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Polymorphism in Cu2ZnSnS4 and new off-stoichiometric crystal structure types

Bosson, Christopher J.; Birch, Max T.; Halliday, Douglas P.; Tang, Chiu C.; Kleppe, Annette K.; Hatton, Peter D.

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Christopher J. Bosson

Max T. Birch

Chiu C. Tang

Annette K. Kleppe


Cu2ZnSnS4 (CZTS) is a very promising material for the absorber layer in sustainable thin-film solar cells. Its photovoltaic performance is currently limited by crystal structure disorder, which causes fluctuations in electrostatic potential that decrease open-circuit voltage. The origin of this disorder is still not fully understood. This work investigates five samples of CZTS over a range of compositions, fabricated by solid-state reaction. Their crystal structures are conclusively identified using high-resolution anomalous X-ray diffraction. Three of the samples display two distinct CZTS phases, evident in minute splitting of some diffraction peaks (by ~0.02°) due to different c/a lattice parameter ratios. These are attributed to different composition types of CZTS, defined by different charge-neutral defect complexes. In addition to such types previously reported, two new types are proposed: G-type, in which [2CuSn3- + CuZn- + Cui+ + 3VS2+] defects are prevalent, and H-type, in which [3Si2- + VCu- + ZnCu+ + 2SnCu3+] defects are prevalent. In both cases, the defects probably do not form a single complex due to their large number. Above the order-disorder phase transition the two CZTS phases generally converge to a single phase. A mechanism of phase formation in CZTS is thus proposed. This is the first time CZTS crystal structures have been investigated with sufficiently high resolution to distinguish these different CZTS phases, thereby establishing polymorphic behavior in CZTS.


Bosson, C. J., Birch, M. T., Halliday, D. P., Tang, C. C., Kleppe, A. K., & Hatton, P. D. (2017). Polymorphism in Cu2ZnSnS4 and new off-stoichiometric crystal structure types. Chemistry of Materials, 29(22), 9829-9839.

Journal Article Type Article
Acceptance Date Oct 30, 2017
Online Publication Date Oct 30, 2017
Publication Date Nov 28, 2017
Deposit Date Nov 7, 2017
Publicly Available Date Oct 30, 2018
Journal Chemistry of Materials
Print ISSN 0897-4756
Electronic ISSN 1520-5002
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 29
Issue 22
Pages 9829-9839


Accepted Journal Article (1.3 Mb)

Copyright Statement
This document is the Accepted Manuscript version of a Published Work that appeared in final form in Chemistry of Materials, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see

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