Exploring Phase Stability and Properties of I‐II 2 ‐III‐VI 4 Quaternary Chalcogenides

Structural diversity of CuZn2InSe4 quaternary chalcogenides: electronic and phonon properties from first principles

First principles simulations are utilized to calculate the electronic and vibrational properties of several metastable structural phases of the CuZn2InSe4 quaternary chalcogenide, including stanite, kesterite, primitive mixed CuAu, wurtzite-stanite, and wurtzite-kesterite lattices. We find that although each phase is formed by nearest cation-chalcogen bonds, the structural diversity due to cation and polyhedral arrangements has direct consequences in the electronic structure. The simulations further indicate that hybrid functionals are needed to account for the s-p and p-d orbital hybridization that is found around the Fermi level, which leads to much enhanced energy band gaps when compared with standard exchange-correlation approaches. We also find that the thermal conductivities for all phases are relatively low, and the main scattering channel comes from a low frequency optical band hybridized with acoustic phonons. Given that CuZn2InSe4 is a material from a larger class of quaternary chalcogenides, other materials may exhibit similar electronic and vibrational properties, which may be useful for electronic and thermal management applications.

Role of Intrinsic Defects in Enhancing the Photoabsorption Capability of CuZn2AlSe4

As a promising candidate for low-cost and eco-friendly thin-film photovoltaics, the emerging quaternary chalcogenide based solar cells have experienced rapid advances over the past decade. Here, we propose quaternary semiconducting chalcogenides CuZn₂AlSe₄ (CZASe) through cross-substitutions (cation mutations). The nonexistence of imaginary modes in the entire Brillouin zone of CZASe represents the inherent dynamic stability of the system. The electronic, optical, and defect properties of stannite CZASe quaternary semiconducting material was systematically investigated using density functional theory calculations. We have found that the chemical-potential control is very important for growing good-quality crystals and also to avoid secondary-phase formations such as ZnSe, Al₂ZnSe₄, and Cu₃Se₂. The observed p-type conductivity is mainly due to antisite defect Cu_Zn, which has the lowest formation energy with a relatively deeper acceptor level than that of the Cu vacant site (V_Cu). The electronic band structures of vacancies and antisite defects by means of hybrid functional calculations show energy band shifting and energy band narrowing or broadening, which eventually tunes the optical band gap and improves the solar energy-conversion performance of semiconducting CZASe. Our results suggest that the stannite CZASe quaternary chalcogenides could be promising candidates for the efficient earth-abundant thin-film solar cells.