本研究使用直接升溫法合成出純相的硒化銅銦鎵 (CuIn0.7Ga0.3Se2；CIGS)粉末，再以非真空製程漿料塗佈法製備硒化銅銦鎵前驅物薄膜，搭配不同外加氣壓進行硒化燒結，找出最佳燒結參數的薄膜製程，然而此燒結方式所製作的吸光層薄膜其表面常有粗糙度較高與二次相Cu2-xSe存在於表面等問題，導致效率降低，本研究使用電化學腐蝕方式來取代現有工業上酸性溶劑腐蝕修飾，以低汙染的方式使薄膜能達到優化的效果。藉由光-暗電流線性伏安法量測，發現未經過修飾的最佳燒結參數樣品再給予偏壓-1V(vs. SCE)時有電流密度值為1.78 mA/cm2，相較於修飾後的薄膜再相同偏壓下能達到3.58 mA/cm2，證明修飾後的薄膜其轉換效率提升，再經過修飾圈數與緩衝層厚度優化後，其電流密度更能達到3.94 mA/cm2。經過分析結果發現經電化學腐蝕修飾之銅銦鎵硒薄膜表面粗糙度下降與表面元素比例改變，粗糙度下降使晶界間電阻變小，整體載子遷移率提高使光電轉換效率增加，修飾後使表面化學組成由富銅轉變為缺銅，使CIGS 表面生成n型Cu(In1-xGax)3Se5 (order vacancy compound, OVC)，因此在CIGS表面形成類同質p-n接面 (pseudo-homojunction)，此接面有助於CdS緩衝層的p-n接面轉換及光激發載子間的分離，也使得CdS與CIGS接面間能隙更為匹配，進而提高太陽能電池之轉換效率。

In this study, the chalcopyrite (CuIn0.7Ga0.3Se2, CIGS) powders were synthesized by the heating-up method and CIGS light-absorbing layer films were prepared by non-vacuum slurry coating method and sintering under different atmospheres. The surface roughness of the as-prepared film was usually higher, and the secondary phase, Cu2-xSe, often occurred on the surface of the film, which led to decrease in the conversion efficiency. A simple electrochemical etching process was used to substitute chemical acid corrosion to modify the CIGS light-absorbing layer and improve the photoelectric conversion efficiency. The current density quality of CIGS thin films was promoted from1.78 mA/cm2 to 3.58 mA/cm2 by using electrochemical etching process. The highest current density of 3.94 mA/cm2 was obtained by optimizing the number of cyclic voltammetry cycles and thickness of the CdS buffer layer. The surface roughness of the CIGS film was reduced by using electrochemical etching process, which led to the decrease in the resistance between grain boundaries, and the increase in the carrier mobility, and hence increasing the photoelectric conversion efficiency. Moreover, the chemical composition changed from copper rich to copper deficiency. The N-type Cu(In1-xGax)3Se5 (order vacancy compound, OVC) was formed on the CIGS surface, and hence a pseudo-homojunction was built. This pseudo-homojunction facilitates the conversion efficiency of the p-n junction of the CdS buffer layer-CIGS and the light-induced charge separation. The surface concentration composition of the CIGS film after electrochemical etching resulted in the energy gap match between the CdS and CIGS junctions, thereby improving the solar cell conversion efficiency.

[1] M. Gloeckler and J. Sites, "Band-gap grading in Cu (In, Ga) Se2 solar cells," Journal of Physics and Chemistry of Solids, vol. 66, no. 11, pp. 1891-1894, 2005.
[2] S. Frontier, "Solar Frontier achieves world record thin-film solar cell efficiency of 22.9%," Solar Frontier, 2017.
[3] J. Palm et al., "CIGSSe thin film PV modules: from fundamental investigations to advanced performance and stability," Thin Solid Films, vol. 451, pp. 544-551, 2004.
[4] M. Powalla and B. Dimmler, "Process development of high performance CIGS modules for mass production," Thin Solid Films, vol. 387, no. 1-2, pp. 251-256, 2001.
[5] 黃哲瑄, 謝嘉民, and 盧廷昌, "以濺鍍/無毒硒化製程製作銅銦鎵硒薄膜太陽能電池," 2010.
[6] R. Caballero and C. Guillen, "Structural and morphological properties of Cu (In, Ga) Se2 thin films on Mo substrate," Applied surface science, vol. 238, no. 1-4, pp. 180-183, 2004.
[7] C.-H. Chen, C.-H. Hsu, C.-Y. Chien, Y.-H. Wu, and C.-H. Lai, "A straightforward method to prepare chalcopyrite CIGS films by one-step sputtering process without extra Se supply," in 2011 37th IEEE Photovoltaic Specialists Conference, 2011: IEEE, pp. 002687-002690.
[8] B. Canava, J. Guillemoles, J. Vigneron, D. Lincot, and A. Etcheberry, "Chemical elaboration of well defined Cu (In, Ga) Se2 surfaces after aqueous oxidation etching," Journal of Physics and Chemistry of Solids, vol. 64, no. 9-10, pp. 1791-1796, 2003.
[9] Y.-C. Wu, "Phase transformation of commercialCuIn0.7Ga0.3Se2 powders during Nano-milling process and photoelectric properties of CIGS absorber films," 2018.
[10] F. Adurodija, M. Carter, and R. Hill, "A novel method of synthesizing p-CuInSe/sub 2/thin films from the stacked elemental layers using a closed graphite box," in Proceedings of 1994 IEEE 1st World Conference on Photovoltaic Energy Conversion-WCPEC (A Joint Conference of PVSC, PVSEC and PSEC), 1994, vol. 1: IEEE, pp. 186-189.
[11] L. Zhang, Q. He, W.-L. Jiang, F.-F. Liu, C.-J. Li, and Y. Sun, "Effects of substrate temperature on the structural and electrical properties of Cu (In, Ga) Se2 thin films," Solar Energy Materials and Solar Cells, vol. 93, no. 1, pp. 114-118, 2009.
[12] A. Romeo et al., "Development of thin‐film Cu (In, Ga) Se2 and CdTe solar cells," Progress in Photovoltaics: Research and Applications, vol. 12, no. 2‐3, pp. 93-111, 2004.
[13] S. Chen, X. Gong, and S.-H. Wei, "Band-structure anomalies of the chalcopyrite semiconductors CuGa X 2 versus AgGa X 2 (X= S and Se) and their alloys," Physical Review B, vol. 75, no. 20, p. 205209, 2007.
[14] M. Powalla et al., "Advances in cost-efficient thin-film photovoltaics based on Cu (In, Ga) Se2," Engineering, vol. 3, no. 4, pp. 445-451, 2017.
[15] A. Chirilă et al., "Highly efficient Cu (In, Ga) Se 2 solar cells grown on flexible polymer films," Nature materials, vol. 10, no. 11, pp. 857-861, 2011.
[16] B. J. Stanbery, "Copper indium selenides and related materials for photovoltaic devices," Critical reviews in solid state and materials sciences, vol. 27, no. 2, pp. 73-117, 2002.
[17] S. H. Kwon, B. T. Ahn, S. K. Kim, K. H. Yoon, and J. Song, "Growth of CuIn3Se5 layer on CuInSe2 films and its effect on the photovoltaic properties of In2Se3/CuInSe2 solar cells," Thin Solid Films, vol. 323, no. 1-2, pp. 265-269, 1998.
[18] S. Cells, "Materials, Manufacture and Operation," ed: Elsevier, 2005.
[19] T. Nakada and A. Kunioka, "Direct evidence of Cd diffusion into Cu (In, Ga) Se 2 thin films during chemical-bath deposition process of CdS films," Applied Physics Letters, vol. 74, no. 17, pp. 2444-2446, 1999.
[20] C. Heske et al., "Observation of intermixing at the buried CdS/Cu (In, Ga) Se 2 thin film solar cell heterojunction," Applied physics letters, vol. 74, no. 10, pp. 1451-1453, 1999.
[21] 鍾文陽, "表面硫化銅銦鎵二硒薄膜應用於太陽能電池之研究," 2012.
[22] 周映傑, "拋棄式奈米孔洞金銅合金電極之製備與應用," 2013.
[23] Y. Hashimoto, N. Kohara, T. Negami, N. Nishitani, and T. Wada, "Chemical bath deposition of Cds buffer layer for GIGS solar cells," Solar Energy Materials and Solar Cells, vol. 50, no. 1-4, pp. 71-77, 1998.
[24] A. Ennaoui, S. Siebentritt, M. C. Lux-Steiner, W. Riedl, and F. Karg, "High-efficiency Cd-free CIGSS thin-film solar cells with solution grown zinc compound buffer layers," Solar Energy Materials and Solar Cells, vol. 67, no. 1-4, pp. 31-40, 2001.
[25] 胡翰叡, "以電鍍法製備銅鋅錫硫薄膜太陽能電池元件之研究," 成功大學機械工程學系學位論文, pp. 1-73, 2013.
[26] 林建宏, "利用濺鍍與硒化製程製作銅鋅錫硒薄膜太陽能電池," 成功大學電機工程學系碩士在職專班學位論文, pp. 1-64, 2013.
[27] 關中杰, "p型Cu(In,Ga)S2及Cu2ZnSnS4光陰極的溶液法製備及其太陽能分解水性能研究," 南京大學研究生畢業論文, 2016.
[28] J. A. Glasscock, P. R. Barnes, I. C. Plumb, and N. Savvides, "Enhancement of photoelectrochemical hydrogen production from hematite thin films by the introduction of Ti and Si," The Journal of Physical Chemistry C, vol. 111, no. 44, pp. 16477-16488, 2007.
[29] B. D. Cullity, Elements of X-ray Diffraction. Addison-Wesley Publishing, 1956.
[30] C. J. Glinka, "Methods of X-Ray and Neutron Scattering in Polymer Science, by Ryong-Joon Roe," Physics Today, vol. 54, no. 3, pp. 60-61, 2001.
[31] G. H. Stout and L. H. Jensen, X-ray structure determination: a practical guide. John Wiley and Sons, 1989.
[32] D. Brandon and W. D. Kaplan, Microstructural characterization of materials. John Wiley & Sons, 2013.
[33] I. Dirnstorfer et al., "Annealing studies on CuIn (Ga) Se2: the influence of gallium," Thin Solid Films, vol. 361, pp. 400-405, 2000.
[34] W. Witte, R. Kniese, and M. Powalla, "Raman investigations of Cu (In, Ga) Se2 thin films with various copper contents," Thin Solid Films, vol. 517, no. 2, pp. 867-869, 2008.
[35] A. W. Welch, P. P. Zawadzki, S. Lany, C. A. Wolden, and A. Zakutayev, "Self-regulated growth and tunable properties of CuSbS2 solar absorbers," Solar Energy Materials and Solar Cells, vol. 132, pp. 499-506, 2015.
[36] T. Chang, Y. Su, and W. Lee, "Improvement on conversion efficiency of CIGS thin film solar cell using electrochemical depleting," Journal of The Electrochemical Society, vol. 161, no. 12, pp. E167-E172, 2014.
[37] J. Kois, S. Bereznev, O. Volobujeva, and E. Mellikov, "Electrochemical etching of copper indium diselenide surface," Thin Solid Films, vol. 515, no. 15, pp. 5871-5875, 2007.
[38] P.-K. Hung, "Investigation of CuInSe2 thin films and CuInSe2 nanowire arrays prepared by using electrodeposition technology for solar cell applications," 2014.
[39] T.-W. Chang, "Studies on CuInSe2 thin-film solar cell by using electrochemical deposition," 2014.
[40] D. Liao and A. Rockett, "Cu depletion at the CuInSe 2 surface," Applied physics letters, vol. 82, no. 17, pp. 2829-2831, 2003.
[41] T. Minemoto et al., "Theoretical analysis of the e! ect of conduction band o! set of window/CIS layers on performance of CIS solar cells using device simulation," Solar Energy Materials & Solar Cells, vol. 67, no. 83, p. 88, 2001.
[42] K. Pal, K. B. Thapa, and A. Bhaduri, "A Review on the Current and Future Possibilities of Copper-Zinc Tin Sulfur Thin Film Solar Cell to Increase More Than 20% Efficiency," Advanced Science, Engineering and Medicine, vol. 10, no. 7-8, pp. 645-652, 2018.
[43] G. Sozzi, F. Troni, and R. Menozzi, "Numerical analysis of the effect of grain size and defects on the performance of CIGS solar cells," Proc. CS-ManTech, pp. 353-356, 2010.
[44] M. Morkel et al., "Flat conduction-band alignment at the CdS/CuInSe 2 thin-film solar-cell heterojunction," Applied Physics Letters, vol. 79, no. 27, pp. 4482-4484, 2001.
[45] T. Löher, A. Klein, C. Pettenkofer, and W. Jaegermann, "Partial density of states in the CuInSe 2 valence bands," Journal of applied physics, vol. 81, no. 12, pp. 7806-7809, 1997.