CN218020905U - Pattern transfer sheet, paste filling unit and photovoltaic solar cell - Google Patents

Abstract

Provided are a pattern transfer sheet, a paste filling unit, and a photovoltaic solar cell. Pattern transfer sheets, paste fill heads, and photovoltaic solar cell sheets are also provided, providing multiple layers of paste stack layers that are transferred onto a receiving substrate in a single irradiation step. The slurry stack is filled layer by layer, possibly with different materials in different layers of the stack, the thickness of the layers of the stack being controlled by parameters of the filling device, such as pressure, angle, speed and flexibility (material) of the blade in case of a blade. In particular, a bottom layer of the stack of layers may be configured to interface with a receiving substrate, while one or more top layers may be configured to optimize the quality of the printed features. For example, the bottom layer may include a layer of barrier material (e.g., copper on a silicon substrate) that bonds to the substrate, modifies the substrate (e.g., forms a Selective Emitter (SE) therein), and/or provides a top layer that is incompatible with the substrate. The release material may be used to support a single release of the stacking line.

Description

Pattern transfer sheet, slurry filling unit and photovoltaic solar cell

Technical Field

The utility model relates to a pattern shifts the printing field, more specifically relates to the printing of many characteristic layer grid lines, pattern transfer printing piece, thick liquids filling unit and photovoltaic solar cell.

Background

U.S. patent No. 9,616,524 (which is incorporated herein by reference in its entirety) teaches a method of depositing a material on a receiving substrate, the method comprising: providing a source substrate having a back surface and a front surface, the back surface carrying at least one sheet of coating material; providing a receiving substrate positioned adjacent to the source substrate and facing the coating material; and radiating light toward the front surface of the source substrate to remove at least one sheet of coating material from the source substrate and deposit the removed at least one sheet as a whole onto the receiving substrate.

Lossen et al (2015), pattern Transfer Printing (PTP) ^TM ) for c-Si Solar cell sizing, 5th Workshop on sizing for Crystalline Silicon Solar cells, energy Procedia 67 (which is incorporated herein by reference in its entirety) teaches pattern transfer printing (PTP. RTM. TM. 156-162 ^TM ) As a non-contact printing technique for advanced front side metallization of c-Si PV solar cells, the technique is based on laser induced deposition of polymer substrates.

However, the prior art does not enable single pass printing of electrode patterns including multi-feature conductive layers.

SUMMERY OF THE UTILITY MODEL

The following is a brief summary that provides a preliminary understanding of the invention. The summary does not necessarily identify key elements nor does it limit the scope of the invention, but merely serves as an introduction to the following description.

An aspect of the utility model provides a pattern transfer sheet, it includes: a plurality of trenches on a source substrate, the trenches arranged in a pattern and configured to be filled with a printing paste and capable of releasing the printing paste from the trenches onto a receiving substrate upon irradiation by a laser beam, wherein the printing paste comprises a stack of layers formed from a multi-layer-shaped paste layer, which can be transferred to the receiving substrate using a single irradiation step, forming a multi-feature layer stack line, i.e., a stack grid line, on the receiving substrate.

Further, the pattern transfer sheet of the present invention, at least two layers of the plurality of layers contain different material components and/or different materials.

Further, the pattern transfer sheet of the present invention, the stack layer comprises a bottom layer comprising a material configured to mechanically or electrically bond the transferred stack layer to a receiving substrate, and at least one top layer comprising a material configured to provide electrical conductivity along the transferred stack line.

Further, the pattern transfer sheet of the present invention, the stack layer comprises a bottom layer comprising a material configured to form a Selective Emitter (SE) on the receiving substrate, and at least one top layer configured to provide electrical conductivity along the transferred stack line and to provide electrical contact with the receiving substrate.

Further, the pattern transfer sheet of the present invention, wherein the at least one top layer comprises silver paste.

Further, the pattern transfer sheet of the present invention, the stack layer comprises a bottom layer comprising a material configured to provide a barrier layer and/or a seed layer on the receiving substrate, and at least one top layer comprising a material configured to provide electrical conductivity along the transferred stack line.

Further, the pattern transfer sheet of the present invention, the bottom layer material comprises at least one of aluminum, silver, chromium, gold, tin, indium, nickel, titanium, tantalum, alloys thereof, and/or combinations thereof, and the at least one top layer material comprises copper. The bottom layer material is aluminum paste, silver paste, chromium paste, gold paste, tin paste, indium paste, nickel paste, titanium paste, or tantalum paste, and the at least one top layer material is copper paste.

Furthermore, the pattern transfer sheet of the present invention has a thickness of the bottom layer of 1 to 5 μm.

Further, the pattern transfer sheet of the present invention, wherein the base layer comprises a release material composition.

Further, the pattern transfer sheet of the present invention, wherein the groove interior is coated with a coating layer configured to decompose upon application of irradiation for transfer paste release, to enhance the release capability of the multi-paste stack layer.

Further, the utility model discloses a pattern transfer printing piece, the pattern transfer printing piece is transparent to laser irradiation, and the slot is in through press forming, pneumatic forming, laser forming or impression formation in the pattern transfer printing piece.

Further, the pattern transfer sheet of the present invention comprises at least one polymer layer, wherein the polymer layer is made of at least one of: polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, fully aromatic polyester, aromatic-aliphatic copolyester, acrylate copolymer, polycarbonate, polyamide, polysulfone, polyethersulfone, polyetherketone, polyamideimide, polyetherimide, aromatic polyimide, alicyclic polyimide, fluorinated polyimide, cellulose acetate, cellulose nitrate, aromatic polyamide, polyvinyl chloride, polyphenol, polyarylate, polyphenylene sulfide, polyphenylene ether, or polystyrene.

An aspect of the present invention provides a photovoltaic solar cell, comprising at least one of the multilayer stacking lines formed by the transfer of the above-mentioned pattern pieces.

An aspect of the utility model provides a thick liquids filling unit sets up in Pattern Transfer Printing (PTP) system, thick liquids filling unit is configured as the patterning slot on the pattern transfer printing piece of carrying with electrically conductive printing thick liquids, wherein thick liquids filling unit includes two or more applied thick liquids fill head, is used for piling up the layer continuous filling slot that the layer is constituteed with a plurality of layers, should pile up the layer and use single step of shining as piling up the transfer printing line by the PTP system and transfer printing to receiving substrate on.

Further, the present invention provides a slurry filling unit, wherein the two or more slurry filling heads comprise respective filling heads, one filling head for filling one slurry layer, and wherein at least one parameter in the slurry filling head is adjustable: pressure applied to the respective blade, blade angle, blade speed, and/or flexibility — to adjust the thickness of at least one of the respective layers.

Further, the pulp filling unit of the present invention has a blade pressure selected within the range of 2-4bar, a blade angle selected within the range of 30-120, a blade speed selected within the range of 25-100mm/sec and/or a blade material selected from the group consisting of stainless steel, plastic and rubber.

Further, the utility model discloses a thick liquids filling unit, at least one fill head are recirculation lotion distributor fill head.

Further, the present invention provides a paste filling unit for filling the top layer of the stack of layers at least the last one of the filling heads is the recirculating paste dispensing device filling head.

Further, the paste filling unit of the present invention further includes a coating unit configured to coat the groove with a release layer before filling the printing paste into the groove.

One aspect of the present invention provides a photovoltaic solar cell, comprising a receiving substrate configured to convert light into electricity transmitted through wires, wherein at least one wire is multi-layered and printed in a single pattern transfer printing step, at least one multi-feature layer grid line comprising at least two layers made of different materials, the layers being transferred to a multi-layered stacking line comprising at least two different types of metal pastes.

Further, the photovoltaic solar cell of the present invention, the at least one multilayer stacking line comprises a bottom layer comprising a material configured to bond the transferred stacking line to the receiving substrate, and at least one top layer comprising a material configured to provide electrical conductivity along the transferred stacking line.

Further, the photovoltaic solar cell of the present invention, wherein the at least one multilayer stack line comprises a bottom layer comprising a material configured to form a Selective Emitter (SE) line on the receiving substrate, and at least one top layer configured to provide electrical conductivity along the transferred stack line and to provide electrical contact with the receiving substrate.

Further, the photovoltaic solar cell of the present invention, the at least one multilayer stacking line comprises a bottom layer comprising a material configured to provide a barrier layer and/or a seed layer on the receiving substrate, and at least one top layer comprising a material configured to provide electrical conductivity along the transferred stacking line.

The utility model discloses use single multilayer to pile up the layer once printing and solved the performance and the production challenge of photovoltaic cell grid line, this technique can be piling up different materials of in situ combination, will receive the compatible requirement of base plate and grid line performance requirement alternate segregation to fundamentally ensures that the thick liquids layer on multi-feature layer just possesses the alignment characteristic that realizes the excellence before the printing.

These, additional and/or other aspects and/or advantages of the present invention are set forth in the detailed description that follows; inferred from the detailed description; and/or may be learned by practice of the invention.

Drawings

For a better understanding of embodiments of the present invention and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which like reference numerals refer to corresponding elements or parts throughout.

In the drawings:

fig. 1,2a and 2B are schematic diagrams of pattern transfer sheets having multiple layers of print paste stacks and pattern transfer methods according to some embodiments of the present invention.

Fig. 2C is a schematic view of a combination of a slurry fill head including doctor blade dispensing and recirculating slurry dispensing according to some embodiments of the present invention.

Fig. 2D is a high-level schematic diagram of a combination of slurry fill cells in a Pattern Transfer Printing (PTP) system, according to some embodiments of the invention.

Fig. 3A provides an example of a multi-feature layer element produced by the disclosed method and system, according to some embodiments of the invention.

Fig. 3B and 3C are high-level schematic diagrams of photovoltaic solar cells with multi-feature layer grid lines according to some embodiments of the present invention.

Fig. 4A and 4B are high-level flow diagrams illustrating pattern transfer methods according to some embodiments of the present invention.

Fig. 5A and 5B are schematic side views of a pattern transfer process for producing multi-feature layer gridlines and utilizing a release layer according to some embodiments of the present invention.

Detailed Description

In the following description, various aspects of the present invention are described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without the specific details presented herein. In addition, well-known features may have been omitted or simplified in order not to obscure the present invention. With specific reference to the drawings, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is applicable to other embodiments and combinations of the disclosed embodiments, which can be practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

An embodiment of the utility model provides an effective and economic method and mechanism for using transfer printing technology to produce the multi-feature layer and pile up the grid line to provide improvement scheme for producing circuit technical field. A pattern transfer sheet and a pattern transfer method are provided that provide a stacking line printed on a receiving substrate in a single irradiation step. The printing paste is filled layer by layer, possibly with different materials in different layers, the layer thickness being controlled by the parameters of the filling element, in the case of a doctor blade, the pressure, angle, speed and flexibility (material) of the doctor blade. In particular, a bottom layer of the stacked lines may be configured to connect with a receiving substrate, while one or more top layers may be configured to optimize the quality of the printed features. For example, the bottom layer may be configured to bond with the substrate (e.g., mechanical and/or electrical), modify the substrate (e.g., form a Selective Emitter (SE) therein), and/or provide a barrier/seed layer with a top layer that may be incompatible with the substrate (e.g., copper on silicon). The release material may be used to support a single release of the stacked layers. Advantageously, the disclosed pattern transfer sheet and method enable printing multi-feature layer grid lines (stacked lines) on PV cells, as well as printing multi-layer bumps, printed resistors and capacitors, and other printed electronics on PCBs.

Fig. 1,2a and 2B are schematic diagrams of a pattern transfer sheet 100 and a pattern transfer method 200 having multiple layers of print paste stack 150 according to some embodiments of the present invention. Fig. 1 schematically illustrates a paste filling and pattern transfer process, while fig. 2B schematically illustrates process parameter adjustments for printing a multilayer stack 150, and fig. 2B also schematically illustrates printing the multilayer stack 150 as a stack line having at least two layers, i.e., a multi-feature layer grid line. Note that for clarity, only two layers 150A, 150B are explicitly shown; however, the disclosed embodiments are not limited to two layers, and in various embodiments, the multilayer stack 150 may include 3, 4, 5, or more layers, prepared and printed according to the principles disclosed herein. Although some illustrate a single groove 110 pattern transfer sheet 100 for clarity, it should be apparent that any of the disclosed embodiments are applicable to pattern transfer sheets having a plurality of grooves 110 arranged in a specified pattern.

Pattern transfer sheet 100 includes a plurality of grooves 110 arranged in a specified pattern (pattern not shown and may have any configuration). Pattern transfer sheet 100 includes a plurality of grooves 110 arranged in a particular pattern (pattern not shown and may be of any configuration). The groove 110 is configured to be filled with printing paste and continuously capable of and supporting the release of printing paste from the groove 110 onto the receiving substrate 70 when irradiated by the laser beam 80. The pattern transfer sheet 100 includes a source substrate that can be flexible (e.g., a polymer sheet) or rigid (e.g., a glass substrate). The support of the pattern transfer sheet 100 may be a stretchable substrate having certain stretching characteristics, such as a polymer substrate, or the support of the pattern transfer sheet 100 may be a rigid substrate, such as a glass substrate.

The printing paste comprises a multi-layered stack 150 of layers (150A, 150B, etc.) which is filled 210 into the trench 110 by one or more filling heads 145 to form a filled trench 115 and transferred onto a receiving substrate 70 using a single irradiation (laser transfer) step 220 to form a stack line 160. Filling the printing paste into the trench 110 (step 210) may be performed in a continuous manner, layer by layer, as shown.

In the non-limiting example shown, two layers of print paste 150 are continuously filled into the trench 110, a first paste material is filled into the trench 110 as layer 150A, for example, using a controlled paste fill head 145A that digs and removes paste from the top of the trench 110, the first paste material is filled into the trench as layer 150A, for example, by the same head of the paste fill head 145A or alternatively by an additional moving blade (not shown). The depth of the scooping can be controlled, for example, by the slurry fill head's blade material, blade angle, blade pressure, and blade movement speed. A second slurry material may be filled on top of layer 150A as layer 150B, filling the remaining volume of trench 110 to produce filled trench 115 in the case of a bilayer implementation. Layer 150B is filled with a second slurry material using a doctor blade fill head 145B (with minimal or no subsequent pick removal).

A continuous pattern transfer 220 is made from layers 160B, 160A of the second and first materials in reverse order by individually illuminating the back side of the pattern transfer sheet 100 to release a stack of layers 150 of the paste to a receiving substrate 70 (e.g., wafer 70) (shown schematically in fig. 1 with the pattern transfer sheet facing down to release the printed paste) -to create a stack line 160, such as a component, line, grid line or bump in an electronic design. The second slurry layer 150B becomes the bottom layer 160B contacting the receiving substrate 70 and the first slurry layer 150A becomes the top layer 160A of the stacking line 160. It should be noted that while inner layer 150A typically contacts most of the surface area of groove 110 in source substrate 100, bottom layer 160B typically provides an interface between stacking line 160 (formed from transferred stack 150) and receiving substrate 70.

In various embodiments, more than two layers of material may be filled 210 into the trench 110 and transferred onto the receiving substrate 70 in succession using a single step 220 to create a stacking line. For example, three, four, five, or more layers may be part of multilayer stack 150 — creating stack line 160.

In certain embodiments, the thickness of the bottom layer 150B may be between 1-5 μm. The top layer 150A may be a few μm thick, for example, in any range of 3-5 μm, 4-7 μm, 5-10 μm, more than 7 μm, or any range thereof.

It is noted that any of the filling heads 145 may comprise a recirculating paste dispensing device as in chinese application nos. CN202110673006.5 and CN202121350578.1, which are incorporated herein by reference in their entirety, the filling head 145 for scooping an upper portion of the filling material (see, e.g., in fig. 2A, 2B below) may comprise a doctor filling head configured to provide the required scooping, while filling the last layer (not scooping) by the filling head 145 may be one recirculating paste dispensing device.

Fig. 2A also schematically illustrates various ways of controlling the thickness of layers in stack of layers 150 and the resulting thickness of layers in stack line 160, according to some embodiments of the present invention. For example, the layer thickness may be controlled by any one or combination of the doctor blade pressure applied by the fill head 145, the angle of the doctor blade, the speed of the doctor blade, and/or the material from which the doctor blade is made. Specifically, the thickness of the applied layer (schematically represented as H1, e.g., layer 150A) decreases with higher blade pressure, greater blade angle, higher blade speed, and softer blade material — leaving more volume to be filled by the continuous layer 150B (with a volume thickness schematically represented as H2). As schematically shown in fig. 1, the transfer of the stack 150 onto the receiving substrate 70 is achieved by irradiation applied to the back side of the pattern transfer sheet 100, the back side of the pattern transfer sheet 100 being placed directly above the receiving substrate 70 and in close proximity to the receiving substrate 70.

In the example shown, increasing the doctor blade pressure (P) of the fill head 145A to fill the layer 150A from P =2.5bar to P =3.5bar (while maintaining the doctor blade pressure of the fill head 145B to fill the layer 150B at 2 bar) reduces the thickness of the layer 150A, leaving more volume to form a thicker top layer 150B (schematically illustrated as fill channels 115A and 115B for lower and higher doctor blade pressures, respectively). Accordingly, in depositing multi-feature layer gridlines, i.e., stacking lines, as the fill blade pressure increases, the bottom layer 160A becomes thicker and the top layer 160B becomes thinner. It has been found experimentally that the thickness of layer 150A decreases with increasing blade pressure due to the increased slurry pick-up with higher blade pressure, e.g., using Heraeus ^TM 9651B, P =2.5bar squeegee pressure of fill head 145A removed about 1 μm of fill paste (115A, leaving 1 μm for layer 150B) and P =3.5bar squeegee pressure of fill head 145A removed about 4 μm of fill paste (115B, leaving 4 μm for layer 150B). It should be noted that the lower pressure of fill head 145B produces a thin and minimally excavated layer 150B on top of layer 150A.

In the illustrated example, the doctor angle (α) of the fill head 145A will be used to fill the layer 150A) Increasing from a =30 ° to a =120 ° (at a doctor blade pressure of P =2.5bar, while maintaining the fill head 145B of the fill layer 150B at a pressure of 2bar, at an angle of a =30 °) reduces the thickness of the 150A layer, leaving more volume to form a thicker top layer 150B (shown schematically as filled trenches 115A and 115B, respectively, for lower and higher doctor blade angles, respectively). Accordingly, as the fill blade angle increases, the bottom 160B becomes thicker and the top 160A becomes thinner as the multi-feature layer gridlines and stack lines are deposited. It has been found that the reduction in thickness of layer 150A with increasing blade angle is due to the increased scooping ability provided by using higher blade angles, e.g., heraeus ^TM 9651B prints the paste, with the alpha =30 ° blade angle of the fill head 145A removing about 1 μm of fill paste (115A, leaving 1 μm for layer 150B), and the alpha =120 ° blade angle of the fill head 145A removing about 4 μm of fill paste (115B, leaving 4 μm for layer 150B). It should be noted that the lower angle of fill head 145B produces a thin and minimally excavated layer 150B on top of layer 150A.

In the example shown, increasing the doctor blade speed (V) used to fill the head 145A in the layer 150A from V =25mm/s to V =100mm/s (at a doctor blade pressure of P =2.5bar and a doctor blade angle of α =30 °, while maintaining the doctor blade pressure of the doctor blade 145B of the fill layer 150B at 2 bar) reduces the thickness of the layer 150A, leaving more volume to form a thicker top layer 150B (schematically illustrated as filled grooves 115A and 115B, respectively, for lower and higher doctor blade speeds, respectively). Accordingly, in depositing a multi-feature layer gridline, i.e., stacking line, as the speed of the filling blade increases, the bottom layer 160B becomes thicker and the top layer 160A becomes thinner. It has been found that the reduction in thickness of layer 150A with increasing blade speed is due to enhanced scooping at higher blade speeds, e.g., using Heraeus ^TM 9651B slurry, doctor speed V =25mm/s of the filling head 145A, virtually without removing any filling slurry (115A, leaving the smallest volume for the layer 150B) and doctor speed V =100mm/s of the filling head 145A removing 3-4 μm of filling slurry (115B, leaving 3-4 μm for the layer 150B). It should be noted that the lower speed of fill head 145B produces a thin and minimally excavated layer 150B on top of layer 150A. Speed of the bladeThe median of (d) yields a duped median.

In the example shown, increasing the blade material flexibility (M) of the fill head 145A of the fill layer 150A, from a standard metal (e.g., stainless steel) blade fill head 145A to a plastic (e.g., polyester or ultra high molecular weight polyethylene-UHMWPE) blade to a rubber blade) decreases the thickness of the layer 150A at the same blade pressure, the same blade angle, and the same blade speed, leaving more volume to form a thicker top layer 150B (schematically illustrated as filled channels 115A and 115B for medium and high blade flexibility, respectively).

Accordingly, in depositing multi-feature layer gridlines, i.e., stacking lines, as the flexibility of the filling blade increases, the bottom layer 160B becomes thicker and the top layer 160A becomes thinner. It has been found that the thickness of layer 150A decreases with increasing blade flexibility due to the increased scooping ability of the more flexible blades, e.g., using Heraeus ^TM 9651B slurry, the metal blade fill head 145A removes almost no fill slurry (115A, leaving a minimum layer 150B), the plastic blade fill head 145A removes 3-4 μm of fill slurry (115B, leaving 3-4 μm for layer 150B), and the rubber blade fill head 145A removes 6-8 μm of fill slurry (filling the trench 115C, leaving 6-8 μm for layer 150B). Note that the lower flexibility of the blade fill head 145B produces a thin and minimally excavated layer 150A on top of layer 150B.

It should be noted that the particular combination of any disclosed parameter and particular value of the parameter may be selected according to requirements associated with the particular slurry used and the predefined layer structure of stacked layer 150. The parameters and their values can be optimized in a pre-production step of the corresponding process development.

In contrast to current screen printing equipment, the disclosed method and system are used to print ultra-fine metallic conductive lines on silicon wafers in PV cells, printed electronics, VLSI (very large scale integration) packaging, and the like. The paste filling step 140 is separated from the pattern transfer step 250 by taking advantage of the non-contact two process step printing of the PTP method. Advantageously, in the disclosed method and system, all layers are formed within the same trench, so they are self-aligned; and since both the filling and printing steps are performed in the same Pattern Transfer Printing (PTP) system and the cycle time is the same as in the case of single layer printing-the disclosed multi-feature layer grid line printing becomes cost effective and enables very high throughput.

For example, the disclosed methods and systems may be used to print silver stack gridlines 160 of PV cells, which may further reduce feature width (e.g., reduce shading loss of the photovoltaic cell) while maintaining or even improving conductivity, e.g., (i) without increasing or even reducing contact resistance (to silicon substrate) by using a bottom layer 160B made of a paste composition, e.g., by adding glass frit, which bottom layer 160B is optimized to make the best electrical contact and good adhesion to the substrate (e.g., TOPCon (tunnel oxide passivation contact to its variant cell), PERC (back contact passivation), etc. PV cells by silicon nitride layer and/or (ii) without increasing or even reducing linear resistance (along the gridline length) by using a top layer 160A made of a paste composition optimized for conductivity along the gridlines, without being constrained by the prior art that must maintain low surface resistance.

In another example, the disclosed methods and systems may be used to print self-aligned Selective Emitter (SE) lines, which is currently a major challenge in the PV industry. In particular, since the SE lines in current silicon substrates are created in a separate process, precise alignment between the printed gate lines and the SE lines is required prior to gate line metallization. Current solutions involve printing wider SE lines (e.g., 100 μm wide) and then covering with narrower metal grid lines (e.g., 30 μm wide) -resulting in more efficiency loss in the short wavelength spectral range in the uncovered SE line region. In contrast, the methods and systems disclosed herein can be used to print SE lines by using a bottom layer 160B containing the doping required to form the SE lines and a top layer 160A made of the paste composition required for gate line metallization-converting the current two-step printing process to a one-step printing process and providing the narrowest SE line, which is exactly coincident with the metal gate line on top of the SE line. Continuously, during the sintering process (high temperature heat treatment), the SE line, the contact to the SE line and the metal grid line are all produced simultaneously (by performing silver sintering). This application may be applicable to PV cells with front side metallization, e.g., TOPCon, PERC, etc., on a silicon nitride layer, for example. The feasibility of this process is reported in the prior art (e.g., rohatgi et al, self-aligned selected-driven emitter for screen printed silicon Solar cells, developed in 17th European photo polymeric Solar Energy Conference and inhibition, germany, but screen printing fails to form multilayer printed features in one printing pass.

In yet another example, the disclosed methods and systems may be used to print copper metal gridlines rather than silver metal gridlines, such as for PV cells. Although copper is substantially better than silver as a metal grid line material for cost and availability considerations, the current use of copper requires the formation of barrier and/or seed layers beneath the copper (e.g., using an expensive sputtering process) or (e.g., using an electroplating process) to avoid diffusion of copper atoms into the receiving substrate 70 (silicon substrate) -resulting in an expensive and complex production process. In contrast, the methods and systems disclosed herein can be used to print a bottom layer 160B made from a paste composition used to provide a barrier layer (e.g., made from any of silver, nickel, titanium, tantalum, etc., combinations and/or alloys thereof) and a top layer 160A made from a copper paste composition. Thus, a stacked line 160 with a very thin barrier layer 160B in contact with the substrate 70 and a relatively thick copper layer 160A enables the use of copper grid lines in a single printing step-providing a significant improvement over prior art practices. In some embodiments, bottom layer 160B may include a seed layer for, for example, electroplating a primary conductive layer made of, for example, copper-in some embodiments, such as shown in fig. 2B, stack layer 150 may include a barrier layer 150C (layer 160C as deposited line 160 contacts receiving substrate 70), a seed layer 150B (deposited as layer 160B on top of layer 160C), and a primary conductive layer 150A (deposited as layer 160A on top of layer 160B) on top thereof-forming respective conductive lines 160 on receiving substrate 70.

Figure 2B schematically illustrates a multilayer stack 150 having more than two layers-for printing a multi-feature gate line 160 having more than two layers of multi-feature gate lines. The thickness of each layer 150A, 150B, 150C (in the non-limiting case of three layers) can be controlled by any of the pressure applied by the doctor blade 145, the angle of the doctor blade 145, the speed of the doctor blade 145, and/or the material. Specifically, the thickness of each applied layer (e.g., H1 for layer 150A and H3 for layer 150B) decreases with higher blade pressure, larger blade angle, higher blade speed, and softer blade material — leaving more volume to be needed to be continuously filled by layer 150B (schematically represented as H2) on layer 150A and continuous layer 150C (schematically represented as H4) on layer 150B. As schematically shown in fig. 1 and 2A, the transfer of multilayer stack 150 onto substrate 70 is accomplished by irradiation applied to the back side of pattern transfer sheet 100, the back side of pattern transfer sheet 100 being placed directly above substrate 70 and in close proximity to substrate 70.

Fig. 2C is a schematic diagram of a combination of slurry fill heads 145, including a doctor blade fill head 145A and a recirculating paste dispensing device fill head 145B, according to some embodiments of the invention. This example is illustrative, and various combinations of one or more doctor blade dispensing heads 145A and/or recirculating paste dispensing device fill heads 145B may be used to fill the slurry layers 150A, 150B, etc. into the trough 110. For example, the recirculating paste dispensing device fill head 145B may be used to fill the top slurry layer without scooping.

The recirculating paste dispensing device 170 comprises a filling head 145, the filling head 145 comprising at least two feed openings (at the junction area of 177, 173), an inner cavity 148 and at least one fluidly communicating dispensing opening 146 (see, e.g., chinese patent applications CN202110673006.5 and CN202121350578.1, incorporated herein by reference), and a pressurized slurry supply unit 180, wherein the pressurized slurry supply unit 180 is configured to circulate the slurry through the filling head 145. The pressure in the pressurized slurry supply unit 180 is adjusted to maintain continuous circulation of the slurry through the feed opening and the inner cavity 148 and to control the distribution of the slurry through the distribution opening 146. For example, the pressurized slurry supply unit 180 mayIncluding a slurry pump 172 and a pressurized slurry reservoir 174 in fluid communication with the internal cavity 148 of the fill head 145, the pressurized slurry reservoir 174 and the slurry pump 172 being configured to circulate slurry through the internal cavity 148 of the fill head 1 145. In a non-limiting example, the slurry pump 172 may include a rotary pressure-sealed displacement system with a self-sealing rotor/stator design, such as from Dymax, for dispensing precise volumes ^TM eco-PEN450 of ^TM 。

Note that the filling head 145 may comprise one or more doctor blade filling heads 145A and/or one or more recirculating paste dispensing device filling heads 145B. For example, one, two or more of the filling heads 145A, 145B, 145C (see e.g. fig. 1,2A, 2B) may comprise a recirculating paste dispensing device filling head, such as the paste dispensing device 170 schematically shown in fig. 2C. Alternatively or additionally, one, two, or more of the fill heads 145A, 145B, 145C may comprise a doctor blade fill head or other type of fill head.

In various embodiments, the paste dispensing apparatus 170 includes at least one pressure sensor 178 configured to measure the pressure of the circulating slurry provided at one or more locations of the slurry supply unit 180. The paste dispensing apparatus 170 may further comprise at least one controller (not shown) configured to adjust the pressure in the pressurized slurry supply unit 180 with respect to the measured pressure of the circulating slurry. The paste dispensing apparatus 170 may further include one or more slurry mixers 176 configured to mix the circulating slurry. The slurry mixer 176 may be, for example, a static mixer that mixes the slurry by pressurizing it. In a non-limiting example, the slurry mixer 176 may include a plastic disposable static mixer made of a large diameter plastic housing containing multiple mixing elements such as from Stamixco ^TM GXF-10-2-ME of ^TM 。

The pressurized slurry supply unit 180 may also be configured to introduce slurry into the inner cavity 148 via at least one inlet opening of the at least two feed openings and to receive circulating slurry via at least one outlet opening of the feed openings in the print head 140. The inlet and outlet openings are located at the top of the fill head 145 opposite the dispensing opening 146, the dispensing opening 146 facing the substrate onto which the slurry is deposited. Alternatively or additionally, the inlet opening and/or the outlet opening may be positioned on a side and/or an extension of the fill head 145.

The pressurized slurry supply unit 180 may include a pressure controlled slurry reservoir 174, a slurry pump 172, and a mixer 176 in fluid communication. The pressure controlled slurry reservoir 174 may be configured to deliver slurry to the slurry pump 172, and the slurry pump 172 may be configured to deliver slurry to the inlet opening through the mixer 176. The pressurized slurry supply unit 180 may also be configured to mix slurry from the outlet opening with slurry delivered to the slurry pump 172 from the pressure controlled slurry reservoir 174. The outlet of the pressure control slurry reservoir 174 is in fluid communication with the inlet of the slurry pump 172. For example, slurry in the slurry reservoir 174 may be delivered to the slurry pump 172 to mix with slurry exiting from the outlet opening of the printhead 145 to be pumped by the slurry pump 172 into the mixer 176. Slurry from the mixer 176 can be delivered to the inlet opening of the print head 145, where the slurry moves along the inner cavity 148 and some of the slurry can be distributed through the distribution opening 146 to uniformly fill the channel 110. The remaining slurry is then mixed with slurry from slurry reservoir 174 (e.g., slurry delivered through nozzles at junction 173) to compensate for the metered amount, and the slurry is circulated through paste dispensing device 170 to maintain the mechanical properties of the slurry and to support continued mixing of the slurry so as to maintain the chemical composition of the slurry. In certain embodiments, the slurry distribution device 170 may also be configured to alter the slurry composition, for example, by adding additives such as solvents, to make the slurry uniform, possibly in relation to the monitored pressure throughout the slurry distribution device 100. For example, additives such as solvents may be added to the slurry entering the mixer 176, if desired.

In various embodiments, the pressure-controlled slurry reservoir 174 and the slurry pump 172 may be open adjacent to the outlet opening of the fill head 145, and the slurry dispensing apparatus 100 may include a conduit 175 connecting the outlet of the mixer 130 to the inlet opening of the fill head 145. In some embodiments, the pressure-controlled slurry reservoir 174 and the slurry pump 172 may be open adjacent the outlet opening of the fill head 145, the mixer 176 may be adjacent the inlet opening 161 of the fill head 145, and the conduit 175 may connect the slurry pump 172 to the mixer 172. The size and orientation of the slurry reservoir 174 and slurry pump 172 may vary, for example, both the slurry reservoir 174 and slurry pump 172 may be set perpendicular to the fill head 145, or one or both of the slurry reservoir 174 and slurry pump 172 may be set at an angle to the fill head 145. For example, the slurry pump 172 may be set at an incline to more evenly distribute the weight of the slurry pump 172 over the fill head 145. In various embodiments, the conduit 175 may be adjusted to conform to any arrangement of the slurry reservoir 174, the slurry pump 172, and the mixer 176 to make the paste dispensing apparatus 170 more compact or adjust it to a given space and weight distribution requirement within the printer.

In various embodiments, the print head 145, the internal cavity 148, and the dispensing slot as the opening 146 bounded by the slot edge 147 (e.g., the metal slot lip 147) may be elongated and configured for slurry properties (e.g., viscosity value), specific throughput and specific characteristics (e.g., length, width, and optional cross-section) of the wire or other element to be dispensed by the fill head 145. In certain embodiments, the dispensing opening 146 may include one or more slits, one or more openings, a plurality of linearly arranged openings, one or more lines of openings, such as circular or oval openings, and the like.

Fig. 2D is a high-level schematic diagram of a combination of slurry fill units 102 in a Pattern Transfer Printing (PTP) system 101 (see also fig. 5B) according to some embodiments of the invention. The paste filling unit 102 is configured to fill the patterned trenches 110 on the transferred pattern transfer sheet 100 with a conductive printing paste, filling the heads 145 with two or more pastes, the heads 145 being applied successively to fill the trenches 110 with a stack of layers 150 made of layers 150A, 150B, etc. It is transferred as a stack layer 150 by the PTP system 101 onto the receiving substrate 70 using a single irradiation step to form a stack line 160 as described herein.

The two or more slurry fill heads 145 can include respective doctor fill heads 145A, fill heads 145B, etc., one for each of the layers 150A, 150B, etc., at least one of the slurry fill heads 145 can be adjusted for doctor pressure, doctor angle, doctor speed, and/or doctor flexibility as described herein-to adjust the thickness of the respective layer. At least one of the paste filling heads 145 may be a recirculating paste dispensing device filling head, such as a paste dispensing device 170 with a pressurized paste supply unit 180, for example, for filling the top layer of the stack 150. The paste filling unit 102 may further comprise a coating unit 103 (schematically illustrated, see chinese patent application No. 202111233805.7, incorporated by reference in its entirety for further details) configured to coat the trench 110 with a release layer (see fig. 5A, 5B) before filling the trench 110 with the multi-layer printing paste.

Fig. 3A through 3C provide examples of multi-feature layer gate lines, i.e., stacked lines 160, produced by the disclosed methods and systems, according to some embodiments of the invention. The illustrated example shows an element with 12 μm copper paste 160A over about 2 μm silver paste 160B (the image is focused on the Ag/Cu boundary to emphasize its multi-layer structure). The element is prepared by first filling a copper paste as material 150A into trench 110 using fill head 145A at α =30 ° and P =2.5bar, then successively filling a silver paste as material 150B using fill head 145B at α =30 ° and P =2 bar-and transferring the multilayer paste from filled trench 115 onto substrate 70 (silicon wafer) to produce the described line.

Fig. 3B and 3C are high-level schematic diagrams of a photovoltaic solar cell 72 having multi-feature layer grid lines, i.e., stacking lines 160, according to some embodiments of the present invention. In various embodiments, the solar cell 72 may include a multi-feature layer grid line, i.e., a stack line 160, produced in a single transfer (illumination) step by the pattern transfer methods disclosed herein, for example, using the disclosed pattern transfer sheet 100. For example, one or more multi-feature layer gridlines, i.e., stacking lines 160, may be used in the photovoltaic solar cell 72 with conductive lines for transmitting the electrical power generated by light conversion by the photovoltaic solar cell 72, e.g., the receiving substrate 70 includes any type of light conversion material, such as semiconductor materials (e.g., various types of single or polycrystalline silicon, various thin film materials configured as single or multi-junction cells) or for any other photovoltaic technology that utilizes conductive lines.

The multi-feature layer grid line, i.e., stacking line 160, may include at least two layers 160A, 160B, 160C, etc. made of different materials that are transferred into the multi-layer stacking line 150, including at least two different types of metal pastes 150A, 150B, 150C, etc., rather than being formed separately, as disclosed herein. After the single-step transfer, the multi-feature layer grid lines, i.e., stacking line 160, may be heat treated to form finished wires depending on the type of paste used (e.g., fired, cured, sintered, co-annealed, etc.). As non-limiting examples, silver pastes may be sintered (e.g., sintered, heated to about 800 ℃ and thereby thermally treated, typically over tens of seconds), silver-epoxy pastes may be cured (e.g., heated to 200 ℃ to 300 ℃ and thereby thermally crosslinked, typically within tens of minutes), copper nanoparticle pastes may be sintered at relatively low temperatures, and so forth. The specific parameters of the thermal treatment of the transferred multilayer stack B to the multi-feature layer grid line, i.e., stacking line 160, such as temperature profile, duration and gas atmosphere, may be adjusted relative to the metal paste composition in the stack layers.

In certain embodiments, the multi-feature layer grid line or stacking line 160 may include a bottom layer (e.g., denoted 160B in fig. 3B, denoted 160C in fig. 3C) comprising a material configured to bond the transferred stacking line 160 to the receiving substrate 70 (mechanical and/or electrical), and at least one top layer (e.g., denoted 160A in fig. 3B, denoted 160A, 160B in fig. 3C) comprising a material configured to provide electrical conductivity along the transferred stacking line 160. For example, the bottom layer may include a paste composition optimized for forming optimal electrical contact and providing good adhesion to the silicon substrate, e.g., with increased glass frit concentration and/or optionally reduced linear resistance (along the length of the grid line), which compensates for the top layer by higher linear conductivity.

In some embodiments, the multi-feature layer gate line 160 may include a bottom layer (e.g., denoted 160B in fig. 3B, denoted 160C in fig. 3C) comprising a material configured to form a Selective Emitter (SE) line 160 on the receiving substrate 70, and at least one top layer (e.g., denoted 160A in fig. 3B, denoted 160A, 160B in fig. 3C) comprising a material configured to provide electrical conductivity along the transferred stacked line 160 and electrical contact to the receiving substrate 70. For example, the bottom layer may include a slurry composition that provides the doping required to form the SE lines and compensates for the potentially reduced conductivity of the top layer by its higher linear conductivity-allowing for the production of thinner SE lines because they are transferred using a single PTP step.

In some embodiments, the multi-feature layer gate line, i.e., stacking line 160, may include a bottom layer (e.g., indicated as 160B in fig. 3B, indicated as 160C in fig. 3B, and optionally 160B) comprising a material configured to provide a barrier layer and/or a seed layer at the receiving substrate 70, and at least one top layer (e.g., indicated as 160A in fig. 3B, and indicated as 160A in fig. 3C) comprising a material configured to provide electrical conductivity along the transferred stacking line 160. For example, the bottom layer may include, for example, silver, nickel, titanium, tantalum, etc., combinations thereof, and/or alloy pastes) as a barrier/seed layer and the top layer includes a copper paste, which provides high linear conductivity at reduced material cost. The barrier/seed layer may comprise one, two or more layers, for example as schematically shown in fig. 3C (the top layer 160A comprises copper).

In various embodiments, the photovoltaic solar cell 72 may include a combination of the multi-feature layer grid lines, i.e., the stacked lines 160, disclosed herein.

Fig. 4A and 4B are flow diagrams illustrating a pattern transfer method 200 according to some embodiments of the present invention. Method steps may be performed using the pattern transfer sheet 100 and/or with respect to a corresponding PTP system, which may optionally be configured to implement the method 200.

The method 200 includes filling a plurality of trenches arranged in a pattern on a source substrate with a printing paste (step 210), wherein the printing paste includes a plurality of stacked layers, and the filling is performed layer by layer, and the printing paste is released from the trenches onto a receiving substrate by laser beam irradiation — transferring the entire stacked layers of the plurality of layers of printing paste onto the receiving substrate using a single irradiation step (step 220).

Filling 210 may be performed by filling the trenches with different slurries of different thicknesses until the trenches in the source substrate are completely filled (step 212). For example, the filling 210 may be performed by a plurality of filling heads, one for each layer, and the pattern transfer method further comprises adjusting the thickness of at least one layer by adjusting at least one of: a blade pressure applied to each layer, a blade angle of the respective blade, a blade speed of the respective blade, and/or a flexibility of the respective blade. For example, the pressure may be chosen between 2 and 4bar, the blade angle may be chosen between 30 and 120, the blade speed may be chosen between 25 and 100mm/s and/or the blade material may be chosen from stainless steel, plastic and rubber.

In some embodiments, at least two of the layers comprise different material compositions and/or different materials, for example selected from: (ii) a bottom layer comprising a material configured to mechanically or electrically connect the transferred stacked lines to a receiving substrate and a top layer comprising a material configured for providing electrical conductivity along the transferred stacked layers, (ii) a bottom layer comprising a material configured to form Selective Emitter (SE) lines on a receiving substrate, and at least one top layer to provide electrical conductivity along the transferred stacked lines and electrical contact with a receiving substrate, and/or (iii) a bottom layer comprising a material configured to provide a barrier layer and/or a seed layer on a receiving substrate and at least one top layer comprising a material configured to provide electrical conductivity along the transferred stacked lines. In certain embodiments, the bottom layer can include a release material composition, for example, as disclosed below.

The method 200 may also optionally include applying a release layer to facilitate printing of the entire stack of layers (step 225), illustrated in more detail in fig. 4B, including, for example, (i) coating and drying the release layer material with the release layer material inside the trenches to form a solid coating of trenches configured to decompose upon irradiation-to facilitate release of the slurry stack filled within the coating trenches (step 230), optionally, cleaning coating residues on the surface of the pattern transfer sheet between the trenches (step 232); (ii) After printing, the receiving substrate is cleaned by removing the decomposition products of the coating (step 240).

Advantageously, the disclosed method and system is capable of printing multi-feature layer grid lines based on non-contact paste transfer. Screen Printing (SP) is a cost-effective production method compared to prior art methods such as Screen Printing (SP), where a single layer of high viscosity paste is printed on a different substrate by performing both screen filling and printing features on the receiving substrate. However, since screen printing is a contact technique, printing multi-feature layer gridlines requires transferring the substrate with the first layer (still wet) to a dryer and then to the same or another printer and aligning the second layer with the previous additional layer. The accuracy of this alignment is limited (primarily because the two different meshes are not the same and differ over time), the process is much more costly, and it is nearly impossible to print very fine multi-feature layer gridlines using prior art SPs.

Fig. 5A and 5B are side view illustrations of a pattern transfer process for creating multi-feature layer gridlines and utilizing a release layer 120, according to some embodiments of the invention. A coating 120 is applied to sheet 100 (as a source substrate) inside of trench 110, coating 120 configured to decompose upon irradiation 80 to enhance release of multiple layers of slurry stack 150. The coated trench filled with multiple layers of slurry is schematically represented by numeral 115. During release of the multi-layer slurry stacking line 150, the coating 120 may decompose (schematically represented by numeral 120A) and deposit on the receiving substrate 70 (wafer) with the released multi-layer slurry stacking layer 150. Thus, the wafer receiving substrate 70 may include multiple slurry stacks released (schematically represented by numeral 150A) and residues (and/or decomposition products) of the coating (schematically represented by numeral 120B) -an intermediate state represented by numeral 176. After pattern transfer, in the process (by PTP system 101), coating residue 120B can be removed from wafer receiving substrate 70, for example by high temperature treatment (e.g., sintering or drying), which is typically used to sinter printed metal paste in photovoltaic cell manufacturing, or by using irradiation 82 to alter and/or remove residue-cleaning the receiving substrate and producing wafer receiving substrate 70 with released paste and without coating decomposition products and residues. The illumination 82 may be the same, similar or different than the illumination 80. In various embodiments, the residue of release material 120B may be removed using any of the following methods: pyrolysis (e.g., sintering), selective laser vaporization, vacuum-assisted evaporation, air blowing, and/or solvent wet washing.

Coating layer 120 (also referred to as release layer 120 for its function) may be a thin layer (e.g., 1 μm to 10 μm thick) deposited on pattern transfer sheet 100 as a source substrate or at least into its grooves 110. In some cases, the material of the release layer 120 (denoted-release material) may be mixed with any component of the multi-layer slurry prior to filling the slurry layer into the trench 110. Non-limiting examples of release materials include the clear weld LD920 series based on acetone and acrylics such as the Spectra 390TM from Epolin.

For example, coating 120 may include coating 210 by applying a coating solution (e.g., having a solids content of 10% to 20%, or 12%, 14%,16%, 18%) (e.g., using a doctor blade, roller, die, etc.) and drying the release layer to form a solid layer of channels, e.g., the thickness of the solid layer may be in the range of 1 μm to 10 μm (e.g., 3 μm,5 μm,7 μm,9 μm). Including cleaning the surface between the grooves of the pattern transfer sheet if desired, for example, using a doctor blade and/or an adhesive roller.

The coating 120 may comprise an organic material such as a NIR absorbing dye. At least one of the materials used for the coating 120 is selected to absorb the laser illumination 80 used in the PTP process (e.g., laser light having a wavelength of 1064nm, 1070nm, or any other wavelength in the NIR spectral range). One or more materials may be selected to have a maximum absorption at the wavelength of illumination. The release material may be configured to change phase, vaporize, and/or be ablated upon absorption of the laser irradiation energy-to create a pushing force that pushes the multi-layer concentrate stacking line 150 out of the trough 110 (without changing the shape of the slurry) and releases the multi-layer slurry stacking line 150 onto the receiving substrate 70. For example, for irradiation 80 using Nd: yag laser light (1060 nm to 1085 nm), the coating 120 may contain a NIR (near infrared) absorbing dye.

The coating 120 may be used to replace or augment the use of the volatile components of the slurry (e.g., added to evaporate and release the paste multilayer slurry stack 150 upon irradiation).

Advantageously, the present inventors have found that the use of the coating 120 enables printing of a paste pattern on the receiving substrate 70 with a much higher aspect ratio, for example at least 0.7 and up to 1 to 2-instead of 0.4 to 0.5 of the prior art; and the ability to print extremely narrow grid lines down to 10 μm wide-rather than the prior art width of more than 25 μm to 30 μm (as disclosed for example in chinese patent CN 202111233805.7). Furthermore, avoiding the use of volatile compounds in the slurry 90 widens the range of printable slurries and makes the process less sensitive to drying of the slurry in a PTP system. Furthermore, although the release layer 120 is much thinner than the paste, lower laser power is required to release the paste and thus printing can be done at higher scanned beam speeds, resulting in higher system throughput. Finally, the use of the release layer 120 allows the printing process to be more precise, thereby avoiding print quality defects of the printed pattern such as paste residue.

In various embodiments, such as disclosed in chinese patent application No. cn202111233805.7, the entire contents of which are incorporated herein by reference, the coating 120 used as the release layer may be deposited or applied by any known technique, such as gravure coating, microgravure coating, transfer roll coating, slot extrusion coating, reverse comma (reverse comma) coating, mayer bar coating, knife coating, or other techniques, applied by a corresponding coater. For example, using a doctor blade, the grooves 110 may be filled with a coating solution while keeping the surface between the grooves 110 clean. After drying the coating solution, the coating 120 is formed within the trench 110 at a thickness determined primarily by the solids content of the coating solution. A closed-cavity blade (protecting or enclosing the coating solution) may be configured to improve the control of the coating solution and ensure cleanliness of the surfaces between the grooves. In another example, the coating solution may be applied to the surface of at least a portion of the pattern transfer sheet 100, for example using a bar laying technique, spraying, slot extrusion, or the like, and dried to form a coating 120 and residue on the surface between the grooves 110. The residue can be removed by various methods, such as a doctor blade set at a specific angle, e.g., made of metal, plastic, rubber, etc.), an adhesive roll, etc. -leaving the coating 120 in the groove 110. The removed residue can be recovered. Any of the disclosed coating processes may be performed in a fixed mode (with a fixed pattern transfer sheet and respective coating elements moving relative thereto) and/or in a continuous mode (with a fixed coating element and pattern transfer sheet moving relative thereto, e.g., using a roller in a roll-to-roll process). The coating process 210 may be performed in advance before the pattern transfer sheet 100 is fed to the PTP system 101, or during their movement in the PTP system 101, for example, immediately before the grooves are filled with the slurry.

In various embodiments, at least the surface of the grooves 110 may be treated using a surface treatment technique such as plasma (e.g., corona), application of a silane additive, or the like to enhance or control adhesion of the coating 120 thereto. The surface treatment can be configured to balance the desired adhesion of the coating within the channels 110, removal of residue from the surface between the channels (if desired), and release of slurry by coating dissolution and possible sheet recycling considerations.

In various embodiments, the PTP system 101 may be configured to inspect and control the coating process and the cleaning process, for example, at a print quality station that controls the print quality of the grid lines, to maintain the process within a predefined process window.

In various embodiments, the coating residue 120B can be removed by any of the following processes: pyrolysis, selective laser vaporization, vacuum assisted vaporization (lowering the boiling point of coating residue 120B), air blowing, and/or solvent washing. The coating residue 120B is removed using a thermal-based process, and the coating material may be selected to have a decomposition temperature and/or boiling temperature that does not affect the deposited grid lines 160 and receiving substrate 70. For example, the coating material may be selected to have a high sintering temperature (about 850 ℃) well below the c-Si PV metallization process, or optionally a decomposition temperature and/or boiling temperature well below the curing temperature of the curing paste (e.g., silver epoxy paste). For example, the decomposition temperature and/or evaporation temperature of the coating residue 120B may be in the range of 200 ℃ to 300 ℃. In certain embodiments, the same laser irradiation 80 used to release the evaporated layer 120 of the slurry stack 150 may also be used to evaporate and/or decompose the coating residue 120B on the wafer 70. It is noted that removing the coating residue 120B may be performed in a single process step or in two or more process steps (e.g., pyrolysis (e.g., by laser irradiation 80 and/or in a drying or sintering furnace), followed by a low temperature wash or purge).

The following non-limiting examples disclose NIR absorbing dyes for use with Nd: yag laser irradiation. In addition to the NIR absorbing dye, the coating 120 may also include a solvent and optionally a binder, a surfactant, and/or a viscosity modifier.

Non-limiting examples of NIR absorbing dye components include diimmonium ion complexes, xylene complexes, and/or phthalocyanines. The illustrated diimmonium ion complex can include, for example, alkyl chains as one or more residues R and a counter ion (not shown), such as 2SbF 6-.

In any disclosed embodiment, additional non-limiting examples of components of the NIR absorbing dye may include any of the following: for example cyanine (tetramethylindole (di) -carbocyanine) dyes with an extended [ CH = CH ] N chain, such as open chain cyanine (R2N + = CH [ CH = CH ] N-NR 2), hemicyanine (aryl = N + = CH [ CH = CH ] N-NR 2), closed chain cyanine (aryl = N + = CH [ CH = CH ] N-N = aryl), neutral cyanine (R2N + = CH [ CH = CH ] N-CN and R2N + = CH [ CH = CH ] N-CHO), or variants or mixtures thereof; phthalocyanine or naphthalocyanine dyes (comprising four isoindole units linked by a ring of nitrogen atoms) or metal complexes thereof (e.g., with aluminum or zinc), dithiolene metal complexes (with one to three dithiolene ligands) (e.g., with nickel), squaraine (squaraine) dyes such as squaraine dye III (squarylium dye III), quinone analogs, diimmonium compounds, and azo derivatives, and/or any variant, derivative, and/or combination thereof.

The solvent included in the coating formulation may be selected to dissolve the dye and optional binders and additives, and may include, for example, acetone, ketones, alcohols, aromatic hydrocarbons, and/or glycol ether solvents.

The coating formulation may also include a binder comprising a polymer and/or polymer precursor, such as polyvinyl butyral, ethyl cellulose and/or derivatives thereof, to form the coating 120 as a continuous film in the channel 110, as long as the decomposition temperature of the binder is below the slurry sintering temperature (e.g., 800 ℃ for silver slurries or 850 ℃,800 ℃,750 ℃,700 ℃,650 ℃,600 ℃,550 ℃,500 ℃,450 ℃, 400 ℃,350 ℃ for silver or other metal slurries or mixtures thereof) or below the slurry curing temperature (e.g., 300 ℃ for silver epoxide slurries 90 ℃, or 300 ℃,250 ℃,200 ℃ for silver epoxide slurries or other metal slurries). The binder may also be selected to minimize the amount of coating residue 120B and/or to simplify removal of the coating residue 120B.

The coating formulation may also include surface wetting additives selected to stabilize the dispersion of the different coating components and/or viscosity modifiers selected to support the application of the coating 120 in the trough 110. The additives and/or viscosity modifiers are selected to have a decomposition temperature below the sintering temperature or curing temperature of the slurry (depending on the type of slurry), and may also be selected to minimize the amount of coating residue 120B and/or simplify removal of the coating residue 120B.

In certain embodiments, the solid content of the coating 120 can be 10 to 20 weight percent to enable a 1 to 10 μm thick coating 120 within a 20 to 30 μm deep trench 110.

In certain embodiments, a coating material or any component thereof, such as a NIR absorbing dye, may be incorporated into at least inner layer 150A of multilayer slurry stack 150, which is the inner (top) layer and is typically the thickest layer, having the greatest contact area with grooves 110 of pattern transfer sheet 100. Mixing a release material into at least inner layer 150A of multilayer slurry stack 150 may enhance release or may be at least partially capable of replacing coating 120 (e.g., in certain areas of pattern transfer sheet 100). For example, at least a portion of the release material may be mixed with at least inner layer 150A of slurry stack 150 (e.g., as a component of the slurry deposited as layer 150A or as an additive mixed during past depositions) to improve the multi-layer slurry stack 150. The disclosed release material may be added to provide a few percent of the inner layer of the multilayer slurry stack 150, such as 1-5% of the inner layer material. In certain embodiments, the coating 120 may be applied and the release material mixed into at least the inner layer slurry component.

Thus, in addition to commercially available printing pastes (e.g., from Heraeus) ^TM SOL9651B of ^TM ) In addition, inner layer 150A of multilayer slurry stack 150 may also include a NIR absorbing dye, such as a diimmonium ion complex, a dithiolene complex, and/or a phthalocyanine as shown herein. Notably, the NIR absorbing dye may be added to a silver paste, a silver epoxy paste, or any other material that is used as an inner layer of the multilayer stack within the trench.

Certain embodiments include a multilayer slurry stack for a pattern transfer process, which includes filling slurry into grooves arranged in a specific pattern in a polymer pattern transfer sheet, and continuously releasing the slurry from the grooves onto a receiving substrate while being irradiated by a laser beam. For example, where the irradiation is in NIR, the slurry comprises a release material configured to enhance the release capability of the slurry from the trench, wherein the release material comprises at least one NIR absorbing dye comprising at least one of: diimmonium ion complexes, dithiolene complexes, phthalocyanines, derivatives thereof, salts thereof, and/or combinations thereof. Non-limiting examples include dyes from TCI (Tokyo Chemical Industry, ltd.), epightTM. 1117 (tetra (decyl) ammonium structure) from Epolin, and/or Lunir5TM from Luminochem.

The disclosed transfer sheet 100 may be used for printing thin lines of thick metal paste on silicon wafers, for example for Photovoltaic (PV) cells, and for producing electronic circuits by creating conductive lines or pads or other features (e.g., on laminates for PCBs) for printed passive electronic components such as resistors or capacitors or for other printed electronic devices. Others shouldThe conductive features are created with a manufacturing process that may include: mobile phone antennas, decorative and functional automotive glass, semiconductor Integrated Circuits (ICs), semiconductor IC package connections, printed Circuit Boards (PCBs), PCB assembly assemblies, optical biological, chemical and environmental sensors and detectors, radio Frequency Identification (RFID) antennas, organic Light Emitting Diode (OLED) displays (passive or active matrix), OLED illumination sheets, printed battery and other applications. For example, in non-limiting solar applications, the metal paste may comprise metal powder, optional glass frit and modifiers, volatile solvents, and non-volatile polymers and/or resins. Non-limiting examples of slurries include those from Heraeus ^TM SOL9651B of ^TM . The metal paste may include silver, copper or other metals and combinations thereof. The metal paste may include silver, copper or other metals and/or combinations and/or alloys thereof. Any of the metal pastes may include any type of conductive adhesive (ECA) paste.

Filling of the slurry into the trench 110 may be performed by any type of slurry fill head operating within any type of PTP system 101. The filling process can be controlled to ensure continuous and uniform filling of the trenches and marks with the slurry.

In certain embodiments, pattern transfer sheet 100 may be transparent to laser beam irradiation 80 and include at least a top polymer layer 114, the top polymer layer 114 including grooves 110 (shown in fig. 1) embossed, press-formed, pneumatically-formed, or laser-formed thereon. In the non-limiting example shown, the grooves 110 are shown as being trapezoidal in cross-section.

The periodic grooves 110 may include grooves, recesses, and/or indentations that are stamped (e.g., press-formed, pneumatically formed, or laser formed) into the top polymer layer 114 in a similar manner, and may have similar or different profiles. For example, the grooves 110 may have various profiles (cross-sectional shapes), such as trapezoidal, circular, square, rectangular, and/or triangular profiles. In various embodiments, the pattern of grooves 110 on transfer sheet 100 may include an array of continuous grooves 110 and/or separation indentations. Note that the term "groove" should not be construed to limit the shape of the groove 110 to a linear element, but is to be broadly construed to include any shape of the groove 110.

Pattern transfer sheet 100 may also include a bottom polymer layer 112, the melting temperature of bottom polymer layer 112 being higher than the imprinting temperature of top polymer layer 114. In one non-limiting example, the top polymer layer 114 may have a melting temperature (Tm) of less than 170 ℃, less than 150 ℃, less than 176 ℃, less than 110 ℃ (or any intermediate range) if it is made of a semi-crystalline polymer, or may have a glass transition temperature (Tg) of less than 160 ℃, less than 140 ℃, less than 120 ℃, less than 100 ℃ (or any intermediate range) if it is made of an amorphous polymer. The melting temperature of the bottom polymer layer 112 can be higher than the melting point of the top polymer layer 114, such as higher than 100 ℃ (e.g., where the top polymer layer 114 is made of polycaprolactone and has a Tm/Tg of about 70 ℃), higher than 120 ℃, higher than 150 ℃, higher than 160 ℃ (e.g., biaxially oriented polypropylene), and up to 400 ℃ (e.g., certain polyimides), or intermediate values.

In various embodiments, the polymer layers 112, 114 can be made of at least one of: polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, wholly aromatic polyesters, other polyester copolymers, polymethyl methacrylate, other acrylate copolymers, polycarbonate, polyamide, polysulfone, polyethersulfone, polyether ketone, polyamideimide, polyetherimide, aromatic polyimide, cycloaliphatic polyimide, fluorinated polyimide, cellulose acetate, cellulose nitrate, aromatic polyamide, polyvinyl chloride, polyphenol, polyarylate, polyphenylene sulfide, polyphenylene ether, polystyrene, or combinations thereof, as long as the melting temperature or glass transition temperature (Tm/Tg) of the top polymer layer 114 is lower than the melting temperature or glass transition temperature (Tm/Tg) of the bottom polymer layer 112 and/or as long as the bottom polymer layer 112 is not affected by the processing conditions of the top polymer layer 114.

In certain embodiments, the bottom polymer layer 112 and the top polymer layer 114 may each be 10 μm to 100 μm thick, such as 15 μm to 80 μm thick, 20 μm to 60 μm thick, 25 μm to 40 μm thick, or any intermediate range, wherein the bottom polymer layer 112 is at least as thick as the top polymer layer 114. The bottom polymer layer 112 and the top polymer layer 114 may be attached by an adhesive layer 113 that is thinner than 10 μm (e.g., thinner than 8 μm, thinner than 6 μm, thinner than 4 μm, thinner than 2 μm, or of any intermediate thickness) that is transparent to the laser beam 80. For example, in certain embodiments, the top polymer layer 114 may be several μm thicker than the depth of the trench 110, such as 5 μm thicker, 3 μm to 7 μm thicker, 1 μm to 9 μm thicker, or up to 10 μm thicker. For example, the trenches 110 may be 20 μm deep, the top polymer layer 114 may be 20 μm to 30 μm thick (e.g., 25 μm thick), and the thickness of the bottom polymer layer 112 may be in the range of 30 μm to 40 μm (note that a thicker bottom polymer layer 112 provides better mechanical properties).

The temperature and thickness of the top polymer layer 114 and the bottom polymer layer 112 may be designed such that the top polymer layer 114 has good moldability, ductility, and some mechanical strength, while the bottom polymer layer 112 has good mechanical strength. Both the top polymer layer 114 and the bottom polymer layer 112 can be designed to have good adhesion properties.

Elements from fig. 1, 2A-2D, 4A and 4B, 5A and 5B may be combined in any operable combination, and the illustration of certain elements in certain figures, but not in other figures, is for illustrative purposes only and is not limiting. It should be noted that the disclosed values may be modified to at least ± 10% of the respective values.

Advantageously, while the prior art fails to achieve printed patterns having features including multiple conductive layers, the disclosed embodiments use a single step, multi-layer stack printing to meet performance and production challenges of conductive lines for electronic circuits, which enables the incorporation of different materials within the stack layers, separating substrate compatibility requirements and gate line performance requirements from each other, and essentially ensuring alignment between the layers.

In the above description, embodiments are examples or implementations of the present invention. The various appearances of "one embodiment," "an embodiment," "certain embodiments," or "some embodiments" are not necessarily all referring to the same embodiments. Although various features of the invention may be described in the context of a single embodiment, these features may also be provided separately or in any suitable combination. Conversely, although the invention may be described herein in the context of separate embodiments for clarity, the invention may also be implemented in a single embodiment. Certain embodiments of the present invention may include features from different embodiments disclosed above, and certain embodiments may incorporate elements from other embodiments disclosed above. Disclosing elements of the present invention in the context of a particular embodiment is not to be construed as limiting the use of the elements only in the particular embodiment. Further, it is to be understood that the invention may be carried out or practiced in various ways and that the invention may be implemented in certain embodiments other than those outlined in the description above.

The present invention is not limited to those figures or the corresponding descriptions. For example, flow need not move through each illustrated box or state or in exactly the same order as illustrated and described. Unless defined otherwise, the meanings of technical and scientific terms used herein are to be commonly understood by one of ordinary skill in the art to which this invention belongs. While the invention has been described with respect to a limited number of embodiments, these should not be construed as limitations on the scope of the invention, but rather as exemplifications of some of the preferred embodiments. Other possible variations, modifications, and applications are also within the scope of the present invention. Accordingly, the scope of the present invention should not be limited by what has been described so far, but should be limited only by the appended claims and their legal equivalents.

Claims (23)

1. A pattern transfer sheet comprising a plurality of grooves provided in the pattern transfer sheet, the grooves being arranged in a pattern and configured to be filled with a printing paste and to be able to release the printing paste from the grooves onto a receiving substrate when irradiated by a laser beam, wherein the printing paste comprises a stack of layers formed by a plurality of layer stacks, the stack being transferred onto the receiving substrate in a single irradiation step.

2. The pattern transfer sheet according to claim 1, wherein at least two of the plurality of layers comprise different material compositions and/or different materials.

3. The pattern transfer sheet according to claim 2, wherein the stack comprises a bottom layer comprising a material configured to mechanically or electrically bond the transferred stack to a receiving substrate, and at least one top layer comprising a material configured to provide electrical conductivity along the transferred stack line.

4. The pattern transfer sheet according to claim 2, wherein the stack of layers comprises a bottom layer comprising a material configured to form a Selective Emitter (SE) on the receiving substrate, and at least one top layer configured to provide electrical conductivity along the transferred stack line and to provide electrical contact with the receiving substrate.

5. The pattern transfer sheet according to claim 3, wherein the at least one top layer comprises silver paste.

6. The pattern transfer sheet of claim 2, wherein the stack layers comprise a bottom layer comprising a material configured to provide a barrier layer and/or a seed layer on the receiving substrate, and at least one top layer comprising a material configured to provide electrical conductivity along the transferred stack lines.

7. The pattern transfer sheet according to claim 6, wherein the bottom layer material is an aluminum paste, a silver paste, a chromium paste, a gold paste, a tin paste, an indium paste, a nickel paste, a titanium paste, or a tantalum paste, and the at least one top layer material is a copper paste.

8. The pattern transfer sheet according to claim 3, wherein the thickness of the base layer is between 1-5 μm.

9. The pattern transfer sheet of claim 3, wherein the base layer comprises a release material composition.

10. The pattern transfer sheet according to claim 1, wherein the interior of the channels is coated with a coating configured to decompose upon application of radiation for transfer paste release to enhance the release capability of the multi-paste stack.

11. The pattern transfer sheet according to claim 1, wherein the pattern transfer sheet is transparent to laser irradiation, and the grooves are formed in the pattern transfer sheet by press forming, pneumatic forming, laser forming, or embossing.

12. The pattern transfer sheet according to claim 11, wherein the pattern transfer sheet comprises at least one polymer layer made of one of: polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, fully aromatic polyester, aromatic-aliphatic copolyester, acrylate copolymer, polycarbonate, polyamide, polysulfone, polyethersulfone, polyetherketone, polyamideimide, polyetherimide, aromatic polyimide, alicyclic polyimide, fluorinated polyimide, cellulose acetate, cellulose nitrate, aromatic polyamide, polyvinyl chloride, polyphenol, polyarylate, polyphenylene sulfide, polyphenylene ether, or polystyrene.

13. A photovoltaic solar cell comprising at least one of a multilayer stacking line formed using the pattern sheet transfer of any of claims 1-12.

14. A paste filling unit provided in a Pattern Transfer (PTP) system, wherein the paste filling unit is configured to fill a patterned trench on a conveyed pattern transfer sheet with a conductive printing paste, wherein the paste filling unit comprises two or more paste filling heads applied to successively fill the trench with a stack of layers, which stack is transferred by the PTP system as a stack line onto a receiving substrate using a single irradiation step.

15. The slurry filling unit according to claim 14, wherein two or more of the slurry filling heads comprise respective filling heads, one filling head for filling one slurry layer, and wherein at least one parameter in the slurry filling heads is adjustable: pressure applied to the respective blade, blade angle, blade speed, and/or flexibility — to adjust the thickness of at least one of the respective layers.

16. Pulp filling unit according to claim 15, wherein the blade pressure is chosen within 2-4bar, the blade angle is chosen within 30 ° -120 °, the blade speed is chosen within 25-100mm/sec and/or the blade material is stainless steel, plastic or rubber.

17. The slurry filling unit according to claim 14, wherein at least one filling head is a recirculating paste dispensing device filling head.

18. The paste filling unit according to claim 17, wherein at least the last of the filling heads for filling the top layer of the stack of layers is the recirculating paste dispensing device filling head.

19. The slurry filling unit according to claim 14, further comprising a coating unit configured to coat the trench with a release layer before filling the printing slurry into the trench.

20. A photovoltaic solar cell comprising a receiving substrate configured to convert light into electricity transmitted through wires, wherein at least one wire is a multi-layer stacked wire and is printed in a single pattern transfer printing step, at least one multi-layer stacked wire comprising at least two layers made of different materials, the layers being transferred as a multi-layer stacked wire comprising at least two different types of metal pastes.

21. The photovoltaic solar cell of claim 20 wherein the at least one multilayer stacking line comprises a bottom layer comprising a material configured to bond the transferred stacking line to a receiving substrate, and at least one top layer comprising a material configured to provide electrical conductivity along the transferred stacking line.

22. The photovoltaic solar cell of claim 20, wherein the at least one multilayer stack line comprises a bottom layer comprising a material configured to form a Selective Emitter (SE) line on a receiving substrate, and at least one top layer configured to provide electrical conductivity along the transferred stack line and to provide electrical contact with the receiving substrate.

23. The photovoltaic solar cell of claim 20, wherein the at least one multilayer stack line comprises a bottom layer comprising a material configured to provide a barrier layer and/or a seed layer on the receiving substrate, and at least one top layer comprising a material configured to provide electrical conductivity along the transferred stack line.

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