A light emitting structure

Abstract

A light emitting structure includes a substrate, a sub-pixel stack on one surface of the substrate, and a dam including a first dam portion and a second dam portion. The sub-pixel stack has a light emitting stack including a light emitting layer between a first transport layer and a second transport layer, a first electrode layer coupled to the first transport layer, and a second electrode layer coupled to the second transport layer. The second dam portion is between the first dam portion and the sub-pixel stack, and the dam at least around the light emitting stack and the first electrode layer forms an internal space over the sub-pixel stack.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to layer and dam structures for emissive devices such as quantum dot light emitting diode (QLED) displays, organic light emitting diode (OLED) displays, and the like. In particular, the present invention relates to a top-emitting structure surrounded by a dam structure configured to redirect light that would normally be lost within the structure. BACKGROUND

[0002] Organic light emitting diodes (OLEDs) are one of the most common LEDs used in display devices. QLEDs are an improvement over OLEDs in that they have better spectral emission and more stable chemical properties. Quantum dots (QDs) or quantum dot light emitting materials are often used as phosphors for blue LEDs and as backlights for liquid crystal displays (LCDs).

[0003] In a layered light emitting display device, light emitting material (e.g., organic electroluminescent dyes for OLEDs and quantum dots for QLEDs) is sandwiched between a hole transport layer and an electron transport layer and electrodes. This structure works like a diode, and when current flows, electroluminescence in the light emitting material produces light, one electrode is made partially transmissive to allow light extraction. For OLEDs (and to a lesser extent QLEDs), the primary form of energy loss is when light cannot be extracted from the light emitting structure. A typical OLED extracts only about 20% of the light produced in air. Two key reasons for such a low percentage of light extraction are that the refractive indices of the layers in a layered light emitting display device are typically quite high (e.g., a large amount of loss due to total internal reflection), and the partially reflective electrode reflects most of the light, while the optical thickness of the layers between the electrodes is on the order of a wavelength, so interference is an important factor to control. Furthermore, this interference depends on wavelength and angle, and when viewed from different angles, produces a shift in color.

[0004] The design of a layered light emitting structure can be optimized, but there is often a trade-off between maximizing efficiency and optimizing the color gamut range, color shift. SUMMARY

[0005] The present invention relates to an emissive display, and in particular to quantum dot light emitting materials for QLEDs or organic electroluminescent dyes for OLEDs in LED arrangements.

[0006] According to a first aspect of the present application, a light emitting structure includes a substrate, a sub-pixel stack on a surface of the substrate, and a dam having a first dam portion and a second dam portion. The sub-pixel stack has a light emitting stack including a light emitting layer between a first transport layer and a second transport layer, a first electrode layer coupled to the first transport layer, and a second electrode layer coupled to the second transport layer. The second dam portion is between the first dam portion and the sub-pixel stack, and at least around the light emitting stack and the first electrode layer forms an internal space above the sub-pixel stack.

[0007] In one embodiment of the first aspect, the second dam portion separates the first dam portion from the light emitting stack such that a portion of light emission from the light emitting stack is diffused through the second dam portion and directed onto at least one surface of the first dam portion.

[0008] In another embodiment of the first aspect, the first dam portion is non-transparent and is at least one of a light scattering material and a light reflecting material, and the second dam portion is at least one of transparent and translucent.

[0009] In yet another embodiment of the first aspect, at least one surface of the first dam portion is at an angle to an axis substantially normal to a top surface of the emission stack.

[0010] In yet another embodiment of the first aspect, the diffused light emission is reflected by at least one surface of the first dam portion in a direction substantially normal to the axis of the top surface of the emission stack.

[0011] In another embodiment of the first aspect, a thickness of the dam is greater than a thickness of the light emitting stack.

[0012] In yet another embodiment of the first aspect, the first electrode layer extends through the second dam portion to the first dam portion, and the first dam portion encloses the first electrode layer and the light emitting stack.

[0013] In yet another embodiment of the first aspect, at least one layer of the light emitting stack other than the light emitting layer extends to cover at least a portion of the dam.

[0014] In another embodiment of the first aspect, at least one surface of the first dam portion includes a concave surface.

[0015] In another embodiment of the first aspect, the concave surface has a focal length that is a distance between the first dam portion and an edge of the light emitting stack.

[0016] In yet another embodiment of the first aspect, the light emitting structure further comprises at least one microlens covering the first dam portion, and the divergent light emission is reflected as divergent light by at least one surface of the first dam portion and refracted by the at least one microlens in an on-axis direction substantially perpendicular to the top surface of the light emitting stack.

[0017] In yet another embodiment of the first aspect, the at least one microlens has a focal length substantially equal to the sum of the distance between the light emitting stack and the first dam portion and the distance between the first dam portion and the at least one microlens.

[0018] In yet another embodiment of the first aspect, the second dam portion comprises a plurality of particles dispersed in the second dam portion, and the divergent light emission propagates to the plurality of particles of the second dam portion, wherein at least some of the divergent light emission is reflected in an off-axis direction at an angle to the on-axis direction substantially perpendicular to the top surface of the light emitting stack.

[0019] In yet another embodiment of the first aspect, the light emitting layer comprises at least one 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 substantially transparent material.

[0020] In yet another embodiment of the first aspect, the light emitting layer comprises at least one 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 having a metallic reflector for reflecting light emitted from the light emitting layer, and the second electrode layer is an anode layer having a substantially transparent material.

[0021] In yet another embodiment of the first aspect, the light emitting layer comprises at least one organic electroluminescent dye, 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 substantially transparent material.

[0022] In yet another embodiment of the first aspect, the light emitting layer comprises at least one organic electroluminescent dye, 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 having a metallic reflector for reflecting light emitted from the light emitting layer, and the second electrode layer is an anode layer having a substantially transparent material.

[0023] According to a second aspect of the present application, a light emitting structure includes a substrate, a sub-pixel stack emitting at least one of a plurality of colors on a surface of the substrate, and a dam including a first dam portion and a second dam portion. The sub-pixel stack has a light emitting stack including a light emitting layer between a first transport layer and a second transport layer, a first electrode layer coupled to the first transport layer, and a second electrode layer coupled to the second transport layer. The second dam portion is between the first dam portion and the sub-pixel stack, and the dam at least around the light emitting stack and the first electrode layer forms an internal space above the sub-pixel stack.

[0024] In an embodiment of the second aspect, the second dam portion separates the first dam portion from the light emitting stack such that a portion of light emission from the light emitting stack is diffused through the second dam portion and directed onto at least one surface of the first dam portion.

[0025] In another embodiment of the second aspect, the first dam portion is non-transparent and is at least one of a light scattering material and a light reflecting material, and the second dam portion is at least one of transparent and translucent. The at least one surface of the first dam portion is at an angle to an axis normal to a top surface of the light emitting stack. The diffused light emission is reflected by the at least one surface of the first dam portion in a direction substantially normal to the axis normal to the top surface of the light emitting stack.

[0026] In yet another embodiment of the second aspect, the light emitting structure further includes at least one of: the first electrode layer extending through the second dam portion to the first dam portion, wherein the first dam portion encloses the first electrode layer and the light emitting stack; at least one layer of the light emitting stack other than the light emitting layer extending to cover at least a portion of the dam; and the at least one surface of the first dam portion including a concave surface.

[0027] In another embodiment of the second aspect, the light emitting structure further includes at least one of: at least one microlens covering the first dam portion, wherein the diffused light emission is reflected by the at least one surface of the first dam portion as divergent light and refracted by the at least one microlens in a direction substantially normal to the axis normal to the top surface of the light emitting stack; and a plurality of particles diffused in the second dam portion, wherein the diffused light emission is propagated to the plurality of particles of the second dam portion and at least some of the diffused light emission is reflected in an off-axis direction at an angle to the normal direction.

[0028] In one or more embodiments of the present invention, the layer and dam structure are applicable to both QLED and OLED displays. However, the light-emitting layer for a QLED display may include quantum dot light-emitting materials, while the light-emitting layer for an OLED display may include organic electroluminescent dyes, and the transport layer for a QLED display may include materials different from those used in the transport layer for an OLED display.

[0029] The light-emitting structure of the present invention includes a double-dam structure having a first dam portion (e.g., an opaque and reflective portion) and a second dam portion (e.g., a transparent portion) between a first dam portion and a light-emitting stack. A significant portion of the light trapped within the light-emitting stack can diverge and propagate through the second dam portion of the double-dam structure to reach a large portion of the first dam portion, thereby improving light extraction. Furthermore, the light-emitting structure extends the first electrode layer to the second dam portion, such that more trapped light from within the light-emitting stack is reflected by the extended first electrode layer to at least one surface of the first dam portion and collimated. Therefore, light extraction efficiency can be further improved, converting to higher on-axis brightness at a given power in a fixed display (e.g., a television) or at a given brightness in a low-power display (e.g., a mobile display). Attached Figure Description

[0030] The various aspects disclosed in the examples can be best understood from the following detailed description when read in conjunction with the accompanying drawings. The features are not drawn to scale. The dimensions of the features may be increased or decreased at will for ease of discussion.

[0031] Figure 1A The subpixel stack of the background technique in the luminescent structure is shown.

[0032] Figure 1B Another background technique for subpixel stacks in a light-emitting structure is shown.

[0033] Figure 2A This is a schematic cross-sectional view of an exemplary light-emitting structure according to an exemplary embodiment of the present invention.

[0034] Figure 2B This is an exemplary embodiment of the present invention. Figure 2A A magnified view of the area within the dashed box.

[0035] Figure 3A This is a schematic cross-sectional view of an exemplary light-emitting structure according to an exemplary embodiment of the present invention.

[0036] Figure 3B This is an exemplary embodiment of the present invention. Figure 3A A magnified view of the area within the dashed box.

[0037] Figure 4A is a schematic cross-sectional view of an exemplary light emitting structure according to an exemplary embodiment of the present invention.

[0038] Figure 4B is a partial enlarged view of the area in dotted line frame in Figure 4A

[0039] Figure 5A is a schematic cross-sectional view of an exemplary light emitting structure according to an exemplary embodiment of the present invention.

[0040] Figure 5B is a partial enlarged view of the area in dotted line frame in Figure 5A

[0041] Figure 6A is a schematic cross-sectional view of an exemplary light emitting structure according to an exemplary embodiment of the present invention.

[0042] Figure 6B is a partial enlarged view of the area in dotted line frame in Figure 6A

[0043] Figure 7A is a schematic cross-sectional view of an exemplary light emitting structure according to an exemplary embodiment of the present invention.

[0044] Figure 7B is a partial enlarged view of the area in dotted line frame in Figure 7A DETAILED DESCRIPTION

[0045] The following disclosure contains specific information pertaining to exemplary embodiments in the present disclosure. The drawings and their accompanying detailed description in the present invention are directed to exemplary embodiments. However, the present invention is not limited to these exemplary embodiments. Other variations and embodiments of the present invention will occur to those skilled in the art.

[0046] Unless otherwise indicated, like or corresponding elements shown in the figures can be designated with like or corresponding reference numerals. Furthermore, the drawings and illustrations in the present invention are generally not drawn to scale, and are not intended to correspond to actual relative sizes.

[0047] For purposes of consistency and ease of understanding, like features can be identified by the same numbers in the example figures (although not shown in some examples). However, features in different embodiments can differ in other ways, and should not be narrowly limited to what is shown in the figures.

[0048] ​​​​The phrase "in one embodiment" or "in some embodiments" appearing in the description is used as a device of reference to refer to one or more embodiments of the same or different subject matter. The term "comprising" means "including, but not necessarily limited to," and specifically indicates open-ended including or membership in a group, collection, series, and equivalent. 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."

[0049] In addition, for the purpose of explanation and not limitation, specific details are set forth, such as functional entities, techniques, protocols, standards, and the like, to provide an understanding of the technology. In other examples, detailed descriptions of well-known methods, techniques, systems, architectures, and the like are omitted so as not to obscure the description with unnecessary detail.

[0050] The present invention relates to an emissive display involving quantum dot light emitting material for QLEDs or organic electroluminescent dyes for OLEDs of light emitting diode (LED) arrangements. Although one or more embodiments of the present invention are described with reference to displays having QLED pixels, the exemplary embodiments provided herein do not limit the scope of the present invention and can also be applied to other displays and structures, such as OLED structures. LED arrangements involving QLED pixels generally include a layer of quantum dot 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, forming a sub-pixel stack. In one or more embodiments of the present invention, a "top" emission (TE) structure is used. The TE structure involves light emission from one side of the TE structure, which is opposite to the glass substrate on which the TE structure is disposed.

[0051] In one or more embodiments of the present invention, the fabrication of a TE device involves a layer of conductive reflective material, typically made of a thick metal (e.g., silver or aluminum) layer deposited on a glass substrate having a HTL layer on the conductive reflective layer (e.g., reflective conductor or reflective electrode), a light emitting layer on the HTL layer, an ETL layer on the light emitting layer, and a transparent electrode layer on the ETL layer. In one preferred embodiment, the thickness of the bottom reflective electrode can be greater than 80 nm (i.e., 10 -9nm. In another preferred embodiment, the reflective electrode includes a silver layer having a thickness of about 100 nm and an ITO (indium tin oxide) layer having a thickness of about 10 nm. In a preferred embodiment, the HTL layer can be made of a PEDOT:PSS (poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) layer having a thickness of about 40 nm and a TFB (poly(9,9'-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)diphenylamine) layer having a thickness of about 35-45 nm on the PEDOT:PSS layer. In one embodiment, an ITO layer or an IZO (indium zinc oxide) layer can be located between the reflective electrode and the PEDOT:PSS layer and can have a thickness between 10-200 nm depending on the materials of the other layers and the emission wavelength. In another preferred embodiment, a light emitting layer having a thickness of about 20 nm can be disposed on the HTL layer and the ETL layer can be disposed on the light emitting layer. In another preferred embodiment, the ETL layer can be made of zinc oxide (ZnO) nanoparticles and can have a thickness of about 30-80 nm. The values of the thickness of each layer can vary slightly and can vary depending on the emission wavelength. In a preferred embodiment, the transparent electrode layer (e.g., the top electrode layer of a TE device) can be a thin metal layer having a thickness sufficient to carry sufficient current, but thin enough to be transparent to light and disposed on the ETL layer. In a preferred embodiment, the transparent top electrode layer is typically made of a thin metal layer, such as silver or a magnesium-silver alloy having a thickness of about 10-20 nm. In one embodiment, the transparent top electrode layer can be "non-metallic", e.g., an ITO layer. The "non-metallic" transparent electrode can have a thickness of 80-100 nm. In one or more embodiments, the ETL layer, the HTL layer, and the light emitting layer can be a light emitting stack.

[0052] The present application 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 layers are reversed. In a preferred embodiment of the present application, the transport layer is thinner than the transport layer disposed closer to the glass substrate regardless of whether the ETL layer or the HTL layer is disposed on the light emitting side of the light emitting layer away from the glass substrate.

[0053] QLED sub-pixel structures typically include an internal space structure (e.g., a cavity structure) that can be outlined by a sub-pixel stack of layers including a light-emitting layer and other layers, and a dam structure surrounding the sub-pixel stack. The internal space structure above the layers within the dam structure can optionally be a filler or encapsulation material that protects the light-emitting layer. Light emission from the light-emitting layer is generated by recombination of electron-hole pairs that emit light in the form of electric dipoles from the HTL and ETL layers. Axes associated with these emitted dipoles are random in direction. Since the refractive indices of the light-emitting layer, the HTL layer, and the ETL layer are typically in the range between 1.5 and 1.9, which is significantly higher than the refractive index of air, a substantial portion of the light emission from the light-emitting layer is "trapped" (understood as light confined within the structure by total internal reflection (TIR), in waveguide modes between the electrodes, or in surface plasmon formation), with only a small portion of the light emission in or near the layer normal direction being extracted into air. In sub-pixel structures where the layer thicknesses are substantially uniform, the trapped emission can propagate between the electrodes until eventually being absorbed by the electrodes.

[0054] In the background art, for QLED and OLED displays including a metallic top transparent electrode, light emission losses limit the most efficient displays to about 20% optical extraction. For QLEDs that can use a non-metallic top transparent electrode, higher optical extraction can be achieved. However, in such a mode, there is still expected to be 40-50% loss, especially if the refractive index of the transparent electrode is lower than the refractive indices of the other layers of the sub-pixel structure in the display.

[0055] The present invention aims to improve light extraction by exploiting a double dam structure to help extract trapped light emission propagating within the light-emitting layer. Furthermore, the extracted light emission can be collimated to improve light extraction efficiency, which can translate into higher on-axis luminance at a given power in a fixed display (e.g., a television) or a given brightness in a low power consumption display (e.g., a mobile display).

[0056] Exemplary embodiments of the present invention are related to QLED structures. However, the present invention is not limited to QLED structures only, but can be applied to various embodiments related to OLED structures.

[0057] Figure 1A A sub-pixel stack in a light-emitting structure showing background art is illustrated. Figure 1B Another sub-pixel stack in a light-emitting structure showing background art is illustrated.

[0058] In Figure 1AIn the prior art, the subpixel stack 100A of the light-emitting structure (not explicitly shown) can be a top-emitting (TE) light-emitting structure, which refers to light emission through the top electrode of the subpixel stack rather than the glass substrate (not explicitly shown). The subpixel stack 100A may include a light-emitting layer 104a, an HTL layer 104b, an ETL layer 104c, a first electrode layer 106, and a second electrode layer 108. For example, the light-emitting layer 104a, located between and cooperating with the HTL layer 104b and the ETL layer 104c, can be the light-emitting stack 104. The HTL layer 104b may include a PEDOT:PSS layer 104b1 and a TFB layer 104b2. The first electrode layer 106 can be disposed on the glass substrate. The light-emitting stack 104 can be disposed on the first electrode layer 106, and the second electrode layer 108 can be disposed on the light-emitting stack 104. The first electrode layer 106 can be a reflective bottom electrode layer, and the second electrode layer 108 can be a transparent top electrode layer.

[0059] exist Figure 1B In the process, the background light-emitting structure 100B may include a glass substrate 102 and a background sub-pixel stack on the glass substrate 102 (e.g., Figure 1A The sub-pixel stack includes a light-emitting stack 104, a first electrode layer 106, and a second electrode layer 108, as well as a dam 110. The sub-pixel stack may include a first electrode layer 106 located on a glass substrate 102, and a light-emitting layer, an HTL layer, and an ETL layer (not explicitly shown but similar) located on the first electrode layer 106. Figure 1A The subpixel stack 104 comprises a light-emitting layer 104a, an HTL layer 104b, and an ETL layer 104c, and a second electrode layer 108 located on the light-emitting stack 104. The dam 110 may have sloping sidewalls surrounding the first electrode layer 106 and the light-emitting stack 104 to form an internal space (not explicitly shown) above the subpixel stack. The second electrode layer 108 may extend to cover a portion of the dam 110. Figure 1B The luminescent stack 104 in the middle can functionally be connected with Figure 1A The light-emitting stack 104 in the subpixel stack 100A is substantially the same. The first electrode layer 106 may be a reflective bottom electrode layer, and the second electrode layer 108 may be a transparent top electrode layer. In some prior art light-emitting structures, filler or encapsulating materials may optionally be added to protect the subpixel stack. The dam 110 may be opaque, wherein the surface of the dam 110 may be light-scattering and / or specularly reflective. The dam 110 may be coated with a highly reflective material, and the second electrode layer 108 may extend to cover a portion of the light-emitting stack 104 to further extract light. The thickness of the dam 110 may be half a micrometer or greater.

[0060] Figure 2A This is a schematic cross-sectional view of an exemplary light-emitting structure according to an exemplary embodiment of the present invention. Figure 2B This is an exemplary embodiment of the present invention. Figure 2A A magnified view of the area within the dashed box.

[0061] exist Figure 2A In the example, the light-emitting structure 200A includes a substrate 202, a first electrode layer 206 on the substrate 202, a light-emitting stack 204 on the first electrode layer 206, and a second electrode layer 208 on the light-emitting stack 204. The light-emitting structure 200A may also include a dam 210 surrounding the first electrode layer 206 and the light-emitting stack 204 to form an internal space above the sub-pixel stack (first electrode layer 206, light-emitting stack 204, and second electrode layer 208). The second electrode layer 208 may extend onto a portion of the dam 210. In one embodiment of the invention, the second electrode layer 208 may extend to cover the entire dam 210. In one or more embodiments of the invention, as described herein, the light-emitting stack 204, the first electrode layer 206, and the second electrode layer 208 may be a sub-pixel stack on the substrate 202, and the light-emitting stack 204 may include a light-emitting layer located between an HTL layer and an ETL layer (not explicitly shown).

[0062] In one or more embodiments of the present invention, the dam 210 may include a first dam portion 211 and a second dam portion 212 (e.g., a double dam structure). The second dam portion 212 may be located between the first dam portion 211 and the light-emitting stack 204 to provide a separation distance between the first dam portion 211 and the light-emitting stack 204. In one or more embodiments of the present invention, the thickness of the dam 210 (e.g., along the z-direction, such as...) Figure 2A The thickness of the dam 210 (as shown) can be greater than that of the light-emitting stack 204. In one or more embodiments, the dam 210 may have a thickness of half a micrometer or more. In one embodiment, the thickness of the dam 210 may be 2-3 micrometers. In one or more embodiments, the first dam portion 211 may be opaque and may include at least one of a light-scattering material and a light-reflecting material, and the second dam portion 212 may be transparent, translucent, or a combination of both. In one embodiment, the light-scattering material or the light-reflecting material may be silver. In one or more embodiments, the refractive index of the second dam portion 212 may be relatively close to the refractive index of the light-emitting stack 204. In a preferred embodiment, the refractive index of the second dam portion 212 (e.g., about 1.5 or 1.6) may be slightly less than the refractive index of the light-emitting layer 204.

[0063] Figure 2B is an enlarged view of the area in dashed box in Figure 2A Figure 2B In Figure 2B In one or more embodiments, the second dam portion 212 can be located between the first dam portion 211 and the light emitting stack 204 to provide a separation distance between the first dam portion 211 and the light emitting stack 204. In one or more embodiments, the separation distance can be substantially equal to the height of the dam structure (e.g., dam 210), but is not limited to the examples given herein. The separation distance is such that a portion of the light emission 204a emitted from the light emitting stack 204 and trapped in the light emitting stack 204 by the first electrode layer 206 and the second electrode layer 208 propagates a few microns within the light emitting stack 204 and then diverges within the second dam portion 212. The diverging light 204a can then encounter the at least one surface 211a of the first dam portion 211 such that the diverging light 204a can be reflected by the at least one surface 211a of the first dam portion 211 in an on-axis direction substantially normal to the top surface of the light emitting stack 204. The light emitting structure 200A includes a double dam structure with a first dam portion 211 (e.g., an opaque and reflective portion) and a second dam portion 212 (e.g., a transparent portion) between the first dam portion 211 and the light emitting stack 204, a larger portion of the light trapped within the light emitting stack 204 can diverge and propagate through the second dam portion 212 to reach a larger portion of the first dam portion 211 and be reflected in an on-axis direction. As a result, light extraction can be improved and the extracted light can be further collimated to increase efficiency, resulting in a higher on-axis brightness for the display.

[0064] Figure 3A is a schematic cross-sectional view of an exemplary light emitting structure according to an exemplary embodiment of the present application. Figure 3B is an enlarged view of the area in dashed box in Figure 3A

[0065] In Figure 3A In one or more embodiments, the exemplary light emitting structure 300A can be substantially similar to the exemplary light emitting structure 200A in Figure 2A Figure 3A ​​​An exemplary light-emitting structure 300A may include a substrate 302, a first electrode layer 306 on the substrate 302, a light-emitting stack 304 on the first electrode layer 306, and a second electrode layer 308 on the light-emitting stack 304. The light-emitting structure 300A may also include a dam 310 surrounding the first electrode layer 306 and the light-emitting stack 304 to form an internal space above the sub-pixel stack (e.g., the first electrode layer 306, the light-emitting stack 304, and the second electrode layer 308). The second electrode layer 308 may extend onto a portion of the dam 310. In one embodiment of the invention, the second electrode layer 308 may extend to cover the entire dam 310. In one or more embodiments of the invention, the light-emitting stack 304, the first electrode layer 306, and the second electrode layer 308 may be a sub-pixel stack on the substrate 302, and the light-emitting stack 304 may include a light-emitting layer located between an HTL layer and an ETL layer (not explicitly shown), as described in the invention.

[0066] In one or more embodiments of the present invention, the dam 310 may include a first dam portion 311 and a second dam portion 312 (e.g., a double dam structure). The second dam portion 312 may be located between the first dam portion 311 and the light-emitting stack 304 to provide a separation distance between the first dam portion 311 and the light-emitting stack 304. In one or more embodiments of the present invention, the thickness of the dam 310 (e.g., along the z-direction, such as...) Figure 3A The thickness of the dam 310 (as shown) can be greater than that of the light-emitting stack 304. In one or more embodiments, the thickness of the dam 310 can be half a micrometer or greater. In one embodiment, the thickness of the dam 310 can be 2-3 micrometers. In one or more embodiments, the first dam portion 311 can be opaque and can include at least one of a light-scattering material and a light-reflecting material, and the second dam portion 312 can be transparent, translucent, or a combination thereof. In one embodiment, the light-scattering material or the light-reflecting material can be silver.

[0067] The present invention Figure 3A The exemplary light-emitting structure 300A in the example and Figure 2A The difference between the exemplary light-emitting structure 200A and the light-emitting structure 300A is that the light-emitting structure 300A may include a first electrode layer 306 extending into the second dam portion 312.

[0068] Figure 3B This is an exemplary embodiment of the present invention. Figure 3A A magnified view of the area within the dashed box. Figure 3BIn the example light emitting structure 300A, the first dam portion 311 can include at least one surface 311a that is at an angle to an axis substantially normal to the top surface of the light emitting stack 304. The second dam portion 312 can be located between the first dam portion 311 and the light emitting stack 304 to provide a separation distance between the first dam portion 311 and the light emitting stack 304. The separation distance is such that a portion of the light emission 304a emitted from the light emitting stack 304 and trapped in the light emitting stack 304 by the first electrode layer 306 and the second electrode layer 308 propagates a few microns within the light emitting stack 304. The first electrode layer 306 extending into the second dam portion 312 can reflect (or emit) more of the trapped light emission 304a within the light emitting stack 304 towards the at least one surface 311a. The reflected light emission 304a can further diverge within the second dam portion 312 and be directed onto the at least one surface 311a of the first dam portion 311 such that the diverging light 304a can be reflected by the at least one surface 311a of the first dam portion 311 in an on-axis direction substantially normal to the top surface of the light emitting stack 304. The light emitting structure 300A includes a double dam structure with a first dam portion 311 (e.g., an opaque and reflective portion) and a second dam portion 312 (e.g., a transparent portion) between the first dam portion 311 and the light emitting stack 304, a larger portion of the light trapped within the light emitting stack 304 can diverge and propagate through the second dam portion 312 of the double dam structure to reach a larger portion of the first dam portion 311 and be reflected in an on-axis direction. Moreover, the example light emitting structure 300A with the first electrode layer 306 extending to the second dam portion 312 is such that more of the trapped light from within the light emitting stack 304 is reflected by the extended first electrode layer 306 to the at least one surface 311a of the first dam portion 311 and collimated, as opposed to a light emitting structure without the extended first electrode layer 306. As a result, light extraction can be further improved and the extracted light can be further collimated to improve efficiency, resulting in a higher on-axis luminance for the display.

[0069] Figure 4A is a schematic cross-sectional view of an example light emitting structure according to an example embodiment of the present invention. Figure 4B is a schematic cross-sectional view of an example light emitting structure according to an example embodiment of the present invention. Figure 4A is a partial enlarged view of the dashed box area in

[0070] In Figure 4A , the example light emitting structure 400A can be substantially similar to the example light emitting structure 200A in Figure 2A . Figure 4AThe exemplary light emitting structure 400A in the present disclosure can include a substrate 402, a first electrode layer 406 on the substrate 402, a light emitting stack 404 on the first electrode layer 406, and a second electrode layer 408 on the light emitting stack 404. The light emitting structure 400A can also include a dam 410 surrounding the first electrode layer 406 and the light emitting stack 404 to form an internal space above the sub-pixel stack (e.g., the first electrode layer 406, the light emitting stack 404, and the second electrode layer 408). The second electrode layer 408 can extend onto a portion of the dam 410. In one embodiment of the present disclosure, the second electrode layer 408 can extend to cover the entire dam 410. In one or more embodiments of the present disclosure, the light emitting stack 404, the first electrode layer 406, and the second electrode layer 408 can be a sub-pixel stack on the substrate 402, and the light emitting stack 404 can include a light emitting layer between an HTL layer and an ETL layer (not explicitly shown) as described in the present disclosure.

[0071] In one or more embodiments of the present disclosure, the dam 410 can include a first dam portion 411 and a second dam portion 412 (e.g., a double dam structure). The second dam portion 412 can be located between the first dam portion 411 and the light emitting stack 404 to provide a separation distance between the first dam portion 411 and the light emitting stack 404. In one or more embodiments of the present disclosure, the thickness (e.g., along the z-direction, as shown) of the dam 410 can be greater than the thickness of the light emitting stack 404. In one or more embodiments, the thickness of the dam 410 can be half a micron or greater. In one embodiment, the thickness of the dam 410 can be 2-3 microns. In one or more embodiments, the first dam portion 411 can be opaque and can include at least one of a light scattering material and a light reflecting material, and the second dam portion 412 can be transparent, translucent, or a combination thereof. In one embodiment, the light scattering material or the light reflecting material can be silver. Figure 4A

[0072] The present disclosure Figure 4A The exemplary light emitting structure 400A in the present disclosure can include a substrate 402, a first electrode layer 406 on the substrate 402, a light emitting stack 404 on the first electrode layer 406, and a second electrode layer 408 on the light emitting stack 404. The light emitting structure 400A can also include a dam 410 surrounding the first electrode layer 406 and the light emitting stack 404 to form an internal space above the sub-pixel stack (e.g., the first electrode layer 406, the light emitting stack 404, and the second electrode layer 408). The second electrode layer 408 can extend onto a portion of the dam 410. In one embodiment of the present disclosure, the second electrode layer 408 can extend to cover the entire dam 410. In one or more embodiments of the present disclosure, the light emitting stack 404, the first electrode layer 406, and the second electrode layer 408 can be a sub-pixel stack on the substrate 402, and the light emitting stack 404 can include a light emitting layer between an HTL layer and an ETL layer (not explicitly shown) as described in the present disclosure. Figure 2A The exemplary light emitting structure 400A in the present disclosure can include a substrate 402, a first electrode layer 406 on the substrate 402, a light emitting stack 404 on the first electrode layer 406, and a second electrode layer 408 on the light emitting stack 404. The light emitting structure 400A can also include a dam 410 surrounding the first electrode layer 406 and the light emitting stack 404 to form an internal space above the sub-pixel stack (e.g., the first electrode layer 406, the light emitting stack 404, and the second electrode layer 408). The second electrode layer 408 can extend onto a portion of the dam 410. In one embodiment of the present disclosure, the second electrode layer 408 can extend to cover the entire dam 410. In one or more embodiments of the present disclosure, the light emitting stack 404, the first electrode layer 406, and the second electrode layer 408 can be a sub-pixel stack on the substrate 402, and the light emitting stack 404 can include a light emitting layer between an HTL layer and an ETL layer (not explicitly shown) as described in the present disclosure.

[0073] ​Figure 4B is an exemplary light emitting structure according to an exemplary embodiment of the present application. Figure 4A is a partial enlarged view of the area in a dashed line box in Figure 4B In the embodiment, the first dam portion 411 can include at least one surface 411a that is at an angle to an axis substantially normal to the top surface of the light emitting stack 404. The second dam portion 412 can be located between the first dam portion 411 and the light emitting stack 404 to provide a separation distance between the first dam portion 411 and the light emitting stack 404. The separation distance is such that a portion of the light emission 404a emitted from the light emitting stack 404 and trapped in the light emitting stack 404 by the first electrode layer 406 and the second electrode layer 408 propagates a few microns within the light emitting stack 404. The trapped light emission 404a can further diverge within the second dam portion 412 and be directed onto the at least one surface 411a of the first dam portion 411 such that the diverging light 404a can be reflected by the at least one surface 411a of the first dam portion 411 in an on-axis direction. The light emitting structure 400A includes a double dam structure with the first dam portion 411 (e.g., an opaque and reflective portion) and the second dam portion 412 (e.g., a transparent portion) between the first dam portion 411 and the light emitting stack 404, a larger portion of the light trapped within the light emitting stack 404 can diverge and propagate through the second dam portion 412 of the double dam structure to reach a larger portion of the first dam portion 411 and be reflected in the on-axis direction. In addition, the exemplary light emitting structure 400A can have any one of the multiple layers within the light emitting stack 404 in addition to the light emitting layer extending onto at least a portion of the dam 412. Thus, light extraction can be improved and the extracted light can be collimated to improve efficiency, resulting in higher on-axis luminance for the display. In addition, by allowing one or more layers of the light emitting structure 400A to be the same over some or all of the pixels, these layers can be deposited simultaneously. In such embodiments, the light emitting structure 400A, as well as other structures described below, can require fewer masking steps or inkjet processes, resulting in a simpler and less expensive manufacturing process.

[0074] Figure 5A is a schematic cross-sectional view of an exemplary light emitting structure according to an exemplary embodiment of the present application. Figure 5B is an exemplary light emitting structure according to an exemplary embodiment of the present application. Figure 5A is a partial enlarged view of the area in a dashed line box in

[0075] In Figure 5A In the embodiment, the exemplary light emitting structure 500A can be substantially similar to the exemplary light emitting structure 200A in Figure 2A . Figure 5AAn exemplary light-emitting structure 500A may include a substrate 502, a first electrode layer 506 on the substrate 502, a light-emitting stack 504 on the first electrode layer 506, and a second electrode layer 508 on the light-emitting stack 504. The light-emitting structure 500A may also include a dam 510 surrounding the first electrode layer 506 and the light-emitting stack 504 to form an internal space above the sub-pixel stack (e.g., the first electrode layer 506, the light-emitting stack 504, and the second electrode layer 508). The second electrode layer 508 may extend onto a portion of the dam 510. In one embodiment of the invention, the second electrode layer 508 may extend to cover the entire dam 510. In one or more embodiments of the invention, the light-emitting stack 504, the first electrode layer 506, and the second electrode layer 508 may be a sub-pixel stack on the substrate 502, and the light-emitting stack 504 may include a light-emitting layer between an HTL layer and an ETL layer (not explicitly shown) as described in this invention.

[0076] In one or more embodiments of the present invention, the dam 510 may include a first dam portion 511 and a second dam portion 512 (e.g., a double dam structure). The second dam portion 512 may be located between the first dam portion 511 and the light-emitting stack 504 to provide a separation distance between the first dam portion 511 and the light-emitting stack 504. In one or more embodiments of the present invention, the thickness of the dam 510 (e.g., along the z-direction, such as...) Figure 5A The thickness of the dam 510 (as shown) can be greater than that of the light-emitting stack 504. In one or more embodiments, the thickness of the dam 510 can be half a micrometer or greater. In one embodiment, the thickness of the dam 510 can be 2-3 micrometers. In one or more embodiments, the first dam portion 511 can be opaque and can include at least one of a light-scattering material and a light-reflecting material, and the second dam portion 512 can be transparent, translucent, or a combination thereof. In one embodiment, the light-scattering material or the light-reflecting material can be silver.

[0077] This invention Figure 5A The exemplary light-emitting structure 500A in the example and Figure 2A The difference of the exemplary light-emitting structure 200A is that the structure 500A may include a first dam portion 511, which has at least a concave surface facing the light-emitting stack 504.

[0078] Figure 5B This is an exemplary embodiment of the present invention. Figure 5A A magnified view of the middle frame area. Figure 5BIn some embodiments, the first dam portion 511 can include at least one surface 511a that is angled with respect to an axis that is substantially normal to the top surface of the light emitting stack 504. In one or more embodiments of the present application, the at least one surface 511a of the first dam portion 511 can be a concave surface facing the light emitting stack 504. In one embodiment, the concave surface can be a curved mirror. In one or more embodiments, the focal length 511b of the concave surface 511a is approximately equal to the distance between the first dam portion 511 (e.g., the concave surface 511a) and the edge of the light emitting stack 504. The second dam portion 512 can be positioned between the first dam portion 511 and the light emitting stack 504 to provide a separation distance between the first dam portion 511 and the light emitting stack 504. The separation distance is such that a portion of the light emission 504a emitted from the light emitting stack 504 and trapped in the light emitting stack 504 by the first electrode layer 506 and the second electrode layer 508 propagates within the light emitting stack 504 for a few microns. The trapped light emission 504a can further diverge within the second dam portion 512 and be directed onto the concave surface 511a of the first dam portion 511 such that the diverging light 504a can be reflected by the concave surface 511a of the first dam portion 511 in an on-axis direction that is substantially normal to the top surface of the light emitting stack 504. The light emitting structure 500A includes a double dam structure having a first dam portion 511 (e.g., an opaque and reflective portion) and a second dam portion 512 (e.g., a transparent portion) between the first dam portion 511 and the light emitting stack 504, a larger portion of the light trapped within the light emitting stack 504 can diverge and propagate through the second dam portion 512 of the double dam structure to reach a larger portion of the first dam portion 511 and be reflected in the on-axis direction. In addition, the concave surface 511a can allow more light to be collimated in the on-axis direction. As a result, light extraction can be further improved and the extracted light can be better collimated to improve efficiency, resulting in a higher on-axis luminance of the display compared to the light emitting structures of other examples in the present application.

[0079] Figure 6A is a schematic cross-sectional view of an exemplary light emitting structure according to an exemplary embodiment of the present application. Figure 6B is a schematic cross-sectional view of an exemplary light emitting structure according to an exemplary embodiment of the present application. Figure 6A is a partial enlarged view of the dashed box region in

[0080] In Figure 6A , the exemplary light emitting structure 600A can be substantially similar to the exemplary light emitting structure 400A in Figure 4A Figure 6A ​The exemplary light emitting structure 600A in the present disclosure can include a substrate 602, a first electrode layer 606 on the substrate 602, a light emitting stack 604 on the first electrode layer 606, and a second electrode layer 608 on the light emitting stack 604. The light emitting structure 600A can also include a dam 610 surrounding the first electrode layer 606 and the light emitting stack 604 to form an internal space above the sub-pixel stack (e.g., the first electrode layer 606, the light emitting stack 604, and the second electrode layer 608). The second electrode layer 608 can extend onto a portion of the dam 610. In one embodiment of the present disclosure, the second electrode layer 608 can extend to cover the entire dam 610. In one or more embodiments of the present disclosure, the light emitting stack 604, the first electrode layer 606, and the second electrode layer 608 can be a sub-pixel stack on the substrate 602, and the light emitting stack 604 can include a light emitting layer between an HTL layer and an ETL layer (not explicitly shown) as described in the present disclosure.

[0081] In one or more embodiments of the present disclosure, the dam 610 can include a first dam portion 611 and a second dam portion 612 (e.g., a double dam structure). The second dam portion 612 can be located between the first dam portion 611 and the light emitting stack 604 to provide a separation distance between the first dam portion 611 and the light emitting stack 604. In one or more embodiments of the present disclosure, the thickness (e.g., along the z-direction, as shown) of the dam 610 can be greater than the thickness of the light emitting stack 604. In one or more embodiments, the dam 610 can have a thickness of half a micron or more. In one embodiment, the thickness of the dam 610 can be 2-3 microns. In one or more embodiments, the first dam portion 611 can be opaque and can include at least one of a light scattering material and a light reflecting material, and the second dam portion 612 can be transparent, translucent, or a combination thereof. In one embodiment, the light scattering material or the light reflecting material can be silver. Figure 6A

[0082] The exemplary light emitting structure 600A in the present disclosure can include a substrate 602, a first electrode layer 606 on the substrate 602, a light emitting stack 604 on the first electrode layer 606, and a second electrode layer 608 on the light emitting stack 604. The light emitting structure 600A can also include a dam 610 surrounding the first electrode layer 606 and the light emitting stack 604 to form an internal space above the sub-pixel stack (e.g., the first electrode layer 606, the light emitting stack 604, and the second electrode layer 608). The second electrode layer 608 can extend onto a portion of the dam 610. In one embodiment of the present disclosure, the second electrode layer 608 can extend to cover the entire dam 610. In one or more embodiments of the present disclosure, the light emitting stack 604, the first electrode layer 606, and the second electrode layer 608 can be a sub-pixel stack on the substrate 602, and the light emitting stack 604 can include a light emitting layer between an HTL layer and an ETL layer (not explicitly shown) as described in the present disclosure. Figure 6A Figure 4A ​​The exemplary light-emitting structure 600A differs in that it may further include at least one microlens 614 on the first dam portion 611. The exemplary light-emitting structure 600A may also include a light-emitting stack 604 extending onto at least a portion of the dam 610. In a preferred embodiment, any layer of the plurality of layers (e.g., HTL layer, ETL layer, etc.) within the light-emitting stack 604, other than the light-emitting layer, may extend onto at least a portion of the dam 612. In one or more embodiments, any layer of the plurality of layers within the light-emitting stack 604, other than the light-emitting layer, may extend onto both the first dam portion 611 and the second dam portion 612.

[0083] Figure 6B This is an exemplary embodiment of the present invention. Figure 6A A magnified view of the area within the dashed box. Figure 6B In the first dam portion 611, at least one surface 611a may be included at an angle to an axis substantially perpendicular to the top surface of the light-emitting stack 604. A second dam portion 612 may be located between the first dam portion 611 and the light-emitting stack 604 to provide a separation distance between them. This separation distance allows a portion of the light emission 604a emitted from the light-emitting stack 604 and captured within it by the first electrode layer 606 and the second electrode layer 608 to propagate within the light-emitting stack 604 for several micrometers. The captured light emission 604a may diverge within the second dam portion 612 and be directed onto at least one surface 611a of the first dam portion 611. The diverging light 604a may be reflected as diverging light by at least one surface 611a of the first dam portion 611 and refracted by at least one microlens 614 in an axial direction substantially perpendicular to the top surface of the light-emitting stack 604. In one or more embodiments, the focal length of at least one microlens 614 may be substantially equal to the sum of the relative distance 611b between the light-emitting stack 604 and the first dam portion 611 and the relative distance 611c between the first dam portion 611 and at least one microlens 614. Regarding the focal length of the microlens 614, in one or more embodiments of the invention, the first dam portion 611 may have an angle of approximately 45° relative to the upper surface of the substrate 602, wherein the dam 610 may be disposed on the upper surface of the substrate 602, and the light emission distribution from the light-emitting stack 604 may be approximately directed towards the lower portion of the first dam portion 611. In another embodiment, the focal length of the microlens 614 may be slightly smaller than in other embodiments because the light emission distribution from the light-emitting stack 604 is directed towards the higher portion of the first dam portion 611, resulting in an angle of greater than 45° to direct the light emission towards the microlens 614.

[0084] The light emitting structure 600A includes a double dam structure with a first dam portion 611 (e.g., an opaque and reflective portion) and a second dam portion 612 (e.g., a transparent portion) between the first dam portion 611 and the light emitting stack 604, a larger portion of light trapped within the light emitting stack 604 can diverge and propagate through the second dam portion 612 of the double dam structure to reach a larger portion of the first dam portion 611 and reflect in the on-axis direction. Further, the example light emitting structure 600A can have any one of the multiple layers within the light emitting stack 604 in addition to the light emitting layer extending onto at least a portion of the dam 612. Further, the example light emitting structure 600A with at least one microlens 614 can allow more light to be collimated in the on-axis direction. In one or more embodiments of the present application, the at least one microlens 614 in the example light emitting structure 600A can be a replacement or addition to the concave surface 51 la of the first dam portion 511 in the example light emitting structure 500A to allow more light to be collimated in the on-axis direction. As a result, light extraction can be improved and the extracted light can be collimated to improve efficiency, resulting in higher on-axis luminance for the display. Figure 5A

[0085] Figure 7A is a schematic cross-sectional view of an example light emitting structure according to an example embodiment of the present application. Figure 7B is a partial enlarged view of the area in dashed lines in Figure 7A

[0086] In Figure 7A , the example light emitting structure 700A can be substantially similar to the example light emitting structure 400A in Figure 4A . Figure 7A The example light emitting structure 700A in can include a substrate 702, a first electrode layer 706 on the substrate 702, a light emitting stack 704 on the first electrode layer 706, and a second electrode layer 708 on the light emitting stack 704. The light emitting structure 700A can further include a dam 710 surrounding the first electrode layer 706 and the light emitting stack 704 to form an internal space above the sub-pixel stack (e.g., the first electrode layer 706, the light emitting stack 704, and the second electrode layer 708). The second electrode layer 708 can extend onto a portion of the dam 710. In one embodiment of the present application, the second electrode layer 708 can extend to cover the entire dam 710. In one or more embodiments of the present application, the light emitting stack 704, the first electrode layer 706, and the second electrode layer 708 can be a sub-pixel stack on the substrate 702, and the light emitting stack 704 can include a light emitting layer between an HTL layer and an ETL layer (not explicitly shown) as described in the present application.

[0087] ​​In one or more embodiments of the present application, the dam 710 can include a first dam portion 711 and a second dam portion 712 (e.g., a double dam structure). The second dam portion 712 can be located between the first dam portion 711 and the light emitting stack 704 to provide a separation distance between the first dam portion 711 and the light emitting stack 704. In one or more embodiments of the present application, a thickness (e.g., along the z-direction, as shown) of the dam 710 can be greater than a thickness of the light emitting stack 704. In one or more embodiments, the thickness of the dam 710 can be half a micron or greater. In one embodiment, the thickness of the dam 710 can be 2-3 microns. In one or more embodiments, the first dam portion 711 can be opaque and can include at least one of a light scattering material and a light reflecting material, and the second dam portion 712 can be transparent, translucent, or a combination of both. In one embodiment, the light scattering material or the light reflecting material can be silver. Figure 7A

[0088] An exemplary light emitting structure 700A in Figure 7A differs from the exemplary light emitting structure 400A in Figure 4A in that the exemplary light emitting structure 700A can include a second dam portion 712 having a plurality of particles 716 dispersed in the second dam portion 712. The exemplary light emitting structure 700A can still include a light emitting stack 704 extending onto at least a portion of the dam 710. In a preferred embodiment, any one of the plurality of layers (e.g., HTL layer, ETL layer, etc.) within the light emitting stack 704 other than the light emitting layer can extend onto at least a portion of the dam 712. In one or more embodiments, any one of the plurality of layers within the light emitting stack 704 other than the light emitting layer can extend onto the first dam portion 711 and the second dam portion 712.

[0089] Figure 7B is a partial enlarged view of the dashed box area in Figure 7A Figure 7B ​​In particular embodiments, the first dam portion 711 can include at least one surface 711a that is at an angle to an axis that is substantially normal to the top surface of the light emitting stack 704. The second dam portion 712 can be positioned between the first dam portion 711 and the light emitting stack 704 to provide a separation distance between the first dam portion 711 and the light emitting stack 704. The separation distance causes a portion of the light emission 704a emitted from the light emitting stack 704 and trapped in the light emitting stack 704 by the first electrode layer 706 and the second electrode layer 708 to propagate for a few microns within the light emitting stack 704. The trapped light emission 704a can further diverge within the second dam portion 712, propagate to the plurality of particles 716 of the second dam portion 712, and be reflected in an off-axis direction that is a direction that is at an angle to the on-axis direction that is substantially normal to the top surface of the light emitting stack 704. The plurality of particles 716 can provide improved light extraction from the light emitting stack 704.

[0090] The light emitting structure 700A includes a double dam structure with a first dam portion 711 (e.g., an opaque and reflective portion) and a second dam portion 712 (e.g., a transparent portion) between the first dam portion 711 and the light emitting stack 704, a larger portion of light trapped within the light emitting stack 704 can diverge and propagate through the second dam portion 712 of the double dam structure to reach a majority of the first dam portion 711 to improve light extraction. Further, the example light emitting structure 700A can have any of the multiple layers within the light emitting stack 704 in addition to the light emitting layer extending over at least a portion of the dam 712. Further, the example light emitting structure 700A with the plurality of particles 716 in the second dam portion 712 can allow for extraction of more trapped light. Thus, light extraction can be improved for displays.

[0091] As can be seen from the disclosure, the concepts described in the disclosure can be implemented using a variety of technologies without departing from the scope of the concepts. Although the concepts have been described with reference to certain implementations, those skilled in the art will recognize that changes can be made in form and detail without departing from the scope of the concepts. Accordingly, the described implementations are to be considered in all respects as illustrative and not restrictive. It should also be understood that the disclosure is not limited to the particular implementations described but can be practiced with modification and alteration within the scope and spirit of the disclosure.

Claims

1. A light emitting structure, characterized by comprises: a substrate and a sub-pixel stack on a surface of the substrate, the sub-pixel stack comprising: a light emitting stack comprising a light emitting layer between a first transport layer and a second transport layer; a first electrode layer coupled to the first transport layer; a second electrode layer coupled to the second transport layer; and a dam comprising a first dam portion and a second dam portion, the second dam portion is between the first dam portion and the sub-pixel stack, the dam, at least around the light emitting stack and the first electrode layer, forms an internal space above the sub-pixel stack, the second dam portion separates the first dam portion from the light emitting stack such that a portion of light emission from the light emitting stack is emitted through the second dam portion to be diverged and directed onto at least one surface of the first dam portion, the first dam portion is opaque and at least one of a light scattering material and a light reflecting material, the second dam portion is at least one of transparent and translucent, the at least one surface of the first dam portion is at an angle to an axis substantially normal to a top surface of the light emitting stack, the diverged light emission is reflected by the at least one surface of the first dam portion in a direction substantially normal to the axis, the at least one surface of the first dam portion comprises a concave surface.

2. The light emitting structure of claim 1, wherein, a thickness of the dam is greater than a thickness of the light emitting stack.

3. The light emitting structure of claim 1, wherein, at least one layer of the light emitting stack other than the light emitting layer extends to cover at least a portion of the dam.

4. The light emitting structure of claim 1, wherein, the concave surface has a focal length that is a distance between the first dam portion and an edge of the light emitting stack.

5. The light emitting structure of claim 1, further comprising: at least one microlens covering the first dam portion; characterized in that the diverged light emission is reflected by the at least one surface of the first dam portion as divergent light and refracted by the at least one microlens in a direction substantially normal to the axis.

6. The light emitting structure of claim 5, wherein, a focal length of the at least one microlens is substantially equal to a sum of a distance between the light emitting stack and the first dam portion and a distance between the first dam portion and the at least one microlens.

7. The light emitting structure of claim 1, wherein the light emitting layer comprises one of a quantum dot light emitting material and an organic electroluminescent dye; 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; the second electrode layer is a cathode layer comprising a substantially transparent material.

8. The light emitting structure of claim 1, wherein, the light emitting layer comprises one of a quantum dot light emitting material and an organic electroluminescent dye; 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 having a metallic reflector for reflecting light emitted from the light emitting layer; the second electrode layer is an anode layer having a substantially transparent material.

9. A light emitting structure, characterized by comprises: A substrate and a sub-pixel stack on a surface of the substrate, the sub-pixel stack comprising: a light emitting stack comprising a light emitting layer between a first transport layer and a second transport layer; a first electrode layer coupled to the first transport layer; a second electrode layer coupled to the second transport layer; and a dam comprising a first dam portion and a second dam portion, the second dam portion is between the first dam portion and the sub-pixel stack, the dam, at least around the light emitting stack and the first electrode layer, forms an internal space above the sub-pixel stack, the second dam portion separates the first dam portion from the light emitting stack such that a portion of light emission from the light emitting stack is diverged through the second dam portion and directed onto at least one surface of the first dam portion, the first dam portion is opaque and at least one of a light scattering material and a light reflecting material, the second dam portion is at least one of transparent and translucent, the at least one surface of the first dam portion is at an angle to an axis substantially normal to a top surface of the light emitting stack, the light emitting structure further comprises: at least one microlens covering the first dam portion; the diverged light emission is reflected as diverged light by the at least one surface of the first dam portion and refracted by the at least one microlens in an on-axis direction substantially normal to a top surface of the light emitting stack.

10. The light emitting structure of claim 9, wherein, the diverged light emission is reflected by the at least one surface of the first dam portion in an on-axis direction substantially normal to a top surface of the light emitting stack.

11. The light emitting structure of claim 10, wherein, a thickness of the dam is greater than a thickness of the light emitting stack.

12. The light emitting structure of claim 10, wherein, at least one layer of the light emitting stack other than the light emitting layer extends to cover at least a portion of the dam.

13. The light emitting structure of claim 9, wherein, a focal length of the at least one microlens is substantially equal to a sum of a distance between the light emitting stack and the first dam portion and a distance between the first dam portion and the at least one microlens.

14. The light emitting structure of claim 9, wherein, the light emitting layer comprises one of a quantum dot light emitting material and an organic electroluminescent dye; 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; the second electrode layer is a cathode layer comprising a substantially transparent material.

15. The light emitting structure of claim 9, wherein, the light emitting layer comprises one of a quantum dot light emitting material and an organic electroluminescent dye; 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 having a metallic reflector for reflecting light emitted from the light emitting layer; the second electrode layer is an anode layer having a substantially transparent material.

16. A light emitting structure, characterized by comprising: a substrate and a sub-pixel stack on a surface of the substrate, the sub-pixel stack comprising: a light emitting stack comprising a light emitting layer between a first transport layer and a second transport layer; a first electrode layer coupled to the first transport layer; a second electrode layer coupled to the second transport layer; and a dam comprising a first dam portion and a second dam portion, the second dam portion is between the first dam portion and the sub-pixel stack, the dam, at least around the light emitting stack and the first electrode layer, forms an internal space above the sub-pixel stack, the second dam portion separates the first dam portion from the light emitting stack such that a portion of light emission from the light emitting stack is diverged through the second dam portion and directed onto at least one surface of the first dam portion, the first dam portion is opaque and at least one of a light scattering material and a light reflecting material, the second dam portion is at least one of transparent and translucent, the at least one surface of the first dam portion is at an angle to an axis substantially normal to a top surface of the light emitting stack, the light emitting structure further comprises: at least one microlens covering the first dam portion; the diverged light emission is reflected as diverged light by the at least one surface of the first dam portion and refracted by the at least one microlens in an on-axis direction substantially normal to a top surface of the light emitting stack. The second dam portion is located between the first dam portion and the sub-pixel stack, at least surrounds the dam of the light emitting stack and the first electrode layer, forms an inner space above the sub-pixel stack, The second dam portion separates the first dam portion from the light emitting stack, so that a part of light emission from the light emitting stack is diverged through the second dam portion and is guided onto at least one surface of the first dam portion, The first dam portion is opaque and at least one of light scattering material and light reflecting material, the second dam portion is at least one of transparent and translucent, The second dam portion includes a plurality of particles dispersed in the second dam portion; and the diverged light emission propagates to the plurality of particles of the second dam portion, wherein at least some of the diverged light emission is reflected in an off-axis direction, the off-axis direction being at an angle to an on-axis direction substantially perpendicular to a top surface of the light emitting stack.

17. The light emitting structure of claim 16, wherein, The at least one surface of the first dam portion is at an angle to an axis substantially perpendicular to a top surface of the light emitting stack.

18. The light emitting structure of claim 17, wherein, The diverged light emission is reflected by the at least one surface of the first dam portion in an on-axis direction substantially perpendicular to a top surface of the light emitting stack.

19. The light emitting structure of claim 18, wherein, The thickness of the dam is greater than the thickness of the light emitting stack.

20. The light emitting structure of claim 18, wherein, At least one layer of the light emitting stack other than the light emitting layer extends to cover at least a portion of the dam.

21. The light emitting structure of claim 18, wherein, The at least one surface of the first dam portion includes a concave surface.

22. The light emitting structure of claim 21, wherein, The concave surface has a focal length, the focal length being a distance between the first dam portion and an edge of the light emitting stack.

23. The light emitting structure of claim 16, wherein, The light emitting layer includes one of quantum dot light emitting material and organic electroluminescent dye; 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; the second electrode layer is a cathode layer including substantially transparent material.

24. The light emitting structure of claim 16, wherein, The light emitting layer includes one of quantum dot light emitting material and organic electroluminescent dye; the first transport layer includes an electron transport layer; the second transport layer includes a hole transport layer; the first electrode layer is a cathode layer having a metal reflector for reflecting light emitted from the light emitting layer; the second electrode layer is an anode layer having substantially transparent material.

25. A light emitting structure, comprising: There is provided: a substrate; a sub-pixel stack on a surface of the substrate emitting at least one of a plurality of colors, the sub-pixel stack having: a light emitting stack including a light emitting layer between a first transport layer and a second transport layer; a first electrode layer coupled to the first transport layer; a second electrode layer coupled to the second transport layer; and a dam including a first dam portion and a second dam portion, The second dam portion is located between the first dam portion and the sub-pixel stack, at least surrounds the dam of the light emitting stack and the first electrode layer, forms an inner space above the sub-pixel stack, The second dam portion separates the first dam portion from the light emitting stack, so that a part of light emission from the light emitting stack is diverged through the second dam portion and is guided onto at least one surface of the first dam portion, The light emitting structure further comprises at least one of: at least one microlens covering the first dam portion, wherein the divergent light emission is reflected as divergent light by the at least one surface of the first dam portion and refracted by the at least one microlens in an on-axis direction substantially normal to a top surface of the light emitting stack; and a plurality of particles dispersed in the second dam portion, wherein the divergent light emission propagates to the plurality of particles of the second dam portion and at least some of the divergent light emission is reflected in an off-axis direction at an angle to the on-axis direction.

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