Are single colour white LEDS more efficient than tricolour LEDS?

Commercial flood lights use single colour LEDS presumably because they are simpler/cheaper to manufacture. Are they any more efficient than using a tricolour LED to make white light?

Yes.
Single white colour LEDs are in fact UV LEDs that shine on a phosphor which then glow white. Where as normal coloured LEDs use the band gap energy transition of electrons in the conductance band of the materials to generate the light.

As there is more energy per photon in UV light than visible light this makes them more efficient and more than compensates for any losses in the secondary action of the phosphor.

Mike, are UV photons produced more efficiently than visible colour photons, i.e. electrical energy in versus light energy out? Do white LEDs not use the band gap energy to generate the UV photons, and if not, how do they work?

Do white LEDs not use the band gap energy to generate the UV photons,

Yes they do.
But as the UV photon carries more energy they are better, and the excitation to UV energies by electricity is more efficient.

RGB LEDs can sort of make white light with three colours, but there are gaps between the colours.
Read up about CRI (colour rendering index) relating to LEDs.

And I would rather use one LED driver than three if only interrested in white light.
Leo..

Grumpy_Mike:
the excitation to UV energies by electricity is more efficient.

OK, but why more efficient than longer wavelengths? What makes production of longer wavelengths less efficient. I mean, obviously more of the input power turns into heat, but why is the process not equally efficient at all wavelengths?

PaulRB:
OK, but why more efficient than longer wavelengths? What makes production of longer wavelengths less efficient. I mean, obviously more of the input power turns into heat, but why is the process not equally efficient at all wavelengths?

It is to do with the excitation of the electron energy into higher bands. With a UV LED the band you excite the LED into is wider, meaning that more electrons end up at the excited state of the valence band than is the case where the valence bands are narrower and many of the excited electrons end up in the conduction band and so are lost to the LED and turn into heat by increasing the current flow.

Interesting! So why don’t they make red LEDs using UV diodes and red phosphor?

PaulRB:
So why don't they make red LEDs using UV diodes and red phosphor?

No idea.
Maybe it is cheaper to do it the way they do?

Hmm, you may be right. Thanks Mike.

An interesting thing about red LEDs is their monochromacity. You can often see diffraction "speckling" even though they are not actual laser diodes. :sunglasses:

PaulRB:
Interesting! So why don't they make red LEDs using UV diodes and red phosphor?

I though warm white LEDs used a touch of red phosphor to give them that color.

Slumpert:
I though warm white LEDs used a touch of red phosphor to give them that color.

They might very well do. But the combination of UV LED plus phosphor is more expensive to make than a conventional red LED. Which is why they don’t do it.