Inverted-Cone-Lens Encapsulant With Gradient Surface for Ring-Remote-Phosphor Structure

Abstract

The ordinary ring-remote-phosphor structure consisting of an inverted-cone-lens encapsulant and a surrounding ring-remote-phosphor layer reduces the probability of the backward light from the phosphor layer to the absorptive lightemitting diode (LED) chip and then increases the package extraction efficiency. However, some of the blue light emitting from the LED chip impinges on the inverted-cone-lens surface and then escapes without hitting the ring-remote-phosphor layer. The blue light leakage from the inverted-cone-lens surface is a serious problem for the ring-remote-phosphor structure devices in use, because it will lower the actual illumination effects and result in discomfort for the eyes. In this paper, we discuss the predominant factors of the blue light leakage from the inverted-cone-lens surface and propose an improve ring-remote-phosphor structure that utilizes an inverted-cone-lens encapsulant with gradient surface to decrease the blue light leakage. Ray-tracing simulations are performed to analyze the blue light leakages from the ordinary and improved inverted-cone-lens encapsulants in the ring-remotephosphor structures. The simulation results show that the improved inverted-cone-lens encapsulants get almost no blue light leakage from the inverted-cone-lens surface directly and then lessen the discomfort for the eyes. Our results further demonstrate that the improved ring-remote-phosphor structure device will have higher angular color uniformity than the ordinary one.Index Terms-Blue light leakage, inverted-cone-lens encapsulant with gradient surface, phosphor-converted white lightemitting diodes (LEDs), ring-remote-phosphor structure.

Investigation of remote-phosphor white light-emitting diodes with improved scattered photon extraction structure

“…To improve the extraction efficiency of the remote phosphor structure with low angular-dependent correlated color temperature (CCT) deviation, the phosphor structures with a textured surface or dual-layer phosphor, obtained using the pulse spray coating method, were used to increase the package efficiency and color uniformity [5]. The ring remote phosphor structure proposed by Lin et al consists of an inverted cone lens encapsulant; a surrounding ring remote phosphor layer was later developed [6][7][8]. The ring remote phosphor layer could increase the extraction of back-transferred light and enhance the luminous efficacy to a greater extent.…”