Research shows how LED efficiency is far from optimal

Discussion in 'Advanced Cultivation' started by Coco123, Dec 2, 2016.

  1. Coco123

    Coco123 New Member

    [​IMG]
    Researchers recently found that light emitting diodes’ efficiency can be impeded by trace amounts of iron, which is a byproduct of LED production. That conclusion was the result of an international study involving KTH Royal Institute of Technology and other universities, including UC Santa Barbara, Rutgers University, the University of Vienna and the Center for Physical Sciences and Technology.

    With the UCSB group, led by Chris Van de Walle, Saulius Marcinkevicius discussed his recent experiments on iron-doped gallium nitride during his recent sabbatical at UCSB. “When they developed a theory explaining our experimental results and wrote the paper, they were kind to include me as a co-author,” he says.

    At KTH, Marcinkevicius and Professor Sebastian Lourdudoss , a researcher in the Department of Material and Nanophysics, have been studying iron-doped semiconductors on and off since 1997.

    Looking forward, Marcinkevicius says he will focus on building on his lab’s enhanced experimental capabilities in ultrafast near-field optical spectroscopy. “Now we are able to map optical properties of materials, among them those of gallium nitride based nanostructures, with unprecedented richness of features. That certainly benefits our collaboration with UCSB.”

    “Lighting is a multibillion dollar industry, and each step in the improvement of LED efficiency produces large benefits,” says Saulius Marcinkevicius, Professor of Optics at KTH. “LEDs are very efficient lighting sources. Still, the efficiency is far from optimal, especially at high powers and in the green spectral region.”

    Better understanding of the physical mechanisms that affect the LED efficiency could lead to their improvement, Marcinkevicius says. “In this paper, we are discussing one such effect.” The investigation was published in Applied Physics Letters. In LED lighting fixtures, each tiny “bulb”, or LED, contributes light through recombination of electrons and electron holes – the two charge carriers in semiconductors.

    When electrons and holes recombine, they basically annihilate each other. The electrons fall into the empty state associated with the hole and what is emitted is the energy difference between the initial and final state of the electron. In the case of a radiative recombination, the emission is in the form of photons – or light.

    In an ultraviolet, blue or green LED, this activity takes place inside a nanostructure based on the semiconductor material, gallium nitride (GaN). A bias voltage is applied via electric leads to inject electrons and holes into the nanostructure.

    However, if the semiconductor material contains many defects and impurities, such as iron, the resulting recombination may be nonradiative, Marcinkevicius says. "That is, it will produce heat instead of light. The faster this nonradiative recombination, the lower the efficiency of the LED."

    The researchers found that unintentional introduction of iron impurities – even at very modest concentrations (1015 cm–3) – leads to a substantial nonradiative recombination, with recombination rates similar to that of the radiative process.

    Where does the iron come from? Apparently it may be introduced unintentionally from stainless steel reactors that are used for making LED structures. “Since even miniscule iron concentrations affect the recombination process, iron in LED structures may be a serious culprit in the quest for the ultimate LED efficiency,” he says.

    The finding is actually a corroboration of ideas Marcinkevicius had already been working with, and a direct result of his recent sabbatical at UCSB. Assisting him was PhD student, Tomas Uzdavinys.

    “Just before this paper, we published an experimental paper on ultrafast electron dynamics in iron-doped gallium nitride, in Journal of Applied Physics. Trying to explain our experimental results, we arrived independently at similar ideas as the UCSB group, which is working with theoretical modelling.”

    Knowing more LEDs, go to
     
    Last edited by a moderator: Dec 2, 2016
    Max Rockatansky likes this.
  2. OldSmokey

    OldSmokey Registered Users

    They've come a long way with LEDs in the last few years.
     
  3. Justcheckingitout

    Justcheckingitout GK Old Timer

    Its all rocket science to me, as long as my gun led shines when I need to shoot some one in the dark and my grow lights grow bud good. Its prob like everything that is China related, will not be 100% great till USA or Germans make it.
     
  4. SirStynkalot

    SirStynkalot A Fat Sticky Bud

    I was wondering about this. I tried to do a heat gain study on a commercial scale and I just couldn't find any good info on LEDs for it and when I ran it myself the efficiency rates didn't hold up to either the LED manufacturer's claim that energy conversion rates were near-perfect or the engineers' claims that every 1 watt makes a flat 3.4 BTU of heat regardless of fixture (that's a pure conversion rate and a big "fuck you" in engineer-speak). It was somewhere in the middle meaning there was at least some loss. Pity - code officers listened to the engineers not me and we had to way, way overbuild our HVAC to get licensed.
     
    Last edited: Mar 25, 2017
  5. Justcheckingitout

    Justcheckingitout GK Old Timer

    On a side note, my onyx bloom and Indus lights from Rapid leds are doing good, I dont have a light meter but they are still growing as big as buds as always. I still get less heat than hps for the area I use them in. Its not huge but still 16+ deg cooler.
     
  6. SirStynkalot

    SirStynkalot A Fat Sticky Bud

    Sorry, got drunk and posted a wall of text. I'll abridge. I like this topic. Don't like RapidLED too much though.
     
    Last edited: Mar 26, 2017
  7. Justcheckingitout

    Justcheckingitout GK Old Timer

    Just courious what you dont like about rapid? I like the bang for the buck with rapid, that and customer service is awsome. I would like to make a one rack custom cob rack but its hard to get everything else done from day to day. One day thou.
     
  8. nappyhawk

    nappyhawk New Sprout

    Also curious of ur issue with rapid. I have one of their cree lights and dealt with them via email with an issue I had. Great people to deal with in my opinion.
     
  9. SirStynkalot

    SirStynkalot A Fat Sticky Bud

    They sent me a broken unit and the customer service was pretty poor when I tried to trade the unit back in. I'm also not sure they're the most efficient model out there and thought that even if the other models were a whole lot more expensive the small efficiency differences would probably make a difference over several years.
     
  10. Justcheckingitout

    Justcheckingitout GK Old Timer

    Yeah I had a unit show up and the shipping company messed it up good. But any time I had a issue they always took care of it fast and even fixed a light that was a month past warrenty. I just paid for shipping and had another they charged me $17 for the part that was broke and I paid shipping and swaped out the part my self. Yeah It was 6 months past the warrenty. They usually try to ship you the part to change out if you can do the work (easy stuff) to get your unit up and
    running faster, so you have less down time and that way you dont have to pay shipping there and back on some stuff. But they usually work with you to get you a working unit the fastest cheapest way. Which is cool. They are quality lights, maybe not the most efficient lights but for the $1,000's of dollars on other lights that do compair, the money saved works good for me to buy more lights. Drucider has some great tech info around here on them that sold me. "LED's lets get serious" was the thread I think. I think he had another one also.
     
    SirStynkalot and nappyhawk like this.

Share This Page