May 24, 2012
New Solar Cells Shine With Potential
Today´s solar cells have several limitations, including high production costs, low efficiency and durability, and reliance on scarce materials for production. Now, a group of Northwestern University researchers say they have developed a new solar cell that minimizes these problems.
The device uses a GrÃ¤tzel cell, a promising low-cost and environmentally friendly solar cell with a significant disadvantage: it leaks. The dye-sensitized cell's electrolyte is made of an organic liquid, which can leak and corrode the solar cell itself.
GrÃ¤tzel cells act in much the same manner as chlorophyll in plants. A molecular dye absorbs sunlight and converts it to electricity. The cells usually last only 18 months, however, which makes production and large-scale use non-profitable. Researchers have looked for a solution to the corrosion problem for many years.
Nanotechnology expert Robert P. H. Chang and chemist Mercouri Kanatzidis collaborated to find a stable way to make GrÃ¤tzel cells.
The dye-coated nanoparticles are packed in, and Kanatzidis' new material, which starts as a liquid, is poured in, flowing around the nanoparticles. Much like paint, the solvent evaporates, and a solid mass results. The sunlight-absorbing dye, where photons are converted into electricity, lies right between the two semiconductors. Each cell is half a centimeter by half a centimeter and about 10 microns thick.
"The GrÃ¤tzel cell is like having the concept for the light bulb but not having the tungsten wire or carbon material," said Kanatzidis of the need to replace the troublesome liquid. "We created a robust novel material that makes the GrÃ¤tzel cell concept work better. Our material is solid, not liquid, so it should not leak or corrode."
Chang said, "This is the first demonstration of an all solid-state dye-sensitized solar cell system that promises to exceed the performance of the GrÃ¤tzel cell. Our work opens up the possibility of these materials becoming state of the art with much higher efficiencies than we've seen so far."
“Our inexpensive solar cell uses nanotechnology to the hilt. We have millions and millions of nanoparticles, which gives us a huge effective surface area, and we coat all the particles with light-absorbing dye. This is only the beginning. Our concept is applicable to many types of solar cells. There is a lot of room to grow."
The paper is titled "All-Solid-State Dye-Sensitized Solar Cells With High Efficiency" and is published in the journal Nature.