Organic Semiconductor-BiVO Tandem Devices for Solar-Driven HO and CO Splitting.

Photoelectrochemical (PEC) devices offer a promising platform toward direct solar light harvesting and chemical storage through artificial photosynthesis. However, most prototypes employ wide bandgap semiconductors, moisture-sensitive inorganic light absorbers, or corrosive electrolytes. Here, the design and assembly of PEC devices based on an organic donor-acceptor bulk heterojunction (BHJ) using a carbon-based encapsulant are introduced, which demonstrate long-term H evolution and CO reduction in benign aqueous media. Accordingly, PCE10:EH-IDTBR photocathodes display long-term H production for 300 h in a near-neutral pH solution, whereas photocathodes with a molecular CO reduction catalyst attain a CO:H selectivity of 5.41±0.53 under 0.1 sun irradiation. Their early onset potential enables the construction of tandem PCE10:EH-IDTBR - BiVO artificial leaves, which couple unassisted syngas production with O evolution in a reactor completely powered by sunlight, sustaining a 1:1 ratio of CO to H over 96 h of operation.