LIGANDS FOR NANO-SIZED MATERIALS

Abstract

The present invention relates to a compound suitable as ligand for binding to the surface of a semiconductor nanoparticle, said compound comprising an anchor group, a linker group and an organic functional group; a semiconductor nanoparticle have said ligand attached to the outermost particle surface; a composition, a formulation and a process for the preparation of said semiconductor nanoparticle; and an electronic device.

Claims

1. Compound comprising in the given order an anchor group, AG, being capable of binding to the surface of a semiconductor nanoparticle, followed by an electronically inert and conjugating interrupting linker group, L, followed by an organic functional group, FG and wherein the compound has a molecular weight of 1000 g/mol or less.

2. The compound according to claim 1, characterized in that the anchor group, AG, is selected from the group consisting of thiols or salts thereof, phosphonic acids or salts thereof, carboxylic acids or salts thereof, selenols or salts thereof, sulfinic acids or salts thereof, mercaptoesters or salts thereof, carbodithioic acids or salts thereof, boronic acids or salts thereof, amines and phosphines.

3. The compound according to claim 1, characterized in that the linker group, L, is selected from the group consisting of a straight-chain alkylene group having 1 to 20 C atoms, or a cyclic or branched alkylene group having 3 to 20 C atoms, wherein one or more non adjacent methylene groups can be replaced by —O—, —S—, —C(═O)O—, —C(═S)S—, aromatic rings or heteroaromatic rings.

4. The compound according to claim 1, characterized in that the organic functional group, FG, is selected from the group consisting of aromatic ring systems having 6 to 60 aromatic ring atoms or heteroaromatic ring systems having 5 to 60 aromatic ring atoms, both of which may optionally be further substituted.

5. The compound according to claim 1, characterized in that the organic functional group, FG, is selected from the group consisting of electron injecting groups, electron transporting groups, hole blocking groups, n-dopant-groups, host-groups, matrix groups, wide band gap groups, fluorescent emitter groups, delayed fluorescent groups, phosphorescent groups, electron blocking groups, hole transporting groups, hole injecting groups or p-dopant groups.

6. The compound according to claim 1, characterized in that the compound has the general formula (1) ##STR00144## wherein the following applies to the symbols and indices wherein X is the anchor group, AG, and wherein X is selected from —SH, —C(═O)OH, —NH.sub.2, —P(═O)(OH)(OH), —SeH, —P(R′R″), —S.sup.−Y.sup.+, —S(═O)OH, —S(═O)O.sup.−Y.sup.+, —C(═O)O.sup.−Y.sup.+, —OC(═O)R′″SH, —OC(═O)R′″S.sup.−Y.sup.+, —P(═O)(OH)(O.sup.−Y+), —Se.sup.−Y.sup.+, —C(═S)SH, —C(═S)S.sup.−Y.sup.+, —B(OH).sub.2, —B(OH)O.sup.−Y.sup.+, —B(O.sup.−Y.sup.+).sub.2, —B(O.sup.−).sub.2Z.sup.2+, —P(═O)(O.sup.−Y.sup.+)(O.sup.−Y.sup.+) or —P(═O)(O.sup.−)(O.sup.−)Z.sup.2+; Y.sup.+ is selected from Na.sup.+, K.sup.+, Li.sup.+, ½ Cd.sup.2+, ½ Zn.sup.2+, ½ Mg.sup.2+, 1.2 Ca.sup.2+, ½ Sr.sup.2+, ⅓ In.sup.3+, ⅓ Ga.sup.3+; Z.sup.2+ is Cd.sup.2+, Zn.sup.2+, Mg.sup.2+, Ca.sup.2+, Sr.sup.2+; R′,R″ are, identically or differently, selected from H, linear or branched alkyl groups having 1 to 20 C atoms; R′″ is selected from linear or branched alkyl groups having 1 to 10 C atoms; n is an integer from 0 to 20.

7. The compound according to claim 1, characterized in that the group FG is an electron transporting group.

8. The compound according to claim 1, characterized in that the group FG is an electron transporting group selected from triazines, pyrimidines, pyridines, pyrazines, pyrazoles, pyridazines, quinolines, isoquinolines, quinoxalines, quinazolines, tiazoles, benzothiazoles, oxazoles, benzoxazoles, benzimidazoles, oxadiazoles, phenoxazines, lactames, phenanthrolines and dibenzofurans.

9. The compound according to claim 1, characterized in that the group FG is an electron transporting group selected from the following groups ##STR00145## wherein the dashed line represents the bonding position to the linker group; Q′ is selected, identically or differently at each occurrence, from CR.sup.1 and N; Q″ is selected from NR.sup.1, O and S; R.sup.1 is, identically or differently at each occurrence, selected from H, D, F, Cl, Br, I, N(R.sup.2).sub.2, CN, NO.sub.2, Si(R.sup.2).sub.3, B(OR.sup.2).sub.2, C(═O)R.sup.2, P(═O)(R.sup.2).sub.2, S(═O)R.sup.2, S(═O).sub.2R.sup.2, OSO.sub.2R.sup.2, a straight-chain alkyl, alkoxy or thioalkoxy group having 1 to 40 carbon atoms or a straight-chain alkenyl or alkynyl group having 2 to 40 carbon atoms or a branched or cyclic alkyl, alkenyl, alkynyl, alkoxy, alkylalkoxy or thioalkoxy group having 3 to 40 carbon atoms, each of which may be substituted by one or more R.sup.2 radicals, where one or more nonadjacent CH.sub.2 groups may be replaced by R.sup.2C═CR.sup.2, C≡C, Si(R.sup.2).sub.2, Ge(R.sup.2).sub.2, Sn(R.sup.2).sub.2, C═O, C═S, C═Se, C═NR.sup.2, P(═O)(R.sup.2), SO, SO.sub.2, NR.sup.2, O, S or CONR.sup.2 and where one or more hydrogen atoms may be replaced by D, F, Cl, Br, I, CN or NO.sub.2, or an aromatic or heteroaromatic ring system which has 5 to 60 aromatic ring atoms and may be substituted in each case by one or more R.sup.2 radicals, or an aryloxy, arylalkyl or heteroaryloxy group which has 5 to 60 aromatic ring atoms and may be substituted by one or more R.sup.2 radicals, or a combination of two or more of these groups or a crosslinkable Q group; wherein two or more adjacent R.sup.1 radicals together may form a mono- or polycyclic, aliphatic or aromatic ring system, wherein it is preferred that two or more adjacent R.sup.1 radicals together do not form a mono- or polycyclic, aliphatic or aromatic ring system; R.sup.2 is the same or different at each instance and is H, D, F, Cl, Br, I, N(R.sup.3).sub.2, CN, NO.sub.2, Si(R.sup.3).sub.3, B(OR.sup.3).sub.2, C(═O)R.sup.3, P(═O)(R.sup.3).sub.2, S(═O)R.sup.3, S(═O).sub.2R.sup.3, OSO.sub.2R.sup.3, a straight-chain alkyl, alkoxy or thioalkoxy group having 1 to 40 carbon atoms or a straight-chain alkenyl or alkynyl group having 2 to 40 carbon atoms or a branched or cyclic alkyl, alkenyl, alkynyl, alkoxy, alkylalkoxy or thioalkoxy group having 3 to 40 carbon atoms, each of which may be substituted by one or more R.sup.3 radicals, where one or more nonadjacent CH.sub.2 groups may be replaced by R.sup.3C═CR.sup.3, C≡C, Si(R.sup.3).sub.2, Ge(R.sup.3).sub.2, Sn(R.sup.3).sub.2, C═O, C═S, C═Se, C═NR.sup.3, P(═O)(R.sup.3), SO, SO.sub.2, NR.sup.3, O, S or CONR.sup.3 and where one or more hydrogen atoms may be replaced by D, F, Cl, Br, I, CN or NO.sub.2, or an aromatic or heteroaromatic ring system which has 5 to 60 aromatic ring atoms and may be substituted in each case by one or more R.sup.3 radicals, or an aryloxy, arylalkyl or heteroaryloxy group which has 5 to 60 aromatic ring atoms and may be substituted by one or more R.sup.3 radicals, or a combination of two or more of these groups; wherein two or more adjacent R.sup.2 radicals together may form a mono- or polycyclic, aliphatic or aromatic ring system; R.sup.3 is the same or different at each instance and is H, D, F or an aliphatic, aromatic and/or heteroaromatic hydrocarbyl radical having 1 to 20 carbon atoms, in which one or more hydrogen atoms may also be replaced by F; wherein two or more R.sup.3 substituents together may also form a mono- or polycyclic, aliphatic or aromatic ring system, and wherein at least one Q′ is N.

10. The compound according to claim 1, characterized in that the group FG is a hole transporting group

11. The compound according to claim 10, characterized in that the group FG is a hole transporting group selected from carbazoles, biscarbazoles, indenocarbazoles, indolocarbazoles, amines, triarylamines, fluoreneamines and spirobifluoreneamines.

12. The compound according to claim 10, characterized in that the hole transporting group is a group ##STR00146##  wherein  Ar.sup.L is, identically or differently on each occurrence, selected from aromatic ring systems having 6 to 40 aromatic ring atoms, which may be substituted by one or more radicals R.sup.4, and heteroaromatic ring systems having 5 to 40 aromatic ring atoms, which may be substituted by one or more radicals R.sup.4;  Ar.sup.1 is, identically or differently on each occurrence, selected from aromatic ring systems having 6 to 40 aromatic ring atoms, which may be substituted by one or more radicals R.sup.4, and heteroaromatic ring systems having 5 to 40 aromatic ring atoms, which may be substituted by one or more radicals R.sup.4;  E is a single bond or is a divalent group selected from —C(R.sup.4).sub.2—, —N(R.sup.4)—, —O—, and —S—; and  k is on each occurrence, identically or differently, 0 or 1; where in the case of k=0, the group Ar.sup.L is not present and the nitrogen atom and the linker group are directly connected;  m is on each occurrence, identically or differently, 0 or 1, where in the case of m=0, the group E is not present and the groups Ar.sup.1 are not connected; R.sup.4 is, identically or differently at each occurrence, selected from H, D, F, C(═O)R.sup.5, CN, Si(R.sup.5).sub.3, N(R.sup.5).sub.2, P(═O)(R.sup.5).sub.2, OR.sup.5, S(═O)R.sup.5, S(═O).sub.2R.sup.5, straight-chain alkyl or alkoxy groups having 1 to 20 C atoms, branched or cyclic alkyl or alkoxy groups having 3 to 20 C atoms, alkenyl or alkynyl groups having 2 to 20 C atoms, aromatic ring systems having 6 to 40 aromatic ring atoms, and heteroaromatic ring systems having 5 to 40 aromatic ring atoms; where two or more radicals R.sup.4 may be connected to each other to form a ring; where the said alkyl, alkoxy, alkenyl and alkynyl groups and the said aromatic and heteroaromatic ring systems may in each case be substituted by one or more radicals R.sup.5, and where one or more CH.sub.2 groups in the said alkyl, alkoxy, alkenyl and alkynyl groups may in each case be replaced by —R.sup.5C═CR.sup.5—, —C≡C—, Si(R.sup.5).sub.2, C═O, C═NR.sup.5, —C(═O)O—, —C(═O)NR.sup.5—, NR.sup.5, P(═O)(R.sup.5), —O—, —S—, SO or SO.sub.2; R.sup.5 is, identically or differently at each occurrence, selected from H, D, F, C(═O)R.sup.6, CN, Si(R.sup.6).sub.3, N(R.sup.6).sub.2, P(═O)(R.sup.6).sub.2, OR.sup.6, S(═O)R.sup.6, S(═O).sub.2R.sup.6, straight-chain alkyl or alkoxy groups having 1 to 20 C atoms, branched or cyclic alkyl or alkoxy groups having 3 to 20 C atoms, alkenyl or alkynyl groups having 2 to 20 C atoms, aromatic ring systems having 6 to 40 aromatic ring atoms, and heteroaromatic ring systems having 5 to 40 aromatic ring atoms; where two or more radicals R.sup.5 may be connected to each other to form a ring; where the said alkyl, alkoxy, alkenyl and alkynyl groups and the said aromatic and heteroaromatic ring systems may in each case be substituted by one or more radicals R.sup.6, and where one or more CH.sub.2 groups in the said alkyl, alkoxy, alkenyl and alkynyl groups may in each case be replaced by —R.sup.6C═CR.sup.6—, —C≡C—, Si(R.sup.6).sub.2, C═O, C═NR.sup.6, —C(═O)O—, —C(═O)NR.sup.6—, NR.sup.6, P(═O)(R.sup.6), —O—, —S—, SO or SO.sub.2; and R.sup.6 is selected, identically or differently at each occurrence, from H, D, F, CN, alkyl groups having 1 to 20 C atoms, aromatic ring systems having 6 to 40 C atoms, and heteroaromatic ring systems having 5 to 40 aromatic ring atoms; where two or more radicals R.sup.6 may be connected to each other to form a ring; and where the said alkyl groups, aromatic ring systems and heteroaromatic ring systems may be substituted by F and CN.

13. Semiconductor nanoparticle comprising a core, one or more shell layers and at least one ligand that is attached to the outermost surface of the one or more shell layers, characterized in that the at least one ligand is selected from the compounds according to claim 1.

14. Semiconductor nanoparticle comprising a core, one or more shell layers and at least one ligand that is attached to the outermost surface of the one or more shell layers, characterized in that the semiconductor nanoparticle comprises at least two different ligands, preferably exactly two different ligands, wherein the ligands are selected from the compounds according to claim 1.

15. The semiconductor nanoparticle according to claim 14, characterized in that the semiconductor nanoparticle comprises a first ligand and a second ligand, and wherein the first ligand comprises an organic functional group selected from an electron transporting group and wherein the second ligand comprises an organic functional group selected from a hole transporting group.

16. Composition comprising at least one first semiconductor nanoparticle according to claim 13 and at least one second semiconductor nanoparticle, or comprising said at least one first semiconductor nanoparticle and at least one further organic functional material selected from electron injecting materials, electron transporting materials, hole blocking materials, n-dopants, host materials, matrix materials, wide band gap materials, fluorescent emitter materials, delayed fluorescent materials, phosphorescent emitter materials, electron blocking materials, hole transporting materials, hole injecting materials and p-dopants.

17. Composition comprising at least one first semiconductor nanoparticle according to claim 13, at least one second semiconductor nanoparticle and at least one further organic functional material selected from electron injecting materials, electron transporting materials, hole blocking materials, n-dopants, host materials, matrix materials, wide band gap materials, fluorescent emitter materials, delayed fluorescent materials, phosphorescent emitter materials, electron blocking materials, hole transport materials, hole injecting materials and p-dopants.

18. Composition comprising at least one first semiconductor nanoparticle and at least one second semiconductor nanoparticle, each of said nanoparticles being according to claim 13, and wherein the at least one second semiconductor nanoparticle and the at least one first semiconductor nanoparticle differ from each other.

19. The composition according to claim 18, characterized in that the at least one first semiconductor nanoparticle comprises at least one ligand attached to its outermost surface which comprises a delayed fluorescent group, and wherein the at least one second semiconductor nanoparticle comprises at least one ligand attached to its outermost surface which comprises a hole transporting group or an electron transporting group.

20. The composition according to claim 18, characterized in that the at least one first semiconductor nanoparticle comprises at least one ligand attached to its outermost surface which comprises a phosphorescent group, and wherein the at least one second semiconductor nanoparticle comprises at least one ligand attached to its outermost surface which comprises a hole transporting group or an electron transporting group.

21. Formulation comprising a compound according to claim 1; or a semiconductor nanoparticle comprising a core, one or more shell layers and at least one ligand that is attached to the outermost surface of the one or more shell layers, characterized in that the at least one ligand is selected from said compound; or a composition comprising said semiconductor nanoparticle and at least one second semiconductor nanoparticle, or comprising semiconductor nanoparticle and at least one further organic functional material selected from electron injecting materials, electron transporting materials, hole blocking materials, n-dopants, host materials, matrix materials, wide band gap materials, fluorescent emitter materials, delayed fluorescent materials, phosphorescent emitter materials, electron blocking materials, hole transporting materials, hole injecting materials and p-dopants; and at least one solvent.

22. Method for the preparation of a semiconductor nanoparticle according to claim 13, characterized in that a semiconductor nanoparticle comprising a core and one or more shell layers is provided into a solvent together with said compound to get a mixture.

23. Semiconductor nanoparticle obtained by a method according to claim 22.

24. Electronic device comprising at least one semiconductor nanoparticle according to claim 13 or a composition comprising said at least one first semiconductor nanoparticle and at least one second semiconductor nanoparticle, or comprising said at least one first semiconductor nanoparticle and at least one further organic functional material selected from electron injecting materials, electron transporting materials, hole blocking materials, n-dopants, host materials, matrix materials, wide band gap materials, fluorescent emitter materials, delayed fluorescent materials, phosphorescent emitter materials, electron blocking materials, hole transporting materials, hold injecting materials and p-dopants.

25. The electronic device according to claim 24, characterized in that the device is an electroluminescent device.

26. The electronic device according to claim 24, characterized in that the device is an electroluminescent device that comprises the semiconductor nanoparticle or the composition in the emissive layer.

Description

EXAMPLES

Working Example 1—Preparation of Compound (1)

[0240] ##STR00132##

1. Biphenyl-4-ylmethyl Phosphonic Acid Diethyl Ester

[0241] 2.3 g of 4-phenylbenzyl chloride (98%, Sigma-Aldrich) is dissolved in 48.52 g of triethylphosphite (98%, Sigma-Aldrich) in a 100 mL, 3-neck round bottom flask, connected to a condenser, under argon atmosphere. The system is heated to 160° C. for 26 hours. The product formed is then separated by column chromatography using silica as adsorbent and ethylacetate and heptane as eluents.

2. Biphenyl-4-ylmethyl Phosphonic Acid (Compound (1))

[0242] 2.0 g of the above obtained product, biphenyl-4-ylmethyl phosphonic acid diethyl ester (96%, determined by gas chromatography-mass spectroscopy (GCMS) on commercially available equipment (HP 6890 Series, 5973 detector)) is mixed with 3.05 g of bromotrimethylsilane in 20 mL of dichloromethane in a 100 mL, 3-neck round bottom flask, connected to a condenser, under argon atmosphere. The mixture is mixed for 16 hours at room temperature. Then the solvent is evaporated using a rotating evaporator. The dried residue is dissolved in methanol (10% water, Sigma Aldrich) and mixed for 16 hours at room temperature, under argon. The suspension is filtrated over a paper filter and washed twice with methanol to obtain the product (yield: 62%).

Working Example 2—Preparation of Compound (2)

[0243] ##STR00133##

1. Bis-biphenyl-4-yl-[4-(3-chloro-propyl)-phenyl]-amine

[0244] In a glove box, 6.48 mL of tert-butyllithium (t-BuLi), 1.7 M solution in pentane (Sigma-Aldrich), is put in a dropping funnel. 2.5 g of bis-biphenyl-4-yl-(4-bromo-phenyl)-amine (Merck) is dissolved in dried tetrahydrofuran (THF) in a 100 mL 3-neck flask and then cooled down to −78° C. using a dry ice bath (Aceton). The dropping funnel with t-BuLi is taken out from glove box and connected to the flask. The t-BuLi is slowly dropped directly into the solution. Afterwards the funnel is carefully rinsed with dry THF. The solution is stirred for 1 hour at −78° C.

[0245] Then, 0.62 mL of 1-bromo-3-chloropropan is slowly added with an argon-flushed syringe to the reaction. The solution is let to heat back to room temperature and then further stirred overnight under argon. Afterwards, the mixture is cooled down again to 0° C. in an ice bath and 10 mL H.sub.2O are slowly added with a syringe. Afterwards 5 mL 1M HCl are slowly added. Additional 5 mL 1M HCl are added after the solution became greenish. The ice bath is removed and the mixture is stirred until it reaches room temperature (RT). The reaction product has two phases. The organic phase is separated and the aqueous phase is extracted with dichloromethane (3×15 mL) and dried with MgSO.sub.4.

2. 3-[4-(Bis-biphenyl-4-yl-amino)-phenyl]propylpphosphonic Acid Diethyl Ester

[0246] 1.34 g bis-biphenyl-4-yl-[4-(3-chloro-propyl)-phenyl]-amine (97%) are mixed with 50 mL TEP in an one neck flask and stirred for 72 hours at 160° C. under argon.

3. {3-[4-(Bis-biphenyl-4-yl-amino)-phenyl]-propyl}-phosphonic Acid (Compound (2))

[0247] 0.77 g of 3-[4-(Bis-biphenyl-4-yl-amino)-phenyl]-propyl}-phosphonic acid diethyl ester are dissolved in 20 mL dichlomethane and mixed with 0.63 g (0.55 mL) bromotrimethyl silane (3 eq) under argon and stirred at room temperature for 12 hours. Methanol (10% H.sub.2O) is added directly to the solution, which becomes whitish. The mixture is stirred at room temperature under argon overnight. Afterwards, the mixture is evaporated and a yellowish gel is formed. The gel is recrystallized in 5 mL acetonitrile, to obtain a white slightly yellowish wax and a yellowish supernatant. The supernatant is removed and the wax washed twice with little amounts of acetonitrile. The wax is recrystallized in 3 mL ethanol. A white wax is received. 5 mL heptane are added and the wax is resuspended at room temperature, filtrated (washed 2× with heptane) and dried in a vacuum chamber. A white slightly greenish solid is received (yield: 38%).

[0248] The synthesis of further compounds (3), (4), (6) and (7)—as shown in Table 2 below—is carried out analogously:

TABLE-US-00002 TABLE 2 com- pound Product Yield (3) [00134] 70% (4) [00135] 35% (6) [00136] 65% (7) [00137] 67% (31) [00138] 80% (33) [00139] 30% (35) [00140] 80%

Working Example 3—Preparation of Semiconductor Nanoparticle

[0249] InP/ZnS core/shell nanoparticles were synthesized in a similar method as described in: Hussain et. al. ChemPhysChem, 2009, 10, 1466-1470 5 mL of a InP/ZnS core/shell nanoparticles (PL emission peak 625 nm) containing solution (50 mg/mL in toluene) are mixed with 0.25 g of a replacing surface ligand (i.e., compound (2) of working example 2) and stirred overnight at 50° C. under argon atmosphere. The mixture is then transferred into a centrifuge vial and 5 mL dried methanol is added. After that, the mixture is centrifuged at 4000 rpm for 5 minutes under argon. Afterwards, the colorless supernatant is removed and the red precipitation is suspended in 5 mL dried toluene.

[0250] Similar procedures can be used for the other ligands according to the invention. Quantities of the added ligand are calculated based on molar amounts.

Working Example 4—Fabrication of Solution Processed OLED (Device E1)

[0251] The production of solution-based OLEDs has already been described many times in the literature, for example in WO 2004/037887 and WO 2010/097155. The process is adapted to the circumstances described below (layer-thickness variation, materials).

[0252] The inventive material combinations are used in the following layer sequence: [0253] substrate, [0254] ITO (50 nm), [0255] Buffer (20 nm), [0256] hole transport layer (20 nm), [0257] emission layer (EML) (30 nm), [0258] electron-transport layer (ETL) (50 nm), [0259] electron injection layer (EIL) (3 nm), [0260] cathode (Al) (100 nm).

[0261] Glass plates coated with structured ITO (indium tin oxide) in a thickness of 50 nm serve as substrate. These are coated with the buffer (PEDOT) Clevios P VP Al 4083 (Heraeus Clevios GmbH, Leverkusen) by spin coating. The spin coating of the buffer is carried out from water in air. The layer is subsequently dried by heating at 180° C. for 10 minutes. The hole transport layers and the emission layers are applied to the glass plates coated in this way.

[0262] For the hole-transport layer, the polymer of the structure shown in Table 3 is used, which is synthesised in accordance with WO 2010/097155. The polymer is dissolved in toluene, so that the solution has a solid content of about 5 g/L, in order to prepare a 20 nm thick layer. The layer is applied by spin coating in an argon atmosphere, and dried by heating at 220° C. for 30 min.

[0263] For the emission layer, red light emitting InP/ZnS nanoparticles according to the invention, that is, quantum dots having attach to their surface ligands according to the invention, are used, which are dissolved in toluene. The solids content of such solutions is about 15 mg/mL, in order to prepare a 30 nm thick layer. The layer is applied by spin coating in an argon atmosphere, and dried by heating at 120° C. for 10 minutes.

TABLE-US-00003 TABLE 3 Structural formulae of the additional materials used for the solution processed layers in OLEDs [00141] HTL

[0264] The materials for the electron-transport layer and the electron injection layer are likewise applied by thermal vapour deposition in a vacuum chamber and are shown in Table 4. The electron-transport layer consists of the material ETL and the electron injection layer consists of EIL. The cathode is formed by the thermal evaporation of an aluminium layer with a thickness of 100 nm.

TABLE-US-00004 TABLE 4 Chemical structures of the materials used for thermally evaporated layers in OLEDs [00142] ETL [00143] EIL

Comparative Example 1—Fabrication of Solution Processed OLED (Device V1)

[0265] A solution-based OLED is prepared in the same way as described in working example 4 above, using the same compounds/materials except that state-of-the-art red light emitting semiconductor nanoparticles, that is, QDs covered with common alkyl ligands, are used for preparation of the emissive layer.

Working Example 5—Device Characterization

[0266] The OLEDs are characterised by standard methods. For this purpose, the electroluminescence spectra and the external quantum efficiency (EQE, measured in %) are determined from current/voltage/luminance characteristic lines (IUL characteristic lines) assuming a Lambertian emission profile. The electroluminescence (EL) spectra are recorded at a luminous density of 100 cd/m.sup.2 and the CIE 1931 x and y coordinates are then calculated from the EL spectrum. The device data of the OLEDs prepared according to working example 4 and comparative example 1 is summarized in Table 5. In the following section, the examples are described in more detail to show the advantages of the OLEDs of the invention.

Use of InP/ZnS Nanoparticles According to the Invention as Emitting Material in OLEDs

[0267] The InP/ZnS nanoparticles according to the invention are especially suitable as emitting material in an OLED device. The properties of the OLEDs prepared are summarised in Table 5. Example E1 shows properties of OLEDs containing materials of the present invention.

TABLE-US-00005 TABLE 5 Device data of solution processed OLEDs Voltage EQE @ @ 10 mA/cm.sup.2 10 cd/m.sup.2 CIE Example V % x y V1 7.6 3.0 0.62 0.36 E1 3.3 4.5 0.62 0.36

[0268] As can be seen from the data shown in Table 5, an OLED using in the emissive layer the semiconductor nanoparticle according to the invention (E1), that is, quantum dots having attached to their surface ligands according to the invention, in this example structure (35) provides a significantly improvement in lower driving voltage and increased EQE compared to the state-of-the-art (V1, i.e. QDs covered with common carboxylic and thiol alkyl ligands, as described in: Hussain et. al. ChemPhysChem, 2009, 10, 1466-1470).