Main group metal complexes as p-dopants for organic electronic matrix materials

Abstract

A metal complex of a metal from groups 13 to 16 uses a ligand of the structure (I), where R.sup.1 and R.sup.2 can independently be oxygen, sulfur, selenium, NH or NR.sup.4, where R.sup.4 an alkyl or aryl and can be connected to R.sup.3. R.sup.3 is an alkyl, long-chain alkyl, alkoxy, long-chain alkoxy, cycloalkyl, halogenalkyl, aryl, arylene, halogenaryl, heteroaryl, heteroarylene, heterocycloalkylene, heterocycloalkyl, halogenheteroaryl, alkenyl, halogenalkenyl, alkynyl, halogenalkynyl, ketoaryl, halogenketoaryl, ketoheteroaryl, ketoalkyl, halogenketoalkyl, ketoalkenyl, halogenketoalkenyl, where in suitable radicals, one or more non-adjacent CH.sup.2-groups can be substituted independently of one another by O, S, NH, NR.sup.o-, SiR.sup.oR.sup.oo-, CO, COO, OCO, OCOO, SO.sub.2-, SCO, COS, CY1CY2 or C.dbd.C, specifically in such a way that O and/or S atoms are not connected directly to one another, are likewise optionally substituted with aryl- or heteroaryl preferably containing 1 to 30 C atoms, as a dopant for matrix materials in organic electronic components.

Claims

1. Metal complex containing at least one Ligand L of the following structure ##STR00014## where R1=R2=oxygen and wherein the ligand is selected from the group consisting of 3,5-bis(trifluoromethyl)benzoic acid, 3-(trifluoromethyl)benzoic acid, and 3,5-difluorobenzoic acid, and wherein the metal is selected from the group consisting of bismuth, and mixtures thereof.

2. The metal complex according to claim 1, wherein the complex is a mononuclear metal complex.

3. The metal complex according to claim 1, wherein the metal complex follows the structure ML3, wherein M represents the metal and L represents the ligand.

4. The metal complex according to claim 1, wherein the complex is a polynuclear metal complex.

5. A metal complex comprising: bismuth atoms bonded to ligands L having the following structure: ##STR00015## where R1=R2=oxygen and wherein the ligand comprises a fluorinated benzoic acid.

6. The metal complex according to claim 5, wherein the ligand is selected from the group consisting of 3,5-bis(trifluoromethyl)benzoic acid, 3-(trifluoromethyl)benzoic acid, and 3,5-difluorobenzoic acid.

7. The metal complex according to claim 5, wherein the ligand is selected from the group consisting of 3,5-bis(trifluoromethyl)benzoic acid and 3-(trifluoromethyl)benzoic acid.

8. The metal complex according to claim 5, wherein the complex is a mononuclear metal complex.

9. The metal complex according to claim 5, wherein the complex is a polynuclear metal complex.

10. The metal complex according to claim 5, wherein the metal complex follows the structure ML3, wherein M represents the metal and L represents the ligand.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other objects and advantages of the present invention will become more apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which:

(2) FIG. 1 is a schematic side view of the structure of an organic light-emitting diode (10). The light-emitting diode is formed from a glass layer (1); transparent conductive oxide (TCO) or PEDOT:PSS or PANI layer (2); hole injector layer (3); hole transport layer (HTL) (4); emitter layer (EML) (5); hole blocker layer (HBL) (6); electron transport layer (ETL) (7); electron injector layer (8) and a cathode layer (9);

(3) FIG. 2 is a schematic side view of the structure of an organic solar cell having PIN structure (20), which converts light (21) to electrical current. The solar cell is formed of a layer of indium tin oxide (22); a p-doped layer (23); an absorption layer (24); an n-doped layer (25) and a metal layer (26);

(4) FIG. 3 is a schematic cross section of an organic field-effect transistor (30). Atop a substrate (31) is applied a gate electrode (32), a gate dielectric (33), a source and drain contact (34+35) and an organic semiconductor (36). The hatched areas show the points where contact doping is helpful.

(5) FIG. 4 is a graph of current density against voltage for an undoped matrix material and for a doped matrix material in a first embodiment;

(6) FIG. 5 is a graph of absorption against wavelength for the materials from FIG. 4;

(7) FIG. 6 is a graph of photoluminescence against wavelength for the materials from FIG. 4;

(8) FIG. 7 is a graph of reflection against wavelength for the doped material from FIG. 4;

(9) FIG. 8 is a graph of current density against voltage for an undoped matrix material and for several doped matrix materials in a second embodiment;

(10) FIG. 9 is a graph of absorption against wavelength for the materials from FIG. 8;

(11) FIG. 10 is a graph of photoluminescence against wavelength for the doped materials from FIG. 8;

(12) FIG. 11 is a graph of reflection against wavelength for the materials from FIG. 8;

(13) FIG. 12 is a graph of current density against voltage for an undoped matrix material and for several doped matrix materials in a third embodiment;

(14) FIG. 13 is a graph of current density against voltage for an undoped matrix material and for several doped matrix materials in a fourth embodiment;

(15) FIG. 14 is a graph of current density against voltage for an undoped matrix material and for several doped matrix materials in a fifth embodiment;

(16) FIG. 15 is a graph of luminescence against voltage for the doped materials from FIG. 14;

(17) FIG. 16 is a graph of current density against voltage for an undoped matrix material and for several doped matrix materials in a sixth embodiment;

(18) FIG. 17 is a graph of luminescence against voltage for the doped materials from FIG. 16.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(19) Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.

Example I

(20) Example I relates to Bi(O.sub.2CCF.sub.3).sub.3 which has been prepared according to literature; see Bo Li Heterometallic Carboxylates Incorporating Bismuth, PhD Thesis, State University of New York at Albany, Chair M. Petrukhina 2007, UMI Number 3277252, and Vera Reiland Chemie und Koordinationschemie von Bismuttri-fluoracetat und verwandten Verbindungen [Chemistry and Coordination Chemistry of Bismuth Trifluoroacetate and Related Compounds], Thesis D368, University of Kaiserslautern 2000.

Vaporization

(21) ITO-prestructured glass substrates were subjected to an oxygen plasma treatment for 10 min and then subsequently transferred as quickly as possible to the vaporizer. The vaporizer was transferred into an argon glovebox in which the oxygen and water concentration was less than 2 ppm.

(22) All the vaporizations were conducted at a vacuum of less than 210.sup.6 mbar base pressure (the pressure then rises in the course of vaporization).

(23) First of all, both the matrix material and doping material were heated to just below the vaporization point, then heating was continued until constant vaporization was observable.

(24) The overall vaporization rate was about 1 /s, with the vaporization rate of the doping material set via the vaporization rate of the matrix material.

(25) Once the shutters had been closed, the system was cooled to 40 C. and flooded with argon, the mask for the deposition of the cathode was changed, and then the system was evacuated again.

(26) The electrode was formed of a 150 nm-thick layer of aluminum, which was applied at an initial vaporization rate of 0.5 /s, which was increased gradually to 5 /s.

(27) FIGS. 4 to 7 relate to Bi(O.sub.2CCF.sub.3).sub.3-doped and undoped HTM-014 (matrix material, from Merck KGaA). In these cases, 200 nm-thick layers of HTM-014 (Merck KGaA) on the one hand, and of HTM-014 doped with 15% Bi(O.sub.2CCF.sub.3).sub.3 on the other hand, were produced.

(28) FIG. 4 shows current density against voltage applied for the two materials. Even in the case of the doped layer, an increase in current density against voltage applied is observed.

(29) To study the optical properties of the proposed dopant material, absorption, photoluminescence and reflection were measured (FIGS. 5 to 7). It can be seen that the complexes are virtually transparent, which makes them suitable for use in (opto)electronic components.

Example II

(30) Example II relates to Bi(O.sub.2CC.sub.6H.sub.2(2,3,4-F.sub.3)).sub.3, which was prepared as follows:

(31) A 50 mL Schlenk flask was charged with 0.251 g (0.57 mmol) of triphenylbismuth(III), followed by 10-15 mL of freshly distilled benzene, and an excess (about 3 mmol) of 2,3,4-trifluorobenzoic acid was added. The mixture is heated under reflux for one hour and then cooled to room temperature; subsequently, the solvent is drawn off under reduced pressure until a white solid precipitates out. The crude product (yield 85-88%) is washed with a little hexane and dried under reduced pressure overnight. Purification can be accomplished by sublimation.

(32) In analogy to example I, four layers, one of an undoped matrix material (HTM-014, Merck), and HTM-014 layers doped with 5%, 13% and 15% Bi(O.sub.2CC.sub.6H.sub.2(2,3,4-F.sub.3)).sub.3, were applied. The layer thickness was 200 nm in each case.

(33) FIG. 8 shows current density against voltage applied for the three materials. Even in the case of the layer with 5% doping, an increase in current density against voltage applied is observed.

(34) To study the optical properties of the dopant material, absorption, photoluminescence and reflection were measured (FIGS. 9 to 11). It can be seen that the complexes are virtually transparent, which makes them suitable for use in (opto)electronic components.

Example III

(35) In the course of a solvent process, a majority charge carrier component is produced, using HIL-012 (matrix material, from Merck KGaA) as polymeric hole conductor and the metal complexes Bi(O.sub.2C.sub.2F.sub.3).sub.3 and BipFbz as dopants.

(36) To produce an undoped hole conductor, a 2% by weight solution of the HIL-012 in anisole and xylene (volume ratio of the solvents 1:1) is applied by a spin-coater to an ITO-coated glass plate. The application is effected for 40 s with a spin speed of 1200 rpm (revolutions per minute) and, after drying at 120 C. for 1 h standard pressure, a 120 nm-thick HIL-012 layer is obtained. For the upper electrode, by a vacuum vaporization process, a 200 nm-thick aluminum layer is applied.

(37) The layers doped with the metal complexes are produced analogously, except that the solutions admixed with the bismuth tris(trifluoroacetate) Bi(O.sub.2C.sub.2F.sub.3).sub.3 or bismuth tris(pentafluorobenzoate) (BipFbz) dopants are processed. The total solids content in these embodiments totals 2% by weight, and the proportion of the dopants in the total solids content is 15% by weight.

(38) The parameters for the spin-coating are found to be 1500 rpm for the element with Bi(O.sub.2C.sub.2F.sub.3).sub.3 as dopant, and 1000 rpm for the element with BipFbz. in total, coating is effected for a period of 40 s, and the layer thickness after drying using the abovementioned parameters is 100 nm for both elements.

(39) The measurements in each case are effected on elements of size 4 mm.sup.2.

(40) FIG. 12 shows the current density-voltage characteristics obtained for the different components in this example. It can be clearly seen that the doping results in an increase in conductivity by several orders of magnitude.

Example IV

(41) In the course of a solvent process, a majority charge carrier component is produced, using spiro-TTB as polymeric hole conductor and the metal complexes Bi(O.sub.2C.sub.2F.sub.3).sub.3 and BipFbz as dopants.

(42) The processing of the dopants with the spiro-TTB hole conductor material, a small molecule, is effected in an analogous manner to example III. For the production of 100 nm-thick layers, a total of 3.5% by weight solutions are produced (anisole:xylene solvent mixture, ratio 1:2), which contain 1.6 mol %, 2 mol % and 10 mol % of dopant, based on the amount of matrix material. The solutions are spun on at 750 rpm for 40 s and dried at 120 C. for 1 h.

(43) FIG. 13 shows the current density-voltage characteristics obtained for the different components in this example. The doping can again achieve a very distinct increase in conductivity compared to the pure hole conductor material. In addition, it is found that about 10 mol % of doping is necessary to achieve a sufficient influence on conductivity.

Example V

(44) The undoped and doped hole conductor layers described in example III are incorporated into red OLEDs. The red OLEDs have the following layer structure: glass/ITO/100 nm HTL varied/10 nm NPB/20 nm emitter layer of 20% NPB, 70% TPBi, 10% ADS076/60 nm TPBi/0.7 nm LiF/200 nm Al.

(45) As dopants, bismuth tris(trifluoroacetate) Bi(O.sub.2C.sub.2F.sub.3).sub.3 and bismuth tris(pentafluorobenzoate) (BipFbz) are used in the concentrations stated in FIG. 14 and FIG. 15. It is found that the OLEDs obtained by a solvent process, with regard to luminance (FIG. 15) and the current-voltage characteristic (FIG. 14), are better than reference OLEDs comprising PEDOT-PSS.

Example VI

(46) Instead of the HIL-012-based HIL from example V, spiro-TTB is utilized as hole conductor and doped with BipFbz. spiro-TTB and BipFbz can be prepared both by the solvent process (characteristic identified by BipFbz) and by the vaporization process (characteristic identified by BipFbz (ev)). The characteristic current density-voltage characteristic and luminance-voltage characteristic are depicted in FIGS. 16 and 17. It is found that the properties of layers produced by the vaporization process are better than those deposited from solution. However, the differences are small.

Example VII

(47) The doped hole conductor layers produced in examples III and IV can also be utilized as hole conductor layers for organic solar cells, especially those with p-i-n structure.

(48) The individual combinations of the constituents and of the features of the executions already mentioned are illustrative; the exchange and the substitution of these teachings for other teachings present in this publication are likewise explicitly contemplated with the publications cited. It will be apparent to the person skilled in the art that variations, modifications and other executions which are described here can likewise occur, without departing from the idea and the scope.

(49) The invention has been described in detail with particular reference to preferred embodiments thereof and examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention covered by the claims which may include the phrase at least one of A, B and C as an alternative expression that means one or more of A, B and C may be used, contrary to the holding in Superguide v. DIRECTV, 69 USPQ2d 1865 (Fed. Cir. 2004).