EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Quaternary chalcogenides, $A$Zn$CX_{4}$ with $A$=Cu,Ag, $C$=Si,Ge, and $X$=S,Se, are potential building blocks for the third generation of thin film solar cells. While the prime examples like Cu$_2$ZnSnS$_4$ and Cu$_2$ZnSnSe$_4$ crystallise in the kesterite structure, for the other quaternary chalcogenides different crystal structures can be found, e.g. stannite, wurtz-kesterite, and wurtz-stannite. Moreover, in order to tune material properties to be more suitable for possible device applications, solid solutions on the $A$, $C$, and $X$ sites have been proposed, leading to a complicated interplay of structural properties of the quaternary end members involved.

Here we present our results on electronic and optical properties of quaternary chalcogenide solid solutions based on density functional theory calculations, employing different levels of sophistication for the exchange and correlation functional [1]. All our structure models are geometry optimised using the recently developed SCAN exchange and correlation functional. In order to obtain more reliable electronic and optical properties, selected optimised structures are subjected to one-shot calculations employing the more accurate hybrid functional HSE06 and subsequent quasiparticle calculations based on the $GW$ method. In order to simulate the different concentrations within the solid solutions, we’re employing a supercell approach and different theoretical methods. All the presented results on the structural, electronic, and optical properties will be critically discussed alongside experimental findings.

This work made use of computational resources provided by the North-German Supercomputing Alliance (HLRN).

[1] D. Fritsch and S. Schorr, J. Phys. Energy 3, 015002 (2021).