Cambridge team uses solar cells in OLED screen to power smartphones

January 22, 2012 by Nancy Owano report
A thin-film system harvests energy from wasted light in an OLED display. Image credit: Arokia Nathan (via IEEE)

( -- With the world's showroom floors crammed with prototype smartphones promising advanced functions, bigger displays, stunning resolution, wouldn’t you think the biggest crowd-pleasers would dominate? The ultimate attraction in a smartphone, the one that never has to be charged again? This ultimate solution at least has scientists working toward that end, to bring in an easier time where users will not need to worry about the batteries wearing out.

A team of researchers at the University of Cambridge are getting closer. Their idea is to harvest energy from wasted light in an display. They are working on technology where users will not need to plug in their smartphones for recharging at least as often. In their project, an OLED screen uses solar cells to absorb scattered and wasted light, sending it back into the screen.

IEEE Fellow Arokia Nathan along with the Cambridge team have developed a prototype device that converts ambient light into electricity. Solar cells used in the prototype are made of thin film hydrogenated amorphous silicon, within the screen.

Only around 36 percent of the light produced by an OLED display is projected forwards; the rest escapes around the edges, in the form of scatter and bleeding from the edges. The researchers worked on a solution where they could harvest what’s lost by installing photovoltaic cells on the back and sides of OLED screens to capture the loss.

They also worked out a solution—a thin-film transistor circuit--to even out the voltage spikes produced by the , as fluctuations in the voltage provided by the solar cell could damage the phone’s battery. The device captures both ambient light and the otherwise wasted screen leaking around the edges.

According to reports, the team worked with the energy group at Cambridge's Centre for Advanced Photonics and Electronics to integrate a thin-film supercapacitor for intermediate energy storage.

The end result is a system that makes use of photovoltaics, transistors, and supercapacitor. The system would achieve an efficiency of 11 percent and peak efficiency, 18 percent.

The numbers, for the smartphone user, would promise at least less strain on their battery. The Cambridge team’s effort is not promising “never-again” recharging but an ability for the user to save a fraction of power.

More work is ahead. The team is exploring different circuit designs and materials with the aim of increasing the energy harvesting system’s efficiency. Nathan has said other energy scavenging schemes such as MEMS based kinetic harvesting may bring improvements.

Explore further: Colored solar cells could make display screens more efficient

More information:
via IEEE

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2.6 / 5 (5) Jan 22, 2012
The MEMS based kinetic energy harvesting is intriguing, where piezoelectric circuits convert vibration into usable electrical energy. Maybe all of this bible-thumping can be put to good use.
2.3 / 5 (9) Jan 22, 2012
A most idiotic thing to put a solar cell in a cellphone.

Where does it spend the majority of time? In your pocket, where the sun doesn't shine.
1.5 / 5 (2) Jan 22, 2012
uses solar cells to absorb scattered and wasted light, sending it back into the screen
IMO the same result could be achieved with using of retroreflector geometry at the display surface. The effectiveness of LED-multiplier-solar cell circuit is well bellow 10 percent, not to say about its price.

2.2 / 5 (5) Jan 22, 2012
I think this is a very wonderfu idea. Anyone who opposes this idea or any idea of advancement should be banned from posting a review.

If this film can collect light from the bottom then combine the film back to back to collect light from both sides.
3.3 / 5 (7) Jan 22, 2012
Solar film is new and increasing in advancements. Congradulations to the engineers who worked hard on this and I hope you conitinue to make our world better as you have done with this product idea. I think it will go far. As you have said. Implementing a number of designs into one product for maximum efficiency is the way to go and it will lead us eventually to build a product that no one has seen.
3.4 / 5 (5) Jan 22, 2012
This design collects light by facing the film down into the face of the screen towards the phone not the sun. If you would spend more of your time in books instead of on Playstation you might learn something.

All you had to do is look at the diagram at the top and it show you the film on top of the screen collecting light escaping from the screen.
5 / 5 (5) Jan 22, 2012
A most idiotic thing to put a solar cell in a cellphone.

Where does it spend the majority of time? In your pocket, where the sun doesn't shine.

Actually, my phone spends more time sitting on my desk or a table. Also, one of purposes of this is to capture the light lost when your phone's screen is lit up.

This might not be the best solution for you; if you don't have your phone's screen on for more than 15 or 20 minutes a day, that would be understandable. That doesn't mean it couldn't greatly benefit some people (myself included) who would be pleased to see this further on in it's development.
3.5 / 5 (2) Jan 22, 2012
Jazzy that's not too open-minded. Can this harvest from ambient light? If not this may be too complicated/expensive to do..rather getting the efficiency of the OLEDs may be more feasible.
3.8 / 5 (8) Jan 22, 2012
" Anyone who opposes this idea or any idea of advancement should be banned from posting a review."- JazzyLawnService

Anyone who proposes censorship outside of racist and hate-mongering remarks on this forum is out of line, but still has the right to post it. Self-promotion of one's business, though, is in bad form, I'd say.
1.3 / 5 (4) Jan 23, 2012
Ok this must be the worst written article today, the writer only just manages to prevent himself from claiming this is a perpetual motion machine i.e a phone that wont ever need charging!
If 64% of OLED light is wasted as scatter, and 18% can be converted to electricity that means 11.5% of the power used by can potentially be saved. Im not sure what percentage of power is used to run the screen, lets be generous and say 80%. So thats 9.2% increase in battery life from this add on, if your phone usually lasts 24 hours between charges, it will now last 2.208 hours longer.
A revolution this is not, and given the cost of the device it will never be put into production since its only saving a few cents worth of power.
@JazzyLawnService : Put down the GreenPeace guide to internet propoganda, try to resist your obviously facist nature and learn some maths.
3 / 5 (2) Jan 23, 2012
Where does it spend the majority of time? In your pocket, where the sun doesn't shine.

There's infrared radiation in your pocket. If the solar cells are tweaked to use primarily that (even though the energy is lower) it could be worth it.

If 64% of OLED light is wasted as scatter, and 18% can be converted to electricity that means 11.5% of the power used by can potentially be saved.

The article also mentions that in addition to the wasted light from the OLED it captures ambient light.
1 / 5 (2) Jan 23, 2012
I may be wrong but since the OLED contains organic compunds would the increased time spent under high energy light from the sun increase the speed of photodegradation and decrease its lifespan. The compound to make blue only maintains a 5 year lifetime at 8 hours a day. Sure most people won't be holding onto their phones after 5 years or if they did they would be expecting something to start dying off. But this could bring there life span way down. Just food for thought.
1 / 5 (1) Jan 28, 2012
Some poor reading comprehension from many posters here.

Yes it uses ambient light as well as light from the screen

No article doesant claim it will never need recharging just that the reserchers are iming for that goal and currently with this tech plugging in to charge will be less often.

Also Jazzy is largly right - exept of course for the somewhat over the top oppinion that any that dissagreed needed to be shall i be kind and say stay silent.
1 / 5 (1) Feb 07, 2012
MArkyMark: A phone which 'never' needed recharging would be a perpetual motion machine, which is impossible. So any reasearcher 'aiming' for it is a fool.
I never claimed the author said it never needed recharging, i merely claimed the author barely held back from doing so in their breathless desperation to overhype this trivial advance. Regarding reading comprehension, people in glass houses Marky...

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