High anisotropic carrier mobility and strong optical absorption in a biphenylene-like BC₃ monolayer

Carbon allotropes with unique ring topologies have attracted considerable research interest due to their potential intrinsic in-plane anisotropy, which may lead to direction-dependent electronic, optical, and mechanical properties. In this study, we inversely design a semiconductor with a biphenylene network by incorporating boron atoms into a carbon framework, yielding a novel biphenylene-like BC₃ monolayer (BL-BC₃). Density functional theory calculations reveal that BL-BC₃ is thermodynamically, dynamically, and mechanically stable, as confirmed by its cohesive energy, phonon spectrum, ab initio molecular dynamics, and elastic constants. The introduction of electron-deficient boron atoms induces a discontinuous charge distribution near the valence band maximum, leading to an indirect bandgap of 1.32 eV at the HSE06 level, and endowing BL-BC₃ with desirable semiconducting characteristics. Specifically, BL-BC₃ exhibits high anisotropic carrier mobilities (>300 cm² V^-1 s^-1 for both electrons and holes) and a higher optical absorption coefficient compared to black phosphorus, underscoring its promising potential for applications in nanoelectronics and photovoltaic devices.