WEB Cu/Zn disorder vs. solar cell efficiency: the Cu2ZnSn(SxSe1-x)4 monograin caseWednesday (23.09.2020) 14:45 - 15:00 F: Functional Materials, Surfaces, and Devices 1 Part of:
Kesterite-type based thin films solar cell technologies are mainly based on polycrystalline absorber layers. A promising low cost alternative technology uses monograins (single crystals of 50-100 μm size) which are fixed in a polymer matrix to form a flexible solar cell .
It is agreed in literature that large band tailing observed in Cu-based kesterite-type semiconductors causes voltage losses limiting the efficiency of kesterite-based devices. The Cu/Zn disorder (CuZn and ZnCu anti-sites in Cu-Zn planes at z=¼ and ¾), which is always present in these compounds , is discussed as a possible reason for band tailing.
The experimental determination of the order parameter Q which is a quantitative measure of the degree of Cu/Zn disorder  requires a differentiation between the isoelectronic cations Cu+ and Zn2+. An in depth analysis of neutron diffraction data provides information on the cation distribution in the crystal structure allowing the determination of type and concentration of intrinsic point defects including a distinction between Cu and Zn . On the other hand neutron diffraction requires large sample volumes, thus kesterite monograins offer the unique possibility to correlate structural disorder in kesterite-type absorbers with solar cell performance parameters.
We will present a detailed structural investigation of CZTSSe monograins based on neutron powder diffraction experiments, the influence of the purity of the starting material as well as small changes in the chemical composition on the Cu/Zn disorder resulting in different power conversion efficiencies of the respective devices.
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