Look Ma, No Heatsink, New 100% Efficient OLEDs - Page 1
Forum section: electronics / general

author: SgtRock
author_rank: Unknown
timestamp: November 25, 2011, 04:37:56 am
content: Greetings EEVBees:--See below link for article from Science Daily, outlining a paper in Advanced Materials about OLEDs that convert all electrons to photons.http://www.sciencedaily.com/releases/2007/04/070416221943.htm--Quote from article:“There is no waste of electricity,” Jabbour says. “All the current you are putting into the device is being used to produce light.--Did I hear that correctly? Did Professor Jabbour just say "no waste of electricity", other that the PS we assume. Advanced Materials is a well respected, peer reviewed scientific journal. The mind boggles. Indeed their may be a catch, but the Prof. did not leave himself much wiggle room. Now, I realize that infrared photons (heat) are "light" also, but that cannot be what he means, can it?"Get ready, little lady. Hell is coming to breakfast."Chief Dan George 1899 1981Best RegardsClear Ether

author: sub
author_rank: Regular Contributor
timestamp: November 25, 2011, 09:00:57 am
content: I suspect that the qualified "internal quantum efficiency" is the key term here. You might get the maximum possible number of emitted photons, but they won't all reach your eyes. One would still experience resistive losses, and some portion of the emitted light will end up being re-absorbed by the device, among other things. It might still be high-efficiency, but certainly not 100%.

author: Unknown
author_rank: Unknown
timestamp: November 25, 2011, 09:13:25 pm
content: Reading theoriginal article (behind a paywall), the key appears to be internal quantum efficiency. The figures showing quantum efficiency are in the 10-20% ballpark. The claim is that the quantum efficiency of 18% at low brightness (10-3to 10-2mA/cm2, not a high power LED) should be close to 100% internal quantum efficiency, because the coupling efficiency is about 22% according to another article. Based on their hypothesis, that article claims that the internal quantum efficiency of their LED should be at least 0.9 at 1.5 uA/cm2. I'm not sure if this was determined for the same optical system. The claim of 100% efficiency is too strong, in my opinion. The 18% is the peak outlier in a figure with no error bars, and this is still less than the 19% that was claimed to be at least 90% efficient in another system.But in the real world, a 100% efficiency at 75nm from the emitter isn't that useful if only 20% is ends up into usable light.

author: Unknown
author_rank: Unknown
timestamp: November 25, 2011, 10:54:52 pm
content: Quote from: alm on November 25, 2011, 09:13:25 pmTough economic times - it seems more than one is following the CERN example.

author: SgtRock
author_rank: Unknown
timestamp: November 25, 2011, 11:06:17 pm
content: Dear Alm& Alex:--I appreciate hearing from folks who not only read Advanced Materials, but know what they are talking about. My understanding of LEDs, light, efficiency, frequency and color temperature are at a beginners level. That is why I posted the article. To paraphrase Fred Allen I guess you could say that my under standing of this subject could be placed "in a gnats navel and still have room for two caraway seeds and the heart of an agent." Or as Enrico Fermi once said: "Before I came here I was confused about this subject. Having listened to your lecture I am still confused. But on a higher level"--I will ponder all that you have said, and when I understand enough to ask an intelligent question, I will endeavor to do so."I could see that, if not actually disgruntled, he was far from being gruntled."P. G. Wodehouse 1881 1975Best RegardsClear Ether

author: Unknown
author_rank: Unknown
timestamp: November 25, 2011, 11:10:32 pm
content: Quote from: SgtRock on November 25, 2011, 11:06:17 pmYou are already at the top 5%.