Organic light emitting device

Abstract

The present disclosure relates to an organic light emitting device including: a first electrode; a second electrode provided to face the first electrode; and an electron transport layer, an emitting layer and a hole transport layer provided between the first electrode and the second electrode, and the emitting layer contains doped protein quantum dots.

Claims

1. A method of preparing protein quantum dots, comprising: preparing a protein solution by dissolving a protein in a primary solvent; preparing protein quantum dots by adding a secondary solvent into the protein solution to self-assemble the protein; and adding a doping material to the protein quantum dots.

2. The method of preparing protein quantum dots of claim 1, wherein the emission wavelength of the protein quantum dots is controlled depending on the doping material.

3. The method of preparing protein quantum dots of claim 2, wherein the doping material contains a metal selected from the group consisting of Ir, Ru, Rh, Os, Tc, Re, Mo, W, and combinations thereof.

4. The method of preparing protein quantum dots of claim 1, wherein the protein includes a protein selected from the group consisting of tert-butyloxycarbonyl-diphenylalanine (Boc-Diphenylalanine), phenylalanine, tryptophan, tyrosine, leucine, valine, isoleucine, histidine, and combinations thereof.

5. The method of preparing protein quantum dots of claim 1, wherein the primary solvent includes a solvent selected from the group consisting of hexafluoroisopropanol (HFIP), formic acid, cresol, xylene, nitrobenzene, dimethylformamide, dimethylacetamide, and combinations thereof.

6. The method of preparing protein quantum dots of claim 1, wherein the secondary solvent includes a solvent selected from the group consisting of ethanol, methanol, water, and combinations thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the detailed description that follows, embodiments are described as illustrations only since various changes and modifications will become apparent to those skilled in the art from the following detailed description. The use of the same reference numbers in different figures indicates similar or identical items.

(2) FIG. 1 shows a structure of an organic light emitting device according to an embodiment of the present disclosure.

(3) FIG. 2 is a schematic diagram illustrating an organic light emitting device according to an embodiment of the present disclosure.

(4) FIG. 3 is a flowchart showing a method of preparing protein quantum dots according to an embodiment of the present disclosure.

(5) FIG. 4A to FIG. 4D are schematic diagrams illustrating a process of forming protein quantum dots by self-assembly according to an example of the present disclosure.

(6) FIG. 5 provides graphs showing absorption and emission wavelengths of protein quantum dots according to an example of the present disclosure, and insets are photoluminescence (PL) images shown when 365 nm UV are irradiated.

(7) FIG. 6A and FIG. 6B provide a schematic diagram of an organic light emitting device according to an example of the present disclosure and a graph showing PL, respectively.

DETAILED DESCRIPTION

(8) Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that the present disclosure may be readily implemented by those skilled in the art.

(9) However, it is to be noted that the present disclosure is not limited to the embodiments but can be embodied in various other ways. In drawings, parts irrelevant to the description are omitted for the simplicity of explanation, and like reference numerals denote like parts through the whole document.

(10) Through the whole document, the term connected to or coupled to that is used to designate a connection or coupling of one element to another element includes both a case that an element is directly connected or coupled to another element and a case that an element is electronically connected or coupled to another element via still another element.

(11) Through the whole document, the terms on, above, on an upper end, below, under, and on a lower end that are used to designate a position of one element with respect to another element include both a case that the one element is adjacent to the other element and a case that any other element exists between these two elements.

(12) Further, through the whole document, the term comprises or includes and/or comprising or including used in the document means that one or more other components, steps, operation and/or existence or addition of elements are not excluded in addition to the described components, steps, operation and/or elements unless context dictates otherwise.

(13) Through the whole document, the term about or approximately or substantially is intended to have meanings close to numerical values or ranges specified with an allowable error and intended to prevent accurate or absolute numerical values disclosed for understanding of the present disclosure from being illegally or unfairly used by any unconscionable third party. Through the whole document, the term step of does not mean step for.

(14) Through the whole document, the term combination of included in Markush type description means mixture or combination of one or more components, steps, operations and/or elements selected from a group consisting of components, steps, operation and/or elements described in Markush type and thereby means that the disclosure includes one or more components, steps, operations and/or elements selected from the Markush group.

(15) Through the whole document, a phrase in the form A and/or B means A or B, or A and B.

(16) Hereinafter, an organic light emitting device according to the present disclosure will be described in detail with reference to embodiments, examples and the accompanying drawings. However, the present disclosure may not be limited to the following embodiments, examples and drawings.

(17) A first aspect of the present disclosure relates to an organic light emitting device including: a first electrode; a second electrode provided to face the first electrode; and an electron transport layer, an emitting layer and a hole transport layer provided between the first electrode and the second electrode, and the emitting layer contains doped protein quantum dots.

(18) According to an embodiment of the present disclosure, the doped protein quantum dots may be doped with a material selected from the group consisting of Ir, Ru, Rh, Os, Tc, Re, Mo, W, and combinations thereof, but may not be limited thereto.

(19) If the doped protein quantum dots are doped with a material containing Ir, the doped protein quantum dots may emit a green light around 530 nm.

(20) If the doped protein quantum dots are doped with a material containing Ru, the doped protein quantum dots may emit a red light around 620 nm.

(21) According to an embodiment of the present disclosure, the doped protein quantum dots may have a nanosphere shape, but may not be limited thereto.

(22) The doped protein quantum dots may further have a nanorod shape and a branched shape, but may not be limited thereto.

(23) According to an embodiment of the present disclosure, the doped protein quantum dots may contain a protein selected from the group consisting of tert-butyloxycarbonyl-diphenylalanine (Boc-Diphenylalanine), phenylalanine, tryptophan, tyrosine, leucine, valine, isoleucine, histidine, and combinations thereof, but may not be limited thereto.

(24) The organic light emitting device uses a protein for an emitting layer instead of a heavy metal such as cadmium. Thus, it is environment friendly and harmless to humans. Further, the protein quantum dots are doped with a material such as Ir, Ru, or the like, and, thus, the emission wavelength thereof can be easily controlled. For example, the protein quantum dots can emit a green light if doped with an Ir compound and can emit a red light if doped with a Ru compound.

(25) A protein has a wide band gap of 5 eV or more and thus has insulating properties. A quantum well is formed in a band diagram, and, thus, carriers such as electrons and holes injected into quantum dots are trapped in the quantum well but cannot escape from the quantum well. Therefore, light is emitted only at a dopant and the emission efficiency is high. Further, by keeping a balance between carriers which are injected in a nonuniform manner due to a mobility difference, it is possible to suppress the occurrence of leakage current caused by excessive carriers. Therefore, it is possible to improve the lifetime and electroluminescent efficiency of the device.

(26) According to an embodiment of the present disclosure, the organic light emitting device may further include a graphene layer and an oxide layer formed on the electron transport layer, but may not be limited thereto.

(27) According to an embodiment of the present disclosure, the graphene layer and the oxide layer may control a Schottky barrier of the organic light emitting device, but may not be limited thereto.

(28) According to an embodiment of the present disclosure, the graphene layer and the oxide layer may protect the emitting layer against oxygen and/or moisture, but may not be limited thereto.

(29) According to an embodiment of the present disclosure, the oxide layer may contain a metal oxide selected from the group consisting of TiO.sub.2, SnO.sub.2, ZnO, WO.sub.3, Nb.sub.2O.sub.5, TiSrO.sub.3, SiO.sub.2, Al.sub.2O.sub.3, MgO, Cr.sub.2O.sub.3, Fe.sub.3O.sub.4, and combinations thereof, but may not be limited thereto.

(30) When a voltage is applied to the organic light emitting device, the graphene functions as an N-type semiconductor due to energy band bending, and, thus, electrons can be easily transported and a Schottky barrier can be controlled. When a negative voltage is applied to the graphene layer, the Schottky barrier is lowered, and, thus, electrons can be easily transported between materials, such as a metal and an organic semiconductor, different in energy level. Therefore, the efficiency of the organic light emitting device can be increased.

(31) Further, the graphene layer and the oxide layer protect the emitting layer against oxygen and/or moisture which may permeate from the outside. Therefore, it is possible to implement a quantum dot-light emitting diode (QD-LED) with high reliability and a long lifetime.

(32) The energy level may collectively refer to work function level, conduction band level, valence band level, Highest Occupied Molecular Orbital (HOMO) level, and Lowest Unoccupied Molecular Orbital (LUMO) level. Specifically, if a target material of the energy level is a metal, the energy level may refer to the work function level. Further, if a target material of the energy level is an inorganic material or an inorganic semiconductor, the energy level may refer to the conduction band level or the valence band level. Furthermore, if a target material of the energy level is an organic material or an organic semiconductor, the energy level may refer to the HOMO level or the LUMO level.

(33) FIG. 1 shows a structure of an organic light emitting device according to an embodiment of the present disclosure.

(34) Referring to FIG. 1, the organic light emitting device may include a first electrode, a second electrode provided to face the first electrode, and an electron transport layer (ETL), an emitting layer (EML) and a hole transport layer (HTL) provided between the first electrode and the second electrode. The organic light emitting device may further include a hole injection layer (HIL), an electron injection layer (EIL), a substrate, and an encapsulation layer. Further, the organic light emitting device may include a graphene layer and an oxide layer.

(35) According to an embodiment of the present disclosure, any one of the first electrode and the second electrode may be an anode and the other one may be a cathode, but may not be limited thereto.

(36) Forward voltage application refers to allowing a current to flow from the anode toward the cathode, and reverse voltage application refers to allowing a current to flow from the cathode toward the anode.

(37) The organic light emitting device may have a sandwich structure in which the first electrode and the second electrode are face-jointed, but may not be limited thereto.

(38) If an appropriate organic layer and/or an appropriate inorganic layer is positioned between the first electrode and the second electrode, when a voltage is applied between the two electrodes, holes are injected from an anode and electrons are injected from a cathode into the organic layer and/or the inorganic layer. The injected holes and electrons are combined into excitons, and when the excitons fall to the ground state again, light is generated and emitted.

(39) The first electrode may be a transparent electrode.

(40) If the first electrode is a transparent electrode, the first electrode may be a conductive oxide such as indium tin oxide or indium zinc oxide. Further, the first electrode may be a translucent electrode. If the first electrode is a translucent electrode, it can be manufactured using a translucent metal such as Ag, Au, Mg, Ca, or an alloy thereof. If the translucent metal is used for the first electrode, the organic light emitting device may have a micro cavity structure.

(41) The anode may be formed of, desirably, a material having a high work function to facilitate hole injection. For example, the material may include metals or alloys including V, Cr, Cu, Zn, Au, and combinations thereof; metal oxides such as zinc oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO); combinations of metals and oxides such as ZnO:Al or SnO.sub.2:Sb; and conductive polymers such as poly(3-methylthiophene), poly[3,4-(ethylene-1,2-dioxy) thiophene] (PEDOT), polypyrrole, and polyaniline, but may not be limited thereto.

(42) The material of the anode is not limited to the anode, but can be used as a material of the cathode.

(43) The cathode may be formed of, desirably, a material having a low work function to facilitate electron injection. For example, the material may include metals or alloys including Mg, Ca, Na, K, Ti, In, Y, Li, Gd, Al, Ag, Sn, Pb, and combinations thereof; and materials having a multilayer structure such as LiF/Al or LiO.sub.2/Al, but may not be limited thereto.

(44) The material of the cathode is not limited to the cathode, but can be used as a material of the anode.

(45) The HTL may be formed of, desirably, a material having a high hole mobility which can receive holes from the anode or the HIL and transfer the holes to the EML. For example, the material may include a material selected from the group consisting of arylamine-based organic materials, conductive polymers, block copolymers having conjugated and non-conjugated blocks, and combinations thereof, but may not be limited thereto.

(46) The EML may be formed of, desirably, a material having a high quantum efficiency with respect to fluorescence or phosphorescence which can receive holes and electrons from the HTL and the ETL, respectively, and combine the holes and electrons to emit visible light. For example, the protein quantum dots are doped with the doping material and thus have a high quantum efficiency.

(47) The ETL may be formed of, desirably, a material having a high electron mobility which can receive electrons from the cathode and transfer the electrons to the EML. For example, the material may include a material selected from the group consisting of Al complexes with 8-hydroxyquinoline; complexes containing Alq3; organic radical compounds; hydroxyflavone-metal complexes, and combinations thereof, but may not be limited thereto.

(48) The encapsulation layer may be formed of a transparent resin layer. The encapsulation layer may function to protect the organic light emitting device against oxygen and pollutants and may be formed of a transparent material in order not to inhibit emission from the organic light emitting device. The transparency may refer to 60% or more transmission of light. Specifically, the transparency may refer to 75% or more transmission of light.

(49) A substrate having excellent transparency, surface smoothness, ease of handling, and water repellency may be used as the substrate. For example, the substrate may include a substrate selected from the group consisting of a glass substrate, a thin-film glass substrate, a transparent plastic substrate, and combinations thereof. The plastic substrate may include a plastic substrate selected from the group consisting of polyether sulfone (PES), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polycarbonate (PC), polystyrene (PS), polyimide (PI), polyethylene (PE), polyether ether ketone (PEEK), and combinations thereof, but may not be limited thereto.

(50) FIG. 2 is a schematic diagram illustrating an organic light emitting device according to an embodiment of the present disclosure.

(51) The present disclosure provides a display apparatus including the organic light emitting device. In the display apparatus, the organic light emitting device can function as a pixel or a backlight. The other components of the display apparatus may be the same as those known in the art.

(52) The present disclosure provides a lighting apparatus including the organic light emitting device. In the lighting apparatus, the organic light emitting device functions as a light emitting unit. The other components required for the lighting apparatus may be the same as those known in the art.

(53) A second aspect of the present disclosure provides a method of preparing protein quantum dots, including: preparing a protein solution by dissolving a protein in a primary solvent; preparing protein quantum dots by adding a secondary solvent into the protein solution to self-assemble the protein; and adding a doping material to the protein quantum dots.

(54) FIG. 3 is a flowchart showing a method of preparing protein quantum dots according to an embodiment of the present disclosure.

(55) Firstly, a protein solution is prepared by dissolving a protein in a primary solvent (S100).

(56) According to an embodiment of the present disclosure, the protein may include a protein selected from the group consisting of tert-butyloxycarbonyl-diphenylalanine (Boc-Diphenylalanine), phenylalanine, tryptophan, tyrosine, leucine, valine, isoleucine, histidine, and combinations thereof, but may not be limited thereto.

(57) According to an embodiment of the present disclosure, the primary solvent may include a solvent selected from the group consisting of hexafluoroisopropanol (HFIP), formic acid, cresol, xylene, nitrobenzene, dimethylformamide, dimethylacetamide, and combinations thereof, but may not be limited thereto.

(58) Then, protein quantum dots are prepared by adding a secondary solvent into the protein solution to self-assemble the protein (S200).

(59) According to an embodiment of the present disclosure, the secondary solvent may include a solvent selected from the group consisting of ethanol, methanol, water, and combinations thereof, but may not be limited thereto.

(60) The self-assembly may be conducted by hydrogen bonds and ionic bonds between functional groups of the protein, but may not be limited thereto.

(61) The functional groups may include amide bonds.

(62) If the secondary solvent is ethanol, the protein quantum dots may have a nanosphere shape, but may not be limited thereto.

(63) If the secondary solvent is water, the protein quantum dots may have a nanowire shape, but may not be limited thereto.

(64) Then, a doping material is added to the protein quantum dots (S300).

(65) According to an embodiment of the present disclosure, the emission wavelength of the protein quantum dots may be controlled depending on the doping material, but may not be limited thereto.

(66) If the protein quantum dots are doped with a material containing Ir, the doped protein quantum dots may emit a green light around 530 nm.

(67) If the protein quantum dots are doped with a material containing Ru, the doped protein quantum dots may emit a red light around 620 nm.

(68) The protein quantum dots may have a nanosphere, nanorod, or branched shape, but may not be limited thereto.

(69) According to an embodiment of the present disclosure, the doping material may contain a metal selected from the group consisting of Ir, Ru, Rh, Os, Tc, Re, Mo, W, and combinations thereof, but may not be limited thereto.

(70) Hereinafter, the present disclosure will be described in more detail with reference to examples. The following examples are provided only for explanation, but do not intend to limit the scope of the present disclosure.

EXAMPLE 1

(71) Protein quantum dots having a nanosphere shape in which tert-butyloxycarbonyl-diphenylalanine was self-assembled were formed by dissolving tert-butyloxycarbonyl-diphenylalanine in hexafluoroisopropanol (HFIP) and adding ethanol thereto.

(72) FIG. 4A to FIG. 4D are schematic diagrams illustrating a process of forming protein quantum dots by self-assembly according to an example of the present disclosure.

(73) Green-protein quantum dots were formed by adding Ir(ppy).sub.3 as a dopant to the protein quantum dots, and red-protein quantum dots were formed by adding Ru(bpy).sub.3.sup.2+ as a dopant to the protein quantum dots.

EXAMPLE 2

(74) A glass substrate coated with an indium tin oxide (ITO) thin film was used to manufacture an organic light emitting device. PEDOT:PSS, PVK, the green-protein quantum dots prepared in Example 1, TPBi, and LiF/Al were coated and/or deposited in sequence on the ITO to manufacture a green-organic light emitting device.

EXAMPLE 3

(75) A glass substrate coated with an indium tin oxide (ITO) thin film was used to manufacture an organic light emitting device. PEDOT:PSS, PVK, the red-protein quantum dots prepared in Example 1, TPBi, ZnO, and LiF/Al were coated and/or deposited in sequence on the ITO to manufacture a red-organic light emitting device.

Test Example

(76) The properties of the green-protein quantum dots and the red-protein quantum dots prepared in Example 1 were checked and the result thereof was as shown in FIG. 5.

(77) FIG. 5 provides graphs showing absorption and emission wavelengths of protein quantum dots according to an example of the present disclosure, and insets are photoluminescence (PL) images shown when 365 nm UV are irradiated.

(78) According to the result shown in FIG. 5, protein absorption occurs at 250 nm and protein emission occurs at 380 nm. Since Ir(ppy).sub.3 of Example 1 was used for doping, green light emission occurred at 530 nm. Further, since Ru(bpy).sub.3.sup.2+ of Example 1 was used for doping, red light emission occurred at 620 nm.

(79) The properties of the green-organic light emitting device and the red-organic light emitting device manufactured in Examples 2 and 3 were checked and the result thereof was as shown in FIG. 6.

(80) FIG. 6A and FIG. 6B provide a schematic diagram of an organic light emitting device according to an example of the present disclosure and a graph showing PL, respectively.

(81) According to the result shown in FIG. 6, since Ir(ppy).sub.3 of Example 1 was used for doping, green light emission occurred. Further, since Ru(bpy).sub.3.sup.2+ of Example 1 was used for doping, red light emission occurred.

(82) The above description of the present disclosure is provided for the purpose of illustration, and it would be understood by those skilled in the art that various changes and modifications may be made without changing technical conception and essential features of the present disclosure. Thus, it is clear that the above-described embodiments are illustrative in all aspects and do not limit the present disclosure. For example, each component described to be of a single type can be implemented in a distributed manner. Likewise, components described to be distributed can be implemented in a combined manner.

(83) The scope of the present disclosure is defined by the following claims rather than by the detailed description of the embodiment. It shall be understood that all modifications and embodiments conceived from the meaning and scope of the claims and their equivalents are included in the scope of the present disclosure.