Research Information System
E-MRS 2022 Spring, 30 May - 03 June 2022, pp.1
The polycrystalline Cu(In,Ga)Se2 thin-film solar cells have attained increased interest due to their lower costs and higher cell efficiency in energy conversion [1]. These polycrystalline absorbers contain a large ratio of grain boundaries which can be detrimental (increase in recombination activity compared to the bulk), neutral (no change in electrical properties relative to grains) or benign (increase in electrical properties) for the cell performance [1, 2]. In the present work, different techniques such as atom probe tomography and electron backscattered diffraction are used to investigate different grain boundaries in order to illustrate the relation between the chemical composition and the electrical properties of the grain boundaries. It is shown that the elemental changes at the grain boundaries such as Cu depletion, In enrichment and segregation of alkali dopants such as Na and Ag, can directly affect their beneficial behavior in favor of cell performance. The experimental findings prove the significant role of Na or Ag additions in improving the cell parameters such as open circuit voltage and fill factor. Although it is also shown that the excessive addition of dopants can have detrimental effects on the cell efficiency by increasing the density of dislocations and interference of deep defects with dopants.
[1] O. Cojocaru-Mirédin, M. Raghuwanshi, R. Wuerz, S. Sadewasser, “Grain boundaries in Cu(In,Ga)Se2: a review on composition-electronic property relationships by atom probe tomography and correlative microscopy,” Advanced functional materials, vol. 31, 2021.
[2] M. Raghuwanshi, R. Wuerz, O. Cojocaru-Mirédin, “Interconnection between Trait, Structure, and Composition of Grain Boundaries in Cu(In,Ga)Se2 Thin-Film Solar Cells,” Advanced functional materials, vol. 30, 2020.