Ultra-High Efficiency White Light Emitting Diodes

概要

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We fabricated the high luminous efficiency white light emitting diode (LED) and the high power white LED by using the patterned sapphire substrates and an indium–tin oxide (ITO) contact as a p-type electrode. The high luminous efficiency white LED was the yellow YAG-phosphors-coated small-size ($240 \times 420$ μm2) high efficiency blue LED with the quantum efficiency of 63.3% at a forward-bias current of 20 mA. The luminous flux ($\Phi$), the forward-bias voltage ($V_{\text{f}}$), the correlated color temperature ($T_{\text{cp}}$), the luminous efficiency ($\eta_{\text{L}}$), and the wall-plug efficiency (WPE) of the high luminous efficiency white LED are 8.6 lm, 3.11 V, 5450 K, 138 lm/W, and 41.7%, respectively. The luminous efficiency is 1.5 times greater than that of a tri-phosphor fluorescent lamp (90 lm/W). The high power white LED was fabricated from the larger-size ($1 \times 1$ mm2) blue LED with the output power of 458 mW at 350 mA. $\Phi$, $V_{\text{f}}$, $T_{\text{cp}}$, $\eta_{\text{L}}$, and WPE of the high power white LED are 106 lm, 3.29 V, 5200 K, 91.7 lm/W, and 27.7%, respectively, at 350 mA. The WPE is greater than that of a fluorescent lamp (25%) in the visible region. Moreover, the luminous flux of the high power white LED reaches to 402 lm at 2 A, which is equivalent to the total flux of a 30 W incandescent lamp.
2006-10-25