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.
Highlights
Preventing optimal structures being achieved such as undesired etching, a low etch rate, and surface non-uniformity
Problems can be encountered as a result of undesired nanostructures being created from voids or fractures in the metal film used as a catalyst[38,40]. This means that a MW solar cell with a greater light trapping efficiency than a planar solar cell may still have a lower power conversion efficiency (PCE)[7] due to the surface non-uniformity created by a non-optimized MacEtch process
It is found that the Au film needs to have a thickness of 30 to 40 nm and a fast deposition rate (≥ 3 Å/s) if high-quality vertically aligned Si MWs are to be obtained without surface damage, and so optimization of the Au catalyst structure was used to increase the length of the high-quality Si MWs obtained
Summary
Preventing optimal structures being achieved such as undesired etching, a low etch rate, and surface non-uniformity. It is found that the Au film needs to have a thickness of 30 to 40 nm and a fast deposition rate (≥ 3 Å/s) if high-quality vertically aligned Si MWs are to be obtained without surface damage (i.e., a high etch rate is needed), and so optimization of the Au catalyst structure was used to increase the length of the high-quality Si MWs obtained. These MWs were subsequently used for the fabrication of photovoltaic devices, the performance of which is discussed
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