Improvement of electroluminescent property of blue LED coated with highly luminescent yellow-emitting phosphors
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- Jang, H.S., Won, YH. & Jeon, D.Y. Appl. Phys. B (2009) 95: 715. doi:10.1007/s00340-009-3484-1
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White light-emitting diodes (WLEDs) were fabricated by combining InGaN-based blue light-emitting diodes (LEDs) with highly luminescent Tb3Al5O12:Ce3+ (TAG:Ce), Y3Al5O12:Ce3+ (YAG:Ce), and Sr3SiO5:Eu2+ (SS:Eu). The TAG:Ce-based WLED showed a color rendering index (Ra) of 79 and a luminous efficiency (ηL) of 34.1 lm/W at 20 mA. The YAG:Ce-based WLED and the SS:Eu-based WLED showed low Ra values of 75 and 57 but high luminous efficiency values of 38.9 and 41.3 lm/W at 20 mA, respectively. When a mixture of YAG:Ce and SS:Eu was coated on a blue LED and the resultant WLED operated at 20 mA, the WLED showed a highly bright white light similar to daylight (ηL=40.9 lm/W, color temperature Tc=5,716 K, and Ra=76). Moreover, the WLED showed stable color coordinates against a considerable variation of applied current.