White light-emitting diodes (white LEDs) have attracted more
and more attention owing to the advantages of high luminous efficiency,
long lifetime, environmental friendliness, small volume and
energy saving [1–2]. Particularly, in the situation of the global
energy crisis, white LEDs gradually become one of the most promising
general illumination sources. Generally, there are two
approaches to obtain white light-emitting diodes at present. One
way is to combine a GaN-based blue LED chip with Y3Al5O12:Ce3+
(YAG:Ce) yellow phosphor. However, white LEDs made by this
means have been limited in applications due to several weaknesses.
The blue LED chip with yellow phosphor has a lack of red
light component, which causes poor color rendering index and
low stability of color temperature [3–5]. The other way is utilizing
a UV chip coated with red, green, and blue tricolor phosphors.
Appropriate warm white light can be achieved by this approach
according to the trichromatic theory. Nevertheless, strong reabsorption
of various phosphors could cause low emission efficiency
and inconsistence of phosphor physical properties might make the
obtained white light unstable and not durable.
White light-emitting diodes (white LEDs) have attracted moreand more attention owing to the advantages of high luminous efficiency,long lifetime, environmental friendliness, small volume andenergy saving [1–2]. Particularly, in the situation of the globalenergy crisis, white LEDs gradually become one of the most promisinggeneral illumination sources. Generally, there are twoapproaches to obtain white light-emitting diodes at present. Oneway is to combine a GaN-based blue LED chip with Y3Al5O12:Ce3+(YAG:Ce) yellow phosphor. However, white LEDs made by thismeans have been limited in applications due to several weaknesses.The blue LED chip with yellow phosphor has a lack of redlight component, which causes poor color rendering index andlow stability of color temperature [3–5]. The other way is utilizinga UV chip coated with red, green, and blue tricolor phosphors.Appropriate warm white light can be achieved by this approachaccording to the trichromatic theory. Nevertheless, strong reabsorptionof various phosphors could cause low emission efficiencyand inconsistence of phosphor physical properties might make theobtained white light unstable and not durable.
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