The effect of Zn1−xSnxOy buffer layer thickness in 18.0% efficient Cd-free Cu(In,Ga)Se2 solar cells
J. Lindahl
Ångström Solar Center, Solid State Electronics, Uppsala University, P.O. Box 534, SE-751 21 Uppsala, Sweden
Search for more papers by this authorJ. T. Wätjen
Ångström Solar Center, Solid State Electronics, Uppsala University, P.O. Box 534, SE-751 21 Uppsala, Sweden
Search for more papers by this authorA. Hultqvist
Ångström Solar Center, Solid State Electronics, Uppsala University, P.O. Box 534, SE-751 21 Uppsala, Sweden
Search for more papers by this authorT. Ericson
Ångström Solar Center, Solid State Electronics, Uppsala University, P.O. Box 534, SE-751 21 Uppsala, Sweden
Search for more papers by this authorM. Edoff
Ångström Solar Center, Solid State Electronics, Uppsala University, P.O. Box 534, SE-751 21 Uppsala, Sweden
Search for more papers by this authorCorresponding Author
T. Törndahl
Ångström Solar Center, Solid State Electronics, Uppsala University, P.O. Box 534, SE-751 21 Uppsala, Sweden
Correspondence: T. Törndahl, Ångström Solar Center, Solid State Electronics, Uppsala University, P.O. Box 534, SE-751 21 Uppsala, Sweden.
E-mail: [email protected]
Search for more papers by this authorJ. Lindahl
Ångström Solar Center, Solid State Electronics, Uppsala University, P.O. Box 534, SE-751 21 Uppsala, Sweden
Search for more papers by this authorJ. T. Wätjen
Ångström Solar Center, Solid State Electronics, Uppsala University, P.O. Box 534, SE-751 21 Uppsala, Sweden
Search for more papers by this authorA. Hultqvist
Ångström Solar Center, Solid State Electronics, Uppsala University, P.O. Box 534, SE-751 21 Uppsala, Sweden
Search for more papers by this authorT. Ericson
Ångström Solar Center, Solid State Electronics, Uppsala University, P.O. Box 534, SE-751 21 Uppsala, Sweden
Search for more papers by this authorM. Edoff
Ångström Solar Center, Solid State Electronics, Uppsala University, P.O. Box 534, SE-751 21 Uppsala, Sweden
Search for more papers by this authorCorresponding Author
T. Törndahl
Ångström Solar Center, Solid State Electronics, Uppsala University, P.O. Box 534, SE-751 21 Uppsala, Sweden
Correspondence: T. Törndahl, Ångström Solar Center, Solid State Electronics, Uppsala University, P.O. Box 534, SE-751 21 Uppsala, Sweden.
E-mail: [email protected]
Search for more papers by this authorABSTRACT
The influence of the thickness of atomic layer deposited Zn1−xSnxOy buffer layers and the presence of an intrinsic ZnO layer on the performance of Cu(In,Ga)Se2 solar cells are investigated. The amorphous Zn1−xSnxOy layer, with a [Sn]/([Sn] + [Zn]) composition of approximately 0.18, forms a conformal and in-depth uniform layer with an optical band gap of 3.3 eV. The short circuit current for cells with a Zn1−xSnxOy layer are found to be higher than the short circuit current for CdS buffer reference cells and thickness independent. On the contrary, both the open circuit voltage and the fill factor values obtained are lower than the references and are thickness dependent. A high conversion efficiency of 18.0%, which is comparable with CdS references, is attained for a cell with a Zn1−xSnxOy layer thickness of approximately 13 nm and with an i-ZnO layer. Copyright © 2012 John Wiley & Sons, Ltd.
REFERENCES
- 1 Jackson P, Hariskos D, Lotter E, Paetel S, Wuerz R, Menner R, Wischmann W, Powalla M. New world record efficiency for Cu(In,Ga)Se2 thin-film solar cells beyond 20%. Progress in Photovoltaics: Research and Applications 2011; 19(7): 894–897.
- 2 Furlong MJ, Froment M, Bernard MC, Cortès R, Tiwari AN, Krejci M, Zogg H, Lincot D. Aqueous solution epitaxy of CdS layers on CuInSe2. Journal of Crystal Growth 1998; 193(1–2): 114–122.
- 3 Doña JM, Herrero J. Dependence of electro-optical properties on the deposition conditions of chemical bath deposited CdS thin films. Journal of the Electrochemical Society 1997; 144(11): 4091–4098.
- 4 Naghavi N, Abou-Ras D, Allsop N, Barreau N, Bücheler S, Ennaoui A, Fischer CH, Guillen C, Hariskos D, Herrero J, Klenk R, Kushiya K, Lincot D, Menner R, Nakada T, Platzer-Björkman C, Kories H, Spiering S, Tiwari AN, Törndahl T. Buffer layers and transparent conducting oxides for chalcopyrite Cu(In,Ga)(S,Se)2 based thin film photovoltaics: present status and current developments. Progress in Photovoltaics: Research and Applications 2010; 18(6): 411–433.
- 5 Hariskos D, Spiering S, Powalla M. Buffer layers in Cu(In,Ga)Se2 solar cells and modules. Thin Solid Films 2005; 480–481: 99–109.
- 6 Contreras MA, Nakada T, Hongo M, Pudov AO, Sites JR. ZnO/ZnS(O,OH)/Cu(In,Ga)Se2/Mo solar cell with 18.6% efficiency. Proceedings of 3rd World Conference on Photovoltaic Energy Conversion, Osaka, vol. 1, 2003; 570–573.
- 7 Rau U, Schmidt M. Electronic properties of ZnO/CdS/Cu(In,Ga)Se2 solar cells — aspects of heterojunction formation. Thin Solid Films 2001; 387(1–2): 141–146.
- 8 Ishizuka S, Sakurai K, Yamada A, Matsubara K, Fons P, Iwata K, Nakamura S, Kimura Y, Baba T, Nakanishi H, Kojim T, Niki S. Fabrication of wide-gap Cu(In1−xGax)Se2 thin film solar cells: a study on the correlation of cell performance with highly resistive i-ZnO layer thickness. Solar Energy Materials and Solar Cells 2005; 87(1–4): 541–548.
- 9 Hultqvist A, Platzer-Björkman C, Törndahl T, Ruth M, Edoff M. Optimization of i-ZnO window layers for Cu(In,Ga)Se2 solar cells with ALD buffers. Proceedings of the 22nd European Photovoltaic Solar Energy Conference, Milano, 2007; 2381–2384.
- 10 Rousset J, Donsanti F, Genevée P, Renou G, Lincot D. High efficiency cadmium free Cu(In,Ga)Se2 thin film solar cells terminated by an electrodeposited front contact. Solar Energy Materials and Solar Cells 2011; 95(6): 1544–1549.
- 11 Bär M, Fischer CH, Muffler HJ, Zweigart S, Karg F, Lux-Steiner MC. Replacement of the CBD-CdS buffer and the sputtered i-ZnO layer by an ILGAR-ZnO WEL: optimization of the WEL deposition. Solar Energy Materials and Solar Cells 2003; 75(1–2): 101–107.
- 12 Hultqvist A, Edoff M, Törndahl T. Evaluation of Zn–Sn–O buffer layers for CuIn0.5 Ga0.5Se2 solar cells. Progress in Photovoltaics: Research and Applications 2011; 19(4): 478–481.
- 13 Hultqvist A, Platzer-Björkman C, Zimmermann U, Edoff M, Törndahl T. Growth kinetics, properties, performance, and stability of atomic layer deposition Zn–Sn–O buffer layers for Cu(In,Ga)Se2 solar cells. Progress in Photovoltaics: Research and Applications 2011. DOI: 10.1002/pip.1153.
- 14 Edoff M, Woldegiorgis S, Neretnieks P, Ruth M, Kessler J, Stolt L. CIGS submodules with high performance and high manufacturability. Proceedings of the 19th European Photovoltaic Solar Energy Conference and Exhibition, Paris, 2004; 1690–1693.
- 15 Field H. UV–VIS–IR spectral responsivity measurements system for solar cells. AIP Conference Proceedings 1999; 462(1): 629–635.
- 16 Hong WQ. Extraction of extinction coefficient of weak absorbing thin films from special absorption. Journal of Physics D: Applied Physics 1989; 22(9): 1384–1385.
- 17 Tauc J. Optical properties and electronic structure of amorphous Ge and Si. Materials Research Bulletin 1968; 3(1): 37–46.
- 18 Abelès F. Optical properties of solids. North-Holland: Amsterdam, 1972; 303.
- 19 Jayaraj MK, Saji KJ, Nomura K, Kamiya T, Hosono H. Optical and electrical properties of amorphous zinc tin oxide thin films examined for thin film transistor application. Journal of Vacuum Science and Technology B 2008; 26(2): 495–501.
- 20 Buchholz DB, Liu J, Marks TJ, Zhang M, Chang RPH. Control and characterization of the structural, electrical, and optical properties of amorphous zinc–indium–tin oxide thin films. ACS Applied Materials & Interfaces 2009; 1(10): 2147–2153.
- 21 Robertson J. Disorder and instability processes in amorphous conducting oxides. Physica Status Solidi B 2008; 245(6): 1026–1032.
- 22 Hegedus SS, Shafarman WN. Thin-film solar cells: device measurements and analysis. Progress in Photovoltaics: Research and Applications 2004; 12(2–3): 155–176.
- 23 Törndahl T, Hultqvist A, Platzer-Björkman C, Edoff M. Growth and characterization of ZnO-based buffer layers for CIGS solar cells. Proceedings of SPIE 2010; 7603(1): 76 030D.
- 24 Sterner J, Kessler J, Bodegå̊rd M, Stolt L. Atomic layer epitaxy growth of ZnO buffer layers in Cu(In,Ga)Se2 solar cells. Proceedings of the 2nd World Conference on Photovoltaic Energy Conversion, 1998; 1145–1148.
- 25 Sterner J, Platzer-Björkman C, Stolt L. XPS/UPS monitoring of ALCVD ZnO growth on Cu(In,Ga)Se2 absorbers. Proceedings of the 17th European Photovoltaic Solar Energy Conference, Munich, vol. II, 2001; 1118–1121.
- 26 Kessler J, Velthaus KO, Ruckh M, Laichinger R, Schock H, Lincot D, Ortega R, Vedel J. Chemical bath deposition of CdS on CuInSe2, etching effects and growth kinetics. Proceedings of the 6th International Photovoltaic Science and Engineering Conference, New Delhi, 1992; 1005–1010.
- 27 Lincot D, Ortega-Borges R, Vedel J, Ruckh M, Kessler J, Velthaus KO, Hariskos D, Schock HW. Chemical bath deposition of CdS on CuInSe2: Combining dry and wet processes for high efficiency thin film solar cells. Proceedings of the 11th European Photovoltaics Solar Energy Conference, Montreux, 1992; 870–873.
- 28 Hunger R, Schulmeyer T, Klein A, Jaegermann W, Sakurai K, Yamada A, Fons P, Matsubara K, Niki S. An option for the surface science on Cu chalcopyrites: the selenium capping and decapping process. Surface Science 2004; 557(1–3): 263–268.
- 29 Platzer-Björkman C, Zabierowski P, Pettersson J, Törndahl T, Edoff M. Improved fill factor and open circuit voltage by crystalline selenium at the Cu(In,Ga)Se2/buffer layer interface in thin film solar cells. Progress in Photovoltaics: Research and Applications 2010; 18(4): 249–256.
- 30 Törndahl T, Coronel E, Hultqvist A, Platzer-Björkman C, Leifer K, Edoff M. The effect of Zn1−xMgxO buffer layer deposition temperature on Cu(In,Ga)Se2 solar cells: a study of the buffer/absorber interface. Progress in Photovoltaics: Research and Applications 2009; 17(2): 115–125.
- 31 Burstein E. Anomalous optical absorption limit in InSb. Physics Review 1954; 93(3): 632–633.
- 32 Moss TS. The interpretation of the properties of indium antimonide. Proceedings of the Physical Society. Section B 1954; 67(10): 775–782.
- 33 Klenk R. Characterisation and modelling of chalcopyrite solar cells. Thin Solid Films 2001; 387(1–2): 135–140.
- 34 Green MA. Solar Cells: Operating Principles, Technology and System Applications. Prentice-Hall: Englewood Cliffs, NJ, 1982; 96.
- 35 Shimizu A, Chaisitsak S, Sugiyama T, Yamada A, Konagai M. Zinc-based buffer layer in the Cu(InGa)Se2 thin film solar cells. Thin Solid Films 2000; 361–362: 193–197.
- 36 Olsen L, Aguilar H, Addis F, Lei W, Li J. CIS solar cells with ZnO buffer layer. Proceedings 25th IEEE photovoltaic Specialists Conference, Washington, 1996; 997–1000.
