石墨烯是僅有一個碳原子厚度的二維材料，具備著許多獨特的優異性質如：高光穿透性、機械可撓性、低阻抗以及高載子遷移率等等，理論上可以與任何具有中等載子密度的半導體產生蕭基接面，在光伏元件的應用上是非常具有發展潛力的材料。
本研究製作石墨烯/矽奈米線蕭基接面太陽能電池，以期能將矽奈米線所擁有的良好抗反射特性與上述石墨烯優異的特性互相結合而提升效率。首先藉由改變蝕刻矽奈米線的時間來控制奈米線長度，實驗發現隨著蝕刻時間的增加，奈米線的長度也呈正相關的成長，之後將不同蝕刻時間的奈米線做成太陽能電池並進行效率量測，發現當蝕刻時間為20分鐘時所製備的電池具有最佳的效率，可達到 1.566 %。
其次則改變了蝕刻矽奈米線的方法，嘗試在蝕刻的溶液中加入過氧化氫來獲得不同表面形貌的矽奈米線，在蝕刻時間為8分鐘時所製備的電池具有最佳的效率，可達到0.937 %。最後則將兩種不同的蝕刻方法做成的元件進行效率比較，可以得出無添加過氧化氫所蝕刻出的矽奈米線所製成的元件，普遍在效率方面有著較佳的表現。

Graphene, as a two-dimensional carbon material with only one carbon atom thickness, has shown many superior material properties, including high optical transmittance, excellent mechanical flexibility, low resistivity, and high carrier mobility. Theoretically, a Schottky junction can be formed by transferring graphene onto the surface of a moderately doped semiconductor. Thus, graphene is expected to have great potential in the field of photovoltaics.
This study aims to fabricate the graphene/silicon nanowires Schottky junction solar cells, with the expectation to enhance the solar cell’s efficiency by combining the excellent antireflection property of silicon nanowires and the advantages of graphene mentioned above. We started at controlling the length of silicon nanowires by changing the etching time, and founded that the silicon nanowires’ length becomes longer with the etching time increased. After fabrication into solar cells, the device made from etching time of 20 minutes showed a maximum efficiency of 1.566%.
And then the H2O2 was added into the etching solution to get silicon nanowires of different structures. The results showed that when the etching time was 8 minutes, the solar cell showed a maximum efficiency of 0.937%. In the end of the study, we compared the solar cells fabricated by both etching methods. In general, the devices made from the H2O2-free etching solution exhibited better efficiencies.

[1] 綠色能源. Available: http://cct.me.ntut.edu.tw/ccteducation/greenenergy/
[2] X. Li, H. Zhu, K. Wang, A. Cao, J. Wei, C. Li, et al., "Graphene-on-silicon Schottky junction solar cells," Adv Mater, vol. 22, pp. 2743-8, Jul 6 2010.
[3] 胡淑芬, "奈米科技發展之介紹," 毫微米通訊, vol. 8, pp. 1-10, 2001.
[4] 奈米的歷史 - 奈米新世界 - 國立科學工藝博物館. Available: http://nano.nstm.gov.tw/NanoConcept/NanoDevelopment/HistoryOfNano.htm
[5] M. B. Mohamed, C. Burda, and M. A. El-Sayed, "Shape dependent ultrafast relaxation dynamics of CdSe nanocrystals: nanorods vs nanodots," Nano Letters, vol. 1, pp. 589-593, 2001.
[6] C. F. Landes, S. Link, M. B. Mohamed, B. Nikoobakht, and M. A. El-Sayed, "Some properties of spherical and rod-shaped semiconductor and metal nanocrystals," Pure and Applied Chemistry, vol. 74, pp. 1675-1692, 2002.
[7] L. Mino, G. Agostini, E. Borfecchia, D. Gianolio, A. Piovano, E. Gallo, et al., "Low-dimensional systems investigated by x-ray absorption spectroscopy: a selection of 2D, 1D and 0D cases," Journal of Physics D: Applied Physics, vol. 46, p. 423001, 2013.
[8] E. F. Schubert, Quantum mechanics and structures, 2003.
[9] Z. L. Wang, R. Yang, J. Zhou, Y. Qin, C. Xu, Y. Hu, et al., "Lateral nanowire/nanobelt based nanogenerators, piezotronics and piezo-phototronics," Materials Science and Engineering: R: Reports, vol. 70, pp. 320-329, 2010.
[10] 馬遠榮, "低維奈米材料," 科學發展, pp. 73-75, 2004.
[11] A. K. Geim and K. S. Novoselov, "The rise of graphene," Nature Materials, vol. 6, pp. 183-191, 2007.
[12] G. Ruess and F. Vogt, "*Hochstlamellarer kohlenstoff aus graphitoxyhydroxyd - uber den ort der aktiven eigenschaften am kohlenstoffkristall," Monatshefte Fur Chemie, vol. 78, pp. 222-242, 1948.
[13] K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V. Dubonos, et al., "Electric field effect in atomically thin carbon films," Science, vol. 306, pp. 666-669, 2004.
[14] A. C. Ferrari, J. C. Meyer, V. Scardaci, C. Casiraghi, M. Lazzeri, F. Mauri, et al., "Raman spectrum of graphene and graphene layers," Physical Review Letters, vol. 97, p. 187401, 2006.
[15] X. Li, W. Cai, J. An, S. Kim, J. Nah, D. Yang, et al., "Large-area synthesis of high-quality and uniform graphene films on copper foils," Science, vol. 324, pp. 1312-4, Jun 5 2009.
[16] A. C. Ferrari and J. Robertson, "Interpretation of Raman spectra of disordered and amorphous carbon," Physical Review B, vol. 61, pp. 14095-14107, 2000.
[17] A. C. Ferrari, "Raman spectroscopy of graphene and graphite: disorder, electron–phonon coupling, doping and nonadiabatic effects," Solid State Communications, vol. 143, pp. 47-57, 2007.
[18] X. Lu, H. Huang, N. Nemchuk, and R. S. Ruoff, "Patterning of highly oriented pyrolytic graphite by oxygen plasma etching," Applied Physics Letters, vol. 75, p. 193, 1999.
[19] X. K. Lu, M. F. Yu, H. Huang, and R. S. Ruoff, "Tailoring graphite with the goal of achieving single sheets," Nanotechnology, vol. 10, pp. 269-272, 1999.
[20] Y. Zhang, J. P. Small, W. V. Pontius, and P. Kim, "Fabrication and electric-field-dependent transport measurements of mesoscopic graphite devices," Applied Physics Letters, vol. 86, p. 073104, 2005.
[21] C. Berger, Z. Song, X. Li, X. Wu, N. Brown, C. Naud, et al., "Electronic confinement and coherence in patterned epitaxial graphene," Science, vol. 312, pp. 1191-1196, 2006.
[22] W. A. de Heer, C. Berger, X. Wu, P. N. First, E. H. Conrad, X. Li, et al., "Epitaxial graphene," Solid State Communications, vol. 143, pp. 92-100, 2007.
[23] M. Sprinkle, M. Ruan, Y. Hu, J. Hankinson, M. Rubio-Roy, B. Zhang, et al., "Scalable templated growth of graphene nanoribbons on SiC," Nat Nanotechnol, vol. 5, pp. 727-31, 2010.
[24] Z.-Y. Juang, C.-Y. Wu, C.-W. Lo, W.-Y. Chen, C.-F. Huang, J.-C. Hwang, et al., "Synthesis of graphene on silicon carbide substrates at low temperature," Carbon, vol. 47, pp. 2026-2031, 2009.
[25] K. V. Emtsev, A. Bostwick, K. Horn, J. Jobst, G. L. Kellogg, L. Ley, et al., "Towards wafer-size graphene layers by atmospheric pressure graphitization of silicon carbide," Nat Mater, vol. 8, pp. 203-207, 2009.
[26] W. S. Hummers and R. E. Offeman, "Preparation of graphitic oxide," Journal of the American Chemical Society, vol. 80, p. 1339, 1958.
[27] S. Stankovich, D. A. Dikin, G. H. Dommett, K. M. Kohlhaas, E. J. Zimney, E. A. Stach, et al., "Graphene-based composite materials," Nature, vol. 442, pp. 282-286, 2006.
[28] X. Li, G. Zhang, X. Bai, X. Sun, X. Wang, E. Wang, et al., "Highly conducting graphene sheets and Langmuir-Blodgett films," Nat Nanotechnol, vol. 3, pp. 538-542, 2008.
[29] H. Terrones, R. Lv, M. Terrones, and M. S. Dresselhaus, "The role of defects and doping in 2D graphene sheets and 1D nanoribbons," Rep Prog Phys, vol. 75, p. 062501, 2012.
[30] A. G. Cano-Marquez, F. J. Rodriguez-Macias, J. Campos-Delgado, C. G. Espinosa-Gonzalez, F. Tristan-Lopez, D. Ramirez-Gonzalez, et al., "Ex-MWNTs: graphene sheets and ribbons produced by lithium intercalation and exfoliation of carbon nanotubes," Nano Letters, vol. 9, pp. 1527-1533, 2009.
[31] L. Jiao, L. Zhang, X. Wang, G. Diankov, and H. Dai, "Narrow graphene nanoribbons from carbon nanotubes," Nature, vol. 458, pp. 877-880, 2009.
[32] D. V. Kosynkin, A. L. Higginbotham, A. Sinitskii, J. R. Lomeda, A. Dimiev, B. K. Price, et al., "Longitudinal unzipping of carbon nanotubes to form graphene nanoribbons," Nature, vol. 458, pp. 872-876, 2009.
[33] J. Cai, P. Ruffieux, R. Jaafar, M. Bieri, T. Braun, S. Blankenburg, et al., "Atomically precise bottom-up fabrication of graphene nanoribbons," Nature, vol. 466, pp. 470-473, 2010.
[34] Q. Yu, J. Lian, S. Siriponglert, H. Li, Y. P. Chen, and S.-S. Pei, "Graphene segregated on Ni surfaces and transferred to insulators," Applied Physics Letters, vol. 93, p. 113103, 2008.
[35] A. Reina, X. Jia, J. Ho, D. Nezich, H. Son, V. Bulovic, et al., "Large area, few-layer graphene films on arbitrary substrates by chemical vapor deposition," Nano Letters, vol. 9, pp. 30-35, 2009.
[36] J.-H. Chen, C. Jang, S. Xiao, M. Ishigami, and M. S. Fuhrer, "Intrinsic and extrinsic performance limits of graphene devices on SiO2," Nature Nanotechnology, vol. 3, pp. 206-209, 2008.
[37] K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, et al., "Large-scale pattern growth of graphene films for stretchable transparent electrodes," Nature, vol. 457, pp. 706-710, 2009.
[38] X. Li, Y. Zhu, W. Cai, M. Borysiak, B. Han, D. Chen, et al., "Transfer of large-area graphene films for high-performance transparent conductive electrodes," Nano Letters, vol. 9, pp. 4359-4363, 2009.
[39] S. V. G. I. V. Antonova, R. A. Soots,A. I. Komonov,V. A. Seleznev,M. A. Sergeev,V. A. Volodin,V. Ya. Prinz, "Comparison of various methods for transferring graphene and few layer graphene grown by chemical vapor deposition to an insulating SiO2/Si substrate," 2014.
[40] 蔡進譯, "超高效率太陽能電池-從愛因斯坦的光電效應談起," 物理雙月刊, pp. 701-719, 2005.
[41] N. R. P. P.S.Priambodo, D. Hartanto,, Solar Cell Technology. INTECH Open Access Publisher.
[42] Photovoltaic Cell I-V Characterization Theory and LabVIEW Analysis Code. Available: http://www.ni.com/white-paper/7230/en/
[43] Q. Yan, F. Liu, L. Wang, J. Y. Lee, and X. S. Zhao, "Drilling nanoholes in colloidal spheres by selective etching," Journal of Materials Chemistry, vol. 16, p. 2132, 2006.
[44] K. Chen, J.-J. He, M.-Y. Li, and R. Lapierre, "Fabrication of GaAs Nanowires by Colloidal Lithography and Dry Etching," Chinese Physics Letters, vol. 29, p. 036105, 2012.
[45] V. Sivakov, F. Voigt, B. Hoffmann, Viktor, and S. Christianse, "Wet - Chemically Etched Silicon Nanowire Architectures: Formation and Properties," 2011.
[46] M.-L. Zhang, K.-Q. Peng, X. Fan, J.-S. Jie, R.-Q. Zhang, S.-T. Lee, et al., "Preparation of Large-Area Uniform Silicon Nanowires Arrays through Metal-Assisted Chemical Etching," The Journal of Physical Chemistry C, vol. 112, pp. 4444-4450, 2008.
[47] S. Li, W. Ma, Y. Zhou, X. Chen, Y. Xiao, M. Ma, et al., "Fabrication of porous silicon nanowires by MACE method in HF/H2O2/AgNO3 system at room temperature," Nanoscale Res Lett, vol. 9, p. 196, 2014.
[48] T.-C. Yang, T.-Y. Huang, H.-C. Lee, T.-J. Lin, and T.-J. Yen, "Applying Silicon Nanoholes with Excellent Antireflection for Enhancing Photovoltaic Performance," Journal of The Electrochemical Society, vol. 159, p. B104, 2012.
[49] S. K. Srivastava, D. Kumar, P. K. Singh, M. Kar, V. Kumar, and M. Husain, "Excellent antireflection properties of vertical silicon nanowire arrays," Solar Energy Materials and Solar Cells, vol. 94, pp. 1506-1511, 2010.
[50] K. Peng, X. Wang, and S.-T. Lee, "Silicon nanowire array photoelectrochemical solar cells," Applied Physics Letters, vol. 92, p. 163103, 2008.
[51] C. Xie, P. Lv, B. Nie, J. Jie, X. Zhang, Z. Wang, et al., "Monolayer graphene film/silicon nanowire array Schottky junction solar cells," Applied Physics Letters, vol. 99, p. 133113, 2011.
[52] G. Fan, H. Zhu, K. Wang, J. Wei, X. Li, Q. Shu, et al., "Graphene/silicon nanowire Schottky junction for enhanced light harvesting," ACS Appl Mater Interfaces, vol. 3, pp. 721-5, Mar 2011.
[53] 反應式離子蝕刻機RIE操作手冊. Available: http://cmnst.ncku.edu.tw/ezfiles/23/1023/img/137/180049156.pdf
[54] Y. Song, X. Li, C. Mackin, X. Zhang, W. Fang, T. Palacios, et al., "Role of interfacial oxide in high-efficiency graphene-silicon Schottky barrier solar cells," Nano Lett, vol. 15, pp. 2104-10, Mar 11 2015.
[55] A. Kikuchi, S. Baba, and A. Kinbara, "Measurement of the adhesion of silver films to oxidized silicon," Thin Solid Films, vol. 164, pp. 153-156, 1988.
[56] Ohmic contact. Available: https://en.wikipedia.org/wiki/Ohmic_contact
[57] J. Q. Liu, C. Wang, T. Zhu, W. J. Wu, J. Fan, and L. C. Tu, "Low temperature fabrication and doping concentration analysis of Au/Sb ohmic contacts to n-type Si," AIP Advances, vol. 5, p. 117112, 2015.
[58] J. r. H. Werner, U. Spadaccini, and F. Banhart, "Low-temperature ohmic Au/Sb contacts to n-type Si," Journal of Applied Physics, vol. 75, p. 994, 1994.
[59] M. Ahmad, T. Ganguli, S. Patil, S. Major, Y. G. K. Patro, and B. M. Arora, "Determination of contact resistivity by a modified Cox and Strack method in case of finite metal sheet resistance," Solid-State Electronics, vol. 38, pp. 1437-1440, 1995.
[60] 林敬倫, "二維石墨烯與矽塊材及砷化鎵薄膜蕭基接面太陽能電池研製," 2015.