Stacked solar cell to power the eye
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A researcher in Australia is developing a stacked solar cell that can be implanted into the eye to provide power to implants.
The focus for the solar cell is on semiconductor materials such gallium arsenide and gallium indium phosphide that are easier to tune the properties for the eye and are also commercial available. This also provides a higher voltage.
The idea is to have a tiny solar panel attached to the eyeball that converts light into the electric impulse that the brain uses to create our visual fields. The panel would be naturally self-powered and portable, doing away for the need to have cables and wires into the
“In order to stimulate neurons, you need a higher voltage than what you get from one solar cell, said Dr Udo Roemer at the University of New South Wales.
“If you imagine photoreceptors being pixels, then we really need three solar cells to create enough voltage to send to the brain. So we’re looking at how we can stack them, one on top of the other, to achieve this. With silicon this would have been difficult, that’s why we swapped to gallium arsenide where it’s much easier.”
This can be used to power implants without the need for external cables.
“People with certain diseases like retinitis pigmentosa and age-related macular degeneration slowly lose their eyesight as photoreceptors at the centre of the eye degenerate,” he said.
“It has long been thought that biomedical implants in the retina could stand in for the damaged photoreceptors. One way to do it is to use electrodes to create voltage pulse that may enable people to see a tiny spot. There have already been trials with this technology. But the problem with this is they require wires going into the eye, which is a complicated procedure.”
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The project is in the proof-of-concept stage.
“So far we’ve successfully put two solar cells on top of each other in the lab on a large area – about 1cm2, which has got some good results,” said Roemer.
The next step will be to make them into the tiny pixels required for sight, and etching the grooves to separate them. It will then be a small step to increase the stack to three solar cells.
The end device should be 2mm2 in size with pixels measuring about 50 microns. He stresses that it’s still a way down the track before this technology will be implantable in the retinas of people with degenerative eye diseases.
“One thing to note is that even with the efficiencies of stacked solar cells, sunlight alone may not be strong enough to work with these solar cells implanted in the retina,” he says.
“People may have to wear some sort of goggles or smart glasses that work in tandem with the solar cells that are able to amplify the sun signal into the required intensity needed to reliably stimulate neurons in the eye.”
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