Stacked photoanodes for solar water splitting: decoupling light harvesting and charge transport through light reuse and spectral complementarity.

Authors

Jing Yang, Fengqiao Li, Haoyun Lei, Hao Zhang, Zhifeng Qin, Yu Wu, Hemin Zhang

Published in

Nanoscale. Sep 30, 2026. Epub Sep 30, 2026.

Abstract

Photoelectrochemical (PEC) water splitting offers a sustainable route for direct solar-to-hydrogen conversion, but its efficiency is often constrained by limited light harvesting and inefficient charge transport in photoanodes. For α-Fe₂O₃ and BiVO₄, increasing film thickness improves light harvesting but lengthens carrier-transport pathways and promotes recombination, whereas wide-bandgap TiO₂ is constrained primarily by limited spectral coverage. Stacked photoanodes provide a device-level strategy by arranging multiple individual photoanodes sequentially along the incident light direction and connecting them in parallel, thereby enabling transmitted-light reuse while allowing each photoanode to retain an independently optimized thickness. This review summarizes recent progress in stacked photoanodes for PEC water splitting, focusing on α-Fe₂O₃, BiVO₄, and TiO₂ as representative metal-oxide systems that illustrate distinct motivations for stacking and have been experimentally demonstrated in stacked configurations. Stacked configurations are classified into homo-type stacks using the same semiconductor and hetero-type stacks combining different semiconductors. Homo-type stacks reuse transmitted light but show diminishing photocurrent gains because of front-layer shading and optical losses. Hetero-type stacks combine complementary absorbers to extend spectral utilization and enable photocurrent summation without the strict band-alignment requirements of conventional heterojunctions. Key performance factors include individual photoanode transparency, optical losses, and the balance between front absorption and rear transmission. Large-area scaling further introduces current-collection and fabrication challenges. Future opportunities lie in absorber selection, optical management, long-term stability, and scalable device engineering.

PMID:
42814438
Bibliographic data and abstract were imported from PubMed on 01 Oct 2026.

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