In the past, I’ve tended to categorize light sources something like this:
- Gas-Discharge Tube,
- LED (Semiconductive, Light-Emitting Diode).
But, there seems to be a light-bulb on the market right now, that defies this system of categorization, as shown here:
The yellowish parts that emit the light will look something like decorative, low-temperature tungsten filaments when lit, but are not in fact filaments at all. They seem to be narrow, tubular, Electroluminescent parts of unknown composition.
What I find most striking about this design, is that it also does not have a power converter in the base, instead just applying the 110 VAC house-current directly to the apparently-electroluminescent material, with passive wires inside the bulb.
When trying to form some sort of guess, as to what the EL material could be, my attention goes next to the fact that by now, organic semiconductors exist. These types of semiconductive polymers are often the basis for OLEDs, also known as Organic Light Emitting Diodes.
With a true LED design, actual, electrical diodes need to exist, that operate at low voltages and correspondingly higher currents, and due to which, the light-bulbs have required power-converters in their base. Those power-converters would also be the main point of failure, that limits the lifespan of an LED light-bulb. Those power-converters have also tended to become quite hot in-use.
But because this type of light-bulb does not form an electrically-correct diode, I would not call this form an LED. What seems to have been done, is that some mixture of organic semiconductors has been pressed into a shape, and the house A/C applied directly to it. This means that they could potentially outlast more-conventional LED-light-bulbs, but should also have slightly lower energy-efficiency.
They look pretty when lit.
The packaging of this light-bulb made some statements which I do not believe to be entirely accurate.
- The lightbulb-type is stated to be an LED,
- It’s said to be equivalent to a 40W incandescent,
- It’s said to have a life-expectancy of 9 years,
- It’s stated to draw 4.5W of real power.
The only packaging-information above which I believe to be accurate, is the consumption of 4.5W.
( Last Updated 08/31/2017 … )
I think that rather than to pay attention to how many Watts of Incandescence-Equivalent they have, one should pay attention to how many Lumens of brightness light-bulbs output, even though I don’t know offhand, how a Lumen is defined. In my mind, a 100W incandescent output approximately 1500 Lumens. A 60W used to output about 1000 Lumens. ( :1 )
(Edit 08/31/2017 : In my own past it used to be, that if we had a standard, 60W incandescent light-bulb, with clear glass, and if we looked at the filament when this light-bulb was turned on, we would actually hurt our eyes, because that filament was too bright to look at. This was also the initial reason for putting frosted glass around it. In the case of a 40W light-bulb, the filament was narrower, for which reason the total amount of light-energy output was lower. But, the surface-brightness was still defined by the temperature of the tungsten filament. :2 )
When an actual tungsten filament is run at ~a lower temperature than usual~ , more-yellowish, warmer-looking light results, which is grouped around longer wavelengths. But then, an even-higher percentage of the energy output by the light-bulb, will be in the infra-red part of the spectrum. resulting in a device which has purely decorative purpose. In that case, as little as 10% of the electrical power drawn, may result in humanly-visible light. (And in that case, it was safe to enclose the light-bulb in clear glass.)
(Edit 08/31/2017 : IIRC, The decorative light-bulbs by design, happened to have power-levels up to a maximum of 40 Watt. This was also a forced outcome, of what the A/C house-voltage was, and of how long or thick a straight filament was allowed to be. But, such decorative light-bulbs also had a different shape from the standard light-bulbs. The decorative ones could have been cylindrical, or otherwise artistic in the shape of the glass. )
So if a seller is selling this light-bulb-type as a replacement for a decorative light-bulb, that decorative light-bulb could indeed once have drawn approximately 40 Watts of power, but only output about 400 Lumens of visible light ! But according to linear equivalence, a buyer today might expect about 600 Lumens from the same light-bulb.
It just so happens that the packaging of the light-bulb I showed above, only promises a brightness-value of “350 Lumens”, which is not printed as largely, as the ~40W~ is printed. Yet, because I am aiming to serve a decorative purpose with these light-bulbs, I’m not offended.
It might be tempting to think, that all that is needed, is a partially-conductive – i.e. ohmic – form of polymer. But indeed, if the type of polymer was really just intrinsically conductive, then current would flow, energy would be converted into heat, but no light would be emitted.
In LEDs, a quantum of light is emitted, when a free electron encounters an electron-hole, and when the two cancel. Therefore, whatever type of polymer they may be using, would need to be able to carry both types of particles, in order to emit light.
1: ) I grew up in the 1970s and 1980s. In those days, the only way to prevent the combustion of the tungsten filaments due to atmospheric oxygen, was to seal them in a high vacuum. I.e., Those light-bulbs had interiors which were anoxic, due to evacuation. This also meant that the glass walls of the light-bulbs needed to be quite thick, to withstand the atmospheric pressure from the outside.
The way similar incandescent light-bulbs are made today, involves filling their interior with a mixture of nitrogen, and inert gasses. This makes their manufacture less expensive than it would have been in the 1970s. Tungsten will not react with nitrogen.
But, nitrogen and other inert gasses, at 1 atmosphere of pressure, are dense enough to transport heat from the filament to the inside surface of the glass, by way of convection. This also makes incandescent light-bulbs today less energy-efficient, than they would have been in the 1970s. Therefore, consumers today should also not expect, that a 100W incandescent will still deliver 1500 Lumens, nor that a 60W incandescent will still deliver 1000 Lumens. They will deliver less brightness, as more of the supplied electricity is heating up the glass, which is heating up air that is touching the glass from the outside…
2: ) One interesting observation about incandescence, would be that the surface-brightness was independent of relief- or depth-geometry in the surface. I.e., the amount of surface brightness of a square centimeter of tungsten at its melting-point, was almost equal to that, of a hollowed-out cubic cavity, 1cm along each length, at the surface of tungsten at its melting-point. I think that the main reason, fw a certain measure of light was defined by the latter, back in the 1960s, was the desire on the part of Scientists to reference the behavior of a Physics-Black-Body, while tungsten does not truly form a black-body. This property happens to be true for Physics-Black-Bodies.
The surface on one face of such a hollowed-out volume would absorb some of the incandescent light emitted by the opposite face, but would not emit more light for having done so.
But one observation I made about practical tungsten filaments designed to work at 110V or 220V, was that they would often have the 3D geometry, not just of a spiral, but in some cases forming a narrower spiral within a wider spiral. And of course a question should arise as to why Engineers did that, if doing so would not affect brightness much.
And the main reason for this, was simply to assure that the filament would have the correct amount of electrical resistance, so that the amount of current that was to flow through it, would become consistent with the total amount of energy radiated from it, especially with light-bulbs above 40 Watt, run on house-current.
Hence, it would be possible just to double the diameter of a working tungsten filament, which would double its cross-sectional circumference, and which would therefore double the surface area of the filament. But then an unintended side-effect could be, that we’d have quadrupled the cross-sectional area, and therefore divided the linear resistance of the filament by 4, so that 4x the current would also flow through it. And then the result we’d get if this was not done in a calculated way, would be a filament which also becomes too hot, and which burns out quickly.
And so, if we wanted to multiply the emitted light-energy by two times the root of two, we’d need to multiply the effective length of the filament by the square root of two as well, so that the matching amount of current would flow from the same supply-voltage. And a more-practical way to proceed, was to increase the degree of helical orbiting, which actually had no effect on surface-brightness, just to simplify the design somewhat.
The resulting filament would have an optical diameter not equal to its real diameter.