Abstract
In this work, evidence for matching blue chips with Ce:YAG single
crystal phosphor is given. Forward current (
${ I} _{\rm f}$
) and red phosphor were investigated and discussed to improve the
electroluminescent properties of WLEDs using Ce:YAG single-crystal
phosphors. Optimum forward current of such a device is chosen at above
45 mA. The structure of
${Sr}_{2}{Si}_{5} {N} _{8}$
:
${Eu}^{2+}$
phosphor/Ce:YAG single crystal/blue chip enormously improved
the color temperature and color rendering index. This method can be
a solution to achieve warm white light. The chromaticity of this structure
with the color temperature of 5629 K and color rendering index of
77.1 is
$({\rm CIE~
x}, {\rm CIE~ y}) = (0.3296, 0.3369)$
closely meeting
the demand for ideal white light for general lighting (0.33, 0.33),
but the luminous efficiency (
$\eta_{\rm L}$
) is lower at 81.04 lm/W
in comparison to that of the Ce:YAG single crystal/blue chip structure
at 94.55
$~$
lm/W.
© 2015 IEEE
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