Abstract
Nanostructured black silicon (b-Si) surfaces with an extremely low reflectance are a promising light-trapping solution for silicon solar cells. However, it is challenging to develop a high-efficiency front-junction b-Si solar cell due to the inferior electrical performance of b-Si emitters, which outweighs any optical gain. This article uses three-dimensional numerical nanoscale simulations, which are corroborated with experiment results, to investigate the effect of the surface nanofeature sizes on the b-Si emitter performance in terms of the sheet resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sheet</sub> ) and the saturation current density (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0e</sub> ). We show that the specific surface area (SSA) is an effective parameter to evaluate the nanofeature size. A shallow surface nanofeature with a large SSA will contribute to a better electrical performance. We will show that b-Si emitter R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sheet</sub> measured by a four-point probe is not a measure of the doping level in the nanofeature, but is ruled by the doping level in the underlying substrate region. We also show that a small nanofeature with SSA > 100 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> and height < 100 nm can lead to a relatively low J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0e</sub> (33 fA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> lower than the best b-Si results reported in the literature) by suppressing surface minority carrier density and minimizing the total Auger recombination loss.
Highlights
B LACK silicon (b-Si) generally refers to a type of lowreflectance silicon surface nanotexture that appears black to the naked eye
As specific surface area (SSA) is a relative size metric associated with the surface area, it would be more meaningful to investigate the nanofeatures with different SSA values but similar enhanced area factor (EAF) values when studying the effects of sizes
The effects of nanofeature sizes on the electrical performance of b-Si emitters were investigated by numerical simulations using Synopsys Sentaurus TCAD
Summary
B LACK silicon (b-Si) generally refers to a type of lowreflectance silicon surface nanotexture that appears black to the naked eye. B-Si shows great potential in solar cell applications, as was demonstrated for interdigitated-back-contact solar cells with an undiffused low-reflectance b-Si front surface [10]–[12]. This application benefits from the atomic-layer-deposited conformal thin films, which overcome b-Si surface passivation challenges [13]–[16]. For applying the low-reflectance b-Si on front-junction solar cells, there are no reported efficiencies higher than 20% This is attributed to the inferior electrical performance which outweighs the gain in optical performance [19], [20]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call