Ultrafast Photodynamics and Quantitative Evaluation of Biohybrid Photosynthetic Antenna and Reaction Center Complexes Generating Photocurrent

A functional linkage between light-harvesting and photocatalytic components is a pivotal issue for using solar energy in chemical conversions; however, this concept is far from being practically realized. Here, we constructed a system that integrates an artificially extended photosynthetic light-harvesting complex 2 (LH2) and a light-harvesting 1-reaction center (RC) core complex (LH1-RC). A biohybrid LH2, whose light-harvesting ability was extended by a covalently attached hydrophobic fluorophore ATTO647N (LH2-ATTO) to cover the absorption gap of LH2, was assembled with LH1-RC in a lipid bilayer. Femtosecond transient absorption spectroscopy revealed that upon an excitation of the ATTO, sequential excitation energy transfer (EET), ATTO → LH2 → LH1 → RC, was followed by a subsequent electron transfer in the RC with rates comparable to those in a native system. As a proof of concept, the functional linkage between light-harvesting and photocatalytic reactions was quantitatively demonstrated through the enhancement in the charge separation yield and photocurrent generation activity of LH2-ATTO/LH1-RC assembled on an electrode.