Phosphor Pink LEDs

Note: Information about phosphor purple LEDs can now be found here.

Radio Shack # 276-0019 Pink 5mm LED, $3.49 (for two)
Purchased 04-26-09, tested on 04-29-09
This is a phosphor-type pink LED in a water-clear 5mm epoxy package.

When the beam spot is viewed on a white surface, this LED produces a pink color without the distinct bluish hotspot seen in the LED directly below this one.


Beam photograph at ~12".

Measures 2,270mcd on a Meterman LM631 (now Amprobe LM631A) light meter.
Viewing angle is listed as 30.

Vf is 3.152 volts at an If of 19.28mA.

Spectrographic analysis
Spectrographic analysis of this LED.
USB2000 Spectrometer graciously donated by P.L.


ProMetric analysis
Beam cross-sectional analysis.
Image made using the ProMetric System by Radiant Imaging.




Radio Shack # 276-0019 Pink 5mm LED, $3.49 (for two)
Purchased 02-14-09, tested on 02-18-09
This is a phosphor-type pink LED in a water-clear 5mm epoxy package.

When the beam spot is viewed on a white surface, this LED produces a pink color with a distinct bluish hotspot.


Beam photograph at ~12".
I do not yet have the target at my new Federal Way WA. USA location, so I shot this photograph onto the white wall just to the right of my "BIG SCARY LASER" poster (sent by www.megagreen.co.uk).

Measures 1,660mcd on a Meterman LM631 (now Amprobe LM631A) light meter.
Vf is 3.023 volts at an If of 19.28mA.

Spectrographic analysis
Spectrographic analysis of this LED.
USB2000 Spectrometer graciously donated by P.L.



5mm phosphor pink LED, Lumex part number SSL-LX5093PC
(Rec'd 07-31-08, tested 08-04-08)
This is one of three LEDs sold as "InspirationLEDs" by Lumex. Although this might look like an ordinary 5mm clear through-hole LED, it differs from most others because it is phosphor-based, and emits a pink light. The phosphor formulation is very likely inorganic and therefore, stable; as this LED is meant to be used on a continuous basis.

It emits a pink light, and it has a beam pattern that's smoother in general profile than any non-phosphor LED - but I rather expected this from a phosphor lamp.


Beam photograph on the test target at 12".
Intensity measures 4,080mcd at an If of 19.28mA. Vf is 3.152 volts.

Spectrographic analysis
Spectrographic analysis of this LED, using newer spectrometer software.


Spectrographic analysis
Spectrographic analysis of this LED when driven at 19.28mA.


Spectrographic analysis
Spectrographic analysis of this LED, driven at ~1.9mA.



Radio Shack # 276-0019.
Received & tested 06-17-08
A well-known lighting expert on the US east coast sent me a couple of these LEDs along with a few others.
This is a 5mm (T1 3/4) through-hole LED in a water-clear expoxy body.

When powered, it emits a slightly bluish-tinted pink light.
Intensity listed on the package is "2,850mcd (typical)"; this one measures 3,170mcd at a drive current of 19.28mA.

The packaging also indicates that these LEDs are RoHS-compliant.
To put it simply, there are no heavy metals like lead, cadmium, or mercury to contaminate the landfill when this LED is disposed of.


Beam on the test target at 12 inches.
The bluish tint is exaggerated in this photograph.
Measures 3,170mcd with a test current of 19.28mA.
Vf (forward voltage) is exactly +3.000 volts.


Spectrographic analysis
Spectrographic analysis of this LED.
USB2000 spectrometer graciously donated by P.L.




LEDTronics # L200-TPP-180D. (http://www.ledtronics.com...), $0.70
Received 04-13-07, tested 04-14-07, repeat spectroscopy performed 02-01-10
This is a phosphor pink LED in a heavily pink-tinted 5mm epoxy package.

It is labelled as being a "fluorescent pink" LED, which I confirmed by irradiating it with 407nm violet radiation from a Blu-ray Violet-Emitting Laser Module - the case fluoresced (glowed) quite brightly when I exposed one of these LEDs to this radiation.

I don't yet know if the phosphor formulation is organic or inorganic, but I believe it is inorganic and won't degrade quickly like a pink LED with an organic phosphor formulation will.


Here's a photograph of the LED itself, showing the bright pink case.


And here's a photograph of all five LEDs fluorescing in deep violet radiation.


Beam on the test target at ~4 inches.
Measures 55mcd with a test current of 19.28mA.

This LED has a 180 viewing angle; and if I've told you once, I've told you 1,000,000 times:
"Wider viewing angles always, always, ALWAYS equal lower mcd values."

Let's try some good old fashioned spectroscopy on this LED and see what happens, shall we?

Spectrographic analysis
Spectrographic analysis of this LED.


Spectrographic analysis
Spectrographic analysis of the same LED; newer spectrometer software & settings used.


Spectrographic analysis
Same as above; yet newer spectrometer software setting used.

USB2000 spectrometer graciously donated by P.L.




Roithner Lasertechnik, pink 5mm LED, 5R4HCA-PH
Received (unknown), tested on 11-01-06
This is a phosphor pink LED in a water-clear 5mm epoxy package.




Measures 2,820mcd with a test current of 19.28mA.
Color appears less bluish than this photograph depicts.

Spectrographic analysis
Spectrographic analysis of this LED.
Ocean Optics USB2000 Spectrometer on loan from TWO-CUBED.



Manshun Int'l Ltd, unknown model
(Received and tested 05-23-05)
I received three of these LEDs from Mike Boyd at InReTECH this afternoon (thank you!!!).

This is a bluish-pink LED in a 5mm water-clear epoxy package. When off, the phosphor inside the LED has a distinct reddish pink color to it. I believe the operating chemistry is a GaN blue-emitting chip, with a reddish emitting phosphor layer over that. I don't yet know if the phosphor formulation is organic or inorganic. I currently have the LED in the test set, where I will allow it to run for a few days and see if there is any deterioration.
I started the continuous burn test at 5:00pm PDT 05-23-05.

23 hours 59 minutes later (4:59pm PDT 05-24-05), I compared this LED with an unused one, and found no difference. So it's a pretty good bet the phosphor formulation in this pink LED is inorganic.
I'll do the same comparison in a couple of more days, just to be certain (as my housemate says "just to be sure it's Westinghouse").

24 hours 1 minute later from yesterday (5:01pm PDT 05-25-05), I once again compared this LED with an unused one, and again found no difference.

25 hours 9 minutes later from yesterday (6:09pm PDT 05-26-05), there's still no degradation evident. So it's pretty clear this LED has an inorganic phosphor in it.

Viewing the LED with a 13,500 lines per inch diffraction grating shows it is a blue LED (looks to be ~470-475nm) with a red-emitting phosphor.


Here is the spectrum as seen through this diffraction grating.


Photograph of the LED's beam on the test target.
The intensity measures 680mcd at an If of 20.52mA.
Vf is +2.961 volts at 20.52mA.

Spectrographic analysis
Spectrographic analysis of this pink LED .
Ocean Optics USB2000 Spectrometer on loan from TWO-CUBED.



Unknown manufacturer, unknown model
(Received 06-14-04, tested 06-15-04)
I received two of these LEDs from a website visitor (R.W.) in the Netherlands yesterday (thank you!!!), along with two 450nm diffused blue LEDs and two 1970s vintage red LEDs (thank you for those too!!!).

This is a bluish-pink LED in a 5mm water-clear epoxy package. When off, the phosphor inside the LED has a distinct reddish pink color to it. I believe the operating chemistry is a GaN blue-emitting chip, with a reddish emitting phosphor layer over that. I don't yet know if the phosphor formulation is organic or inorganic.

Edit 06-22-04:
I have found out these LEDs use an organic phosphor formulation; as they degrade within a matter of hours like Roithner's pink LED did. According to the person who sent them, these LEDs fade to white, and then to a color he describes as "baby blue" with just 1 day's use.

As of 11:00am PDT, I have one of these LEDs in my test set, so I can watch it degrade myself. I'll update this page with my findings when warranted.

A little more than an hour into the test, the LED has appeared to fade and dim, slightly but noticeably.

As of 5:12pm PDT (just a hair over six hours), the pink color of this LED has degraded substantially. Here's a picture I took comparing this LED with it's unused counterpart:


The one that's been in use for six hours is on the left; the unused one is on the right. Yuck!!!
This is when supplying both LEDs with a drive current of approximately 8.8mA.

As 12:06pm PDT on 06-23-04 (just over 25 hours), the tested LED now emits a "baby blue" color with just a hint of a pinkish hue to it; which is mostly visible when viewing the LED from the side. I'll leave it energized in the test set for another day or so to see if it color-shifts any more.
As of 9:51pm PDT the same day, no additional degradation or color shifting is evident.

As of 8:12pm PDT on 06-25-04, very little additional degradation has been detected. The LED emits a main beam that I might call "sky blue", with only a very, very, very faint pink tinge visible when the lamp is viewed off-axis.

As of 8:49pm PDT on 07-02-04, the LED is emitting what I would call a very dark sky blue, or a light azure blue. There is virtually no pink in it anymore, whether the lamp is viewed on or off axis. None when viewed on axis, and a barely detectable pinkish tinge when the LED is viewed from the side.

As of 11:29am PDT on 07-21-04, the LED is emitting a deeper blue color, not all that different from a non-phosphor blue, just somewhat dimmer. It's been running continuously for approximately 696 hours now. But the pink color is only good for less than six hours.

As of 8:45pm PDT on 08-17-04, the LED has been running for approximately 1,344 hours now, and it looks like any other GaN blue LED, except it's not as bright. I'd estimate its dominant wavelength (where you would point to on a color chart) at approximately 473nm.

According to the page I viewed, feed this LED 3.0 to 3.3 volts (3.6 volts maximum) at 20-30mA. Remember, this LED has a very short lifetime as a pink emitter; using it in a short duty cycle blinker would prolong the poor thing's very brief life.

This LED was probably designed to be used in disposable toys, novelties, and other articles that would rarely see a second set of batteries.

You can obtain these LEDs on Ebay from the seller "mckenkenken", by going to his View Seller's Other Items page. He lists a lifetime of 100,000 hours - what a bunch of horse puckey.
Horse puckey! Horse puckey!!! HORSE PUCKEY!!!!!


Here is a photograph of the LED's beam on the target from ~12".
Measures 3,030mcd with a test current of 26mA.



ETG, model ETG-5AX440-45-D, available from ETG
(Added 09-21-02)
Pink LED
This diffused pink LED is ETG's latest offering in the world of stable pink emitting phosphor LEDs. It uses the same chip as the pink LED shown below, but uses a diffused, slightly tinted case to widen its effective viewing angle to no less than 45. Because it is a diffused lamp, a brightness measurement would come out extremely low, even though it emits nearly the same total luminous flux as their other pink LED.

Pink LED on the target
To get a feel for its beam distribution, I held the LED just a couple of inches away from the target to obtain this picture.

Feed this LED the same as you would any shortwave GaN lamp using a sapphire substrate. 3.6 to 3.8 volts at 20mA is a good place to start.

Spectrographic analysis
Spectrographic analysis of this LED.



ETG, model ETG-5AX440-15, available from ETG
(Added 06-27-02, updated 07-12-02)
Finally, somebody else has come out with a true pink LED. This one is made by ETG, a new force in the GaN LED wars. It comes in a standard, water-clear 5mm (T1 3/4) epoxy package, and features a mainly orange emitting phosphor over a narrowband 450-460nm GaN blue LED chip.


Left: The LED while lit.
Right: Closeup, showing the tan or peachy colored phosphor.


The LED's beam on the test target. Measures 1,510mcd.


Spectrographic analysis
Spectrographic analysis of this LED.



This LED has a distinctive, coral-tinted pink color that is unique and attention-getting. It appears to be the first stable pink-emitting LED in the world.

The main concern here is will the phosphor decompose rapidly like the Roithner LED below? Let's find out. I'm going to stick one in the proto-board and let it cook there for awhile It's 9:30pm July 8, current is 21mA. I'll come back in a week and plug the other one in the board next to it and compare the color. Burn baby burn!!
(A few days later, a quick check showed no readily apparent deterioration).

This LED is based on a typical GaN blue emitting formulation; it needs approximately 3.6 volts at 20 milliamps. Beam divergence appears to be approximately 15, give or take. The manufacturer states its useful lifetime at 10,000 hours; it will probably last a lot longer than that, though the color will probably slowly become more (noticeably) bluish as you pass the 10,000 hour mark. Only time will tell for sure though.


Roithner Lasertechnik, model B5-439-E, no longer available (see below)
(Added 02-19-02)
LEDs have come a long ways baby!
Not only can you get them in every primary color of the spectrum, now they come in a delicious looking hot pink as well! This LED is from Roithner Lasertechnik, well-known for selling LEDs of all kinds of bizarre wavelengths and colors, and for their amazing assortment of laser diodes. This is their latest LED masterpiece.

I've seen an attempt at creating a pink LED before, and it wasn't pretty. This one *WORKS*, and does a good job at it too.

sink the pink
Pink Roithner LED compared to a white Nichia at low power.

it still floats
Pink LED by itself on the target. As usual, from about a foot away.

As you can see in the picture, the center of the beam has a slight bluish pink color, while the outer region has more of a magenta tint to it. The camera didn't do too badly at rendering the color of this LED, knowing how it really screws up some of the others; though it did oversaturate the red color in the outer region of the beam. It isn't quite that red.

an LED
Closeup, showing the pink gunk inside the die cup. :)

This LED works by using a pink-emitting phosphor coupled with a blue LED chip. The phosphor can be seen in the photograph above as a reddish material inside the LED's die cup. The chip itself is of the double bond, artificial sapphire variety; probably made by ISP, Uniroyal, or one of the other blue LED manufacturers using this particular technology. It is *not* a Nichia product as far as I am able to determine.

An initial measurement showed a reading of 3,700mcd. I'm not sure how a multispectral output not adding up to white affects this reading; as this meter is not designed for pink light. It can do monochrome and true white, not pastels. :-O

OH NOOOOOO!!!
Only a few hours have gone by since I hooked one of the pink LEDs up and it's already faded! Apparently, the pink emitting phosphor is not very stable.



On the left is a *new* pink LED, and on the right is a still new one, but after it was powered with 18 milliamps of current for only 5 hours!! They've definitely got some work to do on that phosphor formulation, but the LED should still do alright in something like a short duty cycle flasher or other application where its total "on" time is not very long.



"Before" and "After" spectra showing that when the pink phosphor degrades, there is a notable increase of output in the green and yellow regions of the spectrum, resulting in an overall "whitening" of the LED's color.

It would seem the active portion of the phosphor itself isn't affected so much as a material that blocks part of the spectrum (the green) is. That material would seem to be unstable, and no longer capable of blocking out or filtering the green wavelengths, so the LED "fades" into a very light pastel pink, when it started life out a few short hours ago as a shocking day-glow type of pink.

(Update 02-27-02): I heard back from Roithner Lasertechnik, and they also experienced the same degradation when I had them test the LED continuously for about a day. The manufacturer of the LED was already aware of this, but for some reason chose not to disclose this to Roithner. Apparently, the LED was intended for use in "disposable" applications; something that can run for a few hours on pre-installed batteries and then be thrown away, such as toys and novelty items that rarely see a second set of batteries.

The LED itself is as I suspected: a blue LED with an inorganic yellow glowing phosphor (typical formulation for an ordinary white LED); the pink color is from an organic phosphor that is added to the formulation; this organic phosphor degrades rather quickly when exposed to the high flux found close to the surface of the LED die, and the end result of this degradation is you once again have a white LED; though with an ugly pinkish tinge at the edges. Run it long enough, and that may also pretty much vanish; though I doubt it will look quite like an LED that was made to be white to begin with.



International Systems Processing (ISP Korea), part #AL-P52CH, $0.80 in quantities > 30,000 pcs
And this gem is that failed attempt at creating a pink LED I mentioned earlier. This sample was obtained in (I believe) late 2000. Although this is supposed to be a pink LED, the dominant color of this specimen is a sort of irregular brownish magenta with a blue thing in the middle, so I didn't know where else to put it.

Constructed similarly to a white LED, this piece consists of a blue LED chip plus a downconverting phosphor covering the LED's chip & anvil.

I sincerely hope this sample is simply defective, because I was not particularly impressed with either its total light output or its color consistency.
-"pink

As shown by this picture, the LED isn't very bright at all. Just to obtain any image at all, I had to open the camera's iris by two full stops!

Estimated peak brightness at 30mA drive current is less than 150mcd. The spec sheet that came with it claims it has a 1500mcd output at 20mA.
That's one reason I think this LED is defective in some manner.




pink led closeup pink led closeup Here is the other.
See the reddish orange "splotch" in the center of the LED in the closeup picture on the left? For some reason, I sincerely believe it is not supposed to be there, and that a defect in manufacturing has occurred here.


When the LED is energized, this orange area glows weakly, as does the rest of the emitting surface; and imparts the odd reddish corona to the LED's projected beam as seen in the last picture.

When the LED is viewed off-axis at a very specific angle, it does have a warm reddish pink appearance to it. At other angles or directly head-on, it looks like a dead or dying blue LED with a dark brownish red splotch in it.
Even at 30mA of drive current, you can easily (and comfortably) stare directly into it.
The last picture (of its radiation field) was taken by holding the LED a couple of inches away from a white sheet, driving the LED at 23mA, and photographing the whole mess from less than eight inches away.

I have forwarded this data to International Systems Processing for further analysis and some kind of answer.

Care and Feeding: The spec sheet says to feed this LED 3.6 to 4.2 volts at 20 milliamps.
When I first connected it several hours ago, I had to set it for 4.9 to 5.0 volts to get 20mA to flow through. Now this figure is 8 volts, and it continues to increase slowly but steadily!
At 4.2 volts (rated max), the forward current is only 0.5 milliamp.

While writing to the manufacturer, the LED started to randomly flicker like an amphetamine-laced Christmas tree; dimming with each flicker until it finally went out completely.
Defective? You bet.
Mr. Chang, please send another. Judging by its optical and electrical characteristics, this one is BAD.





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