Flexible solar cells based on foldable silicon wafers with blunted edges.

Flexible solar cells have a lot of market potential for application in photovoltaics integrated into buildings and wearable electronics because they are lightweight, shockproof and self-powered. Silicon solar cells have been successfully used in large power plants. However, despite the efforts made for more than 50 years, there has been no notable progress in the development of flexible silicon solar cells because of their rigidity1-4. Here we provide a strategy for fabricating large-scale, foldable silicon wafers and manufacturing flexible solar cells. A textured crystalline silicon wafer always starts to crack at the sharp channels between surface pyramids in the marginal region of the wafer. This fact enabled us to improve the flexibility of silicon wafers by blunting the pyramidal structure in the marginal regions. This edge-blunting technique enables commercial production of large-scale (>240 cm2), high-efficiency (>24%) silicon solar cells that can be rolled similarly to a sheet of paper. The cells retain 100% of their power conversion efficiency after 1,000 side-to-side bending cycles. After being assembled into large (>10,000 cm2) flexible modules, these cells retain 99.62% of their power after thermal cycling between -70 °C and 85 °C for 120 h. Furthermore, they retain 96.03% of their power after 20 min of exposure to air flow when attached to a soft gasbag, which models wind blowing during a violent storm.

Inverted pyramid structures fabricated on monocrystalline silicon surface with a NaOH solution.

Low-cost aqueous alkaline etching has been widely adopted for monocrystalline silicon surface texturing in current industrial silicon solar cells. However, conventional alkaline etching can only prepare upright pyramid structures on mono-crystalline silicon surfaces. This study demonstrates for the first time the use of ethylene glycol butyl ether (EGBE) to regulate aqueous anisotropic alkaline etching and prepare inverted pyramid structures on monocrystalline silicon surfaces. Acidic metal-catalyzed etching solutions are not the best choice for monocrystalline silicon due to their inherent disadvantages, such as noble metal pollution and relatively high costs. The one-step method to produce the inverted pyramid structures by using alkaline etch with EGBE additive is simple and inexpensive, does not generate noble metal pollution, and especially compatible with current industrial silicon solar cell production lines. With the use of a sodium hydroxide (NaOH) solution containing a low-cost additive, inverted pyramid structures can be prepared on mono-crystalline silicon surface in a short time. This method is suitable for various types of silicon wafers and has great potential for industrial solar cell applications.

Heavy Boron-Doped Silicon Tunneling Inter-layer Enables Efficient Silicon Heterojunction Solar Cells.

P-type hydrogenated nanocrystalline silicon (nc-Si:H) has been used as a hole-selective layer for efficient n-type crystalline silicon heterojunction (SHJ) solar cells. However, the presence of an additional valence band offset at the interface between intrinsic amorphous hydrogenated silicon and p-type nc-Si:H films will limit the hole carrier transportation. In this work, it has been found that when a heavily boron-doped silicon oxide layer deposited with high hydrogen dilution to silane (pB) was inserted into their interface, the fill factor of SHJ solar cells increases 3% absolutely because of the reduced valence band offset and the increased opportunity to provide a hopping tunnel assisted by the doping energy level and valence band tail states. Furthermore, the additional boron incorporation in intrinsic amorphous silicon adjacent to pB helps to enhance the built-in electric field, thus increasing the hole selectivity. By these means, the power conversion efficiency was improved from 23.9% to approximately 25%.

Optimization of Multi-Objective Mobile Emergency Material Allocation for Sudden Disasters.

The mobile emergency system is a new emergency mode that provides a solution to deal with increasingly frequent sudden disasters by reasonably allocating mobile emergency facilities and optimizing the allocation of mobile emergency materials. We consider mobile emergency cost and mobile emergency time as two objective functions. This paper establishes a multi-objective mobile emergency material allocation model, and transforms the multi-objective. We choose the emergency material transportation path for coding, and apply the hybrid leapfrog algorithm for material allocation to obtain the optimal solution. Finally, the feasibility of the model is verified by taking Zhengzhou urban area under the "21.7" severe rainstorm and flood disaster in Henan Province. The result analyses show that the model can correspond to each stage of mobile emergency material allocation based on the value of cost preference, and put forward suggestions on the location of mobile emergency facilities and the amount of material allocation.

Silicon surface patterning via galvanic microcontact imprinting lithography.

Surface patterning without requiring expensive facilities and complex procedures is a major scientific and technological challenge. We report a simple surface patterning strategy on a silicon wafer surface. This strategy, termed galvanic microcontact imprinting lithography (GMIL), is based on the spontaneous galvanic oxidation of silicon due to the electrically coupled silicon/gold mold with lithographically defined patterns. The galvanic induced silicon oxide pattern can be selectively removed in dilute HF solution or serve as a robust etchant resist in alkaline solution, enabling the formation of regular silicon microstructures on the silicon surface, affording an accessible, simple and cheap surface patterning method with no requirement of expensive and sophisticated instrumentation and facilities. These results may open exciting prospects for next-generation low-cost lithographic techniques.

Gold-Sensitized Silicon/ZnO Core/Shell Nanowire Array for Solar Water Splitting.

Solar water splitting represents one of the most promising strategies in the quest for clean and renewable energy. However, low conversion efficiency, use of sacrificial agents, and external bias for current water splitting system limit its practical application. Here, a gold-sensitized Si/ZnOcore/shell nanowire photoelectrochemical (PEC) cell is reported for efficient solar water oxidation. We demonstrated gold-sensitized n-Si/n-ZnO nanowire arrays exhibited higher energy conversion efficiency than gold-sensitized p-Si/n-ZnO nanowire arrays due to the favorable energy-band alignment characteristics. Without any assistance from an external electrical source and sacrificial reagents, gold-sensitized n-Si/n-ZnO core/shell nanowire array photoanode achieved unbiased water splitting under simulated solar light illumination. This method opens a promising venue to cost-efficient production of solar fuels.