LCD screen harvests light to power devices

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Summary: Keeping smartphones and laptops charged when there’s no electrical outlet in sight is a perennial challenge. A novel LCD screen developed by UCLA engineers could potentially help solve the problem.

UCLA engineers have developed an LCD screen with built-in photovoltaic polarizers that harvest and recycle energy from ambient light, sunlight, and its own backlight.

The energy-harvesting polarizer, which in technical terms is called a polarizing organic photovoltaic, can potentially boost the function of an LCD by working simultaneously as a polarizer–a photovoltaic device and an ambient light or sunlight photovoltaic panel.

“I believe this is a game-changer invention to improve the efficiency of LCD displays,” said Yang Yang, a professor of materials science at UCLA Engineering and principal investigator on the research. “In addition, these polarizers can also be used as regular solar cells to harvest indoor or outdoor light. So next time you are on the beach, you could charge your iPhone via sunlight.”

LCDs, or liquid crystal displays, shine light through a combination of liquid crystals and polarized glass to produce a visible image, albeit inefficiently. According to the UCLA researchers, a device’s backlight can consume 80 to 90 percent of the device’s power, but as much as 75 percent of the light generated is lost through the polarizers. A polarizing organic photovoltaic LCD could recover much of that lost energy.

Youssry Boutros, program director at Intel Labs, said: “The polarizing organic photovoltaic cell demonstrated by Professor Yang’s research group can potentially harvest 75 percent of the wasted photons from LCD backlight and turn them back into electricity.” Intel supported the research through its Intel Labs Academic Research Office (ARO).

“In the near future, we would like to increase the efficiency of the polarizing organic photovoltaics, and eventually we hope to work with electronic manufacturers to integrate our technology into real products”, Yang said. “We hope this energy-saving LCD will become a mainstream technology in displays.”

Below is a short clip of the UCLA team making the polarizing film using P3HT, an organic polymer widely used in solar cells.

The research is published in the online version of the journal Advanced Materials.

(Source: UCLA)

Christopher Jablonski is a freelance technology writer.

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Scientists create wireless network with LED room light

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Summary: German researchers have demonstrated how regular LEDs can be turned into an optical WLAN with only a “few additional components.”

Lights are no longer just for lighting up.

Scientists from the Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute (HHI) in Berlin, Germany, have developed a new kind of optical WAN with enough throughput to allow four people in a room to watch a film from the Internet on their laptops, in HD quality.

The technology can potentially be used on both laptops and mobile telephones.

Credit: Fraunhofer HHI

The researchers say they’ve achieved a transfer data rate of 100 megabits per second (Mbit/s) without any losses, using LEDs in the ceiling that light up more than ten square meters (90 square feet). This area also marks the radius in which the receiver — a simple photo diode on the laptop — can be placed before it is out of range.

In lab tests, the team pushed speeds even further using red-blue-green-white light LEDs. Those transmitted data at a blistering 800 Mbit/s, setting a record for VLC or visible light communication.

Klaus-Dieter Langer, the project leader said:  “For VLC the sources of light – in this case, white-light LEDs – provide lighting for the room at the same time they transfer information. With the aid of a special component, the modulator, we turn the LEDs off and on in very rapid succession and transfer the information as ones and zeros.”

The system works because the modulation of the light is imperceptible to the human eye. Langer explains: “The diode catches the light, electronics decode the information and translate it into electrical impulses, meaning the language of the computer.“

While rigging a system to turn LEDs into a transfer medium may not require many components, sending data over light waves is not without challenges. The key one is that whenever on object (like a hand) comes between the light and the photo diode the transfer is impaired.

The HHI scientists stress that the optical WAN is not intended to replace other networks, but rather serve as an additional and low-invasive option in environments where radio transmission networks are not desired or not possible, such as hospital surgical rooms.

“Combinations are also possible, such as optical WLAN in one direction and PowerLAN for the return channel. Films can be transferred to the PC like this and also played there, or they can be sent on to another computer,” notes a release.

The scientists will demonstrate how videos are transmitted by light at the International Telecommunications Fair IFA (Internationale Funkausstellung IFA) in Berlin from September 2-7, 2011.

Related:

MIT: built-in motion sensors in devices improve wireless data rates

A wireless radio that can send and receive signals at the same time

‘Microring’ wireless devices could nix wires in homes, offices

Christopher Jablonski is a freelance technology writer.

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