Ligand-Passivated Eu:Y2O3 Nanocrystals as a Phosphor for White Light Emitting Diodes

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• 作者：Qilin Dai ; Megan E. Foley ; Christopher J. Breshike ; Adrian Lita ; Geoffrey F. Strouse
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：October 5, 2011
• 年：2011
• 卷：133
• 期：39
• 页码：15475-15486
• 全文大小：1106K
• 年卷期：v.133,no.39(October 5, 2011)
• ISSN：1520-5126

文摘

Eu(III)-doped Y₂O₃ nanocrystals are prepared by microwave synthetic methods as spherical 6.4 卤 1.5 nm nanocrystals with a cubic crystal structure. The surface of the nanocrystal is passivated by acetylacetonate (acac) and HDA on the Y exposed facet of the nanocrystal. The presence of acac on the nanocrystal surface gives rise to a strong S₀ 鈫?S₁ (蟺 鈫?蟺*, acac) and acac 鈫?Ln³⁺ ligand to metal charge transfer (LMCT) transitions at 270 and 370 nm, respectively, in the Eu:Y₂O₃ nanocrystal. Excitation into the S₀ 鈫?S₁ (蟺 鈫?蟺*) or acac 鈫?Ln³⁺ LMCT transition leads to the production of white light emission arising from efficient intramolecular energy transfer to the Y₂O₃ oxygen vacancies and the Eu(III) Judd鈥揙felt f鈥?/i>f transitions. The acac passivant is thermally stable below 400 掳C, and its presence is evidenced by UV鈥搗is absorption, FT-IR, and NMR measurements. The presence of the low-lying acac levels allows UV LED pumping of the solid phosphor, leading to high quantum efficiency (19%) when pumped at 370 nm, high-quality white light color rendering (CIE coordinates 0.33 and 0.35), a high scotopic-to-photopic ratio (S/P = 2.21), and thermal stability. In a LED lighting package luminosities of 100 lm W^鈥? were obtained, which are competitive with current commercial lighting technology. The use of the passivant to funnel energy to the lanthanide emitter via a molecular antenna effect represents a new paradigm for designing phosphors for LED-pumped white light.