A semiconducting polymer bulk heterojunction photoanode for solar water oxidation

Organic semiconductors hold promise to enable scalable, low-cost and high-performance artificial photosynthesis. However, the performance of systems based on organic semiconductors for light-driven water oxidation have remained poor compared with inorganic semiconductors. Herein, we demonstrate an all-polymer bulk heterojunction organic semiconductor photoanode for solar water oxidation. By engineering the photoanode interlayers we gain important insights into critical factors (surface roughness and charge extraction efficiency) to increase the operational stability, which reaches above 3 h with a 1-Sun photocurrent density, Jph, of >3 mA cm−2 at 1.23 V versus the reversible hydrogen electrode for the sacrificial oxidation of Na2SO3 at pH 9. Optimizing the coupling to an oxygen evolution catalyst yields O2 production with Jph > 2 mA cm−2 at 1.23 V versus the reversible hydrogen electrode (100% Faradaic efficiency and a quantum efficiency up to 27% with 610 nm illumination), demonstrating improved stability (≥1 mA cm−2 for over 30 min of continuous operation) compared with previous organic photoanodes. Conductive polymers are attractive materials for the construction of photoelectrodes in the context of artificial photosynthesis, although their performance is still limited. Now, an organic semiconductor photoanode for water oxidation is presented, which provides high photocurrent density for over 30 minutes.