Raman and Photoluminescence Spectroscopy of Charge Transfer Processes in C60-ZnO interface
Zink oxide (ZnO) is a semiconductor with a wide band gap (3.37 eV), large exciton binding energy (60 meV), and high electrical conductivity and considered as a promising candidate material for new generations of UV light emitting diodes, solar cells, and photocatalysists. At present, a numerous techniques for the growth of high quality ZnO thin films are available.
Physical properties of ZnO thin films can be essentially modified by C60 molecules deposited on the surface of such a semiconductor. However, control of the electronic and optical characteristics of the composition ZnO-C60 required for using in above-indicated applications is still a big challenge. Fullerene molecules, because of their extensively conjugated three-dimensional π-system having a closed-shell configuration, are suitable for efficient electron transfer with minimal changes in their structure and energy. This allows fullerene molecules to accept up to 6 electrons from organic electron-donor molecules, such as Zn-porphyrin, and to compose a supramolecular donor-acceptor system with the absorption spectrum, covering a substantial part of the sunlight energy. The most intriguing aspect in this case is that ZnO can, in turn, serve as an effective secondary electron acceptor from C60 molecules inhibiting back recombination of separated charges, and thus, ZnO-C60 interface may be considered as a key element for constructing new types of organic photovoltaic cells or systems of artificial photosynthesis. I