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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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

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

Solution processed PCBM-CH3NH3PbI3 heterojunction photodetectors with enhanced performance and stability

In this work, an anti-solvent process was used to fabricate a perovskite-PCBM bulk heterojunction, in which PCBM diffused in CH3NH3PbI3 and passivated grain boundary defects. Different concentrations of PCBM were studied in this paper. When a low concentration (5 mg/ml, 10 mg/ml or 15 mg/ml) of PCBM was used, the PCBM-CH3NH3PbI3 transition layer provided efficient electron collection. With the increase of the concentration of PCBM, a thicker PCBM layer was formed in the bulk heterojunction. Such a thick PCBM resulted in rough perovskite morphology and low photo-carrier collection efficiency. SEM images and metallographic microscope images confirmed that the PCBM upper layer gradually covered grain boundaries of perovskite films with the increase of the PCBM concentration. On the other hand, low concentrations of PCBM improved the light absorption and crystallinity of CH3NH3PbI3 films. The PCBM/perovskite heterojunction exhibited a high UV responsivity of 0.18 AW-1 and a response time less than 123 ms. This research provides a way to improve the quality of perovskite films and the performance of perovskite photodetectors