Influence of pyramid size on reflectivity of silicon surfaces textured using an alkaline etchant

Abstract

Surface texturing of p-type monocrystalline silicon (100) is well known as one of the best methods to reduce reflection losses and to increase light trapping and light absorption probability. Pyramid surface textures play a major role in reducing the reflectance of monocrystalline silicon surfaces. In this paper, the size of pyramids formed on the surface of p-type silicon substrates and by changing the etching characteristics during the texturing process of silicon were studied and evaluated. The pyramids that formed on the crystalline silicon surface formed light traps that led to increased light absorption efficiency. The pyramid size effects on the percent reflectivity were evaluated at normal incidence and an inverse relationship between the percent reflectivity and the pyramid size was found. The size of the pyramids was controlled by controlling the texturing process by changing the concentrations of potassium hydroxide (KOH) and isopropyl alcohol (IPA) and by controlling the etching process time. In this work, the optimized etching conditions were determined as a solution prepared with 20 wt% KOH and 3 wt% IPA for wet etching at a reaction temperature of 80 • C and an etching time of 40 min. The lowest value for percent reflectivity of the patterned surfaces was 9.7% and it was achieved for pyramid bases close to 4 μm as measured at a wavelength of 650 nm.

Structural and Optical Properties of Textured Silicon Substrates by Three-Step Chemical Etching

“…Silicon, one of the most abundant materials on earth, is one of the most promising materials for solar cells in the current semiconductor industry. − Additionally, the textured silicon substrate is well known for its low cost, high current efficiency, stable thermal properties, and excellent biocompatibility. ,− Therefore, it is a promising candidate for devices in optoelectronics, − photovoltaics, ,− and biomimetic superhydrophobicity. − Scientists have been working on the fabrication of textured silicon since the 1900s. For example, the pyramidal structure can improve the efficiency of photovoltaic cells since it can collect reflected light and trap the light inside the structure by multiple internal reflections. ,− …”

Broadband angular color stability of dielectric thin film-coated pyramidal textured Si for photovoltaics

“…In the case of monocrystalline silicon, a random upright pyramid texture, created by wet alkaline etching, is most commonly used. [15][16][17][18] This texture reduces reflectance and increases light trapping, and thus contributes to an increase in the current output of the solar cell 15,[19][20][21] and is also cheaper to realize than a perfectly planar substrate surface. In this paper, it is shown that such substrates coloured with single layer thin film coatings possess better angular colour stability than planar substrates coated with identical coatings.…”

Ultra-Low-Reflective, Self-Cleaning Surface by Fabrication Dual-Scale Hierarchical Optical Structures on Silicon

“…In particular, the fabrication of micro-nano structures on the silicon surface is a popular route for surface modification [14][15][16][17][18][19][20][21]. For example, pyramidal structures effectively reduce the surface's reflectivity and improve the efficiency of photovoltaic cells, which is attributed to their ability to collect and capture light through internal reflection [22][23][24][25][26][27][28][29][30].…”