Gaining Long Carrier Lifetime in Organic Semiconductors for Efficient Light to Hydrogen Conversion
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초록
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Organic bulk heterojunctions (BHJs) are promising candidates for solar-driven water splitting. Here, we investigate the role of a PM6 polymer overlayer on the photoexcited carrier dynamics in a Y6:PM6 BHJ photoanode undergoing ascorbic acid oxidation. With the additional polymer layer, the hole lifetime is increased in the solid state BHJ film. When the photoanode is electrically coupled to a hydrogen-evolving platinum cathode, hole polaron states are observed on the timescale of seconds under operational conditions. More importantly, we demonstrate that the organic photoanode with the polymer overlayer shows enhanced performance, reaching over 6 mA cm-2 at 1.23 VRHE without a co-catalyst. An EQE of 18% was observed using 850 nm excitation. We propose that the use of an organic overlayer can be an effective design strategy for generating longer charge carrier lifetimes in organic photoanodes for efficient oxidation catalysis.