MIT Thinks It Has Discovered the 'Perfect' Solar Cell
A new MIT study offers a way out of one of solar power's most vexing problems: the matter of efficiency, and the bare fact that much of the available sunlight in solar power schemes is wasted. The researchers appear to have found the key to perfect solar energy conversion efficiency—or at least something approaching it. It's a new material that can accept light from an very large number of angles and can withstand the very high temperatures needed for a maximally efficient scheme.
Conventional solar cells, the silicon-based sheets used in most consumer-level applications, are far from perfect. Light from the sun arrives here on Earth's surface in a wide variety of forms. These forms—wavelengths, properly—include the visible light that makes up our everyday reality, but also significant chunks of invisible (to us) ultraviolet and infrared light. The current standard for solar cells targets mostly just a set range of visible light.
That makes sense because visible light is the most intense form of light that reaches the Earth's surface. Many other forms, such as microwaves and x-rays, are mostly blocked by the planet's atmosphere, but the full spectrum reaching Earth still extends outward from what's known as the solar cell "band gap." This is the range of frequencies within which a material is able to convert solar energy into electrical energy.
The band gap is a feature of photovoltaic solar cells in particular. This is the scheme in which photons, the carriers of the electromagnetic force, and what we'd usually call "light," collide with atoms in some material. This collision delivers a bunch of extra force to those atoms, which respond by shedding electrons. All those electrons add up to current—electricity. It's an ingenious way to harvest energy, but it's currently not all it could be.
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