Artificial photosynthesis using an organic semiconductor

One class of semiconductors that offers tunable energy levels and processability in many solvents is the π-conjugated organic polymers. While their promising aspects have motivated intense investigation for economical roll-to-roll organic photovoltaic (OPV) devices, due to their poor stability in aqueous conditions, they have not been generally pursued as photoelectrodes for direct solar water splitting. In our work, recently published in JACS as a communication, we demonstrate a π-conjugated organic semiconductor for the sustained direct solar water oxidation reaction. The water oxidation photocurrent density was found to increase with increasing pH and no evidence of semiconductor oxidation was found over testing time on the order of hours with bare BBL films. Molecular O₂ evolution was measured upon functionalization with a Ni-Co catalyst. Overall this demonstration suggests that robust n-type conjugated organic semiconductors are suitable for direct PEC water oxidation and opens a new path for the rational design and optimization of photoanodes for solar water splitting.