New Material Boosts Solar Cells

Wednesday, April 16, 2014 @ 11:04 AM gHale

Cost remains one deterrent to solar power conversion, but there is a material that is so good at absorbing light that it can become a part of a super-efficient solar cell.

The material, a methyl-ammonium lead iodide chloride called perovskite, is inexpensive, easy to work with, and simple to turn into photovoltaics that could match the efficiency of the world’s most efficient solar cells at a fraction of the cost of the most common variety, said researchers at Oxford University.

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The best solar cells use thick layers of silicon to distribute energy across their semiconductors — to spread out the sunlight so it can convert into electricity, rather than overloading the material and just heating it up.

Their efficiency rates are relatively high (close to 25 percent), but they are too heavy and expensive for most applications. The most common type uses a variety of semiconductor materials applied in thin layers to spread and absorb sunlight. It turns the light into electricity at efficiency rates of 17-19 percent.

Very early versions of perovskite-based solar cells produced power at efficiency rates of 12-15 percent, but even researchers in the lab of Oxford University physicist Henry J. Snaith, who discovered the material’s usefulness in solar cells, weren’t sure why.

While trying to produce a thin-film solar cell based on perovskite — and realizing they could do it for a fifth the cost of commercial solar cells — competing researchers at Nanyang Technological University (NTU) in Singapore discovered their organic/inorganic mix of perovskite reacts to light much quicker and far more intensely than other materials used in semiconductors.

“We discovered that in these perovskite materials, the electrons generated in the material by sunlight can travel quite far,” said NTU Assistant Professor Sum Tze Chien. “This will allow us to make thicker solar cells which absorb more light and in turn generate more electricity.”

Chien’s lab used rapidly pulsing lasers to test the perovskite solar cells. The researchers discovered perovskite’s tendency to spread light along its surface while reflecting it turned the solar-cell material into a good light source.

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