This U.S. non-provisional patent application claims priority under 35 U.S.C. §119 of Korean Patent Application No. 10-2014-0112399, filed on Aug. 27, 2014, the entire contents of which are hereby incorporated by reference.
The present invention disclosed herein relates to a method of fabricating a light scattering layer, and an organic light emitting diode including the same.
In recent, demands for product weight reduction, size decrease and inexpensive price are increasing in lighting device and electronic device such as a portable phone or notebook computer. In order to satisfy such demands, an organic light emitting diode (OLED) receives attention as a display device and light emitting device installed in the electronic device and lighting device. In particular, since the OLED has advantages in low power consumption, light weight and inexpensive cost, it is widely used in the electronic device and lighting device.
In recent, researches on increasing light-emitting efficiency of the OLED are being performed. In particular, various researches on showing high light-emitting efficiency even at a lower voltage by externally extracting light emitted from the inside of the OLED are being performed.
The present invention provides a method of fabricating a light scattering layer that has simplified processes.
The present invention also provides an organic light emitting diode (OLED) including a light scattering layer.
Tasks to be performed by the present invention are not limited to the above-mentioned tasks and other tasks not mentioned may be clearly understood by a person skilled in the art from the following descriptions.
Embodiments of the present invention provide methods of fabricating a light scattering layer including: coating a first surface of a substrate with a nano structure; and etching the substrate exposed to the nano structure by using the nano structure as an etching mask to allow the first surface of the substrate to have a recess to form first partitions protruding from the first surface of the substrate.
In other embodiments of the present invention, methods of fabricating a light scattering layer, the method includes coating a substrate with a nano structure; applying heat to the substrate to melt the nano structure to form a nano droplet; and etching the substrate exposed to the nano droplet as an etching mask to allow an upper surface of the substrate to have a recess to form protrusions protruding from the upper surface of the substrate.
In still other embodiments of the present invention, organic light emitting diodes (OLED) include a light scattering layer; a first electrode disposed on the light scattering layer; an organic light emitting layer disposed on the first electrode; and a second electrode disposed on the organic light emitting layer, wherein the light scattering layer includes partitions protruding from a surface of the light scattering layer.
The accompanying drawings are included to provide a further understanding of the present invention, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present invention and, together with the description, serve to explain principles of the present invention. In the drawings:
The advantages and features of the present invention, and implementation methods thereof will be clarified through the following embodiments described with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to make this disclosure complete and fully convey the scope of the present invention to a skilled in the art. Further, the present invention is only defined by the scopes of claims. The same reference numerals throughout the disclosure refer to the same components.
The terms used herein are only for explaining embodiments, not limiting the present invention. The terms in a singular form in the disclosure may also include plural forms unless otherwise specified. The terms used herein “comprises” and/or “comprising” do not exclude the presence or addition of one or more additional components, steps, operations and/or elements other than the components, steps, operations and/or elements that are mentioned.
Also, embodiments in the present disclosure are described with reference to ideal, exemplary cross-sectional views and/or plan views of the present invention. The thicknesses of layers and regions in the drawings are exaggerated for the effective description of technical content. Thus, the forms of exemplary views may vary depending on manufacturing technologies and/or tolerances. Thus, embodiments of the present invention are not limited to shown specific forms and also include variations in form produced according to manufacturing processes. For example, an etch region shown as a rectangular shape may have a round shape or a shape having a certain curvature. Thus, regions illustrated in the drawings are exemplary, and the shapes of the regions illustrated in the drawings are intended to illustrate the specific shapes of the regions of elements and not to limit the scope of the present invention.
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The light scattering layer 10 includes a first surface 11 and a second surface 13 opposite to the first surface 11. The planarization layer 20 is disposed on the first surface 11 of the light scattering layer 10. The light scattering layer 10 may be formed of a transparent material (e.g., glass or polymeric material).
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According to another embodiment of the present invention, referring to
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The first electrode 30 is disposed on the planarization layer 20. The first electrode 30 may be an anode electrode. The first electrode 30 may include a material having a lower refractive index than the planarization layer 20. In other words, a refractive index of the planarization layer 20 is higher than a refractive index of the first electrode 30. The first electrode 30 may include a conductive material having transparency. The first electrode 30 may be a Transparent Conductive Oxide (TCO), such as an Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), carbon based electrode, conductive polymeric material or conductive nano wire.
The hole transfer layer 40 is disposed on the first electrode 30. Specifically, the hole transfer layer 40 may include a hole injection layer (not shown) and a hole transport layer (not shown) that are sequentially stacked on the first electrode 30.
A Highest Occupied Molecular Orbital (HOMO) represents the highest energy level of a valence band and a Lowest Unoccupied Molecular Orbital (LUMO) represents the lowest energy level of a conduction band.
By decreasing the difference between the work function level of the first electrode 30 and the HOMO level of the hole transport layer, the hole injection layer performs a function of facilitating the injection of a hole into the hole transport layer.
The hole transport layer may provide the organic light emitting layer 50 with a hole moving through the hole injection layer. The HOMO level of the hole transport layer may be higher than the HOMO level of the organic light emitting layer 50.
The organic light emitting layer 50 is disposed on the hole transfer layer 40. It may include a fluorescent material or phosphor. The organic light emitting layer 50 may include DPVBi, IDE 120, IDE 105, Alq3, CBP, DCJTB, BSN, DPP, DSB, PESB, PPV derivatives, PFO derivatives, C545t, Ir(ppy)3, or PtOEP, for example. The organic emission layer 50 may be a single layer or multiple layers.
The electron transfer layer 60 is disposed on the organic light emitting layer 50. Specifically, the electron transfer layer 60 includes an electron transport layer (not shown) and an electron injection layer (not shown) that are sequentially stacked on the organic light emitting layer 50.
The electron injection layer may include a material having high electron mobility. The electron injection layer may include lithium (Li), magnesium (Mg), aluminum (Al), calcium (Ca), silver (Ag) or cesium (Cs). The electron injection layer may include lithium fluoride (LiF) or cesium fluoride (CsF). The electron injection layer performs a function of stably supplying an electron to the organic light emitting layer 50.
The second electrode 70 is disposed on the electron transfer layer 60. The second electrode 70 may be a negative electrode. The second electrode 70 may include a conductive material having a lower work function level than the first electrode 30. The second electrode 70 may include a conductive material being semi-transparent or having high reflectance. The second electrode 70 may include aluminum (Al), gold (Au), silver (Ag), iridium (Ir), molybdenum (Mo), palladium (Pd) or platinum (Pt), for example.
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The first electrode 30 is disposed on the light scattering layer 10. The light scattering layer 10 includes a first surface 11 and a second surface 13 opposite to the first surface 11. The first surface 11 of the light scattering layer 10 is a planar surface and may be in direct contact with the first electrode 30.
The second surface 13 the light scattering layer 10 may include a plurality of partitions 15 protruding from the second surface 13. The partitions 15 may be randomly disposed. Since adjacent partitions 15 cross each other, the light scattering layer 10 may have a space 17 (see
Since light not entering the interface between the air and the light scattering layer 10 impinges into the partitions 15, is scattered and enters the organic light emitting layer 50, the light scattering layer 10 may have a function of enhancing light extraction. Thus, the light scattering layer 10 may enhance the external light extraction of the OLED.
The hole transfer layer 40, organic light emitting layer 50, electron transfer layer 60 and second electrode 70 may be sequentially disposed on the first electrode 30.
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The light scattering layer 10 includes a first surface 11 and a second surface 13 opposite to the first surface 11. The planarization layer 20, first electrode 30, hole transfer layer 40, organic light emitting layer 50, electron transfer layer 60 and second electrode 70 are sequentially stacked on the first surface 11 of the light scattering layer 10. The light scattering layer 10 may include a plurality of upper partitions 15a protruding from the first surface 11 of the light scattering layer 10. The upper partitions 15a may be randomly disposed. Since adjacent partitions 15 cross each other, the light scattering layer 10 may have a first space 17a formed by different upper partitions 15a. The bottom portion of the first space 17a may be configured by the first surface 11 of the light scattering layer 10 and the sidewalls of the first space 17a may be configured by different upper partitions 15a. The widths W1 of the upper partitions 15a may be about 100 nm to about 2000 nm. The widths W1 of the upper partitions 15a may be the same or different from one another.
The planarization layer 20 may be disposed on the first surface 11 of the light scattering layer 10. The planarization layer 20 may be configured to cover the light scattering layer 10 and fill the first space 17a in direct contact with the first surface 11 of the light scattering layer 10. The planarization layer 20 may cover the first surface 11 of the light scattering layer 10 to provide a planar surface.
The light scattering layer 10 may include a plurality of lower partitions 15b protruding from the second surface 13 of the light scattering layer 10. The lower partitions 15b may be randomly disposed. Since adjacent lower partitions 15b cross each other, the light scattering layer 10 may have a second space 17b formed by different lower partitions 15b. The bottom portion of the second space 17b may be configured by the second surface 13 of the light scattering layer 10 and the sidewalls of the second space 17b may be configured by different lower partitions 15b. The widths W2 of the lower partitions 15b may be about 100 nm to about 2000 nm. The widths W2 of the lower partitions 15b may be the same or different from one another. The widths W2 of the lower partitions 15b may be the same as or different from the widths W1 of the upper partitions 15a. The upper partitions 15a of the light scattering layer 10 may scatter light confined in the interface between the light scattering layer 10 and the first electrode 30 to allow light to enter the organic light emitting layer 50, and the lower partitions 15b of the light scattering layer 10 may scatter light not entering the interface between the light scattering layer 10 and the air to allow light to enter the organic light emitting layer 50.
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The first surface 11 of the substrate 1 is coated with a nano structure 61. The nano structure 61 may be a nano wire or nano fiber. As an example, when the nano structure 61 is the nano wire, the substrate 1 may be coated with a solution 63 to which the nano wire is sprayed. The nano wire may be mixed with the solution 63 and disposed on the first surface 11 of the substrate 1 when the substrate 1 is coated with the solution 63. The substrate 1 may be coated with the solution 63 by using any one of spray coating and slot die coating methods. The solution 63 may be used as the spray solution of the nano structure 61. As other example, when the nano structure 61 is the nano fiber, the substrate 1 may be coated directly with the nano fiber by using electrospinning As another example, the nano structure 61 may be deposited on the substrate 1 by using Langmuir-Blodgett, Electrospinning or contact printing. In this case, a plurality of nano structures 61 may be aligned in a fashion of stripes.
The nano structure 61 may have a diameter D of about 100 nm to about 2000 nm and a length L of about 300 nm to about 3000 nm but is not limited thereto. A plurality of nano structures 61 may have different diameters on the substrate 1. The nano structure 61 may include a metallic material or an inorganic material. The metallic material may include silver (Ag) or gold (Au), for example.
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The first surface 11 of the substrate 1 has the recess, so it is possible to form partitions 15 protruding from the first surface 11 of the substrate 1. The partitions 15 may be a portion of the substrate 1 not etched by the nano structure 61. The partitions 15 may have the same width W1 as the diameter D of the nano structure 61. Thus, the widths W1 of the partitions 15 may be the same or different from one another. The partitions 15 may be formed to be randomly disposed on the substrate 1. Adjacent partitions 15 on the first surface 11 of the substrate 1 cross one another so that the space 17 may be formed. Thus, the bottom portion of the space 17 may be configured by the first surface 11 of the substrate 1 and the sidewalls of the space 17 may be configured by different partitions 15.
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According to another embodiment, the substrate 1 may be etched by using the plurality of the nano structures 61 aligned in a fashion of stripes as an etching mask. Thus, the light scattering layer 10 having the partitions 15 aligned a fashion of stripes may be formed as shown in
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According to an embodiment of the present invention, the nano structure is used as the etching mask to form the light scattering layer. Since the nano structures are randomly disposed without a planned orientation and used as the etching mask, it is possible to form randomly disposed patterns. Thus, it is possible to form a light scattering layer capable of being applied to light having various wavelengths and the fabricating process of the light scattering layer may be simplified.
While embodiments of the present invention are described with reference to the accompanying drawings, a person skilled in the art may understand that the present invention may be practiced in other particular forms without changing technical spirits or essential characteristics. Therefore, embodiments described above should be understood as illustrative and not limitative in every aspect.
Number | Date | Country | Kind |
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10-2014-0112399 | Aug 2014 | KR | national |