Interface Engineering with Oxygen‐Doped Amorphous Silicon for Stabilizing Light Soaking Gains in Silicon Solar Cells

Abstract Crystalline silicon solar cells dominate over 95% of the photovoltaic market and have achieved record efficiencies beyond 27% through innovations such as silicon heterojunction (SHJ) and heterojunction back contact (BC). Although light soaking enhances efficiency by driving hydrogen migration to passivate interfacial defects, the instability of newly formed Si─H bonds leads to performance degradation. This issue is addressed by introducing an oxygen‐doping strategy at the hydrogenated amorphous/crystalline silicon (a‐Si:H/c‐Si) interface. Incorporating an ultrathin oxygen‐doped layer leverages oxygen electronegativity to suppress hydrogen migration. This approach allows SHJ and hybrid BC to retain 57% and 70% of their initial light soaking efficiency gains over 30 days, respectively, far exceeding 27% and 39% retention of baseline processes. Molecular dynamics (MD) simulations confirm the stabilization mechanism, showing reduced hydrogen diffusion. Meanwhile, a low‐power UV light soaking protocol is developed. This method delivers absolute efficiency gains of 0.34% (from 25.26% to 25.60%) in SHJ and 0.41% (from 26.72% to 27.13% certified at 27.07%) in hybrid BC, matching conventional high‐intensity white light soaking at 30 kW m −2 , while requiring only 4% of energy input at 1.2 kW m −2 . These advances in stabilizing efficiency gains and reducing light soaking energy consumption provide a scalable pathway for industrial high‐performance silicon photovoltaics.