WO2011015550A1

WO2011015550A1 - Evaporator system for organic coatings and components

Info

Publication number: WO2011015550A1
Application number: PCT/EP2010/061202
Authority: WO
Inventors: Bert MÄNNIG; Wolf-Michael Gnehr; Martin Pfeiffer; Karsten Walzer; Andre Weiss
Original assignee: Heliatek Gmbh
Priority date: 2009-08-03
Filing date: 2010-08-02
Publication date: 2011-02-10

Abstract

The invention relates to a method for producing organic coatings, organic multilayer coating systems, or organic components, particularly organic solar cells, organic light-emitting diodes (OLEDs), organic thin-film memory, organic lasers, or organic field effect transistors (OFETs). The invention particularly relates to a method wherein an organic coating or an organic multilayer coating system or an organic component is generated using hypercritical organic materials.

Description

Evaporator system for organic layers and components

The invention relates to a process for producing organic layers, organic multilayer systems or organic components, in particular organic

Solar cells, organic light emitting diodes (OLEDs), organic thin film memory, organic laser or organic field effect transistors (OFET).

Furthermore, the invention relates to organic layers, organic multilayer systems or organic

Components, in particular organic solar cells, organic light emitting diodes (OLEDs), organic thin film memory, organic lasers or organic field effect transistors (OFET), which have been prepared by a method according to any one of claims 1 to 18. Since the demonstration of the first organic solar cell with a percentage efficiency by Tang et al. 1986 [CW. Tang et al. Appl. Phys. Lett. 48, 183 (1986)], organic materials become intense for various

examined electronic and optoelectronic components. Organic solar cells consist of a sequence of thinner ones

Layers (typically lnm to lμm) of organic

Materials which are preferably evaporated in vacuo or spin-coated from a solution. The electric

Contacting can be effected by metal layers, transparent conductive oxides (TCOs) and / or transparent conductive polymers (PEDOT-PSS, PANI).

A solar cell converts light energy into electrical energy. In this sense, the term "photoactive" is understood here, namely the conversion of light energy into electrical power. Unlike inorganic

In organic solar cells, solar cells do not directly generate free charge carriers through light, but excitons are first formed, ie electrically neutral excitation states (bound electron-hole pairs). Only in a second step are these excitons released

Separate charge carriers, which then contribute to the electrical current flow.

The advantage of such organic-based devices over conventional inorganic-based devices (semiconductors such as silicon, gallium arsenide) is the sometimes extremely high optical absorption coefficients (up to 2 × 10 ⁵ cm ^-1 ), which offers the possibility of low material and material costs Energy expenditure to produce very thin solar cells. Further technological aspects are the low cost, the possibility of producing flexible large-area components on plastic films, and the almost unlimited possibilities of variation and the unlimited availability of organic chemistry. One already suggested in the literature

Possible realization of an organic solar cell is a pin diode [Martin Pfeiffer, "Controlled doping of organic vacuum deposited dye layers: basics and applications", PhD thesis TU-Dresden, 1999.] with the following layer structure:

0. carrier, substrate,

1. basic contact, mostly transparent,

2. p-layer (s), 3. i-layer (s), 4. n-layer (s), 5. cover contact. Here, n or p denotes an n- or p-type doping, which leads to an increase in the density of free electrons or holes in the thermal equilibrium state. In this sense, such layers are primarily to be understood as transport layers. In contrast, the term i-layer designates an undoped layer (intrinsic layer). One or more i-layer (s) may in this case consist of layers of a material as well as a mixture of two materials (so-called interpenetrating networks). The light incident through the transparent base contact generates excitons in the i-layer or in the n- / p-layer. These excitons can only by very high electrical

Fields or at suitable interfaces. In organic solar cells, sufficiently high fields are not available, so that all promising concepts for organic solar cells based on the exciton separation at photoactive interfaces. The excitons pass through diffusion to such an active interface, where electrons and holes are separated. This can lie between the p (n) layer and the i-layer or between two i-layers. Im installed

electric field of the solar cell, the electrons are now transported to the n-area and the holes to the p-area. Preferably, the transport layers are transparent or largely transparent materials with a wide band gap (wide-gap). As wide-gap materials here materials are referred to, the absorption maximum in the wavelength range <450 nm, preferably at <400 nm.

Since the excitons are always generated by the light and still no free charge carriers, the plays

low-recombination diffusion of excitons to the active interface plays a critical role in organic

Solar cells. To make a contribution to the photocurrent, must therefore in a good organic solar cell the

Exciton diffusion length the typical penetration depth of the Clearly far exceed light, so that the majority of the light can be used. Structurally and in terms of chemical purity, perfect organic crystals or

Thin films certainly fulfill this criterion. For large area applications, however, the use of monocrystalline organic materials is not possible and the production of multiple layers with sufficient structural perfection is still very difficult.

If the i-layer is a mixed layer

the task of light absorption either takes on only one of the components or both. Of the

The advantage of mixed layers is that the generated excitons only have to travel a very short distance until they reach a domain boundary, where they are separated. Of the

Removal of the electrons or holes is carried out separately in the respective materials. Because in the mixed layer the

Materials are in contact with each other everywhere, it is crucial in this concept that the separate charges have a long life on the respective material and from each location closed percolation paths for both types of charge to the respective contact

available. These closed percolation paths are usually realized by some phase separation in the mixed layer, i. the two components are not completely mixed, but there are

(preferably crystalline) nanoparticles from one each

Material in the mixed layer. This partial segregation is referred to as phase separation.

From US 5,093,698 the doping of organic materials is known: By admixture of an acceptor or

donor-type dopant, the equilibrium charge carrier concentration in the layer is increased and the conductivity is increased. According to US 5,093,698 the doped layers are used as injection layers on the

Interface to the contact materials in used electroluminescent devices. Similar doping approaches are analogous for solar cells

appropriate.

From the literature are different

Realization possibilities for the photoactive i-layer known: So this can be a double layer

(Patent application EP0000829) or a mixed layer

(Hiramoto, Appl. Phys. Lett., 58, 1062 (1991)). Also known is a combination of double and mixed layers (Hiramoto, Appl. Lett., 58, 1062 (1991);

US6559375). It is also known that the

Mixing ratio in different areas of the

Mixed layer is different (patent application US

20050110005) or the mixing ratio has a gradient.

Furthermore, tandem or multiple solar cells are known from the literature (Hiramoto, Chem. Lett., 1990, 327 (1990), patent application DE 102004014046).

Also called ADABCO materials are as

Absorber materials known (WO2006092134), the excitonic ping-pong effect for the generation of charge carriers

Organic components of small molecules are produced by thermal evaporation in vacuo, In the context of the present invention, small molecules are understood to mean non-polymeric organic molecules having monodisperse molecular weights of between 100 and 2,000 Under normal pressure (air pressure of the surrounding atmosphere) and at

Room temperature in solid phase. In particular, these small molecules can also be photoactive, it being understood under photoactive that the molecules are under Light incidence change its charge state. Also known is a deposition in a low-pressure gas phase (organic vapor phase deposition, OVPD, eg US2008311296). In both cases, however, a container is necessary in which the organic material is heated and vaporized.

Depending on the material, the evaporation may be a direct sublimation (solid ==> gaseous) or the organic material melts first and then evaporates (solid ==> liquid ==> gaseous). The liquid phase

arises here due to the elevated temperature. In all of these techniques, in the unheated state, the organic material is in solid form and it is also the only material that is converted to the gas phase. In the container in which the organic material is located, in order to promote evaporation (homogeneity, larger surface area), a ceramic or a metal may be present which preferably has a highly porous form

(WO2006100058).

A big problem with the evaporation is that the

Evaporation temperatures often between 200 and 400 ⁰ C, in some cases even more than 500 ⁰ C and these temperatures survive many organic molecules not decomposition. For a continuous production process, the evaporator sources must be filled with so much material that ideally an uninterrupted production for one week is possible. Even if multiple sources are installed at one location and can be changed between sources without loss of time (so-called turret systems), the organic materials must withstand the high temperatures inside the evaporator without decomposition for at least one or more days. As a solution, so-called tracking systems are currently being discussed: In these systems, the actual amount of organics is in a separate container or chamber and is gradually introduced gradually into the source space. This is eg over pressed pellets, which have a chute in the

actual source of evaporation is possible (further:

small sources are pushed in; Organik Stab nachgoben from below). Technically, this is common

Tracking systems that in the reservoir, the organic material is in solid form. Ideally, these small quantities of material that are being fed evaporate immediately, so that the organic materials only last very little time

Are exposed to evaporation temperature. Such

Tracking system, however, are technically very difficult to implement and thus complex and expensive. A special problem is that the unit that tracks the material must not be evaporated with material, otherwise the tracking system will become "clogged". The invention is therefore based on the object

To provide a simple and reliable evaporator system for organic materials, which is used for deposition of organic materials in vacuo (the base pressure without running coating is in the range 10 ^{~ 2} to ¹⁰ -10 mbar, if the deposition is a gas stream, the pressure suitable surfaces of up to 10 ^~ ° mbar be high) located.

The object is achieved by a method for the deposition of organic materials according to claim 1.

Advantageous embodiments are specified in the dependent claims.

According to the invention the problem is solved in that

(I) the source of the evaporator system is constructed so that in it the organic material to be deposited is mixed in a further material, wherein the further material serves as a carrier material and the mixture of both materials or at least as Carrier material serving further material is present in liquid or supercritical form,

(ii) there is a mechanism under which the

(i) the mixture of materials described can be brought (expanded) through a nozzle into the vacuum system,

(iii) Optionally, another mechanism exists that allows the metering of this expansion into vacuum.

The support material can in this process in a predominant ratio (> 10 times the mol

organic material).

In one embodiment of the invention, a vacuum system containing such a source is one

Recovering system equipped, which allows the material used as a carrier (which is either gaseous or liquid at atmospheric pressure) of the remaining

Separate and reuse for pumped substances.

Basis of the present invention is the idea that the organic material is not solid, but in dissolved form. In the simplest realization possibility, the organic material is simply dissolved in a solvent. For better solubility, it can be the

Solvent under elevated pressure and / or elevated

Temperature are. Furthermore, a second

Solvent (co-solvent) should be present to the

Increase solubility of the organic material. Furthermore, a plurality of organic materials may be dissolved to form a mixed layer or a doped layer of a

To realize evaporator source. As organic materials within the meaning of the invention, both small molecules and polymeric organic materials can be understood.

In a preferred embodiment of the invention is located the solvent in the supercritical state (also called supercritical state or super- / supercritical fluid): In thermodynamics, the three phases are first distinguished solid, liquid and gaseous. In the p (T) diagram (Fig. 1), also called phase diagram, there are clear boundaries of the three phases, which are referred to as sublimation curve, melting curve and vapor pressure curve.

Moreover, with further simultaneous increase in pressure and temperature, one finds the phenomenon that beyond the so-called critical point at (Tc, pc) none

Differentiation of the two phases liquid and gaseous is more possible. At this point, there exists a critical density pc. Above this critical point there is a so-called supercritical phase. It is known that this phase can be used technologically to dissolve substances in formerly liquid or formerly gaseous other substances. This method can be used, for example, to use CO ₂ as a solvent. Of particular advantage is that CO _{2 is} not reactive and thus non-toxic. It therefore serves, for example, the extraction of caffeine

Coffee. Further technical applications of extractions with supercritical fluids are e.g. in Kirk-Othmer

"Encyclopedia of Chemical Technology", pp. 872-893, supplementary volume, third edition, 1984, John Wiley and Sons, New York.

Further, a process for producing nanoparticles "Rapid Expansion of Supercritical Solutions (RESS)" is known (Figure 2), which relies on dissolving a non-volatile organic material in a supercritical fluid and rapidly expanding this solution through a nozzle.

In this method, the solvent is first liquefied in a condenser. Before it flows into the extractor, the fluid becomes the extraction pressure pE

compressed and to the desired extraction temperature TE heated. As it flows through the solids bed in the extractor, the fluid loads with the substance to be micronized. The loading yE depends strongly on the extraction pressure pE, the TE extraction temperature and the residence time in the extractor. On the way to the nozzle, the supercritical solution is heated to the desired pre-expansion temperature TO. On the one hand, depending on the material system, one can influence the size of the particles via the temperature TO, and on the other hand one becomes

Saturation generates a failing of

Prevents solid particles in the pipe. Subsequently, the supercritical solution is expanded by a heated nozzle, which due to strong supersaturations

spontaneous particle formation takes place. The resulting

Particles are deposited on a filter that

Solvent ideally re-liquefied and the

Recycled cycle.

In one embodiment of the present invention, the supercritical phase of a solvent is used to dissolve therein the organic material and then to expand this supercritical mixture through a nozzle into a vacuum system in which the dissolved organic

Material can be deposited on a surface to be coated. This is the formerly supercritical

Solvent pumped off. Subsequently, the solvent coming from the pump can be reprocessed to

then be returned to the supercritical state.

In another embodiment of this embodiment, the nozzle is heated to supply the necessary heat of vaporization for fluid and the organic material to be vaporized and to prevent clogging of the nozzle.

In a preferred embodiment of the present invention

Invention, the organic material to be transported is transferred by the expansion in its gas phase and from this deposited on a surface to be coated or on a heated plate. This is very advantageous if molecular films with particularly low crystallinity are to be produced. A particular advantage of the present invention is that it is possible to use various substances as solvents which otherwise behave completely inert both with regard to the organic substances and with respect to the surfaces to be coated and the organic materials which may have already been deposited on them. Another advantage is the possibility of using substances as solvents which do not dissolve the organic materials to be deposited under normal pressure.

In particular, substances whose critical temperature Tc <600 K and whose critical pressure pc is <25 MPa can be used as the solvent. Particularly suitable are substances with Tc <450K and low pc. These include e.g. at normal pressure gaseous substances with (Tc, pc) such as carbon dioxide (304, 2K, 7,375MPa), xenon (289, 7K, 6,31 MPa), ethane (305K, 4,87MPa), propane (370K, 4,24MPa) Butane (425K, 3.78 MPa), ethyne (308K, 6.4MPa) and ethene (282K, 5.04MPa), but also at normal pressure liquid materials such as ethanol (489K, 6.59MPa) and diethyl ether (467K, 3 , 75MPa). Continue to come as

Solvent nor ammonia, water, methanol, propanol, methane and also fluoroalkanes or hydrofluoroalkanes in question.

In a further embodiment of the invention, more than one organic substance is deposited simultaneously.

This can be used frequently in practice

Simplify mixing vaporizations or doping by using only one common source instead of one source

Source is used. The mixing ratio of the materials to be separated can thus already be adjusted in the supercritical phase. As described above, preferably particles, ie clusters of the organic material, are formed after exiting the nozzle. In such a case, the layers deposited on the substrate will also become bulk of them

Particles or clusters exist. This can be for the

Semiconducting properties of the organic layer

be advantageous because the particles may be in crystalline form. Especially if two different

organic materials can be used, so can the

deposited mixed layer of nanoparticles of the individual organic materials. This phase separation is as already described above especially for organic

Solar cells very desirable.

Furthermore, it may also be advantageous that the organic material is not present in the form of particles in the vacuum, but isolated. In the case of small molecules, at least a large proportion of the molecules should then be present individually.

In another embodiment of the invention, particle formation at the nozzle may be e.g. be prevented by suitable pressure and temperature conditions to evaporate the organic material as completely as possible.

In a further embodiment of the invention, the resulting particles are then separated: Thus, e.g. the solution is sprayed onto a heated component (Figure 3). The primary particles that primarily develop during expansion collide with this component and are vaporized there. This component may be a plate, or a tube, possibly in a porous form with enlarged

Surface. The object formed therefrom can then be referred to as an evaporator and as such for

Coating of surfaces and the production of

Serve components. In a further embodiment of the invention, the organic material is in supercritical carbon dioxide (CO2), xenon, ethane, propane, butane, ethyne, ethene, ethanol,

Diethyl ether, ammonia, water, methanol, propanol, methane, a fluoroalkane or a hydrofluoroalkane dissolved.

In a further embodiment, by means of

According to the invention, an organic component is produced, which is used as an organic pin solar cell or

organic pin tandem solar cell, according to WO

2004083958 is executed.

In a further embodiment, by means of

According to the method of the invention, an organic component is produced, which is pronounced as organic light emitting diode (OLED), organic memory device, organic transistor or organic diode.

At present, no method or apparatus is known in which an organic layer or an organic layer

Multi-layer system or an organic device can be produced using supercritical organic materials.

In a further embodiment of the invention, a process for the production of organic layers, organic multilayer systems or organic

Components, in particular organic solar cells,

used, wherein at least one organic material is mixed in a further, serving as a carrier material and material either the mixture of both

Materials or at least serving as a carrier material further material is formed as a fluid and this

Material mixture is expanded into the vacuum of a coating system. For the purposes of the present invention, a fluid is considered both a liquid phase and a supercritical phase of the carrier material. In one embodiment of the invention, the deposition is via adjustable process parameters, such as

Substrate speed, temperature, pressure, geometry of the nozzle, etc. regulated.

In a further embodiment of the invention, the material mixture is stored in a container. This

Container is located outside of the serving for coating vacuum chamber.

In one embodiment of the invention that stands

Material mixture in the container under elevated pressure

and / or has an elevated temperature. The increased pressure refers relative to the pressure of the

Vacuum chamber.

In a further embodiment of the invention, a further co-carrier material or co-solvent is present in the material mixture.

In one embodiment of the invention, it is a continuous process. In this case, a tracking of the material mixture for the

Coating process necessary.

In a further embodiment of the invention, it is a continuous process which requires refilling at the earliest after 10 hours, preferably after 50 hours.

In a further embodiment of the invention, substances whose critical temperature Tc <600 K, in particular Tc <450 K and their critical pressure pc <25 MPa, are used as carrier material. In a further embodiment of the invention, the organic material is selected in a material selected from the group consisting of carbon dioxide (CO ₂ ), xenon, ethane,

Propane, butane, ethyne, ethene, ethanol, diethyl ether,

Ammonia, water, methanol, propanol, methane, one

Fluoroalkane or a hydrofluoroalkane solved.

In a further embodiment of the invention, more than one organic material is dissolved in the carrier material.

In another embodiment of the invention, more than one organic material is dissolved in the carrier material and the various organic materials are simultaneously deposited on the substrate.

In a further embodiment of the invention, at least one organic material is a small molecule. In a further embodiment of the invention, at least one organic material is a

Polymer.

In a further embodiment of the invention, the deposition is carried out on a heated substrate, wherein the substrate is heated to such a temperature that the

to be deposited organic material on the substrate

is deposited and heated due to the substrate temperature. As a result, at least a partial

Re-evaporation of the deposited organic material from the substrate, resulting in improved homogeneity of the

Layer of the deposited organic material on the substrate is achieved. In a further embodiment of the invention, for the separation of particles or clusters of Material mixture, this sprayed during the expansion of a nozzle into the vacuum chamber into a heated component, wherein primary particles bounce on this component and are evaporated there, whereby a separation of the particles or clusters takes place.

In a further embodiment of the invention, the heated component is a tube. In a further embodiment of the invention, the heated component is a plate.

In a further embodiment of the invention, the heated component is a free-formed surface.

In a further embodiment of the invention, the heated component has a porous shape with enlarged

Surface on. In a further embodiment of the invention, the carrier material is pumped out of the coating plant and then used again for the production of the material mixture. In a further embodiment of the invention, the expansion takes place in the vacuum chamber by means of a nozzle.

In a further embodiment of the invention, the nozzle is heated.

In a development of the above-described embodiment, the nozzle is heated.

In a further embodiment of the invention, by means of the method according to the invention or the device according to the invention an organic layer, an organic

Multilayer system or an organic device, in particular an organic solar cell, an organic light emitting diode (OLED), an organic thin film memory, an organic laser or an organic field effect transistor (OFET).

Claims

claims

1. Process for the preparation of organic layers, organic multilayer systems or organic

Components, in particular organic solar cells, characterized in that

(i) at least one organic material in one

further, serving as a carrier material material is mixed and either the mixture of both materials or at least serving as a carrier material further material as a fluid, in particular in a supercritical phase located,

is trained and

(ii) this material mixture in the vacuum of a

Coating system is expanded into it.

2. The method according to claim 1, characterized in that the deposition can be controlled by adjustable process parameters.

3. The method according to any one of claims 1 and 2, characterized in that the material mixture is stored in a container outside the vacuum chamber.

4. The method according to claim 3, characterized in that the material mixture in the container under elevated pressure is relative to the pressure in the vacuum chamber and / or has an elevated temperature.

5. The method according to any one of claims 1 to 4, characterized in that in the material mixture still another co-carrier material or co-solvent is present.

6. The method according to any one of claims 1 to 5, characterized in that it is a continuous

Process is.

7. The method according to any one of claims 1 to 6, characterized in that it is a continuous process that requires refilling at the earliest after 10 hours, preferably after 50 hours.

8. The method according to any one of claims 1 to 7, characterized in that are used as the carrier material substances whose critical temperature Tc <600 K, in particular Tc <450 K and the critical pressure pc <25 MPa.

9. The method according to claim 8, characterized in that the organic material in a material selected from the group consisting of carbon dioxide (CO ₂ ), xenon, ethane, propane, butane, ethyne, ethene, ethanol, diethyl ether,

Ammonia, water, methanol, propanol, methane, one

Fluoroalkane or a hydrofluoroalkane is dissolved.

10. The method according to any one of claims 1 to 9, characterized in that more than one organic material is mixed in the carrier material.

11. The method according to any one of claims 1 to 10, characterized in that more than one organic material in the carrier material is mixed and the various organic materials are deposited simultaneously on the substrate

12. The method according to any one of claims 1 to 11, characterized in that it is at least in an organic material to small molecules.

13. The method according to any one of claims 1 to 12, characterized in that it is at least one

organic material is a polymer.

14. The method according to any one of claims 1 to 13, characterized in that the deposition on a heated

Substrate takes place, the substrate on such a

Temperature is heated, that the deposited organic material is deposited on the substrate and is heated due to the substrate temperature that at least one

partially re-evaporation of the deposited organic material from the substrate.

15. The method according to any one of claims 1 to 14, characterized in that the material mixture is sprayed in an expansion by means of a nozzle in the vacuum chamber into a heated component, wherein primary particles bounce on this component and are evaporated there again, whereby a separation of the Particles or clusters takes place.

16. The method according to claim 15, characterized in that the heated component is a tube or a plate.

17. The method according to any one of claims 15 or 16, characterized in that the heated component has a porous shape with increased surface area.

18. The method according to claims 15 to 17, characterized in that the nozzle is heated.

19. The method according to any one of claims 1 to 18, characterized in that the carrier material from the

Coating plant is pumped off and then used again for the production of the material mixture.