Photovoltaic properties of Cu(In,Ga)(Se,Te)2 thin film solar cells with different tellurium amounts and a copper-poor stoichiometry

Abstract

In this study, the impact of tellurium addition on the microstructure of the copper indium gallium selenide absorber layer with a copper-poor stoichiometry and the photovoltaic properties of SLG/Mo/CIGS/CdS/ZnO/ITO/Ni-Al-Ni solar cells was investigated. Absorber layer, CdS buffer, ZnO and ITO layers, and the Ni-Al-Ni front contact were produced using three-stage co-evaporation, chemical bath deposition, RF magnetron sputtering, and e-beam evaporation techniques, respectively. The thickness and the composition of the absorber layer were controlled in situ. NaF post deposition treatment were applied to the absorber layer. The addition of tellurium improved the crystal quality by increasing the average grain size and decreased the surface roughness. Decreasing surface roughness increased reflection and thus decreased the amount of sunlight absorbed, which in turn reduced current collection. Open-circuit voltage was effected by impurity level and the grain boundry recombination. While moderate tellurium addition reduced grain boundary recombination, excessive tellurium addition created stress, caused crack formation, and increased recombination by reducing crystal quality. The optimum tellurium amount in the copper-poor CIGS structure was found to be 1.1 atomic percent. The control of the microstructure of the absorber and the efficiency improvement of the solar cell were achieved successfully.

Keywords

• Thin film
• Solar cell
• Tellurium
• Copper-poor stoichiometry

References

1. [1] Bulbul S, Ertugrul G, Arli F. Investigation of usage potentials of global energy systems. International Advanced Researches and Engineering Journal 2018; 2: 58-67.
2. [2] Lee TD, Ebong AU. A review of thin film solar cell technologies and challenges. Renewable and Sustainable Energy Reviews 2017; 70: 1286-1297.
3. [3] Jäger-Waldau A. Status and perspectives of thin film photovoltaics - Thin film solar cells: Current status and future trends. Nova Science Publishers Inc, New York, US, 2010.
4. [4] Fiat S, Polat I, Bacaksiz E, Çankaya G, Koralli P, Manolakos DE, Kompitsas M. Optical and structural properties of nanostructured CuIn0.7Ga0.3(Se(1−x)Tex)2 chalcopyrite thin films—Effect of stoichiometry and annealing. Journal of Nanoscience and Nanotechnology 2014; 14: 5002-5010.
5. [5] Poortmans J, Arkhipov V. Thin film solar cells: Fabrication, characterization, and applications. John Wiley & Sons, West Sussex, England, 2006.
6. [6] Varol SF, Bacaksiz E, Koralli P, Kompitsas M, Çankaya G. A novel nanostructured CuIn0.7Ga0.3(Se0.4Te0.6)2/SLG multinary compounds thin films: For photovoltaic applications. Materials Letters 2015; 142: 273-276.
7. [7] Fiat S, Polat İ, Bacaksiz E, Kompitsas M, Çankaya G. The influence of annealing temperature and tellurium (Te) on electrical and dielectrical properties of Al/p-CIGSeTe/Mo Schottky diodes. Current Applied Physics 2013; 13: 1112-1118.
8. [8] Karatay A, Küçüköz B, Çankaya G, Ates A, Elmali A. The effect of Se/Te ratio on transient absorption behavior and nonlinear absorption properties of CuIn0.7Ga0.3(Se1−xTex)2 (0≤ x≤ 1) amorphous semiconductor thin films. Optical Materials 2017; 73: 20-24.

9. [9] Fiat S, Bacaksiz E, Kompitsas M, Çankaya G. Temperature and tellurium (Te) dependence of electrical characterization and surface properties for a chalcopyrite structured Schottky barrier diode. Journal of Alloys and Compounds 2014; 585: 178-184.
10. [10] Varol SF, Bacaksız E, Çankaya G, Kompitsas M. Optical, structural, and morphological characterization of CuIn0.7Ga0.3(Se0.6Te0.4)2 thin films under different annealing temperatures. Celal Bayar University Journal of Science 2013; 9: 9-16.
11. [11] Minoura S, Kodera K, Maekawa T, Miyazaki K, Niki S, Fujiwara H. Dielectric function of Cu(In, Ga)Se2-based polycrystalline materials. Journal of Applied Physics 2013; 113: 063505.
12. [12] Conibeer GJ, Willoughby A. Solar cell materials: Developing technologies. John Wiley and Sons Ltd, England, 2014.
13. [13] Başol BM, Kapur VK, Leidholm CR, Halani A, Gledhill K. Flexible and lightweight copper indium diselenide solar cells on polyimide substrates. Solar Energy Materials and Solar Cells 1996; 43: 93-98.
14. [14] Wei SH, Zhang SB, Zunger A. Effects of Ga addition to CuInSe2 on its electronic, structural, and defect properties. Applied Physics Letters 1998; 72: 3199-3201.
15. [15] Naghavi N, Mollica F, Goffard J, Posada J, Duchatelet A, Jubault M, Donsanti F, Cattoni A, Collin S, Grand PP, Greffet JJ, Lincot D. Ultrathin Cu(In,Ga)Se2 based solar cells. Thin Solid Films 2017; 633: 55-60.
16. [16] Atasoy Y, Başol B, Olğar M, Tomakin M, Bacaksız E. Cu(In,Ga)(Se,Te)2 films formed on metal foil substrates by a two-stage process employing electrodeposition and evaporation. Thin Solid Films 2018; 649: 30-37.
17. [17] Atasoy Y, Başol B, Polat İ, Tomakin M, Parlak M, Bacaksız E. Cu(In,Ga)(Se,Te)2 pentenary thin films formed by reaction of precursor layers. Thin Solid Films 2015; 592: 189-194.
18. [18] Ağca S, Çankaya G, Sonmezoglu S. Impact of tellurium as an anion dopant on the photovoltaic performance of wide-bandgap Cu(In,Ga)Se2 thin-film solar cells with rubidium fluoride post-deposition treatment. Frontiers in Energy Research 2023; 11: 1215712.
19. [19] Singh R, Parashar M, Sandhu S, Yoo K, Lee JJ. The effects of crystal structure on the photovoltaic performance of perovskite solar cells under ambient indoor illumination. Solar Energy 2021; 220: 43-50.
20. [20] Saive R. Light trapping in thin silicon solar cells: A review on fundamentals and Technologies. Progress in Photovoltaics: Research and Applications 2021; 29:1125-1137.
21. [21] Scholtz L, Ladanyi, L, Mullerova J. Influence of surface roughness on optical characteristics of multilayer solar cells. Advances in Electrical and Electronic Engineering 2015; 12: 631-638.
22. [22] Karki S, Paul P, Rajan G, Belfore B, Poudel D, Rockett A, Danilov E, Castellano F, Arehart A, Marsillac S. Analysis of recombination mechanisms in RbF treated CIGS solar cells. IEEE Journal of Photovoltaics 2018; 9: 313-318.
23. [23] Gloeckler M, Sites JR, Metzger WK. Grain-boundary recombination in Cu(In,Ga)Se2 solar cells. Journal of Applied Physics 2005; 98: 113704.
24. [24] Xing G, Mathews N, Sun S, Lim SS, Lam YM, Gratzel M, Mhaisalkar S, Sum TC. Long-range balanced electron- and hole-transport lengths in organic-inorganic CH3NH3PbI3. Science 2013; 342: 344-347.
25. [25] Yin WJ, Chen H, Shi T, Wei SH, Yan Y. Origin of high electronic quality in structurally disordered CH3NH3PbI3 and the passivation effect of Cl and O at grain boundaries. Advanced Electronic Materials 2015; 1: 1500044.
26. [26] Guirdjebaye N, Ngoupo AT, Ouedraogo S, Tcheum GLM, Ndjaka JMB. Numerical analysis of CdS-CIGS interface configuration on the performances of Cu(In,Ga)Se2 solar cells. Chinese Journal of Physics 2020; 67: 230-237.