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AIP Conference Proceedings [Author(s) SILICONPV 2018, THE 8TH INTERNATIONAL CONFERENCE ON CRYSTALLINE SILICON PHOTOVOLTAICS - Lausanne, Switzerland (19–21 March 2018)] - Atom probe Tomography of fast-diffusing impurities and the effect of gettering in multicrystalline silicon
摘要： This article demonstrates an approach for multiscale characterisation of individual defects, such as grain boundaries, in multicrystalline silicon. The analysis techniques range from macroscale characterisation of average bulk lifetime, through photoluminescence to resolve spatial recombination, and finally to nanoscale analysis of the crystallographic characteristics and impurity decoration of the grain boundary using Transmission Kikuchi Diffraction and Atom Probe Tomography. This method can be used to characterise defects and their response to processing, such as gettering and hydrogen passivation. In this paper it is applied to the test case of Saw Damage Gettering on Red Zone High Performance Multicrystalline Silicon. In both as-cast and gettered samples, copper and chromium were observed at a recombination active, random angle grain boundary. After gettering the copper excess was found to decrease. In contrast, the slower diffusing chromium was found to increase, potentially indicating internal gettering. At a recombination inactive Σ3 grain boundary only oxygen was observed at the boundary before gettering, with no transition metals detected.
关键词： multicrystalline silicon,grain boundaries,gettering,impurities,Atom Probe Tomography
更新于2025-11-21 11:20:48
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Assessment of Bulk and Interface Quality for Liquid Phase Crystallized Silicon on Glass
摘要： This paper reports on the electrical quality of liquid phase crystallized silicon (LPC-Si) on glass for thin-film solar cell applications. Spatially resolved methods such as light beam induced current (LBIC), microwave photoconductance decay (MWPCD) mapping, and electron backscatter diffraction were used to access the overall material quality, intra-grain quality, surface passivation, and grain boundary (GB) properties. LBIC line scans across GBs were fitted with a model to characterize the recombination behavior of GBs. According to MWPCD measurement, intra-grain bulk carrier lifetimes were estimated to be larger than 4.5 μs for n-type LPC-Si with a doping concentration in the order of 1016 cm?3. Low-angle GBs were found to be strongly recombination active and identified as highly defect-rich regions which spatially extend over a range of 40–60 μm and show a diffusion length of 0.4 μm. Based on absorber quality characterization, the influence of intra-grain quality, heterojunction interface, and GBs/dislocations on the cell performance were separately clarified based on two-dimensional (2-D)-device simulation and a diode model. High back surface recombination velocities of several 105 cm/s are needed to get the best match between simulated and measured open circuit voltage (Voc), indicating back surface passivation problem. The results showed that Voc losses are not only because of poor back surface passivation but also because of crystal defects such as GBs and dislocation.
关键词： Bulk lifetime,heterojunction,grain boundaries (GBs),two-dimensional (2-D)-device simulation,liquid phase crystallized silicon (LPC-Si),light beam induced current (LBIC)
更新于2025-11-14 15:25:21
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Revisiting the structures and energies of silicon ?110? symmetric tilt grain boundaries
摘要： Atomistic simulations of 18 silicon ?110? symmetric tilt grain boundaries are performed using Stillinger Weber, Tersoff, and the optimized Modified Embedded Atom Method potentials. We define a novel structural unit classification through dislocation core analysis to characterize the relaxed GB structures. GBs with the misorientation angle h ranging from 13.44° to 70.53° are solely composed of Lomer dislocation cores. For GBs with h less than but close to 70.53°, GB 'step' appears and the equilibrated states with lowest GB energies can be attained only when such GB 'step' is located in the middle of each single periodic GB structure. For the misorientation angles in the range of 93.37° ￡ h ￡ 148.41°, GB structures become complicated since they contain multiple types of dislocation cores. This work not only facilitates the structural characterization of silicon ?110? STGBs, but also may provide new insights into mirco-structure design in multicrystalline silicon.
关键词： silicon,structural units,energies,grain boundaries,atomistic simulations,dislocation cores
更新于2025-09-23 15:22:29
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Grain boundaries and tilt angle-dependent transport properties of 2D Mo2C superconductor
摘要： Grain boundaries (GBs) of graphene and molybdenum disulfide have been extensively demonstrated to have strong influence on their electronic, thermal, optical and mechanical properties. 2D transition metal carbides (TMCs), known as MXenes, are a rapidly growing new family of 2D materials with many fascinating properties and promising applications. However, the GB structure of 2D TMCs and the influence of GB on their properties still remain unknown. Here, we used aberration-corrected scanning transmission electron microscopy combined with electrical measurements to study the GB characteristic of highly crystalline 2D Mo2C superconductor, a newly emerging member of 2D TMC family. 2D Mo2C superconductor shows unique tilt angle-dependent GB structure and electronic transport properties. Different from the reported 2D materials, the GB of 2D Mo2C shows peculiar dislocation configuration or sawtooth pattern depending on the tilt angle. More importantly, we found two new periodic GBs with different periodic structure and crystallographic orientations. Electrical measurements on individual GBs show that GB structure strongly affects the transport properties. In the normal state, an increasingly stronger electron localization behavior is observed at the GB region with increasing tilt angle. In the superconducting state, the magnitude of the critical current across the GBs is dramatically reduced, associated with local suppression of superconductivity at GBs. These findings provide new understandings on the GB structure of 2D TMCs and the influence of GB on 2D superconductivity, which would be helpful for tailoring the properties of 2D TMCs through GB engineering.
关键词： dislocations,MXene,2D materials,grain boundaries,superconductivity
更新于2025-09-23 15:22:29
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Granular Inhomogeneity Formation during Quartz Glass Melting
摘要： This paper examines the formation of fine-grain inhomogeneity in quartz glass. We demonstrate that this defect emerges during the melting of fine-particle crystalline raw materials and the formation of a three-dimensional intergranular network, which contains a high impurity concentration and has a disordered structure. The present results are inconsistent with the existing believe that incomplete melting of quartz grains is the main cause of the development of fine-grain inhomogeneity. In contrast, prolonged high-temperature heat treatment increases the intergranular impurity concentration and intensifies the effect.
关键词： quartz grit grains,grain boundaries,structural impurities,structure of quartz glass
更新于2025-09-23 15:22:29
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The effect of grain-size on fracture of polycrystalline silicon carbide: A multiscale analysis using a molecular dynamics-peridynamics framework
摘要： A robust atomistic to mesoscale computational multiscale/multiphysics modeling framework that explicitly takes into account atomic-scale descriptions of grain-boundaries, is implemented to examine the interplay between grain-size and fracture of polycrystalline cubic silicon carbide (3C-SiC). A salient feature of the developed framework is the establishment of scale-parity between the chosen atomistic and the mesoscale methods namely molecular dynamics (MD) and peridynamics (PD) respectively, which enables the ability to model the effect of the underlying microstructure as well as obtain relevant new insights into the role of grain-size on the ensuing mechanical response of 3C-SiC. Material properties such as elastic modulus, and fracture toughness of single crystals and bicrystals of various orientations are obtained from MD simulations, and using appropriate statistical analysis, MD derived properties are interfaced with PD simulations, resulting in mesoscale simulations that accurately predict the role of grain-size on failure strength, fracture energy, elastic modulus, fracture toughness, and tensile toughness of polycrystalline 3C-SiC. In particular, it is seen that the fracture strength follows a Hall-Petch law with respect to grain-size variations, while mode-I fracture toughness increases with increasing grain-size, consistent with available literature on brittle fracture of polycrystalline materials. Equally importantly, the developed MD-PD multiscale/multiphysics framework represents an important step towards developing materials modeling paradigms that can provide a comprehensive and predictive description of the microstructure-property-performance interplay in solid-state materials.
关键词： Peridynamics,Polycrystalline,Multiscale modeling,3C-SiC,Grain boundaries,Molecular dynamics
更新于2025-09-23 15:22:29
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Investigation of hydrogen effect on phosphorus-doped polysilicon thin films
摘要： Polycrystalline silicon is widely used in microelectronic and photovoltaic applications. The main problem of this material is the recombination of charge carriers at the grain boundaries which affects the efficiency of the polycrystalline silicon solar cells. In order to improve the crystalline quality and the electrical properties of phosphorus-doped poly-silicon thin films, heat treatments under hydrogen were carried out. This allowed the occupation of the dangling bonds at the grain boundaries and made them inactive, which resulted in improved optoelectronic properties of the treated samples. It has been shown that the effect of hydrogen on the electrical characteristics is more pronounced for low doping concentrations where a 20% improvement of the free carrier concentration was obtained. In addition, the results have shown that the introduction of hydrogen in poly-silicon thin films reduces the density of trap states at the grain boundaries.
关键词： hydrogen,passivation,solar cells,grain boundaries,Polycrystalline silicon
更新于2025-09-23 15:21:21
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Effect of Grain Size on the Fracture Behavior of Organic-Inorganic Halide Perovskite Thin Films for Solar Cells
摘要： Organic-inorganic halide perovskite (OIHP) thin ?lms at the heart of the new perovskite solar cells (PSCs) are very brittle, limiting the mechanical reliability of PSCs. Here we show that ?ne-grained MAPbI 3 (prototypical OIHP) ?lms with grain size (~290 nm) smaller than the typical ?lm thickness (~500 nm) tend to fracture intergranularly, resulting in low toughness (0.41 J.m ?2 ). In contrast, MAPbI 3 /substrate interfacial fracture occurs in ?lms with grains larger (~730 nm) than the ?lm thickness, resulting in much higher toughness (1.14 J.m ?2 ). Thus, coarse-grained OIHP ?lms are deemed desirable for not only improved PSCs performance and stability but also mechanical reliability.
关键词： Thin ?lms,Solar cells,Halide perovskites,Mechanical behavior,Grain boundaries
更新于2025-09-23 15:21:01
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A New Strategy for Increasing the Efficiency of Inverted Perovskite Solar Cells to More than 21%: Higha??Humidity Induced Selfa??Passivation of Perovskite Films
摘要： The performance of perovskite solar cells (PSCs) are known to be extremely sensitive to humidity in the preparation environment. However, the main mechanism by which the moisture influences the quality of the perovskite film and the device performance is not yet completely revealed. In this work, we established a new strategy to obtain inverted PSCs with remarkable high VOC by including a high-humidity treatment and sufficient DMSO-atmosphere annealing in the preparation process. We found that the lattice distortion on the surface of perovskite grains caused by the high-humidity treatment played a key role in the self-passivation of perovskite. Inverted (p-i-n) PSCs based on the self-passivated perovskite films showed effective suppression of non-radiative recombination, which increased the device VOC to 1.17 V and achieved the highest efficiency of 21.38 %. It is expected that the findings of this work shed more light on the currently proposed mechanism governing the action of moisture on the performance of the PSCs.
关键词： Self-passivation,High open-circuit voltage,Perovskite solar cells,High-humidity,Grain boundaries
更新于2025-09-23 15:19:57
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Grain Boundaries Limit the Charge Carrier Transport in Pulsed Laser Deposited ?±-SnWO <sub/>4</sub> Thin Film Photoabsorbers
摘要： Recently, α-SnWO4 attracted attention as a material to be used as a top absorber in a tandem device for photoelectrochemical water splitting due to its nearly optimum bandgap of ~1.9?eV and an early photocurrent onset potential of ~0 V vs. RHE. However, the mismatch between the charge carrier diffusion length and light penetration depth—which is typical for metal oxide semiconductors—currently hinders the realization of high photoconversion efficiencies. In this work, the pulsed laser deposition process and annealing treatment of α-SnWO4 thin films are elucidated in order to optimize their charge carrier transport properties. A high temperature treatment is found to enhance the photoconductivity of α-SnWO4 by more than one order of magnitude, as measured with time-resolved microwave conductivity (TRMC). A complimentary analysis by time-resolved terahertz spectroscopy (TRTS) shows that this improvement can be assigned to an increase of the grain size in the heat-treated films. In addition, TRTS reveals electron-hole charge carrier mobilities of up to 0.13 cm2 V-1s-1 in α-SnWO4. This is comparable to values found for BiVO4, which is one of the best performing metal oxide photoanode materials to date. These findings show that there is a significant potential for further improving the properties of α-SnWO4 photoanodes.
关键词： α-SnWO4,metal oxide photoelectrodes,grain boundaries,charge carrier dynamics,pulsed laser deposition
更新于2025-09-23 15:19:57