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1、Phosphor-converted light-emitting diodes (LEDs) technique is an important kind of solid-state illumination 14.In comparison with conventional incandescent and fluorescent lamps, the whi te LED s show many advantages such as high luminescent efficiency, long lifetime, compactness,environment friendly
2、, and designable features. Generally, the white LEDs are realized by a co mbination of a GaN-based blue-LED chip (emitting blue light at 465 nm) with a yellow phosphor (i.e. YAG:Ce3+ -based materials). solid-state lighting based on GaN semi-conductors has attracted great attention due to its long li
3、fetime, high luminescence efficiency, low power consumption, and environment friendliness. The most effective way to produce white light in solid-state lighting is by coating suitable phosphors on blue light-emitting diode LED chips.Among them, Pr3+-activated BaMoO4 deep-red-emitting phosphor has re
4、ceived much more attention, because it can be excited by blue light and provides remarkable deep-red emission, resulting in potential application in pc-white-LEDs based on the InGaN chip.long lifetime, high luminous efficiency, low power consumption, and environment friendliness. The most effective
5、way to produce white light in solid-state lighting is to coat yellow light-emitting phosphors on blue light-emitting diode (LED) chips.White light-emitting diodes (LEDs) as illumination light sources have attracted more and more attention because they have advantages of precise wavelength, color out
6、put, long lifetime, reliability, energy savings, and small packaging.For a variety of applications like UV-lasers, scintillators, and lamp phosphors, the high energetic interconfigurational (4 f24 f 5 d ) and intraconfigurational ( 4 f24 f2) transitions of the Pr3+-ion are of increasing interest. Su
7、ch multiphoton processes are called photon cascade emission (PCE), quantum cutting or down-conversion. The Pr3+-ion is in principle a suitable ion for obtaining PCE, because of its favorable energy level scheme. However, PCE only occurs if the 1S0 level (the highest level of the 4 f2 electron config
8、uration, located at about 46 500 46 900 cm1) is energetically below the energy levels of 4 f 5 d electron configuration (see Fig. 1).Nowadays, the luminescent properties of Pr3+-doped phosphors are of considerable interest because of their wide application prospects. Luminescent compounds doped with
9、 Pr3+ ions are promising materials for e.g. lamp phosphors, scintillators and tunable solid-state lasers as well as the agents improving solar cells efficiency.Pr3+ ion is a well-known luminescent center emitting light from the ultraviolet to the infrared, especially for its prominent red luminescen
10、ce due to the 1D2-3H4 and 3P0-3H6 transitions, respectively, praseodymium is much cheaper than europium. Therefore, Pr3+-doped phosphors have been attractive as the candidate of red phosphor materials. In this paper, novel Pr3+-doped Li2SrSiO4 red phosphors were synthesized and their photoluminescen
11、ce properties were studied for the first time. These phosphors could be effectively excited by a commercial blue LED chip and emit-ted strong red light.Pr3+ ion has rich emission spectral lines in UV, visible, and infrared regions due to its intricate energy level scheme.Therefore, Pr3+ doped materi
12、als have several applications, such as fiber laser amplifier, red-emitting phosphors, visible lasers and mid-infrared laser.In many closed shell transition metal oxides, Pr3+ ions can be excited either directly in the blue(3H4-3P0,1,2, 1I6 intraconfigurational transitions) or in the UV (interconfigu
13、rational 4f2-4f15 d1transitions), or indirectly through UV host excitation followed by an energy transfer and/or an intervalence charge transfer (IVCT) process.A new Pr3+-activated molybdate-based phosphor for application to white LEDs with blue excitation. Red-emitting phosphors were obtained by us
14、ing low-cost Pr3+ ions as the activator and host lattices containing closed-shell transition metal ions.Photoluminescence of Pr3+ -doped materials has many unique features such as quantum cutting (photon cascade emission), UV-tunable luminescence from 4f1-5d1 levels and visible light emissions from
15、3P0 and/or 1D2 levels. Photoluminescence of Pr3+-doped materials has emissions of 3P03F2(650 nm),3P03H6 (616 nm) and 1D23H4(605 nm). Three red emission bands centered at 648, 621 and 602 nm resulted from absorptions at 451, 473 and 489 nm, which was attributable to the 3H4 3PJ(J = 0, 1, 2) transitio
16、ns, respectively. Furthermore, the strong sharp emission peak at 648 nm was attributable to the 3P03F2 transition. The weak red emissions located at 621 and 602 nm were due to the 3P0 3H6 and 1D2 3H4 transitions, respectively, induced by the lack of inversion symmetry at the Pr3+ sites.The trivalent praseodymium ion Pr3+ has an intricate energy level scheme with various energy gaps and a rich emission spectrum extending from the ul
