The phosphors an important effect on the led

Phosphors are key materials for the improvement of color rendering index of LED lighting, and play an important role in white LED energy-efficient lighting devices . this is mainly reason for phosphors use in led . the follow reason that efficiency of light . we are know that phosphors is an interesting alternative to yellow led chip(yellow led = blue led + phosphors). but why would led factory use phosphors? we did it because its low light-to-energy conversion efficiency and limit its large-scale ap-plication.