KR100646292B1 - Efficient white-emitting fluorescent/phosphorescent complex electroluminescent devices via energy transfer from conjugated polymer - Google Patents

Abstract

Provided is a white electroluminescent device which is improved in the chemical miscibility of a conjugated polymer having a high luminous efficiency and a phosphor, is remarkably lowered in drive voltage and is excellent in color stability. The white electroluminescent device(100) is a polymer-based fluorescent/phosphorescent composite electroluminescent device which comprises a transparent substrate(60); a positive electrode layer(10); a hole transport layer(30); a light emitting layer(50); an electron transport layer(40); and a negative electrode layer(20), wherein the light emitting layer comprises a luminous conjugated polymer; a phosphor; and poly(N-vinyl carbazole) or a blend with its derivative as a luminous unconjugated polymer.

Description

White light emitting high efficiency fluorescent / phosphorescent composite electroluminescent device using energy transfer from conjugated polymer

1 is a view for explaining the structure of a polymer electroluminescent device.

2 is a view for explaining the UV absorption and emission characteristics of the light emitting polymer and the phosphor used in the light emitting layer.

Figure 3 is a view for explaining the energy transfer process and white light emission characteristics from the conjugated polymer to the green, red light-emitting phosphor.

4 illustrates the surface morphology at an optimal ratio for white light of a luminescent material in the luminescent layer.

5 is a view for explaining the energy transfer process and white light electroluminescence properties from the conjugated polymer to the green, red light-emitting phosphor.

6 is a view for explaining the electroluminescence characteristics according to the voltage of the white electroluminescent device.

FIG. 7 is a diagram illustrating color purity of a white electroluminescent device according to voltage through CIE color coordinates. FIG.

8 is a view for explaining the driving voltage-current density characteristics of the polymer-based white electroluminescent device according to an embodiment of the present invention.

9 is a view for explaining a driving voltage-luminescence brightness characteristic of a polymer-based white electroluminescent device according to an embodiment of the present invention.

10 is a view for explaining the current density-luminescence efficiency characteristics of the polymer-based white electroluminescent device according to an embodiment of the present invention.

Figure 11 is a photograph when driving the polymer-based white electroluminescent device manufactured according to an embodiment of the present invention.

<Explanation of symbols for main parts of the drawings>

10: anode electrode layer

20: cathode electrode layer

30: hole transport layer

40: electron transport layer

50: light emitting layer

60: substrate

70: encapsulation layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent device, and in particular, doping a phosphor in a light emitting polymer to partially transfer energy from a conjugated polymer to a phosphor, thereby inducing tricolor emission of blue, green, and red from the conjugated polymer and the phosphor. A high efficiency white electroluminescent device of a fluorescent / phosphorescent complex system.

In organic electroluminescence, electrons and holes injected from cathode and anode form excitons in the organic thin film, and light of a specific wavelength is formed from the formed excitons. It is a phenomenon that occurs. The organic electroluminescent device applying this phenomenon has advantages such as light weight, thin film, self-luminous, low voltage driving, and fast switching speed. In particular, the polymer electroluminescent device reported by a research team of Professor RH Friend in the United Kingdom in 1990 forms a thin film by spin coating method, and thus forms a thin film by vapor deposition method. Compared with the low molecular electroluminescent device, there is an advantage of low cost of the manufacturing process.

A brief description will be given of the polymer electroluminescent device with reference to FIG. 1. The polymer electroluminescent device 100 includes a hole transport layer 30, an electron transport layer 40, and an anode electrode layer 10 and a cathode electrode layer 20 on a substrate 60. It is formed in a structure in which an emission layer 50 exists.

As the anode electrode layer 10, a complex metal oxide thin film such as ITO (indium-tin oxide), which is transparent in the visible range and easy to inject holes due to high work function, is mainly used. The cathode electrode layer 20 includes metals such as cesium (Cs), lithium (Li), and calcium (Ca) having a low work function, and stable aluminum (Al), copper (Cu), silver (Ag), etc. having a high work function. Mainly use alloys of metals.

When forward voltage is generated on the anode electrode layer 10 and the cathode electrode layer 20, holes injected from the anode electrode layer 10 pass through the hole transport layer 30 to the light emitting layer 50, and from the cathode electrode layer 20. The injected electrons pass through the electron transport layer 40 and move to the emission layer 50. The holes and electrons injected from the anode and cathode electrode layers 10 and 20 respectively have different mobility, but the mobility of the holes and electrons is similar while passing through the hole transport layer 30 and the electron transport layer 40. . In addition, electrons moved from the cathode electrode layer 20 to the light emitting layer 50 are trapped in the light emitting layer 50 by an energy barrier existing at an interface between the light emitting layer 50 and the hole transport layer 30, thereby forming Hole recombination efficiency is improved. As a result, in the light emitting layer 50, since the density of holes and electrons is balanced, the light emission efficiency of the polymer electroluminescent device 100 may be increased. In particular, by forming a buffer layer (not shown) that serves as a hole injection layer between the anode electrode layer 10 and the hole transport layer 30, the surface of the anode electrode layer 10 is made flat. It may be made to improve the light emission stability of the polymer electroluminescent device 100.

As described above, holes and electrons injected from the anode and cathode electrode layers 10 and 20 respectively recombine in the light emitting layer 50 to generate excitons in the light emitting polymer. These excitons are divided into singlet excitons (hereinafter referred to as "single term excitons") and triplet (excitons) (hereinafter referred to as "triplet excitons"), each of which is 1: 3. Occurs at the rate of. The singlet excitons fall from the excited state to the ground state and emit light of a certain wavelength, thereby luminescence is observed through the substrate 60. The energy of the triplet state is lower than the singlet state by the exchange interaction energy, but transitioning from the singlet state to the triplet state is not allowed because the spin changes. However, spin-orbit coupling allows singlet excitons to intersystem cross into a triplet state. Since the ground state of organic molecules is a spin singlet state, quantum mechanical selectivity prohibits the triplet excitons from shining to the singlet ground state, but the singlet excitons shine and transition to the ground state. ) However, due to perturbation such as spin-orbit coupling, triplet excitons can also make light transitions. This is called phosphorescence. In phosphorescence, since both singlet and triplet excitons can contribute to light emission, unlike fluorescent elements emitting only singlet excitons, the luminous efficiency is excellent and the internal quantum efficiency can theoretically reach 100% ( Y. Cao et al., Nature, 397 , 414-416, 1999).

Since most phosphors emit energy by emitting energy from a host material, an energy providing material is most important. The polymers that have been widely used as energy transfer materials have been poly (N-vinylcarbazole) (PVK) and derivatives thereof having high triplet energy and chemical compatibility with phosphors. Unlike this, the luminous efficiency is low and the driving voltage is high. Since conjugated light emitting polymers have poor compatibility with phosphors, energy transmission does not occur, and PVK has been mainly used as an energy providing material. However, in the case of phosphorescent devices using PVK as a host polymer, it is difficult to find the luminance as a fluorescent device. However, due to the limitations of energy-providing materials such as PVK, the driving voltage also has the disadvantage of being very high.

In addition, a method of blending 2- tert -butylphenyl-5-biphenyl-1,3,4-oxadiazole (PBD) together in the emissive layer is proposed to inject electrons well, but this material is also as large as PVK. Due to the energy band gap, it is difficult to lower the driving voltage by inducing a charge trapping effect (X. Gong et al., Advanced Functional Materials, 13 , 439-444, 2003).

Due to these various problems, phosphors have not been applied to white electroluminescent devices so far, despite the possibility of high efficiency. In addition, since it is difficult to realize all three colors of blue, green, and red for phosphorescent light alone, it is necessary to develop a composite device in which fluorescent polymers and phosphors are properly combined.

Therefore, in order to construct a phosphor-doped white electroluminescent device having improved luminous efficiency, a high luminous efficiency conjugated polymer that can replace PVK is required, and a high driving voltage, which is a problem of the phosphor, has to be solved. It is a task to do.

Therefore, in the present invention, the natural compatibility of the conjugated polymer with excellent luminous efficiency and the phosphor is enhanced to induce natural energy transfer, and the blue light is emitted from the conjugated polymer and the green and red light are emitted from the phosphor, thereby providing high efficiency white light fluorescent / phosphorescence. An object of the present invention is to provide a composite electroluminescent device and to provide a white electroluminescent device having a low driving voltage through efficient energy transfer from a conjugated polymer.

According to a feature of the present invention for achieving the above object, in order to increase the chemical miscibility of the conjugated polymer and the phosphor having excellent luminous efficiency and to easily transfer the triplet energy of the conjugated polymer to the phosphor, A white fluorescent / phosphorescent composite electroluminescent device comprising a light emitting layer by blending PVK together is provided.

Specifically, in the white electroluminescent device of the present invention comprising a transparent substrate, an anode electrode layer, a hole transport layer, a light emitting layer, an electron transport layer and a cathode electrode layer, the light emitting layer is 1) light-emitting conjugated polymer, 2) phosphor and 3) light-emitting non-porous It consists of a blend of poly (N-vinylcarbazole) (PVK) or derivatives thereof as a liquid polymer.

The luminescent conjugated polymer is poly (fluorene) and its derivatives, poly (para-phenylene) and its derivatives, poly (para-phenylenevinylene) and its derivatives and is blue to generate light having a wavelength of 400 to 480 nm. It is a polymer-based light emitting material of the series, the phosphor is an iridium composite, europium composite, platinum composite or osmium composite is a low molecular phosphor that generates light of 450 to 700 nm wavelength.

The transparent substrate that can be used in the white electroluminescent device of the present invention is glass or plastic, and the anode electrode layer may be ITO (indium tin oxide), PEDOT (polyethylene dioxythiophene), carbon nanotube or polyaniline. In addition, the cathode electrode layer may be aluminum, magnesium, lithium, calcium, copper, silver, gold or alloys thereof, but is not limited thereto.

In addition, the white light emission generated in the white electroluminescent device of the present invention can be used for display and surface light source, wherein the light-emitting conjugated polymer is used for blue light emission in the wavelength range of 400 to 480 nm, the phosphor is 490 to 560 nm It is used for green light emission in the wavelength band and red light emission in the wavelength range of 590 to 700 nm, whereby the white electroluminescent device can realize white light emission by simultaneously emitting blue, green and red light.

Alternatively, the white electroluminescent device of the present invention uses a blue light emitting conjugated polymer in the wavelength band of 400 to 480 nm and a green light emitting phosphor in the wavelength range of 490 to 560 nm, and uses blue and green light emission as an energy transfer material, and a wavelength band of 590 to 700 nm. The red light emitting phosphor may be used for red light emission as an energy receiving material to realize white light emission by tricolor co-emission.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the present invention.

1 illustrates the structure of an electroluminescent device comprising a high efficiency light emitting polymer, a phosphor, and a PVK as a light emitting layer. PVK in the light emitting layer increases the chemical miscibility, increases the triplet energy of the conjugated polymer to phosphorescence, and also plays a role of hole transport. Thus, 2,9-dimethyl-4,7-diphenyl is a hole blocking layer. Improves device efficiency by depositing -1,10-phenanthroline (BCP).

As the energy-providing conjugated polymer used in the polymer electroluminescent device according to the present invention, polyfluorene-type blue LEP (Lumation BlueJ Light-Emitting Polymers, Dow Chemical Company) having excellent luminous efficiency compared to PVK , BlueJ), etc., and any blue light emitting conjugated polymer can be used as long as it has good chemical compatibility with PVK. When the high-efficiency light-emitting polymer is used as an energy providing material, the driving voltage of the EL device is reduced by reducing the charge trapping effect, and the luminous efficiency of the device is improved through effective Fosterster energy transfer.

However, this BlueJ polymer and the phosphor used in the present invention (e.g. fac -Tris [2- (2-pyridinyl-kN) (5- (3,4-di-sec-part) for green light emission) Methoxyphenyl) phenyl) -kC] -iridium (III) [Ir (PBPP) ₃ ] and Tris (1-phenylisoquinoline) iridium (III) [Ir (PIQ) ₃ ]) for red luminescence are miscible As a result, phase separation occurs, and the triplet energy of the conjugated polymer is low so that energy transfer does not occur. Therefore, the light emitting layer blends PVK having excellent chemical miscibility with both kinds of materials to induce energy transfer from BlueJ polymer to Ir (PBPP) ₃ and Ir (PIQ) ₃ .

2 shows absorption and luminescence (Photoluminescence, PL) spectra of BlueJ polymer, Ir (PBPP) ₃ , Ir (PIQ) _3, and PVK. In Figure 2, a is the PL of the PVK, b is a abs of BlueJ polymer, c is the the Abs of the PL of BlueJ polymer, d is the Ir (PBPP) _3, e is Ir (PBPP) ₃ PL of, f Denotes Abs of Ir (PIQ) ₃ , and g denotes PL of Ir (PIQ) ₃ .

The emission spectrum of PVK, which is the maximum at 400 nm wavelength, overlaps much of the absorption band of BlueJ polymer, and the energy of PVK is transferred to BlueJ polymer. The emission spectrum of BlueJ overlaps a substantial portion with the metal-ligand charge transfer [MLCT] absorption band of Ir (PBPP) ₃ . Peaks at 0 nm wavelength and 420 nm wavelength mean absorption by transition from the ground state to singlet MLCT and triplet MLCT excited states, respectively. In addition, the emission spectrum of BlueJ closely matches the metal-ligand charge transfer absorption band of Ir (PIQ) ₃ . Peaks at the 430 nm wavelength and the 475 nm wavelength mean absorption by transition from the ground state to the singlet MLCT and triplet MLCT excited states, respectively. Thus, efficient energy transfer occurs from PVK to BlueJ, from BlueJ to Ir (PBPP) ₃ , and from BlueJ to Ir (PIQ) ₃ . Ir (PIQ) ₃ are because they have to be fully compatible chemically and Ir (PBPP) _3, given in part, transferring energy from Ir (PBPP) _3.

The normalized PL spectrum of a film spin-coated onto glass by blending four materials in different proportions is shown in FIG. 3. In Figure 3, a is BlueJ 90 wt% -Ir (PBPP) ₃ 9.7 wt% -Ir (PIQ) ₃ 0.3 wt% of the blend film, b is BlueJ 65 wt% -PVK 25 wt% -Ir (PBPP) ₃ 9.7 wt% -Ir (PIQ) _{3 of} 0.3 wt% blend film, c is b BlueJ 45 wt% -PVK 45 wt% -Ir (PBPP) ₃ 9.7 wt% -Ir (PIQ) ₃ 0.3 wt% blend Of the film, d is b BlueJ 30 wt% -PVK 60 wt% -Ir (PBPP) ₃ 9.7 wt% -Ir (PIQ) ₃ 0.3 wt% of the blend film, e is b BlueJ 20 wt% -PVK 70 wt% -Ir (PBPP) ₃ 9.7 wt% -Ir (PIQ) ₃ Shows the PL spectrum of 0.3 wt% of the blend film.

In blending, the ratios of Ir (PBPP) ₃ and Ir (PIQ) ₃ were fixed at 9.7 wt% and 0.3 wt%, respectively, and PVK and BlueJ polymers were varied at various ratios. The wavelength of the light source to excite the film is 345 nm, the absorption band of PVK. The fixed ratio of Ir (PBPP) ₃ and Ir (PIQ) ₃ is for simultaneous emission at similar intensities of green and red light, respectively. The concentration of Ir (PBPP) ₃ is much higher than the Ir (PIQ) ₃ means that the energy delivered to the Ir (PIQ) ₃ present from Ir (PBPP) _3. In blend films of BlueJ and iridium composites without PVK, energy transfer does not occur due to low miscibility and phase separation. However, the addition of PVK to this blend results in partial energy transfer, and white light by tricolor emission can be achieved by appropriately adjusting the ratio of four materials. As can be seen in FIG. 2, the emission spectrum of BlueJ overlaps the absorption band of Ir (PIQ) ₃ much more than the absorption band of Ir (PBPP) ₃ , and the triplet energy of red light emitting Ir (PIQ) ₃ is higher. Low energy transfers well to Ir (PIQ) ₃ . However, due to the low concentration of Ir (PIQ) ₃ and phosphor saturation, the energy of BlueJ, which no longer contributes to red light, is sequentially transferred to Ir (PBPP) ₃ , which is a green emitter. BlueJ 20: PVK 70: Ir (PBPP) ₃ 9.7: Ir (PIQ) ₃ 0.3 (20: 70: 9.7: 0.3) In the blend, a uniform morphology without phase separation induced complete energy transfer from BlueJ to the phosphorescent complex, The optimal ratio for white luminescence was BlueJ 65: PVK 25: Ir (PBPP) ₃ 9.7: Ir (PIQ) ₃ 0.3 (65: 25: 9.7: 0.3), where similar luminescence intensities of the three luminescent materials were observed. . In this system, PVK not only improves chemical miscibility with fluorescent / phosphorescent materials, but also enhances the triplet excited state of the luminescent conjugated polymers, making the energy transfer much better to the phosphors.

4 shows the morphology of the film blended at the optimal ratio 65: 25: 9.7: 0.3 for white light emission. Atomic Force Microscope (AFM) images of four materials blended show domains formed by phase separation of polymers. Because PVK is chemically very compatible with iridium complexes, the brighter areas of the AFM image are the domains of the highly compatible PVK and phosphors, while the darker areas are occupied by BlueJ polymers. Although BlueJ and the phosphor complex are not compatible with each other, PVK is well mixed with the three materials at the interface of the phase, so that partial energy transfer from BlueJ to the phosphor complex occurs at the interface of the phase despite the microphase separation. The intensity of light emitted from the iridium complex excited by the energy of BlueJ is incomparably large compared to the intensity of light emitted from the iridium complex excited by the energy of PVK.

The present invention will be described in more detail with reference to the following examples, which are intended to illustrate the invention but are not intended to limit the invention.

<Example 1>

Poly (N-vinylcarbazole) (PVK) was purchased from Sigma-Aldrich Co. and purified in the laboratory. Ir (PIQ) ₃ for red light emission was purchased from American Dye Sources, and BlueJ, manufactured by Dow Chemical Company, was used as the luminescent conjugated polymer. PVK, BlueJ, Ir (PBPP) ₃ and Ir (PIQ) ₃ were dissolved in various proportions in chlorobenzene (HPLC grade, from Aldrich). Oxygen plasma treatment of an indium tin oxide (ITO) coated glass substrate, followed by spin coating poly (styrene sulfonate) (PSS): polyethylene dioxythiophene (PEDOT) to a thickness of 20 nm for 120 hours in a vacuum oven Heat treatment in the figure. Then, the solution blended in various ratios was spin-coated to a thickness of 100 nm and the solvent was completely removed. BCP, a hole blocking material, was vacuum deposited to a thickness of 20 nm at a high vacuum of 1 x 10 ^-6 torr, and a lithium: aluminum alloy (Li: Al alloy) electrode was deposited to deposit ITO / PEDOT / blend emitting layer / BCP / Li: Al. An electroluminescent device having an alloy structure was produced.

Example 2 Evaluation of Spectrum and Voltage-Current-Luminous Intensity Characteristics of Each Electroluminescent Device Manufactured in Example 1

The spectrum and voltage-current-luminescence intensity characteristics of each electroluminescent device manufactured in Example 1 were measured using a device composed of a luminance meter (LS-100) and a source-measurement unit (Kiesley 236). The fluorescence spectrometer (ISS Photon Counter Meter) was used as a means for measuring the PL and EL spectra. The color purity of the white light emitting device was measured using a source measuring unit (Keithley 236) and a luminous spectrometer (CS-1000).

5 is a graph showing an EL spectrum at a voltage of 7V of the polymer phosphorescent blend device of various ratios prepared in Example 1. In Figure 5, a is BlueJ 90 wt% -Ir (PBPP) ₃ 9.7 wt% -Ir (PIQ) ₃ 0.3 wt% of a polymer phosphorescent blend device, b is BlueJ 65 wt% -PVK 25 wt% -Ir (PBPP ₃ 9.7 wt% -Ir (PIQ) ₃ 0.3 wt% of the polymer phosphorescent blend device, c is b is BlueJ 45 wt% -PVK 45 wt% -Ir (PBPP) ₃ 9.7 wt% -Ir (PIQ) ₃ 0.3 In the wt% polymer phosphorescent blend device, d is b BlueJ 30 wt% -PVK 60 wt% Ir (PBPP) ₃ 9.7 wt% Ir (PIQ) ₃ 0.3 wt% of the polymer phosphorescent blend device, e is b Shows a PL spectrum of a polymer phosphorescent blend device of BlueJ 20 wt% -PVK 70 wt% -Ir (PBPP) ₃ 9.7 wt% -Ir (PIQ) ₃ 0.3 wt%.

Similar to FIG. 3, as the content of PVK increases, energy transfer from the high efficiency BlueJ polymer to the phosphorescent composite also increases. BlueJ polymers transfer both the energy absorbed from PVK and their energy to the phosphorescent complex. Co-emission of red, green and blue light with similar emission intensity was observed in blend devices of BlueJ 65: PVK 25: Ir (PBPP) ₃ 9.7: Ir (PIQ) ₃ 0.3 (65: 25: 9.7: 0.3) It is an optimum ratio for white LEDs.

FIG. 6 is measured at various voltages of ITO / PEDOT / BlueJ 65: PVK 25: Ir (PBPP) ₃ 9.7: Ir (PIQ) ₃ 0.3 (wt%) blend / BCP / Li: Al device prepared in Example 1 Show the EL spectrum. The spectrum contains main peaks located at 460 nm, 518 nm and 618 nm, which are the light emitted from the BlueJ host, Ir (PBPP) ₃ and Ir (PIQ) ₃ , respectively. The performance of a polymer-based electrophosphorescent device depends mainly on the properties of the energy-providing host polymer, and if the energy of the host polymer is fully transferred, the electrical and optical properties of the phosphor are similar to those of the host polymer. In this system, since the guest material emits light completely by energy transfer from the BlueJ polymer, its properties such as maximum brightness and driving voltage are similar. Thus, the CIE color coordinate system from the observed white light does not change significantly with the applied voltage. PVK not only improves chemical miscibility between materials, but also acts as a hole transport material. Therefore, the BCP as the hole blocking layer effectively lowers the driving voltage of the phosphorescent composite in the portion occupied by PVK (in the AFM image of FIG. 4) than in the region of BlueJ. Therefore, at low voltage, red dominates and blue increases slightly as the voltage increases.

The color purity and luminance according to the voltage of the white LED are shown in FIG. 7. At the driving voltages 6, 7, 8 and 9V, the color coordinates are (0.34, 0.34), (0.34, 0.33), (0.33, 0.33), (0.32, 0.32), and the corresponding luminance is 708, 1996, 4169, 6945. cd / m ² . The EL spectrum of the fluorescent / phosphorescent white LED in this study shows color stability at different voltages.

8 and 9 are graphs showing voltage-current-luminescence intensity characteristics of the respective EL devices manufactured in Example 1; The threshold voltage of the 65: 25: 9.7: 0.3 blend device was 3.4 V, which is the best of the polymer-based white electroluminescent devices reported so far. When energy is transferred from PVK, the driving voltage is high due to the charge trapping effect. However, when energy is transferred in a high-efficiency conjugated polymer such as BlueJ, the driving voltage is significantly lowered because the sterster energy transfer acts as a main mechanism. 65: 25: 9.7: 0.3 The maximum luminous intensity of the blended white LED device is 11730 cd / m ² at 11 V and current density of 207.22 mA / cm ² .

10 is a graph showing a correlation between luminous efficiency and current density. 65: 25: 9.7: 0.3 The maximum luminous efficiency of the blended white light emitting device reached 7.23 mA / cm ² , the driving voltage of 6.2 V, and 12.52 cd / A at 905 cd / m ² , and the external quantum efficiency was 3.2%. To reach In this system, the luminous efficiency of the device is greatly improved by using two phosphors in the white light emitting device.

11 shows a photograph of a white LED operated at 7V. As described in FIG. 5, despite the simultaneous red light emission of red, green, and blue using micro phase separation, it can be seen that the pure white light is uniformly visible.

While the invention has been described and illustrated above with reference to specific embodiments and examples deemed preferred herein, it is to be understood that numerous replacements, modifications and substitutions may be made without departing from the spirit and scope of the invention. The skilled person will understand clearly.

According to the present invention, a polymer-based fluorescent / phosphorescent composite white electroluminescent device using a conjugated polymer having excellent luminous efficiency and a phosphor as a light emitting layer by blending with a PVK, PVK increases the chemical miscibility of two other materials, conjugated Efficient energy transfer from the polymer to the phosphor can be achieved to improve the luminous efficiency of the device. In addition, due to efficient energy transfer in the fluorescent / phosphorescent composite device, the driving voltage is significantly lowered, and pure white light having color stability with voltage is realized. Therefore, when the white light emitting device of the present invention is applied to a large area display, it can be used as a high luminance surface light source, and can also be used as a full color display using a color filter. In addition, the white electroluminescent device of the present invention is expected to be applicable to the next-generation white light illumination having a low driving voltage and excellent luminous efficiency by focusing on the characteristics of high luminance.

Claims (8)

A polymer-based electroluminescent / phosphorescent composite device comprising a transparent substrate, an anode electrode layer, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode electrode layer, wherein the light emitting layer comprises 1) a light emitting conjugated polymer, 2) a phosphor, and 3) a light emitting nonporous. A white electroluminescent device comprising a blend of poly (N-vinylcarbazole) (PVK) or a derivative thereof as a liquid polymer. The method of claim 1, Luminescent conjugated polymers are poly (fluorene) and derivatives thereof, poly (para-phenylene) and derivatives thereof, and poly (para-phenylenevinylene) and derivatives thereof. It is a polymer light emitting material of the phosphorescent material is an iridium composite, europium composite, platinum composite or osmium composite is a low molecular phosphorescent material that generates light of 450 to 700 nm wavelength white electroluminescent device. The method of claim 1, A white electroluminescent device wherein the transparent substrate is glass or plastic and the anode electrode layer is ITO (indium tin oxide), PEDOT (polyethylene dioxythiophene), carbon nanotubes or polyaniline. The method of claim 1, A white electroluminescent device wherein the cathode electrode layer is aluminum, magnesium, lithium, calcium, copper, silver, gold or alloys thereof. The method of claim 1, A white electroluminescent device that transfers energy from a luminescent conjugated polymer to a phosphor, or transfers energy from polyvinylcarbazole (PVK) and its derivatives to a luminescent conjugated polymer and transfers energy from the conjugated polymer to a phosphor. The method of claim 1, White electroluminescent device, wherein the white light is for use in displays and surface light sources. The method of claim 6, The luminescent conjugated polymer is used for blue light emission in the wavelength range of 400 to 480 nm, and the phosphor is used for green light emission in the wavelength range of 490 to 560 nm and red light emission in the wavelength range of 590 to 700 nm, respectively. The white electroluminescent device which implements white light emission and is used for a display and a surface light source. The method of claim 1, A blue light emitting conjugated polymer in the wavelength range of 400 to 480 nm and a green light emitting phosphor in the wavelength range of 490 to 560 nm are used for the blue and green light emission as an energy transfer material, and a red light emitting phosphor in the wavelength range of 590 to 700 nm is used as the energy receiving material. White electroluminescent device that realizes white light emission by tri-color co-emission by using light emission.

Images