Method for chemically modifying surfaces of substrates

Abstract

A method for chemically modifying the surface (10) of a photoelectric cell by exposing the surface to a precursor gas or vapor (100) and heating the surface by radiation (101) and moving the radiation for generate a pattern. Further a solar cell is made by the described method.

Description

METHOD FOR CHEMICALLY MODIFYING SURFACES OF SUBSTRATESCross-Reference to Related Application

[0001] This application claims priority to U.S. provisional application Serial No. 63 / 719,272, filed November 12, 2024, the contents of which are hereby incorporated in their entirety.Background of the Invention

[0002] The present invention is in the technical field of electronic devices. More particularly, the present invention is in the technical field of optoelectronic devices for energy conservation. More particularly, the present invention is in the technical field of converting sun light into electric power for devices, so called solar cells. More particularly, the present invention is in the technical field of manufacturing methods for applying metal contacts to such a device.

[0003] The conventional method for applying metal contacts to solar cells is using a so called screen printing process. It is difficult to print small contacting grid lines using screen printing. Big grid lines have the disadvantage of shading off the sun light, which leads to a loss in efficiency of the solar cell. Small lines have the risk of interruption, especially if the screen is blocked by something. Interruptions leads to yield loss and high cost. With other pattering generation processes, smaller pattering features would be possible. But the application of these processes would require expensive structuring and alignment operation, which makes the use in a cost effective mass production impossible. Conventional metal contact application methods as well as required high thermal budgets (temperature x application time) which the total volume of the substrate (10) is exposed, especially for firing through application. A high thermal budget leads to efficiency and lifetime loss by advanced solar cell concepts such as heterojunction cells, perovskite cells and tandem cells.Summary of the Invention

[0004] The present disclosure relates to a method for applying single or stacked conducting path layers for contacting optoelectronic devices without firing operation after the application process steps. The method uses high energy light for heating the surface of a photoelectric cell and chemically modifies the surfaces with a precursor. The heating is at a low temperature and limited to the area of modification. This enables conductor path applications to temperature sensitive photoelectric cells. Furthermore, it leads the use of bulk metal todecreased line resistivity and the use of deposition and etching in a combined process finally to higher efficiency at lower cost.

[0005] Another aspect of the present disclosure relates to a method of chemically modifying a surface of a photoelectric cell by exposing the surface of the photoelectric cell to a precursor gas or a vapor capable of chemically modifying the surface of the photoelectric cell, heating said surface by irradiation or pulsed irradiation at least in a surface area where the modification takes place, causing the precursor gas or vapor to react with the heated surface in said surface area; and translating the said radiation over the said surface for generating a modified surface pattern.

[0006] The surface pattern comprises a line pattern, an interrupted line pattern, a dot pattern, a line with cross line pattern, and a cross pattern or a combination thereof.

[0007] The precursor gas or vapor contains a metal or a metal compound to create a metal deposit on the surface. In one or more embodiments, the metal comprises one or more of titanium and a titanium alloy or one or more of aluminum and an aluminum alloy.

[0008] A flank angle measured by a scanning electron microscope picture of a cross section of said metal deposit is in a range of 0° to 70°, with respect to the surface of the photoelectric cell.

[0009] A straightness defined by the outline of the metal deposit and a first line with a length of 100 micrometer and a second line with the same length parallel thereto is measured with a scanning electron microscope or a white light interference microscope picture of a top view of the first line and the second line parallel thereto where the orthogonal distance of the two lines is less than 1.5 micrometer.

[0010] In one or more embodiments, a second material is electro plated on said metal deposit. The second material is covered by a second coating. The said metal is deposited on a surface with a first coating or third coating where the first coating or third coating is chemically etched before metal deposition.

[0011] A metal conductor path is deposited on a transparent conducting layer.

[0012] Another aspect of the present disclosure relates to a solar cell produced according to any one of the methods described herein.Brief Description of the Drawings

[0013] FIG. 1 is a top view of a generated conductor pattern on a solar cell according to one or more embodiments described herein;

[0014] FIG. 2 is a cross-sectional view of the generated conductor path of the present disclosure;

[0015] FIG. 3 is a cross-sectional view of the generated conductor path with applied bus bar of the present disclosure;

[0016] FIG. 4 is a cross-sectional view of the generated conductor path with applied conductor plating of the present disclosure;

[0017] FIG. 5 is a cross-sectional view of the generated conductor path on a transparent conductor of the present disclosure;

[0018] FIG. 6 is a cross-sectional view of the generated conductor path with applied conductor plating on a transparent conductor of the present disclosure;

[0019] FIG. 7 is a cross-sectional view of the generated conductor path in a groove of the present disclosure;

[0020] FIG. 8 is a cross-sectional and a top view of the generated conductor path for back contact cells of the present disclosure;

[0021] FIG. 9 is a top view and a cross-sectional view of the generated conductor path on a thin film solar cell of the present disclosure; and

[0022] FIG. 10 is a cross-sectional view of the generated double side conductor path for bifacial cells of the present disclosure; and

[0023] FIG. 11 is a cross-sectional view of a general process configuration; and

[0024] FIG. 12 is a top view of a modified surface showing a methodology for determinate the straightness of the said modification.

[0025] Those skilled in the art will appreciate that elements in the Figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, dimensions may be exaggerated relative to other elements to help improve understanding of the invention and its embodiments. Furthermore, when the terms 'first', 'second', and the like are used herein, their use is intended for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. Moreover, relative terms like 'front', 'back', 'top' and 'bottom', and the like in the Description and / or in the claims are not necessarily used for describing exclusive relative position. Those skilled in the art will therefore understand that such terms may be interchangeable with other terms, and that the embodiments described herein are capable of operating in other orientations than those explicitly illustrated or otherwise described.Detailed Description

[0026] The following description is not intended to limit the scope of the invention in any way as they are exemplary in nature, serving to describe a mode of the invention known to the inventors as of the filing date hereof. Consequently, changes may be made in thearrangement and / or function of any of the elements described in the exemplary embodiments disclosed herein without departing from the spirit and scope of the invention.

[0027] In the embodiments described hereinafter, it is shown how conducting paths can be produced in accordance with the invention, in a photoelectric cell or solar cell. The cell is generally referred to herein as the “substrate”. The paths are produced using a precursor gas or vapor, and these terms are intended to include gases (i.e. materials which are gaseous at ambient temperatures) and vapors (i.e. materials which are solid or liquid at ambient temperatures, but can be evaporated to form a vapor). The terms are intended to include precursor materials comprising only a gas phase, and also gases or vapors which comprise droplets of liquid and / or particles of solid matter, dispersed or suspended in a gas or vapor phase.

[0028] Embodiments described herein include a process as well as a device produced using the described processes.

[0029] Process

[0030] Described herein is a process employing a precursor (100) and a radiation (101) source for irradiating the precursor. The precursor is evaporated and transported by a carrier gas to the process chamber and thus on to the substrate 10 placed within the process chamber. The radiation (101), may be in the spectrum range of 1 pm to 1500 nm, and initiates the deposition process by decomposing the precursor gas or vapor. Typically, the radiation source will emit light in the UV through IR range, or Rontgen (X-ray) radiation. The decomposed precursor can either etch, dope and / or deposit on the substrate (10), depending on the precursor and gas chemistry.

[0031] Examples of precursor materials may include but are not limited to organic chemicals, metal chlorides and gases and may include gases or vapors capable of chemically modifying a surface of a photoelectric cell.. Examples of such precursors include but are not limited to: octacarbonyl dicobalt, tungsten carbonyl, tungsten chloride, tungsten hexafluoride, Pt-tetrakis-trifluorophosphine, Pt-hexafluoro-2,4-pentadionate, Pt-dicarbonyl dichloride, Pt-acetylacetonate, nickel chelate, nickel-alkyl, copper hexafluoroacetyl acetonate, CupraSelect, copper acetyl acetonate, bis(2,2,6,6-tetramethylheptane-3,5-dionato) copper, triethylaluminum, trimethylaluminum, tri-i-butylaluminum, di -i -butyl aluminum chloride, triisobutylaluminum, tris-tertbutylaluminum, diethylaluminum ethoxide tri-tertiarybutylaluminum, dimethylethylamine alane, trimethylamine alane, dimethylaluminum hydride, diethylaluminum ethoxide, aluminum acetylacetonate, diethylaluminum chloride, aluminum chloride, titanium tetrachloride, tetrakis(diethylamino)titanium, tetrakis(tert-butoxy)titanium, tetrakis(dimethylamino) titanium, tetrakis(l-methoxy-2-methyl-2-propoxy)titanium, tris(2.2-bipyridine)titanium, bis(isopropoxy)bis(2, 2,6,6-tetramethylheptane-3,5-dionato)titanium, bis(isopropoxy)bis(l-methoxy-2-methyl-2-propoxy)titanium, phosphorus trichloride, phosphine, tris(dimethylamino) phosphine, arsine, bis(2,2,6,6-tetramethylheptane-3,5-dionato)barium, tris(l-methoxy-2-methyl-2-propoxy)bismuth, tris(2,2,6,6-tetramethylheptane-3,5-dionato)bismuth, boron trichloride, boron-tri chloride dimethyloctylamine complex, tri ethylboron, tetraethoxygermanium, germane, germanium tetrachloride, tetramethoxygermanium, tetrakis(dimethylamino)germanium, tetrakis(tert-butoxy)hafnium, tetrakis(diethylamino) hafnium, tetrakis(dimethylamino)hafnium, tetrakis(ethylmethylamino)hafnium, tetrakis(l-methoxy-2-methyl-2-propoxy)hafnium, bis(tert-butoxy)bis(l-methoxy-2-methyl-2-propoxy)hafnium, hafnium tetrachloride, bis(methyl-5-cyclopentadienyl)dimethylhafnium, bis(methyl-5-cyclopentadienyl) methoxy methyl hafnium, tris(2,2,6,6-tetramethylheptane-3,5-dionato)lanthanum, tri s( 1 -methoxy-2-methyl-2-propoxy)lanthanum-tetraglyme adduct, bis(2,2,6,6-tetramethylheptane-3,5-dionato)lead, pentakis(ethoxy)niobium, pentakis(butoxy)niobium, bis(2,4-dimethylpentadienyl) ruthenium, bis(isopropyl-5-cyclopentadienyl)ruthenium, ruthenium carbonyl, tris(2,2,6,6-tetramethylheptane-3,5-dionato)scandium, tris(dimethylamino)silane, tetrakis(dimethylamino)silane, tetrakis(ethylmethylamino)silane, silane, trisilane, dichlorosilane, trichlorosilane, tetraethylorthosilicate, silicon tetrachloride, bis[pentakis(ethoxy)dimethylaminoethoxy) tantalum] strontium, bis(2,2,6,6-tetramethyl heptane-3,5-dionato)strontium, pentakis (dimethylamino) tantalum, pentakis(ethoxy)tantalum, pentakis(butoxy)tantalum, tetraethoxy(dimethylaminoethoxy)tantalum, tris(diethylamino)-(tert-butylimido)tantalum, tantalum pentachloride, tris(2,2,6,6-tetramethylheptane-3,5-dionato)yttrium, tri s(l -methoxy -2-methyl-2-propoxy)yttrium, tetrakis(dimethylamino) zirconium, tetrakis(2, 2,6,6-tetramethylheptane-3 , 5 -dionato)zirconium, tetraki s(tert-butoxy)zirconium, tri s(i sopropoxy) mono-(2,2,6,6-tetramethylheptane-3,5-dionato)zirconium, tetrakis (ethylmethylamino) zirconium, tetrakis(diethylamino)zirconium, bis(tert-butoxy)bis(l-methoxy-2-methyl-2-propoxy)zirconium, bis(methyl-5-cyclopentadienyl)-methoxymethylzirconium, tris(dimethylamino) antimony, triethylantimony, trimethyl antimony, dimethylcadmium, carbon tetrabromide, carbon tetrachloride, carbon trichlorobromide, tert-butylchloride, trimethylgallium, triethylgallium, trimethylindium, bis(5-cyclopentadienyl)iron, bis(5-cyclopentadienyl)magnesium, bis(methyl-5-cyclopentadienyl) magnesium, bis(methyl-5-cyclopentadienyl)manganese, tert-butylamine, 1,1 -dimethylhydrazine, tert-butylhydrazine,dimethylselenide, ditert-butylselenide, ditert-butylsulphide, dimethyltelluride, diethyltelluride, diisopropyltelluride, tetramethyltin, tetraethyltin, diethylzinc, dimethylzinc, dimethylzinc-triethylamine adduct, ammonia, nitrogen, N2O2, H2, SFe, CF4, C2F6, C3F8, C4F6, NF3, F2, Ch, BCI3 or mixtures of these and combinations thereof.

[0032] Examples of carrier gases include but are not limited to: N2, N2O, CO2, EE, Ar, He or mixtures of thereof.

[0033] Depending on the radiation wavelength, the decomposition of the precursor gas or vapor is forced by the radiation itself, UV radiation and Rontgen, or by the surface of the substrate (10) and the coated surface heated through the radiation. In a deposition process, for example, of metal, the material deposits on the heated surface. In an etching process, for example, an isolator material such as SiN or MgF, the material is etched on the heated surface. Or in embodiments of etching and deposition simultaneously, this processes takes place on the heated surface. Typically, the required surface temperature depends on the precursor and carrier gas(es).

[0034] For generating a conductor path, the radiation spot is moved over the substrate (10). The conductor path may be a linear or non-linear path. The substrate (10) temperature at an illuminated spot area therefore depends on the radiation power and spot moving speed. In embodiments wherein the radiation source is pulsed, additional factors for determining substrate (10) temperature include pulse frequency, pulse duration and pulse power. The process controlled in this way can also be used for an etching process or both processes simultaneously.

[0035] Some of the precursors have etching and depositing capabilities where examples include titanium chloride. By using a precursor with etching and depositing capabilities on a substrate with a SiN, SiCE transparent conductive layer (TCO), or a combination thereof, the substrate material can be contacted through the top layer. The precursor etches the top layer and generates a contact material alloy with the substrate (10). As an example: titanium chloride etches the SiN layer on a silicon substrate and generates a titanium silicide alloy interface and a titanium layer induced by the heat. On top of this structure, a conductor material, for example aluminum or copper, can be deposited by the methods described herein. Alternatively, the first contacting layer can be used as a seed-layer for an electroplating process generating the second, third or greater number of stacked layers. The basic structure of this example with the variations is shown in FIGS. 2, 3 and 4.

[0036] Another possibility provided by the process described herein is the deposition of an alloy by using more than one precursor simultaneously. By controlling a precursorconcentration, a radiation intensity (pulse power and pulse length) and also heat generated on the surface, the alloy mixture can be defined. By this method, a mixture gradient and / or single alloy layers can be generated in the deposited structure.

[0037] Device

[0038] The methods and processes described herein may be used to produce a photoelectric cell or solar cell. The cells formed by one or more processes described herein are illustrated in the figures and described in further detail below.

[0039] Referring to FIG. 1, an illumination pattern is shown. Different patterns such as a line pattern (11), interrupted line pattern (12), dot pattern (13), line with cross line pattern (14) or a cross pattern (15) may be useful, depending on the specific end use or application of methods described herein and device produced. The pattern may be generated, for example by laser light moving over the substrate in a predetermined path.

[0040] An application of the invention is shown in FIG. 2 to FIG. 10. Referring to FIG. 2, a contact metallization for semiconductor-like solar cells with their components, namely: a first material, also referred to as material I (20), substrate (10), a first coating, also referred to as coating I (22) is shown. Titanium and titanium silicide, cobalt and cobalt silicide, aluminum and aluminum silicide, nickel and nickel silicide, tungsten and tungsten silicide, and tantalum silicon nitride and tantalum can be used as a material I (20). It is also possible in some embodiments to apply a diffusion barrier between the material I (20) and a second material, also referred to as material II (30). A diffusion barrier can be made from a material such as or similar to titanium nitride, tantalum nitride, tantalum silicon nitride or tungsten. As a material II (30), aluminum, silver, gold, copper, tungsten, zinc, iron, chromium or other metals can be used.

[0041] FIG. 2 further shows a flank angle (23) of the material I (20), where the flank angle is the angle of the surface area and the side wall of material I (20). The side wall can be a curved area, and in this case the angle refers to the tangent line of the curve.

[0042] In FIG. 3 a metallization is shown with a bus bar (21) for connecting the cells in a solar module in a serial configuration.

[0043] In FIG. 4 the material I (20) and material II (30) are shown where material II (30) is applied with an electro plating process. Within this configuration, material II (30) is covered with a second coating also referred to as coating II (31).

[0044] Referring to FIG. 5, the material I (20) is on a transparent conducting layer (41) such as aluminum or other doped zinc oxide or indium tin oxide covered with or without a third coating, referred to also as coating III (42) for capping. As for coating III (42), silicon nitride,silicon oxide, magnesium fluoride, or other moist, stable, transparent materials can be used.

[0045] The configuration in FIG. 5 is used in hetero-j unction solar cells or thin film solar cells like copper indium gallium selenide absorber (CIGS) cells.

[0046] In FIG. 6 a configuration is shown with an electro plated material II (30).

[0047] In FIG. 7, the material I (20) and the material II (30) are shown in a grooved configuration, made by etching the substrate (10) with gases such as SFe, CF4, C2F6, C3F8, C4F6, NF3, F2, CI2, TiCU, AICI4 or BCI3. The material I (20) and the material II (30) are deposited into the groove. FIG. 7 further shows the flank angel grooved (60) of material I (20) for this configuration.

[0048] In FIG. 8, a back contact cell design is shown with a comb structure design of a conductor path n doped area (70) and conductor path p doped area (71). In this design, one of the doped semiconductors is the base material and the other doped semiconductor is applied by diffusion or plasma immersion and etched in accordance with the invention.

[0049] In FIG. 9, a design of a thin film solar cell with a transparent conducting layer thin film (84) and a solar cell with absorber layer (83) (CIGS, CdTe or others) on a thin film solar cell substrate (81) is shown. The thin film solar cell substrate (81) can be in a flexible or rigid configuration. By using a flexible substrate, the substrate material can be for example made from plastic such as polyimide, flexible glass, or stainless steel. Referring to FIG. 9, a thin film solar cell can be made monolithically integrated using a conductor pattern (80) as an interrupted line where each line is on one cell by an interconnected module design.

[0050] In FIG. 10, a contact metallization for a bifacial solar cell is shown with the material I (20), the material II (30), and the substrate (10) being chosen in accordance with the invention. As a material for the substrate (10), silicon, p or n doped silicon, glass, plastics or metal can be used.

[0051] In FIG. 11, a radiation (101), a precursor (100) and the substrate (10) is shown. This shows a one possible configuration of the process.

[0052] In FIG. 12, a method for determining a straightness (112) of a modified surface area with as an example material I (20) on the substrate (10) is shown in a top view made, for example, by a microscope picture. The described method uses line I (114) going through the two inner border points of the top view of the modified surface at the length 1 (111). Line II (113) is a parallel line to said line I (114) going to the outer border point of the modified area. The distance of the two parallel lines, line I (113) and line II (114) is the straightness (112) in the length I (111).

[0053] While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be a best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention should therefore not be limited by the above described embodiment, method, and examples, but by all embodiments and methods within the scope and spirit of the invention.

[0054] Reference Numbers in the Drawings10 Substrate11 Line pattern12 Interrupted line pattern13 Dot pattern14 Line with cross line pattern15 Cross pattern20 Material I21 Bus bar22 Coating I23 Flank angle30 Material II31 Coating II41 Transparent conducting layer42 Coating III60 Flank angle grooved70 Conductor path n doped area71 Conductor path p doped area80 Conductor pattern81 Thin film solar cell substrate82 Back contact layer83 Solar cell absorber layer84 Transparent conducting layer thin film 85 Material III86 Cross section A:A100 Precursor101 Radiation111 Length I112 Straightness113 Line II114 Line I

Claims

What is Claimed is:

1. A method of chemically modifying a surface of a photoelectric cell, comprising: a) exposing the surface of the photoelectric cell to a precursor gas or a vapor capable of chemically modifying the surface of the photoelectric cell ;b) heating said surface by irradiation or pulsed irradiation at least in a surface area where the modification takes place, causing the precursor gas or vapor to react with the heated surface in said surface area;c) translating the said radiation over the said surface for generating a modified surface pattern.

2. The method of claim 1, wherein said pattern comprises one or more of a line pattern, an interrupted line pattern, a dot pattern, a line with cross line pattern, and a cross pattern or a combination thereof.

3. The method of claim 1 or 2, wherein the precursor gas or vapor contains a metal or a metal compound to create a metal deposit on the surface.

4. The method of claim 3, wherein the said metal comprises one or more of titanium and a titanium alloy.

5. The method of claim 3, wherein the said metal comprises one or more of aluminum and an aluminum alloy.

6. The method of claim 3, wherein a flank angle measured by a scanning electron microscope picture of a cross section of said metal deposit is comprised in a range from 0° to 70° with respect to the surface of the photoelectric cell.

7. The method of claim 3, wherein a straightness (112) is smaller than 1.5 micrometer, and wherein the straightness is defined by the orthogonal distance between a first line and a second line parallel to the first line and is measured with a scanning electron microscope or a white light interference microscope picture of a top view of a metal deposit, and wherein the first line has a length of 100 micrometer and is defined by two inner points of an outline of the metal deposit on an area of measurement and the second line parallel to the first line has a length of 100 micrometers and is defined by an outer point of the outline of the metal deposit on the area of measurement.

8. The method of claim 3, wherein a second material is electro plated on said metal deposit.

9. The method of claim 8, wherein the second material is covered by a second coating.

10. The method of claim 3, wherein the said metal is deposited on a surface with a firstcoating or third coating where the first coating or third coating is chemically etched before metal deposition.

11. The method of claim 1, wherein a metal conductor path is deposited on a transparent conducting layer.

12. A solar cell (10) produced in accordance with the method of claim 1.

13. A solar cell (10) produced in accordance with the method of claim 4.

14. A solar cell (10) produced in accordance with the method of claim 5.

15. A solar cell (10) produced in accordance with the method of claim 6.

16. A solar cell (10) produced in accordance with the method of claim 7.

17. A solar cell (10) produced in accordance with the method of claim 8.

18. A solar cell (10) produced in accordance with the method of claim 9.

19. A solar cell (10) produced in accordance with the method of claim 10.

20. A solar cell (10) produced in accordance with the method of claim 11.

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