A blue fluorescent organic light emitting diode and a preparation method thereof

Abstract

The application discloses a blue fluorescent organic light emitting diode, which comprises a substrate, an anode, a hole injection layer, a hole transport layer, an electron blocking layer, a light emitting layer, an efficiency enhancement layer, an electron transport layer, an electron injection layer and a cathode in sequence; the efficiency enhancement layer material is 4-(2,7-di(naphthalene-2-yl)-9H-carbazole-9-yl)benzonitrile; the light emitting layer is composed of a host material and a fluorescent guest dopant; the host material is 9-(4-(10-phenyl-9-anthryl)phenyl]9H-carbazole; and the fluorescent guest dopant is 1-4-di-[4-(N,N-diphenyl)amino]styrylbenzene. Through a high-energy triplet state anti-inter-system crossing process, the efficiency enhancement layer can obtain 100% of the exciton utilization rate at most, the electroluminescent efficiency of the device is greatly improved, and good stability is maintained.

Description

Technical Field

[0001] This invention relates to the field of organic light-emitting diode (OLED) technology, and in particular to a blue fluorescent organic light-emitting diode and its fabrication method. Background Technology

[0002] Organic light-emitting diodes (OLEDs) possess advantages such as a wide color gamut, self-illumination, and thinness, and can be fabricated into large-area flexible devices. After more than 30 years of rapid development, OLEDs, as a new generation of display and lighting technology, have achieved initial industrial production and application. Currently, red and green OLEDs meet the needs of commercial applications, while blue OLEDs still struggle to achieve breakthroughs in electroluminescent efficiency and stability, thus requiring further development.

[0003] According to spin statistics theory, in the electroluminescence process, traditional fluorescent materials can only achieve radiative transition emission of 25% of singlet excitons, resulting in an electroluminescence efficiency of less than 5% for OLEDs based on traditional fluorescent materials. Therefore, developing new light-emitting mechanisms to further improve the utilization rate of triplet excitons is a key research focus and challenge for blue fluorescent OLEDs.

[0004] In recent years, researchers have discovered mechanisms such as thermally active delayed fluorescence (TADF), triplet-triplet annihilation (TTF), and the "hot exciton process" to maximize the utilization of triplet excitons to 100%. However, blue fluorescent OLEDs based on TADF and hot exciton materials as emitters still face stability issues. While devices using TTF as emitters exhibit good stability, significant breakthroughs in electroluminescence efficiency remain elusive. To further improve the efficiency of TTF-based blue fluorescent OLEDs, researchers have developed new high-performance TTF materials and reported efficiency enhancement layer (EEL) device structures, leading to improved efficiency. Existing EEL layers primarily utilize TTF materials, but the TTF emission mechanism can only utilize a maximum of 62.5% of singlet excitons for emission; therefore, achieving breakthroughs in the efficiency of TTF-based blue fluorescent OLEDs remains challenging. Summary of the Invention

[0005] To overcome the aforementioned shortcomings and deficiencies of the prior art, the present invention aims to provide a blue fluorescent organic light-emitting diode (OLED) that uses 4-(2,7-bis(naphthalene-2-yl)-9H-carbazole-9-yl)benzonitrile (2Na-CzCN) as an efficiency enhancement layer. Through a high-lying triplet states reverse intersystem crossing (hRISC) process, the efficiency enhancement layer can achieve up to 100% exciton utilization, greatly improving the electroluminescence efficiency of the device while maintaining good stability.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned blue fluorescent organic light-emitting diode.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A blue fluorescent organic light-emitting diode, comprising, in sequence, a substrate, an anode, a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, an efficiency enhancement layer, an electron transport layer, an electron injection layer, and a cathode;

[0009] The material of the efficiency enhancement layer is 4-(2,7-bis(naphthal-2-yl)-9H-carbazole-9-yl)benzonitrile;

[0010] The light-emitting layer is composed of a host material and a fluorescent guest dopant;

[0011] The main material is the TTF upconversion material CzPA(9-(4-(10-phenyl-9-anthrayl)phenyl]9H-carbazole);

[0012] The fluorescent guest dopant is DSA-ph (1-4-bis-[4-(N,N-diphenyl)amino]styrene).

[0013] Preferably, the thickness of the efficiency enhancement layer is 5–15 nm.

[0014] Preferably, the doping concentration of the fluorescent guest dopant is 1 to 10 wt.% (mass of DSA-ph / (mass of DSA-ph + mass of CzPA)).

[0015] Preferably, the doping concentration of the fluorescent guest dopant is 1.5 to 2.5 wt.%.

[0016] Preferably, the thickness of the light-emitting layer is 5–30 nm.

[0017] Preferably, the hole injection layer is an organic material HAT-CN (2,3,6,7,10,11-hexacyano-1,4,5,8,9,2-azabenzophenanthrene), or an inorganic material MoO3 (molybdenum oxide) or V2O5 (vanadium pentoxide), with a hole injection layer thickness of 5-15 nm.

[0018] Preferably, the hole transport layer material is TAPC (4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline]), and the thickness of the hole transport layer is 50-100 nm.

[0019] Preferably, the electron blocking layer material is TCTA (4,4',4”-tris(carbazole-9-yl)triphenylamine), or mCBP (3,3'-bis(9H-carbazole-9-yl)-1,1'-biphenyl) with an electron blocking layer thickness of 5-20 nm.

[0020] Preferably, the electron transport layer material is one of TPBi (1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene), BmPyPB (1,3-bis[3,5-bis(pyridinyl)phenyl]benzene) or TmPyPB (3,3'-[5'-[3-(3-pyridinyl)phenyl][1,1':3',1”-terphenyl]-3,3”-diyl]dipyridine), and the thickness of the electron transport layer is 30-60 nm.

[0021] Preferably, the electron injection layer material is one of LiF (lithium fluoride), Li2CO3 (lithium carbonate), or Cs2CO3 (cesium carbonate); the thickness of the electron injection layer is 1-3 nm.

[0022] Preferably, the substrate is one of glass, quartz, polymer material or metal material.

[0023] Preferably, the anode is one of ITO (indium tin oxide), metal, or graphene, and the thickness of the anode is 100-150 nm.

[0024] Preferably, the cathode material is one of metals Al (aluminum), Ag (silver), or Mg:Al (magnesium-aluminum alloy), and the thickness of the cathode is 100-150 nm.

[0025] The method for preparing the blue fluorescent organic light-emitting diode includes the following steps:

[0026] First, the substrate with the anode is pretreated, which includes alkaline ultrasonication, deionized water rinsing, high-pressure nitrogen drying, oven baking, and ultraviolet ozone treatment.

[0027] The substrate with the anode is then placed into the coating machine, and the machine is evacuated to a pressure of 1 × 10⁻⁶ using a mechanical pump and a molecular pump.-4 A blue fluorescent organic light-emitting diode is obtained by sequentially depositing a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, an efficiency enhancement layer, an electron transport layer, an electron injection layer, and a cathode on the surface of a substrate with an anode at a pressure below Pa.

[0028] Preferably, the evaporation rate of the efficiency enhancement layer is

[0029] The principle of this invention is as follows:

[0030] This invention employs 4-(2,7-bis(naphthalene-2-yl)-9H-carbazole-9-yl)benzonitrile as an efficiency enhancement layer. 4-(2,7-bis(naphthalene-2-yl)-9H-carbazole-9-yl)benzonitrile possesses a highly efficient "thermal exciton" channel. Excitons can first be utilized through the hRISC process. Subsequently, since the S1 level of 2Na-CzCN is above the S1 level of CzPA, singlet excitons of 2Na-CzCN can be utilized through… Energy is transferred to CzPA. Simultaneously, since the T1 level of 2Na-CzCN is above the T1 level of CzPA, excitons reaching T1 via internal conversion can be transferred to CzPA via Dexter energy transfer. Then, the triplet excitons are reused through the TTF process in CzPA. Finally, because the S1 level of DSA-ph is lower than the S1 level of CzPA, the energy of CzPA can be transferred through... Energy is transferred to the DSA-ph dopant, causing it to emit light.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] This invention employs 4-(2,7-bis(naphthalene-2-yl)-9H-carbazole-9-yl)benzonitrile as an efficiency enhancement layer, enabling excitons to be utilized first through a "thermal exciton" channel. Because the thermal exciton channel is fast and efficient, it does not cause additional exciton loss, thus effectively improving exciton utilization. Subsequently, internally converted excitons not utilized by the thermal exciton channel can be further utilized through upconversion using TTF material, and ultimately... Energy is transferred to the DSA-ph dopant to achieve efficient radiative luminescence. In addition, since excitons are dispersed in the luminescent layer and the efficiency enhancement layer, the exciton quenching phenomenon is also improved, ultimately resulting in blue fluorescent OLEDs that combine high electroluminescence efficiency and stability. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the device structure of blue fluorescent OLEDs with 2Na-CzCN as the efficiency enhancement layer according to an embodiment of the present invention.

[0034] Figure 2 This is a mechanism diagram of blue fluorescent OLEDs with 2Na-CzCN as the efficiency enhancement layer according to an embodiment of the present invention.

[0035] Figure 3 The graphs show the current efficiency, power efficiency, and external quantum efficiency-brightness characteristics of blue fluorescent OLEDs with 2Na-CzCN as the efficiency enhancement layer according to an embodiment of the present invention.

[0036] Figure 4 The graphs show the current efficiency, power efficiency, and external quantum efficiency-brightness characteristics of blue fluorescent OLEDs with 2Na-CzCN as the efficiency enhancement layer according to an embodiment of the present invention.

[0037] Figure 5 The embodiments of the present invention show blue fluorescent OLEDs with an efficiency enhancement layer (with EEL) and blue fluorescent OLEDs without an EEL at 1000 cd / m². 2 Electroluminescence spectrum of the image.

[0038] Figure 6 The figures show the current density-brightness-voltage characteristics of blue fluorescent OLEDs with 2Na-CzCN as the efficiency enhancement layer (with EEL) and blue fluorescent OLEDs without 2Na-CzCN as the efficiency enhancement layer (without EEL) according to embodiments of the present invention.

[0039] Figure 7 The embodiments of the present invention show blue fluorescent OLEDs with an efficiency enhancement layer (with EEL) and blue fluorescent OLEDs without an EEL at 1000 cd / m². 2 Brightness-time characteristic curve of the device at initial brightness. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto.

[0041] Example

[0042] The blue fluorescent OLEDs of this embodiment, which use 2Na-CzCN as the efficiency enhancement layer, have the following structural schematic diagram: Figure 1 As shown, it includes a substrate, an anode, a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, an efficiency enhancement layer, an electron transport layer, an electron injection layer, and a cathode, which are stacked in sequence.

[0043] In this embodiment, the light-emitting layer is composed of a host material and a dopant material.

[0044] In this embodiment, the host material is the TTF upconversion material CzPA (9-(4-(10-phenyl-9-anthrayl)phenyl]9H-carbazole). The dopant is the conventional blue fluorescent material DSA-ph (1-4-bis-[4-(N,N-diphenyl)amino]styrenebenzene). The doping concentration of DSA-ph is 2 wt.%.

[0045] The method for preparing blue fluorescent OLEDs with 2Na-CzCN as the efficiency enhancement layer in this embodiment includes the following steps:

[0046] First, the conductive ITO glass substrate is ultrasonically treated with an alkaline cleaning agent. Then, it is rubbed with tap water and rinsed with deionized water. After drying with high-purity nitrogen, it is baked in an oven at 120°C for 30 minutes. Next, it is treated with ultraviolet ozone for 6 minutes before being placed in a vacuum coating machine. The process continues until the pressure in the vacuum coating machine decreases to 1×10⁻⁶. -4 At Pa, thin films are sequentially deposited on the surface of a conductive ITO glass substrate. First, the hole injection layer material HAT-CN is deposited at a deposition rate of [missing information]. The evaporation thickness is 10 nm, followed by the sequential evaporation of hole transport layer material TAPC at a evaporation rate of [missing information]. The evaporation thickness is 60 nm; the electron blocking layer material is TCTA, and the evaporation rate is... The evaporation thickness was 5 nm for all layers; the luminescent layer was CzPA:DSA-ph (2 wt.%), and the evaporation rates of CzPA and DSA-ph were respectively... and The luminescent layer has a deposition thickness of 16 nm; the efficiency enhancement layer material is 2Na-CzCN, and the deposition rate is [missing information]. The deposition thickness is 7 nm; the electron transport layer material is BmPyPB, and the deposition rate is... The evaporation thickness is 30 nm; the electron injection layer material is LiF, and the evaporation rate is... The thickness is 1 nm, and the final cathode material Al is deposited by evaporation at a evaporation rate of [missing information]. The thickness is 100nm. The evaporation rate and thickness of each functional layer are controlled by a quartz crystal film thickness gauge. The final device structure of the blue fluorescent OLED with thermal exciton material as the efficiency enhancement layer is: ITO / HAT-CN (10nm) / TAPC (60nm) / TCTA (5nm) / CzPA:DSA-ph (98: 2wt.%, 16nm) / 2Na-CzCN (7nm) / BmPyPB (30nm) / LiF (1nm) / Al (100nm).

[0047] The luminescence mechanism of the blue fluorescent OLEDs prepared in this embodiment, with 2Na-CzCN as the efficiency enhancement layer, is as follows: Figure 2 As shown:

[0048] By employing 4-(2,7-bis(naphthalene-2-yl)-9H-carbazole-9-yl)benzonitrile as an efficiency enhancement layer, 4-(2,7-bis(naphthalene-2-yl)-9H-carbazole-9-yl)benzonitrile possesses a highly efficient "thermal exciton" channel. Excitons can first be utilized through the hRISC process, and then, since the S1 level of 2Na-CzCN is above the S1 level of CzPA, the singlet excitons of 2Na-CzCN can be utilized through... Energy is transferred to CzPA. Simultaneously, since the T1 level of 2Na-CzCN is above the T1 level of CzPA, excitons reaching T1 via internal conversion can be transferred to CzPA via Dexter energy transfer. Then, the triplet excitons are reused through the TTF process in CzPA. Finally, because the S1 level of DSA-ph is lower than the S1 level of CzPA, the energy of CzPA can be transferred through... Energy is transferred to the DSA-ph dopant, causing it to emit light.

[0049] To compare the impact of having or not having a thermal exciton efficiency enhancement layer on the EL performance of the device, blue fluorescent OLEDs without an efficiency enhancement layer were also fabricated. The fabrication method of the blue fluorescent OLEDs without an efficiency enhancement layer in this embodiment includes the following steps:

[0050] First, the conductive ITO glass substrate is ultrasonically treated with an alkaline cleaning agent. Then, it is rubbed with tap water and rinsed with deionized water. After drying with high-purity nitrogen, it is baked in an oven at 120°C for 30 minutes. Next, it is treated with ultraviolet ozone for 6 minutes before being placed in a vacuum coating machine. The process continues until the pressure in the vacuum coating machine decreases to 1×10⁻⁶. -4 At Pa, thin films are sequentially deposited on the surface of a conductive ITO glass substrate. First, the hole injection layer material HAT-CN is deposited at a deposition rate of [missing information]. The evaporation thickness is 10 nm, followed by the sequential evaporation of hole transport layer material TAPC at a evaporation rate of [missing information]. The evaporation thickness is 60 nm; the electron blocking layer material is TCTA, and the evaporation rate is... The evaporation thickness was 5 nm for all layers; the luminescent layer was CzPA:DSA-ph (2 wt.%), and the evaporation rates of CzPA and DSA-ph were respectively... and The luminescent layer has a deposition thickness of 16 nm; the electron transport layer material is BmPyPB, and the deposition rate is... The evaporation thickness is 30 nm; the electron injection layer material is LiF, and the evaporation rate is... The thickness is 1 nm, and the final cathode material Al is deposited by evaporation at a evaporation rate of [missing information]. The thickness is 100nm. The evaporation rate and thickness of each functional layer are controlled by a quartz crystal film thickness gauge. The final device structure of the blue fluorescent OLED without the efficiency enhancement layer is: ITO / HAT-CN (10nm) / TAPC (60nm) / TCTA (5nm) / CzPA:DSA-ph (98: 2wt.%, 16nm) / BmPyPB (30nm) / LiF (1nm) / Al (100nm).

[0051] The current efficiency, power efficiency, and external quantum efficiency-luminance characteristic curves of blue fluorescent OLEDs with 2Na-CzCN as the efficiency enhancement layer in this embodiment of the invention are shown in the figure below. Figure 3 As shown.

[0052] The current efficiency, power efficiency, and external quantum efficiency-luminance characteristic curves of blue fluorescent OLEDs with 2Na-CzCN as the efficiency enhancement layer in this embodiment of the invention are shown in the figure below. Figure 4 As shown.

[0053] Blue fluorescent OLEDs with 2Na-CzCN as the efficiency enhancement layer (with EEL) and blue fluorescent OLEDs without 2Na-CzCN as the efficiency enhancement layer (without EEL) according to embodiments of the present invention have a performance of 1000 cd / m². 2 The electroluminescence spectrum below is as follows Figure 5 As shown.

[0054] The current density-brightness-voltage characteristic curves of blue fluorescent OLEDs with 2Na-CzCN as the efficiency enhancement layer (with EEL) and blue fluorescent OLEDs without 2Na-CzCN as the efficiency enhancement layer (without EEL) according to embodiments of the present invention are shown in the figure. Figure 6 As shown.

[0055] Blue fluorescent OLEDs with 2Na-CzCN as the efficiency enhancement layer (with EEL) and blue fluorescent OLEDs without 2Na-CzCN as the efficiency enhancement layer (without EEL) according to embodiments of the present invention have a performance of 1000 cd / m². 2 The brightness-time characteristic curve of the device at the initial brightness is shown in the figure below. Figure 7 As shown.

[0056] from Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7As can be seen, by introducing 2Na-CzCN as the efficiency enhancement layer, and using the TTF material CzPA as the host and the traditional blue fluorescent dopant DSA-ph as the guest, excitons are efficiently utilized simultaneously through both the "thermal exciton" process and the TTF process, effectively improving the electroluminescence efficiency and stability of the device. The electroluminescence spectrum of the device shows that the emission peaks are all fluorescence emission from the dopant DSA-ph, demonstrating effective energy transfer between the efficiency enhancement layer, the host, and the fluorescent guest. The blue fluorescent OLEDs with 2Na-CzCN as the efficiency enhancement layer achieved a maximum current efficiency, power efficiency, and external quantum efficiency of 25.0 cd / A, 21.5 lm / W, and 15.2%, respectively. In contrast, the blue fluorescent OLEDs without the efficiency enhancement layer achieved only 17.2 cd / A, 15.5 lm / W, and 10.6%, respectively. This indicates that the blue fluorescent OLEDs with the thermal exciton material as the efficiency enhancement layer possess excellent electroluminescence performance, and the device exhibits a very low efficiency roll-off at high brightness. Furthermore, the blue fluorescent OLEDs with 2Na-CzCN as the efficiency enhancement layer achieve a high efficiency at 1000 cd / m². 2 The time it takes for the device brightness to decay to 50% from its initial brightness (LT) 50 Up to 40 hours, while LT blue fluorescent OLEDs without an efficiency enhancement layer... 50 The fact that the device achieved a lifespan of only 7 hours demonstrates that by introducing 2Na-CzCN as an efficiency enhancement layer, excitons can be utilized efficiently and dispersed from the EEL to the EML, reducing the quenching phenomenon of long-lived triplet excitons and improving the stability of the device.

[0057] In the above embodiments, the anode may also be a metal or graphene, and the thickness of the anode is 100-150 nm.

[0058] In the above embodiments, the hole injection layer may also be one of the inorganic materials MoO3 (molybdenum oxide) or V2O5 (vanadium pentoxide), and the thickness of the hole injection layer is 5-15 nm.

[0059] In the above embodiments, the electron blocking layer material may also be mCBP (3,3'-bis(9H-carbazole-9-yl)-1,1'-biphenyl), and the thickness of the electron blocking layer is 2-20 nm.

[0060] In the above embodiments, the electron transport layer material may also be one of BmPyPB (1,3-bis[3,5-bis(pyridinyl)phenyl]benzene) or TmPyPB (3,3'-[5'-[3-(3-pyridinyl)phenyl][1,1':3',1”-terphenyl]-3,3”-diyl]dipyridine), and the thickness of the electron transport layer is 30-60 nm.

[0061] In the above embodiments, the electron injection layer material may also be one of Li2CO3 (lithium carbonate) or Cs2CO3 (cesium carbonate), and the thickness of the electron injection layer is 0.5-3 nm.

[0062] In the above embodiments, the cathode material is a metal, and may also be one of Ag (silver) or Mg:Al (magnesium-aluminum alloy material), and the thickness of the cathode is 100-150 nm.

[0063] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described above. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A blue-phosphor fluorescent organic light-emitting diode, characterized in that, It consists of, in sequence, a substrate, an anode, a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, an efficiency enhancement layer, an electron transport layer, an electron injection layer, and a cathode; The material of the efficiency enhancement layer is 4-(2,7-bis(naphthyl-2-yl)-9H-carbazole-9-yl)benzonitrile; The light-emitting layer is composed of a host material and a fluorescent guest dopant; The main material is 9-(4-(10-phenyl-9-anthrayl)phenyl]9H-carbazole; The fluorescent guest dopant is 1,4-bis-[4-(N,N-diphenyl)amino]styrene. 2.The blue fluorescent OLED according to claim 1, wherein, The thickness of the efficiency enhancement layer is 5~15 nm. 3.The blue fluorescent OLED according to claim 1, wherein, The doping concentration of the fluorescent guest dopant is 1~10 wt.%. ​ 4.The blue fluorescent OLED according to claim 1, wherein, The doping concentration of the fluorescent guest dopant is 1.5~2.5 wt.%. ​ 5.The blue fluorescent OLED according to claim 1, wherein, The thickness of the light-emitting layer is 5~30 nm. 6.The blue fluorescent OLED according to claim 1, wherein, The hole injection layer uses 2,3,6,7,10,11-hexacyano-1,4,5,8,9,2-azabenzo phenanthrene, MoO 3、 One of V2O5, the thickness of the hole injection layer is 5~15 nm.

7. The blue fluorescent OLED according to claim 1, wherein The hole transport layer material is 4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline], and the thickness of the hole transport layer is 50~100 nm.

8. The blue fluorescent organic light-emitting diode according to claim 1, characterized in that, The electron blocking layer material is 4,4',4”-tris(carbazole-9-yl)triphenylamine, and the thickness of the electron blocking layer is 5~20 nm.

9. The blue fluorescent organic light-emitting diode according to claim 1, characterized in that, The electron transport layer is one of 1,3-bis[3,5-bis(pyridin-3-yl)phenyl]benzene, 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene, or 3,3'-[5'-[3-(3-pyridinyl)phenyl][1,1':3',1”-terphenyl]-3,3”-diyl]dipyridine, and the thickness of the electron transport layer is 30~60 nm; The electron injection layer material is one of LiF, Li2CO3 or Cs2CO3, and the thickness of the electron injection layer is 1~3 nm.

10. The method for preparing a blue fluorescent organic light-emitting diode according to any one of claims 1 to 9, characterized in that, Includes the following steps: First, the substrate with the anode is pretreated, which includes alkaline ultrasonication, deionized water rinsing, high-pressure nitrogen drying, oven baking, and ultraviolet ozone treatment. Then, the substrate with the anode is placed into the coating machine, and the coating machine is evacuated to a certain pressure using mechanical and molecular pumps. The following steps involve sequentially depositing a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, an efficiency enhancement layer, an electron transport layer, an electron injection layer, and a cathode on the surface of a substrate with an anode to obtain a blue fluorescent organic light-emitting diode.

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