Some Speculation About Practical Phosphors

In theory, the way fluorescent light-bulbs work, is that they already have a light-source of shorter wavelength – and therefore of higher photon-energy – to excite a phosphor, the latter of which emits a pleasant mixture of wavelengths of light – in general, longer wavelengths than that of the energy-source; any mixture of phosphors will do. The light source is allowed to be a Blue LED, rather than a UV light-source.

What I discover in practice, is that the choice of phosphors manufacturers can work with is rather limited. For LED-Light-Bulbs that are stated to produce a color-temperature of 2700K, they tend to use “Y3Al5O12Ce”. Additionally, I have discovered the availability of a newer type of light-bulb, as shown in this photo:

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In which a higher voltage is applied directly to an Electroluminescent material.

What strikes me as both convenient and remarkable about these light-bulb-types, is that The color matches very closely. What this observation would seem to suggest, is that the EL material used in the newer light-bulb-type is a hard crystal, that matches the composition of the phosphors used in the LEDs, mentioned above. Additionally, this would seem to suggest, that the layer of the phosphors used in the LED-Light-Bulbs described as having 2700K color, is rather thick, so that very little of the Blue LED’s light passes through, since the light produced via EL has no Blue LED to modify its color-quality.

I suppose then, that the manufacturers have simply added another substance to this phosphor – in small quantities – that causes it to become conductive.

Dirk

 

I could make a loose inference, about what Lumens are.

In the later part of my childhood – in the 1970s and 1980s – we had incandescent light-bulbs, and we knew that only a small part of the so-called light they emitted was in the visible part of the spectrum. We often used this light-bulb type, because we had no better alternative. We knew that the visible part of the emitted light might have been 15% or 10% of the consumed energy.

Granted, in Industrial or Commercial Lighting, there existed other types of fixtures, such as mercury-gas-discharge tubes, that excited a phosphor with ultraviolet light, so that the phosphor was made to fluoresce. Or in some cases simply – a gas-discharge tube, with a gas-mixture of a composition unknown to me.

But, when I go to buy light-bulbs today, as an adult, like all the other customers, I see Compact Fluorescent Light-Bulbs, as well as LEDs, the brightness of which is stated in Lumens. What I generally tend to find, is that light-bulbs of the fluorescent family, which are meant to be equivalent to the ~Old, 100W~ incandescents, tend to draw approximately 23W, and are stated on the packaging to produce about 1500 Lumens.

Lightbulbs of the LED family with the same equivalence, are stated to draw about 16W, and to produce about 1500 Lumens. I have actually found LEDs, which are stated to draw about 17W, and to produce 1600 Lumens of visible brightness, but which possess a visibly-larger base, from the other types.

If I could just hazard a guess, I’d say that one way to understand Lumens, is to start with the Watts of light in the visible part of the spectrum, and to multiply those by 100. What this would suggest, is that the most-efficient LEDs waste about 1W as heat, while then fluorescents still tend to waste a bit more energy, such as perhaps 8W – some of that in the form of UV light, making those approximately 65% efficient. But this would also mean, that the efficiency of modern LEDs is hard to improve upon. If the brightest variety only seem to produce 1W of waste heat, out of 16W or 17W consumed, it would make most sense to infer that in that range of efficiencies, the Wattage can be translated into Lumens quite easily. More Watts will simply produce more light, and fewer Watts will produce less light. In percentages, the LEDs would seem to have an efficiency of about 94%.

If we have a new light-bulb type, that draws 4.5W, but that produces visible light amounting to 350 Lumens, it would follow from this thinking, that this type is wasting about 1W / 4.5W. In percentages, this would imply an efficiency of 78%.

I suppose that I can offer a comment on the temperatures which the light-bulb-bases of household LEDs reach…

Continue reading I could make a loose inference, about what Lumens are.

A Type Of Light-Bulb That’s New To Me

In the past, I’ve tended to categorize light sources something like this:

  • Incandescent,
  • Gas-Discharge Tube,
  • Fluorescent,
  • Phosphorescent,
  • Bioluminescent,
  • Electroluminescent,
  • 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:

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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 … )

Continue reading A Type Of Light-Bulb That’s New To Me