First‐Principles Investigation of Electronic and Optical Properties in Two‐Dimensional IV–IV Semiconductors

Using first‐principles calculations, we present the structural, electronic, and optical properties of 2D IV–IV semiconductors. These materials adopt a nonplanar honeycomb structure with mixed sp 2 –sp 3 hybridization, yielding covalent bonds, as confirmed by charge‐density distributions. All materials are narrow‐gap semiconductors, with electronic states near the Fermi level composed of hybridized p orbitals, while deeper valence bands are primarily derived from s orbitals. Including spin–orbit coupling (SOC) induces significant spin splitting at the K point (∼80–400 meV), which is relatively weak in 2D SiGe and stronger in the 2D GePb monolayer. Collectively, the prominent many‐body excitonic features and low exciton binding strengths demonstrate the capability of these monolayers to sustain efficient optical processes, establishing them as promising platforms for emerging 2D optoelectronic, photovoltaic, and spintronic devices.