Hybrid Density Functional Study of Au 2 Cs 2 I 6 , Ag 2 GeBaS 4 , Ag 2 ZnSnS 4 , and AgCuPO 4 for the Intermediate Band Solar Cells

We present a comprehensive investigation of the structural, electronic, mechanical, and optical properties of four promising candidates, namely Au 2 Cs 2 I 6 , Ag 2 GeBaS 4 , Ag 2 ZnSnS 4 , and AgCuPO 4 , for application in photovoltaic devices based on intermediate band (IB) cells. We perform accurate density functional theory calculations by employing the hybrid functional of Heyd, Scuseria, and Erhzerhof (HSE06). Calculations reveal that IBs are present in all proposed compounds at unoccupied states in the range of 0.34–2.19 eV from the Fermi level. The structural and mechanical stability of these four materials are also systematically investigated. Additional peaks are present in the optical spectra of these compounds, as characterised by a broadened energy range and high intensity for light absorption. Our findings, as reported in this work, may provide a substantial breakthrough on the understanding of these materials, and thus help the design of more efficient IB solar devices.