KR20160118988A - Light emitting device and method for fabricating the same - Google Patents

Abstract

The present invention provides a light emitting device having a conductive thin polymer layer interposed between a hole injection layer and a hole transport layer, and a method for manufacturing the same. The light emitting device comprises: i) a first electrode; ii) polyethylene-dioxythiophene:polystyrene-sulfonate (PEDOT:PSS); iii) a hole injection layer including poly(3,4-ethylenedioxythiophene)polystyrene sulfonate; iv) a conductive thin polymer layer positioned on the hole injection layer, and including polyaniline-poly(4-styrenesulfonate) (PANI:PSS); v) a hole transport layer positioned on the conductive thin polymer layer, and including poly-n-vinylcarbazole (PVK); vi) a light emitting layer positioned on the hole transport layer; vii) an electron transport layer positioned on the light emitting layer, and including zinc oxide (ZnO); and viii) a second electrode positioned on the electron transport layer. The light emitting layer includes a core including a cadmium selenide (CdSe) and a shell surrounding the core and including zinc cadmium sulfide (CdZnS).

Description

 BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a light emitting device,

The present invention relates to a light emitting device and a manufacturing method thereof. More particularly, the present invention relates to a light emitting device in which a conductive polymer thin film layer is interposed between a hole injection layer and a hole transporting layer to control an energy level of the hole transporting layer, and a manufacturing method thereof.

The light emitting element has at least one layer capable of conducting current. The light emitting element is composed of two opposing electrodes and organic and inorganic thin films and a light emitting layer having a multilayered semiconductor property located therebetween.

The light emitting device is divided into a front light emitting type, a back light emitting type, and a both surface light emitting type. In the front emission and back emission, one of the two electrodes is light transmissive, and in the two-sided emission type, both electrodes are light transmissive. However, when the light-transmitting element is used as the anode in the light-emitting element, a Schottky barrier is formed at the interface between the light-emitting layer and the light-transmitting electrode, so that hole injection is not smooth.

And to provide a light emitting device capable of controlling the energy level of the hole transport layer. Also, a method of manufacturing the above-described light emitting device is provided.

A light emitting device according to an embodiment of the present invention includes i) a first electrode, ii) a PEDOT: PSS (Polyethylene-Dioxiophene: Polystyrene-Sulfonate, Poly (3,4-ethylenedioxythiophene) (iii) a conductive polymer thin film layer disposed on the hole injection layer and including PANI: PSS (polyaniline-poly (4-styrenesulfonate)), iv) A hole transporting layer containing PVK (poly-n-vinylcarbazole), v) a light emitting layer located on the hole transporting layer, vi) an electron transporting layer located on the light emitting layer and containing zinc oxide (ZnO), and v) And a second electrode located above the first electrode. The light emitting layer includes a core containing cadmium selenide (CdSe) and a shell surrounding the core and containing zinc cadmium sulfide (CdZnS).

The ratio of the PSS (polystyrene-sulfonate) to the PANI (polyaniline) of the conductive polymer thin film layer may be 1: 8 to 1:13. The hole injection layer may further include PANI: PSS (polyaniline-poly (4-styrenesulfonate)). The surface roughness of the conductive polymer thin film layer may be 0.1 nm to 5 nm.

A method of manufacturing a light emitting device according to an embodiment of the present invention includes the steps of: i) providing a substrate; ii) depositing a first electrode on a substrate; iii) depositing a first material including PEDOT: PSS on the first electrode (Iv) spin-coating a second material including PANI: PSS (polyaniline: polystyrene-sulfonate) / poly (4-styrenesulfonate) on the hole injection layer; V) providing a hole transporting layer by spin-coating a material comprising PVK (poly-n-vinylcarbazole poly-vinylcarbazole) on the conductive polymer thin film layer, vi) forming a conductive polymer thin film layer on the conductive polymer thin film layer, Coating a nanostructure including a core containing cadmium and a shell containing zinc cadmium sulfide around the core to provide a light emitting layer, vii) providing a light emitting layer on the light emitting layer, Depositing the transport layer, and viii) a step of depositing a second electrode on the electron transport layer.

A method of manufacturing a light emitting device according to an embodiment of the present invention includes the steps of: i) removing a substrate; and ii) performing a plasma treatment, ultraviolet ozone treatment, or reactive ion etching (RIE) The method comprising the steps of: The method may further include the step of providing another hole transport layer including the second material on the conductive polymer thin film layer before the step of providing the light emitting layer.

The energy level of the hole transport layer can be adjusted by inserting a conductive polymer thin film layer between the hole injection layer and the hole transport layer into the intermediate layer. And the height of the interface energy barrier between the hole transport layer and the light emitting layer or the hole transport layer and the optoelectronic conversion layer can be reduced. Therefore, the efficiency of the light emitting device can be improved

1 is a schematic perspective view of a light emitting device according to a first embodiment of the present invention.
2 is a diagram schematically showing an energy level diagram of the light emitting device of FIG.
3 is a schematic perspective view of a light emitting device according to a second embodiment of the present invention.
4 and 5 are SEM micrographs of the surface of the light emitting device manufactured according to Experimental Example 1 and Experimental Example 2 of the present invention, respectively.
6 is an atomic force microscope photograph of the surface of a light emitting device manufactured according to Experimental Example 3 of the present invention.
7 is a graph showing the current density according to the voltage change of the light emitting device manufactured according to Experimental Example 4 and Comparative Example 1 of the present invention.
8 is a graph showing the log current density according to the log voltage change of the light emitting device manufactured according to Experimental Example 5 and Comparative Example 2. FIG.
9 is a graph of luminance according to voltage change of the light emitting device manufactured according to Experimental Example 6 and Comparative Example 3. FIG.
10 is a graph of luminous efficiency according to voltage change of the light emitting device manufactured according to Experimental Example 7 and Comparative Example 4. FIG.
FIG. 11 is a graph of electroluminescence and photoluminescence according to wavelengths of a light emitting device manufactured according to Experimental Example 8, Comparative Example 5, and Comparative Example 6. FIG.
12 is a color coordinate diagram according to a voltage change of the light emitting device manufactured according to Experimental Example 9 and Comparative Example 7.
13 is a graph of a cutoff according to the binding energy of the light emitting device manufactured according to Experimental Example 10. FIG.
14 is a graph of the HOMO energy level of the light emitting device manufactured according to Experimental Example 11.
15 is an energy level diagram of a light emitting device manufactured according to Experimental Example 12 and Comparative Example 8.
16 is a graph showing the current density according to the voltage change of the light emitting device manufactured according to Experimental Example 13 and Comparative Example 9. FIG.
17 is a graph of a cutoff according to the content ratio of PSS to PANI of the light emitting device manufactured according to Experimental Example 14 and Experimental Example 15. FIG.
18 is an energy level diagram according to the variation of the content ratio of PSS to the PANI of the light emitting device manufactured according to Experimental Example 16. FIG.
19 is a graph of absorption spectrum according to the content ratio of PSS to PANI of a light emitting device manufactured according to Experimental Example 17. FIG.
FIG. 20 is a graph of a transmission spectrum according to the content ratio of PSS to PANI of the light emitting device manufactured according to Experimental Example 18. FIG.
21 is a graph of FT-IR spectrum according to the content ratio of PSS to PANI of the light emitting device manufactured according to Experimental Example 19. FIG.
22 is a graph of a UPS spectrum according to the content ratio of PSS to PANI of a light emitting device manufactured according to Experimental Example 20. FIG.
23 is a graph of a UPS spectrum according to the content ratio of PSS to the PANI of the light emitting device manufactured according to Experimental Example 21. FIG.
24 is a graph showing the electronic structure level of PVK according to the content ratio of PSS to the PANI of the light emitting device manufactured according to Experimental Example 22. FIG.
25 is a graph showing the electronic structure level of PVK according to the content ratio of PSS to the PANI of the light emitting device manufactured according to Experimental Example 23. FIG.
26 is an energy level diagram of a light emitting device manufactured according to Experimental Example 24. FIG.
27 is a graph of current-voltage and luminance-voltage according to the content ratio of PSS to PANI of a light emitting device manufactured according to Experimental Example 25. FIG.
28 is a graph of current-voltage and luminance-voltage according to the thickness variation of the PANI: PSS layer of the light emitting device manufactured according to Experimental Example 26. FIG.
29 is a graph of an electroluminescence spectrum according to the content ratio of PSS to PANI of a light emitting device manufactured according to Experimental Example 27. FIG.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms as used herein include plural forms as long as the phrases do not expressly express the opposite meaning thereto. Means that a particular feature, region, integer, step, operation, element and / or component is specified, and that other specific features, regions, integers, steps, operations, elements, components, and / And the like.

Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Commonly used predefined terms are further interpreted as having a meaning consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or very formal meanings unless defined otherwise.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

1 is a schematic cross-sectional view of a light emitting device 100 according to a first embodiment of the present invention. The structure of the light emitting device 100 of FIG. 1 is merely for illustrating the present invention, and the present invention is not limited thereto. Therefore, the structure of the light emitting device 100 can be modified in other forms.

1, the light emitting device 100 includes a substrate 10, a first electrode 20, a hole injecting layer 30, a conductive polymer thin film layer 40, a hole transporting layer 50, a light emitting layer 60, An electron transport layer 70, and a second electrode 80. [ Meanwhile, the light emitting device 100 may further include other components in addition to the components shown in FIG.

The substrate 10 can be made of well-warped plastic. Also, the substrate 10 can be made of glass or sapphire (Al ₂ O ₃ ) having excellent mechanical strength, thermal stability and waterproofness.

The first electrode (20) is located above the substrate (10). When the first electrode 20 is an anode, the first electrode 20 may be made of a material having a relatively high work function to facilitate hole injection. For example, the first electrode 20 can be made of indium tin oxide (ITO) and can transmit light. Alternatively, the first electrode 20 may be made of indium zinc oxide (IZO), tin oxide (SnO ₂ ), or zinc oxide (ZnO), which is transparent and has excellent conductivity.

The first electrode 20 may include two different materials to form a two-layer structure. The first electrode 20 may be formed by spin coating or sputtering a conductive material. The surface of the first electrode 20 may be subjected to plasma treatment, ultraviolet ozone treatment or reactive ion etching (RIE) using a laser lift off (LLO) process or the like, ).

The hole injection layer 30 is located on the first electrode 20. The hole injection layer 30 may be formed by spin coating, vacuum plating, laser induced thermal imaging, or the like. When the hole injection layer 30 is manufactured by the vacuum deposition method, the deposition temperature is 100 to 500 DEG C, the vacuum degree is 10-8 torr to 10-3 torr, and the deposition rate is 0.01 to 100 ANGSTROM / sec. Can be adjusted. The deposition conditions can be adjusted according to the material to be used for the hole injection layer 30 and the thermal characteristics thereof.

The hole injection layer 30 may be formed of a phthalocyanine compound or an amine derivative such as 4,4 ', 4 "-tri (N-carbazoyl) triphenylamine (TCTA), 4,4' Tris (3-methylphenylamino) triphenylamine (m-MTDATA), and the like. The hole injection layer 30 may be formed of a conductive dissolution material such as PANI: DBSA (polyaniline: dodecylbenzenesulfonic acid) or PEDOT: PSS (polyethylene-dioxythiophene: polystyrene- ethylenedioxythiophene) polystyrene sulfonate, PANI: CSA (polyaniline: camphor sulfonic acid), and the like. Preferably, the hole injection layer 30 may comprise PEDOT: PSS having conductivity with a high work function.

The conductive polymer thin film layer 40 is disposed between the hole injection layer 30 and the hole transport layer 50 and includes PANI: PSS (polyaniline-poly (4-styrenesulfonate)). The ratio of PSS (polystyrene-sulfonate) to PANI (polyaniline) in the conductive polymer thin film layer 40 may be 1: 1 to 1:30. For example, the ratio of PSS (polystyrene-sulfonate) to PANI (polyaniline) of the conductive polymer thin film layer 40 is 1: 1, 1: 2, 1: 3, 1: 4, 1: 1: 7, 1: 8, 1: 9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15. 1:16, 1:17, 1:18, 1:19, 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, 1:26, 1:27, 1: 28, 1:29, 1:30, preferably from 1: 1 to 1:15, more preferably from 1: 8 to 1:13, and in this range, the light emitting element 100 Can be maximized. The conductive polymer thin film layer 40 efficiently transfers holes from the hole injection layer 30 to the hole transport layer 50. The holes generated in the first electrode 20 reach the light emitting layer 60 through the hole injecting layer 30, the conductive polymer thin film layer 40 and the hole transporting layer 50 and are combined with electrons to emit light.

In general, a light emitting device is a structure of an anode, a hole injecting layer, a hole transporting layer, a light emitting layer, an electron transporting layer, and a cathode. A difference in work function of each layer and a large ionization energy (IE) . Also, when the first electrode 20 is used as an ITO electrode, a schottky barrier may be formed at the interface between the anode and the light emitting layer. When a barrier is formed between the respective layers of the light emitting device, the hole mobility is reduced, so that the light emitting efficiency of the light emitting device can be lowered.

The light emitting device 100 may form a conductive polymer thin film layer 40 including PANI: PSS between the hole injection layer 30 and the hole transport layer 50 to control the hole injection barrier. Therefore, the holes generated in the first electrode 20 can be balancedly injected to reach the light emitting layer 60 smoothly, and thus the luminous efficiency of the light emitting device 100 can be increased. More specifically, this will be described in more detail with reference to FIG.

Fig. 2 schematically shows an energy level diagram of the light emitting device of Fig. Since the respective layers are stacked from left to right in FIG. 2, this corresponds to the direction from the lower direction to the upper direction in FIG.

As shown in Fig. 2, the holes h + move from the left to the right, and the electrons e- move from the right to the left, and meet each other to emit light. Here, in order to move the hole (h +) and the electron (e-) well, it is necessary that the band gaps of the respective components are formed conformally. That is, the energy level barrier does not exist, and the band gaps of the respective constituent elements are formed similarly, so that the hole h + can be transferred well. However, since an energy level barrier exists between the hole injection layer of PEDOT: PSS and the hole transport layer of PVK, which is located at the second position from the left in FIG. 2, a conductive polymer thin film layer of PANI: PSS is formed therebetween do. As a result, since the energy levels of the respective layers of the light emitting element are conformed, holes can be transmitted well.

1, the thickness d1 of the conductive polymer thin film layer 40 may be 5 nm to 200 nm. Preferably, the thickness d1 of the conductive polymer thin film layer 40 may be 5 nm to 12 nm. If the thickness d1 of the conductive polymer thin film layer 40 is too large or too small, it is difficult to form the energy level conformally, and the conduction efficiency of holes may be lowered due to the Schottky barrier. Therefore, when the thickness d1 of the conductive polymer thin film layer 40 is in the range of 5 nm to 12 nm, the energy level can be easily formed most conformally, and the conduction efficiency of holes can be maximized. The surface roughness of the conductive polymer thin film layer 40 may be 0.1 nm to 5 nm. If the surface roughness is too low, the production process of the conductive polymer thin film layer 40 becomes complicated, making it difficult to manufacture. In addition, when the surface roughness is too high, the hole transport efficiency is lowered. Therefore, when the surface roughness is in the range of 0.1 nm to 5 nm, the manufacturing process can be simplest and the hole transport efficiency can be maximized.

The hole transport layer (50) is located on the conductive polymer thin film layer (40). The hole transport layer 50 can be manufactured by a method such as spin coating. The hole transport layer 50 may include PANI: PSS which is the same material as the conductive polymer thin film layer 40. Meanwhile, the hole transport layer 50 may include a triphenylamine or a carbazole derivative. For example, the hole transport layer 50 may further include N-phenylcarbazole or poly-n-vinylcarbazole poly-vinylcarbazole (PVK). More preferably, the hole transport layer 50 may comprise PVK.

The light emitting layer 60 is located above the hole transporting layer 50. The light emitting layer 60 may include a fluorescent host, a phosphorescent host, a fluorescent dopant, and a phosphorescent dopant. When the light emitting layer 60 includes a phosphorescent dopant, a hole blocking layer (not shown) may be further formed between the hole transporting layer 50 and the light emitting layer 60. The hole blocking layer prevents holes from diffusing into the electron transport layer 70, so that the holes and electrons in the light emitting layer 60 can be well matched to further improve the luminous efficiency.

The light emitting layer 60 may be formed of a single core structure including cadmium selenide (CdSe) and zinc cadmium sulfide (CdZnS). Alternatively, the light emitting layer 60 may be formed as a core shell structure. That is, the core can be made of cadmium selenide, and the surrounding shell can be made of zinc sulphide cadmium. On the other hand, a hemispherical shell structure may be formed to surround the shell again. When the light-emitting layer 60 is a core-shell structure, it can have both the properties of the material forming the core and the shell, and thus a structure having a complex function can be formed. The light emitting layer 60 may be manufactured by an imprinting method, an associative phase separation of a polymeric material, or an aerosol-assisted self-assembly method using an aerosol.

The electron transport layer 70 is located above the light emitting layer 60. The electron transporting layer 70 may include a mixture of an electron transporting metal organic compound and an electron transporting organic compound. For example, the electron transporting layer 70 may include ZnO and TiO ₂ . The electron transporting layer 70 can be manufactured by co-positioning an electron transporting organic compound. An electron injection layer (not shown) may be formed on the electron transport layer 70 to efficiently transport electrons injected into the second electrode 80.

The second electrode 80 may be made of a material having a relatively low work function. For example, the second electrode 80 may be formed of at least one selected from the group consisting of Li, Mg, Al, Al-Li, Ca, Mg- - silver (Mg-Ag) or the like. Preferably, the second electrode 80 may be made of aluminum. Alternatively, when the light emitting device 100 is manufactured as a top emission type, the second electrode 80 may be made of indium zinc oxide (ITO) or indium zinc oxide (IZO).

FIG. 3 schematically shows a light emitting device 200 according to a second embodiment of the present invention. Since the light emitting device 200 of FIG. 3 is similar to the light emitting device 100 of FIG. 1, the same reference numerals are used for the same parts, and a detailed description of the same parts is omitted for the sake of convenience.

3, the light emitting device 200 includes a substrate 10, a first electrode 20, a hole injection layer 30, a first hole transport layer 52, a conductive polymer thin film layer 40, A hole transporting layer 54, a light emitting layer 60, an electron transporting layer 70, and a second electrode 80. In addition, the light emitting device 100 may further include layers other than the layers shown in FIG.

The first hole transport layer 52 is located above the hole injection layer 30. The first hole transporting layer 52 can be manufactured by a method such as spin coating. The first hole transport layer 52 may include a carbazole derivative. Alternatively, the first hole transporting layer 50 may include N-phenylcarbazole, poly-n-vinylcarbazole poly-vinylcarbazole (PVK), and the like. Preferably, the first hole transport layer 52 may comprise PVK.

The conductive polymer thin film layer 40 is disposed on the first hole transport layer 52 and the second hole transport layer 54 is disposed on the conductive polymer thin film layer 40. That is, the conductive polymer thin film layer 40 is positioned between the hole transporting layers 52 and 54, and efficiently moves the holes to the light emitting layer 60, thereby enhancing the hole transport efficiency. More specifically, the conductive polymer thin film layer 40 adjusts the energy level inside the hole transporting layers 52 and 54 to lower the energy barrier height with the light emitting layer 60, thereby improving the hole transporting efficiency and the light emitting efficiency. On the other hand, the second hole transporting layer 54 can be manufactured in the same manner as the first hole transporting layer 52.

Hereinafter, the present invention will be described in more detail using experimental examples. These experimental examples are only for illustrating the present invention, and the present invention is not limited thereto.

Tissue observation experiment

Experimental Example  One

A light emitting device having the same structure as in Fig. 1 was manufactured. Then, the surface of the light emitting device was tilted by 45 ° and photographed by a scanning electron microscope (SEM). The photographed surface was ITO, PEDOT: PSS thin film, and PANI: PSS coated surface. Here, the PEDOT: PSS thin film is located on ITO and the PANI: PSS coated surface is located on the PEDOT: PSS thin film.

Experimental Example  1

4 is a scanning electron micrograph of the surface of the light emitting device manufactured according to Experimental Example 1 of the present invention. 4 (a) shows a photograph of the ITO surface photographed through a scanning electron microscope, and FIG. 4 (b) shows a surface photograph of a PEDOT: PSS thin film coated on the surface of ITO photographed through a scanning electron microscope . And FIG. 4 (c) shows a surface photograph of PANI: PSS coated on the surface of the PEDOT: PSS thin film taken by scanning electron microscope.

As shown in FIGS. 4 (b) and 4 (c), when the surface of the light emitting device is observed through a scanning electron microscope, PANI: PSS is coated on the coated surface The flatness of the substrate was high. Therefore, it was confirmed that when the PANI: PSS layer is formed in the light emitting device, the flatness between the thin film interfaces is improved and the holes can be transported more efficiently.

Experimental Example  2

The surface of the light emitting device manufactured by the same method as Experimental Example 1 at 45 degrees inclined QDs was photographed with a scanning electron microscope. The surfaces of the light emitting devices were sequentially coated with QDs / PVK / PEDOT: PSS / ITO and QDs / PVK / PANI: PSS / PEDOT: PSS / ITO.

Experimental Example  Experiment result of 2

5 shows scanning electron microscope photographs of the surface of a light emitting device manufactured according to Experimental Example 2 of the present invention. 5 (a) shows a surface photograph of QDs / PVK / PEDOT: PSS / ITO taken through a scanning electron microscope and FIG. 5 (b) shows a QDs / PVK / PANI: PSS / PEDOT: Surface photograph of PSS / ITO.

5 (a) and 5 (b), when the surface of the light emitting device is observed through a scanning electron microscope, the PANI: PSS thin film is more thinner than the flatness of the PVK coated surface in PEDOT: PSS The surface of the PVK-coated surface was found to have a high flatness. Therefore, it was found that when the PANI: PSS layer is formed on the surface of the PVK, the flatness of the light emitting device is improved and the efficiency of transporting the holes can be improved. Thus, a light emitting device having excellent light emitting efficiency could be manufactured.

Experimental Example  3

The surface of the light emitting device manufactured in the same manner as in Experimental Example 1 was photographed with an atomic force microscope (AFM). The surfaces of the light emitting devices were sequentially coated with QDs / PVK / PEDOT: PSS / ITO and QDs / PVK / PANI: PSS / PEDOT: PSS / ITO.

Experimental Example  Experiment result of 3

6 is a scanning electron micrograph of a surface of a light emitting device according to Experimental Example 3 of the present invention. 6 (a) shows a surface photograph of QDs / PVK / PEDOT: PSS / ITO taken through an interatomic attraction microscope and FIG. 6 (b) shows a QDs / PVK / PANI: PSS / PEDOT: Represents a surface photograph of PSS / ITO.

As shown in FIGS. 6A and 6B, when the surface of the light emitting device is observed through an interatomic attraction microscope, the flatness of the surface coated with PVK on PEDOT: PSS is lower than the flatness of PANI: PSS The surface of PVK coated surface was found to be highly flat on the thin film. Therefore, when the PANI: PSS layer is inserted on the PVK surface, the flatness and the internal quantum efficiency between the thin film interfaces are increased, so that a high efficiency quantum dot light emitting device can be manufactured.

Current density variation and leakage Current value  Measurement experiment

Experimental Example  4

A light emitting device was manufactured using the same method as in Experimental Example 1. After the voltage was raised, the change of the current density and the leakage current value of the light emitting device were measured according to the voltage change.

Comparative Example  One

In general, a commercialized light emitting device was tested. The experimental procedure was the same as Experimental Example 4 described above.

Experimental Example  4 and Comparative Example  1

7 is a graph showing the results of experiments on the current density and the leakage current value according to the voltage change in Experimental Example 4 and Comparative Example 1. FIG. In FIG. 7, the current density is represented by a large graph and the leakage current value is represented by a small graph. 7, the square represents the current density and the leakage current value according to the voltage change of the light emitting device in Comparative Example 1, and the circle represents the current density and the leakage current value according to the voltage change of the light emitting device in Experimental Example 4. [

As shown in the large graph of FIG. 7, the threshold voltages of Experimental Example 4 and Comparative Example 1 were measured at 2V. Experimental Example 4 had a high current density above the threshold voltage, and the current density increased linearly when voltage was applied above 6V. On the other hand, Comparative Example 1 had a comparatively low current density above the threshold voltage, and when the voltage was applied above 6V, the current density was gradually saturated.

On the other hand, as shown in the small graph of FIG. 7, it was found that the light emitting device of Experimental Example 4 had a lower leakage current than the light emitting device of Comparative Example 1 below the threshold voltage. Therefore, it was confirmed that the light emitting device of Experimental Example 4 had a higher current density and lower leakage current than conventional ones, and the luminous efficiency of the light emitting device was increased.

Experiment to measure log current density according to log voltage change

Experimental Example  5

A light emitting device was prepared in the same manner as in Experimental Example 1. After increasing the voltage, the change of the log current density was measured according to the log voltage change.

Comparative Example  2

In general, a commercialized light emitting device was tested. The experimental procedure was the same as Experimental Example 6 described above.

Experimental Example  5 and Comparative Example  Experiment result of 2

FIG. 8 is a graph showing the logarithmic current density according to the logarithmic voltage changes of Experimental Example 5 and Comparative Example 2. FIG. 8 shows the log current density according to the log voltage change of the light emitting device in Comparative Example 2 and the circle shows the log current density according to the log voltage change of the light emitting device in Experimental Example 5. [

8, the graphs of the log voltage and the log current density in Experimental Example 5 and Comparative Example 2 are as follows: (i) an ohmic conduction region (J? V), (ii) a trap-limit conduction region (J? V? n> 2), and iii) the space charge limit conduction region (JαV2). In the ohmic conduction region, the log current density in Experimental Example 5 was 10 times smaller than the log current density in Comparative Example 2. In the trap-limit conduction region, the slope of the log current density according to the log voltage change of Experimental Example 5 was measured more steeper than that of Comparative Example 2. [ Therefore, it was confirmed that the light emitting device of Experimental Example 5 had a higher hole mobility than the light emitting device of Comparative Example 2.

Experiment of luminance measurement according to voltage change

Experimental Example  6

A light emitting device was prepared in the same manner as in Experimental Example 1. After the voltage was raised, the luminance of the light emitting device was measured according to the voltage change.

Comparative Example  3

In general, a commercialized light emitting device was tested. The experimental procedure was the same as Experimental Example 6 described above.

Experimental Example  6 and Comparative Example  Experiment result of 3

9 is a graph showing the results of experiments on the luminance according to the voltage changes of Experimental Example 6 and Comparative Example 3. Fig. 9 shows the luminance according to the voltage change of the light emitting device in Comparative Example 3 and the circle shows the luminance according to the voltage change of the light emitting device in Experimental Example 6. [

As shown in FIG. 9, the maximum luminance of Experimental Example 6 was measured at a voltage of 6.5 cd / m 2 at 320 cd / m 2, and the maximum luminance of Comparative Example 3 was measured at a voltage of 5 V at a value of 15 cd / m 2. That is, it was found that the luminance of the light emitting device in Experimental Example 6 was higher than that in Comparative Example 3. [ Therefore, it was confirmed that the brightness and the luminous efficiency of the light emitting device were improved through the experiment 6.

Experiment to measure luminous efficiency by voltage change

Experimental Example  7

A light emitting device was prepared in the same manner as in Experimental Example 1. After the voltage was raised, the luminous efficiency of the light emitting device was measured according to the voltage change.

Comparative Example  4

In general, a commercialized light emitting device was tested. The experimental procedure was the same as in Experimental Example 7 described above.

Experimental Example  7 and Comparative Example  Experiment result of 4

10 is a graph showing the results of experiments on the luminous efficiency according to the voltage changes of Experimental Example 7 and Comparative Example 4. FIG. In FIG. 10, the square represents the luminous efficiency according to the voltage change of the light emitting device in Comparative Example 4, and the circle represents the luminous efficiency according to the voltage change of the light emitting device in Experimental Example 7. FIG.

10, the maximum luminous efficiency of the light emitting device of Experimental Example 7 was measured to be 0.32 cd / A at a voltage of 5.5 V, and the maximum luminous efficiency of the light emitting device of Comparative Example 4 was measured at a voltage of 2 V to 3.5 V 0.06cd / A. That is, it was confirmed that the luminous efficiency of the light emitting device in Experimental Example 7 was higher than that in Comparative Example 4. That is, it can be confirmed that the amount of electrons and the amount of holes that meet in the light emitting layer are balanced by inserting the PANI: PSS layer into the light emitting device.

Wavelength-dependent Field  Luminescence and Photoluminescence  Measurement experiment

Experimental Example  8

A light emitting device was prepared in the same manner as in Experimental Example 1. After increasing the voltage, electroluminescence and photoluminescence of the light emitting device were measured according to the wavelength change.

Comparative Example  5

In general, a commercialized light emitting device was tested. The experimental procedure was the same as that of Experimental Example 8 described above.

Comparative Example  6

To prepare a light emitting layer having a core shell structure. Cadmium selenide (CdSe) was used as the core material and zinc cadmium sulfide (CdZnS) was used as the shell material. The remaining experimental procedure is the same as Experimental Example 8 described above

Experimental Example  8, Comparative Example  5 and Comparative Example  Experiment results of 6

11 is a graph showing the results of experiments of electroluminescence and photoluminescence according to the wavelength change of Experimental Example 8, Comparative Example 5 and Comparative Example 6. Fig. 11 shows the electroluminescence according to the wavelength change in Experimental Example 8, the electroluminescence according to the wavelength change in Comparative Example 5, and the electroluminescence and the photoluminescence according to the wavelength change in Comparative Example 6 in the straight line .

As shown in FIG. 11, the photoluminescence spectrum of the photoluminescence peak having a half width of 27 nm was strong at a wavelength of 630 nm. Experimental Example 8 and Comparative Example 5 were measured at a wavelength of 633 nm and a half-width of 40 nm as a result of electron-hole recombination. Therefore, in Experimental Example 8, the PANI: PSS layer was inserted into the light emitting device, and it was confirmed that the electroluminescence intensity was 50 times larger than that of Comparative Example 5.

Voltage change Color coordinates  Measurement experiment

Experimental Example  9

A light emitting device was prepared in the same manner as in Experimental Example 1. After the voltage was raised, the color coordinates of the light emitting device were measured according to the voltage change.

Comparative Example  7

In general, a commercialized light emitting device was tested. The experimental procedure was the same as Experimental Example 9 described above.

Experimental Example  9 and Comparative Example  Experiment result of 7

12 is a graph showing the results of experiments on the color coordinates according to the voltage changes of Experimental Example 9 and Comparative Example 7. Fig. 12 shows the color coordinates according to the voltage change of the light emitting device in Experimental Example 9, and the circle shows the color coordinates according to the voltage change of the light emitting device in Comparative Example 7. In FIG.

12, the color coordinates of Experimental Example 9 were measured at a value of (0.66, 0.31) ± (0.02, 0.01) which is a short wavelength red color emission color coordinate according to a voltage change of 2.5 V to 8 V, Respectively. On the other hand, the color coordinates of Comparative Example 7 were measured as the values of the color coordinates (0.66, 0.31) as the voltage was applied. That is, it was confirmed that the light emitting device of Experimental Example 9 had stronger red electroluminescence than the Comparative Example 7 in a wide driving voltage range.

Experiment of cutoff measurement according to bonding energy

Experimental Example  10

A light emitting device was prepared in the same manner as in Experimental Example 1. Then, the cutoff of the light emitting device according to the bonding energy was measured.

Experimental Example  10 experimental results

13 is a graph showing a measurement of a cutoff according to binding energy of the light emitting device of Experimental Example 10. Fig. 13 is a graph showing the relationship between the refractive indices of the PVK / PEDOT: PSS / ITO, (ii) PEDOT: PSS / ITO, (iii) PANI: PSS / PEDOT: PSS / ITO, PANI: PSS / PEDOT: PSS / ITO, and (vi) ZnO nanoparticles (NPs).

HOMO energy level measurement experiment by binding energy

Experimental Example  11

A light emitting device was prepared in the same manner as in Experimental Example 1. The highest occupied molecular orbital (HOMO) energy level of the light emitting device was measured according to the bonding energy.

Experimental Example  11 Experimental results

14 is a graph showing a measurement of the HOMO energy level of the light emitting device according to the bonding energy of Experimental Example 11. FIG. 14, the graphs show the relationship between (i) ITO, (ii) PEDOT: PSS / ITO, (iii) PANI: PSS / PEDOT: PSS / ITO, (iv) PVK / PEDOT: PSS / ITO, PANI: PSS / PEDOT: PSS / ITO, and (vi) ZnO nanoparticles (NPs).

The light- Energy level  diagram

Experimental Example  12

A light emitting device was prepared in the same manner as in Experimental Example 1. The energy level diagram was created based on the measurement of secondary electron cutoff and HOMO energy level by ultraviolet photoelectron spectroscopy.

Comparative Example  8

A light emitting device for commercial use was manufactured. The remaining experimental procedure is the same as that of Experimental Example 12 described above.

Experimental Example  12 and Comparative Example  Experiment results of 8

15 shows energy level diagrams of Experimental Example 12 and Comparative Example 8. Fig. FIG. 15A shows the energy level diagram of the light emitting device in Comparative Example 8, and FIG. 15B shows the energy level diagram of the light emitting device in Experimental Example 12. FIG.

As shown in Fig. 15, the hole transporting barrier of the light emitting layer of the light emitting device of Comparative Example 8 was 1.45 eV, and the hole transporting barrier of the light emitting layer of the light emitting device of Experimental Example 12 was 1.23 eV. That is, the HOMO energy level of the PVK layer can be lowered from the Fermi energy by inserting the PANI: PSS layer into the light emitting device. Thus, it was confirmed that the hole transporting barrier of the light emitting layer of the light emitting device is lowered.

Measurement of current density according to voltage change

Experimental Example  13

A light emitting device was prepared in the same manner as in Experimental Example 1. After the voltage was raised, the current density of the light emitting device was measured according to the voltage change.

Comparative Example  9

In general, a commercialized light emitting device was tested. The experimental procedure was the same as in Experimental Example 13 described above.

Experimental Example  13 and Comparative Example  9 Experimental results

16 is a graph showing the results of experiments on the current density according to the voltage changes of Experimental Example 13 and Comparative Example 9. Fig. 16 shows the current density according to the voltage change of the light emitting device in Comparative Example 9 and the circle shows the current density according to the voltage change of the light emitting device in Experimental Example 13. [

As shown in FIG. 16, a small current density was measured at a low voltage of 0 V to 1 V in the current density of Experimental Example 13, and a large current density was measured as the voltage increased. On the other hand, in Comparative Example 9, a comparatively large current density was measured at a low voltage, and a current density was measured gradually as the voltage increased. That is, it was confirmed that the PANI: PSS layer was formed in the light emitting device and the current density was higher than the turn-on voltage. Further, since the rapid change in the current density was measured under the condition that the light emitting element was 0.7 V or more, a high hole transporting rate of the light emitting element was confirmed.

On PANI  About PSS  Cutoff measurement according to change of content ratio

Experimental Example  14

A light emitting device was prepared in the same manner as in Experimental Example 1. The surface of the light emitting device was a PANI: PSS / PEDOT: PSS / ITO coated surface in order. And we measured the cutoff of the light emitting device according to the content ratio of PSS to PANI. PSS content is the content in PANI: PSS.

Experimental Example  15

A light emitting device was prepared in the same manner as in Experimental Example 1. The surface of the light emitting device was a PVK / PANI: PSS / PEDOT: PSS / ITO coated surface in order. And we measured the cutoff of the light emitting device according to the content ratio of PSS to PANI.

Experimental Example  Experimental results 14 to 15

17 is a graph showing a cutoff of the light emitting device according to the content ratio of PSS to PANI in Experimental Examples 14 to 15. FIG. 17 (a) and 17 (b) are graphs showing the ratio of PSS to PANI. As shown in FIG. 17, . The graphs of FIGS. 17C and 17D show the ratio of PSS to PVK / PEDOT: PSS / ITO and PANI, respectively. The graphs are 1: 1, 1: 3, 1: 5, 1: , 1:11, 1:13.

As shown in FIGS. 17 (a) and 17 (b), the work function of the PANI: PSS layer increases as the content ratio of PSS to PANI increases. In FIG. 17 (c), the work function of the PVK thin film on the PANI: PSS layer was confirmed to be small. In FIG. 17 (d), the HOMO energy level of the PVK thin film of the PANI: PSS layer is found to be smaller than the Fermi energy.

On PANI  About PSS  Energy level diagram according to content ratio variation

Experimental Example  16

A light emitting device was prepared in the same manner as in Experimental Example 1. The work function, the energy level and the ionization energy of the light emitting device were measured according to the change of PSS content ratio to PANI, and the energy level diagram was prepared based on the measurement.

Experimental Example  16 experimental results

18 (a) shows a graph of measured work function, energy level and ionization energy of the light emitting device according to the change of PSS content with respect to PANI. In FIG. 18 (a), the stars represent the work functions of PANI: PSS / PEDOT: PSS / ITO, circles represent the HOMO energy levels of PVK / PANI: PSS / PEDOT: PSS / ITO, Respectively. As shown in FIG. 18 (a), it is found that the work function of the PANI: PSS layer becomes larger with 0.03143 slope as the content ratio of PSS increases. It was also found that as the content ratio of PSS to PANI in PANI: PSS layer increases, the work function of PVK on PANI: PSS decreases to 0.01429. As the ratio of PSS to PANI in the PANI: PSS layer increases, the HOMO energy level increases with the 0.01482 slope, but the ionization energy value is almost constant.

FIG. 18 (b) shows an energy level diagram according to the content of PSS. As shown in FIG. 18 (b), it was found that the HOMO energy level gradually decreased as the content ratio of PSS to PANI increased from Fermi energy. Accordingly, it was confirmed that the hole transporting barrier of the light emitting layer of the light emitting device is lowered.

On PANI  About PSS  The absorption spectrum

Experimental Example  17

A light emitting device was prepared in the same manner as in Experimental Example 1. The absorption spectra of PANI were calculated according to the content ratio of PSS.

Experimental Example  17 experimental results

19 is a graph showing the absorption spectrum of PANI: PSS measured according to the content ratio of PSS to PANI. The graph in Fig. 19 shows the ratio of PSS to PANI, PANI, and shows 1: 5 and 1:11. PANI was dominated by π-π * transitions of benzenoids and quinoid rings in emeraldine base and emeraldine salt and absorption bands of 320 nm and 870 nm by π-polaron transitions in emeraldine salt. Near 430 nm is the absorption band due to the polaron- π * transitions of the emeraldine salt. It was confirmed that PANI: PSS follows the tendency of absorption spectrum of PANI.

The transmission spectrum according to the content ratio of PSS to PANI

Experimental Example  18

A light emitting device was prepared in the same manner as in Experimental Example 1. Transmission spectra of PANI were prepared by changing the content ratio of PSS to PANI.

Experimental Example  18 experimental results

20 is a graph showing the transmission spectrum of PANI: PSS according to the content ratio of PSS to PANI. In FIG. 20, the solid line represents the transmission spectrum of ITO / glass, the square represents the transmission spectrum of PVK / PEDOT: PSS / ITO / glass, and the circle represents PVK / PANI: PSS (1:11 and 8 nm thick) / PEDOT: PSS / ITO / glass, respectively. The transmittance around the 630 nm wavelength was 88.0%, 85.4%, and 84.1%, respectively, and it was found that PANI: PSS intercalation layer has high transmittance which does not hinder the luminous efficiency when the red quantum dot light emitting diode is fabricated.

On PANI  About PSS  FT-IR spectrum according to content ratio change

Experimental Example  19

A light emitting device was prepared in the same manner as in Experimental Example 1. And FT-IR spectra were obtained according to the content ratio of PSS to PANI.

Experimental Example  19 experimental results

21 is a graph showing the FT-IR spectrum of PANI: PSS in order to examine the molecular structure of PANI according to the content ratio of PSS to PANI. 21 is a ratio of PSS to PANI. The ratio of PSS to PANI is 1: 1, 1: 3, 1: 5, 1: 7, 1: 9, 1:11, 1:13, 1:15, : 30 respectively. As shown in FIG. 21, it was found that PANI: PSS exists in an electrostatic interaction with PSS in the polymer chain of PANI. Also, it was confirmed that the PANI: PSS polymer can be formed properly without any damage and deformation by increasing the content ratio of PSS to PANI.

On PANI  About PSS  UPS spectrum according to content ratio change

Experimental Example  20

A light emitting device was prepared in the same manner as in Experimental Example 1. And the work function was measured according to the variation ratio of PSS to PANI.

Experimental Example  20 experimental results

22 is a UPS spectrum for a multilayer structure of a secondary electron cutoff region of PANI: PSS / PEDOT: PSS / ITO and PVK / PANI: PSS / PEDOT: PSS / ITO according to the content of PSS. The graph of FIG. 22 shows the ratio of PSS to PANI, which is 1: 1, 1: 3, 1: 5, 1: 7, 1: 9, 1:11, 1:13, 1:15, 1:20, 1: : 30 respectively. At this time, the thickness of PANI: PSS is fixed to 8 nm. As shown in FIG. 22 (a), as the PSS content ratio for PANI changes from 1: 1 to 1:17, the work function of PANI: PSS changes and is constant at a ratio of 1:17 or more . As shown in FIG. 22 (b), it was found that the work function of the PVK thin film of the PANI: PSS thin film layer was increased with the increase of the PSS content from 1: 1 to 1:11 in the PSS content ratio to PANI . Therefore, it was confirmed that the content of PANI: PSS thin film affected the electronic structure of the PVK layer.

On PANI  About PSS  UPS spectrum according to content ratio change

Experimental Example  21

A light emitting device was prepared in the same manner as in Experimental Example 1. The HOMO energy level and the core energy level of the multilayer thin films were measured according to the content ratio of PSS to PANI.

Experimental Example  21 experimental results

23 is a UPS spectrum of the HOMO energy level and the core region energy level of PVK / PANI: PSS / PEDOT: PSS / ITO according to the content ratio of PSS to PANI. 23 is a ratio of PSS to PANI. The ratio of PSS to PANI is 1: 1, 1: 3, 1: 5, 1: 7, 1: 9, 1:11, 1:13, 1:15, 1:20, 1: : 30 respectively. At this time, the thickness of PANI: PSS is fixed to 8 nm. As shown in FIG. 23, the HOMO energy level of the PVK thin film was increased while the content ratio of PSS to PANI was increased from 1: 1 to 1:11, and the content ratio of PSS to PANI was increased from 1:11 to 1: 30, the HOMO energy level of the PVK thin film was decreased. Therefore, it was confirmed that the HOMO energy level of the PVK thin film can be controlled by changing the content of PSS in a wide range. In addition, PVK films showed that all the energy energy levels of PVK core energy level as well as HOMO energy level moved in parallel with each other. Therefore, it was confirmed that the change of PSS content to PANI can cause up-and-down movement of all electronic structures of PVK thin film.

On PANI  About PSS  According to the content ratio change PVK  Energy level

Experimental Example  22

A light emitting device was prepared in the same manner as in Experimental Example 1. The work function (Φ), the interface dipole (Δ), the hole transport barrier (Δh) between PVK and PANI: PSS, and the QD (Pd) depend on the PANI: PSS work function and the PVK ionization energy (Δh ') between PVK and PVK were measured and calculated, and the energy level graph was created based on this measurement.

Experimental Example  Results of experiment 22

FIG. 24 is a graph showing the hole transporting barrier between PANI: PSS work function and PVK ionization energy, work function, interfacial dipole, PVK and PANI: PSS, and the energy of hole transport barrier between QD and PVK according to the change of PSS content relative to PANI Respectively. As shown in FIG. 24, PANI: PSS has a larger work function as the content ratio of PSS to PANI increases. In addition, the electronic structure of the hole transport layer PVK coated on each PANI: PSS shows a characteristic that the ionization energy, the work function decrease, and the HOMO energy level move downward as the content ratio of PSS to PANI increases to 11 there was. In the case of hole transport in the QD layer, it was confirmed that the hole transport barrier between the QD layer and the PVK layer decreased from 1.42 eV to 1.22 eV while the content ratio of PSS was changed from 1 to 11.

PANI: PSS  Thickness variation PVK  Energy level

Experimental Example  23

A light emitting device was prepared in the same manner as in Experimental Example 1. The PANI: PSS work function and PVK ionization energy (IE), work function (Φ), interfacial dipole (Δ), PANI: hole transport barrier (Δh) between PVK and PSS, QD and PVK (Δh ') between the hole transport barrier and the hole transport barrier (Δh').

.

Experimental Example  23 experimental results

Figure 25 shows the relationship between the PANI: PSS work function and the ionization energy, work function, interfacial dipole, the hole transport barrier between PVK and PANI: PSS, and the energy of the hole transport barrier between QD and PVK Graph the levels. At this time, the ratio of PSS to PANI: is fixed at 1:11. As shown in Fig. 25, when the PANI: PSS thickness is 8 nm or more, the work function of PVK is increased when the PANI: PSS thickness is increased from 1 nm to 8 nm while the work function of PVK is kept at a constant value of 5.37 eV. It was found that the work function of PANI: PSS increased from 5.27 eV to 5.38 eV as PANI: PSS thickness increased from 1 nm to 38 nm. It was also confirmed that the PANI: PSS thickness affected the electronic structure of PVK within the range of 1 nm to 8 nm. The increase in the energy levels of PVK in the range of 1 nm to 8 nm of PANI: PSS thickness decreases the hole transport barrier between PVK and PANI: PSS (0.68 eV at 1.03 eV) and increases the hole transport barrier between QD and PVK (0.90 eV to 1.22 eV).

The light- Energy level  diagram

Experimental Example  24

A light emitting device was prepared in the same manner as in Experimental Example 1. Then, an energy diagram of the light emitting device was prepared.

Experimental Example  24 experimental results

26 shows an energy level diagram of QD / PVK / PANI: PSS / PEDOT: PSS. As shown in FIG. 26, the PSS content ratio of the PANI: PSS insertion layer to the PANI changed the HOMO content of PVK It can be seen that when the energy level decreases, the hole transport barrier (Δh ') at the interface between QD and PVK can be lowered and that the lower hole transport barrier can have a higher hole conduction efficiency and better electrical properties and electroluminescence efficiency I could. Also, it was confirmed that the hole transport energy barrier is lowered in the heterojunction between the hole transporting layer and the light emitting layer.

PSS  Current-voltage and luminance-voltage

Experimental Example  25

A light emitting device was prepared in the same manner as in Experimental Example 1. A graph of current - voltage and luminance - voltage with the PSS content of PANI: PSS with a thickness of 8 nm was prepared.

Experimental Example  25 experimental results

27 is a graph in which the thickness of PANI: PSS is 8 nm and the ratio of PSS to PANI is 1: 5, 1:11, 1:30, respectively. 27 (a) is a graph of current-voltage according to PSS content change of PANI: PSS, and FIG. 27 (b) is a graph of luminance-voltage according to PSS content change of PANI: PSS. As shown in FIG. 27, a high luminance characteristic is exhibited in a light emitting device having a PANI: PSS insertion layer of 1:11 as a ratio of PSS to PANI. In particular, in FIG. 27 (b), when the light emitting device having the PANI: PSS inserted therein is compared with the light emitting device not having the inserted PANI: PSS, it can be clearly confirmed that the hole conductivity is increased by the insertion of the PANI: PSS of 1:11.

PANI: PSS  Current-voltage and luminance-voltage

Experimental Example  26

A light emitting device was prepared in the same manner as in Experimental Example 1. And we plot the current - voltage and the luminance - voltage according to the thickness variation of PANI: PSS with the ratio of PSS to PANI: PSS of 1:11.

Experimental Example  26 experimental results

28 shows graphs in which the ratio of PSS to PANI is 1:11 and the thickness of PANI: PSS is 1 nm, 8 nm, 15 nm, and 38 nm, respectively. 28 (a) is a graph of current-voltage according to PANI: PSS thickness variation, and FIG. 28 (b) is a graph of luminance-voltage according to PANI: PSS thickness variation. As shown in FIG. 28, it was found that the ratio of PSS to PANI was 1:11, and the highest luminance was obtained when the thickness of PANI: PSS was 8 nm. In particular, FIG. 28 (b) shows that the brightness and the current density are increased even though the thickness of PANI: PSS is increased from 1 nm to 8 nm and the value of Δh 'is increased.

PSS  According to the content change Field  Luminescence spectrum

Experimental Example  27

A light emitting device was prepared in the same manner as in Experimental Example 1. The electroluminescence spectra of the PSS contents were prepared.

Experimental Example  27 experimental results

FIG. 29 is a photograph of an electroluminescence spectrum and a light emission of a light emitting device according to changes in the content of PSS. The graph of FIG. 29 (a) shows the ratio of PSS to PANI operated at a voltage of 5.5 V, which represents 1: 5, 1:11, 1:30, respectively. FIG. 29 (b) shows a light emitting device having a 1:11 ratio PANI: PSS having a thickness of 8 nm inserted and a light emitting device not inserted. As shown in FIG. 29, it was confirmed that the light emitting device having the PANI: PSS inserted therein had about 34 times higher luminance than the light emitting device having no inserted light emitting device.

It will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the following claims.

10. Substrate
20. First electrode
30. Hole injection layer
40. Conductive polymer thin film layer
50. Hole transport layer
52. First hole transport layer
54. Second hole transport layer
60. Light emitting layer
70. Electron transport layer
80. Second electrode

Claims (7)

The first electrode,
A hole injection layer including PEDOT: PSS (Polyethylene (3,4-ethylenedioxythiophene) -Poly (styrene sulfonate)) located on the first electrode,
A conductive polymer thin film layer disposed on the hole injection layer and including PANI: PSS (polyaniline-poly (4-styrenesulfonate)),
A hole transport layer disposed on the conductive polymer thin film layer and containing poly-n-vinylcarbazole (PVK)
A light emitting layer disposed on the hole transport layer,
An electron transport layer disposed on the light emitting layer and including zinc oxide (ZnO), and
A second electrode located on the electron transport layer,
/ RTI >
Wherein the light emitting layer comprises a nanostructure including a core comprising cadmium selenide (CdSe) and a shell surrounding the core and including zinc cadmium (CdZnS). The method of claim 1,
Wherein the ratio of the PSS (polystyrene-sulfonate) to the PANI (polyaniline) of the conductive polymer thin film layer is 1: 8 to 1:13. The method of claim 1,
Wherein the hole injection layer further comprises PANI: PSS (polyaniline-poly (4-styrenesulfonate)). The method of claim 1,
Wherein the conductive polymer thin film layer has a surface roughness of 0.1 nm to 5 nm. Providing a substrate,
Depositing a first electrode over the substrate,
Coating a first material including PEDOT: PSS on the first electrode by spin coating and then performing heat treatment to provide a hole injection layer;
Providing a conductive polymer thin film layer on the hole injection layer by spin coating a second material including PANI: PSS (polyaniline: polystyrene-sulfonate) / poly (4-styrenesulfonate)
Spin-coating a material including poly-n-vinylcarbazole poly-vinylcarbazole (PVK) on the conductive polymer thin film layer to provide a hole transport layer,
Providing a light emitting layer by coating a nanostructure including a core containing cadmium selenide and a shell containing zinc cadmium sulfide on the conductive polymer thin film layer,
Depositing an electron transport layer containing zinc oxide on the light emitting layer, and
Depositing a second electrode on the electron transport layer
Emitting device. The method of claim 5,
Removing the substrate, and
The surface of the first electrode is subjected to plasma treatment, ultraviolet ozone treatment or reactive ion etching (RIE)
Emitting device. The method of claim 5,
Further comprising the step of providing another hole transport layer including the second material on the conductive polymer thin film layer before the step of providing the light emitting layer.

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