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http://dx.doi.org/10.21218/CPR.2019.7.4.103

Performance Improvement by Controlling Se/metal Ratio and Na2S Post Deposition Treatment in Cu(In,Ga)3Se5 Thin-Film Solar cell  

Cui, Hui-Ling (Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology)
Kim, Seung Tae (Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology)
Chalapathy, R.B.V. (Department of Physics, Vel Tech High Tech Dr Rangarajan Dr Sakunthla Engineering College)
Kim, Ji Hye (Isac Research)
Ahn, Byung Tae (Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology)
Publication Information
Current Photovoltaic Research / v.7, no.4, 2019 , pp. 103-110 More about this Journal
Abstract
Cu(In,Ga)3Se5 (β-CIGS) has a band gap of 1.35 eV, which is an optimum value for high solar-energy conversion efficiency. The effects of Cu and Ga content on the cell performance were investigated previously. However, the effect of Se content on the cell performance is not well understood yet. In this work, β-CIGS films were fabricated by three-stage co-evaporation of elemental sources with various Se fluxes at the third stage instead of at all stages. The average composition of five samples was Cu1.05(In0.59,Ga0.41)3Sey, where the stoichiometric y value is 5.03 and the stoichiometric Se/metal (Se/M) ratio is 1.24. We varied the Se/metal ratio in a range from 1.18 to 1.28. We found that the best efficiency was achieved when the Se/M ratio was 1.24, which is exactly the stoichiometric value where the CIGS grains on the CIGS surface were tightly connected and faceted. With the optimum Se/M ratio, we were able to enhance the cell efficiency of a β-CIGS solar cell from 9.6% to 12.0% by employing a Na2S post deposition treatment. Our results indicate that Na2S post deposition treatment is very effective to enhance the cell efficiency to a level on par with that in α-CIGS cell.
Keywords
Thin-film solar cells; $Cu(In,Ga)_3Se_5$; ${\beta}$-CIGS; Se/metal ratio; $Na_2S$ post deposition treatment;
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Times Cited By KSCI : 2  (Citation Analysis)
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1 Lee, D. Y., Yun, J. H., Yoon, K. H., Ahn, B. T., "Characterization of Cu-poor surface on Cu-rich $CuInSe_2$ thin film prepared by evaporating binary selenide compounds and its effect of solar efficiency", Thin. Solid Films, Vol. 410, pp. 171-176, 2002.   DOI
2 Shin, Y. M., Lee, C. S., Shin, D. H., Kwon, H. S., Park, B. G., Ahn, B. T., "Surface modification of CIGS film by annealing and its effect on the band structure and photovoltaic properties of CIGS solar cells", Curr. Appl. Phys., Vol. 15, pp. 18-24, 2015.   DOI
3 Nishimura, T., Toki, S., Sugiura, H., Nakada, K., Yamada, A., "Interfacial quality improvement of $Cu(In,Ga)Se_2$ thin film solar cells by Cu-depletion layer formation", Appl. Phys. Express, Vol. 9, p. 092301, 2016.   DOI
4 Paszkowicz, W., Lewandowska, R., Bacewicz, R., "Rietveld refinement for $CuInSe_2$ and $CuIn_3Se_5$", J. Alloys Compd. Vol. 362, pp. 241-247, 2004.   DOI
5 Yamazoe, S., Kou, H., Wada, T., "A structural study of Cu-In-Se compounds by x-ray absorption fine structure", J. Mater. Res., Vol. 26, pp. 1504-1516, 2011.   DOI
6 Maeda, T., Gong, W., Wada, T., "Crystallographic and optical properties and band structures of $CuInSe_2$, $CuIn_3Se_5$, and CuIn5Se8 phases in Cu-poor $Cu_2Se-In_2Se_3$ pseudo-binary system", Jpn. J. Appl. Phys., Vol. 55, p. 04ES15, 2016.   DOI
7 Kim, J. H., Shin, Y. M., Kim, S. T., Kwon, H. S., Ahn, B. T., "Fabrication of wide-band $Cu(In,Ga)_3Se_5$ thin films and their application to solar cells", Curr. Photovolt. Res., Vol. 1, pp. 38-43, 2013.   DOI
8 Kim, J. H., Cha, E. S., Park, B. G., Ahn, B. T., "Effect of Se flux and Se treatment on the photovoltaic performance of ${\beta}$-CIGS solar cells", Curr. Photovolt. Res., Vol. 3, pp. 39-44, 2015.   DOI
9 Kim, S. T., Larina, L., Yun, J. H., Shun, B., Ahn, B. T., "Surface passivation and point defect control in $Cu(In,Ga)Se_2$ film with a $Na_2S$ deposition treatment for higher than 19% cell performance", Sustainable Energy & Fuels, Vol. 3, pp. 709-716, 2019.   DOI
10 Ahn, B. T., Yun, J. H., Cha, E. S., Park, K. C., "Understanding the degradation mechanism in CdS/CdTe solar cells using a Cd-deficient CdTe layer", Curr. Appl. Phys., Vol. 12, pp. 174-178, 2012.   DOI
11 Kim, S., Ko, Y. M., Kim, S. T., Choi, Y. W., Park, J. K., Ahn, B. T., "Reduction of point defects and Cu surface composition in $Cu(In,Ga)Se_2$ film by Se annealing with a NaF over layer at intermediate temperature", Curr. Appl. Phys., Vol. 17, pp. 820-828, 2017.   DOI
12 Kim, J. H., Kim, S. T., Larina, L., Ahn, B. T., Kim, K. H., Yun, J. H., "Increase in conversion efficiency of above 14% in $Cu(In,Ga)_3Se_5$ (${\beta}$-CIGS) solar cells by $Na_2S$ incorporation through the surface of ${\beta}$-CIGS film," Sol. Energy Mater. Sol. Cells, Vol. 179, pp. 289-296, 2018.   DOI
13 Kwon, S. H., Park, S. C., Ahn, B. T., Yoon, K. H., Song, J., "Effect of $CuIn_3Se_5$ layer thickness on $CuInSe_2$ thin films and devices", Solar Energy, Vol. 64, pp. 55-66, 1998.   DOI
14 Jackson, P., Wuerz, R., Hariskos, D., Lotter, E., Witte, W., Powalla, M., "Effects of heavy alkali elements in $Cu(In,Ga)Se_2$ solar cells with efficiencies up to 22.6%" Phys. Status. Solidi. RRL, Vol. 10, pp. 583-586, 2016.   DOI
15 Wu, J. L., Hirai, Y., Kato, T., Sugimoto, H., Bermudez, V., "New world record efficiency up to 22.9% for $Cu(In,Ga)(Se,S)_2$ thin film solar cell", 7th World Conference on Photovoltaic Energy Conversion (WCPEC-7), Waikoloa, Hawaii, USA, June 10-15, 2018.
16 Kwon, S. H., Ahn, B. T., Kim, S. K., Yoon, K. H., Song, J., "Growth of $CuIn_3Se_5$ layer on $CuInSe_2$ and its effect on the photovoltaic properties of $In_2Se_3/CuInSe_2$ solar cells", Thin. Solid Films, Vol. 323, pp. 265-269, 1998.   DOI