Stephen Forrest at Michigan University and Yuri Sun at Princeton have their paper describing their new method of building organic light emitting diodes (OLEDs) available in Nature Photonics. Like the semiconductor light emitting diodes (SLEDs) from Purdue’s researchers we looked at last week these scientists are driving to a highly efficient LED based on the organic materials for construction rather than metals on silicon. As for which is best, time will tell, but today the actual paper can be read, the technology examined, and some interesting conclusions reached.

The white organic light emitting diode, or WOLED, is another take on LED that is made with organic sourced materials which offers some advantages over metal and silicon, that has until this breakthrough had very similar problems. For both LEDs, the issue is getting the light out of them as producing the light efficiently to begin with isn’t the problem. One has to remember LEDs are very small. The little lights we see so many of are usually mounted inside a transparent “holder” just to get them big enough to work with. Naked of the holder they are very tiny. This aspect is part of what allows them to be efficient. It also shows that one needs a LOT of them to illuminate instead of simply signaling activity.

OLED Buildup

Like in SLEDs an OLED is a layered up build of materials. The innovation here is that one of the layers is a grid, which in the OLED is a set of “walls” if you will, that keep the light directed up and out rather than trapped within. The next innovation is to drop a polymer micro lense on the glass layer to direct the light out into the surrounding space.

Starting with a clean glass substrate the scientists coated the glass with 120 nm of transparent indium tin oxide, then applied and formed (see the paper at “Methods”) the low-index grid that controls and directs the light. Next is applying the organics that convert the electrical input to light and finally the electrodes that introduce the electricity are applied. That’s massively simplified, yet the construction yields a simple device once made.

OLED Grid Closeups

I suspect that this technology has quite a way to go to reach commercial production. On the other hand should a producer get to a competency for volume the costs should get quite low as the materials are inexpensive organics, glass and a tiny bit of aluminum. It’s the process that looks like a matter to master. The innovation here is in skills over any “new” materials. And that is what is so impressive – the skill and the intellect used to develop it.

The conclusion for me is the surprise of innovation in skill whereas last week’s saw an innovation in materials. Two different approaches to a similar problem in devices made with very different materials. LEDs offer an interesting story that’s getting more so each few months. As they close in on compact florescent for efficiency and costs drop the switch over to LED offers a huge release of generating to do other things. Lighting is said to be as much as 22% of the load for electrical generation, so every reduction is power to do something else. I’m looking forward to the results. For an example of the prowess that LEDs can bring, check out high definition LCD TVs, one with florescent and one with LED. Then you too will share my excitement!


8 Comments so far

  1. McBuild » Blog Archive » Innovating the Organic LED to High Output on July 28, 2008 7:09 AM

    […] Like the semiconductor light emitting diodes (SLEDs) from Purdue=92s resear= chers we looked at last week these scientists are driving to a highly ef= ficient LED based on the organic materials for construction rather than= metals on silicon. …Posted from By Brian Westenhaus […]

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