Three types of white-light LEDs consisted of "blue LED chip and YAG phosphor"

"blue LED chip

YAG phosphor and red phosphor"

and "blue LED chip

green phosphor and red phosphor" were fabricated.Their CIE parameters were also mearsued under 20 mA DC driving.The CIE coordinates are (0.326

0.339)

(0.326

0.339)

and(0.324

0.324);the correlated color temperature T

c

are 5781

5627

and 5937 K;and the color-rendering index Ra are 82.3

86.2

and 92.2

respectively.It shows that the adding of red light into the white light will improve the quality of the white light.The different DC driving

increasing of the current from 5.0 mA to 6.0 mA

results in higher color temperature T

c

and lower color rendering index.It was found that the red phosphor saturated when the current was higher than 30 mA.The phosphors(

M

1

M

2

)

10

(PO

4

)

6

X

2

(

M

1

=Ca

Sr

Ba;

M

2

=Eu

Mn;

X

=F

Cl

Br) have been synthesized in reductive atmosphere at 900～1200℃ for 2.0～8.0h.The phosphors with different compositions give the emission at 455

477

500

and 580 nm when excited by 400 nm near UV light.Three types of white LEDs were fabricated using UV LED chips and the phosphors mentioned above.The constitutions are "UV LED chip

blue phosphor

and YAG phosphor"

"UV LED chip

blue phosphor and red phosphor"

and "UV LED chip

blue phosphor

green phosphor and red phosphor".Their CIE coordinates are(0.303

(0.329))

(0.327

0.328)

and(0.331

0.333);the correlated color temperature T

c

are 7070

5747

(5566) K;and the color-rendering index Ra are 79.2

80.4

and 87.9 under 20 mA DC driving

respectively.The different DC driving

increasing of the current from 5.0 mA to 6.0 mA result in a higher color temperature T

c

and a lower color rendering index.However

CIE coordinate of the white light LED consisted of UV LED chip

blue phosphor and YAG phosphor changed the least.