Light Harvesting, Photosensitized Electron Transfer in Nanocarbon–Sensitizer Hybrids

Abstract

This mini-review highlights the recent advances in the photosensitized electron-transfer processes of nanocarbons decorated with electron-donating or electron-accepting photosensitizer molecules. As nanocarbons, well-characterized fullerenes, size (diameter)-sorted single wall carbon nanotubes (SWCNTs), few-layer graphene and graphene oxide are mainly targeted. Fullerenes linked to light-absorbing electron donors such as porphyrins act as excellent electron acceptors. SWCNTs, in their ground states, act either as electron acceptor or electron donors, depending on the nature of the employed photosensitizers. Diameter sorted semi-conductive SWCNT allows to treat each SWCNT as a “molecule” in the hybrids. The flat graphene has emerged out to be a new candidate to attach photosensitizer molecules to seek photochemical applications. In these studies, for the confirmation of the electron transfer processes, transient absorption methods have been widely used. The kinetic data obtained in solution are found to be quite useful to understand the electron transfer mechanisms and their efficiencies relevant to light energy harvesting of nanocarbon materials. Photovoltaic cells constructed by employing these photosensitizing electron-transfer systems are indicative of their potential use in light energy harvesting, although additional work is needed to optimize the photocells for higher light energy conversion efficiencies.