Abstract
This study demonstrates the application of DBR structure into the remote phosphor structure to improve the angular correlated color temperature (CCT) deviation in white light-emitting diodes (WLEDs). In the experiment, the LED device with DBR structure yielded a higher luminous efficiency than a conventional structure. The CCT deviation can be improved from 1758K to 280K in a range of -70 to 70 degree and the luminous flux increases more than 10% due to the enhancement of the light extraction of the blue light. Moreover, the reflectance of the different DBR structures is analyzed with different angles to reveal the reasons of such improvements. As the result, this LED device with DBR structure shows the great potential to use as the next generation lighting source.
Highlights
White light-emitting diodes (LEDs) have become increasingly popular due to their compactness, long-lifetime and energy-saving features [1,2,3,4]
This study demonstrates the application of DBR structure into the remote phosphor structure to improve the angular correlated color temperature (CCT) deviation in white light-emitting diodes (WLEDs)
The CCT deviation can be improved from 1758K to 280K in a range of −70 to 70 degree and the luminous flux increases more than 10% due to the enhancement of the light extraction of the blue light
Summary
White light-emitting diodes (LEDs) have become increasingly popular due to their compactness, long-lifetime and energy-saving features [1,2,3,4]. There were many crucial factors, including luminous efficiency, color rendering index (CRI) and correlate color temperature, to determine the characteristics of a white LED [5]. Techniques such as nanostructure of the blue chip, the high aspect ratio cone-shape nano-patterned sapphire substrate [6], air voids between GaN nano-pillars and the overgrown GaN layer [7,8] and pattern sapphire substrate methods were reported to improve the light extraction and lumen efficiency for the white LEDs. the dual layer phosphor structure and the imprinting textured phosphor structures were employed to enhance the lumen efficiency [9,10]. It is an importance topic to strike a balance between both the lumen efficiency and CCT uniformity for a LED device
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