Nanosys Inc. garnered U.S. Patent 7,645,397 for luminescent nanocomposites and methods for incorporating luminescent nanostructures into curable matrices while preserving the luminescent properties into the solid state. The nanostructures optionally have ligands bound to their surface, including novel ligands and/or other tightly binding ligands.
Nanosys’ nanofabrication technique produces novel nanostructure ligands that enhance the miscibility of nanostructures in solvents or polymers, increase quantum efficiency of nanostructures, and preserve nanostructure luminescence when the nanostructures are incorporated into a matrix.
Nanosys also developed the nanofabrication processes to produce indium phosphide nanostructures and core-shell nanostructures with Group II-VI shells. The nanostructures have high quantum efficiency, small size, and a narrow size distribution. The nanostructures range in size from 1 nanometer (nm) to 500 nm.
High performance down-converting phosphor technologies will play a prominent role in the next generation of visible light emission, including high efficiency solid-state white lighting (SSWL). In addition, such technologies are also applicable to near infrared (NIR) and infrared (IR) light emitting technologies. Down-conversion from ultraviolet (UV) or blue light emitting semiconductor light emitting diodes (LEDs) into blue, red and green wavelengths offers a fast, efficient and cost-effective path for delivering commercially attractive white light sources.
Unfortunately, existing rare-earth activated phosphors or halophosphates, which are currently the primary source for solid-state down-conversion, were originally developed for use in fluorescent lamps and cathode ray tubes (CRTs), and therefore have a number of critical shortfalls when it comes to the unique requirements of SSWL. As such, while some SSWL systems are available, poor power efficiency (<20 light lumens/watt (lm/W)), poor color rendering (Color Rendering Index (CRI)<75) and extremely high costs (>$200/kilolumen (klm)) limit this technology to niche markets such as flashlights and walkway lighting.
Nanosys breakthrough provides solid state white lighting devices with a power efficiency greater than 200 lm/W. The matrix materials doped with nanocrystals have specific emission and absorption characteristics that also allow for specific tailoring of refractive indexes of the nanocomposites.
The processes used to prepare luminescent nanocomposite polymeric layers for coating active devices (e.g., LEDs), or optical devices (e.g., refractive lenses or reflective elements) were developed for Nanosys by inventors J. Wallace Parce, Paul Bernatis, Robert Dubrow, William P. Freeman, Joel Gamoras, Shihai Kan, Baixin Qian, Jeffery A Whiteford, Andreas Meisel and Jonathan Ziebarth.
The nanostructure are made of an indium phosphide (InP) core, optionally, with a zinc sulfide (ZnS), or zinc selenide (ZnSe), shell, and optionally with a ligand bound to a surface of the nanostructure. The ligand is a dicarboxylic acid moiety that binds to the surface of the member nanocrystal such as decylamine or octylamine.
The nanocrystals have a size and a composition such that they absorb visible, ultraviolet, near-infrared and/or infrared light, and the polymeric layers scatter a minimal portion of light that enters the layers. In certain embodiments, the polymer is silicone.
The polymeric layers can be used to coat optical devices (e.g., refractive lenses or reflective elements) or can be used to encapsulate active devices, such as a light emitting diodes (LEDs). Suitably, the polymeric layers will absorb visible light, red light, blue light and green light.
The nanocrystals utilized throughout will suitably be between about 1-10 nm in size, about 1-4 nanometers (nm) in size or about 1-3 nm in size and can further comprise miscibility-enhancing ligands attached to their surface to aid in mixing with the polymers.
The nanocrystals utilized throughout will suitably be between about 1-10 nm in size, about 1-4 nanometers (nm) in size or about 1-3 nm in size and can further comprise miscibility-enhancing ligands attached to their surface to aid in mixing with the polymers.
Nanosys polymeric layers can have any effective refractive index between that of the pure polymer and the pure nanocrystals, and will suitably have an effective refractive index greater than about 1.5 and in certain embodiments about 1.8.
Nanosys also developed polymeric layers comprised of a polymer and semiconductor nanocrystals embedded within the polymer. The polymeric layer has an effective refractive index greater than the polymer alone, and the polymeric layer scatters a minimal portion of light that enters the polymeric layer. Suitably, the polymeric layers will scatter less than about 50%, to less than about 15% of light that enters the polymeric layers. The nanocrystals will be ZnS nanocrystals and the polymeric layers will be greater than about 0.5 mm in thickness.
