Enhancing Silicon Compound Heterojunction Solar Cells with Vanadium‐Doped MoO_X as Hole Transport Layers

Abstract Crystalline silicon (c‐Si) solar cells dominate the global market, and the development of eco‐friendly and cost‐effective c‐Si compound solar cells with carrier‐selective passivated contacts has attracted increasing attention. This work investigated the impact of oxygen vacancies (V_O) and vanadium (V) doping on molybdenum trioxide (MoO_X), using a combination of first‐principles calculations and device simulations. These V_O defects accumulated from bulk to surface with lower energy barrier of 1.7 eV, compared to 3.4 eV on surface and 3.8 eV from surface to bulk. The surface V_O significantly decreased MoO_X work function from 6.1 eV to 4.8 eV，considering alteration in surface charges from +4 µC cm⁻² to ‐8 µC cm⁻². Vanadium doping increased V_O transport barrier by 0.1 eV, suppressing defect migration. Meanwhile, it raised work function by 0.26 eV and widened the bandgap by 0.6 eV. As hole transport layer, V‐doped MoO_X on illuminated side of c‐Si solar cells boosted absolute efficiency by 1.0%, compared to MoO_X on rear side; of this increase, 0.2% was attributed to higher work function and 0.8% was due to reduced optical losses. These findings emphasize V‐doped MoO_X in enhancing c‐Si compound solar cell performance and in promoting the development of efficient photovoltaic technologies.