A chiral Organic Light Emitting Diode, COLED and corresponding method of manufacturing, device and system.

Abstract

A B S T R A C T A chiral Organic Light Emitting Diode, COLED, comprising a layered stack comprising a transparent anode layer arranged for injecting holes into an organic layer, chiral photonic nanostructures arranged to increase a degree of circular polarization in emitted light from the organic layer, the organic layer stacked on top of the transparent anode layer such that the chiral photonic nanostructures are embedded in this layer, wherein the organic layer is arranged for emitting light and a cathode layer, stacked on top of the organic layer, and arranged for injecting electrons into the organic layer.

Description

& A chiral Organic Light Emitting Diode, COLED and corresponding method of manufacturing, device and system. Technical Field The present disclosure relates to chiral Organic Light Emitting Diodes, COLED, specifically improving the dissymmetry of circularly polarized light resulting from the COLED, which may be used in 3D imaging. Background Organic Light-Emitting Diodes (OLEDs) are a display technology that is used in various applications, including smartphones, televisions and wearable devices. OLEDs rely on organic materials emitting light when an electric current is applied. OLEDs do not require a backlight, unlike Liquid Crystal Displays, LCDs, as each pixel produces their own light. This allows for a thinner display, which may be important in various applications it is used in. Furthermore, the displays may typically have a deeper contrast and an improved energy efficiency. OLEDs may generally emit unpolarized light. This means that the lightwaves oscillate in multiple, random directions ratherthan a specific alignment. However, it may be beneficial to polarize the light of an OLED in a circular manner. Chiral OLEDs, or COLEDs emit circularly polarized light. COLEDs have historically faced significant challenges, including the scarcity of chiral luminescent materials due to complex molecular design and synthesis, low dissymmetry factors. The dissymmetry factor, gum, is defined as two times the difference between the emission of light with different polarization divided by the sum and gives a metric of the degree of polarization. Similar to other 3D-image generation devices, the COLED display could be paired with shutter glasses that the userwears and that alternately block or allowCPL from the display with a certain polarization, providing each eye with the appropriate image and creating a high-quality 3D experience. However COLEDs are set to enhance contrast and reduce perceptual distortion, thereby offering a superior visual experience. However, COLEDs based on chiral luminescent materials have g values typically ranging from 10'4 to 102, and generally lower device performance compared to conventional OLEDs such as reduced luminance. As an infinite contrast between left- and right-handed polarizations gives a g of 2, this is far from the ideal performance. This leads to conventional methods requiring additional polarizers to generate circularly polarized light from unpolarized electroluminescence, leading to significant power loss and poor contrast ratios. Summam Therefore, it would be advantageous to provide COLEDs having an improved dissymmetry factor, without compromising emission efficiency. In a first aspect of the disclosure, there is provided a chiral Organic Light Emitting Diode, COLED, comprising a layered stack comprising: - a transparent layer, preferably a transparent anode layer, with chiral photonic nanostructures on top or in its proximity, the anode layer being arranged for injecting holes into an organic layer; - the chiral photonic nanostructures arranged to increase a degree of circular polarization in emitted light from the organic layer; - the organic layer stacked on top of the transparent anode layer such that the chiral photonic structures are embedded in this layer or in close proximity to it, wherein the organic layer is arranged for emitting light and - an electrode layer, preferably a cathode layer, stacked on top of the organic layer, and arranged for injecting electrons into the organic layer. The inventors have found that by integrating chiral nanostructures into OLEDs, the dissymmetry factor may be increased. The dissymmetry factor is used to describe the degree to which left-handed and / or right-handed circularly polarized light are absorbed or scattered differently by a chiral material. The integration of the chiral nanostructures may be performed without compromising emission quantum efficiency. Furthermore, utilizing these chiral nanostructures allows for a seamless compatibility with existing traditional OLED designs, without altering their original configurations. Nanostructures-based chiral OLEDs address the limitations of traditional OLEDs 3D stereoscopic designs by enhancing contrast and reducing perceptual distortion, thereby offering a superior visual experience and advancing the capabilities of 3D display technology. In an example of the disclosure, the organic layer comprises: - a hole transporting layer arranged for facilitating movement of holes from the anode layer to an emissive layer; - the emissive layer arranged for emitting light when electrons from the cathode layer and holes from the anode layer recombine, and - an electron transporting layer arranged for facilitating movement of electrons from the cathode layer to the emissive layer. The light generated in the emissive layer, which is generated when electrons interact with holes, is directed towards the transparent anode layer. The inventors have found that by providing chiral nanostructures on the transparent anode layer, light with an increase dissymmetry factor, for example of around 1.2, may be achieved. This is much higher than traditional methods of generating a chiral polarized light in OLEDs just by using chiral molecules and without the chiral photonic nanostructures. In an example of the disclosure, chiral molecules may be also deposited in the emissive layer, thereby increasing the dissymmetry factor of the COLED.. These molecules may induce a partial circularly polarized light which is further enhanced by the chiral photonic nanostructures. This may be employed to increase the dissymmetry factor further. However, these molecules may only provide a fraction of the total dissymmetry factor in comparison with the polarization induced by the nanostructures at the transparent anode layer. In an example of the disclosure, the chiral structures have a thickness lower than a thickness of the organic layer, preferably a thickness of the hole transporting layer. emissive layer. The inventors have found that these chiral nanostructures should not have a height exceeding the hole transporting layer, or the emissive layer, as otherwise they may interfere with the process of generating light, by for example creating electrical shorts if the chiral nanostructures are conducting. Furthermore, the interaction between the generated light and the nanostructures may not be properly conducted when the nanostructures are too thick. A too thick organic emissive layer would increase the turn-on voltage and block carriers injection. This may result in an emission efficiency and the dissymmetry factor being considerably lower. In an example of the disclosure, the thickness of the chiral nanostructures is at most 200nm. Typically, the emissive layer is between 100 and 500 nm, depending on the thickness of the chiral nanostructures, which complies with the previous example. In this example the same considerations are made regarding the performance of the chiral nanostructures In an example of the disclosure, the chiral photonic nanostructures are defined such that the nanostructures cannot be superimposed on its mirror image by translations and rotations. This asymmetry may result in light interacting with the plurality of chiral photonic nanostructures to become polarized. ln specific, clockwise and anti-clockwise polarized light may result from the interaction with light and the nanostructures. The interaction with the plurality of chiral photonic nanostructure can also lead to directional emission of polarized light. This directional emission of polarized light can be used for bright displays. The directionality is controlled by the arrangement of chiral photonic nanostructures in periodic or quasi-periodic arrays. In an example of the disclosure, the chiral photonic nanostructures are any of: - displaced bars, - split ring resonators, or - gammadion crosses. Many alternative forms or configurations of chiral nanostructures may be used, and the examples are not limited to these above-mentioned nanostructures. Rather they indicate a range of different options to implement. Unit cells comprising displaced bars may comprise two silicon bars that are spaced apart and have an offset. This layout is used to crease the chirality, not being able to superimpose their mirror images. This size of the bars and the distance between unit cells of displaced bars may be changed to change the wavelengths at which the chiral nanostructures are most optimally configured and the directions over which the circularly polarized emission is preferentially emitted.. Gammadion crosses may also comprise Fylfot crosses. The crosses lead to higher dissymmetric factor due to their asymmetric structures. In an example of the disclosure, a length of the bars is in between 100 and 150 nm and a width of the bars is in between 20 and 60 nm. The length of the bars may be tweaked to optimize for the wavelength of the light to be optimally polarized. Values used to optimize for visible light comprise ranges in between 100 and 300 nm for the length, in between 20 and 100 nm for the width, and in between 10 and 100 nm for the height of the nanostructures. For other nanostructure shapes, other values for the thickness of the nanostructures may be used and the shapes may be scaled to get optimal dissymmetry values. In an example of the disclosure, the bars are offset in a width direction with a distance dy and are offset in a length direction by a distance dx. The inventors have found that the invention of the present disclosure allows for precise control of chiral polarization across different wavelengths by adjusting the structural parameters of the chiral nanostructures. For example, the above-mentioned length and width may be changed, and the offsets may further be tweaked to provide the optimal dissymmetry factor for the desired wavelength. Herein the distance dy may be 10 to 100 percent of the width of the nanostructures, while the distance dx may be 10 to 100 percent of the length of the nanostructures. In an example of the disclosure, the nanostructures comprise any of the following materials: silicon, indium phosphide, lnP, , gallium arsenide, GaAs, gallium nitride, GaN, dielectric materials such as zinc oxide, ZnO, silicon nitride, Si3N4, titanium dioxide, TiOz, and silicon dioxide. SiOz, or metals like silver, Ag, aluminum, Al, and gold, Au. The inventors have found that a wide range of materials may be used for the chiral nanostructures. The principle of polarizing the light in the two rotational directions depends on the shape and size of the nanostructures. In an example of the disclosure, the transparent anode layer comprises lndium Tin Oxide, ITO, glass. Other transparent conductive oxides are also possible. One of the advantages of lTO is its high optical transparency in the visible spectrum, which allows light generated within the OLED to pass through with minimal absorption. This may be important as providing a maximal brightness is an important design goal in OLED displays. Additionally, ITO is an excellent conductor of electricity, which makes it a suitable material for the anode in OLEDs, where it efficiently injects holes into the organic layers of the device. Therefore, the ITO glass lends itself as a suitable choice for the anode while being as transparent as possible. The ITO glass itself may be provided on a substrate layer, which may comprise a transparent material, such as silicon oxide. In a second aspect of the disclosure, there is provided a method of manufacturing a chiral Organic Light Emitting Diode, COLED, in accordance the disclosure, wherein the method comprises the steps of: - providing the transparent anode layer, - providing the chiral photonic nanostructures on top of the transparent anode layer; - stacking the organic layer on top of the transparent anode layer, and - stacking the cathode layer on top of the organic layer. The inventors have found that providing chiral photonic nanostructures , which may be a plurality of chiral photonic nanostructures , on the transparent anode layer may be beneficial in obtaining a large dissymmetry factor of polarized light. In a third aspect of the disclosure, there is provided a device arranged for emitting light, wherein the light comprises a clockwise polarized light component and an anti-clockwise polarized light component, such that a three-dimensional image can be formed at a receiver side, wherein the device comprises at least one COLED in accordance with the disclosure, wherein the at least one COLED is arranged for providing the light having the clockwise polarized light component and the anti- clockwise polarized light component. The device can be a display wherein every pixel is formed by at least 6 COLEDs. 3 of these COLEDs emitting light of the three primary colours that can be mixed in varying amounts to produce a gamut of colours and having the clockwise polarized light emission, and the other 3 COLEDs emitting light of the same three primary colours having the anti-clockwise polarized light emission. The inventors have found that the COLEDs may be implemented in a device, wherein the device is capable of efficiently generating 3D images with high colour contrast, depth perception, and vibrancy. Herein, the COLED consists of conventional OLED configurations and the nanostructures in accordance with the disclosure, which are embedded in the OLED structure. The small size of the nanostructures allows the realization of small COLEDs that define high-resolution displays. The emission colour of the COLEDs can be tuned by controlling the size and arrangement of the nanoparticles forming the nanostructures and the emitting layer. In an example of the disclosure, the device is any of a smartphone, tablet, laptop, television, smartwatch, and a screen. The above-mentioned examples may be suitable for any device which has a display. If the device uses OLED, the COLEDs may be trivial as the implementation of theCOLEDs in accordance with the disclosure in devices may follow similar methods as conventional OLEDs. In a fourth aspect of the disclosure, there is provided a system for enabling a user to view a three-dimensional image, wherein the system comprises: - a device in accordance with the disclosure, and - an eyewear comprising a circular polarized filter such that the clockwise polarized light component is received by one eye of the user and the anti- clockwise polarized light component is received by the other eye of the user. Similar to other 3D-image generation devices, the COLED display is paired with glasses that the user wears and that block or allow CPL from the display with a certain polarization, providing each eye with the appropriate image and creating a high-quality 3D experience. In an example of the disclosure, the eyewear is any of glasses and contact lenses. ln another aspect of the present disclosure, there is provided an assembly of a transparent anode layer arranged for injecting holes into an organic layer, and chiral photonic nanostructures arranged to increase a degree of circular polarization in emitted light from the organic layer, wherein the assembly is to be used in a chiral Organic Light Emitting Diode, COLED, in accordance with any of the previous examples. In the appended figures, similar components and / or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label. The above and other aspects of the disclosure will be apparent from and elucidated with reference to the examples described hereinafter. Brief description of the figures Fig. 1 depicts a layered configuration for a chiral Organic Light-Emitting Diode, COLED; Fig. 2 depicts an example of the layered configuration for a chiral COLED. Detailed description It is noted that in the description of the figures, same reference numerals refer to the same of similar components performing a same of essentially similar function. A more detailed description is made with reference to particular examples, some ofwhich are illustrated in theappended drawings, such thatthe features ofthe present disclosure may be understood in more detail. It is noted that the drawings only illustrate typical examples and are therefore not to be considered to limit the scope of the subject matter of the claims. The drawings are incorporated for facilitating an understanding of the disclosure and are thus not necessarily drawn to scale. Advantages of the subject matter as claimed will become apparent to those skilled in the art upon reading the description in conjunction with the accompanying drawings. The ensuing description above provides preferred exemplary embodiment(s) only, and is not intended to limit the scope, applicability, or configuration of the disclosure. Rather, the ensuing description of the preferred exemplary embodiment(s) will provide those skilled in the art with an enabling description for implementing a preferred exemplary embodiment of the disclosure, it being understood that various changes may be made in the function and arrangement of elements, including combinations offeatures from different embodiments, without departing from the scope of the disclosure. Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise," "comprising," and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to." As used herein, the terms "connected," "coupled," or any variant thereof means any connection or coupling, either direct or indirect, between two or more elements; the coupling or connection between the elements can be physical, logical, electromagnetic, or a combination thereof. Additionally, the words "herein," "above," "below," and words of similar import, when used in this application, refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the Detailed Description using the singular or plural number may also include the plural or singular number respectively. The word "or" in reference to a list of two or more items, covers all the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list. These and other changes can be made to the technology considering the following detailed description. While the description describes certain examples of the technology, and describes the best mode contemplated, no matter how detailed the description appears, the technology can be practiced in many ways. Details of the system may vary considerably in its specific implementation, while still being encompassed by the technology disclosed herein. ln figure 1, a layered configuration 100 for a chiral Organic Light-Emitting Diode, COLED, is depicted. The layered configuration 100 comprises a transparent anode layer 105, a hole transporting layer 104, an emissive layer 103, an electron transporting layer 102 and a cathode layer 101. Each of these layers have a specific function. First, an anode and a cathode are of importance in the COLED. The transparent anode layer 105, being the anode, provides holes in the organic layer. The organic layer comprises the layers in between the anode and the cathode, being the hole transporting layer 104, the emissive layer 103 and the electron transporting layer 102. The cathode layer 101, being the cathode, provides electrons in the organic layer. This cathode may be connected to an external electron source, which is not shown. The electrons and holes travel through their respective transporting layers (being the hole transporting layer 104 and the electron transporting layer 102). In the emissive layer 103, the generation of light happens. Herein the holes and the electrons recombine producing photons. The emissive layer may be formed by chiral molecules or by non-chiral molecules. Deposition of chiral molecules may be performed using vapor deposition techniques or the like. The light produced in the emissive layer may be emitted in different directions, therefore it is beneficial to provide a reflective cathode layer, which may be able to reflect the light to the anode layer, which, as said, is transparent. So preferentially, light is directed towards the anode layer. Here the inventors have found that chiral photonic nanostructures 106 provided on the transparent anode layer may induce a clockwise and / or anti-clockwise circular polarization in the light. Herein the dissymmetry factor is of importance. The maximal dissymmetry value is 2, which practically is difficult to approach. The chiral nanostructures 106 are aimed to approach this optimally, resulting in a dissymmetry value of approximately 1.2. The polarized light then travels through the transparent anode layer 105 and a possible transparent substrate layer (not shown) to emit the light to external surroundings. ln figure 2, the configuration is depicted in more detail. Herein the transparent anode layer 105 is positioned on a transparent substrate layer 202. Further, part of the organic layer 201 not comprising the hole transporting layer 105 is depicted. Positioned on the transparent anode layer 105 and surrounded by the hole transporting layer 105 are the chiral nanostructures 106. In more detail they are provided, wherein the chiral nanostructures comprise a height 26 a width 20 and a length 21. They are offset from each other by an offset distance 23. Further they are positioned at a certain distance 22 as not to overlap or be too far away. All these parameters may be tweaked in order to find the optimal dissymmetry value of the COLED. The chiral photonic nanostructures can be fabricated using a variety of methods, including UV lithography, hard and soft imprint lithography, roll-to-roll and roll-to- plate nanoimprint Iithography, electron-beam lithography Furthermore, theshape ofthe chiral nanostructures 106 may be chosen. This may result in a different configuration than as shown in the figure. It may be that the offset is not present anymore or that it is inherent in the alternative chiral nanostructures. The chiral nanostructure may follow a gammadion or fylfot shape. These shapes may be beneficial in reaching high dissymmetry values. As noted above, particular terminology used when describing certain features or aspects of the technology should not be taken to imply that the terminology is being redefined herein to be restricted to any specific characteristics, features, or aspects of the technology with which that terminology is associated. ln general, the terms used in the following claims should not be construed to limit the technology to the specificexamples disclosed in the specification, unless the Detailed Description section explicitly defines such terms. Accordingly, the actual scope of the technology encompasses not only the disclosed examples, but also all equivalent ways of practicing or implementing the technology under the claims.

Claims

1. A Chiral Organic Light-Emitting Diode, COLED, comprising a layered stack, comprising: - a transparent layer designed for injecting holes in an organic layer; - chiral photonic nanostructures designed to a degree of to increase circular polarization in emitted light from the organic layer; - the organic layer stacked on top of the transparent layer so that the chiral photonic nanostructures are embedded in this layer, whereby the organic layer is designed to emit light, and - an electrode layer, stacked on top of the organic layer, and configured for injecting electrons into the organic layer.

2. The COLED within the meaning of claim 1, where at least one of: - the transparent layer is a transparent anode layer, and - the electrode layer is a cathode layer.

3. The COLED according to one of the preceding conclusions, whereby the organic layer comprises: - a hole transport layer designed to facilitate movement from the gate of the anode layer to a transmitting layer; - the transmitting layer configured for emitting light when electrons from the cathode layer and holes from the anode layer recombine, and - an electron transport layer configured to facilitate movement of electrons from the cathode layer to the emitting layer.

4. The COLED according to claim 3, where the chiral nanostructures a have a thickness greater than a thickness of the organic layer, preferably a thickness lower than a thickness of the hole transport layer.

5. The COLED according to claim 4, where the thickness of the chiral nanostructures are a maximum of 200nm.

6. The COLED according to one of the preceding conclusions, whereby the Chiral photonic nanostructures are defined such that the nanostructures do not have can be superimposed as mirror images of each other through translations and rotations.

7. The COLED according to one of the preceding conclusions, whereby the Chiral nanostructures are one of: - displaced bars, - split-ring resonators, or - gammadion crosses.

8. DeCOLED in accordance with claim 7, where a length of the bars between the is 100 and 300nm and a width of the bars is between 20 and 100nm and the the height of the bars is between 10 and 200 nm.

9. The COLED according to claim 8, where the bars in a periodic have grids with distances between neighboring bars in the range of 100-1000 nm.

10. The COLED according to claim 9, using the periodic grid to decouple circularly polarized, with preference in certain directions, causing the clarity in these directions to increase.

11. The COLED according to one of the claims 7 10, where the bars are offset in a width direction with a distance dy and are offset in a length direction with a distance dx.

12. The COLED according to one of the preceding conclusions, whereby the nanostructures include one of the following materials: silicon, indium phosphide lnP, gallium arsenide, GaAs, zinc oxide, ZnO, gallium nitride, GaN, dielectric materials such as silicon nitride, Si3N4, titanium dioxide, TiOz and silicon dioxide, SiOz, or metals such as silver, Ag, aluminium, A| and gold, Au.

13. The COLED according to one of the preceding conclusions, whereby the transparent anode layer comprises a transparent conduction oxide and glass.

14. A method for manufacturing a chiral Organic Light- Transmitting Diode, COLED, pursuant to one of the preceding claims, where the method the steps include: - providing the transparent anode layer, - providing the chiral photonic nanostructures above on the transparent anode layer; - stacking the organic layer on top of the transparent one anode layer, - stacking the cathode layer on top of the organic layer.

15. A device designed for emitting light, whereby the light with a clockwise circularly polarized light component and a counter-clockwise circular one polarized light component, so that a three-dimensional image can be formed at a receiver side, where the device comprises at least one COLED according to one of the preceding conclusions, whereby at least one COLED is configured for providing the light that is circularly polarized in a clockwise direction light component and has the counterclockwise circularly polarized light component.

16. An establishment within the meaning of claim 14, where the establishment is one of a smartphone, tablet, laptop, television, smartwatch, and a screen.

17. A system for enabling a user to a to be seen in three dimensions, where the system comprises: - an establishment within the meaning of one of the conclusions 15 16, and - an eye accessory (eyewear) comprising a circular polarized filter so that the clockwise circularly polarized light component is received by the eye of the user and the counter-clockwise circular The polarized light component is received by the user's other eye.

18. A system within the meaning of claim 17, where the eye accessory (eyewear) one is of glasses and lenses.

19. an assembly of a transparent anode layer designed for the injecting holes into an organic layer, and chiral photonic nanostructures designed to increase a degree of circular polarization in the emitted light of the organic layer, where the assembly must be used in a chiral Organic Light-Emitting Diode, COLED, according to one of the claims 1 13. 1 / 2 101 102 103 104 105 106 Fig. 1

Images