傳統化石燃料在不斷開採下愈來愈少，綠色能源的使用逐漸成為全球趨勢，其中又以太陽能電池為熱門替代能源。因此，更多關於矽基太陽能電池生產的細節必須被開發。本研究使用兩種低成本創新的漿料及兩種高低溫燒結技術來完成正面銅電極製作，目的為取代傳統正銀電極材料成本太高以及含鉛玻璃的使用，希望能開發出低成本高導電率之正銅電極。
本研究使用已完成抗反射膜沉積及背鋁印製之多晶矽太陽能電池，在高溫燒結過程中，先將自製金屬漿料透過細線網版印刷印於基板上，再經過兩階段熱處理形成歐姆接觸。第一階段在空氣中進行，由鉛玻璃蝕刻抗反射層並在矽表面結晶出奈米銀完成燒結形成歐姆接觸；第二階段則在還原氣氛中將氧化銅還原回銅，藉由氫氣、銀與鉛玻璃的交互作用使鉛揮發，達到無含鉛環保的目標。
而在低溫燒結過程中，將自製的銀包銅粉體配置出高固含量的漿料，再利用已雷射切割抗反射層形成H-pattern的矽基板進行網印，最後經過熱處理形成歐姆接觸。藉由表面生成之奈米銀做為金屬銅粉接觸的黏著劑，而其包覆率大於90%能在低溫燒結中避免銅粉氧化。另一方面可使導電率大幅提升，對於提升導電率及降低燒結溫度都有極大的幫助。各製程結束後分別透過透射電子顯微鏡、X光射線繞射分析儀、場放射型掃描式電子顯微鏡、四點探針及TLM方法來分析。
透過實驗與分析，推得各階段時的反應機構，同時也驗證透過創新的漿料及製程，可同時達成正電極所需之歐姆接觸與良好的電阻率與特徵接觸電阻。量測結果中高溫系統之特徵接觸電阻約為0.003Ωcm2，最佳正銅電極電阻率為4.5×10-6 Ωcm，太陽能電池轉換效率初步結果為9.3%。而在低溫系統之特徵接觸電阻約為0.004Ωcm2，最佳正銅電極電阻率為7.5×10-6 Ωcm ，太陽能電池轉換效率結果為10.2%，本研究最終成功開發出高導低成本之正銅電極。

Of the rapid development in the world today, tradition fossil fuel were reduced with mining. The application of green energy become the global trend gradually. Solar cell is one of the most popular alternative energy, so more details about manufacturing solar cells should be developed stringently. The aim of this study is to construct ohmic contact between front electrode and Si-based solar cell by two Newly-invented low-cost paste and high/low temperature sintering process. In order to develop a low-cost, high-conductivity copper front electrode to replace the traditional silver front electrode, which is high-cost and with Pb inside.
This study uses self-made paste to screen printed on polycrystalline Si solar cell which has already finished the deposition of anti-reflection coatings and back Al electrode. In the high temperature firing process, paste was first screen printed on silicon substrate, then two-step firing process was applied. In the first firing stage, the atmosphere was in air, PbO-based glass frit etched the ARC and Ag recrystallized at the interface of Si, constructing the ohmic contact. The second stage was in reducing atmosphere. In this step, CuO reduced to Cu and Pb will volatile due to the interactions between Ag, H2 and PbO-based glass frit, reach the environmental protection goal of Pb free.
During low temperature firing stage, using self-made CucoreAgshell powder to make high solid content paste, then screen printing the fine line on laser-opening H-pattern silicon substrate and applying firing process. Because the silver coverage is more than 90% and silver nanoparticles start to melt at 200℃. This mechanism can not only prevent copper from oxidized, but enhance the conductivity. TEM, EDS, SEM, four-point probe and transmission line model were employed to analyze the results after each process.
By experiment and analysis, reaction mechanism in each stage was surmised, and it was also proven that ohmic contact for front electrode could be obtained. In high temperature firing system, the lowest specific contact resistivity was 0.003Ωcm2 and the lowest resistivity of front electrode measured was 4.5×10-6 Ωcm, and the efficiency of solar cell is about 9.3%. And in low temperature firing system, the lowest specific contact resistivity was 0.004Ωcm2 and the lowest resistivity of front electrode measured was 7.5×10-6 Ωcm, and the efficiency of solar cell is about 10.2%. Our research finally develop a low-cost, high-conductivity copper front electrode for solar cell.

1.Blakers AW, Green MA, T. L, H. O, B. R. The Role of Photovoltaics in Reducing Greenhouse Gas Emissions. Canberra: Australian Government Publishing Service; 1991.
2.Green MA. Photovoltaics: Coming of Age. 21st IEEE Photovoltaic Specialists Conference [Internet]. 1990:1-8.
3.Becquerel, Memoire Sur Les Effects D´Electriques Produits Sous L´Influence Des Rayons Solaires. Annalen der Physick und Chemie, 1839. ;9:145-149.
4.Wolf M. Historical Development of Solar Cells.1976 .
5.Mulligan, W. P., Rose, D. H., Cudzinovic, M. J., De Ceuster, D. M., McIntosh, K. R.,Smith, D. D., Swanson, R. M., Manufacture of solar cells with 21% efficiency, in: Proceedings of the 19th European Photovoltaic Solar Energy Conference, pp. Paris, France, 2004,387-390.
6.Green, M. A., The path to 25% silicon solar cell efficiency: History of silicon cell evolution, Progress in Photovoltaics 17 (3), 2009, 183-189.
7.C. Honsberg and S. Bowden, Pv Education [Online] Available Www.Pveducation.Org. 2014.
8.Kerr, M. J., Cuevas, A., Campbell, P., Limiting efficiency of crystalline silicon solar cells due to Coulomb-enhanced Auger recombination, Progress in Photovoltaics: Research and Applications 11 (2), 2003, 97-104.
9.Tajima, M., Ikebe, M., Ohshita, Y., Ogura, A., Photoluminescence analysis of iron contamination effect in multicrystalline silicon wafers for solar cells, Journal of Electronic Materials 39 (6), 2010, 747-750.
10. Bauer G. Absolutwerte der optischen Absorptionskonstanten von Alkalihalogenidkristallen im Gebiet ihrer ultravioletten Eigenfrequenzen. Annalen der Physik. 1934 ;411 (4):434 - 464.
11.Bustarret, E., Bensouda, M., Habrard, M. C., Bruyere, J. C., Configurational statistics in a-SixNyHz alloys: A quantitative bonding analysis, Physical Review 1988ㄝB 38 (12), 8171.
12.Hezel, R., Jaeger, K., Low-temperature surface passivation of silicon for solar cells, Journal of the Electrochemical Society 136 (2), 1989, 518-523.
13.Szlufcik, J., De Clercq, K., De Schepper, P., Poortmans, J., Buczkowski, A., Nijs, J., Mertens, R., Improvement in multicrystalline silicon solar cells after thermal treatment of PECVD silicon nitride Ar coating, in: Proceedings of the 12th European Photovoltaic Solar Energy Conference, pp. 1018-1021, Amsterdam, The Netherlands, 1994.
14.O. V. Sulima, A. W. Bett, F. Dimroth, S. Keser, G. Stollwerck, and W.wettling, Iii/V Materials Tandem-Concentrator Solar Cell Application. 1997.
15.S. Glunz. Photonics for High-Efficiency Crystalline Silicon Solar Cells. in EU-PVSEC. 2013.
16.Mardesich, N., Pepe, A., Bunyan, S., Edwards, B., Olson, C., A low-cost photovoltaic cell process based on thick film techniques, in: Proceedings of the 14th IEEE Photovoltaic Specialists Conference, pp. 943-947, San Diego, California, USA, 1980.
17.S.W. Glunz, J. Dicker, M. Esterie, M. Hermie, J. Iserberg, F. Kamerewerd, J. Knobloch, D. Kray, A. Leimenstoll, F. Lutz, D. O wald, R. Preu, S. Rein, E. Schäffer, C. Schetter, H. Schmidhuber, H. Schmidt, M. Steuder, C. Vorgrimler, G. Willeke, High-efficiency silicon solar cells for low-illumination applications, Proceedings of the Photovoltaic Specialists Conference, New Orleans, 2002, 450-453.
18.Huster, F., Schubert, G., ECV doping profile measurements of aluminium alloyed back surface fields, in: Proceedings of the 20th European Photovoltaic Solar Energy Conference, pp. 1462-1465, Barcelona, Spain, 2005.
19.Bentzen, A., Phosphorus diffusion and gettering in silicon solar cells Dissertation, University of Oslo, 2006.
20.Bentzen, A., Phosphorus diffusion and gettering in silicon solar cells Dissertation, University of Oslo, 2006.
21.C. J. J. Tool, A. R. Burgers, P. Manshanden, and A. W. Weeber, Influence of Wafer Thickness on the Performance of Multicrystalline Si Solar Cells; an Experimental Study.
22.M. Wolf and H. Rauschenbach, Serie Resistance Effects on Solar Cell. Advanced Energy Convension, 1963. 3: p. 455-479.
23.B. v. Roedern and G. H. Bauer, Why Is the Open-Circuit Voltageof Crystalline Si Solar Cells So Critically Dependent on Emitter- and Base-Doping. 1999.
24.J. E. Fink, Fine Line Metallization of Silicon Heterojunction Solar Cells Via Collimated Aerosol Beam Direct Write 2012.
25.Schubert, G., Horzel, J., Kopecek, R., Huster, F., Fath, P., Silver thick film contact formation on lowly doped phosphorous emitters, in: Proceedings of the 20th European Photovoltaic Solar Energy Conference, pp. 934-937, Barcelona, Spain, 2005.
26.Ballif, C., Huljic, D. M., Willeke, G., Hessler-Wyser, A., Silver thick-film contacts on highly doped n-type silicon emitters: structural and electronic properties of the interface, Applied Physics Letters 82 (12), 2003, 1878-1880.
27.A. W. Blakers, Shading Losses of Solar-Cell Metal Grids. American Institute of physics, 1992.
28.Mardesich, N., Pepe, A., Bunyan, S., Edwards, B., Olson, C., A low-cost photovoltaic cell process based on thick film techniques, in: Proceedings of the 14th IEEE Photovoltaic Specialists Conference, pp. 943-947, San Diego, California, USA, 1980.
29.Lindholm FA, Fossum JG, Burgess EL. Application of the superposition principle to solar-cell analysis. IEEE Transactions on Electron Devices. 1979 ; 26:165–171.
30.Sinton RA, Cuevas A. Contactless determination of current–voltage characteristics and minority-carrier lifetimes in semiconductors from quasi-steady-state photoconductance data. Applied Physics Letters [Internet]. 1996 ; 69:2510-2512.
31.Levy MY, Honsberg CB. Rapid and precise calculations of energy and particle flux for detailed-balance photovoltaic applications. Solid-State Electronics. 2006 ;50:1400-1405.
32.Green MA. Solar cell fill factors: General graph and empirical expressions. Solid-State Electronics. 1981 ;24:788 - 789.
33.Baruch P, De Vos A, Landsberg PT, Parrott JE. On some thermodynamic aspects of photovoltaic solar energy conversion. Solar Energy Materials and Solar Cells. 1995 ;36:201-222.
34.M. Wu, B. Lin, Y. Cao, Y. Sun, H. Yang, and X. Zhang, Preparation and Sintering Properties in Air of Silver-Coated Copper Powders and Pastes. J Mater electron, 2013.
35.M. Alemán, N. B. D. Rudolph, T. Rublack, and S. W. Glunz, Front-Side Metallization Beyond Silver Paste: Silicide Formation / Alternative Technologies. 2008.
36.B.Raabe, F. Huster, M. McCann, P. Fath, "High Aspect Ratio Screen Printed Fingers", 20th EUPVSEC, BarcelonaG. Schmid, Adv. Eng. Mater., 2001, 3, 737.
37.M. Galiazzo et al. "DOUBLE PRINTING OF FRONT CONTACT AG IN c-Si SOLAR CELLS" , 25th EUPVSEC, Valencia 2010.
38.M. Galiazzo et al. 'New Technologies for Improvement of Metallization Line', 24th EUPVSEC, Hamburg 2009.
39.T.Falcon 3rd metallization workshop, 2011 Double printing.
40.D.Buzby and A. Dobie, "Fine Line Screen Printing of Thick Film Pastes on Silicon Solar Cells" 41st International Symposium of Microelectronics, IMAPS.
41.X. Gao et al., "ONE-STEP SCREEN-PRINTING METALLIZATION FORMING HIGH ASPECT RATIO GRID LINES ON CRYSTALLINE SOLAR CELLS" 25th EUPVSEC (2010) Valencia.
42.T.Falcon 3rd metallization workshop, 2011 Double printing.
43.M. M. Hilali, A. Rohatgi, and B. To, A Review Understanding of Screen-Printined Contacts and Selective-Emitter Formation. 2004.
44.L. Frisson, M. Honore, R.-Mertens,R. Govaerts, and~R. Van Overstraeten,.“Siliconnsolar cells. wifh scceen printed diffusion andmetallization,” in Proc. 14th IEEE Photovoltaic Specialists Conf., 1980, pp. 941-942.
45.J. Zhao, A. Wang, and M. A. Green, Sol. Energy Mater. And Sol. Cells. 2001.
46.S. Schubert, F. Huster, and P.fath, Pvsec-14. 2003: p. 441-442.
47.G. Schubert, F. Huster, P. Fath, Physical understanding of printed thick-film front contacts of crystalline Si solar cells—Review of existing models and recent developments, Sol. Energy Mater. Sol. Cells 90 (2006) 3399-3406.
48.Z.G. Li, L. Liang, A.S. Lonkin, B.M. Fish, M.E. Lewittes, L.K. Cheng, K.R. Mikeska, Microstructural comparison of silicon solar cells‘ front-side Ag contact and the evolution of current conduction mechanisms, J. Applied Phys. 110 (2011) 074304.
49.D. Pysch, A. Mette, A. Filipovic, S.W. Glunz, Comprehensive analysis of advanced solar cell contacts consisting of printed fine-line seed layers thickened by silver plating, Progress in Photovoltaics: Research and Applications 17 (2009) 101–114.
50.L.K. Cheng, L. Liang, Z.G. Li, Nano-Ag colloids assisted tunneling mechanism for current conduction in front contact of crystalline Si solar cells, Photovoltaic Specialists Conference 34 (2009) 002344-002348.
51.K.K. Hong, S.B. Cho, J.S. You, J.W. Jeong, S.M. Bea, J.Y. Huh, Mechanism for the formation of Ag crystallites in the Ag thick-film contacts of crystalline Si solar cells, Sol. Energy Mater. Sol. Cells 93 (2009) 898-904.
52.Z.G. Li, L. Liang, A.S. Lonkin, B.M. Fish, M.E. Lewittes, L.K. Cheng, K.R. Mikeska, Microstructural comparison of silicon solar cells' front-side Ag contact and the evolution of current conduction mechanisms, J. Applied Phys. 110 (2011) 074304.
53.C. Ballif, D. Huljic, G. Willeke, and A. Hessler-Wyser, Appl. Phys. Lett. 82, 1878. 2003.
54.Z. G. Li, L. Liang, and L. K. Cheng, J. Appl. Phys. 105, 66102. 2009.
55.M.M. Hilali, S. Sridharan, C. Khadilkar, A. Shaikh, A. Rohatgi, S. Kim, Effect of glass frit chemistry on the physical and electrical properties of thick-film Ag contacts for silicon solar cells, J. Elec. Mater. 35 (2006) 2041-2047.
56.M. Hilali, K. Nakayashiki, C. Khadilkar, R. Reedy, A. Rohatgi, A. Shailh, S. Kim, and S. Sridharan, J. Electrochem. Soc. 153, A5. 2006.
57.A. Goetzberg, J. Knobloch, B. Voß, Crystalline silicon solar cells. John Wiley and Sons, 1994.
58.E.G. Woelk, H. Kräutle, H. Beneking, Measurement of low resistance ohmic contacts on semiconductors, IEEE Transactions on Electron Device 33/1 (1986) 19-22.
59.Berger, H. H., Solid State Electronics, Volume 15, Issue 2, p. 145-158. Models for contacts to planar devices (1972).
60.A. Drygala A. The influence of laser texturing on photovoltaic properties of polycrystalline silicon, Doctoral dissertation, The main library of Silesian University, Gliwice, 2007.
61.Gunnar Schubert, Frank Huster, Peter Fath, CURRENT TRANSPORT MECHANISM IN PRINTED AG THICK FILM CONTACTS TO AN N-TYPE EMITTER OF A CRYSTALLINE SILICON SOLAR CELL.
62.J. Zhao, D. Zhang, J. Zhao, J. Solid State Chem. 184, 2339 (2011).
63.S. Dieter, Semiconductor Material and Device Characterization. 2nd ed. 1998.
64.Douglas Giancoli (2009) [1984]. "25. Electric Currents and Resistance". In Jocelyn Phillips. Physics for Scientists and Engineers with Modern Physics (4th ed.). Upper Saddle River, New Jersey: Prentice Hall. p. 658. ISBN 0-13-149508-9.
65.T. Trupke, E. Pink, R. A Bardos, and M. D. Abbott, "Spatially resolved series resistance of silicon solar cells obtained from luminescence imaging", Appl.Phys. Lett. 90,093506 (2007).
66.S Kontermann, M. Horteis, A Ruf, S. Feo, and R. Preu, "Spatially resolved contact-resistance measurements on crystalline silicon solar cells", Phys. Status Solidi A 206, No. 12, 2866-2871 (2009).
67.H. H. Berger, "Contact resistance on diffused resistors", Solid-State Circuits Conference. Digest of Technical Papers. I 969 IEEE. 160 - 161.
68.G. K. Reeves and H. B. Harrison, "Obtaining the specific contact resistance from transmission line model measurements", IEEE ELECTRON DEVICE LETTERS, VOL. EDL-3, NO, 5, MAY 1982.
69.D Hinken, K Ramspeck, K Bothe, B Fischer, and R Brendel , "Series resistance imaging of solar cells by voltage dependent electroluminescence",Appl. Phys. Lett. 91, 182104 (2007).