Bilayer Chlorophyll-Based Biosolar Cells Inspired from the Z‑Scheme Process of Oxygenic Photosynthesis

The Z-scheme process in chlorophyll-based natural photosynthesis shows the pathway of photoinduced electron transport from photosystem II (PSII) to photosystem I (PSI) through an electron transfer chain. Inspired by the interesting Z-scheme of oxygenic photosynthesis, we imitated the dual photosynthesis systems into biosolar cells (BSCs). The device structure fabricated here is ITO/ZnO/Chl-A/Chl-D1, -D2, -D3, or -D4 (Chl-Ds)/MoO3/Ag. Due to higher HOMO/LUMO energy levels of Chl-A than those of Chl-Ds, the sublayer Chl-A corresponds to PSI, and the upper layer Chl-Ds are equivalent to PSII, leading to double photoexcited electron transfer from Chl-Ds to Chl-A. The energy alignment of the photoactive layers here is in conflict with the traditional comprehension of photovoltaic devices. Interestingly, such an uncommon device can still work well. A power conversion efficiency of 1.30% was reached based on the Chl-A/Chl-D4 device under standard AM1.5 illumination.