WO2006112582A1

WO2006112582A1 - Deuterated organic electroluminescent material, preparation method thereof and organic light emitting diode using the same

Info

Publication number: WO2006112582A1
Application number: PCT/KR2005/003840
Authority: WO
Inventors: Kyoung-Soo Kim; Kyu-Man Youn; Tae-Hyung Kim; Hyeon-Jin Seo; Myung-Soo Ko; Sang-Hoon Lee; Dong-Wan Ryu; Yeong-Eun Kim
Original assignee: Doosan Corp
Current assignee: Doosan Corp
Priority date: 2005-04-21
Filing date: 2005-11-11
Publication date: 2006-10-26
Anticipated expiration: 2007-10-21
Also published as: KR20060111048A; KR100676966B1

Abstract

Provided are a deuterated organic electroluminescent material, a preparation method thereof and an organic light emitting diode using the same. The organic light emitting diode using the deuterated organic electroluminescent material of the present invention has remarkably improved emitting efficiency, brightness, power efficiency, thermal stability and the like.

Description

DEUTERATED ORGANIC ELECTROLUMINESCENT MATERIAL, PREPARATION METHOD THEREOF AND

ORGANIC LIGHT EMITTING DIODE USING THE SAME

Technical Field

[1] The present invention relates to a deuterated organic electroluminescent material, a preparation method thereof and an organic light emitting diode using the same.

Background Art

[2] U.S. Patent No. 6,699,599 discloses a phosphorescent material that hydrogen atoms of Ir(ppy) are partially or entirely substituted with deuterium. In general, the substitution of hydrogen of a compound with the deuterium makes exciton formed easily, resulting in enhancing light emitting efficiency. The reason is that the bond strength between carbon and deuterium is stronger than that between carbon and hydrogen, and thus, if a substitution with deuterium is performed, the bond length between carbon and deuterium is shortened, and a van der Waals' force becomes smaller, so that higher light emitting efficiency can be achieved.

[3] However, U.S. Patent No. 6,699,599 does not present in numerical values of the extent to which the efficiency has been improved, where hydrogen(s) of the Ir(ppy) is substituted with deuterium, compared with the case that hydrogen is not substituted. Rather, it can be only presumed that the efficiency has been slightly improved. Disclosure of Invention

Technical Problem

[4] Therefore, it is an object of the present invention to provide a deuterated low molecular weight organic electroluminescent material, which can be applied to an emitting layer, a hole transport layer and/or an electron transport layer of an organic light emitting diode, a preparation method thereof and an organic light emitting diode using the same.

[5] It is another object of the present invention to provide a d euterated organic electroluminescent material, which can remarkably enhance emitting efficiency, thermal stability or the like of an emitting diode compared with a conventional organic electroluminescent material, a preparation method thereof and an organic light emitting diode using the same.

[6] It is still another object of the present invention to provide deuterated organic electroluminescent material, capable of being operated at a low voltage, expressing various colors and having a fast response, a preparation method thereof and an organic light emitting diode using the same. Technical Solution

[7] To achieve the above and other objects of the invention, there is provided a compound having a structure of a stilbene or a biphenyl ring substituted with a hetero- aromatic ring selected from the group consisting of a substituted or unsubstituted carbazole, aryl, aromatic amine, aliphatic amine, phenoxazine and phenothiazine, and having more than one or more deuterium within the compound.

Advantageous Effects

[8] According to the present invention, a deuterated organic electroluminescent material, a preparation method thereof and an organic light emitting diode using the same. The organic light emitting diode using the deuterated organic electroluminescent material has remarkably improved emitting efficiency, brightness, power efficiency, thermal stability and the like.

[9] Accordingly, the compound according to the present invention can be applied to an emitting layer, a hole transport layer and/or an electron transport layer of an organic light emitting diode.

[10] The compound according to the present invention is a low molecular weight chromophore compound, and thus, if it is applied to a light emitting diode, a blue light can take place at a low voltage. Also, the compound according to the present invention is an organic matter having a conjugated double bond, and thus, various colors can be embodied by employing another emitting material as a dopant. Furthermore, the compound according to the present invention is super in its brightness and light emitting efficiency.

Description of Drawings

[11] Fig. 1 shows efficiency test results of diodes comprising Compound A and

Compound B ( H : Compound A; and • : Compound B);

[12] Fig. 2 shows an efficiency test results of diodes comprising Compound C and

Compound D ( B : Compound C; and • : Compound D); and

[13] Fig. 3 shows an efficiency test results of diodes comprising Compound E and

Compound F ( B : Compound E; and • : Compound F).

Mode for Invention

[14] In an aspect of the present invention, there is provided a compound having a structure of a stilbene or a biphenyl ring substituted with a hetaro-aromatic ring selected from the group consisting of a substituted or unsubstituted carbazole, aryl, aromatic amine, aliphatic amine, phenoxazine and phenothiazine, and having more than one or more deuterium within the compound.

[15] Therefore, an organic electroluminescent material of the present invention has a structure represented by Formula 1 as follows: [16] Formula 1

[17]

[ 18] wherein m and n represent 0 or 1 , respectively;

[19] B is N in the case of n=0 ;

[20] A is carbon and B is CH in the case of n=l ;

[21] Ar and Ar' are independently the same as or different from each other and represent an aromatic group selected from the group consisting of phenyl, tolyl, biphenyl, naphthyl, carbazole and fluorenyl which may optionally be substituted with deuterium, CN, F, Cl or Br; wherein Ar and Ar' may be connected to each other by means of a linker selected from the group consisting of S, N-aryl, N-R, CH and SiR , or may be directly connected to each other without a linker; and

[22] R and R' are independently selected from the group consisting of hydrogen, deuterium, CN, F and CH ;

[23] provided that the compound of Formula 1 has one or more deuterium within a molecule.

[24] The compound of Formula 1, in which m=l, can be prepared by reacting a secondary amine compound represented by Formula 2 with a stilbene compound represented by Formula 3 via Ullmann reaction or C-N bonding reaction using a palladium catalyst.

[25] Formula 2

[26]

Ar- NH - Ar¹

[27] Formula 3

[28]

[29] The compound of Formula 1, in which m=l, can also be obtained by reacting the compound of Formula 2 with a benzaldehyde compound represented by Formula 4 to obtain a compound of Formula 5, followed by coupling the compound of Formula 5 with each other. [30] Formula 4

[31]

[32] Formula 5

[33]

[34] Meanwhile, the compound of Formula 1, in which n=0, can be obtained by converting a biphenyl compound represented by Formula 6 into a phosphonate compound so as to activate, followed by reacting the activated phosphonate compound with benzophenone.

[35] Formula 6

[36]

W \-/ _x

[37] In Formulas 2 to 6, the Ar, Ar', R and R' are the same as defined for the compound of Formula 1 ; and X and Y are independently a halogen atom selected from the group consisting of fluorine, chlorine, bromine and iodine.

[38] In preparing the compound of Formula 1 according to the present invention, deuterium may be introduced in a manner that a compound to which deuterium is introduced is added to an aqueous solution in which boron trifluoride is dissolved in heavy water, and the resulting solution is then stirred for at least 48 hours. At this time, the deuterium may be introduced in a manner of obtaining un-deuterated compound of Formula 1 from an un-deuterated starting material, followed by deuterating un- deuterated compound of Formula 1, or in a manner of deuterating the starting material, followed by obtaining the deuterated compound of Formula 1 using the deuterated starting material.

[39] The present invention also relates to a light emitting diode using the compound of

Formula 1. The compound of Formula 1 according to the present invention is applied between an anode for injecting a hole comprising indium tin oxide (ITO) having a high work function and a cathode for injecting an electron comprising a metal such as aluminum, lithium fluoride/aluminum, copper, silver, calcium, gold, magnesium or the like, or alloys thereof having various work functions. The compound of Formula 1 can also be applied to an emitting layer, a hole transport layer and/or an electron transport layer of a light emitting diode.

[40] EXAMPLES

[41] Hereinafter, the present invention will now be described in detail with reference to the following examples. However, such examples are exemplary for the present invention, and accordingly, the scope of the present invention will not be limited thereto.

[42] In the present invention, the structures of the compounds prepared in examples were determined by H-NMR, elemental analysis, mass spectrometry and the like. UV and PL spectra were measured in a solution of a compound in dichloromethane. Organic light emitting diodes were prepared so as to evaluate emitting properties thereof.

[43] Example 1 : Preparation of Deuterated 4,4'-di(9-carbazolyl)stilbene-d4 (Compound

A)

[44] After 50 ml of heavy water was put in a 100 ml flask, 12 g (0.07 mole) of carbazole was added thereinto, and boron trifluoride gas was then injected for 15 minutes while stirring, and the resulting solution was stirred at an ambient temperature for 48 hours. After, the reaction mixture was poured into 200 ml of distilled water, sodium hydroxide was added thereto so as to neutralize until pH of the solution reached 7. The reaction mixture was then filtered and the filtrate was dried. The dried residue was dissolved in toluene and purified using a silica gel column chromatography, to obtain 10.8 g (0.064 mole) of carbazole-d2 (yield: 89%).

[45] 1O g (60 mmol) of the carbazole-d2 and 7.45 g (60 mmol) of 4-fluoro benzaldehyde

(available from Aldrich Co.) were put into a 100 ml flask. After 16.5 g of potassium carbonate was added into the flask, the reaction mixture was refluxed with stirring using N,N-dimethylformamide as a solvent for 4 hours. The completion of the reaction was confirmed by thin layer chromatography (TLC). After completion of the reaction, the reaction mixture was purified by a column chromatography to obtain 14 g (0.051 mole) of 4-carbazolyl benzaldehyde-d2 (yield: 87%).

[46] After 5 g (0.0182 mole) of 4-carbazolyl benzaldehyde-d2 was put into a flask and dissolved in dried tetrahydrofuran, 3.0 g (0.0455 mole) of zinc powder was added thereto. Titanium tetrachloride was then gradually added to the reaction mixture for 30 minutes. After the addition of the titanium tetrachloride was completed, the reaction mixture was refluxed with stirring for 6 hours. The product was purified by a column chromatography and recrystallized from toluene to obtain 3.7 g (0.0071 mole) of the desired compound (Compound A). The yield of the final product was 78.5 %, and the produce has a very stable form.

[47] ¹H-NMR (CDCl , 300MHz) δ (ppm) 8.16(d), 7.8(d), 7.6(d), 7.5-7.4(m) and 7.3(t) [48] In order to compare with the emitting properties of the compound obtained in Example 1, 4,4'-dicarbazolylstilbene (Compound B) was prepared. Using Compound B and the compound prepared in Example 1, respectively, organic light emitting diodes were constructed as described below, and their light emitting properties were evaluated.

[49] ITO/m-MTDATA(600 nm)/NPB(200 nm)/Compound A(300 nm)/Alq3(250 nm) / LiF(IO nm)/Al [50] ITO/m-MTDATA(600 nm)/NPB(200 nm)/Compound B(300 nm)/Alq3(250 nm) / LiF(IO nm)/Al [51] Table 1 shows brightness and current efficiency of Compound A, and Table 2 shows brightness and current efficiency of Compound B. As shown in Tables 1 and 2, it can be confirmed that the brightness and current efficiency of Compound A according to Example 1 are remarkably superior to those of Compound B.

[52] Table 1 [53]

[54] [55]

[56] The efficiency depending on the current among the above results was illustrated in Figure 1. [57] Example 2: Preparation of 4,4'-bis(2,2'-diphenylethen-l-yl)biphenyl-dlO (Compound C)

[58] After 18 g (0.21 mole) of benzene-d6, 20 g (0.14 mole) of benzoyl chloride and 6.8 g (0.05 mole) of aluminum trichloride were put into a 100 ml flask, the resulting mixture was refluxed for 6 hours. The reaction mixture then poured in 100 ml of water and then extracted with toluene. Organic layer was purified by silica gel chromatography, to give 24 g (0.128 mole) of benzophenone-d5 with an yield of 90%.

[59] 20 g (0.057 mole) of 4,4'-bromomethylbiphenyl and 37 ml (0.22 mole) of tri- ethylphosphite were added to a 100 ml flask, and the resulting mixture was refluxed for two hours. The reaction mixture was cooled down to room temperature, and stirred for two more hours after adding 50 ml of hexane thereto. The reaction mixture was then to obtain 21 g (0.0497 mole) of 4,4'-bis(diethoxyphosphorylmethyl)biphenyl with an yield of 87%.

[60] After 2.4 g (0.013 mole) of benzophenone-d5 and 2.17 g (0.05 mole) of 4,4'-bis

(diethoxyphosphorylmethyl)biphenyl were added to a 100 ml flask, anhydrous tetrahydrofuran was further added, and then, 0.37 g (0.015 mole) of sodium hydride was added. The reaction mixture was then refluxed for 12 hours. After the reaction solution was poured into methanol, the generated precipitate was filtered off, and the filtrate was concentrated. The concentrate was purified by a silica gel chromatography to obtain 1.1 g (0.021 mole) of 4,4'-bis(2,2-diphenyl- ethen-l-yl)biphenyl-dlθ. The final product was obtained with an yield of 41% and is in a very stabilized form.

[61] ¹H-NMR(CDCl ₃ , 300MH z) δ (ppm) 7.35-7.32(m), 7.26(s), 7.25-7.2 (m), 7.4(d),

6.98(s)

[62] 4,4'-Bis(2,2-diphenyl-ethen-l-yl)biphenyl (Compound D) was synthesized, in order to compare its emitting properties with those of the deuterated compound (Compound C) prepared in Example 2, organic light emitting diodes were constructed using Compounds C and D as emitting layers, respectively, as described below. Then, emitting properties of such emitting diodes were evaluated.

[63] ITO/m-MTDATA(450 nm)/NPB(150 nm)/Compound C(300 nm)/Alq3(250 nm) /

LiF(IO nm)/Al

[64] ITO/m-MTDATA(450 nm)/NPB(150 nm)/Compound D(300 nm)/Alq3(250 nm)/

LiF(IO nm)/Al

[65] Table 3 shows brightness and current efficiency of Compound C, and Table 4 shows brightness and current efficiency of Compound D. As shown in Tables 3 and 4, it can be confirmed that the brightness and current efficiency of Compound C of Example 2 are remarkably superior to those of Compound D.

[66] Table 3

[68] Table 4 [69]

[70] Fig. 2 shows an illustration of the current efficiency data among the results shown in Tables 3 and 4.

[71] Example 3: Preparation of 4,4'-bis(l,2'-dinaphthylamino)stilbene-d4 (Compound E) [72] After 10 g (0.069 mole) of 2-naphthol, 10 g (0.070 mole) of 1-naphthylamine (available from Aldrich Co.) and 0.8 g of phosphoric acid were added to a 100 ml flask, and the resulting mixture was refluxed with stirring using 1,2-dichlorobenzene as a solvent for 12 hours. The completion of the reaction was checked by TLC. After the reaction was completed, the reaction mixture was purified by a column chromatography to obtain 14 g (0.052 mole) of l,2'-dinaphthylamine (yield: 75%).

[73] 1 g (2.96 mmol) of 4,4'-dibromostilbene and 1.8 g (6.79 mmol) of l,2'-dinaphthylamine were dissolved in 20 ml of toluene. After 0.14 g (0.15 mmol) of tris(dibenzylideneacetone)dipalladium was introduced into the resulting mixture under nitrogen atmosphere, 1.1 g (11.4 mmol) of NaOBu' was added thereto. 0.3 g (1.48 mmol) of (t-Bu) P was further added into the reaction mixture, which was then stirred for 12 hours. After confirming completion of the reaction by TLC, the temperature of the reaction mixture was cooled down to an ambient temperature. The reaction solution was poured onto a thin silica pad so as to perform a short column chromatography, and then washed with dichloromethane. The residue was distilled under reduced pressure so as to remove solvent and then dried. The obtained residue was added into a 100 ml flask. After 50 ml of heavy water was added into the flask, boron trifluoride gas was introduced into the reaction mixture for 15 minutes, and then the resulting mixture was stirred at an ambient temperature for 48 hours. The reaction mixture was poured into 200 ml of distilled water and sodium hydroxide was added until pH of the solution became 7 so as to neutralize. The reaction mixture was then filtered and then the filtrate was dried. The dried residue was dissolved in toluene and purified by a silica gel chromatography, to obtain 1.64 g (2.29 mmol) of

4,4'-bis(l,2'-dinaphthylamino)stilbene-d4 (Compound E). The final product was obtained with an yield of 78% and is in a very stabilized form.

[74] ¹H-NMR(CDCl₃ , 300MHz) δ (ppm) 7.92(q), 7.8(d), 7.67-7.75(m), 7.4-7.53(m), 7.23-7.38(m), 7.02(d), 6.9(s) [75] 4,4'-bis(l,2'-dinaphthylamino)stilbene (Compound F) was prepared, and in order to compare its emitting properties with those of the deuterated compound (Compound E) prepared in Example 3, organic light emitting diodes were constructed using Compounds E and F as a dopant of each emitting layer, respectively, as described below. Their emitting properties were evaluated.

[76] ITO/m-MTDATA(450 nm)/NPB(150 nm)/DPVBi(275 nm)+Compound E(25 nm) / Alq3(250 nm)/LiF(10 nm)/Al [77] ITO/m-MTDATA(450 nm)/NPB(150 nm)/DPVBi(275 nm)+Compound F(25 nm) / Alq3(250 nm)/LiF(10 nm)/Al [78] Table 5 shows brightness and current efficiency of the Compound E, and Table 6 shows brightness and current efficiency of the Compound F. As shown in Tables 5 and 6, it can be confirmed that the brightness and current efficiency of the Compound E of Example 3 of the present invention are remarkably superior to those of the Compound F, and its color purity has also been improved.

[79] Table 5 [80]

[81] Table 6 [82]

[83] Fig. 3 shows an illustration of the current efficiency data among the results shown in Tables 5 and 6. [84] As described above, the deuterated compound according to the present invention exhibits similar light emitting properties, with remarkably superior brightness and current efficiency, compared with the corresponding un-deuterated compound.

[85] It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover such modifications and variations of the invention provided that they come within the scope of the appended claims and their equivalents.

Claims

[ 1 ] A deuterated compound represented by the following Formula 1 :

Formula 1

wherein m and n are 0 or 1, respectively;

B represents a nitrogen atom in case of n=0; A represents a carbon atom and B represents CH in case of n=l ;

Ar and Ar' are independently the same as or different from each other and represent an aromatic group selected from the group consisting of phenyl, tolyl, biphenyl, naphthyl, carbazole and fluorenyl which may optionally be substituted with deuterium, CN, F, Cl or Br; wherein Ar and Ar' may be connected to each other by means of a linker selected from the group consisting of S, N-aryl, N-R,

CH and SiR , or may be directly connected to each other without a linker; and

R and R' are independently selected from the group consisting of hydrogen, deuterium, CN, F and CH ; provided that the compound of Formula 1 essentially has one or more deuterium within a molecule.

[2] The compound according to claim 1, wherein the Ar and Ar' are connected to each other so as to form a carbazole ring.

[3] The compound according to claim 1, wherein m is 1 and n is 0, and the Ar and Ar' are connected to each other so as to form a carbazole ring.

[4] The compound according to claim 1, wherein m is 1 and n is 0, and each of the Ar and Ar' is a naphthyl group.

[5] The compound according to claim 1, wherein m is 0 and n is 1, and each of the Ar and Ar' is a phenyl group.

[6] A preparation method of a compound of Formula 1 according to claim 1, comprising reacting an amine compound represented by Formula 2 with a compound represented by Formula 3: Formula 1

r Ar¹ Formula 2 Ar — NH-Ar¹ Formula 3

wherein m and n are O or 1, respectively;

Ar and Ar' are independently the same as or different from each other and represent an aromatic group selected from the group consisting of phenyl, tolyl, biphenyl, naphthyl, carbazole and fluorenyl which may optionally be substituted with deuterium, CN, F, Cl or Br; wherein Ar and Ar' may be connected to each other by means of a linker selected from the group consisting of S, N-aryl, N-R, CH and SiR , or may be directly connected to each other without a linker; R and R' are independently selected from the group consisting of hydrogen, deuterium, CN, F and CH ; provided that the compound of Formula 1 essentially has one or more deuterium within a molecule.

[7] A preparation method of the compound of Formula 1 according to claim 1 , comprising:

(1) reacting an amine compound represented by Formula 2 with a compound represented by Formula 4 to obtain a compound represented by Formula 5; and

(2) coupling the compound of Formula 5 with each other to obtain a compound of Formula 5:

Formula 1

Formula 2 Ar — NH-Ar' Formula 4

Formula 5

V-<T )VCHO

Ar wherein m and n are O or 1, respectively;

Ar and Ar' are independently the same as or different from each other and represent an aromatic group selected from the group consisting of phenyl, tolyl, biphenyl, naphthyl, carbazole and fluorenyl which may optionally be substituted with deuterium, CN, F, Cl or Br; wherein Ar and Ar' may be connected to each other by means of a linker selected from the group consisting of S, N-aryl, N-R, CH and SiR , or may be directly connected to each other without a linker; and R and R' are independently selected from the group consisting of hydrogen , deuterium, CN, F and CH ; provided that the compound of Formula 1 essentially has one or more deuterium within a molecule.

[8] A preparation method of a compound of Formula 1 according to claim 1, comprising:

(a) converting a compound represented by Formula 6 into an activated phophonate compound; and

(b) reacting the activated phosphonate compound with benzophenone to obtain the compound of Formula 1:

Formula 1

Formula 6

wherein m and n are 0 or 1, respectively;

[9] An organic light emitting diode comprising the compound according to any one of claims 1 to 5.