Organic Semiconductive Layer Comprising Phosphine Oxide Compounds

Abstract

The present invention relates to an organic semiconductive layer which is an electron transport layer and/or an electron injection layer and/or an n-type charge generation layer, the organic semiconductive layer comprising at least one compound of formula (1)

##STR00001## wherein R.sup.1 and R.sup.2 are each independently selected from C.sub.1 to C.sub.16 alkyl; Ar.sup.1 is selected from C.sub.6 to C.sub.14 arylene or C.sub.3 to C.sub.12 heteroarylene; Ar.sup.2 is independently selected from C.sub.14 to C.sub.40 arylene or C.sub.8 to C.sub.40 heteroarylene; R.sup.3 is independently selected from H, C.sub.1 to C.sub.12 alkyl or C.sub.10 to C.sub.20 aryl; wherein each of Ar.sup.1, Ar.sup.2 and R.sup.3 may each independently be unsubstituted or substituted with at least one C.sub.1 to C.sub.12 alky group; n is 0 or 1; and m is 1 in case of n=0; and m is 1 or 2 in case of n=1, phosphine oxide compounds comprised therein and to organic electroluminescent devices comprising such layers and compounds.

Claims

1. A compound of formula (1): ##STR00194## wherein R.sup.1 and R.sup.2 are each independently selected from C.sub.1 to C.sub.16 alkyl; Ar.sup.1 is selected from C.sub.6 to C.sub.14 arylene or C.sub.3 to C.sub.12 heteroarylene; Ar.sup.2 is independently selected from C.sub.14 to C.sub.40 arylene comprising a conjugated system of at least 14 delocalized electrons or C.sub.8 to C.sub.40 heteroarylene comprising a conjugated system of at least 14 delocalized electrons; R.sup.3 is independently selected from H, C.sub.1 to C.sub.12 alkyl, or C.sub.10 to C.sub.20 aryl; Ar.sup.1, Ar.sup.2, and R.sup.3 may each independently be unsubstituted or substituted with at least one C.sub.1 to C.sub.12 alkyl group; n is 1; and m is 1 or 2.

2. The compound of claim 1, wherein R.sup.1 and R.sup.2 are the same.

3. The compound of claim 1, wherein R.sup.1 and R.sup.2 are each independently selected from C.sub.1 to C.sub.4 alkyl.

4. The compound of claim 1, wherein Ar.sup.1 is selected from the group consisting of phenylene, biphenylene, naphthylene, fluorenylene, pyridylene, quinolinylene, and pyrimidinylene.

5. The compound of claim 1, wherein Ar.sup.2 is selected from the group consisting of pyrenylene, carbazoylene, benzo[c]acridinylene, dibenzo[c,h]acridinylene, dibenzo[a,j]acridinylene, ##STR00195## ##STR00196## ##STR00197##

6. The compound of claim 1, wherein Ar.sup.2 is not benzo[c]acridinylene, not dibenzo[c,h]acridinylene, and not dibenzo[a,j]acridinylene.

7. The compound of claim 1, wherein Ar.sup.2 is selected from the group consisting of pyrenylene, benzo[c]acridinylene, dibenzo[c,h]acridinylene, and dibenzo[a,j]acridinylene.

8. The compound of claim 1, wherein R.sup.3 is selected from the group consisting of hydrogen, phenyl, biphenyl, terphenyl, fluorenyl, naphthyl, phenanthryl, pyrenyl, carbazoyl, dibenzofuranyl, and dinaphthofuranyl.

9. The compound of claim 1, wherein the compound is selected from the group consisting of ##STR00198##

10. The compound of claim 1, wherein the compound is selected from the group consisting of ##STR00199##

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0291] 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:

[0292] FIG. 1 is a schematic sectional view of an organic light-emitting diode (OLED), according to an exemplary embodiment of the present invention;

[0293] FIG. 2 is a schematic sectional view of an OLED, according to an exemplary embodiment of the present invention.

[0294] 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

[0295] 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.

[0296] 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.

[0297] 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 comprising or consisting of the compound of formula (1) is formed directly 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.

[0298] Instead of a single electron transport layer 160, optional an electron transport layer stack (ETL) can be used.

[0299] 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.

[0300] 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. The electron transport layer (ETL) 160 and/or the electron injection layer (EIL) 180 comprise or consist of the compound of formula (1).

[0301] 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 120 is formed, on the anode electrode 120, an hole injection layer 130, hole transport layer 140, optional an electron blocking layer 145, an emission layer 150, optional a hole blocking layer 155, optional at least one electron transport layer 160, optional at least one electron injection layer 180, and a cathode 190 are formed, in that order or the other way around.

[0302] 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 and a second emission layer.

[0303] 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 which may comprise compound of formula (1), a 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. The electron transport layers (ETL) 160 and 161 and/or the electron injection layer (EIL) 180 and/or the n-type charge generation layer (n-type CGL) 185 comprise or consist of the compound of formula (1).

[0304] In the description above the method of manufacture an OLED 200 of the present invention is started with a substrate 110 onto which an anode 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 at least one first electron transport layer 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, an optional electron injection layer 181, and a cathode 190 are formed, in that order or the other way around.

[0305] 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.

[0306] 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.

Examples

[0307] Preparation of Compounds of Formula (1)

[0308] Dialkyphosphine oxides may be prepared using known procedures (method a: Hays, R. H., The Journal of Organic Chemistry 1968 33 (10), 3690-3694; method b: W. Voskuil and J. F. Arens Org. Synth. 1968, 48, 47).

[0309] Method 1

[0310] Synthesis of Dialkylphosphine Oxide with R.sup.1=R.sup.2

##STR00109##

[0311] Diethyl phosphonate (0.95 eq) is added to an ice cooled Grignard solution in THF (3 eq) at such a rate that a temperature of the reaction mixture is maintained at 20-30? C. After stirring at room temperature for 1 h the mixture is hydrolyzed by mixing it with an ice-cold saturated aqueous solution of potassium carbonate (3 eq). Precipitated magnesium carbonate is removed by filtration and washed several time with ethanol. Combined filtrates are concentrated in vacuum to give a crude material, which could be further purified by distillation or re-crystallization from an appropriate solvent.

[0312] Method 2

##STR00110##

[0313] Grignard solution in THF or Et.sub.2O (2 eq.) was added dropwise to an solution of phosphorus trichloride (1 eq) in diethyl ether (2 ml/mmol of PCl3) at ?40? C. The reaction mixture is stirred for 30 min at ?40? and then allowed to reach room temperature over 3 h. Reaction is terminated by addition of water (?3 eq). A solvent is evaporated at reduced pressure, an oily residue with some solid is diluted with dichloromethane, filtered, the solution is evaporated to dryness yielding an clear oil. This oily residue is then dissolved in a boiling heptane/ethyl acetate mixture (1:10), the solution allowed to cool down to the room temperature, two liquid phases are formed upon cooling. The upper (heptane) phase is discharged; the lower phase is concentrated in vacuum yielding a crude product. Additional purification could be achieved by re-crystallization or by vacuum distillation.

TABLE-US-00003 Starting materials and products Yield/MS Starting compound Method Product data Methylmagnesium 1 Dimethylphosphine oxide 70.8%/ chloride 78 [M].sup.+ Ethylmagnesium 1 Diethyphosphine oxide */106 [M+] bromide Isopropylmagnesium 2 Diisopropylphosphine */134 [M+] bromide oxide Tert-butylmagnesium 2 Di-tert-butylphosphine */162 [M+] bromide oxide Butylmagnesium 1 Dibutylphosphine oxide bromide Cyclohexylmagnesium 2 Dicyclohexylphosphine 100%/ bromide oxide 214 [M].sup.+

[0314] Typical Procedure for Coupling of Dialkylphosphine Oxide with Arylhalides

##STR00111##

[0315] Schlenck flask is charged with arylhalide (1 eq), dialkylphoshine oxide (1 eq.) and sealed with a rubber septum. Atmosphere is replaced by Argon and the starting compounds are dissolved in anhydrous dioxane or suspended in dioxane-THF mixture (1:1 vol.) In a separate vial, a mixture of tris(dibenzylideneacetone)dipalladium (0.005 eq), Xantphos (0.01 eq) and triethylamine (1.17 eq.) is dissolved in anhydrous dioxane (75 ml/mmol) at 24? C. for 10 min.

[0316] This catalyst solution is added to the mixture of phosphine oxide and aryl halide and the reaction mixture was stirred for 12-24 h at 24? C.

[0317] Work up procedure 1: A precipitated solid (trimethylamine salt) is separated by filtration through sintered glass filter (Pore size 4), washed two times with dioxane, combined filtrates are evaporated to a dryness under reduced pressure using a rotary evaporator. The residue is dissolved in water, pH is set to alkaline (?14) using aqueous potassium hydroxide solution. Resulting yellow turbid aqueous layer is sequentially extracted with hexane and diethyl ether. Combined organic layers are extracted with ?0.5M aqueous KOH solution, aqueous phases are combined, acidified by hydrochloric acid and extracted with dichloromethane. Combined extracts are washed with saturated sodium hydrocarbonate solution, brine and dried over magnesium sulfate. Solvent is removed under reduced pressure, residue is triturated with hexane, white crystalline precipitate is collected by vacuum filtration, washed with hexane and dried.

[0318] Work up procedure 2: Reaction mixture is diluted with water, precipitated material is collected by suction using a sintered glass filter (pore 4), washed with water, methanol and dried. Crude product could be further purified by re-crystallization from appropriate solvent. Final purification is achieved by sublimation in a high vacuum.

TABLE-US-00004 Starting materials and products Starting compound(s) Product/(work-up procedure) Yield/MS data 1-bromo-4-iodobenzene, (4-bromophenyl)dimethylphosphine 75%/232 [M].sup.+ dimethylphosphine oxide oxide/(a-1) 1-bromo-3-iodobenzene, (3-bromophenyl)dimethylphosphine 70.8%/232 [M].sup.+ dimethylphosphine oxide oxide/(a-1) 1-bromo-4-iodobenzene, (4-bromophenyl)diethylphosphine 88.6%/262 [M].sup.+ diethylphosphine oxide oxide/(a-1) Diisopropylphosphine oxide, (4-bromophenyl)diisopropylphosphine 73.21%/288[M].sup.+ 1-bromo-4-iodobenzene oxide/(a-1) Diisopropylphosphine oxide, (3-bromophenyl)diisopropylphosphine 66.37%/288[M].sup.+ 1-bromo-3-iodobenzene oxide/(a-1) Chlorodiisopropylphosphine, (3-bromophenyl)diisopropylphosphine 66.2%/288[M].sup.+ 1-bromo-3-iodobenzene oxide/(b) Chlorodiisopropylphosphine, (4-bromophenyl)diisopropylphosphine 61.6%/288[M].sup.+ 1-bromo-4-iodobenzene oxide/(b) Di-tert-butylphosphine oxide, (4-bromophenyl)di-tert- 1-bromo-4-iodobenzene, butylphosphine oxide/(b) Di-tert-butylphosphine oxide, (3-bromophenyl)di-tert- 1-bromo-3-iodobenzene butylphosphine oxide/(b) Dibutylphosphine oxide, (4-bromophenyl)dibutylphosphine 1-bromo-4-iodobenzene oxide/(a-1) Dibutylphosphine oxide, (3-bromophenyl)dibutylphosphine 1-bromo-3-iodobenzene oxide/(a-1) Dicyclohexylphosphine oxide, (4-bromophenyl)dicyclohexylphosphine 1-bromo-4-iodobenzene, oxide/(a-1) Dicyclohexylphosphine oxide, (3-bromophenyl)dicyclohexylphosphine 59.42%/368[M].sup.+ 1-bromo-3-iodobenzene oxide [00112] [00113] 76.5%/432[M + H].sup.+, 885 [2M + Na].sup.+ [00114] [00115] 55.36%/432[M + H].sup.+, 454[M + Na].sup.+, 885[2M + Na].sup.+ [00116] [00117] 41.6%/406[M].sup.+ [00118] [00119] 66%/381[M] + 403[M + Na].sup.+

[0319] Procedures for Suzuki-Miyaura Coupling

[0320] Method a.

[0321] A three neck round bottom flask, equipped with dropping funnel, reflux condenser and magnetic stir bar is charged with boronic ester (1 eq) and bromophenyldialkylphosphine oxide (1.5 eq), the flask is sealed with a rubber septum, evacuated and back-filled with argon (2 times). Anhydrous THF (10 ml/mmol of boronic ester) is added through the septum using a double-tipped needle. Separately, a catalyst is prepared by suspending of bis(dibenzylidenaceton)palladium (0.02 eq) and tri-tert-butylphosphane (0.04 eq) in a small amount of anhydrous THF under Argon. The catalyst suspension is added to the reaction mixture through the septum with a syringe. Deoxygenated aqueous solution of tetrabutylammonium hydroxide (?20% wt., 2 eq) is added dropwise to the reaction mixture at room temperature (addition time ?30 min). Reaction mixture is stirred at room temperature for 2 h, precipitated product is separated by filtration, washed with water, methanol, and hexane, dried in vacuum at 40? C. for 48 h. Crude product is then triturated with hot dichloromethane/hexane mixture (1:1 vol, ?300 ml), hot filtered and dried in vacuum at 50? C. for 1 h and at 120? for 1 h. Final purification is achieved by sublimation in a high vacuum.

[0322] Method b.

[0323] Potassium carbonate (51.4 mmol, 3 eq.) is dissolved in ?25 ml of deionized water, the solution is degassed with N.sub.2 for 30 min. Glyme (175 ml) is degassed in a 500 mL 3-necked round bottom flask with N.sub.2 for 30 min. The flask is then charged with boronic ester (17.14 mmol, 1 eq.), bromophenyldialkylphosphine oxide (17.99 mmol, 1.05 eq.) and tetrakis(triphenylphosphin)palladium(0) (0.51 mmol, 0.03 eq.) under a positive nitrogen pressure. The degassed potassium carbonate solution is added using a syringe, nitrogen purged reflux condenser is attached to the flask and a reaction mixture heated to 90? C. with stirring for 12 h. The mixture is allowed to cool down to the room temperature, a precipitate is collected by filtration, washed with water, methanol, dried in vacuum at 40? C. to give a crude product, which could be further purified by re-crystallization or trituration with appropriate solvents. Final purification is achieved by sublimation in a high vacuum.

[0324] Method c.

[0325] Potassium carbonate (20 mmol, 2 eq.) is dissolved in ?10 ml of deionized water, the solution is degassed with N.sub.2 for 30 min. Dioxane (40 ml) is degassed in a 100 mL 3-necked round bottom flask with N.sub.2 for 30 min. The flask is then charged with corresponding arylboronic acid, arylbromide or arylchloride (10 mmol, 1 eq.), dialkylphosphine oxide derivative (22 mmol, 1.1 eq.) and tetrakis(triphenylphosphin)palladium(0) (0.2 mmol, 0.02 eq.) under a positive nitrogen pressure. The degassed potassium carbonate solution is added using a syringe, nitrogen purged reflux condenser is attached to the flask and a reaction mixture heated to 90? C. with stirring for 12 h. The mixture is allowed to cool down to the room temperature, a precipitate is collected by filtration, washed with water, methanol, dried in vacuum at 40? C. to give a crude product, which could be further purified by re-crystallization or trituration with appropriate solvents. Final purification is achieved by sublimation in a high vacuum.

[0326] Method d.

[0327] Potassium carbonate (40 mmol, 2 eq.) is dissolved in ?20 ml of deionized water, the solution is degassed with N.sub.2 for 30 min. A mixture of toluene and ethanol (15:6 vol., 112 ml) is degassed in a 500 mL 3-necked round bottom flask with N.sub.2 for 30 min. The flask is then charged with trifluoromethanesulfonate (20 mmol, 1 eq.), boronic acid pinacol ester (22 mmol, 1.1 eq.) and [1,1-Bis(diphenylphosphino)ferrocene]dichloropalladium(II) (0.40 mmol, 0.02 eq.) under a positive nitrogen pressure. The degassed potassium carbonate solution is added using a syringe, nitrogen purged reflux condenser is attached to the flask and a reaction mixture heated to 90? C. with stirring for 12 h. The mixture is allowed to cool down to the room temperature, a precipitate is collected by filtration, washed with water, methanol, dried in vacuum at 40? C. to give a crude product, which could be further purified by re-crystallization or trituration with appropriate solvents. Final purification is achieved by sublimation in a high vacuum.

TABLE-US-00005 Starting materials and products Startng compound(s),/ Yield/ coupling method Product MS data [00120] [00121] 89.6%/ 483[M + H].sup.+ [00122] [00123] 20.7%/ 457[M + H].sup.+ [00124] [00125] 71.3%/ 457[M + H].sup.+ [00126] [00127] 508[M].sup.+ [00128] [00129] 51.1%/ 541[M + Na].sup.+ [00130] [00131] 32.9%/ 509[M + H].sup.+ [00132] [00133] 54.9%/ 433[M + H].sup.+ [00134] [00135] 37.7%/ 433[M + H].sup.+ [00136] [00137] 51.4%/ 421[M + H].sup.+ [00138] [00139] 57.3%/ 443[M + Na].sup.+ [00140] [00141] 61.8%/ 479[M + Na].sup.+ [00142] [00143] 97.5%/ 331[M + H].sup.+ [00144] [00145] 62.35%/ 407[M + H].sup.+ [00146] [00147] 83.11%/ 407[M + H].sup.+ [00148] [00149] 94.5%/ 483[M + H].sup.+ [00150] [00151] 58.7%/ 483[M + H].sup.+ [00152] [00153] 52.9%/ 533[M + Na].sup.+ [00154] [00155] 46.42%/ 561[M + Na].sup.+ [00156] [00157] 87%/ 483[M + H].sup.+ [00158] [00159] 91.7%/ 555[M + Na].sup.+ [00160] [00161] 45.47%, 555[M + Na].sup.+ [00162] [00163] 60.11%, 593[M + H].sup.+ [00164] [00165] 31.4%, 513[M + H].sup.+ 535[M + Na].sup.+ [00166] [00167] 49.42%, 507[M + Na].sup.+ [00168] [00169] 71%, 809[M + Na].sup.+ [00170] [00171] 81.5%/ 382[M + H].sup.+ 404[M + Na].sup.+ [00172] [00173] 32%/ 382[M + H].sup.+ [00174] [00175] 33.85%/ 530[M + Na].sup.+ [00176] [00177] 63.55%/ 508[M + H].sup.+ 530[M + Na].sup.+ [00178] [00179] 31.4%/ 508[M + H].sup.+ [00180] [00181] 16.58%, 584[M + H].sup.+ [00182] [00183] 62.57%, 458[M + H].sup.+, 480[M + Na].sup.+ [00184] [00185] 68.57%/ 462[M + H].sup.+, 484[M + Na].sup.+, 945[2M + H].sup.+ [00186] [00187] 71.26%/ 462[M + H].sup.+, 484[M + Na].sup.+ [00188] [00189] 35.67%/ 462[M + H].sup.+, 945[2M + Na].sup.+

[0328] Synthesis of Asymmetrical Dialkylphosphine Oxides

##STR00190##

[0329] General Procedure for Diethyl Phosphonites

[0330] Aryl bromide (0.15 mol) is dissolved in dry tetrahydrofuran (150 mL) under N.sub.2, the solution is cooled down to ?78? C. nBuLi (0.158 mol, 1.05 eq) is added dropwise to the reaction mixture at this temperature, the mixture is stirred for 1 h at ?78? C. for additional 1 hour. Magnesium bromide ethyl etherate (0.165 mol, 1.1 eq) is added at this temperature, and the mixture is allowed to reach a room temperature during 1 h. Triethylphosphite (0.1 mol, 0.66 eq) is added in one portion at room temperature, the mixture is then stirred at 50? for additional 1-3 h to complete the reaction. After removal the solvent under reduced pressure the crude materials is obtained. Further purification could be achieved by vacuum distillation.

TABLE-US-00006 Starting materials and products Starting compound(s) Product 1,4-dibromobenzene diethyl (4-bromophenyl)phosphonite 1.3-dibromobenzene diethyl (3-bromophenyl)phosphonite

[0331] General Procedure for Phosphinate

[0332] The phosphonite (55.0 mmol) is added drop-wise to a two neck round bottom flask containing alkyl iodide (1.6 mmol, neat or a solution in THF) at a rate to maintain a steady reflux. The reaction was stirred for a further 18 h, and then purified via vacuum distillation.

TABLE-US-00007 Starting materials and products Starting compound(s) Product diethyl (4- ethyl (4- bromophenyl)phosphonite bromophenyl)(methyl)phosphinate diethyl (3- ethyl (3- bromophenyl)phosphonite bromophenyl)(methyl)phosphinate diethyl (4- ethy (4-bromophenyl)(ethyl)phosphinate bromophenyl)phosphonite diethyl (3- ethyl (3-bromophenyl)(ethyl)phosphinate bromophenyl)phosphonite

[0333] General Procedure for Phosphinic Chloride

[0334] Phosphinate (35.0 mmol) is dissolved in 1,2-dichloroethane (30 ml) and phosphorus pentachloride (35.1 mmol) is added at a rate to maintain the temperature at 40? C. Following complete addition, the reaction is stirred overnight. The volatiles are removed under reduced pressure to afford a crude material, which could be further purified by vacuum distillation or re-crystallization from an appropriate solvent.

TABLE-US-00008 Starting materials and products Starting compound(s) Product ethyl (4- (4- bromophenyl)(methyl)phosphinate bromophenyl)(methyl)phosphinic chloride ethyl (3- (3- bromophenyl)(methyl)phosphinate bromophenyl)(methyl)phosphinic chloride ethyl (4- (4-bromophenyl)(ethyl)phosphinic bromophenyl)(ethyl)phosphinate chloride ethyl (3- (3-bromophenyl)(ethyl)phosphinic bromophenyl)(ethyl)phosphinate chloride

[0335] General Procedure for Alkyl (Alkyl) Phosphine Oxides

A solution of phosphinic chloride (10 mmol) in anhydrous THF (10 ml) is slowly added to Grignard solution in THF (10.5 mmol) in THF or diethyl ether. The reaction mixture is stirred under reflux for 1 h, then cooled with an ice bath and quenched with saturated aqueous ammonium chloride solution. The mixture is poured into water, acidified with diluted hydrochloric acid, extracted with chloroform. The combined extracts were washed with saturated aqueous sodium hydrocarbonate solution, brine, dried over magnesium sulfate and concentrated in vacuum to give a crude product.

[0336] Further purification could be achieved by vacuum distillation or by re-crystallization from an appropriate solvent.

TABLE-US-00009 Starting materials and products Starting compounds(s) Products (4-bromophenyl)(methyl)- phosphinic chloride [00191] (3-bromophenyl)(methyl)- phosphinic chloride [00192]

[0337] General Procedure for OLEDs with One Emission Layer (Single OLED)

[0338] General procedure for organic light-emitting diodes comprising of Examples 1 to 11 as well as of Comparative examples 1 to 3, comprising an organic semiconductive layer of formula (1) as electron transport layer and/or electron injection layer and/or n-type charge generation layer.

[0339] Bottom Emission Devices

[0340] For bottom emission devicesExamples 1 to 11 and comparative examples 1 to 3, a 15 ?/cm.sup.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.

[0341] 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) for comparative examples 1 to 3 or Biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine and 8 wt.-% of 2,2,2-(cyclopropane-1,2,3-triylidene)tris(2-(p-cyanotetrafluorophenyl)acetonitrile) for Examples 1 to 8 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) for comparative examples 1 to 3 or Biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine for examples 1 to 8 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.

[0342] Bottom Emission Devices Comprising Organic Semiconductive Layer as Electron Transport Layer (ETL)

[0343] Then the organic semiconductive layer comprising compound of formula (1) is formed by depositing the compound, also named ETL matrix compound, according to Example 1 to Example 11 and Comparative examples 1 to 3 by deposing the compound from a first deposition source directly on the EML

[0344] Further, the thickness d (in nm) of the ETL can be taken from Table 3.

[0345] An optional electron injection layer is deposited directly on top of the electron transport layer. The composition and thickness of the electron injection layer can be taken from Table 3.

[0346] Bottom Emission Devices Comprising Organic Semiconductive Layer as Electron Injection Layer (EIL)

[0347] Then the organic semiconductive layer comprising compound of formula (1) is formed by depositing the compound, also named EIL matrix compound, according to Example 1 to Example 11 and Comparative examples 1 to 3 by deposing the matrix compound from a first deposition source and the lithium organic complex or zero-valent metal dopant from a second deposition source directly on the EML

[0348] The wt.-% of the lithium organic complex for the EIL can be taken from Table 4, whereby the wt.-% amount of the matrix compound is added to 100 wt.-%, respectively. That means, that the EIL matrix compound are added in a wt.-% amount such that the given wt.-% of the lithium organic complex for the EIL and the matrix compound of the EIL are in total 100 wt.-%, based on the weight of the EIL. Further, the thickness d (in nm) of the EIL can be taken from Table 4.

[0349] The wt.-% of the zero-valent metal dopant for the EIL can be taken from Table 5, whereby the wt.-% amount of the matrix compound is added to 100 wt.-%, respectively. That means, that the EIL matrix compound are added in a wt.-% amount such that the given wt.-% of the zero-valent metal dopant for the EIL and the matrix compound of the EIL are in total 100 wt.-%, based on the weight of the EIL. Further, the thickness d (in nm) of the EIL can be taken from Table 5.

[0350] The cathode was evaporated at ultra-high vacuum of 10.sup.?7 bar. Therefore, a thermal single co-evaporation of one or several metals was performed with a rate of 0, 1 to 10 nm/s (0.01 to 1 ?/s) in order to generate a homogeneous cathode with a thickness of 5 to 1000 nm. The cathode electrode was formed from 100 nm aluminum.

[0351] 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.

[0352] The beneficial effect of inventive compounds of formula (1) on the performance of bottom emission devices can be seen in Tables 3, 4 and 5.

[0353] Top Emission Devices

[0354] For top emission devices, the anode electrode was formed from 100 nm silver on glass substrate which is prepared by the same methods as described above.

[0355] 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 130 nm. 97 wt.-% of ABH113 (Sun Fine Chemicals) as a host and 3 wt.-% of NUBD370 (Sun Fine Chemicals) as a dopant are deposited on the HTL, to form a blue-emitting EML with a thickness of 20 nm.

[0356] Top Emission Device Comprising Organic Semiconductive Layer of Compound of Formula (1)

[0357] The organic semiconductive layer comprising compound of formula (1) is deposited as described for bottom emission devices above.

[0358] The cathode electrode is formed from 13 nm magnesium (90 vol.-%) and silver (10 vol.-%) alloy, followed by 60 nm biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine (CAS 1242056-42-3).

[0359] 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. 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 15 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 the device is measured at ambient conditions (20? C.) and 15 mA/cm.sup.2, using a Keithley 2400 sourcemeter, and recorded in hours. 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.

[0360] 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/cm.sup.2.

[0361] 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 15 mA/cm.sup.2.

[0362] Technical Effect of the Invention

[0363] 1. Bottom Emission Device Comprising an Organic Semiconductive Layer Comprising Compound of Formula (1) which is Free of Dopant

[0364] In Table 3, the performance is shown of bottom emission devices with an organic semiconductive layer which is free of dopant. The organic semiconductive layer has the function of an electron transport layer (ETL) and compound of formula (I) is an ETL matrix compound. The thickness of the ETL is 36 nm.

[0365] To improve electron injection, an electron injection layer is deposited on top of the electron transport layer. In comparative example 1 and examples 1 to 3, LiQ is deposited to a thickness of 1.5 nm, see Table 3.

[0366] In comparative example 1, ETL matrix compound MX 12 is used. In matrix compound MX 12 three aryl substituents are bonded to the phosphorus atom. The operating voltage is 5.25 V and the external quantum efficiency EQE is 2.5%, see Table 3. As the efficiency is so low, the lifetime has not been measured.

##STR00193##

[0367] In Example 1 and 2, compounds of formula (1) have been tested as electron transport layer. In example 1, compound (f) is used as ETL matrix compound. The operating voltage is reduced to 4.5 V compared to comparative example 1. Additionally, the efficiency EQE is improved from 2.5 to 5.1%. A reduction in operating voltage has the benefit that the energy required to operate the OLED can be reduced. Additionally, an increase in efficiency EQE is beneficial for power consumption. The OLEDs of the present invention show a significant reduction in operating voltage and/or a significant increase in efficiency EQE which is an improvement in saving electrical energy compared to the prior art. The lifetime is 17 hours. An increase in lifetime means that the device has improved stability over time.

[0368] In example 2, compound (d) is used as ETL matrix compound. The operating voltage is reduced further to 4 V and the efficiency EQE is increased further to 5.7 V. The lifetime is also much improved, see Table 3.

[0369] In example 3, compound (c) is used as ETL matrix compound. the operating voltage is reduced further to 3.8 V and the efficiency is improved to 6.4% EQE. The lifetime is also much improved to 84 hours.

[0370] The main difference between compounds (c), (d) and (f) and MX 12 is the substitution pattern on the phosphorus atom. In MX 12, three aryl groups are bonded to the phosphorus atom, while in compound (c), (f) and compound (d), two alkyl and one aryl group are bonded to the phosphorus atom.

TABLE-US-00010 TABLE 3 Bottom emission device comprising an organic semiconductive layer comprising compound of formula (1) which is free of dopant ETL ETL EIL Voltage Effi- matrix thick- thick- at 10 ciency Life- com- ness ness mA/cm.sup.2 EQE time pound (mn) EIL (nm) (V) (%) (hours) Compar- MX 12 36 LiQ 1.5 5.25 2.5 ative example 1 Example 1 Com- 36 LiQ 1.5 4.5 5.1 17 pound (f) Example 2 Com- 36 LiQ 1.5 4.0 5.7 46 pound (d) Example 3 Com- 36 LiQ 1.5 3.8 6.4 84 pound (c)

[0371] 2. Bottom Emission Devices Comprising an Organic Semiconductive Layer Comprising Compound of Formula (1) and a Alkali Organic Complex or Alkali Halide

[0372] In Table 4. the performance is shown of bottom emission devices with an organic semiconductive layer comprising a compound of formula (1) and a lithium organic complex. The organic semiconductive layer has the function of an electron injection layer (EIL) and compound of formula (I) is an EIL matrix compound. The thickness of the EIL is 36 nm.

[0373] In comparative example 2, EIL matrix compound MX 12 is used. In matrix compound MX 12 three aryl substituents are bonded to the phosphorus atom. The EIL matrix compound is doped with 50 wt.-% LiQ which is a lithium organic complex. The operating voltage is 4.9 V and the external quantum efficiency EQE is 5.4%, see Table 4. As the operating voltage is so high, the lifetime has not been measured.

[0374] In example 4, compound (b) is used as EIL matrix compound. The matrix compound is doped with the same lithium organic complex at the same concentration as in comparative example 2.

[0375] The operating voltage is reduced from 4.9 to 4.6 V without detrimental impact on efficiency. The lifetime has not been measured.

[0376] In example 5, the same matrix compound is used as in example 4. However, a different lithium organic complex is used. Li-1 is a lithium borate complex. The concentration of the lithium borate complex is 25 wt.-%. The operating voltage is further decreased to 3.6 V without detrimental impact on efficiency. The lifetime is 10 hours.

[0377] In example 6, compound (c) is used. The same lithium organic complex is used as in example 5. The operating voltage is reduced further to 3.4 V without detrimental impact on efficiency or lifetime. Doping with lithium borate has a particularly beneficial effect on the operating voltage.

[0378] In example 7, compound (f) is used. The same lithium organic complex is used as in comparative example 2 and example 4. The operating voltage is reduced compared to comparative example 2 and example 4. Additionally, the efficiency is increased to 6.7% and the lifetime is exceptionally high at 130 hours (Table 4).

[0379] In summary, a substantial improvement in the performance of OLEDs is achieved through compounds of formula (1) doped with lithium organic complexes.

TABLE-US-00011 TABLE 4 Bottom emission devices comprising an organic semiconductive layer comprising compound of formula (1) and a lithium organic complex wt.-% Voltage EIL Lithium Lithium EIL at 10 matrix organic organic thickness mA/cm.sup.2 Efficiency Lifetime compound complex complex *.sup.1 (nm) (V) EQE (%) (hours) Comparative MX 12 LiQ 50 36 4.9 5.4 Example 2 Example 4 Compound (b) LIQ 50 36 4.6 5.3 Example 5 Compound (b) Li-1 25 36 3.6 5.5 10 Example 6 Compound (c) Li-1 25 36 3.4 5.3 9 Example 7 Compound (f) LiQ 50 36 4.3 6.7 130 *.sup.1 = the wt.-% of the matrix compound and the wt.-% of the lithium organic complex are in total 100 wt.-% based on weight of the EIL

[0380] 3. Bottom Emission Devices Comprising an Organic Semiconductive Layer Comprising Compound of Formula (1) and a Zero-Valent Metal Dopant

[0381] In Table 5, the performance is shown of bottom emission devices with an organic semiconductive layer comprising a compound of formula (1) and a zero-valent metal dopant. The organic semiconductive layer has the function of an electron injection layer (EIL) and compound of formula (I) is an EIL matrix compound. The thickness of the EIL is 36 nm.

[0382] In comparative example 3, EIL matrix compound MX 12 is used. In matrix compound MX 12 three aryl substituents are bonded to the phosphorus atom. The EIL matrix compound is doped with 5 wt.-% Mg. The operating voltage is 3.8 V and the external quantum efficiency EQE is 4.8%, see Table 5. The lifetime is 3 hours.

[0383] In example 8, compound (d) is used as EIL matrix compound. The matrix compound is doped with Mg at the same concentration as in comparative example 3. The operating voltage is reduced from 3.8 to 3.55 V, the efficiency is improved from 4.8 to 5.5% and the lifetime is improved significantly from 3 to 56 hours.

[0384] In example 9, compound (c) is used as EIL matrix compound. The matrix compound is doped with Mg at the same concentration as in comparative example 3. The operating voltage is reduced from 3.8 to 3.5 V, the efficiency is improved from 4.8 to 6.1% and the lifetime is improved significantly from 3 to 33 hours.

[0385] In example 10, compound (c) is used as EIL matrix compound. The matrix compound is doped with Yb at the same concentration as in comparative example 3. The operating voltage is reduced from 3.8 to 3.7 V, the efficiency is improved from 4.8 to 6.7% and the lifetime is improved significantly from 3 to 53 hours.

[0386] In example 11, compound (d) is used as EIL matrix compound. The operating voltage is 3.7 V. The efficiency is increased further to 6.9% EQE and the lifetime is very high at 52 hours.

[0387] In summary, a beneficial effect is obtained when using compounds of formula (1) doped with zero-valent metal as electron injection layer.

TABLE-US-00012 TABLE 5 Bottom emission devices comprising an organic semiconductive layer comprising compound of formula (1) and a zero-valent metal dopant Voltage EIL wt.-% EIL at 10 matrix Metal Metal thickness mA/cm.sup.2 Efficiency Lifetime compound dopant dopant *.sup.1 (nm) (V) EQE (%) (hours) Comparative MX 12 Mg 5 36 3.8 4.8 3 example 3 Example 8 Compound (d) Mg 5 36 3.55 5.5 56 Example 9 Compound (c) Mg 5 36 3.5 6.1 33 Example 10 Compound (c) Yb 5 36 3.7 6.7 53 Example 11 Compound (d) Yb 5 36 3.7 6.9 52 *.sup.1 = the wt.-% of the matrix compound and the wt.-% of the Metal dopant are in total 100 wt.-% based on weight of the EIL

[0388] 4. n-Type Charge Generation Layer in Electron-Only Device

[0389] Electron-only devices were fabricated comprising an organic semiconductive layer comprising a compound of formula (1) and a metal dopant as n-type charge generation layer (n-CGL), see example 12 to 17 in Table 6.

[0390] A glass substrate 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. Then the anode electrode was formed from 100 nm aluminium on the glass substrate.

[0391] Then, 90 wt.-% of Biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine and 10 wt.-% of 2,2,2-(cyclopropane-1,2,3-triylidene)tris(2-(p-cyanotetrafluorophenyl)acetonitrile) was vacuum deposited on the electrode, to form a HIL having a thickness of 10 nm.

[0392] Then, an electron transport layer was formed from 2,4-diphenyl-6-(3-(triphenylen-2-yl)-[1,1-biphenyl]-3-yl)-1,3,5-triazine (CAS 1638271-85-8) on the HIL having a thickness of 30 nm.

[0393] Then, the organic semiconductive layer comprising 95 wt.-% compound of formula (1) and 5 wt.-% Yb is deposited on the electron transport layer to form an n-type charge generation layer (n-CGL) having a thickness of 50 nm, see Table 6.

[0394] Then, a p-type charge generation layer (p-CGL) consisting of 90 wt.-% of Biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine and 10 wt.-% of 2,2,2-(cyclopropane-1,2,3-triylidene)tris(2-(p-cyanotetrafluorophenyl)acetonitrile) was vacuum deposited on the n-type charge generation layer, to form a p-type charge generation layer having a thickness of 10 nm.

[0395] Then, Biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine was deposited on the p-CGL to form a hole transport layer (HTL) having a thickness of 30 nm.

[0396] Ag is vacuum deposited on the HTL to form a cathode having a thickness of 100 nm.

[0397] Low operating voltage is obtained in electron-only devices, see Table 6.

TABLE-US-00013 TABLE 6 Electron-only devices with n-type charge generation layer comprising an organic semiconductive layer comprising compound of formula (1) and a zero-valent metal dopant n-CGL matrix Metal wt.-% Metal n-CGL thickness Voltage at 10 compound dopant dopant*.sup.1 (nm) mA/cm.sup.2 (V) Example 12 Compound (c) Yb 5 50 4.5 Example 13 Compound (i) Yb 5 50 4.5 Example 14 Compound (k) Yb 5 50 4.5 Example 15 Compound (o) Yb 5 50 4.45 Example 16 Compound (p) Yb 5 50 4.45 *.sup.1= the wt.-% of the matrix compound and the wt.-% of the Metal dopant are in total 100 wt.-% based on weight of the n-CGL

[0398] 5. Tandem OLED Device

[0399] General Procedure for OLEDs with Two Emission Layers (Tandem OLED)

[0400] For bottom emission devices, a 15 ?/cm.sup.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.

[0401] For top emission devices, the anode electrode was formed from 100 nm silver on glass which was prepared by the same methods as described above.

[0402] 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) was 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 was vacuum deposited on the HIL, to form a HTL having a thickness of 135 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 25 nm.

[0403] Then, an optional hole blocking layer is deposited directly on the emission layer.

[0404] Then, the organic semiconductive layer comprising compound of formula (1) is deposited on the emission layer or hole blocking layer, if present. If the organic semiconductive layer is the n-type charge generation layer, a p-type charge generation layer consisting of 92 wt.-% of Biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine and 8 wt.-% of 2,2,2-(cyclopropane-1,2,3-triylidene)tris(2-(p-cyanotetrafluorophenyl)acetonitrile) was vacuum deposited on the n-type charge generation layer, to form a p-type charge generation layer having a thickness of 10 nm.

[0405] If the organic semiconductive layer is the electron transport layer, a n-type charge generation layer of compound of formula (X) is deposited on the electron transport layer, followed by the p-type charge generation layer comprising compound of formula (Y).

[0406] Then Biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine was vacuum deposited on the p-type charge generation layer, to form a HTL having a thickness of 30 nm.

[0407] Then N3,N3-di([1,1-biphenyl]-4-yl)-N3,N3-dimesityl-[1,1-biphenyl]-3,3-diamine (CAS 1639784-29-4) was vacuum deposited on the HTL to form a triplet control layer having a thickness of 15 nm. 90 wt.-% EL-GHB914S (Samsung SDI) as a host and 10 wt.-% EL-GD0108S (Samsung SDI) as phosphorescent green emitter are vacuum deposited on the triplet control layer, to form a green emitting EML having a thickness of 30 nm. MX 11 or compound of formula (1) is vacuum deposited on the green emitting EML, to form an electron transport layer (ETL) having a thickness of 35 nm. LiQ is vacuum deposited on the ETL to form an electron injection layer (EIL) having a thickness of 2 nm. Aluminium is vacuum deposited on the EIL to form a cathode having a thickness of 100 nm.

[0408] Top-emitting tandem OLED devices were fabricated comprising an organic semiconductive layer comprising a compound of formula (1) and a metal dopant as n-type charge generation layer (n-CGL), see comparative example 4 and example 17 in Table 7.

[0409] A glass substrate 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. The anode electrode was formed from 100 nm silver on the glass substrate.

[0410] 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) was 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 was vacuum deposited on the HIL, to form a HTL having a thickness of 115 nm.

[0411] Then, N,N-bis(4-(dibenzo[b,d]furan-4-yl)phenyl)-[1,1:4,1-terphenyl]-4-amine (CAS 1198399-61-9) was vacuum deposited on the HTL to form a first electron blocking layer (EBL) with a thickness of 10 nm.

[0412] 97 wt.-% of ABH113 (Sun Fine Chemicals) as a host and 3 wt.-% of BD200 (Sun Fine Chemicals) as a dopant was vacuum deposited on the EBL, to form a first blue-emitting EML with a thickness of 20 nm.

[0413] Then, 2,4-diphenyl-6-(3-(triphenylen-2-yl)-[1,1-biphenyl]-3-yl)-1,3,5-triazine (CAS 1638271-85-8) was vacuum deposited on the first blue-emitting EML to form a first electron transporting layer (ETL) having a thickness of 25 nm.

[0414] Then, the organic semiconductive layer comprising 99 vol.-% compound of formula (1) and 1 vol.-% Yb was vacuum deposited on the first electron transporting layer to form a n-CGL having a thickness of 10 nm, see example 17 in Table 7. In comparative example 4, 99 vol.-% 1,3-bis(9-phenyl-1,10-phenanthrolin-2-yl)benzene MX 13 (CAS 721969-94-4) and 1 vol.-% Yb was vacuum deposited on the first electron transporting layer to form a n-CGL having a thickness of 10 nm, see Table 7.

[0415] Then, a p-type charge generation layer consisting of 90 wt.-% of Biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine and 10 wt.-% of 2,2,2-(cyclopropane-1,2,3-triylidene)tris(2-(p-cyanotetrafluorophenyl)acetonitrile) was vacuum deposited on the n-type charge generation layer, to form a p-type charge generation layer having a thickness of 10 nm.

[0416] Then, Biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine was vacuum deposited on the p-type charge generation layer, to form a HTL having a thickness of 50 nm.

[0417] Then, N,N-bis(4-(dibenzo[b,d]furan-4-yl)phenyl)-[1,1:4,1-terphenyl]-4-amine (CAS 1198399-61-9) was vacuum deposited on the HTL to form a second electron blocking layer (EBL) with a thickness of 10 nm.

[0418] 97 wt.-% of ABH113 (Sun Fine Chemicals) as a host and 3 wt.-% of BD200 (Sun Fine Chemicals) as a dopant were deposited on the HTL, to form a second blue-emitting EML with a thickness of 20 nm.

[0419] Then, 2,4-diphenyl-6-(3-(triphenylen-2-yl)-[1,1-biphenyl]-3-yl)-1,3,5-triazine (CAS 1638271-85-8) was vacuum deposited on the second blue-emitting EML to form a second electron transporting layer (ETL) having a thickness of 25 nm.

[0420] Then, 95 wt.-% 3-Phenyl-3H-benzo[b]dinaphtho[2,1-d:1,2-f]phosphepine-3-oxide (CAS 597578-38-6) was vacuum deposited on the second electron transporting layer to form an electron injection layer (EIL) having a thickness of 10 nm.

[0421] Ag was vacuum deposited on the EIL to form a cathode having a thickness of 11 nm.

[0422] Then, Biphenyl-4-yl(9,9-diphenyl-9H-fluoren-2-yl)-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-amine was vacuum deposited on the cathode to form a capping layer having a thickness of 60 nm.

[0423] 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.

[0424] The performance is assessed as described in the general procedure for single OLEDs. Operating voltage, external quantum efficiency and/or lifetime are improved compared to tandem OLEDs without an organic semiconductive layer comprising compound of formula (1).

[0425] In Table 7, results are shown for top-emitting tandem OLED devices comprising an n-type charge generation layer comprising a matrix compound and Yb dopant.

[0426] In comparative example 4, the n-CGL comprises MX 13 and Yb dopant. MX 13 comprises two phenanthroline groups. The operating voltage is 8.3 V and the external quantum efficiency is 21.6%.

[0427] In example 17, the n-CGL comprises compound (c) and Yb dopant. The operating voltage is reduced to 8 V and the external quantum efficiency is increased substantially to 25%.

[0428] In summary, a substantial improvement in performance may be obtained when the n-type charge generation layer comprises a compound of formula (1).

TABLE-US-00014 TABLE 7 Top emission tandem OLED comprising an n-type charge generation layer organic semiconductive layer comprising compound of formula (1) and a zero-valent metal dopant Voltage Efficiency n-CGL vol.-% n-CGL at 10 EQE at 10 matrix Metal Metal thickness mA/cm.sup.2 mA/cm.sup.2 compound dopant dopant *.sup.1 (nm) (V) (%) Comparative MX 13 Yb 1 10 8.3 21.6 example 4 Example 17 Compound (c) Yb 1 10 8 25 *.sup.1 = the vol.-% of the matrix compound and the wt.-% of the Metal dopant are in total 100 wt.-% based on weight of the n-CGL

[0429] From the foregoing detailed description 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.