Tandem OLED with intermediate alloy layer

Abstract

A tandem OLED device is provided that includes an anode, a cathode, at least two electroluminescent units disposed between the anode and the cathode, and an alloy thin film disposed between the two electroluminescent units.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to pending U.S. Provisional Patent Application Serial No. 63 / 413,557, entitled Tandem OLED with Intermediate Alloy Layer, filed October 5, 2022.

[0002] The present invention relates to a tandem OLED device, and more particularly to an OLED device having an intermediate layer. [Background technology]

[0003] An organic light-emitting diode device (OLED) generally comprises an anode, a cathode, and an organic electroluminescent layer sandwiched between the anode and the cathode. The organic electroluminescent layer generally comprises a hole transport layer, an emissive layer, and an electron transport layer. OLEDs are attractive due to their low driving voltage, high brightness, wide viewing angle, and performance for full-color displays and other applications. Tang et al. described multilayer OLEDs in their U.S. Patent Nos. 4,769,292 and 4,885,211.

[0004] OLEDs can emit different colors, such as red, green, blue, or white, depending on the emitting properties of their light-emitting layers.

[0005] Tandem OLED structures (sometimes called stacked OLEDs or cascade OLEDs) have been disclosed, for example, by Jones et al. in U.S. Pat. No. 6,337,492, by Tanaka et al. in U.S. Pat. No. 6,107,734, by Kido et al. in Japanese Patent Application Publication No. 2003 / 045676A and U.S. Patent Application Publication No. 2003 / 0189401A1, and by Liao et al. in U.S. Pat. No. 6,717,358 and U.S. Patent Application Publication No. 2003 / 0170491A1.

[0006] Tandem OLEDs are fabricated by vertically stacking multiple individual OLED units and using a single power supply to drive the stack. The advantages are improved current efficiency, lifetime, or both. However, the following problems arise: 1. A tandem structure having multiple OLED units requires a high driving voltage (almost proportional to the number of OLED units), which is unfavorable in terms of power consumption. 2. Higher voltage requirements necessitate larger capacitor sizes. The high voltages required to drive OLEDs make it difficult to fabricate backplanes for displays with very small pixels, such as microdisplays. Therefore, it is essential to reduce the driving voltage and improve the power efficiency of tandem OLED devices for their widespread application in OLED displays.

[0007] US Pat. No. 7,955,719 (Hatwar et al.) is of general background and teaches a tandem OLED device with an intermediate connector. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] U.S. Patent No. 4,769,292 [Patent Document 2] U.S. Patent No. 4,885,211 [Patent Document 3] U.S. Patent No. 6,337,492 [Patent Document 4] U.S. Patent No. 6,107,734 [Patent Document 5] Japanese Patent Application Laid-Open No. 2003-045676 [Patent Document 6] US Patent Application Publication No. 2003 / 0189401 [Patent Document 7] U.S. Patent No. 6,717,358 [Patent Document 8] US Patent Application Publication No. 2003 / 0170491 [Patent Document 9] U.S. Patent No. 7,955,719 Summary of the Invention [Problem to be solved by the invention]

[0009] Despite these developments, there remains a need to improve the efficiency and driving voltage of tandem OLED devices while maintaining good broadband emission.

[0010] All references cited herein are incorporated by reference in their entirety. [Means for solving the problem]

[0011] The present invention relates to a tandem OLED device including an anode, a cathode, at least two electroluminescent units disposed between the anode and the cathode, and an alloy thin film disposed between the two electroluminescent units.

[0012] Each OLED unit may include a hole-injection layer (HIL), a hole-transport layer (HTL), an electron-blocking layer (EBL), an emissive layer (EML), a hole-blocking layer (HBL), an electron-transport layer (ETL), and / or an electron-injection layer (EIL). An alloy film may be disposed between a p-type film and an n-type film. The alloy film may include a first metal and a second metal, or a first metal, a second metal, and a third metal. The alloy film may be a bilayer including a first layer including two different metals and a second layer including a third metal. The first metal may be, for example, a noble metal. The second metal may be, for example, an alkaline earth metal or a rare earth metal. The third metal may be, for example, an alkali metal halide or an organic compound containing an alkali metal. The first metal, second metal, and third metal may be co-deposited by thermal evaporation to form the alloy film. The thickness of the alloy film may be, for example, 1 nm to 8 nm. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a simplified isometric view of a tandem OLED configuration having an alloy film connecting the OLED units according to an exemplary embodiment of the present invention.In a tandem OLED, two or more OLED units can be stacked. [Figure 2] 1 is a graph of current density versus voltage (JV) for a tandem OLED according to the present invention using three different metals as interlayers. DETAILED DESCRIPTION OF THE INVENTION

[0014] Referring now to the drawing figures, where like reference numbers refer to like elements throughout the several views, Figure 1 shows a tandem OLED 10 having an alloy thin film 12 as an interlayer between OLED units 14, 16 according to an exemplary embodiment of the invention. The tandem OLED 10 includes two or more typical OLED units, each including a hole-injection layer (HIL), a hole-transport layer (HTL), an electron-blocking layer (EBL), an emissive layer (EML), a hole-blocking layer (HBL), an electron-transport layer (ETL), and an electron-injection layer (EIL).

[0015] The alloy thin film 12 is disposed between the p-type film 18 and the n-type film 20. The alloy film 12 may be a single layer, or may be composed of two materials (e.g., metal 1 and metal 2), or three materials (e.g., metal 1, metal 2, and material 3). The alloy film may be a two-layer structure containing metals 1 and 2 as one layer and material 3 as another layer. Metal 1 may be, for example, a noble metal (e.g., Ag, Au, Pt) with a mass ratio of 1% to 99% in the alloy. Metal 2 may be, for example, an alkaline earth metal (e.g., Mg, Ca) or a rare earth metal (e.g., Yb) with a mass ratio of 1% to 99% in the alloy. Material 3 may be, for example, an alkali metal halide (e.g., LiF, CsF) or an organic compound containing an alkali metal (e.g., LiQ). The alloy film may be fabricated by co-depositing metal 1, metal 2, and / or material 3 by thermal evaporation. The thickness of the alloy film may be, for example, 1 nm to 8 nm. [Example]

[0016] Three green tandem (two-unit) OLED devices were fabricated using calcium, Mg:Ag alloy, and Mg:Ag:LiF alloy as the intermediate metal thin film, respectively. The current density-voltage (JV) curves of the tandem OLED devices are shown in Figure 2. The tandem OLED with the alloy film exhibited a lower driving voltage than the one with the Ca layer, even at the same current density of 50 mA / cm. 2 In the graphs, the driving voltages are 13.8 V for Ca, 12.6 V for Mg:Ag, and 12.3 V for Mg:Ag:LiF, respectively.

[0017] Examples of benefits: The proposed alloy layer will be used in tandem OLED devices, which will enable: (1) High efficiency; (2) long life; (3) Low power consumption due to reduced drive voltage; and (4) Lower voltage requirements on the backplane enable higher resolution microdisplays.

[0018] The present invention is applicable to both white OLEDs with color filters and directly patterned OLEDs.

[0019] It should be understood that this disclosure teaches only one example of an illustrative embodiment, that many variations of the invention can be readily devised by those skilled in the art after reading this disclosure, and that the scope of the invention is determined by the claims that follow. [Explanation of symbols]

[0020] 10 Tandem OLED 12 Alloy thin film 14 OLED units 16 OLED units 18 p-type membrane 20 n-type membrane

Claims

1. (a) Anode; (b) cathode; (c) at least two electroluminescent units disposed between the anode and the cathode; and (d) an alloy thin film disposed between the two electroluminescent units; A tandem OLED device comprising:

2. 10. The tandem OLED device of claim 1, wherein each of the electroluminescent units comprises a hole-injection layer (HIL), a hole-transporting layer (HTL), an electron-blocking layer (EBL), an emissive layer (EML), a hole-blocking layer (HBL), an electron-transporting layer (ETL), and an electron-injection layer (EIL).

3. 10. The tandem OLED device of claim 1, wherein the alloy film is disposed between a p-type film and an n-type film.

4. 10. The tandem OLED device of claim 1, wherein the alloy film comprises a first metal and a second metal.

5. 10. The tandem OLED device of claim 1, wherein the alloy film comprises a first metal, a second metal, and a third metal.

6. 10. The tandem OLED device of claim 1, wherein the alloy film is a bilayer comprising a first layer containing two different metals and a second layer containing a third metal.

7. 5. The tandem OLED device of claim 4, wherein the first metal is a noble metal.

8. 5. The tandem OLED device of claim 4, wherein the second metal is an alkaline earth metal or a rare earth metal.

9. 6. The tandem OLED device of claim 5, wherein the third metal is an alkali metal halide or an organic compound containing an alkali metal.

10. 6. The tandem OLED device of claim 5, wherein each of the first metal, the second metal, and the third metal is co-deposited by thermal evaporation to create the alloy film.

11. 2. The tandem OLED device according to claim 1, wherein the thickness of the alloy film is 1 nm to 8 nm.

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