Friday, July 25, 2008

OLED breakthrough at U. of Michigan and Princeton: 70 Lumens/Watt!


OLED Light Microscope photo

Paradoxically, technology both moves very fast yet more slowly than we sometimes wish. New things are coming out all the time (like this big LED breakthrough from Purdue and telescopic pixel screens), but we get used to them so fast that we're always looking ahead and it never seems to get there fast enough. It was only a few months ago that we wrote about a big organic light-emitting diode (OLED) breakthrough by Osram who had succeeded in making OLEDs that produced 46 lumens per watt.

Better OLEDs!
Now researchers at the U. of Michigan and Princeton are saying they made OLEDs that can produce 70 lumens per watt (compared to 15 lumens per watt for incandescent), and that they might be able to do even better than that. To achieve that impressive efficiency, they are using a grid combined with micro-lenses, all of it on the nano-scale (the lenses are 5 micrometers wide).

OLED Breakthrough Technical Details

Technology Review:

In OLEDs, white light is generated by using electricity to send an electron into nanometer-thick layers of organic materials that behave like semiconductor materials. Typically, the light in the substrate is internally reflected and runs parallel and not perpendicular. That's the crux of the problem because the light can't escape in the vertical direction without some coaxing. In Forrest's devices, the grids refract the trapped light, sending it to the five micrometers dome-shaped micro lenses. The light is sent off in a vertical orientation that helps release the trapped rays.

Small OLED screen photo

Benefits of OLEDs
A little while ago, Collin wrote a little primer on LED and OLEDs. If you are curious about the benefits of this technology from a green perspective, check out his post LED and OLED Home Lighting Systems Almost Ready for Prime Time. There's also HowStuffWork's article on OLEDs.

You can also read about Osram's OLED research in this post: Osram Claims Warm White Organic LED Breakthrough.

The bottom line is: Better and cheaper OLEDs can mean greener flat screens and light sources.

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