Engineering Cascade Bio‐Solar Cells Inspired by the Z‐Scheme of Oxygenic Photosynthesis: Layered Chlorophyll and Bacterio‐Chlorophyll Derivatives.

The natural Z‐scheme of oxygenic photosynthesis efficiently drives electron transfer from photosystem II (PSII) to photosystem I (PSI) via an electron transport chain, despite the lower energy levels of PSII. Inspired by this sophisticated mechanism, we present a layered cascade bio‐solar cell (CBSC) that emulates the Z‐scheme. In this design, chlorophyll derivatives (Chl) act as PSI analogs, while bacteriochlorophyll derivatives (BChl) serve as PSII analogs in the active layer. The resulting photocurrent, prominently detected in the near‐infrared region, is validated through external quantum efficiency measurements. Sub‐nanosecond transient absorption spectroscopy reveals a prolonged charge transfer (CT) state from BChl to Chl (Chl–/BChl+ species) compared to the reverse direction (Chl+/BChl– species). This asymmetry highlights a dominant electron flow from BChl (PSII analog) to Chl (PSI analog) under simultaneous excitation, effectively replicating the natural Z‐scheme electron transfer. These findings represent a significant advance in the design of bio‐inspired solar cells, paving the way for artificial photosynthesis systems and offering profound insights into improving photovoltaic theory and efficiency. [ABSTRACT FROM AUTHOR]