Patent Application
20140151645
The present invention generally relates to a novel fluorene compound and organic electroluminescent (herein referred to as organic EL) device using the compound. More specifically, the present invention relates to the fluorene compound having general formula(A), an organic EL device employing the fluorene compound as fluorescence host material.
Organic EL device has many advantages such as self-emitting, wider viewing angles, faster response speeds and highly luminescence. Their simpler fabrication and capable of giving clear display comparable with LCD, making organic EL device an industry display of choice. Organic EL device contain emissive materials which are arranged between a cathode and a anode, when a applied driving voltage is added, an electron and a hole were injected into the emissive layer and recombined to form an exciton. The exciton which results from an electron and a hole recombination have a singlet spin state or triplet spin state. Luminescence from a singlet spin state emits fluorescence and luminescence from triplet spin state emits phosphorescence.
Organic EL device are generally composed of functionally divided organic multi-layers, e.g., hole injection layer (HIL), hole transporting layer (HTL), emissive layer (EML), electron transporting layer (ETL) and electron injection layer (EIL) and so on. A emissive material have good charge carrier mobility and excellent operational durability can lower driving voltage and power consumption, Increasing efficiency and half-lifetime of Organic EL device.
For full-colored flat panel displays in AMOLED, the compounds used for the blue emissive layer are still unsatisfactory in half-lifetime and emissive colour. Many fluorene compounds are used for fluorescence blue host in emissive layer. U.S. Pat. No. 7,691,492 used 1,1′-(9,9-dimethyl-9H-fluorine-2,7-diyl)dipyrene (DFDP) as host for blue emissive electroluminescence device. U.S. Pat. No. 8,158,835 described fluorene compound used as blue, green, or red host. U.S. Pat. No. 8,110,294 also claim fluorene compound used as phosphorescence host. These compounds still have disadvantages for industrial practice use. Especially for AMOLED, except prolong half-lifetime, deep blue emission (CIE y coordinates under 0.15) is necessary for improvement.
In accordance with the present invention, the fluorene compound and their use for emissive material for Organic EL device are provided. the fluorene compound can overcome the drawbacks of the conventional materials like as shorter half-life time, lower efficiency and CIE colour purity, especially for blue fluorescent emissive material in the present invention. For full-colored flat panel displays, the blue emissive material is still not satisfied for practice use for its shorter life and CIE colour purity.
An object of the present invention is to provide the fluorene compound which can be used as emissive material for Organic EL device.
Another object of the present invention is to apply the fluorene compound for blue emissive material of Organic EL device and improve CIE colour purity & Dominate Wavelength.
Another object of the present invention is to apply the fluorene compound for blue emissive material of Organic EL device and improve the half-lifetime, lower driving voltage, lower power consumption and increase the efficiency.
The present invention has the economic advantages for industrial practice. Accordingly, the present invention discloses the fluorene compound which can be used for Organic EL device is disclosed. The mentioned the fluorene compound are represented by the following formula(A):
Wherein R1 to R6 are identical or different. R1 to R6 are independently selected from the group consisting of a hydrogen atom, a halide, alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted aralkyl group having 6 to 30 carbon atoms, a substituted or unsubstituted heteroaryl group having 6 to 30 carbon atoms. R7˜R13 are identical or different R7 to R13 are independently selected from the group consisting of hydrogen atom, halide, alkyl group, aryl group, heteroaryl group. m and n are independently an integer of 0 to 3, X is selected from carbon or nitrogen atom.
What probed into the invention is the fluorene compound and organic EL device using the compound. Detailed descriptions of the production, structure and elements will be provided in the following to make the invention thoroughly understood. Obviously, the application of the invention is not confined to specific details familiar to those who are skilled in the art. On the other hand, the common elements and procedures that are known to everyone are not described in details to avoid unnecessary limits of the invention. Some preferred embodiments of the present invention will now be described in greater detail in the following. However, it should be recognized that the present invention can be practiced in a wide range of other embodiments besides those explicitly described, that is, this invention can also be applied extensively to other embodiments, and the scope of the present invention is expressly not limited except as specified in the accompanying claims.
In a first embodiment of the present invention, the fluorene compound which can be used as emissive material of Organic EL device are disclosed. The mentioned fluorene compound are represented by the following formula(A):
Wherein R1 to R6 are identical or different. R1 to R6 are independently selected from the group consisting of a hydrogen atom, a halide, alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted aralkyl group having 6 to 30 carbon atoms, a substituted or unsubstituted heteroaryl group having 6 to 30 carbon atoms. R7˜R13 are identical or different R7 to R13 are independently selected from the group consisting of hydrogen atom, halide, alkyl group, aryl group, heteroaryl group. m and n are independently an integer of 0 to 3, X is selected from carbon or nitrogen atom.
In this embodiment, some fluorene compounds are shown below:
The fluorene compound for formula(A) can be prepared starting with two units of dioxaborolane substituted Indeno[2,1-b]triphenylene Suzuki coupling with dibromide substituted fluorene compounds.
Detailed preparation for formula(A) could be clarified by exemplary embodiments, but the present invention is not limited to exemplary embodiments.
A mixture of 35.2 g (100 mmol) of 2,7-dibromo-9,9-dimethyl-9H-fluorene, 21.8 g (110 mmol) of biphenyl-2-ylboronic acid, 2.31 g (2 mmol) of Tetrakis(triphenylphosphine)palladium, 75 ml of 2M Na2CO3, 150 ml of EtOH and 300 ml toluene was degassed and placed under nitrogen, and then heated at 100° C. for 12 h. After finishing the reaction. The mixture was allowed to cool to room temperature. The organic layer was extracted with ethyl acetate and water, dried with anhydrous magnesium sulfate, the solvent was removed and the residue was purified by column chromatography on silica (hexane-dichloromethane) to give product (26.8 g, 63.0 mmol, 63%) as a white solid. 1H NMR (CDCl3, 400 MHz): δ 7.61 (d, J=7.8 Hz, 1H), 7.55˜7.53 (m, 2H), 7.49˜7.42 (m, 5H), 7.29 (d, J=8.0 Hz, 1H), 7.20˜7.14 (m, 5H), 6.98 (s, 1H), 1.21 (s, 6H)
In a 3000 ml three-necked flask that had been degassed and filled with nitrogen, 26.8 g (60 mmol) of 2-(biphenyl-2-yl)-7-bromo-9,9-dimethyl-9H-fluorene was dissolved in anhydrous Dichloromethane (1500 ml), 97.5 g (600 mmol) Iron(III) chloride was then added, and the mixture was stirred one hour. Methanol 500 ml were added to the mixture and the organic layer was separated and the solvent removed in vacuo. The residue was purified by column chromatography on silica (hexane-dichloromethane) afforded a white solid (10.7 g, 25.3 mmol, 40%). 1H NMR (CDCl3, 400 MHz): δ 8.95 (s, 1H), 8.79˜8.74 (m, 2H), 8.69˜8.68 (m, 3H), 7.84 (d, J=8.0 Hz, 1H), 7.72˜7.65 (m, 5H), 7.57 (d, J=8.0 Hz, 1H), 1.66 (s, 6H).
A mixture of 10.7 g (25.3 mmol) of 12-bromo-10,10-dimethyl-10H-Indeno[1,2-b]triphenylene, 7.7 g (30.3 mmol) of bis(pinacolato)diboron, 0.3 g (0.26 mmol) of Tetrakis(triphenylphosphine)palladium, 7.4 g (75.4 mmol) of potassium acetate, and 300 ml 1,4 dioxane was degassed and placed under nitrogen, and then heated at 90° C. for 16 h. After finishing the reaction. The mixture was allowed to cool to room temperature. The organic phase separated and washed with ethyl acetate and water. After drying over magnesium sulfate, the solvent was removed in vacuo. The residue was purified by column chromatography on silica (hexane-dichloromethane) to give product (9.5 g, 20.2 mmol, 80%) as a light-yellow solid. 1H NMR (CDCl3, 400 MHz): δ 9.03 (s, 1H), 8.81 (d, J=7.84 Hz, 1H), 8.77 (d, J=7.88 Hz, 1H), 8.70˜8.67 (m, 3H), 8.02˜7.93 (m, 3H), 7.71˜7.67 (m, 4H), 1.69 (s, 6H), 1.42 (s, 12H)
A mixture of 4.9 g (14 mmol) of 2,7-dibromo-9,9-dimethyl-9H-fluorene, 7.53 g (16 mmol) of 2-(10,10-dimethyl-10H-indeno[1,2-b]triphenylen-12-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, 0.16 g (0.14 mmol) of Tetrakis(triphenylphosphine)palladium, 11 ml of 2M Na2CO3, 30 ml of EtOH and 65 ml toluene was degassed and placed under nitrogen, and then heated at 90° C. for 12 h. After finishing the reaction, the mixture was allowed to cool to room temperature. Than 500 ml MeOH was added, while stirring and the precipitated product was filtered off with suction. To give 3.7 g (yield 43%) of yellow product which was recrystallized from toluene.
A mixture of 6.6 g (28 mmol) of 1,4-dibromobenzene, 15.1 (32 mmol) of 2-(10,10-dimethyl-10H-indeno[1,2-b]triphenylen-12-yl)-4,4,5,5-teramethyl-1,3,2-dioxaborolane, 0.32 g (0.28 mmol) of Tetrakis(triphenylphosphine)palladium, 22 ml of 2M Na2CO3, 60 ml of EtOH and 130 ml toluene was degassed and placed under nitrogen, and then heated at 90° C. for 12 h. After finishing the reaction, the mixture was allowed to cool to room temperature. Than 500 ml MeOH was added, while stirring and the precipitated product was filtered off with suction and the residue was purified by column chromatography on silica (hexane-dichloromethane) to give product 7.4 g (53%) as a white solid.
A mixture of 7.4 g (14.8 mmol) 12-(4-bromophenyl)-10,10-dimethyl-10H-indeno[2,1-b]triphenylene, 4.9 g (19.3 mmol) of bis(pinacolato)diboron, 0.17 g (0.148 mmol) of Tetrakis(triphenylphosphine)palladium, 2.9 g (29.6 mmol) of potassium acetate, and 50 ml 1,4 dioxane was degassed and placed under nitrogen, and then heated at 90° C. for 24 h. After finishing the reaction, the mixture was allowed to cool to room temperature. The organic phase separated and washed with ethyl acetate and water. After drying over magnesium sulfate, the solvent was removed in vacuo. The residue was purified by column chromatography on silica (hexane-dichloromethane) to give product (5.9 g, 73%) as a white solid.
A mixture of 3.7 g (6 mmol) of 12-(7-bromo-9,9-dimethyl-9H-fluoren-2-yl)-10,10-dimethyl-10H-indeno[2,1-b]triphenylene, 3.6 g (6.6 mmol) of 2-(4-(10,10-dimethyl-10H-indeno[2,1-b]triphenylen-12-yl)phenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, 0.07 g (0.06 mmol) of Tetrakis(triphenylphosphine) palladium, 6 ml of 2M Na2CO3, 15 ml of EtOH and 50 ml toluene was degassed and placed under nitrogen, and then heated at 90° C. for 24 h. After finishing the reaction. The mixture was allowed to cool to room temperature. Than 100 ml MeOH was added, while stirring and the precipitated product was filtered off with suction. To give 3.5 g (yield 61%) of yellow product which was recrystallized from chloroform. MS (m/z, FAB+): 954.1 1H NMR (d6-DMSO, 400 MHz): δ 8.75 (s, 2H), 8.46˜8.40 (m, 6H), 8.06˜7.95 (m, 4H), 7.66˜7.36 (m, 15H), 7.27˜7.19 (m, 9H), 1.76 (s, 12H), 1.69 (s, 6H).
A mixture of 3.52 g (10 mmol) of 2,7-dibromo-9,9-dimethyl-9H-fluorene, 10.35 g (22 mmol) of 2-(10,10-dimethyl-10H-indeno[1,2-b]triphenylen-12-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, 0.12 g (0.1 mmol) of Tetrakis(triphenylphosphiue)palladium, 15 ml of 2M Na2CO3, 30 ml of EtOH and 100 ml toluene was degassed and placed under nitrogen, and then heated at 90° C. for 24 h. After finishing the reaction, The mixture was allowed to cool to room temperature. Than 100 ml MeOH was added, while stirring and the precipitated product was filtered off with suction. To give 5.9 g (yield 68%) of yellow product which was recrystallized from chloroform. MS (m/z, FAB+): 879.8 1H NMR (d6-DMSO, 400 MHz): δ 9.36 (s, 2H), 9.08 (d, J=6.0 Hz, 2H), 9.03 (s, 2H), 9.01 (d, J=6.8 Hz, 2H), 8.83 (d, J=7.2 Hz, 4H), 8.34 (d, J=6.4 Hz, 2H), 8.04 (s, 4H), 8.01 (d, J=6.4 Hz, 2H), 7.88 (d, J=6.8 Hz, 2H), 7.83 (d, J=6.0 Hz, 2H), 7.78˜7.72 (m, 8H), 1.74 (s, 12H), 1.67 (s, 6H).
A mixture of 2.64 g (10 mmol) of 1,4-dibromo-2,5-dimethylbenzene, 10.35 g (22 mmol) of 2-(10,10-dimethyl-10H-indeno[1,2-b]triphenylen-12-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, 0.12 g (0.1 mmol) of Tetrakis(triphenylphosphine)palladium, 15 ml of 2M Na2CO3, 30 ml of EtOH and 100 ml toluene was degassed and placed under nitrogen, and then heated at 90° C. for 24 h. After finishing the reaction, The mixture was allowed to cool to room temperature. Than 100 ml MeOH was added, while stirring and the precipitated product was filtered off with suction. To give 4.5 g (yield 57%) of yellow product which was recrystallized from chloroform. MS (m/z, FAB+): 790.9 1H NMR (CDC3, 400 MHz): δ 9.03 (s, 2H), 8.86 (d, J=8.00 Hz, 2H), 8.76 (d, J=8.00 Hz, 2H), 8.74 (s, 2H), 8.69 (d, J=8.00 Hz, 4H), 8.10 (d, J=8.00 Hz, 2H), 7.89˜7.82 (m, 6H), 7.76 (d, J=8.00 Hz, 2H), 7.74˜7.67 (m, 4H), 7.21 (s, 2H), 2.75 (s, 6H), 1.75 (s, 12H).
A solution of benzo[h]quinoline (6 g, 33.5 mmol) and KOH (5.6 g, 100.5 mmol) in water (400 mL) was boiled. A hot solution of KMnO4 (14.8 g, 93.8 mmol) in water (240 mL) was added dropwise over 1 hour to the boiling solution. The mixture was refluxed for another 6 hours and filtered hot. The filtrate was allowed to cool to room temperature. The organic layer was extracted with chloroform and water, dried with anhydrous magnesium sulfate. After solvent removal, the residue was purified by column chromatography on silica (acetone-petroleum ether) to give product 2.5 g (42%) as a yellow solid.
A mixture of 18.1 g (100 mmol) of 5H-indeno[1,2-b]pyridin-5-one, 27 ml (400 mmol) of hydrazine monohydrate, and 500 ml diethylene glycol was degassed and placed under nitrogen, and then heated at 170° C. for 12 h. After the reaction finish, the mixture was allowed to cool to room temperature. The organic layer was extracted with ethyl acetate and water, dried with anhydrous magnesium sulfate, the solvent was removed to give product 13.5 g (81%).
13.5 g (80.7 mmol) of 5H-indeno[1,2-b]pyridine was dissolved in 120 ml dry tetrahydrofuran, and 22.7 g (202 mmol) of potassium tert-butoxide was added to the solution at −10° C. The reaction mixture was maintained at −10° C. for 1 hour. Then the iodomethane 28.7 g (202 mmol) was added dropwise; the solution was then warmed slowly to room temperature and stirred for 6 h. After the reaction completion, water was added to the mixture to terminate the reaction. The reaction mixture was extracted with ethyl acetate and water, dried with anhydrous magnesium sulfate, the solvent was evaporated in vacuo, and the residue was crystallized with toluene to give the 5,5-dimethyl-5H-indeno[1,2-b]pyridine, 13.5 g (86%)
5,5-dimethyl-5H-indeno[1,2-b]pyridine (13.5 g, 69.1 mmol) was dissolved in chloroform (300 mL), protected from light and bromine (23.2 g, 145.1 mmol) diluted in chloroform (50 ml) was added dropwise. The mixture was stirred for 24 hours at room temperature, after which water (600 ml) was added, then the precipitated product was filtered off with suction, washed with MeOH and recrystallized from chloroform to give the 3,7-dibromo-5,5-dimethyl-5H-indeno[1,2-b]pyridine 13 g (53%)
A mixture of 13 g (36.8 mmol) of 3,7-dibromo-5,5-dimethyl-5H-indeno[1,2-b]pyridine, 8.7 g (44 mmol) of biphenyl-2-ylboronic acid, 0.43 g (0.368 mmol) of Tetrakis(triphenylphosphine) Palladium, 28 ml of 2M Na2CO3,50 ml of EtOH and 120 ml toluene was degassed and placed under nitrogen, and then heated at 90° C. for 24 h. After the reaction finish, the mixture was allowed to cool to room temperature. The organic layer was extracted with ethyl acetate and water, dried with anhydrous magnesium sulfate, the solvent was removed and the residue was washed with MeOH to give the structural isomerism product (10.4 g, 66%) which was used without further purification.
In a 2000 ml three-necked flask that had been degassed and filled with nitrogen, 10.4 g (24.4 mmol) of structural isomerism with 7-(biphenyl-2-yl)-3-bromo-5,5-dimethyl-5H-indeno[1,2-b]pyridine and 3-(biphenyl-2-yl)-7-bromo-5,5-dimethyl-5H-indeno[1,2-b]pyridine was dissolved in anhydrous dichloromethane (600 ml), 39.5 g (244 mmol) Iron(I) chloride was then added, and the mixture was stirred one hour. Methanol 500 ml were added to the mixture and the organic layer was separated and the solvent removed in vacuo. The residue was purified by column chromatography on silica (hexane-dichloromethane) to give 12-bromo-10,10-dimethyl-10H-cyclopenta[b]pyridino[1,2-b]triphenylene (1.8 g, 17.4%); 1H NMR (CDCl3, 400 MHz): δ 9.08 (s, 1H), 8.76 (s, 1H), 8.46˜8.41 (m, 2H), 8.38 (s, 14H), 8.05 (d, J=8.00 Hz, 1H), 7.96 (d, J=8.00 Hz, 1H), 7.74 (s, 1H), 7.66˜7.49 (m, 4H), 1.73 (s, 6H), and 12-bromo-10,10-dimethyl-10H-dibenzo[f,h]indeno[1,2-b]quinoline (3.7 g, 35.7%); 1H NMR (CDCl3. 400 MHz): δ 8.62˜8.52 (m, 3H), 8.31 (s, 1H), 8.02 (d, J=8.00 Hz, 1H), 7.66˜7.57 (m, 3H), 7.30 (t, J=8.00 Hz, 1H), 7.22 (s, 1H), 7.14˜7.00 (m, 2H), 1.79 (s, 6H).
A mixture of 3 g (7 mmol) 12-bromo-10,10-dimethyl-10H-cyclopenta[b]pyridino[1,2-b]triphenylene, 2 g (7.9 mmol) of bis(pinacolato)diboron, 0.085 g (0.07 mmol) of Tetrakis(triphenylphosphine) Palladium, 2 g (21 mmol) of potassium acetate, and 50 ml 1,4 dioxane was degassed and placed under nitrogen, and then heated at 90° C. for 8 h. After the reaction finish, the mixture was allowed to cool to room temperature. The organic phase separated and washed with ethyl acetate and water. After drying over magnesium sulfate, the solvent was removed in vacuo. The residue was purified by column chromatography on silica (hexane-dichloromethane) to give product (2.65 g, 80%) as a light-yellow solid.
A mixture of 2.36 g (10 mmol) of 1,3-dibromobenzene, 10.37 g (22 mmol) of 4,4,5,5-tetramethyl-1,3,2-dioxaborolane-10,10-dimethyl-10H-cyclopenta[b]pyridino[1,2-b]triphenylene, 0.12 g (0.1 mmol) of tetrakis(triphenylphosphine) palladium, 15 ml of 2M Na2CO3, 30 ml of EtOH and 100 ml toluene was degassed and placed under nitrogen, and then heated at 90° C. for 24 h. After finishing the reaction, the mixture was allowed to cool to room temperature. Than 100 ml MeOH was added, while stirring and the precipitated product was filtered off with suction. To give 5.2 g (yield 68%) of yellow product which was recrystallized from chloroform. MS (m/z, FAB+): 764.8 1H NMR (CDCl3, 400 MHz): δ 9.56 (s, 1H), 8.89 (s, 2H), 8.80 (s, 2H), 8.53 (s, 2H), 8.46˜8.41 (m, 4H), 8.06˜7.90 (m, 5H), 7.66˜7.49 (m, 8H), 7.26 (d, 2H), 7.07 (s, 2H), 1.77 (s, 12H).
A mixture of 4.2 g (10 mmol) of 12-bromo-10,10-dimethyl-10H-indeno[1,2-b]triphenylene, 5.2 g (11 mmol) of 2-(10,10-dimethyl-10H-indeno[1,2-b]triphenylen-12-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, 0.12 g (0.1 mmol) of Tetrakis(triphenylphosphine)Palladium, 15 ml of 2M Na2CO3, 30 ml of EtOH and 100 ml toluene was degassed and placed under nitrogen, and then heated at 90° C. for 24 h. After finishing the reaction, The mixture was allowed to cool to room temperature. Than 100 ml MeOH was added, while stirring and the precipitated product was filtered off with suction. To give 3.3 g (yield 49%) of yellow product which was recrystallized from chloroform. MS (m/z, EI): 686.7. 1H NMR (CDCl3, 400 MHz): δ 9.05 (s, 2H), 8.86 (d, J=7.88 Hz, 2H), 8.79 (d, J=7.76 Hz, 2H), 8.74 (s, 2H), 8.71 (d, J=7.84 Hz, 4H), 8.10 (d, J=7.64 Hz, 2H), 7.84 (s, 2H), 7.81 (d, J=7.80 Hz, 2H), 7.76˜7.67 (m, 8H), 1.77 (s, 12H).
ITO-coated glasses with 12Ω□−1 in Resistance and 120 nm in thickness are provided (hereinafter ITO substrate) and cleaned in a number of cleaning steps in an ultrasonic bath (e.g. detergent, deionized water). Before vapor deposition of the organic layers, cleaned ITO substrates are further treated by UV and ozone. All pre-treatment processes for ITO substrate are under clean room (class 100)
These organic layers are applied onto the ITO substrate in order by vapor deposition in a high-vacuum unit (10−6 Torr), such as: resistively heated quartz boats. The thickness of the respective layer and the vapor deposition rate (0.1˜0.3 nm/sec) are precisely monitored or set with the aid of a quartz-crystal monitor. It is also possible, as described above, for individual layers to consist of more than one compound, i.e. in general a host material doped with a guest material. This is achieved by co-vaporization from two or more sources.
Dipyrazino[2,3-f;2′,3′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (Hat-CN) is used as hole injection layer in this OLEDs. N,N-Bis(naphthalene-1-yl)-N,N′-bis(phenyl)-benzidine (NPB) is most widely used as the hole transporting layer and 2,9-bis(naphthalene-2-yl)-4,7-diphenyl-1,10-phenanthroline(NBphen) is used as electron transporting material in OLEDs for its high thermal stability and long life-time than BPhen/BCP. 9,10-di(naphtha-2-yl)anthrance (AND) and 1,1′-(9,9-dimethyl-9H-fluorene-2,7-diyl)dipyrene (DFDP) is used as emissive host and (E)-6-(4-(diphenylamino)styryl)-N,N-diphenylnaphthalen-2-amine (DPASN) is used as guest. The above OLED materials for producing standard OLEDs in this invention shown its chemical structure as following:
A typical OLED consists of low work function metals, such as Al, Mg, Ca, Li and K, as the cathode by thermal evaporation, and the low work function metals can help electrons injecting the electron transporting layer from cathode. In addition, for reducing the electron injection barrier and improving the OLED performance, a thin-film electron injecting layer is introduced between the cathode and the electron transporting layer. Conventional materials of electron injecting layer are metal halide or metal oxide with low work function, such as: LiF, MgO, or Li2O.
On the other hand, after the OLEDs fabrication, EL spectra and CIE coordination are measured by using a PR650 spectra scan spectrometer. Furthermore, the current/voltage, luminescence/voltage and yield/voltage characteristics are taken with a Keithley 2400 programmable voltage-current source. The above-mentioned apparatuses are operated at room temperature (about 25° C.) and under atmospheric pressure.
Using a procedure analogous to the abovementioned general method, fluorescent blue-emitting OLEDs having the following device structure were produced (See
In the above preferred embodiments, we show that the fluorene compound of the present invention used as fluorescent blue host than comparable example DFDP with deep-blue colour coordinates and longer half-lifetime for some examples. The PL for the fluorene compounds of the present invention show blue shift than the prior art (DFDP) from
To sum up, the present invention discloses a fluorene compound which can be used for organic EL device is disclosed. The mentioned fluorene compound are represented by the following formula(A).
Wherein R1 to R6 are identical or different. R1 to R6 are independently selected from the group consisting of a hydrogen atom, a halide, alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted aralkyl group having 6 to 30 carbon atoms, a substituted or unsubstituted heteroaryl group having 6 to 30 carbon atoms. R7˜R13 are identical or different R7 to R13 are independently selected from the group consisting of hydrogen atom, halide, alkyl group, aryl group, heteroaryl group. m and n are independently an integer of 0 to 3, X is selected from carbon or nitrogen atom.
Obvious many modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims the present invention can be practiced otherwise than as specifically described herein. Although specific embodiments have been illustrated and described herein, it is obvious to those skilled in the art that many modifications of the present invention may be made without departing from what is intended to be limited solely by the appended claims.
