Abstract
We have successfully demonstrated the enhanced luminous flux and lumen efficiency in white light-emitting diodes by the randomly textured phosphor structure. The textured phosphor structure was fabricated by a simple imprinting technique, which does not need an expensive dry-etching machine or a complex patterned definition. The textured phosphor structure increases luminous flux by 5.4% and 2.5% at a driving current of 120 mA, compared with the flat phosphor and half-spherical lens structures, respectively. The increment was due to the scattering of textured surface and also the phosphor particles, leading to the enhancement of utilization efficiency of blue light. Furthermore, the textured phosphor structure has a larger view angle at the full width at half maximum (87°) than the reference LEDs.
Highlights
In recent years, white light-emitting diodes (LEDs) have become important sources of illumination because of their high brightness, reliability, low power consumption, and long lifetime compared to conventional lighting sources [1]
More yellow light can be extracted by the textured phosphor structure
It was noticeable that the haze intensity of the textured phosphor structure can reach 80%, and the flat phosphor structure shows only 45%
Summary
White light-emitting diodes (LEDs) have become important sources of illumination because of their high brightness, reliability, low power consumption, and long lifetime compared to conventional lighting sources [1]. This method can excellently increase the amount of blue light to excite the yellow phosphor in white LEDs, but the blue and yellow light still experience total internal reflection at the interface of air and silicone glue, which leads to the limitation of lumen efficiency in white LEDs. On the other hand, high light extraction efficiency could be attained by the design with a half-spherical lens, but the cost of the mold machine is high, and application is limited due to the large volume of the lens.
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