Abstract
The rapid growth of the solar energy industry is driving a strong demand for high performance, efficient photoelectric materials. In particular, ferroelectrics composed of earth-abundant elements may be useful in solar cell applications due to their large internal polarization. Unfortunately, wide band gaps prevent many such materials from absorbing light in the visible to mid-infrared range. Here, we address the band gap issue by investigating the effects of substituting sulfur for oxygen in the perovskite structure ZnSnO3. Using evolutionary methods, we identify the stable and metastable structures of ZnSnS3and compare them to those previously characterized for ZnSnO3. Our results suggest that the most stable structure of ZnSnS3is the monoclinic structure, followed by the metastable ilmenite and lithium niobate structures. The latter structure is highly polarized, possessing a significantly reduced band gap of 1.28 eV. These desirable characteristics make it a prime candidate for solar cell applications.
Highlights
Ferroelectrics are materials that possess spontaneous electric polarization
Upon using the modified Becke-Johnson exchange potential [55], the correct sizes of the band gaps are calculated for these crystals
We find that for ZnSnO3, t = 0.724, while for ZnSnS3, t = 0.721
Summary
Ferroelectrics are materials that possess spontaneous electric polarization. This results from a lack of inversion symmetry; all ferroelectric crystals are noncentrosymmetric. Among the most important ferroelectrics are metal oxide perovskites with the general formula ABO3, where A and B are metal cations (B is usually a transition metal) Wellknown examples of such ferroelectrics are BaTiO3 and LiNbO3. These oxides have relatively large internal electric fields that could be exploited in photovoltaic applications. Progress in this area has been hampered by the fact that these ferroelectrics have a large band gap (3-4 eV), which makes them unsuitable for efficient light harvesting. In ABO3, the highest valence band is derived from oxygen 2p orbitals, while the low conduction bands are derived from the transition metal 3d states
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