EP3284110A1

EP3284110A1 - Sol-gel-based printable and parasitic diffusion-inhibiting doping media for local doping of silicon wafers

Info

Publication number: EP3284110A1
Application number: EP16711776.1A
Authority: EP
Inventors: Oliver Doll; Ingo Koehler; Sebastian Barth
Original assignee: Merck Patent GmbH
Current assignee: Merck Patent GmbH
Priority date: 2015-04-15
Filing date: 2016-03-24
Publication date: 2018-02-21
Also published as: US20180062022A1; WO2016165810A1; KR20170137837A; TW201710185A; CN107532300A

Abstract

The present invention relates to a novel printable paste in the form of a hybrid gel on the basis of inorganic oxide precursors which can be used in a simplified process for the production of solar cells, the hybrid gel according to the invention functioning as a doping medium as well as a diffusion barrier.

Description

The present invention relates to a novel printable paste in the form of a hybrid gel based on precursors of inorganic oxides, which can be used in a simplified process for the production of solar cells, wherein the hybrid gel according to the invention both as

Doping medium and acts as a diffusion barrier.

State of the art

The production of simple solar cells or of the solar cells currently represented in the market with the largest market share comprises the essential production steps outlined below:

1) saw damage etching and texture

A silicon wafer (monocrystalline, multicrystalline or quasi-monocrystalline, p- or n-type base doping) is freed of adherent saw damage by means of an etching process and "simultaneously", usually in the same etching bath, texturized under texturing is in this case the creation of a preferred Surface (texture) as a result of the etching step or simply to understand the targeted, but not particularly oriented roughening of the wafer surface

Surface of the wafer now as a diffuse reflector and thus reduces the directional, weillängenlänge- and the angle of impact dependent reflection, which ultimately leads to an increase in the absorbed portion of the incident light on the surface and thus the

Conversion efficiency of the solar cell increased.

In the case of monocrystalline wafers, the aforementioned etching solutions for treating the silicon wafers typically consist of dilute potassium hydroxide solution to which isopropyl alcohol has been added as solvent. Instead, other alcohols having a higher vapor pressure or higher boiling point than isopropyl alcohol may be added, provided that desired etching result can be achieved. Typically, the desired etch result is a morphology that is randomly-etched, or rather etched out of the original surface.

Pyramids is characterized by square base. The density, the height and thus the base area of the pyramids can be influenced by a suitable choice of the above-mentioned constituents of the etching solution, the etching temperature and the residence time of the wafers in the etching basin.

Typically, the texturing of the monocrystalline wafer in

Temperature range of 70 - <90 ° C performed, with Ätzabträge of up to 10 pm per wafer side can be achieved.

In the case of multicrystalline silicon wafers, the etching solution may consist of potassium hydroxide solution with an average concentration (10-15%). However, this etching technique is hardly used in industrial practice. More often becomes one

Etching solution consisting of nitric acid, hydrofluoric acid and water used. This etching solution can be modified by various additives such as sulfuric acid, phosphoric acid, acetic acid, N-methylpyrrolidone and also surfactants, which u. a. Wetting properties of the etching solution and their etch rate can be specifically influenced. These acid etch mixtures produce a morphology of interstitially arranged etch pits on the surface. The etching is typically carried out at temperatures in the range between 4 ° C to <10 ° C and the Ätzabtrag here is usually 4 pm to 6 pm. Immediately following the texturing, the silicon wafers are included

Water is thoroughly cleaned and treated with dilute hydrofluoric acid to prepare the chemical oxide layer formed as a result of the preceding treatment steps and impurities absorbed therein as well as adsorbed thereon in preparation of the following

To remove high temperature treatment. 2) diffusion and doping

The wafers etched and cleaned in the previous step (in this case p-type base doping) are heated at higher temperatures,

typically between 750 ° C and <1000 ° C, treated with steam consisting of phosphorus oxide. The wafers are exposed in a tube furnace in a controlled atmosphere quartz glass tube consisting of dried nitrogen, dried oxygen and phosphoryl chloride. The wafers are introduced at temperatures between 600 and 700 ° C in the quartz glass tube. The gas mixture is transported through the quartz glass tube. During transport of the gas mixture through the highly heated tube, the phosphoryl chloride decomposes to a vapor consisting of phosphorus oxide (eg P 2 O 5) and chlorine gas. The vapor of phosphorus oxide u. a. on the wafer surfaces down (occupancy). At the same time, the silicon surface is oxidized at these temperatures to form a thin oxide layer. In this layer, the deposited phosphorus oxide is embedded, whereby a mixed oxide of silicon dioxide and phosphorus oxide formed on the wafer surface.

This mixed oxide is called phosphosilicate glass (PSG). This PSG glass has different softening points and, depending on the concentration of the contained phosphorus oxide

different diffusion constants with respect to the phosphorus oxide. The mixed oxide serves the silicon wafer as a diffusion source, wherein in the course of the diffusion, the phosphorus oxide diffuses in the direction of the interface between PSG glass and silicon wafer and is reduced there by reaction with the silicon on the wafer surface (silicothermally) to phosphorus. The resulting phosphor has a solubility which is orders of magnitude greater in silicon than in the glass matrix from which it is formed, and thus dissolves preferentially in silicon due to the very high segregation coefficient. After its dissolution, the phosphorus diffuses in the

Silicon along the concentration gradient in the volume of silicon. In this diffusion process, concentration gradients of the order of 105 between typical

Surface concentrations of 1021 atoms / cm ² and the base doping in the range of 1016 atoms / cm ² . The typical diffusion depth is 250 to 500 nm and is of the selected diffusion temperature (for example 880 ° C) and the total exposure time (heating & loading phase & driving phase & cooling) of the wafers in the highly heated atmosphere. During the coating phase, a PSG layer is formed, which typically has a layer thickness of 40 to 60 nm. in the

Following the wetting of the wafers with the PSG glass, during which diffusion into the volume of the silicon already takes place, the drive-in phase follows. This can be decoupled from the assignment phase, but is conveniently conveniently in time directly to the

Occupancy coupled and therefore usually takes place at the same temperature. The composition of the gas mixture is adjusted so that the further supply of phosphoryl chloride is suppressed. During driving, the surface of the silicon is further oxidized by the oxygen contained in the gas mixture, whereby a phosphorus depleted silicon dioxide layer is also generated between the actual doping source, the phosphorus oxide highly enriched PSG glass and the silicon wafer

Contains phosphorus oxide. The growth of this layer is much faster in relation to the mass flow of the dopant from the source (PSG glass), because the oxide growth is accelerated by the high surface doping of the wafer itself (acceleration by one to two

Orders of magnitude). As a result, in some way a depletion or separation of the doping source is achieved, whose penetration with

is influenced by the flow of phosphorus depending on the temperature and thus the diffusion coefficient. In this way, the doping of the silicon can be controlled within certain limits. A typical duration of diffusion consisting of loading and driving phase is for example 25 minutes. Following this treatment, the tube furnace is automatically cooled and the wafers can be removed from the process tube at temperatures between 600 ° C to 700 ° C.

In the case of boron doping, the wafer in the form of an n-type base doping, another method is run, which will not be explained separately here ^'. The doping is in these cases, for example, with

Boron trichloride or boron tribromide. Depending on the choice of

Composition of the gas atmosphere used for doping, can the formation of a so-called boron skin on the wafers are detected. This boron skin is dependent on various influencing factors: decisive for the doping atmosphere, the temperature, the doping time, the

Source concentration and the coupled (or linear combined) aforementioned parameters.

In such diffusion processes, it goes without saying that there can be no regions of preferred diffusion and doping in the wafers used (with the exception of those which have arisen due to inhomogeneous gas flows and inhomogeneous gas packets resulting therefrom), unless the substrates are in advance of a corresponding one

Pretreatment were subjected (for example, their structuring with diffusion-inhibiting and / or -unterbindenden layers and

Materials).

For the sake of completeness, it should be pointed out here that there are still other diffusion and doping technologies which have established themselves to varying degrees in the production of crystalline solar cells based on silicon. So be mentioned

Ion implantation, doping, mediates via the gas phase deposition of mixed oxides, such as those of PSG and BSG (borosilicate) glass, by means of APCVD, PECVD, MOCVD and LPCVD methods,

(Co) sputtering of mixed oxides and / or ceramic materials and hard materials (eg, boron nitride), the gas phase deposition of both

the latter, the purely thermal gas phase deposition starting from solid dopant sources (eg boron oxide and boron nitride) as well as

• the liquid phase deposition of doping liquids

(Inks) and pastes.

The latter are often used in the so-called in-line doping, in which the corresponding pastes and inks on the side to be doped of the Wafers are applied by suitable methods. After or even during application, the solvents contained in the compositions used for doping are removed by temperature and / or vacuum treatment. As a result, the actual dopant remains on the wafer surface. As liquid

Doping sources, for example, dilute solutions of phosphoric or boric acid, as well as sol-gel-based systems or solutions of polymeric Borazilverbindungen can be used. Appropriate

Doping pastes are almost exclusively due to the use of

additional thickening polymers characterized, and contain dopants in a suitable form. At the evaporation of

Solvents from the aforementioned doping media are usually followed by a high-temperature treatment during which undesirable and interfering additives which cause the formulation are either "burned" and / or pyrolyzed., The removal of solvents and the burn-out may or may not , take place simultaneously.

Subsequently, the coated substrates usually pass through a continuous furnace at temperatures between 800 ° C and 1000 ° C, to shorten the cycle time, the temperatures in comparison to

Gas phase diffusion in the tube furnace can be slightly increased. The prevailing in the continuous furnace gas atmosphere can according to the

Be different from the requirements of the doping and from dry nitrogen, dry air, a mixture of dry oxygen and dry nitrogen and / or, depending on the version; of the oven to be passed, zones of one and the other of the above

Gas atmospheres exist. Other gas mixtures are conceivable, but currently have little industrial significance. One

Characteristic of the inline diffusion is that the occupation and the

Driving the dopant can in principle be decoupled from each other.

3) Dopant source removal and optional edge isolation

The wafers present after the doping are coated on both sides with more or less glass on both sides of the surface. More or less, in this case, refers to modifications made in the context of Doping process can be applied: double-sided diffusion vs. quasi one-sided diffusion mediated by back-to-back arrangement of two wafers in a parking space of the process boats used. The latter

Variant allows a predominantly one-sided doping, but does not completely prevent the diffusion on the back. In both cases, it is currently state of the art to remove the glasses present after doping by etching in dilute hydrofluoric acid from the surfaces. For this purpose, the wafers are on the one hand transhipped in batches in wet process boats and with their help in a solution of dilute hydrofluoric acid, typically 2% to 5%, immersed and left in this until either the surface is completely removed from the glasses, or Process cycle has expired, which represents a sum parameter of the necessary Ätzdauer and the automatic process automation. The complete removal of the glasses can be determined, for example, by the complete dewetting of the silicon wafer surface by the dilute aqueous hydrofluoric acid solution. The complete removal of a PSG glass is achieved under these process conditions, for example with 2% hydrofluoric acid solution within 210 seconds at room temperature. The etching of corresponding BSG glasses is slower and requires longer process times and possibly also higher

Concentrations of hydrofluoric acid used. After etching, the wafers are rinsed with water.

On the other hand, the etching of the glasses on the wafer surfaces can also be carried out in a horizontally operating method in which the wafers are introduced in a constant flow into an etching system in which the wafers pass through the corresponding process tanks horizontally (inline system). The wafers are conveyed on rollers and rollers either through the process tanks and the etching solutions contained therein or the etching media are transposed onto the wafer surfaces by means of roller application. The typical residence time of the wafers in the case of etching the PSG glass is about 90 seconds, and the hydrofluoric acid used is somewhat more concentrated than in the batch process

Method to compensate for the shorter residence time due to an increased etch rate. The concentration of hydrofluoric acid is typically 5%. Optionally, in addition, the tank temperature compared to the

Room temperature slightly increased (> 25 ° C <50 ° C).

In the method outlined last, it has become established to carry out the so-called edge isolation sequentially simultaneously, which results in a slightly modified process flow: edge insulation -> glass etching. The edge insulation is a process engineering necessity, which results from the system-inherent characteristics of the double-sided diffusion, even with intentional unilateral back-to-back diffusion. On the (later) back side of the solar cell, there is a large-scale parasitic p-n transition, which, although due to process technology, is partly, but not completely, removed in the course of the later processing. As a result, the front and back of the solar cell are parasitic and parasitic

remaining p-n junction (tunnel junction), which reduces the conversion efficiency of the subsequent solar cell. To remove this transition, the wafers are unilaterally via an etching solution

consisting of nitric acid and hydrofluoric acid. The etching solution may contain as minor constituents, for example, sulfuric acid or phosphoric acid. Alternatively, the etching solution is imparted via rollers to the

Rear side of the wafer transported. The etch removal typically achieved with these methods is about 1 pm of silicon at temperatures between 4 ° C. and 8 ° C. (including that on the surface to be treated

present glass layer). In this method, the serves on the

opposite side of the wafer still existing glass layer as a mask, which exerts a certain protection against Ätzübergriffen on this page. This glass layer is subsequently removed using the glass etching already described.

In addition, the edge isolation can also be done with the help of

Plasma etching processes are performed. This plasma etching is then usually carried out before the glass etching. For this purpose, several wafers are stacked on each other and the outer edges become the plasma

exposed. The plasma is filled with fluorinated gases, for example

Tetrafluoromethane, fed. The plasma decay of these gases

occurring reactive species etch the edges of the wafer. In connection to the plasma etching is then generally the glass etching

carried out.

4) Coating the front with an antireflection coating

Following the etching of the glass and the optional

Edge insulation finds the coating of the front of the later

Solar cells with an anti-reflection coating instead, which usually consists of amorphous and hydrogen-rich silicon nitride. alternative

Antireflection coatings are conceivable. Possible coatings may include titanium dioxide, magnesium fluoride, tin dioxide and / or

corresponding stack layers of silicon dioxide and silicon nitride exist. But there are also different compounds

Antireflection coatings technically possible. The coating of the wafer surface with the silicon nitride mentioned above is fulfilled in

Essentially two functions: On the one hand, the layer generates an electric field due to the numerous incorporated positive charges, that charge carriers in the silicon can keep away from the surface and the recombination speed of these charge carriers at the

On the other hand, depending on its optical parameters, such as refractive index and layer thickness, this layer generates a reflection-reducing property which contributes to the fact that more light can be coupled into the later solar cell. Both effects can increase the conversion efficiency of the solar cell. typical

Properties of the layers currently used are: a layer thickness of ~ 80 nm using only the above-mentioned silicon nitride, which has a refractive index of about 2.05. The antireflection reduction is most pronounced in the wavelength range of the light of 600 nm. The directional and non-directional reflection shows a value of about 1% to 3% of the originally incident light (perpendicular incidence to the surface normal of the silicon wafer).

The above-mentioned silicon nitride films are currently generally deposited on the surface by a direct PECVD method. For this purpose, a gas atmosphere of argon, a plasma is ignited, in which silane and Ammonia are introduced. The silane and the ammonia are converted in the plasma by ionic and radical reactions to silicon nitride and thereby deposited on the wafer surface. The properties of the layers can z. B. adjusted and controlled by the individual gas flows of the reactants. The deposition of the above-mentioned silicon nitride layers can also be carried out using hydrogen as the carrier gas and / or the reactants alone. Typical deposition temperatures are in the range between 300 ° C to 400 ° C. Alternative deposition methods may be, for example, LPCVD and / or sputtering.

5) Generation of the front side electrode grid

After depositing the antireflection coating is on with

Silicon nitride coated wafer surface defines the front electrode. In industrial practice, the electrode has been established using the screen printing method using metallic

To produce sinter pastes. This is just one of many

different ways to produce the desired metal contacts. In screen printing metallization is usually a strong with

Silver particles enriched paste (silver content <= 80%) used. The sum of the residual constituents results from the necessary for the formulation of the paste theological aids, such as solvents, binders and thickeners. Furthermore, the silver paste contains a special Glasfrit mixture, mostly oxides and mixed oxides based on

Silica, borosilicate glass as well as lead oxide and / or bismuth oxide. The glass frit fulfills essentially two functions: on the one hand it serves as a bonding agent between the wafer surface and the mass of the silver particles to be sintered, on the other hand it is responsible for the penetration of the silicon nitride covering layer in order to enable the direct ohmic contact to the underlying silicon. The penetration of the silicon nitride takes place via an etching process with subsequent diffusion of silver present dissolved in the glass frit matrix into the silicon surface, whereby the ohmic contact formation is achieved. In practice, the silver paste is deposited by screen printing on the wafer surface and then at temperatures of about 200 ° C to 300 ° C for a few Dried for a few minutes. For the sake of completeness, it should be mentioned that double-printing processes also find industrial application, which make it possible to print on an electrode grid generated during the first printing step, a congruent second. Thus, the strength of the

Silver metallization increases, which can positively influence the conductivity in the electrode grid. During this drying, the solvents contained in the paste are expelled from the paste. Subsequently, the printed wafer passes through a continuous furnace. Such an oven generally has several heating zones, which can be independently controlled and tempered. When passivating the

Continuous furnace, the wafers are heated to temperatures up to about 950 ° C. However, the single wafer is typically exposed to this peak temperature for only a few seconds. During the remaining run-up phase, the wafer has temperatures of 600 ° C to 800 ° C. In these

Temperatures are contained in the silver paste contained organic impurities, such as binders, and the etching of the

Silicon nitride layer is initiated. During the short time interval of the prevailing peak temperatures, contact formation occurs

Silicon instead. Subsequently, the wafers are allowed to cool.

The process of contact formation outlined so briefly is usually carried out simultaneously with the two remaining contact formations (see Figures 6 and 7), which is why in this case one also speaks of a co-firing process. The front electrode grid consists of thin fingers

(typical number> = 68), which have a width of typically 80 pm to 140 pm, as well as collecting buses with widths in the range of 1, 2 mm to 2.2 mm (depending on their number, typically two to three). The typical height of the printed silver elements is typically between 10 pm and 25 ym. The aspect ratio is rarely greater than 0.3.

6) Generation of the backward bus buses

The rear bus buses are also usually by means of

Screen printing applied and defined. For this purpose, one of the similar silver paste used for front metallization is used. This paste is similarly composed, but contains an alloy of silver and aluminum, wherein the proportion of aluminum is typically 2%. In addition, this paste contains a lower glass frit content. The bus busses, usually two, will be printed with a typical width of 4 mm on the back of the wafer by screen printing and, as already described under point 5, compacted and sintered.

7) Generation of the back electrode

The back electrode is defined following the pressure of the bus buses. The electrode material is made of aluminum, therefore, to define the electrode, an aluminum-containing paste by screen printing on the remaining free area of the wafer back with a

Edge distance <1 mm is printed. The paste is <= 80% off

Aluminum assembled. The remaining components are those already mentioned under point 5 (such as solvents, binders, etc.). The aluminum paste is bonded to the wafer during co-firing by causing the aluminum particles to start to melt during heating and remove silicon from the wafer in the wafer

dissolves molten aluminum. The melt mixture acts as a dopant source and gives aluminum to the silicon (solubility limit: 0.016 atomic percent), whereby the silicon is p + doped as a result of this drive-in. As the wafer cools, it will precipitate on the wafer surface u. a. a eutectic mixture of aluminum and silicon, which solidifies at 577 ° C and has a composition with a mole fraction of 0.12 Si.

As a result of the driving of the aluminum into the silicon, a highly doped p-type layer is formed on the back side of the wafer, which acts as a kind of mirror on parts of the free charge carriers in the silicon ("electric mirror"). These charge carriers can not do this potential wall

overcome and thus become very efficient from the backward

Keep remote wafer surface, which thus manifests itself in an overall reduced recombination of charge carriers on this surface. This potential wall is generally referred to as the back surface field or back surface field.

The sequence of process steps described in items 5, 6 and 7 may or may not be the same as outlined herein. The skilled person will see that the sequence of

described process steps can be executed in principle in any imaginable combinatorics. 8) Optional edge insulation

If the edge isolation of the wafer has not already been carried out as described under point 3, this is typically carried out after co-firing with the aid of laser beam methods. For this purpose, a laser beam is directed to the front of the solar cell and the front p-n junction is severed by means of the energy coupled in by this beam. This trench with a depth of up to 15 μηη due to

Action of the laser generated. This silicon is over a

Ablation mechanism removed from the treated area or thrown out of the laser ditch. Typically, this laser trench is 30 μιτι to 60 μητι wide and about 200 μιη away from the edge of the solar cell.

After their production, the solar cells are characterized and

Classified according to their individual performance in individual performance categories.

The person skilled in the art knows solar cell architectures with both n-type and p-type base material. These solar cell types include u. a. · PERC solar cells

• PERL solar cells

• PERT solar cells

• As a result, MWT-PERT and MWT-PERL solar cells

• Bifacial solar cells

»Backside contact cells

• backside contact cells with interdigitating contacts (IBC cells) The choice of alternative doping technologies, as an alternative to the gas phase doping already described above, can usually be the

Do not resolve the problem of creating locally differently doped regions on the silicon substrate. As alternative technologies here the deposition of doped glasses, or of amorphous mixed oxides, by means of PECVD and APCVD method mentioned. From these glasses, a thermally induced doping of the silicon located under these glasses can be easily achieved. To create locally differently doped regions, however, these glasses must be etched by means of mask processes in order to extract the corresponding structures from them

prepare. Alternatively, structured diffusion barriers may be deposited on the silicon wafers prior to depositing the glasses to define the regions to be doped. A disadvantage of this method, however, is that in each case only one polarity (n or p) of

Something simpler than the structuring of the doping sources or that of any diffusion barriers is the direct laser beam driven driving in of dopants from previously on the

Wafer surfaces deposited dopant sources. This method makes it possible to save costly structuring steps. However, it can not compensate for the disadvantage of a possible simultaneous simultaneous doping of two polarities on the same surface at the same time (co-diffusion), since this method is also based on a predeposition of a dopant source, which is activated only subsequently for the emission of the dopant. Disadvantage of this (post-) doping from such sources is the inevitable laser damage to the substrate: the laser beam must by absorbing the radiation into heat

being transformed. Since the conventional dopant sources off

Mixed oxides of the silicon and the dopants to be introduced, ie of boron oxide in the case of boron, are consequently the optical properties of these mixed oxides quite similar to those of the silicon oxide. Therefore, these glasses (mixed oxides) have a very low absorption coefficient for radiation in the relevant wavelength range. For this reason, the silicon located under the optically transparent glasses is used as the absorption source. The silicon is partially heated to the melt, and as a result heats the glass above it. This allows the diffusion of the dopants - by one Many times faster than the normal ones

Diffusion temperatures would be expected, resulting in a very short diffusion time for the silicon (less than 1 second). The silicon should cool down relatively quickly after the absorption of the laser radiation due to the strong removal of the heat in the remaining, unirradiated volume of silicon and thereby epitaxially on the not

solidify molten material. The overall process, however, is in reality accompanied by the formation of laser-induced defects, possibly due to incomplete epitaxial solidification and the formation of crystal defects. This can be attributed, for example, to dislocations and formation of voids and voids as a result of the shocking process. Another disadvantage of laser-assisted diffusion is the relative inefficiency when larger areas are to be rapidly doped because the laser system scans the surface in a dot-matrix process. For narrow areas to be doped, this disadvantage has no weight. However, laser doping requires sequential deposition of the aftertreatable glasses. Object of the present invention

The in the industrial production of solar cells usually

used doping technologies, namely by the

gas-phase-mediated diffusion with reactive precursors, such as

Phosphorylchlond and / or boron tribromide, do not allow to selectively generate local dopants and / or locally different dopants on silicon wafers. The creation of such structures is possible by using known doping technologies only by consuming and costly structuring of the substrates. When structuring different

Masking processes are coordinated, which makes the industrial mass production of such substrates very complex. For this reason, concepts for the production of solar cells, which require such a structuring, have not been able to prevail. It is therefore an object of the present invention to provide an inexpensive, easy to carry out method, as well as a usable in this method medium, whereby these problems and the normally required masking steps are obsolete and thus eliminated. In addition, the locally applicable doping source is characterized in that it preferably by means of

Screen printing process can be applied to wafer surfaces. For this purpose, the doping source must have a sufficiently pasty

Have behavior that can and must be targeted, contrary to the classical approach without the use of viscosity-influencing polymeric additives, which in turn can represent an uncontrolled source of contamination. It has been shown that a sufficient pastiness through a controlled

Gelation of the hybrid gels of the invention can be adjusted. The intrinsic viscosity of the hybrid gels can be further adjusted as desired by the addition of waxes and waxy additives and additives as desired. As a result of formulations adapted in this way, it is possible to obtain pastes which are very readily adjustable in their intrinsic viscosity and which are sufficiently resistant to shear. The waxes and waxy additives used for the formulation are dissolved and / or melted in gelled paste mixture. As a result of suitable choice of previously mentioned compounds and, if necessary, their

Mixtures, as well as, if necessary, with the addition in the broader context of precisely named auxiliaries, are very good silkscreened, homogeneous

(single-phase) to form emulsifying (two-phase) formulated screen printing pastes obtained. The waxes and waxy additives used in the formulation act associatively and co-thickening in synthesized and gelled pastes, without the additives being thickeners in the classical sense. Furthermore, the associative, intrinsic viscosity-affecting waxes and waxy compounds have an advantageous effect on the adjustment of the glass layer thickness resulting from the printed hybrid gels as well as on their individual drying resistance to stress.

Brief description of the invention

The subject of the present invention is therefore printable,

pasty hybrid gels based on precursors, such as

Silica, alumina and boron oxide, which preferably by means of of the screen printing method on silicon surfaces for the purpose of local and / or full-area, one-sided diffusion and doping in the production of solar cells, preferably of highly efficient structured doped solar cells, printed, nachlagernd dried and then by means of a suitable high-temperature process for

Delivery of the Boroxidprecursors contained in the hybrid gel are placed on the under the hybrid gel substrate for the targeted doping of the substrate itself. These are paste-form, printable hybrid gels with a viscosity of> 500 mPa ^* s based on precursors of the following oxide materials: a) Silica: one to fourfold symmetric and asymmetric

substituted carboxy, alkoxy and alkoxyalkylsilanes, explicitly

Containing alkylalkoxysilanes in which the central silicon atom has a degree of substitution of 1 to 4 with at least one directly to the

Silicon atom may have attached hydrogen atom, such as triethoxysilane, and further wherein a

Degree of substitution refers to the number of possible existing carboxy and / or alkoxy groups, which have both single and different saturated, unsaturated branched, unbranched aliphatic, alicyclic and aromatic radicals in each case at alkyl and / or alkoxy and / or carboxy groups, which in turn at any position of the alkyl, alkoxide or carboxy radical may be functionalized by heteroatoms selected from the group O, N, S, Cl and Br, as well as mixtures of the abovementioned

precursors; individual compounds which satisfy the abovementioned claims are: tetraethylorthosilicate and the like, triethoxysilane, ethoxytrimethylsilane, dimethyldimethoxysilane,

Dimethyldiethoxysilane, triethoxyvinylsilane, bis [triethoxysilyl] ethane and bis [diethoxymethylsilyl] ethane b) Aluminum oxide: symmetrically and asymmetrically substituted

Aluminum alcoholates (alkoxides), such as aluminum triethanolate,

Aluminum trisopropylate, aluminum tri-sec-butylate, aluminum tributylate, aluminum triamylate and aluminum tri-iso-pentoxide, aluminum tris (-β-diketones), such as aluminum acetylacetonate or aluminum tris (1, 3) cyclohexanedionates), aluminum tris (-β-ketoesters), aluminum monoacetylacetonate monoalcoholate, aluminum tris (hydroxyquinolates), aluminum soaps such as mono- and dibasic aluminum stearate and aluminum tristearate, aluminum carboxylates such as basic

Aluminum acetate, aluminum triacetate, basic aluminum format, aluminum triformate and aluminum trioctoate, aluminum hydroxide,

Aluminummetahydroxide and aluminum trichloride and the like, and mixtures thereof c) Boron oxide: Diboroxide, simple Borsäurealkylester, such as triethylborate, trisopropylborate, boric acid esters of functionalized 1, 2-glycols, such as ethylene glycol, functionalized 1, 2, 3-triols, such as glycerol functionalized 1, 3-glycols, such as, for example, 1,3-propanediol, boric acid esters with boric acid esters containing structural motifs as structural subunits, such as 2,3-dihydroxysuccinic acid and its enantiomers, boric acid esters, ethanolamine, diethanolamine, triethanolamine, propanolamine, Dipropanolamine and tripropanolamine, mixed anhydrides of boric acid and carboxylic acids, such as Tetracetoxydiborat, boric acid, metaboric acid, and mixtures of previously mentioned precursors under aqueous or anhydrous conditions using the sol-gel technique either simultaneously or sequentially to partial or complete intra- and / or interspecific condensation are brought about, as a result of the set condensation conditions, such as precursor concentrations, water content, catalyst content, reaction temperature and time, the addition of condensation-controlling agents, such as various of the above complex and chelating agents, various solvents and their individual volume fractions, as well as the targeted elimination of volatile reaction auxiliaries and unfavorable by-products, the degree of gelation of the resulting hybrid gel can be specifically controlled and influenced in the desired manner, so that storage-stable, very good screen printable and pressure stable and thus sufficiently shear stable formulations are obtained. The resulting printable paste hybrid gels as described in U.S. Pat

Described in more detail below, can be selected by choosing appropriate

In terms of their degree of condensation, reaction conditions can be influenced by the fact that highly viscous mixtures are in the form of pasty formulations or also pastes which mix with printing processes suitable for such mixtures, preferably the

Screen printing process, process on substrates in the already claimed manner and apply. The printable paste hybrid gel according to the invention is a composition which can be adjusted by the addition of waxes and waxy compounds in an amount of up to 25% based on the final total mixture of the paste in terms of its pasty and pseudoplastic properties, the waxes and waxy compounds selected from the group consisting of beeswax, synchro wax, lanolin, carnauba wax, jojoba, Japan wax and the like, fatty acids and fatty alcohols, fatty glycols, esters

Fatty acids and fatty alcohols, fatty aldehydes, fatty ketones and fatty β-diketones and mixtures thereof, the abovementioned

Substance classes should each contain branched and unbranched carbon chains with chain lengths greater than or equal to twelve carbon atoms, single-phase and / or biphasic, emulsifying or suspending, thickening and thus make the classical use of polymeric thickeners superfluous.

The hereby made available, inventive printable

Hybrid gel, is particularly well suited for use as a doping medium in the processing of silicon wafers for photovoltaic, microelectronic, micromechanical and micro-optical applications.

In particular, the novel paste-like ones described herein are

Hybrid gels are suitable for the production of PERC, PERL, PERT, IBC solar cells and other high-performance solar cells, which feature further architectural features such as MWT, EWT, Selective Emitter, Selective Front Surface Field, Selective Back Surface Field and Bifaciality. To be particularly advantageous, it has been shown that the printable hybrid gels according to the invention for the production of grip and abrasion resistant

Layers on silicon wafers, can be used. For the production of these layers, after application in a temperature range between 50 ° C. and 750 ° C., preferably between 50 ° C. and 500 ° C., particularly preferably between 50 ° C. and 400 ° C., the hybrid gel is applied using one or more to be carried out sequentially Temperschritten (tempering by means of a step function) and / or an annealing ramp, dried and compacted to the glazing, which forms grip and abrasion resistant layers with a thickness of up to 500 nm.

Furthermore, it has been shown by experiments that through the

Using the printable hybrid gel according to the invention can influence the conductivity of the substrate by drying corresponding to surfaces applied to layers, compacted and vitrified and from the vitrified layers by heat treatment at a

Temperature in the range between 750 ° C and 1100 ° C, preferably between 850 ° C and 1100 ° C, more preferably between 850 ° C and 1000 ° C, silicon doping atoms, as in this case boron, are released to the substrate.

Be particularly advantageous in the use of

Printable pasty hybrid gels according to the invention have been found to have different dopings of different regions in one

Allow process step, and that by suitable

Temperature treatment, a doping of the printed substrate and simultaneously and / or sequentially doping of the unprinted

Silicon wafer surfaces with dopants of opposite polarity is induced by conventional gas phase diffusion and wherein the printed hybrid gel acts as a diffusion barrier to the dopants of opposite polarity. Process for the preparation of

Solar cells using the paste-shaped hybrid gel according to the invention are characterized in that a) hybrid gels are printed on silicon wafers, dried and compacted onto the printed gels, and then subjected to subsequent gas phase diffusion with, for example, phosphoryl chloride to yield p-type dopants in the printed areas of the wafers and n-type dopants in the areas exclusively exposed to gas-phase diffusion,

or

b) hybrid gel deposited on the silicon wafer and / or densified and initiated from the dried and / or compacted paste by means of laser irradiation, the local doping of the underlying substrate material, followed by a high-temperature diffusion and doping for the production of two-stage p-type Doping levels is induced in the silicon,

or

c) the silicon wafer is printed locally with the hybrid gel, wherein the structured landfill may optionally have alternating lines, the printed structures dried and compacted and subsequently over the entire surface with the aid of PVD and / or CVD-deposited doped glasses doping in silicon of opposite polarity, can be coated and encapsulated, and the

overlapping overall structure is brought to the structured doping of the silicon wafer by suitable high-temperature treatment, wherein the printed hybrid gel acts as a diffusion barrier with respect to the glass above it and the dopant contained therein.

Detailed description

It has been found that the problems described above can be solved by a process for preparing printable, high viscosity oxide media (viscosity> 500mPas) when in a sol-gel based synthesis by condensation of suitable precursors of silica and alumina mixed with precursors Boroxides, and by controlled gelation pasty high viscosity media (pastes) are produced. In this context, a paste is to be understood as meaning a composition which, due to the sol-gel-based synthesis, has a high viscosity of more than 500 mPa ^* s and is no longer flowable. According to the invention, the printable, highly viscous oxide media, also referred to below as hybrid gels, can be prepared in arbitrary proportions from suitable precursors of at least the following oxides: aluminum oxide, silicon dioxide and boron oxide - the precursors designated accordingly being at least the following compounds and classes of compounds:

Silicon dioxide: one to fourfold symmetric and asymmetric

substituted carboxy, alkoxy and alkoxyalkylsilanes, explicitly

Silicon atom may have attached hydrogen atom, such as

For example, triethoxysilane, and further wherein a degree of substitution refers to the number of possible existing carboxy and / or alkoxy groups, which in both alkyl and / or alkoxy and / or

Carboxy groups have individual or different saturated, unsaturated branched, unbranched aliphatic, alicyclic and aromatic radicals, which in turn may be functionalized at any position of the alkyl, alkoxide or the carboxy radical by heteroatoms selected from the group O, N, S, Cl and Br, and mixtures of the aforementioned precursors. Individual compounds which are mentioned in the above

Claims are: tetraethyl orthosilicate and the like,

Triethoxysilane, ethoxytrimethylsilane, dimethyldimethoxysilane,

Dimethyldiethoxysilane, triethoxyvinylsilane, bis [triethoxysilyl] ethane and bis [diethoxymethylsilyl] ethane.

Alumina: symmetrically and asymmetrically substituted

Aluminum alcoholates (alkoxides), such as aluminum triethanolate,

Aluminum trisopropylate, aluminum tri-sec-butylate, aluminum tributylate, aluminum triamylate and aluminum tri-iso-pentoxide, A! Uminium tris (-β-diketones), such as aluminum acetylacetonate or aluminum tris (1,3-cyclohexanedionates), aluminum tris (- ketoester), aluminum monoacetylacetonate monoalcoholate, aluminum tris (hydroxyquinolates), aluminum soaps, such as mono- and dibasic aluminum stearate and

Aluminum tristearate, aluminum carboxylates such as basic aluminum acetate, aluminum triacetate, basic aluminum formate, aluminum tri-formate and aluminum trioctoate, aluminum hydroxide, aluminum metahydroxide and

Aluminum trichloride and the like, and mixtures thereof,

Boron oxide: diboroxide, simple boric acid alkyl esters, such as triethyl borate,

Trisopropyl borate, boric acid esters of functionalized 1, 2-glycols, such as ethylene glycol, functionalized 1, 2, 3-triols, such as

for example, glycerol, functionalized 1, 3-glycols, such as, for example,

1, 3-propanediol, boric acid esters with boric acid esters containing the aforementioned structural motifs as structural subunits, such as

2, 3-dihydroxysuccinic acid and its Enantionmere, boric acid esters, from ethanolamine, diethanolamine, triethanolamine, propanolamine, dipropanolamine and tripropanolamine, mixed anhydrides of boric acid and

Carboxylic acids, such as tetraacetoxy diborate, boric acid,

Metaboric acid, and mixtures of previously mentioned precursors. The possible combinations are furthermore not necessarily limited to the abovementioned composition possibilities: as additional components, it is possible for the hybrid gels to contain further substances which can confer advantageous properties on the gels. They may be: oxides, basic oxides, hydroxides, alkoxides, carboxylates, β-diketonates, β-ketoesters, silicates and the like of cerium, tin, zinc, titanium, zirconium, hafnium, zinc, germanium, gallium, niobium, yttrium, which in the sol-gel synthesis can be used directly or pre-condensed application. The

Hybrid gels can be prepared using anhydrous as well as hydrous sol-gel synthesis. As further auxiliaries in the formulation of the gels, the following substances can be used advantageously:

Surfactants, tensio-active compounds for influencing the wetting and drying behavior,

• defoamer and deaerator to influence the drying behavior, · strong carboxylic acids to initiate the condensation reaction of

Oxid precursors, as suitable carbonyls can at least serve: Formic acid, acetic acid, oxalic acid, trifluoroacetic acid, mono-, di- and trichloroacetic acid, glyoxylic acid, tartaric acid, maleic acid, malonic acid, pyruvic acid, malic acid, 2-oxoglutaric acid

High and low-boiling polar protic and aprotic solvents for influencing the particle size distribution, the degree of precondensation,

Condensation, wetting and drying and printing behavior,

• particulate additives to influence the theological

Properties,

• particulate additives (eg aluminum hydroxides and

Aluminas, colloidally precipitated or fumed silica, tin dioxide, boron nitride, silicon carbide, silicon nitride, aluminum titanate,

Titanium dioxide, titanium carbide, titanium nitride, titanium carbonitride) for influencing the dry film thicknesses resulting after drying and their morphology,

• particulate additives (eg aluminum hydroxides and

Titanium dioxide, titanium carbide, titanium nitride, titanium carbonitride) for influencing the scratch resistance of the dried films,

Capping agent selected from the group acetoxytrialkylsilanes,

Alkoxytrialkylsilanes, Halogentrialkylsilane and their derivatives to

Influencing condensation rates and storage stability

Waxes and waxy compounds, such as beeswax,

Synchrowachs, Lanolin, Carnauba Wax, Jojoba, Japan Wax and

the like, fatty acids and fatty alcohols, fatty glycols, esters

Substance classes should each contain branched and unbranched carbon chains with chain lengths greater than or equal to twelve carbon atoms. The hybrid gels can be prepared by adding appropriate

Masking agents, complex and chelating in a sub stoichiometric to a stoichiometric ratio on the one hand sterically stabilize and on the other hand in terms of their condensation and gelling rate but also in terms of the rheological properties targeted influence and control. Suitable masking and complexing agents, as well

Chelating agents, for example, acetylacetone,, 3-cyclohexanedione, isomeric compounds of dihydroxybenzoic acids, acetaldoxime, as well as those disclosed and contained in the patent applications WO 2012/1 9686 A, WO20121 19685 A1, WO20121 19684 A, EP12703458.5 and EP12704232.3. The content of these publications is therefore included in the disclosure of the present application.

The hybrid gels can be applied to the surface of silicon wafers using printing and coating techniques. suitable

These can be: spin coating or dip coating, drop casting, curtain or slot dye coating, screen printing or flexoprinting, gravure, ink jet or aerosol jet printing, offset printing, microcontact printing,

Electrohydrodynamic dispensing, roller or spray coating, ultrasonic spray coating, pipe jetting, laser transfer printing, pedd printing or rotary screen printing. Preferably, printing of the hybrid gels is accomplished by the screen printing method. The on the surfaces of

Silicon wafers printed hybrid gels are subjected to a drying step following their landfill. This drying may, but not necessarily, be done in a continuous furnace. During the drying of the gels, they are compacted as a result of the spewing out of solvents, as well as the thermal degradation of formulation auxiliaries and of the oxide precursors into homogeneous and tightly closing vitreous layers.

The thus prepared, printable and dried hybrid gels are particularly well suited for use as a doping medium in the

Processing of silicon wafers for photovoltaic, microelectronic, micromechanical and micro-optical applications.

Correspondingly prepared hybrid gels are particularly suitable for the production of PERC, PERL, PERT, IBC solar cells (BJBC or BCBJ) and others, wherein the solar cells further architectural features, such as MWT, EWT, selective emitter, selective front surface field, selective Have back surface field and bifaciality. Furthermore, the

Oxide media according to the invention for the production of thinner, denser

Glass layers, which act as a sodium and potassium diffusion barrier in the LCD technology due to a thermal treatment, in particular for Production of thin, dense glass layers on the cover glass of a display, consisting of doped S1O2, which prevent the diffusion of ions from the cover glass into the liquid-crystalline phase.

With the aid of the hybrid gels prepared and printable according to the invention, it is possible to produce a grip and abrasion-resistant layer on silicon wafers. This may be done in a process wherein the surface-printed hybrid gel prepared by a process within the scope of the invention is particularly preferred in a temperature range between 50 ° C and 750 ° C, preferably between 50 ° C and 500 ° C between 50 ° C and 400 ° C, using one or more, to be carried out sequentially Temperschritten (tempering by a step function) and / or an annealing ramp, dried and compacted to the glazing, forming a grip and abrasion resistant layer, may have thicknesses of up to 500 nm.

Subsequently, a heat treatment of the vitrified on the surfaces layers at a temperature in the range between 750 ° C and 1100 ° C, preferably between 850 ° C and 1 00 ° C, more preferably between 850 ° C and 1000 ° C. As a result, atoms doped with silicon, such as boron in the present case, become silicothermal

Reduction of their oxides at the substrate surface of this release, whereby the conductivity of the silicon substrate is specifically influenced beneficial. It is particularly advantageous that due to the heat treatment of the printed substrate, the dopants depending on the

Treatment duration and the treatment temperature can be transported in depths of up to 1 μιτι, and electrical layer resistances of less than 10 Ω / sqr are adjustable. The surface concentration of the dopant can reach values greater than or equal 1 ^* 10 ¹⁹ 1 ^* 0 ²⁰ to several

Atoms / cm ³ and depends on the type of dopant used in the printable hybrid gel. It has proved to be particularly advantageous hereby that subsequently the

Surface concentration of the parasitic doping of not intentionally protected (masked) and with the printable hybrid gels uncovered surface areas of the silicon substrate over such Areas that have been specifically printed with the printable hybrid gels to distinguish at least two powers of ten from each other. In addition, this result can be achieved by printing the hybrid gel as a doping medium on hydrophilic (wet-chemical and / or native oxide) and / or hydrophobic (silane-terminated) silicon wafer surfaces. By the thin formed from the hybrid gels applied to the substrate surfaces

Oxide layers, it is thus possible over the choice of the following

Setting parameters

Composition of the hybricle (proportions of the doping oxide precursor to those of the accompanying oxide precursors, mainly but not exclusively glass forming)

• The pre-treatment of the glass, such as those due to the irradiation of high-intensity light, such as laser radiation

• Duration of treatment

Treatment temperature directly via the diffusivity of the dopant, in this case of boron, its segregation coefficient in the thin oxide layer and from it

as a result of its effective dose of doping

Silicon wafer surfaces to decide and thus the

Targeted influence on doping conditions. The same applies to its diffusion-inhibiting and / or excluding and suppressing properties against undesired parasitic diffusion in the areas printed with the hybrid gel induced by the simultaneous

Application of conventional doping sources, which produce an opposite doping, as a rule, such with phosphorus, in areas not printed with the invention, locally applied and dried hybrid gels (so-called co-diffusion).

In general terms, this process can be used to produce grip and abrasion-resistant oxidic layers which have a doping effect on silicon and silicon wafers a) silicon wafers are printed with the hybrid gels according to the invention, the printed Dotiermedien dried, compacted and

Subsequently, a subsequent gas phase diffusion with boron trichloride or boron tribromide are exposed, whereby high doping is obtained in the printed areas and a lower doping in the

Areas exposed exclusively to gas-phase diffusion

or

b) Previously under a) Described, as well as for the following points

mitgeltend, and the usually obtained at the wafer surface

Borhaut

I. consumed by means of oxidative treatment at the end of the diffusion process, or

II. By means of oxidative treatment during the diffusion process

used up, or

III. is removed from the wafer surface by means of subsequent sequential wet chemical treatment with nitric and hydrofluoric acid or

c) silicon wafer structured with the hybrid gels according to the invention

printed, dried, densified and then treated in the same manner with an oppositely doped acting medium using the negative previously used print layout, for example, with subsequent gas phase diffusion

Phosphoryl chloride in the case of a used n-type doping medium or with, for example, boron trichloride or boron tribromide in the case of a p-type doping medium used, whereby high dopings in the non-printed areas and lower

Dopings can be obtained in the printed areas, insofar as the source concentration of the hybrid gels used

controlled by synthesis was set sufficiently low, and the glass obtained from the hybrid gel according to the invention and the oppositely acting doping each have a diffusion barrier against those from the gas phase to the wafer surface

represent transported and deposited gas phase diffusanten or Silicon wafer with the hybrid gels according to the invention structured printed, dried, compacted and then treated in the same manner with an oppositely doped acting medium using the negative pressure layout previously used, a subsequent gas phase diffusion with, for example

Phosphoryl chloride in the case of a used n-type doping medium or with, for example, boron trichloride or boron tribromide in the case of a p-type doping medium used can be obtained, whereby low doping in the non-printed areas and high dopants in the printed areas can be obtained, in that

Source concentration of the hybrid gels used was controlled by synthesis sufficiently controlled, and the glass obtained from the hybrid gel according to the invention and the

oppositely acting doping each have a diffusion barrier against those from the gas phase to the wafer surface

represent transported and deposited gas phase diffusanten or

hybrid gel deposited over the entire surface of the silicon wafer is dried and / or compacted and from the compacted hybrid doping gel with the aid of laser irradiation, the local doping of the underlying substrate material is initiated,

or

dried on the silicon wafer over the entire surface deposited hybrid gel according to the invention and compacted, and from the compacted doped hybrid gel with the aid of suitable

Heat treatment initiated the doping of the underlying substrate and subsequently with subsequent local

Laser irradiation, the local doping of the underlying

Reinforced substrate material and the dopant is driven deeper into the volume of the substrate,

or

the silicon wafer either over the entire surface or locally with the

printed hybrid structures according to the invention, optionally by alternating structures, the printed structures are dried and compacted, the negatives of the alternating structures are printed by means of oppositely doping acting materials and as a result of suitable heat treatment for structured doping of the

Substrates are brought

or

h) the silicon wafer either over the entire surface or locally with the

The hybrid gels according to the invention are optionally printed in an alternating structure sequence of arbitrary structure width, for example line width, adjacent to non-printed silicon surface also characterized by an arbitrary structure width, the printed structures are dried and compacted, after which the wafer of a conventional

Gas phase diffusion and doping is subjected by means of phosphoryl chloride or phosphorus pentoxide and thereby acts either locally or over the entire area applied hybrid gel as a diffusion barrier to the mediated via the gas phase dopant and consequently not printed with the hybrid gel according to the invention

Wafer surfaces of an opposite doping, in this case with phosphorus, are subjected; if necessary, the opposite surface printed with the hybrid gel must or can be suitably etched back by means of suitable wet-chemical etching steps, or

i) the silicon wafer either over the entire surface or locally with the

The hybrid gels according to the invention are optionally printed in an alternating structure sequence of arbitrary structure width, for example line width, adjacent to non-printed silicon surface likewise characterized by any structure width, the printed structures are dried and compacted, after which the entire surface of the wafer is coated with a

Opposite inducing dopant

Majority carrier polarity on the already printed

Wafer surface as well as still open, d. H. unprinted

Wafer surface can be provided (encapsulation), the latter doping media printable sol-gel-based oxidic dopants, other printable dopants and / or pastes, doped APCVD and / or PECVD glasses and dopants from conventional gas phase diffusion and doping can be, and the overlapping arranged and doping acting doping due to suitable heat treatment for doping of the substrate are brought and in this context, the bottom befindliches printed hybrid dot-acting hybrid gel due to suitable segregation coefficients and insufficient diffusion lengths as a diffusion barrier to behave over it, the contrasting majority majority carrier polarity inducing doping medium must behave; further comprising the other side of the wafer surface by means of an otherwise and otherwise deposited (printed, CVD, PVD) diffusion barrier, such as

Silicon dioxide or silicon nitride or silicon oxynitride, may be covered, but need not necessarily be

or

the silicon wafer either over the entire surface or locally with the

Opposite inducing dopant

Majority carrier polarity on the already printed

Wafer surface as well as still open, d. H. unprinted

Wafer surface can be provided (encapsulation), after which then the wafer surface over the entire surface with a doping opposite inducing majority charge carrier polarity can be provided on the already printed wafer surface, the latter doping media printable sol-gel-based oxide dopants, other printable Dotiertinten and / or Pastes may be doped APCVD and / or PECVD glasses as well as dopants from conventional gas phase diffusion and doping, and the overlapping arranged doping and doping acting dopants due to appropriate heat treatment for doping of the substrate are brought and this context to support As a result of suitable segregation coefficients and inadequate

Diffusion lengths as a diffusion barrier over the above need to behave, the majority controlling charge carrier polarity inducing, doping medium must behave; further comprising the other side of the wafer surface by means of a different and otherwise deposited dopant source (Sol-gel-based oxidic

Doping materials, other printable doping inks and / or pastes, with

Dopants provided APCVD and / or PECVD glasses as well as dopants from conventional gas phase diffusion), which may be the same or opposite doping, as may induce from the bottom layer of the opposite wafer surface, covered, but need not necessarily be.

In the method characterized in this way, a simultaneous co-diffusion takes place in a simple manner by temperature treatment of the layers formed from the printed hybrid gels with the formation of n- and p-type layers or of such layers exclusively of one single layer

Majority carrier polarity, differing cans

May have dopant. For the formation of hydrophobic silicon wafer surfaces are in this process after the printing of the invention

Hybrid gels, their drying, and compression and / or doping by thermal treatment resulting glass layers with a

Acid mixture containing hydrofluoric acid and optionally phosphoric acid etched, wherein the etching mixture used as etchant hydrofluoric acid in a concentration of 0.001 to 10 wt .-% or 0.001 to 10 wt .-%

Can contain hydrofluoric acid and 0.001 to 10 wt .-% phosphoric acid in the mixture. The dried and compacted doping glasses can the

Further removed from the wafer surface with the following etching mixtures: buffered hydrofluoric acid (BHF), buffered

Oxidätzmischungen, etching mixtures, consisting of flow and

Nitric acid, such as the so-called p-etching, R-etching, S-etching or etch mixtures, etching mixtures consisting of flux and

Sulfuric acid, the aforementioned list is not exhaustive. The novel high-viscosity doping pastes can be synthesized on the basis of the sol-gel process and, if necessary, can be formulated further. A synthetic method is based on the dissolution of oxide precursors of the alumina in a solvent or a solvent mixture, preferably selected from the group of high-boiling glycol ethers or preferably high-boiling glycol ethers and alcohols, which

then with a suitable acid, preferably a carboxylic acid, and in this case particularly preferably with formic acid or acetic acid, and by the addition of suitable complexing and chelating agents, such as

for example, suitable β-diketones, such as acetylacetone or for example 1, 3-cyclohexanedione, α- and β-ketocarboxylic acids and their esters, such as pyruvic acid and its esters acetoacetic acid and ethyl acetoacetate, dihydroxybenzoic acids, such as 3, 5 -dihydroxybenzoic acid, and / or oximes , such as acetaldoxime, as well as other such cited compounds, as well as any mixtures of the aforementioned complex, chelating and condensation degree controlling agents, is completed. The solution of the alumina precursor is then at room temperature with a mixture consisting of the o. G. Solvent or solvent mixture, and water added dropwise and then heated at 80 ° C for up to 24 h under reflux. The gelation of the aluminum oxide precursor can be controlled in a targeted manner via the molar ratio of the aluminum oxide precursor to water, to the acid used and to the amounts of substance and the type of complexing agent used. The necessary ones

Synthesis times are also of the aforementioned

Substance ratios dependent. The readily volatile and desired parasitic by-products which occur during the reaction are subsequently removed by means of vacuum distillation from the finished reaction mixture and, if appropriate, already further diluted. The vacuum distillation is achieved by gradually reducing the final pressure to 30 mbar at a constant temperature of 70 ° C. The hybrid gels are either after or even before the distillation treatment by targeted addition suitable and the rheology and printability of the paste

favoring solvents, such as high-boiling glycols, Glycol ethers, Glycolethercarboxylate and further solvents such as

Terpineol, texanol, butyl benzoate, benzyl benzoate, dibenzyl ether,

Butylbenzyl phthalate, and solvent mixtures adjusted to their desired properties and optionally diluted. In parallel with the dilution and adjustment of the paste properties is a mixture consisting of condensed oxide precursors of

Silcium dioxide and Boroxids, added. For this purpose, precursors of the boron oxide in a solvent, such as dibenzyl ether,

Butylbenzylphthalat, benzyl benzoate, butyl benzoate, THF or comparable, initially charged, with a suitable carboxylic anhydride, such as acetic anhydride, formyl acetate or propionic anhydride or comparable, added and dissolved under refluxing or reacted until a clear solution is present. To this solution are added suitable precursors of the silicon dioxide, optionally pre-dissolved in the reaction solvent used, drop by drop. The reaction mixture is then heated or refluxed for up to 24 hours. After mixing all

Components, the paste rheology can continue to be adjusted and rounded according to and with the also previously described in detail auxiliaries and additives according to specific requirements, the use of waxes and waxy compounds according to the invention has a special role. The waxes and

waxy compounds are dissolved or melted in the gelled paste mixture, if necessary. Refluxing and with intimate stirring. The entire formulation is then allowed to cool with intimate stirring, adjusting the desired properties of the final pseudoplastic mixture. Depending on the nature of the waxes and waxy compounds used according to the invention, homogeneously monophasic or emulsified biphasic mixtures are obtained. An alternative method of synthesis is based on the preparation of a condensed sol of oxide precursors of silicon dioxide and

Boron oxide. For this purpose, precursors of the boron oxide in a solvent, such as, for example, dibenzyl ether, butyl benzyl phthalate,

Benzyl benzoate, butyl benzoate, THF or comparable, initially charged, with a suitable carboxylic anhydride, such as acetic anhydride,

Formyl acetate or propionic anhydride or comparable, and dissolved under reflux or reacted until a clear solution is present. To this solution are added suitable precursors of the silicon dioxide, optionally pre-dissolved in the reaction solvent used, drop by drop. The reaction mixture is then heated or refluxed for up to 24 hours. Thereafter, the sol is treated with suitable solvents such as, for example, glycols, glycol ethers, glycol ether carboxylates and also solvents such as terpineol, texanol, butyl benzoate, benzyl benzoate, dibenzyl ether, butyl benzyl phthalate, or their solvent mixtures in which suitable complexing and chelating agents, for example suitable β- Diketones, such as acetylacetone or, for example, 1, 3-cyclohexanedione, α- and β-ketocarboxylic acids and their esters, such as pyruvic acid and its esters

Acetoacetic acid and ethyl acetoacetate, dihydroxybenzoic acids, such as, for example, 3, 5-dihydroxybenzoic acid, and / or oximes, such as

For example, acetaldoxime, and other such cited compounds, as well as any mixtures of the aforementioned complex, chelating agents and the degree of condensation controlling agents are already pre-dissolved in the accompaniment of water, added and stirred, if necessary. At the same time increases the temperature of the reaction mixture. The duration of mixing of the two solutions can be between 0.5 minutes and five hours.

The total mixture is tempered with the aid of an oil bath whose temperature is usually set to 155 ° C. After completing a suitable known duration of mixing of the two partial solutions completed

Total solution, this is then a suitable alumina precursor, which in turn was pre-dissolved in one of the above solvent or solvent mixtures, the reaction mixture is added dropwise or allowed to flow so that the addition will be completed in a time window of five minutes since the beginning of adding. The now

The reaction mixture thus completed is then heated to reflux for one to four hours. The warm gelled mixture can now be prepared using other excipients already mentioned above,

especially and especially preferably, however, by the use of the waxes and waxy waxes to be used according to the invention

Compounds in their rheological properties accordingly

be adapted to desirable requirements. Depending on the nature of the waxes and waxy compounds used according to the invention Homogeneously single-phase or emulsified biphasic mixtures are obtained.

In the following examples, the preferred embodiments of the present invention are shown.

As stated above, the present description enables a person skilled in the art to comprehensively apply the invention. Without further explanation, it is therefore assumed that a person skilled in the art can make the most of the above description.

Any ambiguity goes without saying, the quoted

Publications and patent literature. Accordingly, these documents are considered part of the disclosure of the present specification.

For a better understanding and clarification of the invention, examples are given below which are within the scope of the present invention. These examples are also used for

Illustration of possible variants. Due to the general

Validity of the invention described principle, however, the examples are not suitable to reduce the scope of the present application only to this. Furthermore, it is self-evident to the person skilled in the art that both in the given examples and in the remainder of the description, the amounts of components contained in the compositions amount in the sum to only 100% by weight, molar or vol Aggregate composition and can not exceed it, even if higher values could result from the indicated percentage ranges. Unless otherwise stated, therefore,% data are in terms of weight, mol or vol.%.

The temperatures given in the examples and the description as well as in the claims are always in ° C. Examples

EXAMPLE 1 A glass flask is charged with 55.2 g of ethylene glycol monobutyl ether (EGB) and 20.1 g of aluminum tri-sec-butylate (ASB) and stirred until a homogeneous mixture is obtained. To this mixture are added 7.51 g of glacial acetic acid, 0.8 g of acetaldoxime and 0.49 g of acetylacetone with stirring.

Subsequently, 1.45 g of water dissolved in 5 g of EGB are added dropwise, and the mixture is refluxed at 80 ° C for five hours.

After heating, the mixture is subjected to vacuum distillation at 70 ° C until reaching a final pressure of 30 mbar. Of the

Mass loss of volatile reaction products is 12.18 g. The distilled mixture is then diluted with 62.3 g of Texanol and another 65 g of EGB, and mixed with a mixed condensed sol consisting of precursors of boron oxide and silicon dioxide. The hybrid sol of silica and boron oxide is prepared as follows: 6.3 g Tetraacetoxydiborat be presented in 40 g of benzyl benzoate and treated with 15 g of acetic anhydride. The mixture is heated in an oil bath to 80 ° C and after a clear solution is formed, 4.6 g

Added dimethyldimethoxysilane and allowed to react the whole mixture with stirring for 45 minutes. The hybrid sol is then also subjected to a vacuum distillation at 70 ° C until reaching a final pressure of 30 mbar, the mass loss of volatile reaction products is 7.89 g. The 110 g of the total mixture is mixed with 9 g of synchro wax and heated with stirring to 150 ° C until complete dissolution and clear mixing. Subsequently, the mixture is allowed to cool with intensive stirring. The result is a pseudoplastic and very good printable paste.

Example 2

In a glass flask, 40 g of benzyl benzoate and 6.3 g

Tetraacetoxydiborat and 15 g of acetic anhydride and heated to 80 ° C with stirring in an oil bath. After obtaining a clear solution, silicon dioxide precursors, in this case a Mixture consisting of 2.3 g of dimethyldimethoxysilane and 3.4 g

Bis [triethoxysilyl] ethane, added dropwise. The mixture is allowed to react for 30 minutes at 80 ° C with stirring. Then 75 g of Texanol, 150 g of EGB, 1 g of water, 1 g of 3, 5-dihydroxybenzoic acid and 1, 75 g of 1, 3-cyclohexanedione are added to this mixture. The mixture is stirred for 20 minutes, raising the temperature of the oil bath to 155 ° C. After mixing the solution, 21 g of ASB dissolved in 60 g of benzyl benzoate are added dropwise to this solution. The completed mixture is left to react for one hour with vigorous stirring. After the reaction, the mixture becomes a

Subjected to vacuum distillation at 70 ° C until reaching a final pressure of 30 mbar, wherein the mass loss is 20.3 g. 120 g of the mixture are mixed with 8.2 g of beeswax and heated with stirring to 150 ° C until a clear solution is formed. This solution is slowly cooled while stirring. In a parallel approach are also

120 g of the mixture with 9.5 g Synchrowachs added and also heated to 150 ° C until a clear solution is formed, which is cooled with vigorous stirring. Pseudoplastic and very good printable pastes are obtained.

Example 3:

The paste according to Example 1, using a conventional screen printing machine and a screen with 350 mesh, 16 ym thread size (stainless steel) and an emulsion thickness of 8 - 12 pm using a doctor speed of 170 mm / s and a squeegee pressure of 1 bar to one Wafer printed and then subjected to drying in a continuous furnace. The heating zones in the continuous furnace are set to 350/350/375/375/375/400/400 ° C.

FIG. 1 shows a silicon wafer printed with the hybrid gel according to the invention after it has been dried in a continuous furnace. The hybrid gel used corresponds to a composition prepared according to Example 3. Example 4:

The paste according to Example 1 is prepared by means of a conventional

Screen printing machine and a screen with 280 mesh and 25 μιτι yarn thickness (stainless steel) over a large area on a rough CZ wafer surface (n-type) printed. The wet application is 1.5 mg / cm ² . The printed wafer is then dried on a conventional laboratory hotplate for 3 minutes at 300 ° C and then subjected to a diffusion process. For this purpose, the wafer at about 700 ° C in a

Introduced diffusion furnace, and the furnace is then placed on a

Diffusion temperature of 950 ° C heated. The wafer is held at this plateau temperature for 30 minutes and kept in an atmosphere of nitrogen at 0.2% v / v oxygen. Following the

On boron diffusion, the wafer is exposed to phosphorous diffusion with phosphoryl chloride at low temperature, 880 ° C, in the same process tube. After the diffusion and the cooling of the wafer, it is freed from the glasses present on the wafer surfaces by means of etching with dilute hydrofluoric acid. The area, which previously with the

Boron paste according to the invention was printed, has a hydrophilic

Wetting behavior when rinsing the wafer surface with water, which is a clear indication of the presence of a boron skin in this area. The sheet resistance determined in the surface area printed with the boron paste is 195 Ω / sqr (p-type doping). The areas not protected by the boron paste have one

Sheet resistance of 90 Ω / sqr to (n-type doping). In the region of the surface which was printed by means of the boron paste according to the invention, the SIMS (secondary ion mass spectrometry) depth profile of the dopants is determined. In the B-paste-covered region, except for the n-type base doping, a boron doping from the wafer surface to that of the silicon is determined. The printed

Paste layer thus acts as diffusion barrier against a typical phosphorus diffusion.

FIG. 2 shows the SIMS profile of a rough silicon surface, which is printed with the boron paste according to the invention and subsequently printed

Has been subjected to gas phase diffusion with phosphoryl chloride. Due to the rough surface, only relative concentrations in the form of count rates can be obtained.

Example 5:

481.3 g of ethylene glycol monobutyl ether (EGB) and 82 g of aluminum tri-sec-butylate (ASB) are placed in a glass flask and stirred until a homogeneous mixture is formed. To this mixture, 31 g of glacial acetic acid, 3.2 g of acetaldoxime and 2.2 g of 1, 3-cyclohexanedione in the mentioned

Added sequence with stirring. Subsequently, 12.1 g

Water, dissolved in 20 g of EGB, was added dropwise and the mixture was refluxed at 120 ° C. for 180 minutes (mixture 1). In a further glass flask 25.4 g Tetraacetoxydiborat and 192 g of benzyl benzoate are presented. In the template 61, 4 g of acetic anhydride and 18.5 g Dimethoxydimethylsilan are stirred, and after the complete

Mixing the mixture is allowed to reflux in a tempered at 130 ° C oil bath (mixture 2). After cooling the mixture, mixture 1 and mixture 2 are combined in a glass flask of suitable size with the addition of 261 g Texanol and 40 g

Ethylene glycol. The total mixture is then concentrated on a rotary evaporator at 70 ° C until reaching a final pressure of 30 mbar. The reaction yield is 1160 g. in the

Connection, the gel hybrid sol is transferred to a stirred tank of suitable size and mixed with 116 g Synchrowachs ERLC. Under heating and intensive stirring of the mixture to 150 ° C is the

Wax melted and dissolved in the heat in the gel. After complete dissolution of the wax, the heat supply is interrupted and the mixture is allowed to cool while stirring. After cooling, a buttery, pseudoplastic, yellowish-white, very good printable paste is obtained.

The viscosity of the paste is 7.5 Pa ^* s at a shear rate of 25 / s and a temperature of 23 ° C.

The paste is made by means of a screen printer using a trampoline sieve with stainless steel mesh (400 mesh, 18 μm

Wire diameter, calendered, 8-12 emulsion over the fabric) on alkaline luster etched wafers using the following Print parameters printed:

a sieve jump of 2 mm, a printing speed of 200 mm / s, a flood speed of 200 mm / s, a squeegee pressure of 60 N during printing and a squeegee pressure of 20 N during flooding, and using a carbon fiber squeegee with polyurethane rubber of Shore hardness of 65 °.

The printed wafers are then heated to 400 ° C

heated continuous furnace dried. The belt speed is 90 cm / s. The length of the heating zones is 3 m. The paste transfer is 0.65 mg / cm ² .

FIG. 3 shows the micrograph of a line screen printed and dried with a doping paste according to Example 5. FIG. 4 shows a micrograph of a paste surface screen-printed and dried with a doping paste according to Example 5.

FIG. 5 shows a micrograph of a paste surface screen-printed and dried with a doping paste according to Example 5.

In another embodiment, both alkaline gloss etched, as well as alkaline textured and by means of one-sided acid etching

post-polished CZ-n-type silicon wafers printed over almost the entire surface (~ 93%) with the doping paste.

The printing is done with a sieve with stainless steel mesh (400/18, 10 pm

Emulsion thickness over the fabric). The paste application is 0.9 mg / cm ² . The wafers are left on a hotplate for three minutes at 400 ° C

dried and then co-diffused at a

Plateau temperature of 950 ° C for 30 minutes subjected. In co-diffusion, the wafer is boron-doped and doped with boron on the side printed with the boron paste, whereas the wafer side or surface, which is not printed with boron paste, is diffused with phosphorus and doped. The phosphorus diffusion is in this case with the help of

Phosphorylchloriddampf achieved, which, transported by a stream of inert gas, is introduced into the hot furnace atmosphere. Due to the high temperature prevailing in the oven and at the same time in the oven Oxygen furnace atmosphere, the phosphoryl chloride is burned to phosphorus pentoxide. The phosphorus pentoxide precipitates in conjunction with a silicon dioxide forming on the wafer surface due to the presence of oxygen in the furnace atmosphere. The mixture of the silicon dioxide with the phosphorus pentoxide is also referred to as PSG glass. From the PSG glass on the

Surface doping of the silicon wafer takes place. On

Surface areas on which soft Boron paste is already present, a PSG glass can form only on the surface of the boron paste. If the boron paste acts as a diffusion barrier to phosphorus, then at those points where the boron paste is already present, there can be none

Phosphorus diffusion takes place, but only one of Born itself, which diffuses from the paste layer in the silicon wafer. This type of co-diffusion can be carried out in various embodiments. In principle, the phosphoryl chloride can be burned in the furnace at the beginning of the diffusion process. At the beginning of the process, one generally understands one in the industrial production of solar cells

Temperature range between 600 ° C and 800 ° C, in which the wafers to be diffused can be retracted into the diffusion furnace. Furthermore, it can be burned during the heating of the furnace to the desired process temperature in the furnace chamber. Accordingly, the introduction of phosphoryl chloride may also be introduced into the furnace during the holding of the plateau temperature, as well as during the cooling of the furnace, or perhaps after reaching a second plateau temperature, which may be higher and / or lower than the first plateau temperature. Of the aforementioned

Possibilities can, depending on the particular requirements, also any combinations of the phases of the possible entry of phosphoryl chloride are made in the diffusion furnace. Some of these options are outlined. In Figure 6, the possibility of using a second plateau temperature is not shown.

The wafers printed with the boron paste are subjected to a co-diffusion process, as shown, in which the entry of the

Phosphoryl chloride in the diffusion furnace before reaching the

Plateau temperature takes place, which to achieve a boron diffusion necessary, in this case 950 ° C. During diffusion, the wafers in the process boat are arranged in pairs in such a way that their sides printed with boron paste are in each case facing one another. In each case, a wafer is received in a slot of the process boat. The nominal distance between the substrates is thus about 2.5 mm. in the

Following the diffusion, the wafers are subjected to glass etching in dilute hydrofluoric acid and then their

Sheet resistances measured by four-point measurement. The side of the wafer diffused with the boron paste has one

Sheet resistance of 41 Ω / D, while that of the printed with the boron paste opposite side of the wafer has a sheet resistance of 68 Ω / D. With the aid of a p-n tester, it is shown that the side, which has a layer resistance of 41 Ω / D, is doped exclusively with p-, ie with boron, whereas the

opposite side, which has a sheet resistance of 68 Ω / D, only n, that is doped with phosphorus. There is no fundamental difference between the sheet resistances on the alkaline-gloss-etched wafers and those in which the alkaline texture was acid-repolished on one side, both on the phosphor side and on the boron-doped wafer side.

FIG. 6 shows a micrograph of a line screen printed and dried with a doping paste according to Example 5.

FIG. 7 shows an arrangement of wafers in a process boat during a co-diffusion process. The printed with Borpaste

Wafer surfaces are opposite.

Example 6:

In a glass flask are in 50.2 g of 1, 4-dioxane, 6, 16 g

Dimethoxydimethylsilane, 30.13 g Aluminiumdiisopropylatacetessigester- chelate and 8.41 g Tetraacetoxydiborat dissolved and suspended. The

Reaction mixture is heated in an oil bath to 80 ° C and for the Refluxed for 8 hours to 60 hours. During the reaction, the transparent mixture turns from colorless to yellow-orange. After completion of the reaction, the reaction mixture is at

Rotary evaporator treated and concentrated to dryness. Of the

Distillation loss is 60.02 g. 10 g of the residue are dissolved in 35.9 g Diethylenglycoletherdibenzoat and then diluted with 34.7 g Butoxyethoxyethylacetat and 5 g Triethylorthoformiat. The solution is then heated to 90 ° C and treated with 8.5 g of ERLC wax (one triglyceride having chain lengths of the fatty acids included from C18 to C36) and dissolved in the mixture. The solution is allowed to cool with vigorous stirring. During cooling, part of the wax separates from the solution and is emulsified in the mixture. The result is a structurally viscous, viscoelastic paste (dynamic viscosity of 1 1, 2 Pa ^* s at a shear rate of 25 1 / s and a temperature of 23 ° C), which is very well under the pressure parameters mentioned in the above examples glanzgeätzte

Silicon wafer surfaces can be printed. The paste is made with the help of a0

Screen printer using a trampoline sieve with

Stainless steel mesh (400 mesh, 18 μm wire diameter, calendered, 8-12 emulsion over tissue) on alkaline gloss etched wafers, printed using the following printing parameters:

5 a sieve jump of 2 mm,

a printing speed of 200 mm / s,

a flood speed of likewise 200 mm / s,

a squeegee pressure of 60 N during printing and a squeegee pressure of 20 N during flooding, and using a carbon fiber squeegee with polyurethane rubber of Shore hardness of 65 °.

The printed wafers are then heated to 400 ° C

heated continuous furnace dried. The belt speed is 90 cm / s. The length of the heating zones is 3 m. The paste transfer is 1.15 mg / cm ² . FIG. 8 shows the micrograph of a line screen-printed with a doping paste according to Example 6, and dried.

Claims

P A T E N T A N S P R E C H E

Printable hybrid gels based on precursors of inorganic oxides, which by means of a suitable printing method

Silicon surfaces for the purpose of local and / or full-surface, one-sided diffusion and doping for the production of solar cells, selectively or over the entire surface printed on surfaces of the substrate, dried and then by means of a suitable

High-temperature process for delivering the Boroxidprecursors contained in the printed layer to the underlying underneath

Substrate for targeted doping of the substrate itself be brought.

Printable paste-like hybrid gels according to claim 1, characterized in that they are compositions based on precursors of silicon dioxide, aluminum oxide and boron oxide.

Hybrid gels according to claim 1 or 2, characterized in that they are compositions based on precursors of the

Silica, alumina and boron oxide is used in the mixture.

Printable, pasty hybrid gels according to claims 1, 2 or 3, characterized in that they are based on precursors of the silicon dioxide selected from the group of

mono- to quadruple symmetrical and asymmetrically substituted carboxy, alkoxy and alkoxyalkylsilanes, in particular alkylalkoxysilanes, in which the central silicon atom has a degree of substitution of 1 to 4 with at least one directly bonded to the silicon atom

May have hydrogen atom, and further wherein a

Degree of substitution refers to the number of possible existing carboxy and / or alkoxy groups, which are single or different in both alkyl and / or alkoxy and / or carboxy

having saturated, unsaturated branched, unbranched aliphatic, alicyclic and aromatic radicals, which in turn may be attached to any position of the alkyl, alkoxide or carboxy radical by heteroatoms selected from the group consisting of O, N, S, Cl and Br may be functionalized, and mixtures of these precursors have been obtained.

Printable, pasty hybrid gels according to claims 1, 2 or 3, characterized in that they are based on precursors of the silicon dioxide selected from the group consisting of tetraethyl orthosilicate, triethoxysilane, ethoxytrimethylsilane, dimethyldimethoxysilane,

Dimethyldiethoxysilane, triethoxyvinylsilane, bis [triethoxysilyl] ethane and bis [diethoxymethylsilyl] ethane, and mixtures thereof have been obtained.

Printable, pasty hybrid gels according to claims 1, 2 or 3, characterized in that they are based on precursors of the alumina selected from the group of

symmetrically and asymmetrically substituted aluminum alcoholates (alkoxides), aluminum tris (β-diketones), aluminum tris (β-ketoesters), aluminum soaps, aluminum carboxylates, and mixtures thereof have been obtained.

Printable paste-like hybrid gels according to claims 1, 2 or 3, characterized in that they are based on precursors of the aluminum oxide selected from the group of aluminum triethanolate, aluminum trisopropylate, aluminum tri-sec-butylate, aluminum tributylate, aluminum triamylate and aluminum tri-iso-pentoxide,

Aluminum acetylacetonate or aluminum tris (1,3-cyclohexanedionates), aluminum monoacetylacetonate monoalcoholate, aluminum tris- (hydroxyquinolates), mono- and dibasic aluminum stearate and

Aluminum tristearate, aluminum acetate, aluminum triacetate, basic aluminum format, aluminum triformate and aluminum trioctoate,

Aluminum hydroxide, Aluminiummetahydroxid and aluminum trichloride, and mixtures thereof have been obtained.

Printable, pasty hybrid gels according to claims 1, 2 or 3, characterized in that they are based on precursors of the boron oxide selected from the group of boric acid alkyl esters,

Boric acid esters of functionalized, 2-glycols, boric acid ester of Alkanolamines, mixed anhydrides of boric acid and carboxylic acids, and mixtures thereof have been obtained.

9. Printable, pasty hybrid gels according to claims 1, 2 or 3, characterized in that they are based on precursors of

Boroxids, selected from the group boron oxide, diboroxide, triethyl borate, trisopropyl borate, Borsäureglykolester, Borsäureethylenglykolester, Borsäureglycerinester, boric acid esters of 2,3-Dihydroxbernsteinsäure, Tetracetoxydiborat, and boric acid esters of alkanolamines ethanolamine, diethanolamine, triethanolamine, propanolamine, dipropanolamine and

Tripropanolamine have been obtained.

10. Printable, pasty hybrid gels according to claims 1, 2 or 3, obtainable by precursors of claims 4 to 9 under aqueous or anhydrous conditions using the sol-gel technique either simultaneously or sequentially to partial or complete intra- and / or interspecific Condensation are brought to storage-stable, very good printable and pressure-stable formulations of viscosity> 500 mPa * s are formed.

11. Printable, pasty hybrid gels according to claim 10, obtainable by removing the volatile reaction auxiliary and by-products during the condensation reaction.

12. Printable, pasty hybrid gels according to claim 10 or 11,

obtainable by adjusting the precursor concentrations, the water and catalyst content, and the reaction temperature and time.

13. Printable, pasty hybrid gels according to one or more of claims 10 to 12, obtainable by targeted addition of

condensation control agents, in the form of complex and / or chelating agents, various solvents in fixed amounts based on the total volume, whereby the degree of gelation of the resulting hybrid sols and gels is controlled in a targeted manner.

14. Printable, pasty hybrid gels according to one or more of claims 10 to 13, containing waxes and / or waxy compounds in an amount of up to 25% based on the

Total amount of composition for adjusting pasty and pseudoplastic properties, waxes and waxy

Compounds selected from the group of beeswax,

Synchrowax, Lanolin, Carnauba Wax, Jojoba, Japan Wax,

Fatty acids and fatty alcohols, fatty glycols, esters of fatty acids and fatty alcohols, fatty aldehydes, fatty ketones and fatty ß-diketones and mixtures thereof, wherein the aforementioned substance classes each contain branched and unbranched carbon chains with chain lengths greater than or equal to twelve carbon atoms,

the one-phase and / or two-phase, emulsifying or suspending, thickening act.

15. Use of the printable, pasty hybrid gels according to one or more of claims 1 to 14 in a method for

Preparation of solar cells, wherein these are printed by means of screen printing on silicon surfaces for the purpose of local and / or full-area, one-sided diffusion and doping in the production of solar cells, dried and then by means of a suitable high-temperature process for delivering the Boroxidprecursors contained in the gel to that under the hybrid gel located substrate for targeted doping of the substrate itself be brought.

16. Use of the printable, pastelike hybrid gels according to one or more of claims 1 to 14 in a method according to claim 14 for the production of highly efficient structured doped solar cells.

17. Use of the printable, pastelike hybrid gels according to one or more of claims 1 to 14 for the processing of

Silicon wafers for photovoltaic, microelectronic,

micromechanical and micro-optical applications.

18. Use of the printable paste hybrid gels according to one or more of claims 1 to 14 for the production of PERC, PERL, PERT, IBC solar cells and others, wherein the solar cells further architectural features, such as MWT, EWT, selective emitter, Selective Front Surface Field, Selective Back Surface Field and

Have bifaciality.

19. Use of the printable, pastelike hybrid gels according to one or more of claims 1 to 14 for producing a grip and abrasion resistant layer on silicon wafers by the hybrid gel printed on the surface in a temperature range between 50 ° C and 750 ° C, preferably between 50 ° C and 500 ° C, more preferably between 50 ° C and 400 ° C, using one or more, to be carried out sequentially Temperschritten,

optionally heat treatment by means of a step function, and / or a

Temper ramp, dried and compacted for glazing, which forms grip and abrasion resistant layers with a thickness of up to 500 nm. 20. Use according to claim 19 for influencing the conductivity of the substrate by heating from the vitrified on the surfaces by heat treatment at a temperature in the range between 750 ° C and 1100 ° C, preferably between 850 ° C and 1100 ° C, more preferably between 850 ° C and 1000 ° C, silicon doping boron atoms are delivered.

21. Use of the printable, pastelike hybrid gels according to one or more of claims 1 to 14 for doping a printed substrate by suitable temperature treatment, wherein simultaneously and / or sequentially doping of the unprinted

Silicon wafer surfaces with dopants of the opposite polarity is induced by conventional gas phase diffusion and wherein the printed hybrid gel against the dopants of the

opposite polarity acts as a diffusion barrier.

22. A method for doping silicon wafers, characterized in that

a) silicon wafers with the paste-like hybrid gels according to one or more of claims 1-14 locally on one or both sides or on one side over the entire surface are printed, the printed gel dried, compacted and then exposed to a subsequent gas phase diffusion with, for example, phosphoryl chloride, whereby p-type dopants in the printed areas and n-type dopants in the areas exposed exclusively to gas-phase diffusion,

or b) printed on the silicon wafer over a large area, paste-like hybrid gel according to one or more of claims 1-14 and / or compressed and initiated from the dried and / or compacted paste by means of laser irradiation, the local doping of the underlying substrate material, followed by one

High-temperature diffusion and doping for the production of two-stage p-type doping levels in silicon,

or c) the silicon wafer is locally printed on one side with the paste-like hybrid gel, wherein the structured landfill may optionally have alternating lines, the printed structures dried and compacted and subsequently over the entire surface with the aid of PVD and / or CVD-deposited doped glasses, which in Silicon can induce doping of opposite polarity, be coated and encapsulated, and the overlapping

Overall structure is brought by suitable high temperature treatment for structured doping of the silicon wafer, wherein the printed hybrid gel acts as a diffusion barrier relative to the overlying glass and the dopant contained therein.