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arXiv · 2510.17694

Hydrogenated Aluminum Doped Zinc Oxide as Highly Transparent and Passivating Indium-Free Recombination Junction for TOPCon-Based Bottom Cell

Gökhan Altıner·Jons Bolding·Yiğit Mert Kaplan·Floor Souren·Hindrik de Vries·Raşit Turan·Hisham Nasser
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Abstract

Tandem solar cells offer a promising alternative to exceed the efficiency limits of single-junction silicon photovoltaics, yet they require high-performance recombination junctions that are transparent, passivating, and electrically efficient. Indium tin oxide (ITO), which is conventionally used as a recombination junction material, faces challenges related to indium scarcity and sputter-induced damage. This work investigates hydrogenated aluminum-doped zinc oxide (AZO:H) deposited by spatial atomic layer deposition (s-ALD) as a viable indiumfree alternative for TOPCon-based bottom cells. The deposited AZO:H films demonstrate excellent transparency, exceeding 90% in the 380-1200 nm wavelength range. When applied to n-TOPCon surfaces with an AlOx capping layer, the stack achieves an outstanding passivation quality, indicated by implied open-circuit voltage (iVoc) values up to 734 mV after annealing. The AlOx capping layer proved crucial for enhancing thermal stability by preventing hydrogen effusion at higher temperatures. While the contact resistivity was high for the 20 nm thick films tested, the combination of superior optical and passivation properties establishes spatial ALD-deposited AZO:H as a highly promising material for creating efficient and indiumfree recombination junctions in next-generation tandem solar cells.

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Gökhan Altıner, Jons Bolding, Yiğit Mert Kaplan, Floor Souren, Hindrik de Vries, Raşit Turan, Hisham Nasser. 2025-10-20. Hydrogenated Aluminum Doped Zinc Oxide as Highly Transparent and Passivating Indium-Free Recombination Junction for TOPCon-Based Bottom Cell. https://arxiv.org/abs/2510.17694

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