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HL: Fachverband Halbleiterphysik

HL 6: Photovoltaics I

HL 6.4: Vortrag

Montag, 12. März 2018, 10:15–10:30, EW 203

Band-gap tuning of Cu₂ZnSn(S,Se)₄ solar cell absorbers via defined adjustment of the chalcogenide ratio using a post-sulphurization process — •Markus Neuwirth¹, Elisabeth Seydel¹, Jasmin Seeger¹, Alexander Welle^2,3, Heinz Kalt¹, and Michael Hetterich⁴ — ¹Institute of Applied Physics, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany — ²Institute of Functional Interfaces, Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen — ³Karlsruhe Nano Micro Facility, Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen — ⁴Light Technology Institute, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe

Kesterite Cu₂ZnSn(S,Se)₄ (CZTSSe) thin-film solar cells are promising candidates for the future photovoltaic market. One of their very interesting and useful features is the tunability of their absorber band gap. In our work we achieve this by tuning the chalcogenide ratio x = [S]/([S]+[Se]) from close to 0 up to 1, which corresponds to a band-gap range of about 1.0 eV up to 1.5 eV. Experimentally this is done by post-annealing selenium-rich (x = 0.1) absorbers in a sulphur atmosphere. By varying the temperature and process hold time during this post-sulphurization step, we are able to accurately adjust x. Studies of the elemental composition give insight into the sulphur incorporation process which seems to be strongly correlated with the absorber’s morphology before post-sulphurization. Further morphology studies and current-voltage characteristics of the solar cells show a clear trend for the dependency of the device performance on process parameters.