Studying the sodium effect on the Mo layer by varying the growth pressure on CIGS solar absorption Layer
DOI:
https://doi.org/10.62638/ZasMat1334Abstract
Efficiency degradation in flexible Cu(In,Ga)Se (CIGS) solar cells on stainless-steel (STS) substrates occurs due to iron impurity diffusion into the absorber layer. As the primary component of stainless-steel, iron can penetrate the back contact and enter the CIGS absorber, where Fe impurities are known to diminish solar cell performance. In this study, we developed a Sodium doped Molybdenum (Mo-Na) layer as a diffusion barrier on STS substrate using various growth pressures. We examined the Mo-Na diffusion barrier layer using Scanning Electron Microscopy (SEM), X-r diffractometer (XRD), and Uv-Vis Spectrophotometer. XRD analysis revealed that films grown on STS substrates exhibited a pure chalcopyrite phase with a preferred (112) orientation. We deposited Mo back contact and CIGS layer through co-sputtering and selenization processes, respectively, to investigate Na diffusion through the barrier into the CIGS absorption layer. Secondary ion mass spectroscopy (SIMS) was employed to measure Na and Fe concentrations diffused in the CIGS layer. The SIMS depth profile and optical measurement results clearly showed that Na diffusion into the CIGS absorber layer could be regulated by adjusting the working pressure of the Mo-Na layer. Furthermore, we anticipate significant improvement in CIGS solar cell performance with the Mo-Na diffusion barrier layer, as Na concentration in the CIGS absorption layer affects the efficiency of CIGS solar cells.
Keywords:
Flexible Cu(In,Ga)Se2 (CIGS), Stainless steel, Sputtering, Diffusion barrier, Fe diffusion.References
P. Reinhard Chirila, F. Pianezzi, P. Bloesch, A.R. Uhl, C. Fella, L. Kranz, D. Keller, C. Gretener, H. Hagendorfer, D. Jaeger, R. Erni, S. Nishiwaki, S. Buecheler, A.N. Tiwari (2013) Potassium-induced surface modification of Cu(In,Ga,)Se2 thin films for high-efficiency solar cells. Nat. Mater. 12, 1107-1111, https://doi.org/10.1038/nmat3789.
J.E. Granata, J.R. Sites, S. Asher, R.J. Matson (1997) Quantitative incorporation of sodium in CuInSe2 and Cu(In,Ga)Se2 photovoltaic devices. Proceedings of the Conference Record of 26Th IEEE Photovoltaic Specialists Conference, p.387-390, https://doi.org/10.1109/PVSC.1997.654109.
Y. Sakurai, A. Yamada, P. Fons, K. Matsubara, T. Kojima, S. Niki, T. Baba, T. Tsuchimochi, Y. Kimura, Nakanishi (2003) Adjusting the Sodium diffusion into CuInGaSe2 absorbers by preheating of Mo/SLG substrates. J. Phys. Chem. Solids, 64, 1877-1880, https://doi.org/10.1016/S0022-3697(03)00173-2.
F. Kessler, D. Rudmann (2004) Technological effects of flexible CIGS solar cells and modules. Sol Energy, 77, 685-695, https://doi.org/10.1016/j.solener.2004.04.010.
S.H. Wei, S.B. Zhang, A. Zunger (1999) Effects of Na on the electrical and structural properties of CuInSe2. J. Appl. Phys., 85, 7214-7218, https://doi.org/10.1063/1.370534.
E. Wallin, U. Malm, T. Jarmar, O. Lundberg, M. Edoff, and L. Stolt (2012) World-record Cu(In,Ga)Se2-based thin-film sub-module with 17.4% efficiency. Prog. Photovoltaics: Res. Appl., 20, 851-854, https://doi.org/10.1002/pip.2246.
M. Bodegard, K. Granath, L. Stolt (2000) Growth of Cu(In,Ga)Se2 thin films by coevaporation using alkaline precursors. Thin Solid Films, 361-362, 1-16, https://doi.org/10.1016/S0040-6090(99)00828-7.
D. Rudmann, A.F. Da Cunha, M. Kaelin, F. Kurdesau, H. Zogg, A.N. Tiwari, G. Bilger (2004) Efficiency enhancement of Cu(In.Ga)Se2 solar cells due to post-deposition Na incorporation. Appl. Phys. Lett., 84, 1129-1131, https://doi.org/10.1063/1.1646758.
D.W. Niles, K. Ramanathan, F. Hasoon, R. Noufi, B.J. Tielsch, and J.E. Fulghum (1997) Na impurity chemistry in photovoltaic CIGS thin films:Investigation with x-ray photoelectron spectroscopy. J.Vac.Sci.Technol. A, 15, 3044-3049, https://doi.org/10.1116/1.580902.
X. Song, R. Caballero, R. Felix, D. Gerlach, C.A. Kaufmann, H.-W. Schock, R.G. Wilks, M. Bar (2012) Na incorporation into Cu(In,Ga)S2 thin-film solar cells absorbers deposited on polyimide: Impact on the chemical and electronic surface structure. J. Appl. Phys., 111, 034903-1-034903, https://doi.org/10.1063/1.3679604.
D.J. Schroeder, A.A. Rockett (1997) Electronic effects of sodium in epitaxial CuIn1-xGaxSe2. J. Appl. Phys., 82, 4982-2985, https://doi.org/10.1063/1.366365.
M. Ruckh, D. Schmid, M. Kaiser, R. Schiffler, T. Walter, H.W. Schock (1996) Influence of substrates on the electrical properties of Cu(In,Ga)Se2 thin films. Solar Energy Mater. Solar Cells, 41-42, 335-434, https://doi.org/10.1016/0927-0248(95)00105-0.
R. Kaigawa, Y. Satake, K. Ban, S. Merdes, R. Klenk (2011) Effects of Na on the properties of Cu(In,Ga)S2 Solar Cells. Thin Solid Films, 516, 16, 5535-5538, https://doi.org/10.1016/j.tsf.2011.02.044.
F. Pianezzi, A. Chirila, P. Blosch, S. Seyrling, S. Buecheler, L. Kranz, C. Fella, A.N. Tiwari (2010) Electronic properties of Cu(In,Ga)Se2 solar cells on stainless steel foils without diffusion barrier. Prog. Photovolt. Res. Appl., 20, 253, https://doi.org/10.1002/pip.1247.
P. Jackson, D. Hariskos, E. Lotter, S. Paetel, R. Wuerz, R. Menner, W. Wischmann, M. Powalla (2011) New world record efficiency for Cu(In,Ga)Se2 thin-film solar cells beyond 20%. Prog. Photovolt. Res. Appl.,19, 894, https://doi.org/10.1002/pip.1078.
P. Jackson, P. Grabitz, A. Strohm, G. Bilger, H. W. Schock (2004) Contamination of Cu(In,Ga)Se2 solar cells by metallic substrate elements. Proceedings of the 19th European Photovoltaic Solar Energy Conference, 1936-1938.
C. P. Bjorkman, S. Jani, J. Westlinder, M. K. Linnarsson, J. Scragg, M. Edoff 2013 Diffusion of Fe and Na in co-evaporated Cu(In,Ga)Se2 devices on steel substrates. Thin Solid Films, 535, 188–192, https://doi.org/10.1016/j.tsf.2012.11.067.
D. Bae, S. Kwon, J. Oh, W. K. Kim, H. Park (2013) Investigation of Al2O3 diffusion barrier layer fabricated by atomic layer deposition for flexible Cu(In,Ga)Se2 solar cells. Renewable Energy, 55, 62–68, https://doi.org/10.1016/j.renene.2012.12.024.
K. Herz, F. Kessler, R. Wachter, M. Powalla, J. Schneider, A. Schulz, and U. Schumacher (2002) Dielectric barriers for flexible CIGS solar modules. Thin Solid Films, 403–404, 84 – 389, https://doi.org/10.1016/S0040-6090(01)01516-4.
D. Rudmann, G. Bilger, M. Kaelin, F.-J. Haug, H. Zogg, A.N. Tiwari (2003) Effects of NaF coevaporation on structural properties of Cu(In,Ga)Se2 thin films. Thin Solid Films, 421-432, 37-40, https://doi.org/10.1016/S0040-6090(03)00246-3.
S. Ye, X. Tan, M. Jiang, B. Fan, K. Tang, S. Zhuang (2010) Impact of different Na incorporating methods on Cu(In,Ga)Se2 thin film solar cells with a low-Na substrate. Appl. Opt., 49, 1662-1665, https://doi.org/10.1364/AO.49.001662.
J.H. Yun, K.H. Kim, M. Kim, B.T. Ahn, S.J. Ahn, J.C. Lee, K.H. Yoon (2007) Fabrication of CIGS solar cells with a Na-doped Mo layer on a Na-free substrate. Thin Solid Films, 515, 5876-5879, https://doi.org/10.1016/j.tsf.2006.12.156.
C. Chuan Chen, X. Qi, M.G. Tsai, Y.F. Wu, I.G. Chen, C.Y. Lin, P.H. Wu, K.P. Chang (2013) Low-temperature growth of Na doped CIGS films on flexible polymer substrates by pulsed laser ablation from a Na containing target. Surface and Coatings Technology, 231, 209-213, https://doi.org/10.1016/j.surfcoat.2012.06.065.
J. Parravicini, M. Acciarri, M. Murabito, A.L. Donne, A. Gasparotto, S. Binetti (2018) In-depth photoluminescence spectra of pure CIGS thin films. Appl. Opt., 57, 1849-1856, https://doi.org/10.1364/AO.57.001849.
