Strategy for One‐Step Optimization of Metal Oxide Passivating Contact Materials for Si Heterojunction Solar Cells through Growth Angle Variation

Abstract High‐efficiency silicon (Si) heterojunction (SHJ) solar cell technology is currently limited by multi‐step fabrication protocol required for optimal passivation and carrier selectivity. Here, a novel, one‐step oblique‐angle reactive sputtering strategy is presented that leverages angle‐dependent ion‐bombardment to simultaneously tailor the bulk and interfacial properties of metal oxide contact material on Si via in situ ion assisted oxidation. Using vanadium oxide (V₂O_5‐x) as a model system, it has been demonstrated that the deposition at a glancing angle of 80° yields a phase‐pure, high‐work‐function V₂O_5‐x film—essential for field effect passivation, while also facilitating stoichiometric improvement of the retained native silicon oxide layer on Si surface. An intermediate growth angle of 40°, produces a mixed‐phase V₂O_5‐x film, without compromising interfacial quality. Monte Carlo simulations, supported by time‐of‐flight secondary ion mass spectrometry data, reveal that growth angle governs the V‐Si‐O intermixing depth across the interface through variations in ion incidence geometry and energy deposition profile, critically influencing the interfacial layer properties. This simple, one‐step, room temperature, angle‐tuned reactive sputtering method circumvents multi‐step chemical pre‐treatments of the silicon surface and offers a viable pathway for integrating carrier selective metal oxides in SHJ solar cells, with broader applicability across silicon‐based electronic and optoelectronic devices.