Mixed-Anion-Induced Asymmetric Orbital Hybridization Governs Carrier Transport and Photoresponse in Monolayer TiOS

Abstract Mixed-anion coordination in monolayer TiOS induces orbital-selective hybridization, tailoring its electronic structure for multifunctional applications. First-principles calculations demonstrate that monolayer TiOS is dynamically and thermally stable with a low cleavage energy of 0.452 J m–2, indicating high feasibility for mechanical exfoliation. It features a direct HSE06 band gap of 1.92 eV and a high room-temperature electron mobility of 5524.7 cm2 V–1 s–1. The resulting transport asymmetry suppresses the conductivity–Seebeck coefficient trade-off, yielding a maximum power factor greater than 1.5 × 103 μW cm–1 K–2 and an electronic thermoelectric figure of merit (ZTe) of 0.92 at 300 K. These findings establish mixed-anion-enabled asymmetric hybridization as a general mechanism for designing multifunctional two-dimensional semiconductors.