Why don’t power-thirsty smartphones incorporate solar cells, to
reduce the reliance on batteries? Because in general, the kind
of solar cell that can be fabricated in a lightweight, flexible
and durable form does not capture enough energy per square inch
to make it worthwhile. But a Silicon Valley solar power company
thinks it has found a way to adapt the highest-efficiency solar
cell chemistry, gallium arsenide, into a form that can be
attached to a portable electronic device like a smartphone or a
tablet. And a panel the size of a cellphone or a tablet would
add measurably to the device’s longevity. 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