Wafer-Scale Fabrication of Silicon Nanocones via Controlling Catalyst Evolution in All-Wet Metal-Assisted Chemical Etching

Investigations on Optical Absorption and the Pyro-phototronic Effect with Selectively Patterned Black Silicon for Advanced Photodetection

A novel property existing in the stain-etching technique that eliminates the need for expensive etchant masks in the texturization process of silicon wafers was identified. Through the combination of grayscale lithography and stain-etching methodologies, selective patterning of silicon with AR-P 3510 T, a positive-photoresist mask, was carried out. The etch area ratio was varied in nine different patterns of various feature sizes ranging from 400 to 1500 μm. The optical characteristics of the patterned substrates were determined from diffuse reflectance spectroscopy analysis, and the results were supported with finite-difference time-domain simulations. Complimenting the improvement in optical properties, the electrical losses in microwell-patterned photodetector devices have been reduced with an electro-optic optimum value of the surface enhancement factor, γ. The photodetecting efficiency of a selectively patterned microwell photodetector device exceeded the planar and black silicon photodetector devices with a considerable improvement in the pyro-phototronic effect. This work suggests an alternative for black silicon optoelectronic devices providing a new route to fabricate selectively patterned substrates with an achieved detectivity 16- and 20-fold higher than black and planar silicon photodetector devices, respectively.

Modulating the density of silicon nanowire arrays for high-performance hydrovoltaic devices

Hydrovoltaic devices (HDs) based on silicon nanowire (SiNW) arrays have received intensive attention due to their simple preparation, mature processing technology, and high output power. Investigating the impact of structure parameters of SiNWs on the performance of HDs can guide the optimization of the devices, but related research is still not sufficient. This work studies the effect of the SiNW density on the performance of HDs. SiNW arrays with different densities were prepared by controlling the react time of Si wafers in the seed solution (tseed) in metal-assisted chemical etching. Density of SiNW array gradually decreases with the increase oftseed. HDs were fabricated based on SiNW arrays with different densities. The research results indicate that the open-circuit voltage gradually decreases with increasingtseed, while the short-circuit current first increases and then decreases with increasingtseed. Overall, SiNW devices withtseedof 20 s and 60 s have the best output performance. The difference in output performance of HDs based on SiNWs with different densities is attributed to the difference in the gap sizes between SiNWs, specific surface area of SiNWs, and the number of SiNWs in parallel. This work gives the corresponding relationship between the preparation conditions of SiNWs, array density, and output performance of hydrovoltaic devices. Density parameters of SiNW arrays with optimized output performance and corresponding preparation conditions are revealed. The relevant results have important reference value for understanding the mechanism of HDs and designing structural parameters of SiNWs for high-performance hydrovoltaic devices.

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.

Rationally designed nanoarray catalysts for boosted photothermal CO2 hydrogenation

It is of emerging interest to convert CO₂ and green H₂ into solar fuels with great efficiency through photothermal CO₂ hydrogenation. However, designing photothermal catalysts with improved sunlight harvesting ability, intrinsic catalytic activity, and thermal management to prevent heat dissipation still remains rather challenging. Herein, we report a facile structural engineering strategy for preparing efficient nanoarray-based photothermal catalysts with strong light absorption ability, high metal dispersity, and effective thermal management. Optimizing the 120 μm-SiNCs@Co catalyst allowed it to reach a record high Co-based photothermal CO₂ conversion rate of 1780 mmol g_Co^-1 h^-1. This study provides insight into the structural engineering of photothermal catalysts for enhanced catalytic performance and lays a foundation for efficient photothermal CO₂ catalysis.