Patent Application
20170074485
The present application relates to quantum dot emission technology, and to localized optics involving quantum dots.
Semiconductor nanocrystallites (quantum dots) whose radii are smaller than the bulk exciton Bohr radius constitute a class of materials intermediate between molecular and bulk forms of matter. Quantum confinement of both the electron and hole in all three dimensions leads to an increase in the effective band gap of the material with decreasing crystallite size. Consequently, both the optical absorption and emission of quantum dots shift to the blue (higher energies) as the size of the dots gets smaller.
Incorporating quantum dots in display devices, such as LCDs, has been shown to produce highly vibrant colors while reducing the overall power consumption. The quantum dots are typically dispersed within a film that stretches along the area of the display.
Embodiments of the present application relate to localizing the use of quantum dot films over LEDs. The embodiments of the present application provide advantages over the traditional technique of providing a film that covers the entire area of a display screen.
According to an embodiment, a local optic includes an optical source on a substrate, a housing, and a film that includes quantum dots. The housing is designed to fit around the optical source and has a cross-sectional area along a plane parallel to a surface of the substrate. The film is designed to sit on top of the housing and has a substantially similar cross-sectional area to the cross-sectional area of the housing.
According to another embodiment, a local optic includes an optical source on a substrate, an enclosure coupled to a surface of the substrate, and a film that includes quantum dots. The enclosure surrounds the optical source above the surface of the substrate. The film is located along an inner surface of the enclosure.
According to another embodiment, a local optic includes an optical source on a substrate, and an enclosure coupled to a surface of the substrate. The enclosure surrounds the optical source above the surface of the substrate and includes quantum dots dispersed within the material of the enclosure. Each quantum dot dispersed within the material of the enclosure is encased within a glass bead.
The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present embodiments and, together with the description, further serve to explain the principles of the present embodiments and to enable a person skilled in the relevant art(s) to make and use the present embodiments.
The features and advantages of the present embodiments will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.
Although specific configurations and arrangements may be discussed, it should be understood that this is done for illustrative purposes only. A person skilled in the pertinent art will recognize that other configurations and arrangements can be used without departing from the spirit and scope of the present invention. It will be apparent to a person skilled in the pertinent art that this invention can also be employed in a variety of other applications beyond those specifically mentioned herein.
It is noted that references in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Further, when a particular feature, structure or characteristic is described in connection with an embodiment, it would be within the knowledge of one skilled in the art to effect such feature, structure or characteristic in connection with other embodiments whether or not explicitly described.
Before describing the details of the embodiments herein, a brief description of quantum dots and the film that the quantum dots are commonly dispersed in will be discussed. Quantum dots may be used in a variety of applications that benefit from having sharp, stable, and controllable emissions in the visible and infrared spectrum.
Core material 102 includes a semiconducting material that emits light upon absorption of higher energies. Examples of core material 102 include indium phosphide (InP), cadmium selenide (CdSe), zine sulfide (ZnS), lead sulfide (PbS), indium arsenide (InAs), indium gallium phosphide, (InGaP), and cadmium telluride (CdTe). Any other III-V, tertiary, or quaternary semiconductor structures that exhibit a direct band gap may be used as well. Of these materials, InP and CdSe are most often used, but InP is more desirable to implement over CdSe due to the toxicity of CdSe dust. CdSe may exhibit emissions having a full-width-half-max (FWHM) range of around 30 nm while InP may exhibit emissions having a FWHM range of around 40 nm.
Buffer layer 104 may surround core material 102. Buffer layer 104 may be zinc selenide sulfide (ZnSeS) and is typically very thin (e.g., on the order of 1 monolayer). Buffer layer 104 may be utilized to help increase the bandgap of core material 102 and improve the quantum efficiency.
Shell material 106 may be on the order of two monolayers thick and is typically, though not required, also a semiconducting material. The shells provide protection to core material 102. A commonly used shell material is zinc sulfide (ZnS), although other materials may be used as well. Shell material 106 may be formed via a colloidal process similar to that used to form core material 102.
Ligands 108 may be adsorbed or bound to an outer surface of shell material 106. Ligands 108 may be included to help separate (e.g., disperse) the quantum dots from one another. If the quantum dots are allowed to aggregate as they are being formed, the quantum efficiency drops and quenching of the optical emission occurs. Ligands 108 may also be used to impart certain properties to quantum dot 102, such as hydrophobicity, or to provide reaction sites for other compounds to bind. A wide variety of ligands 108 exist that may be used with quantum dot 102. In an embodiment, ligands 108 from the aliphatic amine or aliphatic acid families are used. Further details on the fabrication of the quantum dots may be found in U.S. application Ser. No. 13/803,596, filed Mar. 14, 2013, the disclose of which is incorporated herein by reference.
Bottom layer 206 and top layer 208 may be a variety of materials that are substantially transparent to the wavelengths being emitted by optical source 204 and the quantum dots trapped within quantum dot layer 210. For example, bottom layer 206 and top layer 208 may be glass or polyethylene terephthalate (PET). Bottom layer 206 and top layer 208 may also by polyester coated with aluminum oxide. Other polymers may be used as well that exhibit low oxygen permeability and low absorption for the wavelengths being emitted by the quantum dots trapped within quantum dot layer 210. It is not necessary that bottom layer 206 and top layer 208 be comprised of the same material.
Quantum dot layer 210 includes a plurality of quantum dots within an adhesive material. According to an embodiment, quantum dot layer 210 has a thickness between about 50 and 150 micrometers (μm) and is used as a light down conversion layer. Quantum dot layer 210 may have a thickness around 100 μm. The adhesive material binds to both bottom layer 206 and top layer 208, holding the sandwich-like structure together.
In an embodiment, the plurality of quantum dots includes sizes that emit in at least one of the green and red visible wavelength spectrums. The quantum dots are protected in quantum dot layer 210 from environmental effects and kept separated from one another to avoid quenching. The quantum dots may be spatially separated by enough distance such that quenching processes like excited state reactions, energy transfer, complex-formation and collisional quenching do not occur.
In one example, quantum dots are mixed within an amino silicone liquid and are emulsified into an epoxy resin that is coated to form quantum dot layer 210. Other example materials for use in quantum dot layer 210 include acrylates, epoxies, acrylated epoxies, ethylene-vinyl acetate, thiol-enes, polyurethane, polyethers, polyols, and polyesters. Further details regarding the fabrication and operation of quantum dot enhancement films may be found in U.S. application Ser. No. 13/287,616, filed on Nov. 2, 2011, the disclosure of which is incorporated herein by reference.
Embodiments herein relate to using quantum dot films and quantum dots dispersed in other materials. The localization of the quantum dot films may greatly reduce fabrication costs.
A housing 306 is disposed around optical source 304. Housing 306 may be opaque to the wavelengths generated by optical source 304. Housing 306 is attached to a top surface of substrate 302 and can have any cross-sectional shape along a plane parallel to the top surface of substrate 302. For example, housing 306 may have a circular, oval, square, or rectangular cross section. The exact size of housing 306 varies based on the application. When a high density of optical sources are used, each housing around a corresponding optical source may be made smaller to fit each of the housings on the same substrate.
The top portion of housing above optical source 304 is kept open. A quantum dot film 308 may be placed on a top surface of housing 306 as illustrated in
An inner surface of enclosure 402 includes a quantum dot film 406. According to an embodiment, quantum dot film 406 does not require barrier layers to protect the quantum dots from oxygen in the atmosphere, because enclosure 402 is substantially impermeable to oxygen. The area enclosed within enclosure 402 may also be filled with an inert gas. The barrier layers are similar to the first and second layers discussed with reference to
Light generated from optical source 304 shines through quantum dot film 406, thus exciting the quantum dots dispersed therein. Shining the light through a dome-like structure may help to provide more uniform light to a display when local optic 400 is arrayed along substrate 302. By exciting quantum dots along a domed surface, the generated light is spread out further. In some embodiments, enclosure 402 includes other optical elements, such as lenses, mirrors, gratings, or diffusors, integrated with enclosure 402.
Local optic 400 may also include a reflective surface 408 on substrate 302 beneath enclosure 402. Reflective surface 408 may be formed using fabrication methods known to a person skilled in the art. Reflective surface 408 may be provided to reflect any stray light that has reflected back off of either quantum dot film 406 or enclosure 402.
Although only one local optic 400 is illustrated, any number of local optic devices may be provided on substrate 302 to provide light across a display screen.
According to an embodiment, enclosure 502 includes quantum dots dispersed within the material of enclosure 502. Enclosure 502 may be a polymer or glass. The quantum dots may each be encapsulated within a glass bead before being dispersed within the material of enclosure 502. The glass beads protect the quantum dots while they are dispersed within the material of enclosure 502. Local optic 500 may also include reflective surface 408, as previously discussed. In one example, enclosure 502 has a diameter between about 0.5 and 1 inch. According to an embodiment, enclosure 502 is substantially transparent to the light generated by optical source 304 and from the quantum dots disposed within the material of enclosure 502. A thickness of enclosure 502 may be varied. In one example, a uniform thickness of enclosure 502 may be selected such that there are either more or fewer quantum dots being excited by optical source 304. In another example, a thickness of enclosure 502 may vary along the surface of enclosure 502, which can help maintain color uniformity.
Other reflective elements may be included along the inner walls of either enclosure 402 or enclosure 502. These reflective elements may be used to either increase the intensity of light that ultimately impinges upon the quantum dots, or to direct the light out of a particular portion of the enclosure.
It is to be appreciated that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present invention as contemplated by the inventor(s), and thus, are not intended to limit the present invention and the appended claims in any way.
The present invention has been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.
The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance.
The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
This application claims the benefit of U.S. provisional application No. 62/218,291 filed Sep. 14, 2015, the disclosure of which is incorporated by references herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62218291 | Sep 2015 | US |
