample surface during focused ion beam processing was simulated using the level set method and experimentally studied by milling a silicon dioxide layer covering a crystalline silicon substrate. The simulation took into account the redeposition of atoms simultaneously sputtered from both layers of the sample as well as the influence of backscattered ions on the milling process. Monte Carlo simulations were applied to produce tabulated data on the angular distributions of sputtered atoms and backscattered ions. Two sets of test structures including narrow trenches and rectangular boxes with different aspect ratios were experimentally prepared, and their cross sections were visualized in scanning transmission electron microscopy images. The superimposition of the calculated structure profiles onto the images showed a satisfactory agreement between simulation and experimental results. In the case of boxes that were prepared with an asymmetric cross section, the simulation can accurately predict the depth and shape of the structures, but there is some inaccuracy in reproducing the form of the left sidewall of the structure with a large amount of the redeposited material. To further validate the developed simulation approach and gain a better understanding of the sputtering process, the distribution of oxygen atoms in the redeposited layer derived from the numerical data was compared with the corresponding elemental map acquired by energy-dispersive X-ray microanalysis.

Elastic Stretch Limit Exceeding 10% for Silicon Wires with Submicron to Micron Diameters

It is significant to modulate the bandgap of crystalline silicon (c‐Si) by applying large strains on it through controlled stretch. However, investigations on the stretchability of c‐Si are still insufficient, especially for samples with feature sizes in the submicron to micron scale. In this work, the large stretchability of silicon wires with submicron to micron diameters (SiMWs) is reported for the first time by using vapor–liquid–solid grown ultralong SiMWs. The diameters of the SiMW specimens range from 400 nm to 1.8 μm. The loading speed for stretching SiMWs is 100 nm s−1. It is found that the SiMWs with micron diameter have a stretch limit over 10%, while the stretch limit for samples with submicron diameter can reach 12%. The results fill the gaps in the knowledge of micron‐scale silicon materials’ stretchability. The average Young's modulus of SiMWs is measured as 115 GPa. Cyclic loading tests indicate that the tensile deformation of SiMWs is elastic and reversible with no plastic deformation observed. In this work, it is shown that large stretch of SiMWs can be achieved without the need of harsh experimental conditions, which will greatly facilitate the study of large strain engineering on c‐Si to modulate their properties and broaden their applications.

Optimizing Solar Power Generation in Urban Industrial Blocks: The Impact of Block Typology and PV Material Performance

The block-scale application of photovoltaic technology in cities is becoming a viable solution for renewable energy utilization. The rapid urbanization process has provided urban buildings with a colossal development potential for solar energy in China, especially in industrial areas that provide more space for the integration of PV equipment. In developing solar energy resources, the block layout and the PV materials are two critical factors affecting the distribution of solar radiation and generation. However, few studies have analyzed how to select the most suitable PV materials for different layouts of industrial blocks to obtain the best generation. This study considered the layout of industrial blocks and PV materials simultaneously, and the generation yield was calculated when combined. A total of 40 real industrial block cases were constructed, and radiation distribution data on building surfaces of different block cases were calculated. Data on both were combined to calculate the generation of different PV materials for each block type. The findings indicated that single-story industrial blocks possessed the highest potential for solar radiation, primarily due to the higher percentage of roof area. The influence of PV materials on the installation rate of different building facades varied, with the installation rate of the west facade being the most impacted by PV performance and the roof being the least impacted. Using different PV materials in industrial blocks could lead to a 59.2% difference in solar generation capacity. For single-layer industrial blocks, mono crystalline and poly crystalline silicon were preferable to achieve higher power generation. In contrast, multi-story and high-rise industrial blocks were best suited for a-Si and CIGS to attain higher cost performance. The methods and results of this study guided the selection and installation of PV equipment in various block typologies, thereby improving the refinement of solar resource development, maximizing solar resource utilization, and promoting the development of energy conservation and carbon reduction in cities.

Cohesive behavior of single crystalline silicon carbide scribing by nanosecond laser

Cohesive behavior of single crystalline silicon carbide scribing by nanosecond laser

Versatile femtosecond laser interference patterning applied to high-precision nanostructuring of silicon

We present a high-precision nanostructuring technique based on beam interference from a commercial Ti:Sa femtosecond amplified laser (800 nm, 120 fs, 1 kHz, 1 mJ). Its potential and versatility is illustrated by applying the technique to the nanostructuring of silicon. Employing commercial and ad-hoc laser-fabricated diffractive optical elements together with standard optical components, periodic line gratings and spot arrays with tunable periods down to 650 nm can readily be fabricated. Moreover, fabrication of millimeter-size diffraction gratings via multipulse irradiation at processing speeds up to 0.5 mm/s is demonstrated. The variety of structures written in crystalline silicon feature amorphous fringes and dots with widths down to 300 nm. The corresponding complex topography profiles consist of surface elevations and depressions with sizes down to 120 nm that can be controlled by the laser fluence and fringe width, demonstrating the presence of several competing matter reorganization processes in the molten phase. The exceptional high-contrast ratio of the fringe intensity together with a near-Gaussian intensity envelope of the laser spot enable patterning with well-defined local fluences, paving the way for single-pulse fluence-dependent studies. The high-quality experimental data that can be obtained with this technique can prove critical for modelling attempts aimed at unravelling the underlying formation mechanisms of complex surface topographies in a wide range of materials. Furthermore, the technique presented here has outstanding potential for the rapid and versatile fabrication of high-precision metasurfaces.

Single-beam low-frequency loss modulation technique for two-photon absorption measurement

We present a straightforward and reliable single-beam configuration designed for the assessment of two-photon absorption (2PA) through the utilization of the loss modulation technique. Mechanical rotation of a half-wave plate induces a sinusoidal modulation in the envelope of the probe pulse train. The elimination of spurious signals is achieved by determining the difference of the lock-in amplifier output at the focused and defocused positions of the sample. Our findings, based on measurements with dye solutions and crystalline silicon, demonstrate the feasibility of determining the 2PA coefficient, subject to preliminary calibration of the setup with reference samples. Remarkably, the acquisition of the 2PA signal in silicon at 1030 nm is accomplished with less than 200 pJ energy of the laser pulse, overcoming the challenge posed by concurrent linear absorption. Additionally, a signal of 3PA is revealed despite the presence of 2PA and linear absorption.

Rational design and elucidation of interfacial dynamics in PMMA/PVDF compatibilized blends through solution blending for stable quasi-solid-state dye-sensitized solar cells

In the photovoltaic market, the widespread adoption of traditional dye-sensitized solar cells (DSSCs) faces obstacles due to inherent stability challenges. The solution to these issues involves replacing liquid electrolytes with quasi-solid electrolytes. In this work, quasi-solid state electrolytes were synthesized by employing a polymer blend and inorganic salt. The polymeric blends, comprising polymethyl methacrylate (PMMA) and polyvinylidene fluoride (PVDF), were meticulously prepared through the solution blending technique. The investigation of blend compatibility, crystallinity, and stability involved analyses through differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-degradation assessments, respectively. The findings indicated that the concentration of ingredients significantly influenced the compatibility, crystallinity, and stability of the blends. The compatibilized blend was employed in crafting polymer gel electrolytes (PEGs), demonstrating that both the concentration and type of salts significantly influence the ionic conductivity of PEGs. The highest conductivity, reaching 2 mS/cm, was achieved with a mixed salt concentration of 50w%/50w% (NH4I/KI). Subsequently, this electrolyte was incorporated into the fabrication of quasi-solid state DSSC. The results showed that the DSSC with PEG achieved 2.81 % efficiency, while the traditional DSSC had 4.11 % efficiency. Notably, after fifteen days, the efficiency of the traditional DSSC dropped to 0.20 %, while the PEG-based DSSC remained stable (2.58 %).

Tunnel oxide thickness-dependent dominant carrier transport in crystalline silicon solar cells

Silver consumption reduction is a current development in commercial tunnel passivated contact (TOPCon) crystalline silicon solar cell devices aimed at lowering the entire production cost of photovoltaic energy sources. It depends on the number of fingers and/or finger spacing (SP) on a cell area. In this paper, we analyze the possibility of minimizing silver use with respect to the dominant carrier transport mechanism. The carrier transporting mechanism, such as “pinhole” and/or “tunnel” models, is identified by examining temperature-dependent I–V characteristics of polysilicon passivating contact as a function of tunnel oxide (TO) thickness from 0.6 to 2.2 nm. Thermal oxidation was used to produce ultrathin TO films (0.6–2.2 nm) with temperature and gas ratio controlled. We find that the “pinholes” transport mechanism prevails when the TO thickness exceeds 1.6 nm, whereas the “tunnel” mode dominates when the TO thickness is less than 1.4 nm. The pinhole density is critical in pinhole mode for increasing SP. It is found that low pinhole densities and thick TO thickness (more than 1.6 nm) are two of the primary causes of narrow SP in TOPCon devices, which need a considerable quantity of silver. The experimental TOPCon devices as a function of TO thickness show a considerable trade-off between open circuit voltage (Voc) and fill factor (FF). While Voc rises, FF drops as TO thickness increases. The mechanism is described.

Comparative analysis of phase coherence length in polycrystalline CdO films on two distinct substrates

The role of substrates in thin film growth encompasses structural and morphological characteristics which, as a consequence, can also affect electronic properties. This article reports studies on the structural, morphological, and magnetotransport properties of Cadmium Oxide (CdO) films grown on two distinct substrates, amorphous glass, and crystalline silicon, by spray pyrolysis technique. The crystallinity of CdO grown on Silicon (CdO/Si) is higher as compared to the CdO grown on glass (CdO/glass), although CdO/Si morphology presents a dome-like surface. In both cases, samples showed exponential behavior in the electrical resistance curves in the temperature ranges between 1.9 K to 300 K and negative magnetoresistance, due to the weak localization effect, for temperatures lower than 110 K. The highest electronic mobility for CdO/Si is attributed to the better crystallinity of the domes. The weak localization effect is correlated by the 3D Kawabata model, fitting the magnetoresistance curves to determine the phase coherence length over a temperature range of 4.2 K to 100 K. Despite the huge differences in the morphological and electrical properties, the linear behavior of temperature-dependent phase coherence length, attributed to the electron-electron interaction in this temperature range, is found to be independent of the employed substrate. This remarkable result indicates the potential application of the low-cost spray pyrolysis technique for producing high-speed photodetectors.