WO2019233945A1

WO2019233945A1 - Method and polymer composition for preparing optoelectronic devices

Info

Publication number: WO2019233945A1
Application number: PCT/EP2019/064338
Authority: WO
Inventors: Ralf Grottenmueller; Andreas Benker; Oliver Doll; Fabian BLUMENSCHEIN; Bernd LOEFFEL; Semhar YOHANNES
Original assignee: Merck Patent Gmbh
Priority date: 2018-06-05
Filing date: 2019-06-03
Publication date: 2019-12-12
Also published as: TW202006023A

Abstract

The present invention relates to a method for preparing an optoelectronic device comprising a crosslinked polymer material which is prepared from a crosslinkable polymer formulation comprising a polymer with a silazane repeating unit M1 and a metal amide.There is further provided a crosslinkable polymer formulation comprising a silazane and/or siloxazane polymer which is particularly suitable for the preparation of encapsulation materials for optoelectronic devices.

Description

Method and Polymer Composition

for Preparing Optoelectronic Devices

Technical field

The present invention relates to a method for preparing an optoelectronic device comprising a crosslinked polymer material which is prepared from a crosslinkable polymer formulation comprising a polymer with a repeating unit M¹ selected from silazane repeating units and a metal amide. The metal amide permits uniform curing of the crosslinkable polymer formulation at low temperatures and gives rise to improved mechanical features of the crosslinked polymer material. In particular, the metal amide allows a fast and complete crosslinking of polymers having silazane and optionally siloxane repeating units to prepare crosslinked polymer materials under mild conditions, such as at moderate temperatures of less than 200°C. The obtained crosslinked polymer materials are of very high purity and high hardness and do not show any material deterioration, such as e.g. cracking or discolouration, when exposed to heat and/or radiation. They are therefore particularly suitable as encapsulation materials for optoelectronic devices where a homogeneous and uniform material texture, optical transparency and/or light fastness are required, such as e.g. in light emitting diodes (LEDs) and organic light emitting diodes (OLEDs).

The present invention further relates to optoelectronic devices which are obtainable by the described method. The optoelectronic devices show improved barrier properties, optical transparency, adjustable refractive index, mechanical stability (non-stickiness) and thermal and UV stability.

Beyond that, a specific crosslinkable polymer formulation is provided which comprises silazane and optionally siloxane repeating units and a metal amide. Said crosslinkable polymer formulation is particularly suitable for the preparation of encapsulation materials for optoelectronic devices where a homogeneous and uniform material texture, optical transparency and/or light fastness are required, such as e.g. in light emitting diodes (LEDs) and organic light emitting diodes (OLEDs). Background of the invention

Polymers which contain siloxane repeating units are typically referred to as polysiloxanes or siloxanes and polymers which contain silazane repeating units are typically referred to as polysilazanes or polysiloxazanes. Whilst polysilazanes are composed of one or more different silazane repeating units, polysiloxazanes additionally contain one or more different siloxane repeating units. Polysiloxanes, polysilazanes and polysiloxazanes are usually liquid polymers which become solid at molecular weights of ca. > 10.000 g/mol. In most applications liquid polymers of moderate molecular weights, typically in the range from 2.000 to 8.000 g/mol, are used. For preparing a solid coating from such liquid polymers, a curing step is required which is usually carried out at elevated temperatures after applying the material on a substrate, either as a pure material or as a formulation. Polysilazanes or polysiloxazanes are crosslinked by a hydrolysis reaction, wherein moisture from the air reacts according to the mechanisms as shown by Equations (I) and (II) below:

Equation (I): Hydrolysis of Si-N bond

RsSi-NH-SiRs + H₂0 R₃Si-0-SiR₃ + NH₃

Equation (II): Hydrolysis of Si-H bond

R₃Si-H + H-SiR₃ + H₂0 R₃Si-0-SiR₃ + 2H₂ During the hydrolysis reactions the polymers crosslink and the increasing molecular weight leads to a solidification of the material. Hence, the crosslinking reactions lead to a curing of the polysilazane or polysiloxazane material. For this reason, in the present application the terms“curing” and “crosslinking” and the corresponding verbs“cure” and“crosslink” are interchangeably used as synonyms.

Usually, curing is performed by hydrolysis at ambient conditions or at elevated temperatures of up to 220°C or more. If possible, however, the curing time should be as low as possible.

Various additives have been described in the state of the art to accelerate the crosslinking process of polysilazanes under thermal conditions: WO 2007/028511 A2 relates to the use of polysilazanes as permanent coatings on metal and polymer surfaces for preventing corrosion, increasing scratch resistance and to facilitate easier cleaning. Additives such as e.g. organic amines, organic acids, metals and metal salts may be used for curing polysilazane formulations to obtain permanent coatings. Depending on the polysilazane formulation and additive, curing takes place even at room temperature, but can be accelerated by heating.

Similarly, N-heterocyclic compounds, organic or inorganic acids, metal carboxylates, fine metal particles, peroxides, metal chlorides or

organometallic compounds are suggested in WO 2004/039904 A1 for curing polysilazane formulations under thermal conditions.

The coatings produced with the aforementioned methods require a relatively long curing time. Owing to the low film thickness, void formation is quite high and the barrier characteristics of the coatings are unsatisfactory. Hence, there is a strong need to improve the crosslinking of polymers containing silazane repeating units, such as e.g. polysilazanes and polysiloxazanes, especially at temperatures up to 200°C, and to improve the mechanical properties of the crosslinked polymers.

Depending on the type of application, it is sometimes possible to use higher temperatures for curing, such as e.g. 220°C or above. However, there are applications which do not tolerate high temperatures, or it is simply not possible to apply heat. Examples of such applications are the coating of railcars or subway trains or the coating of building facades in order to apply a protective layer against dirt and graffiti. In addition, elevated temperatures may be excluded due to the nature of the substrate to be coated. For example, most plastics start to degrade and decompose at temperatures of above 100°C. Until now, however, the curing of pure liquid polysilazanes or polysiloxazanes at ambient conditions is a rather slow process. Depending on the chemical composition, it might take several days to completely crosslink a polysilazane or polysiloxazane based coating.

Technical problem and object of the invention

It is an object of the present invention to provide a method for preparing optoelectronic devices having a crosslinked polymer material as

encapsulation material with an improved hardness which does not suffer from material deterioration, such as e.g. cracking or discolouration, when exposed to heat and/or radiation. The method shall overcome the disadvantages in the state of the art and allow a fast and efficient production of optoelectronic devices. It is a further object of the present invention to provide optoelectronic devices which are obtainable by said method. Moreover, it is an object of the present invention to find a new crosslinkable polymer formulation which overcomes the disadvantages in the state of the art and which allows a fast and efficient preparation of encapsulation materials for optoelectronic devices where a homogeneous and uniform material texture, optical transparency and/or light fastness are required, such as e.g. in light emitting diodes (LEDs) and organic light emitting diodes (OLEDs). The crosslinkable polymer formulation should give crosslinked polymer materials with an improved hardness that do not suffer from material deterioration, such as cracking or discolouration, when exposed to heat and/or radiation and which are therefore particularly suitable as encapsulation materials for optoelectronic devices.

Summary of the invention

The present inventors have surprisingly found that the above objects can be solved either individually or in any combination by the embodiments as provided in the claims below. The present inventors have found that specific metal amides permit uniform curing of crosslinkable polymer formulations containing silazane and optionally siloxane repeating units at low temperatures and give rise to improved material properties of the crosslinked polymer material. Hence, there is provided a method for preparing an optoelectronic device comprising a crosslinked polymer material which is prepared from a crosslinkable polymer formulation, wherein the method comprises the following steps:

(a) applying a crosslinkable polymer formulation to a precursor of an

optoelectronic device; and

(b) curing said crosslinkable polymer formulation to obtain a crosslinked polymer material;

characterized in that the crosslinkable polymer formulation is obtained from mixing

a polymer which contains a repeating unit M¹, wherein M¹ is a silazane repeating unit, and

a metal amide which is represented by formula (1 ): M(NR₂)mLn (1 ) wherein

M is selected from the group consisting of B, Al, Ga, Ti and Zr;

R may be the same or different at each occurrence and is selected independently from the group consisting of hydrogen, straight-chain alkyl having 1 to 20 carbon atoms, straight-chain alkenyl having 2 to 20 carbon atoms, branched-chain alkyl or alkenyl having 3 to 20 carbon atoms, cyclic alkyl or alkenyl having 3 to 20 carbon atoms, and aryl or heteroaryl having 4 to 18 carbon atoms, wherein one or more hydrogen atoms may be optionally replaced by F and wherein one or more non-adjacent CFh groups may be optionally replaced by -0-, -(C=0)- or -(C=0)-0-;

L is a ligand other than NR₂ which may be the same or different at each occurrence and is selected from the group consisting of anionic ligands, neutral ligands and radical ligands;

m is an integer greater than or equal to 1 ; and

n is an integer greater than or equal to 0;

wherein m + n = 3, if M = B, Al or Ga; and m + n = 4, if M = Ti or Zr.

In addition, an optoelectronic device is provided which is obtainable by the above method.

Furthermore, a crosslinkable polymer formulation is provided which is obtained from mixing a polymer, and a metal amide; wherein the polymer contains a repeating unit M¹ and further optionally (i) a repeating unit M² or M³ or (ii) a repeating unit M² and M³, wherein the repeating unit M¹ is represented by formula (I), the repeating unit M² is represented by formula (II) and the repeating unit M³ is represented by formula (III):

-[-SiR¹R²-NR³-]- (I)

-[-SiR⁴R⁵-NR⁶-]- (II) -[-SiR⁷R⁸-[0-SiR⁷R⁸-]_a-NR⁹-]- (III) wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ are independently from each other selected from the group consisting of hydrogen, organyl and organoheteryl, and a is an integer from 1 to 60; and

characterized in that the metal amide is represented by formula (1 ):

M(NR₂)mL_n (1 ) wherein

M is selected from the group consisting of B, Al, Ga, Ti and Zr;

R may be the same or different at each occurrence and is selected independently from the group consisting of hydrogen, straight-chain alkyl having 1 to 20 carbon atoms, straight-chain alkenyl having 2 to 20 carbon atoms, branched-chain alkyl or alkenyl having 3 to 20 carbon atoms, cyclic alkyl or alkenyl having 3 to 20 carbon atoms, and aryl or heteroaryl having 4 to 18 carbon atoms, wherein one or more hydrogen atoms may be optionally replaced by F and wherein one or more non-adjacent CH₂ groups may be optionally replaced by -0-, -(C=0)- or -(C=0)-0-;

m is an integer greater than or equal to 1 ; and

n is an integer greater than or equal to 0;

wherein m + n = 3, if M = B, Al or Ga; and m + n = 4, if M = Ti or Zr.

The crosslinkable polymer formulation of the present invention is

particularly suitable for the preparation of encapsulation materials for optoelectronic devices where a homogeneous and uniform material texture, optical transparency and/or light fastness are required, such as e.g. in light emitting diodes (LEDs) and organic light emitting diodes (OLEDs). Hence, the crosslinkable polymer formulation may be used as encapsulation material for the preparation of converter layers of phosphor-converted LEDs (pcLEDs) with high refractive index. The crosslinkable polymer formulation shows a higher curing rate when compared to conventional polymer formulations and thereby allows a more efficient processability. Moreover, the crosslinked polymer material has an improved hardness and does not show any material deterioration, such as cracking or discolouration, when exposed to heat such as e.g. temperatures of > 220°C and/or to radiation.

Preferred embodiments of the invention are described in the dependent claims.

Brief description of the figure

FIG.1 : Schematic representation of the formation of polymer-metal amide adducts after mixing polysilazane polymers with metal amide species Zr(NMe2)4. The metal amide coordinates with cleavage of HNMe2 to a nitrogen atom of the polysilazane chain. Multiple coordination with the same or another polysilazane chain is possible. Detailed description of the invention

Definitions

The term“crosslinkable polymer formulation” refers to a formulation comprising at least one crosslinkable polymer compound. A“crosslinkable polymer compound” is a polymer compound which may be crosslinked thermally, by the influence of radiation and/or a catalyst. A crosslinking reaction involves sites or groups on existing polymers or an interaction between existing polymers that results in the formation of a small region in a polymer from which at least three chains emanate. Said small region may be an atom, a group of atoms, or a number of branch points connected by bonds, groups of atoms or oligomeric or polymeric chains. The term“polymer” includes, but is not limited to, homopolymers, copolymers, for example, block, random, and alternating copolymers, terpolymers, quaterpolymers, etc., and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term“polymer” shall include all possible configurational isomers of the material. These configurations include, but are not limited to isotactic, syndiotactic, and atactic symmetries. A polymer is a molecule of high relative molecular mass, the structure of which essentially comprises the multiple repetition of units (i.e. repeating units) derived, actually or conceptually, from molecules of low relative mass (i.e. monomers).

The term“monomer” as used herein refers to a molecule which can undergo polymerization thereby contributing constitutional units (repeating units) to the essential structure of a polymer.

The term“homopolymer” as used herein stands for a polymer derived from one species of (real, implicit or hypothetical) monomer. The term“copolymer” as used herein generally means any polymer derived from more than one species of monomer, wherein the polymer contains more than one species of corresponding repeating unit. In one embodiment the copolymer is the reaction product of two or more species of monomer and thus comprises two or more species of corresponding repeating unit. It is preferred that the copolymer comprises two, three, four, five or six species of repeating unit. Copolymers that are obtained by

copolymerization of three monomer species can also be referred to as terpolymers. Copolymers that are obtained by copolymerization of four monomer species can also be referred to as quaterpolymers. Copolymers may be present as block, random, and/or alternating copolymers. The term“block copolymer” as used herein stands for a copolymer, wherein adjacent blocks are constitutionally different, i.e. adjacent blocks comprise repeating units derived from different species of monomer or from the same species of monomer but with a different composition or sequence distribution of repeating units.

Further, the term“random copolymer” as used herein refers to a polymer formed of macromolecules in which the probability of finding a given repeating unit at any given site in the chain is independent of the nature of the adjacent repeating units. Usually, in a random copolymer, the sequence distribution of repeating units follows Bernoullian statistics.

The term“alternating copolymer” as used herein stands for a copolymer consisting of macromolecules comprising two species of repeating units in alternating sequence.

The term“polysilazane” as used herein refers to a polymer in which silicon and nitrogen atoms alternate to form the basic backbone. Since each silicon atom is bound to at least one nitrogen atom and each nitrogen atom to at least one silicon atom, both chains and rings of the general formula [R¹R²Si-NR³]_m occur, wherein R¹ to R³ can be hydrogen atoms or organic substituents; and m is an integer. If all substituents R¹ to R³ are H atoms, the polymer is designated as perhydropolysilazane, polyperhydrosilazane or inorganic polysilazane ([FhSi-NHj_m). If at least one substituent R¹ to R³ is an organic substituent, the polymer is designated as organopolysilazane.

The term“polysiloxazane” as used herein refers to a polysilazane which additionally contains sections in which silicon and oxygen atoms alternate. Such section may be represented for example by [0-SiR⁴R⁵]_n, wherein R⁴ and R⁵ can be hydrogen atoms or organic substituents; and n is an integer. If all substituents of the polymer are H atoms, the polymer is designated as perhydropolysiloxazane. If at least one substituents of the polymer is an organic substituent, the polymer is designated as organopolysiloxazane.

The term“optoelectronic device” as used herein refers to electronic devices that operate on both light and electrical currents. This includes electrically driven light sources such as laser diodes, LEDs, OLEDs, OLETs (organic light emitting transistors) components for converting light to an electrical current such as solar and photovoltaic cells and devices that can

electronically control the propagation of light.

The term "LED" as used herein refers to light emitting devices comprising one or more of a semiconductor light source (LED chip), lead frame, wiring, solder (flip chip), converter, filling material, encapsulation material, primary optics and/or secondary optics. A LED may be prepared from a LED precursor containing a semiconductor light source (LED chip) and/or lead frame and/or gold wire and/or solder (flip chip). In a LED precursor neither the LED chip nor the converter is enclosed by an encapsulation material. Usually, the encapsulation material and the converter form part of a converter layer. Such converter layer may be either arranged directly on a LED chip or alternatively arranged remote therefrom, depending on the respective type of application.

The term“OLED” as used herein refers to organic light emitting devices comprising electroactive organic light emitting materials generally, and includes but is not limited to organic light emitting diodes. An OLED device comprises at least two electrodes with an organic light-emitting material disposed between the two electrodes. Organic light-emitting materials are usually electroluminescent materials which emit light in response to the passage of an electric current or to a strong electric field.

The term“converter” as used herein means a material that converts light of a first wavelength to light of a second wavelength, wherein the second wavelength is different from the first wavelength. Converters are inorganic materials such as phosphors or quantum materials.

A“phosphor” is a fluorescent inorganic material which contains one or more light emitting centers. The light emitting centers are formed by activator elements such as e.g. atoms or ions of rare earth metal elements, for example La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, and/or atoms or ions of transition metal elements, for example Cr, Mn, Fe, Co, Ni, Cu, Ag, Au and Zn, and/or atoms or ions of main group metal elements, for example Na, Tl, Sn, Pb, Sb and Bi. Examples of suitable phosphors include phosphors based on garnet, silicate, orthosilicate, thiogallate, sulfide, nitride, silicon-based oxynitride, nitridosilicate, nitridoaluminumsilicate, oxonitridosilicate, oxonitridoaluminumsilicate and rare earth doped sialon. Phosphors within the meaning of the present application are materials which absorb electromagnetic radiation of a specific wavelength range, preferably blue and/or ultraviolet (UV) electromagnetic radiation, and convert the absorbed electromagnetic radiation into electromagnetic radiation having a different wavelength range, preferably visible (VIS) light such as violet, blue, green, yellow, orange or red light.

A“quantum material” is a semiconductor nanocrystal forming a class of nanomaterials with physical properties that are widely tunable by controlling particle size, composition and shape. Among the most evident size dependent property of this class of materials is the tunable fluorescence emission. The tunability is afforded by the quantum confinement effect, where reducing particle size leads to a‘particle in a box’ behavior, resulting in a blue shift of the band gap energy and hence the light emission. For example, in this manner, the emission of CdSe nanocrystals can be tuned from 660 nm for particles of diameter of ~6.5 nm, to 500 nm for particles of diameter of ~2 nm. Similar behavior can be achieved for other

semiconductors when prepared as nanocrystals allowing for broad spectral coverage from the UV (using ZnSe, CdS for example) throughout the visible (using CdSe, InP for example) to the near-IR (using InAs for example). Changing the nanocrystal shape was demonstrated for several

semiconductor systems, where especially prominent is the rod shape.

Nanorods show properties that are modified from the spherical particles.

For example, they exhibit emission that is polarized along the long rod axis, while spherical particles exhibit unpolarized emission. Moreover, we showed that nanorods have advantageous properties in optical gain, presenting potential for their use as laser materials (Banin et al., Adv.

Mater., (2002) 14, 317). Single nanorods were also shown to exhibit a unique behavior under external electric fields - the emission can be switched on and off reversibly (Banin et. al., Nano Letters., (2005) 5, 1581 ).

The term "encapsulation material" or "encapsulant" as used herein means a material which covers or encloses a converter. Preferably, the

encapsulation material forms part of a converter layer which contains one or more converters. The converter layer may be either arranged directly on a semiconductor light source (LED chip) or alternatively arranged remote therefrom, depending on the respective type of application. The converter layer may be present as a film having different thicknesses or having an uniform thickness. The encapsulation material forms a barrier against the external environment of the LED device, thereby protecting the converter and/or the LED chip. The encapsulating material is preferably in direct contact with the converter and/or the LED chip. Usually, the encapsulation material forms part of a LED package comprising a LED chip and/or lead frame and/or gold wire, and/or solder (flip chip), the filling material, converter and a primary and secondary optic. The encapsulation material may cover a LED chip and/or lead frame and/or gold wire and may contain a converter. The encapsulation material has the function of a surface protection material against external environmental influences and

guarantees long term reliability that means aging stability. Preferably, the converter layer containing the encapsulation material has a thickness of 1 pm to 1 cm, more preferably of 10 pm to 1 mm.

The external environmental influences against which the encapsulation material needs to protect the LED may be chemical such as e.g. moisture, acids, bases, oxygen within others, or physical such as e.g. temperature, mechanical impact, or stress. The encapsulation material can act as a binder for the converter, such as a phosphor powder or a quantum material (e.g. quantum dots). The encapsulant can also be shaped in order to provide primary optic functions (lens).

It is noted that the terms“layer” and“layers” are used interchangeably throughout the application. A person of ordinary skill in the art will understand that a single“layer” of material may actually comprise several individual sub-layers of material. Likewise, several“sub-layers” of material may be considered functionally as a single layer. In other words the term “layer” does not denote a homogenous layer of material. A single“layer” may contain various material concentrations and compositions that are localized in sub-layers. These sub-layers may be formed in a single formation step or in multiple steps. Unless specifically stated otherwise, it is not intended to limit the scope of the invention as embodied in the claims by describing an element as comprising a“layer” or“layers” of material.

For the purposes of the present application the term“organyl” is used to denote any organic substituent group, regardless of functional type, having one free valence at a carbon atom.

For the purposes of the present application the term“organoheteryl” is used to denote any univalent group containing carbon, which is thus organic, but which has the free valence at an atom other than carbon being a

heteroatom. As used herein, the term“heteroatom” will be understood to mean an atom in an organic compound that is not a H- or C-atom, and preferably will be understood to mean N, O, S, P, Si, Se, As, Te or Ge. An organyl or organoheteryl group comprising a chain of 3 or more C atoms may be straight-chain, branched-chain and/or cyclic, including spiro and/or fused rings.

Preferred organyl and organoheteryl groups include alkyl, alkoxy, alkylsilyl, alkylsilyloxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy and

alkoxycarbonyloxy, each of which is optionally substituted and has 1 to 40, preferably 1 to 25, more preferably 1 to 18 C atoms, furthermore optionally substituted aryl, aryloxy, arylsilyl or arylsilyloxy having 6 to 40, preferably 6 to 25 C atoms, furthermore alkylaryloxy, alkylarylsilyl, alkylarylsilyloxy, arylalkylsilyl, arylalkylsilyloxy, arylcarbonyl, aryloxycarbonyl,

arylcarbonyloxy and aryloxycarbonyloxy, each of which is optionally substituted and has 7 to 40, preferably 7 to 20 C atoms, wherein all these groups do optionally contain one or more heteroatoms, preferably selected from N, O, S, P, Si, Se, As, Te and Ge.

The organyl or organoheteryl group may be a saturated or unsaturated acyclic group, or a saturated or unsaturated cyclic group. Unsaturated acyclic or cyclic groups are preferred, especially aryl, alkenyl and alkynyl groups (especially ethynyl). Where the Ci-C₄o organyl or organoheteryl group is acyclic, the group may be straight-chain or branched-chain. The Ci-C₄o organyl or organoheteryl group includes for example: a Ci-C₄o alkyl group, a Ci-C₄o fluoroalkyl group, a Ci-C₄o alkoxy or oxaalkyl group, a C₂- C₄o alkenyl group, a C2-C₄o alkynyl group, a C3-C₄o allyl group, a C₄-C₄o alkyldienyl group, a C₄-C₄o polyenyl group, a C2-C₄o ketone group, a C2-C₄o ester group, a C6-C₁₈ aryl group, a C6-C₄o alkylaryl group, a C6-C₄o arylalkyl group, a C₄-C₄o cycloalkyl group, a C₄-C₄o cycloalkenyl group, and the like. Preferred among the foregoing groups are a C₁-C₂₀ alkyl group, a C₁-C₂0 fluoroalkyl group, a C2-C20 alkenyl group, a C2-C20 alkynyl group, a C3-C20 allyl group, a C₄-C2o alkyldienyl group, a C2-C20 ketone group, a C2-C20 ester group, a C6-C12 aryl group, and a C₄-C2o polyenyl group, respectively. Also included are combinations of groups having carbon atoms and groups having heteroatoms, such as e.g. an alkynyl group, preferably ethynyl, that is substituted with a silyl group, preferably a trialkylsilyl group.

The terms "aryl" and "heteroaryl" as used herein preferably mean a mono-, bi- or tricyclic aromatic or heteroaromatic group with 4 to 18 ring C atoms that may also comprise condensed rings and is optionally substituted with one or more groups L, wherein L is selected from halogen, -CN, - NC, -NCO, -NCS, -OCN, -SCN, -C(=O)NR⁰R⁰⁰, -C(=0)X°, -C(=0)R°, -NH₂, -NR°R⁰⁰, -SH, -SR°, -SOsH, -SO2R⁰, -OH, -NO2, -CF₃, -SFs, optionally substituted silyl, or organyl or organoheteryl with 1 to 40 C atoms that is optionally substituted and optionally comprises one or more heteroatoms, and is preferably alkyl, alkoxy, thioalkyl, alkylcarbonyl, alkoxycarbonyl or alkoxycarbonyloxy with 1 to 20 C atoms that is optionally fluorinated, and R°, R⁰⁰ and X° have the meanings as given below. Very preferred substituents L are selected from halogen, most preferably F, or alkyl, alkoxy, oxaalkyl, thioalkyl, fluoroalkyl and fluoroalkoxy with 1 to 12 C atoms or alkenyl, and alkynyl with 2 to 12 C atoms.

Especially preferred aryl and heteroaryl groups are phenyl,

pentafluorophenyl, phenyl wherein one or more CH groups are replaced by N, naphthalene, thiophene, selenophene, thienothiophene,

dithienothiophene, fluorene and oxazole, all of which can be unsubstituted, mono- or polysubstituted with L as defined above. Very preferred rings are selected from pyrrole, preferably N-pyrrole, furan, pyridine, preferably 2- or 3-pyridine, pyrimidine, pyridazine, pyrazine, triazole, tetrazole, pyrazole, imidazole, isothiazole, thiazole, thiadiazole, isoxazole, oxazole, oxadiazole, thiophene, preferably 2-thiophene, selenophene, preferably 2-selenophene, thieno[3,2-b]thiophene, thieno[2,3-b]thiophene, furo[3,2-b]furan, furo[2,3- b]furan, seleno[3,2-b]selenophene, seleno[2,3-b]selenophene, thieno[3,2- b]selenophene, thieno[3,2-b]furan, indole, isoindole, benzo[b]furan, benzo[b]thiophene, benzo[1 ,2-b;4,5-b']dithiophene, benzo[2,1-b;3,4- b']dithiophene, quinole, 2- methylquinole, isoquinole, quinoxaline, quinazoline, benzotriazole, benzimidazole, benzothiazole, benzisothiazole, benzisoxazole, benzoxadiazole, benzoxazole, benzothiadiazole, all of which can be unsubstituted, mono- or polysubstituted with L as defined above. Further examples of aryl and heteroaryl groups are those selected from the groups shown hereinafter.

An alkyl or alkoxy radical, i.e. where the terminal CFte group is replaced by - 0-, can be straight-chain or branched-chain. It is preferably straight-chain (or linear). Suitable examples of such alkyl and alkoxy radical are methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, octoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy. Preferred alkyl and alkoxy radicals have 1 , 2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms. Suitable examples of such preferred alkyl and alkoxy radicals may be selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, octoxy, nonoxy and decoxy. An alkenyl group, wherein one or more CFte groups are replaced by -

CH=CH- can be straight-chain or branched-chain. It is preferably straight- chain, has 2 to 10 C atoms and accordingly is preferably vinyl, prop-1 -enyl, or prop-2-enyl, but-1 -enyl, but-2-enyl or but-3-enyl, pent-1 -enyl, pent-2-enyl, pent-3-enyl or pent-4-enyl, hex-1 -enyl, hex-2-enyl, hex-3-enyl, hex-4-enyl or hex-5-enyl, hept-1 -enyl, hept-2-enyl, hept-3-enyl, hept-4-enyl, hept-5-enyl or hept-6-enyl, oct-1 -enyl, oct-2-enyl, oct-3-enyl, oct-4-enyl, oct-5-enyl, oct-6-enyl or oct-7-enyl, non-1 -enyl, non-2-enyl, non-3-enyl, non-4-enyl, non-5-enyl, non-6-enyl, non-7-enyl or non-8-enyl, dec-1 -enyl, dec-2-enyl, dec-3-enyl, dec-4-enyl, dec-5-enyl, dec-6-enyl, dec-7-enyl, dec-8-enyl or dec-9-enyl. Especially preferred alkenyl groups are C2-C7-I E-alkenyl, C₄-C₇-3E-alkenyl, C5-C7-4-alkenyl, C6-C7-5-alkenyl and C7-6-alkenyl, in particular C2-C7-I E- alkenyl, C₄-C₇-3E-alkenyl and Cs-C₇-4-alkenyl. Examples for particularly preferred alkenyl groups are vinyl, 1 E-propenyl, 1 E-butenyl, 1 E-pentenyl, 1 E-hexenyl, 1 E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl and the like. Alkenyl groups having up to 5 C atoms are generally preferred.

An oxaalkyl group, i.e. where one Chte group is replaced by -0-, is preferably straight-chain 2-oxapropyl (= methoxymethyl), 2-(ethoxymethyl) or 3-oxabutyl (= 2-methoxyethyl), 2-, 3-, or 4-oxapentyl, 2-, 3-, 4-, or

5-oxahexyl, 2-, 3-, 4-, 5-, or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl or 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl, for example. Oxaalkyl, i.e. where one Chte group is replaced by -0-, is preferably straight-chain 2-oxapropyl (= methoxymethyl), 2-oxabutyl (= ethoxymethyl) or 3-oxabutyl (= 2-methoxyethyl), 2-, 3-, or 4-oxapentyl,

2-, 3-, 4-, or 5-oxahexyl, 2-, 3-, 4-, 5-, or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl or 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl, for example. In an alkyl group wherein one Chte group is replaced by -O- and one by - C(O)-, these radicals are preferably neighboured. Accordingly, these radicals together form a carbonyloxy group -C(0)-0- or an oxycarbonyl group -O-C(O)-. Preferably, this group is straight-chain and has 2 to 6 C atoms. It is accordingly preferably selected from the group consisting of acetyloxy, propionyloxy, butyryloxy, pentanoyloxy, hexanoyloxy,

acetyloxymethyl, propionyloxymethyl, butyryloxymethyl,

pentanoyloxymethyl, 2-acetyloxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 3-acetyloxypropyl, 3-propionyloxypropyl,

4-acetyloxybutyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxy- carbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl,

2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl, 2-(propoxy- carbonyl)ethyl, 3-(methoxycarbonyl)propyl, 3-(ethoxycarbonyl)propyl, and 4-(methoxycarbonyl)-butyl.

An alkyl group wherein two or more Chte groups are replaced by -O- and/or -C(0)0- can be straight-chain or branched-chain. It is preferably straight- chain and has 3 to 12 C atoms. Accordingly, it is preferably selected from the group consisting of bis-carboxy-methyl, 2,2-bis-carboxy-ethyl, 3,3-bis- carboxy-propyl, 4,4-bis-carboxy-butyl, 5,5-bis-carboxy-pentyl, 6,6-bis- carboxy-hexyl, 7,7-bis-carboxy-heptyl, 8,8-bis-carboxy-octyl, 9,9-bis- carboxy-nonyl, 10,10-bis-carboxy-decyl, bis-(methoxycarbonyl)-methyl,

2,2-bis-(methoxycarbonyl)-ethyl, 3,3-bis-(methoxycarbonyl)-propyl, 4,4-bis- (methoxycarbonyl)-butyl, 5,5-bis-(methoxycarbonyl)-pentyl, 6,6-bis- (methoxycarbonyl)-hexyl, 7,7-bis-(methoxycarbonyl)-heptyl, 8,8-bis- (methoxycarbonyl)-octyl, bis-(ethoxycarbonyl)-methyl, 2,2-bis- (ethoxycarbonyl)-ethyl, 3,3-bis-(ethoxycarbonyl)-propyl, 4,4-bis-

(ethoxycarbonyl)-butyl, and 5,5-bis-(ethoxycarbonyl)-hexyl.

A thioalkyl group, i.e. where one CFh group is replaced by -S-, is preferably straight-chain thiomethyl (-SCH3), 1 -thioethyl (-SCH2CH3), 1 -thiopropyl (= -SCH2CH2CH3), 1 -(thiobutyl), 1 -(thiopentyl), 1 -(thiohexyl), 1 -(thioheptyl),

1 -(thiooctyl), l-(thiononyl), 1 -(thiodecyl), l -(thioundecyl) or l-(thiododecyl), wherein preferably the Chte group adjacent to the sp² hybridised vinyl carbon atom is replaced. A fluoroalkyl group is preferably perfluoroalkyl, CiFz+i , wherein i is an integer from 1 to 15, in particular CF3, C2F5, C3F7, C₄Fg, C5F11 , C6F13, C7F15 or CsF ₁₇, very preferably C6F₁₃, or partially fluorinated alkyl, in particular 1 ,1 -difluoroalkyl, all of which are straight-chain or branched-chain.

Alkyl, alkoxy, alkenyl, oxaalkyl, thioalkyl, carbonyl and carbonyloxy groups can be achiral or chiral groups. Particularly preferred chiral groups are 2- butyl (=1 -methylpropyl), 2-methylbutyl, 2-methylpentyl, 3-methylpentyl, 2- ethylhexyl, 2-propylpentyl, in particular 2-methylbutyl, 2-methylbutoxy, 2- methylpentoxy, 3-methylpentoxy, 2-ethyl-hexoxy, 1 -methylhexoxy, 2- octyloxy, 2-oxa-3-methylbutyl, 3-oxa-4-methyl-pentyl, 4-methylhexyl, 2- hexyl, 2-octyl, 2-nonyl, 2-decyl, 2-dodecyl, 6-meth-oxyoctoxy, 6- methyloctoxy, 6-methyloctanoyloxy, 5-methylheptyloxy-carbonyl, 2- methylbutyryloxy, 3-methylvaleroyloxy, 4-methylhexanoyloxy, 2- chloropropionyloxy, 2-chloro-3-methylbutyryloxy, 2-chloro-4-methyl-valeryl- oxy, 2-chloro-3-methylvaleryloxy, 2-methyl-3-oxapentyl, 2-methyl -3-oxa- hexyl, 1 -methoxypropyl-2-oxy, 1 -ethoxypropyl-2-oxy, 1 -propoxypropyl-2- oxy, 1 -butoxypropyl-2-oxy, 2-fluorooctyloxy, 2-fluorodecyloxy, 1 ,1 ,1- trifluoro-2-octyloxy, 1 ,1 , 1 -trifl uoro-2-octy 1 , 2-fluoromethyloctyloxy for example. Very preferred are 2-hexyl, 2-octyl, 2-octyloxy, 1 ,1 ,1 -trifl uoro-2- hexyl, 1 ,1 ,1 -trifl uoro-2-octyl and 1 ,1 ,1 -trifluoro-2-octyloxy.

Preferred achiral branched groups are isopropyl, isobutyl (= methylpropyl), isopentyl (= 3-methylbutyl), tert. butyl, isopropoxy, 2-methyl-propoxy and 3- methylbutoxy. In a preferred embodiment, the organyl and organoheteryl groups are independently of each other selected from primary, secondary or tertiary alkyl or alkoxy with 1 to 30 C atoms, wherein one or more FI atoms are optionally replaced by F, or aryl, aryloxy, heteroaryl or heteroaryloxy that is optionally alkylated or alkoxylated and has 4 to 30 ring atoms. Very preferred groups of this type are selected from the group consisting of the following formulae

wherein "ALK" denotes optionally fluorinated, preferably linear, alkyl or alkoxy with 1 to 20, preferably 1 to 12 C-atoms, in case of tertiary groups very preferably 1 to 9 C atoms, and the dashed line denotes the link to the ring to which these groups are attached. Especially preferred among these groups are those wherein all ALK subgroups are identical.

As used herein, "halogen" includes F, Cl, Br or I, preferably F, Cl or Br, more preferably F and Cl, and most preferably F.

For the purposes of the present application the term“substituted” is used to denote that one or more hydrogen present is replaced by a group R^s as defined herein.

R^s is at each occurrence independently selected from the group consisting of any group R^T as defined herein, organyl or organoheteryl having from 1 to 40 carbon atoms wherein the organyl or organoheteryl may be further substituted with one or more groups R^T and organyl or organoheteryl having from 1 to 40 carbon atoms comprising one or more heteroatoms selected from the group consisting of N, O, S, P, Si, Se, As, Te, Ge, F and Cl, with N, O and S being preferred heteroatoms, wherein the organyl or organoheteryl may be further substituted with one or more groups R^T. Preferred examples of organyl or organoheteryl suitable as R^s may at each occurrence be independently selected from phenyl, phenyl substituted with one or more groups R^T, alkyl and alkyl substituted with one or more groups R^T, wherein the alkyl has at least 1 , preferably at least 5, more preferably at least 10 and most preferably at least 15 carbon atoms and/or has at most 40, more preferably at most 30, even more preferably at most 25 and most preferably at most 20 carbon atoms. It is noted that for example alkyl suitable as R^s also includes fluorinated alkyl, i.e. alkyl wherein one or more hydrogen is replaced by fluorine, and perfluorinated alkyl, i.e. alkyl wherein all of the hydrogen are replaced by fluorine.

R^T is at each occurrence independently selected from the group consisting of F, Br, Cl, -CN, -NC, -NCO, -NCS, -OCN, -SCN, -C(O)NR⁰R⁰⁰, -C(0)X°,

-C(0)R°, -NH₂, -NR°R⁰⁰, -SH, -SR°, -SO₃H, -SO₂R°, -OH, -OR⁰, -NO₂, -SF₅ and -SiR°R⁰⁰R⁰⁰⁰. Preferred R^T are selected from the group consisting of F, Br, Cl, -CN, -NC, -NCO, -NCS, -OCN, -SCN, -C(O)NR⁰R⁰⁰, -C(0)X°, -C(0)R°, -NH₂, -NR°R⁰⁰, -SH, -SR°, -OH, -OR⁰ and -SiR°R⁰⁰R⁰⁰⁰.

R°, R⁰⁰ and R⁰⁰⁰ are at each occurrence independently of each other selected from the group consisting of H, F, organyl or organoheteryl having from 1 to 40 carbon atoms. Said organyl or organoheteryl preferably have at least 5, more preferably at least 10 and most preferably at least 15 carbon atoms. Said organyl or organoheteryl preferably have at most 30, even more preferably at most 25 and most preferably at most 20 carbon atoms. Preferably, R°, R⁰⁰ and R⁰⁰⁰ are at each occurrence independently of each other selected from the group consisting of H, F, alkyl, fluorinated alkyl, alkenyl, alkynyl, phenyl and fluorinated phenyl. More preferably, R°, R⁰⁰ and R⁰⁰⁰ are at each occurrence independently of each other selected from the group consisting of H, F, alkyl, fluorinated, preferably

perfluorinated, alkyl, phenyl and fluorinated, preferably perfluorinated, phenyl. It is noted that for example alkyl suitable as R°, R⁰⁰ and R⁰⁰⁰ also includes perfluorinated alkyl, i.e. alkyl wherein all of the hydrogen are replaced by fluorine. Examples of alkyls may be selected from the group consisting of methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl (or "t-butyl"), pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl,

tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl and eicosyl (-C2OH₄I ).

X° is a halogen. Preferably X° is selected from the group consisting of F, Cl and Br.

Preferred embodiments

The present invention relates to a method for preparing an optoelectronic device comprising a crosslinked polymer material which is prepared from a crosslinkable polymer formulation, wherein the method comprises the following steps:

(a) applying a crosslinkable polymer formulation to a precursor of an

optoelectronic device; and

characterized in that the crosslinkable polymer formulation is obtained from mixing a polymer which contains a repeating unit M¹, wherein M¹ is a silazane repeating unit, and

a metal amide which is represented by formula (1 ):

M(NR₂)mL_n (1 ) wherein

M is selected from the group consisting of B, Al, Ga, Ti and Zr;

R may be the same or different at each occurrence and is selected independently from the group consisting of hydrogen, straight-chain alkyl having 1 to 20 carbon atoms, straight-chain alkenyl having 2 to 20 carbon atoms, branched-chain alkyl or alkenyl having 3 to 20 carbon atoms, cyclic alkyl or alkenyl having 3 to 20 carbon atoms, and aryl or heteroaryl having 4 to 18 carbon atoms, wherein one or more hydrogen atoms may be optionally replaced by F and wherein one or more non-adjacent CFte groups may be optionally replaced by -0-, -(C=0)- or -(C=0)-0-;

L is a ligand other than NR2 which may be the same or different at each occurrence and is selected from the group consisting of anionic ligands, neutral ligands and radical ligands;

m is an integer greater than or equal to 1 ; and

n is an integer greater than or equal to 0;

wherein m + n = 3, if M = B, Al or Ga; and m + n = 4, if M = Ti or Zr.

Preferably, m is an integer selected from 1 , 2, 3 and 4.

Preferably, n is an integer selected from 0, 1 , 2 and 3. More preferably, n is 0.

It is preferred that M is trivalent, if M = B, Al or Ga. It is preferred that M is tetravalent, if M = Ti or Zr.

Preferably, the polymer contains a repeating unit M¹ and a further repeating unit M², wherein M¹ and M² are silazane units which are different from each other. Preferably, the polymer contains a repeating unit M¹ and a further repeating unit M³, wherein M¹ is a silazane unit and M³ is a siloxazane unit. More preferably, the polymer contains a repeating unit M¹, a further repeating unit M² and a further repeating unit M³, wherein M¹ is a silazane unit, M² is a silazane unit which is different from M¹, and M³ is a siloxazane unit. In a preferred embodiment the polymer is a polysilazane which may be a perhydropolysilazane or an organopolysilazane. Preferably, the

polysilazane contains a repeating unit M¹ and optionally a further repeating unit M², wherein M¹ and M² are silazane units which are different from each other.

In a further alternative preferred embodiment the polymer is a

polysiloxazane which may be a perhydropolysiloxazane or an

organopolysiloxazane. Preferably, the polysiloxazane contains a repeating unit M¹ and a further repeating unit M³, wherein M¹ is a silazane unit and M³ is a siloxazane unit. More preferably, the polysiloxazane contains a repeating unit M¹, a further repeating unit M² and a further repeating unit M³, wherein M¹ and M² are silazane units which are different from each other and M³ is a siloxazane unit.

In a particularly preferred embodiment the polymer is a mixture of a polysilazane which may be a perhydropolysilazane or an

organopolysilazane and a polysiloxazane which may be a

perhydropolysiloxazane or an organopolysiloxazane.

As noted above, one component of the crosslinkable polymer composition, which is used in the method according to the present invention, is a polymer containing a repeating unit M¹. Preferably, the repeating unit M¹ is a silazane repeating unit represented by formula (I):

-[-SiR¹R²-NR³-]- (I) wherein R¹, R² and R³ are independently from each other selected from the group consisting of hydrogen, organyl and organoheteryl.

It is preferred that R¹, R² and R³ are independently from each other selected from the group consisting of hydrogen, alkyl having 1 to 40 carbon atoms, alkenyl having 2 to 40 carbon atoms and aryl having from 6 to 30 carbon atoms. More preferably, R¹, R² and R³ are independently from each other selected from the group consisting of hydrogen, alkyl having 1 to 20 carbon atoms, alkenyl having 2 to 20 carbon atoms and phenyl. Most preferably, R¹, R² and R³ are independently from each other hydrogen, methyl or vinyl. In a preferred embodiment, the polymer contains besides the repeating unit M¹ a further repeating unit M² which is a silazane repeating unit

represented by formula (II):

-[-SiR⁴R⁵-NR⁶-]- (II) wherein R⁴, R⁵ and R⁶ are at each occurrence independently from each other selected from the group consisting of hydrogen, organyl and organoheteryl; and wherein M² is different from M¹. It is preferred that R⁴, R⁵ and R⁶ in formula (II) are independently from each other selected from the group consisting of hydrogen, alkyl having 1 to 40 carbon atoms, alkenyl having 2 to 40 carbon atoms and aryl having from 6 to 30 carbon atoms. More preferably, R⁴, R⁵ and R⁶ are independently from each other selected from the group consisting of hydrogen, alkyl having 1 to 20 carbon atoms, alkenyl having 2 to 20 carbon atoms and phenyl. Most preferably, R⁴, R⁵ and R⁶ are independently from each other hydrogen, methyl or vinyl.

In a further preferred embodiment, the polymer is a polysiloxazane which contains besides the repeating unit M¹ a further repeating unit M³ which is represented by formula (III):

-[-SiR⁷R⁸-[0-SiR⁷R⁸-]_a-NR⁹-]- (III) wherein R⁷, R⁸, R⁹ are independently from each other selected from the group consisting of hydrogen, organyl and organoheteryl; and a is an integer from 1 to 60, preferably from 1 to 50. More preferably, a may be an integer from 5 to 50 (long chain monomer M³); or a may be an integer from 1 to 4 (short chain monomer M³).

It is preferred that R⁷, R⁸ and R⁹ in formula (III) are independently from each other selected from the group consisting of hydrogen, alkyl having 1 to 40 carbon atoms, alkenyl having 2 to 40 carbon atoms and aryl having from 6 to 30 carbon atoms. More preferably, R⁷, R⁸ and R⁹ are independently from each other selected from the group consisting of hydrogen, alkyl having 1 to 20 carbon atoms, alkenyl having 2 to 20 carbon atoms and phenyl. Most preferably, R⁷, R⁸ and R⁹ are independently from each other hydrogen, methyl or vinyl.

With respect to R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ preferred organyl groups may be independently selected from the group consisting of alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, substituted alkenyl, alkadienyl, substituted alkadienyl, alkynyl, substituted alkynyl, aryl, and substituted aryl.

With respect to R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ more preferred organyl groups be independently selected from the group consisting of alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, substituted alkenyl, alkadienyl and substituted alkadienyl.

With respect to R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ even more preferred organyl groups may be independently selected from the group consisting of alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkadienyl and substituted alkadienyl.

With respect to R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ still even more preferred organyl groups may be independently selected from the group consisting of alkyl and substituted alkyl. With respect to R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ most preferred organyl groups may be independently selected from alkyl.

With respect to R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ preferred alkyl may be selected from alkyls having at least 1 carbon atom and at most 40 carbon atoms, preferably at most 30 or 20 carbon atoms, more preferably at most 15 carbon atoms, still even more preferably at most 10 carbon atoms and most preferably at most 5 carbon atoms. With respect to R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ alkyl having at least 1 carbon atom and at most 5 carbon atoms may be independently selected from the group consisting of methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso- butyl, tert-butyl, n-pentyl, iso-pentyl (2,2-methyl-butyl) and neo-pentyl (2,2- dimethyl-propyl); preferably from the group consisting of methyl, ethyl, n- propyl and iso-propyl; more preferably from methyl or ethyl; and most preferably from methyl.

With respect to R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ preferred cycloalkyl may be selected from cycloalkyl having at least 3, preferably at least 4 and most preferably at least 5 carbon atoms. Preferred cycloalkyl may be selected from cycloalkyl having at most 30, preferably at most 25, more preferably at most 20, even more preferably at most 15, and most preferably at most 10 carbon atoms. With respect to R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ preferred examples of cycloalkyl may be selected from the group consisting of cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl.

With respect to R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ preferred alkenyl may be selected from alkenyl having at least 2 carbon atoms and at most 20, more preferably at most 15, even more preferably at most 10, and most preferably at most 6 carbon atoms. Said alkenyl may comprise the C=C double bond at any position within the molecule; for example, the C=C double bond may be terminal or non-terminal.

With respect to R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ alkenyl having at least 2 and at most 10 carbon atoms may be vinyl or allyl, preferably vinyl.

With respect to R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ preferred alkadienyl may be selected from alkadienyl having at least 4 and at most 20, more preferably at most 15, even more preferably at most 10, and most preferably at most 6 carbon atoms. Said alkenyl may comprise the two C=C double bonds at any position within the molecule, provided that the two C=C double bonds are not adjacent to each other; for example, the C=C double bonds may be terminal or non-terminal. With respect to R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ alkadienyl having at least 4 and at most 6 carbon atoms may, for example, be butadiene or hexadiene.

With respect to R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ preferred aryl may be selected from aryl having at least 6 carbon atoms, and at most 30, preferably at most 24 carbon atoms.

With respect to R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ preferred examples of aryl may be selected from the group consisting of phenyl, naphthyl, phenanthrenyl, anthracenyl, tetracenyl, benz[a]anthracenyl, pentacenyl, chrysenyl, benzo[a]pyrenyl, azulenyl, perylenyl, indenyl, fluorenyl and any of these wherein one or more (for example 2, 3 or 4) CH groups are replaced by N. Of these phenyl, naphthyl and any of these wherein one or more (for example 2, 3 or 4) CH groups are replaced by N. Phenyl is most preferred. With respect to R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ preferred

organoheteryl groups may be independently selected from the group consisting of alkoxy, alkylsilyl, alkylsilyloxy, alkylcarbonyloxy and

alkoxycarbonyloxy, each of which is optionally substituted and has 1 to 40, preferably 1 to 20, more preferably 1 to 18 C atoms; optionally substituted aryloxy, arylsilyl and arylsilyloxy each of which has 6 to 40, preferably 6 to 20 C atoms; and alkylaryloxy, alkylarylsilyl, alkylarylsilyloxy, arylalkylsilyl, arylalkylsilyloxy, arylcarbonyl, aryloxycarbonyl, arylcarbonyloxy and aryloxycarbonyloxy, each of which is optionally substituted and has 7 to 40, preferably 7 to 20 C atoms, wherein all these groups do optionally contain one or more heteroatoms, preferably selected from N, O, S, P, Si, Se, As, Te, Ge, F and Cl. The organoheteryl group may be a saturated or unsaturated acyclic group, or a saturated or unsaturated cyclic group.

Unsaturated acyclic or cyclic groups are preferred. Where the

organoheteryl group is acyclic, the group may be straight-chain or branched-chain.

With respect to R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ further preferred organoheteryl groups may be selected from the organoheteryl groups as defined in the definitions above.

It is understood that the skilled person can freely combine the above- mentioned preferred and more preferred embodiments relating to the substituents R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ in the polymer in any desired way.

Preferably, the polymer is a copolymer such as a random copolymer or a block copolymer or a copolymer containing at least one random sequence section and at least one block sequence section. More preferably, the polymer is a random copolymer or a block copolymer. Preferably, the polymers used in the present invention have a molecular weight M_w, as determined by GPC, of at least 1 ,000 g/mol, more preferably of at least 2,000 g/mol, even more preferably of at least 3,000 g/mol.

Preferably, the molecular weight M_w of the polymers is less than 100,000 g/mol. More preferably, the molecular weight M_w of the polymers is in the range from 3,000 to 50,000 g/mol.

Preferably, the total content of the polymer in the crosslinkable polymer formulation is in the range from 0.1 to 99.9% by weight, preferably from 0.5 to 99.8% by weight.

In a preferred embodiment of the present invention the substituent R in the metal amide is at each occurrence selected independently from the group consisting of hydrogen, straight-chain alkyl having 1 to 12 carbon atoms, straight-chain alkenyl having 2 to 12 carbon atoms, branched-chain alkyl or alkenyl having 3 to 12 carbon atoms, cyclic alkyl or alkenyl having 3 to 12 carbon atoms, and aryl or heteroaryl having 4 to 10 carbon atoms, wherein one or more hydrogen atoms may be optionally replaced by F and wherein one or more non-adjacent CFte groups may be optionally replaced by -0-, -(C=0)- or -(C=0)-0-.

In a more preferred embodiment of the present invention the substituent R in the metal amide is at each occurrence selected independently from the group consisting of hydrogen, straight-chain alkyl having 1 to 10 carbon atoms, branched-chain alkyl having 3 to 10 carbon atoms, cyclic alkyl having 3 to 10 carbon atoms, and aryl or heteroaryl having 4 to 10 carbon atoms, wherein one or more hydrogen atoms may be optionally replaced by F and wherein one or more non-adjacent CFh groups may be optionally replaced by -0-, -(C=0)- or -(C=0)-0-.

In a most preferred embodiment the substituent R is at each occurrence selected from the group consisting of hydrogen, methyl, ethyl and propyl. As mentioned above, L is at each occurrence independently selected from anionic ligands, neutral ligands or radical ligands. The anionic ligands and neutral ligands may be monodentate, bidentate or tridentate. The radical ligands may be monovalent, bivalent or trivalent.

Preferred anionic and neutral ligands are halides or organic ligands which coordinate M via one, two or more than two heteroatoms such as e.g. N, O, P and S.

Preferred anionic ligands are selected from the group consisting of halides, cyanide, alcoholates, carboxylates, deprotonated keto acids, deprotonated keto esters and deprotonated diketones. Preferred halides include fluoride, chloride, bromide and iodide. Preferred alcoholates include methylate, ethylate, propylate, butylate, pentylate, hexylate, heptylate, octylate, 1 ,2-diolates such as ethylene glycolate, 1 ,3- diolates such as propylene glycolate, 1 ,4-diolates such as butylene glycolate, 1 ,5-diolates such as pentylene glycolate, and glycerolate, and their isomers. Preferred carboxylates include formate, acetate, propionate, butanoate, pentanoate, hexanoate, heptanoate, octanoate, oxalate, malonate, succinate, glutarate, adipate, oxylate, and citrate, and their isomers. Preferred deprotonated keto acids include deprotonated species derived from alpha-keto acids such as pyruvic acid, oxaloacetic acid and alpha-ketoglutaric acid, beta-keto acids such as acetoacetic acid and beta- ketoglutaric acid, and gamma-keto acids such as levulinic acid. Preferred deprotonated keto esters include deprotonated species derived from a keto acid ester such as e.g. methylacetoacetate, ethylacetoacetate,

propoylacetoacetate and butyl acetoacetate. Preferred deprotonated diketones include deprotonated species derived from 1 ,3-diketones such as acetylacetone. Particularly preferred anionic ligands are selected from the group consisting of acetate, propionate, acetylacetonate, cyanide and ethylacetoacetate.

Preferred neutral ligands are selected from the group consisting of alcohols and carbon monoxide.

Preferred alcohols include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, glycerol, and their isomers.

Particularly preferred neutral ligands are selected from the group consisting of carbon monoxide.

Radical ligands are organic ligands which coordinate M via one, two or more than two radical carbon atoms. Preferred radical ligands are selected from the group consisting of hydrogen, straight-chain alkyl having 1 to 20 carbon atoms, straight-chain alkenyl having 2 to 20 carbon atoms, branched-chain alkyl or alkenyl having 3 to 20 carbon atoms, cyclic alkyl or alkenyl having 3 to 20 carbon atoms, and aryl or heteroaryl having 4 to 18 carbon atoms, wherein one or more hydrogen atoms may be optionally replaced by F and wherein one or more non-adjacent CFte groups may be optionally replaced by -0-, -(C=0)- or -(C=0)-0-.

More preferably, radical ligands are selected from the group consisting of hydrogen, straight-chain alkyl having 1 to 12 carbon atoms, straight-chain alkenyl having 2 to 12 carbon atoms, branched-chain alkyl or alkenyl having 3 to 12 carbon atoms, cyclic alkyl or alkenyl having 3 to 12 carbon atoms, and aryl or heteroaryl having 4 to 10 carbon atoms, wherein one or more hydrogen atoms may be optionally replaced by F and wherein one or more non-adjacent CFh groups may be optionally replaced by -0-, -(C=0)- or -(C=0)-0-. Most preferably, radical ligands are selected from the group consisting of hydrogen, straight-chain alkyl having 1 to 10 carbon atoms, branched-chain alkyl having 3 to 10 carbon atoms, cyclic alkyl having 3 to 10 carbon atoms, and aryl or heteroaryl having 4 to 10 carbon atoms, wherein one or more hydrogen atoms may be optionally replaced by F and wherein one or more non-adjacent CFte groups may be optionally replaced by -0-, -(C=0)- or -(C=0)-0-.

Particularly preferably, radical ligands are selected from the group consisting of hydrogen, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, phenyl and naphthyl, which optionally may be partially of fully fluorinated. Most preferably, radical ligands are selected from the group consisting of hydrogen, methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, t-butyl, n-pentyl, 2-pentyl, 3-pentyl, 2-methylbutyl, 3-methyl butyl,

3-methylbut-2-yl, 2-methylbut-2-yl, 2,2-dimethylpropyl, n-hexyl, 2-hexyl, 3-hexyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 2-methylpent-2-yl, 3-methylpent-2-yl, 2-methylpent-3-yl, 3-methyl pent-3-yl, 2-ethylbutyl, 3-ethylbutyl, 2,3-dimethylbutyl, 2,3-dimethylbut-2-yl, 2,2-dimethylbutyl, n-heptyl, n-octyl, n-nonyl, n-decyl, phenyl and naphthyl, which optionally may be partially of fully fluorinated. In a particularly preferred embodiment of the present invention the metal amide in the crosslinkable polymer formulation is selected from the group consisting of Ti(NMe2)4, Zr(NMe2)4, AI(NMe2)3 and B(NMb2)3.

Depending on the metal amide used, the presence of moisture or oxygen may play a role in the curing. The skilled worker is familiar with these influences and will adjust the atmospheric conditions appropriately by means of suitable optimization methods. In a preferred embodiment of the present invention the content of the metal amide in the crosslinkable polymer formulation is 0.001 to 10.00 weight-%, preferably 0.005 to 5.00 weight-%, more preferably 0.01 to 3.00 weight-%, most preferably 0.02 to 2.00 weight-%, based on the total weight of the crosslinkable polymer formulation.

Solvents suitable for the crosslinkable polymer formulation are, in particular, organic solvents which contain no water and also no reactive groups such as hydroxyl groups. These solvents are, for example, aliphatic or aromatic hydrocarbons, halogenated hydrocarbons, esters such as ethyl acetate or butyl acetate, ketones such as acetone or methyl ethyl ketone, ethers such as tetrahydrofuran or dibutyl ether, and also mono- and polyalkylene glycol dialkyl ethers (glymes), or mixtures of these solvents.

In a preferred embodiment, the crosslinkable polymer formulation

comprises solvents in an amount of < 5 weight-% based on the total weight of the crosslinkable polymer formulation. In an alternative preferred embodiment, the crosslinkable polymer formulation comprises solvents in an amount of > 5 weight-% based on the total weight of the crosslinkable polymer formulation.

Preferably, the formulation may comprise one or more additives selected from the group consisting of nanoparticles, converters, viscosity modifiers, surfactants, additives influencing film formation, additives influencing evaporation behavior and cross-linkers. Most preferably, said formulation further comprises a converter. Nanoparticles may be selected from nitrides, titanates, diamond, oxides, sulfides, sulfites, sulfates, silicates and carbides which may be optionally surface-modified with a capping agent. Preferably, nanoparticles are materials having a particle diameter of < 100 nm, more preferably < 80 nm, even more preferably < 60 nm, even more preferably < 40 nm, and most more preferably < 20 nm. The particle diameter may be determined by any standard method known to the skilled person, such as e.g. dynamic light scattering (DLS), microscopy (SEM or TEM) or calcu- lation of the average particle size from BET surface area measurement.

It is preferred that in step (a) of the method for preparing an optoelectronic device the crosslinkable polymer formulation is provided on a surface of an optoelectronic device precursor using an application method for applying liquid formulations. Such application methods include, for example, a method of wiping with a cloth, a method of wiping with a sponge, spray coating, flow coating, roller coating, dip coating, slot coating, dispensing, screen printing, stencile printing or ink-jet printing. Further methods include, for example, blade, spray, gravure, dip, hot-melt, roller, slot-die, printing methods, spinning or any other method.

It is further preferred that the crosslinkable polymer formulation is applied in step (a) as a layer in a thickness of 1 pm to 1 cm, more preferably of 10 pm to 1 mm. In a preferred embodiment, the formulation is applied as a layer having a thickness of 1 to 800 pm and more preferably of 10 to 500 pm. In an alternative preferred embodiment, the formulation is applied as a layer having a thickness of 200 pm to 1 cm, more preferably of 200 pm to 5 mm and most preferably of 200 pm to 1 mm.

It is preferred that in step (b) of the method for preparing an optoelectronic device the curing is carried out at elevated temperature, preferably in the range from 140 to 200°C, more preferably in the range from 150 to 190°C and most preferably in the range from 160 to 185°C.

Preferably, the curing in step (b) is carried out on a hot plate, in a furnace, or in a climate chamber. In a preferred embodiment, the curing in step (b) is carried out on a hot plate or in a furnace at a temperature selected from 140 to 200°C, more preferably from 150 to 190°C, and most preferably from 160 to 185°C. In an alternative preferred embodiment, the curing in step (b) is carried out in a climate chamber having a relative humidity in the range from 50 to 99%, more preferably from 60 to 95%, and most preferably from 80 to 90%, at a temperature selected from 10 to 95°C, more preferably from 15 to 85°C, and most preferably from 20 to 85°C.

The optoelectronic device which is obtainable by the method as described above may be an electronic devices that operate on both light and electrical currents. Preferably, the optoelectronic device obtainable by said method is a laser diode, LED, OLED, OLET (organic light emitting transistor), solar cell or photovoltaic cell.

Particular preference is given here to a LED comprising a semiconductor light source (LED chip) and at least one converter, preferably a phosphor or quantum material. The LED is preferably white-emitting or emits light having a certain colour point (colour-on-demand principle). The colour-on- demand concept is taken to mean the production of light having a certain colour point using a pc-LED (= phosphor-converted LED) using one or more phosphors. The encapsulation material forms a barrier against the external environment of the LED device, thereby protecting the converter and/or the LED chip. The encapsulating material is preferably in direct contact with the converter and/or the LED chip.

In a preferred embodiment the semiconductor light source (LED chip) contains a luminescent indium aluminum gallium nitride which preferably is of the formula In.Ga_jAl_kN, where 0 < i, 0 < j, 0 < k, and i + j + k = 1. In a further preferred embodiment the LED is a luminescent arrangement based on ZnO, TCO (transparent conducting oxide), ZnSe or SiC. In a further preferred embodiment the LED is a light source which exhibits electroluminescence and/or photoluminescence.

It is preferred that the crosslinked polymer material is comprised in a converter layer of the LED. Preferably, the converter layer contains the crosslinked polymer material and one or more converters which are preferably selected from phosphors and/or quantum materials.

The converter layer is either arranged directly on the semiconductor light source (LED chip) or alternatively arranged remote therefrom, depending on the respective type of application (the latter arrangement also includes "remote phosphor technology"). The advantages of remote phosphor tech- nology are known to the person skilled in the art and are revealed, for example, by the following publication: Japanese J. of Appl. Phys. Vol. 44, No. 21 (2005), L649-L651.

The optical coupling between the semiconductor light source (LED chip) and the converter layer can also be achieved by a light-conducting arrange- ment. This makes it possible for the semiconductor to be installed at a central location and to be optically coupled to the converter layer by means of light-conducting devices, such as, for example, optical fibres. In this way, it is possible to achieve lamps adapted to the lighting wishes which merely consist of one or various phosphors, which can be arranged to form a light screen, and an optical waveguide, which is coupled to the light source. In this way, it is possible to place a strong light source at a location which is favourable for electrical installation and to install lamps comprising phos- phors which are coupled to the optical waveguides at any desired locations without further electrical cabling, but instead only by laying optical wave- guides. Preferably, the converter is a phosphor, i.e. a substance having

luminescent properties. The term“luminescent” is intended to include both, phosphorescent as well as fluorescent. For the purposes of the present application, the type of phosphor is not particularly limited. Suitable phosphors are well known to the skilled person and can easily be obtained from commercial sources. For the purposes of the present application the term“phosphor” is intended to include materials that absorb in one wavelength of the electromagnetic spectrum and emit at a different wavelength.

Examples of suitable phosphors are inorganic fluorescent materials in particle form comprising one or more emitting centers. Such emitting centers may, for example, be formed by the use of so-called activators, which are preferably atoms or ions selected from the group consisting of rare earth elements, transition metal elements, main group elements and any combination of any of these. Example of suitable rare earth elements may be selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. Examples of suitable transition metal elements may be selected from the group consisting of Cr, Mn, Fe, Co, Ni, Cu, Ag, Au and Zn. Examples of suitable main group elements may be selected from the group consisting of Na, Tl, Sn, Pb, Sb and Bi. Examples of suitable phosphors include phosphors based on garnet, silicate, ortho- silicate, thiogallate, sulfide, nitride, silicon-based oxynitride, nitridosilicate, nitridoaluminumsilicate, oxonitridosilicate, oxonitridoaluminumsilicate and rare earth doped sialon.

Phosphors which may be employed as converters in the crosslinkable polymer formulation of the present invention are, for example:

Ba₂Si0₄:Eu²⁺, Ba₃Si0₅:Eu²⁺, (Ba,Ca)₃Si0₅:Eu²⁺,

BaSi₂N₂0₂:Eu,BaSi₂0₅:Pb²⁺, Ba₃Si60i₂N₂:Eu, Ba_xSri_-xF2:Eu²⁺ (0 £ x £ 1 ), BaSrMgSi₂0₇:Eu²⁺, BaTiP₂0₇, (Ba,Ti)₂P₂0₇:Ti, BaY₂F₈:Er³⁺,Yb⁺,

Preferably, a LED precursor contains a semiconductor light source (LED chip) and/or lead frame and/or gold wire and/or solder (flip chip). The LED precursor may further optionally contain a converter and/or a primary optic and/or a secondary optic. The converter layer may be arranged either directly on a semiconductor light source (LED chip) or alternatively remote therefrom, depending on the respective type of application. The

encapsulation material forms a barrier against the external environment of the LED device, thereby protecting the converter and/or the LED chip. The encapsulation material is preferably in direct contact with the converter and/or the LED chip.

It is preferred that the crosslinkable polymer formulation which is applied to a LED precursor forms part of a converter layer. It may be further preferred that the converter layer is in direct contact to a LED chip or is arranged remote therefrom.

Preferably, the converter layer further comprises one or more converters such as a phosphor and/or quantum material as defined above.

LEDs prepared according to the method of the present invention may, for example, be used for backlights for liquid crystal (LC) displays, traffic lights, outdoor displays, billboards, general lighting, to name only a few non- limiting examples.

Typical LEDs may be prepared similarly to the ones described in US 6,274,924 B1 and US 6,204,523 B1. Moreover, a LED filament as described in US 2014/0369036 A1 may be prepared using the present crosslinkable polymer formulation as a package adhesive layer. Such LED filaments include a substrate, a light emitting unit secured onto at least one side surface of the substrate, and a package adhesive layer surrounded on the periphery of the light emitting unit. The substrate is configured to be of an elongated bar construction. The emitting unit includes a plurality of blue light chips and red light chips regularly distributed on the substrate and sequentially connected to one another in series. The package adhesive layer is made from the crosslinkable polymer formulation according to the present invention which contains a converter. The present invention further relates to a crosslinkable polymer formulation which is obtained from mixing a polymer, and a metal amide; wherein the polymer contains a repeating unit M¹ and further optionally (i) a repeating unit M² or M³ or (ii) a repeating unit M² and M³, wherein the repeating unit M¹ is represented by formula (I), the repeating unit M² is represented by formula (II) and the repeating unit M³ is represented by formula (III):

-[-SiR¹R²-NR³-]- (I) -[-SiR⁴R⁵-NR⁶-]- (II)

-[-SiR⁷R⁸-[0-SiR⁷R⁸-]_a-NR⁹-]- (III) wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ are independently from each other selected from the group consisting of hydrogen, organyl and organoheteryl, and a is an integer from 1 to 60; and

characterized in that the metal amide is represented by formula (1 ):

M(NR₂)mL_n (1 ) wherein

M is selected from the group consisting of B, Al, Ga, Ti and Zr;

L is a ligand other than NR₂ which may be the same or different at each occurrence and is selected from the group consisting of anionic ligands, neutral ligands and radical ligands; m is an integer greater than or equal to 1 ; and

n is an integer greater than or equal to 0;

wherein m + n = 3, if M = B, Al or Ga; and m + n = 4, if M = Ti or Zr. Preferably, m is an integer selected from 1 , 2, 3 and 4.

It is preferred that a is an integer from 1 to 50. More preferably, a may be an integer from 5 to 50 (long chain monomer M³); or a may be an integer from 1 to 4 (short chain monomer M³).

In a preferred embodiment, R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ are independently from each other selected from the group consisting of hydrogen, alkyl having 1 to 40 carbon atoms, alkenyl having 2 to 40 carbon atoms and aryl having 6 to 30 carbon atoms. More preferably, R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ are independently from each other selected from the group consisting of hydrogen, alkyl having 1 to 20 carbon atoms, alkenyl having 2 to 20 carbon atoms and phenyl. Most preferably, R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ are independently from each other hydrogen, methyl or vinyl.

Further preferred substituents R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ are the same as described above in connection with the crosslinkable polymer formulation used in the method for preparing an optoelectronic device. For the substituent R in the metal amide, the preferred, more preferred and most preferred embodiments as described above in connection with the crosslinkable polymer formulation used in the method for preparing an optoelectronic device apply.

Preferred ligands L of the metal amide in the formulation of the present invention are the same as described above in connection with the crosslinkable polymer formulation used in the method for preparing an optoelectronic device.

In a particularly preferred embodiment the metal amide in the crosslinkable polymer formulation according to the present invention is selected from the group consisting of Ti(NMe2)4, Zr(NMe2)4, AI(NMe2)3 and B(NMb2)3.

Depending on the metal amide used, the presence of moisture or of oxygen may play a role in the curing. The skilled worker is familiar with these influences and will adjust the atmospheric conditions appropriately by means of suitable optimization methods.

In a preferred embodiment of the present invention the content of the metal amide in the crosslinkable polymer formulation is 0.001 to 10.00 weight-%, preferably 0.005 to 5.00 weight-%, more preferably 0.01 to 3.00 weight-%, most preferably 0.02 to 2.00 weight-%, based on the total weight of the crosslinkable polymer formulation.

Suitable solvents for the crosslinkable polymer formulation of the present invention are the same as described above in connection with the crosslinkable polymer formulation used in the method for preparing an optoelectronic device.

Preferably, the formulation of the present invention may comprise one or more additives selected from the group consisting of nanoparticles, converters, viscosity modifiers, surfactants, additives influencing film formation, additives influencing evaporation behavior and cross-linkers. Most preferably, said formulation further comprises a converter.

Nanoparticles may be selected from nitrides, titanates, diamond, oxides, sulfides, sulfites, sulfates, silicates and carbides which may be optionally surface-modified with a capping agent. Preferably, nanoparticles are materials having a particle diameter of < 100 nm, more preferably < 80 nm, even more preferably < 60 nm, even more preferably < 40 nm, and most more preferably < 20 nm. The particle diameter may be determined by any standard method known to the skilled person. The crosslinkable polymer formulation of the present invention is prepared by mixing the polymer with the metal amide. The same applies also to the crosslinkable polymer formulation which is used in the method for preparing an optoelectronic device of the present invention. In a preferred

embodiment, the metal amide is added to the polymer and then mixed. In an alternative preferred embodiment the polymer is added to the metal amide and then mixed. The polymer and/or metal amide may be present in a solution. After mixing, the polymer and metal amide may form polymer- metal amide adducts as generally shown in Figure 1. It is preferred that the formulation is prepared at ambient temperature.

Ambient temperature refers to a temperature selected from the range of 20 to 25°C. However, the formulation may also be prepared at temperatures of > 25°C, preferably at temperatures of > 25°C to 150°C. It is preferred that the formulation is prepared under an inert gas

atmosphere such as e.g. under argon or nitrogen.

The crosslinkable polymer formulation of the present invention may be used in the inventive method for preparing an optoelectronic device as described hereinbefore. The present invention is further illustrated by the examples following hereinafter which shall in no way be construed as limiting. The skilled person will acknowledge that various modifications, additions and alternations may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims.

Examples

Example 1 (Reference Material, Siloxazane 2020)

A 4 I pressure vessel was charged with 1 ,500 g of liquid ammonia at 0°C and a pressure of between 3 bar and 5 bar. A mixture of 442 g

dichloromethylsilane and 384 g 1 ,3-dichlorotetramethyldisiloxane were slowly added over a period of 3 h. After stirring the resulting reaction mixture for an additional 3 h the stirrer was stopped and the lower phase was isolated and evaporated to remove dissolved ammonia. After filtration 429 g of a colourless viscous oil remained. 100 g of this oil were dissolved in 100 g 1 ,4-dioxane and cooled to 0°C. 100 mg KH were added and the reaction solution was stirred for 4h, until gas formation stopped. 300 mg chlorotrimethylsilane and 250 g xylene were added and the temperature was raised to room temperature. The turbid solution was filtrated and the resulting clear solution was reduced to dryness at a temperature of 50°C under a vacuum of 20 mbar or less. 95 g of a colourless highly viscous oil of Siloxazane 2020 remained. Example 2 (Reference Material, Siloxazane 2020 containing Triphenyl Aluminum Catalyst)

20 g of Siloxazane 2020 and 2 g of a 10 weight-% solution of triphenyl aluminum solution in THF were placed in a 50 ml flask under nitrogen atmosphere and stirred at 25°C for 4 h until the mixture was completely homogeneous. The flask was connected to a rotary evaporator and at a temperature of 50°C and a pressure of 20 mbar the THF was completely removed. The residue was a clear viscous liquid. Example 3

20 g of Siloxazane 2020 and 0.2 g of Tris-(dimethylamino)-aluminum were placed in a 50 ml flask under nitrogen atmosphere and stirred at 25°C for 4 h until the mixture was completely homogeneous. The product was a clear viscous liquid.

Example 4

20 g of Siloxazane 2020 and 0.2 g of Tris-(dimethylamino)-aluminum were placed in a 50 ml flask under nitrogen atmosphere and stirred at a temperature of 100°C for 6 h. The mixture was cooled down to room temperature. The product was a clear liquid with slightly increased viscosity compared to the raw material Siloxazane 2020. Example 5

20 g of Siloxazane 2020 and 0.2 g of Tetrakis-(dimethylamino)-zirconium were placed in a 50 ml flask under nitrogen atmosphere and stirred at 25°C for 4 h until the mixture was completely homogeneous. The product was a clear viscous liquid.

Example 6

20 g of Siloxazane 2020 and 0.2 g of Tetrakis(dimethylamino)-titanium were placed in a 50 ml flask under nitrogen atmosphere and stirred at 25°C for 4 h until the mixture was completely homogeneous. The product was a clear coloured viscous liquid.

Curing Conditions

Condition I: 150°C in heating cabinet for times of 2 h, 4 h and 6 h.

Condition 11: 180°C in heating cabinet for times of 2 h, 4 h and 6 h. Application Test procedure: Shore A Hardness of cured films

The materials prepared according to the Examples 1 and 3 to 6 were applied on glass plates by doctor-blade coating at a film thickness of 90 pm - 100 pm. The glass plates were then exposed to 150°C and 180°C for different times of 2 h, 4, h and 6 h (as described under Curing Conditions I and II) and after cooling down to room temperature the Shore-A values were measured using a Shore-A Hardness Testing equipment of type “Shore A nano Typ SHAN.01” from q-tec GmbH.

Table 1 : Shore A Hardness after curing at 150°C for 2 h, 4 h and 6 h (Curing Conditions I)

Table 2: Shore A Hardness after curing at 180°C for 2h, 4h and 6h (Curing Conditions II) These results show the effect of the presence of the metal amide on the curing rate of organopolysiloxazanes. The curing rate, expressed as change (increase) of the Shore-A hardness with time is significantly increased in comparison to the pure Siloxazane of Example 1. Furthermore, the comparison between the material of Example 3 and the material of Example 4 shows no significant difference between the two preparation methods of room temperature and elevated temperature reaction.

Application Test procedure: Crack formation of cured films

The materials prepared according to the Examples 1 to 6 were applied on glass plates by doctor-blade coating at film thicknesses of 50 pm up to 300 pm in steps of 50 pm. The glass plates were then exposed to 180°C for 4 h and subsequently to 220°C for 4 h in a heating cabinet. The samples were removed from heating cabinet, cooled down to room temperature and optically examined to detect cracks in the films.

220°C.“NO” indicates no crack formation,“YES” indicates crack formation

Compared to the reference material of Example 1 , which shows cracks at 200 pm, the metal amide containing materials of Examples 3 to 6 do not form cracks up to 300 pm film thickness. Addition of other metal additives as demonstrated in Example 2, has a small positive effect on higher film thickness without cracks, too, however no film thickness of more than 200 pm can be achieved hereby. Application Test procedure: LED Reliability Test

To show its usefulness for LED devices, the materials prepared according to the Examples 1 , 3, 4 and 5 were tested on an Excelitas LED package. Each material was mixed by using a planetary centrifugal mixer with a phosphor (isiphor® YYG 545 200, available from MERCK KGaA) in a weight ratio of 4 : 1 (material mass to phosphor mass). The resulted slurry was then dispensed on a LED package (available from Excelitas) by means of an automated dispensing equipment. The target colour point was chosen to be at a Correlated Colour Temperature (CCT) of 5500 K ± 200 K. The LED-package was cured at 180°C for 6 h on a hot plate under air atmosphere. The LEDs were then operated at a current of 1000 mA at ambient conditions for 1000 h and the change in colour coordinates (Dc and Ay in the CIE 1931 chromaticity coordinate system) was measured. The target is no or at least a very small change in colour coordinates (lower change is better).

Table 4: Deviation of colour point after 1000h ⁽¹⁾ Measurement error = +/- 0.001

The comparison of entry 1 with entry 2, 3 and 4 shows an improved colour stability (reduced colour point shift Dc and Ay) of the materials containing metal amides.

Claims

1. A method for preparing an optoelectronic device comprising a

crosslinked polymer material which is prepared from a crosslinkable polymer formulation, wherein the method comprises the following steps:

(a) applying a crosslinkable polymer formulation to a precursor of an optoelectronic device; and

(b) curing said crosslinkable polymer formulation to obtain a

crosslinked polymer material;

a metal amide which is represented by formula (1 ):

M(NR₂)mL_n (1 ) wherein

M is selected from the group consisting of B, Al, Ga, Ti and Zr;

R may be the same or different at each occurrence and is selected independently from the group consisting of hydrogen, straight-chain alkyl having 1 to 20 carbon atoms, straight-chain alkenyl having 2 to 20 carbon atoms, branched-chain alkyl or alkenyl having 3 to 20 carbon atoms, cyclic alkyl or alkenyl having 3 to 20 carbon atoms, and aryl or heteroaryl having 4 to 18 carbon atoms, wherein one or more hydrogen atoms may be optionally replaced by F and wherein one or more non-adjacent CH₂ groups may be optionally replaced by

-0-, -(C=0)- or -(C=0)-0-;

n is an integer greater than or equal to 0;

wherein m + n = 3, if M = B, Al or Ga; and m + n = 4, if M = Ti or Zr. 2. The method for preparing an optoelectronic device according to claim

1 ,

wherein the repeating unit M¹ is a silazane repeating unit represented by formula (I): -[-SiR¹R²-NR³-]- (I) wherein R¹, R² and R³ are independently from each other selected from the group consisting of hydrogen, organyl and organoheteryl. 3. The method for preparing an optoelectronic device according to claim

2,

wherein R¹, R² and R³ are independently from each other selected from the group consisting of hydrogen, alkyl having 1 to 40 carbon atoms, alkenyl having 2 to 40 carbon atoms and aryl having from 6 to 30 carbon atoms.

4. The method for preparing an optoelectronic device according to one or more of claims 1 to 3,

wherein the polymer contains a further repeating unit M², wherein M² is a silazane repeating unit represented by formula (II):

-[-SiR⁴R⁵-NR⁶-]- (II) wherein R⁴, R⁵ and R⁶ are independently from each other selected from the group consisting of hydrogen, organyl and organoheteryl; and

wherein M² is different from M¹.

5. The method for preparing an optoelectronic device according to claim 4,

wherein R⁴, R⁵ and R⁶ are independently from each other selected from the group consisting of hydrogen, alkyl having 1 to 40 carbon atoms, alkenyl having 2 to 40 carbon atoms and aryl having from 6 to 30 carbon atoms.

The method for preparing an optoelectronic device according to one or more of claims 1 to 5,

wherein the polymer contains a further repeating unit M³, wherein M³ is represented by formula (III):

-[-SiR⁷R⁸-[0-SiR⁷R⁸-]_a-NR⁹-]- (III) wherein R⁷, R⁸, R⁹ are independently from each other selected from the group consisting of hydrogen, organyl and organoheteryl; and a is an integer from 1 to 60. 7. The method for preparing an optoelectronic device according to claim

6,

wherein R⁷, R⁸ and R⁹ are independently from each other selected from the group consisting of hydrogen, alkyl having 1 to 40 carbon atoms, alkenyl having 2 to 40 carbon atoms and aryl having 6 to 30 carbon atoms.

8. The method for preparing an optoelectronic device according to one or more of claims 1 to 7,

wherein the content of the metal amide in the crosslinkable polymer formulation is 0.001 to 10.00 weight-%, preferably 0.005 to 5.00 weight-%, more preferably 0.01 to 3.00 weight-%, most preferably

0.02 to 2.00 weight-%, based on the total weight of the crosslinkable polymer formulation.

9. The method for preparing an optoelectronic device according to one or more of claims 1 to 8,

wherein R is at each occurrence selected independently from the group consisting of hydrogen, straight-chain alkyl having 1 to 12 carbon atoms, straight-chain alkenyl having 2 to 12 carbon atoms, branched-chain alkyl or alkenyl having 3 to 12 carbon atoms, cyclic alkyl or alkenyl having 3 to 12 carbon atoms, and aryl or heteroaryl having 4 to 10 carbon atoms, wherein one or more hydrogen atoms may be optionally replaced by F and wherein one or more non- adjacent CFh groups may be optionally replaced by -0-, -(C=0)- or -(C=0)-0-.

10. The method for preparing an optoelectronic device according to one or more of claims 1 to 9, wherein

the anionic ligands are selected from halides, cyanide, alcoholates, carboxylates, deprotonated keto acids, deprotonated keto esters and deprotonated diketones;

the neutral ligands are selected from alcohols and carbon monoxide; and

the radical ligands are selected from the group consisting of hydrogen, straight-chain alkyl having 1 to 20 carbon atoms, straight- chain alkenyl having 2 to 20 carbon atoms, branched-chain alkyl or alkenyl having 3 to 20 carbon atoms, cyclic alkyl or alkenyl having 3 to 20 carbon atoms, and aryl or heteroaryl having 4 to 18 carbon atoms, wherein one or more hydrogen atoms may be optionally replaced by F and wherein one or more non-adjacent CFh groups may be optionally replaced by -0-, -(C=0)- or -(C=0)-0-.

11. The method for preparing an optoelectronic device according to one or more of claims 1 to 10,

wherein the curing in step (b) is carried out at elevated

temperature, preferably in the range from 140 to 200°C, more preferably in the range from 150 to 190°C and most preferably in the range from 160 to 185°C.

12. An optoelectronic device,

obtainable by the method according to one or more of claims 1 to 1 1 .

13. A crosslinkable polymer formulation which is obtained from mixing: a polymer, and

a metal amide;

characterized in that the polymer contains a repeating unit M¹ and further optionally (i) a repeating unit M² or M³ or (ii) a repeating unit M² and M³, wherein the repeating unit M¹ is represented by formula (I), the repeating unit M² is represented by formula (II) and the repeating unit M³ is represented by formula (III):

-[-SiR¹R²-NR³-]- (I)

-[-SiR⁴R⁵-NR⁶-]- (II)

-[-SiR⁷R⁸-[0-SiR⁷R⁸-]_a-NR⁹-]- (III) wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ are independently from each other selected from the group consisting of hydrogen, organyl and organoheteryl, and a is an integer from 1 to 60; and characterized in that the metal amide is represented by formula (1 ):

M(NR₂)mL_n (1 )

wherein

M is selected from the group consisting of B, Al, Ga, Ti and Zr; R may be the same or different at each occurrence and is selected independently from the group consisting of hydrogen, straight-chain alkyl having 1 to 20 carbon atoms, straight-chain alkenyl having 2 to 20 carbon atoms, branched-chain alkyl or alkenyl having 3 to 20 carbon atoms, cyclic alkyl or alkenyl having 3 to 20 carbon atoms, and aryl or heteroaryl having 4 to 18 carbon atoms, wherein one or more hydrogen atoms may be optionally replaced by F and wherein one or more non-adjacent CFte groups may be optionally replaced by -0-, -(C=0)- or -(C=0)-0-;

m is an integer greater than or equal to 1 ; and

n is an integer greater than or equal to 0;

wherein m + n = 3, if M = B, Al or Ga; and m + n = 4, if M = Ti or Zr.

14. The crosslinkable polymer formulation according to claim 13,

wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ are independently from each other selected from the group consisting of hydrogen, alkyl having 1 to 40 carbon atoms, alkenyl having 2 to 40 carbon atoms and aryl having 6 to 30 carbon atoms.

15. The crosslinkable polymer formulation according to claim 13 or 14, wherein the content of the metal amide in the crosslinkable polymer formulation is 0.001 to 10.00 weight-%, preferably 0.005 to 5.00 weight-%, more preferably 0.01 to 3.00 weight-%, most preferably 0.02 to 2.00 weight-%, based on the total weight of the crosslinkable polymer formulation. 16. The crosslinkable polymer formulation according to one or more of claims 13 to 15, wherein R is at each occurrence selected independently from the group consisting of hydrogen, straight-chain alkyl having 1 to 12 carbon atoms, straight-chain alkenyl having 2 to 12 carbon atoms, branched-chain alkyl or alkenyl having 3 to 12 carbon atoms, cyclic alkyl or alkenyl having 3 to 12 carbon atoms, and aryl or heteroaryl having 4 to 10 carbon atoms, wherein one or more hydrogen atoms may be optionally replaced by F and wherein one or more non- adjacent CFte groups may be optionally replaced by -0-, -(C=0)- or -(C=0)-0-.

17. The crosslinkable polymer formulation according to one or more of claims 13 to 16,

wherein L is selected from the list consisting of anionic ligands, neutral ligands and radical ligands.