Realization of Conformal Phosphor Coating by Ionic Wind Patterning for Phosphor-Converted White LEDs

Conformal phosphor coating is one of the most attractive phosphor layer arrangements for white light-emitting diodes (wLEDs) due to its excellent angular color uniformity (ACU). In this letter, conformal phosphor coating was realized by ionic wind patterning. WLEDs with different average correlated color temperatures (CCTs) were fabricated successfully through adjusting the thicknesses of phosphor layers. The enhancement effects on the light efficiency (LE) and ACU are demonstrated by experiments. Results indicate that compared with the conventional dispensing coating method, the proposed method improves the optical performances significantly. The LE is enhanced from 0.3253 to 0.3287 (1%) at 250 mA and 0.2591 to 0.2719 (5%) at 450 mA. The angular CCT deviations at 350 mA are reduced from 772 to 220 K, 1630 to 488 K, 2420 to 880 K, and 2845 to 1755 K, when the averaged CCTs are about 4500, 5500, 6500, and 8000 K, respectively.