A method for removing defect layers on the surface of silicon nanowire solar cells by oxidation and etching

Abstract

The invention relates to solar cell materials and battery manufacturing technology, especially for the monocrystalline silicon nanowire array prepared by metal nanoparticle-assisted electroless chemical corrosion method. The invention first uses the first dry oxygen oxidation process. The oxidation rate is very low. By controlling the oxidation time, an oxide layer with a controllable thickness can be formed on the silicon nanowires; or an oxide layer can be formed on the silicon nanowires by hydrogen peroxide oxidation; The silicon oxide layer on the surface, while removing this layer of silicon oxide, removes the defect layer on the surface of the silicon nanowires without destroying the shape of the silicon nanowires. This method can reduce the surface charge recombination rate and effectively improve the silicon nanowires. The minority carrier life, thereby improving the battery efficiency.

Description

technical field [0001] The invention relates to solar cell materials and cell manufacturing technology, especially for single crystal silicon nanowire arrays prepared by metal nanoparticle-assisted electroless chemical etching method, using oxidation + corrosion method to remove metal-assisted chemical etching on silicon nanowires A layer of defects formed on the surface, thereby increasing the efficiency of silicon nanowire cells. Background technique [0002] As the demand for energy continues to increase, people pay more and more attention to renewable energy, especially solar energy. As an important way to utilize solar energy, photovoltaic applications have always been a research hotspot. Pollution is small, and silicon solar cells occupy a dominant position in the commercial solar cell market. At present, improving the optical properties of cells through various anti-reflection coatings and silicon surface texturing technologies is still an important way to improve the...

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Problems solved by technology

Due to the extremely low reflectivity of silicon nanostructures, this silicon material is called black silicon; silicon nanowire solar cells based on this do not require a special anti-reflection structure. At present, the newly developed metal nanoparticle assisted Although the electroless chemical etching method can prepare silicon nanowire arrays at low cost, and the surface reflectivity of the silicon nanowire arrays can be reduced very low, the metal nanoparticle-assisted electroless chemical etching method forms many defects on the silicon surface, thereby This leads to a decrease in cell efficiency. For example, if a silicon nanowire solar cell is fabricated using conventional monocrystalline silicon cell technology (diffusion method), the conversion efficiency is only 9.31% [K.Q.Peng, Y.Xu, Y.Wu, Y.J.Yan, S.T.Lee, and J.Zhu, Alignedsingle-crystallineSinanowirearraysforphotovoltaicapplications,Small1(2005)pp.1062-1067], changing the direction of the nanowire array from vertical to slightly inclined, the cell conversion efficiency increased to 11.37% [H.Fang, X.D.Li, S.Song, Y.Xu, and J.Zhu, Nanotechnology19(2008)pp.255703], but still far lower than the efficiency of monocrystalline silicon cells with traditional pyramid structure, the minority carrier lifetime (referred to as minority carrier lifetime) is the limit of semiconductor materials An important parameter, which has an important impact on the efficiency of solar cells. If the minority carrier lifetime is high, the cell efficiency will be high. The effective minority carrier lifetime of silicon materials is related to the bulk minority carrier lifetime and the surface minority carrier lifetime; The surface area is huge. If the surface defects are high, it is reflected in the high recombination of surface carriers and the low lifetime of surface minority carriers. As a result, the photocurrent of nanowire cells is small and the cell efficiency is low. Therefore, to improve cell efficiency, silicon nano The surface defect layer of the wire is treated [Y.Dan, K.Seo, K.Takei, J.H.Meza, A.Javey, and K.B.Crozier, NanoLetters11(2011)pp.2527-2532] to improve the minority carrier lifetime of silicon nanowires

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