銅銦鎵硒(Cu(In,Ga)Se2,CIGS)為一現今熱烈發展的太陽能電池吸收層材料，其優點具有直接能隙，有相當高的吸收係數，可製作成薄膜太陽能電池，減少材料使用，薄膜厚度的太陽能電池更可適用於可撓式基板及可攜式裝置。然而，高效率CIGS於成長時需要經歷一段高溫硒化(約攝氏600度)的反應過程，而部分可撓式基板無法承受如此高溫的反應溫度因而限制了可撓式CIGS的應用。有鑑於此，本研究開發成長後轉移元件的方式，避免了可撓式基板經歷高溫硒化的製程，可以成功的將CIGS應用在各式可撓式基板上。
　　轉移後的CIGS透過掃描式電子顯微鏡觀察其表面及橫截面，皆呈現了與轉移前一致的結構，拉曼光譜分析證實了轉移後的CIGS與轉移前一致的振動能。X光繞射分析及光激發分析顯示了CIGS晶格有些微的錯置，但仍舊保持良好特性。電性分析表現了近70％的光轉換效率仍能維持。
　　此研究所開發的方法不但可以將CIGS應用至更廣泛的可撓式基板上，原本成長於不銹鋼基板因製程高溫而導致的鐵擴散效應也可避免，更可應用於除了CIGS以外的太陽能電池元件。此製程更因製程步驟簡單，可大面積處理，便於應用於工業化製程。

To date, 21.7 % is the highest reported efficiency for inorganic Cu(In,Ga)Se2 (CIGS) thin-film photovoltaic solar cells (PV). However, the high temperature post-selenization process used in the fabrication of CIGS restricts its application on variety of low cost and flexible device substrates; in turn impeding the use of CIGS based PV in the next generation of consumer electronic products. In this work, a process enabling the direct transfer of conventional soda-lime glass (SLG) based CIGS devices onto arbitrary substrates has been developed and demonstrated. Raman analysis is performed to examine the material characteristics after the transfer process showing no significant differences, while Photoluminescence (PL) and X-ray Diffraction (XRD) show little distortion in the film crystallinity. Between the pre and post-transferred CIGS devices, 70% of power conversion efficiency is maintained. This approach utilizes a chemical-mechanical polishing (CMP)-like procedure to etch away the SLG used in the regular CIGS device structure, thus allowing the remaining device to be transferred to arbitrary substrates. SEM revealed the quality of CIGS films remain the same after the etching procedure. We demonstrate the transfer of our CIGS devices onto three different kinds of flexible substrate (Stainless steel, polyimide (PI) and paper) to establish the flexibility of our method. We believe that this approach can not only further stimulate the development of low cost flexible thin film solar cells, but also benefit the broader field of flexible electronics in general.

致謝 I
摘要 II
Abstract III
Table of Content IV
List of Table VII
List of Figure VIII
Chapter 1 Introduction 1
1.1 Preface 1
1.2 Motivation 2
Chapter 2 Literature Review 3
2.1 Solar cells 3
2.1.1 P-N junction of solar cells 3
2.1.2 Current-Voltage analysis 4
2.1.3 Theoretical efficiency of P-N junction solar cells 6
2.2 Copper Indium Gallium diselenide (CIGS) solar cells 8
2.2.1 Crystal structure of CIGS 8
2.2.2 Optical property of CIGS 9
2.2.3 Recombination mechanism in CIGS 11
2.2.4 Structure of CIGS solar cells 13
2.3 Flexible solar cells 15
2.3.1 Stainless Steel substrate 16
2.3.2 Polyimide substrate 17
2.4 Transfer printing process 18
2.4.1 Sacrificial layer addition 18
2.4.2 Porous Si modified layer 19
2.4.3 Control crack spalling 19
2.4.4 Water assisted lift off 20
2.4.5 Laser assisted lift off 20
2.4.6 CIGS Lift off approach 21
Chapter 3 Experimental Techniques 22
3.1 Analysis Equipment 22
3.1.1 Field-emission scanning electron microscopy 22
3.1.2 Raman spectrum analysis 23
3.1.3 X-ray diffraction analysis, XRD 24
3.1.4 UV-visible-NIR Spectrophotometers 25
3.1.5 Photoluminescence system, PL 26
3.1.6 Time-Resolved Photoluminescence, TRPL 27
3.1.7 Solar simulator system and 4-point probe measurement 27
Chapter 4 Experimental Process 29
4.1 Preparation of CIGS Solar cells 29
4.2 Chemical-assisted Lift off process 29
4.3 Characterization 29
Chapter 5 Results and Discussion 31
5.1 Transfer process modified 31
5.1.1 Transfer method A 31
5.1.2 Transfer method B 32
5.1.3 Transfer method C 34
5.2 Material Characterization 35
5.2.1 FE-SEM analysis 36
5.2.2 Raman spectrum analysis 37
5.2.3 X-ray diffraction analysis 38
5.2.4 Reflectance 39
5.2.5 Photoluminescence and Time-resolve Photoluminescence 41
5.3 Device Characterization 43
5.3.1 Performance drop 45
5.3.2 Larger scale approach 46
5.3.3 Adhesion issue 47
Chapter 6 Conclusion and Future work 48
6.1 Conclusion 48
6.2 Future Work 49
Reference 50

[1] (2015). PVCDROM.
[2] D. S. Purnomo Sidi Priambodo, Wahyudi Purnomo, Harry Sudibyo and Djoko Hartanto, Electric Energy Management and Engineering in Solar Cell System, Solar Cells - Research and Application Perspectives, 2013.
[3] A. V. Shah, R. Platz, and H. Keppner, "Thin-Film Silicon Solar-Cells - a Review and Selected Trends," Solar Energy Materials and Solar Cells, vol. 38, pp. 501-520, Aug 1995.
[4] J. S. Park, Z. Dong, S. Kim, and J. H. Perepezko, "CuInSe2 phase formation during Cu2Se/In2Se3 interdiffusion reaction," Journal of Applied Physics, vol. 87, pp. 3683-3690, Apr 15 2000.
[5] S. H. Wei, S. B. Zhang, and A. Zunger, "Effects of Ga addition to CuInSe2 on its electronic, structural, and defect properties," Applied Physics Letters, vol. 72, pp. 3199-3201, Jun 15 1998.
[6] J. Nelson, The physics of solar cells. London,England: Imperial College Press, 2003.
[7] R. B. Jonathan, L. P. Katie, P. B. Thomas, and F. B. Stacey, "Nanoengineering and interfacial engineering of photovoltaics by atomic layer deposition," Nanoscale, vol. 3, pp. 3482-3508, 2011.
[8] U. Malm, J. Malmström, C. Platzer-Björkman, and L. Stolt, "Determination of dominant recombination paths in Cu(In,Ga)Se2 thin-film solar cells with ALD–ZnO buffer layers," Thin Solid Films, vol. 480-481, p. 208212, 2005.
[9] S. H. Wei, S. B. Zhang, and A. Zunger, "Effects of Na on the electrical and structural properties of CuInSe2," Journal of Applied Physics, vol. 85, pp. 7214-7218, May 15 1999.
[10] E. S. Mungan, X. F. Wang, and M. A. Alam, "Modeling the Effects of Na Incorporation on CIGS Solar Cells," Ieee Journal of Photovoltaics, vol. 3, pp. 451-456, Jan 2013.
[11] Y. Ju-Heon, C. Sunghun, K. Won Mok, P. Jong-Keuk, B. Young-Joon, L. Taek Sung, et al., "Optical analysis of the microstructure of a Mo back contact for Cu(In,Ga)Se2 solar cells and its effects on Mo film properties and Na diffusivity," Solar Energy Materials and Solar Cells, vol. 95, p. 29592964, 2011.
[12] D.-H. Cho, Y.-D. Chung, K.-S. Lee, N.-M. Park, K.-H. Kim, H.-W. Choi, et al., "Influence of growth temperature of transparent conducting oxide layer on Cu(In,Ga)Se2 thin-film solar cells," Thin Solid Films, vol. 520, pp. 2115-2118, 2012.
[13] A. Jasenek, U. Rau, K. Weinert, I. M. Kotschau, G. Hanna, G. Voorwinden, et al., "Radiation resistance of Cu(In,Ga)Se-2 solar cells under 1-MeV electron irradiation," Thin Solid Films, vol. 387, pp. 228-230, May 29 2001.
[14] I. Repins, M. A. Contreras, B. Egaas, C. DeHart, J. Scharf, C. L. Perkins, et al., "19·9%-efficient ZnO/CdS/CuInGaSe2solar cell with 81·2% fill factor," Progress in Photovoltaics: Research and Applications, vol. 16, pp. 235-239, 2008.
[15] A. Chirila, S. Buecheler, F. Pianezzi, P. Bloesch, C. Gretener, A. R. Uhl, et al., "Highly efficient Cu(In,Ga)Se2 solar cells grown on flexible polymer films," Nat Mater, vol. 10, pp. 857-61, Nov 2011.
[16] F. Kessler and D. Rudmann, "Technological aspects of flexible CIGS solar cells and modules," Solar Energy, vol. 77, pp. 685-695, 2004.
[17] M. G. Faraj, K. Ibrahim, and A. Salhin, "Investigation of CIGS Solar Cells on Polyethylene Terephthalate Substrates," International Journal of Polymeric Materials, vol. 60, pp. 817-824, 2011.
[18] P. Reinhard, A. Chirila, P. Blosch, F. Pianezzi, S. Nishiwaki, S. Buecheler, et al., "Review of Progress Toward 20% Efficiency Flexible CIGS Solar Cells and Manufacturing Issues of Solar Modules," IEEE Journal of Photovoltaics, vol. 3, pp. 572-580, 2013.
[19] F. Pianezzi, A. Chirila, P. Blosch, S. Seyrling, S. Buecheler, L. Kranz, et al., "Electronic properties of Cu(In,Ga)Se2 solar cells on stainless steel foils without diffusion barrier," Progress in Photovoltaics, vol. 20, pp. 253-259, May 2012.
[20] D. Rudmann, D. Brémaud, H. Zogg, and A. N. Tiwari, "Na incorporation into Cu(In,Ga)Se[sub 2] for high-efficiency flexible solar cells on polymer foils," Journal of Applied Physics, vol. 97, p. 84903, 2005.
[21] A. N. Tiwari, M. Krejci, F. J. Haug, and H. Zogg, "12.8% Efficiency Cu(In,Ga)Se2 solar cell on a flexible polymer sheet," Progress in Photovoltaics: Research and Applications, vol. 7, pp. 393-397, 1999.
[22] K. Makoto, S. Mitsunori, and T. Kiyoshi, "High efficiency GaAs thin film solar cells by peeled film technology," Journal of Crystal Growth, 1978.
[23] L. Chi Hwan, K. Dong Rip, and Z. Xiaolin, "Transfer Printing Methods for Flexible Thin Film Solar Cells: Basic Concepts and Working Principles," ACS Nano, vol. 8, pp. 8746-8756, 2014.
[24] F. Balestra, A. Nazarov, V. S. Lysenko, Y. Takao, and S. Kifofumi, "Progress in SOI Structures and Devices Operating at Extreme Conditions," springer, 2002.
[25] S. W. Bedell, D. Shahrjerdi, B. Hekmatshoar, K. Fogel, P. A. Lauro, J. A. Ott, et al., "Kerf-Less Removal of Si, Ge, and III-V Layers by Controlled Spalling to Enable Low-Cost PV Technologies," IEEE Journal of Photovoltaics, vol. 2, pp. 141-147, 2012.
[26] C. H. Lee, D. R. Kim, I. S. Cho, N. William, Q. Wang, and X. Zheng, "Peel-and-stick: fabricating thin film solar cell on universal substrates," Sci Rep, vol. 2, p. 1000, 2012.
[27] G. J. Hayes and B. M. Clemens, "Laser liftoff of gallium arsenide thin films," Mrs Communications, vol. 5, pp. 1-5, Mar 2015.
[28] B. Fleutot, D. Lincot, M. Jubault, Z. J. Li Kao, N. Naghavi, J.-F. Guillemoles, et al., "GaSe Formation at the Cu(In,Ga)Se2/Mo Interface-A Novel Approach for Flexible Solar Cells by Easy Mechanical Lift-Off," Advanced Materials Interfaces, vol. 1, pp. n/a-n/a, 2014.
[29] W. Zhou, Wang, Zhong Lin, Scanning Microscopy for Nanotechnology: Springer-Verlag New York, 2007.
[30] G. Ledoux, O. Guillois, F. Huisken, B. Kohn, D. Porterat, and C. Reynaud, "Crystalline silicon nanoparticles as carriers for the Extended Red Emission," Astronomy & Astrophysics, vol. 377, pp. 707-720, Oct 2001.
[31] S. Shirakata and T. Nakada, "Time-resolved photoluminescence in Cu(In,Ga)Se2 thin films and solar cells," Thin Solid Films, vol. 515, pp. 6151-6154, 2007.
[32] A. Rockett, "The effect of Na in polycrystalline and epitaxial single-crystal CuIn1−xGaxSe2," Thin Solid Films, vol. 480-481, p. 27, 2005.
[33] T. T. Wu, F. Hu, J. H. Huang, C. H. Chang, C. C. Lai, Y. T. Yen, et al., "Improved efficiency of a large-area Cu(In,Ga)Se(2) solar cell by a nontoxic hydrogen-assisted solid Se vapor selenization process," ACS Appl Mater Interfaces, vol. 6, pp. 4842-9, Apr 9 2014.
[34] A. W. Czanderna and F. J. Pern, "Encapsulation of PV modules using ethylene vinyl acetate copolymer as a pottant: A critical review," Solar Energy Materials and Solar Cells, vol. 43, pp. 101-181, Sep 1 1996.
[35] F. J. Pern, S. H. Glick, and A. W. Czanderna, "EVA encapsulants for PV modules: Reliability issues and current R&D status at NREL," Renewable Energy, vol. 8, pp. 367-370, May-Aug 1996.
[36] A. M. Terry and W. F. Stephen, "A molecular interpretation of stress corrosion in silica," Nature, vol. 295, pp. 511-512, 1982.
[37] W. Wolfram, K. Robert, and P. Michael, "Raman investigations of Cu(In,Ga)Se2 thin films with various copper contents," Thin Solid Films, vol. 517, p. 867869, 2008.
[38] C. M. Ruiz, X. Fontané, A. Fairbrother, V. Izquierdo-Roca, C. Broussillou, S. Bodnar, et al., "Impact of electronic defects on the Raman spectra from electrodeposited Cu(In,Ga)Se2 solar cells: Application for non-destructive defect assessment," Applied Physics Letters, vol. 102, p. 91106, 2013.
[39] V. Kumar, S. Kr. Sharma, T. P. Sharma, and V. Singh, "Band gap determination in thick films from reflectance measurements," Optical Materials, vol. 12, pp. 115-119, May 1999.
[40] S.-U. Park, R. Sharma, K. Ashok, S. Kang, J.-K. Sim, and C.-R. Lee, "A study on composition, structure and optical properties of copper-poor CIGS thin film deposited by sequential sputtering of CuGa/In and In/(CuGa+In) precursors," Journal of Crystal Growth, vol. 359, pp. 1-10, 2012.
[41] Q. Cao, O. Gunawan, M. Copel, K. B. Reuter, S. J. Chey, V. R. Deline, et al., "Defects in Cu(In,Ga)Se2 Chalcopyrite Semiconductors: A Comparative Study of Material Properties, Defect States, and Photovoltaic Performance," Advanced Energy Materials, vol. 1, pp. 845-853, 2011.
[42] U. Rau, K. Taretto, and S. Siebentritt, "Grain boundaries in Cu(In, Ga)(Se, S)2 thin-film solar cells," Applied Physics A, vol. 96, pp. 221-234, 2009/07/01 2009.
[43] S. Takeaki, T. Keiki, I. Muhammad Monirul, I. Shogo, Y. Akimasa, M. Koji, et al., "Time-Resolved Microphotoluminescence Study of Cu(In,Ga)Se 2," Japanese Journal of Applied Physics, vol. 50, p. 05FC01, 2011.
[44] J. Chantana, D. Hironiwa, T. Watanabe, S. Teraji, K. Kawamura, and T. Minemoto, "Investigation of Cu(In,Ga)Se2 absorber by time-resolved photoluminescence for improvement of its photovoltaic performance," Solar Energy Materials and Solar Cells, vol. 130, pp. 567-572, 2014.
[45] R. Wuerz, A. Eicke, F. Kessler, and F. Pianezzi, "Influence of iron on the performance of CIGS thin-film solar cells," Solar Energy Materials and Solar Cells, vol. 130, pp. 107-117, 2014.