Cold-Charge Generation Enhances Photocatalytic Hydrogen Evolutions in Organic Heterojunction Nanoparticles
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The present conventional photocatalyst based on organic semiconductor (OSC) exhibit inefficient photocatalytic activities due to their high exciton binding energy and short exciton diffusion lengths (EDL). Here, we introduce a novel strategy to significantly enhance the photocatalytic activity of OSCs by using “dark excitonic” heterojunction nanoparticles (NPs) having core-shell and bulk heterostructure morphology modulated by compositional and molecular engineering. The photocatalytic investigation demonstrates that these NPs exhibit a high rate of hydrogen evolution under 500-1100 nm illumination. A comprehensive spectroscopic investigation reveals that disordered NPs are capable of exhibiting “dark excitonic” behavior, which accompanies efficient cold-charge generation bypassing the conventional exciton dissociation pathways. Additionally, the short EDL is found to be derived from a high polaron yield, promoting the efficient generation of long-lived photoelectrons and holes.