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| VOLUME 98 (2013) | ISSUE 5 | PAGE 292 |
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Optically induced structural transformation in disordered kesterite Cu2ZnSnS4
M. Ya. Valakh, V. M. Dzhagan, I. S. Babichuk, X. Fontane+, A. Perez-Rodriquez+*, S. Schorr×°
Lashkaryov Institute of Semiconductor Physics of NAS of Ukraine, 03028 Kyiv, Ukraine +Catalonia Institute for Energy Research, 08930 Sant Adria del Besos (Barcelona), Spain *Departament d'Electronica, Universitat de Barcelona, 08028 Barcelona, Spain × Helmholtz-Zentrum Berlin fur Materialien und Energie, D-14109 Berlin, Germany °Freie Universitat Berlin, Institute of Geological Sciences, 12249 Berlin, Germany
Abstract
The kesterite-structured semiconductor Cu2ZnSnS4 is one of the most promising compound for earth-abundant low-cost solar cells. One of the complex problem on this way deals with its stoichiometry. In this work Raman spectra of Cu-rich Cu2ZnSnS4 crystals are discussed in connection with the non-stoichiometric composition and disordering within the cation sublattice of the kesterite. The shift of the main A-peak from 338 to 331 cm-1 and its broadening are attributed here to transition from the kesterite (I-symmetry) to the disordered kesterite structure (I2m-symmetry). It is shown that this transition may also be driven by an intense light, which could stimulate transformation of Cu+-ion to Cu2+-ions and facilitates generation of CuZn-defects on 2d-crystalographic positions. |