Tandem OLED structure with patterned intermediate layer

Abstract

A tandem OLED display is provided that includes a substrate backplane, an anode layer, at least two stacked OLED layers, each OLED layer including a plurality of pixels, at least one charge generating layer (CGL), where each CGL is disposed between two adjacent stacked OLED layers, and a cathode layer. At least one of the CGLs is patterned, wherein the pattern provides a gap between each of the plurality of pixels.

Description

[0001] Cross - reference to related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 415,888, filed on October 13, 2022, entitled "Tandem OLED Structure with Patterned Intermediate Layers". Technical Field

[0003] The present invention relates to tandem OLED devices. More particularly, the present invention relates to tandem OLED devices having a patterned intermediate layer. Background Art

[0004] Organic light-emitting diode devices (OLEDs) typically include an anode, a cathode, and an organic electroluminescent layer sandwiched between the anode and the cathode. The organic electroluminescent layer typically includes a hole transport layer, a light-emitting layer, and an electron transport layer. OLEDs are attractive due to their low driving voltage, high brightness, wide viewing angle, and ability for full-color display and for other applications. Tang et al. describe such multi-layer OLEDs in U.S. Patent Nos. 4,769,292 and 4,885,211. OLEDs can emit different colors, such as red, green, blue, or white, depending on the light-emitting properties of their light-emitting layers.

[0005] A "tandem" OLED is made by vertically stacking a plurality of individual OLED units and driving the stack with a single power source. Jones et al. disclose a tandem OLED structure (sometimes referred to as a stacked OLED or a tandem OLED) in U.S. Patent No. 6,337,492, Tanaka et al. in U.S. Patent No. 6,107,734, Kido et al. in Japanese Patent Publication No. 2003 / 045676A and in U.S. Patent Application Publication No. 2003 / 0189401A1, and Liao et al. in U.S. Patent No. 6,717,358 and U.S. Patent Application Publication No. 2003 / 0170491A1. Compared to conventional OLEDs, tandem OLEDs have received extensive attention due to their excellent current efficiency, brightness, and operating lifetime. In a tandem OLED, a plurality of individual electroluminescent (EL) units are serially electrically connected via a connection stack (sometimes referred to as a connection electrode) that serves as a charge generation layer (CGL), where holes and electrons are generated and injected into adjacent hole transport layers (HTLs) and electron transport layers (ETLs), respectively. In principle, for a tandem device with an effective CGL, device characteristics such as voltage, brightness, and current efficiency are linearly proportional to the number of EL units.

[0006] Due to the increase in current efficiency, brightness, and operating lifetime, the tandem structure is an important architecture for manufacturing high-performance OLED devices. A key element in manufacturing high-performance tandem OLED devices is the CGL that connects the OLED units, which plays an important role in charge generation and charge injection. In recent years, high-performance CGLs have been developed and typically include high charge mobility (p / n-doped) materials and / or even thin metal films. For example, see U.S. Patent Cases Nos. 8,283,054 and 7,821,201.

[0007] FIG. 1 illustrates a prior art conventional tandem OLED subpixel 100, including a backplane substrate 110, an anode layer 120, a first organic emission layer 130, an n-type doped semiconductor layer 140, a p-type doped semiconductor layer 150, a second organic emission layer 160, and a cathode layer 170. The n-type doped semiconductor layer and the p-type doped semiconductor layer respectively form the CGL between the first organic emission layer 130 and the second organic emission layer 160.

[0008] The CGL plays an important role in tandem OLED performance and is composed of an n-doped semiconductor layer and a p-doped semiconductor layer junction for injecting electrons and holes respectively. In the initial stage of device operation, free electrons and holes are supplied by the CGL. In subsequent stages, when a bias voltage is applied to the device, these free electrons and holes in the CGL can be transported and injected into their adjacent EL units; at the same time, electrons and holes from the cathode and anode are also injected into the EL units respectively. Thereafter, the bipolar current gradually reaches a steady state.

[0009] In the case of using a highly conductive CGL as a common layer in a tandem OLED display, lateral current leakage is a problem, especially when the gap between pixels is small in a high-resolution display. FIG. 2 depicts a prior art tandem OLED display having a substrate backplane 210, an anode layer 220, an OLED-1 layer 230, a CGL 240, an OLED-2 layer 250, and a cathode layer 260. As shown in FIG. 1, when pixel 1 is turned on, the lateral current can leak through the CGL 240 to adjacent pixels (pixel 2, pixel 3), resulting in emission crosstalk due to the undesired emission from OLED-2 250. This is particularly severe in the case of doped transport layer materials. It is highly desirable to prevent this lateral current leakage and emission crosstalk.

[0010] The entire content of all references cited herein is incorporated herein by reference. SUMMARY OF THE INVENTION

[0011] It should be understood that the Summary of the Invention is provided to introduce some concepts in a simplified form, which will be further described in the Detailed Description below. The Summary of the Invention is not intended to limit the scope of the claimed subject matter.

[0012] In a first exemplary embodiment of the present invention, a tandem OLED display is provided, which includes a substrate backplane, an anode layer, at least two stacked OLED layers, each OLED layer having a plurality of pixels, at least one charge generation layer (CGL), wherein each CGL is disposed between two adjacent stacked OLED layers, and a cathode layer. At least one of the CGLs is patterned, wherein the pattern provides a gap between each of the plurality of pixels.

[0013] The patterned CGL can be made of an organic material. Alternatively, the patterned CGL can be made of metal. The patterned CGL can be processed in a high vacuum by thermal expansion. The patterned CGL can have at least two layers. The thickness of the patterned CGL can range from, for example, about 0.5 um to 50 um. The gap in the CGL layer can range from, for example, 0.2 um to 50 um.

[0014] The anode layer can also be patterned, having a gap between each of the plurality of pixels. The cathode layer can also be patterned, having a gap between each of the plurality of pixels. At least one of the OLED layers can be patterned, having a gap between each of the plurality of pixels.

[0015] In a second exemplary embodiment of the present invention, a tandem OLED display is provided, which includes a substrate backplane, an anode layer, at least two stacked OLED layers, each OLED layer including a plurality of pixels, at least one charge generation layer, wherein each CGL is disposed between two adjacent stacked OLED layers, and a cathode layer. At least one of the CGLs is patterned, wherein the pattern provides a gap between each of the plurality of pixels. The anode layer is patterned, having a gap between each of the plurality of pixels, the cathode layer is patterned, having a gap between each of the plurality of pixels, and at least one of the OLED layers is patterned, having a gap between each of the plurality of pixels.

[0016] The patterned CGL can be made of an organic material. Alternatively, the patterned CGL can be made of metal. The patterned CGL can be processed in a high vacuum by thermal expansion. The patterned CGL can comprise at least two layers. The thickness of the patterned CGL can range from, for example, about 0.5 um to 50 um. The gap in the CGL layer can range from, for example, 0.2 um to 50 um. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Embodiments of the present invention will be more readily understood by the following detailed description with reference to the accompanying drawings, which are not necessarily drawn to scale, wherein:

[0018] Figure 1 depicts a conventional OLED sub-pixel of the prior art including a CGL.

[0019] Figure 2 is a simplified block diagram of a conventional tandem OLED display of the prior art having a common CGL.

[0020] Figure 3 is a simplified block diagram of a tandem OLED display having a patterned CGL according to an exemplary embodiment of the present invention.

[0021] Figure 4 is a simplified block diagram of a tandem OLED display having a patterned CGL and other layers according to another exemplary embodiment of the present invention. Detailed Description

[0022] Referring now to the drawings, in which like reference numerals refer to like elements in several views, Figure 3 shows a tandem OLED display having a patterned intermediate layer 10 according to an exemplary embodiment of the present invention.

[0023] The tandem OLED display 10 includes a substrate backplane 12, an anode layer 14, an OLED-1 layer 16, a CGL 18, an OLED-2 layer 20, and a cathode layer 22. According to an exemplary embodiment of the present invention, for each individual pixel, the CGL 18 is patterned with gaps 24, 26 between the active pixels 28, 30, 32.

[0024] The patterned CGL 18 can be, for example, an organic material or a metal. As is well known, patterning of the CGL 12 can be processed, for example, by thermal evaporation in a high vacuum. The patterned CGL 18 can be one layer, or it can be more than one layer. The patterned CGL 18 can be, for example, 0.5 μm to 50 μm thick. The gap between the patterned CGL 18 and the adjacent layer can be, for example, 0.2 μm to 50 μm.

[0025] In an alternative embodiment of the present invention as shown in Figure 4 shows a tandem OLED display 50, which includes a substrate backplane 52, an anode layer 54, an OLED-1 layer 56, a CGL 58, an OLED-2 layer 60, and a cathode layer 62. In this tandem OLED display 50, in addition to the CGL 58, the anode layer 54, the OLED-1 layer 56, and the OLED-2 layer 58 can be layered in a manner similar to the CGL 58. This additionally prevents lateral current leakage and emission crosstalk.

[0026] The present device is applicable to white OLEDs with color filters and directly patterned OLEDs.

[0027] The present invention provides many advantages over the prior art. First, as mentioned above, the tandem OLED display having the patterned CGL 10 will substantially reduce the lateral current leakage and crosstalk in the display 10. In addition, the display 10 of the present invention provides high resolution, high efficiency, and long operating life.

[0028] It should be understood that the present disclosure only teaches an example of an illustrative embodiment and those skilled in the art can easily design many variations of the present invention after reading the present disclosure and the scope of the present invention is determined by the appended claims.

Claims

1. A tandem OLED display, which comprises: (a) a substrate backplane (b) an anode layer (c) at least two stacked OLED layers, each OLED layer including a plurality of pixels; (d) at least one charge generation layer (CGL), wherein each CGL is disposed between two adjacent stacked OLED layers; (e) a cathode layer; and (f) wherein at least one of the CGLs is patterned, and the pattern provides a gap between each of the plurality of pixels.

2. The tandem OLED display according to claim 1, wherein the patterned CGL is made of an organic material.

3. The tandem OLED display according to claim 1, wherein the patterned CGL is made of metal.

4. The tandem OLED display according to claim 1, wherein the patterned CGL is processed by thermal expansion in a high vacuum.

5. The tandem OLED display according to claim 1, wherein the patterned CGL comprises at least two layers.

6. The tandem OLED display according to claim 1, wherein the thickness of the patterned CGL ranges from about 0.5 um to 50 um.

7. The tandem OLED display according to claim 1, wherein the gap in the CGL layer ranges from 0.2 um to 50 um.

8. The tandem OLED display according to claim 1, wherein, the anode layer is patterned with a gap between each of the plurality of pixels.

9. The tandem OLED display according to claim 1, wherein, the cathode layer is patterned with a gap between each of the plurality of pixels.

10. The tandem OLED display according to claim 1, wherein, at least one of the OLED layers is patterned with a gap between each of the plurality of pixels.

11. A tandem OLED display, which comprises: (a) a substrate backplane (b) an anode layer (c) at least two stacked OLED layers, each OLED layer including a plurality of pixels; (d) at least one charge generation layer (CGL), wherein each CGL is disposed between two adjacent stacked OLED layers; (e) a cathode layer; (f) wherein at least one of the CGLs is patterned, and the pattern provides a gap between each of the plurality of pixels; (g) wherein the anode layer is patterned with a gap between each of the plurality of pixels; (h) wherein the cathode layer is patterned with a gap between each of the plurality of pixels; and (i) wherein at least one of the OLED layers is patterned with a gap between each of the plurality of pixels.

12. The tandem OLED display according to claim 11, wherein the patterned CGL is made of an organic material.

13. The tandem OLED display according to claim 11, wherein the patterned CGL is made of metal.

14. The tandem OLED display according to claim 11, wherein the patterned CGL is processed by thermal expansion in a high vacuum.

15. The tandem OLED display according to claim 11, wherein the patterned CGL comprises at least two layers.

16. The tandem OLED display according to claim 11, wherein the thickness of the patterned CGL ranges from about 0.5 um to 50 um.

17. The tandem OLED display according to claim 11, wherein the gap in the CGL layer ranges from 0.2 um to 50 um.

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