Quantum dot LED display device

Abstract

A quantum dot LED display device includes a substrate on which a plurality of levees are arranged. A plurality of red light-emitting LED sub-pixels, green light-emitting LED sub-pixels, and blue light-emitting LED sub-pixels are individually arranged between the levees. Each of the red light-emitting LED sub-pixels, the green light-emitting LED sub-pixels, and the blue light-emitting LED sub-pixels has a light-emitting layer, wherein each of the light-emitting layers includes quantum dots, an organic matrix, and a photoinitiator. A first concentration of the photoinitiator in the light-emitting layer of the blue light-emitting LED sub-pixel is lower than a second concentration of the photoinitiator in the light-emitting layer of the red light-emitting LED sub-pixel, and is lower than a third concentration of the photoinitiator in the light-emitting layer of the green light-emitting LED sub-pixel.

Description

Technical Field

[0001] The present invention relates to a light-emitting layer in a quantum dot LED, which emits blue light and can be spatially patterned by exposure to ultraviolet or near-ultraviolet light. The resulting quantum dot LED can be used as a blue sub-pixel in a display device. Background Art

[0002] Several ways of using red, green, and blue quantum dot LEDs as sub-pixels in a display device are known. For example, electroluminescent quantum dot LEDs can be patterned to form R, G, B sub-pixels in a wide color gamut display device. One method of generating a patterned light-emitting layer is to use inkjet printing. Quantum dot ink formulations can be used to form a light-emitting layer by depositing the ink into the desired location. The ink can be heated to remove the solvent, and then the ink is dried to leave a solid quantum dot layer.

[0003] Another method of spatial patterning of quantum dots is to use photolithography. A photosensitive mixture containing nanoscale fluorescent materials (such as quantum dots) is patterned by exposure to light to form a color conversion film. There are many other examples of such color conversion films that have additional features, such as light scattering particles or antioxidants that can be used in combination with LCD or OLED displays. The present invention also provides a method that details the steps of forming a color conversion film by photolithography using a positive or negative quantum dot photoresist.

[0004] Direct patterning of quantum dot LED light-emitting layers for electroluminescent devices by photolithography is less well known, but examples exist. Quantum dots can be used with crosslinkable ligands that are sensitive to ultraviolet light. Additionally, light-emitting layers for quantum dot LEDs can include quantum dots in a charge transport matrix that is crosslinked by exposure to ultraviolet light.

[0005] During the photolithography process, residual film may remain in the developed areas that were not directly exposed to UV light during the photolithography process. One way to reduce the residual film remaining is to change the composition of the liquid used to deposit the quantum dot photoresist. Another method is to use black light absorbing materials for the pixel definition layers (e.g., "banks") to reduce the impact of scattered UV light during the curing process. Summary of the invention

[0006] A quantum dot light-emitting diode (LED) display device includes a substrate on which a plurality of dams are provided. A plurality of red-emitting LED sub-pixels, green-emitting LED sub-pixels, and blue-emitting LED sub-pixels are separately provided between the dams. Each of the red-emitting LED sub-pixels, the green-emitting LED sub-pixels, and the blue-emitting LED sub-pixels has a light-emitting layer, and each of the light-emitting layers includes quantum dots, an organic matrix, and a photoinitiator. A first concentration of the photoinitiator in the light-emitting layer of the blue-emitting LED sub-pixels is lower than a second concentration of the photoinitiator in the light-emitting layer of the red-emitting LED sub-pixels and lower than a third concentration of the photoinitiator in the light-emitting layer of the green-emitting LED sub-pixels.

[0007] In the quantum dot LED display device, the absorption coefficient of the photoinitiator in the blue-emitting LED sub-pixels for blue light between 400 nm and 500 nm is lower than that of the photoinitiator in the red-emitting LED sub-pixels and the photoinitiator in the green-emitting LED sub-pixels. In addition, the absorption wavelength of the photoinitiator in the blue-emitting LED sub-pixels can be in the ultraviolet wavelength range of 0 nm to 400 nm.

[0008] The surface area of the quantum dots in the blue-emitting LED sub-pixels is the same as or larger than the surface area of the quantum dots in the green-emitting LED sub-pixels. The quantum dots in the blue-emitting LED sub-pixels include a core of Cd x Zn 1-x Se (0 ≤ x < 1) or ZnSe y Te 1-y (0 < y ≤ 1). The quantum dots in the blue-emitting LED sub-pixels include a shell of Cd x Zn 1-x Se y S 1-y (0 ≤ x ≤ 1; 0 ≤ y < 1). The organic matrix includes a crosslinked charge transport material.

[0009] The quantum dot LED display device includes one or more second electrodes formed as a continuous layer shared by all of the red-emitting LED sub-pixels, the green-emitting LED sub-pixels, and the blue-emitting LED sub-pixels. It also includes a plurality of first charge transport layers, with one or more of the first charge transport layers in each of the red-emitting LED sub-pixels, the green-emitting LED sub-pixels, and the blue-emitting LED sub-pixels. The one or more first charge transport layers in the red-emitting LED sub-pixels, the one or more first charge transport layers in the green-emitting LED sub-pixels, and the one or more first charge transport layers in the blue-emitting LED sub-pixels have different thicknesses.

[0010] The quantum dot LED display device includes one or more second charge transport layers disposed above the light emitting layer. The one or more second charge transport layers are shared by all of the red light emitting LED sub-pixels, the green light emitting LED sub-pixels, and the blue light emitting LED sub-pixels. The quantum dot LED display device further includes a reflector between the substrate and the plurality of first electrodes, wherein the one or more second electrodes are partially transparent, and the quantum dot LED display device emits light through the one or more second electrodes.

[0011] One or more of the second electrodes are shared by the red light-emitting LED sub-pixel, the green light-emitting LED sub-pixel, and the blue light-emitting LED sub-pixel. The quantum dot LED display device further comprises a plurality of partially transmissive first electrodes and one or more reflective second electrodes, wherein the quantum dot LED display device emits light through the substrate. In this embodiment, one or more of the reflective second electrodes are shared by the red light-emitting LED sub-pixel, the green light-emitting LED sub-pixel, and the blue light-emitting LED sub-pixel. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Combined with Figure 1 The exemplary disclosed aspects are best understood from the following detailed description when read in conjunction with the following detailed description. The various features are not drawn to scale, and the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0013] Figure 1 A cross-sectional view of a QLED device is shown.

[0014] Figure 2 A QLED light-emitting layer with quantum dots in an organic matrix formed by photolithography is shown.

[0015] Figure 3 A cross-sectional view showing a photolithography step for forming a light-emitting layer of a QLED.

[0016] Figure 4 Shown by Figure 3 A cross-sectional view of the light-emitting layer and other structures obtained by the photolithography process.

[0017] Figure 5 A cross-sectional view of a QLED display device with red, green and blue sub-pixels is shown.

[0018] Figure 6 The photoluminescent emission characteristics of quantum dots in an organic layer when illuminated with ultraviolet light according to an exemplary embodiment of the present disclosure are shown.

[0019] Figure 7A graph comparing photoinitiator absorption coefficients for wavelengths of blue, red, and green quantum dot photoluminescence is shown according to an exemplary embodiment of the present disclosure.

[0020] Figure 8 A cross-sectional view of a sub-pixel extending beyond the confines of a sub-pixel defining layer and into an adjacent sub-pixel is shown according to an exemplary embodiment of the present disclosure.

[0021] Fig. 9 A red light emitting layer photoresist having a photoinitiator according to an exemplary embodiment of the present disclosure is shown.

[0022] Fig.10 A green light emitting layer photoresist with a photoinitiator according to an exemplary embodiment of the present disclosure is shown.

[0023] Fig.11 A blue light emitting layer photoresist with reduced photoinitiator according to an exemplary embodiment of the present disclosure is shown.

[0024] Fig.12 A graph comparing a blue photoresist photoinitiator absorption spectrum to red and green photoresist photoinitiator absorption spectra is shown according to an exemplary embodiment of the present disclosure.

[0025] Fig.13 An alternative embodiment of a red light emitting layer photoresist according to an exemplary embodiment of the present disclosure is shown.

[0026] Fig.14 An alternative embodiment of a green light emitting layer photoresist according to an exemplary embodiment of the present disclosure is shown.

[0027] Fig.15 An alternative embodiment blue light emitting layer photoresist according to an exemplary embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0028] The following description contains specific information related to the embodiments in the present disclosure. The drawings and their illustrations in the present disclosure only relate to the embodiments. However, the present disclosure is not limited to these embodiments. Other variations and embodiments of the present disclosure will occur to those skilled in the art. Unless otherwise indicated, the same or corresponding elements in the drawings may be represented by the same or corresponding reference numerals. In addition, the drawings and descriptions in the present disclosure are generally not to scale and are not intended to correspond to actual relative sizes.

[0029] For the purpose of consistency and ease of understanding, similar features may be identified by reference numerals in the example figures (although not shown in some examples). However, features in different embodiments may differ in other aspects and therefore should not be limited to what is shown in the drawings.

[0030] This description uses the phrases "in one embodiment," or "in some embodiments," which phrases may each refer to one or more of the same or different embodiments. The term "coupled" is defined as connected, whether directly or indirectly through intervening components, and is not necessarily limited to physical connections. The term "comprising," when used, means "including, but not necessarily limited to," and refers specifically to unrestricted membership or membership in the combinations, groups, series, and equivalents so described.

[0031] In addition, for the purpose of explanation and non-limiting, specific details such as functional entities, technologies, protocols, standards, etc. are set forth to provide an understanding of the described technology. In other examples, detailed descriptions of well-known methods, technologies, systems, architectures, etc. are omitted so as not to obscure the description with unnecessary details.

[0032] The present disclosure relates to structures and materials for light-emitting layers of an electroluminescent quantum dot LED (e.g., also referred to as "QLED," "QD-LED," or "EL-QD") display comprising red, green, and blue sub-pixels (hereinafter "QLED"). As part of a photolithography process, these light-emitting layers are patterned by exposure to light of a specific wavelength.

[0033] The light-emitting layer discussed herein can be used as a light-emitting layer of a typical QLED structure, which is described as: a first electrode disposed on a substrate, a second electrode disposed opposite to the first electrode, and a light-emitting layer comprising quantum dots disposed between the first electrode and the second electrode. A bias applied to these electrodes causes first charge carriers (e.g., holes) to be injected into the light-emitting layer from the first electrode, and causes opposite charge carriers (e.g., electrons) to be injected into the light-emitting layer from the second electrode. These charge carriers recombine in the quantum dots of the light-emitting layer, causing light to be emitted from the QLED. Additional layers such as charge injection layers, charge transport layers, or charge blocking layers may be arranged between the light-emitting layer and the electrodes.

[0034] A QLED display can include multiple QLEDs having light-emitting layers configured to emit one of red, green, or blue light under an applied bias, arranged on a common substrate and separated by inert pixel-defining layers ("banks"). In this case, each QLED is a sub-pixel of the display. One or more layers of the QLEDs can be shared by all QLEDs of the display, while other layers can be patterned so that they are dedicated to individual QLEDs. For example, a first electrode can be patterned and a second electrode shared, and each sub-pixel can emit a different amount of light by individually controlling the voltage applied to the first electrode of each sub-pixel and maintaining the second electrode at a fixed potential.

[0035] A patterning process is required to configure the light-emitting layer to emit light of different wavelengths depending on its position. For example, inkjet printing or photolithography can be used. Inkjet printing advantageously deposits material only in the sub-pixels where it is needed, thereby reducing the total amount of material used. However, the resolution of inkjet printing is limited by the size of the droplets that can be produced during the printing process. Therefore, for high-resolution displays, photolithography processes are preferred.

[0036] In the photolithography process, a photoresist is deposited on the area of ​​interest. It is then patterned by exposure to light (e.g., UV light) through a mask containing one or more apertures. In response to the application of light, a chemical reaction occurs in the photoresist. The molecules that initiate this reaction are called photoinitiators. In a "positive" process, the photoresist that has been exposed becomes soluble in the developer, while the unexposed photoresist is insoluble in the developer. Conversely, in a "negative" process, the photoresist that has been exposed becomes insoluble in the developer, while the unexposed photoresist is soluble in the developer. As part of the photolithography process, there may be multiple other steps, such as pre-exposure annealing and post-exposure annealing.

[0037] For a QLED display, a photoresist containing quantum dots that emit red light under electrical excitation is deposited on the active area of ​​the display and patterned so that, after development, the red light-emitting layer does not exist in the green or blue sub-pixels. The process is repeated with a second photoresist containing green quantum dots, and the second photoresist is patterned so that the green light-emitting layer does not exist in the red or blue sub-pixels. The process is repeated again with a third photoresist containing blue quantum dots, and it is patterned so that the blue light-emitting layer does not exist in the red or green sub-pixels. The order of the patterning steps can be changed, and it should be understood that the red, green, and blue patterning steps do not have to follow the order presented here.

[0038] A desired property in a display is high color purity capable of achieving a wide color gamut. This corresponds to light emitted from a single sub-pixel having a narrow spectrum, and the spectrum emitted from each sub-pixel of the same color is uniform in profile. QLEDs are known to be able to emit light with a narrow emission spectrum. However, in display devices manufactured using photolithography, it is important to remove all soluble quantum dot materials during the development process. Any remaining quantum dots may emit light of undesired wavelengths and reduce the color purity of the display. For example, red quantum dots may remain in the green sub-pixel, resulting in unwanted green and red light being emitted from the green sub-pixel during operation.

[0039] Specifically, during the patterning process of the light-emitting layer containing blue quantum dots, undesirable photoresist may still remain. Typically, the light used in the photolithography process is ultraviolet light, to which photoinitiators are sensitive and effectively initiate chemical reactions. The sensitivity of photoinitiators generally decreases with increasing wavelength, but many photoinitiators still show sensitivity to blue light. During the exposure process, ultraviolet light incident on the photoresist will be absorbed by the blue quantum dots instead of being absorbed by the photoinitiator, and then re-emit blue light through photoluminescence. This blue light can be re-emitted in any direction, so a large amount of this light will propagate in the plane of the light-emitting layer (for example, perpendicular to the direction of UV irradiation) and be captured by total internal reflection. The absorption coefficient of both the photoinitiator and the quantum dots for blue light will be lower than the absorption coefficient of ultraviolet light, so this blue light may propagate a considerable distance from where it is generated before being absorbed, for example, in a neighboring sub-pixel. If the blue light is reabsorbed by the photoinitiator, a chemical reaction may be initiated in an unexpected and undesirable area, resulting in the presence of blue quantum dots in the red or green sub-pixel.

[0040] Photoluminescence of red and green quantum dots will occur during the photolithography process, but the impact on the patterning process will be significantly reduced due to the lower absorption of longer wavelength light by the photoinitiator. In addition, the lower energy of longer wavelength light may not be sufficient to initiate chemical reactions.

[0041] In one embodiment of the present disclosure, the concentration of photoinitiator in the photoresist containing blue quantum dots is lower than the concentration of photoinitiator in red and green photoresists. This advantageously reduces the sensitivity to blue light re-emitted from quantum dots in the non-directly exposed portion of the photoresist.

[0042] In another embodiment of the present disclosure, a photoinitiator is used that has a decreased sensitivity to visible wavelengths. The decreased sensitivity may be due to the photoinitiator having a lower absorption coefficient in the blue portion of the spectrum. The decreased sensitivity may be due to a reduction in the amount of blue light that helps initiate the chemical reaction. For example, the absorbed blue light may be re-emitted as light with a longer wavelength or lost as heat. The decreased sensitivity of the photoinitiator advantageously reduces the sensitivity to blue light re-emitted from quantum dots in portions of the photoresist that are not directly exposed.

[0043] Lowering the absorption coefficient of the photoinitiator for blue light can also lower the absorption coefficient of the photoinitiator for ultraviolet light. This can be compensated by lowering the wavelength of light used during the exposure step of the photolithography process (e.g., using shorter wavelength ultraviolet light). This effectively reduces the processing time, which is desirable to increase throughput in the manufacturing process.

[0044] In another embodiment of the present disclosure, the photoresist of the blue sub-pixel contains large quantum dots. The emission wavelength of the quantum dots is defined by the material and size of the quantum dot core. Therefore, the thickness of the shell can be increased without affecting the wavelength of light emitted from the quantum dots and therefore from the QLED display device. For a given concentration (mass concentration) of quantum dots in the photoresist, the relative surface area of ​​the quantum dots is larger when the volume of the quantum dots is smaller. The surface of the quantum dots is covered with organic ligands to passivate the surface and reduce non-radiative recombination, which improves the efficiency of the QLED and, therefore, the efficiency of the display device. These ligands may interfere with the chemical reactions of the photolithography process. Therefore, by increasing the surface area of ​​the quantum dots, and thereby increasing the number of ligands, crosslinking can be advantageously prevented in the photoresist in areas that are not directly exposed during the photolithography process.

[0045] These embodiments can be used alone or in combination to realize a QLED display manufactured using a photolithographic process with high color purity and low blue light emission from the red and green sub-pixels.

[0046] Reference Figure 1 , a quantum dot LED (QLED) 100 is shown. A reflector 102 is disposed on a substrate 101. In one embodiment, the reflector 102 has a reflectivity greater than 80% at the wavelength of light emitted by the QLED 100. In another implementation, the reflector 102 has a reflectivity greater than 90% at the wavelength of the QLED 100. 100nm aluminum and 100nm silver are examples of suitable materials and thicknesses for the reflector 102. An anode 103 is disposed on the reflector 102. In one embodiment, 10nm indium tin oxide (ITO) may be used as the anode 103. Alternatively, a metal reflector 102 may be used as the anode 103.

[0047] A hole injection layer 104 is provided on the anode 103. 40 nm PEDOT:PSS is an example of a suitable hole injection layer 104 material. A hole transport layer 105 and a light emitting layer 106 are provided on the hole injection layer 104 by solution processing using a photoresist (not shown). The photoresist includes a hole transport material, quantum dots 107 ( Figure 2 ) and a solution mixture of a photoinitiator and a solvent. The solution is deposited onto the hole injection layer 104 (e.g., by spin coating), heated on a hot plate, exposed to ultraviolet light, and heated again to form these layers. During the spin coating process, the quantum dots 107 separate from the hole transport material, resulting in a hole transport layer 105 below and a light emitting layer 106 above.

[0048] Reference Figure 2 , showing in detail the light emitting layer 106. The light emitting layer 106 comprises quantum dots 107 in a matrix of a hole transport material 108 and an amount of a photoinitiator 109. Suitable materials include: OTPD for the hole transport material 108, core-shell InP, CdSe and ZnSe quantum dots 107, and OPPI for the photoinitiator 109 in a photoresist.

[0049] Refer again Figure 1 , an electron transport layer 110 is disposed on the light emitting layer 106. 60nm zinc oxide nanoparticles are an example of a suitable electron transport layer 110. A partially transparent cathode 111 is disposed on the electron transport layer 110. In one embodiment, the cathode 111 has a transmittance greater than 20%. In another embodiment, the cathode 111 has a transmittance greater than 40%. 15nm silver and 15nm Mg 0.1 Ag 0.9 are examples of materials and thicknesses suitable for cathode 111 .

[0050] The hole injection layer 104 and the electron transport layer 110 may be deposited from solution, such as by spin coating, slot coating or inkjet printing.The reflector 102, anode 103 and cathode 111 may be deposited by techniques such as sputter coating or thermal evaporation.

[0051] When an electrical bias is applied between the anode 103 and the cathode 111, light is emitted from the quantum dots 107 ( Figure 2 ) emission. Light emitted toward cathode 111 may be transmitted through partially transparent cathode 111 and observed by an external observer. Light emitted toward anode 103 may be reflected by reflector 102 and directed toward cathode 111.

[0052] The above example produces a top emitting QLED 100 having a conventional layer structure. It should be appreciated that the reflector 102 is removed and the cathode 111 is made reflective to make a bottom emitting QLED (not shown). It should be appreciated that the layer structure can be reversed, with the cathode 111 closest to the reflector 102 and emitting light through the anode 103, making an inverted QLED (not shown). The devices described herein are equally applicable to any of these QLED architectures.

[0053] refer to Figure 3 , 4 5, certain manufacturing steps of a QLED display device 200 are shown. A hole injection layer 104 is deposited on an anode layer 103, which is deposited on a reflective layer 102, all separated by a bank 202. These layers have been deposited on a backplane substrate 201 containing a thin film transistor (TFT), which is electrically connected to the anode layer 103. A first photoresist layer 203 is deposited on the hole injection layer 104 and extends across the bank 202. In an exemplary photolithography process, the photoresist layer 203 includes InP quantum dots 206 that emit red light. Referring to FIG. Figure 3 , a portion of the photoresist layer 203 is exposed to ultraviolet (UV) light 204 through a mask 205 .

[0054] Reference Figure 4 , a developer (not shown) is applied to the light emitting layer 106, thereby removing the photoresist layer 203 ( Figure 3 ),like Figure 3 The process is repeated (not shown), wherein the second photoresist layer includes, for example, InP quantum dots 207 ( Figure 5 ), through mask 205 ( Figure 3 ) offset, exposing different areas of the substrate to UV light 204 ( Figure 3 ). This process is repeated again (not shown), where the third photoresist layer includes, for example, ZnSe quantum dots 208 that emit blue light ( Figure 5 ), through mask 205 ( Figure 3 ) offset, exposing different areas of the substrate to UV light 204 ( Figure 3 ). Then, refer to Figure 1 The remaining layers described (electron transport layer 110, cathode layer 111) are arranged on the obtained light-emitting layer 106 containing quantum dots 206, 207, 208, so as to obtain Figure 5 QLED200 display device structure shown in cross section.

[0055] Reference Figure 6 and Figure 7, shows the luminescent properties of the photoluminescence of the quantum dots 301 in the light-emitting layer 300 when illuminated by UV light 302, and a comparison of the photoinitiator absorption spectrum with the photoluminescence emission wavelengths from the blue quantum dots (e.g., blue light 305), the green quantum dots (e.g., green light 306), and the red quantum dots (e.g., red light 307). Figure 6 A light emitting layer 300 is shown comprising quantum dots 301 (not to scale) illuminated by UV light 204 during an exposure step of photolithographic fabrication. Ultraviolet light 302 is absorbed and re-emitted by the quantum dots 301 in all directions of photoluminescence 303. As shown, a portion of this light will propagate in the plane of the layer shown.

[0056] Reference Figure 7 , in the case of blue light 305, in one example, quantum dots 301 ( Figure 6 The emission spectrum of the QLED (e.g., multiple quantum dots) includes wavelengths of light at which the photoinitiator absorbs (e.g., within the photoinitiator absorption coefficient 304) the QLED, which appears after the photolithography process such as Figure 8 (discussed below).

[0057] Reference Figure 8 , in quantum dot 301( Figure 6 ) contains the emission spectrum of the photoinitiator absorption coefficient 304 ( Figure 7 ) in the wavelength of light (such as blue light 305 ( Figure 7 )), the light emitting layer 106 obtained after the photolithography process extends beyond the boundary of the sub-pixel limiting layer and enters the adjacent sub-pixel. Figure 4 This is disadvantageous compared to the layering shown in , and detrimentally reduces the color purity of the final display, reducing the achievable color gamut. Typically, only blue light 305 ( Figure 7 ) is related to this effect. In quantum dot 301 ( Figure 6 ) includes only wavelengths of light that are not absorbed by the photoinitiator, such as green light 306 and red light 307 ( Figure 7 ), if Figure 5 As shown in , the resulting light-emitting layer will be correctly patterned.

[0058] refer to Figures 9 to 11 In one embodiment, a QLED display with high color purity can be manufactured by photolithography as follows: Fig. 9 and Fig.10 The red light emitting layer photoresist 401 and the green light emitting layer photoresist 402 of the red and green sub-pixels can be manufactured according to the previously described embodiments. Fig.11, the concentration of the photoinitiator 109 in the blue light-emitting layer photoresist 403 of the blue sub-pixel is changed relative to the red light-emitting layer photoresist 401 of the red sub-pixel and the green light-emitting layer photoresist 402 of the green sub-pixel. Specifically, the amount of the photoinitiator 109 contained in the blue light-emitting layer photoresist 403 of the blue sub-pixel is reduced. Preferably, the concentration of the photoinitiator 109 in the blue light-emitting layer photoresist 403 is at least five times lower than the concentration of the photoinitiator 109 in the red light-emitting layer photoresist 401 or the green light-emitting layer photoresist 402. More preferably, the concentration of the photoinitiator 109 in the blue light-emitting layer photoresist 403 is at least ten times lower than the concentration of the photoinitiator 109 in the red light-emitting layer photoresist 401 or the green light-emitting layer photoresist 402.

[0059] In the photolithography process, not all of the photoinitiator 109 is used. Therefore, after the photolithography process, the hole transport layer (e.g., Figure 1 105) and a light-emitting layer (e.g., Figure 1 106 in the final cured layer will still contain a large amount of unused photoinitiator 109. Similar to the photoresist, the concentration of photoinitiator 109 in the final cured layer is preferably five times lower in the blue sub-pixel than in the red or green sub-pixel. More preferably, the concentration of photoinitiator 109 in the final cured layer is ten times lower in the blue sub-pixel than in the red or green sub-pixel.

[0060] Reference Fig.12 , shows an alternative embodiment in which the sensitivity of the photoinitiator to blue light is reduced in the blue sub-pixel. This is achieved by using a photoinitiator 109 ( Fig.11 ) is achieved, the photoinitiator 109 is compared with the photoinitiator 109 ( Fig. 9 , Fig.10 ) (e.g., for red photoresist and green photoresist), have a lower absorption coefficient 501. The lower absorption coefficient 501 results in a reduced overlap 504 with the blue quantum dot wavelength region 503 compared to the conventional overlap 505 of the spectrum of light emitted in the blue quantum dot wavelength region 503 with a photoinitiator 109 having a conventional absorption coefficient 502. Advantageously, this produces a blue sub-pixel with a light-emitting layer that does not extend beyond the boundaries of the bank, resulting in a display with high color purity.

[0061] Still refer to Fig.12 , by using a photoinitiator 109 ( Fig.11)Reducing the absorption coefficient (e.g., absorption sensitivity) in the blue quantum dot emission wavelength region 503 can also reduce the absorption of the photoinitiator 109 in the ultraviolet region of the spectrum. Therefore, light of a shorter wavelength can be used in the exposure step of the lithography process. For example, 365 nm light from a UVA LED, a filtered mercury lamp, or a filtered xenon lamp can be used to expose the light-emitting layers of the red and green sub-pixels. In contrast, to expose the light-emitting layer of the blue sub-pixel, exemplary light sources include: deep ultraviolet LED emission having a peak wavelength between 240 nm and 300 nm, the 254 nm emission line from a mercury lamp, and emission between 297 nm and 334 nm from a mercury lamp, a filtered xenon lamp, or a filtered deuterium lamp.

[0062] Referring Figure 13-Figure 15 , in another alternative embodiment, quantum dots of different sizes can be employed in the blue sub-pixel relative to the red and green sub-pixels. Fig.13 and 14 The embodiments shown in Fig.11 and 12 correspond to the embodiments shown in Fig.15 and have red quantum dots 206 and green quantum dots 207 in the hole transport material 108, respectively. However, in the embodiment shown in Fig.15 , the hole transport material 108 of the blue light-emitting layer photoresist 603 includes large quantum dots 608 that have an increased size relative to the red quantum dot photoresist 401 and the green quantum dot photoresist 402. Large quantum dots 608 having a core size and material suitable for emitting light of the desired blue wavelength and a thick shell are included in the blue quantum dot photoresist 603 for depositing the blue light-emitting layer. Cd x Zn 1-x Se (0 ≤ x < 1) and ZnSe y Te 1-y (0 < y ≤ 1) are examples of suitable materials for the core of the quantum dots 608. Cd x Zn 1-x Se y S 1-y (0 ≤ x ≤ 1; 0 ≤ y < 1) are examples of suitable shell materials. The composition of the large quantum dots 608 can vary continuously within the core, within the shell, or between the core and the shell as a function of the distance from the center of the large quantum dots 608.

[0063] Increasing the size of the quantum dots increases their surface area. Organic ligands are attached to the quantum dot surface to passivate surface defects and increase the efficiency of converting excitons (electron-hole pairs) into photons. These ligands contain functional groups that interfere with the crosslinking of the photoresist during the photolithography process. The increased ligand concentration can effectively terminate the crosslinking process, which is initiated by the blue light re-emitted by the blue quantum dots during the photolithography process, thereby reducing the probability that the light-emitting layer extends beyond the pixel-defining layer, such as Figure 8 shown.

Claims

1. A quantum dot LED display device, It is characterized in that include: a substrate having a plurality of banks disposed thereon; as well as A plurality of red light-emitting LED sub-pixels, green light-emitting LED sub-pixels and blue light-emitting LED sub-pixels are individually arranged between the banks. Each of the red light-emitting LED sub-pixel, the green light-emitting LED sub-pixel and the blue light-emitting LED sub-pixel has a light-emitting layer; wherein each of the light-emitting layers comprises quantum dots, an organic matrix and a photoinitiator; and The first concentration of the photoinitiator in the blue LED sub-pixel light-emitting layer is lower than the second concentration of the photoinitiator in the red LED sub-pixel light-emitting layer and lower than the third concentration of the photoinitiator in the green LED sub-pixel light-emitting layer.

2. The quantum dot LED display device according to claim 1, It is characterized in that The absorption coefficient of the photoinitiator in the blue-emitting LED sub-pixel for blue light with a wavelength between 400nm and 500nm is lower than the absorption coefficient of the photoinitiator in the red-emitting LED sub-pixel for blue light with a wavelength between 400nm and 500nm and the absorption coefficient of the photoinitiator in the green-emitting LED sub-pixel for blue light with a wavelength between 400nm and 500nm.

3. The quantum dot LED display device according to claim 1, It is characterized in that The absorption wavelength of the photoinitiator in the blue light-emitting LED sub-pixel is within the ultraviolet wavelength range of 200nm to 400nm.

4. The quantum dot LED display device according to claim 1, It is characterized in that The surface area of ​​the quantum dots in the blue-emitting LED sub-pixel is the same as or larger than the surface area of ​​the quantum dots in the green-emitting LED sub-pixel.

5. The quantum dot LED display device according to claim 1, It is characterized in that The quantum dots in the blue-emitting LED sub-pixel include Cd x Zn 1-x Se or ZnSe y Te 1-y The kernel of , where 0≤x<1, 0 <y≤1。 6. The quantum dot LED display device according to claim 1, It is characterized in that The quantum dots in the blue-emitting LED sub-pixel include Cd x Zn 1-x Se y S 1-y The shell of , where 0≤x≤1; 0≤y<1.

7. The quantum dot LED display device according to claim 1, It is characterized in that The organic matrix includes a cross-linked charge transport material.

8. The quantum dot LED display device according to claim 1, It is characterized in that One or more second electrodes are included, and the second electrodes are formed as a continuous layer shared by all of the red light-emitting LED sub-pixels, the green light-emitting LED sub-pixels, and the blue light-emitting LED sub-pixels.

9. The quantum dot LED display device according to claim 1, It is characterized in that A plurality of first charge transport layers are included, and each of the red light-emitting LED sub-pixel, the green light-emitting LED sub-pixel and the blue light-emitting LED sub-pixel has one or more first charge transport layers.

10. The quantum dot LED display device according to claim 9, It is characterized in that One or more of the first charge transport layers in the red light-emitting LED sub-pixels, one or more of the first charge transport layers in the green light-emitting LED sub-pixels, and one or more of the first charge transport layers in the blue light-emitting LED sub-pixels have different thicknesses.

11. The quantum dot LED display device according to claim 1, It is characterized in that One or more second charge transport layers are included and disposed above the light emitting layer.

12. The quantum dot LED display device according to claim 11, It is characterized in that One or more of the second charge transport layers are shared by all of the red light-emitting LED sub-pixels, the green light-emitting LED sub-pixels, and the blue light-emitting LED sub-pixels.

13. The quantum dot LED display device according to claim 1, It is characterized in that It further includes a reflector between the substrate and the plurality of first electrodes, wherein the plurality of second electrodes are partially transparent and are electrically connected to the plurality of first electrodes through a corresponding one of the light-emitting layers, and the quantum dot LED display device emits light through one or more of the second electrodes.

14. The quantum dot LED display device according to claim 13, It is characterized in that One or more of the second electrodes are shared by the red light-emitting LED sub-pixel, the green light-emitting LED sub-pixel, and the blue light-emitting LED sub-pixel.

15. The quantum dot LED display device according to claim 1, It is characterized in that It also includes a plurality of partially transmissive first electrodes and one or more reflective second electrodes, wherein the quantum dot LED display device emits light through the substrate.

16. The quantum dot LED display device according to claim 15, It is characterized in that One or more of the reflective second electrodes are shared by the red-emitting LED sub-pixel, the green-emitting LED sub-pixel, and the blue-emitting LED sub-pixel.

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