Gold nanoparticles boost organic solar cell efficiency
By Ben Coxworth
August 19, 2011
Carbon-based organic photovoltaic cells, which use organic polymers or small molecules as semiconductors, are significantly thinner and cheaper than their inorganic silicon-based counterparts. Unfortunately, they are also much less efficient at converting sunlight into electricity. That could be on its way to changing, however, as an international team of researchers have reportedly boosted the efficiency of organic photovoltaic cells by 20 percent ... with some help from gold nanoparticles.
The team was led by UCLA's Prof. Yang Yang, who worked with Xing Wang Zhang from Beijing's Chinese Academy of Science, and Ziruo Hong from Japan's Yamagata University.
In their experiments, the scientists sandwiched a layer of gold nanoparticles between two light-absorbing subcells in a tandem polymer organic solar cell. This caused what is known as a plasmonic effect, in which the particles created an electromagnetic field that served to concentrate the light, so that more of it could be absorbed by the subcells.
"The plasmonic effect happening in the middle of the interconnecting layer can enhance both the top and bottom subcells simultaneously - a 'sweet spot' - leading to an improvement in the power conversion efficiency of the tandem solar cell from 5.22 percent to 6.24 percent" said Yang. "The enhancement ratio is as high as 20 percent."
Of course, even 6.24 percent falls far below the overall efficiency record of over 42 percent, which was set by an inorganic solar cell. The much lower cost of organic cells needs to be taken into account, however, as does the fact that such cells could be multi-stacked for a higher combined output. Also, it would be interesting to see what would happen if the gold nanoparticles were incorporated into Konarka's Power Plastic organic cells, which already manage a record-setting 8.3 percent efficiency.
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