| AVS 63rd International Symposium & Exhibition | |
| Electronic Materials and Photonics | Thursday Sessions |
| Session EM-ThP |
| Session: | EMPD Poster Session |
| Presenter: | Lorenzo Mangolini, University of California Riverside |
| Authors: | A. Alvarez Barragan, University of California Riverside S.A. Exarhos, University of California Riverside L. Mangolini, University of California Riverside |
| Correspondent: | Click to Email |
The quaternary chalcogenide Cu2ZnSnS4 (CZTS) is composed of earth-abundant elements and has interesting optoelectronic properties that project it as an important candidate for thin-film photovoltaics. Among several synthesis methods, sulfurization of metallic stacked layers has been heavily used because it does not rely on toxic compounds and provides good control over the final stoichiometry of the sample [1-3]. We present an in-depth structural and compositional analysis of CZTS synthesized by this technique. A first study exhibits preferential segregation of hexagonal SnS2 when increasing the sulfurization pressure in a closed annealing chamber. Variations in film morphology suggest that different reaction pathways take place as the pressure is raised. Formation of gaseous SnS is favored at lower pressure, while nucleation of solid SnS2 preferentially occurs at higher pressure. In addition to this investigation, an individual grain study sheds light on the complexity of this material system. Elemental analysis shows significant grain-to-grain variations in composition despite dealing with an overall close-to-ideal stoichiometry. High resolution Raman spectroscopy indicates that this is accompanied by grain-to-grain structural variations as well. The intensity from the 337 cm-1 Raman peak, generally assigned to the kesterite phase of CZTS, remains constant over a large area of the sample. On the other hand, signals from secondary phases at 376 cm-1 (copper-tin-sulfide) and 351 cm-1 (zinc-sulfide) show significant variation over the same area. These results demonstrate how a seemingly homogeneous CZTS thin film can actually have considerable structural and compositional variations that are often overlooked.
References
[1] Dhakal, T. P.; Peng, C.; Tobias, R. R.; Dasharathy, R.; Westgate, C. R. Characterization of a CZTS thin film solar cell grown by sputtering method. Sol. Energy2014, 100, 23–30.
[2] Hong, S.; Kim, C. Characteristics of Cu2ZnSnS4 Thin Films Fabricated by Sulfurization of Two Stacked Metallic Layers. Mol. Cryst. Liq. Cryst.2014, 602, 134–143.
[3] Cheng, A.-J.; Manno, M.; Khare, A.; Leighton, C.; Campbell, S. A.; Aydil, E. S. Imaging and phase identification of Cu2ZnSnS4 thin films using confocal Raman spectroscopy. J. Vac. Sci. & Technol. A: Vacuum, Surfaces, Films2011, 29.