Large-Area Crystalline Silicon Solar Cell Using Novel Antireflective Nanoabsorber Texturing Surface by Multihollow Cathode Plasma System and Spin-On Doping
We present 11.7% efficient p-type crystalline silicon solar cells with a nanoscale textured surface and no dielectric antireflection coating. We propose nanocrystalline-like textured surface consisting of nanocrystalline columnar structures of diameters from 50 to 100？nm and depth of about 500？nm formed by reactive-ion etching (RIE) in multihollow cathode system. This novel nano textured surface acts as an antireflective absorbing surface of c-Si abbreviate as ARNAB (antireflective nanoabsorber). Light shining on the surface of RIE-etched silicon bounces back and forth between the spikes in such a way that most of it never comes back. Radio frequency (RF) hollow cathode discharge allows an improvement of plasma density by an order of magnitude in comparison to standard RF parallel-plate discharge. Desirable black silicon layer has been achieved when RF power of about 20？Watt per one hollow cathode glow is applied for our multihollow cathode system. The RF power frequency was 13.56？MHz. The antireflection property of ARNAB textured surface has been investigated and compared with wet-textured and PECVD coated silicon samples. Solar cell using low-cost spin-on coating technique has been demonstrated in this paper. We have successfully achieved 11.7% efficient large area (98？cm2) ARNAB textured crystalline silicon solar cell using low-cost spin-on coating (SOD) doping. 1. Introduction Surface texturization is usually promoted to enhance the light absorption in silicon solar cells [1]. Wet anisotropic chemical etching technique used to form random pyramidal structure on 100 mono-crystalline silicon wafers usually is not effective in texturing of low-cost multicrystalline silicon wafers because of random orientation nature. The quality of lower cost multicrystalline silicon (mc-Si) solar cell performance is close to that of monocrystalline solar cell, with the major difference resulting from the inability to texture mc-Si surface. Expensive antireflection layers like silicon nitride and magnesium fluoride have been applied to mc-Si solar cells front surface to reduce light reflection. Recently, various forms of surface texturing approach have been applied to mc-Si surface including laser structuring [2], mechanical diamond saw cutting [3], porous-Si etching [4–7], photo-lithographically defined etching [8], and reactive-ion etching (RIE) method [9]. From the Sandia report (S. H. Zaidi, SAND2000-0919, Sandia contract #BE-8229, April 2000), it is evident that different gas mixture can be used for fabrication of nanotextured silicon surfaces. Jansen et al. [10]
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