Organic electronic device having lithoxy group and phosphine oxide group material

Abstract

The present invention relates to an organic electronic device, comprising a first electrode (11), a second electrode (14), and, between the first and the second electrode, a substantially organic layer (13) comprising a heterocyclic compound bearing at least one lithoxy group and containing at least one heterocyclic ring comprising a phosphine oxide group directly bound to three carbon atoms; a compound for use in such an organic electronic device and to a semiconducting material comprising the respective compound.

Claims

1. Organic electronic device, comprising a first electrode, a second electrode, and, between the first and the second electrode, a substantially organic layer comprising a heterocyclic compound bearing at least one lithoxy group and containing at least one heterocyclic ring comprising a phosphine oxide group directly bound to three carbon atoms.

2. Organic electronic device according to claim 1, wherein the lithoxy group is directly attached to an aromatic or heteroaromatic structural moiety.

3. Organic electronic device according to claim 1, wherein the heterocyclic ring comprising the phosphine oxide group is a five-, six- or seven-membered ring.

4. Organic electronic device according to claim 1, wherein the heterocyclic compound bearing at least one lithoxy group and containing at least one heterocyclic ring comprising a phosphine oxide group directly bound to three carbon atoms has formula (I): ##STR00011## wherein A.sup.1 is a C.sub.6-C.sub.30 arylene or C.sub.2-C.sub.30 heteroarylene, each of A.sup.2 and A.sup.3 is independently selected from a C.sub.6-C.sub.30 aryl and C.sub.2-C.sub.30 heteroaryl, and A.sup.2 with A.sup.3 are linked to each other.

5. Organic electronic device according to claim 1, wherein the substantially organic layer comprises an electron transport matrix compound.

6. Organic electronic device according to claim 5, wherein the electron transport matrix compound comprises an imidazole or a PO functional group.

7. Organic electronic device according to claim 5, wherein the heterocyclic compound and the electron transport matrix compound are present in the substantially organic layer in the form of a homogeneous mixture.

8. Organic electronic device according to claim 1, wherein the device is an organic light emitting diode, an organic solar cell, or an organic field effect transistor.

9. Organic electronic device according to claim 8, wherein the device is the organic light emitting diode with the first electrode being an anode, the second electrode being a cathode, and the device further comprising a light emitting layer between the anode and the cathode and wherein the substantially organic layer is arranged between the cathode and the light emitting layer.

10. Heterocyclic compound bearing at least one lithoxy group and containing at least one heterocyclic ring comprising a phosphine oxide group directly bound to three carbon atoms has formula (I) ##STR00012## wherein A.sup.1 is a C.sub.6-C.sub.30 arylene or C.sub.2-C.sub.30 heteroarylene, each of A.sup.2 and A.sup.3 is independently selected from a C.sub.6-C.sub.30 aryl and C.sub.2-C.sub.30 heteroaryl, and A.sup.2 with A.sup.3 are linked to each other.

11. Compound according to claim 10, wherein A.sup.1 is C.sub.6-C.sub.12 arylene or C.sub.2-C.sub.12 heteroarylene.

12. Compound according to claim 10, wherein each of A.sup.2 and A.sup.3 is independently selected from a C.sub.6-C.sub.10 arylene or C.sub.2-C.sub.12 heteroarylene.

13. Compound according to claim 10, wherein A.sup.1 is selected from phenylene and pyridyl-diyl.

14. Compound according to claim 10, wherein A.sup.1, A.sup.2 and A.sup.3 are o-phenylene.

15. Compound having formula (Ia) ##STR00013## wherein A.sup.1 is a C.sub.6-C.sub.30 arylene or C.sub.2-C.sub.30 heteroarylene, each of A.sup.2 and A.sup.3 is independently selected from a C.sub.6-C.sub.30 aryl and C.sub.2-C.sub.30 heteroaryl, and A.sup.2 with A.sup.3 are linked to each other, as a penultimate precursor for compound of claim 10 having formula (I).

16. Electrically doped semiconducting material comprising at least one electron transport matrix compound and at least one heterocyclic compound bearing at least one lithoxy group and containing at least one heterocyclic ring comprising a phosphine oxide group directly bound to three carbon atoms.

Description

SHORT SUMMARY OF THE FIGURES

(1) FIG. 1 illustrates a first embodiment of an inventive organic electronic device;

(2) FIG. 2 illustrates a second embodiment of an inventive organic electronic device;

(3) FIG. 3 shows a third embodiment of an inventive organic electronic device.

ORGANIC ELECTRONIC DEVICES

(4) FIG. 1 illustrates a first embodiment of an inventive organic electronic device in the form of a stack of layers forming an OLED or a solar cell. In FIG. 1, 10 is a substrate, 11 is an anode, 12 is an EML or an absorbing layer, 13 is a EIL (electron injection layer), 14 is a cathode.

(5) The layer 13 can be a pure layer of the heterocyclic compound bearing at least one lithoxy group and containing at least one heterocyclic ring comprising a phosphine oxide group directly bound to three carbon atoms, preferably a compound according to formula (I). At least one of the anode and cathode is at least semi-transparent. Inverted structures are also foreseen (not illustrated), wherein the cathode is on the substrate (cathode closer to the substrate than the anode and the order of the layers 11-14 is reversed). The stack may comprise additional layers, such as ETL, HTL, etc.

(6) FIG. 2 represents a second embodiment of the inventive organic electronic device in the form of a stack of layers forming an OLED or a solar cell. Here, 20 is a substrate, 21 is an anode, 22 is an EML or an absorbing layer, 23 is an ETL, 24 is a cathode. The layer 23 comprises an electron transport matrix material and a compound according to formula (I).

(7) FIG. 3 illustrates a third embodiment of the inventive device in the form of an OTFT, with semi-conductor layer 32, a source electrode 34 and a drain electrode 35. An unpatterned (unpatterned between the source and drain electrodes) injection layer 33 provides charge carrier injection and extraction between the source-drain electrodes and semi-conducting layer. OTFT also comprises a gate insulator 31 (which could be on the same side as the source drain electrodes) and a gate electrode 30, which gate electrode 30 is on the side of the layer 31 which is not in contact with the layer 32. Obviously, the whole stack could be inverted. A substrate may also be provided. Alternatively, insulator layer 31 may be the substrate.

EXAMPLES

(8) Following compounds were used as electron transporting matrices for testing the effects of inventive compounds:

(9) ##STR00004##

(10) A1 is described in the application EP13187905, A2 was prepared by procedure generally described in the application WO2011/154131, A3 also encompasses the procedures used in EP13187905. Their syntheses are further described in detail.

(11) All reactions were performed under inert atmosphere. Commercial reactants and reagents were used without further purification. Reaction solvents tetrahydrofuran (THF), acetonitrile (AcN) and dichioromethane (DCM) were dried by a solvent purification system (SPS). CV stands throughout this application for cyclic voltammetry, not for curriculum vitae.

(12) Electron Transport Matrix Preparation

(13) General Procedure A: Triphenylphosphinoxide Synthesis

(14) The halogen compound was dissolved in THF. 2.5M n-BuLi solution in hexane was slowly dropped to this solution chilled to 80 C. (temperature measured directly in the solution). The stirring was continued for one hour. Diphenyl phosphine chloride or phenylphosphine dichloride, respectively, was added slowly at 80 C. The reaction mixture was allowed to warm to RT and stirred overnight. After methanol addition and reduction to dryness, the residue was dissolved in DCM. The organic phase was washed with water, dried over Na.sub.2SO.sub.4 and reduced to dryness.

(15) The residue was dissolved in DCM again and oxidized with 30 wt. % aqueous hydrogen peroxide solution. After stirring overnight, the organic solution was washed with water, dried over Na.sub.2SO.sub.4 and reduced to dryness. The crude product was purified by column chromatography.

(16) General Procedure B: Suzuki Coupling

(17) The halogen compound, the boronic acid, Pd(P.sup.tBu.sub.3).sub.4 and the solvent were mixed together. A degassed 2M aqueous K.sub.2CO.sub.3 solution was added. The mixture was stirred at 85 C. (oil bath temperature) for 18 h and cooled afterwards. In case that a solid precipitated, the solid was filtered off and purified by column chromatography directly. Otherwise, the organic phase was washed with water, dried over Na.sub.2SO.sub.4, reduced to dryness and purified by column chromatography afterwards.

(18) Precursor Compounds

(19) (3-bromophenyl)diphenylphosphine oxide

(20) ##STR00005##

(21) According to general procedure A

(22) 1,3-dibromobenzene: 10.00 g (42.4 mmol, 1.0 eq)

(23) n-butyl lithium, 2.5M in hexane: 17 mL (42.4 mmol, 1.0 eq)

(24) chlorodiphenylphosphine: 9.35 g (42.4 mmol, 1.0 eq)

(25) THF: 50 mL

(26) DCM: 50 mL

(27) H.sub.2O.sub.2, 30 wt. % in water: 10 mL

(28) Column chromatography: SiO.sub.2, ethyl acetate, R.sub.f=0.52

(29) Yield: 9.6 g white solid (63%)

(30) mp: 95 C.

(31) GC-MS: m/z=356, 358

(32) (4-bromophenyl)diphenylphosphine oxide

(33) ##STR00006##

(34) According to general procedure A)

(35) 1,4-dibromobenzene: 10.00 g (42.4 mmol, 1.0 eq)

(36) n-butyllithium, 2.5M in hexane: 17 mL (42.4 mmol, 1.0 eq)

(37) chlorodiphenylphosphine: 9.35 g (42.4 mmol, 1.0 eq)

(38) THF: 50 mL

(39) DCM: 50 mL

(40) H.sub.2O.sub.2, 30 wt. % in water: 10 mL

(41) Column chromatography: SiO.sub.2, ethyl acetate

(42) Yield: 6.84 g white solid (45% theoretical)

(43) mp: 166 C.

(44) GC-MS: m/z=356, 358

(45) bis(4-bromophenyl)(phenyl)phosphine oxide

(46) ##STR00007##

(47) According to general procedure A

(48) 1,4-dibromobenzene: 10.00 g (42.4 mmol, 1.0 eq)

(49) n-butyl lithium, 2.5M in hexane: 17 mL (42.4 mmol, 1.0 eq)

(50) phenyl dichlorophosphine: 3.79 g (21.2 mmol, 0.5 eq), dissolved in 50 mL THF

(51) THF: 100 mL

(52) DCM: 50 mL

(53) H.sub.2O.sub.2, 30 wt. % in water: 10 mL

(54) Column chromatography: SiO.sub.2, ethyl acetate

(55) Yield: 5.0 g viscous oil (54%)

(56) mp: 125 C.

(57) GC-MS: m/z=433, 435, 437

(58) ETL matrices

(59) (3-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)diphenylphosphine oxide (A1)

(60) According to general procedure B

(61) (3-bromophenyl)diphenylphosphine oxide: 1.9 g (5.3 mmol, 1.0 eq)

(62) (9,10-di(naphthalen-2-yl)anthracen-2-yl)boronic acid: 3.0 g (6.3 mmol, 1.2 eq)

(63) Pd(PPh.sub.3).sub.4: 183 mg (0.16 mmol, 3 mol. %)

(64) K.sub.2CO.sub.3, 2M: 8 mL

(65) DME: 20 mL

(66) Column chromatography: SiO.sub.2, ethyl acetate

(67) Yield: 3.1 g (83%) yellow solid

(68) mp: n.a. (glassy)

(69) EI-MS: m/z=706

(70) reduction potential (CV, reversible in THF)-2.38 V.

(71) (3-(dibenzo[c,h]acridin-7-yl)-[1,1-biphenyl]-4-yl)diphenylphosphine oxide (A2)

(72) The compound has been prepared from diphenyl(3-(5,6,8,9-tetrahydrodibenzo[c,h]acridin-7-yl)-[1,1-biphenyl]-4-yl)phosphine oxide by oxidation with 4,5-dichloro-3,6-dioxocyclohexa-1,4-diene-1,2-dicarbonitrile (DDQ), by a general dehydrogenation procedure described in WO2013/079217. The penultimate intermediate has been prepared by Kumada coupling from (4-bromophenyl)diphenylphosphine oxide described above and 7-(3-bromophenyl)-5,6,8,9-tetrahydrodibenzo[c,h]acridine described as intermediate f (CAS 1352166-94-9) in WO2013/079217.

(73) Melting point 289.7 C. (DSC peak), reduction potential (CV, reversible in THF)-2.25 V.

(74) phenylbis(4-(anthracen-9-yl)phenyl)phosphine oxide (A3)

(75) According to general procedure B

(76) bis(4-bromophenyl)(phenyl)phosphine oxide: 5.0 g (1.0 eq, 11.5 mmol)

(77) anthracen-9-ylboronic acid: 9.33 g (3.66 eq, 41.4 mmol)

(78) tetrakis(triphenylphosphine)palladium (0): 0.529 g (4 mol %, 0.46 mmol)

(79) potassium carbonate 6.33 g (4.0 eq, 45.8 mmol)

(80) 1,2-dimethoxyethane 60 mL

(81) Column chromatography: SiO.sub.2, ethyl acetate/hexane (volume ratio 1:1), ethyl acetate

(82) Yield: 3.7 g (51%) pale yellow solid

(83) Melting point 294.7 C. (DSC peak), reduction potential (CV, reversible in THF)-2.42 V.

(84) Synthetic Procedure for Preparing the Compounds of Formula (I)

Synthesis Example 1: lithium 2-(5-oxidobenzo[b]phosphindol-5-yl)phenolate (D1)

(85) Step 1: 2,2-dibrom-1,1-biphenyl

(86) ##STR00008##

(87) TABLE-US-00001 1,2-dibrombenzene 20 g, 1.0 eq, 84.8 mmol n-butyllithium 17.0 mL, 0.5 eq, 42.4 mmol THF 150 mL

(88) Starting compounds were dissolved in dry THF and the 2.5 M butyllithium solution in hexanes had been added very slowly at 78 C. The reaction mixture was kept at this temperature for 1 h, then the temperature was allowed to reach the room temperature (RT). After further 3 h stirring, 80 mL water were added and the formed immiscible layers allowed to separate. The organic phase was then washed 3 times with 80 mL water to remove residual lithium salt by-products, dried over anhydrous magnesium sulphate and evaporated under reduced pressure, to afford a brown oil that under dissolution in hot ethanol and cooling crystallized as a white solid.

(89) Yield: 9.7 g (73%), white powder

(90) .sup.1H-NMR (CDCl.sub.3, 300 MHz): (ppm) 7.97 (dd, J=8 Hz and 1 Hz, 2H), 7.44 (ddd, J=7.6 Hz, 7.6 Hz and 1 Hz, 2H), 7.22 (dd, J=7.6 Hz and 1.5 Hz, 2H), 7.11 (ddd, J=8 Hz, 7.6 Hz and 1.5 Hz, 2H).

(91) Step 2: 5-phenyl-5H-benzo[b]phosphindole-5-oxide

(92) ##STR00009##

(93) TABLE-US-00002 2,2-dibrom-1,1-biphenyl 9.7 g, 1.0 eq., 31.0 mmol phenylphosphine dichloride 5.5 mL, 1.3 eq., 40.0 mmol THF 100 mL n-butyl lithium (n-BuLi) 25.0 mL, 2.0 eq., 62.5 mmol Hydrogen peroxide 20 mL, excess

(94) 2,2-dibrom-1,1-biphenyl was dissolved in dry THF and cooled to 78 C. 2.5M n-BuLi solution in hexanes was added dropwise under stirring to the reaction mixture at this temperature and the mixture was further stirred for 2 h. Then, phenyl dichlorophosphine was added at 78 C. dropwise, the temperature was allowed to rise slowly to room temperature and the reaction mixture left stirring at RT overnight. Hydrogen peroxide (aqueous solution, 27 wt. %) was added slowly at RT and the mixture was stirred at RT for 1 h. The mixture was diluted with water and extracted with ethyl acetate. The organic phase was dried over magnesium sulphate and the solvent removed under reduced pressure. The obtained colorless oil was dissolved in ethyl acetate and purified by column chromatography on silica with ethyl acetate/n-heptane mixture (1:1 volume ratio) as eluent (R.sub.f=0.2).

(95) Yield: 6.0 g (75%), white powder

(96) .sup.1H-NMR (CD.sub.2Cl.sub.2, 300 MHz): (ppm)=7.88 (m, 2H), 7.72-7.57 (m, 6H), 7.51 (m, 1H), 7.44-7.36 (m, 4H). .sup.31P-NMR (CD.sub.2Cl.sub.2, 121 MHz): (ppm)=32.0 (s)

(97) Step 3: 5-(2-hydroxyphenyl)-5H-benzo[b]phosphindole-5-oxide

(98) ##STR00010##

(99) TABLE-US-00003 5-phenyl-5H-benzo[b]phosphindole-5-oxide 21.07 g, 1.0 eq., 103.4 mmol lithium diisopropylamide (LDA) 14 mL, 2.0 eq., 20.8 mmol 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2- 6.3 mL, 3.0 eq., 31.2 mmol dioxaborolane THF 60 mL chloroform 60 mL hydrogen peroxide 20 mL

(100) 5-phenyl-5H-benzo[b]phosphindole-5-oxide was dissolved in dry THF and cooled to 78 C. 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane was added at the same temperature and after 20 minute stirring, the 1.5M LDA solution in cyclohexane was added dropwise under stirring, the reaction mixture was allowed to warm to RT and further stirred for 24 h. The solvent was removed under reduced pressure and the residue dissolved in chloroform. Hydrogen peroxide (aqueous solution, 27 wt. %) was added slowly at 0 C. and the mixture was stirred at RT overnight. After chloroform extraction and washing the organic phase with brine, drying over magnesium sulphate and evaporation under reduced pressure, the residue was dissolved in DCM and precipitated with pentane. The purified solid was filtered off, washed with pentane and dried in vacuum.

(101) Yield: 1.9 g (63%), white powder

(102) .sup.1H-NMR (CDCl.sub.3, 300 MHz): (ppm)=11.17 (s, 1H, OH), 7.87-7.76 (m, 4H), 7.47-7.32 (m, 3H), 7.01 (ddd, J=5.09 Hz, 8.48 Hz and 0.75 Hz, 1H, OH.sub.ortho), 6.64 (m, 1H), 6.52 (ddd, J=7.72 Hz, 1.70 Hz and 15.45 Hz, 1H).

(103) .sup.31P-NMR (CDCl.sub.3, 121 MHz): (ppm)=46.4 (s)

(104) Step 4: lithium 2-(5-oxidobenzo[b]phosphindol-5-yl)phenolate (D1)

(105) TABLE-US-00004 5-(2-hydroxypheny1)-5H- 3.1 g, 1.0 eq., 10.5 mmol benzo[b]phosphindole-5-oxide lithium tert-butoxide 0.84 g, 1.0 eq., 10.5 mmol acetonitrile 120 mL

(106) The starting material was suspended in dry acetonitrile. Lithium tert-butoxide was added at room temperature and the mixture was heated at reflux for 13 hours. The solid was filtered off, washed with acetonitrile and dried in vacuum. Further purification was made by Soxhlet extraction with dry ethanol/acetonitrile mixture (1:1 volume ratio).

(107) Yield: 2.5 g (80%)

Device Examples

(108) Lithium 2-(diphenylphosphoryl)phenolate (C2), described in an earlier application PCT/EP/2012/074127, and the well-known lithium 8-hydroxyquinolinolate (LiQ, C3) were used as comparative electrical n-dopants; lithium 2-(5-oxidobenzo[b]phosphindol-5-yl)phenolate was used as inventive n-dopant.

Device Example 1

(109) A blue emitting device was made on a commercially available glass substrate with deposited indium tin oxide (ITO) 90 nm thick layer as an anode. A 10 nm layer of HTM3 doped with 2,2,2-(cyclopropane-1,2,3-triylidene)tris(2-(p-cyanotetrafluorophenyl)acetonitrile) (PD2) (matrix to dopant weight ratio of 92:8) was subsequently deposited as hole injection and transport layer, followed by a 120 nm undoped layer of HTM3. Subsequently, a blue fluorescent emitting layer of ABH113 (Sun Fine Chemicals) doped with NUBD370 (Sun Fine Chemicals) as an emitter (matrix dopant ratio of 97:3 wt. %) was deposited with a thickness of 20 nm. A 36 nm thick ETL having a composition given in the Table 1 was deposited on the emitting layer. A 1 nm thick layer of lithium quinolate (LiQ) followed the ETL, followed by 100 nm thick aluminium layer as a cathode.

(110) The results are shown in the Table 1.

(111) TABLE-US-00005 TABLE 1 Voltage at 10 mA/cm.sup.2 Quantum efficiency at LT.sub.97 ETL [V] 10 mA/cm.sup.2 [%] [h] A1:D1 (50:50 wt. %) 4.4 5.9 44 A1:C2 (50:50 wt. %) 4.0 6.5 42 A1:C3 (50:50 wt. %) 4.2 5.6 39 A2:D1 (50:50 wt. %) 4.7 6.3 66 A2:C2 (50:50 wt. %) 4.4 7.0 49 A2:C3 (50:50 wt. %) 4.6 5.5 250 A3:D1 (50:50 wt. %) 5.0 4.6 300 A3:C2 (50:50 wt. %) 4.5 5.5 140 A3:C3 (50:50 wt. %) 5.0 4.0 19

(112) LT97 stands for the timespan within the luminance of the device operated at given current density had not changed more than 3% of its initial value. Voltage rise is another important operational characteristic of OLEDs. In stable devices operated at constant current, the voltage remains constant. Should the voltage in a testing device raise more than 5% of its initial value during the desired lifetime, it is a sign that the tested material makes the device instable.

(113) Advantages of the Invention

(114) Experimental results listed in Table 1 show that performance of inventive OLEDs is fully comparable with OLEDs using state-of-the-art ETM additives C2 and C3. Inventive heterocyclic compounds bearing at least one lithoxy group and containing at least one heterocyclic ring comprising a phosphine oxide group directly bound to three carbon atoms thus significantly broaden the offer of additives for improving electron transport and/or electron injection in organic electronic devices and allow further improving and optimizing performance of organic electronic devices beyond limits known in the art.

(115) Moreover, it was surprisingly found that the presence of the phosphine oxide group in a ring structure increases thermal stability of the additive in comparison with similar structures lacking the ring.

(116) Thus, C2 has an onset of the decomposition peak estimated from TGA-DSC measurement at the temperature 432 C. and decomposition peak at 442 C., whereas its cyclic analog D1 showed decomposition onset at 484 C. and decomposition peak 495 C.

(117) It was further found that in couples of compounds with comparable molecular weight and structure, like C2 and D1, the compound wherein the phosphine oxide group is a part of a ring has lower evaporation temperature in high vacuum than the compound with acyclic phosphine oxide group. As a result, electron transport additives according this invention offer, in comparison with conventional phosphine oxide additives, significantly broader processing window in vacuum thermal evaporation, representing significant advantage in contemporary manufacturing processes used for mass production of organic electronic devices.

(118) The features disclosed in the foregoing description, the claims and in the drawings may both separately and in any combination thereof, be material for realising the invention in diverse forms thereof.

ABBREVIATIONS USED THROUGHOUT THE APPLICATION

(119) Alq3 aluminium tris(8-hydroxyquinolinolate)

(120) BPhen bathophenanthroline

(121) CV cyclic voltammetry

(122) DCM dichloromethane

(123) EML (light) emitting layer

(124) eq. equivalent

(125) ETL electron transport layer

(126) ETM electron transport material

(127) GCMS gas chromatography (combined with) mass spectroscopy

(128) .sup.1H-NMR proton magnetic resonance

(129) HBL hole blocking layer

(130) HIL hole injecting layer

(131) HOMO highest occupied molecular orbital

(132) HTL hole transport layer

(133) LiQ lithium 8-hydroxyquinolinolate

(134) LUMO lowest unoccupied molecular orbital

(135) mol, molar (e.g. percent)

(136) OLED organic light emitting device

(137) OTFT organic thin film transistor

(138) HPLC-MS high performance liquid chromatography-mass spectroscopy

(139) THF tetrahydrofuran

(140) TGA-DSC thermogravimetric analysisdifferential scanning calorimetry

(141) TCO transparent conductive oxide

(142) VTE vacuum thermal evaporation

(143) wt. % weight percent