We investigated the possibility of band structure engineering of pyroxene silicates with chemical formula A+1B+3Si2O6 by proper cation substitution. Typically, band gaps of naturally formed pyroxene silicates such as NaAlSi2O6 are quite high (≈5eV). Therefore, it is important to find a way to reduce band gaps for these materials below 3eV to make them usable for optoelectronic applications operating at visible light range of the spectrum. Using first-principles calculations, we found that appropriate substitutions of both A+ and B3+ cations can reduce the band gaps of these materials to as low as 1.31eV. We also discuss how the band gap in this class of materials is affected by cation radii, electronegativity of constituent elements, spin-orbit coupling, and structural modifications. In particular, the replacement of Al3+ in NaAlSi2O6 by another trivalent cation Tl3+ results in the largest band-gap reduction and emergence of intermediate bands. We also found that all considered materials are still thermodynamically stable. This work provides a design approach for new environmentally benign and abundant materials for use in photovoltaics and optoelectronic devices.
- Absorption coefficient
- Band gaps
- Chemical stability
- Electronic structure
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- Physical and Theoretical Chemistry