Photoelectrochemical Properties of Carbon Nanotube/SnO 2 Nanostructures Prepared by Three Different Methods
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Photoelectrochemical Properties of Carbon Nanotube/SnO 2 Nanostructures Prepared by Three Different Methods
Baleeswaraiah Muchharla and Lifeng Dong Department of Physics, Astronomy, and Materials Science, Missouri State University, Springfield, MO 65897, U.S.A.
ABSTRACT In this work, we employed three different methods to fabricate solar cell structures on indium tin oxide (ITO) substrates. For the first method, multi-layered structures were prepared by using single walled carbon nanotubes (SWCNTs) and tin oxide (SnO2). First, a SWCNT layer was deposited on the ITO substrate; and photoactive material was then coated on the top of the SWCNT layer. For the second method, photoactive particles were added to a solution of SWCNTs. The SWCNT/SnO2 solution was mechanically stirred and then deposited on the ITO substrate. For the third method, we synthesized photoactive particles on SWCNTs through a chemical-solution routine using SnCl4 as a precursor. We characterized the morphology and structure of the SWCNTs coated with SnO2 nanoparticles prepared with the three different methods by using a field emission scanning electron microscope equipped with an X-ray energy dispersive spectrometer. We characterized the photoelectrochemical properties of all electrodes by using an electrochemical station; mainly, we examined the photocurrent generated under periodic illumination. Our results indicate that there are significant differences in the photocurrent in the presence of SWCNTs. We propose the following hypothetical mechanism: without carbon nanotubes, generated electrons (when light is absorbed by SnO 2 particles) must cross the particle network to reach an electrode. Many electrons never escape this network to generate an electrical current. The carbon nanotubes "collect" the electrons and provide, therefore, a more direct route to the electrode, thus improving the efficiency of the solar cells.
INTRODUCTION The ever increasing demand on natural energy resources forces one to seek out alternative sources of energy. In addition, the burning of fossil fuels releases carbon dioxide into the atmosphere; this is the major cause for the greenhouse effect. Renewable energy sources such as solar energy, wind power, water power, bio fuels and geothermal energy have not been found to have any dangerous effect on the atmosphere; however, utilization of these resources is a cost consuming process. There is a need to develop low cost techniques to use these energy resources. Harvesting energy from the sun can be accomplished by a device called a solar cell, which converts solar energy into electrical energy. The majority of solar cells being used today are inorganic, and manufacturing these cells requires heavy infrastructure which increases the production cost. On the other hand, organic solar cells can be made with a simple infrastructure and a lower production cost compared to inorganic solar cells. An electrochemical solar cell consists of a photoactive material in conjunction with a transparent electrode and a liquid
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