The development of high‐performance dopant‐free silicon solar cells is severely bottlenecked by opaque electron selective contact. In this paper, high transmittance (80.5% on glass) and low work function (2.92 eV) lithium fluoride (LiF x )/MgF x O y electron contact stack by tailoring the composition of MgF x O y hybrid film is reported. This hybrid structure exhibits a high conductivity (2978.4 S cm −1 ) and a low contact resistivity (2.0 mΩ cm 2 ). The element profile of LiF x /MgF x O y contact is measured and the reaction kinetics is analyzed. As a proof‐of‐concept, this electron selective contact is applied for dopant‐free silicon solar cells. An impressive efficiency of 21.3% is achieved on dopant‐free monofacial solar cell with molybdenum oxide (MoO x )/zinc‐doped indium oxide (IZO) hole contact. An efficiency bifaciality of 71% is obtained for dopant‐free bifacial solar cell with full‐area LiF x /MgF x O y /ITO (tin‐doped indium oxide) transparent electron contact. It is the highest efficiency bifaciality so far for dopant‐free bifacial solar cells to the best knowledge. Both cell configurations with LiF x /MgF x O y contacts show excellent environment stability. The cell efficiency maintains more than 95% of its initial value after keeping in air for 1500 h. This work provides a new idea to achieve transparent electron contact, showing a great potential for high‐efficiency and low‐cost optoelectronic devices.

Pipe is the main transportation way for oil and natural gas. Fault movement mainly caused by earthquake, which will induce pipe bending, tension and compression. Then oil or gas leakage appear. Based on the moving mechanism of strike‐slip fault and reverse fault, a numerical simulation model was employed to study the buckling evolution mechanism of the buried steel pipe under fault movements. The evolution processes of buried pipe under the fault moving action were analyzed, and the effects of pipe internal pressure, fault displacement, and pipe diameter‐to‐thickness ratio on the pipe buckling were discussed. The results demonstrate that there are three mechanical evolution stages on the pipe in the process of fault movement. High stress appears on the bending regions of pipe wall, and axial strain always fluctuates along the axial length. When the fault displacement is large, pipe collapsing and wrinkling patterns occur, which can be reflected by a sharp fluctuation of axial strain. The high‐pressure pipe under the action of reverse fault is prone to failure than the low‐pressure pipe. The pipe with a large D/t in the hanging wall is easier to be buckled than that with a small  D/t in the footwall. The results obtained can be used for the design and evaluation of buried oil and gas pipes.

Multistaged hydraulic fracturing of a horizontal well may significantly improve the permeability of the calcareous shale reservoir, but hard to improve the transport capacity of gas in nanopores, resulting in insufficient gas supply from the shale matrix to fractures and rapid production decline after the stimulation. Nevertheless, the seepage capacity and production will increase due to the water-rock interaction during the soaking process after fracturing. Our research proposes to utilize the reaction between persulfate and calcareous shale to strengthen the water-rock interaction, achieving oxidative dissolution and swelling. Ammonium persulfate was selected as the fracturing fluid additive to analyze the effect of oxidative dissolution and swelling on the macroscopic and microscopic seepage capacity of calcareous shale through technical means such as stress sensitivity test, NMR, and SEM. We conclude that persulfate’s oxidative dissolution and swelling will greatly promote fractures and increase permeability in calcareous shale reservoirs to reconstruct the seepage channels. The findings of this study have implications for determining and optimizing the fracturing fluid’s performance and the postfracturing production management system to develop calcareous shale reservoirs in a green and efficient manner.

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Highly efficient dopant-free silicon solar cell requires effective electron-and hole-selective contacts. We have recently reported a remarkable efficiency of 21.3% for dopant-free silicon solar cells with a low work function and transparent and conductive MgF x O y electron extraction. The transparent conductive oxide (TCO) films and molybdenum oxide (MoO x ) front hole contact also play significant roles in the high efficiency of dopant-free solar cells. In this study, zinc-doped indium oxide (IZO), tin-doped indium oxide (ITO), and titanium-doped indium oxide (ITiO) have been deposited via magnetron sputtering at room temperature. The work function and optoelectrical properties of TCO films and energy band bending together with the MoO x layer are investigated. The impact of this band bending on the photoelectrical performances of devices is analyzed in detail as a function of the MoO x / TCO work function mismatch. The optimized IZO film presents the highest work function (5.21 eV) and conductivity (2140 S/ cm), resulting in reduced barrier height at the MoO x /TCO interface and enhanced hole-selective transport. The light-soaking treatment is introduced to repair the sputtered damage during the IZO deposition. Finally, an impressive cell efficiency of 21.0%, together with V oc , FF, and J sc of 712.4 mV, 76.4%, and 38.6 mA/cm 2 , respectively, shows great potential and provides an effective solution to obtain highly efficient dopant-free silicon solar cells.