Abstract
Owing to its extremely low light absorption, black silicon has been widely investigated and reported in recent years, and simultaneously applied to various disciplines. Black silicon is, in general, fabricated on flat surfaces based on the silicon substrate. However, with three normal fabrication methods—plasma dry etching, metal-assisted wet etching, and femtosecond laser pulse etching—black silicon cannot perform easily due to its lowest absorption and thus some studies remained in the laboratory stage. This paper puts forward a novel secondary nanostructured black silicon, which uses the dry-wet hybrid fabrication method to achieve secondary nanostructures. In consideration of the influence of the structure’s size, this paper fabricated different sizes of secondary nanostructured black silicon and compared their absorptions with each other. A total of 0.5% reflectance and 98% absorption efficiency of the pit sample were achieved with a diameter of 117.1 μm and a depth of 72.6 μm. In addition, the variation tendency of the absorption efficiency is not solely monotone increasing or monotone decreasing, but firstly increasing and then decreasing. By using a statistical image processing method, nanostructures with diameters between 20 and 30 nm are the majority and nanostructures with a diameter between 10 and 40 nm account for 81% of the diameters.
Highlights
High reflectance, or so-called low absorption, badly limits the applications of silicon-based photon sensitive and optical devices
Since 1995, in order to reduce the reflectance of silicon surfaces, black silicon was studied with SF6/O2 plasma and was proposed as a tool to identify the optimal conditions for vertical silicon deep etching [1]
As for plasma dry etching, Zaidi et al studied a solar cell textured by reactive ion etching (RIE), but paid little attention to the secondary nanostructures [2]
Summary
-called low absorption, badly limits the applications of silicon-based photon sensitive and optical devices. Three methods for black silicon fabrication were developed, which were plasma dry etching, metal-assisted wet etching, and femtosecond laser pulse etching. In addition to alkaline treatment, acid treatment after wet etching was investigated but showed a higher reflectance than the no acid treatment sample [19] Those two studies noticed that surface modification could influence the reflectance of black silicon. Micro-nano secondary structures are beneficial for absorbing the infrared spectrum of solar radiation, from which a solar cell can absorb more thermal energy Such an absorption may reduce the forbidden gap of silicon because a negative correlation exists between temperature and the forbidden gap value. The morphology and structures of the samples were characterized by a scanning electron microscope (SEM), from SEC (Suwon, Gyeonggi-do, Korea) and the Zeiss Company (Oberkochen, Germany)
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