Quasiparticle Band Structure and Bonding Properties of NaAg3$_{3}$O2$_{2}$: A Promising Direct‐Bandgap Semiconductor for Tandem Solar Cells

NaAgO is investigated as a potential top‐cell material for tandem solar cell configurations. To assess its suitability, the structural, bonding, and electronic properties of this semiconductor are examined using density functional theory with the PBEsol exchange–correlation functional and the GW approximation. The material crystallizes in an orthorhombic crystal structure ( Ibam space group) and exhibits polar covalent bonding with a bulk modulus of 67.4 GPa. NaAg 3 O 2 is found to be a direct (at Γ) semiconductor with a bandgap of 1.79 eV. The calculated dielectric and optical properties show that NaAgO is transparent to low‐energy photons but exhibits a sharp increase in light absorption near its bandgap of 1.79 eV, reaching absorption coefficient as high as cm, motivating experimental synthesis and further investigation. The bandgap, combined with its bonding and optical characteristics, suggests its potential as a top‐cell material in tandem solar cell configurations.