New Ultra-Thin Solar Cell Could Massively Boost Battery Life Of Personal Mobile Devices

Alta Devices CEO Christopher Norris

A Silicon Valley solar company has developed a method for manufacturing light, ultra-thin, flexible, and durable solar cells that manage to convert a record 30.8 percent of the energy in light into electricity. The company, Alta Devices, previously set a record of 28.8 percent conversion efficiency with another form of solar cell.

It hopes its latest creation could be adapted to fit small mobile devices such as smartphones and iPad tablets, which until now have only been able to fit conventional solar cells that are much less efficient and charge slowly.

Here’s the quick summary, via Energy Matters:

Alta Devices has announced a record 30.8 percent efficiency with its latest generation dual-junction thin-film solar cell, a breakthrough the company says has the potential to vastly improve the battery life of mobile systems.

The record efficiency has been verified by the USA’s National Renewable Energy Laboratory (NREL), the same body which last year confirmed Alta’s record of 28.8 percent efficiency for its single-junction solar cell.

Alta’s technology is based on flexible thin-film solar wafers made from gallium arsenide (GaAs). GaAs solar cells are far more expensive to manufacture than traditional PV cells, but with such high energy conversion levels, the new dual-junction cell allows for more energy to be generated over a smaller area, making them perfect for use in devices such as smartphones, tablets and other portable devices.

The gallium arsenide layer, while not the entirety of the completed cell, is incredibly then — approximately one micron, or one-fortieth the width of a human hair — reports the New York Times, which also has a more detailed description of the cells’ construction process.

Alta has already developed a prototype cover for a Samsung Galaxy phone and is working on designs for other smartphones. If it works out, the solar cells could vastly improve the battery life of most mobile devices for very little cost:

It wouldn’t do away with the battery. But depending on the light level where the device was carried, it could add 80 percent to the battery life. The main benefit would be outdoors or on a windowsill, because sunlight has about 100 times more energy than the light typically provided by fluorescent or incandescent lamps. Indoors, it might add only 10 to 15 percent. But the efficient type, gallium arsenide, is not only better overall at capturing energy; it is also better suited to capturing energy in low-light conditions that the ordinary silicon solar cells.…

A smartphone would probably take a patch of film with a peak output, in full sunlight, of 1.5 watts, he said, which is probably only about $3 worth of materials. (A cellphone plugged into a wall outlet generally draws 3 to 5 watts, [Christopher S. Norris, the chief executive of Alta Devices] said, and an iPad, about 10 watts.) “If you’re in full sun, a watt and a half for 10 minutes will give you an hour of talk time,” he said.

Alta has even posted a calculator online that can estimate the benefits of the cells in different types of light.

The technology remains in the development phase: Alta’s only actual customer so far is the military, which uses the cells to cut down on the batteries soldiers have to bring into the field, to reduce diesel fuel consumption at fixed bases, to power drones, and to sew into everything from backpacks to tents. But the company is already eying an advance into the automobile market: while the surface area of a car wouldn’t provide enough energy to power the motor, it could power additional functions like air conditioning, power steering or power brakes.

Alta already has a pilot manufacturing line to take care of the demand from the military, and a 40-megawatt factory on track to begin construction next year solar components for smartphones and other mobile devices. “[The 30.8 percent target is] also an important step toward our target of 38 percent efficient cells,” Norris said. “We continue to redefine the boundaries of what is possible with solar power.”

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