Microstructure and surface chemistry of nanoporous &amp;#x201C;black silicon&amp;#x201D; for photovoltaics

Yan, Yanfa; Yuan, Hao-Chih; Yost, Vernon E.; Jones, K. M.; Al‐Jassim, Mowafak; Branz, Howard M.

doi:10.1109/pvsc.2010.5615853

Cited by 5 publications

(3 citation statements)

References 5 publications

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“…In contrast, the metal‐catalyzed wet chemical etching is free of ion damage. On the other hand, the MCE process is highly oxidizing and can leave behind surface regions of elevated defect concentrations associated with sub‐oxide fractions 13. Recently it was shown that an additional anisotropic etching step in tetramethylammonium hydroxide (TMAH) reduces the surface area of the nano‐structure, leading to an increase in the effective lifetime 7…”

Section: Introductionmentioning

confidence: 99%

Improved Black Silicon for Photovoltaic Applications

Algasinger

Paye

Werner

et al. 2013

Advanced Energy Materials

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The morphology and the electronic properties of monocrystalline Si (c‐Si) with a nano‐textured “black” surface, obtained by a metal‐catalyzed wet etching process, and the improvement by an additional chemical treatment are examined with regard to solar cell applications. Photoluminescence and optical reflectivity measurements show the presence of a nano‐porous Si (np‐Si) phase in the as‐prepared nano‐texture. It is found that an additional wet chemical treatment with the standard clean 1 of the common RCA cleaning process removes the np‐Si fraction and significantly alters the surface of the nano‐structure. Cross‐sectional scanning electron microscopy images reveal a pronounced reduction of the surface area, to values of only 3–6 times that of a planar surface. Electron spin resonance measurements were performed to investigate the type and quantity of defects induced by the nano‐texturing process. The optimized nano‐texture exhibits a Si dangling bond density comparable to planar c‐Si wafers. Electrically detected magnetic resonance spectra reveal an additional paramagnetic defect present in the nano‐textured Si, linked to a hydrogen‐ or oxygen‐related double donor. In addition, initial results on the passivation of surface defects via atomic layer deposition of Al2O3 are presented. Photoconductance decay measurements of passivated samples show a tenfold increase of the effective lifetime for nano‐textures which have received the additional etching treatment. The improved electronic quality of the nano‐textured surface makes it an interesting candidate for application as an anti‐reflection surface in solar cells.

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Section: Introductionmentioning

confidence: 99%

Improved Black Silicon for Photovoltaic Applications

Algasinger

Paye

Werner

et al. 2013

Advanced Energy Materials

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“…Lv et al reviewed the recent achievements and applications of black silicon with femtosecond laser pulses [ 28 ]. In this review, black silicon was applied to many fields, such as photodiodes [ 29 , 30 , 31 , 32 ], photodetectors [ 33 , 34 , 35 , 36 , 37 ], solar cells [ 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ], field emission [ 50 , 51 , 52 , 53 ], luminescence [ 54 , 55 ], hydrophobic surface [ 56 , 57 , 58 ], etc. They pointed out that the laser-irradiated process is relatively slow compared to other methods and that the laser-irradiated process needs to be studied further.…”

Section: Introductionmentioning

confidence: 99%

Anti-Reflectance Optimization of Secondary Nanostructured Black Silicon Grown on Micro-Structured Arrays

Tan

Tao

et al. 2018

Micromachines

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Owing to its extremely low light absorption, black silicon has been widely investigated and reported in recent years, and simultaneously applied to various disciplines. Black silicon is, in general, fabricated on flat surfaces based on the silicon substrate. However, with three normal fabrication methods—plasma dry etching, metal-assisted wet etching, and femtosecond laser pulse etching—black silicon cannot perform easily due to its lowest absorption and thus some studies remained in the laboratory stage. This paper puts forward a novel secondary nanostructured black silicon, which uses the dry-wet hybrid fabrication method to achieve secondary nanostructures. In consideration of the influence of the structure’s size, this paper fabricated different sizes of secondary nanostructured black silicon and compared their absorptions with each other. A total of 0.5% reflectance and 98% absorption efficiency of the pit sample were achieved with a diameter of 117.1 μm and a depth of 72.6 μm. In addition, the variation tendency of the absorption efficiency is not solely monotone increasing or monotone decreasing, but firstly increasing and then decreasing. By using a statistical image processing method, nanostructures with diameters between 20 and 30 nm are the majority and nanostructures with a diameter between 10 and 40 nm account for 81% of the diameters.

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“…A thin layer of 10-to 20-nm thermally grown SiO 2 has been used at NREL to passivate the front surface of black Si solar cells. Thermally grown SiO 2 conformally covers the Si nanostructure [6] and provides reasonable passivation quality [1,2]. However, this step often takes a separated hightemperature oxidation and could compromise the cost benefit of the liquid-phase black Si antireflection.…”

Section: Introductionmentioning

confidence: 99%

Antireflection and SiO<inf>2</inf> surface passivation by liquid-phase chemistry for efficient black silicon solar cells

Yuan

Zhang³

et al. 2012

2012 38th IEEE Photovoltaic Specialists Conference

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We report solar cells with both black Si antireflection and SiO 2 surface passivation provided by inexpensive liquid-phase chemistry, rather than by conventional vacuum-based techniques. The best cell efficiency from our first efforts was 16.4%. Nanoporous black Si antireflection on crystalline Si by aqueous etching promises low surface reflection for high photon utilization, together with lower manufacturing cost compared to vacuum-based antireflection coating. Agnanoparticle-assisted black Si etching and post-etching chemical treatment recently developed at NREL enables excellent control over the pore diameter and pore separation. Performance of black Si solar cells, including open-circuit voltage, short-circuit current density, and blue response, has benefited from these improvements. Prior to this study, our black Si solar cells were all passivated by thermal SiO 2 produced in a tube furnace. Although this passivation is effective, it is not ideal for ultra-lowcost manufacturing. In this study, we report, for the first time, the integration of black Si with a proprietary liquid-phase deposition (LPD) passivation from Natcore Technology. The Natcore LPD forms a layer of <10-nm SiO 2 on top of the black Si surface in a relatively mild chemical bath at room temperature. We demonstrate black Si solar cells with LPD SiO 2 with a spectrum-weighted average reflection lower than 5%, similar to the more costly thermally grown SiO 2 approach. However, LPD SiO 2 provides somewhat better surface-passivation quality according to the lifetime analysis by the photo-conductivity decay measurement. Moreover, black Si solar cells with LPD SiO 2 passivation exhibit higher spectral response at short wavelength compared to those passivated by thermally grown SiO 2 . With further optimization, the combination of aqueous black Si etching and LPD could provide a pathway for low-cost, highefficiency crystalline Si solar cells.Index Terms -black silicon, metal-assisted porous silicon etching, antireflection, liquid-phase deposition, surface passivation, photovoltaic cells.

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Microstructure and surface chemistry of nanoporous “black silicon” for photovoltaics

Cited by 5 publications

References 5 publications

Improved Black Silicon for Photovoltaic Applications

Improved Black Silicon for Photovoltaic Applications

Anti-Reflectance Optimization of Secondary Nanostructured Black Silicon Grown on Micro-Structured Arrays

Antireflection and SiO<inf>2</inf> surface passivation by liquid-phase chemistry for efficient black silicon solar cells

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