In order to develop a yellow phosphor that emits efficiently under the 450–470 nm excitation range, we have synthesized a Eu2+-activated Sr3SiO5 yellow phosphor and attempted to develop white light-emitting diodes (LEDs) by combining them with a InGaN blue LED chip (460 nm). Two distinct emission bands from the InGaN-based LED and the Sr3SiO5:Eu phosphor are clearly observed at 460 nm and at 570 nm, respectively. These two emission bands combine to give a spectrum that appears white to the naked eye. Our results showed that InGaN (460 nm chip)-based Sr3SiO5:Eu exhibits a better luminous efficiency than that of the industrially available product InGaN (460 nm chip)-based YAG:Ce.

We have synthesized a Eu2+-activated Sr2SiO4 yellow phosphor and investigated an attempt to develop white light-emitting diodes (LEDs) by combining it with a GaN blue LED chip. Two distinct emission bands from the GaN-based LED and the Sr2SiO4:Eu phosphor are clearly observed at 400 nm and at around 550 nm, respectively. These two emission bands combine to give a spectrum that appears white to the naked eye. Our results showed that GaN (400-nm chip)-based Sr2SiO4:Eu exhibits a better luminous efficiency than that of the industrially available product InGaN (460-nm chip)-based YAG:Ce.

The shifts of the emission band to longer wavelength (yellow-orange) of the Sr3SiO5:Eu yellow phosphor under the 450–470 nm excitation range have been achieved by adding the codoping element (Ba2+) in the host. In order to apply to white-light-emitting diodes (LEDs) with warm white and high color rendering index, we have fabricated white LEDs through the integration of the InGaN blue LED chip and the two phosphor blends (Sr2SiO4:Eu yellow phosphor +Ba2+ co-doped Sr3SiO5:Eu yellow-orange phosphor) into a single package. By employing two phosphors, covering a red region, the white LEDs show a warm white in the range of 2500–5000 K correlated color temperature and a good color rendering of over 85.

Combinatorial chemistry has been widely applied to the synthesis of a variety of materials such as drugs, various inorganic functional materials, etc. 1-3 In regard to the inorganic materials, most of investigations, which dealt with the combinatorial chemistry, are focused on the solid-state combinatorial chemistry based on thin film technology. [2][3][4][5][6] The present investigation aims at applying the liquid state combinatorial chemistry method to the synthesis of phosphor powders. Unlike the solid-state combinatorial chemistry method based on thin film technology, the method used by the authors adopted a solution method so that it could rather be similar to the combinatorial chemistry used in the pharmaceutical industry. It is, however, noted that the present combinatorial chemistry method is much simpler than the conventional one in that the number of compounds in a batch is far less than the conventional method developed by others. [1][2][3][4][5][6] In this respect, the method adopted in the present investigation is called pseudocombinatorial chemistry method (PCCM). Notwithstanding the above-described shortcoming, PCCM has a great potential when applied to the fine screening of well-known phosphor compounds.PCCM has several merits when applied to the phosphor synthesis, the most significant one of which is the capability of combining the synthesis and the characterization in a very efficient way. The conventional solid-state combinatorial chemistry, in which phosphors are dealt with based on thin film technology, 3-6 is carried out on a very large scale, that is, a huge number of compounds are given on the small substrate and synthesized at the same time, but the amount of each compound is too small to be characterized properly. In the case of the phosphor, the host composition which has been already developed, requires only the fine-tuning of the composition. It is, however, actually very hard to discern the optimum composition among a large number of phosphors showing a similar level of emission intensity. PCCM adopted in the present investigation makes it possible to characterize all the properties of an individual compound in the same way that is adopted for the conventional powder sample. Thus the measurement of conventional spectroscopy, decay, X-ray diffraction (XRD), and scanning electron microscopy (SEM) possible.The main purpose of the present investigation is to find out the composition of BaAl 12 O 19 :Mn phosphor that exhibits the highest luminous efficiency adaptable for plasma display panel (PDP). In fact, only the Zn 2 SiO 4 :Mn phosphor has served as a green component in PDP but recently the BaAl 12 O 19 :Mn phosphor have began to be considered as an alternative. Even though the fact that the BaAl 12 O 19 :Mn phosphor does not fluoresce under UV (254 nm) excitation causes some difficulties in the process of phosphor painting, 7 the emission efficiency of this phosphor under VUV excitation is almost tantamount to that of conventional Zn 2 SiO 4 :Mn phosphor. It should be, however, note...

A narrow-band red emission is a seminal issue for establishing the color-rendering index and color gamut of phosphor-converted white light emitting diode (pc-WLED) applications. In this regard, Mn 4+ -activated K 2 SiF 6 phosphors (referred to as K216) have recently attracted a great deal of attention after their successful commercialization. As with K216 phosphors, Mn 4+ -activated K 3 SiF 7 (referred to as K317) phosphors perform in a manner that is similar to that of K216 phosphors and have been introduced as a narrow-band red phosphor. Despite the acceptable performances of both versions of phosphors, slower decay remains a shortcoming for applications to high-powered LEDs. We introduced K317 derivatives by replacing K with Rb and Cs. As a result, Mn 4+ -activated (Rb,Cs) 3 SiF 7 phosphors were synthesized with different Rb:Cs ratios and exhibited faster decay times by comparison with both the K216 and the K317 phosphors. The present study involved both structural and luminescent investigations along with density functional theory (DFT) calculations for novel (Rb,Cs) 3 SiF 7 :Mn 4+ phosphors. This study reveals the possibility of a completely solid solution with single-phase formation within the entire range of Rb−Cs with retention of the tetragonal structure in the P4/mbm space group.