Light-Harvesting and Photocurrent Generation by Gold Electrodes Modified with Mixed Self-Assembled Monolayers of Boron−Dipyrrin and Ferrocene−Porphyrin−Fullerene Triad

Three different kinds of mixed self-assembled monolayers have been prepared to mimic photosynthetic energy and electron transfer on a gold surface. Pyrene and boron−dipyrrin were chosen as a light-harvesting model. The mixed self-assembled monolayers of pyrene (or boron−dipyrrin) and porphyrin (energy acceptor model) reveal photoinduced singlet−singlet energy transfer from the pyrene (or boron−dipyrrin) to the porphyrin on the gold surface. The boron−dipyrrin has also been combined with a reaction center model, ferrocene−porphyrin−fullerene triad, to construct integrated artificial photosynthetic assemblies on a gold electrode using mixed monolayers of the respective self-assembled unit. The mixed self-assembled monolayers on the gold electrode have established a cascade of photoinduced energy transfer and multistep electron transfer, leading to the production of photocurrent output with the highest quantum yield (50 ± 8%, based on the adsorbed photons) ever reported for photocurrent generation at monolayer-modified metal electrodes and across artificial membranes using donor−acceptor linked molecules. The incident photon-to-current efficiency (IPCE) of the photoelectrochemical cell at 510 and 430 nm was determined as 0.6% and 1.6%, respectively. Thus, the present system provides the first example of an artificial photosynthetic system, which not only mimics light-harvesting and charge separation processes in photosynthesis but also acts as an efficient light-to-current converter in molecular devices.