Browsing by Author "Oehlke, Alexander"

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Impact of Black Silicon on Light- and Elevated Temperature-Induced Degradation in Industrial Passivated Emitter and Rear Cells
(2019-10-21) Pasanen, Toni; Modanese, Chiara; Vähänissi, Ville; Laine, Hannu; Wolny, Franziska; Oehlke, Alexander; Kusterer, Christian; Heikkinen, Ismo T. S.; Wagner, Matthias; Savin, Hele
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Light and elevated-temperature induced degradation (LeTID) is currently a severe issue in passivated emitter and rear cells (PERC). In this work, we study the impact of surface texture, especially a black silicon (b-Si) nanostructure, on LeTID in industrial p-type mc-Si PERC. Our results show that during standard LeTID conditions the b-Si cells with atomic-layer-deposited aluminum oxide (AlOx) front surface passivation show no degradation despite the presence of a hydrogen-rich AlOx/SiNx passivation stack on the rear. Furthermore, b-Si solar cells passivated with silicon nitride (SiNx) on the front lose only 1.5 %rel of their initial power conversion efficiency, while the acidic-textured equivalents degrade by nearly 4 %rel under the same conditions. Correspondingly, clear degradation is visible in the IQE of the acidic-textured cells, especially in the ~850–1100 nm wavelength range confirming that the degradation occurs in the bulk, while the IQE remains nearly unaffected in the b-Si cells. The observations are supported by spatially-resolved photoluminescence (PL) maps, which show a clear contrast in the degradation behavior of b-Si and acidic-textured cells, especially in the case of SiNx front surface passivation. The PL maps also suggest that the magnitude of LeTID scales with surface area of the texture, rather than wafer thickness that was recently reported, although the b-Si cells are slightly thinner (140 vs. 165 µm). The results indicate that b-Si has a positive impact on LeTID, and hence, benefits provided by b-Si are not limited only to the excellent optical properties, as commonly understood.
Industrial Applicability of Antireflection-Coating-Free Black Silicon on PERC Solar Cells and Modules
(2018) Pasanen, Toni; Vähänissi, Ville; Wolny, Franziska; Oehlke, Alexander; Wagner, Matthias; Juntunen, Mikko A.; Heikkinen, Ismo T. S.; Salmi, Emma; Sneck, Sami; Vahlman, Henri; Tolvanen, Antti; Hyvärinen, Jaakko; Savin, Hele
A4 Artikkeli konferenssijulkaisussa
Black silicon (b-Si) is of particular interest within the photovoltaic community due to its ability to texture diamond wire-sawn multicrystalline silicon wafers. In this work, we apply a deep dry-etched black silicon nanotexture, which possesses less than 1 % solar-weighted reflectance with no antireflection coating (ARC), to industrial Passivated Emitter and Rear Cells (PERC). Additionally, the cells are processed further into small solar modules, which are characterized by their electrical and optical performance. The fragile nanostructures remain intact during industrial cell and module fabrication, maintaining the excellent optical properties until the final product. We show that b-Si modules with a typical cover glass retain their performance until incident angles larger than 60°, whereas the heavily increased reflectance of acidic-textured modules decreases their efficiency already after a 30° tilt. Furthermore, at an incidence angle of 70°, the efficiency of b-Si modules has reduced only 7 %, while that of the acidic-textured equivalents has decreased more than 25 %. Hence, the excellent optical properties of ARC-free b-Si are maintained also at module level. The results demonstrate that deep dry-etched b-Si nanostructures are fully applicable to current industrial PERC production facilities.