Graphene oxide-metal composite, light-emitting element comprising same, and manufacturing method thereof

Abstract

This graphene oxide-metal composite may comprise: a graphene oxide layer containing an oxygen functional group partially formed on the surface thereof; and one or more metal particles bonded to the surface of the graphene oxide layer. The metal particles form the composite by being bonded to a portion of the graphene oxide layer to which the oxygen functional group is not bonded, and may be made of a material in which the Fermi energy of the composite is located between the conduction band energy level and the valence band energy level of the composite. The graphene oxide-metal composite can be used as a light-emitting source of which the emission wavelength can be controlled according to the type of metal. This novel light-emitting source has excellent light-emitting efficiency and thus can be manufactured into a thin film and used as a flexible and transparent light-emitting element. In addition, the light-emitting source can be manufactured by a cheap and simple process and thus has the advantage of enabling cost reduction and mass production.

Description

Graphene oxide-metal composite, light-emitting device containing the same, and method for manufacturing the same

[0001] The embodiments relate to a graphene oxide-metal composite and a light-emitting device comprising the same, a method for manufacturing the light-emitting device, and a method for generating light using the graphene oxide-metal composite. More specifically, the embodiments relate to a technology for implementing a light-emitting source capable of controlling the band gap by hybrid orbitals by depositing metal nanoparticles on graphene oxide to manufacture a graphene oxide-metal composite.

[0002] A quantum dot (QD) light-emitting device is a device that utilizes the optical properties that arise from the quantized energy levels of electrons and holes by confining them to a dimension smaller than the Bohr radius of excitons. For example, Patent Publication No. 10-2021-0000074 discloses a quantum dot light-emitting diode, a method for manufacturing the same, and a quantum dot light-emitting display device, wherein the quantum dot light-emitting layer includes an organic material having a higher HOMO (Highest Occupied Molecular Orbital) level than the quantum dot and hole-assist layer materials.

[0003] Meanwhile, in a light-emitting device using quantum dots, it was confirmed through research that by forming cadmium selenide (CdSe) nanocrystals between an indium tin oxide (ITO) electrode and p-paraphenylene vinylene (PPV) and ITO / PPV, magnesium (Mg) layers, the light-emitting diode (LED) characteristics of the cadmium selenide (CdSe) quantum dots and the quantum size effect can be controlled according to the size of the nanocrystals, thereby controlling the wavelength of light.

[0004] Recently, active research has been conducted on crystal engineering, composition engineering, and changes in surface and ligand bonding properties to manufacture quantum dots that enable efficient radiative recombination of excitons, lower energy transfer between quantum dots, and efficient charge injection.

[0005] However, these conventional light-emitting sources utilizing quantum dots have the problem of being difficult to apply to light-emitting devices used in everyday life because they use quantum dots based on cadmium (Cd), which is classified as a hazardous substance. There is research using indium phosphide (InP) / zinc selenium sulfur alloy (ZnSeS) as quantum dots instead of cadmium (Cd), but this material has the disadvantage of having a lower luminous efficiency (Quantum Yield; QY) than cadmium (Cd). In addition, when providing a blue quantum dot light-emitting source, materials other than cadmium (Cd) have low luminous efficiency, making it difficult to apply them to real devices.

[0006] Also, unlike organic light-emitting diodes (OLEDs), which are thin-film light-emitting sources that can be uniformly formed over a large area through a deposition process, quantum dot light-emitting devices are difficult to utilize in large-area displays because they use aqueous solution-based spincoating or spray coating processes that make it difficult to control uniformity and impurities. Recently, research has been conducted on a quantum dot process through inkjet printing to solve this problem, but the materials used are cadmium selenide (CdSe) / cadmium sulfide (CdS) / zinc sulfide (ZnS), which has the disadvantage of containing cadmium (Cd), a hazardous substance.

[0007] According to one aspect of the present invention for solving the problems of the above-mentioned prior art, a graphene oxide-metal composite having good luminescence efficiency and a process with high uniformity is possible, so that it can be applied to a large-area light-emitting device, and can be used for implementing a new quantum dot light-emitting source that does not use hazardous substances such as cadmium (Cd), a light-emitting device including the same, a method for manufacturing the light-emitting device, and a method for generating light using the graphene oxide-metal composite can be provided.

[0008] A graphene oxide-metal composite according to one aspect of the present invention comprises: a graphene oxide layer including oxygen functional groups partially formed on a surface; and one or more metal particles bonded to the surface of the graphene oxide layer.

[0009] At this time, the metal particle is bonded to a portion of the graphene oxide layer where the oxygen functional group is not bonded to form the complex, and is made of a material in which the Fermi energy of the complex is located between the conduction band energy level and the valence band energy level of the complex. The metal particle can form a hybrid orbital by bonding with the graphene oxide.

[0010] In one embodiment, the surface of the graphene oxide layer includes a first region corresponding to a graphene quantum dot and a second region insulated by the oxygen functional group, and the fast particle includes a nanoparticle bonded to the graphene quantum dot on the first region.

[0011] In one embodiment, the metal particles are made of a metal material capable of forming hybrid orbitals by combining with the graphene quantum dots of the graphene oxide layer.

[0012] In one embodiment, the complex has a band gap corresponding to one of the infrared band, the visible band, or the ultraviolet band.

[0013] In one embodiment, the metal particles are comprised of one or more materials selected from the group consisting of platinum (Pt), chromium (Cr), molybdenum (Mo), palladium (Pd), tungsten (W), and alloys thereof.

[0014] In one embodiment, the size of the metal particles is 1 to 10 nm.

[0015] In one embodiment, the graphene oxide layer comprises one or more nanosheets.

[0016] A light-emitting device according to one aspect of the present invention comprises: a graphene oxide-metal composite according to the above-described embodiments; and a control unit configured to apply energy corresponding to a band gap of the composite to the composite for light generation by the composite.

[0017] In one embodiment, a light-emitting device has a frequency at which light is generated by the complex determined based on the type of the metal particles.

[0018] In one embodiment, the control unit comprises a light source configured to irradiate the complex with pumping light for excitation of the complex.

[0019] In one embodiment, the control unit comprises one or more electrodes electrically connected to the complex for applying a current to the complex.

[0020] A method for manufacturing a light-emitting device according to one aspect of the present invention comprises the steps of forming a graphene oxide layer including an oxygen functional group partially formed on a surface; and forming a graphene oxide-metal composite by bonding one or more metal particles on the surface of the graphene oxide layer.

[0021] In one embodiment, the step of forming the graphene oxide-metal composite comprises the step of depositing the metal particles on the graphene oxide layer by electron beam deposition.

[0022] In one embodiment, the step of forming the graphene oxide-metal composite comprises the step of spin-coating a solution in which the metal particles are dispersed onto the graphene oxide layer.

[0023] A method for manufacturing a light-emitting device according to one embodiment further includes, before the step of forming the graphene oxide layer, a step of forming an electrode layer for electron injection on the substrate.

[0024] A method for manufacturing a light-emitting device according to one embodiment further includes a step of forming a protective layer on the graphene oxide-metal composite.

[0025] In one embodiment, the protective layer is made of graphene oxide.

[0026] A method for manufacturing a light-emitting device according to one embodiment further includes a step of forming an electrode layer made of a conductive material on the protective layer.

[0027] A method for generating light using a graphene oxide-metal composite according to one aspect of the present invention comprises the steps of preparing a graphene oxide-metal composite including a graphene layer having an oxygen functional group partially bonded to a surface thereof, and one or more metal particles bonded to a portion of the graphene oxide layer where the oxygen functional group is not bonded; and the step of applying energy to the composite for excitation of the composite. At this time, the metal particle is made of a material in which the Fermi energy of the composite is located between a conduction band energy level and a valence band energy level of the composite.

[0028] In one embodiment, the step of applying energy comprises applying pumping light having a wavelength band below ultraviolet to the complex.

[0029] In one embodiment, the step of applying energy comprises applying a current to the complex via an electrode.

[0030] A graphene oxide-metal composite according to one aspect of the present invention can operate as a light-emitting source capable of controlling a band gap by means of hybrid orbitals formed when metal particles (e.g., nanoparticles) are deposited on graphene quantum dots that are not oxidized other than the oxidized portion by attaching an oxygen functional group to the graphene oxide.

[0031] A light-emitting device using a graphene oxide-metal composite according to one aspect of the present invention has the advantage of being able to be used as a light-emitting source even when manufactured into a thin film due to its excellent light-emitting efficiency, and thus can be utilized as a transparent display.

[0032] In addition, a light-emitting device using a graphene oxide-metal composite according to one aspect of the present invention has the advantage of being resistant to bending and warping, being able to be manufactured into a thin film, and being unconstrained by a substrate, so that it can be utilized as a light-emitting source for a flexible display.

[0033] In addition, a light-emitting device using a graphene oxide-metal composite according to one aspect of the present invention has the advantages of simple thin film formation and metal particle adsorption processes, low cost of materials and process facilities required for the process, and ease of manufacturing through a simple process, thereby reducing process costs and facilitating mass production.

[0034] In addition, a light-emitting device using a graphene oxide-metal composite according to one aspect of the present invention can form a graphene oxide-metal composite through a simple spin coating process, and metal particles can be adsorbed on a graphene oxide thin film through a physical vapor deposition (PVD) method, so it is easy to manufacture a uniform thin film light-emitting source over a large area, and thus has the advantage of being usable as a large-area display.

[0035] In addition, the light-emitting device using the graphene oxide-metal composite according to one aspect of the present invention uses graphene oxide that is not oxidized when exposed to the air and thus has excellent chemical and mechanical stability, so there is no need for formation of a separate supplementary layer to protect the light-emitting source, and thus has the advantage of reducing process costs compared to existing light-emitting sources.

[0036] Furthermore, a light-emitting device using a graphene oxide-metal composite according to one aspect of the present invention has the advantage of being advantageously utilized in a display light-emitting device, as the hybrid orbitals formed depending on the metal material are different, and thus the band gap can be controlled by selecting the type of metal, and a tunable light-emitting source having a desired emission wavelength band (e.g., from ultraviolet to infrared) can be produced due to high color purity.

[0037] FIG. 1 is a flowchart showing each step of a method for manufacturing a light-emitting device including a graphene oxide-metal composite according to one embodiment.

[0038] Figure 2 is a schematic diagram showing an insulating portion and a conductive portion formed by oxygen functional groups on a graphene oxide nanosheet.

[0039] FIG. 3 is a schematic diagram showing a form in which a graphene oxide-metal complex is formed on the graphene oxide nanosheet illustrated in FIG. 2 according to one embodiment.

[0040] FIGS. 4 and 5 are schematic diagrams for explaining changes in the luminescence wavelength band through the formation of a graphene oxide-metal composite according to one embodiment.

[0041] FIGS. 6A to 6C are graphs showing the emission wavelength modulation of the ultraviolet emission spectrum of graphene oxide generated from graphene oxide-metal composites according to embodiments.

[0042] Figures 7a to 7c are photographs showing the photoluminescence of graphene oxide samples and graphene oxide-chromium (Cr) nanoparticle composites according to examples.

[0043] FIGS. 8a and 8b are further graphs showing the emission wavelength modulation of the ultraviolet emission spectrum of graphene oxide generated from graphene oxide-metal composites according to embodiments.

[0044] Figures 9a and 9b are photographs showing the photoluminescence of graphene oxide samples and graphene oxide-platinum (Pt) nanoparticle composites according to examples.

[0045] Figure 10 is a graph showing the results of calculating the HOMO (Highest Occupied Molecular Orbital) - LUMO (Lowest Unoccupied Molecular Orbital) gap for the metal types constituting the graphene oxide-metal complex corresponding to various emission colors.

[0046] FIG. 11 is a schematic diagram of a structure used to analyze changes in optical properties according to the types of graphene quantum dots and transition metals in a graphene oxide-metal composite according to one embodiment.

[0047] Figures 12a to 12f are graphs showing the results of calculating absorption spectra according to the type of metal constituting the graphene oxide-metal composite according to the examples.

[0048] Fig. 13 is a flowchart showing each step of a light generation method using a light-emitting element according to one embodiment.

[0049] FIG. 14 is a conceptual diagram of a light-emitting device according to one embodiment that operates through ultraviolet pumping.

[0050] Figure 15 is a conceptual diagram of a light-emitting element according to another embodiment that operates as an electroluminescent element.

[0051] Figures 16 to 18 are cross-sectional views showing each step of a method for manufacturing a light-emitting element according to one embodiment.

[0052] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0053] In describing the embodiments of this specification, if a detailed description of a known configuration or function is judged to obscure the gist of the embodiments of this specification, a detailed description thereof will be omitted. In addition, parts of the drawings that are not related to the description of the embodiments of this specification have been omitted, and similar parts have been designated with similar drawing reference numerals.

[0054] In the embodiments of this specification, when a component is said to be "connected," "coupled," or "connected" to another component, this may include not only a direct connection, but also an indirect connection in which another component exists in between. Furthermore, when a component is said to "include" or "have" another component, unless otherwise specifically stated, this does not exclude the other component, but rather implies that the other component may be included.

[0055] In the embodiments of this specification, the terms first, second, etc. are used only for the purpose of distinguishing one component from another component, and do not limit the order or importance between components unless specifically stated otherwise. Therefore, within the scope of the embodiments of this specification, a first component in an embodiment may be referred to as a second component in another embodiment, and similarly, a second component in an embodiment may be referred to as a first component in another embodiment.

[0056] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0057] When a layer is referred to herein as being "on" another layer or substrate, it may be formed directly on the other layer or substrate, or a third layer may be interposed therebetween. Furthermore, directional expressions such as "upper," "upper," and "top" in this specification may be interpreted to mean "lower," "lower," and "bottom," depending on the reference. In other words, expressions of spatial direction should be understood as relative directions and should not be construed as limiting them to mean absolute directions.

[0058] FIG. 1 is a flowchart showing each step of a method for manufacturing a light-emitting device including a graphene oxide-metal composite according to one embodiment.

[0059] Referring to FIG. 1, in the method for manufacturing a light-emitting device according to the present embodiment, a graphene oxide layer is formed (S11), and a graphene oxide-metal complex can be formed by bonding metal particles (e.g., nanoparticles) to non-oxidized graphene quantum dots on the graphene oxide layer (S12).

[0060] The graphene oxide layer can take the form of a thin film. The graphene oxide used in this film form is preferably in the form of a flexible sheet, and may be composed of, for example, nanosheets.

[0061] Metal particles are bonded to graphene quantum dots on a graphene oxide layer by a method such as deposition, thereby forming a composite having a structure in which the metal particles are surrounded by graphene oxide layers. The graphene oxide-metal composite according to the embodiments has a stable form in which the graphene quantum dots on the graphene oxide layer and the metal particles are bonded. In addition, the metal particles are made of a material in which the Fermi energy of the composite is located between the conduction band energy level and the valence band energy level of the composite. In other words, the metal particles are made of a metal material that forms a composite having the aforementioned energy level characteristics by bonding with the graphene oxide to form a hybrid orbital.

[0062] That is, the metal particles may be made of a metal that can form hybrid orbitals through bonding with graphene quantum dots, and may be made of, for example, transition metals such as Group 6 elements such as chromium (Cr), molybdenum (Mo), and tungsten (W), or platinum (Pt) and palladium (Pd) belonging to the platinum group (Pt group). In another embodiment, the metal particles may be made of other types of transition metals such as those exemplified below.

[0063] - Group 3 elements such as yttrium (Y)

[0064] - Group 4 elements such as titanium (Ti), zirconium (Zr), and hafnium (Hf)

[0065] - Group 5 elements such as vanadium (V) and tantalum (Ta)

[0066] - Group 7 elements such as manganese (Mn)

[0067] - Group 8 elements such as iron (Fe) and ruthenium (Ru)

[0068] - Group 9 elements such as cobalt (Co) and iridium (Ir)

[0069] - Group 10 elements such as nickel (Ni)

[0070] - Group 11 elements such as copper (Cu), silver (Ag), and gold (Au)

[0071] - Group 12 elements such as zinc (Zn), cadmium (Cd), and mercury (Hg)

[0072] FIG. 2 is a schematic diagram showing an insulating portion and an insulating portion formed due to an oxygen functional group on a graphene oxide nanosheet, and FIG. 3 is a schematic diagram showing a form in which a graphene oxide-metal complex according to one embodiment is formed on the graphene oxide nanosheet illustrated in FIG. 2.

[0073] Referring to FIG. 2, the partially oxidized graphene oxide layer (1) includes a first region (11) corresponding to a conductive portion where the graphene quantum dot is exposed, and a second region (12) insulated by an oxygen functional group. The first region (11) has a form in which the graphene is isolated by the insulating portion and thus operates as a quantum dot. At this time, when a metal particle (20) is combined on the first region (11) by deposition or the like, a hybrid orbital of the graphene oxide and the metal is formed, thereby reducing the HOMO (Highest Occupied Molecular Orbital) - LUMO (Lowest Unoccupied Molecular Orbital) gap.

[0074] The graphene oxide-metal complex (1') formed in this way can control the quantum confinement effect of graphene quantum dots by the formation of hybrid orbitals, and can be pumped by applying ultraviolet irradiation or an electric field. The graphene oxide-metal complex (1') excited by ultraviolet pumping forms excitons and emits light corresponding to the gap between the conduction band and the valence band through recombination. In addition, the graphene oxide-metal complex (1') to which an electric field is applied emits light as electrons and holes recombine within the graphene oxide-metal complex (1').

[0075] For example, the graphene oxide-metal complex (1') can generate light (32) in the ultraviolet band when pumping light (31) is applied as shown in FIG. 4, or can generate light (42) in the visible light and / or infrared band when pumping light (41) is applied as shown in FIG. 5, depending on the size of the HOMO-LUMO gap.

[0076] Therefore, by selecting the metal material of the metal particles (20) bonded to the graphene oxide layer (1), a light-emitting device that generates light in a desired wavelength band can be implemented. According to the light-emitting device using the graphene oxide-metal composite (1'), desired light emission in the visible light, infrared, and ultraviolet wavelength bands can be obtained by using various metal materials, and thus, the material limitations of the conventional quantum dot light-emitting source technology can be overcome.

[0077] In the above graphene oxide-metal complex (1'), a red shift of the emission wavelength band occurs due to a reduction in the energy band gap through the bonding of the graphene oxide and the metal, so the graphene oxide layer (1) can be oxidized so that the diameter of the first region (11) corresponding to the graphene quantum dot is about several tens of nm. In this case, the band gap of the graphene quantum dot corresponds to a wavelength band of ultraviolet to blue, so that it can be advantageously utilized as a light-emitting element of a display device. In addition, the metal particle (20) bonded to the first region (11) can have a diameter of 1 to 10 nm so that the bonding with the graphene quantum dot occurs smoothly.

[0078] Referring back to FIG. 1, in a method for manufacturing a light-emitting device according to one embodiment, an additional graphene oxide layer (also referred to as a protective layer) may be formed on the graphene oxide-metal composite (S13). This additional graphene oxide layer may form a light-emitting layer by bonding with metal particles on the underlying graphene oxide-metal composite, while simultaneously protecting the graphene oxide-metal composite from external particles.

[0079] In one embodiment, the graphene oxide layer (e.g., graphene nanosheet) itself for forming the graphene oxide-metal composite may be composed of a single layer or multiple layers.

[0080] In addition, in one embodiment, an electrode layer for electroluminescence of the graphene oxide-metal composite may be further formed on the graphene oxide-metal composite (S14).

[0081] According to some aspects of the present invention, steps S11 to S14 illustrated in FIG. 1 are described in more detail as follows.

[0082] The graphene oxide layer can be formed as a layer on a substrate using graphene oxide in an aqueous solution form (S11). For example, the graphene oxide layer can be formed by depositing an aqueous graphene oxide solution on a substrate through spin coating and then drying it. At this time, the substrate (not shown) may be a hydrophilic substrate on which the graphene oxide in an aqueous solution can easily be formed into a thin film through spin coating. For example, the substrate may be a quartz substrate composed of hydrophilic silicon oxide (SiO2), but the substrate material is not limited to quartz, and substrates made of other materials can also be used.

[0083] The graphene oxide-metal composite can be formed by physical vapor deposition (PVD) or spin-coating metal particles in an aqueous solution onto the graphene oxide layer formed as described above (S12). PVD can be used to achieve highly uniform metal particle adsorption. The metal particles bonded to the graphene oxide layer form a graphene oxide-metal composite with a light-emitting function.

[0084] The step (S13) of forming an additional graphene oxide layer on the graphene oxide-metal composite can be performed by depositing graphene oxide in the form of an aqueous solution on the graphene oxide-metal composite through spin coating and drying it.

[0085] In one embodiment, by repeating the above-described steps S11 to S13 multiple times to form a laminated structure in which one or more layers of graphene oxide-metal composite are laminated on a substrate, a graphene oxide-metal composite light-emitting device having a multilayered thin film light-emitting layer with high luminous efficiency can be manufactured.

[0086] The electrode layer for injecting electrons into the graphene oxide-metal composite may be formed of a metal or other suitable conductive material (S14). In this case, the electrode layer may be formed of a commonly used electrode material such as a metal.

[0087] In one embodiment, the electrode layer may be formed of a material having a lower work function than graphene oxide to facilitate electron injection into the graphene oxide-metal composite. For example, the electrode layer may be formed of aluminum (Al).

[0088] In another embodiment, the electrode layer may be formed of a material having a higher work function than graphene oxide to facilitate the injection of holes into the graphene oxide-metal composite and their recombination with electrons in the graphene oxide-metal composite light-emitting layer. For example, the electrode layer may be formed of indium tin oxide (ITO), a transparent electrode capable of efficiently emitting light through its upper surface.

[0089] The graphene oxide-metal composite and light-emitting device manufactured according to the embodiments described above have the advantage of a simple manufacturing process and low manufacturing costs due to less materials required for manufacturing compared to conventional light-emitting sources.

[0090] Furthermore, in the graphene oxide-metal composite according to one embodiment, the oxygen functional groups located on the graphene oxide act as an insulator, preventing exciton conduction between quantum dots, thereby achieving high luminescence efficiency. Therefore, the graphene oxide-metal composite can be formed into a thin film and utilized in transparent light-emitting devices.

[0091] In addition, graphene oxide is a stable material that does not undergo oxidation or reduction even at room temperature and high temperatures (e.g., 180°C), and a light-emitting device using a graphene oxide-metal composite containing it has the advantage of reducing process costs because it does not require an additional protective layer for the light-emitting layer.

[0092] In the graphene oxide-metal composite according to the embodiments, the graphene oxide layer can be formed over a large area through spin coating using an aqueous solution, and the metal particles can be bonded to the graphene oxide layer in a very uniform size through a method such as PVD. Therefore, the graphene oxide-metal composite according to the embodiments is advantageous for implementing a large-area display light-emitting element with high uniformity.

[0093] In addition, graphene oxide has high mechanical stability and is resistant to bending, so light-emitting devices using graphene oxide-metal composites have the advantage of being usable as flexible light-emitting devices.

[0094] Hereinafter, a method for manufacturing a graphene oxide-metal composite and a light-emitting device according to some embodiments of the present invention will be described in more detail. However, the present invention is not limited to the following embodiments.

[0095]

[0096] Example 1

[0097] According to the first embodiment of the present invention, a graphene oxide-metal composite can be manufactured through physical vapor deposition (PVD).

[0098] In one embodiment, the substrate on which the graphene oxide-metal composite is to be formed may be surface treated for a predetermined period of time (e.g., 10 minutes) in a UV-Ozone treatment device to have a hydrophilic surface. However, this step may be omitted.

[0099] The present inventors formed a thin-film graphene oxide layer by rotating a substrate at 1500 rpm using a spincoater device and dropping 1 to 5 drops of an aqueous solution of graphene oxide having an insulating portion and a conductive portion, which was appropriately oxidized as shown in Fig. 2. The formed graphene oxide layer was dried at room temperature to 80 degrees Celsius for 5 minutes after deposition.

[0100] Next, chromium (Cr) nanoparticles were deposited on a graphene oxide layer having quantum dots isolated by an insulating portion using an electron beam evaporator. At this time, the deposition was stopped before the chromium (Cr) thin film was completely formed, so that chromium (Cr) particles in the form of nanoparticles were formed in a form combined with the graphene oxide, as illustrated in Fig. 3. Specifically, the metal was deposited to a thickness of 0.5 to 2.0 nm at a deposition rate of 0.1 to 0.5 A / s.

[0101] When a graphene oxide-metal composite is formed through a process according to the present embodiment, the graphene oxide-metal composite can be made to have luminescence characteristics in a relatively short wavelength band (e.g., ultraviolet band), as illustrated in FIG. 4.

[0102] Next, the graphene oxide-metal composite film was rotated at a speed of 1500 rpm, and 1 to 5 drops of graphene oxide in aqueous solution were dropped to form another graphene oxide layer positioned on the graphene oxide-metal composite film. The graphene oxide layer thus formed was dried at a temperature of room temperature to 80 degrees Celsius for 5 minutes.

[0103] In addition, by repeating the process of forming the above graphene oxide-metal composite in multiple steps, a graphene oxide-metal composite thin film having a light-emitting source of a layered structure can be formed.

[0104]

[0105] Experimental example according to the first embodiment

[0106] The present inventors measured the photoluminescence (PL) characteristics of the graphene oxide-metal composite manufactured according to the first embodiment of the present invention, and the results are shown in FIGS. 6a to 6c.

[0107] The experimental equipment used was JASCO's FP-8300, which uses a xenon (Xe) lamp with an output of 150 W. The excitation wavelength was 350 nm, and the light emission was measured in the range of 400 to 750 nm.

[0108] Figure 6a shows the ultraviolet emission spectrum of the graphene oxide layer, Figure 6b shows the ultraviolet emission spectrum of a composite in which chromium (Cr) nanoparticles of 1 nm in size are bonded to the graphene oxide layer, and Figure 6c shows the ultraviolet emission spectrum of a composite in which chromium (Cr) nanoparticles of 2 nm in size are bonded to the graphene oxide layer.

[0109] As shown, the pure graphene oxide layer has a broad peak around a wavelength of 525 nm, but the height of the peak changes as chromium (Cr) particles are adsorbed, confirming that the luminescence characteristics change. In addition, the thicker the chromium (Cr) is stacked, the larger the nanoparticles are bound to the graphene oxide. As the size of the chromium (Cr) nanoparticles increases, the hybrid orbital formation effect by the transition metal becomes stronger, confirming that the luminescence peak appears narrow and strong around 520 nm.

[0110] Through this, it was confirmed that it is possible to cause a change in luminescence characteristics through the adsorption of metal nanoparticles to the graphene oxide layer, and that it is possible to finely control the luminescence spectrum by controlling the width of the luminescence peak through a change in the size of the transition metal bonded to the graphene oxide.

[0111] Figures 7a to 7c are photographs showing the results of observing the luminescence of graphene oxide or graphene oxide-metal composites illustrated in Figures 6a to 6c using an ultraviolet laser having a wavelength of 355 nm, respectively. Through the photographs, a red shift in the luminescence wavelength band due to the adsorption of chromium (Cr) particles on graphene oxide can be clearly observed.

[0112]

[0113] Example 2

[0114] According to the second embodiment of the present invention, a graphene oxide-metal composite can be manufactured through spin coating.

[0115] In one embodiment, the substrate on which the graphene oxide-metal composite is to be formed may be surface treated to have a hydrophilic surface, which is the same as that described above in relation to the first embodiment, and thus a detailed description thereof is omitted.

[0116] The present inventors prepared an aqueous composition in which an aqueous solution containing evenly dispersed platinum (Pt) in the form of nanoparticles of a certain size (e.g., 3 nm) is mixed with isopropyl alcohol (IPA). In order to increase the adsorption ratio of platinum (Pt) through spin coating, the platinum (Pt) and IPA in the composition can be mixed in a ratio of 1:0.5. For example, a platinum (Pt) nanoparticle size of 3 nm and a concentration of 1,000 ppm can be mixed with 2.5 ml of IPA in 5 ml of the aqueous solution, and the bottle can be shaken to prepare an aqueous solution of platinum (Pt) nanoparticles mixed with IPA. However, the mixing ratio of platinum (Pt) and IPA is not limited thereto.

[0117] Next, a spin coater was used to rotate the substrate at 1500 rpm, and 1 to 5 drops of an aqueous solution of graphene oxide, which was appropriately oxidized and had insulating and conductive portions, were dropped as shown in Fig. 2 to form a thin-film graphene oxide layer. The formed graphene oxide layer was dried at room temperature to 80 degrees Celsius for 5 minutes after deposition.

[0118] Next, the graphene oxide film with quantum dots isolated by the insulating portion was rotated at 1500 rpm, and 1 to 5 drops of a platinum (Pt)-IPA aqueous solution were dropped to form a bond between the graphene quantum dots and platinum (Pt) nanoparticles present on the graphene oxide layer, as shown in Fig. 3.

[0119] Next, the graphene oxide-metal composite film was rotated at a speed of 1500 rpm, and 1 to 5 drops of graphene oxide in aqueous solution were dropped to form another graphene oxide layer positioned on the graphene oxide-metal composite film. The graphene oxide layer thus formed was dried at a temperature of room temperature to 80 degrees Celsius for 5 minutes.

[0120] In addition, by repeating the process of forming the above graphene oxide-metal composite in multiple steps, a graphene oxide-metal composite thin film having a light-emitting source of a layered structure can be formed.

[0121]

[0122] Experimental example according to the second embodiment

[0123] The present inventors measured the PL characteristics of a graphene oxide-metal composite manufactured according to the second embodiment of the present invention, and the results are shown in Figures 8a and 8b. Since the experimental equipment used was the same as that used in the first embodiment, a detailed description is omitted.

[0124] Figure 8a shows the ultraviolet emission spectrum of the graphene oxide layer, and Figure 8b shows the ultraviolet emission spectrum of a composite in which platinum (Pt) nanoparticles of 3 nm in size are bonded to the graphene oxide layer.

[0125] As shown, the pure graphene oxide layer has a broad peak around a wavelength of 525 nm, but the photoluminescence peak changes to 700 nm as platinum (Pt) particles are spin-coated. Considering the change in the luminescence properties of graphene oxide due to platinum (Pt) adsorption, it can be confirmed that the graphene oxide-platinum (Pt) composite is suitable as a red luminescent source.

[0126] Figures 9a and 9b are photographs showing the results of observing the luminescence of graphene oxide or graphene oxide-metal composites illustrated in Figures 8a and 8b using an ultraviolet laser having a wavelength of 355 nm, respectively. Through the photographs, a red shift in the luminescence wavelength band due to the adsorption of platinum (Pt) particles on graphene oxide can be clearly observed.

[0127]

[0128] Emission wavelength band according to the type of transition metal

[0129] The graphene oxide-metal composite according to the embodiment can be configured to emit blue, green, or red light through selection of a transition metal to be bonded to the graphene oxide layer.

[0130] Fig. 10 is a graph showing the results of calculating the HOMO-LUMO gap for the metal types constituting the graphene oxide-metal composite corresponding to various emission colors. Referring to Fig. 10, when using graphene oxide having a blue emission wavelength band (2.48 to 3.26 eV), it can be confirmed that it is possible to manufacture a graphene oxide-composite light-emitting source having a green emission wavelength band (1.98 to 2.48 eV) and a red emission wavelength band (1.59 to 1.98 eV) by selecting a transition metal to be bonded thereto from among platinum (Pt), chromium (Cr), molybdenum (Mo), palladium (Pd), and tungsten (W).

[0131] In addition, the inventors of the present invention calculated the change in the emission spectrum of graphene oxide-metal complexes according to the transition metal using the density functional theory, which is a first-principles calculation method. As shown in Fig. 11, the optical property changes were calculated for the results of bonding chromium (Cr), molybdenum (Mo), and tungsten (W) atoms to the hollow sites of graphene quantum dots of GQD-27 consisting of 27 atoms, GQD-55 consisting of 55 atoms, and GQD-67 consisting of 67 atoms, and platinum (Pt) and palladium (Pd) atoms to the bridge sites.

[0132] Figures 12a to 12f show the changes in the HOMO-LUMO gap that occur when five transition metals are bonded to graphene quantum dots consisting of 27, 55, and 67 atoms. The luminescence is generated by the emission corresponding to the energy gap between the HOMO and LUMO. For example, when tungsten (W) is bonded to GQD-27, the HOMO-LUMO gap decreases by 2.37 eV, when molybdenum (Mo) is bonded, the HOMO-LUMO gap decreases by 1.95 eV, when chromium (Cr) is bonded, the HOMO-LUMO gap decreases by 1.74 eV, when platinum (Pt) is bonded, the HOMO-LUMO gap decreases by 1.18 eV, and when palladium (Pd) is bonded, the HOMO-LUMO gap decreases by 0.55 eV.

[0133] Using the above principle, when using graphene oxide quantum dots having a blue emission wavelength band (HOMO-LUMO gap 2.48 to 3.26 eV), it can be expected that a red emission source will be formed at approximately 1.3 to 2.08 eV when forming a complex with platinum (Pt), and a green emission source will be formed at approximately 1.93 to 2.71 eV when using palladium (Pd).

[0134] In addition, through the absorption spectrum calculation results in Figs. 12a to 12f, it can be confirmed that the main peak occurs in the blue wavelength band for GQD-27 with transition metals combined, in the green wavelength band for GQD-55, and in the red wavelength band for GQD-66. Through this, it is possible to implement a desired emission wavelength band such as blue, green, or red depending on the selection of the transition metal through the graphene oxide-metal complex according to the embodiments.

[0135]

[0136] Light-emitting device and light-generating method

[0137] A light-emitting device according to embodiments of the present invention comprises a graphene oxide-metal composite according to the above-described embodiments, and a control unit configured to apply energy corresponding to a band gap of the composite to the composite for light generation by the composite.

[0138] Fig. 13 is a flowchart showing each step of a light generation method using a light-emitting element according to one embodiment.

[0139] Referring to FIG. 13, a method for generating light using a light-emitting element may include a step (S21) of forming a graphene oxide-metal complex through a manufacturing method according to the above-described embodiments, a step (S22) of applying optical energy and / or electrical energy for excitation to the formed graphene oxide-metal complex, and a step (S23) of generating light corresponding to a band gap of graphene oxide including hybrid orbitals by recombination of excited excitons or electrons-holes.

[0140] FIG. 14 is a conceptual diagram of a light-emitting device according to one embodiment that operates through ultraviolet pumping.

[0141] Referring to FIG. 14, a light-emitting device (2) according to the present embodiment includes a graphene oxide-metal composite (200) manufactured according to the embodiments and a light source (3) as a control unit for applying energy for light generation to the graphene oxide-metal composite (200). In one embodiment, the graphene oxide-metal composite (200) may be positioned on a substrate (100).

[0142] The graphene oxide-metal composite (200) is configured to generate light (40) using pumping light (30) provided by a light source (3). For example, in order to excite the graphene oxide-metal composite (200) having an emission wavelength band of visible light (1.59 to 3.26 eV) and infrared light, in one embodiment, the light source (3) may be configured to irradiate pumping light (30) having a wavelength band below ultraviolet light. The graphene oxide-metal composite (200) excited through ultraviolet light pumping forms excitons, and through recombination, generates light (40) corresponding to the gap between the conduction band and the valence band.

[0143] Figure 15 is a conceptual diagram of a light-emitting element according to another embodiment that operates as an electroluminescent element.

[0144] Referring to FIG. 15, a light-emitting device (2) according to the present embodiment includes a graphene oxide-metal composite (200) manufactured according to the embodiments and a power source (4) as a control unit for applying electrical energy for light generation to the graphene oxide-metal composite (200). In one embodiment, the graphene oxide-metal composite (200) may be positioned on a substrate (100). In addition, the graphene oxide-metal composite (200) may be in electrical contact with a pair of electrodes (150, 250) for injection of current (i.e., electrons and holes), respectively.

[0145] In this embodiment, the graphene oxide-metal composite (200) operates in an electroluminescent manner through injection of electrons and holes. In order to achieve electroluminescence of the graphene oxide-metal composite (200), electrons and holes must be injected through the electrodes (150, 250). In order for the electrons and holes to recombine within the graphene oxide-metal composite (200), the electrodes (150, 250) may be formed of a conductive material such as a metal having an appropriate work function. To enable efficient luminescence, in one embodiment, the lower electrode (150) and / or the upper electrode (250) may be formed of a transparent electrode.

[0146] In one embodiment, the power source (4) can apply a voltage between the electrodes (150, 250) that is sufficient to enable electroluminescence of the graphene oxide-metal composite (200) while not causing combustion of the graphene oxide-metal composite (200). For example, in the case of a graphene oxide-metal composite (200) having an emission wavelength band of visible light (1.59 to 3.26 eV), the voltage applied by the power source (4) can be 4 to 5 V.

[0147] In one embodiment, the cathode for injecting electrons among the electrodes (150, 250) may be made of aluminum (Al) considering the work function. In this case, since aluminum (Al) is not transparent, the lower electrode (150) that is not exposed to the device surface may be configured as a cathode to form an aluminum (Al) electrode. At this time, the anode may be a transparent electrode such as ITO that can inject holes into the graphene oxide-metal composite (200) and efficiently emit emitted light, and the upper electrode (250) corresponds to this. However, the roles of the upper and lower electrodes or the constituent materials of each electrode in the light-emitting devices according to the embodiments are not limited thereto.

[0148] Figures 16 to 18 are cross-sectional views showing each step of a method for manufacturing a light-emitting element by patterning through etching according to one embodiment.

[0149] This embodiment corresponds to a method for manufacturing a light-emitting element that operates in an electroluminescent manner. Referring to FIG. 16, first, an electrode (150) for electron (or hole) injection is formed on a substrate (100), and then a graphene oxide-metal composite thin film (200) formed through lamination according to the first or second embodiment described above can be formed on the electrode (150) (200).

[0150] Next, a photoresist (PR) (300) is applied on the graphene oxide-metal composite thin film (200) through spin coating or the like, and then a PR (300) pattern can be formed through exposure and development.

[0151] Next, as illustrated in Fig. 17, the portion of the graphene oxide-metal composite film (200) and electrode (150) where the PR (300) pattern is not formed can be removed. The removal of the PR (300) can be performed through reactive ion etching (RIE), but is not limited thereto.

[0152] Next, as illustrated in Fig. 18, an electrode (250) capable of injecting holes (or electrons) can be formed on the patterned graphene oxide-metal composite thin film (200). For example, the electrode (250) may be formed of a transparent electrode, but is not limited thereto. The light-emitting element configured as described above can operate in an electroluminescent manner by applying voltage through the electrodes (150, 250).

[0153] While the present invention has been described above with reference to the embodiments illustrated in the drawings, these are merely exemplary, and those skilled in the art will appreciate that various modifications and variations of the embodiments are possible. However, such modifications should be considered within the technical protection scope of the present invention. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

[0154] The embodiments relate to a graphene oxide-metal composite and a light-emitting device comprising the same, a method for manufacturing the light-emitting device, and a method for generating light using the graphene oxide-metal composite. More specifically, the embodiments relate to a technology for implementing a light-emitting source capable of controlling the band gap by hybrid orbitals by depositing metal nanoparticles on graphene oxide to manufacture a graphene oxide-metal composite.

Claims

1. As a graphene oxide-metal complex, A graphene oxide layer comprising oxygen functional groups partially formed on the surface; and Comprising one or more metal particles bonded to the surface of the above graphene oxide layer, The above metal particles are, In the above graphene oxide layer, the oxygen functional group is bonded to a non-bonded portion to form the above complex, A graphene oxide-metal composite comprising a material in which the Fermi energy of the composite is located between the conduction band energy level and the valence band energy level of the composite.

2. In paragraph 1, The surface of the above graphene oxide layer includes a first region corresponding to a graphene quantum dot and a second region insulated by the oxygen functional group, The above rapid particle is a graphene oxide-metal composite including nanoparticles combined with the graphene quantum dots on the first region.

3. In paragraph 2, A graphene oxide-metal composite comprising a metal particle capable of forming a hybrid orbital by combining with the graphene quantum dots of the graphene oxide layer.

4. In paragraph 3, The above complex is a graphene oxide-metal complex having a band gap corresponding to any one of an infrared band, a visible light band, or an ultraviolet band.

5. In paragraph 3, The above metal particles are graphene oxide-metal composites composed of one or more materials selected from the group consisting of platinum (Pt), chromium (Cr), molybdenum (Mo), palladium (Pd), tungsten (W), and alloys thereof.

6. In paragraph 3, A graphene oxide-metal composite having a metal particle size of 1 to 10 nm.

7. In paragraph 1, The above graphene oxide layer is a graphene oxide-metal composite comprising one or more nanosheets.

8. A graphene oxide-metal composite according to any one of claims 1 to 7; and A light-emitting device comprising a control unit configured to apply energy corresponding to a band gap of the complex to the complex for light generation by the complex.

9. In paragraph 8, A light-emitting element in which the frequency at which light is emitted by the complex is determined based on the type of the metal particles.

10. In paragraph 8, The above control unit is a light emitting element including a light source configured to irradiate the complex with pumping light for excitation of the complex.

11. In paragraph 8, The control unit is a light emitting element including one or more electrodes electrically connected to the complex for applying current to the complex.

12. A step of forming a graphene oxide layer including oxygen functional groups partially formed on the surface; and Comprising a step of forming a graphene oxide-metal composite by bonding one or more metal particles on the surface of the graphene oxide layer, The above metal particles are, In the above graphene oxide layer, the oxygen functional group is bonded to a non-bonded portion to form the above complex, A method for manufacturing a light-emitting device comprising a material in which the Fermi energy of the complex is located between the conduction band energy level and the valence band energy level of the complex.

13. In paragraph 12, A method for manufacturing a light-emitting device, wherein the step of forming the graphene oxide-metal complex includes the step of depositing the metal particles on the graphene oxide layer by electron beam deposition.

14. In paragraph 12, A method for manufacturing a light-emitting device, wherein the step of forming the above graphene oxide-metal complex includes the step of spin-coating a solution in which the metal particles are dispersed onto the graphene oxide layer.

15. In paragraph 12, A method for manufacturing a light-emitting device, further comprising a step of forming an electrode layer for electron injection on the substrate prior to the step of forming the above graphene oxide layer.

16. In paragraph 12, A method for manufacturing a light-emitting device further comprising the step of forming a protective layer on the graphene oxide-metal composite.

17. In paragraph 16, A method for manufacturing a light-emitting device, wherein the above protective layer is made of graphene oxide.

18. In paragraph 16, A method for manufacturing a light-emitting element further comprising the step of forming an electrode layer made of a conductive material on the protective layer.

19. A step of preparing a graphene oxide-metal composite comprising a graphene oxide layer including oxygen functional groups partially bonded to a surface, and one or more metal particles bonded to a portion of the graphene oxide layer where the oxygen functional groups are not bonded; and A step of applying energy for excitation of the complex to the complex is included, A method for generating light using a graphene oxide-metal complex, wherein the metal particles are made of a material in which the Fermi energy of the complex is located between the conduction band energy level and the valence band energy level of the complex.

20. In paragraph 19, A method for generating light using a graphene oxide-metal composite, wherein the step of applying the energy includes a step of applying pumping light having a wavelength band below ultraviolet light to the composite.

21. In paragraph 19, A method for generating light using a graphene oxide-metal composite, wherein the step of applying the energy includes a step of applying a current to the composite through an electrode.

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