Room-Temperature Electron Paramagnetic Resonance Study of a Copper-Related Defect in Cu2ZnSnS4Colloidal Nanocrystals

Vorona I, Dzhagan V, Nosenko V, Kondratenko S, Selyshchev O, Valakh M, Okulov S, Mazur N, Raievska O, Stroyuk OL, Zahn DR (2021)

Publication Type: Journal article

Publication year: 2021

Journal

Journal of Physical Chemistry C American Chemical Society

DOI: 10.1021/acs.jpcc.1c02176

Abstract

We report on electron paramagnetic resonance (EPR) spectroscopy of Cu-Zn-Sn-S (CZTS) nanocrystals (NCs) synthesized by a colloidal chemistry method. The chemical composition of the NCs is characterized by a strong deficit of tin and slight zinc enrichment with respect to the "ideal"stoichiometry of kesterite Cu2ZnSnS4. Nevertheless, X-ray photoemission spectroscopy (XPS) shows that the net cation/anion ratio is very close to 1:1 and the valence states of the constituents correspond to those of Cu2ZnSnS4, in particular, Cu+. The kesterite crystal structure of the NCs is confirmed by X-ray diffraction and Raman spectroscopy. Observing the EPR features for such CZTS NCs characteristic of individual Cu2+ embedded in the crystal lattice can be directly related to cationic disorder and nonstoichiometry. In particular, as a result of Cu-Zn antisites, Sn deficiency, and likely multivalence, a very small fraction of copper ions may occur in the Cu2+ state. The concentration of Cu2+ sites of ∼1017-1018 cm-3 assessed from the EPR spectra is below the sensitivity of XPS; therefore, the latter is dominated by the prevailing Cu+ species. The temperature dependence of the I-V curves reveal a level at about 0.2 eV above the valence band that can be assigned to the CuZn antisite (with copper presumably in the Cu2+ state) and a 14 meV level above the valence band that can correspond to VCu. The new insights, reported here, into the relation between the structure and electronic states of CZTS NCs are important for advancing their applications.

Involved external institutions

National Academy of Sciences of Ukraine (NAN) / Національна академія наук України UA Ukraine (UA) Taras Shevchenko National University of Kyiv (KNU) / Київський національний університет імені Тараса Шевченка UA Ukraine (UA) Technische Universität Chemnitz DE Germany (DE) Forschungszentrum Jülich / Research Centre Jülich (FZJ) DE Germany (DE)

How to cite

APA:

Vorona, I., Dzhagan, V., Nosenko, V., Kondratenko, S., Selyshchev, O., Valakh, M.,... Zahn, D.R. (2021). Room-Temperature Electron Paramagnetic Resonance Study of a Copper-Related Defect in Cu2ZnSnS4Colloidal Nanocrystals. Journal of Physical Chemistry C. https://dx.doi.org/10.1021/acs.jpcc.1c02176

MLA:

Vorona, Igor, et al. "Room-Temperature Electron Paramagnetic Resonance Study of a Copper-Related Defect in Cu2ZnSnS4Colloidal Nanocrystals." Journal of Physical Chemistry C (2021).

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