Abstract
Ge-substituted Cu2ZnSnS4 (CZTS) thin films are
promising for solar cell manufacturing, especially for graded-band-gap
solar cells and multi-junction solar cells. However, there is no
systematic research on the change of structural properties of Cu2Zn(GexSn1−x)S4 (CZTGS) as the function of alloy composition x.
In this work, polycrystalline CZTGS thin films were prepared by
sulfurizing sputtered Zn/Cu/Ge/Sn metallic precursor stacks.
Energy-dispersive X-ray spectroscopy (EDS) line scans conducted in a
transmission electron microscopy (TEM) system shows uniform element
distribution (except of some ZnS segregation) throughout the synthesized
films. The analysis of X-ray diffraction (XRD) and Raman spectroscopy
confirms that Cu2ZnGeS4 is successfully obtained by sulfurizing metallic stacks at 580 °C for 2 h. The lattice constants a and c of CZTGS as derived from XRD patterns follow the Vegard’s rule that lattice constants vary linearly with Ge content (x).
Raman spectra shows an A1 mode shift towards high frequency when Sn is
gradually replaced by Ge. Chemical composition study indicates the
increase in x value leads to higher (Ge + Sn) element loss
during the sulfurization process, which can be explained by the high
vapour pressure of Ge sulfides. By alloying with Ge, the grain size of
CZTS is enlarged which also leads to a rough surface.
Original language | English |
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Pages (from-to) | 154-161 |
Number of pages | 8 |
Journal | Journal of Alloys and Compounds |
Volume | 621 |
DOIs | |
Publication status | Published - 5 Feb 2015 |
Externally published | Yes |
Keywords
- Cu₂Zn(GexSn₁−x)S₄ thin films
- Magnetron sputtering
- Element loss
- Lattice parameter
- Raman
- XRD