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Strain Mapping of CdTe Grains in Photovoltaic Devices
摘要： Strain within grains and at grain boundaries (GBs) in polycrystalline thin-film absorber layers limits the overall performance because of higher defect concentrations and band fluctuations. However, the nanoscale strain distribution in operational devices is not easily accessible using standard methods. X-ray nanodiffraction offers the unique possibility to evaluate the strain or lattice spacing at nanoscale resolution. Furthermore, the combination of nanodiffraction with additional techniques in the framework of multimodal scanning X-ray microscopy enables the direct correlation of the strain with material and device parameters such as the elemental distribution or local performance. This approach is applied for the investigation of the strain distribution in CdTe grains in fully operational photovoltaic solar cells. It is found that the lattice spacing in the (111) direction remains fairly constant in the grain cores but systematically decreases at the GBs. The lower strain at GBs is accompanied by an increase of the total tilt. These observations are both compatible with the inhomogeneous incorporation of smaller atoms into the lattice, and local stress induced by neighboring grains.
关键词： X-ray microscopy,nanodiffraction,X-ray diffraction (XRD),solar cells,multimodal,CdTe,X-ray,strain,X-ray fluorescence (XRF),photovoltaic,X-ray beam induced current (XBIC)
更新于2025-09-19 17:13:59
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Fabrication of silicon carbide nanoparticles using picosecond pulsed laser ablation in acetone with characterizations from TEM and XRD
摘要： We fabricated SiC nanoparticles (NPs) using a laser ablation method in acetone with a picosecond pulsed laser and characterized the resulting sizes, shapes, and crystal structures using transmission electron microscopy (TEM) and X-ray diffraction (XRD). We revealed two formation processes for the SiC NPs. The main process was the formation of spherical NPs with diameters primarily less than 10 nm. The crystal structure was 3C-SiC, which did not depend on a target polytype. Therefore, it is concluded that these NPs are grown from atomic molecules that disassociate from targets in the ablation process. As a result of a Rietbelt analysis of the XRD patterns, we clearly found that almost all NPs were single crystals. In addition, a stacking fault in the crystal was observed in the TEM image, which affects the XRD pattern. The other process was the formation of NPs with diameters from 30 to 80 nm with crystal structures that were the same as the targets. This indicates that these NPs were generated as fragments of the target. Our findings are useful for applications of SiC NPs to selectively control their size, shape, and crystal structure using laser ablation.
关键词： silicon carbide nanoparticles,3C-SiC,picosecond pulsed laser ablation,TEM,XRD
更新于2025-09-19 17:13:59
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Visualizing different crystalline states during the infrared imaging of calcium phosphates
摘要： Methods utilizing relatively simple mathematical operations during physical analyses to enable the visualization of otherwise invisible correlations and effects are of particular appeal to researchers and students in pedagogical settings. At the same time, discerning the amorphous phase from its crystalline counterpart in materials is challenging with the use of vibrational spectroscopy and is nowhere as straightforward as in phase composition analytical methods such as X-ray diffraction. A method is demonstrated for the use of first- and second-order differentiation of Fourier transform infrared spectra of calcium phosphates to distinguish their amorphous states from the crystalline ones based on the exact line positioning rather than on comparatively vaguer band broadening and splitting effects. The study utilizes a kinetic approach, focusing on the comparison of spectral features of amorphous precursors annealed in air at different temperatures or aged for different periods of time in an aqueous solution until transforming to one or a mixture of crystalline phases, including hydroxyapatite and α- and β-tricalcium phosphate. One of the findings challenges the concept of the nucleation lag time preceding the crystallization from amorphous precursors as a “dead” period and derives a finite degree of constructive changes occurring at the atomic scale in its course. The differential method for highlighting spectral differences depending on the sample crystallinity allows for monitoring in situ the process of conversion of the amorphous calcium phosphate phase to its crystalline analogue(s). One such method can be of practical significance for synthetic solid state chemists testing for the chemical stability and/or concentration of the reactive amorphous phase in these materials, but also for biologists measuring the maturity of bone and medical researchers evaluating its phase composition and, thus, the state of metabolic and mechanical stability.
关键词： Hydroxyapatite,XRD,Derivative method,Crystallization,Amorphous,FTIR,Tricalcium phosphate
更新于2025-09-19 17:13:59
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Aga??doped PbS thin films by nebulizer spray pyrolysis for solar cells
摘要： Silver (Ag)-doped PbS (PbS:Ag) thin films of 616 to 745 nm in thickness were prepared on glass substrates via cost-effective nebulizer spray method by adding different Ag levels from 2% to 8% at 200°C. For solar cell applications, the effect of Ag doping concentration on structural, morphological, optical, photoluminescence, and electrical chattels of PbS thin film has been studied. X-ray diffraction pattern confirmed the polycrystalline behavior of the prepared PbS:Ag films with cubic crystalline nature. The crystalline size and texture coefficient were increased by increasing Ag doping concentration. From the morphological studies by scanning electron microscope (SEM) and atomic force microscope (AFM), the grain size of the films and surface roughness values were increased for the increase in Ag doping concentration. EDS spectra confirmed the existence of Ag, Pb, and S elements in the select 6% Ag-doped PbS film. Peaks related to silver oxide started to emerge at 6% of Ag doping level. The optical direct band gap value was reduced from 1.51 to 1.17 eV for Ag doping from 2% to 6% and thereby slightly increased as 1.79 eV for 8% Ag doping level. For all PbS:Ag films, the photoluminescence spectrum emitted a strong near band edge (NBE) emission at approximately 580 nm, meaning better optical quality. Hall effect measurements evidenced that Ag doping provides enhancement on the characteristics of mobility, carrier concentration, and resistivity with p-type conducting nature. The observed high carrier concentration and low resistivity values were 4.32 × 1014 cm?3 and 80 Ωcm, for 6% Ag-doped PbS film. The FTO/CdS/PbS:Ag heterostructure solar cell was formed from 6% Ag-doped film.
关键词： XRD,hall effect,thin film,PbS:Ag,solar cell
更新于2025-09-19 17:13:59
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Size-controlled MoS<sub>2 </sub>nanosheet through ball milling exfoliation: parameter optimization, structural characterization and electrocatalytic application
摘要： Unique properties and potential applications of 2D materials draw much attention for mass production of thin-layer 2D materials. Ball milling exfoliation of 2D materials has been rarely used, in spite of a promising dry phase production method, because of the superficial information in the mechanism and the effect of the operating parameters on the yield, size and thickness. Here, we investigate systematically the ball milling operating parameters in the exfoliation of bulk MoS2 in the presence of sodium cholate (SC) as an exfoliant. The yield and dimensions of the exfoliated MoS2 nanosheet were monitored by changing the parameters such as the weight ratio of bulk MoS2 and SC (SC/MoS2), the filling ratio in the volume of milling ball and container (!), milling ball size (dB), milling revolution speed (nR), and initial mass of bulk MoS2 (mMoS2). The yield of exfoliation is found to be 95% at the optimum ball milling conditions (SC/MoS2 = 0.75, ! = 50%, mMoS2 = 0.20 g). In addition, yield and size of the exfoliated MoS2 were controlled by the conditions of the ball milling. As for the evaluation of size and thickness of the ball-milled MoS2 powder with less than 30% difference from those determined by the well-known absorption method. Finally, the size and thickness of the MoS2 nanosheets prepared by ball milling exfoliation were correlated with their electrocatalytic and photoelectrocatalytic activities.
关键词： electrocatalyst,sodium cholate,nanosheet,exfoliation,Ball milling,molybdenum disulfide,XRD
更新于2025-09-19 17:13:59
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A multi-level optical storage scheme via two-step picosecond laser irradiations: time/space modulations of microstructure and its optical property
摘要： China has a considerable lignite deposit in the Xinjiang province, but surface and underground coal seam fires pose a threat to the resources, environment, economy, and health. As the chemical and physical structure impacts coal fire propensity and behavior, two raw Xinjiang lignites were examined from the Shaerhu (SEH) and Piliqing (PLQ) Collieries. The SEH lignite is more prone to spontaneous combustion (from regional observations). These coals were of the same geological age and were both inertinite-rich 69.8 and 95.6% for SEH and PLQ, respectively (by the point counting approach). The more spontaneous combustion prone lignite had a significantly higher micropore contribution and surface area (92.4% and 195.6 m2/g), while both coals had similar micro- and mesopore size distribution ranges. Despite being classified as lignite by the mean vitrinite random reflectance (Rr, 0.30 and 0.26%) the inertinite contribution displaces some of the structural properties to be similar to the vitrinite-rich, high-volatile bituminous rank. The lignite coals had similar carbon content (74.6 and 78.4 wt % for SEH and PLQ) and vitrinite reflectance but differed in ash, volatile matter, total moisture, and fixed carbon yields. The crystallite parameters [from X-ray diffraction (XRD)], the interlayer spacing, crystallite height, crystallite diameter, and the numbers of aromatic layer indicated the more inertinite-rich coal (PLQ) was slightly less ordered. Both coals were highly aromatic for lignites (fa values of 0.72 and 0.71 for SEH and PLQ), as the inertinite-rich components are more aromatic and polycondensed than huminite-rich (a low rank counterpart of vitrinite) coals of similar reflectance values. Image analysis of high-resolution transmission electron microscopy lattice fringes determined the aromatic fringe length distributions, with contributions between 0.25 and 0.50 nm accounting for 37.1% for PLQ, while SEH had a lower contribution of 28.0% but also a greater contribution of longer fringes (larger polycyclic aromatic hydrocarbon cluster sizes). Image analysis of the lattice fringe orientation and XRD analysis also indicated that the SEH lignite was more ordered. These two coals are potential coals for further exploration of spontaneous combustion behavior for inertinite-rich coals.
关键词： inertinite,lignite,spontaneous combustion,LDIMS,HRTEM,solid-state 13C NMR,XRD
更新于2025-09-19 17:13:59
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Strategy of Residual Stress Determination on Selective Laser Melted Al Alloy Using XRD
摘要： Selective laser melting (SLM) is known to generate large and anisotropic residual stresses in the samples. Accurate measurement of residual stresses on SLM-produced samples is essential for understanding the residual stress build-up mechanism during SLM, while a dramatic fluctuation can be observed in the residual stress values reported in the literature. On the basis of studying the influence of surface roughness on residual stress measured using X-ray diffraction (XRD), we propose a procedure coupling XRD technique with pretreatment consisting of mechanical polishing and chemical etching. The results highlight that residual stresses measured using XRD on as-built SLM-produced samples with high surface roughness are significantly lower than those measured on samples with finished surface, which is due to the stress relaxation on the spiked surface of as-built samples. Surface distribution of residual stresses and the effect of scanning strategy were systematically investigated for SLM-produced AlSi10Mg samples. Microstructural morphology was observed at the interface between sample and building platform and was linked to the surface distribution of residual stresses. This procedure can help us accurately measure the residual stresses in SLM-produced samples and thus better understand its build-up mechanism during the SLM process.
关键词： X-ray diffraction (XRD),residual stresses,AlSi10Mg,selective laser melting,surface roughness
更新于2025-09-19 17:13:59
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Synthesis and characterization of inorganic K3Bi2I9 perovskite thin films for lead-free solution processed solar cells
摘要： Bismuth halide perovskites have been proposed as a non-toxic and chemically stable alternative to lead halide perovskites. Despite being highly stable, the devices based on bismuth perovskites have not been able to compete with the lead counterparts in terms of its ef?ciencies. The compounds that have been extensively studied i.e. Cs3Bi2I9 and MA3Bi2I9 form 0D (dimer) structures that possess wide indirect band gaps and poor charge transport properties which hinders the performance of devices based on these materials. Theoretical studies have revealed that replacing bigger A cation like Cs/MA by smaller cation like potassium (K) could favor the formation of layered 2D structures rather than 0D structure. We have synthesized inorganic K3Bi2I9 perovskite thin ?lms by facile one-step spin coating method and investigated its structural, optical and morphological properties. The fabricated ?lms showed strong absorption in UV and visible region of solar spectrum and possess optical band gap (cid:1)2 eV. On comparison with the Cs analogue, it is observed that reduction in the cation size (Cs to K) hardly changes the band gap of K3Bi2I9 ?lms which implies that the band gap of A3Bi2I9 perovskite is insensitive to A-site variation. Films deposited on preheated substrates showed comparatively good coverage without voids on the ?lm surface. Our preliminary studies on this material showed that the ?lms deposited by one-step solution method favored 0D structure rather than the expected 2D layered structure.
关键词： Thin ?lms,K3Bi2I9 perovskite,XRD,Spin coating,XPS
更新于2025-09-19 17:13:59
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Structure and thermal investigation of the effect of laser radiation in Chitosan-MgO nanocomposite film
摘要： In this study, Chitosan-MgO nanocomposite was prepared using a simple chemical precipitation method and characterized using scanning electron microscopy (SEM). Chitosan-MgO nanocomposite samples were exposed to laser pulses with fluencies ranging from 2 to 25 J/cm2. The structural modifications in the exposed nanocomposite samples were studied as a function of laser fluencies using various characterization techniques such as X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results indicate that the laser exposure up to 25 J/cm2 results in the production of broken molecular chains, reducing the thermal stability of the Chitosan-MgO nanocomposite. In addition, the melting temperature is found to be sensing the crystalline domains. Higher laser fluences cause the generation of defects that can lead to lowering the melting temperature.
关键词： laser,XRD,Nanocomposites,FTIR,thermal properties
更新于2025-09-19 17:13:59
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Binary transition metal sulfides as an economical Pt-free counter electrodes for dye-sensitized solar cells
摘要： Binary CuxCoySz sulfide based Pt-free counter electrodes (CE) were prepared in one-step solvothermal synthesis process. The obtained CEs were characterized by SEM, XRD, and Raman spectroscopy methods. EDX analysis showed uniform distribution of Cu, Co and S. SEM images revealed different level of coverage of the FTO glass by the binary metal sulfide products. DSSCs were constructed using proposed CEs with N719 dye, and their photovoltaic and electrochemical performances were assessed against Pt reference cell. The efficiency of the CuxCoySz-3 CE produced an 11% improvement of its photovoltaic efficiency compared to the reference cell.
关键词： Cu-Co-S complex,SEM,XRD,Solvothermal synthesis,Raman
更新于2025-09-16 10:30:52