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Crystal structure and anti-site boundary defect characterisation of Cu2ZnSnSe4

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Journal Journal of Materials Chemistry A
DateAccepted/In press - 24 Nov 2017
DateE-pub ahead of print - 7 Dec 2017
DatePublished (current) - 2018
Number of pages9
Early online date7/12/17
Original languageEnglish

Abstract

The crystal structure identification of the photovoltaic material Cu2ZnSnSe4 (CZTSe) is challenging due to the distinguishing feature between the two polymorphs, kesterite and stannite, being the arrangement of Cu and Zn ions. Here an energy dispersive X-ray (EDX) technique, based on electron beam channeling along specific crystallographic planes in a transmission electron microscope (TEM), is used to identify the structure. Regions a few 100 nm in size can be analysed using this method, unlike neutron or anomalous X-ray scattering. The parent crystal structure of CZTSe, annealed on either side of the order-disorder transition temperature, was correctly identified as being kesterite. The presence of 1/2[110] (001) and 1/4[201] (101) anti-site boundaries (ASBs) has also been investigated. The density of ASBs is higher above the transition temperature, due to a smaller energy penalty for disordering on the 2c and 2d Wyckoff sites. A nearest neighbour cation analysis predicted the 1/2[110] (001) ASB to have the lowest formation energy. From density functional theory (DFT) simulations the 1/2[110] (001) ASB energy is only 43 mJ m-2 and furthermore it is not a recombination site or current blocking layer, so that photovoltaic device performance is not significantly degraded.

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© The Royal Society of Chemistry 2017. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details

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