NH4OH-B Silicon Texturing of Periodic V-Groove Channels, Upright, and Inverted Pyramids Structures

Hugo S Alvarez,Audrey R Silva,Alfredo R Vaz,Jose A Diniz,Luana C J Espinola

doi:10.1109/jphotov.2021.3059421

Hugo S Alvarez, Audrey R Silva + Show 3 more

https://doi.org/10.1109/jphotov.2021.3059421

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Periodic V-grooves channels, upright, and inverted pyramids structures were texturized on monocrystalline silicon (c-Si) substrates using ammonium hydroxide (NH 4 OH) solution. This cheap and CMOS compatible etching solution aims at the integration of circuits with photovoltaic (PV) cells for monolithic purposes. To obtain these structures, lithographed silicon dioxide (SiO 2 ) patterns were used to delimit the c-Si surface regions to be etched by the NH 4 OH solution. After the SiO 2 removal, a scanning electron microscopy images of the surface of the samples showed that the NH 4 OH etch exposed the <;111> facets, outlined by the SiO 2 patterns, creating periodic V-groove channels, inverted, and upright pyramids structures with depths of 5.9 ± 0.1, 5.7 ± 0.4, and height of 6.9 ± 0.1 μm, respectively. These ordered structures reduced a polished c-Si control sample reflectance by 57.6 ± 0.1%, 53.3 ± 0.1%, and 51.6 ± 0.1%, measured by a spectrophotometer with integrating sphere and having reflectance values of 16.5%, 18.2%, and 18.9%, respectively. These results indicate that the etched periodic structures using a cheap and CMOS compatible NH4OH solution, increases the c-Si light trapping, by reducing its reflectance for values lower than 20%, which could be used to increase the light absorption on PV cells.

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