DE102011052902A1 - Method for printing metal contact on solar cell substrate for solar cell module, involves imprinting metalliferous paste on contact finger by printing device such that height of contact finger section is enlarged - Google Patents

Method for printing metal contact on solar cell substrate for solar cell module, involves imprinting metalliferous paste on contact finger by printing device such that height of contact finger section is enlarged

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Publication number
DE102011052902A1
DE102011052902A1 DE201110052902 DE102011052902A DE102011052902A1 DE 102011052902 A1 DE102011052902 A1 DE 102011052902A1 DE 201110052902 DE201110052902 DE 201110052902 DE 102011052902 A DE102011052902 A DE 102011052902A DE 102011052902 A1 DE102011052902 A1 DE 102011052902A1
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DE
Germany
Prior art keywords
solar cell
printing
contact fingers
metal
characterized
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
DE201110052902
Other languages
German (de)
Inventor
Steffen Sterk
Tobias Friess
Frederic Walter
Christian Ehling
Andreas Teppe
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
centrotherm photovoltaics AG
Original Assignee
centrotherm photovoltaics AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Priority to DE102011108140 priority Critical
Priority to DE102011108140.6 priority
Application filed by centrotherm photovoltaics AG filed Critical centrotherm photovoltaics AG
Priority to DE201110052902 priority patent/DE102011052902A1/en
Publication of DE102011052902A1 publication Critical patent/DE102011052902A1/en
Application status is Ceased legal-status Critical

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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H01L31/00Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus peculiar to the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02Details
    • H01L31/0224Electrodes
    • H01L31/022408Electrodes for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/022425Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H01L31/00Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus peculiar to the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus peculiar to the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/042PV modules or arrays of single PV cells
    • H01L31/05Electrical interconnection means between PV cells inside the PV module, e.g. series connection of PV cells
    • H01L31/0504Electrical interconnection means between PV cells inside the PV module, e.g. series connection of PV cells specially adapted for series or parallel connection of solar cells in a module
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05KPRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00Apparatus or processes for manufacturing printed circuits
    • H05K3/10Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
    • H05K3/12Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using thick film techniques, e.g. printing techniques to apply the conductive material or similar techniques for applying conductive paste or ink patterns
    • H05K3/1216Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using thick film techniques, e.g. printing techniques to apply the conductive material or similar techniques for applying conductive paste or ink patterns by screen printing or stencil printing
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05KPRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2203/00Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
    • H05K2203/14Related to the order of processing steps
    • H05K2203/1476Same or similar kind of process performed in phases, e.g. coarse patterning followed by fine patterning
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05KPRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00Apparatus or processes for manufacturing printed circuits
    • H05K3/22Secondary treatment of printed circuits
    • H05K3/24Reinforcing the conductive pattern
    • H05K3/245Reinforcing conductive patterns made by printing techniques or by other techniques for applying conductive pastes, inks or powders; Reinforcing other conductive patterns by such techniques
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/50Photovoltaic [PV] energy

Abstract

The method involves imprinting metalliferous paste (8) in the form of contact finger on a side of a solar cell substrate (2) by a printing device (20). The metalliferous paste is imprinted on the contact finger by the same printing device such that height of contact finger section is enlarged. An electrically conducting manifold is formed in a portion of the contact finger. Several solar cell substrates are interconnected with each other by cell connectors. Independent claims are included for the following: (1) a device for printing metal contact on solar cell substrate; (2) a solar cell; and (3) a solar cell module.

Description

  • The invention relates to a method for printing on metal contacts on a solar cell substrate according to the preamble of claim 1, an apparatus for performing this method, a solar cell manufactured by the method and a solar cell module.
  • Arranged on a front side of a solar cell substrate metal contacts have a significant impact on the efficiency of the finished solar cell. In this case, the front side of the solar cell substrate is to be understood as that large-area side of the solar cell substrate which, during operation, is aligned with the incident solar radiation. In order to generate the highest possible currents and thus high efficiencies, the metal contacts should shade the front of the solar cell as little as possible. On the other hand, it is necessary that the metal contacts have the lowest possible electrical resistance in order to minimize the line losses. In order to meet these conflicting requirements, contact paths with the largest possible ratio of the height of the contact track to the width of the contact track, which is sometimes referred to as an aspect ratio or aspect ratio, are desired. As a rule, a larger aspect ratio leads to better efficiencies of the finished solar cell.
  • Frequently, printing processes are used to form the metal contacts. In particular screen printing processes have proven themselves in this context and are frequently used. Due to the development of improved screen printing pastes already larger aspect ratios could be realized. Further improvements are possible by printing the screen-printing pastes several times vertically one above the other in order to realize contact paths with a greater height. However, this requires that the solar cell substrate to be printed in the printing devices must be aligned exactly relative to the screen stencils used. If, in a later printing step, the screen printing paste applied in a preceding printing step is not exactly hit, this leads to a wetting of the contact web. The contact path is thus not only increased, but also widened, which is accompanied by an increased shading active solar cell surface and thus brings losses in efficiency with it.
  • This situation is illustrated by the schematic illustrations of the 1 and 2 , 1 shows a schematic partial representation of a solar cell substrate 2 at the moment of a first printing step, in which metal-containing paste 8th on the solar cell substrate 2 is printed. The printing of the metal-containing paste 8th done by screen printing technology. For this purpose, a screen template is used. This sieve template has a sieve 4 on whose permeability in a conventional manner by a on the sieve 4 applied emulsion 6 is defined. Through in the sieve template 4 . 6 existing openings through the metal-containing paste 8th on the solar cell substrate 2 printed. In another, in 2 schematically reproduced printing step is attempted, another Siebschablone relative to the solar cell substrate 2 and the metal-containing paste thereon 8th to arrange such that openings of the other screen template on the already printed, metal-containing paste 8th to come to rest. The further screen template again has one with an emulsion 7 coated sieve 5 on. Good, as in the 2 case shown, the alignment is not, so will more metal-containing paste 10 not exactly on the previously printed metal-containing paste 8th printed. Instead it comes to the one described above and in 2 discernible marking out of the metal-containing paste 8th and the other metal-containing paste 10 formed contact track, which adversely affects the efficiency of the finished solar cell.
  • The likelihood that the required alignment will fail and cause it to smear out the contact path as in 2 is, is high, since the alignment has to be made to 5 to 20 microns accurate. However, such an alignment accuracy is difficult to realize in known printing methods, in particular screen printing methods. For example, the screen stencils used in screen printing processes already have a tolerance of ± 20 μm in their overall extent as a result of production. In addition, the screen templates distort in the course of their use, so that even initially identical screen templates are no longer congruent after a short period of use. In addition, there are tolerances and inaccuracies in printing devices in which the screen templates are arranged.
  • Against this background, the object of the present invention is to provide an improved method for printing metal contacts.
  • This object is achieved by a method having the features of claim 1.
  • Furthermore, the invention is based on the object to provide an apparatus for performing this method.
  • This object is achieved by a device having the features of claim 12.
  • In addition, the invention is based on the object to provide an improved solar cell available.
  • This object is achieved by a solar cell having the features of claim 15.
  • Advantageous developments are each the subject of dependent claims.
  • The inventive method for printing metal contacts on a solar cell substrate provides that in a first printing step by means of a printing device metal-containing paste is printed in the form of contact fingers on a first side of a solar cell substrate. In at least one further printing step, further metal-containing paste is printed on the contact fingers and in this way a height of the contact fingers is increased at least in sections. The at least one further printing step is carried out with the same printing device as the first printing step.
  • Under metal contacts in the present sense are to be understood contacts made of metal-containing material. Contact fingers are narrow, elongated contact structures, which are often referred to simply as fingers and usually together with busbars form a contact network, which is often referred to as a grid. The term printing device includes all items required for printing the solar cell substrate. In principle, all printing methods known per se can be used. If, for example, screen printing methods are used, the term printing device includes inter alia the screen template used. Alternatively, for example, stamp printing methods can be used. In this case, the term printing device includes inter alia the associated stamp.
  • By carrying out the at least one further printing step with the same printing device as the first printing step, many factors of inaccuracy in the alignment of the various printing steps can be eliminated. For example, depending on the printing technology used, the same screen or stamp is always used. Alignment inaccuracies due to the use of different pressure devices with varying stops or other differences are eliminated. The risk of Ausschmierens the printed contact fingers can thus be significantly reduced.
  • In addition, self-adjusting effects can occur in that the metal-containing paste applied during the first printing step protrudes into the emulsion of a screen template used during the at least one further printing step and pulls the screen template into the correct, congruent position on possibly not exactly aligned areas. Furthermore, the penetration of the metal-containing paste into the emulsion during the at least one further printing step can cause the further metal-containing paste to be applied in a smaller amount than the metal-containing paste from the first printing step in the at least one further printing step. In this way, metal-containing paste can be saved, which reduces production costs, especially when using silver-containing screen printing paste.
  • The first side of the solar cell substrate may, in particular, be a front side of the solar cell substrate, that is to say a side of the solar cell substrate which is aligned with the light which is incident during operation of the finished solar cell.
  • In particular, a monocrystalline or multicrystalline silicon solar cell substrate can be used as the solar cell substrate.
  • In a variant of the method, during the first printing step, at least one collecting line which electrically conductively connects at least one part of the contact fingers is printed and its height is increased in the at least one further printing step. This allows a comfortable application of the manifolds, without the need for additional printing devices would be required.
  • In an alternative variant of the method, at least one collecting line electrically connecting at least a part of the contact fingers is formed in a collecting line forming step separate from the first and the at least one further pressing step. In this way, the at least one collecting line can be formed independently of the first and the at least one further printing step. As a result, methods may be used which allow for further metal-paste saving or otherwise reduce manufacturing costs. In particular, the contact fingers and the at least one collecting line can each be applied with a special, matched to them printing device. For example, the at least one bus may be printed with a lower height than the contact fingers. In this way, metal-containing paste can be saved, as in the case of at least one manifold a lower height is sufficient for optimal power drainage. In addition, the printing of the contact fingers in the first and the at least one further printing step when using the screen printing technology is not disturbed by a bus extending transversely to the direction of movement of a doctor blade used during said printing steps. Therefore, unlike other methods, the squeegee can not sink into an emulsion opening associated with the at least one manifold, resulting in unclean pressure the immediately adjacent contact finger areas would lead.
  • The at least one manifold does not necessarily have to be applied by means of a printing process. Instead, it can be advantageously applied with laser-induced forward transfer.
  • Preferably, however, in the manifold formation step, the at least one manifold is printed, more preferably by screen printing a metal-containing paste or by printing a conductive liquid. The conductive liquid may, for example, be printed by means of an inkjet printing process, often referred to as an inkjet process.
  • In practice, it has been proven that the at least one further pressure step consists of exactly one further pressure step. This enables a triple pressure, in which first the contact fingers are formed in the first and the exactly one further printing step, and subsequently the at least one collecting line is printed in the separate busbar forming step.
  • Further savings in the printing material consumption can be realized by providing the at least one collecting line with recesses. Accordingly, at least one bus is printed, which has a corresponding hole pattern. A good solderability of the at least one collecting line in a solar cell module can be realized despite the recesses due to the width of the at least one manifold.
  • In one variant of the method, at least one collecting line which connects in an electrically conductive manner to at least one part of the contact fingers is formed by electrically conductively connecting the at least one part of the contact fingers to a cross connector. This can be done in the separate manifold formation step. The electrically conductive connection between the at least one part of the contact fingers and the cross connector is advantageously realized by means of an electrically conductive adhesive material. Preferably, a liquid conductive adhesive or an electrically conductive adhesive tape is used as the adhesive material.
  • The cross connector preferably extends over the at least one part of the contact fingers.
  • Advantageously, the cross connector is designed as a cell connector, by connecting a plurality of solar cell substrates are electrically interconnected by him. Particularly preferably, the cell connector is used in a solar cell module for electrically interconnecting a plurality of solar cell substrates. As a rule, ready-made solar cells are already present in the solar cell module at the time of the electrical connection of the solar cell substrates. In this stage of the process, the solar cell substrates could therefore also be referred to as solar cells, even if they have no manifold. The use of the cross connector as a cell connector, as it were, blends the solar cell manufacturing process and the solar cell module manufacturing process, and avoids the duplication of material consumption that results in the formation of busbars and additional cell connectors.
  • Advantageously, the height of the contact fingers is increased over at least 80% of a total contact finger length resulting from a sum of the lengths of all contact fingers. In this way, the aspect ratio of the contact fingers can be improved over a substantial portion of the total contact finger length.
  • The metal-containing paste or the further metal-containing paste is preferably dried before at least one further printing step. Particularly preferably, the drying takes place before each further printing step. For this purpose, the solar cell substrate is fed to a drying device before the respective further printing step. The drying of the metal-containing or further metal-containing paste in this drying apparatus can be realized, for example, by means of infrared irradiation, a hot air stream or a gas mixture stream or by means of heated plates, so-called hot plates.
  • The drying time is advantageously chosen to be sufficiently short, so that the solar cell substrate can be supplied to the following, further printing step before the printing device used has undergone significant changes. If, for example, a screen printing device is used, then it has proven useful to select the drying time such that the solar cell substrate can be returned to the screen printing device before more than 200 further solar cell substrates have been printed by means of this screen printing device. When choosing the drying time, the time required for the recycling of the solar cell substrate to the printing device used is obviously to be considered.
  • In the case of at least one further printing step, the further metal-containing paste is advantageously printed offset relative to the metal-containing paste printed by means of the first printing step in a longitudinal extension direction of the contact fingers. In this case, an offset in the longitudinal direction of the contact fingers of less than 1 mm, more preferably of less than or equal to 500 microns, provided. In this way, any contact finger interruptions and / or constrictions of the contact fingers resulting during a preceding printing step can be filled up with the further metal-containing paste. If the contact fingers are printed, for example, by means of a screen printing method, such contact finger interruptions or contact finger constrictions may arise, inter alia, as a result of local blockage or constriction of openings of the screen template used.
  • The first printing step and the at least one further printing step are preferably carried out as screen printing steps. Particularly preferably, they are realized by means of a flat screen printing device. In addition, however, rotary screen printing devices can be used. As a result, the same stencil sheet is always used in the first printing step and the at least one further printing step.
  • An apparatus for carrying out the method according to the invention has a printing device for printing metal-containing paste in the form of contact fingers on solar cell substrates and a return device, which is adapted to re-supply solar cell substrates to the printing device after being printed by the printing device.
  • Advantageously, a drying device is furthermore provided for drying metal-containing paste printed on the solar cell substrates. This drying device, the solar cell substrates are fed at least after their first printing by the printing device. Preferably, the solar cell substrates after each printing by the printing device of the drying device can be fed. As a drying device, for example, an infrared radiation furnace or heated plates, so-called hot plates, can be provided. Alternatively, a hot air oven may be provided or a drying apparatus which provides a gas mixture flow for drying purposes.
  • Advantageously, a control device is provided, which is set up to control whether the printing device is supplied with an unprinted solar cell substrate or by means of the return device an already printed solar cell substrate. In this way, the device can be conveniently integrated into an automated production line. In addition, the control device makes it possible to ensure that an already printed solar cell substrate is re-supplied to the printing device in good time before it shows due to signs of wear relevant deviations from their properties at the time of the previous printing of the solar cell substrate. In the example of a screen printing device, these signs of wear and relevant deviations can exist, for example, in a delay of the screen stencil used.
  • A solar cell according to the invention has contact fingers, wherein the contact fingers each have a lower height at at least one end region than in their remaining regions. As stated above, in such solar cells interruptions or constrictions of the contact fingers can be at least partially compensated, resulting in an improved efficiency of the solar cell.
  • The solar cell can be produced by the method according to the invention and its developments described above.
  • The at least one end region preferably extends over a length of less than 1 mm, particularly preferably over a length of less than or equal to 500 μm, along the longitudinal extension direction of the respective contact finger. These values have proven particularly useful in practice.
  • It has proved to be advantageous to form the contact fingers by at least two layers of a metal-containing paste offset from one another in the longitudinal direction of extension of the contact fingers. This allows, among other things, an inexpensive production of the solar cell.
  • A solar cell module according to the invention has solar cell substrates provided with contact fingers and at least one cell connector, by means of which a plurality of solar cell substrates are electrically conductively connected to one another. The at least one cell connector is electrically connected to the contact fingers of the plurality of solar cell substrates. On arranged between the at least one cell connector and the contact fingers manifolds is omitted. The cost of materials for the formation of the arranged between the at least one cell connector and the contact fingers manifolds can thus be omitted, which has a favorable effect on the production costs required for the solar cell module.
  • Advantageously, the at least one cell connector is electrically conductively connected to the contact fingers by means of electrically conductive adhesive material. Apart from this adhesive material, the at least one cell connector is preferably connected directly to the contact fingers of the plurality of solar cell substrates.
  • As the electrically conductive adhesive material, a solidified conductive adhesive or an electrically conductive adhesive tape is preferably provided, the latter being particularly preferred.
  • Furthermore, the invention will be explained in more detail with reference to figures. Where appropriate, elements having the same effect here are given the same reference numbers. The invention is not limited to the embodiments shown in the figures - not even in terms of functional features. The previous description as well as the following description of the figures contain numerous features, which are reproduced in the dependent subclaims in part to several summarized. However, those features as well as all the other features disclosed above and in the following description of the figures will also be considered individually by the person skilled in the art and put together to form meaningful further combinations. In particular, these features can be combined individually and in any suitable combination with the method and / or the device for its implementation and / or the solar cell and / or the solar cell module of the independent claims. Show it:
  • 1 Schematic representation of a first printing step according to the prior art
  • 2 Schematic representation of a second printing step according to the prior art
  • 3 Schematic representation of an embodiment of a second pressure step performed according to the inventive method
  • 4 Schematic representation of an embodiment of the method according to the invention and a device for its implementation
  • 5 Schematic representation of a first embodiment variant of the embodiment 4
  • 6 Schematic representation of a second embodiment variant of the embodiment of 4
  • 7 Embodiment of a solar cell in a schematic representation
  • 8th Partial section through 7 along the line AA
  • 9 Detailed representation of subregion C 6
  • 10 Schematic representation of a third embodiment variant of the embodiment 4
  • 11 Partial sectional view through a solar cell module along the line BB 10 ,
  • 4 shows a schematic diagram of an embodiment of the method according to the invention and a device for its implementation. The device for carrying out the method has a printing device 20 on, by means of which metal-containing paste can be printed in the form of contact fingers on solar cell substrates. Not yet provided with contact fingers solar cell substrates and thus unprinted in the present sense solar cell substrates of the printing device 20 by means of a feeding device 26 be supplied. After onto such an unprinted solar cell substrate by means of the printing device 20 metal-containing paste has been printed in the form of contact fingers on a first side of the solar cell substrate, this, as indicated by an arrow, a drying device 22 fed. This drying device 22 serves to dry the metal-containing paste printed on the solar cell substrate. As a drying device 22 For example, an infrared radiation oven, a hot air oven or heated plates may be provided. A mixed gas flow can also serve as a drying device.
  • After drying of the metal-containing paste printed in the first printing step, the solar cell substrate, as indicated by an arrow, a feedback device 24 supplied by means of which the solar cell substrate again the printing device 20 is supplied. By means of the printing device 20 , and thus with the same printing device 20 As in the first printing step, then further metal-containing paste is printed on the contact fingers in a further printing step and in this way increases a height of the contact fingers. After this further printing step, the solar cell substrate can again the drying device 22 supplied and by means of the return device 24 be fed again to the printing device. Preferably, however, after the said further printing step, the printing of the contact fingers is ended and the solar cell substrate is fed to further process steps, which in the schematic illustration of FIG 4 indicated by three points. For example, after the said further printing step, a drying of the further metal-containing paste applied during the further printing step can first take place. In this case, a further drying device would be provided.
  • To control if the printing device 20 by means of the feeding device 26 a unprinted Solar cell substrate or by means of the return device 24 an already printed solar cell substrate is supplied, is a control device 28 intended. This is by means of control lines 29 . 30 with the return device 24 , or the feeding device 26 , connected. The control device 28 allows to ensure that by means of the return device 24 a printed solar cell substrate again the printing device 20 is supplied before their properties have changed due to wear effects such that the printed in the further printing step further metal-containing paste is aligned differently to the relevant extent than the metal-containing paste printed in the first printing step. Used as a printing device 20 used a screen printing device, it can be ensured, for example, that between the first printing step and the subsequent further printing step on the solar cell substrate not more than 200 solar cell substrates with the printing device 20 have been printed. In this way it can be prevented in this example case, that a screen template used in the printing device warps to a relevant extent, before the further printing step takes place.
  • 3 shows a schematic representation of an embodiment of a second printing step, which is carried out according to the inventive method, for example according to the schematic diagram of 4 , As for the first printing step, by means of which the metal-containing paste 8th on the solar cell substrate 2 has been applied, and in the first further, so second printing step, the same printing device is used, which comes from the sieve 4 and the emulsion disposed thereon 6 existing slide template in the second printing step with increased accuracy over the metal-containing paste 8th to lie. The further metal-containing paste 10 can therefore with good accuracy on the metal-containing paste 8th can be printed. An embossing of the other metal-containing paste 10 as in the 2 illustrated case can be avoided with good reliability.
  • 5 shows a schematic representation of a first embodiment variant of the embodiment 4 , In this embodiment variant, in a first printing step 40a by means of the printing device 20 Contact fingers and these contact fingers electrically conductive connecting manifolds printed on the solar cell substrate. In the design variant of 5 is used as a printing device, a screen printing device. 5 Illustrates in a schematic way the screen template used here 45 , which contact finger openings 46 and manifolds 48 having. After in the first printing step 40a through these contact finger openings 46 and manifolds 48 through metal-containing paste has been printed on the solar cell substrate, this is by means of the drying device 22 dried and by means of the return device 24 again the printing device 20 fed. This is followed by the second pressure step 42a in which due to the use of the same printing device 20 as in the first printing step 40a also the same slide template 45 Use finds. During the second printing step 42a Thus, the height of the contact fingers as well as the manifolds is increased. The resulting contact fingers as well as the resulting busbars have substantially the same height.
  • However, it has been shown that a significantly lower height can be provided for the manifolds, without this leading to a deterioration of the finished solar cell. A comparison with the height of the contact fingers reduced height of the manifolds would therefore desirable for reasons of material savings.
  • 6 illustrates a second embodiment variant of the embodiment 4 with which headers of lesser height can be realized. In this embodiment variant, in a first printing step 40b by means of the printing device 20 , which in turn is designed in this embodiment variant as a screen printing device, printed only contact fingers. A used stencil 50 accordingly has only contact finger openings 52 on. After drying the solar cell substrate in the drying apparatus 22 this is done by means of the return device 24 again the printing device 20 fed. In a second printing step 42b is then further metal-containing paste on the already in the first printing step 42a through the contact finger openings 52 printed on the solar cell substrate applied metal-containing paste. Thereafter, the solar cell substrate, the three points in the representation of 4 accordingly, fed to a further printing device and in a third printing step 44 then manifolds are printed on the solar cell substrate. The third printing step 44 can in principle be carried out with any printing device. In the illustrated embodiment, again a screen printing device with a screen template 54 used which manifold openings 56 having.
  • In that the third pressure step 44 which represents a manifold formation step, separate from the first pressure step 40b and the second pressure step 42b can be done, the printing devices and printing parameters for the various printing steps 40b . 42b . 44 be set optimally. So can by means of the first 40b and second pressure step 42b contact fingers can be printed with a high aspect ratio, while in the third pressure step, or bus conductor forming step, lower level headers can be formed.
  • 7 shows a schematic representation of an embodiment of a solar cell 60 , which, for example, with the embodiment variant according to 6 can be produced. She has contact fingers 62 as well as manifolds 64 on. As from the in 8th shown partial sectional view along the line AA 7 recognizable, have the manifolds 64 a lower height than the contact fingers 62 , Furthermore, it can be seen that the contact fingers 62 are formed by two layers printed on one another 62a . 62b made of metal-containing paste. In the design variant of 6 becomes the first layer of metal-containing paste 62a during the first printing step 40b imprinted, before in the subsequent second printing step 42b the second layer 62b made of metal-containing paste is printed.
  • A height 66 the contact finger 62 is larger than the height of the manifolds 64 , which in the embodiment variant according to 6 in the context of a simple, third printing step 44 can be applied.
  • As in 8th recognizable, are the two layers 62a . 62b made of metal-containing paste in the longitudinal direction of the contact fingers offset printed on each other. The contact fingers 62 consequently have an end area 68 a lower height 66 on than in their remaining areas. Constrictions or interruptions of the contact fingers 62 can thus be avoided in the manner described above or at least significantly reduced. In the embodiment variant according to 6 becomes the described lower altitude 66 in the end area 68 realized by at the second pressure step 42b the further metal-containing paste over the means of the first printing step 40b imprinted metal-containing paste is printed offset in a longitudinal direction of the contact fingers. For this purpose, the solar cell substrate to be printed becomes the second printing step 42b in the longitudinal direction of the contact fingers 62 , or contact finger openings 52 , arranged with an offset Δ. The offset Δ is preferably less than 1 mm and more preferably is less than or equal to 500 μm.
  • The solar cell 60 has a back contact on its back 65 on, which in the present case is designed as a planar back contact. In principle, however, any known per se Rückkontaktausgestaltung is possible.
  • In the embodiment variant according to 6 For example, the manifolds may be recessed to reduce the consumption of metal-containing paste. For this purpose, the manifold openings 56 with closure areas 57 be provided, as shown schematically in 9 is shown in the enlarged detail of the portion C. At the solar cell 60 out 7 would the manifolds 64 then at the appropriate places recesses 67 exhibit. In that regard, can 9 Also as an enlarged detail of a portion of a with recesses 67 provided collecting line of the solar cell 60 be considered.
  • 10 shows a schematic representation of a third embodiment variant of the embodiment 4 , In this first, the first printing step 40b and the second pressure step 42b out 6 carried out. On the thus obtained, provided with contact fingers solar cell substrates 2 but not in a third printing step 44 Manifolds printed. Instead, one becomes the contact fingers 74 electrically conductively connecting busbar formed by the contact fingers electrically conductive with itself over the contact fingers 74 extending cell connectors 76 get connected. As in 10 shown, thereby several solar cell substrates through the respective cell connector 76 electrically connected to each other. For this purpose, the cell connectors 76 connected by means of an electrically conductive adhesive material with the contact fingers. For example, liquid conductive adhesive or an electrically conductive adhesive tape can be used as the electrically conductive adhesive material.
  • The solar cell substrates 2 , their contact fingers 74 electrically conductive with the cell connectors 76 are connected, as in the 10 shown schematically, in a solar cell module 80 arranged. The cell connectors 76 Become the electrical interconnection of several solar cell substrates 2 used. A hitherto usual material overhead incurred by the use of manifolds and cell connectors can thus be avoided.
  • 11 shows a partial sectional view through the solar cell module 80 off along the BB line 10 , As can be seen herein, in the embodiment variant of the 10 again at the second pressure step 42b the further metal-containing paste over the means of the first printing step 40b printed metal-containing paste in a longitudinal direction of the contact fingers 74 offset imprinted. Accordingly, the contact fingers 74 formed by a longitudinal direction of the contact fingers 74 offset to a first layer 74a metal-containing paste printed second layer 74b metal-containing paste. The cell connectors 76 are in the illustrated embodiment by means of an electrically conductive adhesive tape 78 with the contact fingers 74 , or the second layer 74b made of metal-containing paste, connected. On the back of the solar cell substrate 2 Again, for example, is a flat back contact 65 intended. The solar cell substrate 2 is in the embodiment of 11 between a backsheet 70 and a glass plate 84 arranged, which with a potting material 82 are poured out. In principle, however, another solar cell module structure can also be selected.
  • In the above embodiments, no distinction has been made between fired or unfired metal-containing pastes, since this difference is of secondary importance to the present invention. Depending on the time considered in the solar cell or solar cell module manufacturing process, there are fired or unfired metal-containing pastes. Furthermore, in the representations of the 7 . 8th . 10 and 11 For the sake of clarity, the description of customary and partially required constituents of solar cells, such as emitter doping or antireflection coating, is dispensed with.
  • LIST OF REFERENCE NUMBERS
  • 2
    solar cell substrate
    4
    scree
    5
    scree
    6
    emulsion
    7
    emulsion
    8th
    metal-containing paste
    10
    another metal-containing paste
    20
    printing device
    22
    drying device
    24
    Recirculation device
    26
    feeder
    28
    control device
    29
    control line
    30
    control line
    40a
     first printing step
    40b
     first printing step
    42a
     second printing step
    42b
     second printing step
    44
    third pressure step
    45
    screen stencil
    46
    Contact finger opening
    48
    Header aperture
    50
    screen stencil
    52
    Contact finger opening
    54
    screen stencil
    56
    Header aperture
    57
    closure area
    60
    solar cell
    62
    contact fingers
    62a
     first layer of metal-containing paste
    62b
     second layer of metal-containing paste
    64
    manifold
    65
    back contact
    66
    Height contact fingers
    67
    recess
    68
    end
    70
    Back sheet
    74
    contact fingers
    74a
     first layer of metal-containing paste
    74b
     second layer of metal-containing paste
    76
    cell connectors
    78
    duct tape
    80
    solar cell module
    82
    grout
    84
    glass plate
    Δ
    offset

Claims (18)

  1. Method for printing metal contacts on a solar cell substrate ( 2 ), in which - in a first printing step ( 40a ; 40b ) by means of a printing device ( 20 ) metal-containing paste ( 8th ) in the form of contact fingers ( 62a ) on a first side of the solar cell substrate ( 2 ) is printed; In at least one further printing step ( 42a ; 42b ) further metal-containing paste ( 10 ) on the contact fingers ( 62a ) and in this way a height ( 66 ) the contact finger ( 62a . 62b ) is increased at least in sections; characterized in that the at least one further printing step ( 42a ; 42b ) with the same printing device ( 20 ), like the first printing step ( 40 ).
  2. A method according to claim 1, characterized in that at least one at least a part of the contact fingers electrically conductively connecting manifold ( 48 ) during the first printing step ( 40a ) and in the at least one further printing step ( 42a ) whose height is increased.
  3. Method according to claim 1, characterized in that at least one at least part of the contact fingers ( 62 ) electrically conductive connecting line ( 64 ) in one of the first ( 40b ) and the at least one further printing step ( 42b ) separate manifold formation step ( 44 ) is formed, preferably by means of laser-induced forward transfer.
  4. Method according to claim 3, characterized in that in the manifold formation step ( 44 ) the at least one collecting line ( 64 ) is printed, preferably by screen printing a metal-containing paste or by printing a conductive liquid.
  5. A method according to claim 4, characterized in that the at least one further printing step ( 42a ; 42b ) from exactly one further printing step ( 42a ; 42b ) consists.
  6. Method according to claim 1 or 3, characterized in that at least one at least part of the contact fingers ( 74 ) electrically conductive connecting line ( 76 ) is formed by the at least a part of the contact fingers ( 74 ) electrically conductive with one over the at least a portion of the contact fingers ( 74 ) extending cross connector ( 76 ) is connected.
  7. Method according to claim 6, characterized in that the transverse connector ( 76 ) as a cell connector ( 76 ) is carried out by a plurality of solar cell substrates ( 2 ) are electrically connected to each other.
  8. Method according to claim 7, characterized in that the cell connector ( 76 ) in a solar cell module ( 80 ) for the electrical interconnection of a plurality of solar cell substrates ( 2 ) is used.
  9. Method according to one of the preceding claims, characterized in that in the at least one further printing step ( 42a ; 42b ) the height of the contact fingers ( 64 ; 74 ) over at least 80% of a sum of the lengths of all the contact fingers ( 64 ; 74 ) resulting total contact finger length is increased.
  10. Method according to one of the preceding claims, characterized in that the metal-containing ( 6 ) or the further metal-containing paste ( 8th ) before at least one further printing step ( 42a ; 42b ), preferably before each further printing step ( 42a ; 42b ), is dried.
  11. Method according to one of the preceding claims, characterized in that in at least one further printing step ( 42b ) the further metal-containing paste ( 10 ) compared to the first printing step ( 40b ) printed metal-containing paste ( 8th ) in a longitudinal direction of the contact fingers ( 62 ) is offset, wherein an offset (Δ) in the longitudinal direction of the contact fingers ( 62 ) of preferably less than 1 mm and more preferably of less than or equal to 500 microns is provided.
  12. Device for carrying out the method according to one of the preceding claims, comprising - a printing device ( 20 ) for printing metal-containing paste ( 8th . 10 ) in the form of contact fingers ( 62 ) on solar cell substrates ( 2 ); A return device ( 24 ), which is adapted to solar cell substrates ( 2 ) after being printed by the printing device ( 20 ) again the printing device ( 20 ).
  13. Apparatus according to claim 12, characterized by a drying device ( 22 ) for drying on the solar cell substrates ( 2 ) printed, metal-containing paste ( 8th . 20 ) containing the solar cell substrates ( 2 ) at least after its first printing by the printing device ( 20 ) can be supplied.
  14. Device according to one of claims 12 to 13, characterized by a control device ( 28 ) which is adapted to control whether the printing device ( 20 ) an unprinted or by means of the return device ( 24 ) an already printed solar cell substrate ( 2 ) is supplied.
  15. Solar cell ( 60 ) with contact fingers, characterized in that the contact fingers ( 62 ) each at at least one end region ( 68 ) a lower height ( 66 ) than in their other areas.
  16. Solar cell according to claim 15, characterized in that the at least one end region ( 68 ) over a length of less than 1 mm, preferably over a length less than or equal to 500 microns, along the longitudinal direction of the respective contact finger ( 62 ).
  17. Solar cell according to one of claims 15 to 17, characterized in that the contact fingers ( 62 ) are formed by at least two in the longitudinal direction of the contact fingers ( 62 ) offset each other printed layers ( 62a . 62b ) of a metal-containing paste.
  18. Solar cell module ( 80 ) - with contact fingers ( 74 ) provided solar cell substrates ( 2 ), - at least one cell connector ( 76 ), by means of which several solar cell substrates ( 2 ) are electrically conductively connected to each other, characterized in that waiving the between at least one cell connector ( 76 ) and the contact fingers ( 74 ) arranged collecting lines of the at least one cell connector ( 76 ) with the contact fingers ( 74 ) of the plurality of solar cell substrates ( 2 ) is electrically connected.
DE201110052902 2011-07-21 2011-08-22 Method for printing metal contact on solar cell substrate for solar cell module, involves imprinting metalliferous paste on contact finger by printing device such that height of contact finger section is enlarged Ceased DE102011052902A1 (en)

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DE102011108140.6 2011-07-21
DE201110052902 DE102011052902A1 (en) 2011-07-21 2011-08-22 Method for printing metal contact on solar cell substrate for solar cell module, involves imprinting metalliferous paste on contact finger by printing device such that height of contact finger section is enlarged

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102013207189A1 (en) 2013-04-22 2014-10-23 Robert Bosch Gmbh Method and device for producing a photovoltaic cell

Citations (5)

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Publication number Priority date Publication date Assignee Title
US4301322A (en) * 1980-04-03 1981-11-17 Exxon Research & Engineering Co. Solar cell with corrugated bus
WO2000044051A1 (en) * 1999-01-20 2000-07-27 Stichting Energieonderzoek Centrum Nederland Method and apparatus for applying a metallization pattern to a substrate for a photovoltaic cell
DE112004002853T5 (en) * 2004-05-07 2007-04-12 Mitsubishi Denki K.K. Solar battery and manufacturing method thereof
DE112006003262T5 (en) * 2005-12-05 2008-10-30 Massachusetts Institute Of Technology, Cambridge Light trapping by patterned solar cell bus wires
WO2011026892A1 (en) * 2009-09-03 2011-03-10 Applied Materials, Inc. Printing method for printing electronic devices and relative control apparatus

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4301322A (en) * 1980-04-03 1981-11-17 Exxon Research & Engineering Co. Solar cell with corrugated bus
WO2000044051A1 (en) * 1999-01-20 2000-07-27 Stichting Energieonderzoek Centrum Nederland Method and apparatus for applying a metallization pattern to a substrate for a photovoltaic cell
DE112004002853T5 (en) * 2004-05-07 2007-04-12 Mitsubishi Denki K.K. Solar battery and manufacturing method thereof
DE112006003262T5 (en) * 2005-12-05 2008-10-30 Massachusetts Institute Of Technology, Cambridge Light trapping by patterned solar cell bus wires
WO2011026892A1 (en) * 2009-09-03 2011-03-10 Applied Materials, Inc. Printing method for printing electronic devices and relative control apparatus

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102013207189A1 (en) 2013-04-22 2014-10-23 Robert Bosch Gmbh Method and device for producing a photovoltaic cell

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