A phosphor-converted light-emitting diode structure with an increased phosphor extraction efficiency owing to the ring remote phosphor structure achieves a maximum luminous efficacy of 145 lm/W at 20 mA and a maximum luminous flux of 132 lm at 400 mA. The ring remote phosphor structure consists of an inverted cone lens encapsulant and a surrounding ring remote phosphor layer. Ray-tracing simulations demonstrate that the phosphor extraction efficiency of the ring remote phosphor structure exceeds 93%. A high phosphor extraction efficiency is achieved by decreasing the re-emitting light from the ring remote phosphor layer to the absorptive light-emitting diode (LED) chip. Our results further demonstrate that the ring remote phosphor structure device has a radiation pattern as a bi-wing, which is more appropriate for solid-state lighting owing to the low glare.

This study of the optoelectronic properties of blue light-emitting diodes under direct current stress. It is found that the electroluminescence intensity increases with duration of stress, and the efficiency droop curves illustrated that the peak-efficiency and the peak-efficiency-current increases and decreases, respectively. We hypothesize that these behaviors mainly result from the increased internal quantum efficiency.

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