Oxford researchers have discovered a material that is so good at absorbing light that it can be made into super-efficient solar cells. Scientists have also demonstrated that it is so reflective it can be made into cheap lasers.
The material, a methylammonium 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.
The best solar cells use thick layers of silicon to distribute energy across their semiconductors -- to spread out the sunlight so it can be converted to electricity, rather than overloading the material and just heating it up. Their efficiency rates are relatively high (close to 25%), 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%.
Very early versions of perovskite-based solar cells produced power at efficiency rates of 12-15%, but even researchers in the lab of Oxford University physicist Henry J. Snaith, who gets credit for discovering perovskite's usefulness in solar cells (subscription required), weren't sure why.
Perovskite has potential as a solar cell material.
(Source: Nanyang Technological University)
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 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," NTU Assistant Professor Sum Tze Chien said in a press release announcing publication of the team's discovery in the Oct. 18 edition of Science (subscription required). "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 that perovskite's tendency to spread light along its surface while reflecting it turned the solar-cell material into a good light source.