Jan 21, 2009
Nanowires improve dye-sensitized solar cells
With the effects of climate change increasingly being felt across the globe, many researchers are exploring alternative energy technologies. The most direct of these is the solar cell, which converts sunlight straight into electrical energy to do useful work, without any of the pollutants produced when coal, oil or gas are burnt to generate electricity.
While much solar-cell research is on silicon-based devices, there is another class of solar cells, called dye-sensitized solar cells, that holds promise as a cheaper alternative to silicon cells, especially for smaller, more mobile or less power-intensive applications. Basically, dye-sensitized solar cells are electrochemical cells in which a light-absorbing dye, placed on titanium dioxide, is used to convert the energy from photons of light into electricity; the more light that is converted into electricity, the higher the conversion efficiency and therefore the performance of these cells.
One important factor in determining conversion efficiency is how quickly the electrons are removed from the titanium-dioxide layer, before they are lost in a process known as recombination. To exit the titanium dioxide, and do useful work in an electrical cell, the electrons must pass into an adjoining electrode, which is typically a conductive glass made from indium-tin oxide (ITO).
As reported recently in Nanotechnology, a team from Taiwan and Australia have created a three-dimensional electrode interface by means of wet chemistry, seeking to maximize the interfacial area between the titanium dioxide and the ITO, and so reduce recombination and improve conversion efficiency. Their process involved electrophoretic deposition of oxide precursors within a template, and thereby allowed the team to produce an electrode made from arrays of ITO nanowires in a cost-effective way. The researchers applied electron microscopy to characterize the structures of the nanowires and their arrays, and they measured the performance of the resulting solar cells. As hoped, solar cells made with the nanostructured, three-dimensional electrode showed as much as a 13–46% increase in conversion efficiency over the traditional flat electrodes.
Following on from the promising results of this preliminary study, the team is looking to further improve the solar-cell performance by refining the synthesis routes and optimizing the geometry of the nanowire arrays.
About the author
Hong-Wen Wang, Chi-Feng Ting and Miao-Ken Hung are based at the Center for Nanotechnology, Chung-Yuan Christian University, Taiwan, Republic of China. Chwei-Huann Chiou is a researcher at the Institute of Nuclear Energy Research, Taiwan, Republic of China. Ying-Ling Liu is from the R&D Center for Membrane Technology, Taiwan, Republic of China. Zongwen Liu, Kyle R Ratinac and Simon P Ringer work at the Australian Key Centre for Microscopy and Microanalysis, University of Sydney, Australia.