High Efficiency Green‐Emitting LuAG:Ce Ceramic Phosphors for Laser Diode Lighting

Abstract

CP because it can be achieved white light directly combined with blue LDs. [19][20][21][22][23] Recently, yellow/green/red CPs were discovered to rich spectral components and modify the color quality for white LD lighting. [24][25][26][27][28] Lu 3 Al 5 O 12 :Ce (LuAG:Ce) is a well-known green color converter due to its high thermal stability and high efficiency. [29][30][31] LuAG:Ce CPs are regarded as the best type that is robust irradiated by high-power LD light (15-25 W, up to 49 W mm −2 ). [32][33][34][35][36] The luminous efficacy (LE) of LuAG:Ce CPs in LD lighting has been greatly enhanced from about 54 to 205 lm W −1 by designing geometric structures and introducing scattering centers. [32][33][34][35][36][37] However, LuAG CPs are usually sintered higher than 1700 °C, SiO 2 or TEOS is commonly added as sintering aid. [32][33][34] SiO 2 begins to react with the garnets at about 1400 °C, [38] and defects are inevitable due to the size and charge mismatches between Si 4+ and Lu 3+ /Al 3+ . [39] The defects decline the thermal stability that is directly related with the performance of LuAG:Ce in LD lighting. [19] Thus, how to depress the defect and maintain the high thermal stability is the hardest challenge in fabricating LuAG CPs and achieving high LE value.As we know, heavy atom can depress lattice relaxation and improve thermal stability. [40,41] Considering valence state, in this work, we design the Ba 2+ -Si 4+ pair to substitute the Lu 3+ -Al 3+ pair to keep charge balance. SiO 2 powder are used as sintering aid and BaCO 3 provides the Ba 2+ to control defects and adjust thermal stability. Combining annealing process in air to eliminate oxygen vacancies, LuAG:Ce CPs manifest high LE of 213.7-216.9 lm W −1 in LD lighting, which is the best performance up to date. These results demonstrate that suitable strategies further improve LuAG:Ce CPs properties, thus in turn making great contributions to high-brightness and efficient white LD lighting. The tunable thermal stability by Ba 2+ -Si 4+ pairs and relationships with performance of LuAG:Ce CPs in LD lighting are detailed in present report. Results and DiscussionNominal compositions of Lu 2.995−x Ba x Al 5−x Si x O 12 :0.005Ce (LuAG:0.5%Ce+xBS, x = 0, 0.005, 0.01, 0.015, and 0.02) CPs sintered in vacuum are dark yellow (unannealed samples in Figure 1a), especial for x = 0, due to a lot of color centers Lu 3 Al 5 O 12 :Ce 3+ (LuAG:Ce 3+ ) ceramic phosphors (CPs) are regarded as the most promising green color converter and play a key role in high quality white light in the next-generation laser diode (LD) lighting. High efficient LuAG:Ce 3+ CPs are still urgent for high luminous efficacy (LE) LD lighting devices. By designing the Ba 2+ -Si 4+ pair to keep charge balance and annealing in air to remove oxygen vacancy defects, the luminescent properties of LuAG:Ce CPs are greatly enhanced. The LE is promoted to 216.9 lm W −1 , which is the best performance of LuAG:Ce in LD lighting so far. Strategies for optimizing LuAG:Ce 3+ CPs are detailed. It is believed ...

Evolutionary Generation of Phosphor Materials and Their Progress in Future Applications for Light-Emitting Diodes

“…This result reveals that the thermal stability of LuAG is even better than that of YAG phosphor, indicating its superb thermal stability. Furthermore, its robust stability also renders it suitable for high-power laser-diode systems. − …”

Design of a Novel La3Si6N11:Ce3+ Phosphor-in-Glass Film for High Power Laser Lighting: Luminous Efficiency toward 200 lmW–1

“…Compared to blue light-emitting diodes (LEDs), laser diodes (LDs) are free of the “efficiency droop” effect and can withstand high input current density. − Thanks to high directionality, excellent brightness, highly concentrated beams, and superior monochromaticity, LD devices that generate high power white light by pumping color converters are a significant alternative light source, which make it spring up in an adverse range of displays, projectors, automobile headlights, light communication, and other ultrahigh brightness lighting. , Unfortunately, traditional solid state lighting encapsulant materials such as organic resin and silicone have low thermal conductivity and poor stability, which make them inadequate for practical use in laser lighting. , Therefore, the all-inorganic color converter with strong heat resistance such as phosphor-ceramic (CP), phosphor-in-glass (PiG), single-crystal phosphor (SCP), and phosphor-in-glass film (PiF) has been widely investigated in laser lighting (see refs − ). CP with high thermal stability shows good luminescence properties; but it is costly, and the preparation process is complicated as well.…”

A Triple-Doped Phosphor Strategy for the Conversion of Cool and Warm White Light

“…Since mankind entered the fourth-generation lighting era, phosphors for light-emitting diode (LED) lamps have always been a research hotspot. − Scientists have long been committed to the development of energy-saving, color adjustable, stable, and uniform high lumination and high efficiency phosphors. − At present, there are two main methods for realizing the white light LED lighting. One is the combination of blue chips with a Y 3 Al 5 O 12 : Ce 3+ (YAG: Ce 3+ ) yellow phosphor, and another is using ultraviolet (UV) chips with a three-color primary phosphor. , The former lacks green and red light components, leading to a high color temperature and low color rendering index (Ra), which is mostly used for outdoor lighting. , Due to the different stabilities of the three primary color phosphors and the presence of spectral reabsorption, the mixing ratio of the latter is difficult to determine and needs high process requirements. , Therefore, it is particularly important to develop a single-substrate full-spectrum emission phosphor.…”