Micro-Prism Patterned Remote Phosphor Film for Enhanced Luminous Efficiency and Color Uniformity of Phosphor-Converted Light-Emitting Diodes.

Jiadong Yu,Shudong Yu,Yong Tang,Ting Fu

doi:10.3390/mi12091117

Jiadong Yu, Shudong Yu + Show 2 more

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https://doi.org/10.3390/mi12091117

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Abstract

In this work, we propose micro-prism patterned remote phosphor (RP) films to enhance both luminous efficiency and color uniformity (CU) of remote phosphor-converted light-emitting diodes (rpc-LEDs) simultaneously. On the incident surface of the RP film, one micro-prism film is used to extract backward light by double reflection. On the exit surface, the other micro-prism film is adopted to retain blue light inside the RP film, thus enhancing the phosphor excitation. Experimental results show that double prism-patterned RP (DP-RP) film configuration shows a luminous flux of 55.16 lm, which is 45.1% higher than that of RP film configuration at 300 mA. As regards the CU, the DP-RP film configuration reduces the angular CIE-x and CIE-y standard variations by 68% and 69.32%, respectively, compared with the pristine device. Moreover, the DP-RP film configuration shows excellent color stability under varying driving currents. Since micro-prism films can be easily fabricated by a roll-to-roll process, the micro-prism patterned RP film can be an alternative to a conventional RP layer to enable the practical application of rpc-LEDs.

Highlights

Since micro-prism films can be fabricated by a roll-to-roll process, the micro-prism patterned remote phosphor (RP) film can be an alternative to a conventional RP layer to enable the practical application of remote phosphor-converted phosphor-converted light-emitting light-emitting diode diode (rpc-LED)
The optical power P is defined as the integration of spectrum intensity from 360–830 nm and the luminous flux (LF) is integrated from the spectrum by weighting the human visual function
The micro-prism films were fabricated by a roll-to-roll process and integrated on the dual sides of a RP film to form a single-prism-patterned RP (SP-RP) film and a DPRP film, respectively

Summary

Introduction

White light-emitting diodes (WLEDs) are very promising light sources in general lighting, automotive headlamp, and liquid-crystal backlight due to their high efficiency, long lifetime, compact size and environmental friendliness [1,2,3]. The most widely used configuration to generate white light is the combination of a blue GaN chip and down-converted yellow phosphor, namely phosphor-converted light-emitting diodes (pc-LEDs), which has excellent durability, low cost and easy scalability [4,5,6]. It is well known that luminous efficiency (LE) and color uniformity (CU) are two important indexes of pc-LEDs [7,8,9]. In a traditional LED package, phosphor-silicone mixture is directly dispensed on a GaN chip, which leads to a low light extraction efficiency of LEDs due to the backscattered issue [8]

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