Electronic devices including semiconducting layers comprising at least one borate complex and methods for preparing the same

Abstract

Electronic devices and methods for preparing electronic devices. Electronic devices may include a semiconducting layer, which may include at least one borate complex. Borate complex may include a metal, such as Ca or Sr, and at least one borate ligand. Borate ligands may include a heterocyclic group. Methods may include evaporating a borate complex.

Claims

1. Electronic device comprising a semiconducting layer, wherein the semiconducting layer comprises at least one borate complex comprising (i) Sr and (ii) at least one borate ligand, wherein the borate ligand comprises at least one heterocyclic group.

2. Electronic device according to claim 1, wherein the heterocyclic group is a heteroaryl group.

3. Electronic device according to claim 2, wherein the heterocyclic group is a C.sub.2-C.sub.30 heteroaryl group.

4. Electronic device according to claim 1, wherein the heterocyclic group comprises one or more heteroatoms independently selected from N, O and S.

5. Electronic device according to claim 1, wherein the heterocyclic group comprises a five-membered heterocyclic ring.

6. Electronic device according to claim 1, wherein the heterocyclic group comprises an azole or a diazole ring.

7. Electronic device according to claim 1, wherein the heterocyclic group is a 1,2-diazole group.

8. Electronic device according to claim 1, wherein the borate ligand comprises at least two heterocyclic groups.

9. Electronic device according to claim 8, wherein at least two heterocyclic groups in the borate ligand have, each individually, their heteroatoms in the beta-position with respect to the central boron atom of the borate ligand.

10. Electronic device according to claim 1, wherein the borate complex has the following formula (I) ##STR00022## wherein M is Sr; and R.sup.1 to R.sup.4 are independently selected from the group consisting of H, substituted or unsubstituted C.sub.6 to C.sub.30 aryl and substituted or unsubstituted C.sub.2 to C.sub.30 heteroaryl.

11. Electronic device according to claim 1, wherein the semiconducting layer is a charge transport layer and/or a charge injection layer and/or a charge generation layer.

12. Electronic device according to claim 11, wherein the charge transport layer is an electron transport layer and/or the charge injections layer is an electron injection layer and/or the charge generation layer is an electron generation layer.

13. Electronic device according to claim 1, wherein the semiconducting layer further comprises at least one organic matrix compound.

14. Electronic device according to claim 1, wherein the electronic device is an electroluminescent device.

15. Electronic device according to claim 14, wherein the electronic device is an organic light emitting diode.

16. Method for preparing an electronic device according to claim 1, wherein the process comprises the steps of (i) evaporating a borate complex comprising Sr and at least one borate ligand, wherein the borate ligand comprises at least one heterocyclic group, at an elevated temperature and optionally at a reduced pressure, and (ii) depositing the vapor of the borate complex on a solid support.

17. Method according to claim 16, wherein the borate complex has the general formula (I) ##STR00023## wherein M is Sr; and R.sup.1 to R.sup.4 are independently selected from the group consisting of H, substituted or unsubstituted C.sub.6 to C.sub.30 aryl and substituted or unsubstituted C.sub.2 to C.sub.30 heteroaryl.

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) FIG. 1 is a schematic sectional view of an organic light-emitting diode (OLED), according to an exemplary embodiment of the present invention;

(3) FIG. 2 is a schematic sectional view of an OLED, according to an exemplary embodiment of the present invention.

(4) FIG. 3 is a schematic sectional view of a tandem OLED comprising a charge generation layer, according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

(5) 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.

(6) Herein, when a first element is referred to as being formed or disposed “on” or “onto” 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” or “directly onto” a second element, no other elements are disposed there between.

(7) FIG. 1 is a schematic sectional view of an organic light-emitting diode (OLED) 100, according to an exemplary embodiment of the present invention. The OLED 100 includes a substrate 110, an anode 120, a hole injection layer (HIL) 130, a hole transport layer (HTL) 140, an emission layer (EML) 150, an electron transport layer (ETL) 160. The electron transport layer (ETL) 160 is formed on the EML 150. Onto the electron transport layer (ETL) 160, an electron injection layer (EIL) 180 is disposed. The cathode 190 is disposed directly onto the electron injection layer (EIL) 180.

(8) Instead of a single electron transport layer 160, optionally an electron transport layer stack (ETL) can be used.

(9) FIG. 2 is a schematic sectional view of an OLED 100, according to another exemplary embodiment of the present invention. FIG. 2 differs from FIG. 1 in that the OLED 100 of FIG. 2 comprises an electron blocking layer (EBL) 145 and a hole blocking layer (HBL) 155.

(10) Referring to FIG. 2, the OLED 100 includes a substrate 110, an anode 120, a hole injection layer (HIL) 130, a hole transport layer (HTL) 140, an electron blocking layer (EBL) 145, an emission layer (EML) 150, a hole blocking layer (HBL) 155, an electron transport layer (ETL) 160, an electron injection layer (EIL) 180 and a cathode electrode 190.

(11) FIG. 3 is a schematic sectional view of a tandem OLED 200, according to another exemplary embodiment of the present invention. FIG. 3 differs from FIG. 2 in that the OLED 100 of FIG. 3 further comprises a charge generation layer (CGL) and a second emission layer (151).

(12) Referring to FIG. 3, the OLED 200 includes a substrate 110, an anode 120, a first hole injection layer (HIL) 130, a first hole transport layer (HTL) 140, a first electron blocking layer (EBL) 145, a first emission layer (EML) 150, a first hole blocking layer (HBL) 155, a first electron transport layer (ETL) 160, an n-type charge generation layer (n-type CGL) 185, a hole generating layer (p-type charge generation layer; p-type GCL) 135, a second hole transport layer (HTL) 141, a second electron blocking layer (EBL) 146, a second emission layer (EML) 151, a second hole blocking layer (EBL) 156, a second electron transport layer (ETL) 161, a second electron injection layer (EIL) 181 and a cathode 190.

(13) While not shown in FIG. 1, FIG. 2 and FIG. 3, a sealing layer may further be formed on the cathode electrodes 190, in order to seal the OLEDs 100 and 200. In addition, various other modifications may be applied thereto.

(14) Hereinafter, one or more exemplary embodiments of the present invention will be described in detail with, reference to the following examples. However, these examples are not intended to limit the purpose and scope of the one or more exemplary embodiments of the present invention.

(15) Experimental Part

(16) The inventors compared the performance of the representative compounds E1 and E2 with previous art compound B1 as a n-dopant and as a neat hole injection layer and in a model tandem OLED device.

(17) ##STR00012##

(18) An additional comparative material is compound B2

(19) ##STR00013##

(20) The closest state-of-art material already was disclosed as an efficient n-dopant in various matrices is lithium tetrakis(H-pyrazol-1-yl)borate,

(21) ##STR00014##
Device Experiments
Generic Procedures

(22) OLEDs with two emitting layers were prepared to demonstrate the technical benefit of an organic electronic device comprising a hole injection layer and/or a hole generating layer according to the present invention. As proof-of-concept, the tandem OLEDs comprised two blue emitting layers.

(23) A 15 Ω/cm.sup.2 glass substrate with 90 nm ITO (available from Corning Co.) was cut to a size of 150 mm×150 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.

(24) The organic layers are deposited sequentially on the ITO layer at 10.sup.−5 Pa, see Table 1 and 2 for compositions and layer thicknesses. In the Tables 1 to 3, c refers to the concentration, and d refers to the layer thickness.

(25) Then, the cathode electrode layer is formed by evaporating aluminum at ultra-high vacuum of 10.sup.−7 mbar and deposing the aluminum 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.

(26) The device is protected from ambient conditions by encapsulation of the device with a glass slide. Thereby, a cavity is formed, which comprises a getter material for further protection.

(27) Current voltage measurements are performed at the temperature 20° C. using a Keithley 2400 source meter, and recorded in V.

(28) Experimental Results

(29) Using following model blue OLED device, performance of the inventive n-dopants/electron injection materials was compared with the closest state-of-art material C1 and with magnesium analogue B1.

(30) Materials Used in Device Experiments

(31) The formulae of the supporting materials mentioned in tables below are as follows:

(32) F1 is

(33) ##STR00015##

(34) biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine, CAS 1242056-42-3,

(35) F2 is

(36) ##STR00016##

(37) N,N-bis(4-(dibenzo[b,d]furan-4-yl)phenyl)-[1,1′:4′,1″-terphenyl]-4-amine, CAS 1198399-61-9;

(38) F3 is

(39) ##STR00017##

(40) 9-([1,1′-biphenyl]-3-yl)-9′-([1,1′-biphenyl]-4-yl)-9,9′H-3,3′-bicarbazole, CAS 1643479-47-3:

(41) F4 is

(42) ##STR00018##

(43) 2,4-diphenyl-6-(3′-(triphenylen-2-yl)-[1,1′-biphenyl]-3-yl)1,3,5-triazine, 1638271-85-8;

(44) PD-2 is

(45) ##STR00019##
4,4′,4″-((1E,1′E,1″E)-cyclopropane-1,2,3-triylidenetris (cyanomethanylylidene))tris(2,3,5,6-tetrafluorobenzonitrile), CAS 1224447-88-4.

(46) H06 is an emitter host and DB-200 is a blue fluorescent emitter dopant, both commercially available from SFC, Korea.

(47) Exemplary ETL matrix compounds M1 and M2 have the following formulae:

(48) M1 is

(49) ##STR00020##
diphenyl(3′-(10-phenylanthracen-9-yl)-[1,1′-biphenyl]-4-yl)phosphine oxide, CAS 2138371-45-4, published in EP 3 232 490 and WO2017/178392, and in the present invention serves as an ETL matrix for the inventive n-dopants.

(50) M2 is

(51) ##STR00021##
dimethyl(3′-(10-phenylanthracen-9-yl)-[1,1′-biphenyl]-3-yl)phosphine oxide, CAS 2101720-06-1, published in WO2017/102822, and in the present invention serves as an ETL matrix for the inventive n-dopants.

(52) Structure of the model device is shown in Table 1a

(53) TABLE-US-00001 TABLE 1a layer composition c [wt %] d [nm] anode Ag 100 100 HIL F1:PD-2 92:8 10 HTL F1 100 117.5 EBL F2 100 5 EML H06:BD200 97:3 20 HBL F3:F4 70:30 5 ETL ETL matrix:n-dopant 7030 31 EIL Yb 100 2 cathode Ag 100 11 cap layer F1 100 75

(54) Performance of the model device in terms of the operational voltage U, CIE coordinate yin the color space, luminance, current density j, current efficiency C.sub.eff, lifetime (defined as a time in which the luminance of the device operated at the current density j falls to 97% of its initial value) and voltage rise d(U) after 100 hour operation at 85° C. is given in Table 1b.

(55) TABLE-US-00002 TABLE lb ETL Lumi- dU (100 compo- U CIE nance j C.sub.eff LT.sub.97 h) [%] sition [V] 1931 y [cd/m.sup.2] [A/m.sup.2] [cd/A] [h] at 85° C. M1:C1 3.62 0.048 953 122 7.8 240 3.6 M1:B1 5.09 0.047 932 196 4.8  34 8.5 M1:E1 3.61 0.047 932 122 7.6 238 3.4 M1:E2 3.57 0.047 932 123 7.6 233 2.7 M2:C1 3.56 0.049 974 121 8.0 234 3.7 M2:B1 3.54 0.049 974 121 8.0 221 1.4 M2:E1 3.55 0.048 953 121 7.9 232 1.6 M2:E2 3.55 0.048 953 122 7.8 242 1.8

(56) In comparison with state-of-art compound C1, the selection of Ca and especially of Sr borates brings improved operational voltage stability at elevated temperatures.

(57) Ca and Sr borates exhibit applicability in abroad spectrum of phosphine oxide matrices, whereas magnesium analogues are suitable only for dialkyl phosphine oxide matrices, particularly for dimethyl phosphine oxide matrices.

(58) In comparison with Ba analogues, Ca and Sr borates exhibit favourable thermal properties. Compounds E1 and E2 can be preparatively sublimed at pressures about 10.sup.−3 Pa and co-deposited with suitable matrices in state-of-art industrial vacuum thermal evaporation (VTE) facilities, whereas their Ba analogue decomposes. Poor thermal stability preventing their utilizability in industrial VTE processes has been generally observed by the inventors also for other borate salts lacking the heterocyclic group.

(59) It can be summarized that it was surprisingly found by the inventors that compounds E1 and E2 in accordance with the invention show superior performance over the compounds B1 and B2 of the prior art.

(60) The features disclosed in the foregoing description, in the claims and/or in the accompanying drawings may, both separately and in any combination thereof be material for realizing the invention in diverse forms thereof.