Periodic nano/micro-hole array silicon solar cell
© Lai et al.; licensee Springer. 2014
Received: 30 June 2014
Accepted: 20 November 2014
Published: 3 December 2014
In this study, we applied a metal catalyst etching method to fabricate a nano/microhole array on a Si substrate for application in solar cells. In addition, the surface of an undesigned area was etched because of the attachment of metal nanoparticles that is dissociated in a solution. The nano/microhole array exhibited low specular reflectance (<1%) without antireflection coating because of its rough surface. The solar spectrum related total reflection was approximately 9%. A fabricated solar cell with a 40-μm hole spacing exhibited an efficiency of 9.02%. Comparing to the solar cell made by polished Si, the external quantum efficiency for solar cell with 30 s etching time was increased by 16.7%.
Previous studies have reported that nanostructure surfaces can efficiently couple incident light into semiconductors [1–3]. Efficient light harvesting is vital for solar cells [4, 5]. In addition to light coupling, efficient carrier transport in a nanowire structure has been suggested to increase the short-circuit current [6–8]. Therefore, several studies on solar cells have employed nanostructures to enhance performance [9–15]. The difficulty in establishing contact in nanostructures limits progress. In one study, a conducting polymer was adopted because it easily filled the space between nanostructures, enabling high efficiency to be achieved . Creating microholes might be an appropriate approach ; however, using microholes may cause the advantages of light harvesting to be lost. In this study, we propose a microhole array structure to facilitate fabrication by implementing metal catalyst etching. Inside the hole, we spontaneously produced a nanowire array to achieve low reflectance. The optical reflectance of nano/microhole arrays with various spacings was evaluated. A solar cell was manufactured using this structure to demonstrate the possibility of attaining high efficiency.
A 10-μm-deep microhole after being etched for 15 min is illustrated in the cross-sectional scanning electron microscopy (SEM) image shown in Figure 1c. As shown in Figure 1c, the diameter of the hole is 10 μm. Inside the hole, Si nanowires were clearly observed. After being etched, the Ag was removed using a HCl/HNO3 (3:1 (v/v)) mixed solution. The structure was named ‘nano/microhole array.’ The n + emitter in a solar cell was fabricated by spraying H3PO4 onto a p-Si wafer and then annealing the sample in a furnace at 900°C for 30 min . The doping concentration of phosphorus was calculated by converting the resistivity of Si into carrier concentration, in which the resistivity of Si was measured by a spreading resistance profiler. By doping concentration profile, the phosphorus diffuse into Si around 0.2 μm. The solar cells were then implemented by depositing top and bottom electrodes. The area of the solar cell was 1.0 cm2.
Results and discussion
where I(λ) is the wavelength-dependent solar irradiance.
The photovoltaic parameters for the nano/micro hole array Si solar cell with different etching times
Etching time (min)
The depth of hole at specific etching time and the corresponding wavelength with the same absorption depth
Etching Time (min)
In this study, we demonstrated the formation of a nano/microhole array in Si by using a simple metal-catalyst etching method. The specular reflectance of this structure can be as low as 1%. The solar spectrum-related total reflection was approximately 9% for the 40-μm spacing sample. Efficiency of 9.02% was achieved by using this nano/microhole array without a surface passivation layer.
We thank the Ministry of Science and Technology of Taiwan for the financial support under grant NSC 102-2221-E-005-087.
- Raut HK, Ganesh VA, Nair AS, Ramakrishna S: Anti-reflective coatings: a critical, in-depth review. Energy Environ Sci 2009, 4: 3779.View ArticleGoogle Scholar
- Pei TH, Thiyagu S, Pei Z: Ultra high-density silicon nanowires for extremely low reflection invisible regime. Appl Phys Lett 2011, 99: 153108. 10.1063/1.3650266View ArticleGoogle Scholar
- Thiyagu S, Devi BP, Pei Z, Chen YH, Liu JC: Ultra-low reflectance, high absorption microcrystalline silicon nano-stalagmite (μc-SiNS). Nanoscale Res Lett 2012, 7: 171. 10.1186/1556-276X-7-171View ArticleGoogle Scholar
- Hu L, Chen G: Analysis of optical absorption in silicon nanowire arrays for photovoltaic applications. Nano Lett 2007, 7(11):3249. 10.1021/nl071018bView ArticleGoogle Scholar
- Muskens OL, Rivas JG, Algra RE, Bakkers M, Lagendijk A: Design of light scattering in nanowire materials for photovoltaic applications. Nano Lett 2008, 8(9):2638. 10.1021/nl0808076View ArticleGoogle Scholar
- Kayes BM, Atwater HA, Lewis NS: Comparison of the device physics principles of planar and radial p-n junction nanorod solar cells. Appl Phys Lett 2005, 97: 114302.Google Scholar
- Pei Z, Chang ST, Liu CW, Chen YC: Numerical simulation on the photovoltaic behavior of an amorphous-silicon nanowire-array solar cell. IEEE Electron Device Lett 2009, 30: 1305–1307.View ArticleGoogle Scholar
- Kumar D, Srivastava SK, Singha PK, Husainb M, Kumar V: Fabrication of silicon nanowire arrays based solar cell with improved performance. Sol Energy Mater Sol Cells 2011, 95: 215. 10.1016/j.solmat.2010.04.024View ArticleGoogle Scholar
- Peng K, Xu Y, Wu Y, Yan Y, Lee ST, Zhu J: Aligned single-crystalline Si nanowire arrays for photovoltaic applications. Small 2005, 1: 1062. 10.1002/smll.200500137View ArticleGoogle Scholar
- Fang H, Li X, Song S, Xu Y, Zhu J: Fabrication of slantingly-aligned silicon nanowire arrays for solar cell applications. Nanotechnology 2008, 19: 255703. 10.1088/0957-4484/19/25/255703View ArticleGoogle Scholar
- Stelzner T, Pietsch M, Andrä G, Falk F, Ose E, Christiansen SH: Silicon nanowire-based solar cells. Nanotechnology 2008, 19: 295203. 10.1088/0957-4484/19/29/295203View ArticleGoogle Scholar
- Thiyagu S, Devi BP, Pei Z: Fabrication of large area high density, ultra-low reflection silicon nanowire arrays for efficient solar cell applications. Nano Res 2011, 4(11):1136. 10.1007/s12274-011-0162-5View ArticleGoogle Scholar
- Jung JY, Guo Z, Jee SW, Um HD, Park KT, Hyun MS, Yang JM, Lee JH: A waferscale Si wire solar cell using radial and bulk p–n junctions. Nanotechnology 2010, 21: 445303. 10.1088/0957-4484/21/44/445303View ArticleGoogle Scholar
- Huang BR, Yang YK, Lin TC, Yang WL: A simple and low-cost technique for silicon nanowire arrays based solar cells. Sol Energy Mater Sol Cells 2012, 98: 357.View ArticleGoogle Scholar
- Thiyagu S, Hsueh CC, Liu CT, Syu HJ, Lin TC, Lin CF: Hybrid organic–inorganic heterojunction solar cells with 12% efficiency by utilizing flexible film-silicon with a hierarchical surface. Nanoscale 2014, 6: 3361. 10.1039/c3nr06323bView ArticleGoogle Scholar
- Chang YA, Li ZU, Kuo HC, Lu TC, Yang SF, Lai LW, Lai LH, Wang SC: Efficiency improvement of single-junction InGaP solar cells fabricated by a novel micro-hole array surface texture process. Semicond Sci Technol 2009, 24: 085007. 10.1088/0268-1242/24/8/085007View ArticleGoogle Scholar
- Bouhafs D, Moussi A, Boumaour M, Abaïdia SEK, Mahiou L: N+ silicon solar cells emitters realized using phosphoric acid as doping source in a spray process. Thin Solid Films 2006, 510: 325. 10.1016/j.tsf.2006.01.005View ArticleGoogle Scholar
- Zhong X, Qu Y, Lin YC, Liao L, Duan XF: Unveiling the formation pathway of single crystalline porous silicon. ACS Appl Mater Interfaces 2011, 3: 261. 10.1021/am1009056View ArticleGoogle Scholar
- Green MA, Keevers M: Optical properties of intrinsic silicon at 300 K. Prog Photovolt 1995, 3: 189. 10.1002/pip.4670030303View ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.