What is the biggest challenge to improve white LEDs?

[LotsEp]

Here are some of my thoughts:
- thermal management of individual LEDs in a RBG system
- photon absorption in phosphor coating
- exponential decay in intensity
- CCT/ CRT?

 

[Spinnor]

They are expensive!

LEDs at Home Depot
http://www.homedepot.com/p/Cree-75W...MF-12DE26-1U100/204730892?N=5yc1vZbm79Z2bctr8
Cheaper compact fluorescent,
http://www.homedepot.com/p/Philips-...4-Pack-E-434365/202827129?N=5yc1vZbmatZ2bctr8

And other problems,
https://www.google.com/search?safe=...msedr...0...1c.1.64.serp..7.7.390.McqIUEkPtGA

I use the cfls. Only problem is they have a warm up period.

 

[Spinnor]

Price on LEDs falling fast, $3 bucks for dimmable 60w equivalent,

http://www.homedepot.com/p/Philips-...19-Dimmable-LED-Light-Bulb-E-452978/204730356