Atomic layer deposition (ALD) of passivating, carrier-selective oxides for silicon photovoltaics

Crystalline silicon (c-Si) photovoltaics dominate the solar industry, yet further advancements hinge on passivating and carrier-selective contacts to overcome efficiency limitations. This review explores the pivotal role of atomic layer deposition (ALD) in enabling metal oxide films for high-performance c-Si solar cells, bridging material innovation with industrial scalability. Historically, ALD-grown Al2O3 enabled the effective passivation of p-type Si surfaces via its high negative fixed charge, which made localized rear contacts viable and facilitated the transition from aluminum back surface field to passivated emitter rear contact architectures, ultimately lowering J0 and boosting efficiency. However, emerging carrier-selective contacts demand materials that simultaneously minimize recombination and resistive losses while avoiding parasitic absorption. Metal oxides, leveraging tunable optoelectronic properties and ALD's atomic-scale precision, offer a promising alternative to conventional silicon-based films (e.g., a-Si:H and poly-Si). We analyzed 373 studies to map trends in ALD metal oxide applications, highlighting the dominance of Al2O3 and TiO2, alongside growing interest in multi-metal oxides. The review underscores ALD's unique ability to tailor chemical and field-effect passivation mechanisms while addressing challenges in stoichiometric control and interfacial engineering. Targeting both ALD specialists and PV engineers, we propose standardized metrics for evaluating passivating contacts, aiming to accelerate cross-disciplinary innovation. Finally, we outline future opportunities for ALD-derived metal oxide in next-generation photovoltaics, including tandem and thin-film technologies, advocating for systematic research to unlock their full potential.