Solar cells could soon add power to your smartphones and tablets

March 9, 2013
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Soon you can charge your smartphone while sunbathing, with a gallium arsenide solar cell chemistry from Alta Devices.

Soon you can charge your smartphone while sunbathing, with a gallium arsenide solar cell chemistry from Alta Devices.

Power efficiency can make or break a mobile device. If we weren’t constrained with the power supply, then our mobile devices would probably be even faster and more powerful than they are now. But even as mobile CPUs and GPUs are increasingly becoming power efficient, we still find ourselves finding the need to plug in at the end of the day (or even at the middle of the day). If all goes well with a new technology being developed by Alta Devices, we might be able to rely on the sun or other light sources to augment our batteries or even power our devices altogether.

As it stands, solar cells are currently very inefficient at absorbing energy from the sun, especially if the surface area were only to cover, say, the back end of a mobile phone or tablet. The highest-efficiency solar cell chemical could, theoretically, power a mobile phone, but in its current form, it would be very impractical to incorporate in a mobile device.

Gallium arsenide is better-able to capture light than traditional solar cells, and is currently used in space-bound craft such as satellites. The problem is that gallium arsenide is usually synthesized in a crystalline form — quite cumbersome to add onto a mobile device. Alta Devices, a Silicon Valley startup, has found a way to synthesize the material onto a thin film, and the resulting solar cells can convert up to 30.8% of the energy from light into electricity.

Alta Devices solar cells

The resulting film is about 1 micron thin — about a fourth of the width of human hair. The solar cells have two layers, one of which consists of indium gallium phosphide, which converts light with lower wavelengths into electricity.

The end result: a smartphone battery cover that can output about 1.5 watts of electricity at peak, such as when exposed to sunlight. Alta Devices has actually developed a prototype for a Samsung galaxy smartphone (model unspecified). CEO Christopher S. Norris says this can charge a mobile phone in about three times the time it would take to charge from a wall outlet. But while that’s still less than ideal, the point here is to reduce dependency on he grid. “If you’re in full sun, a watt and a half for 10 minutes will give you an hour of talk time.”

At this point, the main benefit would not necessarily be taking out the need to plug in altogether, but to augment power from the grid and to extend usage while unplugged. If you’re curious, you can check out Alta Devices’ battery life extension calculator, to determine how much you can extend your battery life. If you’re mostly outdoors and if you carry your phone on your belt, this could be as much as an 83% extension. Students with time spent outdoors get about 54% extension of their battery life.

While this would be a great addition to smartphones in the developed world, the real benefit would be in emerging markets, where mobile devices have proliferated faster than the electricity grid, reports the New York Times.

But going beyond mobile phones, Alta Devices’ technology can also be applied to cars. While Alta Devices solar cells mounted onto a car’s surface area would not necessarily be able to power the entire vehicle, it can help reduce the load on the internal combustion engine by, say, delivering power to the electronics. This is something that certain hybrid vehicles currently do with their gas-powered engine, plus battery technology.

Would you be willing to carry your smartphone on your belt, in order to absorb as much energy from the sun possible?

Featured image credits: Shutterstock / Solar cell film image credit: Alta Devices

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