Detection of ZnS Phases in CZTS Thin-Films by EXAFS

Katy Hartman, Bonna K. Newman, J. L. Johnson, Hui Du, P. A. Fernandes, Vardaan Chawla, Trudy Bolin, Bruce M. Clemens, Antonio F. Da Cunha, Glenn Teeter, Michael A. Scarpulla, Tonio Buonassisi

Research output: Contribution to conferencePaperpeer-review

8 Scopus Citations


Copper zinc tin sulfide (CZTS) is a promising Earth-abundant thin-film solar cell material; it has an appropriate band gap of ∼1.45 eV and a high absorption coefficient. The most efficient CZTS cells tend to be slightly Zn-rich and Cu-poor. However, growing Zn-rich CZTS films can sometimes result in phase decomposition of CZTS into ZnS and Cu 2SnS 3, which is generally deleterious to solar cell performance. Cubic ZnS is difficult to detect by XRD, due to a similar diffraction pattern. We hypothesize that synchrotron-based extended X-ray absorption fine structure (EXAFS), which is sensitive to local chemical environment, may be able to determine the quantity of ZnS phase in CZTS films by detecting differences in the second-nearest neighbor shell of the Zn atoms. Films of varying stoichiometries, from Zn-rich to Cu-rich (Zn-poor) were examined using the EXAFS technique. Differences in the spectra as a function of Cu/Zn ratio are detected. Linear combination analysis suggests increasing ZnS signal as the CZTS films become more Zn-rich. We demonstrate that the sensitive technique of EXAFS could be used to quantify the amount of ZnS present and provide a guide to crystal growth of highly phase pure films.

Original languageAmerican English
Number of pages4
StatePublished - 2011
Event37th IEEE Photovoltaic Specialists Conference, PVSC 2011 - Seattle, WA, United States
Duration: 19 Jun 201124 Jun 2011


Conference37th IEEE Photovoltaic Specialists Conference, PVSC 2011
Country/TerritoryUnited States
CitySeattle, WA

NREL Publication Number

  • NREL/CP-5200-55717


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