2006 Fiscal Year Final Research Report Summary
Development of new phosphors for high Ra white LEDs in the next generation
| Project/Area Number |
16360009
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied materials science/Crystal engineering
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| Research Institution | Yamaguchi University |
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Principal Investigator |
TAGUCHI Tsunemasa Yamaguchi University, Graduate School of Science and Engineering, Professor, 大学院理工学研究科, 教授 (90101279)
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| Co-Investigator(Kenkyū-buntansha) |
YAMADA Yoichi Yamaguchi University, Graduate School of Science and Engineering, Associate Professor, 大学院理工学研究科, 助教授 (00251033)
KURAI Satoshi Yamaguchi University, Graduate School of Science and Engineering, Research Associate, 大学院理工学研究科, 助手 (80304492)
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| Project Period (FY) |
2004 – 2006
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| Keywords | Semiconductor Optical Characterization / Crystal Growth / Thin film phosphor / Color Rendering / II-VI Compound Semiconductor / White Light-emitting Diode |
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| Research Abstract |
We have investigated the growth and characterization of thin film phosphors based on Zn_xCd_<1-x>S : I and ZnS_xTe_<1-x> : I. We have also investigated the optimization of structures of white LEDs based on nUV-LED excited phosphor system.
1) Yellow near band emission and red SA emission were simultaneously observed in the PL spectrum of Zn_<0.55>Cd_<0.45>S : I thin film phosphor excited by nUV-LED (405 nm).
2) Strong blue-green emission around 490nm related to Te_2 cluster in ZnS was observed from ZnS_<1-x>Te_x thin film phosphor(x=0.003〜0.020). The highest internal quantum efficiency of ZnS_<1-x>Te_x was calculated to be 25 % at Te composition of 0.020.
3) Very broad spectra covering whole visible light, which originate to Te_2 clusters and SA centers in ZnS, was taken from ZnS_<0.98>Te_<0.02>:I thin film phosphor. The highest Ra was obtained to be 88 by the optimization of C_2H_5I flow rate. High quality white light was realized by single material of ZnSTe:I.
4) The efficiency and color rendering of white LEDs using mixed RGB phosphor system were affected by energy transfer between R, G, and B phosphor. On the other hand, white LEDs using separated RGB phosphor system was demonstrated, and it have much advantage of high efficiency and high uniformity of color rendering. These results indicated the high-quality white LED with separated thin film phosphor system by using such as lithography technique.
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