Organic light emitting diode comprising an organic semiconductor layer
11145817 · 2021-10-12
Assignee
Inventors
- Regina Luschtinetz (Dresden, DE)
- Francois Cardinali (Dresden, DE)
- Julien Frey (Dresden, DE)
- Domagoj Pavicic (Dresden, DE)
Cpc classification
H10K71/00
ELECTRICITY
C07F9/5325
CHEMISTRY; METALLURGY
H10K85/615
ELECTRICITY
H10K85/621
ELECTRICITY
International classification
Abstract
The invention relates to an Organic light emitting diode comprising an anode electrode, a cathode electrode, at least one emission layer and an organic semiconductor layer, wherein the organic semiconductor layer is arranged between the anode electrode and the cathode electrode and the organic semiconductor layer comprises an alkali organic complex and a compound of formula 1 wherein X is selected from O, S or Se; and R.sup.1 and R.sup.2 are independently selected from the group consisting of C.sub.6 to C.sub.18 aryl group and C.sub.5 to C.sub.18 heteroaryl group, wherein each of R.sup.1 and R.sup.2 may independently be unsubstituted or substituted with at least one C.sub.1 to C.sub.12 alkyl group or C.sub.1 to C.sub.12 alkoxy group, preferably C.sub.1 to C.sub.4 alkyl group or C.sub.1 to C.sub.4 alkoxy group; and each R.sup.3, R.sup.4, R.sup.5, and R.sup.6 are independently selected from the group consisting of H, C.sub.1 to C.sub.12 alkyl group or C.sub.1 to C.sub.12 alkoxy group, preferably H, C.sub.1 to C.sub.4 alkyl group or C.sub.1 to C.sub.4 alkoxy group; a method for preparing the same and the compound of Formula 1 comprised therein.
Claims
1. Organic light emitting diode comprising an anode electrode, a cathode electrode, at least one emission layer and an organic semiconductor layer, wherein the organic semiconductor layer is arranged between the anode electrode and the cathode electrode and the organic semiconductor layer comprises an alkali organic complex and a compound of formula 1 ##STR00102## wherein X is selected from O, S or Se; and R.sup.1 and R.sup.2 are independently selected from the group consisting of C.sub.6 to C.sub.18 aryl group and C.sub.5 to C.sub.18 heteroaryl group, wherein each of R.sup.1 and R.sup.2 may independently be unsubstituted or substituted with at least one C.sub.1 to C.sub.12 alkyl group or C.sub.1 to C.sub.12 alkoxy group; and each R.sup.3, R.sup.4, R.sup.5, and R.sup.6 are independently selected from the group consisting of H, C.sub.1 to C.sub.12 alkyl group or C.sub.1 to C.sub.12 alkoxy group.
2. Organic light emitting diode according to claim 1, wherein the compound of formula 1 comprises (i) a biphenylene group comprising R.sup.5 and R.sup.6, (ii) a phosphorous containing group comprising X, R.sup.1, and R.sup.2, and (iii) an anthracenylene group comprising R.sup.4, wherein the biphenylene group is attached to the adjacent phosphorous containing group and/or the adjacent anthracenylene group in meta-position.
3. Organic light emitting diode according to claim 1, wherein the organic semiconductor layer is arranged between the emission layer and the cathode electrode.
4. Organic light emitting diode according to claim 1, wherein the organic light emitting diode further comprises an electron transport layer arranged between the emission layer and the organic semiconductor layer.
5. Organic light emitting diode according to claim 1, wherein the cathode electrode comprises at least one substantially metallic cathode layer comprising a first zero-valent metal selected from the group consisting of alkali metal, alkaline earth metal, rare earth metal, group 3 transition metal and mixtures thereof.
6. Organic light emitting diode according to claim 5, wherein the substantially metallic cathode layer further comprises a second zero-valent metal, wherein the second zero-valent metal is selected from a main group metal or a transition metal; and wherein the second zero-valent metal is different from the first zero-valent metal.
7. Organic light emitting diode, according to claim 6, wherein the second zero-valent metal is selected from the group consisting of Li, Na, K, Cs, Mg, Ca, Sr, Ba, Sc, Y, Yb, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ag, Au, Al, Ga, In, Sn, Te, Bi, Pb and mixtures thereof.
8. Organic light emitting diode according to claim 1, wherein the alkali organic complex is a lithium organic complex.
9. Method for preparing an organic light emitting diode according to claim 1, the method comprising a step of: co-depositing at least one alkali organic complex and at least one compound of formula 1 as defined in claim 1 ##STR00103## on the anode electrode, on the cathode electrode, or on one or more layers formed on the anode electrode or the cathode electrode.
10. Method according to claim 9, comprising the steps of: depositing the anode electrode on a substrate; depositing the at least one emission layer on the anode; depositing the organic semiconductor layer on the emission layer; and depositing the cathode electrode on the organic semiconductor layer.
11. Method according to claim 9, wherein depositing the organic semiconductor layer comprises vacuum thermal evaporation.
12. A compound of formula 1 ##STR00104## wherein X is selected from O, S or Se; R.sup.1 and R.sup.2 are independently selected from the group consisting of C.sub.6 to C.sub.18 aryl group and C.sub.5 to C.sub.18 heteroaryl group, wherein each of R.sup.1 and R.sup.2 may independently be unsubstituted or substituted with at least one C.sub.1 to C.sub.12 alkyl group or C.sub.1 to C.sub.12 alkoxy group; and each R.sup.3, R.sup.4, R.sup.5, and R.sup.6 are independently selected from the group consisting of H, C.sub.1 to C.sub.12 alkyl group or C.sub.1 to C.sub.12 alkoxy group.
13. The compound according to claim 12, wherein R.sup.1 and R.sup.2 are independently selected from C.sub.6 to C.sub.18 aryl group.
14. The compound according to claim 12, wherein X is selected as O.
15. The compound according to claim 12, wherein the compound of formula 1 comprises (i) a biphenylene group comprising R.sup.5 and R.sup.6, (ii) a phosphorous containing group comprising X, R.sup.1, and R.sup.2, and (iii) an anthracenylene group comprising R.sup.4, wherein the biphenylene group is attached to the adjacent phosphorous containing group and/or the adjacent anthracenylene group in meta-position.
16. Organic light emitting diode according to claim 1, wherein each of R.sup.1 and R.sup.2 may independently be unsubstituted or substituted with at least one C.sub.1 to C.sub.4 alkyl group or C.sub.1 to C.sub.4 alkoxy group.
17. Organic light emitting diode according to claim 1, wherein each R.sup.3, R.sup.4, R.sup.5, and R.sup.6 are independently selected from the group consisting of H, C.sub.1 to C.sub.4 alkyl group, and C.sub.1 to C.sub.4 alkoxy group.
18. Organic light emitting diode according to claim 4, wherein the electron transport layer comprises a first organic matrix compound with a dipole moment of about ≥0 and ≤2.5 Debye.
19. Organic light emitting diode according to claim 7, wherein the second zero-valent metal is selected from the group consisting of Ag, Au, Zn, Te, Yb, Ga, Bi, Ba, Ca, Al and mixtures thereof.
20. Organic light emitting diode according to claim 7, wherein the second zero-valent metal is selected from the group consisting of Ag, Zn, Te, Yb, Ga, Bi and mixtures thereof.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) These and/or other aspects and advantages of the present invention will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings, of which:
(2)
(3)
(4)
(5)
DETAILED DESCRIPTION
(6) Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The exemplary embodiments are described below, in order to explain the aspects of the present invention, by referring to the figures.
(7) Herein, when a first element is referred to as being formed or disposed “on” a second element, the first element can be disposed directly on the second element, or one or more other elements may be disposed there between. When a first element is referred to as being formed or disposed “directly on” a second element, no other elements are disposed there between.
(8)
(9)
(10) Referring to
(11)
(12) Referring to
(13)
(14) Referring to
(15) In the description above the method of manufacture an OLED 100 of the present invention is started with a substrate 110 onto which an anode electrode 120 is formed, on the anode electrode 120, a first hole injection layer 130, first hole transport layer 140, optional a first electron blocking layer 145, a first emission layer 150, optional a first hole blocking layer 155, optional an ETL 160, an n-type CGL 185, a p-type CGL 135, a second hole transport layer 141, optional a second electron blocking layer 146, a second emission layer 151, an optional second hole blocking layer 156, an optional at least one second electron transport layer 161, the organic semiconductor layer 170, a first cathode electrode layer 191 and an optional second cathode electrode layer 192 are formed, in that order or the other way around.
(16) While not shown in
EXAMPLES
(17) General Procedures
(18) Synthesis of Compounds of Formula 1
(19) Compounds for formula 1 may be synthesized via two different routes, see Scheme 1.
(20) ##STR00091##
(21) In Route A, Intermediate 1 is reacted with Intermediate 2 under Suzuki conditions to yield Intermediate 3. Intermediate 3 is reacted with Intermediate 4 under Suzuki conditions to yield compound of formula 1.
(22) In Route B, Intermediate 4 is reacted with Intermediate 2 under Suzuki conditions to yield Intermediate 5. Intermediate 5 is reacted with Intermediate 1 to yield compound of formula 1.
(3′-bromo-[1,1′-biphenyl]-4-yl)diphenylphosphine oxide
(23) A 1-L-Schlenk flask was flushed with nitrogen and charged with diphenyl(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)phosphine oxide (50.8 g, 126 mmol), 1-bromo-3-iodobenzene (71.1 g, 252 mmol), and Pd(PPh.sub.3).sub.4 (4.4 g, 3.78 mmol). De-aerated glyme (500 mL) and aq. 2 M K.sub.2CO.sub.3 (52 g, 378 mmol K.sub.2CO.sub.3 in 190 mL water) were added and the resulting mixture was stirred at 95° C. under a nitrogen atmosphere. After 18 h, the reaction mixture was allowed to cool down to room temperature and glyme was evaporated under reduced pressure. Dichloromethane was added and the mixture was washed with water. The organic phase was dried over MgSO.sub.4, filtered, and concentrated. The obtained oil poured onto a pad of silica gel and rinsed with dichloromethane. After elution of the impurities, the product was eluted with ethyl acetate. The ethyl acetate fraction was concentrated to a minimal amount and precipitation was induced by addition of MTBE. The formed precipitate was collected by suction filtration and washed with additional MTBE. After drying, 45.6 g (84%) of a beige solid were obtained. HPLC: 99.34%, GC/MS 98.8%, m/z=433 ([M].sup.+).
(3′-bromo-[1,1′-biphenyl]-3-yl)diphenylphosphine oxide
(24) Following the procedure described for (3′-bromo-[1,1′-biphenyl]-4-yl)diphenylphosphine oxide above using diphenyl(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)phosphine oxide (25.0 g, 62 mmol), 1-bromo-3-iodobenzene (26.2 g, 93 mmol), Pd(PPh.sub.3).sub.4 (2.2 g, 1.9 mmol), glyme (250 mL), and aq. 2 M K.sub.2CO.sub.3 (26 g, 186 mmol K.sub.2CO.sub.3 in 95 mL water), 24.4 g (90%) of a yellowish solid were obtained. HPLC/ESI-MS: 98.20%, m/z=434 ([M+H].sup.+).
(25) MX3
(26) A 1-L-Schlenk flask was flushed with nitrogen and charged with (3′-bromo-[1,1′-biphenyl]-4-yl)diphenylphosphine oxide (45.4 g, 105 mmol), (10-phenylanthracen-9-yl)boronic acid (34.4 g, 116 mmol), and Pd(PPh.sub.3).sub.4 (2.4 g, 2.1 mmol). De-aerated glyme (350 mL) and aq. 2 M K.sub.2CO.sub.3 (29 g, 210 mmol K.sub.2CO.sub.3 in 105 mL water) were added and the resulting mixture was stirred at 95° C. under a nitrogen atmosphere. After 18 h, the reaction mixture was allowed to cool down to room temperature. The precipitate was collected by suction filtration and washed with n-hexane. The obtained solid was dissolved in dichloromethane and filtered over a pad of Florisil®. The filtrate was concentrated to a minimal volume under reduced pressure and n-hexane was added. The obtained solid was collected by suction filtration and washed with n-hexane. After drying, 50.0 g (82.4 mmol, 78%) of a bright yellow solid were obtained. HPLC/ESI-MS: 99.93%, m/z=607 ([M+H].sup.+). Further purification was achieved by sublimation (HPLC: 100%).
(27) MX2
(28) Following the procedure described for MX3 using 9-(4-bromophenyl)-10-phenylanthracene (5.7 g, 13.8 mmol), diphenyl(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)phosphine oxide (6.2 g, 15.2 mmol), Pd(PPh.sub.3).sub.4 (0.32 g, 0.28 mmol), glyme (50 mL), and 2 M aq. K.sub.2CO.sub.3 (5.7 g, 41.3 mmol K.sub.2CO.sub.3 in 21 mL water), 4.83 g (8.0 mmol, 58%) of an off-white solid were obtained. HPLC/ESI-MS: 100.00%, m/z=629 ([M+Na].sup.+).
(29) MX4
(30) Following the procedure described for MX3 using (3′-bromo-[1,1′-biphenyl]-3-yl)diphenylphosphine oxide (24.0 g, 55.4 mmol) and (10-(naphthalen-2-yl)anthracen-9-yl)boronic acid (18.2 g, 61.0 mmol), Pd(PPh.sub.3).sub.4 (1.28 g, 1.11 mmol), glyme (200 mL), and aq. 2 M K.sub.2CO.sub.3 (15.3 g, 111 mmol K.sub.2CO.sub.3 in 56 mL water), 26.8 g (44.2 mmol, 80%) of a bright yellow solid were obtained. HPLC/ESI-MS: 98.82%, m/z=629 ([M+Na].sup.+). Further purification was achieved by sublimation (HPLC: 99.94%).
(31) MX1
(32) Following the procedure described for MX3 using 9-(4-bromophenyl)-10-phenylanthracene (8.0 g, 19.5 mmol), diphenyl(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)phosphine oxide (8.3 g, 20.5 mmol), Pd(PPh.sub.3).sub.4 (0.45 g, 0.39 mmol), glyme (70 mL), and 2 M aq. K.sub.2CO.sub.3 (8.1 g, 58.6 mmol K.sub.2CO.sub.3 in 30 mL water), 7.23 g (14.0 mmol, 61%) of a yellowish solid were obtained. HPLC/ESI-MS: 99.60%, m/z=607 ([M+H].sup.+). Further purification was achieved by sublimation (HPLC: 99.84%).
(33) Glass Transition Temperature
(34) The glass transition temperature is measured under nitrogen and using a heating rate of 10 K per min in a Mettler Toledo DSC 822e differential scanning calorimeter as described in DIN EN ISO 11357, published in March 2010.
(35) Rate Onset Temperature
(36) The rate onset temperature is determined by loading 100 mg compound into a VTE source. The VTE source is heated at a constant rate of 15 K/min at a pressure of less than 10.sup.−5 mbar and the temperature inside the source measured with a thermocouple. Evaporation of the compound is detected with a QCM detector which detects deposition of the compound on the quartz crystal of the detector. The deposition rate on the quartz crystal is measured in ng-strom per second. To determine the rate onset temperature, the deposition rate is plotted against the VTE source temperature. The rate onset is the temperature at which noticeable deposition on the QCM detector occurs. For accurate results, the VTE source is heated and cooled three time and only results from the second and third run are used to determine the rate onset temperature.
(37) To achieve good control over the evaporation rate of an organic compound, the rate onset temperature may be in the range of 200 to 255° C. If the rate onset temperature is below 200° C. the evaporation may be too rapid and therefore difficult to control. If the rate onset temperature is above 255° C. the evaporation rate may be too low which may result in low takt time and decomposition of the organic compound in VTE source may occur due to prolonged exposure to elevated temperatures.
(38) The rate onset temperature is an indirect measure of the volatility of a compound. The higher the rate onset temperature the lower is the volatility of a compound.
(39) Bottom Emission Devices with an Evaporated Emission Layer
(40) For bottom emission devices—Examples 1 to 4 and comparative examples 1 to 6, a 15 Ω/cm 2 glass substrate (available from Corning Co.) with 100 nm ITO was cut to a size of 50 mm×50 mm×0.7 mm, ultrasonically cleaned with isopropyl alcohol for 5 minutes and then with pure water for 5 minutes, and cleaned again with UV ozone for 30 minutes, to prepare a first electrode.
(41) Then, 92 wt.-% of N4,N4″-di(naphthalen-1-yl)-N4,N4″-diphenyl-[1,1′:4′,1″-terphenyl]-4,4″-diamine and 8 wt.-% of 2,2′,2″-(cyclopropane-1,2,3-triylidene)tris(2-(p-cyanotetrafluorophenyl)acetonitrile) was vacuum deposited on the ITO electrode, to form a HIL having a thickness of 10 nm. Then N4,N4″-di(naphthalen-1-yl)-N4,N4″-diphenyl[1,1′:4′,1″-terphenyl]-4,4″-diamine was vacuum deposited on the HIL, to form a HTL having a thickness of 130 nm. 97 wt.-% of ABH113 (Sun Fine Chemicals) as a host and 3 wt.-% of NUBD370 (Sun Fine Chemicals) as a dopant were deposited on the HTL, to form a blue-emitting EML with a thickness of 20 nm.
(42) Then, the organic semiconductor layer is formed by deposing a matrix compound and LiQ according to examples 1 to 4 and comparative example 1 and 7 by deposing of the matrix compound from a first deposition source and LiQ from a second deposition source directly on the EML. The organic semiconductor layer comprises 50 wt.-% matrix compound and 50 wt. % LiQ. In examples 1 to 4 the matrix compound is a compound of formula 1. The thickness of the organic semiconductor layer is 36 nm.
(43) Then, the cathode electrode layer is formed by evaporating aluminium at ultra-high vacuum of 10.sup.−7 bar and deposing the aluminium layer directly on the organic semiconductor layer. A thermal single co-evaporation of one or several metals is performed with a rate of 0, 1 to 10 nm/s (0.01 to 1 Å/s) in order to generate a homogeneous cathode electrode with a thickness of 5 to 1000 nm. The thickness of the cathode electrode layer is 100 nm.
(44) The OLED stack is protected from ambient conditions by encapsulation of the device with a glass slide. Thereby, a cavity is formed, which includes a getter material for further protection.
(45) Bottom Emission Devices with a Solution-Processed Emission Layer
(46) For bottom emission devices, a 15 Ω/cm 2 glass substrate (available from Corning Co.) with 100 nm ITO was cut to a size of 50 mm×50 mm×0.7 mm, ultrasonically cleaned with iso-propyl alcohol for 5 minutes and then with pure water for 5 minutes, and cleaned again with UV ozone for 30 minutes, to prepare a first electrode.
(47) Then, PEDOT:PSS (Clevios P VP AI 4083) is spin-coated directly on top of the first electrode to form a 55 nm thick HIL. The HIL is baked on hotplate at 150° C. for 5 min. Then, a light-emitting polymer, for example MEH-PPV, is spin-coated directly on top of the HIL to form a 40 nm thick EML. The EML is baked on a hotplate at 80° C. for 10 min. The device is transferred to an evaporation chamber and the following layers are deposited in high vacuum.
(48) Compound of formula 1 and an alkali organic complex are deposed directly on top of the EML to form the organic semiconductor layer with a thickness of 4 nm. A cathode electrode layer is formed by deposing a 100 nm thick layer of aluminium directly on top of the organic semiconductor layer.
(49) Top Emission Devices
(50) For top emission devices—Examples 5 to 8, the anode electrode was formed from 100 nm silver on glass which is prepared by the same methods as described above for bottom emission devices.
(51) Then, 92 wt.-% of biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine (CAS 1242056-42-3) and 8 wt.-% of 2,2′,2″-(cyclopropane-1,2,3-triylidene)tris(2-(p-cyanotetrafluorophenyl)acetonitrile) is vacuum deposited on the ITO electrode, to form a HIL having a thickness of 10 nm. Then biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine (CAS 1242056-42-3) is vacuum deposited on the HIL, to form a HTL having a thickness of 117 nm. Then N,N-bis(4-(dibenzo[b,d]furan-4-yl)phenyl)-[1,1′:4′,1″-terphenyl]-4-amine is deposed directly on top of the HTL to form an EBL with a thickness of 5 nm.
(52) 97 wt.-% of 2-(10-phenyl-9-anthracenyl)-benzo[b]naphtho[2,3-d]furan as a host and 3 wt.-% of blue emitter dopant described in WO2015-174682 are deposited on the EBL, to form a blue-emitting EML with a thickness of 20 nm.
(53) Then, the organic semiconductor layer is formed by deposing compound of formula 1 according to examples 5 and 6 from a first deposition source and Li-1 from a second deposition source directly on the EML. The organic semiconductor layer comprises 70 wt.-% compound of formula 1 and 30 wt.-% Li-1. Further, the thickness d (in nm) of the organic semiconductor layer can be taken from Table 5.
(54) In examples 7 and 8, an electron transport layer (ETL) is formed by deposing 5 nm of first matrix compound ETM-39 directly on the EML. ETM-39 is 2,4-diphenyl-6-(4′,5′,6′-triphenyl[1,1′:2′,1″:3″,1′″:3′″,1′″-quinquephenyi]-3′″-yl)-1,3,5-triazine. Then, the organic semiconductor layer is formed by deposing 70 wt.-% compound of formula 1 according to examples 5 and 6 from a first deposition source and 30 wt.-% Li-1 from a second deposition source directly on the ETL. Further, the thickness d (in nm) of the organic semiconductor layer can be taken from Table 5.
(55) Then, the first cathode electrode layer is evaporated at ultra-high vacuum of 10.sup.−7 bar. Therefore, a thermal single co-evaporation of one or several metals is performed with a rate of 0, 1 to 10 nm/s (0.01 to 1 Å/s) in order to generate a homogeneous cathode electrode with a thickness of 5 to 1000 nm. Then, the second cathode electrode layer is deposed directly on to top of the first cathode electrode layer under the same conditions. The first cathode layer is formed by deposing 2 nm Yb directly onto the organic semiconductor layer. Then, the second cathode layer is formed by deposing 11 nm Ag directly onto the first cathode layer. 60 n biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine (CAS 1242056-42-3) is deposed directly on top of the second cathode electrode layer.
(56) The OLED stack is protected from ambient conditions by encapsulation of the device with a glass slide. Thereby, a cavity is formed, which includes a getter material for further protection.
(57) To assess the performance of the inventive examples compared to the prior art, the current efficiency is measured under ambient conditions (20° C.). Current voltage measurements are performed using a Keithley 2400 sourcemeter, and recorded in V. At 10 mA/cm.sup.2 for bottom emission and 10 mA/cm.sup.2 for top emission devices, a calibrated spectrometer CAS140 from Instrument Systems is used for measurement of CIE coordinates and brightness in Candela. Lifetime LT of bottom emission device is measured at ambient conditions (20° C.) and 10 mA/cm.sup.2, using a Keithley 2400 sourcemeter, and recorded in hours. Lifetime LT of top emission device is measured at ambient conditions (20° C.) and 8 mA/cm.sup.2. The brightness of the device is measured using a calibrated photo diode. The lifetime LT is defined as the time till the brightness of the device is reduced to 97% of its initial value.
(58) In bottom emission devices, the emission is predominately Lambertian and quantified in percent external quantum efficiency (EQE). To determine the efficiency EQE in % the light output of the device is measured using a calibrated photodiode at 10 mA/cm2.
(59) In top emission devices, the emission is forward directed, non-Lambertian and also highly dependent on the micro-cavity. Therefore, the efficiency EQE will be higher compared to bottom emission devices. To determine the efficiency EQE in % the light output of the device is measured using a calibrated photodiode at 10 mA/cm2.
Technical Effect of the Invention
(60) In Table 4, the glass transition temperature, rate onset temperature and device performance in bottom emission devices are shown of examples 1 to 4 and comparative examples 1 to 7. The organic semiconductor layer comprises 50 wt.-% matrix compound and 50 wt.-% alkali organic complex LiQ. The organic semiconductor layer is contacting sandwiched between the emission layer and the cathode electrode layer. In example 1 to 4, the matrix compound is selected from a compound of formula 1.
(61) In comparative example 1, compound A is used as matrix compound. Compound A comprises a phenylene group attached to the adjacent phosphorus containing group and the adjacent anthracenylene group. The operating voltage is 4.9 V and the external quantum efficiency is 4.9% EQE.
(62) In comparative example 2, compound B is used as matrix compound. Compound B comprises a phenylene group attached to the adjacent phosphorus containing group and the adjacent anthracenylene group and a 2-napthyl substituent in 10-position on the anthracenylene group. The Tg is 134° C. but the rate onset temperature is too high for manufacturing of OLEDs. Operating voltage is similar to comparative example 1 but the efficiency is slightly improved to 5.4% EQE.
(63) In comparative example 3, compound C is used as matrix compound. Compound C comprises a phenylene group attached to the adjacent phosphorus containing group and the adjacent anthracenylene group and a 1-napthyl substituent in 10-position on the anthracenylene group. The Tg is even higher at 139° C. and the rate onset is in the range suitable for manufacturing of OLEDs. Operating voltage and external quantum efficiency are in a similar range to comparative example 2.
(64) In comparative example 4, compound D is used as matrix compound. Compound D comprises a phenylene group attached to the adjacent phosphorus containing group and the adjacent anthracenylene group and a biphenyl substituent in 10-position on the anthracenylene group. The Tg is slightly lower than in comparative examples 2 and 3 and the rate onset temperature is also reduced. Operating voltage and external quantum efficiency are in a similar range to comparative example 2 and 3.
(65) In example 1 to 4, the matrix compound is a compound of formula 1. The matrix compound comprises a biphenylenen group attached to the adjacent phosphorus containing group and the adjacent anthracenylene group and a phenyl substituent in 10-position on the anthracenylene group. The Tg and rate onset temperature are in a range suitable for manufacturing of OLEDs. The operating voltage is significantly decreased to 4.2 to 4.4 V compared to comparative examples 1 to 4. The external quantum efficiency is significantly increased to 6.7 to 7.4% EQE. Particularly high external quantum efficiency is observed for compounds of formula 1 which contain a biphenylene group attached to the adjacent phosphorus containing group and/or the adjacent anthracenylene group in meta-position. The highest efficiency is obtained for matrix compound MX2.
(66) In comparative example 5, compound E is used as matrix compound. Compound E comprises a biphenylene group attached to the adjacent phosphorus containing group and the adjacent anthracenylene group and a 2-naphthyl substituent in 10-position on the anthracenylene group. The rate onset temperature is extremely high at 293° C. Therefore, this compound is not suitable for manufacturing of OLEDs as thermal degradation in the VTE source may occur during the manufacturing process. Additionally, the external quantum efficiency is significantly lower compared to examples 1 to 4.
(67) In comparative example 6, compound F is used as matrix compound. Compound F comprises a biphenylene group attached to the adjacent phosphorus containing group and the adjacent anthracenylene group and a biphenyl substituent in 10-position on the anthracenylene group. The rate onset temperature is even higher at 310° C. No devices have been fabricated due to the extremely low volatility of the compound.
(68) In conclusion, compounds of formula 1 offer a unique benefit in terms of Tg, rate onset temperature and OLED performance. Organic light emitting devices comprising a semiconductor layer comprising an alkali organic complex and a compound of formula 1 may have lower operating voltage, higher efficiency and therefore lower power consumption.
(69) In Table 5, the performance is shown of top emission devices comprising an organic semiconductor layer comprising 70 wt.-% compound of formula 1 and 30 wt.-% Li-1. Li-1 is an alkali organic complex, see Table 1.
(70) In example 5 and 6, the organic semiconductor layer is contacting sandwiched between the emission layer and the cathode electrode. Very low operating voltages and high external quantum efficiencies are obtained.
(71) In examples 7 and 8, the organic semiconductor layer is contacting sandwiched between an electron transport layer and the cathode electrode. ETM-39 is a compound having a dipole moment ≥0 and ≤2.5 Debye. In comparison to examples 5 and 6, the operating voltage is comparable but the external quantum efficiency is significantly improved from 14% to 17% EQE.
(72) In summary, a surprising improvement in performance is achieved when using an organic semiconductor layer comprising a compound of formula 1 and an alkali organic complex. A substantial increase in external quantum efficiency can be achieved when an electron transport layer is arranged between the emission layer and the organic semiconductor layer.
(73) TABLE-US-00004 TABLE 4 Performance data of the compounds and bottom emission devices comprising an organic semiconductor layer comprising 50 wt.-% matrix com- pound and 50 wt.-% LiQ rate onset temper- U at EQE at Matrix Tg ature 10 mA/ 10 mA/ compound Structure of matrix compound [° C.] [° C.] cm.sup.2 [V] cm.sup.2 [%] Comparative example 1 Compound A
(74) TABLE-US-00005 TABLE 5 Performance data of top emission devices comprising an organic semiconductor layer comprising 70 wt.-% compound of formula 1 and 30 wt.-% Li-1, an optional electron transport layer (ETL) and a cathode electrode layer comprising a first and second cathode layer. The ETL comprises a first matrix compound. First matrix Thickness ETL Compound of Thickness organic semi- U at 10 mA/ EQE at 10 mA/ compound [nm] formula 1 conductor layer [nm] cm.sup.2 [V] cm.sup.2 [%] Example 5 — 0 MX3 37 3.6 14 Example 6 — 0 MX2 36 3.5 14 Example 7 ETM-39 5 MX3 30 3.6 17 Example 8 ETM-39 5 MX2 30 3.5 17
(75) From the foregoing detailed description, claims and examples, it will be evident that modifications and variations can be made to the compositions and methods of the invention without departing from the spirit and scope of the invention. Therefore, it is intended that all modifications made to the invention without departing from the spirit and scope of the invention come within the scope of the appended claims.