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

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.

Using Ultraprecision Machining to Fabricate LED Packaging Exhibiting High Luminous Intensity

In this study, a phosphor was coated on a microstructured film to achieve light control. This process resulted in a large-area phosphor film and enabled the microstructure to be packaged directly into the LED body. Thus, the LEDs retain their air and water barrier functions, control light, achieve higher forward luminous intensity, and have a wider scope of applications. Roll-to-roll processing was performed to mold a microstructure and phosphor on polyethylene terephthalate (PET) film by applying ultraviolet light. This approach expedited the preparation of a large-area phosphor film and enabled the precise control of the thickness and evenness of the phosphor layer, thus ensuring uniform light distribution and eliminating the yellow halo within the light body induced by the uneven thickness of the phosphor layer. The experimental results revealed that the luminous intensity of the LED to which the microstructured PET film was attached at 0° (center) increased by 11.88% relative to the luminous intensity of the LED without the film. Moreover, at 30° to −30°, the luminous intensity of the LED with the film improved by 10.36%. Therefore, the device retained its color uniformity and achieved higher forward luminous intensity.

Optical Model of Laminated Remote Phosphor Films and Its Application in White LED

Based on Mie scattering and Monte Carlo ray tracing method, the transmission process of light in the remote phosphor film is described and the optical model of red and green laminated phosphor films is constructed. The photochromic properties of the phosphor films were studied by TM-30-15 method proposed by the North American Lighting Association. The investigation discloses that the normalized cross correlation of single-layer phosphor film spectral power distribution between the simulation and experimental results is about 99%, and the deviation of color coordinates is within 0.01. Based on the monochrome phosphor optical model, we establish bicolor optical model of red and green laminated phosphor film layers to form white light and can predict its color performance. The experimental results show that the normalized cross correlation of laminated phosphor film spectral power distribution between the simulation and experiment is about 97%, and the optical model of red and green laminated phosphor film can accurately predict the index Rf and Rg. When the red and green phosphor mass ratio is 0.05:0.5, the simulated color is optimal, Rf reaches 90, and Rg reaches 100, whose corresponding experimental values are Rf=90, Rg=101.