Carbon Single Walled Nanotubes- Electron Acceptor Molecules for Improving the Efficiency of the Photoexcitation of TiO2 for Solar-Driven Technologies

Abstract

Abstract : Photoluminescence (PL) spectroscopy and infrared(IR)spectroscopy have been used to measure the surface condition of TiO2 powder. The adsorption of electron acceptor and donor molecules has been shown to modify band bending at the TiO2 surface. Single walled nanotubes (SWNTs) are shown to be electron acceptor molecules. The PL was used to observe the buildup during UV irradiation of surface photovoltage, and it was found that TiO2 particles, fused and pressed together by water treatment + drying, led to enhanced interparticle conductivity compared to TiO2 particles pressed in a dry condition and considered to be isolated. The conductivity can be used to monitor conduction through the TiO2 bed and through the bed containing SWNT linkers. It was found that while SWNTs are good acceptors, no added conductivity from isolated TiO2 grain to grain was seen even for 10% mixtures. It was shown that PL gives insight into the electronic state of the very outermost TiO2 particles in a packed bed. Such beds are used in photovoltaic cells. The PL-IR spectrometer is unique in the field, allowing both chemical and electronic properties to be measured for the surfaces of small semiconductor particles.