WO2014161100A1

WO2014161100A1 - Silane functionalized buffer layers and electronic devices comprising the same

Info

Publication number: WO2014161100A1
Application number: PCT/CH2014/000042
Authority: WO
Inventors: Norman Albert Lüchinger; Samuel Claude Halim; Tobias STUBHAN; Christoph Brabec
Original assignee: Nanograde Ag
Priority date: 2013-04-03
Filing date: 2014-04-02
Publication date: 2014-10-09
Also published as: KR20150137101A; EP2981992A1; CN105074952A

Abstract

The present invention relates to the field of organic electronics, such as OLEDs, OPVs and organic photodetectors with inverted structure. Said device comprises a substrate and a multitude of layers, wherein at least one of said layers is a buffer layer, wherein said buffer layer comprises metal oxide nanoparticles coated with unsubstituted or substituted alkyl-alkoxy-silanes. Preferably, the buffer layer is used as a cathode buffer layer.

Description

Silane functionalized buffer layers and electronic devices comprising the same

The present invention relates to the field of organic electronics, such as OLEDs, OPVs and photodetectors . It particularly provides intermediate goods and materials suitable for manufacturing such organic electronics, to specific manufacturing methods and to specific uses. It is known to use buffer layers in organic electronics, such as organic light emitting diodes (OLED) or organic photovoltaic cells (OPV) , in order to increase device efficiency and life-time. Such buffer layers comprise metal oxides, such as ZnO, TiOx, WOx, NiO, NbyOx, or doped metal oxides, such as Al-doped ZnO ("AZO") . Generally, such metal oxides in particulate form are known. Typically, the above named oxidic buffer layers are manufactured by thermal evaporation under high vacuum; which is disadvantageous in terms of low-cost, large-area manufacturing processing.

It is also known that polymer solar cells (OPV) offer a promising approach for a low-cost and flexible photovoltaic technology with certified efficiencies exceeding 10 %. Before widespread commercialization, large area production and stability issues have to be solved. For the reliable large area production with high yield and low shunts, thick, stable, robust and printable buffer layers are a prerequisite . It is also known to use channel layers in transistors, particularly in TFTs. Such channel layers comprise metal oxides, such as ZnO, or mixed oxides, such as indium zinc oxide (ZITO) , indium gallium zinc oxide (IGZO) or ZnSn03. Generally, such metal oxides in particulate form are known. As discussed above, such oxidic layers are manufactured by thermal evaporation under high vacuum; which is disadvantageous in terms of low-cost, large-area manufacturing processing. Leidolph et al (EP2157053) describe specific ZnO particles, which are optionally coated, and the manufacturing thereof. It is further speculated about the use of such particles, for example in solar cells.

Rohe et al (WO2006/092443) describe surface-modified ZnO particles and the manufacturing thereof. It is further speculated about the use of such particles in photogalvanic and photoelectric cells.

Yip et al. (Adv. Mater., 2008, 20, 2376-2382) report on a solution-processed nanoparticulate ZnO buffer layer in organic solar cells. The coating liquid is a suspension of unmodified ZnO nanopart icles in 1-butanol. This suspension was applied on organic layers without damaging them and secondly, a temperature post-treatment of < 100°C was sufficient. Direct contact of the deposited ZnO layer with a silver electrode resulted in low performance devices with low fill factors. In order to improve the contact between the ZnO and the silver, Yip et al apply a self assembled monolayer (SAM) at the interface ZnO/Ag. Application of a SAM layer includes a separate and additional processing step, which is considered disadvantageous. Stubhan et al. (Solar Energy Materials & Solar Cells, 107 (2012), 248-251) report on solution-processed AZO ETL layers which are produced by a sol-gel technique. A temperature treatment of such layers below 150°C is sufficient in order to obtain high performance organic solar cells. But still, this material is limited to inverted device architectures because deposition of the sol-gel precursor liquid on top of an active organic layer will damage this layer. This disadvantageous effect is shown in the present application (see examples for the sol- gel produced AZO (LT-AZO) .

Puetz et al. (Solar Energy Materials, 2011, 579) disclose unmodified, Indium doped Zinc oxide nanoparticle suspension and its use between an active layer and a silver electrode .

Hsu et al. (WO2009/086337 ) disclose buffer bilayers for electronic devices. These devices may be obtained by coating a substrate with a suspension comprising a mixture of TiOx, Si02, ZrOx and an unspecified silane coupling reagent. However, the layers containing these particles are not suited as buffer layers itself. Rather bilayers are required according for obtaining sufficient buffering effect. Further, the suspensions used for manufacturing such buffer layers show insufficient stability, resulting in inhomogeneous films with high surface roughness and manufacturing processes difficult to control.

Saneto et al. (US2009/0243477 ) disclose organic electronic display devices comprising a multitude of layers. These layers may comprise T1O2 coated particles, which are comparatively large. The cited layers are not buffer layers, but high refractive index (high RI) layers.

Until now, no metal oxide buffer layers (particularly no ZnO or AZO ETL layers) for organic electronics are known which are present between an active organic layer and a silver electrode ("inverted architecture") meeting industrial demands. The reason for this is that either the coating liquid is damaging the active layer (see above, Stubhan et al) or is forming an insufficient contact with the silver electrode (see above, Yip et al) .

Thus, it is an object of the present invention to mitigate at least some of these drawbacks of the state of the art. In particular, it is an aim of the present invention to provide compositions suitable for thin film formation on a plurality of substrates. It is a further aim to provide manufacturing methods for thin films avoiding vapor phase processes and to provide improved electrical devices and intermediate goods. These objectives are achieved by a device as defined in claim 1 and an intermediate good as defined in claim 9 and the uses as defined in claim 12. Further aspects of the invention are disclosed in the specification and independent claims, preferred embodiments are disclosed in the specification and the dependent claims.

The present invention will be described in detail below. It is understood that the various embodiments, preferences and ranges as provided / disclosed in this specification may be combined at will. Further, depending of the specific embodiment, selected definitions, embodiments or ranges may not apply. Unless otherwise stated, the following definitions shall apply in this specification:

The terms "a", "an", "the" and similar terms used in the context of the present invention are to be construed to cover both the singular and plural unless otherwise indicated herein or clearly contradicted by the context. Further, the terms "including", "containing" and "comprising" are used herein in their open, non-limiting sense. The term "containing" shall include both, "comprising" and "consisting of".

Percentages are given as weight-%, unless otherwise indicated herein or clearly contradicted by the context. The term "electronic device" is known in the field. In the context of the present invention, any device comprising functional thin films is encompassed, including inorganic LEDs, inorganic solar cells or inorganic transistors; but specifically organic electronics as defined below.

The terms "organic electronics", "OLED", "OPV" , "organic photodetector" are known in the field and relate to electronic devices comprising a substrate and a multitude of layers, wherein at least one layer is an electron transport layer (ETL) . Depending on the remaining layers, its structure and connection, these devices serve a multitude of purposes, such as an OLED, an OPV cell or an organic photo detector.

The term "Buffer layer" denotes an interface layer in electronic devices, typically in OPV or OLED devices. Buffer layer is the general term for layers with different functions such as hole transport (HTL) , hole injection (HIL) , hole extraction (HEL) , electron transport (ETL) , electron injection (EIL) or electron extraction (EEL). In the context of the present invention the term buffer layer is generally representing the different specific functions. A buffer layer is often also referred as charge selective layer (CTL) . Accordingly, the term buffer layer includes both, electron selective layers and hole selective layers. Buffer layers may be present in the form of a "bilayer" or in the form of a "monolayer". According to this invention it is possible, and preferred, obtaining buffer layers in the form of mono-layers.

The term "active material" denotes a material which is photoactive and either converts light into electrical energy (light absorbing; e.g. solar cells or photodetectors ) or converts electrical energy into light (light emitting; e.g. LED's). Active materials are inorganic or organic. Organic active materials are either polymers or small molecules. Thus, the term "active materials" shall include "photoactive polymers" and "photoactive small molecules" as used herein.

The term "nanoparticle" is known and particularly relates to solid amorphous or crystalline particles having at least one dimension in the size range of 1 - 100 nm. Preferably, nanoparticles are approximately isometric (such as spherical or cubic nanoparticles ) . Particles are considered approximately isometric, in case the aspect ratio (longest : shortest direction) of all 3 orthogonal dimensions is 1 - 2. In an advantageous embodiment, the nanoparticles have a mean primary particle size of 2 - 60 nm, preferably 5 - 30 nm (measured by transmission electron microscopy) .

The term "nanoparticle layer" denotes a film composed of nanoparticles. The thickness of the nanoparticle layer may vary over a broad range, but typically is 3 - 1000 nm, preferably 10 - 300 nm. A nanoparticle layer can be composed of a monolayer of nanoparticles, thus having a thickness equal to the size of the used nanoparticles and thus defining a lower limit of the thickness. A nanoparticle layer can be composed of nanoparticles with a single size or with a bimodal or multimodal size distribution. Bimodal or multimodal size distributions are believed to result in a higher packing density of the nanoparticle layer. Further, the volume porosity of a nanoparticle layer typically is less than 95%, preferably less than 70%.

The term "Metal oxide nanoparticles" includes (i) nanoparticles of pure oxides, (ii) nanoparticles of doped oxides and (iii) core shell nanoparticles, whereby the core and shell are composed of different oxides. Accordingly, Si02 nanoparticles are not considered metal oxide nanoparticles .

The term "AZO" is known in the field and includes Aluminum doped Zinc oxides meaning that the Aluminum is atomically dispersed in the Zinc oxide lattice (solid solution) . Similarily, Nb-doped TiOx means that Nb is atomically dispersed in the titanium oxide lattice (solid solution) .

The term "SAM" is known in the field and denotes a self- assembled monolayer. Self-assembled monolayers of organic molecules are molecular assemblies formed spontaneously on surfaces by adsorption and are organized into more or less large ordered domains. The term "organic solvent" is known in the field and particularly includes alcohols (particularly glycol- ethers), nitriles, ketones, esters, ethers, aldehydes and aliphatic solvents. The above organics can be substituted or unsubstituted and include linear, branched and cyclic derivatives. There can also be unsaturated bonds in the molecule. The above derivatives typically have 1 - 12 carbon atoms, preferably 1 - 7 carbon atoms. The terms "surfactant", "dispersant" and "dispersing agent" are known in the field and have essentially the same meaning. In the context of the present invention, these terms denote an organic substance, other than a solvent, which is used in suspensions or colloids to improve the separation of particles and to prevent agglomeration or settling. Surfactants, dispersants and dispersing agents can be polymers or small molecules and typically contain functional groups. Surfactants, dispersants and dispersing agents are physically or chemically attached on the particle surface either before or after adding the particles to the external phase. In the context of the present invention, water and organic solvent molecules (e.g. ethanol, methanol or isopropanol) are not considered surfactants, dispersants or dispersing agents.

The term "suspension" is known and relates to a heterogeneous fluid of an internal phase (i.p.) that is a solid and an external phase (e.p.) that is a liquid. In the context of the present invention, a suspension typically has a kinetic stability of at least 1 day (measured according to complete particle sedimentation) . In an advantageous embodiment, the invention provides for a composition with (hydrodynamic size D90 of less than 100 nm) a shelf-life of more than 7 days, particularly more than 2 months. The external phase typically comprises one or more solvents, such as water, ethanol, ethanol/water and the like. The term "solution-processing" is known in the field and denotes the application of a coating or thin film to a substrate by the use of a solution-based (=liquid) starting material. In the context of the present invention, solution processing relates to the fabrication of organic electronics and intermediate goods comprising thin nanoparticle films by the use of one or more liquid suspensions; typically the application of the suspension ( s ) is/are conducted at ambient pressure.

The present invention will be better understood by reference to the figures .

Fig. 1 outlines the various aspects of the present invention. In summary, the invention describes electronic devices from the group of organic electronics (DEV; 1^st aspect of the invention) having specific buffer layer (s); intermediate goods (INT, 2^nd aspect) suitable for manufacturing the above organic electronics; compositions in the form of a suspension (COMP, 3^rd aspect) suitable for manufacturing the above intermediate goods by wet phase processing. These compositions may be obtained by combining known starting materials, such as MOx nanoparticles (N.P.), alkyl-alkoxy-silanes (ADD) and solvents (SOLV) .

Fig. 2 shows the essential layers of an intermediate good (INT), useful for the manufacturing of organic electronics, wherein (3) is a buffer layer as described herein, (1) is an organic active layer (e.g. a polymeric active layer or a small-molecule active layer) and (2) is a second buffer layer (opposite polarization compared to the first buffer layer) . The second buffer layer can either have a composition according to this invention or to a different material (e.g. state-of-the art material). Typically, the three depicted layers are only part of a more complex layer architecture forming an intermediate product; underneath or on top of the depicted layers can be an electrode which can be transparent or non-transparent or can be additional buffer layers (either according to this invention or not) .

Figure 3 shows a schematic illustration for an inventive nanoparticle layer composition comprising (3) ZnO or AZO as the electron selective layer. An Ag electrode (4) directly attached to the ETL layer. No SAM layer is present between the Ag electrode and the electron selective layer. Figure 4 shows a side-by-side test of the stability of suspensions containing coated nanoparticles as described in example 2: according to this invention (sample C) and according to the prior art (sample A and B) . In a first aspect, the invention relates to an electronic device selected from the group of organic electronics wherein said device comprises a substrate and a multitude of layers, wherein at least of said layers is a buffer layer, wherein said buffer layer comprises metal oxide nanoparticles coated with an unsubstituted or substituted alkyl-alkoxy-silane .

In more general terms, the invention relates to buffer layers in an electronic device such as OPV or OLED, said buffer layers having a specific and beneficial composition containing a metal oxide as described below and silanes as described below. It was found that the present inventive ETL compositions show beneficial properties because: (i) no post-treatment (e.g. plasma cleaning or annealing temperatures > 150°C) is required to achieve good device performance and (ii) such buffer layers are directly compatible with vacuum deposited Ag electrodes without the need of an additional SAM layer. Without being bound to theory, it is believed the coating of nanoparticles with the above named silanes provides specific beneficial properties to said nanoparticles: The alkyl-alkoxy-silanes used have the same function as a surfactant or dispersant. Thereby, manufacturing of the electronic devices is facilitated and/or performance is improved.

This aspect of the invention shall be explained in further detail below.

Electronic device: In the context of the present invention, any device comprising functional thin films is encompassed, including electronic devices, inorganic LEDs inorganic solar cells or inorganic transistors; specifically organic electronic devices. The term organic electronics is defined above .

In one embodiment, the device is selected from the group of organic solar cells (OPV) , organic light emitting diodes (OLED) and organic photodetectors ; particularly OPV and OLED, very particularly OPV.

In one embodiment, the multitude of layers of the device is arranged in normal architecture. Accordingly, the invention relates to an OPV or OLED device where the electron transport layer is applied between a silver electrode and an organic active material. In one embodiment, the multitude of layers of the device is arranged in inverted architecture.

In a further embodiment, the invention relates to an OPV device with tandem architecture.

In a further embodiment, the invention relates to an OPV device with tandem architecture whereby an inventive layer of this invention is part of the recombination layer. In one embodiment, the buffer layer is selected from the group consisting of hole transport (HTL) , hole injection (HIL) , hole extraction (HEL) , electron transport (ETL) , electron injection (EIL) and electron extraction (EEL) layers . In one embodiment, the substrate is selected from hydrophobic or hydrophilic organic materials, preferably PEDOT:PSS, photoactive polymers (absorbers or emitters) or photoactive small molecules (absorbers or emitters). Generally, suitable materials possess a surface free energy below 40 mJ/m².

In one further embodiment, the substrate is selected from a hydrophilic inorganic material, preferably ITO or silver (including a vacuum deposited dense Ag layer or a solution processed porous Ag nanowire layer) .

In one embodiment, the top electrode of the device is a silver, a copper or a nickel electrode, particularly a Ag- , Cu- or Ni- nano wire electrode. The nano wires of such electrodes can be embedded in the hydrophilic or hydrophobic organic materials as defined above, particularly in PEDOT:PSS. In one embodiment, the top and bottom electrodes are both made from metal nanowires. This embodiment provides transparent or semitransparent electronic devices. The nano wires of such electrodes can be embedded in the hydrophilic or hydrophobic organic materials as defined above, particularly in PEDOT:PSS.

In one embodiment, the top and/or bottom electrode is pure PED0T:PSS. In one further embodiment, the top and/or bottom electrode is a combination of PEDOT:PSS with a regular metal collector grid (such as an Ag-, Cu- or Ni- collector grid) .

Metal oxide nanoparticles : The term metal oxide nanoparticles is defined above.

In one embodiment, the nanoparticles are selected from the group consisting of pure metal oxides, preferably Ox, VyOx, MoyOx, NiO, and NbyOx. A particularly preferred pure metal oxide is ZnO. A further particularly preferred pure metal oxide is TiOx.

In one embodiment, the nanoparticles are selected from the group consisting of mixed metal oxides, preferably zinc containing mixed metal oxides, most preferably indium gallium zinc oxide (IGZO), indium zinc oxide (IZO), zinc tin oxide (ZnSn0₃) . In one embodiment, the nanoparticles are selected from the group consisting of doped metal oxides, particularly doped WOx, VyOx, MoyOx, NiO, and NbyOx, most preferably ZnO and TiOx. Suitable dopants and amounts of dopants are known in the field. The term doped metal oxide relates to compositions of M0_X where Metal (M) is substituted by one or more metals ( ="dopants") . The dopant atoms are incorporated into the ΜγΟ_χ crystal lattice either substitutional^ or interstitially forming a homogeneous single-phase (a "solid solution") . In the context of the present invention, separated multiphase systems (e.g. MO_x + Fe20₃) are not considered doped oxides. Doping of oxides can enable the fine tuning of the properties of the inventive thin films, such as electrical conductivity, work function and / or optical absorbance.

In a preferred embodiment said metal oxides are doped with 0.001-30wt%, preferably 0.01-15wt%, most preferably 0.1- 10wt% (with respect to the metal), by one or more metals. In a preferred embodiment, said dopant atoms are selected from the group consisting of transition metals, alkaline metals and earth-alkaline metals.

In one embodiment, the nanoparticles (pure metal oxides, doped metal oxides) additionally contain carbonaceous material. The amount of carbonaceous material may be in the range of 0.2-4wt%. The carbonaceous material may be present in sp2 and/or sp3 hybridization, saturated with hydrogen at the terminal positions. The carbonaceous material may form a separate phase within the metal oxide nanopart icle , e.g. by forming a core or by forming dotted areas. Such materials are known and described e.g. in Leidolph et al, cited above. In one embodiment, the nanoparticles are selected from ZnO, Al-doped ZnO ("AZO") , ZnO containing carbonaceous material, AZO containing carbonaceous material. In one further embodiment, the nanoparticles are selected from TiOx and Nb-doped TiOx.

Alkyl-alkoxy-silane: Alkyl-alkoxy-silanes are also termed silane coupling agents or simply ^silanes' and are known in the field. Suitable silanes are of formula (I) [ (R^2')xSi (ORⁱ)y] (I) wherein R¹ and R²~ represent Ci-Cio alkyl, substituted C -Cio alkyl; x = 1 and y = 3 or x = 2, y = 2 or x = 3 and y = 1. Such silanes may be partly condensed.

In one embodiment, such silanes are of formula (II) {R^lO) 3-Si-R²-FG (II) wherein

R¹ represents C1-C4 alkyl (preferably methyl, ethyl, isopropyl, butyl) , Ci-Cj-alkoxy-C i - Ci-alkyl (preferably methoxyethyl ) ,

R² represents C1 -C10 alkyl, saturated or unsaturated C3-C10 carbocyclic groups,

FG represents -OH, -NH₂, -P (O) (OR^1' ) 2 , -OP (0) (OM) R , -SH, - C(0) (OH) , -C(0) (OR ), -vinyl, -acrylate, -epoxy, - aldehyde, -NR ₃X (X halogen) , -azide, -halogen, isocyanate, -thiophene, pyridyl, phenyl, benzyl, nitro, -CiOJNR¹, -benzotriazole, where R is C1-C6 alkyl, Ci-C-j-alkoxy-Ci-C-j-alkyl and M is hydrogen or alkali metal, preferably Na. In one preferred embodiment, the substituents are as defined in the claims.

In one preferred embodiment, such silane is 3-Trihydroxy- silylpropylmethyl-phosphonate , sodium salt.

In one preferred embodiment, such silane is Diethylphosphato-ethyl-triethoxysilane . In one alternative embodiment, such silane contains semiconducting functionalities or pi-conjugated bond sequences. These functionalities are believed to enhance the electronic charge transport properties of nanoparticle layers. Suitable are, for example, conjugated derivatives. In this embodiment, FG represents a conjugated C4-C12 polyalkene derivative.

Coating: Without being bound to theory, it is believed that the passivation of the nanoparticle oxide surface by siloxane functionalities has a beneficial effect on the electronic properties of corresponding buffer layers. As used herein, the term coating includes (i) direct chemical bonding (e.g. a covalent bond) between the metal oxides as defined herein and the silanes as defined herein and (ii) adsorption of the silanes on the surface of the metal oxides (e.g. physisorption) . An equilibrium between chemical bonding/adsorption and free components may exist, depending on the metal oxide and the silane. Given the above, the terms "coated nanoparticles" and "functionalized nanoparticles" may be used synonymously.

In one embodiment, the invention provides a buffer layer with a composition as described herein wherein said layer consists of metal oxide nanoparticles and an alkyl-alkoxy- silane.

In one embodiment, said metal oxide nanoparticles are coated ( functionalized) with one type of alkyl-alkoxy- silane as defined herein. In one alternative embodiment, said metal oxide nanoparticles are coated ( functionalized) with two or more types of alkyl-alkoxy-silanes as defined herein. In this embodiment, either an individual nanoparticle is coated ( functionalized) with said two or more types of silanes or a first group on nanoparticles is coated ( functionalized) with a first silane, a second group of nanoparticles is coated ( functionalized) with a second silane and so on.

In a further embodiment, the invention provides a buffer layer with the following composition:

80 - 99wt% Metal oxide

0.1 - 5wt% Silicon.

80 - 99 wt% Metal oxide

0.1 - 5 wt% Silicon

0.1 - 5 wt% Phosphorus.

The layers described herein have beneficial properties and have advantageous uses as outlined below. It was found that the inventive layers show good device performance in a device architecture where an Ag electrode is in direct contact with the inventive ETL layers.

In an advantageous embodiment, the invention provides a buffer layer as described herein containing 80-99wt%, preferably 90 - 98 wt% ZnO nanoparticles and 1 - 20 wt%, preferably 2 - 10 wt% Dieth-P.

In an advantageous embodiment, the invention provides a buffer layer as described herein containing 80-99wt%, preferably 90 - 98 wt% AZO nanoparticles and 1 - 20 wt%, preferably 2 - 10 wt% Dieth-P.

In a further embodiment, the invention provides an electronic device as described herein wherein said buffer layers have a film thickness of 3 - 1000 nm, preferably 10 - 500 nm, much preferably 15 - 100 nm. Thickness may be determined by profilometry or atomic force microscopy. In a further embodiment, the invention provides an electronic device as described herein wherein said oxide nanoparticles have a primary particle diameter of 1 - 200 nm, preferably 4 - 50nm (measured by nitrogen absorption, X-Ray diffraction or transmission electron microscopy) .

In a further embodiment, the invention provides an electronic device as described herein wherein said oxide nanoparticles exhibit a bimodal or multimodal size distribution. It is believed that bimodal or multimodal size distributions result in higher particle packing densities, thus resulting in lower layer porosity.

In a further embodiment, the invention provides an electronic device as described herein wherein said buffer layers have a mean surface roughness below 100 nm, especially below 30 nm (determined by electron microscopy, atomic force microscopy or profilometry) .

In a further embodiment, the invention provides an electronic device as described herein wherein said buffer layer has an electrical conductivity of 10^~8 - 10² S/cm, preferably 10^~6 - 1 S/cm (determined by 4-point conductivity measurement) . In a further embodiment, the invention provides an electronic device as described herein wherein said buffer layer is present in the form of a mono-layer.

In a further embodiment, the invention relates to an OLED wherein the ETL (i) is obtained by a method as described herein or (ii) consists of metal oxide nanoparticles coated with an unsubstituted or substituted alkyl-alkoxy-silane as described herein. In this embodiment, the OLED preferably comprises a substrate selected from the group of organic polymers (e.g. PET) or glass.

In a further embodiment, the invention relates to an organic solar cell (OPV) wherein the ETL (i) is obtained by a method as described herein or (ii) consists of metal oxide nanoparticles coated with an unsubstituted or substituted alkyl-alkoxy-silane as described herein. In this embodiment, the OPV preferably comprises a substrate selected from the group of organic polymers, metals or glass .

In a further embodiment, the invention relates to an organic photodetector wherein the ETL (i) is obtained by a method as described herein or (ii) consists of metal oxide nanoparticles coated with at least one type of an unsubstituted or substituted alkyl-alkoxy-silane as described herein. In a further embodiment, the invention relates to an electronic device wherein the ETL (i) is obtained by a method as described herein or (ii) consists of metal oxide nanoparticles coated with at least one type of an unsubstituted or substituted alkyl-alkoxy-silane as described herein.

In a second aspect, the invention relates to an intermediate good comprising a sheet-like substrate coated with a multitude of layers. This aspect of the invention shall be explained in further detail below.

Intermediate good: As outlined above, there is a need for manufacturing organic electronics by solution based processes. Accordingly, an intermediate good is manufactured by suitable solution based processes, such as coating or printing; the thus obtained material is than finished to obtain the final device (the organic electronic) . In one embodiment, the invention provides an intermediate good as defined herein, wherein said layers have the sequence electrode / HEL / active material / EEL / electrode, ("normal architecture").

In one further embodiment, the invention provides an intermediate good as defined herein, wherein said layers have the sequence electrode / EEL / active material / HEL / electrode, ("inverted architecture").

In one further embodiment, the invention provides an intermediate good as defined herein, wherein said layers comprise the sequence electrode / EEL / active material / HEL. This intermediate may also be the basis of a tandem cell.

In one further embodiment, the invention provides an intermediate good as defined herein, wherein said layers comprise the sequence electrode / HEL / active material / EEL. This intermediate may also be the basis of a tandem cell.

In one further embodiment, the invention provides an intermediate good as defined herein, wherein said layers have the sequences:

(a) Transparent electrode / HEL / active material / EEL

(b) Non-transparent electrode / HEL / active material /

(c) Transparent electrode /EEL / active material / HEL (d) Non-transparent electrode / EEL / active material /

HEL,

whereby the transparent electrode is selected from the group consisting of: PEDOT:PSS, Metal nanowires

(including Silver nanowires, Copper nanowires, Nickel nanowires) , Graphene, Carbon nanotubes and ITO; and whereby the non-transparent electrode is selected from the group consisting of dense silver, dense aluminum, dense copper, dense gold, thick (opaque) carbon nanotube layer and thick (opaque) graphene-based layer.

In one further embodiment, the invention provides an intermediate good as defined herein, wherein no additional layer is present.

In one further embodiment, the invention provides an intermediate good as defined herein, wherein the buffer layer has a thickness between 3 - 1000 nm, preferably 10 - 500 nm, much preferably 15 - 100 nm.

In one further embodiment, the invention provides an intermediate good as defined herein, wherein the buffer layer has a mean surface roughness below 30 nm

In one further embodiment, the invention provides an intermediate good as defined herein, wherein the substrate is as defined in the first aspect of the invention.

In one further embodiment, the invention provides an intermediate good as defined herein, wherein the silicon content of the buffer layer is in the range of 0.1 - 5 %. In a third aspect, the invention relates to a composition in the form of a suspension, said composition containing metal oxide nanoparticles , solvent (s) and alkyl-alkoxy- silanes. This aspect of the invention shall be explained in further detail below.

The term suspension is defined above. Suspensions comprising the components (i) metal oxide nanoparticles, (ii) solvent (s) and (iii) alkyl-alkoxy-silanes are known and described e.g. in Leidolph et al. As previously discussed, when combining components (i) , (ii) and (iii), the metal oxides will be coated with the silanes to form coated metal oxide nanoparticles. Before alkyl-alkoxy- silanes can be coated (silanized) onto the nanoparticle surface, the alkyl-alkoxy groups hydrolize and are released as alkyl-alcohol from the silane. The hydrolyzed groups of the silane then react with the oxide surface which typically contains metal hydroxide groups. By the corresponding reaction water is released as the condensation product, forming a highly stable metal siloxane bond (Me-O-Si-R) .

The use of such suspensions as UV stabilizer in polymers is known. However, the use of such suspensions for manufacturing thin films, such as buffer layers, is novel and subject of the present invention.

Accordingly, the invention provides for the use of metal oxide nanoparticles coated with an unsubstituted or substituted alkyl-alkoxy-silane for manufacturing of an intermediate good as defined herein. The invention further provides for the use of metal oxide nanoparticles coated with an unsubstituted or substituted alkyl-alkoxy-silane for manufacturing an electronic device as described herein, particularly selected from the group of OLEDs and OPVs. Further, the invention provides for the use of a suspension, comprising metal oxide nanoparticles coated with an unsubstituted or substituted alkyl-alkoxy-silane as described herein and a solvent (preferably selected from the group consisting of water, alcohols (such as glycol- ethers) and ketones), for manufacturing of an intermediate good as defined herein or for manufacturing an electronic device as described herein (particularly selected from the group of OLEDs, OPVs and organic photo detectors) . Further, certain of the above defined suspensions are novel and thus subject of the present invention. Accordingly, the invention provides for a composition in the form of a suspension comprising (i) nanoparticles selected from the group of metal oxide nanoparticles but excluding ZnO nanoparticles, and (ii) one or more solvents and (iii) alkyl-alkoxy-silanes of formula (II)

(R^x0) 3-Si-R²-FG (II) wherein

R¹ represents H, C1-C4 alkyl, preferably methyl, ethyl, n- propyl, isopropyl, methoxyethyl ,

R² represents C1-C10 alkyl, saturated or unsaturated C3-C10 carbocyclic groups,

FG represents -OH, -NH₂, -P (0) (OR^1*) 2, -OP (0) (OM) R^1' , -SH, - C(0) (OH), - C(0) (OR ), -vinyl, -acrylate, -epoxy, - aldehyde, NR 3 (X halogen) , -azide, -halogen, isocyanate, -thiophene, pyridyl, phenyl, benzyl, nitro, -C(0)NR¹, -benzotriazole , where R^1' is C1-C6 alkyl, Ci-C4-alkoxy-Ci-C4-alkyl and M is hydrogen or alkali metal, preferably Na.

In one embodiment, the substituents are as defined in the claims .

In one embodiment, such silane contains semiconducting functionalities or pi-conjugated bond sequences, in particularly as defined above.

In one embodiment, such silane is 3-Trihydroxy- silylpropylmethyl-phosphonate, sodium salt (Silyl-P) .

In one preferred embodiment, such silane is Diethylphosphato-ethyl-triethoxysilane (Dieth-P) .

In a further embodiment, two or more different silanes are used. One silane might be responsible for the suspension stability and the other one for a different functionality (e.g. work function tuning or conductivity enhancement) . The different silanes can both be present on individual nanoparticles (each silane partly covering the particle surface) or they can be separately present on different nanoparticles .

In a further advantageous embodiment, the nanoparticles in suspension have a hydrodynamic size D90 of less than 100 nm (measured by dynamic light scattering or centrifugal sedimentation techniques) .

In a further advantageous embodiment, the nanoparticles are synthesized by a gas phase process, preferably flame spray synthesis.

The amount of nanoparticles in the inventive composition may - depending on the intended use - vary over a broad range, but typically is in the range of 0.1 - 60 wt% (preferably 1 - 40 wt%) of the composition.

In a fourth aspect, the invention relates to the manufacturing of the inventive compositions, intermediate goods and devices disclosed herein and to inventive compositions, intermediate goods and devices obtained according to these methods. This aspect of the invention shall be explained in further detail below.

Manufacturing of suspensions: The manufacturing of suspensions is a known procedure. The coating of nanoparticles is also a known procedure. These procedures may be applied to the starting materials of the inventive suspensions .

In one embodiment, solvent and nanoparticles are combined, for example by mixing or ball milling. To the obtained initial suspension, the alkyl-alkoxy-silanes are added. Coating takes place at room temperature or upon heating and mixing.

In one alternative embodiment, solvent and alkyl-alkoxy- silanes are combined, for example by mixing. To the obtained initial solution, the nanoparticles are added. Coating takes place at room temperature upon heating and mixing . Manufacturing of intermediate goods: The intermediate goods according to the present invention may by obtained by solution process. This is considered a significant advantage, as it enables manufacturing of all layers by simple technologies applicable to large areas and continuous processing.

In one embodiment, the invention provides for a method for manufacturing an intermediate good as defined herein, wherein the buffer layer is manufactured comprising the steps of (a) applying a suspension on a substrate or coated substrate, said suspension comprising metal oxide nanoparticles coated with an unsubstituted or substituted alkyl-alkoxy-silane and a solvent and removing the solvent from said composition and (b) removing the solvent from the obtained thin film and (c) optionally treating the dry layer at elevated temperature.

Step (a) Application of a suspension: Many processes are known to apply a liquid composition to a substrate to result in a wet thin film; a person skilled in the art is in a position to appropriately select. Suitable are, for example coating, particularly roll-to-roll-, slot-die-, spray-, ultrasonic spray-, dip-, reel-to-reel-, blade- coating; or by printing, particularly ink-jet-, pad-, offset-, screen-, gravure-, intaglio-, sheet-to-sheet- printing. Such processes are generally considered advantageous for large scale production, when compared to vacuum-based processes. Depending on the composition used in step (a) , this step may be repeated (i.e. may be performed multiple times) . This embodiment is considered advantageous in order to fine tune the final film thickness .

Step (b) Drying and film formation: Many processes are known to remove a liquid from a wet thin film of a coated substrate; a person skilled in the art is in a position to appropriately select. Suitable are, for example drying at room temperature or elevated temperature. Drying may take place in air, in a protecting gas, such as nitrogen or argon. Especially suited are gases with low humidity content (e.g. nitrogen, dry air, argon) .

Step (c) : Temperature cleaning step: A cleaning step in the form of a temperature annealing can optionally be conducted at temperatures below 150 °C. In an advantageous embodiment, the dried nanoparticle film in step (c) is annealed at 80°C - 150°C in air or in a protecting gas. In an advantageous embodiment, all layers of the intermediate good are manufactured by coating or printing.

Manufacturing of devices: The manufacturing of devices starting from the above described intermediate goods is known per se, but not yet applied to the specific intermediate goods of the present invention.

Accordingly, the invention provides for a method for manufacturing an electronic device as defined herein comprising the steps of (a) providing an intermediate good as defined herein, (b) contacting the layers of said good with an electrical circuit, (d) finishing the obtained product .

Product by process: Due to the novel buffer layer obtained according to the inventive method, the electronic devices and intermediate goods are also novel. Due to the outstanding stability and performance obtained according to the inventive method, the suspensions are also novel. The invention thus provides for a suspension obtained by a method comprising the step of combining metal oxide nanoparticles , alkyl-alkoxy-silanes and solvent.

The invention thus provides for an intermediate good, obtained by a method comprising the steps of applying a suspension on a substrate or coated substrate, said suspension comprising (i) metal oxide nanoparticles coated with an unsubstituted or substituted alkyl-alkoxy-silane and (ii) a solvent and removing the solvent from said composition and optionally treating the dry layer at elevated temperature.

The invention thus provides for an electronic device, obtained by a method comprising the steps of providing an intermediate good as defined herein, contacting the layers with an electrical circuit, finishing the obtained product. In a fifth aspect, the invention relates to an electronic device, selected from the group of transistors, wherein said device comprises a substrate and a multitude of layers, wherein at least one of said layers is a channel layer, wherein said channel layer comprises metal oxide nanoparticles coated with an alkyl-alkoxy-silane as described herein. This aspect of the invention shall be explained in further detail below. It was surprisingly found that the thin films as described herein are not only suitable in manufacturing organic electronics but also in the manufacturing of transistors and related electronic devices. It is thus possible to apply the materials and methods disclosed above (1^st to 4^th aspect of the invention) to this aspect of the invention.

In this aspect, the invention relates to channel layers in an electronic device such as TFT, said channel layers having a specific and beneficial composition containing a metal oxide as described in the first aspect of the invention and alkyl-alkoxy-silane (s) as described in the first aspect of the invention. It was found that the present inventive compositions show beneficial properties because no post-treatment (e.g. plasma cleaning or annealing temperatures > 150°C) is required to achieve good device performance (high mobility) .

In one specific embodiment, the invention provides for an electronic device selected from the group of inorganic electronics, wherein said device comprises a substrate and a multitude of layers, wherein at least one of said layers is a channel layer, wherein said channel layer comprises metal oxide nanoparticles coated with at least one alkyl- alkoxy-silane as described herein, wherein said alkyl- alkoxy-silane is of formula (II)

wherein R¹ represents H, C1-C4 alkyl, Ci-C4-alkoxy-Ci-C4-alkyl, R² represents C1-C10 alkyl, saturated or unsaturated C3- C10 carbocyclic groups,

FG represents -P(O) (OR )₂, -OP(O) (OM)R¹, where R is Ci- C6 alkyl, Ci-C4-alkoxy-Ci-C4-alkyl and M is hydrogen or alkali metal, preferably Na.

In a preferred embodiment, the substituents are as defined in the claims.

In one further specific embodiment, the invention provides for a device as described herein, selected from the group of transistors. In a further specific embodiment, the invention relates to an inorganic transistor wherein the channel material is obtained by a method as described herein or (ii) consists of metal oxide nanoparticles coated with an alkyl-alkoxy- silane as described herein.

In a further specific embodiment, the invention relates to an inorganic transistor wherein the metal oxide nanoparticles are selected from the group consisting of ZnO, AZO, IZO, IGZO, and ZnSn0₃.

To further illustrate the invention, the following examples are provided. These examples are provided with no intent to limit the scope of the invention. Example 1

The following ETL layers were compared against each other: (i) Vacuum deposited calcium (benchmark cells; no solution- processed ETL); (ii) Sol-gel processed AZO (comparative example) ; (iii) ZnO nanoparticle ETL (inventive) ; (iv) AZO nanoparticle ETL (inventive)

Device fabrication: OPV cells having different types of ETL layers were manufactured in the standard architecture. The stack (layer) sequence was as follows: Glass /ITO / PEDOT:PSS / Si-PCPDTBT : PC ( 70 ) BM / ETL / Ag; the Si- PCPDTBT: PC (70) BM is denoted as "SiZZ".

The devices were processed in ambient atmosphere. Prestructured ITO coated glass substrates ( eidner Glas GmbH) were cleaned in acetone and then isopropyl alcohol. After drying, the substrates were coated with a PEDOT:PSS (VP Al 4083, Heraeus) layer (ca. 50 nm) . An approximately 100 nm thick active layer was doctor bladed from a dichlorobenzene solution of Si-PCPDTBT (Fa. Konarka) and PC[70]BM ( [ 6, 6] -phenyl-C 71 butyric acid methyl ester, Solenne) in weight ratio 1:1.5. Then the ZnO/AZO layers were doctor bladed on top of the active layer and annealed at 80 °C for 5 min. The final thickness for all ZnO/AZO layers was set to 50 nm. The devices were finalized by the evaporation of a Ag (100 nm) top electrode. For reference devices, the ETL layer consisted of a vacuum deposited 15 nm Ca layer. The active area of the investigated devices was 10.4 mm2. Current density-voltage (j-V) characteristics were measured with a source measurement unit from BoTest. Illumination was provided by an Oriel Sol 1A solar simulator with AM1.5G spectra at 0.1 W/cm2.

In one experiment, 6 cells were fabricated with each ETL material. Totally, 2 experiment batches were conducted. The results represent average values over all experiments and devices.

ZnO and AZO nanoparticle suspensions with Dieth-P : Aluminum doped Zinc oxide nanoparticles with a nominal composition of 2 wt% AI2O3 in ZnO were synthesized by flame spray synthesis. For the preparation of the precursor, 33g Zn- acetate (Aldrich) and 1.9g Al-acetylacetonate (Aldrich) was added to 200g of 2-ethylhexanoic acid and dissolved by heating the mixture for 1 hour at 150°C. The obtained solution was diluted with THF 1:2 by weight. The precursor then was fed (5 ml min^-1, HNP Mikrosysteme, micro annular gear pump mzr-2900) to a spray nozzle, dispersed by oxygen (7 1 min^-1, PanGas tech.) and ignited by a premixed methane- oxygen flame (CH₄: 1.2 1 min^"1, 0₂ : 2.2 1 min^"1) . The off- gas was filtered through a glass fiber filter (Schleicher & Schuell) by a vacuum pump (Busch, Seco SV1040CV) at about 20 m³ h^_1. The obtained oxide nanopowder was collected from the glass fiber filter.

For the synthesis of ZnO nanoparticles , no Al- acetylacetonate was used in the precursor.

Suspensions with either ZnO or AZO were prepared as following :

"Dieth-P" was purchased from ABCR. For the preparation of suspensions 5 wt% of nanopowder (as described above) was dispersed by ball-milling for 6 h in a mixture of 92.5 wt% dry ethanol, 2 wt% H2O and 0.5 wt% Diethylphosphato-ethyl- triethoxysilane . The finally prepared suspension is transparent and stable for more than 3 months. After 3 months, the hydrodynamic particle size (D50) was determined as 18 nm for AZO and 13 nm for the pure ZnO (measured by a centrifugal particle sizer (Lumisizer) ) .

AZO nanoparticle suspension with Silyl-P : Aluminum doped Zinc oxide nanoparticles with a nominal composition of 2 wt% AI2O3 in ZnO were synthesized by flame spray synthesis. For the preparation of the precursor, 33g Zn-acetate (Aldrich) and 1.9g Al-acetylacetonate (Aldrich) was added to 200g of 2-ethylhexanoic acid and dissolved by heating the mixture for 1 hour at 150 °C. The obtained solution was diluted with THF 1:2 by weight. The precursor then was fed (5 ml min^-1, HNP Mikrosysteme, micro annular gear pump mzr-2900) to a spray nozzle, dispersed by oxygen (7 1 min^~ ¹ , PanGas tech.) and ignited by a premixed methane-oxygen flame (CH₄: 1.2 1 min^"1, 0₂ : 2.2 1 min^"1) . The off-gas was filtered through a glass fiber filter (Schleicher & Schuell) by a vacuum pump (Busch, Seco SV1040CV) at about 20 m³ h^_1. The obtained oxide nanopowder was collected from the glass fiber filter. Suspensions with AZO and "Silyl-P" were prepared as following :

Silyl-P was purchased from Aldrich (42% in water) . For the preparation of suspensions 5 wt% of nanopowder (as described above) was dispersed by ball-milling for 3 h in a mixture of 93.9 wt% methanol and 1.1 wt% Silyl-P (42% in H2O) . The finally prepared suspension is transparent and stable for more than 3 months. After 3 months, the hydrodynamic particle size (D50) was determined as 17 nm (measured by a centrifugal particle sizer (Lumisizer) ) .

Deposition of ZnO and AZO suspensions: ZnO or AZO nanoparticle films (for Dieth-P and Silyl-P formulations above) were doctor-bladed on the organic active layer (SiZZ) resulting in homogeneous and defect-free oxide films. The thickness of the deposited oxide films was determined by profilometry . Annealing of the obtained films for 5 min at 80°C in air resulted in high performance devices .

Sol-gel AZO coating liquid: An AZO sol-gel coating liquid was prepared identically to Stubhan et al. (cited above). In detail, 2.17g Zn-acetate x 2H₂0 0.037g Al-nitrate x 9H₂0 were mixed in lOOmL of ethanol. The mixture was heated at 80 °C for 3 hours and afterwards filtered through a 0.45 micron PTFE filter to remove insoluble materials.

Results: The results described in the table below were obtained. The data show, that all inventive compositions result in high performance OPV devices, whereas sol-gel processed AZO formulations damage the active layer (=no performance) .

ETL type description Fill factor PCE

(%) (¾)

Prior art

Ca not solution 61 3.7

processable

AZO sol-gel solution 7 0

processable inventive

ZnO np (Dieth-P) solution 50 3.0

processable

AZO np (Dieth-P) solution 59 3.65

processable

AZO np (Silyl-P) solution 41 2.4

processable

Example 2

The following suspensions were compared against each other: According to this invention: 2.5 wt% ZnO, 2 wt% H₂0 and 0.5 wt% Diethylphosphato-ethyl-triethoxysilane and 95 wt% dry ethanol (Figure 4; sample C) was dispersed by ball-milling for 6h.

According to Hsu et al (WO2009/086337 ) : Allyltrimethoxy- silane was chosen as the comparative silane coupling agent. One suspension was prepared with 2.5% ZnO, 2 wt% H₂O, 0.5 wt% allyltrimethoxysilane and 97 wt% dry ethanol (Figure 4; sample A) and dispersed by ball-milling for 6h.

A second suspension was prepared with 2.5 wt% ZnO, 0.5 wt% allyltrimethoxysilane and 95 wt% toluene (Figure 4; sample B) and dispersed by ball-milling for 6h.

The inventive suspension was compared optically against both prior art suspensions 5 days after finishing the dispersion .

The data show, that the inventive suspension results in a stable and transparent suspension (Figure 4; sample C) , whereas both suspensions of the prior art (sample A (ethanol) and sample B (toluene)) result in agglomerated and completely sedimented suspensions (no stability) . Given these results, it is expected that the suspensions of the prior art are difficult to process, particularly when aiming at smooth and even coatings with low surface roughness. High quality coatings with low surface roughness are essential for high performance OLED and OPV devices.

Claims

1. An electronic device selected from the group of organic electronics,

wherein said device comprises a substrate and a multitude of layers,

wherein at least one of said layers is a buffer layer, wherein said buffer layer comprises metal oxide nanoparticles coated with at least one unsubst ituted or substituted alkyl-alkoxy-silane,

wherein said nanoparticles have at least one dimension in the size range of 1 - 100 nm,

wherein said alkyl-alkoxy-silane is of formula (II)

wherein

R¹ represents H, C1-C4 alkyl, Ci-C4-alkoxy-Ci-C4-alkyl, R² represents C1-C10 alkyl, saturated or unsaturated

C3-C10 carbocyclic groups,

FG represents -P(O) (OR )2, -OP(O) (OM) R^1' , where R^1' is

Ci-Ce alkyl, Ci-C₄-alkoxy-Ci-C₄-alkyl and M is hydrogen or alkali metal.

2. The device according to claim 1, selected from the group consisting of OPV, OLEDs and organic photo- detectors .

3. The device according to any of the preceding claims, wherein said multitude of layers is arranged in normal architecture or inverted architecture.

4. The device according to any of the preceding claims, wherein said buffer layer is selected from the group consisting of hole transport (HTL) , hole injection (HIL) , hole extraction (HEL) , electron transport (ETL) , electron injection (EIL) and electron extraction (EEL) layers . The device according to any of the preceding claims, wherein said nanoparticles are selected from the group consisting of ZnO, TiOx, WOx, NiO, VyOx, MoyOx and NbyOx;

said metal oxides optionally being doped with other metals; and /' or

said metal oxides optionally containing carbonaceous material .

The device according to any of the preceding claims, wherein said metal oxide nanoparticles are selected from the group consisting of ZnO, Al-doped ZnO ("AZO") , ZnO containing carbonaceous material, AZO containing carbonaceous material, TiOx and Nb-doped TiOx.

The device according to any of the preceding claims, wherein said alkyl-alkoxy-silane is of formula (II) is selected from

^■ 3-Trihydroxy-silylpropylmethyl-phosphonate,

sodium salt and

^■ Diethylphosphato-ethyl-triethoxysilane .

The device according to any of the preceding claims, wherein said substrate is selected from

(a) an active material; or

(b) an additional buffer layer; or

(c) an inorganic conductive electrode material,

preferably ITO, Ag, Cu or Ni; or

(d) an organic conductive electrode material,

preferably PEDOTrPSS; or

(e) a combination of (c) and (d) .

9. An intermediate good comprising a sheet-like substrate coated with a multitude of layers, wherein said layers (a) have the sequence electrode / HEL / active material / EEL / electrode ("normal

architecture") ;

(b) have the sequence electrode / EEL / active

material / HEL / electrode, ("inverted

architecture") ;

(c) comprise the sequence electrode / EEL / active material / HEL;

(d) comprise the sequence electrode / HEL / active material / EEL.

(e) comprise the sequence electrode / HIL / HTL /

active material / ETL / EIL / Electrode,

wherein in each case (a) to (e) one or more of the buffer layers contain coated nanoparticles as defined in claim 1 or claim 6.

The intermediate good of claim 9

wherein the buffer layer has a thickness between 3 - 1000 nm and / or

wherein the buffer layer has a mean surface roughness below 30 nm; and / or

wherein the substrate is selected from the group of ITO, silver, copper, nickel, PEDOT:PSS or an active material; and / or

wherein no additional layer is present; and / or wherein the silicon content is in the range of 0.1-5 wt% .

A composition in the form of a suspension comprising

(a) nanoparticles selected from the group of metal oxide nanoparticles, and

(b) alkyl-al koxy-silanes of formula (II) or mixtures thereof,

wherein R¹ represents H, C1-C4 alkyl, Ci-C4-alkoxy-Ci-C4- alkyl ,

FG represents -P (0) (OR^1' ) 2, -OP (0) (OM) R^1' , where

R^1' is C1-C6 alkyl, Ci-C₄-alkoxy-Ci-C4-alkyl and M is hydrogen or alkali metal;

(c) solvents, preferably selected from the group consisting of alcohols (particularly glycol- ethers), water and ketones.

Use of a composition in the form of a suspension, comprising

(a) metal oxide nanoparticles as defined in claim 1,

(b) a solvent preferably selected from the group

consisting of water, alcohols (particularly glycol-ethers ) and ketones,

for manufacturing of an intermediate good according to claim 9 or 10 or for manufacturing an electronic device selected from the group of OLEDs, OPVs and organic photodetectors .

A method for manufacturing an intermediate good according to claim 9, wherein the buffer layer is manufactured comprising the steps of

(a) applying a suspension on a substrate or coated substrate, said suspension comprising (i) metal oxide nanoparticles coated with an unsubstituted or substituted alkyl-alkoxy-silane and (ii) a solvent and

(b) removing the solvent from said composition and

(c) optionally treating the dry layer at elevated temperature . 1 . The method of claim 13, wherein

(a) the suspension of step (a) is applied by coating or printing; and / or (b) the solvent of step (b) is removed under air or a protecting gas with a low humidity content; and/ or

(c) the dried nanoparticle film in step (c) is annealed at 80°C - 150°C in air or in a protecting gas.

15. The method of claim 13 or 14, wherein all layers are manufactured by coating or printing. 16. A method for manufacturing an electronic device according to any of claim 1-9 comprising the steps of

(a) providing an intermediate good according to claim 9,

(b) contacting the layers of said good with an electrical circuit,

(c) finishing the obtained product.

An electronic device, obtained by a method comprising the steps of

(a) providing an intermediate good according to claim 9,

(b) contacting the layers with an electrical circuit,

(c) finishing the obtained product. 18. An intermediate good, obtained by a method comprising the steps of

(b) removing the solvent from said composition and

(c) optionally treating the dry layer at elevated temperature .