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[ASME ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - San Francisco, California, USA (Monday 27 August 2018)] ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - The Effects of Temperature, Strain Rate, and Aging on the Poisson’s Ratio of SAC Lead Free Solders
摘要： In this study, we have conducted a combined numerical and experimental study on the Poisson’s ratio of SAC lead free solders. The Poisson’s ratio (PR) is one of the basic mechanical properties used in many material constitutive models. Although often not measured, it is important property in many finite element method (FEM) calculations. The value of the Poisson’s ratio of SAC lead free solders is relatively unexplored compared to other material properties, and for FEA simulations it is typically assumed to be ? = 0.3. In the current work, we have shown the effects of the chosen value of the solder joint Poisson’s ratio on the finite element results for BGA components subjected to thermal cycling. In the finite element models, the reliability predictions were based on the Morrow-Darveaux energy-based fatigue model. Several sizes (5, 10, 15 mm) of PBGA components with SAC305 solder joints with 0.4 and 0.8 mm spacing were modeled. The packages were subjected to a time dependent cyclic temperature distribution from -40 to 125 oC. The package assemblies were assumed to be in a stress-free state at 25 oC (room temperature), with no residual stresses induced in the manufacturing process. The simulation results have demonstrated that for specified range of Poisson’s ratio values of 0.15 < ??< 0.40, the solder Plastic Work varied over 20% and the Predicted Reliability Varied over 50%. To determine the actual Poisson’s ratio experimentally, uniaxial tensile stress-strain tests were carried out on SAC305 (96.5Sn3.0Ag0.5Cu) specimens using a micro tension/torsion testing machine with two strain rates (0.0001, and 0.00001 (sec-1)), four testing temperatures (T = 25, 50, 75, 100 oC), and several durations of prior aging at T = 125 oC. Deformations and strains in axial and transverse directions were measured using strain gages with automatic data acquisition from LabVIEW software. The recorded transverse strain vs. axial strain data were then fit with a linear regression analysis to determine the Poisson’s ratio values. A test matrix of experiments was developed to study the effects of temperature, strain rate, alloy composition, and solidification cooling profile on the value of solder Poisson’s ratio. The Poisson’s ratio was found to increase with increasing temperature, and decrease with increasing strain rate. Using a slower solidification cooling profile led to an increase in the solder Poisson’s ratio value. Finally, the microstructural coarsening that occurs during isothermal aging lead to an increase in the Poisson’s ratio.
关键词： FEA,Lead Free Solder,Reliability,DAQ,PBGA Packaging
更新于2025-09-23 15:21:21
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Formation of stable 2D methylammonium antimony iodide phase for lead-free perovskite-like solar cells
摘要： The presence of lead in novel hybrid perovskite-based solar cells remains a significant issue regarding commercial applications. Therefore, antimony-based perovskite-like A3M2X9 structures are promising new candidates for low toxicity photovoltaic applications. So far, MA3Sb2I9 was reported to only crystallize in the ‘zero-dimensional’ (0D) dimer structure with wide indirect bandgap properties. However, the formation of the 2D layered polymorph is more suitable for solar cell applications due to its expected direct and narrow bandgap. Here, we demonstrate the first synthesis of phase pure 2D layered MA3Sb2I9, based on antimony acetate dissolved in alcoholic solvents. Using in situ XRD methods, we confirm the stability of the layered phase towards high temperature, but the exposure to 75 % relative humidity for several hours leads to a rearrangement of the phase with partial formation of the 0D structure. We investigated the electronic band structure and confirmed experimentally the presence of a semi-direct bandgap at around 2.1 eV. Our work shows that careful control of nucleation via processing conditions can provide access to promising perovskite-like phases for photovoltaic applications.
关键词： antimony,perovskite solar cells,2D materials,lead-free,photovoltaic applications
更新于2025-09-23 15:21:01
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A Guide to Small-Scale Energy Harvesting Techniques || Quest for Lead-Free Perovskite-Based Solar Cells
摘要： Today, the perovskite solar cells (PSCs) are showing excellent potentials in terms of simple processing, abundance of materials, and architectural integration, as well as very promising device’s power conversion efficiencies (PCEs), rocketed from 3.8% in 2009 to 23.3% in 2018. However, the toxic lead (Pb) element containing the chemical composition of typically used organic-inorganic halide perovskites hinders the practical applications of PSCs. This chapter starts with a general discussion on the perovskite crystal structure along with the serious efforts focused on Pb replacement in these devices. Section 2 will elaborate the fundamental features of tin (Sn)-based perovskites together with their performance in the PSCs. Other alternative elements, such as copper (Cu), germanium (Ge), bismuth (Bi), and antimony (Sb), will be discussed in Section 3. The end will summarize the challenges and opportunities based on the chapter contents.
关键词： stability,lead-free perovskites,chemical composition,toxicity
更新于2025-09-23 15:21:01
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Lead-free perovskite/organic semiconductor vertical heterojunction for highly sensitive photodetectors
摘要： In recent years, photodetectors based on organic-inorganic lead halide perovskites have been studied extensively. However, the inclusion of lead in those materials can cause severe human health and environmental problems, which is undesirable for practical applications. Here, we report high-performance photodetectors with a tin-based perovskite/PEDOT:PSS vertical heterojunction. The device demonstrates broadband photo-response from NIR to UV. The maximum responsivity and gain are up to 2.6 × 106 A/W and 4.7 × 106, respectively. Moreover, a much shorter response time and higher detectivity can be achieved by reducing the thickness of PEDOT:PSS. The outstanding performance is due to the excellent optoelectronic properties of the perovskite and the photo-gating effect originated from the heterojunction. Furthermore, devices fabricated on flexible substrates can demonstrate not only high sensitivity but also excellent bending stability. This work opens up the opportunity of using lead-free perovskite in highly sensitive photodetectors with vertical heterojunctions.
关键词： Photo-gating,heterojunction,organic semiconductors,Photodetectors,Lead free perovskites
更新于2025-09-23 15:21:01
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Controlled-Atmosphere Sintering of KNbO3
摘要： The e?ect of sintering atmosphere (O2, air, N2, N2-5% H2, and H2) on the densi?cation, grain growth, and structure of KNbO3 was studied. KNbO3 powder was prepared by solid state reaction, and samples were sintered at 1040 C for 1–10 h. The sample microstructure was studied using Scanning Electron Microscopy (SEM). The sample structure was studied using X-Ray Di?raction (XRD). H2-sintered samples showed reduced density, whereas other sintering atmospheres did not a?ect density much. Samples sintered in N2-5% H2 showed abnormal grain growth, whereas sintering in other atmospheres caused stagnant (O2, air, N2) or pseudo-normal (H2) grain growth behavior. Samples sintered in reducing atmospheres showed decreased orthorhombic unit cell distortion. The grain growth behavior was explained by the mixed control theory. An increase in vacancy concentration caused by sintering in reducing atmospheres led to a decrease in the step free energy and the critical driving force for appreciable grain growth. This caused grain growth behavior to change from stagnant to abnormal and eventually pseudo-normal.
关键词： lead-free piezoelectric,microstructure grain growth,alkali niobate
更新于2025-09-23 15:21:01
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Laser-Induced Optoelectronic and Crystallographic Tuning of Methyl Ammonium Iodobismuthate Perovskite for Improved Performance of Sandwiched a?? Type Photodetectors
摘要： Towards development of high-performance perovskite based photodetectors, it is required that optical and crystallographic properties of perovskites materials be enhanced through perovskites materials modification. Many attempts on this quest result in alteration of chemical structure of perovskites materials through introduction of dopants. Here in, we present a clean and structural preservative technique of tuning optical and crystallographic properties of bismuth based lead free perovskite materials through irradiation with 2.5 mJ laser pulses ejected from Nd:YAG LASER operating in its second harmonics. XRD spectra show improved crystallinity and reduced crystallite size, SEM images show defect – minimized surface morphology, PL spectra show minimized rate of Auger recombination and absorbance spectra show improved absorbance at a constant band gap value. Consequently, simplified sandwiched architectural type photodetectors fabricated with the modified bismuth based perovskite materials display maximum photodetectivity of 4.5 × 109 Jones, maximum photoresponsivity of 25 μA/W, maximum photosensitivity of about 104 and minimum optical switching times of 10 ms under testing conditions of -2 V bias voltage, 15 mW/cm2 incident solar light and room temperature. Thus, laser pulses irradiation presents an alternative method of enhancing optical and crystallographic properties of perovskite materials from which highly efficient classes of photonics and photovoltaic devices can be developed.
关键词： Laser Irradiation,crystallographic properties,optical properties,perovskite photodetectors,lead free perovskites materials
更新于2025-09-23 15:21:01
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Tin halide perovskite films made of highly oriented 2D crystals enable more efficient and stable lead-free perovskite solar cells
摘要： Low toxicity and an ideal energy bandgap make 2D Ruddlesden-Popper tin-based halide perovskites a promising photovoltaic material. However, the disordered crystal orientation and the oxidation of Sn2+ to Sn4+ still need to be addressed. Here, we demonstrate that the annealing of FASnI3 assisted by phenyl ethyl ammonium chloride enables the formation of more ordered 2D tin-based perovskite crystals oriented vertically. We use in-situ synchrotron-based grazing incident X-ray diffraction (GIXRD) to correlate the higher crystal orientation to the better device performance. We measured a maximum power conversion efficiency of >9%. Furthermore, we demonstrate that the phenyl ethyl ammonium chloride acts as a barrier layer at the surface of the crystals protecting the tin from the oxidation. Hence, this work paves the way for more efficient and stable lead-free perovskite solar cells.
关键词： phenyl ethyl ammonium chloride,photovoltaic material,crystal orientation,lead-free perovskite solar cells,oxidation of Sn2+,2D Ruddlesden-Popper tin-based halide perovskites,power conversion efficiency
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Room Temperature Synthesis of Lead-Free Sn/Ge-Based Perovskite Quantum Dots
摘要： Metal halide perovskites have received remarkable attention as photovoltaic (PV) devices. These have already achieved power conversion efficiency higher than 23% rivaling that of silicon-based PV. However, these outstanding efficiencies can only be acquired with lead-based perovskites and the devices are chemically unstable in air and moisture. Therefore, the key to the widespread deployment of perovskite-based solar cell will come down to address their “toxicity” and instability problems. We have taken the challenge to replace lead with other nontoxic or less toxic elements, e.g., Sn, and Ge. We have synthesized Cs(Sn,Ge)X3 (X=I, Br, and Cl) quantum dots (QDs) using room temperature process. The XRD data showed that the synthesized QDs were yellow hexagonal phase, which was further confirmed by the hexagonal shape of the TEM images of the crystals.
关键词： solar cell,nanoparticle,photoluminescence,doping,Lead-free perovskite
更新于2025-09-23 15:21:01
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Indenea??C <sub/>60</sub> Bisadduct Electron Transporting Material with the High LUMO Level Enhances Open-Circuit Voltage and Efficiency of Tin-Based Perovskite Solar Cells
摘要： Tin-based halide perovskite materials are promising eco-friendly light absorbers with similar optoelectronic properties to lead-based ones. However, their solar cells have suffered from considerably low open-circuit voltage (VOC) arising from mismatched energy levels between tin-based perovskite and charge-transporting layers because they imitate typical device structures developed for lead-based ones. Herein we report the unoccupied molecular orbital (LUMO) level of electron transporting layer (ETL) significantly affects VOC of tin-based perovskite solar cells (PSCs) in contrast to lead-based ones. The indene?C60 bisadduct (ICBA) ETL with the much higher LUMO level than typical ETLs decreases an energy off-set with the conduction band minimum of mixed formamidinium/phenylethylammonium tin iodide (FA0.9PEA0.1SnI3)-based perovskite material. The resultantly reduced VOC loss at their interface gives a VOC of 0.651 V, the highest to date for FASnI3-based PSCs. An achieved champion PCEs reaches 7.05%. This result highlights the importance of redesigning device structures dedicated to tin-based PSCs.
关键词： open-circuit voltage,electron transportation,perovskite solar cells,lead-free,tin
更新于2025-09-23 15:21:01
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Energy storage properties in BaTiO <sub/>3</sub> -Bi <sub/>3.25</sub> La <sub/>0.75</sub> Ti <sub/>3</sub> O <sub/>12</sub> thin films
摘要： Developing lead-free film dielectric capacitors with high-performance of energy storage density, efficiency, fatigue endurance, and thermal stabilities is desirable. Here, we report energy storage properties in (1-x)BaTiO3-xBi3.25La0.75Ti3O12 thin films. It is revealed that a 0.6BaTiO3-0.4Bi3.25La0.75Ti3O12 thin film with a thickness of 280 nm and a crystallization temperature of 650 °C shows a breakdown strength of 3.23 MV/cm with a large polarization value and dielectric constant. An ultrahigh energy storage density of 61.1 J/cm3 and an efficiency of 84.2% are simultaneously achieved at room temperature. Additionally, excellent fatigue endurance after 6 × 109 cycles and good thermal stability up to 150 °C are observed, implying excellent energy storage performance in 0.6BaTiO3-0.4Bi3.25La0.75Ti3O12 thin films.
关键词： energy storage,thin films,BaTiO3-Bi3.25La0.75Ti3O12,dielectric capacitors,lead-free
更新于2025-09-23 15:21:01