Photoinduced charge separation is one of the most basic processes in physics, chemistry, and biology. For instance, the nanostructured reaction center of natural photosynthesis, photoinduced ET generates a long-lived charge separation (CS) state with ~100% efficiency, leading to light-to-chemical energy conversion. In contrast, photoinduced CS at the interfaces of organic photovoltaic cells and dye-sensitized solar cells generates an electron-hole pair, followed by charge transport, eventually achieving light-to-electricity conversion. However, the interfaces of semiconductor/dye and donor/acceptor (D/A) in artificial photosynthesis and organic photovoltaic cells often suffer from the partial or even large loss of the CS state, which has still been controversial and not been fully understood owing to inevitable inhomogeneous spatial distribution of D-A components.
In this context D-bridge (B)-A linked systems have generated remarkable interest for the last few decades. The covalent linkage between D and A with a suitable bridge can eliminate complex factors and assess the photoinduced CS precisely with the help of homogenous spatial distribution of the D-B-A components. So far these systems have provided basic information on photoinduced CS. Impact of various ET parameters on ET rate has been evaluated by using elaborated D-B-A linked molecules. In particular, a well-defined D-B-A linked molecule with a rigid bridge has allowed us to shed light on photoinduced CS more accurately.
In this talk I will give an overview of our initiatives on the basis of D-B-A nanostructures and interfaces. In particular, I highlight the following three main topics : i) porphyrin-fullerene and pyrene-carbon nanotube linked molecules, ii) porphyrin-sensitized TiO2 solar cells and solar fuels and conjugated polymer-fullerene derivative bulk heterojunction solar cells, and iii) donor-acceptor linked molecules in biological cell membranes.
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