| Compared with traditional solid-state lighting technologies(such as incandescent lamps and fluorescent lamps), white-light-emitting diodes(WLED) have several advantages, such as lower voltage, longer lifetime, wider application, higher color-rendering index, and environmental friendship. At present, the tricolor phosphors commonly used for near-ultraviolet(UV) LEDs have the disadvantages of chemical instability and low efficiency. Therefore, it is important to explore novel phosphors for near-UV In Ga N-based white LED. In this paper, a series of phosphors based on three different host compounds were synthesized by solid-state method, and characterized by X-ray powder diffraction(XRD). Their photo-luminescent properties were investigated. At last, LEDs were fabricated by coating the chosen phosphors on ~395 nm In Ga N chips, and their electro-luminescent properties were investigated. The main contents are as follows.(1) La BSi O5: Ln3+(Ln3+ = Eu3+, Tb3+, Ce3+) phosphors: Firstly, the luminescent properties of La1-xBSi O5: x Eu3+ were investigated. These samples could be efficiently excited by near-UV light with the strongest excitation peak at 395 nm. The main emission peak is located at 619 nm. The emission intensity of La1-xBSi O5: x Eu3+ was optimized by introducing Al3+ ions. The emission intensity of La0.70B0.75 Si O5: 0.30Eu3+, 0.25Al3+ is about 3.8 times that of Y2O2S: 0.05Eu3+ under 395 nm light excitation. Bright red light can be observed from the LEDs based on the phosphor La0.70B0.75 Si O5: 0.30Eu3+, 0.25Al3+. Secondly, the luminescent properties of La1-xBSi O5: x Tb3+ and La1-yBSi O5: y Ce3+ were investigated. The excitation spectra of La1-xBSi O5: x Tb3+ were recorded by monitoring emission at 544 nm. The broad excitation band from 270 to 300 nm is due to the charge transition band, and the series of sharp peaks in the range of 300 ~ 390 nm is due to the f- f transitions of Tb3+. La1-yBSi O5: y Ce3+ exhibits emission with the two broad peaks at 355 nm and 376 nm under 330 nm light excitation. At last, intense green emission was observed from the La1-x-zBSi O5: x Tb3+, z Ce3+ phosphor by Ce3+ and Tb3+ co-doping, and the energy transfer from Ce3+ to Tb3+ was investigated.(2) La Mo BO6: Ln3+(Ln3+ = Eu3+, Sm3+, Tb3+) phosphors: Firstly, La1-xMo BO6: x Eu3+ were investigated. These red phosphors could be efficiently excited by 395 nm light. When the content of Eu3+ is 40 %, the sample shows the strongest red emission. The emission intensity of La1-xMo BO6: x Eu3+ was optimized by introducing Al3+ ions. The red emission intensity of La0.60 Mo B0.70O6: 0.40Eu3+, 0.30Al3+ is about 1.4 times as strong as that of La0.60 Mo BO6: 0.40Eu3+ under 395 nm light excitation. Secondly, La1-xMo BO6: x Sm3+ were prepared by the solid state reaction. They exhibit the characteristic emission peaks of Sm3+(598 nm,4G5/2 â†' 6H7/2)under 403 nm excitation. At last, the luminescent properties of La1-xMo BO6: x Tb3+ were investigated. No concentration quenching of Tb3+ ions was observed in the series samples of La1-xMo BO6: x Tb3+. The green emission intensity of Tb Mo BO6 was enhanced by introducing W6+ ions(10 %).(3) La2Mo2O9: Ln3+(Ln3+ = Eu3+, Sm3+) phosphors: Firstly, La2(1-x)Mo2O9: 2x Eu3+ shows intense red emission with intense excitation peaks in near UV regions. When the content of Eu3+ is 0.60, the sample La1.40Mo2O9: 0.60Eu3+ shares the strongest red emission. Secondly, the excitation and emission intensities of La1.40Mo2O9: 0.60Eu3+ were enhanced by introducing an appropriate amount of W6+ ions. The red emission intensity of La1.40Mo1.84O9:0.60Eu3+,0.16W6+ under 395 nm excitation was the strongest, which was about 1.23 times that of La1.40Mo2O9: 0.60Eu3+. At last, the red light LED device was fabricated by coating In Ga N chip(~395 nm emission) with the phosphor La1.40Mo1.84O9: 0.60Eu3+, 0.16W6+. Red light with high brightness was observed from the LED by naked eyes. |
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