1,955 research outputs found
Reflection seismic waveform tomography of physical modelling data
Waveform tomography is commonly tested using numerically generated synthetic seismic data, before the method is applied to field seismic data. However, there are often noticeable differences between idealized synthetic data and real field data, and many factors in the field data, such as noise, irregular source/receiver geometry, affect the inversion solutions. For exploring the potential of reflection seismic waveform tomography, we presented a more realistic test than the synthetic data test, by applying it to physical modelling data, to reconstruct a laboratorial model with complex velocity variation. First, we provided a formulation of the perfectly matched layer absorbing boundary condition, associated with the second-order acoustic wave equation, in order to suppress artificial reflections from subsurface model boundaries in seismic waveform simulation and tomography. Then, we demonstrated the successful implementation of a layer-striping inversion scheme applicable to reflection seismic waveform tomography. Finally, we confirmed the effectiveness of frequency grouping, rather than a single frequency at each iteration, a strategy specifically for the frequency-domain waveform tomography
Inhibition of PKCβ2 overexpression ameliorates myocardial ischaemia/reperfusion injury in diabetic rats via restoring caveolin-3/Akt signaling
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An optimized SPDMFE extrapolation approach based on the POD technique for 2D viscoelastic wave equation
A POD-based reduced-order TSCFE extrapolation iterative format for two-dimensional heat equations
Enhanced efficiency and environmental stability of planar perovskite solar cells by suppressing photocatalytic decomposition
The environmental instability of perovskite solar cells caused by the ultraviolet photocatalytic effect of metal
oxide layers is a critical issue that must be solved. In this paper, we report improved environmental stability
of ZnO film-based planar heterojunction perovskite solar cells, by suppressing photocatalytic activities
induced by the ZnO electron transfer layer. The photovoltaic performance and stability in an ambient
environment under continuous illumination are effectively improved by applying an aluminum oxide
interlayer on the ZnO film to suppress the photocatalytic degradation of perovskites. The highest
efficiency of solar cells has increased from 14.62% to 17.17%, and after 250 h of continuous exposure
under full spectrum simulated sunlight in air, the efficiency remains as high as 15.03%. The results
suggest that effective suppression of photocatalytic degradation of perovskites with a modified electron
transfer layer is a new solution to improve the long-term environmental stability of perovskite solar cells
Interface engineering of high efficiency perovskite solar cells based on ZnO nanorods using atomic layer deposition
Despite the considerably improved efficiency of inorganic–organic metal hybrid perovskite solar cells (PSCs), electron transport is still a challenging issue. In this paper, we report the use of ZnO nanorods prepared by hydrothermal self-assembly as the electron transport layer in perovskite solar cells. The efficiency of the perovskite solar cells is significantly enhanced by passivating the interfacial defects via atomic layer deposition of Al2O3 monolayers on the ZnO nanorods. By employing the Al2O3 monolayers, the average power conversion efficiency of methylammonium lead iodide PSCs was increased from 10.33% to 15.06%, and the highest efficiency obtained was 16.08%. We suggest that the passivation of defects using the atomic layer deposition of monolayers might provide a new pathway for the improvement of all types of PSCs.
Mesoporous PbI2 assisted growth of large perovskite grains for efficient perovskite solar cells based on ZnO nanorods
Perovskite solar cells (PSCs) have attracted great attention due to their low cost and high power conversion efficiency (PCE). However, the defects and grain boundaries in perovskite films dramatically degrade their performance. Here, we show a two-step annealing method to produce mesoporous PbI2 films for growth of continuous, pinhole-free perovskite films with large grains, followed by additional ethanol vapor annealing of perovskite films to reduce the defects and grain boundaries. The large perovskite grains dramatically suppress the carrier recombination, and consequently we obtain ZnO-nanorod-based PSCs that exhibit the best efficiency of 17.3%, with high reproducibility
Theoretical lifetime extraction and experimental demonstration of stable cesium-containing tri-cation perovskite solar cells with high efficiency
Despite the high power conversion efficiency, the severe performance degradation of organic-inorganic lead halide perovskite solar cells caused by moisture and thermal phase transition is an obstacle to commercialization of the perovskite solar cells. We propose the theoretical lifetime extraction of perovskite solar cells with a mixed-cations lead halide perovskite absorber containing CH3NH3+, CH3(NH2)2+ and Cs+. The estimated mean time to failure (MTTF) of the triple cation perovskite solar cells is up to 180 days in ambient. Compared with the perovskite solar cells based on CH3NH3PbI3, the triple-cation perovskite solar cells, whose power conversion efficiency reaches 18.2% in this study, have a much better performance in terms of thermal stability and humidity stability. Improvements of both performance and stability pave the way for commercialization of perovskite solar cells
Enhanced electronic transport in Fe3+-doped TiO2 for high efficiency perovskite solar cells
Oxygen vacancies in non-stoichiometric TiO2 electron transport layers can capture injected electrons and act as recombination centers. In this study, the compact TiO2 electron transport layers of perovskite solar cells (PSCs) are doped with different molar ratios of Fe3+ in order to passivate such defects and improve their electron transport properties. The electrical conductivity, absorption, crystal structure, and the performance of the PSCs are systematically studied. It shows that Fe3+-doping improves the conductivity of TiO2 compact layers compared with the pristine TiO2, boosting the photovoltaic performance of PSCs. The reduced trap-filled limit voltage (VTFL) of the Fe3+-doped TiO2 compact layers suggests that trap density in the Fe3+-TiO2 films is much lower than that of a pristine TiO2 film. With the optimized doping concentration (1 mol%) of Fe3+, the best power conversion efficiency of PSCs is improved from 16.02% to 18.60%
Stitching triple cation perovskite by a mixed anti-solvent process for high performance perovskite solar cells
With the rapid development of organic-inorganic lead halide perovskite photovoltaics, increasingly more attentions are paid to explore the growth mechanism and precisely control the quality of perovskite films. In this study, we propose a “stitching effect” to fabricate high quality perovskite films by using chlorobenzene (CB) as an anti-solvent and isopropyl alcohol (IPA) as an additive into this anti-solvent. Because of the existence of IPA, CB can be efficiently released from the gaps of perovskite precursors and the perovskite film formation can be slightly modified in a controlled manner. More homogeneous surface morphology and larger grain size of perovskite films were achieved via this process. The reduced grain boundaries ensure low surface defect density and good carrier transport in the perovskite layer. Meanwhile, we also performed the Fourier transform infrared (FTIR) spectroscopy to investigate the film growth mechanism of unannealed and annealed perovskite films. Solar cells fabricated by using the “stitching effect” exhibited a best efficiency of 19.2%. Our results show that solvent and solvent additives dramatically influenced the formation and crystallization processes for perovskite materials due to their different coordination and extraction capabilities. This method presents a new path towards controlling the growth and morphology of perovskite films
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