Currently, the major commercial white light‐emitting diode (WLED) is the phosphor‐converted LED made of the InGaN blue‐emitting chip and the Ce3+:Y3Al5O12 (Ce:YAG) yellow phosphor dispersed in organic epoxy resin or silicone. However, the organic binder in high‐power WLED may age easily and turn yellow due to the accumulated heat emitted from the chip, which adversely affects the WLED properties such as luminous efficacy and color coordination, and therefore reduces its long‐term reliability as well as lifetime. Herein, an innovative luminescent material: transparent Ce:YAG phosphor‐in‐glass (PiG) inorganic color converter, is developed to replace the conventional resin/silicone‐based phosphor converter for the construction of high‐power WLED. The PiG‐based WLED exhibits not only excellent heat‐resistance and humidity‐resistance characteristics, but also superior optical performances with a luminous efficacy of 124 lm/W, a correlated color temperature of 6674 K and a color rendering index of 70. This easy fabrication, low‐cost and long‐lifetime WLED is expected to be a new‐generation indoor/outdoor high‐power lighting source. 相似文献
Sr6BP5O20:Eu2+ phosphor was prepared by the solid-state reaction method under a weak reductive atmosphere and the photoluminescence properties
were studied systematically. The bluish-green emission band of Sr6BP5O20:Eu2+ phosphor is peaking at 475 nm, and the excitation bands are broad with peaks at about 290 and 365 nm with a shoulder around
390 nm, respectively. By combining with Ga(In)N-based near-ultraviolet LEDs, a bluish-green LED was fabricated based on the
Sr6BP5O20:Eu2+ phosphor, and a novel intense white LED was fabricated based on the bluish-green phosphor Sr6BP5O20:Eu2+ and the red phosphor (Sr,Ca)5(PO4)3Cl:Eu2+,Mn2+. When this two-phosphor white LED is operated under 20-mA forward-bias current at room temperature, the Commission Internationale
de l’Eclairage(CIE) chromaticity coordinates (x,y), the correlated color temperature Tc, and the color rendering index Ra
are calculated to be (0.3281,0.3071), 5687 K, and 87.3, respectively. The dependence of the bluish-green and two-phosphor
white LEDs on different forward-bias currents from 5 mA to 50 mA shows a similar behavior. As the current increases, the relative
intensity simultaneously increases. The CIE chromaticity coordinates (x,y) of the two-phosphor white LED tend to decrease.
Consequently, the correlated color temperature Tc increases from 3800 K to 9400 K and the color rendering index Ra of the
two-phosphor white LED increases from 83.4 to 91.8 simultaneously.
PACS 07.60.-j; 42.70.-a; 71.55.Eq 相似文献
A mathematical model for the spectra of monocolor light-emitting diodes (LEDs) and phosphor-coated white LEDs at different drive currents is established.The simulation program of the color rendering of a white light LED cluster is developed based on this model.The program can predict not only the spectral power distribution and color rendering index (CRI),but also the number of LEDs,drive currents,input power,and luminous efficacy of a white light LED cluster at a given color temperature according to the requirement of the luminous flux.The experimental results show that the relative spectral power distributions (SPDs) and chromaticity coordinates of the model LED are very close to that of the real LED at different drive currents.Moreover,the correlated color temperature (CCT),CRI,special color rendering index (R9) luminous flux,input power,and luminous efficacy of the white light LED cluster predicted by simulation are also very close to the measured values.Furthermore,a white/red cluster with high rendering (CCT=2903 K,CRI=91.3,R9=85) and a color temperature tunable warm-white/red/green/blule LED cluster with high rendering (CCT=2700 6500 K,CRI 〉 90,R9 〉 96) are created. 相似文献
White-light-emitting diodes (WLEDs) were fabricated by combining a yellow Sr3SiO5:Ce3+, Li+ phosphor with a blue light-emitting diode (LED) (460 nm chip) or a near ultraviolet (n-UV) LED (405 nm chip), respectively. Color temperature (Tc) of Sr3SiO5:Ce3+, Li+-based WLEDs could be tuned from 6500 to 100,000 K (blue LED pumping) and from 4900 to 50,000 K (n-UV LED pumping) without mixing with other phosphors. The blue LED-pumped WLED showed excellent white light (luminous efficiency=31.7 lm/W, Tc=6857 K) at 20 mA. This WLED showed a stable color coordinates property against an increase of the forward current. An n-UV LED-pumped WLED also showed bright white light (25.0 lm/W, 5784 K) at 20 mA. 相似文献
Solid‐state lighting (SSL) is now the most efficient source of high color quality white light ever created. Nevertheless, the blue InGaN light‐emitting diodes (LEDs) that are the light engine of SSL still have significant performance limitations. Foremost among these is the decrease in efficiency at high input current densities widely known as “efficiency droop.” Efficiency droop limits input power densities, contrary to the desire to produce more photons per unit LED chip area and to make SSL more affordable. Pending a solution to efficiency droop, an alternative device could be a blue laser diode (LD). LDs, operated in stimulated emission, can have high efficiencies at much higher input power densities than LEDs can. In this article, LEDs and LDs for future SSL are explored by comparing: their current state‐of‐the‐art input‐power‐density‐dependent power‐conversion efficiencies; potential improvements both in their peak power‐conversion efficiencies and in the input power densities at which those efficiencies peak; and their economics for practical SSL. 相似文献
The future generation of modern illumination should not only be cheap and highly efficient, but also demonstrate high quality of light, light which allows better color differentiation and fidelity. Here we are presenting a novel approach to create a white solid‐state light source providing ultimate color rendition necessary for a number of applications. The proposed semi‐hybrid device combines a monolithic blue‐cyan light emitting diode (MBC LED) with a green‐red phosphor mixture. It has shown a superior color rendering index (CRI), 98.6, at correlated color temperature of around 3400 K. The MBC LED epi‐structure did not suffer from the efficiency reduction typical for monolithic multi‐color emitters and was implemented in the two most popular chip designs: “epi‐up” and “flip‐chip”. Redistribution of the blue and cyan band amplitudes in the white‐light emission spectrum, using the operating current, is found to be an effective tool for fine tuning the color characteristics.