Versatile control of metal-assisted chemical etching for vertical silicon microwire arrays and their photovoltaic applications

Abstract

A systematic study was conducted into the use of metal-assisted chemical etching (MacEtch) to fabricate vertical Si microwire arrays, with several models being studied for the efficient redox reaction of reactants with silicon through a metal catalyst by varying such parameters as the thickness and morphology of the metal film. By optimizing the MacEtch conditions, high-quality vertical Si microwires were successfully fabricated with lengths of up to 23.2 μm, which, when applied in a solar cell, achieved a conversion efficiency of up to 13.0%. These solar cells also exhibited an open-circuit voltage of 547.7 mV, a short-circuit current density of 33.2 mA/cm2, and a fill factor of 71.3% by virtue of the enhanced light absorption and effective carrier collection provided by the Si microwires. The use of MacEtch to fabricate high-quality Si microwires therefore presents a unique opportunity to develop cost-effective and highly efficient solar cells.

Evidences for redox reaction driven charge transfer and mass transport in metal-assisted chemical etching of silicon

“…The difference lies in how the reagents and by-products are transported into and out of the metal/Si interface. Model II describes this transport via the boundary of the metal/Si interface23262728 while Model III describes the transport through the porous metal film41518.…”

“…However, we do not rule out other possible contributing factors in the formation of the cracks or pores. Mechanical stresses from unequal etch rates may possibly cause some crack formation for micrometer size structures415, while other causes including the pressure created from hydrogen generation and the transport of reagents/by-products can all add to the dynamic redistribution process in the eventual formation of pores.…”

“…In particular, silicon nanowires (NWs) find a wide array of usage in areas such as electronics12, photovoltaics34, energy storage5, optical devices67, catalysis8, drug delivery9, thermoelectrics10, as well as biological and chemical sensors111213. The importance of fabricating reliable Si nanowires has provided the motivation for the exploration of many different fabrication methods.…”

“…In particular, there is still a lack of understanding in the fundamental reasons behind the stop-etch phenomenon shown by metals like chromium (Cr)22232425, and also debates about the mass transport during etching415182023262728. This knowledge is important to understand the basic MacEtch mechanism.…”

Silicon Nanowires Substrates Fabrication for Ultra-Sensitive Surface Enhanced Raman Spectroscopy Sensors

“…Therefore the choice of the appropriate substrate for a specific analyte and the analyte vicinity to metal NP is of the high importance. [9,10] Among non-colloidal substrates, silicon nanostructures such as porous silicon [6] and silicon nanowires [2][3][4][5]7] (SiNWs) draw attention owing to their low-cost fabrication and high SERS measurement reproducibility. SiNWs can be produced by chemical vapour deposition, laser ablation, vapour transport and condensation, molecular beam epitaxy, annealing of catalytic nanoclusters on silicon, solution growth, and catalytic etching.…”