Patterned structure of REMOTE PHOSPHOR for phosphor-converted white LEDs

Hao-Chung Kuo,Cheng-Wei Hung,Chao-Hsun Wang,Chia-Chi Yeh,Chin-Wei Sher,Cheng-Huan Chen,Yuh-Jen Cheng,Kuo-Ju Chen,Hsin-Chu Chen,Chien-Chung Lin

doi:10.1364/oe.19.00a930

Abstract

High efficiency white light-emitting diodes with superior color-mixing have been investigated. It is suggested that the patterned remote phosphor structure could improve the uniformity of angular-dependent correlated color temperature (CCT) and achieve high chromatic stability in wider operating current range, as compared to the conventional remote phosphor coating structure. In this experiment, we employed a pulse spray coating method to place the patterned phosphor on the package and to leave a window region. The window area, a clear space without coating of the phosphor not only increases the extraction efficiency of blue rays at large angle, but also improves the stability of angular-dependent CCT. Moreover, the CCT deviation could be reduced from 1320 K to 266 K by this patterned remote phosphor method, and the stray blue/yellow light within the package can be effectively reduced and controlled. The design was verified both experimentally and theoretically.

Highlights

Solid-state lighting (SSL) for highly efficient white light-emitting diodes (LEDs) has been vigorously developed to replace traditional lighting sources [1]
It is suggested that the patterned remote phosphor structure could improve the uniformity of angular-dependent correlated color temperature (CCT) and achieve high chromatic stability in wider operating current range, as compared to the conventional remote phosphor coating structure
The CCT deviation could be reduced from 1320 K to 266 K by this patterned remote phosphor method, and the stray blue/yellow light within the package can be effectively reduced and controlled

Summary

Introduction

Solid-state lighting (SSL) for highly efficient white light-emitting diodes (LEDs) has been vigorously developed to replace traditional lighting sources [1]. In generic pc-WLED configurations, the yellow-emitting phosphor powders were mixed with transparent encapsulated resin and dispersed in a cup reflector or directly coated on the LED chip surface Even though the latter direct dispensing method is the most common approach in mass production; in some types of phosphors, an increase in LED device temperature could shift the excitation wavelength and affect the downconversion process. In order to solve the low output power under high-current operation condition caused by the thermal problem, a phosphor with thermal-isolated package has been demonstrated [7] This thermal-isolated encapsulant material can effectively reduce heat transfer from the LED chip to the phosphor coating layer; the phosphor with the cooling method can be an effective way to improve luminous efficiency and to decrease the color variation. This clear region is designed to improve extraction of blue rays at large angle, and to reduce the angular-dependent CCT deviation

Experiment

Measurement and analysis

Simulation

Conclusion