White light-emitting-diodes(LEDs) are known as a new generation lighting source.The luminous flux

color temperature and color rendering property are the three main index in light source.Using a blue LED with a phosphor layer which is excited by blue light and down-converting to the second light

such as yellow light

white light can be produced.Now white-LED is a hot-spot of research

the point of designing white-LED used for lighting is its colour temperature and efficience

and the phosphor layer in white-LED is very important to this.The placement of the phosphor

the geometry of the encapsulation dome

and the reflector cup influence on the optical loss

and hence on the device efficiency.We can find the energy loss term in the one-dimensional model and observe the phosphor layer thickness and boundary effect.Finally we can optimize the phosphor-type white LEDpackage to obtain higher light extraction efficiency.Recently

it has been demonstrated that a large separation between the phosphor and the primary LED emitter

which we refer to as remote phosphor arrangement

enhances the phosphorescence extraction by reducing the optical power absorbed by the LED chip.The experimental enhancement of phosphor efficiency is 24% for blue-pumped yellow phosphor at 20 mAforward current.This improvement is mainly due to the reason:the phosphor-on-top arrangement reduces absorption of phosphorescence the LED chip.it is not known what will happen to the yellow light when it strikes the phosphor medium.To the best of our knowledge

there are no past studies that have quantified the transmission and reflection properties of light outside the excitation wavelength region of YAG:Ce phosphor.By analysing

the color coordinate

color temperature

Luminous flus

Lumen efficiency varied with forward current.From the result of the experiment

we know that color coordinate x and y is minish varing slowly with the increasing forward cureent.The color coordinate and the color temperature is the same uptrend.The luminous flux increases with increasing forward current

but the lumen efficiency decreases with increasing the forward current.