CN110783383A - Display substrate and display device - Google Patents

Display substrate and display device Download PDF

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CN110783383A
CN110783383A CN201910887341.8A CN201910887341A CN110783383A CN 110783383 A CN110783383 A CN 110783383A CN 201910887341 A CN201910887341 A CN 201910887341A CN 110783383 A CN110783383 A CN 110783383A
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layer
pixel
sub
interface layer
functional material
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甄常刮
顾辛艳
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Najing Technology Corp Ltd
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/10—OLED displays
    • H10K59/12—Active-matrix OLED [AMOLED] displays
    • H10K59/122—Pixel-defining structures or layers, e.g. banks
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/80—Constructional details
    • H10K50/86—Arrangements for improving contrast, e.g. preventing reflection of ambient light
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/10—OLED displays
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass

Abstract

The invention discloses a display substrate and a display device. The display device comprises a display substrate including a pixel defining layer disposed on a substrate, the pixel defining layer defining a plurality of sub-pixel pits, and an interface layer at least covering an inner surface of the sub-pixel pits, the interface layer having a surface energy of not less than 70mN/m and an impedance of not less than 1ohm cm 2And not more than 2000ohm cm 2(ii) a The display device also comprises a light-emitting device arranged on the display substrate, wherein the light-emitting device comprises at least one functional layer arranged in the sub-pixel pit, at least part of the functional layer is prepared by drying functional material ink, and the surface energy of the functional material ink is not more than 70mN/m, so that the functional material ink can infiltrate the interface layer. The display substrate of the invention is beneficial to the uniform spreading of the functional material ink in the sub-pixel pits to formAnd the functional layer has good thickness uniformity, so that the display device with good display performance is obtained.

Description

Display substrate and display device
Technical Field
The invention relates to the technical field of photoelectric devices, in particular to a display substrate and a display device.
Background
With the increasing image quality, the requirement of pixel density (PPi) is higher and higher, and higher requirements are also put forward on the manufacturing process of the display light-emitting device. In the prior art, in order to ensure that printing ink can fall into a sub-pixel and is not adhered to a pixel definition layer, a low-surface-energy resin is generally selected to manufacture the pixel definition layer, when the ink falls into the sub-pixel, the liquid level is obviously in a bag shape, and along with the drying of the ink, the film layer can be in thickness distribution with thin middle and thick two ends in the sub-pixel, so that a display device with good luminous performance is not obtained.
Disclosure of Invention
The inventors found that the higher PPi, the more frequent the short-circuit phenomenon of the light emitting device occurs due to various defects, and analyzed and found that the main causes of the short-circuit phenomenon include: defects in the first electrode on the substrate (e.g., defects caused by particulate matter, pinholes, etc.), resulting in current flow easily from the electrode peaks; or the functional layer has poor thickness uniformity, which causes current to easily flow away from the thin portion of the functional layer. The above reasons cause the problem that the light emitting device emits light and becomes dark or even does not emit light due to short circuit, and the display effect of the display device is seriously affected. In order to overcome the disadvantages of the prior art, it is an object of the present invention to provide a display substrate which is advantageous for forming a uniform film of ink in sub-pixel pits and can reduce short circuits, and a display device with good display performance can be obtained by using the display substrate.
According to one aspect of the present invention, there is provided a display substrate comprising a pixel defining layer provided on a substrate, the pixel defining layer defining a plurality of sub-pixel pits, the display substrate further comprising an interface layer covering at least inner surfaces of the sub-pixel pits, the interface layer having a surface energy of not less than 70mN/m and a resistance of not less than 1ohm cm 2And not more than 2000ohm cm 2。
In some of the embodiments, the visible light transmittance of the interface layer is not lower than 80%, and preferably, the visible light transmittance of the interface layer is not lower than 90%.
In some embodiments, the material of the interfacial layer is a metal compound, and the metal compound is selected from one or more of metal oxide, metal fluoride, and metal sulfide, and preferably, the material of the interfacial layer is selected from one or more of the following: zinc oxide, molybdenum oxide, nickel oxide, tin oxide, aluminum fluoride.
In some embodiments, the interfacial layer has a thickness of 5nm to 100 nm.
In some of these embodiments, the side surfaces of the sub-pixel pits are at angles α > 90, preferably α ≧ 120, to the bottom surface of the sub-pixel pit.
According to other aspects of the present invention, there is provided a display device including:
the display substrate of the invention; and a light emitting device disposed on the display substrate, wherein the light emitting device includes at least one functional layer disposed in the sub-pixel pits, at least a portion of the functional layer is made of a functional material ink dried, and a surface energy of the functional material ink is not more than 70 mN/m.
In some of these embodiments, the side surfaces of the sub-pixel pits are at angles α > 90, preferably α ≧ 120, to the bottom surface of the sub-pixel pit.
In some embodiments, the contact angle between the functional material ink and the interface layer is β 1，(180°-α)≤β 1Less than 90 degrees, and the contact angle of the functional material ink and the bottom interface thereof is β degrees 2，β 2＜90°。
In some of these embodiments, the roll angle of the functional material ink on the interface layer is γ, γ < 180 ° - α.
In some of the embodiments, the equivalent resistance of the light emitting device is a and the resistance of the interface layer is 10a or more at a specific luminance.
The interface layer is arranged to improve the thickness uniformity of the functional layer, so that the short circuit phenomenon caused by poor thickness uniformity of the functional layer can be reduced. Therefore, the invention has the beneficial effects that: the display substrate is beneficial to uniformly spreading the functional material ink in the sub-pixel pits to form a functional layer with good thickness uniformity, and reduces short circuit, thereby obtaining the display device with good display performance.
The above as well as additional technical features and advantages of the present invention will be further elucidated in the following description.
Drawings
FIG. 1 is a schematic longitudinal sectional view of an embodiment of a display device of the present invention, showing only one sub-pixel unit;
FIG. 2 is a schematic longitudinal cross-sectional view of one embodiment of a display substrate of the present invention, showing only one sub-pixel unit;
FIG. 3 is a schematic longitudinal cross-sectional view of an embodiment of a display device of the present invention, showing only one sub-pixel unit;
FIG. 4 is a schematic diagram showing the film thickness distribution of a PEDOT/PSS layer in comparative example 1;
FIG. 5 is a schematic diagram showing the film thickness distribution of the PEDOT/PSS layer of example 1;
FIG. 6 is a photomicrograph of the device of example 1 when lit at a voltage of 3V;
FIG. 7 is a photomicrograph of the device of comparative example 1 when lit at a voltage of 3V;
in the figure:
100. a display substrate; 110. a substrate; 120. a pixel defining layer; 121. a sub-pixel pit; 130. an interfacial layer; 200. a light emitting device; 210. and a functional layer.
Detailed Description
The present invention is further described below with reference to specific embodiments, and it should be noted that, without conflict, any combination between the embodiments or technical features described below may form a new embodiment.
In the description of the present invention, it should be noted that, for the terms of orientation, such as "central", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., it indicates that the orientation and positional relationship shown in the drawings are based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, but does not indicate or imply that the device or element referred to must have a specific orientation, be constructed in a specific orientation, and be operated without limiting the specific scope of protection of the present invention.
It is noted that the terms first, second and the like in the description and in the claims of the present application are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It should be understood that the data so used may be interchanged under appropriate circumstances such that embodiments of the application described herein may be used. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The invention provides a display substrate 100, comprising a pixel defining layer 120 disposed on a substrate 110, the pixel defining layer 120 defining a plurality of sub-pixel pits 121. The display substrate 100 further includes an interface layer 130, the interface layer 130 covering at least an inner surface of the sub-pixel pits 121, a surface energy of the interface layer 130 being not less than 70 mN/m. Fig. 2 is a schematic diagram illustrating an embodiment of a substrate 100. The display substrate 100 includes a substrate 110, a pixel defining layer 120, and an interface layer 130, the pixel defining layer 120 is disposed on the substrate 110 and defines a plurality of sub-pixel pits 121, the interface layer 130 covers at least inner surfaces of the sub-pixel pits 121, and a surface energy of the interface layer 130 is not less than 70 mN/m. By limiting the impedance of the interface layer 130 to not less than 1ohm cm 2And not more than 2000ohm cm 2In this range, even if the film layer provided in contact with the interface layer has a defect, since the interface layer has a higher resistance than a normal film layer (a film layer other than the defect), when the display light emitting device on the display substrate operates, a current does not pass through the defect, and thus the performance of the display light emitting device is not affected, that is, by controlling the impedance of the interface layer 130, it is advantageous to suppress the short circuit phenomenon of the light emitting device 200.
In some embodiments, the impedance of the interface layer 130 is not less than 1 ohm-cm 2And not more than 2000ohm cm 2。
As the impedance value is far beyond the range of the existing detection equipment for a device with a small light-emitting area, such as a pixel, the sheet resistance value which can be indirectly tested is limited to a proper impedance value range which is calculated by theory. The impedance required by the interface layer 130 is calculated according to the area of the actual sub-pixel pit and the estimated area of the short circuit point, so that the light-emitting device can be normally driven under different brightness and pixel requirements. The specific derivation of selecting the above impedance range is as follows.
For a display device, gray scale requirements require that a light emitting device can present different brightness, and under different brightness, the equivalent resistance of the light emitting device is different, and the impedance requirements on an interface layer are also different; for devices with different pixel densities, the aperture ratios are different, that is, the occupied areas of the light emitting active regions are different, so that the tolerable defect sizes of the devices with different pixel densities are different, and the impedance characteristics of the interface layer are discussed by taking the pixel densities of 100ppi (corresponding to the pixel density of a television) and 500ppi (corresponding to the pixel density of a mobile phone) as examples.
The calculation formula is as follows: the initial maximum brightness of the device is L 0Luminance L/(optical loss n due to circular polarizer) when the device is used, device impedance a 0Current efficiency of the device I/initial maximum brightness of the device L 0. The impedance of the interface layer was calculated as follows: assuming the area size S of the defect, the area S of a single pixel unit of the light emitting device 1Device aperture ratio m 1Effective light-emitting area S of single pixel unit 2Equivalent resistance R of light emitting device is A 0/S 2Minimum resistance R required for interfacial layer 110R (for effective leakage improvement, the required interfacial layer resistance is ten times the device resistance), then: minimum value of impedance in thickness direction of interface A 1＝S*R 1Maximum value of impedance A in thickness direction of interface 2＝10％*A 0(in order to ensure that the introduced interface layer does not place an excessive burden on the device resistance, the resistance in the thickness direction of the interface layer should not exceed the resistance A of the device itself 010% of).
Assuming that the maximum luminance of the light emitting device at the time of final use is 500cd/m 2The aperture ratio of the device was 20%, and the addition of a circular polarizer to suppress the influence of ambient light caused a light loss of 50%, the maximum luminance required for the initially displayed light emitting device was 5000cd/m 2Assuming that the current efficiency of the device is 20cd/A and the applied voltage is 5v, if the light emitting device is completed without a short-circuit point, the equivalent impedance in the thickness direction is 200. omega. cm 2。
Assuming that the size of the defect is 1 μm 2(10 -8cm 2) For a 100ppi display device, the aperture ratio may be relatively high due to the small pixel density, and as the pixel density increases, the aperture ratio may gradually decrease due to the process, and the effective light emitting area per pixel is shown in the following table, and for a 100ppi display device, the effective light emitting area is 4 x 10 at an aperture ratio of 62% -4cm 2The equivalent resistance of the device can be calculated according to the resistance value in the thickness direction and is 5 x 10 5Omega, the resistance of the required interface layer is ten times that of the light emitting device in order to effectively improve the leakage current, and therefore we find that the minimum resistance required by the interface layer is 5 x 10 6Omega, we can show that the lowest thickness-direction impedance of the interfacial layer is 0.05 omega cm in combination with the area of the defect 2Since the impedance value in the thickness direction of the device itself is 200. omega. cm 2Since the impedance in the thickness direction of the interface layer is not preferably more than one tenth of the impedance of the device itself in order to ensure that the introduced interface layer does not give an excessive load to the device resistance, the upper limit of the impedance in the thickness direction of the interface layer is 20 Ω · cm 2. The calculation of 500ppi is the same. Therefore, the concentration is 5000cd/m 2For a defect area of 1 μm 2The required impedance range in the thickness direction of the display device is 0.05-20 omega cm 2。
Figure BDA0002207715170000061
Assuming a minimum luminance of 1cd/m at the end of use 2Then the minimum luminance of the original device is 10cd/m 2If of the deviceThe current efficiency and the voltage are unchanged, and the equivalent impedance of the device in the thickness direction is 1 x 10 5Ω·cm 2The results of the calculations at different ppis are shown in the table below, at which brightness the defect area is 1 μm 2The required impedance range in the thickness direction of the display device is 25 to 10 4Ω·cm 2。
Figure BDA0002207715170000071
In summary, it can be seen that for a display device with a low ppi, the tolerable defect size is relatively large (corresponding to a large pixel area, and naturally tolerable defect area is also relatively large), and from the lowest to highest impedance ratio, the maximum tolerable defect area of a 100ppi device is 4 to 10 -6cm 2(1μm 2400 times) for a high pixel density device, such as 500ppi, a tolerable maximum defect area of 6.45 x 10 -8cm 2(1um 26.45 times) and therefore it is more important to introduce an interfacial layer to improve stability for high pixel density panel fabrication. In combination with the actual panel design of different ppi, different display brightness and different defect size, the inventors believe that the impedance of the interface layer in the thickness direction is 1-2000 Ω · cm 2And the short-circuit prevention characteristic of the display device can be better ensured. In some embodiments, the impedance of the interfacial layer is 100-1500 Ω -cm 2. In some embodiments, the impedance of the interfacial layer is 200-1000 Ω -cm 2. In some embodiments, the impedance of the interfacial layer is 500-800 Ω -cm 2。
In some embodiments, the material of the interfacial layer 130 is a metal compound, which may be a metal oxide, a metal fluoride, or a metal sulfide. In some embodiments, the aforementioned metal compound may be a metal compound doped with an atom or compound. Such as AlF 3Doped ZnO, Ga-doped ZnO, Ni-doped ITO, etc. Doping can increase the transmittance of the film, improve the conductivity of the film, adjust the work function of the film, and the like.
In some embodiments, the material of the interface layer 130 may be one or more of: zinc oxide, molybdenum oxide, nickel oxide, tin oxide, aluminum fluoride.
In some embodiments, the interfacial layer 130 has a thickness of 5nm to 100 nm. When the interface layer is a metal compound, the metal compound can obtain a complete film layer at a film thickness of 5nm under conventional conditions, the interface improvement characteristics can be shown, and when the film thickness exceeds 100nm, the carrier transport property of the light-emitting device and the like can be influenced.
In some embodiments, interface layer 130 covers the entire surface of pixel definition layer 120 and the bottom surface of sub-pixel wells 121, as shown in fig. 3.
In some embodiments, the surface of the interface layer is provided with a chemical modifier, a first group of the chemical modifier is chemically linked to the interface layer, and a second group of the chemical modifier (e.g., hydroxyl, amino, alkane chain, etc.) is used to affinity the functional material ink. The chemical modifier is used to improve the surface affinity of the interface layer 130. The chemical modifier may be various coupling agents, and one end of the chemical modifier is bonded to the interface layer 130 (e.g., silicon-oxygen bonded), and the other end of the chemical modifier is in contact with the functional material ink (e.g., hydroxyl, amino, alkane chain, etc.), so as to improve the wettability of the functional material ink. The chemical modifier may be obtained by, but is not limited to, plasma treatment or coating with the chemical modifier.
In some embodiments, the appropriate interface layer and the appropriate fabrication process are selected according to the surface energy, visible light transmittance, and impedance requirements of the interface layer.
In some embodiments, the interface layer 130 may be formed by physical vapor deposition or chemical vapor deposition. The specific composition and microstructure of the interface layer 130 can be controlled by adjusting the process (e.g., the atmosphere, oxygen partial pressure, deposition rate, doping elements, etc.) for forming the interface layer 130, so as to obtain the interface layer 130 with satisfactory surface energy, impedance, and light transmittance.
In some embodiments, the side surfaces of sub-pixel pit 121 form an angle α of > 90 ° with the bottom surface of sub-pixel pit 121, that is, the longitudinal cross-section of sub-pixel pit 121 is in the form of an inverted trapezoid with a narrow lower portion and a wide upper portion in some embodiments α ≧ 120.
The light emitting device 200 comprises at least one functional layer 210 disposed in the sub-pixel pits 121, wherein at least a part of the functional layer 210 is made of functional material ink dried, and the surface energy of the functional material ink is not more than 70mN/m, so that the functional material ink can wet the interface layer 130.
The inner surface of sub-pixel pit 121 includes the bottom surface of sub-pixel pit 121, that is, the upper surface of substrate 110, and the side surface of sub-pixel pit 121, that is, the side surface of pixel defining layer 120.
The functional layer 210 of the light emitting device 200 may be, but is not limited to, one or more of a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer, and the functional layer 210 in fig. 1 and 2 is only schematic and does not mean that the light emitting device 200 needs to have the number or thickness of the functional layers 210 shown in the figures. It will be understood by those skilled in the art that the substrate 110 includes a first electrode, the light emitting device 200 includes a second electrode (not shown in the figures), and each of the functional layers 210 is between the first electrode and the second electrode.
The surface tension of the functional material ink is controlled within the range of 30 mN/m-70 mN/m, and the surface energy of the interface layer 130 is not less than 70mN/m, so that the ink has good affinity with the ink, and the ink is favorable for uniformly spreading various inks in the sub-pixel pits.
According to the invention, the bottom surface and the side surface of the sub-pixel pit 121 are covered with the interface layer 130, when the functional material ink is arranged in the sub-pixel pit 121, the functional material ink has better affinity with the bottom and the peripheral side of the sub-pixel pit 121, the spreading uniformity of the functional material ink in the sub-pixel pit 121 is better than that of the functional material ink which is not provided with the interface layer in the prior art, the liquid level of the ink is basically horizontal or slightly convex, and the functional layer 210 with uniform thickness can be obtained after drying. The thickness uniformity of the functional layer 210 is increased, which is advantageous for improving the light emitting performance of the light emitting device 200, thereby obtaining the light emitting device 200 having good consistency of the light emitting area and the design value.
In some embodiments, light emitting device 200 includes a plurality of functional layers 210 disposed within sub-pixel wells 121, and interface layer 130 also covers an upper surface of at least one functional layer 210, as shown in fig. 3. When the sub-pixel pits 121 include a plurality of functional layers 210, the bottom interface and the peripheral interface of the functional layer 210 which are arranged first are the interface layers 130, that is, the wettability of the functional material ink to the peripheral interface and the bottom interface is consistent, and the thickness uniformity of the prepared functional layer 210 is good; if the functional material ink is directly disposed on the prepared functional layer 210 when the subsequent functional layer 210 is prepared, the wettability of the functional material ink with the peripheral side interface and the bottom interface may be inconsistent, and in order to ensure that each functional layer 210 has good thickness uniformity, the interface layer 130 may be disposed on the prepared functional layer 210, so that the bottom interface and the peripheral side interface of the functional material ink are both the interface layer 130 when the subsequent functional layer 210 is prepared, and the wettability is consistent, which may ensure that the functional material ink is uniformly spread.
In a specific embodiment, the substrate 110 is a TFT substrate, the light emitting device 200 includes a PEDOT hole transport layer, a TFB hole injection layer, a quantum dot light emitting layer, a zinc oxide electron transport layer, and an Ag electrode, which are sequentially disposed from bottom to top, and the interface layer 130 covers a surface of the TFT substrate.
In some embodiments, the angle α between the side surface of sub-pixel pit 121 and the bottom surface of sub-pixel pit 121 is greater than 90 °, i.e., the longitudinal cross-section of sub-pixel pit 121 is in the shape of an inverted trapezoid with a narrow bottom and a wide top, as shown in FIG. 2, more preferably α ≧ 120 °.
In some embodiments, the functional material ink has a contact angle of β with the interface layer 130 1，(180°-α)≤β 1Less than 90 degrees, and the contact angle of the functional material ink and the bottom interface thereof is β degrees 2，β 2＜90°。
As will be appreciated by those skilled in the art, the contact angle β 1、β 2Are both less than 90 deg., indicating that the functional material ink is hydrophilic to both the peripheral side interface and the bottom interface, the functional material ink can spread uniformly within sub-pixel wells 121, and the contact angle β between the functional material ink and the peripheral side interface 1Less than 90 DEG limiting ink protrusionTo the extent that the ink level is substantially parallel to or slightly raised from the bottom surface of the sub-pixel pit 121, the thickness uniformity of the functional layer 210 after drying is controlled within a reasonable range.
When the surface of the substrate 110 itself has a high affinity for the functional material ink (for example, the contact angle of the functional material ink with the surface of the substrate 110 is 10 °), the contact angle may increase (for example, the contact angle of the functional material ink with the interface layer 130 is 30 °) after the interface layer 130 is added, and although the affinity of the functional material ink with the interface layer at the bottom thereof may be worse than before the interface layer 130 is provided, the interface layer 130 can play a role of suppressing the functional material ink from being excessively spread. Particularly, for the functional material ink with small surface energy, if the contact angle with the interface is too small, the functional material ink is easily spread into large droplets, so that the edges of the droplets are very thin, the edges of the thin droplets are very easy to dry, and the generation of 'coffee rings' is aggravated, and the increase of the interface layer 130 can inhibit the functional material ink from being excessively spread, thereby being beneficial to improving the thickness uniformity of the film layer.
It should be noted that, since the solvent in the functional material ink may volatilize, the contact angle between the functional material ink and other interfaces in the present invention refers to the contact angle when the functional material ink initially contacts the interface.
Furthermore, the rolling angle of the functional material ink on the interface layer 130 is gamma, gamma is less than 180- α, when the value of α is larger, the rolling angle gamma is smaller, the ink is easier to roll, and when the functional material ink is dried in the sub-pixel pit 121, the ink adhered to the side surface of the sub-pixel pit 121 can continuously slide along the interface layer 130, so that the ink can be prevented from being adhered to the side wall.
The solvent system of the functional material ink may be water system, alcohol system, alkane system, etc., and those skilled in the art may select an appropriate material as the solute of the functional material ink by combining the specific functions of the functional layer 210, which is not limited in the present invention.
The impedance referred to herein is an impedance in the thickness direction, and generally, the resistivity of the material is expressed in Ω · cm, and when the thickness of the interface layer 130 is known, the product of the resistivity of the material of the interface layer 130 and the thickness of the interface layer 130 is the impedance of the interface layer 130. In some embodiments, when the equivalent resistance of the device at a specific brightness is a, the resistance of the added interface layer 130 satisfies 10a or more than 10a, and the short-circuit prevention effect is significant.
[ example 1 ]
(1) Providing a TFT pixel substrate, wherein the size of a sub-pixel is 36 mu m by 64 mu m, the included angle between the side surface of a sub-pixel pit and the bottom surface of the sub-pixel pit is 150 degrees, and the thickness of an ITO electrode in the sub-pixel is 150 nm;
(2) the TFT pixel substrate is cleaned, dried, processed with plasma, and then placed in a sputtering chamber at 10 f -6In a Torr vacuum degree, MoO with a thickness of 25nm was sputtered on the entire surface of the TFT pixel substrate 3；
(3) To the coating with MoO 3And cleaning, drying and plasma processing the substrate of the layer, then sequentially printing each functional material ink in each sub-pixel pit and performing vacuum drying, thereby sequentially forming a 40 nm-thick PEDOT (PSS layer) (a hole injection layer), a 30 nm-thick TFB layer (a hole transmission layer), a 30 nm-thick GQD layer (a quantum dot light emitting layer) and a 50 nm-thick ZnO nano-crystal layer (an electron transmission layer), finally evaporating a 100 nm-thick Ag electrode, and then packaging to finish the device manufacturing.
Wherein the surface tension of the functional material ink for forming the PEDOT/PSS layer is about 40 mN/m.
Comparative example 1
(1) Providing a TFT pixel substrate, wherein the size of a sub-pixel is 36 mu m by 64 mu m, the included angle between the side surface of a sub-pixel pit and the bottom surface of the sub-pixel pit is 150 degrees, and the thickness of an ITO electrode in the sub-pixel is 150 nm;
(2) and cleaning the TFT pixel substrate, drying, processing by using plasma, sequentially printing each functional material ink in each sub-pixel pit, and drying in vacuum to sequentially form a 40 nm-thick PEDOT (PSS layer) (a hole injection layer), a 30 nm-thick TFB layer (a hole transmission layer), a 30 nm-thick GQD layer (a quantum dot light emitting layer) and a 50 nm-thick ZnO nano-crystal layer (an electron transmission layer), finally evaporating a 100 nm-thick Ag electrode, and packaging to finish the device manufacturing.
Wherein the surface tension of the functional material ink for forming the PEDOT/PSS layer is about 40 mN/m.
MoO measurement in example 1 Using a Fischer 70mN/m dyne Pen 3Surface energy of the coating and the ITO film layer of comparative example 1, wherein the dyne pen is in MoO 3The coating and the ITO film can write smoothly, which shows that the surface energy of the two film layers is more than 70 mN/m. We measured the contact angle of PEDOT PSS ink on both films using a PGX plus 40b contact angle tester, where the ink is in MoO 3The contact angle on the plating was 15 deg., and the contact angle on the ITO film was 5 deg., and it is clear that the surface energy of the original ITO film layer was relatively higher, although both film layers had surface energies greater than 70 mN/m. The device prepared in example 1 and comparative example 1 was tested for efficiency using a PR670 spectrometer from Photoresearch, with external quantum efficiencies of 4.55% and 3.69%, respectively.
FIG. 4 shows the thickness distribution of the PEDOT PSS layer of comparative example 1 measured by a KLA-Tencor P6 type profile gauge, and it can be seen that the PEDOT PSS material is gathered in a large amount at the outer ends of the sub-pixel pits, resulting in a thin film distribution at the middle and thick at the outer ends, and the difference between the thickness of the PEDOT PSS layer at the outer ends and the thickness of the PEDOT PSS layer at the middle is about 50 nm. FIG. 5 shows the film thickness distribution of the PEDOT/PSS layer of example 1 measured by a profilometer, and it can be seen that the film thickness distribution in the sub-pixel pits is uniform. From the contact angle test data, MoO 3The surface energy of the layer is lower than that of the ITO, when the PEDOT PSS ink is printed into the sub-pixel pits in the embodiment 1, the ink is spread on the slope of the pixel limiting structure to a small extent, the probability of flowing into the sub-pixel pits under the action of surface tension and gravity is improved during drying, and the PEDOT PSS layer with uniform film thickness distribution is obtained after drying; when the PEDOT: PSS ink is printed into the sub-pixel pit of the comparative example 1, the ink drop spreads greatly on the slope surface of the sub-pixel pit, so that the liquid film at the edge of the ink drop is thin and is dried quickly, meanwhile, the ink at the center of the sub-pixel pit volatilizes quickly due to the thin liquid film, and finally, the ink is gathered in a large amount at the outer end of the sub-pixel pit, so that the film thickness distribution with the thin middle part and the thick outer end is caused.
FIG. 6 is a photomicrograph of the device of example 1 when lit, showing that the device of example 1 emits light uniformly with a uniform light emitting area per subpixel; while the external quantum efficiency of the device of comparative example 1 is low, fig. 7 is a photomicrograph of the device of comparative example 1 when it is lit up, and it can be seen that the light emitting areas of the sub-pixels are different in size and irregular in shape. In combination with the measurement results of the profiler, it can be presumed that it is the stack of the two thick and thin films that leads to the reduction of the light emitting area of the sub-pixel, because the excessively thick film will affect the carrier injection and transport, and it will require higher voltage or current to be input to make it possible to make it emit light, but the high voltage or current will accelerate the aging of the device.
Because the impedance value of the light-emitting device with small light-emitting area, such as a single pixel, can indirectly test the sheet resistance value far exceeding the measuring range of the existing detection equipment, only the proper value range is calculated by theory; the effect can be indirectly shown by the yield ratio (see below), i.e. the number of short circuits of the device is greatly reduced after the interface layer is applied.
According to the manufacturing processes in the examples and comparative examples, the inventors performed comparative experiments on 16 devices in total of 8 devices each, in which MoO was added 3All display devices of the interface layer can be uniformly lightened, the yield is 100%, the device without the interface layer has serious electric leakage, one of 8 pieces can not be lightened almost, 6 pieces have serious electric leakage, the device generates heat seriously during measurement, the external quantum efficiency is below 1%, only one piece has relatively reasonable indexes in all aspects (namely comparative example 1), but the luminous uniformity is general.
The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the protection scope of the present invention.

Claims (11)

1. A display substrate comprising a substrate and a pixel defining layer disposed on the substrate, the pixel defining layer defining a plurality of sub-pixel pits, wherein the display substrate further comprises an interface layer covering at least inner surfaces of the sub-pixel pits, the interface layer having a surface energy of not less than 70mN/m and an impedance of not less than 1 ohm-cm 2And not more than 2000ohm cm 2。
2. The display substrate of claim 1, wherein the interface layer has a visible light transmittance of not less than 80%, preferably not less than 90%.
3. The display substrate of claim 1, wherein the material of the interface layer is a metal compound selected from one or more of metal oxides, metal fluorides, and metal sulfides.
4. The display substrate of claim 3, wherein the interface layer is made of a material selected from one or more of the following: zinc oxide, molybdenum oxide, nickel oxide, tin oxide, aluminum fluoride.
5. The display substrate according to any one of claims 1 to 4, wherein the interface layer has a thickness of 5nm to 100 nm.
6. A display substrate according to any one of claims 1 to 4, wherein the side surfaces of the sub-pixel pits are angled with respect to the bottom surface of the sub-pixel pit by α > 90 °, preferably α ≧ 120 °.
7. A display device, comprising:
the display substrate of any one of claims 1-6; and
and the light-emitting device is arranged on the display substrate and comprises at least one functional layer arranged in the sub-pixel pits, at least part of the functional layer is prepared by drying functional material ink, and the surface energy of the functional material ink is not more than 70 mN/m.
8. A display device as claimed in claim 7, wherein the side faces of the sub-pixel pits are angled with respect to the bottom face of the sub-pixel pit at α > 90 °, preferably α ≧ 120 °.
9. The display device according to claim 7, wherein the contact angle of the functional material ink with the interface layer is β 1，(180°-α)≤β 1Less than 90 degrees, and the contact angle of the functional material ink and the bottom interface thereof is β degrees 2，β 2＜90°。
10. The display device according to claim 7, wherein a roll angle of the functional material ink on the interface layer is γ, γ < 180 ° - α.
11. The display device according to any one of claims 7 to 10, wherein the equivalent resistance of the light-emitting device is a and the resistance of the interface layer is 10a or more at a specific luminance.
CN201910887341.8A 2019-09-19 2019-09-19 Display substrate and display device Pending CN110783383A (en)

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