Light emitting structure, display device and sub-pixel structure

Abstract

A light emitting structure includes a substrate, a plurality of sub-pixel stacks emitting different colors on the substrate, a bank surrounding the sub-pixel stacks and forming an inner space above the sub-pixel stacks, a first fill material in the inner space, a second fill material on the first fill material, and an interface between the first fill material and the second fill material. Each of the plurality of sub-pixel stacks includes a light emitting layer between a first transport layer and a second transport layer, a first electrode layer coupled with the first transport layer, and a second electrode layer coupled with the second transport layer. The plurality of sub-pixel stacks each has a substantially uniform distance between the light emitting layer and the first electrode layer. Each of the plurality of sub-pixel stacks emits a main emission peak through the interface in a direction perpendicular to a top surface of each of the plurality of sub-pixel stacks.

Description

Technical Field

[0001] The present disclosure generally relates to layer and bank structures for emissive devices, particularly for quantum dot light emitting diode (LED) displays. In particular, the present disclosure seeks to improve efficiency, reduce color shift, and increase on-axis brightness for a top-emitting structure embedded in a high-refractive-index encapsulant surrounded by banks, while maintaining constant layer thickness for all subpixels (e.g., red, green, and blue). Background Art

[0002] Organic light-emitting diodes (OLEDs) are one of the most commonly used LEDs in display devices, and quantum dots have been proposed as an improvement to OLEDs due to their better spectral emission and chemical stability. Quantum dots are commonly used as phosphors for blue LEDs and exist as backlights for liquid crystal displays (LCDs). Conventional LED displays have adopted an improvement method that exploits the cavity in the LED structure and its effect on light. For example, Kodak (US2006 / 0158098) describes a top-emitting structure, and Samsung (US9583727) describes an OLED and QLED structure with a light-emitting region between reflective regions, one of which is partially transmissive.

[0003] Other displays involve methods to improve the luminance of cavities in LEDs. For example, Samsung (US2015 / 0084012) describes the use of dispersion layers in OLED structures, Samsung (US8894243) describes the use of microstructured scattering to improve efficiency, and 3M (WO2017 / 205174) describes enhancing luminescence by using surface plasmon nanoparticles or nanostructures in transport layers.

[0004] Methods involving modifications to the cavity (or cavities) are often difficult to implement because they require very small features or control of the layers. An alternative approach to modifying the cavity is to use a thick top "filler" layer with a high refractive index, which can reduce Fresnel reflections and increase transmittance through the top electrode. However, light in the high-index layer may be primarily trapped by total internal reflection (TIR). To extract the trapped light, reflective and / or scattering banks surrounding the filler layer are used to couple out the light trapped by TIR.

[0005] TCL (CN106876566) and JOLED (US9029843) describe such pixel arrangements with banks, and a fill material between the organic layers over the cavity and the banks. Hitachi (US7091658) describes banks that can be reflective using electrode metal materials, Cambridge Display Technology (KR1020150020140) describes banks that can be shaped in different structures using different assembly steps, and Sharp (US10090489) describes shaped reflectors under the organic layers.

[0006] Another approach is to control the fill material. For example, Global OLED (US8207668) describes a fill layer that can be controlled, where the fill layer and organic layer have different thicknesses for different sub-pixels to maximize light output as a function of wavelength.

[0007] Another approach is to control the organic layer, which can be achieved by appropriate material selection (e.g. lyophilic / lyophobic). For example, Seiko Epson (US7902750) describes a cavity layer that is curved, but the encapsulation is a planarization layer, and JOLED (US9312519) describes an organic layer that is both convex and concave in orthogonal directions.

[0008] In another approach, Lee et al. (“Three-dimensional pixel configuration for optical coupling of OLED displays - Optical simulation”, 2019 SID Display Week Proceedings) describe a design that utilizes the OLED light-emitting layer to simulate a pixel bank structure. This approach utilizes a bank structure that maximizes the efficiency of a real bank structure to simulate the best extraction efficiency. The best solution involves only green light and ITO electrodes, which is not practical in such a device because the emission spectrum is too broad, the color gamut is poor, and on-axis luminance (the user’s apparent brightness) is not considered.

[0009] Prior art documents

[0010] Patent documents

[0011] US Patent Publication US 2006 / 0158098 Al (Eastman Kodak Company, published July 20, 2006).

[0012] US Patent US 9,583,727 B2 (Samsung Display Co., Ltd., notice of allowance February 28, 2017).

[0013] US Patent Publication US 2015 / 0084012 Al (Samsung Display Co., Ltd., published March 26, 2015).

[0014] US Patent US 8,894,243 B2 (Samsung Corning Precision Materials Co., Ltd., notice of allowance November 25, 2014).

[0015] International patent publication WO 2017 / 205174 Al (3M Innovation Co., published November 30, 2017).

[0016] Chinese patent publication CN 106876566 A (TCL, published June 20, 2017).

[0017] U.S. patent US 9,029,843 B2 (JOLED Co., Ltd., issued May 12, 2015).

[0018] U.S. patent US 7,091,658 B2 (Hitachi, issued August 15, 2006).

[0019] KR 1020150020140 (Cambridge Display Technology, published February 25, 2015).

[0020] U.S. patent US 10,090,489 B2 (Sharp Kabushiki Kaisha, issued October 2, 2018).

[0021] U.S. patent US 8,207,668 B2 (Universal OLED Technology LLC, issued June 26, 2012).

[0022] U.S. patent US 7,902,750 B2 (Seiko Epson Corp., issued March 8, 2011).

[0023] U.S. patent US 9,312,519 B2 (JOLED Co., Ltd., issued April 12, 2016).

[0024] Non-patent literature

[0025] Lee et al. (“Three-dimensional pixel configuration for optical coupling of OLED displays - optical simulation,” SID 2019 Digest, published 2019). SUMMARY

[0026] The present disclosure is directed to a self-emissive display including quantum dot electroluminescent material in an LED arrangement.

[0027] In a first aspect of the present disclosure, a light emitting structure includes: a substrate; a plurality of sub-pixel stacks emitting different colors on a surface of the substrate, each of the plurality of sub-pixel stacks including: a light emitting layer between a first transport layer and a second transport layer; a first electrode layer coupled with the first transport layer; and a second electrode layer coupled with the second transport layer; a bank surrounding and forming an inner space above each of the plurality of sub-pixel stacks; a first filling material in the inner space and having a first refractive index; a second filling material on the first filling material and having a second refractive index lower than the first refractive index; and an interface between the first filling material and the second filling material, wherein the plurality of sub-pixel stacks have a uniform distance between the light emitting layer and the first electrode layer; wherein at least one of the plurality of sub-pixel stacks emits a main emission peak into the filling material along an on-axis direction perpendicular to a top surface of the at least one of the plurality of sub-pixel stacks; and wherein the at least one of the plurality of sub-pixel stacks is configured as an optical mode of N = 1, such that a phase shift associated with emission from the light emitting layer of the at least one of the plurality of sub-pixel stacks to the first electrode of the at least one of the plurality of sub-pixel stacks and back to the light emitting layer of the at least one of the plurality of sub-pixel stacks is 2π.

[0028] In an implementation form of the first aspect, at least one of the plurality of sub-pixel stacks is configured to emit light at a plurality of wavelengths having a center wavelength.

[0029] In a further implementation form of the first aspect, emission in an off-axis direction away from the on-axis direction is reflected by an inclined surface of the bank and at least reflected once by the interface via total internal reflection before being emitted in the on-axis direction by the first filling material.

[0030] In yet another implementation form of the first aspect, in at least one of the plurality of sub-pixel stacks, a phase shift associated with emission from the light emitting layer to the first electrode layer and back to the light emitting layer is less than 2π or greater than 2π to cause a luminance variation in the main emission peak.

[0031] In yet another implementation form of the first aspect, emission in an off-axis direction away from the on-axis direction of the at least one of the plurality of sub-pixel stacks is reflected by an inclined surface of the bank and at least reflected once by the interface via total internal reflection before being emitted in the on-axis direction by the first filling material.

[0032] In yet another implementation form of the first aspect, the main emission peak is utilized to calibrate the emission in the off-axis direction reflected by the tilted facet to compensate for variations in luminance in the main emission peak.

[0033] In yet another implementation form of the first aspect, the second fill material covers an entire top surface of the first fill material.

[0034] In yet another implementation form of the first aspect, the second fill material covers a portion of a top surface of the first fill material.

[0035] In yet another implementation form of the first aspect, sizes of sub-pixels associated with the plurality of sub-pixel stacks are different to optimize color shift.

[0036] In yet another implementation form of the first aspect, the light-emitting layer comprises quantum dot light-emitting material; the first transport layer comprises a hole transport layer; the second transport layer comprises an electron transport layer; the first electrode layer is an anode layer comprising a metallic reflector for reflecting light emitted from the light-emitting layer; and the second electrode layer is a cathode layer comprising a transparent material that is not metallic.

[0037] In yet another implementation form of the first aspect, the main emission peak emitted from the at least one sub-pixel stack through the interface has least light reflected on all pixels by total internal reflection.

[0038] In yet another implementation form of the first aspect, the main emission peak is emitted through the interface along the on-axis direction in a specific area of at least one sub-pixel stack of the light-emitting structure.

[0039] In yet another implementation form of the first aspect, the light-emitting layer comprises quantum dot light-emitting material; the first transport layer comprises an electron transport layer; the second transport layer comprises a hole transport layer; the first electrode layer is a cathode layer comprising a metallic reflector for reflecting light emitted from the light-emitting layer; and the second electrode layer is an anode layer comprising a transparent material that is not metallic.

[0040] In yet another implementation form of the first aspect, the light-emitting structure is comprised in a display device.

[0041] In a second aspect of the disclosure, a sub-pixel structure includes: a plurality of sub-pixel stacks emitting different colors, each of the plurality of sub-pixel stacks including: a light-emitting layer between a first transport layer and a second transport layer; a first electrode layer coupled with the first transport layer; and a second electrode layer coupled with the second transport layer; a bank surrounding each of the plurality of sub-pixel stacks and forming an internal space above each of the plurality of sub-pixel stacks; a first filling material in the internal space and having a first refractive index; a second filling material on the first filling material and having a second refractive index lower than the first refractive index; and an interface between the first filling material and the second filling material, wherein the plurality of sub-pixel stacks have a uniform distance between the light-emitting layer and the first electrode layer; wherein at least one of the plurality of sub-pixel stacks is configured to emit a plurality of wavelengths with a central wavelength; wherein the distance between the light-emitting layer and the first electrode layer is predetermined such that the at least one of the plurality of sub-pixel stacks emits a main emission peak into the filling material along an on-axis direction perpendicular to a top surface of the at least one of the plurality of sub-pixel stacks; and wherein the main emission peak emitted from the at least one of the plurality of sub-pixel stacks through the interface has a least amount of light reflected on all pixels by total internal reflection.

[0042] In an implementation form of the second aspect, in the at least one of the plurality of sub-pixel stacks, a phase shift associated with emission from the light-emitting layer to the first electrode and back to the light-emitting layer is 2π.

[0043] In another implementation form of the second aspect, in at least another one of the plurality of sub-pixel stacks, a phase shift associated with emission from the light-emitting layer to the first electrode and back to the light-emitting layer is less than 2π or greater than 2π to cause a luminance variation in the main emission peak.

[0044] In yet another implementation form of the second aspect, emission in an off-axis direction away from the on-axis direction of the at least another one of the plurality of sub-pixel stacks is reflected by a tilted surface of the bank and emitted in the on-axis direction through the first filling material before being reflected at least once by total internal reflection via the interface.

[0045] In yet another implementation form of the second aspect, the emission in the off-axis direction reflected by the tilted surface is calibrated with the main emission peak to compensate for the luminance variation in the main emission peak.

[0046] In yet another implementation form of the second aspect, sizes of sub-pixels associated with the plurality of sub-pixel stacks are different to optimize color shift. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] When with Figure One The aspects of the example disclosure are best understood from the following detailed description when read together. Various features are not drawn to scale. The dimensions of various features may be arbitrarily increased or decreased for clarity of discussion.

[0048] Figure 1 is a schematic cross-sectional view of a prior art sub-pixel stack in a light emitting structure.

[0049] Figure 2 is a schematic cross-sectional view of another prior art sub-pixel stack in a light emitting structure.

[0050] Figure 3 is a schematic cross-sectional view of yet another prior art sub-pixel stack in a light emitting structure.

[0051] Figure 4A 、 Figure 4B and Figure 4C is a detailed schematic cross-sectional view of three example sub-pixel stacks of another example light emitting structure according to an example implementation of the present disclosure.

[0052] Figure 4D A portion of an example light emitting structure according to an example implementation of the present disclosure is shown.

[0053] Figure 4E As shown in Figure 4D Example angular distribution graph of the main emission peak measured in the example light emitting structure.

[0054] Figure 4F 、 Figure 4H and Figure 4J are schematic cross-sectional views of three example light emitting structures according to example implementations of the present disclosure.

[0055] Figure 4G 、 Figure 4I and Figure 4K They are Figure 4F 、 Figure 4H and Figure 4J Example angular distribution diagrams of three example light-emitting structures in .

[0056] Figure 5 is a schematic diagram illustrating an angular distribution of example light emitting structures according to an example implementation of the present disclosure.

[0057] Figure 6A is a schematic diagram illustrating extraction efficiency of example light emitting structures with various distances according to an example implementation of the present disclosure.

[0058] Figure 6B It shows Figure 6AGraphical representation of peak luminance of example light emitting structures with various distances.

[0059] Figure 7 is a graphical representation of peak luminance of example light emitting structures in relation to Lambertian emission. Figure 5 DETAILED DESCRIPTION

[0060] The following disclosure contains specific information relating to example implementations in the present disclosure. The drawings in the present disclosure and their accompanying detailed description are directed to example implementations only. The present disclosure is not, however, limited to these example implementations. Other variations and implementations of the present disclosure will occur to those of ordinary skill in the art.

[0061] Unless otherwise stated, similar or corresponding elements between the drawings can be indicated by similar or corresponding reference numbers. Furthermore, the drawings and illustrations in the present disclosure are generally not drawn to scale, and are not intended to correspond to actual relative dimensions.

[0062] For purposes of consistency and ease of understanding, similar features in the example drawings can be identified by the same number, although in some examples, they are not shown. Features in different implementations can differ in other respects as well, and therefore should not be narrowly construed by the illustrations shown.

[0063] The specification uses phrases such as “in one implementation” or “in some implementations,” each of which can refer to one or more of the same or different implementations. The term “comprising” means “including, but not necessarily limited to,” and specifically indicates open-ended including or membership in a composition, group, series, and the like. The expression “at least one of A, B, and C” or “at least one of the following: A, B, and C” means “only A, or only B, or only C, or any combination of A, B, and C.”

[0064] In addition, for purposes of explanation and non-limitation, specific details are set forth such as functional entities, techniques, protocols, standards, etc. in order to provide an understanding of the described technology. In other instances, detailed descriptions of well-known methods, techniques, systems, architectures, etc. are omitted so as not to obscure the description with unnecessary detail.

[0065] The present disclosure relates to a self-emissive display that includes quantum dot electroluminescent material in a light emitting diode (LED) arrangement. The LED arrangement generally includes a layer of quantum dot (QD) light emitting material (e.g., a light emitting layer) sandwiched between an electron transport layer (ETL) and a hole transport layer (HTL). The three layers are sandwiched between two conductive layers to form a sub-pixel stack. In one or more implementations of the present disclosure, a “top” emission (TE) structure is used. The TE structure involves light emission from a side of the TE structure opposite a glass substrate on which the TE structure is disposed.​

[0066] In one or more implementations of the present disclosure, the fabrication of a TE device involves a thick layer of conductive reflective material, typically made of a metal (e.g., silver or aluminum) deposited on a glass substrate, wherein the HTL is on the conductive reflective layer (e.g., a reflective conductor or reflective electrode), the light-emitting layer is on the HTL, the ETL is on the light-emitting layer, and the transparent electrode layer is on the ETL. In a preferred implementation, the thickness of the reflective electrode is greater than 80 nm (i.e., 1 nm = 10 -9 m). In another preferred embodiment, the reflective electrode includes a silver layer with a thickness of about 100 nm and an indium tin oxide (ITO) layer with a thickness of about 10 nm. In a preferred embodiment, the HTL is made of a PEDOT:PSS (sodium poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) layer with a thickness of about 40 nm, and a TFB (poly(9,9'-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)diphenylamine)) layer with a thickness of about 20 nm on the PEDOT:PSS layer. In other embodiments, other HTL materials may also be applicable to the present disclosure and are not limited to the examples provided herein. In another preferred embodiment, a light-emitting layer with a thickness of about 20 nm is disposed on the HTL and an ETL is disposed on the light-emitting layer. In another preferred embodiment, the ETL layer is made of zinc oxide (ZnO) nanoparticles and has a thickness of about 30 to 80 nm. In a preferred embodiment, the transparent electrode layer is a thin metal layer disposed on the ETL layer that is thick enough to carry sufficient current but thin enough to be transparent to light. In a preferred embodiment, the transparent electrode layer is an ITO layer having a thickness of approximately 80 nm. It should be noted that the thickness of the above layers can vary depending on the preferred optical configuration and is therefore not limited to the examples provided herein.

[0067] In one or more implementations of the present disclosure, the angular emission distribution from the light-emitting layer can be determined by the thickness (or distance) between the light-emitting layer and the reflective electrode layer (e.g., at the bottom of the sub-pixel stack). This distance directly depends on the thickness of the HTL and the refractive index of each layer in the HTL.

[0068] In one implementation where the reflective electrode is an ideal mirror, the reflective electrode layer is located a distance of half a wavelength (e.g., λ / 2) away from the light emitting layer. The distance away from the light emitting layer can be 0.5, 1, or any integer multiple of 0.5 times the wavelength. In example implementations where the reflective electrode is not an ideal mirror (e.g., in other words, there is a phase shift), the reflection point will not be accurately located at the surface of the reflective electrode. In one implementation, the reflective electrode is located, for example, a distance of about half a wavelength away from the light emitting layer in order to generate a main emission peak. However, in order to counteract the effect of the phase shift in the reflective electrode, for most common materials, the distance is adjusted to be about 0.2 times the wavelength. The term “emission” described in this disclosure can refer to a distribution of wavelengths of emission, but is not limited to a single wavelength. The term “wavelength” in this disclosure can be used to describe a peak or center wavelength in a plurality of wavelengths, but is not limited to the description provided herein.

[0069] The present disclosure is not limited to the examples provided, as the basic principles of the disclosed structures still apply if the arrangement of the ETL and HTL are reversed. In one preferred implementation of the present disclosure, the transport layer is thinner than the transport layer disposed closer to the glass substrate, regardless of whether the ETL or HTL is disposed further from the glass substrate on the emission side of the light emitting layer.

[0070] Example implementations of the present disclosure can be related to QLED structures. However, the present disclosure is not limited to QLED structures only and can be applicable to various implementations related to OLED structures.

[0071] In QLED sub-pixels, an internal space structure (e.g., a cavity structure) can be outlined by the sub-pixel stack and a bank structure surrounding the sub-pixel stack. A fill material with a higher refractive index can be disposed in the internal space structure above the sub-pixel stack. The bank structure can have a height that is at least the same or higher than the fill material with a high refractive index. In some implementations, the height of the bank structure can also be lower than the fill material. The fill material with a higher refractive index can extract more light from the light emitting layer compared to going directly into air, as the refractive index of the fill material is more closely matched to the light emitting layer and the Fresnel reflection loss is much lower. A low refractive index layer is disposed on the fill material. An upper layer disposed above the low refractive index layer can include an encapsulation glass or other material. The low refractive index layer traps off-axis light in the fill material by total internal reflection. In one or more implementations, the low refractive index layer can be an air gap, a siloxane-based nanocomposite polymer from Inkron with a refractive index as low as 1.15, poly(l,l,l,3,3,3-hexafluoroisopropyl acrylate) with a refractive index of 1.375, and poly(2,2,3,3,4,4,4-heptafluorobutyl acrylate) with a refractive index of 1.377.

[0072] In the present disclosure with internal spatial structure and a top transparent electrode, the thickness (or distance) between the light-emitting layer and the reflective electrode can be tuned in one color sub-pixel stack so that the main emission peak can be directly emitted from the light-emitting layer in an on-axis direction substantially perpendicular to the top surface of the sub-pixel stack with minimal total internal reflection (TIR). Light can also be emitted in off-axis directions away from the on-axis direction. Off-axis emission can be reflected at least once by the top surface (e.g., the interface) of the filling material via TIR and thus propagate in the filling material, reflecting off the light-emitting layer and the TIR surface before being reflected off the inclined surface of the bank and reflected towards the on-axis direction so that the on-axis emission can be used to calibrate all the internally reflected emission. The bank structure at each pixel end can be designed so that the bank angle (e.g., the bank angle) of the bank structure is half the average angle of the off-axis portion of the emission in the filling material that is subject to total internal reflection. In one or more implementations, the bank angle is between 0 and 80 degrees. In a preferred implementation, the bank angle is about 20 to 30 degrees. In yet another preferred implementation, the bank angle is about 30 degrees.

[0073] The effective angular distribution is determined by the interference between each individual dipole source in the light-emitting layer and its reflection in the bottom reflector. Since the thickness (or distance) between the bottom reflector and the light-emitting layer primarily determines this separation and the interference primarily depends on the wavelength of the source light emission (e.g., the sub-pixel stack), the design of each color sub-pixel stack (e.g., red, green, and blue, etc.) is different. As shown in Figures 1-3 different thicknesses for the HTL in different color sub-pixel stacks to ensure that the distance (thickness) between the light-emitting layer and the reflective electrode is tuned for each particular colored sub-pixel stack to achieve optimal on-axis brightness and efficiency. The thickness difference in the HTL requires a separate patterning step during manufacturing for different colored sub-pixel stacks, which can result in additional and expensive masking processes. In sub-pixel structures that apply different thicknesses for different colored sub-pixel stacks of the HTL, the example structure of the sub-pixel stack as shown in Figures 1-3 can achieve optimal peak on-axis brightness and efficiency, although expensive. Furthermore, in sub-pixel structures that apply different thicknesses for different colored sub-pixel stacks of the HTL, thin layers in the sub-pixel structure can result in lower absorption than thick layers if the material in the HTL absorbs light.

[0074] In one or more implementations of the application, if all of the HTLs of the sub-pixel stacks of different colors are fabricated to have substantially equal thicknesses (e.g., a substantially uniform thickness (or distance) between the light-emitting layer and the bottom reflector across all of the sub-pixel stacks of different colors), the manufacturing method of the display can be simplified and the cost can be significantly reduced. The optimized HTL thickness depends on the wavelength of the light emission. If the light-emitting structure has a transparent electrode on each of the red, green, and blue light-emitting sub-pixel stacks, and the red, green, and blue light-emitting sub-pixel stacks each include a very thin HTL with substantially equal thicknesses (uniform distance), the light-emitting structure with thin and substantially equal thicknesses (e.g., uniform distance) of the HTL can produce relatively similar emission characteristics to the light-emitting structure with different thicknesses (non-uniform distance) of the HTL when used with the bank and high-index filler and low-index layer described herein. This similar emission characteristic is achievable because the phase shift of the HTL propagation and the reflection phase shift back to the light-emitting layer is close to 2π (e.g., one wavelength of the center light-emitting color (e.g., green)), so the light emission pattern into the filler material is wide and has its peak on axis. Furthermore, the HTL thickness is nominally half of the wavelength, but, since the bottom reflector is a real material (e.g., a reflective metal), there is a phase shift associated with the real properties of the metal layer and depends on the metal used for the bottom reflector. Thus, the phase shift associated with the light emission from the light-emitting layer to the bottom reflector and back to the light-emitting layer is substantially 2π to achieve a substantially uniform thickness (or distance). The light-emitting structure with uniform distance (or thickness) can provide reduced brightness and efficiency compared to the configuration with different distances (e.g., thicknesses). However, when used with the appropriate pixel filler arrangement described above, the resulting angular distribution from the sub-pixel stack structure with substantially uniform distance is relatively insensitive to the distance between the bottom reflector and the light-emitting layer. Thus, in the light-emitting structure applying substantially the same thickness (e.g., uniform distance) of the HTL in the sub-pixel stacks emitting different wavelengths (e.g., red, green, blue emission), the red and blue emissions (e.g., if the center light emission is green) can still have similar angular distributions to the green emission, thus providing low color shift while reducing cost.

[0075] In particular, low color shift can be achieved because while most light exits directly from the fill material (e.g., the primary emission peak that is emitted on-axis), a small but significant amount of light is propagated by total internal reflection (TIR) in the fill material to the banks, and then collimated by the banks (e.g., light that is emitted off-axis). The effect of changing the wavelength is to reduce the brightness of the on-axis emission. However, the effect of the reduction in on-axis emission brightness is compensated by the increase in off-axis emission that is captured by TIR and propagated to the banks. Since both of these light propagations ultimately collimate the light, these two factors compensate for each other, and the final angular distribution of the various wavelengths (e.g., red, green, blue) is nearly unchanged. Thus, a light emitting structure can be obtained that has substantially the same layer thickness (e.g., substantially the same HTL thickness for all color sub-pixel stacks) and low off-axis color shift. Light emitting structures with similar thicknesses (e.g., substantially uniform distances) can provide reduced brightness and efficiency compared to constructions with different thicknesses (e.g., different distances), but the angular spread of the light is wider and the manufacturing is simpler, which can be suitable for large displays (e.g., TB-sized displays).

[0076] According to the present disclosure, on-axis brightness, as well as user-perceived brightness, is maximized even if the overall light output efficiency is not maximized. Since light emitted on-axis is typically perceived by a user in the central region of the pixel, while light emitted off-axis is typically perceived at the edges of the banks, the distribution of light from these different spectral regions can provide a more balanced color distribution at all angles, thereby minimizing color shift at various angles. Similar angular distributions need to be obtained for each of the red, green, and blue pixels to prevent perceived color from changing with viewing angle, and this is an inherent problem with such thin-layer self-emitting displays (e.g., OLEDs). The use of transparent electrodes and pixel banks can improve color shift performance. In such thin-layer and pixel bank structures, the high tolerance of angular distribution to wavelength can require further tuning to further improve color shift performance without adding additional masking steps. One such method is to set different sizes of pixels for red, green, and blue. The pixel size of a sub-pixel stack is the distance between the banks around the sub-pixel stack. For example, a larger pixel can require more TIR light reflection to reach the banks, and thus absorb more light from such light (but not on-axis non-TIR light), such that the balance is changed. In this case, the balance between on-axis light and off-axis light can be changed to better match the angular distribution. In general, the pixels can have different sizes to obtain the best results in most cases, but can not be necessary for the essence of the present disclosure. In the present disclosure, the pixel sizes of the sub-pixels are different, such that the color shift of each sub-pixel stack is optimized.

[0077] Another alternative is to have different QD EML layer thicknesses. Since the individual layers require different emitting QDs, the layer needs to be masked, so a masking step is required in any case. Only the layer can be changed, but there is a practical limit to how much difference can be achieved.

[0078] The example light emitting structure in this implementation can include a substrate, a sub-pixel stack, a bank, a first fill material, a second fill material, and a glass cover as described above, so details of the elements of the light emitting structure are omitted for brevity. In one or more implementations of the present disclosure, the first fill material can be a higher refractive index material, and the second fill material can be a lower refractive index material relative to the first fill material. The sub-pixel stack can be disposed on the substrate, and the bank surrounds the sub-pixel stack to form an internal space above the sub-pixel stack.

[0079] In one implementation of the present disclosure, the first fill material can be disposed in the internal space formed by the bank surrounding the sub-pixel stack. The second fill material can be continuously disposed over the first fill material and the bank.

[0080] In another implementation, the second fill material can be partially disposed on the first fill material. In one or more implementations, the thickness of the bank can be greater than the thickness of the first fill material. In one or more implementations, the bank is in contact with the substrate. In a preferred implementation, the bank can be in contact or nearly in contact with the second fill material. In one or more implementations, the glass cover can be continuously disposed over the second fill material.

[0081] In one or more implementations, light is emitted from the sub-pixel stack through the first fill material, the second fill material, and the glass cover. The first fill material can have a higher refractive index than air, such that the first fill material can extract light from the sub-pixel stack to a greater extent than air as a fill material. Light trapped in the sub-pixel stack can be quickly absorbed, while light trapped in the first fill material can propagate to the edge of the bank and be extracted by reflection.

[0082] In one or more implementations, the first fill material can have a higher refractive index than the sub-pixel stack and the second fill material. In one implementation, the second fill material (e.g., a lower refractive index layer) can be an air gap. In one or more implementations, the bank can be opaque. The surface of the bank facing the first fill material can be diffusely reflective or specularly reflective, and can be angled (e.g., tilted) relative to the plane of the substrate (e.g., a glass substrate).

[0083] In the present disclosure, the light emitting layer in a sub-pixel stack can emit light in a wavelength range having a center wavelength that is generally considered to be a primary emission peak. The center wavelength is the wavelength in a light emission spectrum of a light emitting source at which the spectral brightness is the highest. In the present disclosure, for wavelengths longer than the center wavelength emitted by the light emitting layer, off-axis emission can be produced that is stronger in intensity than on-axis emission. For wavelengths shorter than the center wavelength, on-axis emission is stronger in intensity than off-axis emission.

[0084] Figure 1 is a schematic cross-sectional view of a prior art sub-pixel stack in a light emitting structure. Figure 2 is a schematic cross-sectional view of another prior art sub-pixel stack in an example light emitting structure. Figure 3 is a schematic cross-sectional view of yet another prior art sub-pixel stack in an example light emitting structure. Referring to Figures 1-3 , the example sub-pixel stack structures 100, 200, and 300 can be sub-pixel stack structures that emit light having different wavelengths (e.g., red, green, blue).

[0085] In one or more implementations of the present disclosure, Figure 1 , Figure 2 and Figure 3 Each of the example sub-pixel stacks 100, 200, and 300 in

[0086] As shown in Figure 1 , the HTL 104d can include a TFB layer 104dl and a PEDOT:PSS layer 104d2. In another implementation, the HTL 104d can include other layers and is not limited to the example layers provided here. In another implementation, the previous arrangement of the HTL 104d and the ETL 104b can be reversed depending on the arrangement of the first electrode layer 104a and the second electrode layer 104e.

[0087] In one or more implementations of the present disclosure, the first electrode layer 104a can be a transparent top electrode and the second electrode layer 104e can be a bottom reflective electrode. The first electrode layer 104a can be a non-metal, substantially transparent, and a cathode layer disposed on the ETL layer 104b. The second electrode layer 104e can be disposed on the substrate 102 and can be an anode layer that is a metallic reflector that reflects light emitted from the light emitting layer 104c.

[0088] However, the arrangement of the first electrode layer 104a and the second electrode layer 104e is not limited to the examples provided herein and can be reversed. For example, the first electrode layer 104a can be a bottom anode layer that is a metallic reflector that reflects light emitted from the light emitting layer 104c and the second electrode layer 104e can be a non-metal and substantially transparent top cathode layer.

[0089] In one implementation with reference to Figures 1-3 the HTLs 104d, 204d, and 304d have different distances (e.g., HTL thicknesses t R , t G , t B ) for the three sub-pixel stacks 100, 200, and 300 that emit different colors (e.g., different wavelengths of red, green, blue), which can result in optimal brightness and low color shift. However, fabricating the sub-pixel stacks 100, 200, and 300 in a display can be complex and expensive because multiple masks and patterning steps are needed to form the HTLs 104d, 204d, and 304d with different thicknesses. Specifically, in the light emitting structure of the present application with different distances (e.g., different HTL thicknesses, e.g., 104d, 204d, 304d) for different sub-pixel stacks, high efficiency and on-axis brightness can be achieved. However, as shown in Figures 1-3 such an arrangement shows different thicknesses for each color (e.g., red, green, blue) sub-pixel stack to obtain the same emission characteristics for each sub-pixel stack and to match the angular distribution of the colors, thereby reducing excessive color shift of the light emitting structure. Because fabricating the HTLs in different color sub-pixel stacks (e.g., patterning and masking processes in the HTL layering in the sub-pixel stacks) is complex and expensive, especially for panels with large display areas, additional layer thickening processes are needed to properly achieve the same optical characteristics for all sub-pixel stacks that emit different colors. In one implementation, Figure 2 the example green sub-pixel stack 200 in FIG. 1 is set to a phase difference that can be closest to the 4p phase shift (associated with emission from the light emitting layer to the first electrode and back to the light emitting layer) or an optical mode N=2 sub-pixel stack, where the thickness between the first electrode and back to the light emitting layer is about one wavelength.

[0090] Figure 4A 、 Figure 4B and Figure 4C are detailed schematic cross-sectional views of three example sub-pixel stacks 400A, 400B, 400C of another example light emitting structure according to example implementations of the present disclosure.

[0091] In one or more implementations of the present disclosure, the three example sub-pixel stacks 400A, 400B, 400C can be sub-pixel stack structures that emit light of different wavelengths (e.g., red, green, blue) that include, for example, sub-pixel stack layers 404 of the example light emitting structure 400D in Figure 4D The example light emitting structure in the present implementation can include a substrate, sub-pixel stacks, banks, a first fill material, a second fill material, and a glass cover as described above, and can be similar to the elements described with reference to Figures 1-3 , and thus details of the light emitting structure are omitted for brevity.

[0092] Figures 4A-4C The three example sub-pixel stacks 400A, 400B, 400C in Figures 1-3 differ from the three example sub-pixel stacks 100, 200, 300 in Figure 1 , Figure 2 , Figure 3 the HTLs in the three example sub-pixel stacks 400A, 400B, 400C have substantially uniform distances (e.g., t R , t G , t B ) in contrast to the different distances (e.g., t R , t G , t B ) of the HTLs in the three example sub-pixel stacks 100, 200, 300 in Figure 4A , Figure 4B , Figure 4C . In contrast to the example light emitting structure with the three example sub-pixel stacks 100, 200, 300 in Figures 1-3 with different distances, the example light emitting structure with the three example sub-pixel stacks 400A, 400B, 400C in Figure 4A , Figure 4B , Figure 4C with substantially uniform thicknesses can still provide low color shift while significantly reducing manufacturing costs. By substantially uniform thickness, it is meant that the processing of the manufacturing layers is the same for each pixel, or all are done at the same time in the same way. There can be some manufacturing variations, but this is to be expected.

[0093] In one or more implementations, Figures 4A-4C The example sub-pixel stacks 400A to 400C in each include a first electrode layer 404a, an ETL 404b, a light-emitting layer 404c, an HTL 404d including a TFB layer 404d1 and a PEDOT:PSS layer 404d2, and a second electrode layer 404e. In one implementation, the first electrode layer 404a can be a transparent electrode, and the second electrode layer 404e can be a reflective electrode. However, the arrangement of the first electrode layer 404a and the second electrode layer 404e can be reversed depending on the direction of light emission, for example, the first electrode layer 404a can be a reflective electrode, and the second electrode layer 404e can be a transparent electrode. The arrangement of the first electrode layer 404a and the second electrode layer 404e can be different and is not limited to the examples provided herein. In one or more implementations, the three example structures 400A to 400C are sub-pixel stacks of three color pixels (for example, red, green, and blue pixels, respectively). It should be understood that implementations of the present disclosure are not limited to three colors, and four or more colors can be used. For example, four sub-pixel stacks for four individual color pixels (eg, red, green, yellow, blue, etc.) may be implemented. The thickness (or distance) between the light emitting layer 404c and the reflective electrode 404e or the thickness (eg, Figure 4A 、 Figure 4B 、 Figure 4C t in R , t G , t B ) can be tuned so that only the main on-axis emission peak on the structure is emitted. In one or more implementations, Figures 4A-4C The HTL 404d of the three example sub-pixel stacks 400A to 400C is shown in FIG. Figures 1-3 The HTLs 104d, 204d, 304d of the three example sub-pixel stacks 100 to 300 are different in that all HTLs 404d of the three example sub-pixel stacks 400A to 400C have substantially the same thickness (eg, t R , t G , t B ). In other words, the three example sub-pixel stacks 400A to 400C have substantially uniform distances between the corresponding light emitting layer 404c and the second electrode layer 404e. In one or more implementations, Figures 4A-4C For one of the HTL 404d of the three example subpixel stacks 400A to 400C in FIG. 4 , a preferred phase shift associated with light emission from the light emitting layer 404c (e.g., the first electrode layer) to the bottom reflector 404e (the second electrode layer 404e) and back to the light emitting layer 404c may be 2π. In one or more implementations, Figure 4BThe example green subpixel stack 400B in FIG. 4 is set to the closest possible phase offset of 2π associated with emission from the light emitting layer to the first electrode and back to the light emitting layer, or a subpixel stack with optical mode N=1. The optical mode N is the number of complete 2π phases from the light emitting layer to the first electrode and back to the light emitting layer. The red subpixel stack (e.g., Figure 4A 400A in) and the blue sub-pixel stack (e.g., Figure 4C 400C in the figure) may be detuned because the HTL thickness (e.g., t R and t for blue B ) may no longer match the phase requirement of the corresponding central emission color (e.g., a phase shift of 2π). For example, a red subpixel stack (e.g., Figure 4A 400A in) and the blue sub-pixel stack (e.g., Figure 4C 400C) in can have a phase offset greater than or less than 2π.

[0094] In one or more preferred implementations, the red sub-pixel stack (e.g., Figure 4B 400B in FIG) is set to a phase shift closest to 2π (the phase shift associated with emission from the light emitting layer to the first electrode and back to the light emitting layer) or a sub-pixel stack with optical mode N=1. The green sub-pixel stack (e.g., Figure 4A 400A in) and the blue sub-pixel stack (e.g., Figure 4C 400C in the green) may be "detuned" because the HTL thickness (t G and t for blue B ) may no longer match the phase requirement of the corresponding central emission color (e.g., a phase shift of 2π). For example, a green sub-pixel stack (e.g., Figure 4A 400A in) and the blue sub-pixel stack (e.g., Figure 4C 400C in the embodiment of the present invention) can have a phase offset greater than or less than 2π. In one or more implementations, the green subpixel stack or the red subpixel stack (e.g., as the subpixel stack) that is set to a phase offset closest to 2π (the phase offset associated with emission from the light-emitting layer to the first electrode and back to the light-emitting layer) Figure 4B 400B) provides a more preferred optical mode.

[0095] Figure 4D A portion of an example light emitting structure according to an example implementation of the present disclosure is shown. Figure 4E As shown in Figure 4D Example angular distribution graph of the main emission peak measured in the example light emitting structure. Figure 4F 、 Figure 4H and Figure 4Jare schematic cross-sectional views of three example light emitting structures according to example implementations of the present disclosure. Figure 4G , Figure 4I and Figure 4K are example angular distribution plots for three example light emitting structures in Figure 4F , Figure 4H and Figure 4J .

[0096] Figure 4A Example structure 400A in Figure 4B Example structure 400B in Figure 4C Example structure 400C in Figure 4D may each be included in example light emitting structure 400D in

[0097] In one or more implementations of the present application, light emitting structures including differently colored sub-pixel stacks with uniform distances (e.g., substantially the same thickness for all HTLs 404d) (e.g., sub-pixel stacks 400A-C in Figures 1-3 may have a thinner optical arrangement compared to light emitting structures having differently colored sub-pixel stacks with different thicknesses (e.g., sub-pixel stacks 100-300 in Figures 4A-4C In one implementation, example light emitting structures having color sub-pixel stacks 400A, 400B, and 400C can have substantially uniform thicknesses. For example, as shown in Figure 4B the distance or thickness of the HTL 404d between the second electrode layer 404e and the light emitting layer 404c for the green sub-pixel stack 400B (e.g., t G ) is configured such that the phase shift associated with the emission from the light emitting layer 404c to the second electrode layer 404e and back to the light emitting layer 404c is 2p (i.e., 2p round trip phase shift). It is noted that Figure 4A , Figure 4B and Figure 4C have different round trip phase shifts for the light emitting layer due to the different wavelengths. Thus, only one of the three sub-pixels can meet the optimal requirement.

[0098] In one example, the center wavelength of any of the red, green, or blue sub-pixel stacks can be used to determine the thickness in the sub-pixel stack. In other examples, the wavelength at the center of the entire wavelength range can be used to determine the thickness in the red, green, and blue sub-pixel stacks. The angular distribution from the green sub-pixel stack 400B can be approximately Lambertian (satisfying the pattern requirement of having optimal on-axis brightness) in the first and second fill materials (e.g., 410, 412). Most of the on-axis light from the green sub-pixel stack 400B can be the main emission peak (e.g., 410, 412) of the first and second fill materials (e.g., 410, 412) that passes directly through the light emitting structure 400D. Figure 4D Example structure 400D, Figure 4E Example angular distribution diagram 400E, Figure 4H Example structures 400H and Figure 4I The main emission peak 414 in the example angular distribution diagram 400I of FIG. 4 is shown. Light emitted in off-axis directions (e.g., off-axis emission 418 from the sub-pixel stack 404, as shown in FIG. 4B ). Figure 4D 、 Figure 4F 、 Figure 4J ) can be reflected by interface 420 onto bank 406 via TIR and collimated (eg, 416 ) as part of main emission peak 414 .

[0099] In one or more implementations, referring to Figure 4F 、 Figure 4G 、 Figure 4J and Figure 4K Different color emitting layers (e.g., in red subpixel stack 400F or blue subpixel stack 400J) other than the green emitting layer (e.g., of green subpixel stack 400H) may be detuned because the HTL thickness (e.g., t for red) R and t for blue B ) may no longer imply a 2π round trip phase shift and form a main transmit "double peak" 414 (e.g., Figure 4G The less obvious two peaks indicated by 414 in the (the on-axis brightness will be reduced and the side lobes will be more obvious, Figure 4G The bimodality in is usually not quite correct) and Figure 4K This detuning of the different color light-emitting layers reduces on-axis brightness but can increase the amount of off-axis emission that can be reflected via TIR (e.g., Figure 4F 、 Figure 4G 、 Figure 4J and Figure 4K 418 in ). This off-axis emission can propagate to the bank and recalibrate (e.g., Figure 4F and Figure 4J416 in) to compensate for the brightness loss from the on-axis emission 414, resulting in minimal change in the overall angular distribution. In one embodiment, the center wavelength of the green light emission is set to optimal emission so that the HTL thickness constitutes a 2π round-trip phase shift, while the angular characteristics of the red and blue light emissions are different from the green emission. In one or more preferred embodiments, the center wavelength of the red light emission is set to optimal emission so that the round-trip phase shift is 2π. To achieve minimal change in the overall angular distribution, the amount of off-axis light emission reflected by the interface through TIR is increased or decreased proportionally to the amount of on-axis light emission transmitted through the filler material. The embankment then recalibrates the off-axis light emission reflected through TIR, which compensates for the loss in the amount of on-axis light emission transmitted through the filler material. Therefore, in one or more embodiments in which all HTLs of the differently colored sub-pixel stacks have substantially the same thickness, the tolerance of the angular distribution for different wavelengths is increased compared to an embodiment in which all HTLs of the differently colored sub-pixel stacks have different HTL thicknesses. Therefore, a light-emitting structure with low color shift having the same HTL thickness can be achieved. The three sub-pixel stacks may require different pixel sizes in order to tune the ratio of TIR light (inversely proportional to pixel size) to on-axis light (independent of pixel size). In one or more implementations, the HTL thickness is equal, however, the equal thickness or uniform distance between the differently colored sub-pixel stacks is not limited to the example HTL thickness but can also apply to any layer within the HTL (e.g., TFB layer or PEDOT:PSS layer).

[0100] Compared to implementations where the HTL thickness is typically one wavelength, for example to give a phase shift of 4π or higher, the implementation of the present application where all HTLs of the differently colored sub-pixel stacks have substantially the same thickness may result in a wider angular distribution, which may significantly excite high-loss modes in the filler layer (particularly emission near the TIR angle). However, manufacturing HTLs with uniform thickness can eliminate multiple manufacturing steps, thereby simplifying and improving manufacturing yields, thereby reducing costs.

[0101] Figure 5 is a schematic diagram illustrating the angular distribution of an example light emitting structure according to an example implementation of the present disclosure. Graph 500 simulates the angular distribution of a red emitting sub-pixel stack, a green emitting sub-pixel stack, and a blue emitting sub-pixel stack measured in a fill material in an example light emitting structure applying an HTL having a substantially uniform distance (e.g., substantially equal HTL thickness). The example light emitting structure in this implementation may be similar to Figure 4D Example light emitting structure 400D, Figure 4F 400F, Figure 4H 400H and Figure 4J 400J in.

[0102] In this implementation, an example light emitting structure can include a substrate, a red emitting sub-pixel stack, a green emitting sub-pixel stack, and a blue emitting sub-pixel stack on the substrate, a first fill material on the sub-pixel stacks, a second fill material on the first fill material, an interface between the first fill material and the second fill material, a glass substrate on the second fill material, and a bank surrounding the sub-pixel stacks. Each of the three sub-pixel stacks can include a second electrode made of a silver back reflector and a 10 nm thick ITO layer on the silver reflector, an HTL including a 40 nm thick PEDOT:PSS layer on an ITO layer and a 20 nm thick TFB layer on the PEDOT:PSS layer, an emission layer on the HTL, an ETL on the emission layer, and a transparent first electrode on the ETL. In this implementation, a transparent ITO cathode can be used. In this implementation, the red emission layer can emit a red emission, the thickness and material of the red emission layer (assuming thin) and the ETL can be a 20 nm indium phosphide (InP) QD red emission layer and a 20 nm magnesium zinc oxide (MgZnO) ETL. In this implementation, referring to the schematic diagram 500 of Figure 5 , the phase shift associated with the emission from the emission layer to the bottom reflector and back to the emission layer in the red emitting sub-pixel stack (high density dashed line in Figure 5 ) is substantially 2p, while the phase difference for the green sub-pixel stack (solid line in Figure 5 ) has a smaller shift relative to the red emitting sub-pixel stack, and the blue sub-pixel stack (lower density dashed line in Figure 5 ) is significantly different from the red emitting sub-pixel stack, however, the angular distribution of the blue sub-pixel stack on either side of the total internal reflection line TIR is similar in the schematic diagram 500 of FIG. 500. Using this similar angular distribution, the light recalibrated by the bank can compensate for the difference in the angular distribution of the green sub-pixel stack and the blue sub-pixel stack relative to the red sub-pixel stack L C . On the left side of the TIR line, the emission L I transmits through the fill material. On the right side of the TIR line, the emission L TIR is reflected by the bank (through the TIR angle on the fill material). The emission close to the TIR angle can result in a large loss of luminance due to multiple emissions in the fill material, so the difference in the angular distribution is further reduced. In this implementation, the different color emitting sub-pixel stacks of the example light emitting structure have substantially uniform thickness, the TFB layer can be 20 nm thick and the phase shift can be 2p (N = 1), while in another implementation in which the sub-pixel stacks of different colors have non-uniform thickness, the TFB layer can be 150 to 190 nm thick and the phase shift of all the sub-pixel stacks can be 4p (N = 2).

[0103] Figure 6Ais a plot showing the extraction efficiency of example light emitting structures with various distances according to example implementations of the present disclosure. Figure 6B is a plot showing Figure 6A the peak brightness of example light emitting structures with various distances in Figure 6A The plot 600A in FIG. 6A simulates the results of the extraction efficiency of example light emitting structures with various distances (e.g., HTLs with different thicknesses (e.g., 32 nm, 65 nm, 120 nm, 150 nm, and 190 nm)) under different bank angles. The plot 600A simulates the extraction efficiency from the entire sub-pixel stack into air, where the fill material is assumed to be 2.5 pm thick, the bank height is equal, and the low-index layer (e.g., the first fill material) has a refractive index of 1.2. These simulations also assume a known limited spectral width of red for typical QD emission types (red emission is closest to the optical mode of N = 1 or a phase offset of 2p associated with emission from the light emitting layer to the first electrode and back to the light emitting layer). The extraction efficiency or angular distribution for the various HTL thicknesses of 32 nm, 65 nm, and 120 nm show little variation, as shown in Figure 6A . Figure 6B The plot 600B in FIG. 6B simulates the results of the peak brightness of example light emitting structures with various distances (e.g., HTLs with different thicknesses (e.g., 32 nm, 65 nm, 120 nm, 150 nm, and 190 nm)) in Figure 6A .

[0104] In one implementation where the light emitting structure can have an HTL thickness of 190 nm, the extraction efficiency (630A in FIG. 6A) and the peak brightness (630B in FIG. 6B) are the highest among the HTL thicknesses in the plot 600A in FIG. 6A and the plot 600B in FIG. 6B. Figure 6A . Figure 6B In one or more implementations where the light emitting structure can have an HTL thickness of 32 nm, 65 nm, or 120 nm, the extraction efficiency (circles 640A in FIG. 6A) and the peak brightness (circles 640B in FIG. 6B) in the plot 600A in FIG. 6A and the plot 600B in FIG. 6B are the highest among the HTL thicknesses. Figure 6B .

[0105] In one or more implementations where the light emitting structure can have an HTL thickness of 32 nm, 65 nm, or 120 nm, the extraction efficiency (circles 640A in FIG. 6A) and the peak brightness (circles 640B in FIG. 6B) in the plot 600A in FIG. 6A and the plot 600B in FIG. 6B are the highest among the HTL thicknesses. Figure 6A . Figure 6A In one or more implementations where the light emitting structure can have an HTL thickness of 32 nm, 65 nm, or 120 nm, the extraction efficiency (circles 640A in FIG. 6A) and the peak brightness (circles 640B in FIG. 6B) in the plot 600A in FIG. 6A and the plot 600B in FIG. 6B are the highest among the HTL thicknesses. Figure 6B . Figure 6BThe extraction efficiency (630A) and peak luminance (630B) for a 32 nm, 65 nm, or 120 nm HTL thickness is lower relative to a 190 nm HTL thickness (630B) in the circle 640B). In one or more implementations, although the efficiency and peak luminance can be lower for a 32 nm, 65 nm, or 120 nm HTL thickness compared to a 190 nm HTL thickness, the tolerance for a given wavelength range (e.g., red, green, or blue emission) for a constant HTL thickness (e.g., a thickness in the range of 32 nm to 120 nm) can be higher. Thus, one HTL thickness (e.g., in the range of 32 nm to 120 nm) or uniform distance can be used for all three different color emission (e.g., red, green, and blue) sub-pixel stacks to provide preferred on-axis luminance and reduced color shift with equal HTL thickness for all color sub-pixel stacks while reducing cost.

[0106] Figure 7 is a plot showing Figure 5 a schematic plot of the angular distribution of the example light emission structure in Figure 7 the plot 700 in shows the on-axis luminance (e.g., the luminance at 0 degrees) for the red, green, and blue emission sub-pixel stacks with uniform distance (e.g., substantially equal HTL thickness) compared to Lambertian emission (e.g., the dashed line in Figure 7 the plot 700 in Figure 5 a plot of the center luminance normalized angular distribution for the red, green, and blue emission sub-pixel stacks with uniform distance (e.g., substantially equal HTL thickness) for the example light emission structure in

[0107] As can be seen from the present disclosure, the concepts described in this disclosure can be implemented using a variety of techniques. While the concepts have been described with specificity in terms of the particular implementations, this is not intended to exhaust the scope of the concepts, which are expressly set forth with particular reference to the claims. Persons of ordinary skill in the art will recognize that changes can be made in form and detail without departing from the scope of the concepts.

[0108] Therefore, the described implementations are to be considered in all respects as illustrative and not restrictive. It should also be understood that the present disclosure is not limited to the particular implementations described herein but can be practiced with modification and alteration within the scope of the disclosure.

Claims

1. A light-emitting structure, comprising: substrate; a plurality of sub-pixel stacks emitting different colors on a surface of the substrate, each of the plurality of sub-pixel stacks comprising: a light-emitting layer between a first transmission layer and a second transmission layer, a first electrode layer coupled to the first transmission layer, and a second electrode layer coupled to the second transmission layer; a bank surrounding each of the plurality of sub-pixel stacks and forming an inner space above each of the plurality of sub-pixel stacks; a first filling material in the interior space and having a first refractive index; a second filler material on the first filler material and having a second refractive index lower than the first refractive index; and The interface between the first filling material and the second filling material, in: The plurality of sub-pixels are stacked at a uniform distance between the light emitting layer and the first electrode layer. At least one of the plurality of sub-pixel stacks emits a main emission peak into the first filling material and the second filling material along an on-axis direction perpendicular to a top surface of the at least one sub-pixel stack among the plurality of sub-pixel stacks, and The at least one subpixel stack of the plurality of subpixel stacks is constructed in an optical mode with N=1 such that a phase shift associated with emission from the light emitting layer of the at least one subpixel stack of the plurality of subpixel stacks to the first electrode of the at least one subpixel stack of the plurality of subpixel stacks and back to the light emitting layer of the at least one subpixel stack of the plurality of subpixel stacks is 2π, Emission in an off-axis direction away from the on-axis direction is reflected at least once by the interface via total internal reflection before being reflected by the inclined surface of the bank and emitted in the on-axis direction through the first filling material. The second filling material is at least one of an air gap, a siloxane-based nanocomposite polymer, poly (1,1,1,3,3,3-hexafluoroisopropyl acrylate) and poly (2,2,3,3,4,4,4-heptafluorobutyl acrylate), The bank is opaque.

2. The light emitting structure according to claim 1, wherein: At least one sub-pixel stack of the plurality of sub-pixel stacks is configured to emit light at a plurality of wavelengths having a center wavelength.

3. The light emitting structure according to claim 1, wherein: In at least one of the multiple subpixel stacks, a phase shift associated with emission from the light-emitting layer to the first electrode layer and back to the light-emitting layer is less than 2π or greater than 2π to cause a brightness change in the main emission peak.

4. The light emitting structure according to claim 3, wherein: Emission in the off-axis direction away from the on-axis direction of at least one sub-pixel stack in the multiple sub-pixel stacks is reflected at least once by total internal reflection by the interface before being reflected by the inclined surface of the embankment and emitted in the on-axis direction through the first filling material. The light emitting structure according to claim 4 , wherein: The main emission peak is used to calibrate the emission in the off-axis direction reflected by the inclined surface to compensate for the brightness variation in the main emission peak. The light emitting structure according to claim 1 , wherein: The second filling material covers the entire top surface of the first filling material.

7. The light emitting structure according to claim 1, wherein: The second filling material covers a portion of a top surface of the first filling material. The light emitting structure according to claim 1 , wherein: The sub-pixels associated with the plurality of sub-pixel stacks are sized differently to optimize color shifting.

9. The light emitting structure according to claim 1, wherein: The light-emitting layer includes quantum dot light-emitting material; The first transport layer includes a hole transport layer; The second transport layer includes an electron transport layer; The first electrode layer is an anode layer including a metal reflector for reflecting light emitted from the light emitting layer; and The second electrode layer is a cathode layer including a non-metallic transparent material.

10. The light emitting structure according to claim 1, wherein: The main emission peak emitted from the at least one sub-pixel stack through the interface has minimal light reflected across all pixels by total internal reflection. The light emitting structure according to claim 1 , wherein: In a specific region of at least one sub-pixel stack of the light emitting structure, the main emission peak is emitted through the interface along the on-axis direction.

12. The light emitting structure according to claim 1, wherein: The light-emitting layer includes quantum dot light-emitting material; The first transport layer includes an electron transport layer; The second transport layer comprises a hole transport layer; The first electrode layer is a cathode layer including a metal reflector for reflecting light emitted from the light emitting layer; and The second electrode layer is an anode layer including a non-metallic transparent material. 13 . A display device comprising the light emitting structure according to claim 1 .

14. A sub-pixel structure comprising: a plurality of sub-pixel stacks emitting different colors, each of the plurality of sub-pixel stacks comprising: a light-emitting layer between a first transmission layer and a second transmission layer, a first electrode layer coupled to the first transmission layer, and a second electrode layer coupled to the second transmission layer; a bank surrounding each of the plurality of sub-pixel stacks and forming an inner space above each of the plurality of sub-pixel stacks; a first filling material in the interior space and having a first refractive index; a second filler material on the first filler material and having a second refractive index lower than the first refractive index; and The interface between the first filling material and the second filling material, in: The plurality of sub-pixels are stacked at a uniform distance between the light emitting layer and the first electrode layer; at least one sub-pixel stack of the plurality of sub-pixel stacks is configured to emit light at a plurality of wavelengths having a center wavelength; The distance between the light-emitting layer and the first electrode layer is predetermined so that at least one of the plurality of sub-pixel stacks emits a main emission peak into the first filling material and the second filling material along an axial direction perpendicular to a top surface of the at least one sub-pixel stack among the plurality of sub-pixel stacks; and The main emission peak emitted from the at least one sub-pixel stack through the interface has the least amount of light reflected across all pixels by total internal reflection, Emission in the off-axis direction away from the on-axis direction of at least another sub-pixel stack of the plurality of sub-pixel stacks is reflected at least once by total internal reflection by the interface before being reflected by the inclined surface of the bank and emitted in the on-axis direction through the first filling material, The second filling material is at least one of an air gap, a siloxane-based nanocomposite polymer, poly (1,1,1,3,3,3-hexafluoroisopropyl acrylate) and poly (2,2,3,3,4,4,4-heptafluorobutyl acrylate), The bank is opaque.

15. The sub-pixel structure according to claim 14, wherein: In the at least one subpixel stack in the plurality of subpixel stacks, a phase shift associated with emission from the light emitting layer to the first electrode and back to the light emitting layer is 2π.

16. The sub-pixel structure according to claim 14, wherein: In at least another subpixel stack of the plurality of subpixel stacks, a phase shift associated with emission from the light-emitting layer to the first electrode and back to the light-emitting layer is less than 2π or greater than 2π to cause a brightness change in the main emission peak.

17. The sub-pixel structure according to claim 14, wherein: The main emission peak is used to calibrate the emission in the off-axis direction reflected by the inclined surface to compensate for brightness variations in the main emission peak.

18. The sub-pixel structure according to claim 14, wherein: The sub-pixels associated with the plurality of sub-pixel stacks are sized differently to optimize color shifting.

Images