CdSe Quantum Dot-Fullerene Hybrid Nanocomposite for Solar Energy Conversion: Electron Transfer and Photoelectrochemistry

The development of organic/inorganic hybrid nanocomposite systems that enable efficient solar energy conversion has been important for applications in solar cell research. Nanostructured carbon-based systems, in particular C-60, offer attractive strategies to collect and transport electrons generated in a light harvesting assembly. We have assembled CdSe-C-60 nanocomposites by chemically linking CdSe quantum dots (QDs) with thiol-functionalized C-60. The photoinduced charge separation and collection of electrons in CdSe QD-C-60 nanocomposites have been evaluated using transient absorption spectroscopy and photoelectrochemical measurements. The rate constant for electron transfer between excited CdSe QD and C-60 increased with the decreasing size of the CdSe QD (7.9 x 10(9) s(-1) (4.5 nm), 1.7 x 10(10) s(-1) (3.2 nm), and 9.0 x 10(10) s(-1) (2.6 nm)). Slower hole transfer and faster charge recombination and transport events were found to dominate over the forward electron injection process, thus limiting the deliverance of maximum power in CdSe QD-C-60-based solar cells. The photoinduced charge separation between CdSe QDs and C-60 opens up new design strategies for developing light harvesting assemblies.