TWI849252B - Electroluminescence wire - Google Patents

Abstract

The present disclosure provides an electroluminescent wire including a center conductive wire, a hole transport layer, a light emitting layer, an electron transport layer, and a transparent conductive layer. The hole transport layer wraps the center conductive wire. The light emitting layer wraps the hole transport layer, and includes a hole host material represented by formula (1), , an electron host material represented by formula (2), , and a luminescent material represented by formula (3),

Description

Electroluminescence

The present disclosure relates to an electroluminescent light emitting device, and more particularly to an electroluminescent light emitting device having a hole host material and an electron host material.

In recent years, electroluminescent light sources have been widely used in various display lighting devices. In existing electroluminescent elements, high voltage is usually required to achieve high luminous brightness. However, there are concerns and risks in the safety of using high-voltage electroluminescent elements.

In order to improve the luminous brightness or light output, existing linear electroluminescent elements often configure additional functional layers on their central electrodes, such as a strong reflective layer, an inner electron emission layer or an outer electron emission layer. However, this method complicates the manufacturing process, resulting in increased costs and line diameter, thereby limiting the application range of linear electroluminescent elements. Therefore, there is an urgent need for a novel electroluminescent element to solve the above problems.

The present disclosure provides an electroluminescent line having a hole host material and an electron host material doped in an electroluminescent layer, so as to enhance the overall luminous brightness of the electroluminescent line.

According to some embodiments of the present disclosure, the electroluminescent line of the present disclosure includes a central conductor, a hole transport layer, an electroluminescent layer, an electron transport layer, and a transparent conductive layer. The hole transport layer surrounds the central conductor. The electroluminescent layer surrounds the hole transport layer, wherein the electroluminescent layer includes a hole host material represented by formula (1), The electronic host material represented by formula (1) and formula (2), Formula (2), and the luminescent material represented by formula (3), Formula (3), and when calculated based on the total weight of the electroluminescent layer, the content of the hole host material is between 46.5wt% and 49.5wt%, the content of the electron host material is between 46.5wt% and 49.5wt%, and the content of the luminescent material is between 1.0wt% and 7.0wt%. The electron transport layer surrounds the luminescent layer. The transparent conductive layer surrounds the electron transport layer.

In some embodiments, the dipole moment formed by the hole host material and the electron host material is between 4.6D and 5.0D.

In some embodiments, the thickness of the electroluminescent layer is between 20 nm and 40 nm.

In some embodiments, the thickness of the hole transport layer is between 40 nm and 60 nm.

In some embodiments, the highest occupied molecular orbital (HOMO) of the hole transport layer is between -5.1 eV and -5.9 eV.

In some embodiments, the thickness of the electron transport layer is between 30 nm and 50 nm.

In some embodiments, the lowest unoccupied molecular orbital (LUMO) of the electron transport layer is between -4.2 eV and -2.7 eV.

In some embodiments, the diameter of the center conductor is between 150 μm and 170 μm.

In some embodiments, the work function of the center conductor is between -4.4 eV and -5.6 eV.

In some embodiments, the electroluminescent line further includes a transparent protective layer surrounding the transparent conductive layer.

According to the above-mentioned embodiments of the present disclosure, the electroluminescent line has a hole host material, an electron host material and a luminescent material doped in the electroluminescent layer. By matching the hole host material and the electron host material, the arrangement direction of the luminescent material in the electroluminescent layer can be changed to increase the light extraction rate of the luminescent material, thereby increasing the overall luminescent brightness of the electroluminescent line. In addition, by adjusting the respective contents of the hole host material, the electron host material and the luminescent material, it is further helpful to further increase the overall luminescent brightness of the electroluminescent line.

The following will disclose multiple embodiments of the present disclosure with drawings. For the purpose of clarity, many practical details will be described together in the following description. However, it should be understood that these practical details should not be used to limit the present disclosure. In other words, in some embodiments of the present disclosure, these practical details are not necessary and therefore should not be used to limit the present disclosure. In addition, in order to simplify the drawings, some commonly used structures and components will be depicted in the drawings in a simple schematic manner. In addition, in order to facilitate the reader's viewing, the size of each component in the drawings is not drawn according to the actual scale.

The present disclosure provides an electroluminescent line having a hole host material and an electron host material doped in an electroluminescent layer. By matching the hole host material and the electron host material, the arrangement direction of the luminescent material in the electroluminescent layer can be changed to increase the light extraction rate of the luminescent material, thereby increasing the overall luminous brightness of the electroluminescent line.

FIG. 1 is a three-dimensional exploded schematic diagram of an electroluminescent line 100 according to some embodiments of the present disclosure. FIG. 2 is a cross-sectional schematic diagram of the electroluminescent line 100 along the line segment a-a' of FIG. 1. Please refer to FIG. 1 and FIG. 2 simultaneously. The electroluminescent line 100 includes a central conductive line 110, a hole transport layer 120, an electroluminescent layer 130, an electron transport layer 140, and a transparent conductive layer 150. The transparent conductive layer 150 surrounds the electron transport layer 140, the electron transport layer 140 surrounds the electroluminescent layer 130, the electroluminescent layer 130 surrounds the hole transport layer 120, and the hole transport layer 120 surrounds the central conductive line 110. It should be specially noted that the “enclosing a component” mentioned in this article refers to “enclosing and surrounding the extended surface of the component”, which will not be repeated in the following.

The center conductor 110 is configured to serve as a center electrode of the electroluminescent line 100. In some embodiments, the material of the center conductor 110 may include a conductive metal, such as copper, gold, silver, nickel, platinum, palladium, or any combination thereof. In other embodiments, the material of the center conductor 110 may include a conductive metal oxide, such as indium tin oxide. By selecting the above materials, the center conductor 110 may have a work function within a specific range, thereby improving the conductivity of the center conductor 110. In some embodiments, the work function of the center conductor 110 may be, for example, between -4.4 eV and -5.6 eV.

The hole transport layer 120, the electroluminescent layer 130, and the electron transport layer 140 are sequentially arranged on the central conductive line 110 to perform electroluminescence. In the cross-sectional view of the electroluminescent line 100, as shown in FIG. 2, the hole transport layer 120 surrounds the central conductive line 110, the electroluminescent layer 130 surrounds the hole transport layer 120, and the electron transport layer 140 surrounds the electroluminescent layer 130.

The electroluminescent layer 130 includes a hole host material 132, an electron host material 134, and a luminescent material 136. The hole host material 132 is represented by formula (1): Formula (1), referred to as CBP; the electronic host material 134 is represented by formula (2), Formula (2), referred to as B3PYMPM; and the luminescent material 136 is represented by formula (3), Formula (3), referred to as Irppy ₂ acac. By mixing the hole host material 132 and the electron host material 134 and doping them in the electroluminescent layer 130, a certain degree of dipole moment can be formed in the electroluminescent layer 130, so that the luminescent material 136 is induced by the dipole moment to change the orientation of its molecules, thereby improving the light extraction rate of the luminescent material 136, thereby improving the luminous brightness of the electroluminescent line 100. In detail, the mixed hole host material 132 and the electron host material 134 may form a dipole moment, and the direction of the dipole moment may be, for example, from the charge center of the hole host material 132 to the charge center of the electron host material 134, and the luminescent material 136 may be induced to be arranged along the direction of the dipole moment, thereby improving the light extraction rate of the luminescent material 136. Specifically, the arrangement direction of the luminescent material 136 may be parallel to the direction of the dipole moment. In some embodiments, the dipole moment formed by the hole host material 132 and the electron host material 134 may be between 4.6D and 5.0D, thereby providing sufficient driving force to induce the luminescent material 136 to rearrange. Specifically, when the dipole moment formed by the hole host material 132 and the electron host material 134 is less than 4.6D, the dipole moment formed by the two may not be able to fully induce each luminescent material 136 to be arranged in the same direction, resulting in too low light extraction rate of the luminescent material 136, thereby affecting the overall luminescence brightness of the electroluminescent line 100.

When the total weight of the electroluminescent layer 130 is calculated, the content of the hole host material 132 is between 46.5wt% and 49.5wt%, the content of the electron host material 134 is between 46.5wt% and 49.5wt%, and the content of the luminescent material 136 is between 1.0wt% and 7.0wt%. In other words, in the electroluminescent layer 130, the total proportion of the hole host material 132 and the electron host material 134 is larger than the proportion of the luminescent material 136. In this way, it can be ensured that the dipole moment formed by the hole host material 132 and the electron host material 134 provides sufficient driving force to induce the luminescent material 136 to rearrange. Specifically, by adding a relatively small amount (relative to the total content of the hole host material 132 and the electron host material 134) of the luminescent material 136, it is ensured that each luminescent material 136 receives a sufficiently large dipole moment to be well arranged. On the other hand, by adjusting the content of the hole host material 132 and the electron host material 134 to be close to the same, the direction of the formed dipole moment can be better controlled to promote the regular arrangement of the luminescent materials 136.

The hole transport layer 120 and the electron transport layer 140 are disposed on opposite surfaces of the electroluminescent layer 130. More specifically, the electron transport layer 140 surrounds the electroluminescent layer 130, and the electroluminescent layer 130 surrounds the hole transport layer 120. In some embodiments, the highest occupied molecular orbital of the hole transport layer 120 is between -5.1 eV and -5.9 eV, and the lowest unoccupied molecular orbital of the electron transport layer 140 is between -4.2 eV and -2.7 eV. The hole transport layer 120 and the electron transport layer 140 are configured to respectively reduce the energy barriers of hole and electron injection into the electroluminescent layer 130, so as to increase the charge transfer speed in the electroluminescent line 100. Specifically, through the mutual matching between the highest occupied molecular orbital domain of the hole transport layer 120 and the lowest unoccupied molecular orbital domain of the electron transport layer 140, a step-by-step charge injection method can be provided, which can reduce the energy gap between each layer and simultaneously increase the capacitance value of the electroluminescent layer 130, thereby increasing the luminous brightness of the electroluminescent layer 130.

In some embodiments, the material of the hole transport layer 120 may include p-type metal oxide, p-type organic polymer, p-type organic compound, p-type organic metal compound, or any combination thereof. For example, the p-type metal oxide may be molybdenum trioxide (MoO ₃ ), tungsten trioxide (WO ₃ ), or any combination thereof; the p-type organic polymer may be PEDOT:PSS; the p-type organic compound and the p-type organic metal compound may be NPB, TCTA, TAPC, dppf, CuPc, or any combination thereof. By selecting the above materials, the highest occupied molecular orbital domain of the hole transport layer 120 may be within an appropriate range.

In some embodiments, the material of the electron transport layer 140 may include an n-type organometallic compound, an n-type organic compound, or any combination thereof. For example, the n-type organometallic compound may be rhenium trioxide (ReO ₃ ), zinc oxide (ZnO), Liq, RbCO ₃ , or any combination thereof; the n-type organic compound may be Alq ₃ , TPBi, B3PYMPM, TmPyPB, POT ₂ T, or any combination thereof. By selecting the above materials, the lowest unoccupied molecular orbital of the electron transport layer 140 may be within a suitable range.

The transparent conductive layer 150 surrounds the electron transport layer 140. In some embodiments, the transparent conductive layer 150 may include a plurality of silver nanowires, wherein the line diameter of each silver nanowire may be between 50 nm and 100 nm, and the line length thereof may be between 5 μm and 50 μm. In some embodiments, silver nanowires having a content of about 5 wt% may be uniformly mixed in ethanol (i.e., the content of the silver nanowires is about 5 wt% based on the total weight of the two) to form a silver nanowire suspension, and the silver nanowire suspension is disposed to surround the electron transport layer 140 by a wet coating method, thereby forming the transparent conductive layer 150.

In some embodiments, the electroluminescent line 100 may further include a transparent protective layer 160. The transparent protective layer 160 is configured to uniformly surround and protect the transparent conductive layer 150, thereby preventing the transparent conductive layer 150 and the electroluminescent line 100 from being damaged during use. In some embodiments, the material of the transparent protective layer 160 may include ethylene vinyl acetate (EVA), polyvinyl acetate (PVAC), or any combination thereof.

The electroluminescent line 100 disclosed herein may have a specific thickness and flexibility, making it suitable for application in various types of electroluminescent elements. In some embodiments, the diameter D1 (i.e., line diameter D1) of the electroluminescent line 100 may be between 190 μm and 260 μm, and its bending radius may be between 3.5 mm and 4.5 mm, so that the electroluminescent line 100 can be applied to products such as wires, fabrics, or advertising box backlights. The diameter D1 of the electroluminescent line 100 may be controlled, for example, by the diameter or thickness of each layer therein. In some embodiments, the diameter D2 of the center conductor 110 may be between 150 μm and 170 μm, so that it has good flexibility. In some embodiments, the thickness H1 of the hole transport layer 120 may be between 40 nm and 60 nm, preferably 50 nm, and the thickness H3 of the electron transport layer 140 may be between 30 nm and 50 nm, preferably 40 nm. Since the hole transport layer 120 and the electron transport layer 140 each have a small thickness, the electroluminescent line 100 can increase the transfer speed of the charge in the electroluminescent line 100 without significantly increasing its overall thickness, thereby increasing the overall luminous brightness of the electroluminescent line 100. In some embodiments, the thickness H2 of the electroluminescent layer 130 may be between 20 nm and 40 nm, preferably 30 nm, thereby reducing the energy loss of light during transmission. In some embodiments, the thickness H4 of the transparent conductive layer 150 may be between 30 μm and 40 μm to provide good electron transmittance, thereby improving the overall luminous efficiency of the electroluminescent line 100. In some embodiments, the thickness H5 of the transparent protective layer 160 may be between 40 μm and 50 μm to provide good protection.

In some embodiments, the manufacturing method of the electroluminescent line 100 may include sequentially forming a hole transport layer 120, an electroluminescent layer 130, an electron transport layer 140, a transparent conductive layer 150, and a transparent protective layer 160 by wet or dry coating, and configuring the above layers in a wire-drawing manner to wrap around the central conductor 110. The electroluminescent line 100 and the layers therein formed by the above method may have a suitable and uniform diameter or thickness, so that the layers in the electroluminescent line 100 can uniformly wrap around the central conductor 110 with a suitable thickness, thereby improving the luminous uniformity of the electroluminescent line 100 and increasing the application range of the electroluminescent line 100.

In the following description, the brightness of the electroluminescent wires of each comparative example and each embodiment will be tested. The manufacturing method of the electroluminescent wire of each embodiment refers to the manufacturing method of the electroluminescent wire mentioned above, and will not be repeated here. In the electroluminescent wires of each comparative example and each embodiment, the central conductor has a thickness of 160μm, and its material is indium tin oxide; the hole transport layer has a thickness of 50 nm; the electron transport layer has a thickness of 40 nm; the electroluminescent layer has a thickness of 30 nm; the transparent conductive layer has a thickness of 34μm, and its material includes the above-mentioned silver nanowires; and the material of the transparent protective layer is polyurethane resin (purchased from Dick Technology Co., Ltd., product model ITK-5527). In addition, each experimental example uses a direct current of 25 volts for brightness testing and uses a colorimeter (purchased from TOPCON, product model BM-7AC) for brightness measurement. > Experimental Example 1: Test of the influence of hole host material and electron host material on the luminous brightness of electroluminescent line>

In this experimental example, the electroluminescent lines of each embodiment have both a hole host material and an electron host material; the electroluminescent lines of comparative examples 1 to 4 do not have any electron host material; and the electroluminescent lines of comparative examples 5 to 7 do not have any hole host material. The types and contents of the hole host material, the electron host material and the luminescent material in the electroluminescent lines of each comparative example and each embodiment, as well as the brightness test results of the electroluminescent lines are shown in Table 1. It should be particularly noted that the electron host material used in the electroluminescent lines of comparative examples 5 to 7 can be expressed by formula (4), Formula (4), abbreviated as CBPB3PYPM.

Table I Hole host material (content) Electronic main material (content) Luminescent material (content) Luminance(cd/m ² ) Embodiment 1 CBP (49.5%) B3PYMPM (49.5%) Irppy ₂ acac (1%) 932 Embodiment 2 CBP (48.5%) B3PYMPM (48.5%) Irppy ₂ acac (3%) 1042 Embodiment 3 CBP (47.5%) B3PYMPM (47.5%) Irppy ₂ acac (5%) 1189 Embodiment 4 CBP (46.5%) B3PYMPM (46.5%) Irppy ₂ acac (7%) 1119 Comparison Example 1 CBP (99%) No Additive Irppy ₂ acac (1%) 452 Comparison Example 2 CBP (97%) No Additive Irppy ₂ acac (3%) 621 Comparison Example 3 CBP (95%) No Additive Irppy ₂ acac (5%) 853 Comparison Example 4 CBP (93%) No Additive Irppy ₂ acac (7%) 732 Comparison Example 5 No Additive CBPB3PYPM (99%) Irppy ₂ acac (1%) 648 Comparative Example 6 No Additive CBPB3PYPM (97%) Irppy ₂ acac (3%) 862 Comparison Example 7 No Additive CBPB3PYPM (93%) Irppy ₂ acac (7%) 904

It can be seen from the experimental results that the luminescence brightness of the electroluminescent line of each embodiment is greater than the luminescence brightness of the electroluminescent line of each comparative example, that is, the combination of the hole host material and the electron host material does help to improve the luminescence brightness of the electroluminescent line. > Experimental Example 2: Test on the influence of different contents of hole host material and electron host material on the luminescence brightness of the electroluminescent line>

In this experimental example, the electroluminescent lines of each embodiment have different contents of hole host materials and electron host materials, wherein the hole host material is CBP, the electron host material is B3PYMPM, and the luminescent material is Irppy ₂ acac. The contents of the hole host material, the electron host material and the luminescent material in the electroluminescent lines of each embodiment and the brightness test results of the electroluminescent lines are shown in Table 2.

Table II Hole host material content Electronic main material content Luminescent material content Luminance(cd/m ² ) Embodiment 5 76% 19% 5% 892 Embodiment 6 57% 38% 5% 967 Embodiment 1 47.5% 47.5% 5% 1189 Embodiment 7 38% 57% 5% 1092 Embodiment 8 19% 76% 5% 1002

It can be seen from the experimental results that when the content of the hole host material and the content of the electron host material are close to the same, the electroluminescent line has a greater luminous brightness. As mentioned above, by adjusting the content of the hole host material and the content of the electron host material to be close to the same, the direction of the formed dipole moment can be better controlled to promote the regular arrangement of the luminescent material, thereby improving the overall luminous brightness of the electroluminescent line. > Experimental Example 3: Test of the influence of different types of hole host materials and electron host materials on the luminous brightness of electroluminescent lines>

In this experimental example, the electroluminescent lines of each embodiment have different types of hole host materials and electron host materials, wherein the content of each of the hole host materials and the electron host materials is 47.5%; the luminescent material is Irppy ₂ acac, and its content is 5%. The types of hole host materials and electron host materials in the electroluminescent lines of each embodiment and the brightness test results of the electroluminescent lines are shown in Table 3.

Table 3 Hole Host Material Electronic main materials Luminance(cd/m ² ) Embodiment 3 CBP B3PYMPM 1189 Embodiment 9 mCP B3PYMPM 973 Embodiment 10 TAPC B3PYMPM 1321 Embodiment 11 NPB B3PYMPM 1115 Embodiment 12 TAPC PcqI 1321 Embodiment 13 TAPC POT ₂ T 1264

Please refer to Table 1 and Table 3 at the same time. It can be seen from the experimental results that the combination of various types of hole host materials and electron host materials can make the electroluminescent lines of each embodiment have greater luminous brightness than the electroluminescent lines of each comparative example. In other words, the combination of hole host materials and electron host materials does help to improve the luminous brightness of electroluminescent lines.

According to the above-mentioned embodiments of the present disclosure, the electroluminescent line has a hole host material, an electron host material and a luminescent material doped in the electroluminescent layer. By matching the hole host material and the electron host material, the arrangement direction of the luminescent material in the electroluminescent layer can be changed to increase the light extraction rate of the luminescent material, thereby increasing the overall luminescent brightness of the electroluminescent line. In addition, by adjusting the respective contents of the hole host material, the electron host material and the luminescent material, it is further helpful to further increase the overall luminescent brightness of the electroluminescent line.

Although the present disclosure has been disclosed in the above implementation form, it is not intended to limit the present disclosure. Anyone skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be determined by the scope of the attached patent application.

100: electroluminescent line 110: central conductor 120: hole transport layer 130: electroluminescent layer 132: hole host material 134: electron host material 136: luminescent material 140: electron transport layer 150: transparent conductive layer 160: transparent protective layer H1~H5: thickness D1~D2: diameter a-a': line segment

In order to make the above and other purposes, features, advantages and embodiments of the present disclosure more clearly understandable, the attached drawings are described as follows: FIG. 1 is a three-dimensional exploded schematic diagram of an electroluminescent line according to some embodiments of the present disclosure; and FIG. 2 is a cross-sectional schematic diagram of the electroluminescent line along the line segment a-a' of FIG. 1 .

Domestic storage information (please note in the order of storage institution, date, and number) None Foreign storage information (please note in the order of storage country, institution, date, and number) None

110: Center wire

120: Hole transport layer

130: Electroluminescent layer

132:Hole host material

134: Electronic main materials

136: Luminescent material

140:Electron transmission layer

150: Transparent conductive layer

160: Transparent protective layer

H1~H5:Thickness

D1~D2: Diameter

a-a': line segment

Claims (10)

An electroluminescent line comprises: a central conductor; a hole transport layer surrounding the central conductor; an electroluminescent layer surrounding the hole transport layer, wherein the electroluminescent layer comprises: a hole host material represented by formula (1),

The electronic host material represented by formula (2) is:

; and a luminescent material represented by formula (3),

, wherein, based on the total weight of the electroluminescent layer, the content of the hole host material is between 46.5wt% and 47.5wt%, the content of the electron host material is between 46.5wt% and 47.5wt%, and the content of the luminescent material is between 5.0wt% and 7.0wt%; an electron transport layer surrounding the luminescent layer; and a transparent conductive layer surrounding the electron transport layer. The electroluminescent line as described in claim 1, wherein the dipole moment formed by the hole host material and the electron host material is between 4.6D and 5.0D. The electroluminescent line as described in claim 1, wherein the thickness of the electroluminescent layer is between 20nm and 40nm. The electroluminescent line as described in claim 1, wherein the thickness of the hole transport layer is between 40nm and 60nm. An electroluminescent line as described in claim 1, wherein the highest occupied molecular orbital (HOMO) of the hole transport layer is between -5.1eV and -5.9eV. The electroluminescent line as described in claim 1, wherein the thickness of the electron transport layer is between 30nm and 50nm. An electroluminescent line as described in claim 1, wherein the lowest unoccupied molecular orbital (LUMO) of the electron transport layer is between -4.2eV and -2.7eV. An electroluminescent line as described in claim 1, wherein the diameter of the central conductor is between 150 μm and 170 μm. An electroluminescent line as described in claim 1, wherein the work function of the central conductor is between -4.4eV and -5.6eV. The electroluminescent line as described in claim 1 further includes a transparent protective layer surrounding the transparent conductive layer.

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