| EOSL is headquarters for the Phosphor Technology Center of Excellence (PTCOE) funded by the Advanced Research Projects Agency. Phosphor research at EOSL focuses on the development of materials and devices for high-power microwave and flat-panel displays. Through the Phosphor Technology Center of Excellence , a consortium of universities and industry hosted by Georgia Tech, new phosphor materials and better techniques for thin-film deposition of color phosphors are developed. The center conducts joint research with leading U.S. manufacturers of high-definition flat-panel displays to develop new electroluminescent, cathodoluminescent, plasma and field-emission displays for commercial and military markets.
This research is funded by the Defense Advanced Research Projects Agency , the Georgia Research Alliance and industry.
Phosphor Technologies
Whether driving down a dark highway at night or flying an airplane during a storm, people rely on the brightness of the dials and meters on their dashboards to get them safely to their destinations. The same phosphor technology that makes those dials glow is also at work in high-definition television, medical instrument monitors, computer screens, virtual environment displays and other high-tech applications, making it indispensable to our health and welfare, and of growing importance to the economy.
Because they glow without any increase in temperature, phosphors are an important and highly researched area for a number of emerging flat-panel display technologies.
PTCOE is active in research in this area, including improving low-voltage thin-film electroluminescence displays, field emissions display films and thin-film cathode ray tube films. PTCOE researchers are working to develop novel phosphor materials and structures. They already have made significant progress toward developing a new phosphor material for use as a blue emitter, and also for electroluminescent displays in developing low temperature processing techniques that will enable low-cost manufacturing on glass substrates. We've developed new phosphor coating techniques that have also shown promise for improving the performance of low-voltage phosphors for field emission displays, an important first step in reducing the power consumption of these displays.
Background
The Phosphor Technology Center of Excellence (PTCOE) was established by the Defense Advanced Research Projects Agency (DARPA) in 1993 and funded for nine years as a university-led consortium comprising a government/ university/industry partnership. The center, headquartered at Georgia Tech, was established to support the DARPA High Definition Display Technology Program and included nine universities, three national and government laboratories and over 30 companies.
Research Directions
Since its inception PTCOE has been involved in the growth, synthesis and characterization of phosphor materials and thin-film structures for all types of display applications such as photoluminescent LCDs, field emission displays, cathode ray tubes, plasma display panels, and electroluminescent displays. In the last several years, PTCOE's focus has broadened considerably out of traditional displays into applications such as image intensifiers, X-ray cameras/detection, solid state lighting, powder/organic electroluminescence, UVC phosphors for bio-decontamination, quantum dots for drug screening and neural electrodes. Additionally, some of the technology developed under the PTCOE is being applied to passivation/sealing techniques for organic, high power density electronics and electrical distribution components, as well as chem./bio detection.
Phosphor Laboratory Capabilities
The Phosphor Center at EOSL offers an extensive set of modeling, physical, optical, electrical and cathodoluminescent characterization capabilities. The physical characterization facilities include SEM, energy dispersive X-ray, TEM, X-ray diffraction, particle size analysis and rheometry. These facilities are complemented by a wide variety of synthesis and fabrication capabilities ranging from the standard microelectronics facilities (e.g., photolithography to 0.6 m m, metallization, hybrid assembly and packaging, etc.) to thin film, phosphor powder and screen synthesis facilities. These include, for example, controlled atmosphere tube furnaces to 8” diameter and 1700°C, screen printing, settling and large area ion assisted physical vapor deposition.
Also available for phosphor analysis is an extensive array of optical characterization tools ranging from luminance, chromaticity, color rendering index to photoluminescence (PL), PL excitation spectroscopy and spectral transmission and reflection. The excitation capabilities of these systems cover from 115nm to 2 m m with pulses as short as 600ps over a temperature range of 1.6 to 350K while the detection range for these systems range from the vacuum UV to the long wavelength IR region (~10 m m). Additionally, an IR microscope with thermal imaging resolution to ~3 m m is available to investigate thermal issues of high power density devices such as LEDs for solid-state lighting. The electrical characterization facilities include standard microelectronics capabilities as well as capacitance-voltage, current-voltage, brightness-voltage, charge-voltage, efficiency-voltage, and charge deep level transient spectroscopy for luminescent materials and devices.
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