Patent Application
20220158107
The present disclosure relates to a layer structure applicable in an emissive device, in particular for a Quantum Dot LED. Specifically, a QLED structure and a method to patterned red, green and blue subpixels are disclosed herein.
A common architecture for a light-emitting device includes an anode, which functions as a hole injector; a hole transport layer disposed on the anode; an emissive material layer disposed on the hole transport layer; an electron transport layer disposed on the emissive material layer; and a cathode, which functions as an electron injector, disposed on the electron transport layer. When a forward bias is applied between the anode and cathode, holes and electrons are transported in the device through the hole transport layer and the electron transport layer, respectively. The holes and electrons recombine in the emissive material layer; light is generated and emitted from the device. When the emissive material layer includes an organic material, the light-emitting device is referred to as an organic light-emitting diode (OLED). When the emissive material layer includes nanoparticles, sometimes known as quantum dots (QDs), the device is commonly referred to as either a QD light-emitting diode (QLED, QD-LED) or an electroluminescent QD light-emitting diode (ELQLED, QDEL).
The above described layers are deposited on a substrate, different structures can be achieved by changing an order of deposition of the layers. In a non-inverted (e.g., standard) structure, the first layer deposited on the substrate is the anode, followed by the hole transporting layer, the emissive layer, the electron transporting layer and finally by the cathode. In an inverted structure, these layers are deposited on the substrate on the opposite order, starting with the cathode and finishing with the anode.
Difference methods can be utilized to deposit each of the above described layers of the light-emitting device, such as thermal evaporation methods and solution process methods. Thermal evaporation methods used for OLEDs are more complex, and have higher costs of fabrication as compared to solution process methods. Solution process methods are thus preferred as they are less complex and more cost effective.
However, in the fabrication of devices with the solution methods, finding appropriate (e.g., non-damaging) solvents is important because during the deposition of a particular layer, the process should not dissolve or otherwise damage the previously deposited layer. Such a non-damaging solvent is typically referred to as “orthogonal” to the previous layer (See Organic Electronics 30 (2016) 18e29; http://dx.doi.org/10.1016/j.orgel.2015.12.008).
To include QLEDs in multi-color high resolution displays, different manufacturing methods have been designed. These methods typically include depositing three different types of QDs on three different regions of a substrate such that each region emits light (through electrical injection; i.e., by electroluminescence) of three different colors, particularly red (R), green (G) and blue (B). Sub-pixels that respectively emit red, green, or blue light may collectively form a pixel, which in turn may be a part of an array of pixels of the display.
Despite the fact that inverted structures for QLEDs are common in applications, most of the reported solution processed methods for including QLEDs in multi-color high resolution displays, are designed principally for QLEDs with non-inverted (e.g., standard) structures. Therefore, there is a need to achieve patterned QLEDs in both inverted and non-inverted structures and manufacturing methods of the same.
WO 2017/117994 by Li et al., published Jul. 13, 2017.
WO 2017/121163 by Li et al., published Jul. 20, 2017.
Alternative Patterning Process for Realization of Large-Area′ by Park et al., Full-Color, Active Quantum Dot Display, Nano Letters, 2016, pages 6946-6953.
CN106374056A by X. Chao, published Jan. 2, 2017.
The present disclosure is related to a QLED structure and a method to patterned red, green and blue subpixels.
According to a first aspect of the present disclosure, a light-emitting device includes an anode, a cathode, an electron transporting or injecting layer between the cathode and the anode, an emissive layer having quantum dots between the anode and the electron transporting or injecting layer, and a cross-linked hole transporting or injecting layer between the anode and the emissive layer.
According to an implementation of the first aspect, the cross-linked hole transporting or injecting layer comprises a cross-linked material formed by a cross-linkable material cross-linked by at least one of a stimulus or an initiator.
According to another implementation of the first aspect, the stimulus is an external stimulus including one of light, a change in temperature, a change in pressure and a change in pH value.
According to yet another implementation of the first aspect, the light-emitting device further includes a hole injecting layer between the cross-linked hole transporting or injecting layer and the anode.
According to yet another implementation of the first aspect, the light-emitting device further includes at least one electron blocking layer, wherein the at least one electron blocking layer is situated in at least one of the following positions: between the emissive layer and the cross-linked hole transporting layer; and between the electron transporting layer and the emissive layer.
According to yet another implementation of the first aspect, the initiator is a photo initiator that initiates polymerization of the cross-linkable material in response to a light stimulus.
According to yet another implementation of the first aspect, the light stimulus that activates the photo initiator is in an ultraviolet (UV) wavelength range of an electromagnetic spectrum.
According to yet another implementation of the first aspect, the cross-linkable material is deposited on the emissive layer in a solution.
According to a second aspect of the present disclosure, a light-emitting device includes an anode, a cathode, a hole transporting or injecting layer between the cathode and the anode, an emissive layer having quantum dots between the cathode and the hole transporting or injecting layer, and a cross-linked electron transporting or injecting layer between the cathode and the emissive layer.
According to an implementation of the second aspect, the cross-linked electron transporting or injecting layer comprises a cross-linked material formed by a cross-linkable material cross-linked by at least one of a stimulus or an initiator.
According to another implementation of the second aspect, the stimulus is an external stimulus including one of light, a change in temperature, a change in pressure and a change in pH value.
According to yet another implementation of the second aspect, the light-emitting device further includes a hole injecting layer between the hole transporting or injecting layer and the anode.
According to yet another implementation of the second aspect, the light-emitting device further includes at least one electron blocking layer, wherein the at least one electron blocking layer is situated in at least one of the following positions: between the emissive layer and the cross-linked electron transporting layer; and between the hole transporting layer and the emissive layer.
According to yet another implementation of the second aspect, the initiator is a photo initiator that initiates polymerization of the cross-linkable material in response to a light stimulus.
According to yet another implementation of the second aspect, the light stimulus that activates the photo initiator is in an ultraviolet (UV) wavelength range of an electromagnetic spectrum.
According to yet another implementation of the second aspect, the cross-linkable material is deposited on the emissive layer in a solution.
According to a third aspect of the present disclosure, a light-emitting device includes a substrate and a plurality of sub-pixel structures over the substrate. At least one of the plurality of sub-pixel structures includes: an anode, a cathode, an electron transporting or injecting layer between the cathode and the anode, an emissive layer having quantum dots between the anode and the electron transporting or injecting layer, and a cross-linked hole transporting or injecting layer between the anode and the emissive layer.
According to an implementation of the third aspect, the cross-linked hole transporting or injecting layer includes a cross-linked material formed by a cross-linkable material cross-linked by at least one of a stimulus or an initiator.
According to another implementation of the third aspect, a thickness of the emissive layer in each of the plurality of sub-pixel structures is different.
According to another implementation of the third aspect, at least one of a thickness and a composition of the cross-linked hole transporting or injecting layer in each of the plurality of sub-pixel structures is different.
Aspects of the example disclosure are best understood from the following detailed description when read with the accompanying figures. Various features are not drawn to scale. Dimensions of various features may be arbitrarily increased or reduced for clarity of discussion.
The following description contains specific information pertaining to example implementations in the present disclosure. The drawings in the present disclosure and their accompanying detailed description are directed to merely example implementations. However, the present disclosure is not limited to merely these example implementations. Other variations and implementations of the present disclosure will occur to those skilled in the art. Unless noted otherwise, like or corresponding elements among the figures may be indicated by like or corresponding reference numerals. Moreover, the drawings and illustrations in the present disclosure are generally not to scale, and are not intended to correspond to actual relative dimensions.
For consistency and ease of understanding, like features may be identified (although, in some examples, not shown) by numerals in the example figures. However, the features in different implementations may be different in other respects, and thus shall not be narrowly confined to what is shown in the figures.
The phrases “in one implementation,” or “in some implementations,” may each refer to one or more of the same or different implementations. The term “coupled” is defined as connected, whether directly or indirectly through intervening components, and is not necessarily limited to physical connections. The term “comprising” means “including, but not necessarily limited to” and specifically indicates open-ended inclusion or membership in the so-described combination, group, series and equivalents. The expression “at least one of A, B and C” or “at least one of the following: A, B and C” means “only A, or only B, or only C, or any combination of A, B and C.”
Additionally, any two or more of the following paragraphs, (sub)-bullets, points, actions, behaviours, terms, alternatives, examples, or claims described in the following disclosure may be combined logically, reasonably, and properly to form a specific method. Any sentence, paragraph, (sub)-bullet, point, action, behaviours, terms, or claims described in the following disclosure may be implemented independently and separately to form a specific method. Dependency, e.g., “according to”, “more specifically”, “preferably”, “In one embodiment”, “In one implementation”, “In one alternative” etc., in the following disclosure refers to just one possible example which would not restrict the specific method.
For explanation and non-limitation, specific details, such as functional entities, techniques, protocols, and standards are set forth for providing an understanding of the described technology. In other examples, detailed description of well-known methods, technologies, system, and architectures are omitted so as not to obscure the description with unnecessary details.
The present disclosure is related to a specific structure of a QLED, a method to achieve it and a fabrication method to achieve multi-color high resolution displays based on QLEDs with this structure.
It will be appreciated that while the present disclosure primarily describes the QDs as core-shell QDs, in some implementations the QDs may not be of the core-shell type or they may be of a core/multiple-shells type having more than one shell. The non-core-shell type QDs may be made from one or more of the above-mentioned materials, and the QDs in accordance with the present disclosure may not include a core-shell configuration.
The present disclosure may be understood with reference to
In the non-inverted structure 300 in
When an electrical bias is applied to the QLED 300 or 307, holes are conducted from the anode 302 to the EML 304, and electrons are conducted from the cathode 306 to the EML. Holes and electrons recombine at the QDs in the EML 304, thereby generating light. Some of this light is emitted out of the QLED 300 or 307 where it may be perceived by an external viewer, thereby providing a light-emitting device. Light may be emitted through the substrate 301, in which case the device is called “bottom-emitting”, or opposite the substrate, in which case the device is called “top-emitting”.
In the present disclosure, an inverted bottom emitting QLED structure is first described. The structure, depicted in
The cross-linkable hole transporting material can be intrinsically cross-linkable or it may need an initiator of the polymerisation. If the HTM is intrinsically cross-linkable (it can be cross-linked simply applying an external stimulus), the deposited solution that forms the HTL may comprise only a cross-linkable material and a solvent. If the HTM is not intrinsically cross-linkable (it cannot be cross-linked simply applying an external stimulus), this solution may also include one or more initiators of the polymerisation. The initiator can be defined based on the external stimulus (light, temperature, pressure, and change in pH) that activate it. For example, a photo initiator is a material that initiates polymerization in response to light stimuli. In various implementations of the present disclosure, the photo initiator may generate one or more radicals, ions, acids, and/or species that may initiate such polymerization. In the same fashion, a thermal initiator is a material that initiates polymerization in response to thermal stimuli, as a change in temperature.
In this structure, the HTL 407 adjacent to the EML 404 is cross-linked and results in a layer that is resistant to solvent rinsing. This is beneficial because it allows the use of an HIL that can be deposited with a solution processed method (e.g. spin coating, spray coating, inkjet coating and the like) without damaging the HTL and EML. As seen in the prior art, most of inverted QLED structures include a HTL and HIL deposited by vacuum thermal evaporation (J. Mater. Chem. C, 2014, 2, 510, DOI: 10.1039/c3tc31297f; ACS Appl. Mater. Interfaces 2018, 10, 17295-17300, DOI: 10.1021/acsami.8b05092; Nanoscale, 2018, 10, 592, DOI: 10.1039/c7nr06248f).
To include QLEDs in multi-color high resolution displays, three different types of QDs on three different regions of a substrate should be deposited such that each region emits light (through electrical injection; i.e. by electroluminescence) at three different colors, particularly red (R), green (G) and blue (B). Sub-pixels that respectively emit red, green, or blue light may collectively form a pixel, which in turn may be a part of an array of pixels of the display.
In some implementations of the present disclosure, a light emitting structure having RGB patterned QLEDs with inverted structures is provided.
In the fabrication of the QLED according to the present disclosure, it is important to find the appropriate solvents such that during the deposition of a particular layer, a rinsing process will not dissolve or otherwise damage the previously deposited layer. Such a non-damaging solvent is typically referred to in the art as “orthogonal” to the previous one (See Organic Electronics 30 (2016) 18e29; http://dx.doi.org/10.1016/j.orgel.2015.12.008).
To deposit multiple layers in a QLED structure using solution process methods, solution of different materials in adjacent orthogonal solvents should be deposited. Solution process methods include, but are not limited to, methods of drop casting, spin coating, dip coating, slot die coating, spray coating, and inkjet printing.
In one implementation, the electron transporting material (e.g. ZnO) is dissolved and deposited in Ethanol, the emissive material (e.g. QDs) is dissolved and deposited in octane, the cross-linkable hole transporting material (e.g. OTPD) is dissolved and deposited in toluene (or in PGMEA, or in THF, or in chlorobenzene, or in 1,4-dioxane), and the hole injection material (e.g. PEDOT:PSS-MoO3) is dissolved and deposited in an ethanol/2-propanol mixture, or PEDOT:PSS is dissolved and deposited in Toluene.
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The thickness of each layers deposited in
The method can be applied also for a non-inverted structure and a cross-linkable electron injecting/transporting layer. This will be detailed in one of the implementations.
A three color display can be produced utilizing the above described structure and the method described in the present disclosure. The three color display has the following characters:
In some implementations of the present disclosure, a light emitting structure having patterned QLEDs with non-inverted structures is provided.
In some implementations of the present disclosure, a light emitting structure having RGB patterned QLEDs with non-inverted structures is provided.
Light-emitting devices may be arranged such that the light-emitting devices are separated at least in part by one or more insulating materials. This arrangement may also be referred to as a “bank structure.”
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The thickness of each layers deposited in
In some implementations of the present disclosure, a light emitting structure having RGB patterned QLEDs with inverted structures and different types of QDs and HTLs of different thicknesses is provided.
When the 505A of QDs A, 505B of QDs B and 505C of QDs C are deposited in
In some implementations of the present disclosure, a light emitting structure having RGB patterned QLEDs with non-inverted structures and different types of QDs and ETL of different thicknesses is provided.
When the 705A of QDs A, 705B of QDs B and 705C of QDs C are deposited in
In some implementations of the present disclosure, a light emitting structure having RGB patterned QLEDs with inverted structures and different X-HTLs is provided.
In one implementation, the example structure 1000 may be obtained from the method described above regarding
The example structure 1000 of the three different areas A, B, and C, i.e., the subpixels of the display, may be thus controlled. In the implementations where the three QDs of different properties such as conduction and valence energy levels, band gap, etc., are deposited on a same substrate, structures of each subpixel should be different to produce the most efficient devices.
In some implementations, the light emitting structure of
In some implementations of the present disclosure, a light emitting structure having RGB patterned QLEDs with non-inverted structures and different X-HTLs is provided.
In one implementation, the example structure 1100 may be obtained from the method described above regarding
The structure of the three different areas A, B, and C, i.e., the subpixels of the display, maybe thus controlled. In the implementations where the three QDs of different properties such as conduction and valence energy levels, band gap, etc., are deposited on the same substrate, structures of each subpixel should be different to produce the most efficient devices.
In some implementations, the light emitting structure of
In various implementations of the present disclosure, the solvent used for rinsing is the same solvent used in the deposition of the QDs or of the cross-linkable hole transporting material. In other implementations, the solvent used for rinsing is a similar solvent or orthogonal solvent to the solvent used deposition of the QDs or of the cross-linkable hole transporting material.
Accordingly, as shown in
In one implementation, subsequent to the application of UV light as shown in
Factors such as the UV exposure times, UV-intensity, amount of photo initiator, type and thickness of the deposition surface (including ligands), surface treatments (as UV-ozone or plasma) and ratio between cross-linkable material and photo initiator may allow for control of the morphology of the emissive material and of the hole transporting layer. For example, UV exposure time may range from 0.001 seconds to 15 minutes, and/or UV exposure intensity may range from 0.001 to 100,000 mJ/cm2. The amount of photo initiator may range from 0.001 to 15 wt. % of the total concentration of the cross-linkable material in solution. The concentration of the ligands of the QDs may range from 0 to 35 wt % of the total weight of the QDs. The thickness of the deposition surface may range from 0.1 to 1000 nm. The deposition surface may be composed of any suitable organic, metalorganic or inorganic materials.
In one implementation, the UV exposure intensity ranges from 1 to 100 mJ/cm2 at a UV exposure time of 0.01 to 200 seconds, the concentration of the cross-linkable material in the solution may range from 0.5 and 10 wt. %, and the photo initiator concentration ranges from 0 and 5 wt. % of the concentration of the cross-linkable material in solution, and the thickness of the deposition surface ranges from 1 to 1000 nm.
During the fabrication of devices with the above discussed methods, it is important to find the appropriate solvents such that during the deposition of a particular layer, the process will not dissolve or otherwise damage the previously deposited layer. Such a non-damaging solvent is typically referred to in the art as “orthogonal” to the previous one (See Organic Electronics 30 (2016) 18e29; http://dx.doi.org/10.1016/j.orgel.2015.12.008).
In various implementations of the present disclosure, the solvent used for rinsing is the same solvent used in the deposition of the QDs or of the cross-linkable hole transporting material. In other implementations, the solvent used for rinsing is a similar solvent or orthogonal solvent to the solvent used deposition of the QDs or of the cross-linkable hole transporting material.
To deposit multiple layers in a typical QLED structure using solution process methods, solution of different materials in adjacent orthogonal solvents should be deposited. Solution process methods include, but are not limited to, methods of drop casting, spin coating, dip coating, slot die coating, spray coating, and inkjet printing.
In one implementation, the electron transporting material (e.g. ZnO) is dissolved and deposited in Ethanol, the emissive material (e.g. QDs) is dissolved and deposited in octane, the cross-linkable hole transporting material (e.g. OTPD) is dissolved and deposited in toluene (or in PGMEA, or in THF, or in chlorobenzene), the hole injection material (e.g. PEDOT:PSS-MoO3) is dissolved and deposited in an ethanol/2-propanol mixture.
The disclosed substrates may be made from any suitable material(s) as are typically used in light-emitting devices, such as glass substrates and polymer substrates. More specific examples of substrate materials include polyimides, polyethenes, polyethylenes, polyesters, polycarbonates, polyethersulfones, polypropylenes, and/or polyether ether ketones.
The disclosed substrates may be any suitable shape and size. In various implementations of the present disclosure, the dimensions of the substrate allow for more than one light-emitting device to be provided thereon. In an example, a major surface of the substrate may provide an area for multiple light-emitting devices to be formed as sub-pixels of a pixel, with each sub-pixel emitting light of a different wavelength such as red, green, and blue. In another example, a major surface of the substrate may provide an area for multiple pixels to be formed thereon, each pixel including a sub-pixel arrangement of multiple light-emitting devices.
In various implementations of the present disclosure, the disclosed electrodes may be made from any suitable material(s) as are typically used in light-emitting devices. At least one of the electrodes is a transparent or semi-transparent electrode for light emission, and the other of the electrodes is a reflective electrode to reflect any internal light toward the light-emitting side of the device.
In bottom-emitting devices according to various implementations of the present disclosure, the first electrode may be transparent or semi-transparent. Typical materials for the transparent or semi-transparent electrode include indium-doped tin oxide (ITO), fluorine doped tin oxide (FTO) or indium-doped zinc oxide (IZO), aluminum-doped zinc-oxide (AZO), indium-doped cadmium-oxide and other similar materials.
In top-emitting devices according to various implementations of the present disclosure, the first electrode may be made of any suitable reflective metal such as silver or aluminium. In bottom-emitting devices according to various implementations of the present disclosure, the second deposited electrode is a reflective electrode. Suitable materials used for the reflective electrode include metals such as aluminium or silver (cathodes for an existing structure) and gold, aluminium, silver or platinum (anodes for an inverted structure). Top-emitting structures will use a semi-transparent as the second deposited electrode such as thin (<20 nm) silver, a metallic bilayer (e.g. 2 nm Aluminium/15 nm Silver), a silver nanowires layer or a magnesium-silver alloy.
The disclosed electrodes may also be provided in any suitable arrangement. As an example, the electrodes may address a thin-film transistor (TFT) circuit.
In various implementations of the present disclosure, materials for the disclosed QD core and shell include one or more of. InP, CdSe, CdS, CdSexS1−x, CdTe, CdxZn1−xSe, CdxZn1−xSeyS1−y, ZnSe, ZnS, ZnSxTe1−x, ZnSexTe1−x, perovskites of the form ABX3, ZnwCuzIn1−(w+z)S, and carbon, where 0≤w, x, y, z≤1. Materials for the disclosed ligands include alkyl, -alkenyl, -alkynyl or aryl (linear, branched or cyclic) thiols with 1 to 30 atoms of carbon; alkyl, -alkenyl, -alkynyl or aryl (linear, branched or cyclic) alcohols with 1 to 30 atoms of carbon; alkyl, -alkenyl, -alkynyl or aryl (linear, branched or cyclic) carboxylic acids with 1 to 30 atoms of carbon; tri-alkyl, -alkenyl, -alkynyl or aryl (linear, branched or cyclic) phosphine oxides with 1 to 60 atoms of carbon; alkyl, -alkenyl, -alkynyl or aryl (linear, branched or cyclic) amines with 1 to 30 atoms of carbon; salts formed from any of the above listed compounds (the anion or the cation are the binding moieties); halogen salts (the anion or the cation are the binding moieties).
It will be appreciated that while the present disclosure primarily describes the QDs as core-shell QDs, in some implementations the QDs may not be of the core-shell type or they may be of a core/multiple-shells type having more than one shell. The non-core-shell type QDs may be made from one or more of the above-mentioned materials, and the QDs in accordance with the present disclosure may not include a core-shell configuration.
In various implementations of the present disclosure, a solvent, a mixture of solvents, a mixture or a solution can be used as developer for the QDs and the cross-linkable material not polymerised (and the photo initiator, if included). For example, the solvent may be selected such that the quantum dots, the cross-linkable material when not polymerised (and the photo initiator, if included) is soluble therein.
In various implementations of the present disclosure, example solvents include, but are not limited to, the following or mixtures including the following: acetone, dichloromethane, chloroform, linear or branched alkyl acetates (e.g. ethyl acetate, n-butyl acetate, 2-butyl acetate), linear or branched alkanes with 3 to 30 atoms of carbon (e.g., pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane), linear or branched alcohols with 1 to 20 atoms of carbon (e.g., butanol, 2-propanol, propanol, ethanol, methanol), linear or branched alkoxy alcohols with 2 to 20 atoms of carbon (e.g., 2-Methoxyethanol, 2-Ethoxyethanol), mono, di and tri halogen substituted benzenes (e.g., chlorobenzene, 1,2-dibromobenzene, 1,3-dibromobenzene, 1,4-dibromobenzene, 1,3,5-tribromobenzene, 1,2,4-tribromobenzene), linear or branched ethers with 2 to 20 atoms of carbon, and/or mono, di and tri alkyl substituted benzenes (e.g., toluene, 1,2-Dimethylbenzene, 1,3-Dimethylbenzene, 1,4-Dimethylbenzene), benzene, dioxane, propylene glycol monomethyl ether acetate (PGMEA), 1-methoxy-2-propanol, water.
In various implementations of the present disclosure, example solutions may include any alkaline or acidic material in one or in a mixture of the previously disclosed solvents. The particular solvent or developer that is utilized may depend on the specific QDs, cross-linkable material, and photo initiator that are selected.
In various implementations of the present disclosure, the solvent used for rinsing is the same solvent used in the deposition of the QDs or of the cross-linkable hole transporting material. In other implementations, the solvent used for rinsing is a similar solvent or orthogonal solvent to the solvent used deposition of the QDs or of the cross-linkable hole transporting material.
In various implementations of the present disclosure, example insulating materials for the banks may include, but are not limited to, polyimides. In some examples, the insulating material may include a surface treatment, such as for example fluorine, to modify the insulating material wetting properties.
For example, the insulating material may be made hydrophilic to prevent the deposited material from sticking on the banks and to ensure the subpixel is filled properly. The insulating material thus forms wells and the bottoms may include different electrodes (e.g., anodes) for each subpixel.
In various implementations of the present disclosure, the cross-linked hole transporting layer is formed using one or more photo-initiators. As such, the layer described in this application may include one or more photo-initiators. A photo initiator is a material that initiates polymerization in response to light stimuli. In various implementations of the present disclosure, the photo initiator may generate one or more radicals, ions, acids, and/or species that may initiate such polymerization.
In various implementations of the present disclosure, the initiator is a photo initiator. Example photo initiators include sulfonium- and iodonium-salts (e.g. triphenylsulfonium triflate, diphenyliodonium triflate, iodonium, [4-(octyloxy)phenyl]phenyl hexafluorophosphate, bis(4-methylphenyl)iodonium hexafluorophosphate, diphenyliodonium hexafluoroarsenate, diphenyliodonium hexafluoroantimonate, etc), chromophores containing the benzoyl group (benzoin ether derivatives, halogenated ketones, dialkoxyacetophenones, diphenylacetophenones, etc), hydroxy alkyl heterocyclic or conjugated ketones, benzophenone- and thioxanthone-moiety-based cleavable systems (such as benzophenone phenyl sulfides, ketosulfoxides, etc), benzoyl phosphine oxide derivatives, phosphine oxide derivatives, trichloromethyl triazines, biradical-generating ketones, peroxides, diketones, azides and aromatic bis-azides, azo derivatives, disulfide derivatives, disilane derivatives, diselenide and diphenylditelluride derivatives, digermane and distannane derivatives, peresters, barton's ester derivatives, hydroxamic and thiohydroxamic acids and esters, organoborates, titanocenes, chromium complexes, aluminate complexes, tempo-based alkoxyamines, oxyamines, alkoxyamines, and silyloxyamines.
In various implementations of the present disclosure, when the specific area of the deposited layer is exposed to UV light, the photo initiator initiates the polymerization of the cross-linkable material. QDs, ligands of the QDs, cross-linkable material, charge transporting material, and photo-initiator can be selected to create uniform dispersion in the deposition solvent. Materials with similar polarity indexes can be selected to ensure homogeneity of the deposited mixtures.
In various implementations of the present disclosure, the electron transport and/or electron injection layers may include individual or combinations of. ZnO, 8-quinolinolato lithium (Liq.), LiF, Cs2CO3, MgxZn1−xO, AlxZn1−xO, GaxZn1−xO, 2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi), TiO2, ZrO2, N4,N4′-Di(naphthalen-1-yl)-N4,N4′-bis(4-vinylphenyl)biphenyl-4,4′-diamine (VNPB), 9,9-Bis[4-[(4-ethenylphenyl)methoxy]phenyl]-N2,N7-di-1-naphthalenyl-N2,N7-diphenyl-9H-Fluorene-2,7-diamine (VB-FNPD), where 0≤x≤1.
In various implementations of the present disclosure, the electron blocking layers may include individual or combinations of: any of the materials used as hole transporting and electron transporting layers, polyethylenimine (PEI) and Polyethylenimine, 80% ethoxylated (PEIE), Poly(methyl methacrylate) (PMMA), molybdenum oxide, aluminium, and the like.
In various implementations of the present disclosure, the hole transport and/or hole injection layers may include individual or combinations of: poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), poly(9,9-dioctylfluorene-co-N-(4-sec-butylphenyl)-diphenylamine) (TFB), poly(9-vinylcarbazole) (PVK), poly(N,N′-bis(4-butylphenyl)-N,N′-bisphenylbenzidine) (PolyTPD), V2O5, NiO, CuO, WO3, MoO3, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), 1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile (HATCN), N4,N4′-Bis(4-(6-((3-ethyloxetan-3-yl)methoxy)hexyl)phenyl)-N4,N4′-diphenylbiphenyl-4,4′-diamine (OTPD), N4,N4′-Bis(4-(6-((3-ethyloxetan-3-yl)methoxy)hexyloxy)phenyl)-N4,N4′-bis(4-methoxyphenyl)biphenyl-4,4′-diamine (QUPD), N,N′-(4,4′-(Cyclohexane-1,1-diyl)bis(4,1-phenylene))bis(N-(4-(6-(2-ethyloxetan-2-yloxy)hexyl)phenyl)-3,4,5-trifluoroaniline) (X-F6-TAPC), 3,5-di-9H-carbazol-9-yl-N,N-bis[4-[[6-[(3-ethyl-3-oxetanyl)methoxy]hexyl]oxy]phenyl]-benzenamine (Oxe-DCDPA).
In various implementations of the present disclosure, the disclosed cross-linked materials are originated from the polymerisation of a cross-linkable organic (or organo-metallic) material. UV-induced cross-linked charge transport materials include UV-induced cross-linked hole transport materials and/or UV-induced cross-linked electron transport materials. Accordingly, the matrix of one or more UV-induced cross-linked charge transport materials may be formed from one or more types of cross-linkable materials. Such materials include one or more hole transport materials and/or one or more electron transport materials.
In various implementations of the present disclosure, the cross-linkable hole transport material may be a material which is an effective hole transporter both without and with crosslinking. In other implementations, the cross-linkable hole transport material may be a material which is an effective hole transporter only when cross-linked.
In various implementations of the present disclosure, the cross-linkable electron transport material may be a material which is an effective electron transporter both without and with crosslinking. In other implementations, the cross-linkable electron transport material may be a material which is an effective electron transporter only when crosslinked. In some implementations, the cross-linked charge transport materials can include one or more of hole injection materials, electron injection materials, hole blocking materials, electron blocking materials, and/or interconnecting materials (ICM).
In various implementations of the present disclosure, the cross-linkable material from which the UV-induced crosslinked charge transport material may be formed includes at least two moieties with different characteristics. As an example, one of the at least two moieties of the molecule may provide charge transporting properties and another of the at least two moieties of the molecule may provide UV-cross-linking capabilities. Exemplary moieties that may provide charge transporting properties include, but are not limited to, tertiary, secondary, and primary aromatic or aliphatic amines, heterocyclic amines, tryaryl phosphines, and quinolinolates. Exemplary moieties that may provide UV-cross-linking capabilities include, but are not limited to, oxetane, epoxy, thiol, alkane, alkene, alkyne, ketone, azide, and aldehyde units. In some implementations, the two moieties may be connected and there may be a distance of less than 20 nm between them.
In various implementations of the present disclosure, the mixture of the cross-linkable material with the QDs can include a small molecule co-monomer that allows polymerization. The co-monomer may contain at least one functional group X that may interact with a functional group Y of the cross-linkable material. The cross-linkable material may include such functional group Y at two or more molecular sites.
For example, the functional group X may be at two ends of the co-monomer; the functional groups Y may be at two ends of the cross-linkable material. In one implementation, the functional groups X may be a thiol, and the function groups Y may be an alkene or alkyne, or vice versa. In another implementation, the functional groups X may be an azide, and the function groups Y may be an alkane or alkene or alkyne, or vice versa.
Ligands of the QDs, co-monomers and cross-linkable materials included in the mixture can be selected to create uniform dispersion in the deposition solvent. Materials with similar polarity indexes can be selected to ensure homogeneity of the deposited mixtures.
One implementation of a cross-linkable material from which the structure described above may be formed is N4,N4′-Bis(4-(6-((3-ethyloxetan-3-yl)methoxy)hexyl)phenyl)-N4,N4′-diphenylbiphenyl-4,4′-diamine (OTPD), shown below in Formula 1.
Another example of a cross-linkable material from which the structure described above may be formed is N4,N4′-Bis(4-(6-((3-ethyloxetan-3-yl)methoxy)hexyloxy)phenyl)-N4,N4′-bis(4-methoxyphenyl)biphenyl-4,4′-diamine (QUPD), shown below in Formula 2.
Another example of a cross-linkable material from which the structure described above may be formed is N,N′-(4,4′-(Cyclohexane-1,1-diyl)bis(4,1-phenylene))bis(N-(4-(6-(2-ethyloxetan-2-yloxy)hexyl)phenyl)-3,4,5-trifluoroaniline) (X-F6-TAPC), shown below in Formula 3.
An example of a cross-linkable material from which the structure described above may be formed is N4,N4′-Di(naphthalen-1-yl)-N4,N4′-bis(4-vinylphenyl)biphenyl-4,4′-diamine (VNPB), shown below in Formula 4.
Another example of a cross-linkable material from which the structure described above may be formed is 9,9-Bis[4-[(4-ethenylphenyl)methoxy]phenyl]-N2,N7-di-1-naphthalenyl-N2,N7-diphenyl-9H-Fluorene-2,7-diamine (VB-FNPD), shown below in Formula 5.
Another example of a cross-linkable material from which the structure described above may be formed is 3,5-di-9H-carbazol-9-yl-N,N-bis[4-[[6-[(3-ethyl-3-oxetanyl)methoxy]hexyl]oxy]phenyl]-benzenamine (Oxe-DCDPA), shown below in Formula 6.
In various implementations of the present disclosure, for top-emitting devices that include reflective electrodes (e.g. the first electrodes) and partially reflective electrodes (e.g. the second electrode), an optical cavity can be established for the light emitted from QDs by electroluminescence. The distance between the QDs emitting light and the first electrode, and the distance between the QDs emitting light and the second electrode, can have a significant effect on the optical mode of the cavity, and consequently on the properties of the light emitted through the second electrode.
For example, such parameters can affect the efficiency of light escaping from the light emitting device, and the dependence of intensity and wavelength on emission direction. Therefore, it is often preferable to select the thickness of layers disposed between the QDs and the electrodes to provide a favorable optical cavity for optimal light efficiency. Suitable thicknesses are different for different wavelengths of light (e.g. different between a device emitting red light and a device emitting green light).
It is evident that various techniques can be utilized for implementing the concepts described in the present disclosure without departing from the scope of those concepts. Moreover, while the disclosure is with regard to specific implementations, a person of ordinary skill in the art will recognize that changes may be made in form and detail without departing from the scope of the disclosure. As such, the disclosure is to be considered in all respects as illustrative and not restrictive. It should also be understood that the present disclosure is not limited to the particular implementations described since many rearrangements, modifications, and substitutions are possible without departing from the scope of the present disclosure.
