TW201232564A - Conductive paste composition containing lithium, and articles made therefrom - Google Patents

Abstract

A lead-free paste composition contains an electrically conductive silver powder, one or more glass frits or fluxes, and a lithium compound dispersed in an organic medium. The paste is useful in forming an electrical contact on the front side of a solar cell device having an insulating layer. The lithium compound aids in establishing a low-resistance electrical contact between the front-side metallization and underlying semiconductor substrate during firing.

Description

201232564 VI. INSTRUCTIONS: This application claims the benefit of U.S. Provisional Application No. 61/424,259, filed on December 17, 2010, which is incorporated herein by reference. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium-containing lead-free paste composition suitable for use in the manufacture of a conductive structure, which can be used for various types of electrical and electronic materials including photovoltaic cells (ph〇t〇v〇ltaic cdi). Device. [Prior Art] A conventional photovoltaic cell structure is constructed by combining n-type and p-type semiconductors to form a p_n junction. A negative electrode is typically located on one side of the battery exposed to the light source (ie, the "front" side, in the case of a solar cell, on one side of the sunlight), and a positive electrode is on the other side of the battery (ie, "back" side). The appropriate wavelength radiation system that falls on the junction of a semiconductor body acts as an external source of energy to create an electron hole pair within the body. Since the electromotive force difference exists between the ρ_η junctions, the holes and the electrons move in opposite directions to pass through the junction, causing a current to flow and transferring the power to an external circuit. Most industrial photovoltaic cells (including solar cells) are provided in the form of a structure, for example, based on a doped crystalline germanium wafer, and the structure has been metallized, that is, the structural system is provided The electrode in the form of a conductive metal contact generates a current that can be (iv) flowed to the external circuit load. Photovoltaic cells are typically fabricated with a front side insulating layer that provides an anti-reflective property to the cell to maximize the utilization of incident light. However, in this configuration, it is normally necessary to remove the insulating layer so that a front side electrode is brought into contact with the underlying semiconductor surface. The front side electrode is typically formed by depositing a metal powder with a conductive paste composition and forming it into a suitable pattern by screen printing. The paste is then fired to remove or otherwise penetrate the insulating layer and burn the metal powder to form an electrical connection with the semiconductor. The ability of the paste composition to penetrate the antireflective coating during firing and to form a strong bond with the substrate is highly correlated with the composition and firing conditions of the conductive paste. Efficiency is a critical measure of the performance of a photovoltaic cell that is also affected by the quality of electrical contact between the fired conductive paste and the substrate.

A thick film conductor composition that can be bonded to a ceramic substrate formed of aluminum nitride is disclosed in U.S. Patent Nos. 5,089,172 and 5,393,558. While various methods and compositions are known for forming devices such as photovoltaic cells, there is still a need for a patterned composition that is capable of fabricating patterned conductive structures and improving overall device electrical performance as well as facilitating efficient fabrication of such devices. Composition. Particularly desirable is a lead-free composition. SUMMARY OF THE INVENTION In one aspect, the present invention provides a paste composition comprising an inorganic solid portion, the inorganic solid portion comprising: (a) from about 75% to about 99% by weight of the solid metal source of a conductive metal; 4 201232564 (b) From about 0.1% to about 10% by weight of the solids of the glass component, comprising: 1-25 wt.% SiO 2 ; 0.1-3 wt.% Al 2 〇 3 ; 50-85 wt.% At least one of the following: cerium oxide and fluorinated, the amount of oxidized wire is at least 10 wt.% and the amount of lanthanum fluoride is at most 50 wt.%; and at least 1 wt.% of at least one of the following: Ti02, ZrO2, Li20, ZnO, P205, LiF, NaF, KF, K2O, V2O5, Ge〇2, Ce〇2 or a mixture thereof; wherein the weight percentage is based on the total glass component; and (c) is about 0.1 to the solid weight About 5% of a lithium-containing additive; wherein the inorganic solid portion is dispersed in an organic medium and the paste composition is substantially lead-free. In another aspect, provided is an article comprising: (a) a semiconductor substrate having a first major surface; and (b) - a preselected portion of one of the major surfaces of the semiconductor substrate A substantially lead-free paste composition is deposited, wherein the paste composition comprises an inorganic solid portion dispersed in an organic medium, the inorganic solid portion comprising: (1) from about 75% to about 99% by weight of the solid metal source of a conductive metal, 201232564 (ii) from about 0.1% to about 10% by weight of the solids of the glass component; and (iii) from about 0.1% to about 5% by weight of a lithium-containing additive; in yet a further aspect, provided A method comprising: (a) providing a semiconductor substrate having a first major surface; (b) applying a substantially lead-free paste composition to a preselected portion of the first major surface, wherein The paste composition comprises an inorganic solid portion dispersed in an organic medium, and the inorganic solid portion comprises: (i) from about 75% to about 99% by weight of the solid metal source; (ii) solid weight About 0.1 From about 10% to about 10% of the glass component; and (iii) from about 0.1% to about 5% by weight of the solids; and (c) firing the substrate and the paste composition, thereby removing the paste The organic medium of the composition forms an electrode that is in electrical contact with the semiconductor substrate. In various embodiments, provided are an article and a photovoltaic cell fabricated using the foregoing methods. [Embodiment] 6 201232564 Solar-powered photovoltaic systems are considered to be environmentally friendly 'because they reduce the demand for fossil fuels. However, most of the existing photovoltaic systems are based on components containing relatively high levels of elemental lead. Reducing lead and other heavy metals in the environment is also considered an important environmental goal. To achieve this, lead-free photovoltaic systems will be very advantageous. The present invention satisfies the demand for a method of manufacturing a high-performance semiconductor device and produces a semiconductor device using an electrode which does not require a lead conductor composition and which is mechanically strong and highly conductive. Photovoltaic devices must form good electrical contact even if there is a front side insulating layer (typically included in such devices), and the conductive paste compositions provided herein will be used in the fabrication of the front side electrodes of photovoltaic devices. There are benefits. In one aspect, the invention provides a paste composition comprising: a functional electrically conductive component, such as a source of electrically conductive metal; a substantially error free glass component; and an organic medium. The paste composition also includes a lithium-containing component such as an additive comprising lithium oxide, lithium hydroxide, a mineral acid or an organic acid or a mixture thereof. The lithium compound helps to etch an insulating layer (also referred to as an insulating film) which is commonly used as an anti-reflective coating on the front surface of a semiconductor substrate and contributes to the metallization layer on the front side thereof A low resistance electrical contact is established between the semiconductor substrates. The insulating layer commonly used as an anti-reflective coating is nitrite. The cream composition can include additional ingredients. The paste composition may comprise, in a blended form, an inorganic solid portion comprising (a) from about 75% to about 99% by weight of a source of a conductive metal, (b) from about 0.1% to about 10% by weight. A substantially unleaded glass 201232564 glass component; and (C) from about 1% to about 5% by weight, or about 〇·ΐ/ by weight. Up to about 3%, or from about 2% to about 1% by weight, of at least one of the above-mentioned π agents, wherein the towel contains 4 based on the total weight of all components of the inorganic solid portion of the composition. As further illustrated in the latter, the composition also includes an organic medium as a carrier for the inorganic solid portion dispersed therein. In one embodiment, the inorganic solid portion of the paste composition comprises from about 85% to about 95% by weight of the total composition, with the remainder being organic. In one embodiment, the inorganic solid portion of the paste composition comprises from about .87% to about 93% by weight of the total composition. The above paste composition can be used to form a conductive electrode for use in an electrical or electronic device such as a photovoltaic cell or an array of such cells. Alternatively, the composition can be used to form a conductor that can be used with a circuit component in a semiconductor module that is incorporated into an electrical or electronic device. The paste composition described herein may be referred to as "conducting", meaning that the electrode structure formed on the substrate using the composition and then fired exhibits a current sufficient to conduct current between the devices or between the circuits connecting them. Conductivity. In one embodiment, the conductive metal source-based conductive metal powder of the functional conductive component is provided in the paste composition and directly incorporated into a portion of the inorganic solid of the composition. In another embodiment, a mixture of two or more such metals is directly incorporated. Alternatively, the conductive metal may be supplied by a metal oxide or salt which decomposes upon exposure to heat of firing to form the metal. Suitable conductive metals include the following or the following: gold, silver, copper, nickel and/or palladium, and alloys or mixtures thereof. Silver is the better. As used herein, the term "silver" in 201232564 is understood to mean the reference element silver metal, silver alloy and mixtures thereof, and T progress includes silver oxide (Ag2〇) or silver salts such as Agci, AgN〇3, AgOOCCH3 (silver acetate). ), Ag〇〇CF3 (silver trifluoroacetate), AgsPO4 (silver orthophosphate) or a mixture thereof. In one embodiment, the paste composition contains from about 75 to about 99% by weight, or from about 8 Torr to about 9% by weight of a conductive metal source. The weight percent is based on the inorganic portion. The conductive metal may be supplied as finely divided particles having any one or more of the following forms: a powder form, a flake form, a globular form, a granular form, a nodular form, a crystalline form, An irregular form or a mixture thereof. In one embodiment, the inorganic portion of the conductive metal component can comprise from about 70 to about 90 wt.% metal particles and from about 1 to about 9 wt% metal flakes based on the total weight of the inorganic material. In another embodiment, the inorganic portion of the metal component can comprise from about 70 to about 90 wt% metal flakes and from about 1 to about 9 colloidal metal. In a further embodiment, the inorganic portion of the metal component can comprise from about 60 to about 90 wt% of metal particles or flakes and from about 〇丨 to about 20 wt% of colloidal metal. The metal particle size used in the paste composition is not subject to any particular limitation. As used herein, it is intended to mean "average particle size" as "median particle size", which means a 50% volume distribution particle size. The volume distribution particle size can be determined by a variety of methods known to those skilled in the art including, but not limited to, laser diffraction and dispersion by a Microtrac particle size analyzer (Montgomeryville, PA). Dynamic light scattering methods as well as direct microscopy can also be used. Instruments for such measurements are commercially available, such as the LA-910 Particle Size Analyzer from Horiba Instruments Inc., Irvine, CA. In the various embodiments of 201232564, the average particle size of the metal particles of the present paste composition is 1 μm or less than 5 μm. The genus or its source may also be provided as a colloidal suspension, in which the ruthenium is calculated as the percentage of the colloidal carrier in the human inorganic material (the colloidal material is part). The conductive metal herein may be coated or uncoated; for example, it may be at least partially coated with a sexual agent. Suitable coated surface activities include, for example, stearic acid, stearic acid, stearic acid Salt, palmitate and its mixture. Others can also make = surface activity _ including lauric acid, oleic acid, citric acid, oleic acid oleic acid and its mixture. Others can still make surface activity _ including polythene (polyethylene) Oxide), polyethylene glycol, benzotris-diol) acetic acid and other similar organic molecules. - CountereMon for applying - a surfactant, including but not limited to hydrogen, ammonium, potassium and mixtures thereof. When the conductive metal is silver, it may be coated as a phosphorus-containing compound. In the embodiment, in addition to the surfactant included as a coating of the conductive metal powder (for the paste composition), one or more surfactants may be included in the organic medium. As described further in the latter, the conductive metal may be dispersed in a enamel, which serves as a carrier for the metal phase and other components present in the formulation.另一 Another component in the composition of the paste is a glass material such as a glass fnt or a mixture of two or more glass materials. The glass composition may comprise, for example, a substantially amorphous glass material such as a glass forming agent (f_ei*), an oxide and/or a modifying agent. For example, 0 201232564 ί ί: used in the patent application scope attached to the book, the term "substantially lead-free" means a composition of lead (or elemental compound or other) Similar substances are added), and the amount of the two components or impurities is more than 1000 ^ per million. In certain embodiments, there is a trace component 5', the mouth L1 is less than 500 parts per million (ppm), or less than 3 〇〇 l^P or J at 100 ppm. Making the error in the composition of the present invention facilitates the disposal or recovery of the person constructed by the singer and reduces the health risks associated with the known toxicity of the slant-containing substance, such as This composition. An exemplary glass former can have a high bond coordination (b 0 n d coordmation) and a small ion size, and can form a bridge covalent bond upon heating and quenching from a solution. The brooding agents of the stalks include, but are not limited to, Si02, b2o3, p2〇5, v2〇5, Te〇2, Ge〇2 and the like. The intermediate county compound can replace the stalking agent, and the phase intermediate oxide includes but is secreted by TiQ2, Ta2〇5, Nb2G5, Zr〇2.

Ce02, Gd203, Sn02, Al2〇3, Hf〇2 and the like. Glass modifiers are typically more ionic in nature and can terminate bonding or affect specific properties such as viscosity or glass wettability. Exemplary modifiers include, but are not limited to, oxides such as alkali metal oxides, alkaline earth oxides,

CuO, ZnO, Bi203, Ag2〇, Mo〇3, w〇3 and the like. Optionally, the viscosity of a glass can be reduced by the introduction of fluoride anions. For example, fluorine may be supplied from at least one of the following fluorides: A

Li, Na, K, Mg, Ca, Sr, Ba, Zn, Bi, Ta, Zr, Hf, Mo, W, Gd, Ce, Ti, Mn, Sn, Ru, Co, Fe, Cu,

If Cr or a mixture thereof is present, the amount of fluoride is such that the glass forms the elemental fluorine of 201232564 ί. In the specific embodiment of the invention herein. I'm a program that dissolves silver oxide in the glass gasification user's term "glass frit" means the amorphous solid M ϋ two forms, in the immediate vicinity of any selected atom Ξ ilLtllzT'mrst c〇〇 Rdinati〇n rmg)^} ^ disappears, ie, force = order, but it is at a larger molecular level than the lower gland': a long range of periodic order frits traditionally = by - will have The main body is ground into a granular state. A recorded component may also include a fluxing material that is ..., helps, causes, or otherwise actively participates in the reaction of the substance - "soluble material" - the material often helps the glass in the interface - or Promoting the sintering of the conductive metal. A fluxing agent can be added to other host materials to provide a larger flow cut than the host material at a selected temperature. - The flux material can be completely non- The crystal, or the crystallinity of its extensible degree, such that the powder X-ray diffraction pattern may include - either or both of the broad amorphous sharp crystal peaks, which are defined by Zhao Brad's law The distance between the atoms of the feature. In addition, the addition of a non-enamel glass frit or a lining (four) material may cause it to be partially or fully devitdfied. A frit material may have a similar flux. The wetting, melting or flow properties of the material, and vice versa. Those skilled in the art will recognize that there is a continuum between the refining agent and the frit. An exemplary crystalline flux material 201232564 can be a Or an oxide thereof, and may contain material

Bi2〇3 or similar. 1 3. It is believed that the glass material used in the composition is fired and partially or completely penetrates the oxidized 2 nitride insulating layer on the conductor substrate. As described herein, this at least a portion of & s facilitates the formation of a strong electrical contact between the two regions of the photovoltaic device structure under the conductive structure (using the composition printer). In the embodiment, the paste composition may contain about 10% by weight of the spoon, or about 0.5 to about 8% by weight, or about 5% to about 5% by weight, or A glass frit component of from about i to about 3% by weight. In the materials, and in the examples, the composition includes a crystalline cosolvent material. A enamel glass frit material, such as a glass transition temperature (at about 300 to 600. (: range of frit material. In an embodiment, the glass component is substantially error-free and comprises _: quinone bismuth, aluminum and bismuth and is in addition to at least one of oxygen and fluorine. More specifically, the glass component comprises 1-25. Wt.% of a 2, 〇.1_3 wt·% of AI2O3; 50-85 wt·% of at least the following persons ·\· Bl2〇3, BiF3 or a mixture thereof, with the limitation that Bi203 is at least 10 wt.% And the BiF3 content is at most 50 wt.%; and at least one of the following is less than 1 wt.〇/o: Ti〇2, Zr〇2, Li2〇, ^η0, P2〇5, LiF, NaF, KF, K2〇, V205, Ge02, Te02, eC> 2' Gd2〇3 or a mixture thereof, wherein the weight percentage is based on the total cerium component. In another embodiment, the glass component comprises 8-25 wt % ΛΑ q · 1 2, 0.1-3 wt.% of AI2O3; 50-85 wt% of at least the following · Bi2〇3, BiFs or a mixture thereof, the limitation is that Bi2〇3 201232564 content is up to 10 wt·% and BiF3 content is at most 50 wt.%; and at least 1 wt.°/〇 of at least one of the following: Ti02, Zr02, Li20, ZnO, P205, LiF, NaF, KF, K20, V205, Ge02 , Te02, Ce02, Gd203, or a mixture thereof, wherein the weight percentage is based on the total glass component. In yet another embodiment, the glass component is substantially lead free and consists essentially of: 8-25 wt.% Si〇 2; 0.1-3 wt.% of Al2〇3; 50-85 wt.% of at least one of: Bi2〇3, BiF3 or a mixture thereof, with the limitation that the Bi2〇3 content is at least 10 wt.% The BiF3 content is at most 50 wt.%; 0_10 wt·% of B2O3; 0-5 wt.% of at least one of: Li20, Na20 or Κ·2〇; 0-5 wt.% of at least one of the following : oxide of at least one of: MgO, CaO, SrO or BaO; 0-5 wt.°/〇: Zn, Ta, Zr, Hf, Mo, W, Gd, Ce, Te, Ti, Mn, Sn , Ru, Co, Fe, Cu, Cr or a mixture thereof; and 0-10 wt.% of at least one of the following fluorides: Al, Li, Na, K, Mg, Ca, Sr, Ba, Zn, Ta , Zr, Hf, Mo, W, Gd, Ce, Ti Mn, Sn, Ru, Co, Fe, Cu, Cr or mixtures thereof; wherein the weight percent is based on total glass composition. 14 201232564 The various compounds of the compositions described herein are specified based on the most prevalent valence of the individual cations. However, those skilled in the art will recognize that certain cations, such as Bi, may be present in other valence states which may be used in suitable amounts to formulate the glass composition. Thus, Bi cations are available from Bi as a compound of any possible valence state, not just the most common trivalent state. Glass materials, such as those having the formulations set forth above, may be used individually or as a push of a plurality of materials, wherein the proportions of the ingredients are adjusted to provide the desired properties, including etching any of the photovoltaic cells present in a photovoltaic cell. The insulating layer and the formation of a high quality electrical contact, as described in further detail below. An oxide or fluoride material contained in each of one or more glass materials (for the glass component of the paste composition) may be melted into one before being incorporated into the paste composition to form a fee Intimate mixture. The glass materials used in the composition of the paste may have different average particle diameters. In one embodiment, the average particle size may range from about 至5 to 3 5 iim. In another embodiment, the average particle size may range from about 〇 8 to 1.2 μηη. The glass material can be produced by existing glass making techniques, including, for example, weighing the ingredients and mixing in the desired proportions, and heating in a platinum alloy crucible in a suitable furnace to form a melt. The heating is carried out at a temperature of from about 1 Torr C to 1200 ° C for a time sufficient to completely convert the melt to a liquid state and to a homogeneous phase. Thereafter, the molten glass is quenched and ground to provide a desired particle size. In one embodiment, the glass material is supplied as a powder and its 5% by volume distribution (d5G) is between 1 and 3 microns. Alternatively, synthetic techniques can also be used to make the glass components useful in the composition of the paste. These techniques include, but are not limited to, water quenching, dissolution 201232564 gelation, mouth mist pyrolysis, or other suitable for the manufacture of glass powder forms. The composition further includes a separate clock-containing additive material such as a tantalum-containing lithium compound or a lithium-containing salt or a mixture of two or more of the foregoing. - Suitable axial inclusions may be in powder form and may include at least one species such as lithium carbonate (Li2C03), lithium oxide jl2(R) lithium hydroxide (Li〇H), lithium fluoride (LiF), lithium phosphate Ll3P 〇4), other organic or inorganic acid lithium salts (including lithium soap) or compounds which produce a bell metal oxide during the firing process, and mixtures thereof. In one embodiment, the additive may also be a mixed oxide of lithium with other metals. The bell-containing additive comprises from about 0.1% to about 5% by weight or from about 01% to about 3% by weight, or from about 0.2% to about 1% by weight of the lithium-containing component, based on the paste. The solid of the composition. The clock-containing component (such as Li2C03) has an average particle size in the range of from about 1 nanometer to about 10 micrometers, or in the range of from about 4 nanometers to about 5 micrometers, or from about 60 nanometers to about 3 micrometers. The range is from about 1.1 to about 1.7 microns, or from about 〇.3 to about 1.3 microns, or less than 0.1 mm. In one embodiment, the 2::3 is present in the range of 0.1 to 5% by weight of the paste composition. In yet a further embodiment, the LifO3 system is present to 3 by weight. The scope of the invention is not limited by any particular theory of operation, but according to L, during firing, the composition of the clock is separated from the glass material in the composition of the paste to promote etching of the insulating layer. With rapid decomposition, this insulating layer is conventionally used for the front side of a photovoltaic cell. This effective etching 201232564 results in the formation of a low-resistance front side electrical contact between the conductive metal of the composition and the substrate underneath it. Ideally , the firing process will essentially remove the kinetic layer completely, and the metal will not be combined with the Si substrate underneath. The axis is known to be certain oxide glass p, but the red knife is separated by one or more The Li compound form is included in the cream set, and it is believed that the etching action of the layer can be improved. 2 It is surprising that the use of the paste set with the inclusion of the additive makes it possible to produce a highly efficient photovoltaic cell. In preparing the invention of the invention In this case, the above-mentioned money component can be mixed with a two-machine medium (for example, by mechanical mixing) to form a "known as a sticky age product" which has a consistency and rheology suitable for printing difficult printing such as screen printing. Typically, the vehicle is dispersible in the towel and has good stability. It is preferred that the composition not only has the desired manufacturing, transport and storage compatibility = stability, but also Conditional cooperation encountered during deposition (eg, by screen printing procedures). Ideally, the rheological properties of the medium will impart excellent application properties to the composition, including stable and uniform solid dispersion, suitable for use in Viscosity and thixotropy of screen printing, wettability of paste solids on substrates subjected to printing, rapid drying rate after deposition, and stable firing properties. A wide variety of inert viscosities that can be used in organic media of the composition. Materials include, but are not limited to, an inert, non-aqueous liquid, which may or may not contain a thickener, stabilizer, or surfactant. By "inert" means that it can be removed by a firing operation without Any material that leaves a substantial residue that is detrimental to the properties of the final wire. The most widely used solvents for forming such paste compositions are ester alcohols and terpene such as aipha or beta 17 201232564 ( Beta) terpineol or a mixture thereof with other solvents such as kerosene, dibutyl phthalate, butyl carbitol, butyl butyl acetate, hexyl Alcohols and high-boiling alcohols and alcohol esters. In another embodiment, the '§-organic medium can be a solution of one or more polymers in a granule. The polymer 5# is ethyl cellulose. Other examples of suitable polymers include ethylhydroxyethyl cellulose, wood rosin, mixtures of ethyl cellulose and enzyme resins, polydecyl acrylates of lower alcohols, and polyethylene glycol-B. Monobutyl ether 〇f polyethylene glycol monoacetate. When a polymer is present in the organic medium, its content may range from about 8 wt.% to about 11 wt.%. When the composition of the present invention is formed into a paste having good wettability, it typically contains 85 to 95 wt.% of an inorganic component and 5 to 15 wt.% of an organic medium. In one embodiment, the LbCO3 system is present in the range of from 0.1 to 5% by weight of the solids. In still another embodiment, the Lj2c〇3 system is present in the range of 0.1 to 3%. As a paste, the present composition can be applied to a preselected portion of the substrate, and can be applied in various configurations or patterns, such as a rod or a wire, for use as an electrode. Alternatively, the preselected portion may substantially cover all of the major surface of one of the three substrates. The electrode is formed by depositing the paste on the substrate in a preselected pattern, drying the paste (optionally by exposure to a moderately elevated temperature), and then firing the paste. Deposition and drying paste. The firing process removes the organic medium, sinters the conductive metal in the composition, and establishes electrical contact between the semiconductor substrate and the fired conductive metal. The substrate can be 201232564 as a semiconductor such as a thin single crystal or polycrystalline lithographic wafer having H and a second major surface on opposite sides; the substrate is preferably a junction, plate. The firing can be carried out in an atmosphere consisting of air, gas, or inert gas or - oxygen and nitrogen and a mixed gas. The paste composition can be deposited on the substrate by various procedures such as printing. Unusual printing procedures include screen printing, electroplating, extrusion, inkjet, shaping, multiple or ribbon printing. A conductor formed by printing and firing a paste (as provided herein) is often referred to as a "thick film" conductor because it is typically substantially thicker than a trace formed by an atomic process, such as Used to manufacture integrated circuits. For example, the thickness of the thick tantalum conductor after firing may be from about 1 to (10) _. Therefore, it is possible to provide a conductive paste which is suitable for use in a printing process, or a "conductive ink". The thick, paste composition can be printed on the substrate in any useful pattern. If the substrate comprises an insulating surface layer, the composition can be printed &amplified on top of the shape. For example, the electrode pattern for the front side of the photovoltaic cell includes a narrow gate line or finger that is connected in plurality to - or a plurality of bus bars. In one embodiment, the conductive finger electrode has a line of 20 to 200 μm, 40 to 15 〇 or 6 〇 to 1 〇〇 宽, and 忉 to 30 μηη, and the finger electrodes are spaced apart from the center. 2 to 3 mm. The conductive finger electrode may have a line thickness of 5 to 50 μm; 1 〇 to Βμηι; or 15 to 30 μΓη. Since the pattern features are opaque, the battery is unable to convert the light that impinges on the pattern of the pattern, resulting in a reduction in apparent battery efficiency. However, reducing the feature size of the conductor would increase the resistance. The possibility of increasing the section ^ by the thickness of the aee) is due to the fact that the actual printing or other deposition process is difficult to reach 19 201232564; ^纟,, typically, the battery design (4) the electrode feature size is macro X balances the effect of actively collecting area and ohmic losses. This - Figure 2:: f current can be taken without excessive resistance loss. The area of the front side of the cover cannot be converted and the area of the front side of the block is minimized. Ideally, the feature structure of the case should be sufficient (4) and should be made to have high electrical conductivity and low contact resistance (with the structure below). 2 Lai, make the material in the ring thief parts, or dry by exposure, moderate temperature. Thereafter, the paste is fired, and the burning curve condition is typically set such that there is a quality: the knot is 2 t enough to be completely burned and removed (when the paste has dried on the substrate =). Typically, the firing will be accompanied by some volatilization and/or thermal cracking = s to remove the organic (d). In the same embodiment, the burn rate may range from about 3 GSt to about _. (3) The scope, or approximately to approximately. 525 C ' or from about 300 ° C to about 650. (:, or about 650 ° c - 1 GGGC. The firing can make the county a suitable heat source. In the case, the system is made by passing the substrate with the printed conductor at a high rate - the belt furnace _ furnaee) is achieved, for example, every minute, ", 〇 to about 500 cm, and the resulting residence time is about (10) $. The knife can use multiple temperature intervals to control the desired temperature and the number of intervals can be For example, between 3 and U intervals. The temperature of the belt is used to specify the temperature of the furnace. The actual peak temperature is usually found in the substrate. 20 201232564 In another cancer sample, the invention relates to a method of making a device, such as an electrical, 蛩2, ..., a semiconductor or photovoltaic device. An embodiment includes the following steps (a) providing a t-conductor substrate having a -first-major surface; (a pre-selected portion of one of the major surfaces is applied with a paste composition, and a substantially lead-free inorganic solid portion of the 刀3 knife dispersed in an organic medium And wherein the no-body part contains : (1) from about 75% to about 99% by weight of the solid-conductive metal source; (8) from about 0.1% to about 10% by weight of the solids, substantially no lead-free glass component; and (U1) about G by weight of solids From 1% to about 5% of at least one of the bell-containing components; and (C) thereafter firing the cast substrate and the paste composition, f is removed, the organic medium is removed, and the conductive metal is sintered and formed - an electrode having electrical contact with the underlying casting substrate. After the product is accumulated, the paste is first selectively dried by exposure to a degree of enthalpy. The firing time/temperature curve condition is 4 & is the organic material used in the above method, it is to be used in the table, in the case of the second (four): = two insulation layer and the firing step is better Establish contact. The galvanic paste grade and the substrate between them 21 201232564 The following method using a 2-conductor substrate is carried out selectively including a heart-shaped f-cut, siNx:h (nitrogen cut, which is contained in Ϊ =: During the work, the gas used for passivation), the oxidized stone 夕 = = Γ Γ can be in the form of a single layer or multiple layers. In some real: side > 匕 in some In the only example, the deposition processing conditions are adjusted to change the chemical amount of (4) 'to modify the properties such as the refractive material to a desired value. For a nitride having a refractive index of about L9 to 2.G, about A thickness of from 700 to 900 A (70 to 90 nm) is suitable. In an embodiment, the insulating layer can be deposited on the substrate by methods known in the art of microelectronics, such as any form of chemical gas. Phase deposition ("CVD") (including electropolymerization enhanced cVD ("PECVD") or thermal CVD), thermal oxidation of gold plating. In another implementation, the substrate is decomposed or reacted with the substrate under heat treatment. Forming the absolute liquid material coating. In still another embodiment, the substrate is heat treated in the presence of an oxygen or nitrogen containing atmosphere to form an insulating layer. Alternatively, the insulating layer is not particularly applied to the substrate, but a naturally formed substance such as yttrium oxide on a germanium wafer acts as an insulating film. After deposition, the paste is fired, optionally dried by exposure to a moderately elevated temperature and then fired. The firing time/temperature profile conditions are typically set to relate to 22 201232564. In various embodiments, any portion of the insulating layer (whether specially applied or naturally occurring) may be partially removed to enhance the bond between the paste composition and the underlying semiconductor substrate. Electrical contact. Preferably, the glass component and the inclusion additive function to at least partially dissolve the insulating layer to establish contact. In the example, the possible steps of the foregoing method for fabricating a photovoltaic cell are illustrated in Figures i(a) through 1(f). Figure i(a) shows a p-type substrate 1〇 which may be single crystal, polycrystalline or reticular. The substrate 1 can be cut, for example, from an ingot which is formed into a self-drawing or casting process. Surface damage (for example, by wire-cutting) and chamber dyeing can be removed by removing the surface of the substrate by about 20 μm, or using an aqueous solution such as an aqueous solution of potassium hydroxide or sodium hydroxide, or hydrogen. a mixture of fluoric acid and nitric acid. Further, the step of washing the substrate with a mixture of hydrogen acid and hydrogen peroxide may be added to remove heavy metals (such as iron) adhering to the surface of the substrate. The base = 10 may have a -th main surface 12 and the rest have lines to reduce light reflection. Nutra can produce an aqueous solution such as an aqueous potassium hydroxide solution or an aqueous sodium hydroxide solution by (iv) an aqueous solution_a major surface. (J, in Fig. 1(b), an n-type diffusion layer 20 is formed to create a p_n junction below p. The n-type diffusion layer can be formed by any suitable doping process, doping procedure The track diffusion such as "phosphorus provides _i_P〇Cl3). Without any specific modification, the I忒-type diffusion layer 2 is formed on the entire top surface of the Shishi p-type substrate. The depth of the diffusion layer can be tailored by varying its diffusion temperature and time and is typically formed to a thickness ranging from about 〇3 to 〇5 microns. 23 201232564 • The sheet resistivity of the expanded layer can range from tens of thousands of squares per square up to about 120 ohms per square or more. y after protecting one surface of the n-type diffusion layer 20 with a photoresist or the like, the n-type diffusion layer 2 is removed from most of the surface by etching so as to remain only on the substrate On a major surface 12, as shown in Figure 1(e). The resistance is then removed using an organic solvent or the like.

Next, as shown in Fig. 1 (4), an insulating layer 30 (also acting as a primary, a film, a layer) is formed on the n-type diffusion layer 2g. The insulating layer is typically tantalum nitride, but may also be a film of another material, such as siNx:H (ie, the insulating germanium contains hydrogen for subsequent purification), oxidized cerium oxide, mixed cerium oxide/oxidation Titanium or alumina. The insulating layer may be in the form of a single layer or multiple layers. Next, an electrode system is formed on the two main surfaces 12, ^4 of the substrate. As shown in FIG. 1(e), the paste composition of the present invention is printed on the first surface 12 The insulating layer 3G is then dried. For photovoltaic cells, the paste composition 500 is typically applied in a predetermined pattern of conductors. The pattern of conductors extends from a busbar that occupies a predetermined portion of the surface. Further, the back side silver paste 7G was screen-printed on the back side (the second main surface M of the substrate) and then dried. This screen printing job can be turned on in any order. For the sake of production efficiency, all of these pastes are typically heated by air or oxygen-containing atmosphere (eG_Mng) to add a king temperature f (TC to about _ range, co-firing period (four) j to, ten minutes Traditionally, an infrared heating belt furnace is used to = to high 201232564. As shown in Fig. 1(f), the firing causes the green paste composition 500 (on the front side) to be sintered and penetrate the insulating layer 3G. Therefore, electrical contact is made with the n-type diffusion layer 20, that is, a condition of "burn through" (such as "seven"). The burn-through state, that is, the extent to which the paste reacts with the insulating layer, and penetrates the (10) The degree of the layer depends on the quality and thickness of the insulating layer, the composition of the f, and the firing conditions. The firing thus converts the paste 500 into an electrode 5〇1 as shown in Fig. 1(f). The firing will further cause |g to be diffused from the back side to the stone substrate to form - (4) 40, which contains a germanium concentration. The layer is commonly referred to as the back surface electric field (BSF) layer, and Helping to improve the energy conversion efficiency of the solar cell. The firing converts the freshly dried aluminum paste 6 turns into an aluminum back electrode 61. The back side silver paste 7 is simultaneously fired and converted into a silver or silver/aluminum back electrode 71. During firing, the boundary between the back side aluminum and the back side silver exhibits an alloy state to achieve electrical connection. Most of the area of the back electrode is occupied by the aluminum electrode, in part because a P+ layer 40 needs to be formed. Since the incident light does not need to penetrate the back side, the entire surface can be substantially covered. Meanwhile, since the aluminum electrode cannot Soldering, so a silver or silver/shoring electrode is formed on a limited area of the back side as an electrode so that the interconnected copper strip or the like can be attached by soldering. Preferably, it is selected for its ability to rapidly decompose the insulating layer. For example, the paste composition may contain first and second glass components. In this case, the second glass component may be designed to be associated with the first glass component. Slowly blending, but hindering its chemical activity. A stop condition can occur, and the insulating layer is at least partially removed but not attacked by the emitter diffused region, which may make 25 201232564 The device produces a shunt that is eroded in the device. The glass component can be characterized by having a sufficient viscosity to provide a stable manufacturing window to remove the insulating layer without damaging the semiconductor. The diffusion pn junction region of the substrate. Ideally, the firing process substantially completely removes the insulating layer and does not have a further bond with the substrate. Although the invention is not limited by any particular theory of operation, However, it is believed that the composition of the clock present in the composition of the paste during firing promotes etching of the barrier layer so that a low electrical resistance front side electrical contact can be formed between the metal of the composition and the substrate beneath it. a The burn-through state (that is, the characteristic of forming the composition of the paste as an electrode after firing, melting and penetrating the edge layer of the wafer and contacting the substrate) depends on the quality of the insulating layer With the thickness, the layer is ίϊίΓί firing conditions. It is believed that a high quality burn-through condition is critical to the high conversion efficiency of the first battery. 1 _ _ paste composition and branches can also be used to form electrodes, package, a photovoltaic front battery front electrode, in the photovoltaic battery: the second type 2 and the figure "the opposite structure, so the substrate is the type And a Ρ-type material is formed on the front side. Included in the invention is a semiconductor device provided by the present invention, which is present on the substrate == body substrate; - selectively on the first main = And a conductive electrode pattern on the surface to be deposited having a preselected two-layer formed by firing a paste composition as described above. The semiconductor device fabricated as described above is one to one In a photovoltaic cell, the invention (4) provides a photovoltaic 26 201232564: a cell f column which includes a plurality of semiconductor devices as described, and is fabricated as described herein. In the 'photovoltaic battery, the battery is made of nitrogen, shaped rolled body or other inert gas fired. In the embodiment, the structure may not include an applied insulating film 'but may contain _ naturally occurring substances (such as oxidation) Shi Xi), for Insulating film. In one aspect of this embodiment, the frit or flux is an embodiment of the invention that is not related to a semiconductor device formed by the method described herein. One embodiment of the present invention The invention relates to a solar cell comprising an electrode comprising a metal powder and one or more glass frits or fluxes, wherein the glass frit or flux is lead-free. Instances Some of the operations and effects of the embodiments of the present invention may be under a series of The examples are to be understood as an example. The examples in which the examples are based are merely representative, and the examples are chosen to illustrate the aspects of the present invention and do not represent materials, ingredients, reactants, conditions not mentioned in the examples. , technology and / or configuration does not apply to this article, or the subject matter not mentioned in the examples is excluded from the scope of the accompanying patent application and its equivalents. The meaning represented by the examples is obtained by comparing The results are more closely understood from the results of the cavities in some of the test trials, which are not counted as control experiments and provide the basis for this comparison because They do not contain a lithium component in the conductive paste. 27 201232564 Preparation of the paste ^ All the metal components except 'the inorganic component P glass component and the lithium-containing additive component used in the following examples) are all opened in a polyethylene container. In the t-step, the ball is oxidized by a ball with a suitable solvent, until it is in the range of 〇5_〇7 μηη. The glass component is as follows. The error-free glass frit. Oxidation meridian by 趟Α· (# 41832, "Ί) supply, lithium carbonate is supplied by Sigma_Aldrich (#431559, "/〇); and lithium fluoride is supplied by Sigma-Aldrich (#203645, 99.98%). All organic components (including solvents, Agents, surfactants, binders and viscosity modifiers) in Thinky (Thinky USA, Inc,

The Laguna Hills, CA) was mixed in a tank and Thinky was mixed at 2000 rpm for 2 to 4 minutes until fully blended. All inorganic ingredients were placed in a glass jar and shaken for 15 minutes. One-third of the inorganic component was then added to a Thinky jar containing organic ingredients and mixed for 1 minute at 2 Torr Rmm. Repeat this procedure until all inorganics are added and mixed. The paste was cooled' and the viscosity was adjusted to be between 2 Torr and 5 〇〇 Pa-s by adding a solvent and mixing it with Thinky at 2 rpm for 1 minute. Repeat this step until the correct viscosity is reached. Roll milling was then carried out using a three roll mill (Charles Ross & Son Co., Hauppauge, New York) under a 1 mil gap, passing three times at zero pressure and three times at 75 PSI. The degree of dispersion is determined by the fineness of grinding (FOG) using a test instrument in accordance with ASTM Standard Test Method D 1210-05, which is published by ASTM International, West Conshohocken, PA, and is incorporated by reference. Incorporated herein. In an embodiment 28 201232564, the largest particles in the composition of the paste (measured using the FOG test) may be approximately 20 μm in size and the median particle size may be about 1 μm. After 24 hours of storage time, to ensure that the paste composition has rheological properties suitable for screen printing, measure its viscosity and, if necessary, add solvent to mix with Thinky to adjust its viscosity to between 200 and 320 Pa. -s. Viscosity was measured using a Brookfield viscometer (Bro〇kfield Inc., Middleboro, ΜΑ) with #14 axis and #6 cup. The viscosity value was measured at 10 RPM after 3 minutes. Photovoltaic cell fabrication The performance of the inventive and comparative conductive pastes was evaluated using a 160 micron thick Q.Cell (Q-Cells SE, OT Thalheim, Germany) polycrystalline silicon wafer fabricated with a 160 micron thick wafer. Phosphorus doped emitter layer of ohm/sq (prepared by P0C13 diffusion process). As provided, the s-ray wafer has a surface that is textured by acid etching. A 70-nm thick 8-inch anti-reflective coating has been applied to the front major surface using a PECVD process. For convenience, use the "cut down" wafer for manufacturing and electrical testing, even if the diamond wafer dicing saw is cut from the 156 mm X 156 mm starting wafer by 28 mm X 28 mm wafer. Use AMI-Presco (AMI, North Branch, NJ) MSP-485 screen printer to screen test wafers, first use the existing A1 paste (DuPont PV381) to form a fully grounded planar backside conductor, and then use this article Various exemplary pastes form a bus bar and a truss wire (0.254 cm pitch) on the front surface. The battery is placed at 150 after printing the back side. (: drying for 20 minutes, and drying again after printing the front side. The dried and printed battery was fired in a multi-zone belt furnace of 29 201232564 BTUIntemation. The firing temperature shown in the following example is the hottest furnace. The furnace set point temperature in the interval. It is found that the δ 疋 point/visibility of the furnace is about 125 higher than the actual peak temperature of the wafer obtained during the passage of the furnace. (:: After firing, the median of the wire The linewidth is 120 μπι and the average line height is 15. mm. The performance of the battery is affected by the edge effect, and the overall solar cell fill factor (FF) is reduced by about 5 〇/〇 compared to the full-size wafer. Battery electrical measurement

The performance of the photovoltaic cell is measured using the ST__, Tele_STV W tester under the pit ±. The Xe arc lamp in the w tester simulates daylight and illuminates the front surface of the cell with known intensity. The tester measures the current (1) and voltage (v) using a four-contact method at approximately 400 load resistance settings to determine the i v : line of the battery. Photovoltaic (four) cell efficiency _, fill factor (four) and series resistance (= are calculated from the λ R curve. For - photovoltaic battery or not, two Eff and FF values and low Rs value is desired. Rs is especially affected, The contact resistance (6) and the resistance of the wire are affected. Because the different wires have the same wire resistance (3.〇gQ_cm), the difference in Rs is mainly from pc. The ideal factor (Ide fine or) is confirmed by Sims-VOC technology. The ideal factor data is better than (4) in the G" sun, which provides a more sensitive diode quality indication and a more effective Pn junction damage measure than the data obtained at the 1_0 solar irradiance level. The factor is ideal. , 30 201232564 Yes before: Bungee it: The string of ideal factor values is derived from the photovoltaic cell. For the 2 components, the components are manufactured and tested. Performance values of these batteries

Comparative Example A,, '·Product ii--Paste: This group is loaded up to 7 wt. (10)_ and the more A is based on the weight of the total frit composition.

Table A 3 BI2O3 BiF3 Ζτ〇2~~"" 7 42.25 17.67 ~ΐ~54~~' ^UkJ ~~'~m --- 20.28

88% adjusts the silver concentration to provide - the level of inorganic solids in the paste. The organic medium used for its reuse has the nominal composition listed in Table 1 below, based on the total organics present.

Table I Organic components of the paste composition, j-1,3-pentanediol monoisobutyrate (50-52% ethoxy), vitamin (48-50% ethoxy), 3-diamine Base propylene dioleate

Wt.% 46.42 ^17 〇Ti? ~S33 31 201232564 Hydrogenated castor oil 4.17 --^ H9 Alcohol tetraester 10.42 --- ίτ* — 1 — A cool 26.25 ---- /3⁄4 — Acid — A cool 2.92 Use this A total of 25 samples were printed on the plaster screen. Five of these samples were in. Fired at each of the following peak temperatures: 870, 890, 910, 930, and 95 (TC. The best performance was seen in samples fired at a spike firing temperature of 89 () <t, with an average efficiency of 78 〇/〇. Example 1 The experiment described in Comparative Example A was repeated with the same organic medium, but incorporating a U2C〇3 additive (based on the paste composition at a content of wt·6 wt.%) To maintain an inorganic solids content of 88%. The best performance was seen again at the peak firing temperature of _, but the average efficiency of the five samples increased to 14 37%, with an efficiency of more than 0.5% relative to the battery of Comparative Example A. Net increase.

Comparative Example B 1 The same procedure as described in Comparative Example A was repeated for the same organic medium, but the glass I was reduced to 4% and the Li component was not added. The silver concentration was adjusted so that the solid content of the second machine was 88%. At an optimum firing temperature of 950 ° C, the average efficiency of the five samples was 12.76%. Examples 2 and 3 The experiments described in Example B were repeated under the same organic medium and 1% and 6% glass frit, but Li2C03 was added to 0.2 wt.%. In the 32 201232564 two examples, the adjustment was made to maintain the no-body content at 88%. Under 1% frit conditions, the best performance occurs at a peak temperature of C and the average efficiency of the five samples is 138%, with a net increase in efficiency of more than 1% compared to Comparative Example B. Under the conditions of 6% glass frit, the best performance was observed at a peak temperature of 91 (rc and the average efficiency of the five samples was M.3%, with a net increase in efficiency over i5 relative to Comparative Example B. 4 Statmically-designed experiment was performed using 12 different compositions to determine the optimum content of frit and u-containing additive. These compositions used the same glass frit as used in the comparative example. The change from i to 9%, and the addition of Li2C03 content varies from 〇 to (10). In each composition, the silver concentration was adjusted to maintain the inorganic solid content at 88%. Use of Mickey 15 (Minitab Inc., State College, PA) A statistical analysis of the experimental results was performed to predict that the best efficiency occurred at 0 6% Li2C〇3 and about 8% glass frit.

Comparative Example C A paste sample was prepared with the same organic medium as used in Comparative Example A and silver. The frit was loaded as a 2% integral paste composition and the following nominal compositions given in Table B were used:

Table B

Si〇2 AI2O3 B2O3 Bi2〇3 T1O2 Zr02 Na2〇 21.92 ] 0.2B 3.84 64 2.01 4.81 1.64 1.5 — 33 201232564 Adjust the silver concentration to maintain the inorganic solid content at 88%. The screen was printed and fired at a peak temperature of 840, 865, 890, 915 and 94 〇t. The best performance occurs at a peak temperature of 94 〇r and the average efficiency of = is 丨.09%, which is too low for a commercially desirable photovoltaic cell. Examples 5 and 6 The experiment described in Comparative Example C was repeated except that the frit loading was 2 wt.% and the content of nano ALi2C〇3 was 〇4 and i 2 tree%. The silver concentration was adjusted again to maintain the inorganic solids content at 88%. The best performance of the 0.4% sample was at a peak firing temperature of 89 (the rcT appeared and the ruling efficiency was 1415% among the five samples, which was significantly higher than that of the comparative example c and improved compared to the example A. The optimum performance of the n sample occurs at a peak firing temperature of 8 5 G 并且 and the median efficiency of the five samples is 10.81%. This value is significantly higher than that obtained in Comparative Example c. Any composition of the glass frit will have the best LhCO3, but the addition of the separated u2c〇3 to the composition of the paste is still a matter of the superiority of the photovoltaic cell, which is lacking.

Ll2C〇3 or other alternatives used in the separation of U-containing additives used herein are more advantageous. Example 7-10

Sample Table C was formulated with the same organic medium and silver used for the same as _A. The frit is loaded as a 2% integral paste composition, and: The following nominal composition is given in: 34 201232564 Table c

Si〇2 Al2〇3 Zr02 B2〇3 1.86 0.34 0.27 12.95

Li2〇 Bi2〇3 — .___Μ 9 82.57 Prepared by separating LhCO3 additive as shown in Table II. The silver concentration was adjusted to maintain the sample composition as follows. The sample was screen printed on a Si wafer and fired in the body 3 at 88%, 875, 890 and 905 °C. The maximum peak temperature is 860,

Electrical properties. Presented in PV cells with the best firing temperature. The battery data is shown in Table II.

Table II

Series Resistance (Ω) 0.235 0.237 0.239 0.268 Ideal Factor 3.7 3.1 ΊΎ T9- The PV cell efficiency values shown in Table II are better than those shown in Comparative Examples, 3 and C. The characteristics shown in the other tables η also show that the battery is adequately suited for its intended use. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fully understood and its advantages will be more apparent from the following detailed description of the preferred embodiments of the invention. - IF sequentially depicts a method by which a semiconductor module can be fabricated. The module can then be incorporated into a photovoltaic cell. The component symbols used in FIG. 1 include the following: 10: p-type substrate 12: first main surface of substrate 10 (front side) 14: second main surface of substrate 10 (back side) 20: n-type diffusion layer 30: insulation Layer 40: ρ+ layer 60: aluminum paste 61 formed on the back side: aluminum back electrode (obtained by firing the back side aluminum paste) 70: silver paste or silver/aluminum paste 71 formed on the back side: a silver or silver/aluminum back electrode (obtained by firing a back side silver paste) 500: a silver paste 501 formed on the front side according to the present invention: a silver front electrode according to the present invention (by firing a front side silver paste Forming) 36 201232564 [Description of main component symbols] 10. P-type substrate 12... First main surface 14.. Second major surface 20: η-type diffusion layer 30.. Insulation layer 40·. .ρ+ layer 500.. . Silver paste 501.. Silver front electrode 60 ... I Lu paste 61.. . Aluminum back electrode 70.. Silver paste or silver / aluminum paste 71.. . Silver or silver / Aluminum back electrode 37

Claims (1)

201232564 VII. Patent Application Range: 1. A paste composition comprising an inorganic solid portion comprising: (a) from about 75% to about 99% by weight of the solid metal source; (b) A substantially error-free glass composition having a solid weight of from about 1 〇/〇 to about 10 〇/〇, comprising: ... 1-25 wt.% of SiO 2 ; 0.1-3 wt.% of Al 2 〇 3 ; At least one of 85 wt. ° / 〇: yttrium oxide and silver fluoride - the amount of silver oxide is at least 10% and the amount of silver fluoride is at most 50 wt. 0 / 〇; and at least 1 wt% of at least the following One of: Ti〇2, Zr02, Li20, ZnO, P2〇5, LiF, NaF, KF, K20, V2O5, Ge02, Te02, Ce02, Gd203 or a mixture thereof; wherein the weight percentage is based on the total glass component; (c) from about 〇 to about 5% by weight of the solids of a lithium-containing additive; wherein the inorganic solid portion is dispersed in an organic medium and the paste composition is substantially lead-free. The paste composition of claim 1, wherein the lithium-containing additive is at least one of the following: an oxidation clock, a hydroxide, a mineral salt of an inorganic or organic acid, or a mixture thereof. 3. The paste composition of claim 2, wherein the lithium-containing additive is UF. 38 201232564 4. The paste composition of claim 2, wherein the lithium-containing additive is Li2C03. 5. The paste composition of claim 1 wherein the substantially lead-free glass component comprises 8-25 wt.% Si〇2 based on total glass composition. 6. The paste composition of claim 1, wherein the conductive metal is at least one of the following: gold, silver, copper, nickel, or alloys or mixtures thereof. 7. The paste composition of claim 6, wherein the conductive metal is silver. 8. The paste composition of claim 1 wherein the source of conductive metal is finely divided silver particles. 9. An article comprising: (a) a semiconductor substrate having a first major surface; and (b) - a substantially error-free paste composition deposition on a preselected portion of a major surface of the semiconductor substrate, Wherein the paste composition comprises an inorganic solid portion dispersed in an organic medium, the inorganic solid portion comprising: (1) from about 75% to about 99% by weight of the solid metal source; (ii) about the weight of the solid 0_1% to about 10% of a substantially lead-free glass component; and 39 201232564 (iii) from about 0.1% to about 5% by weight of a lithium-containing additive. 10. The article of claim 9, wherein an insulating layer is present on the first major surface of the semiconductor substrate and the paste composition is deposited on the insulating layer. 11. The article of claim 10, wherein the paste set system has been fired to remove the organic medium and form an electrode that is in electrical contact with the semiconductor substrate. 12. The article of claim 10, wherein the semiconductor substrate is a germanium wafer. 13. A method comprising: (a) providing a semiconductor substrate having a first major surface; (b) applying a substantially lead-free paste composition to a preselected portion of the first major surface, Wherein the paste composition comprises an inorganic solid portion dispersed in an organic medium, and the inorganic solid portion comprises: (1) from about 75% to about 99% by weight of the solid metal source; (ii) by weight of solids From about 0.1% to about 10% of a substantially lead-free glass component; and (iii) from about 0.1% to about 5% by weight of the solids of a lithium-containing additive; and 40 201232564 (C) firing the substrate with the paste composition The article 'by this removes the organic medium composed of the paste and forms an electrode which is in electrical contact with the semiconductor substrate. 14. The method of claim 13, wherein an insulating layer is disposed on the first surface and the paste composition is applied to the insulating layer. The method of the worker is described in the above, wherein the insulating layer comprises at least the following ones: alumina, titania, tantalum nitride, SiNx:H, cerium oxide or cerium oxide/titanium oxide. The method of claim 14, wherein the insulating layer is a naturally occurring layer. The method of claim I3, wherein the insulating layer is applied to the first major surface in a preselected pattern. The method of claim 13, wherein the firing is performed in air or an oxygen-containing gas. The method of claim 13, wherein the conductive metal is finely dispersed silver, and the amount of ^ f is in the range of about 75% to 99% by weight based on the inorganic solid portion. The method of claim 13, wherein the substantially error-free glass component comprises: wt·% of SiO 2 ; 41 201232564 0.1-3 wt·% of AI 2 O 3 , 50-95 wt.°/〇 of at least one of the following The amount of yttrium oxide or yttrium fluoride is at least 10 wt.% and the amount of lanthanum fluoride is at most 50 wt.%; at least 1 wt.% of at least one of the following: Ti02, Zr〇2, Li20, ZnO, P2〇5, LiF, NaF, KF, K20, V2〇5, Te〇2, Ge〇2, Ce〇2, Gd2〇3 or a mixture thereof; wherein the weight percentage is based on the total glass component and the fluorine is present The amount of the compound is such that the glass component contains up to 5 wt. ° / 元素 elemental fluorine. 21. The method of claim 20, wherein the substantially slanted glass component comprises 8-25 wt.% SiO 2 based on total glass composition. An article manufactured using the method of claim 13. A photovoltaic cell, which is fabricated using the method of claim 13. 42