A transparent electrode for deep ultraviolet LED and preparation method thereof

Abstract

The invention relates to a transparent electrode for a deep ultraviolet LED and a preparation method thereof. The method comprises the following steps: depositing a silver film on a deep ultraviolet LED epitaxial structure; spin-coating a carbon nanotube suspension on the silver film; performing a first rapid annealing in an inert atmosphere after drying to form a silver / carbon nanotube composite structure consisting of carbon nanotubes and silver nanospheres attached to the carbon nanotube walls; depositing an aluminum oxide film layer on the silver / carbon nanotube composite structure; and performing a second rapid annealing in an inert atmosphere to form a transparent electrode of the silver / carbon nanotube / aluminum oxide composite structure. The transparent electrode has strong bonding strength and mechanical strength, and has good light transmittance and electrical conductivity.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectric materials, and in particular to a transparent electrode for a deep ultraviolet LED and a preparation method thereof. Background Art

[0002] As a new type of optoelectronic device, deep ultraviolet LEDs require electrode materials with high transmittance and conductivity to improve photoelectric conversion efficiency. Traditional transparent electrode materials, such as indium tin oxide (ITO), suffer from brittleness and poor deep ultraviolet performance, necessitating the development of alternatives. Carbon nanotubes, due to their high transmittance, conductivity, and flexibility, are considered an ideal transparent electrode alternative.

[0003] However, the use of carbon nanotubes also has certain problems. When carbon nanotubes are used directly as transparent electrodes, there is a problem of insufficient bonding strength with the LED epitaxial structure, resulting in a loss of related properties such as conductivity. When carbon nanotubes are doped with metals or oxides to improve overall performance, chemical plating or direct deposition methods are often used to deposit metal on the surface of the carbon nanotubes to form a composite structure. In this case, the surface of the carbon nanotubes is prone to metal accumulation, resulting in reduced light transmittance. Currently, there is a need for a method to strengthen the bonding strength between carbon nanotubes and deep ultraviolet LED epitaxial structures without affecting light transmittance and conductivity. Summary of the Invention

[0004] In response to the technical problems existing in the prior art, the primary purpose of the present invention is to provide a transparent electrode for deep ultraviolet LEDs and a preparation method thereof. While ensuring transmittance and conductivity, the bonding strength between the carbon nanotubes and the chip and their conductivity are enhanced, and an aluminum oxide film is added to the top layer to ensure bonding strength without affecting conductivity and transmittance, thereby improving the overall performance of the transparent electrode.

[0005] In one aspect, the present invention provides a method for preparing a transparent electrode for a deep ultraviolet LED, comprising the following steps:

[0006] Depositing a thin silver film on the deep ultraviolet LED epitaxial structure;

[0007] Spin coating a carbon nanotube suspension on the silver film;

[0008] After drying, a first rapid annealing is performed in an inert atmosphere to form a silver / carbon nanotube composite structure consisting of carbon nanotubes and silver nanospheres attached to the carbon nanotube walls on the deep ultraviolet LED epitaxial structure;

[0009] depositing an aluminum oxide thin film layer on the silver / carbon nanotube composite structure;

[0010] A second rapid annealing is performed in an inert atmosphere to form the transparent electrode with a silver / carbon nanotube / aluminum oxide composite structure.

[0011] Furthermore, the thickness of the silver film is 2 to 10 nm.

[0012] Furthermore, the carbon nanotube suspension is formed by mixing carbon nanotubes, a solvent and a surfactant and then ultrasonically treating the mixture. The surfactant is sodium dodecylbenzenesulfonate or sodium dodecyl sulfate. The mass proportion of carbon nanotubes in the suspension is 1% to 20%. The ultrasonic treatment time is 30 to 120 minutes.

[0013] Furthermore, in the spin coating step, the spin coating speed is 1000 to 4000 rpm, and the spin coating time is 1 to 10 minutes.

[0014] Furthermore, the thickness of the aluminum oxide film layer is 10 to 100 nm.

[0015] Furthermore, in the first annealing, annealing is performed in a nitrogen atmosphere, the annealing temperature is 300-700° C., and the annealing time is 30s-120s;

[0016] In the second annealing, annealing is performed in a nitrogen atmosphere, the annealing temperature is 300-700° C., and the annealing time is 30s-120s.

[0017] Another aspect of the present invention provides a transparent electrode for a deep ultraviolet LED. The transparent electrode is arranged on a deep ultraviolet LED epitaxial structure. The transparent electrode is a silver / carbon nanotube / aluminum oxide composite structure. The silver / carbon nanotube / aluminum oxide composite structure is composed of a silver / carbon nanotube composite structure and an aluminum oxide film layer covering the silver / carbon nanotube composite structure. The silver / carbon nanotube composite structure is composed of a carbon nanotube layer and silver nanospheres attached to the carbon nanotube wall.

[0018] Furthermore, the thickness of the aluminum oxide film layer is 10 to 100 nm.

[0019] Furthermore, the particle size of the silver nanospheres is 2 to 10 nm.

[0020] Furthermore, the carbon nanotubes are at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes; and the carbon nanotube layer is a single layer to three layers.

[0021] The silver / carbon nanotube composite structure is obtained by thermally evaporating a silver layer on a deep ultraviolet LED epitaxial structure, then spin-coating a carbon nanotube layer on the silver layer, and finally undergoing an annealing process.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] The present invention is based on the good transmittance of carbon nanotubes and aluminum oxide to deep ultraviolet light. By arranging silver nanospheres on the carbon nanotube walls to form a silver / carbon nanotube composite structure, the bonding strength between the carbon nanotube layer and the deep ultraviolet LED epitaxial structure is improved while ensuring light transmittance and excellent electrical conductivity. An aluminum oxide film layer is arranged on the silver / carbon nanotube composite structure to form a transparent electrode of the silver / carbon nanotube / aluminum oxide composite structure, which protects the carbon nanotubes and further enhances the bonding strength and mechanical strength of the transparent electrode, thereby obtaining a deep ultraviolet transparent electrode with good light transmittance and electrical conductivity.

[0024] The present invention avoids the problem of uneven metal accumulation caused by methods such as chemical electroplating. The preparation method of the present invention deposits a silver film on a deep ultraviolet LED epitaxial structure, then spin-coats carbon nanotubes on the silver film, utilizes the annealing spheroidization property of silver, and forms silver nanospheres attached to the carbon nanotube walls after rapid annealing, forming a silver / carbon nanotube composite structure. This improves the bonding strength between the carbon nanotube layer and the deep ultraviolet LED epitaxial structure while ensuring light transmittance and excellent electrical conductivity. Further, an aluminum oxide film is deposited on the silver / carbon nanotube composite structure to form a transparent electrode of the silver / carbon nanotube / aluminum oxide composite structure. The transparent electrode has high shape retention, good bonding strength and light transmittance, and excellent electrical conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 FIG. 1 is a schematic diagram of a carbon nanotube suspension after spin coating in one embodiment of the present invention.

[0026] Figure 2 Schematic diagram of a silver / carbon nanotube / aluminum oxide composite structure obtained in one embodiment of the present invention. DETAILED DESCRIPTION

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by ordinary technicians in this field without making creative work are all within the scope of protection of the present invention. The experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials, unless otherwise specified, can be obtained from public commercial channels.

[0028] Spatially relative terms such as "below," "beneath," "below," "above," "upper," etc. are used in this specification to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures.

[0029] In addition, the use of terms such as "first," "second," and the like to describe various elements, layers, regions, sections, and the like is not intended to be limiting. The use of "having," "containing," "including," and "comprising" are open-ended terms that indicate the presence of stated elements or features, but do not exclude additional elements or features, unless the context clearly indicates otherwise.

[0030] The present invention discloses a transparent electrode for a deep ultraviolet LED, formed on a deep ultraviolet LED epitaxial structure. The electrode comprises a silver / carbon nanotube composite structure formed on the deep ultraviolet LED epitaxial structure and an aluminum oxide thin film layer covering the silver / carbon nanotube composite structure. The aluminum oxide thin film layer has a thickness of 10 to 100 nm, a range that ensures the electrode's ultraviolet light transmittance. The aluminum oxide thin film layer is preferably deposited on the silver / carbon nanotube composite structure using a magnetron sputtering process, although other suitable deposition processes may also be used.

[0031] The silver / carbon nanotube composite structure consists of a carbon nanotube layer and silver nanospheres attached to the carbon nanotube wall. The carbon nanotube layer is a single-layer carbon nanotube, a double-layer carbon nanotube, or a triple-layer carbon nanotube, and the carbon nanotube is a single-walled carbon nanotube or a multi-walled carbon nanotube. The silver / carbon nanotube composite structure is obtained by thermally evaporating a silver layer on a deep ultraviolet LED epitaxial structure, then spin-coating a carbon nanotube layer on the silver layer, and finally undergoing an annealing process. The silver / carbon nanotube composite structure obtained by this process avoids the problems of uneven deposition and accumulation of silver electroplated on carbon nanotubes in the traditional process. This method utilizes the annealing ball aggregation characteristics of silver to form silver nanospheres on the carbon nanotube wall, thereby improving the bonding strength between the carbon nanotube and the chip while ensuring the light transmittance of the electrode.

[0032] The present invention also provides a method for preparing a transparent electrode of a deep ultraviolet LED, which comprises:

[0033] First, a silver film with a thickness of 2 to 10 nm is deposited on the deep ultraviolet LED epitaxial structure. The deposition process is, for example, a thermal evaporation process. In a preferred embodiment, the thickness of the silver film is 5 nm, 7 nm, or 10 nm. The interior of the evaporation chamber is in a vacuum state (approximately 6*10 -4 Pa), and the growth rate is about 0.3 nm / s.

[0034] Carbon nanotubes are mixed with a solvent and a surfactant to form a suspension. The carbon nanotubes may include single-walled carbon nanotubes and multi-walled carbon nanotubes. The surfactant is sodium dodecylbenzenesulfonate or sodium dodecyl sulfate; the surfactant is added to ensure high dispersibility. The solvent is an organic solvent or an inorganic solvent, such as anhydrous ethanol or acetone, or an inorganic solvent such as deionized water. After the carbon nanotubes, solvent, and surfactant are mixed, ultrasonic treatment is performed to obtain a suspension. The ultrasonic treatment time is 30 to 120 minutes, and the mass proportion of the carbon nanotubes in the prepared suspension is 1% to 20%. In a preferred embodiment, the mass proportion of the carbon nanotubes in the prepared suspension is 5%, the amount of sodium dodecylbenzenesulfonate added is 0.2 g / L, and the ultrasonic treatment time is 30 minutes to obtain a carbon nanotube suspension.

[0035] The carbon nanotube suspension is then spin-coated onto the silver film at a speed of 1000-4000 rpm for 1-10 minutes, followed by heat drying the epitaxial structure. In a preferred embodiment, the epitaxial structure is spin-coated onto the silver film at a speed of 2000 rpm for 2 minutes, followed by heating in an oven at 65°C for 15 minutes to obtain a dried deep ultraviolet LED epitaxial structure.

[0036] The dried deep ultraviolet LED epitaxial structure is placed in an annealing furnace and annealed in a nitrogen atmosphere at a nitrogen flow rate of 0.5 L / min, an annealing temperature of 300-700°C, and an annealing time of 30-120 seconds, preferably 30-90 seconds, to obtain a silver / carbon nanotube composite structure formed on the deep ultraviolet LED epitaxial structure, comprising carbon nanotubes and silver nanospheres attached to the carbon nanotube walls. In a preferred embodiment, the annealing temperature is 500°C and the annealing time is 1 minute.

[0037] Next, a 10-100 nm thick aluminum oxide film is deposited on the silver / carbon nanotube composite structure. In one embodiment, magnetron sputtering is used to deposit the aluminum oxide film. This process can produce high-quality films with high conformal properties, uniform thickness, and high coverage. The sputtering thickness is controlled by controlling the sputtering time to 22 minutes, 64 minutes, and 105 minutes, resulting in corresponding sputtering thicknesses of 20 nm, 60 nm, and 100 nm.

[0038] A second annealing step is then performed, placing the epitaxial structure, after depositing the aluminum oxide thin film layer, in an annealing furnace and annealing in a nitrogen atmosphere. During the annealing process, the nitrogen flow rate is 0.5 L / min, the annealing temperature is 300-700°C, and the annealing time is 30-120 seconds, preferably 30-90 seconds, to obtain a silver / carbon nanotube composite structure formed on the deep ultraviolet LED epitaxial structure, consisting of carbon nanotubes and silver nanospheres attached to the carbon nanotube walls. In a preferred embodiment, the annealing temperatures are 400°C, 500°C, or 600°C, and the annealing time is 1 minute.

[0039] The above preparation method finally obtained a silver / carbon nanotube / aluminum oxide transparent electrode with good light transmittance, improved conductivity and good bonding strength.

[0040] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a transparent electrode for a deep ultraviolet LED, characterized in that: The steps include: Depositing a thin silver film on the deep ultraviolet LED epitaxial structure; Spin coating a carbon nanotube suspension on the silver film; After drying, a first rapid annealing is performed in an inert atmosphere to form a silver / carbon nanotube composite structure consisting of carbon nanotubes and silver nanospheres attached to the carbon nanotube walls on the deep ultraviolet LED epitaxial structure; depositing an aluminum oxide thin film layer on the silver / carbon nanotube composite structure; A second rapid annealing is performed in an inert atmosphere to form the transparent electrode with a silver / carbon nanotube / aluminum oxide composite structure.

2. The preparation method according to claim 1, characterized in that The thickness of the silver film is 2-10 nm.

3. The preparation method according to claim 1 or 2, characterized in that The carbon nanotube suspension is prepared by mixing carbon nanotubes, a solvent and a surfactant and then ultrasonically preparing the mixture. The surfactant is sodium dodecylbenzenesulfonate or sodium dodecyl sulfate. The mass proportion of carbon nanotubes in the suspension is 1% to 20%. The ultrasonic time is 30 to 120 minutes.

4. The preparation method according to claim 3, characterized in that In the spin coating step, the spin coating speed is 1000-4000 rpm and the spin coating time is 1-10 min.

5. The preparation method according to claim 1, 2 or 4, characterized in that: The thickness of the aluminum oxide film layer is 10-100 nm.

6. The preparation method according to claim 5, characterized in that In the first rapid annealing, annealing is performed in a nitrogen atmosphere at a temperature of 300-700° C. for a time of 30s-120s; In the second rapid annealing, annealing is performed in a nitrogen atmosphere, the annealing temperature is 300-700° C., and the annealing time is 30s-120s.

7. A transparent electrode for a deep ultraviolet LED obtained by the preparation method according to any one of claims 1 to 6, wherein the transparent electrode is arranged on a deep ultraviolet LED epitaxial structure, characterized in that: The transparent electrode is a silver / carbon nanotube / aluminum oxide composite structure, which is composed of a silver / carbon nanotube composite structure and an aluminum oxide film layer covering the silver / carbon nanotube composite structure. The silver / carbon nanotube composite structure is composed of a carbon nanotube layer and silver nanospheres attached to the carbon nanotube wall.

8. The transparent electrode according to claim 7, wherein: The thickness of the aluminum oxide film layer is 10-100 nm.

9. The transparent electrode according to claim 7 or 8, characterized in that: The particle size of the silver nanospheres is 2-10 nm.

10. The transparent electrode according to claim 9, characterized in that The carbon nanotubes are at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes; and the carbon nanotube layer is a single layer to three layers.

Images