Phosphor in powder form. (KLuTa2O7: Eu3+)
This research challenge is aimed at studying materials architectures suitable for SSL wavelength down-conversion. Particular materials we have focused on in this research challenge are Eu3+-doped phosphors and group II-VI semiconductor quantum dots (QDs).
Among the principal criteria for such wavelength down-conversion materials are a
- high quantum yield (QY);
- narrow-linewidth emission (particularly in the range of 610-620 nm);
- broad blue absorption that is well matched to the emission of the blue pump LED;
- low thermal quenching;
- photo and thermal stability; and
- potential for directionality and chromaticity tuning desirable for higher functionality light.
The Eu3+ phosphors are based on tantalate and niobate oxides, and take advantage of the narrow red emission lines characteristic of electronic transitions in the Eu3+ f-shell. The QDs are based on CdZn-VI materials, synthesized currently using colloidal methods.
Solutions of nanocolloidal phosphors.
QDs have numerous long-term and fundamental advantages over rare-earth phosphors, including:
- a broad and a five-orders-of-magnitude-greater blue absorbance;
- a relatively good accommodation of strain, which can enable a wide range of alloy compositions and emission wavelengths;
- the possibility of active chromaticity tuning (through Stark-effect-based modification of absorption oscillator strengths) for higher functionality light; and
- synergy with the light-emission-physics Scientific Research Challenges 3, 4, 5, and 6.
We initially focused on a low-temperature inverse-micellar-solution method for QD synthesis. We now believe, however, that luminescent quantum yields of QDs synthesized in this low-temperature manner will always be relatively low. We are now pursuing high-temperature colloidal methods for QD synthesis, bringing in a collaborator and expert at these methods, Professor David Kelley of UC Merced.
Research Challenge Publications
- Dr. Jim Martin (SNL) – Principal Investigator, primarily responsible for QD synthesis; participates in characterization.
- Prof. David Kelley (UC Merced) – Guides the synthesis of the QD core/shell heterostructures, especially through developing simulation codes for computing the QD strain energy, and performs electronic structure simulations.
- Dr. May Nyman (SNL) – Hydrothermal synthesis of phosphors and their structural characterization.
- Dr. Lauren Rohwer (SNL) – Photophysical characterization of both the Eu3+ phosphors and the quantum dots; also guides synthesis and development of the phosphors.
- Shea-Rohwer, Lauren E.; Martin, James E.; Cai, Xichen; and Kelley, David F. Red-emitting quantum dots for solid-state lighting, ECS J. Solid State Sci. Technol., 2, R3112 (2012). [10.1149/2.015302jss]
- Tsao, Jeffrey Y.; Brener, Igal; Kelley, David F.; and Lyo, S. Ken Quantum-Dot-Based Solid-State Lighting With Electric-Field-Tunable Chromaticity, J. Disp. Technol., (2012). [10.1109/JDT.2012.2225407]
- Bleier, Grant C.; Nyman, May; Rohwer, Lauren E. S.; and Rodriguez, Mark A. Seeking the optimal LaTaO4:Eu phosphor, Journal of Solid State Chemistry, 184, 3221 (2011). [10.1016/j.jssc.2011.10.008]
- Forbes, Tori Z.; Nyman, May; Rodriguez, Mark A.; and Navrotsky, Alex The Energetics of Lanthanum Tantalate Materials, J. Solid State Chem., 183, 2516 (2010). [10.1016/j.jssc.2010.08.024]
- Carmele, A.; Kabuss, Julia; and Chow, Weng W. Highly-detuned Rabi oscillations in a quantum-dot-microcavity system, Phys. Rev. B, (2013).
- Lingnau, Benjamin; Ludge, Kathy; Chow, Weng W.; and Scholl, Eckehard Failure of the α factor in describing dynamical instabilities and chaos in quantum-dot lasers, Phys. Rev. E, 86, 065201(R) (2012). [10.1103/PhysRevE.86.065201]
- Lingnau, Benjamin; Ludge, Kathy; Chow, Weng W.; and Scholl, Eckehard INFLUENCING MODULATION PROPERTIES OF QUANTUM-DOT SEMICONDUCTOR LASERS BY CARRIER LIFETIME ENGINEERING, Appl. Phys. Lett., 101, 131107 (2012). [10.1063/1.4754588]
- Carmele, A.; Kabuss, Julia; Richter, M.; Knorr, A.; and Chow, Weng W. Quantum optics in a semiconductor quantum dot, Journal of Modern Optics, 58, 1951 (2011). [10.1080/09500340.2011.596630]
- Luk, Ting Shan; Xiong, Shisheng; Chow, Weng W.; Miao, Xiaoyu; Subramania, Ganesh; Resnick, Paul J.; Fischer, Arthur J.; and Brinker, Jeffrey C. Anomalous enhanced emission from PbS quantum dots on a photonic-crystal microcavity, Journal of the Optical Society of America B: Optical Physics, 28, 1365-1373 (2011). [10.1064/JOSAB.28.001365]
- Miao, Xiaoyu; Brener, Igal; and Luk, Ting Shan Nanocomposite plasmonic fluorescence emitters with core/shell configurations, J. Opt. Soc. Am. B, 27, 1561 (2010). [10.1364/JOSAB.27.001561]