Organic semiconductor-BiVO4 tandems for solar-driven H2O and CO2 splitting

Photoelectrochemical (PEC) systems offer a promising platform towards direct solar light harvesting and chemical storage. However, most prototypes employ wide bandgap semiconductors, moisture-sensitive inorganic light absorbers, or corrosive electrolytes. Here, we introduce PEC devices based on an organic donor-acceptor bulk heterojunction (BHJ), which demonstrate long-term H2 evolution and CO2 reduction in benign aqueous media using a carbon-based encapsulant. Accordingly, PCE10:EH-IDTBR photocathodes display long-term H2 production for 300 h in a near-neutral pH solution, whereas photocathodes with a molecular CO2 reduction catalyst attain a CO:H2 selectivity of 5.41±0.53 under 0.1 sun irradiation. Their early onset potentials enable the assembly of PCE10:EH-IDTBR - BiVO4 artificial leaves, which couple unassisted syngas production with O2 evolution, sustaining a 1:1 ratio of CO to H2 over 96 h of operation.