Photoluminescent Nanofibers for Solid-State Lighting Applications
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1240-WW09-07
Photoluminescent Nanofibers for Solid-State Lighting Applications J. Lynn. Davis, Li Han, Paul Hoertz, Kim Guzan, Karmann C. Mills, Howard J. Walls, Teri A.Walker, and Damaris Magnus-Aryitey RTI International PO Box 12194 Research Triangle Park, NC 27709-2194 U.S.A.
ABSTRACT Photoluminescent nanofibers (PLN) can be formed by combining electrospun polymeric nanofibers and luminescent particles such as quantum dots (QD). The physical properties of PLNs are dependent upon many different nanoscale parameters associated with the nanofiber, the luminescent particles, and their interactions. By understanding and manipulating these properties, the performance of the resulting optical structure can be tailored for desired end-use applications. For example, the quantum efficiency of quantum dots in the PLN structure depends upon multiple parameters including quantum dot chemistry, the method of forming the PLN nanocomposites, and preventing agglomeration of the quantum dot particles. This is especially important in solution-based electrospinning environments where some common solvents may have a detrimental effect on the performance of the PLN. With the proper control of these parameters, high quantum efficiencies can be readily obtained for PLNs. Achieving high quantum efficiencies is critical in applications such as solid-state lighting where PLNs can be an effective secondary conversion material for producing white light. Methods of optimizing the performance of PLNs through nanoscale manipulation of the nanofiber are discussed along with guidelines for tailoring the performance of nanofibers and quantum dots for application-specific requirements. . INTRODUCTION Solid-state lighting (SSL) is an emerging illumination technology that leverages advances in light emitting diode (LED) technology to provide general illumination for both indoor and outdoor applications. In SSL devices, blue light, which has low photopic sensitivity, is provided by a LED and used as the pump wavelength in phosphor-converted light emitting diodes (pcLEDs). Photoluminescent processes occurring in a phosphor or other luminescent material convert the blue pump light into broad-spectrum visible radiation encompassing the spectral region from 400 to 750 nm, producing light emissions in spectral regions with greater photopic sensitivity than the blue LED emission. The luminous flux produced by such a device is significantly higher than that of the blue LED alone. Core-shell quantum dots (QD), such as those with a cadmium selenide (CdSe) core and a zinc sulfide (ZnS) shell, can be used to provide light emissions across the visible spectrum, and nanofibers containing QDs or other luminescent nanoparticles have been demonstrated to provide efficient secondary emission of broadband visible radiation to produce white light [1]. These structures, termed photoluminescent nanofibers (PLN), provide multiple benefits in lighting applications including serving as mass producible, light diffusion materials with excellent color rendering properties.
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