Tunable visible light emitter using the 7 element framework

Objectives that should be achieved by the emitter are

1. No phosphors. It should be a direct emission. Electrical energy converted to light energy.

2. Electrically tunable. We should be able to modulate the color of the light by changing the voltage applied.

3. Our light source should be warm white by default.

4. It must not use complicated packaging. Should be rugged by default.

And finally it must be built with the 7 widely available elements (h,c,n,o,na,si,fe)

The obvious answer is to make sic which has proven electroluminescent properties. However the large energy needed for its synthesis & comparatively lower efficiencies reduce its appeal. While the latest research on this subject has put forward new ideas of improving efficiencies chief among them being fabricating nanowires & engineering defects in the crystal ,the high energy required is still a problem.

One of the methods of reducing energy for synthesis of sic based leds would be to use a molten salt system. And efficiencies can be improved considerably(17%) by doping sic with donor acceptor molecules. Another way is to use the exceptional fluorescent properties of sic and use them as phosphors excited by UV(which can be generated with sic or carbon field emitters).

Even after making these adjustments we don't have control over the leds. And such a device will cause problems in making TVs for example.We will be limited to reflector/transmitter based designs. If the size of leds can be controlled,then it would be possible to make micro led tvs which are conceptually a lot simpler than lcds or crts. Individual pixels can be turned on or off.

Carbon based materials allow us to pattern down to a micrometer level.But light emission from them is still a problem. The major problems with carbon based leds are

1. Lack of band gap in carbon nano materials. Those that have a band gap like nanotubes have so in the IR range.

2. While carbon has an excellent black body emission pattern this renders it susceptible to oxidation reducing its lifetime. And efficiency while decidedly better than filaments it's still less than leds.

3. Fluorescent quantum dots are functionalized and while they have the good quantum yield, making such devices would force us to deal with the same limitations as sic leds but worse because functionalized carbon quantum dots are not as stable in the UV regime.

The solution here is to make nano carbon composites that combine the best properties of carbon nanotubes & quantum dots. Pure carbon materials with tunable gap enclosed within a stable & patternable structure. This kind of a design looks like nano tubelight in which fluorescent materials light up on application of high enough electric fields.Experimentally the composite structure has been demonstrated(from carbon nanobuds,nanopeas to growth of carbon chains with a band gap of upto 2.3 ev within cnts) but it has not yet been effectively used to create lighting devices.

Black body radiators can achieve max efficiency of 43%(in visible light radiation) its about the same for leds. Current devices are at about 18-25% and we are targeting the same lower end.

The key differentiating factor for us will be innovation in materials. Specifically getting rid of rare earths in production of light. Possibility exists to get close to the maximum efficiency with carbon based materials but that can be left for some other time. Our goal is achieved if we can make it work at 18%.

https://akshatjiwannotes.blogspot.com/2024/11/optical-properties-of-carbon-allotropes.html

https://akshatjiwannotes.blogspot.com/2024/11/band-gap-engineering-with-nano-carbon.html

https://akshatjiwannotes.blogspot.com/2024/11/doping-strategy-for-all-carbon-materials.html

https://akshatjiwannotes.blogspot.com/2024/10/thoughts-on-synthesis-of-carbon.html

https://akshatjiwannotes.blogspot.com/2024/10/some-recent-breakthroughs-that-solidify.html

Comments

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Notes by Akshat Jiwan Sharma

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