Flat Lights: The Light Emitting Capacitor

[twilight_sailing]

We've talked about flat lights before, most notably, OLED and PHOLED systems which are basically light emitting diodes (like the one that makes your flash drive glow) but created with organic plastics so they can be flat and transparent. But we haven't brought you the story of light emitting capacitors (LECs) which use a fundamentally different technology, with spectacular results.

Capacitors are making a big comeback, what with their super-powered cousins showing up in electric vehicles and possibly saving the world by collecting star power. But this capacitor has a layer of phosphorescent gel coating the top of the dielectric substance. So, when the current passes from the front electrode to the rear electrode, the capacitor emits light.
http://www.ecogeek.org/content/view/338/

[skids]

1. Very interesting...

I wonder if the phosphors they are using are quantum dots or regular chemicals, and if the latter whether quantum dots could be used to improve the product.

This and better LEDs and quantum-dot-coated LEDs mean in 20 years you'll never have to worry about breaking a glass lightbulb again -- not to mention the lower electricity bills.

[bluerum]

2. self delete

[bluerum]

3. self delete

[bluerum]

4. Capaciters do not conduct current. I suspect that the gel is some

type of poled coating that emits owing to some type of field effect.

Although, if the coating is in electrical contact with the electrodes of the capacitor then there may be something else going on.

[skids]

6. Capacitors do conduct current -- alternating current.

This device appears to use the displacement current (in this case since there is a dielectric, a real current, using the term as it was originally used not as the field effect equivalence) resulting from AC charge/discharge.

[Syncronaut Seven]

5. Old technology? See here

http://members.misty.com/don/oddbulb.html

Electroluminescent/"Limelight"/"Californeon"/"Indiglo" lights
An electroluminescent lamp is basically a capacitor with a "lossy" dielectric that includes some sort of phosphor to make light from part of the dielectric loss. They must have AC, or at least very unsteady DC, in order to work. These typically require somewhat high voltages. A minimum of something like 20 volts or so is needed to make them work, and these typically use 100-140 volts AC, up to 200 volts if the waveform is a square wave. At power line frequencies of 50-60 Hz, electroluminescent lamps are not bright, but last several years. To get more brightness, AC of higher frequencies of a few hundred Hz (possibly even a few KHz?) is needed.
The "Lime Light" is an electroluminescent night light that has an appearance something like a miniaturized TV set (with no controls, speaker, antenna, etc). It consumes some very small amount of power (I forget exactly) like about 1/16 watt. The screen glows with a slightly whitish, maybe slightly bluish shade of green roughly like that of many green traffic lights. The light output is a bit more than that of NE-2G green neon lamps, easily enough to illuminate even a large room or two for night vision. The luminous efficiency is comparable to that of incandescent lamps, although much higher for night vision.

"Californeon" is a name for flexible electroluminescent strips that can be worn by cyclists, joggers, Trick-or-treaters, partyers, etc. These come with an inverter that produces the necessary high voltage higher frequency AC from batteries. I believe these are the bright, slightly whitish green things I have seen before.

For more info on the web for "Californeon", go to Altavista (http://www.altavista.com) and do a simple search on californeon. You will get about a hundred hits including some places that sell this stuff.

Other suppliers of electroluminescent stuff include:

Flatlite.

Neontrim, which sells electroluminescent "wire".

Coollight, another supplier of "neon wire".

Elam, a manufacturer.

Some LCD computer screens used in laptop computers have electroluminescent backlights. These usually glow with a color roughly like that of a "cool white" fluorescent lamp. An inverter is used to supply AC with a voltage around 100 volts or more and a frequency in the hundreds of Hz or maybe one or two KHz. Some miniaturized TV sets also have electroluminescent backlights. So do a few building entry intercoms and maybe other things with LCD displays.

"Indiglo" is a brand name of smaller electroluminescent lighting devices used in some watches and a nightlight and maybe a few calculators and the like.

Some smaller screens have LED backlights.

Many computer screens and maybe a few TVs have fluorescent backlights. If you have a spectroscope, or even a diffraction grating or a CD to use as a diffraction grating (requires practice), you can tell the difference. Fluorescent lamps emit a spectrum containing mercury lines as well as the spectrum of the phosphor (which varies). The mercury spectrum has significant lines in the yellowish green and violetish blue, and weaker lines in the yellow and deep violet. Phosphor spectra vary, sometimes basically continuous and spanning most of the visible spectrum, sometimes consisting of bands. A few phosphor bands have been known to be very narrow, resembling lines. Such is the orange-red line/band found in the spectra of most compact fluorescent lamps.

[JohnWxy]

7. interesting!