Using multiple excitation wavelengths in nanostructure-based display devices

Abstract

Embodiments of a display device are described. The display device includes a first sub-pixel having a first quantum dot (QD) film and a first filter element. The QD film receives both UV light and blue light and converts a portion of the received light to emit secondary light different from UV and blue light. An optical filter element is disposed on the quantum dot film and allows the secondary light to pass through the optical filter element, and the optical filter element blocks an unconverted portion of the received light from passing through the optical filter element. The second sub-pixel has a second filter element that allows the blue light to pass through the second filter element, and the second filter element blocks the UV light from passing through the second filter element.

Description

[0001] This application is a divisional application of the patent application with the filing date of August 23, 2018, application number 201880054843.6, and invention title "Using Multiple Excitation Wavelengths in Nanostructure-Based Display Devices". Technical Field

[0002] The present invention relates to a display device including a phosphor film having light-emitting nanostructures such as quantum dots (QDs). Background Art

[0003] Light-emitting nanostructures (NSs) such as quantum dots (QDs) represent a class of phosphors that have the ability to emit light under a single spectral peak with a narrow linewidth, thereby generating highly saturated colors. The emission wavelength can be adjusted based on the size of the NS. NS films are used to generate NS films that can be used as color down-conversion layers in display devices (e.g., liquid crystal display (LCD) devices, organic light-emitting diode (OLED) display devices). The use of a color down-conversion layer in an emissive display can improve system efficiency by down-converting white light, blue light, or ultraviolet (UV) light to more red-shifted light, green-shifted light, or both before the light passes through a color filter. This use of the color down-conversion layer can reduce the loss of light energy due to filtering.

[0004] Due to their broad absorption and narrow emission spectra, NSs can be used as conversion materials. Since the density of NSs required for such applications is very high in a very thin color down-conversion layer of about 3 μm - 6 μm, the optical properties of NSs prepared using current methods are quenched when NSs are closely packed with each other in a thin NS film. Therefore, current NS-based display devices using NS films as color down-conversion layers suffer from the problem of low quantum yield (QY).

[0005] One of the factors defining the image quality of a display device is the gamut coverage of the standard RGB color space provided by the display device, such as Rec.2020, Rec.709, DCIP3, NTSC, or sRGB. Figure 1 Illustrates the definition of the gamut coverage of a display device. In Figure 1In [the figure], the region 101 formed between the 1976 CIE color coordinates 101a - 101c represents the gamut of the standard RGB color space (e.g., Rec. 2020) on the 1976 CIE u’-v’ chromaticity diagram 100. The region 102 formed between the 1976 CIE color coordinates 102a - 102c represents the gamut of the display device on the 1976 CIE u’-v’ chromaticity diagram 100. The gamut coverage of the display device can be defined as the ratio of the overlapping region 103 between the regions 101 and 102 to the region 101. Assuming that other factors contributing to image quality are optimized, the wider the gamut coverage of the display device, the wider the range of colors (i.e., the visible spectrum) that can be recognized by the human eye presented by the display device, and thus the image quality of the display device is improved.

[0006] Current display devices have to make a compromise between achieving the desired brightness (e.g., the brightness required by the high dynamic range (HDR) imaging standard) and the desired gamut coverage of the standard RGB color space (e.g., greater than 85%). For example, in order to achieve a gamut coverage of more than 90% of the DCI-P3, some display devices lose about 30% of their brightness. Therefore, using current technologies, in order to achieve a gamut coverage of a color space wider than DCI-P3 (e.g., Rec. 2020), the brightness loss in the display device will be significantly higher.

[0007] Another drawback of current display devices lies in the leakage of un-converted light through the conversion material (e.g., NS film) of the display device, which can adversely affect the gamut coverage of the display device. For example, some display devices have unwanted blue light leakage through their green and / or red pixels. This can occur when the blue light incident on the conversion material from a blue light source is not completely absorbed by the conversion material and converted into green and / or red light. In addition, since the output blue light has a higher radiant intensity compared to the converted green and red light, it may be challenging to achieve the desired white point when using a blue backlight. Summary of the Invention

[0008] Therefore, there is a need for a display device having an improved gamut coverage and an improved quantum efficiency of the down-conversion layer for generating red and green light.

[0009] According to one embodiment, a display device includes a backlight unit having a plurality of light sources and a liquid crystal display (LCD) module. The plurality of light sources includes one or more first light sources configured to emit light having a first peak emission wavelength in the ultraviolet (UV) range of the electromagnetic (EM) spectrum and one or more second light sources configured to emit light having a second peak emission wavelength in the blue range of the EM spectrum. The LCD module includes a pixel array having at least one pixel with a first sub-pixel and a second sub-pixel. The first sub-pixel includes a first phosphor film and a first filter element. The first phosphor film receives light from the plurality of light sources and converts a portion of the received light to emit secondary light having a third peak emission wavelength different from the first peak emission wavelength and the second peak emission wavelength. The first filter element is optically coupled to the phosphor film and allows the secondary light having the third peak emission wavelength to pass through the first filter element, and blocks the unconverted portion of the light from the plurality of light sources from passing through the first filter element. The second sub-pixel includes a second filter element that allows the light having the second peak emission wavelength to pass through the second filter element and blocks the light having the first peak emission wavelength from passing through the second filter element.

[0010] According to one embodiment, a display device includes a pixel array. A pixel of the pixel array includes a first sub-pixel and a second sub-pixel. The first sub-pixel has a first quantum dot (QD) film and a first filter element. The QD film receives light having a first peak emission wavelength in the ultraviolet (UV) range of the EM spectrum and a second peak emission wavelength in the blue range of the EM spectrum and converts a portion of the received light to emit secondary light having a third peak wavelength. The third peak wavelength is different from the first peak wavelength and the second peak wavelength. The filter element is disposed on the quantum dot film and allows the secondary light having the third peak emission wavelength to pass through the filter element, and the filter element blocks the unconverted portion of the received light from passing through the filter element. The second sub-pixel has a second filter element that allows the light having the second peak emission wavelength to pass through the second filter element, and the second filter element blocks the light having the first peak emission wavelength from passing through the second filter element.

[0011] The present invention includes the following:

[0012] Embodiment 1. A display device, the display device comprising:

[0013] A backlight unit, the backlight unit comprising a plurality of light sources, wherein the plurality of light sources includes one or more first light sources configured to emit light having a first peak emission wavelength in the ultraviolet (UV) range of the electromagnetic (EM) spectrum and one or more second light sources configured to emit light having a second peak emission wavelength in the blue range of the EM spectrum; and

[0014] Liquid crystal display (LCD) module, the module comprising:

[0015] A pixel array, wherein at least one pixel in the pixel array comprises:

[0016] A first sub-pixel, the first sub-pixel comprising:

[0017] A first phosphor film configured to receive light from the plurality of light sources and convert a portion of the received light to emit secondary light having a third peak emission wavelength different from the first peak emission wavelength and the second peak emission wavelength, and

[0018] A first filter element optically coupled to the phosphor film and configured to allow the secondary light having the third peak emission wavelength to pass through the first filter element and block an unconverted portion of the light from the plurality of light sources from passing through the first filter element, and

[0019] A second sub-pixel, the second sub-pixel comprising:

[0020] A second filter element configured to allow the light having the second peak emission wavelength to pass through the second filter element and block the light having the first peak emission wavelength from passing through the second filter element.

[0021] Embodiment 2. The display device according to Embodiment 1, wherein the first filter element is configured to absorb an unconverted portion of the received light, and the second filter is configured to absorb the light having the first peak emission wavelength.

[0022] Embodiment 3. The display device according to Embodiment 1, wherein the first filter element is configured to scatter an unconverted portion of the primary light, and the second filter is configured to scatter the light having the first peak emission wavelength.

[0023] Embodiment 4. The display device according to any one of Embodiments 1-3, wherein the first filter element is disposed on the first phosphor film.

[0024] Embodiment 5. The display device according to any one of Embodiments 1-3, wherein the first filter element is disposed on a substrate, and the substrate is disposed on the first phosphor film.

[0025] Embodiment 6. The display device according to any one of Embodiments 1-5, wherein at least one pixel in the pixel array further comprises:

[0026] A third sub-pixel, the third sub-pixel comprising:

[0027] A second phosphor film configured to receive light from the plurality of light sources and convert a portion of the received light to emit secondary light having a fourth peak emission wavelength different from the first peak emission wavelength, the second peak emission wavelength, and the third peak emission wavelength, and

[0028] A third filter element optically coupled to the second phosphor film and configured to allow the secondary light having the fourth peak emission wavelength to pass through the third filter element and block an unconverted portion of the light from the plurality of light sources from passing through the third filter element.

[0029] Embodiment 7. The display device according to Embodiment 6, wherein:

[0030] The first phosphor film includes a first population of luminescent nanostructures configured to emit red light; and

[0031] The second phosphor film includes a second population of luminescent nanostructures configured to emit green light.

[0032] Embodiment 8. The display device according to any one of Embodiments 1-7, wherein:

[0033] The second sub-pixel further includes:

[0034] A third phosphor film configured to receive light from the plurality of light sources and convert a portion of the received light to emit secondary light having the second peak emission wavelength.

[0035] Embodiment 9. The display device according to Embodiment 8, wherein the third phosphor film includes a third population of nanostructures configured to emit the secondary light having the second peak emission wavelength.

[0036] Embodiment 10. The display device according to any one of Embodiments 1-9, wherein the ratio of the first light source to the second light source is between 3:1 and 1:1.

[0037] Embodiment 11. The display device according to any one of Embodiments 1-10, wherein the first peak emission wavelength is less than 420 nm, and the second peak emission wavelength is between 445 nm and 455 nm.

[0038] Embodiment 12. The display device according to any one of Embodiments 1-11, wherein the first peak emission wavelength is between 400 nm and 410 nm.

[0039] Embodiment 13. The display device according to any one of Embodiments 1-11, wherein the first peak emission wavelength is between 360 nm and 370 nm.

[0040] Embodiment 14. The display device according to any one of Embodiments 1-13, the display device further comprising an optical cavity, wherein the plurality of light sources are located within the optical cavity.

[0041] Embodiment 15. The display device according to any one of Embodiments 1-14, the display device further comprising a light guide plate, wherein the plurality of light sources are coupled to the light guide plate from the outside.

[0042] Embodiment 16. A display device, the display device comprising a pixel array, the pixels of the pixel array comprising:

[0043] A first sub-pixel having:

[0044] A first quantum dot (QD) film configured to receive light having a first peak emission wavelength in the ultraviolet (UV) range of the electromagnetic (EM) spectrum and a second peak emission wavelength in the blue range of the EM spectrum and convert a portion of the received light to emit secondary light having a third peak emission wavelength different from the first peak emission wavelength and the second peak emission wavelength; and

[0045] A first filter element disposed on the quantum dot film and configured to allow the secondary light having the third peak emission wavelength to pass through the filter element and block the unconverted portion of the received light from passing through the filter element; and

[0046] A second sub-pixel having:

[0047] A second filter element configured to allow the light having the second peak emission wavelength to pass through the second filter element and block the light having the first peak emission wavelength from passing through the second filter element.

[0048] Embodiment 17. The display device according to Embodiment 16, wherein the first QD film of the first sub-pixel has a first QD population configured to emit red light and the pixel further comprises:

[0049] A third sub-pixel comprising a second QD film having a second QD population configured to emit green light.

[0050] Embodiment 18. The display device according to Embodiment 17, wherein the second sub-pixel further includes a third QD film having a third QD population configured to emit blue light.

[0051] Embodiment 19. The display device according to any one of Embodiments 16-18, wherein the first filter element is configured to absorb an unconverted portion of the received light, and the second filter is configured to absorb the light having the first peak emission wavelength.

[0052] Embodiment 20. The display device according to any one of Embodiments 16-18, wherein the first filter element is configured to scatter an unconverted portion of the received light, and the second filter is configured to scatter the light having the first peak emission wavelength.

[0053] Embodiment 21. The display device according to any one of Embodiments 16-20, wherein the first filter element is disposed on the first QD film.

[0054] Embodiment 22. The display device according to any one of Embodiments 16-20, wherein the first filter element is disposed on a substrate, and the substrate is disposed on the first QD film.

[0055] Embodiment 23. The display device according to any one of Embodiments 16-22, the display device further includes one or more first light sources configured to generate UV light and one or more second light sources configured to generate blue light, wherein a ratio of the first light source to the second light source is between 3:1 and 1:1.

[0056] Embodiment 24. The display device according to any one of Embodiments 16-23, wherein the first peak emission wavelength is less than 420 nm, and the second peak emission wavelength is between 445 nm and 455 nm.

[0057] Embodiment 25. The display device according to any one of Embodiments 16-24, wherein the first peak emission wavelength is between 400 nm and 410 nm.

[0058] Embodiment 26. The display device according to any one of Embodiments 16-24, wherein the first peak emission wavelength is between 360 nm and 370 nm.

[0059] Embodiment 27. The display device according to any one of Embodiments 23-26, the display device further includes an optical cavity, wherein the one or more first light sources and the one or more second light sources are located in the optical cavity.

[0060] Embodiment 28. The display device according to any one of Embodiments 23-27, further comprising a light guide plate, wherein the one or more first light sources and the one or more second light sources are coupled to the light guide plate from the outside.

[0061] Other features and advantages of the present invention and the structure and operation of various embodiments of the present invention are described in detail below with reference to the accompanying drawings. It should be noted that the present invention is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Based on the teachings contained herein, other embodiments will be apparent to those skilled in the relevant art. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The accompanying drawings are incorporated herein and form a part of the specification, illustrate embodiments of the present invention and, together with the specification, are also used to explain the principles of the embodiments of the present invention and enable those skilled in the relevant art to implement and use the embodiments of the present invention.

[0063] Figure 1 CIE 1976 u'v' chromaticity diagram for the Rec. 2020 color gamut and the color gamut of the display device.

[0064] Figures 2-3 Exploded cross-sectional view of a liquid crystal display (LCD) device according to one embodiment.

[0065] Figure 4A Schematic diagram of a light source array for a backlight unit according to one embodiment.

[0066] Figure 4B Schematic diagram of a light source array for a side light unit according to one embodiment.

[0067] Figure 5 Schematic diagram of a cross-sectional view of a nanostructure according to one embodiment.

[0068] Figure 6 Schematic diagram of a nanostructure film according to one embodiment.

[0069] The features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which like reference characters always denote corresponding elements. In the drawings, like reference numerals generally denote the same, functionally similar, and / or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit in the corresponding reference numeral. Unless otherwise indicated, the drawings provided throughout this disclosure should not be construed as being drawn to scale. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0070] Although specific configurations and arrangements may be discussed, it should be understood that this is for illustrative purposes only. Those skilled in the relevant art should 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 those skilled in the relevant art that the present invention can also be used in a variety of other applications other than those specifically mentioned herein. It should be understood that the specific embodiments shown and described herein are examples and are not intended to limit the scope of the present application in any way.

[0071] It should be noted that references in the specification to "embodiments", "implementations", "example implementations", etc. indicate that the described embodiments may include specific features, structures, or characteristics, but not necessarily every embodiment includes this specific feature, structure, or characteristic. Moreover, such expressions do not necessarily refer to the same embodiment. In addition, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in connection with other embodiments will be within the knowledge of those skilled in the art, whether or not explicitly described.

[0072] Unless otherwise explicitly stated, all numbers in this specification indicating amounts of materials, material ratios, physical properties of materials, and / or uses of materials should be understood to be modified by the word "about".

[0073] In an embodiment, the term "display device" refers to an arrangement of elements that allows data to be visually presented on a display screen. Suitable display screens can include various flat, curved, or other shaped screens, films, sheets, or other structures for visually displaying information to a user. The display devices described herein can be included in, for example, display systems, which include liquid crystal displays (LCDs), televisions, computers, mobile phones, smart phones, personal digital assistants (PDAs), gaming devices, e-reading devices, digital cameras, tablet computers, wearable devices, automotive navigation systems, etc.

[0074] As used herein, the term "about" indicates that the value of a given quantity varies by ±10% based on that value. For example, "about 100 nm" encompasses a range of sizes from 90 nm to 110 nm, including the end values.

[0075] As used herein, the term "substantially" means that the value of a given quantity varies between ±1% and ±5% of that value.

[0076] In an embodiment, the term "forming a reaction mixture" or "forming a mixture" means combining at least two components in a container under conditions suitable for the components to react with each other to form a third component.

[0077] In an embodiment, the terms "light guide plate", "light guide", and "light guide panel" may be used interchangeably and refer to an optical component suitable for guiding electromagnetic radiation (light) from one location to another.

[0078] In an embodiment, the term "optically coupled" means that components are positioned such that light can be transferred from one component to another without substantial interference.

[0079] As used herein, the term "nanostructure" refers to a structure having at least one region or characteristic dimension less than about 500 nm. In some embodiments, the nanostructure has dimensions less than about 200 nm, less than about 100 nm, less than about 50 nm, less than about 20 nm, or less than about 10 nm. Typically, the region or characteristic dimension will be along the smallest axis of the structure. Examples of such structures include nanowires, nanorods, nanotubes, branched nanostructures, nanorods, tripods, bipods, nanocrystals, nanodots, QDs, nanoparticles, etc. The nanostructure can be, for example, substantially crystalline, substantially single crystal, polycrystalline, amorphous, or a combination thereof. In some embodiments, each of the three dimensions of the nanostructure has a size less than about 500 nm, less than about 200 nm, less than about 100 nm, less than about 50 nm, less than about 20 nm, or less than about 10 nm.

[0080] As used herein, the term "QD" or "nanocrystal" refers to a substantially single crystal nanostructure. The nanocrystal has at least one region or characteristic dimension less than about 500 nm and as low as on the order of less than about 1 nm. It will be readily understood by those of ordinary skill in the art that the terms "nanocrystal", "QD", "nanodot", and "dot" denote the same structure and are used interchangeably herein. The present invention also encompasses the use of polycrystalline or amorphous nanocrystals.

[0081] When referring to the use of nanostructures, the term "heterostructure" refers to a nanostructure characterized by at least two different and / or distinguishable material types. Generally, one region of the nanostructure contains a first material type while a second region of the nanostructure contains a second material type. In some embodiments, the nanostructure includes a core of a first material and at least one shell of a second (or third, etc.) material, where the different material types are radially distributed about, for example, the long axis of a nanowire, the long axis of an arm of a branched nanowire, or the center of a nanocrystal. The shell may, but does not necessarily, completely cover the adjacent material to be considered a shell or to cause the nanostructure to be considered a heterostructure; for example, a nanocrystal characterized by a core of one material covered with islands of a second material is a heterostructure. In other embodiments, the different material types are distributed at different locations within the nanostructure; for example, along the main (long) axis of a nanowire or along the long axis of an arm of a branched nanowire. The different regions within a heterostructure may contain completely different materials, or the different regions may contain a base material (e.g., silicon) with different dopants or different concentrations of the same dopant.

[0082] As used herein, the term "diameter" of a nanostructure refers to the diameter of a cross-section perpendicular to a first axis of the nanostructure, where the first axis has the greatest length difference relative to second and third axes (the second and third axes being the two axes whose lengths are closest to equal). The first axis is not necessarily the longest axis of the nanostructure; for example, for a disk-shaped nanostructure, the cross-section will be a substantially circular cross-section perpendicular to the short longitudinal axis of the disk. In cases where the cross-section is not circular, the diameter is the average of the major and minor axes of the cross-section. For an elongated or high aspect ratio nanostructure, such as a nanowire, the diameter is measured on a cross-section perpendicular to the longest axis of the nanowire. For a spherical nanostructure, the diameter is measured from one side to the other through the center of the sphere.

[0083] When used in connection with nanostructures, the terms "crystalline" or "substantially crystalline" refer to the fact that the nanostructure typically exhibits long-range order across one or more dimensions of the structure. Those skilled in the art will understand that the term "long-range order" will depend on the absolute size of the particular nanostructure, since the order of a single crystal cannot extend beyond the boundaries of the crystal. In such cases, "long-range order" will refer to substantial order over at least a majority of the dimensions of the nanostructure. In some cases, the nanostructure may carry an oxide or other coating, or may consist of a core and at least one shell. In such cases, it should be understood that the oxide, one or more shells or other coatings may or may not exhibit such order (e.g., it may be amorphous, polycrystalline or in other forms). In such cases, the expressions "crystalline", "substantially crystalline", "substantially single crystal" or "single crystal" refer to the central core of the nanostructure (excluding the coating or shell). As used herein, the terms "crystalline" or "substantially crystalline" are also intended to cover structures that contain various defects, stacking faults, atomic substitutions, etc., provided that the structure exhibits substantial long-range order (e.g., order over at least about 80% of the length of at least one axis of the nanostructure or its core). Additionally, it should be understood that the interface between the core and the outside of the nanostructure, or between the core and an adjacent shell, or between a shell and a second adjacent shell may contain non-crystalline regions and may even be amorphous. This does not prevent the nanostructure from being crystalline or substantially crystalline as defined herein.

[0084] When used in connection with nanostructures, the term "single crystal" indicates that the nanostructure is substantially crystalline and contains substantially a single crystal. When used in connection with nanostructure heterostructures that contain a core and one or more shells, "single crystal" indicates that the core is substantially crystalline and contains substantially a single crystal.

[0085] As used herein, the term "ligand" refers to a molecule that is capable of interacting (weakly or strongly) with one or more faces of a nanostructure, for example, by covalent, ionic, van der Waals or other molecular interactions with the surface of the nanostructure.

[0086] As used herein, the term "quantum yield" refers to the ratio of photons emitted, for example, by a nanostructure or a population of nanostructures to photons absorbed. As is known in the art, the quantum yield is typically determined by a comparative method using a well-characterized standard sample with a known quantum yield value.

[0087] As used herein, the term "wavelength of the main emission peak" refers to the wavelength at which the emission spectrum exhibits the highest intensity.

[0088] As used herein, the term "full width at half maximum" (FWHM) refers to a measure of the spectral width. In the case of an emission spectrum, the FWHM may refer to the width of the emission spectrum at half of the peak intensity value.

[0089] As used herein, the term Förster radius is also referred to in the art as Förster distance.

[0090] As used herein, the terms "luminance" and "brightness" are used interchangeably and refer to the photometric measure of the luminous intensity per unit area of a light source or an illuminated surface.

[0091] The terms "specular reflector", "specular reflecting surface", and "reflecting surface" are used herein to refer to an element, material, and / or surface capable of specular reflection.

[0092] The term "specular reflection" is used herein to refer to the mirror-like reflection of light (or other types of waves) from a surface when incident light strikes the surface.

[0093] The term "nanostructure (NS) film" is used herein to refer to a film having luminescent nanostructures.

[0094] The term "red sub-pixel" is used herein to refer to the region of a pixel that emits light having a main emission peak wavelength in the red wavelength region of the visible spectrum. In some embodiments, the red wavelength region may include wavelengths ranging from about 620 nm to about 750 nm.

[0095] The term "green sub-pixel" is used herein to refer to the region of a pixel that emits light having a main emission peak wavelength in the green wavelength region of the visible spectrum. In some embodiments, the green wavelength region may include wavelengths ranging from about 495 nm to about 570 nm.

[0096] The term "blue sub-pixel" is used herein to refer to the region of a pixel that emits light having a main emission peak wavelength in the blue wavelength region of the visible spectrum. In some embodiments, the blue wavelength region may include wavelengths ranging from about 435 nm to about 495 nm.

[0097] The term "emission surface of a sub-pixel" is used herein to refer to the uppermost surface of the sub-pixel from which light is emitted towards the display screen of a display device.

[0098] The patents, patent applications, websites, company names, and scientific literature mentioned herein are hereby incorporated by reference in their entirety as if each were specifically and individually indicated to be incorporated by reference. Any conflict between any of the references cited herein and the specific teachings of this specification shall be resolved in favor of the latter. Similarly, any conflict between the definition of a word or expression understood in the technical field and the definition of the word or expression as specifically taught in this specification shall be resolved in favor of the latter.

[0099] Unless otherwise defined, the technical and scientific terms used herein have the meanings commonly understood by those of ordinary skill in the art to which this application belongs. Reference is made herein to various methods and materials known to those of ordinary skill in the art.

[0100] Overview

[0101] The present disclosure provides various embodiments of nanostructure-based display devices, which help to improve or eliminate the existing trade-off between achieving a desired brightness and a desired color gamut in a display device. These various embodiments also help to improve the display performance, such as color gamut coverage, of the nanostructure-based display device by reducing or substantially eliminating leakage of unwanted light through one or more pixels of the display device. These various embodiments also help to improve color balance.

[0102] Example Embodiment of a Liquid Crystal Display (LCD) Device

[0103] Figure 2 FIG. schematically illustrates an exploded cross-sectional view of an LCD display device 200 according to one embodiment. Those of ordinary skill in the art will recognize that Figure 2 the view of the display device in is shown for illustrative purposes and may not be drawn to scale. According to one embodiment, the LCD display device 200 may include a backlight unit (BLU) 202 and an LCD module 204.

[0104] The BLU 202 may include an optical cavity 212 and an array of light-emitting diodes (LEDs) 210 (e.g., white LEDs, blue LEDs, UV LEDs, or combinations thereof) coupled to the optical cavity 212. In one embodiment, the LEDs 210 include only a given ratio of blue LEDs and UV LEDs. The optical cavity 212 may include a top side 203, a bottom side 205, side walls 207, and an enclosed volume defined by the top side 203, the bottom side 205, and the side walls 207. The LEDs 210 may be coupled within the enclosed volume to the top surface 205a of the bottom side 205. The LEDs 210 may be configured to provide primary light (e.g., blue light, white light, UV light, or a combination of blue and UV light), which may be processed by the LCD module 204 and subsequently transmitted to and distributed over the display screen 230 of the LCD display device 200. In some embodiments, the LEDs 210 include blue LEDs that emit light having a peak emission wavelength between about 440 nm and about 470 nm or between about 445 nm and about 455 nm. In some embodiments, the LEDs 210 include white LEDs that emit light in the range of about 440 nm to about 700 nm or in other possible optical wavelength ranges. In some embodiments, the LEDs 210 include UV LEDs that emit light having a peak emission wavelength less than 420 nm, or between about 400 nm and about 410 nm, or between about 360 nm and about 370 nm. In one embodiment, the array of LEDs 210 may include a two-dimensional array of LEDs that extends over the area of the top surface 205a and that area may be equal to the surface area of the display screen 230.

[0105] In some embodiments, the LEDs 210 include a mixture of both blue LEDs and UV LEDs. The ratio of UV LEDs to blue LEDs may be 3:1, or 1:1, or any ratio therebetween. In some embodiments, the LEDs 310 include a ratio of UV LEDs to blue LEDs greater than 3:1.

[0106] It should be noted that although Figure 2 two side walls 207 are shown, those skilled in the art will understand that, according to various embodiments, the optical cavity 212 may include any number of side walls 207. For example, the optical cavity 212 may have a rectangular parallelepiped shape and may include four side walls similar to the side walls 207. The optical cavity 212 is not limited to a rectangular parallelepiped shape, nor is it limited to having other straight-sided shapes. According to various embodiments, the optical cavity 212 may be configured in any type of geometry, such as but not limited to cylindrical, trapezoidal, spherical, or elliptical, without departing from the spirit and scope of the present invention. It should also be noted that as Figure 2The rectangular cross-sectional shape of the optical cavity 212 shown is for illustrative purposes and not limiting. According to various embodiments, the optical cavity 212 may have other cross-sectional shapes (e.g., trapezoidal, rectangular, rhomboid) without departing from the spirit and scope of the present invention.

[0107] The top side 203 of the optical cavity 212 may be configured as an optically diffusive and transmissive layer such that light from the LED 210 can exit the optical cavity 212 through the top side 203, having a substantially uniform brightness distribution on the top surface 203a of the top side 203. In one embodiment, the top side 203 may include optically transparent regions and optically semi-transparent regions that are strategically arranged above the LED 210 to provide a substantially uniform distribution of the light brightness exiting from the top side 203. In another embodiment, the top side 203 may include pores of different diameter sizes and optically semi-transparent regions that are strategically arranged to provide a substantially uniform distribution of the light brightness exiting from the top side 203.

[0108] The bottom side 205 and / or the sidewalls 207 may be constructed of one or more materials (e.g., metal, non-metal, and / or alloy) that are respectively configured to have a specularly reflective top surface 205a and / or a specularly reflective sidewall inner surface 207a. For example, the top surface 205a and / or the sidewall inner surface 207a may be a specular surface having specular reflection properties. In some embodiments, the top surface 205a and / or the sidewall inner surface 207a may be completely specularly reflective or partially specularly reflective and partially scattering. In some other embodiments, the top surface 205a and / or the sidewall inner surface 207a include diffusers.

[0109] In an alternative embodiment, the optical cavity 212 may include a specular reflector 209 coupled to the sidewall inner surface 207a. The specular reflector 209 may be coupled to the sidewall inner surface 207a using an optically transparent adhesive. The optically transparent adhesive may include tape, various glues, polymer compositions such as silicone, etc. According to various examples, additional optically transparent adhesives may include various polymers, including but not limited to poly(vinyl butyral), poly(vinyl acetate), epoxy resins, and polyurethanes; silicones and silicone derivatives, including but not limited to polyphenylmethylsiloxane, polyphenylalkylsiloxane, polydiphenylsiloxane, polydialkylsiloxane, fluorinated silicones, and vinyl- and hydride-substituted silicones; acrylic polymers and copolymers formed from monomers including but not limited to methyl methacrylate, butyl methacrylate, and lauryl methacrylate; styrene-based polymers; and polymers crosslinked with difunctional monomers such as divinylbenzene.

[0110] The top surface 205a with specular reflection, the inner sidewall surface 207a, and the specular reflector 209 can significantly reduce the absorption of light from the LED 210 through the bottom side 205 and / or the sidewall 207, and thus significantly reduce the brightness loss in the optical cavity 212 and increase the light output efficiency of the BLU 202.

[0111] In an alternative embodiment, the BLU 202 may further include one or more brightness enhancement films (BEFs) (not shown) disposed between the optical cavity 212 and the LCD module 204. The one or more BEFs may include reflective and / or refractive films, reflective polarizing films, light extraction features, light recycling features, prism films, grooved films, grooved prism films, prisms, pitches, grooves, or other suitable brightness enhancement features. The brightness enhancement features of the BEF may be configured to reflect a portion of the primary light (e.g., blue light and UV light from the optical cavity 212) back into the optical cavity 212, thereby providing recycling of the primary light.

[0112] The LCD module 204 may be configured to process the light received from the BLU 202 to the desired characteristics for transmission to and distribution on the display screen 230. In some embodiments, the LCD module 204 may include one or more polarization filters such as the first and second polarization filters 214 and 222, one or more optically transparent substrates such as the first and second optically transparent substrates 216 and 228, switching devices 218.1 to 218.6 arranged in a 2-D array on the first substrate 216, a liquid crystal (LC) solution layer 220, a plurality of pixels such as pixels 224.1 and 224.2 arranged in a 2-D array, and a display screen 230.

[0113] In some embodiments, pixel 224.1 may include sub-pixels 226.1 to 226.3, and pixel 224.2 may include sub-pixels 226.4 to 226.6. In some embodiments, each of pixels 224.1 and 224.2 may be tricolor, for example, having red sub-pixels 226.1 and 226.4, green sub-pixels 226.2 and 226.5, and blue sub-pixels 226.3 and 226.6, respectively.

[0114] The term "red subpixel" is used herein to refer to the region of a pixel that emits light having a peak emission wavelength in the red wavelength region of the visible spectrum. In some embodiments, the red wavelength region may include wavelengths ranging from about 620 nm to about 750 nm. The term "green subpixel" is used herein to refer to the region of a pixel that emits light having a peak emission wavelength in the green wavelength region of the visible spectrum. In some embodiments, the green wavelength region may include wavelengths ranging from about 495 nm to about 570 nm. The term "blue subpixel" is used herein to refer to the region of a pixel that emits light having a peak emission wavelength in the blue wavelength region of the visible spectrum. In some embodiments, the blue wavelength region may include wavelengths ranging from about 435 nm to about 495 nm.

[0115] The arrangement order of the red, green, and blue subpixels 226.1 to 226.6 in the corresponding pixels 224.1 and 224.2 is illustrative and not restrictive. The red, green, and blue subpixels in each of the pixels 224.1 and 224.2 can be arranged in any order relative to each other. In some embodiments, the pixel 224.1 and / or 224.2 can be monochromatic, having red, green, or blue subpixels 226.1 to 226.6. Figure 2 The number of pixels and switching devices shown is illustrative and not restrictive. The LCD module 204 can have any number of switching devices and pixels without departing from the spirit and scope of the present disclosure.

[0116] Light from the BLU 202 can be polarized by the first polarization filter 214 and the polarized light can be transmitted to the LC solution layer 220. The LC solution layer 220 can include an LC 232 having rod-shaped molecules, which can act as a light shutter to control the amount of light transmitted from the LC solution layer 220. In some embodiments, the LC 232 can be arranged in a 3-D array. The columns 234.1 to 234.6 of the 3-D array of LC can be independently controlled by the corresponding switching devices 218.1 to 218.6. In some embodiments, the switching devices 218.1 to 218.6 can include transistors, such as thin film transistors (TFTs). By controlling the LC 232, the amount of light traveling from the columns 234.1 to 234.6 to the corresponding subpixels 226.1 to 226.6 can be controlled, and thus the amount of light transmitted from the subpixels 226.1 to 226.6 can be controlled.

[0117] The LC 232 can be twisted to different degrees according to the voltages applied to columns 234.1 to 234.6 by the corresponding switching devices 218.1 to 218.6. By controlling the twist of the LC 232, the polarization angle of the light passing through the LC solution layer 220 can be controlled. The light leaving the LC solution layer 220 can then pass through the second polarization filter 222, which can be positioned at 90 degrees relative to the first polarization filter 214. The polarization angle of the light leaving the LC solution layer 220 and entering the second polarization filter 222 can determine how much light can pass through and exit from the second polarization filter 222. The second polarization filter 222 can attenuate light, block light, or allow light to pass through without attenuation based on its polarization angle.

[0118] Portions of the light traveling through columns 234.1 to 234.6 of the LC and exiting from the second polarization filter 222 can then enter the corresponding sub-pixels among sub-pixels 226.1 to 226.6. These portions of the light can undergo a color filtering stage through the corresponding sub-pixels among sub-pixels 226.1 to 226.6 to achieve the optical characteristics required for the distribution of light on the display screen 230. In some embodiments, each of sub-pixels 226.1 to 226.6 can include a phosphor film 236, and the phosphor film 236 can include elements that down-convert a portion of the received light entering sub-pixels 226.1 to 226.6.

[0119] According to some embodiments, the phosphor film 236 can include luminescent nanostructures such as QDs (e.g., QD 600 as described in Figure 6 ). The phosphor film 236 can be a down-converter, where a portion of the light (also referred to as primary light) entering the corresponding sub-pixels among sub-pixels 226.1 to 226.6 can be absorbed, for example, by the luminescent nanostructures in the phosphor film 236 and re-emitted as secondary light having lower energy or a longer wavelength than the primary light.

[0120] In embodiments where the primary light includes both blue light and UV light, the luminescent nanostructures will absorb more UV light compared to the blue light absorbed by the same number of luminescent nanostructures. Additionally, by replacing some of the blue LEDs with UV LEDs in the LED 210, the total amount of emitted blue light will be reduced, which can make it easier to filter out the unwanted blue light in both the red sub-pixels 226.1 and 226.4 and the green sub-pixels 226.2 and 226.5.

[0121] In some embodiments, the phosphor films 236 of the red sub-pixels 226.1 and 226.4 may include luminescent nanostructures that absorb primary light and emit a first secondary light having a main emission peak wavelength in the red wavelength region of the visible spectrum light. In some embodiments, the phosphor films 236 of the green sub-pixels 226.2 and 226.5 may include luminescent nanostructures that absorb primary light and emit a second secondary light having a main emission peak wavelength in the green wavelength region of the visible spectrum light. In some embodiments, the phosphor films 236 of the blue sub-pixels 226.3 and 226.6 may include luminescent nanostructures that absorb primary light and emit a third secondary light having a main emission peak wavelength in the blue wavelength region of the visible spectrum light.

[0122] In some embodiments, the blue sub-pixels 226.3 and 226.6 may have a non-phosphor film instead of the phosphor film 236, or may have no film at all. In some other embodiments, the blue sub-pixels 226.3 and 226.6 include a scattering material instead of the phosphor film 236. The scattering material can be used to provide an angular distribution of blue light from the blue sub-pixels 226.3* and 226.6* that matches the angular distribution of light from the green sub-pixels 226.2 and 226.5 and the red sub-pixels 226.1 and 226.4. When the BLU 202 includes blue LEDs, the non-phosphor film may not include luminescent nanostructures such as QDs and may be optically transmissive to blue light because there is no need to down-convert the primary light from the blue LEDs for the blue sub-pixels 226.3 and 226.6. In embodiments where the LED 210 includes both blue LEDs and UV LEDs, the blue sub-pixels 226.3 and 226.6 may include light-blocking elements 238 that include UV-blocking filters.

[0123] In some embodiments, the phosphor film 236 can be a segmented film that is placed adjacent to each other on the second polarizing filter 222 or on an optically transparent substrate (not shown). The segmented phosphor films 236 can be placed in such a way that the gap at the interface between adjacent phosphor films 236 is negligible to prevent leakage of primary light through the interface. In an alternative embodiment, each phosphor film 236 can be a different region of a continuous phosphor film.

[0124] Additionally, according to some embodiments, each of the sub-pixels 226.1 to 226.6 may include a light-blocking element 238 disposed on the phosphor film 236. The secondary light emitted from the phosphor film 236 can be filtered by a corresponding one of the light-blocking elements 238 before traveling to the display screen 230.

[0125] The light-blocking element 238 can be configured to allow secondary light (e.g., the first, second, and / or third secondary light discussed above) to pass through and block a portion of the primary light (e.g., blue light, UV light, or a combination of blue light and UV light) that is not absorbed by the phosphor film 236 and down-converted into secondary light. An unwanted portion of the primary light that may have leaked from the phosphor film 236 can be blocked by absorption and / or by scattering. The leakage of the unconverted primary light from the phosphor film 236 to the display screen 230 may adversely affect the color gamut coverage of the LCD display device 200. Using the light-blocking element 238 to prevent such leakage can also help reduce the manufacturing cost of the LCD display device 200 by reducing the density of the luminescent nanostructures contained in the phosphor film 236. The density of the luminescent nanostructures can be reduced because any portion of the primary light that is not absorbed in the phosphor film 236 can be filtered out by the light-blocking element 238 instead of using the luminescent nanostructures to absorb substantially all of the primary light. In some embodiments, by using a UV LED mixed with a blue LED, the density of the luminescent nanostructures in the phosphor film 236 can be further reduced because more UV light will be absorbed and converted into secondary light by the luminescent nanostructures compared to the blue light absorbed by the luminescent nanostructures.

[0126] The light-blocking element 238 can also be configured to adjust the spectral emission width (also referred to as the width of the emission spectrum) of the secondary light (e.g., the first, second, and / or third secondary light discussed above) to achieve the desired color gamut coverage of the LCD display device 200. Adjusting the spectral emission width may require absorbing one or more wavelengths from the secondary light to narrow their spectral emission width to achieve the desired color gamut coverage without significantly reducing the brightness. For example, compared to a display device without the light-blocking element 238, the reduction in brightness may be less than 10% (e.g., about 8%, about 5%, about 3%, or about 1%) due to this adjustment process. Since the secondary light from the phosphor film 236 having luminescent nanostructures such as QDs typically exhibits a narrow spectral emission width, the adjustment process may not require absorbing a wide range of wavelengths to achieve the desired color gamut coverage, as is required for current non-QD-based display devices to achieve a similar color gamut coverage.

[0127] When the LED 210 uses only blue LEDs, the blue light emitted from the blue sub-pixels 226.3 and 226.6 has a higher total radiant intensity than the red or green light emitted from the other sub-pixels, making color balance more difficult due to the higher blue component. By replacing some of the blue LEDs in the LED 210 with UV LEDs, the total blue luminance will be reduced, and at the same time, the UV light can be easily filtered, resulting in better color balance. In some embodiments, the ratio of UV LEDs to blue LEDs is selected such that the blue light output from the blue sub-pixels 226.3 and 226.6 is optimized to have approximately equal luminance to both the red light emitted from the red sub-pixels 226.1 and 226.4 and the green light emitted from the green sub-pixels 226.2 and 226.5.

[0128] A wide spectral emission width is one of the limitations of current non-QD-based display devices (e.g., YAG-phosphor-based display devices) in achieving wide color gamut coverage such as that of the Rec. 2020 color space. The use of absorption elements such as the light-blocking element 238 in current non-QD-based display devices can achieve wide color gamut coverage (e.g., 80%-90% Rec. 2020 color gamut coverage), but at the cost of a significant reduction in luminance. This reduction in luminance not only may adversely affect the image quality of current display devices but also may not meet the luminance levels required by HDR imaging standards.

[0129] The light-blocking element 238 may comprise one or more non-phosphor materials. That is, the one or more non-phosphor materials exhibit optical absorption properties and / or optical scattering properties but do not exhibit optical emission properties. The one or more non-phosphor materials may be selected based on their optical absorption properties and / or their scattering properties to absorb and / or scatter only one or more wavelengths or wavelength ranges that need to be absorbed and / or scattered during the above blocking and adjustment processes. In some embodiments, the one or more non-phosphor materials may have the same absorption properties. In some embodiments, each of the one or more non-phosphor materials has different absorption properties from each other.

[0130] The one or more non-phosphor materials can be selected such that they can be inexpensively disposed on the phosphor film 236 or any other layer / structure of the display device 200 to form the light-blocking element 238. For example, the one or more non-phosphor materials can be dyes (e.g., narrow-band organic exciton P491 dye), inks, coatings, polymeric materials, and / or any materials that can be spray-coated, brush-coated, spin-coated, printed, or applied by any other suitable low-temperature (e.g., below 100 °C) deposition method. Printing can be performed using, for example, a plotter, an inkjet printer, or a screen printer. In some embodiments, the one or more non-phosphor materials can be directly disposed on the phosphor film 238. In some embodiments, the one or more non-phosphor materials can be scattering materials, which include films or particles of titanium oxide, zinc oxide, zinc sulfide, silicone, or a combination thereof (e.g., particles having a diameter ranging from about 100 nm to about 500 μm). In some embodiments, the light-blocking element 238 can include a substrate on which the one or more non-phosphor materials are disposed.

[0131] In some embodiments, the light-blocking element 238 can be a segmented film that is placed adjacent to each other on the phosphor film 236 or on an optically transparent substrate (not shown). The segmented light-blocking elements 238 can be placed in such a way that the gaps at the interfaces between adjacent light-blocking elements 238 are negligible. In an alternative embodiment, each light-blocking element 238 can be a different region of a continuous film placed on the phosphor film 236. Thus, Figure 2 Not drawn to scale.

[0132] In some embodiments, the light-blocking element 238 can not be as Figure 2Rather than the separate structure shown in [description], it may be included in the phosphor film 236. That is, the phosphor film 236 may be a composite film that includes the luminescent nanostructures described above together with the light-blocking element 238. One or more non-phosphor materials of the light-blocking element 238, such as dyes, inks, coatings, polymer materials, scattering materials (e.g., particles with a diameter ranging from about 100 nm to about 500 μm), or combinations thereof, may be introduced or embedded in the matrix of the phosphor film 236. The one or more non-phosphor materials may include nanostructured materials that are dispersible in the matrix of the phosphor film 236. These nanostructured materials may exhibit optical absorption properties and / or optical scattering properties and may not exhibit any optical emission properties. In some embodiments, the light-blocking element 238 may be included in the optically transparent substrate 228, which may also be configured to provide environmental sealing to the underlying layers and / or structures of the LCD module 204 and / or the BLU 202. In an alternative embodiment, the light-blocking element 238 may be included in the second polarizing filter 222, which may be located between the substrate 228 and the phosphor film 236. In some embodiments, the light-blocking element 238 may be a dichroic filter that, for example, reflects primary light (e.g., blue light, UV light, or a combination of UV light and blue light) while transmitting secondary light. The light-blocking element 238 may include a specific UV light filtering component to remove any unconverted UV light from the red and green subpixels and / or UV light from the blue subpixels.

[0133] The display screen 230 may be configured to generate an image. According to one embodiment, the display screen 230 may be a touch screen display. The LCD display device 200 may also include one or more dielectric materials (not shown) that are disposed between any adjacent elements in the LCD display device 200, e.g., between the optical cavity 212 and the LCD module 204, on either side of the LC solution layer 220, or between any other elements of the LCD display device 200. The one or more dielectric materials may include, but are not limited to, substrates, vacuum, air, gases, optical materials, adhesives, optical adhesives, glass, polymers, solids, liquids, gels, cured materials, optical coupling materials, refractive index matching or refractive index mismatching materials, refractive index gradient materials, overcoats or anti-overcoats, spacers, epoxies, silicones, organosilicons, brightness enhancement materials, scattering or diffusing materials, reflective or anti-reflective materials, wavelength selective materials, wavelength selective anti-reflective materials, or other suitable dielectric materials. Suitable materials may include silicones, silicone gels, silicones, epoxies (e.g., Loctite TM Epoxy E-30CL), acrylates (e.g., 3M TMAdhesive 2175). The one or more dielectric materials may be applied as a curable gel or liquid and cured during or after deposition, or pre-formed and pre-cured prior to deposition. Curing methods may include UV curing, thermal curing, chemical curing, or other suitable curing methods known in the art. Dielectric materials with a refractive index match may be selected to minimize optical losses between the BLU 202 and the components of the LCD module 204.

[0134] According to various embodiments, the LCD display device 200 may have a geometry, such as but not limited to cylindrical, trapezoidal, spherical, or elliptical, without departing from the spirit and scope of the present invention. The LCD display device 200 is not limited to a rectangular parallelepiped shape, nor is it limited to having other straight-edge shapes. It should be noted that the rectangular cross-sectional shape of the LCD display device 200 is for illustrative purposes and not restrictive. According to various embodiments, the LCD display device 200 may have other cross-sectional shapes (e.g., trapezoidal, oblong, rhomboid), without departing from the spirit and scope of the present invention. It should also be noted that although the optical cavity 212, substrates 216 and 218, polarizing filters 214 and 222, and display screen 230 are Figure 2 shown as having similar dimensions along the X-axis in, those skilled in the art will understand that, according to various embodiments, each of these components may have different dimensions from each other in one or more directions.

[0135] Figure 3 Schematically shows an exploded cross-sectional view of a side-lit LCD display device 300 according to one embodiment. The LCD display device 300 may include a BLU 302 and an LCD module 204. Figure 3 The elements in are the same as those described above Figure 2 and have the same annotations.

[0136] The BLU 302 may include an edge array of LEDs 310 (e.g., blue LEDs, white LEDs, UV LEDs, or a combination of blue and UV LEDs), a light guide plate (LGP) 312, and a reflector 308. The BLU 302 may be configured to provide primary light (e.g., blue light, white light, UV light, or a combination of blue and UV light), which may be processed by the LCD module 204 and subsequently transmitted to and distributed on the display screen 230. In some embodiments, the LED 310 includes a blue LED that emits light having a peak emission wavelength between about 440 nm and about 470 nm or between about 445 nm and about 455 nm. In some embodiments, the LED 310 includes a white LED that emits light in the range of about 440 nm to about 700 nm or in other possible light wavelength ranges. In some embodiments, the LED 210 includes a UV LED that emits light having a peak emission wavelength less than 420 nm, or between about 400 nm and about 410 nm, or between about 360 nm and about 370 nm. According to one embodiment, the blue LED may be, for example, a GaN LED that emits blue light with an emission wavelength of 450 nm. The LED 310 may be arranged in a line extending, for example, along the Y-axis.

[0137] In some embodiments, the LED 310 includes a mixture of both blue LEDs and UV LEDs. The ratio of UV LEDs to blue LEDs may be 3:1, or 1:1, or any ratio therebetween. In some embodiments, the LED 310 includes a ratio of UV LEDs to blue LEDs greater than 3:1.

[0138] According to some embodiments, the LGP 312 may include an optical fiber cable, a polymer, or a glass solid, such as a plate, a film, a container, or other structures. The size of the LGP 312 may depend on the final application and characteristics of the LED 310. The thickness of the LGP 312 may be compatible with the thickness of the LED 310. Other dimensions of the LGP 312 may be designed to extend beyond the size of the LED 310 and may be from about 10 millimeters to 10 centimeters to 100 centimeters.

[0139] In some embodiments, the material of the LGP 312 may include polycarbonate (PC), polymethyl methacrylate (PMMA), methyl methacrylate, styrene, acrylic polymer resin, glass, or other suitable LGP materials. Suitable manufacturing methods for the LGP 312 may include injection molding, extrusion, or other suitable embodiments. The LGP 312 may be configured to provide uniform primary light emission such that the primary light entering the LCD module 204 may have uniform color and brightness. The LGP 312 may include a substantially uniform thickness across the surface of the LGP 312. Alternatively, the LGP 312 may have a wedge shape. In some embodiments, the LGP 312 may be optically coupled to the LED 310 and may be physically connected to the LED 310 or physically disconnected from the LED 310. To physically connect the LGP 312 to the LED 310, an optically transparent adhesive (not shown) may be used.

[0140] In some embodiments, the BLU 302 may include an array of LEDs (not shown), each of which may be similar in structure and function to the LED 310. The array of LEDs may be adjacent to the LGP 312 and may be configured to provide primary light to the LCD module 204 for processing and subsequent transmission to the display screen 230, as discussed above with reference to Figure 2 discussed.

[0141] In some embodiments, the reflector 308 may be configured to increase the amount of light emitted from the LGP 312. The reflector 308 may include suitable materials such as mirrors, films of reflector particles, reflective metal films, or other suitable conventional reflectors. In some embodiments, the reflector 308 may include a white film. In some embodiments, the reflector 308 may include additional functions or features such as scattering, diffusing, or brightness enhancement features.

[0142] Figure 4A An example of a top view of the LED 210 in the X-Y plane according to some embodiments is illustrated. The LED 210 may include one or more first LEDs 402 that emit light having a peak emission wavelength in the UV range of the EM spectrum. The LED 210 may also include one or more second LEDs 404 that emit light having a peak emission wavelength in the blue range of the EM spectrum. The UV range may be defined as any wavelength below 420 nm, while the blue range may be defined as any wavelength between approximately 435 nm and approximately 495 nm. LEDs with emission wavelengths between 420 nm and 435 nm may be considered UV LEDs or blue LEDs. It should be noted that Figure 4AThe total number of LEDs illustrated is merely an example and should not be considered limiting. Those skilled in the art will recognize that any number of rows and any number of columns of LEDs can be part of LED 210. Additionally, each LED of LED 210 need not be directly adjacent to an adjacent LED.

[0143] The array 210 of LEDs can include a given arrangement of UV LEDs 402 and blue LEDs 404, which can be random or can have a specific pattern. Example patterns include alternating blue LEDs 404 and UV LEDs 402 row by row or column by column, alternating each individual LED between a UV LED 402 and a blue LED 404, or using a repeating sequence of UV LEDs 402 to blue LEDs 404. In some embodiments, any group of four LEDs selected from LED 210 cannot have more than one blue LED 404 in the group. In some embodiments, any group of four LEDs selected from LED 210 cannot have any more than two blue LEDs 404 in the group. In one example, each of the UV LEDs 402 and blue LEDs 404 is mounted on a package having dimensions of approximately 3 mm by approximately 3 mm in the X-Y plane.

[0144] Figure 4B An example of a side view of LED 310 along the Y-direction is illustrated according to one embodiment. LED 310 can include one or more first LEDs 406 that emit light having a peak emission wavelength in the UV range of the EM spectrum. LED 210 can also include one or more second LEDs 408 that emit light having a peak emission wavelength in the blue range of the EM spectrum. The UV range can be defined as any wavelength below 420 nm, and the blue range can be defined as any wavelength between approximately 435 nm and approximately 495 nm. LEDs having an emission wavelength between 420 nm and 435 nm can be considered either UV LEDs or blue LEDs. It should be noted that Figure 4B the total number of LEDs illustrated is merely an example and should not be considered limiting. Additionally, each LED of LED 310 need not be directly adjacent to an adjacent LED.

[0145] LED 310 can include a given arrangement of UV LEDs 402 and blue LEDs 404, which can be random or can have a specific pattern. Example patterns include alternating each individual LED between a UV LED 402 and a blue LED 404, or using some other repeating sequence of UV LEDs 402 to blue LEDs 404.

[0146] Exemplary Embodiments of Nanostructures Coated with a Barrier Layer

[0147] Figure 5 Schematically illustrates a cross-sectional structure of a luminescent nanostructure (NS) 500 coated with a barrier layer according to one embodiment. In some embodiments, a population of NSs 500 may be included in a phosphor film 236. The NS 500 coated with a barrier layer includes an NS 501 and a barrier layer 506. The NS 501 includes a core 502 and a shell 504. The core 502 contains a semiconductor material that emits light when absorbing higher energy. Examples of semiconductor materials for the core 502 include indium phosphide (InP), cadmium selenide (CdSe), zinc sulfide (ZnS), lead sulfide (PbS), indium arsenide (InAs), indium gallium phosphide (InGaP), cadmium zinc selenide (CdZnSe), zinc selenide (ZnSe), and cadmium telluride (CdTe). Any other II-VI, III-V, ternary, or quaternary semiconductor structure exhibiting a direct bandgap may also be used. In one embodiment, for example, the core 502 may further include one or more dopants such as metals, alloys. Examples of metal dopants may include, but are not limited to, zinc (Zn), copper (Cu), aluminum (Al), platinum (Pt), chromium (Cr), tungsten (W), palladium (Pd), or combinations thereof. The presence of one or more dopants in the core 502 may improve the structural and optical stability as well as the QY of the NS 501 compared to an undoped NS.

[0148] According to one embodiment, the diameter of the core 502 may be less than 20 nm. In another embodiment, the diameter of the core 502 may be between about 1 nm and about 5 nm. The ability to "tailor" the size of the core 502 and thus the size of the NS 501 in the nanoscale range allows for light emission coverage across the entire spectrum. Generally, larger NSs will emit light towards the red end of the spectrum, while smaller NSs will emit light towards the blue end of the spectrum. This effect is caused because the energy level spacing of larger NSs is closer than that of smaller NSs. This allows the NSs to absorb photons with less energy, i.e., those closer to the red end of the spectrum.

[0149] The shell 504 surrounds the core 502 and is disposed on the outer surface of the core 502. The shell 504 may include cadmium sulfide (CdS), zinc cadmium sulfide (ZnCdS), zinc selenium sulfide (ZnSeS), and zinc sulfide (ZnS). In one embodiment, the shell 504 may have a thickness 504t, e.g., one or more monolayers. In other embodiments, the shell 504 may have a thickness 504t between about 1 nm and about 5 nm. The shell 504 may be used to help reduce the lattice mismatch with the core 502 and improve the QY of the NS 501. The shell 504 may also help passivate and remove surface trap states on the core 502, such as dangling bonds, to improve the QY of the NS 501. The presence of surface trap states may provide non-radiative recombination centers and cause a reduction in the emission efficiency of the NS 501.

[0150] In an alternative embodiment, the NS 501 may include a second shell disposed on the shell 504 or more than two shells around the core 502 without departing from the spirit and scope of the present invention. In one embodiment, the second shell may be on the order of two single-layer thicknesses and is generally, but not necessarily, also a semiconductor material. The second shell may provide protection for the core 502. The second shell material may be zinc sulfide (ZnS), but other materials may be used without departing from the scope or spirit of the present invention.

[0151] The barrier layer 506 is configured to form a coating layer on the NS 501. In one embodiment, the barrier layer 506 is disposed on the outer surface 504a of the shell 504 and is in substantial contact with the outer surface 504a of the shell 504. In embodiments of the NS 501 having one or more shells, the barrier layer 506 may be disposed on the outermost shell of the NS 501 and is in substantial contact with the outermost shell of the NS 501. In an exemplary embodiment, the barrier layer 506 is configured to act as a spacer between the NS 501 and one or more NSs in, for example, a solution, composition, and / or film having a plurality of NSs, where the plurality of NSs may be similar to the NS 501 and / or the NS 500 coated with the barrier layer. With such an NS solution, NS composition, and / or NS film, the barrier layer 506 may help prevent aggregation of the NS 501 with neighboring NSs. Aggregation of the NS 501 with neighboring NSs may result in an increase in the size of the NS 501 and thus a reduction or quenching of the light emission properties of the aggregated NSs (not shown) containing the NS 501. In a further embodiment, the barrier layer 506 protects the NS 501 from, for example, moisture, air, and / or harsh environments (e.g., high temperatures and chemicals used during the lithographic processing of NSs and / or during the manufacturing process of NS-based devices), which may adversely affect the structural and optical properties of the NS 501.

[0152] The barrier layer 506 comprises one or more amorphous, optically transparent, and / or non-electrically active materials. Suitable barrier layers comprise inorganic materials such as, but not limited to, inorganic oxides and / or nitrides. According to various embodiments, examples of materials for the barrier layer 506 include oxides and / or nitrides of Al, Ba, Ca, Mg, Ni, Si, Ti, or Zr. In various embodiments, the barrier layer 506 may have a thickness 506t ranging from about 8 nm to about 15 nm.

[0153] As Figure 5As shown, according to one embodiment, the barrier-coated NS 500 may additionally or optionally include a variety of ligands or surfactants 508. According to one embodiment, the ligands or surfactants 508 may be adsorbed or bound to the outer surface of the barrier-coated NS 500, such as on the outer surface of the barrier layer 506. The variety of ligands or surfactants 508 may include a hydrophilic or polar head 508a and a hydrophobic or nonpolar tail 508b. The hydrophilic or polar head 508a may bind to the barrier layer 506. The presence of the ligands or surfactants 508 may help to separate the NS 500 and / or NS 501 from other NS during their formation, in, for example, solutions, compositions, and / or membranes. If the NS are allowed to aggregate during their formation, the quantum efficiency of the NS such as NS 500 and / or NS 501 may decrease. Ligands or surfactants 508 may also be used to impart certain properties to the barrier-coated NS 500, such as hydrophobicity to provide miscibility in nonpolar solvents, or to provide reaction sites for the binding of other compounds (e.g., reverse micelle systems).

[0154] There is a wide range of ligands that can be used as ligands 508. In some embodiments, the ligand is a fatty acid selected from lauric acid, caproic acid, myristic acid, palmitic acid, stearic acid, and oleic acid. In some embodiments, the ligand is an organophosphine or organophosphine oxide selected from trioctylphosphine oxide (TOPO), trioctylphosphine (TOP), diphenylphosphine (DPP), triphenylphosphine oxide, and tributylphosphine oxide. In some embodiments, the ligand is an amine selected from dodecylamine, oleylamine, cetylamine, and octadecylamine. In some embodiments, the ligand is trioctylphosphine (TOP). In some embodiments, the ligand is oleylamine. In some embodiments, the ligand is diphenylphosphine.

[0155] There is a wide range of surfactants that can be used as surfactants 508. In some embodiments, nonionic surfactants may be used as surfactants 508. Some examples of nonionic surfactants include polyoxyethylene(5)nonylphenyl ether (trade name IGEPAL CO-520), polyoxyethylene(9)nonylphenyl ether (IGEPAL CO-630), octylphenoxypoly(ethyleneoxy)ethanol (IGEPAL CA-630), polyethylene glycol oleyl ether (Brij 93), polyethylene glycol cetyl ether (Brij52), polyethylene glycol stearyl ether (Brij S10), polyoxyethylene(10)isooctylcyclohexyl ether (Triton X-100), and polyoxyethylene branched nonylcyclohexyl ether (Triton N-101).

[0156] In some embodiments, an anionic surfactant can be used as surfactant 508. Some examples of anionic surfactants include sodium dioctyl sulfosuccinate, sodium stearate, sodium lauryl sulfate, sodium monolauryl phosphate, sodium dodecylbenzenesulfonate, and sodium myristyl sulfate.

[0157] In some embodiments, NS 501 and / or 500 can be synthesized to emit light in one or more different color ranges, such as the red, orange, and / or yellow ranges. In some embodiments, NS 501 and / or 500 can be synthesized to emit light in the green and / or yellow ranges. In some embodiments, NS 501 and / or 500 can be synthesized to emit light in the blue, indigo, violet, and / or ultraviolet ranges. In some embodiments, NS 501 and / or 500 can be synthesized to have a main emission peak wavelength between about 505 nm and about 650 nm, between about 510 nm and about 550 nm, or between about 300 nm and about 480 nm.

[0158] NS 501 and / or 500 can be synthesized to exhibit a high QY. In some embodiments, NS 501 and / or 500 can be synthesized to exhibit a QY between 80% and 95% or between 85% and 90%.

[0159] Thus, according to various embodiments, NS 500 can be synthesized such that the presence of the barrier layer 506 on NS 501 substantially does not change or quench the light emission properties of NS 501.

[0160] Example embodiments of nanostructured films

[0161] Figure 6 Schematically shows a cross-sectional view of NS film 500 according to one embodiment. In some embodiments, the phosphor film 236 can be similar to NS film 500.

[0162] According to one embodiment, NS film 500 can comprise a plurality of core-shell NS 500s coated with a barrier layer ( Figure 6 ) and a matrix material 610. According to some embodiments, NS 500 can be embedded or otherwise disposed in the matrix material 610. As used herein, the term "embedded" is used to indicate that the NS is surrounded or encapsulated within the matrix material 610 that constitutes the main component of the matrix. It should be noted that in one embodiment, NS 500 can be uniformly distributed throughout the matrix material 610, but in other embodiments, NS 500 can be distributed according to an application-specific uniformity distribution function. It should be noted that even though NS 500 is shown as having the same diameter size, those skilled in the art should understand that NS 500 can also have a size distribution.

[0163] In one embodiment, the NS 500 can include a uniform population of NSs having dimensions that emit in the blue visible wavelength spectrum, the green visible wavelength spectrum, or the red visible wavelength spectrum. In other embodiments, the NS 500 can include a first population of NSs having dimensions that emit in the blue visible wavelength spectrum, a second population of NSs having dimensions that emit in the green visible wavelength spectrum, and a third population of NSs that emit in the red visible wavelength spectrum.

[0164] The matrix material 610 can be any suitable matrix material capable of accommodating the NS 500. The suitable matrix material can be chemically and optically compatible with the NS 500 and any surrounding packaging materials or layers used when applying the NS film 500 to a device. The suitable matrix material can include a non-yellowing optical material that is transparent to both primary light and secondary light, thereby allowing the primary light and secondary light to transmit through the matrix material. In one embodiment, the matrix material 610 can completely surround each NS 500. In applications where a flexible or moldable NS film 500 is desired, the matrix material 610 can be flexible. Alternatively, the matrix material 610 can include a high-strength non-flexible material.

[0165] The matrix material 610 can include polymers and organic and inorganic oxides. Suitable polymers for use in the matrix material 610 can be any polymers known to those of ordinary skill in the art that can be used for such purposes. The polymers can be substantially translucent or substantially transparent. The matrix material 610 can include, but is not limited to: epoxy resins; acrylates; norbornenes; polyethylene; poly(vinyl butyral); poly(vinyl acetate); polyureas; polyurethanes; silicones and silicone derivatives, including but not limited to amino silicones (AMS), polyphenylmethylsiloxane, polyphenylalkylsiloxane, polydiphenylsiloxane, polydialkylsiloxane, silsesquioxane, fluorinated silicones, and vinyl- and hydride-substituted silicones; acrylic polymers and copolymers formed from monomers including but not limited to methyl methacrylate, butyl methacrylate, and lauryl methacrylate; styrene-based polymers such as polystyrene, amino polystyrene (APS), and poly(acrylonitrile styrene) (AES); polymers crosslinked with difunctional monomers such as divinylbenzene; crosslinking agents suitable for crosslinking ligand materials; epoxides that combine with ligand amines (e.g., APS or PEI ligand amines) to form epoxy resins; etc.

[0166] In some embodiments, the matrix material 610 includes scattering microbeads such as TiO2 microbeads, ZnS microbeads, or glass microbeads that can improve the light conversion efficiency of the NS film 500. In some embodiments, the matrix material 610 can include light-blocking elements such as the light-blocking elements 238 and / or 548 described above with reference to Figures 2-3 and 5.

[0167] In another embodiment, the matrix material 610 may have low oxygen and moisture permeability, exhibit high light and chemical stability, exhibit a favorable refractive index, and adhere to the outer surface of the NS 500, thereby providing an airtight seal to protect the NS 500. In another embodiment, the matrix material 610 may be cured by UV or thermal curing methods to facilitate roll-to-roll processing.

[0168] According to some embodiments, the NS film 500 may be formed by mixing the NS 500 in a polymer (e.g., a photoresist) and casting the NS-polymer mixture onto a substrate, mixing the NS 500 with monomers and polymerizing them together, mixing the NS 500 in a sol-gel to form an oxide, or any other method known to those skilled in the art.

[0169] According to some embodiments, the formation of the NS film 500 may include a film extrusion process. The film extrusion process may include forming a homogeneous mixture of the matrix material 610 and a core-shell NS such as NS 500 coated with a barrier layer, introducing this homogeneous mixture into a top-mounted hopper that feeds into an extruder. In some embodiments, the homogeneous mixture may be in the form of pellets. The film extrusion process may further include extruding the NS film 500 from a slot die and passing the extruded NS film 500 through a quench roll. In some embodiments, the extruded NS film 500 may have a thickness of less than about 75 μm, e.g., a thickness in the range of about 70 μm to about 40 μm, about 65 μm to about 40 μm, about 60 μm to about 40 μm, or about 50 μm to about 40 μm. In some embodiments, the NS film 500 has a thickness of less than about 10 μm. In some embodiments, the formation of the NS film 500 may optionally include a second process after the film extrusion process. The second process may include processes such as co-extrusion, thermoforming, vacuum forming, plasma treatment, molding, and / or embossing to provide a texture to the top surface of the NS film 500. The textured top surface of the NS film 500 may help to improve, for example, the defined optical diffusion properties and / or the defined angular optical emission properties of the NS film 500.

[0170] Exemplary embodiments of luminescent nanostructures

[0171] Various compositions having luminescent nanostructures (NS) are described herein. The various properties of the luminescent nanostructures, including their absorption properties, emission properties, and refractive index properties, can be "tailored" and adjusted for various applications.

[0172] The material properties of the NSs can be substantially uniform or, in certain embodiments, non-uniform. The optical properties of the NSs can be determined by their particle size, chemical, or surface composition. The ability to "tailor" the luminescent NS size to be in the range of between about 1 nm and about 15 nm can enable light emission coverage across the spectrum to provide versatility in color rendering. Particle encapsulation can provide robustness against chemical and UV degrading agents.

[0173] Any method known to those skilled in the art can be used to produce the luminescent NSs for the embodiments described herein. Suitable methods and examples of nanocrystals are disclosed in U.S. Patent No. 7,374,807, U.S. Patent Application Serial No. 10 / 796,832 filed on March 10, 2004, U.S. Patent No. 6,949,206, and U.S. Provisional Patent Application No. 60 / 578,236 filed on June 8, 2004, the respective disclosures of which are incorporated herein by reference in their entireties.

[0174] The luminescent NSs for the embodiments described herein can be prepared from any suitable material, including inorganic materials, more suitably inorganic conducting materials or semiconductor materials. Suitable semiconductor materials can include those disclosed in U.S. Patent Application Serial No. 10 / 796,832 and can include any type of semiconductor, including II-VI, III-V, IV-VI, and IV group semiconductors. Suitable semiconductor materials can include, but are not limited to, Si, Ge, Sn, Se, Te, B, C (including diamond), P, BN, BP, BAs, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe, BeS, BeSe, BeTe, MgS, MgSe, GeS, GeSe, GeTe, SuS, SnSe, SnTe, PbO, PbS, PbSe, PbTe, CuF, CuCl, CuBr, CuI, Si3N4, Ge3N4, Al2O3, (Al, Ga, In)2(S, Se, Te)3, Al2CO, and suitable combinations of two or more such semiconductors.

[0175] In certain embodiments, the luminescent NS may have a dopant selected from a p-type dopant or an n-type dopant. The NS may also have a II-VI or III-V semiconductor. Examples of II-VI or III-V semiconductor NS may include any combination of elements from Group II of the periodic table such as Zn, Cd, and Hg with any element from Group VI of the periodic table such as S, Se, Te, and Po; and any combination of elements from Group III of the periodic table such as B, Al, Ga, In, and Tl with any element from Group V of the periodic table such as N, P, As, Sb, and Bi.

[0176] The luminescent NS described herein may further comprise ligands conjugated, complexed, associated, or attached to its surface. Suitable ligands may include any group known to those skilled in the art, including those disclosed in U.S. Patent No. 8,283,412, U.S. Patent Publication No. 2008 / 0237540, U.S. Patent Publication No. 2010 / 0110728, U.S. Patent No. 8,563,133, U.S. Patent No. 7,645,397, U.S. Patent No. 7,374,807, U.S. Patent No. 6,949,206, U.S. Patent No. 7,572,393, and U.S. Patent No. 7,267,875, the disclosures of each of which are incorporated herein by reference. The use of such ligands can enhance the ability of the luminescent NS to incorporate into various solvents and matrices, including polymers. Increasing the miscibility of the luminescent NS in various solvents and matrices (i.e., the ability to mix without separating) can allow them to be distributed throughout the polymer composition such that the NS do not aggregate together and thus do not scatter light. Such ligands are described herein as "miscibility enhancing" ligands.

[0177] In certain embodiments, there are provided compositions having luminescent NS distributed or embedded in a matrix material. Suitable matrix materials can be any material known to one of ordinary skill in the art, including polymeric materials, organic and inorganic oxides. The compositions described herein can be layers, encapsulants, coatings, sheets, or films. It should be understood that in the embodiments described herein where reference is made to layers, polymer layers, matrices, sheets, or films, these terms can be used interchangeably, and the embodiments so described are not limited to any one type of composition but encompass any matrix material or layer described herein or known in the art.

[0178] Down-converting NS (e.g., as disclosed in U.S. Patent No. 7,374,807) utilize the emission properties of luminescent nanostructures that are "tailored" to absorb light at a specific wavelength and then emit at a second wavelength, thereby providing enhanced performance and active source (e.g., LED) efficiency.

[0179] While any method known to one of ordinary skill in the art can be used to produce luminescent NSs, a solution-phase colloidal method can also be used to achieve controlled growth of inorganic nanomaterial phosphors. See Alivisatos, A.P., “Semiconductor clusters, nanocrystals, and quantum dots,” Science 271:933 (1996); X. Peng, M. Schlamp, A. Kadavanich, A.P. Alivisatos, “Epitaxial growth of highly luminescent CdSe / CdS Core / Shell nanocrystals with photostability and electronic accessibility,” J. Am. Chem. Soc. 30:7019-7029 (1997); and C.B. Murray, D.J. Norris, M.G. Bawendi, “Synthesis and characterization of nearly monodisperse CdE (E = sulfur, selenium, tellurium) semiconductor nanocrystallites,” J Am. Chem. Soc. 115:8706 (1993), the disclosures of which are incorporated herein by reference in their entireties.

[0180] According to one embodiment, in one example, for visible light down-conversion, CdSe can be used as the NS material because the synthesis of this material is relatively mature. Due to the use of general surface chemistry, cadmium-free NSs can also be used as an alternative.

[0181] In semiconductor NSs, light-induced emission arises from the band-edge states of the NSs. The band-edge emission of luminescent NSs competes with radiative and non-radiative decay channels originating from surface electronic states. X. Peng, et al., J Am. Chem. Soc. 30:7019-7029 (1997). As a result, the presence of surface defects such as dangling bonds provides non-radiative recombination centers and causes a reduction in emission efficiency. An effective and permanent method to passivate and remove surface trap states can be to epitaxially grow an inorganic shell material on the surface of the NSs. X. Peng, et al., J. Am. Chem. Soc. 30:7019-7029 (1997). The shell material can be selected such that the electronic energy levels are type-I relative to the core material (e.g., having a larger bandgap to provide a potential energy level that localizes electrons and holes in the core). As a result, the likelihood of non-radiative recombination can be reduced.

[0182] A core-shell structure can be obtained by adding a metal-organic precursor containing the shell material to a reaction mixture containing the core NS. In this case, rather than growing after a nucleation event, the core acts as a nucleus and the shell can grow from their surfaces. The temperature of the reaction is kept low to favor the adduction of the shell material monomers to the core surface while preventing the independent nucleation of the nanocrystals of the shell material. A surfactant is present in the reaction mixture to direct the controlled growth of the shell material and ensure solubility. A uniform and epitaxial growth of the shell can be obtained when the lattice mismatch between the two materials is low.

[0183] Example materials for preparing core-shell luminescent nanostructures can include, but are not limited to, Si, Ge, Sn, Se, Te, B, C (including diamond), P, Co, Au, BN, BP, Bas, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTc, BeS, BcSe, BcTe, MgS, MgSe, GeS, GeS, GeTe, SnS, SnSe, SnTe, PbO, PbS, PbSe, PbTe, CuP, CuCl, CuBr, CuI, Si3N4, Ge3N4, Al2O3, (Al, Ga, In)2(S, Se, Te)3, AlCO. The shell luminescent NS for implementing the present invention include, but are not limited to, (expressed as core / shell) CdSe / ZnS, InP / ZnS, InP / ZnSe, PbSe / PbS, CdSe / CdS, CdTe / CdS, CdTe / ZnS, etc.

[0184] The luminescent NS sizes for the embodiments described herein can be less than about 100 nm, as small as less than about 2 nm and absorb visible light. As used herein, visible light is electromagnetic radiation with wavelengths between about 380 and about 780 nanometers visible to the human eye. Visible light can be divided into various colors of the spectrum, such as red, orange, yellow, green, blue, indigo, and violet. Blue light can include light with wavelengths between about 435 nm and about 495 nm, green light can include light with wavelengths between about 495 nm and 570 nm, and red light can include light with wavelengths between about 620 nm and about 750 nm.

[0185] According to various embodiments, the luminescent NSs can have sizes and compositions such that they absorb photons in the ultraviolet, near-infrared, and / or infrared spectra. The ultraviolet spectrum can include light having wavelengths between about 100 nm and about 400 nm, the near-infrared spectrum can include light having wavelengths between about 750 nm and about 100 μm, and the infrared spectrum can include light having wavelengths between about 750 nm and about 300 μm.

[0186] Although luminescent NSs of other suitable materials can be used in the various embodiments described herein, in certain embodiments, the NSs can be ZnS, InAs, CdSe, or any combination thereof to form a population of nanocrystals for use in the embodiments described herein. As discussed above, in other embodiments, the luminescent NSs can be core / shell nanocrystals, such as CdSe / ZnS, InP / ZnSe, CdSe / CdS, or InP / ZnS.

[0187] Suitable luminescent nanostructures, methods of preparing luminescent nanostructures, including the addition of various solubility enhancing ligands, can be found in U.S. Patent Publication No. 2012 / 0113672, the disclosure of which is incorporated herein by reference in its entirety.

[0188] It should be understood that although certain embodiments are illustrated and described herein, the claims are not limited to the specific forms or arrangements of the parts described and shown. In the specification, illustrative embodiments are disclosed, and although specific terms are used, they are used in a general and descriptive sense only and not for purposes of limitation. Modifications and variations of the embodiments are possible in light of the above teachings. It should thus be understood that the embodiments can be practiced in a manner different from that specifically described.

Claims

1. A display device, the display device comprising a pixel array, the pixel array being disposed between a display screen and an LC solution layer, the pixels of the pixel array comprising: A first sub-pixel, the first sub-pixel having: A first quantum dot (QD) film, the first QD film configured to receive light having a first peak emission wavelength in the ultraviolet (UV) range of the electromagnetic (EM) spectrum and a second peak emission wavelength in the blue range of the EM spectrum and to convert a portion of the received light to emit secondary light having a third peak emission wavelength different from the first peak emission wavelength and the second peak emission wavelength; and A first filter element, the first filter element being disposed on the quantum dot film and configured to allow the secondary light having the third peak emission wavelength to pass through the filter element and to block the unconverted portion of the received light from passing through the filter element; and A second sub-pixel, the second sub-pixel having: A second filter element, the second filter element configured to allow the light having the second peak emission wavelength to pass through the second filter element and to block the light having the first peak emission wavelength from passing through the second filter element.

2. The display device according to claim 1, wherein the first QD film of the first sub-pixel has a first QD population configured to emit red light and the pixel further comprises: A third sub-pixel, the third sub-pixel comprising a second QD film, the second QD film having a second QD population configured to emit green light.

3. The display device according to claim 2, wherein the second sub-pixel further comprises a third QD film, the third QD film having a third QD population configured to emit blue light.

4. The display device according to any one of claims 1-3, wherein the first filter element is configured to absorb or scatter the unconverted portion of the received light, and the second filter is configured to absorb or scatter the light having the first peak emission wavelength.

5. The display device according to any one of claims 1-4, wherein the first filter element is disposed on the first QD film.

6. The display device according to any one of claims 1-5, the display device further comprising one or more first light sources configured to generate UV light and one or more second light sources configured to generate blue light, wherein the ratio of the first light source to the second light source is between 3:1 and 1:

1.

7. The display device according to any one of claims 1-6, wherein the first peak emission wavelength is less than 420 nm, and the second peak emission wavelength is between 445 nm and 455 nm.

8. The display device according to any one of claims 6-7, the display device further comprising an optical cavity, wherein the one or more first light sources and the one or more second light sources are located within the optical cavity.

9. The display device according to any one of claims 6-8, the display device further comprising a light guide plate, wherein the one or more first light sources and the one or more second light sources are coupled to the light guide plate from the outside.

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