CN105280731A - Paste for light receiving surface electrode of solar cell, manufacturing method and solar cell unit - Google Patents

Paste for light receiving surface electrode of solar cell, manufacturing method and solar cell unit Download PDF

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Publication number
CN105280731A
CN105280731A CN201510303050.1A CN201510303050A CN105280731A CN 105280731 A CN105280731 A CN 105280731A CN 201510303050 A CN201510303050 A CN 201510303050A CN 105280731 A CN105280731 A CN 105280731A
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glass
additive
solar cell
electrode
paste
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杉山高启
角田航介
林博道
吉野泰
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Noritake Co Ltd
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Noritake Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0224—Electrodes
    • H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/20—Conductive material dispersed in non-conductive organic material
    • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

The invention provides a paste for a light receiving surface electrode of a solar cell, wherein the paste can form an electrode that has high binding strength with a substrate and low contact resistance and furthermore high output can be obtained on condition that an LDE substrate is used, and a manufacturing method of the paste, and a solar cell unit with high output. The conductive paste for forming the light receiving surface electrode comprises leadless tellurite glass with various compositions. Various lead-containing additives and an additive with high-melting-point metal are mixed in the paste. Preferably the lead is carried in appropriate methods of false firing, chemical method, mechanical method, etc. Therefore if the electrode of the light receiving surface is formed through a fire-through manner, an erosion surface which appropriately has recesses and projections can be obtained. Therefore a requirement for a high electric characteristic and high binding strength can be satisfied. Furthermore, because the light receiving surface electrode (28) contains high-melting-point metals and lead, recombination is suppressed. Therefore high output can be obtained even the LDE substrate is equipped.

Description

Solar cell sensitive surface paste for use in electrode, its manufacture method and solar battery cell
Technical field
The present invention relates to compatibly for adopting the solar cell sensitive surface paste for use in electrode, its manufacture method and the solar battery cell (cell) that burn till the electrode of solar battery purposes that through method (firethroughmethod) is formed.
Background technology
Such as, general silicon system solar cell has following structure, that is, at the upper surface of the silicon substrate as p-type poly semiconductor across n +layer possesses antireflection film and sensitive surface electrode, and, at lower surface across p +layer possesses backplate (following, when not distinguishing them referred to as " electrode "), and the electricity produced at the pn knot of semiconductor by light is obtained by electrode.Above-mentioned antireflection film is for guaranteeing sufficient transmission of visible light, and reduces surface reflectivity raising by the film of optical efficiency, is made up of the film of silicon nitride, titanium dioxide, silicon dioxide etc.
The resistance value of above-mentioned antireflection film is high, and therefore in order to efficiency obtains the electricity produced at the pn knot of semiconductor well, the part forming sensitive surface electrode needs to remove antireflection film.Therefore, the sensitive surface electrode of solar cell such as adopts to be called as and burns till through method and formed.Such as, in this electrode forming method, at n +whole on layer described antireflection film is set after, adopt such as silk screen printing (screen painting) method to be coated on this antireflection film with suitable shape by the electrode material of conductive paste and pasty state, and implement burn till process.Thus, while electrode material is by heat fused, the antireflection film be in contact with it is melted, sensitive surface electrode and semiconductor contact.Above-mentioned conductive paste, such as with silver powder, frit (by frit melting and after chilling, the flake pulverized as required or pulverous glass fragment), organic vehicle and organic solvent be the paste of principal component, in sintering process, glass ingredient in this conductive paste destroys antireflection film, therefore by the conductor composition in conductive paste and n +layer forms ohmic contact.Therefore, compared with the situation partly removing antireflection film before being formed with at electrode, there is the advantage that operation became simply, can not produce the dislocation of remove portion and electrode forming position.
In the sensitive surface electrode of solar cell as described above is formed, require the bond strength guaranteeing substrate and electrode, and reduce contact resistance, guarantee good ohmic contact, and then make battery export raising.All the time, the various motion for improving these bond strengths and contact resistance was once proposed.
In addition, as the motion seeking contact resistance improvement, the such as oriented Ag of comprising powder is used as the paste of any one (for example, referring to patent documentation 1) added in the paste of conductor composition in Mo, W, Ni.According to this paste, the silicon oxide film generated when burning till is reduced by Mo, W, Ni, therefore, it is possible to burn till at low temperatures, and due to contact resistance step-down, therefore FF value becomes large, but do not have consideration to be applied to burn till through, through forming sensitive surface electrode if existed by burning till, can not get the problem of sufficient bond strength.
In addition, once proposed and such as comprised among Ag powder, V, Mo, W at least a kind, the conductive composition used for solar batteries (for example, referring to patent documentation 2) of frit and organic vehicle.This conductive composition, by can be realized by easy fired burning till through for the purpose of.According to this conductive composition, refractory metal and Ag carry out solid phase reaction and form composite oxides, and Ag spreads via these composite oxides thus carries out particle growth from low temperature.In addition, the liquation of the composite oxides at high temperature melted promotes the sintering of Ag, and by the antireflection film of substrate surface and/or the fusing of insulation tunicle, make the diffusion of the Ag in insulation tunicle easy, therefore contact resistance reduces.
In addition, once proposed and use following conductive paste to form electrode, described conductive paste contains silver powder, frit, organic vehicle and organic solvent, and at least one (for example, referring to patent documentation 3) among the oxide containing Ti, Bi, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Si, Al, Ge, Sn, Pb, Zn as additive.This conductive paste, being the paste for the purpose of contact resistance is little, bond strength is high to be formed electrode, by being contained in electrode layer using the oxide of lead, boron, silicon etc. as additive dividually with frit, contact resistance can being made further to reduce.But, in the conductive paste described in these patent documentations 2,3, when stronger as corroding when frit use lead glass, therefore male and fomale(M&F) becomes large, contact resistance uprises, corrode more weak when using crown glass, therefore contact resistance uprises and bond strength step-down, is all difficult to obtain good result.
In addition, to consider environmental problem and to improve for the purpose of bond strength and contact resistance, once proposed the conductive paste used for solar batteries (for example, referring to patent documentation 4) using unleaded tellurium system glass as principal component.Demonstrate: this conductive paste, be the paste of the tellurium system glass containing 0.1 ~ 10 weight portion relative to the electroconductive powder of 100 weight portions, this tellurium system glass is preferably following composition: containing wantonly more than a kind 5 ~ 60 (mol%), the zinc oxide 0 ~ 50 (mol%) in tellurium oxide 25 ~ 90 (mol%), tungsten oxide and molybdenum oxide, bismuth oxide 0 ~ 25 (mol%), aluminium oxide 0 ~ 25 (mol%).According to such conductive paste, be used in environmentally preferred crown glass, bond strength excellence can be obtained and can carry out well burning till through, that battery behavior is excellent solar cell.
In addition, as the example similarly employing unleaded tellurium system glass, once the conductive paste of following solar cell device was proposed, this paste employs tellurium system glass, described tellurium system glass, converts, containing tellurium oxide 30 ~ 80 (mol%), tungsten oxide 10 ~ 50 (mol%), bismuth oxide 5 ~ 25 (mol%) by oxide, the total content of these oxides is more than 80 (mol%) (for example, referring to patent documentations 5).According to this conductive paste, burn till connectivity and be promoted, therefore can obtain excellent electrical contact.
In addition, as another example, once proposed a kind of paste for use in electrode, this paste contains glass for electrode composition, metallic, resin binder and solvent, described glass for electrode composition contains silver, phosphorus, oxygen and not leaded in fact (for example, referring to patent documentation 6).This electrode paste is the paste of the sensitive surface electrode etc. for the formation of solar cell, if use crown glass, for tackling the paste that resistance increases.Preferred glass contains tellurium.As the preferred composition of glass for electrode, exemplified with: convert by oxide, Ag 2o is 5 ~ 60 % by weight, P 2o 5be 5 ~ 50 % by weight, V 2o 5be 0 ~ 50 % by weight, TeO 2be 0 ~ 30 % by weight, other oxide is 0 ~ 40 % by weight, and Ag 2o and V 2o 5add up to 30 ~ 86 % by weight, P 2o 5with TeO 2add up to 14 ~ 50 % by weight.Other oxide above-mentioned is BaO, WO 3, MoO 3, Fe 2o 3, MnO 2with ZnO etc.
But, comprise in the conductive paste of unleaded tellurium glass at these, excessively weak to the erosion of substrate, be therefore still difficult to fully reduce contact resistance.
At first technical literature
Patent documentation
Patent documentation 1: Japanese Laid-Open Patent Publication 59-033869 publication
Patent documentation 2: Japanese Unexamined Patent Publication 10-326522 publication
Patent documentation 3: Japanese Unexamined Patent Publication 2008-042095 publication
Patent documentation 4: Japanese Unexamined Patent Publication 2011-096747 publication
Patent documentation 5: Japan Patent No. 5011428 publication
Patent documentation 6: Japan is table 2012/020694 publication again
Patent documentation 7: Japanese Unexamined Patent Publication 2013-533188 publication
Patent documentation 8: Japanese Unexamined Patent Publication 2013-254726 publication
Summary of the invention
But, by burn till be formed through sensitive surface electrode time, in order to obtain the good ohmic contact of sensitive surface electrode, require the uniform erosion at silicon substrate interface, but the concavo-convex of erosion surface becomes violent when using lead glass as frit, that corroded weak when using unleaded tellurium glass, no matter therefore all can not get fully low contact resistance on the one hand.Because the lead in glass is necessary in the redox reaction of the Si with formation substrate, if therefore there is no it, be difficult to corrode substrate, but excessive erosion improves contact resistance on the contrary.
On the other hand, the scheme (for example, referring to patent documentation 7) using and comprise the electrode paste of the low-melting glass such as lead-tellurium glass, lead-tellurium-lithium glass was once proposed.While such, comprise glass that is plumbous and tellurium, erosion surface becomes level and smooth, and Ag increases to the meltage in the glassy layer of electrode-silicon interface, and therefore contact resistance reduces, and becomes and more easily guarantees ohmic contact.But, if erosion surface is formed uniformly, becomes level and smooth, although then electrical characteristics excellence has the tendency of bond strength step-down.About various glass, once proposed the scheme of adding the compounds such as zinc oxide in order to improve bond strength in electrode paste, but there is the problem exporting reduction with battery in the paste comprising these additives.
Moreover, using the paste comprising the frit of lead glass system by burning till in the through sensitive surface electrode formation carried out, except such scheme, also proposed the motion of various improvement contact resistances all the time.Such as, once a kind of conductive paste composition was proposed, said composition comprises metallic, inorganic reaction system material and organic solvent, and described inorganic reaction system material comprises the tellurium element (for example, referring to patent documentation 8) of leaded composition and 5 ~ 95 % by weight of 5 ~ 95 % by weight.This paste composite is to improve battery efficiency and to reduce for the purpose of contact resistance.Above-mentioned inorganic reaction system material is the material of the effect of the frit replaced in the past, is glass, pottery, at high temperature can generates the material etc. of matrix (matrix: matrix).Do not illustrate which kind of composition frit except also comprising containing except Pb and Te, but be considered to can comprise Mg, Ni, Te, W, Zn, Mg, Cd, Ce, Zr, Ti, Mn, Sn, Ru, Co, Fe, Cu, Cr as inorganic additive in paste.
In addition, as improving the technology that solar cell exports, having and being such as called as low doping concentration emitter (LightlyDopedEmitter; LDE) technology.LDE technology, the donor concentration of sensitive surface side that makes compared with the past reduces, and makes n layer thinning, and by using LDE substrate to form shallow emitter structure, surperficial recombination velocity reduces, therefore, it is possible to obtain more electric current, exports and improves.But in LDE technology, the result that the donor concentration as surface is lowered, the stop barrier existed between Ag-Si increases, is difficult to the problem of the ohmic contact guaranteeing sensitive surface electrode.In addition, because pn knot shoals, therefore also exist as by burn till through abundant destruction antireflection film and electrode do not invade pn tie depth of invasion control to become difficult problem.
The paste recorded in above-mentioned patent documentation 1 ~ 8, as mentioned above all when defining sensitive surface electrode, bond strength is still insufficient or contact resistance is high, requires further to improve.And, for employing the shallow emitter structure of LDE substrate all without any consideration, if they are applied to LDE substrate, then being more difficult to bond strength and electrical characteristics are had both, the high solar cell exported can not be obtained.Can think that this is caused by following reason.If want the appropriateness when forming sensitive surface electrode corrode substrate and obtain ohmic contact, then directly engaging of Ag and Si becomes many under the electrodes, and then recombination velocity uprises.When the existing substrate just high for recombination velocity originally, even if recombination velocity uprises under the electrodes, the impact of open-circuit voltage Voc is also little.On the other hand, in the solar cell employing LDE substrate, because recombination velocity is low, if therefore under the electrodes recombination velocity uprise, then the impact of open-circuit voltage Voc is large, and the reduction of the efficiency that easily changes and then export reduces.
The present invention for background and proposing with above-mentioned situation, its object is to provide and can form and electrode that contact resistance low high with the bond strength of substrate and also can obtain the solar battery cell that high solar cell sensitive surface paste for use in electrode, its manufacture method and the height exporting the solar cell of (high-output power) export when employing LDE substrate.
For reaching this object, the purport of the 1st invention is a kind of solar cell sensitive surface paste for use in electrode, it comprises electroconductive powder, frit and vehicle, described frit is made up of unleaded tellurium glass, this paste is on the face of by coating silicon substrate and process is burnt till in enforcement, through burning till through and forming the sensitive surface electrode of solar cell, this paste comprises: at least a kind of refractory metal among (a) tungsten, molybdenum and chromium; (b) leaded additive.
In addition, purport for the manufacture method reaching the solar cell sensitive surface paste for use in electrode of the 2nd invention of above-mentioned purpose is, comprise: the additive supporting procedures that (a) is leaded, this operation make leaded additive part or all support on the frit be made up of unleaded tellurium glass, described unleaded tellurium glass contains at least a kind of refractory metal among tungsten, molybdenum and chromium; B () mixed processes, electroconductive powder, described frit, described leaded additive and vehicle mix by this operation.
In addition, purport for the manufacture method reaching the solar cell sensitive surface paste for use in electrode of the 3rd invention of above-mentioned purpose is, comprise: (a) containing the additive supporting procedures of refractory metal, this operation make the additive of at least a kind of refractory metal among containing tungsten, molybdenum and chromium part or all support on the frit be made up of unleaded tellurium glass; (b) mixed processes, this operation is by electroconductive powder, described frit, the described additive containing refractory metal, leaded additive and vehicle mixing.
In addition, the purport for the 4th invention of reaching above-mentioned purpose is a kind of solar battery cell, its n on the face being formed at p-type silicon substrate +layer possesses antireflection film, and is provided with sensitive surface electrode by burning till through, described sensitive surface electrode is generated by the solar cell sensitive surface paste for use in electrode of described 1st invention.
According to described 1st invention, solar cell sensitive surface paste for use in electrode, comprise unleaded tellurium glass and be used as frit, and at least a kind of refractory metal comprised in paste among tungsten, molybdenum, chromium and leaded additive, this leaded additive and glass are added dividually, if therefore use this paste throughly to form sensitive surface electrode to silicon substrate by burning till, then can obtain the irregular erosion surface of appropriate tool, therefore can obtain the low and electrode that bond strength is high of contact resistance.Leaded additive (such as Pb contained in paste 3o 4), in the same manner as situation about containing as network former in glass, between itself and the silicon (Si) forming substrate, produce redox reaction.The SiO formed by redox reaction 2, being included in glass and being etched, therefore can obtain desirable aggressivity when burning till through.Now, the Pb be added as leaded additive dividually with glass, is contained in the situation in glass, brings uneven corrosion function compared to it.Therefore, in the coefficient part of Te and Pb, erosion surface becomes level and smooth, on the other hand, in the part that the corrosion function of Pb is strong, the concavo-convex of erosion surface becomes violent, therefore produce the moderately irregular erosion surface of tool as a whole, electrical characteristics and bond strength can be obtained as mentioned above simultaneously.And, use above-mentioned paste for use in electrode to define the solar cell of sensitive surface electrode, due to again in conjunction with suppressed, even therefore LDE substrate, also can obtain high output.If comprise refractory metal, then when forming sensitive surface electrode, can form refractory metal oxide skin(coating) at erosion surface, directly engaging of Ag and Si reduces.Its result, can think that the ratio that the electronics produced passes through from the part of the direct joint of Ag and Si reduces, because this ensure that contact resistance is lower, and again in conjunction with suppressed.Moreover in this application, " leaded additive " means lead or the lead compound of simple substance.
Moreover, in the viewpoint forming the coefficient part of Te and Pb unevenly, also can consider to use lead glass and Te compound on the contrary with formation of the present invention.But, if add tellurium in the conductive paste comprising lead glass, then because lead glass is higher than fusing point with tellurium glassy phase, therefore needing to improve firing temperature to make tellurium include in lead glass, therefore difficulty being become to rodent control.Particularly, if want the additive containing tellurium to be supported on lead glass with in advance aftermentioned leaded additive like that being supported in the same manner as the mode on tellurium glass, if then the vacation burning of low temperature just can not support Te compound, therefore there is the problem generating the high Pb-Te oxide of fusing point, softening point rising.Moreover in this application, " supporting " is no matter mean to adopt which kind of method to make other particle be fixed on frit particles surface.
Solar cell sensitive surface paste for use in electrode of the present invention as described above, be adapted to pass through the purposes burning till to be formed electrode, owing to having stable Ohm resistive, therefore the substrate that film resistor is low certainly needless to say, even if for high film resistor substrate, the such as LDE substrate of 80 ~ 120 (Ω/) left and right, also fully low contact resistance can be obtained.Therefore, making electrode material not invade pn knot by controlling to burn till through etc. condition, leakage current step-down (namely parallel resistance Rsh uprises) can be obtained, Fill factor FF does not reduce, current value greatly and the high solar cell of photoelectric conversion rate.
In addition, according to described 2nd invention, when manufacturing solar cell sensitive surface paste for use in electrode, in leaded additive supporting procedures, part or all making leaded additive supports on the frit be made up of unleaded tellurium glass, described unleaded tellurium glass contains at least a kind of refractory metal among tungsten, molybdenum and chromium, in mixed processes, by electroconductive powder, frit, leaded additive (comprising the leaded additive supported on frit) and vehicle being mixed, obtain solar cell sensitive surface paste for use in electrode.Therefore, when modulating conductive paste composition, to be mixed in vehicle by advance part or all of leaded additive being supported the state making them combine on frit, therefore use solar cell sensitive surface paste for use in electrode by burn till through form electrode time, uneven corrosion function can be obtained by the Pb be added dividually with glass, therefore produce the moderately irregular erosion surface of tool as a whole, electrical characteristics and bond strength can be obtained simultaneously.And can obtain the partially coefficient effect of Pb and Te further significantly, the result that the flatness as this part is improved, electrical characteristics improve further.Therefore, it is possible to obtain the further excellent and electrode that bond strength is fully high of electrical characteristics.And, refractory metal is owing to being contained in unleaded tellurium glass, together be present in unleaded tellurium glass with the lead compound be included in sintering process, therefore the effect suppressing in the substrate interface after erosion to combine again can be obtained further significantly, even if also output high further can be obtained for LDE substrate.
In addition, according to described 3rd invention, when manufacturing solar cell sensitive surface paste for use in electrode, in the additive supporting procedures containing refractory metal, make containing tungsten, part or all of the additive of at least a kind of refractory metal among molybdenum and chromium supports on the frit be made up of unleaded tellurium glass, in mixed processes, by electroconductive powder, frit, with the additive (comprising the additive containing refractory metal supported on frit) containing refractory metal, leaded additive, mix with vehicle, obtain solar cell sensitive surface paste for use in electrode thus.Therefore, use solar cell sensitive surface paste for use in electrode by burn till through form electrode time, Pb by being added dividually with glass obtains uneven corrosion function, therefore produces as a whole the moderately irregular erosion surface of tool, can obtain electrical characteristics and bond strength simultaneously.And, when modulating solar cell sensitive surface paste for use in electrode, to be mixed in vehicle by advance part or all of additive containing refractory metal being supported the state making them combine on frit, therefore support refractory metal on frit in sintering process easily and lead compound be together included in unleaded tellurium glass.Therefore, refractory metal is together present in unleaded tellurium glass with plumbous after sintering, therefore can obtain the effect suppressing in the substrate interface after erosion to combine again further significantly, even if also can obtain output high further for LDE substrate.
In addition, according to described 4th invention, the sensitive surface electrode of solar battery cell is formed by the solar cell sensitive surface paste for use in electrode of described 1st invention, and therefore this sensitive surface electrode comprises conductor composition; Unleaded tellurium glass; Plumbous; And, at least a kind of refractory metal among tungsten, molybdenum and chromium, therefore there is by tellurium glass and plumbous synergism the moderately irregular erosion surface of tool, there is electrical characteristics and bond strength simultaneously, and based on comprising refractory metal, the low and solar battery cell of high output of recombination velocity can be obtained.
At this, in described 1st invention, preferred described refractory metal is added dividually with the form of the additive containing refractory metal and described tellurium glass, and the described additive containing refractory metal comprises at least a kind among these refractory metals of tungsten, molybdenum and chromium.So, compared with being contained in the situation in tellurium glass with refractory metal, the bond strength of substrate and electrode improves.Can think, suppress the formation of the alloy of Sn and the Ag in solder due to refractory metal, therefore can improve the bond strength of electrode.Moreover the additive containing refractory metal is simple substance or the compound of refractory metal, as compound, in addition to an oxide, the ammonium salt or acetate etc. of oxyacid, oxyacid can be enumerated.
In addition, preferably part or all containing the additive of refractory metal described supports on described frit.Additive containing refractory metal together can be mixed in glass with electroconductive powder etc., if but support in advance on frit, then can obtain the effect suppressing in the substrate interface after erosion to combine again further significantly.The reason obtaining such effect is not yet determined, but can think owing to supporting the refractory metal on frit, is more easily together included in unleaded tellurium glass with lead compound when burning till through, generates appropriate oxidation film at erosion surface.When above-mentioned paste is modulated and tellurium glass add dividually in the mode containing the additive of refractory metal, think and lack the part of refractory metal owing to producing when substrate corrodes, the direct joint of Ag and Si relatively increases, and therefore recombination velocity uprises.Containing the supporting of additive of refractory metal, can adopt such as with described frit mixed be incorporated in the vacation implemented at the following temperature of 500 (DEG C) in oxidizing atmosphere burn process, mechanochemical reaction etc. carries out.When adopting false burning, preferably make containing a part for the additive of refractory metal condition remaining in the form of an oxide.
Moreover, " mechanochemical reaction " is the pulverizing-married operation of non-heated, such as the powder of handling object is put into possess in the container of rotor, impulsive force, compression stress, shearing force is made to act on each powder particle equably by making rotor high-speed rotate, utilize mechanical energy destroy crystal structure or cut off bonding state and make it activate, promote the method for solid phase reaction thus.According to mechanochemical reaction, heat is not applied to handling object thing, therefore also there is the advantage of the chemical reaction that can suppress unnecessary.The processing unit used in " chemical mechanical pulping ", possess the cylindrical shape such as extended to axle center general horizontal direction mixer and as mentioned above impulsive force etc. act on the rotor of the special shape of each particle equably, this rotor preferably can carry out the High Rotation Speed that such as peripheral speed is more than 50 (m/s).
In addition, part or all of preferred described leaded additive is supported on described frit.In addition, described 3rd invention, preferably includes leaded additive supporting procedures, this operation make described leaded additive part or all support on described frit.Leaded additive, together can be mixed in glass with electroconductive powder etc., if but support in advance on frit, then can obtain the partially coefficient effect of Pb and Te further significantly, electrical characteristics are extra-high further.Moreover, also can the whole of leaded additive be supported on frit, if but support its part, make leaded additive remaining in the form of an oxide, be formed as the state that there is leaded additive in electrode paste, then when burning till through, can present significantly further by the rodent inequality comprising leaded additive and bring, what can form electrical characteristics and bond strength takes into account more preferably electrode.
In addition, preferred described leaded additive by implementing vacation and burns with mixed being incorporated in oxidizing atmosphere of described frit and process and supported on this frit at the following temperature of 500 (DEG C).In addition, in described 2nd invention and the 3rd invention, described leaded additive supporting procedures is mixed by the powder of described frit with described leaded additive, in oxidizing atmosphere, implement false operation of burning process at the following temperature of 500 (DEG C).So, the part that easily can obtain leaded additive is supported the state on frit.Moreover, under temperature is burnt in above-mentioned vacation, a part for leaded additive is supported on frit, remainder is not supported on frit remaining as former state, if but false temperature of burning is more than 500 (DEG C), produces the chemical reaction of glass and leaded additive, generate Pb-Te oxide, therefore softening point easily rises.Therefore, preferably false temperature of burning controls at 500 (DEG C) below.
In addition, described leaded additive, also can mix with described frit, and adopts mechanochemical reaction to make its particle support particle surface in this frit.
In addition, preferably: described leaded additive, with by the PbO/ frit weight ratio of oxide conversion (that is: being converted into oxide) be 0.5 ~ 1.0 scope in ratio contained.Even if PbO/ glass is lower than 0.5 or more than 1.0, also can see and improve effect, if but PbO tails off, then relative to the electrode paste composition not adding PbO, rodent change diminishes, in addition, if PbO becomes many, then with compared with the situation in above-mentioned scope, the remarkable grow of aggressivity, improve effect all to diminish, be therefore more preferably above-mentioned scope.If be set in above-mentioned scope, then can obtain the fully high output counting more than 77 with FF value.
In addition, preferably: described refractory metal, by being converted into the value after oxide separately, with relative to frit except WO 3, MoO, Cr 2o 3the total quality G of composition in addition, (WO 3/ G)+2 (MoO 3/ G)+4Cr 2o 3/ G be 0.04 ~ 0.40 scope in ratio by containing at least a kind.If refractory metal is contained with ratio more than above-mentioned lower limit, then can obtain additive effect significantly further.In addition, if be below above-mentioned higher limit, then softening point when being included in glass is controlled as fully low value.Each of refractory metal, respectively to be converted into the value after oxide, relative to frit except WO 3, MoO, Cr 2o 3the total quality G of composition in addition, preferred A=WO 3/ G be 0.04 ~ 0.35 scope in, B=MoO 3/ G be 0.02 ~ 0.20 scope in, C=Cr 2o 3/ G is in the scope of 0.01 ~ 0.09, but when comprising multiple refractory metal, if with above-mentioned calculated value (A+2B+4C) be 0.04 ~ 0.40 scope in ratio contained, even if then also harmless lower than respective lower limit respectively.
Moreover, in the present invention, without particular limitation of the composition of unleaded tellurium glass, when using the glass of various composition, can enjoy by leaded additive and glass to be added to dividually in electrode paste and comprise the improvement effect that refractory metal brings in electrode paste.But, below enumerate an example of particularly preferred glass composition.
Such as, preferred described unleaded tellurium glass comprises the TeO being scaled 54 ~ 80 (mol%) by oxide 2, and the Li of 0.4 ~ 18 (mol%) 2o.If within the scope of these, then easily can obtain electrical characteristics further excellent, solar cell that such as FF value is more than 75 (%).
In addition, preferably unleaded tellurium glass comprises and is scaled 25 (mol%) Bi below by oxide 2o 3, 5 (mol%) CuO and 20 (mol%) SiO below below 2.If within the scope of these, then easily can obtain electrical characteristics further excellent, solar cell that such as FF value is more than 75 (%).
In addition, preferably unleaded further tellurium glass comprises and is scaled 6 (mol%) ZnO below, 6 (mol%) MgO below, 5 (mol%) Fe below by oxide 2o 3, 5 (mol%) NiO below, 18 (mol%) WO below 3, 16 (mol%) MoO below 3, 8 (mol%) Cr below 2o 3.If within the scope of these, then easily can obtain electrical characteristics further excellent, solar cell that such as FF value is more than 75 (%).
In addition, unleaded tellurium glass can suitably containing the composition beyond above-mentioned composition.Such as can enumerate example and be scaled 18 (mol%) B below by oxide 2o 3, 5 (mol%) Al below 2o 3, 12 (mol%) TiO below 2, 19 (mol%) P below 2o 5, 26 (mol%) V below 2o 5, 15 (mol%) BaO etc. below.
In addition, described leaded additive is not specially limited, and can use various leaded additives, can enumerate such as plumbous, lead oxide (such as PbO, Pb 3o 4), leaded alloy, leaded organic compound (レ ジ ネ ー ト; Resinate), plumbi nitras, ceruse, lead stearate, other leaded compound.
In addition, described leaded additive, can use the leaded additive of suitable shape of particle and particle diameter, the scope that such as preferable shape is aspherical, particle diameter is 1 ~ 5 (μm).If use such particle, then can obtain, with the good dispersiveness of frit, supporting and becoming easy.
In addition, preferred described electroconductive powder is Ag powder.Apply electroconductive powder contained in paste for use in electrode of the present invention not to be specially limited, can Au, Ag, Cu, Al etc. be enumerated.Wherein, the meltage that Ag can obtain significantly being existed by Te and bring increases effect, therefore particularly preferably as application of the present invention.
In addition, the average grain diameter (D50) of preferred described frit is in the scope of 0.3 ~ 10 (μm).If the average grain diameter of frit is too small, then when the burning till of electrode, fusing accelerates, and is therefore difficult to obtain sufficient electrical characteristics.If average grain diameter is more than 0.3 (μm), be then difficult to produce such problem, and owing to being difficult to condense, therefore can obtain dispersiveness good further when sticking with paste modulation.In addition, when the average grain diameter of frit is greater than the average grain diameter of electroconductive powder significantly, the dispersiveness of powder mass reduces, if but be 10 (μm) below, dispersiveness good further can be obtained.And, the further meltbility of glass can be obtained.
Moreover the average grain diameter of above-mentioned frit is the value adopting air permeability method to record.Air permeability method refers to by fluid (such as air) permeability relative to powder layer to measure the method for the specific area of powder.What become the basis of this assay method is represent the wetted surface area of all particles forming powder layer, Kang Caini Kaman (Kozeny-Carmann) formula with the flow velocity of fluid passed through from this layer and the relation of Pressure Drop, measure the flow velocity relative to the powder layer of filling under the condition determined according to device and Pressure Drop, obtain the specific area of sample.The gap of filled powder particle is considered as pore by the method, obtains the wetted surface area flowing of air being formed to the population of resistance, the value that display is less than the specific area adopting gas adsorption method to obtain usually.The average grain diameter assuming powder particle can be calculated by calculated above-mentioned specific area and particle density.
In addition, the silver powder in the scope of preferred described electroconductive powder to be average grain diameter (D50) be 0.3 ~ 3.0 (μm).As electroconductive powder, also can copper powders, nickel by powder etc. be used, but in order to obtain high conductivity, most preferably silver powder.In addition, if the average grain diameter of silver powder be 3.0 (μm) below, then can obtain better dispersiveness, the conductivity therefore can more increased.In addition, if be more than 0.3 (μm), then condense suppressed, better dispersiveness can be obtained.Moreover the remarkable high price of the silver powder lower than 0.3 (μm), is therefore also preferably more than 0.3 (μm) from manufacturing cost aspect.In addition, if the average grain diameter of electroconductive powder, frit be all 3.0 (μm) below, then when with thread pattern printing formed electrode also have be difficult to occur blocking advantage.
Moreover described silver powder is not specially limited, graph thinning can both be realized under the state guaranteeing conductivity when using the powder of any shapes such as spherical, flakey.But when using spherical powder, printing is excellent, and the filling rate of the silver powder in coated film uprises, therefore complement each other with using the high silver of conductivity, with use other shapes such as flakey silver powder situation compared with, the conductance of the electrode generated by this coated film uprises.Therefore, it is possible to make line width thinner under the state guaranteeing required conductivity, therefore particularly preferably.
In addition, the viscosity of preferred described solar cell sensitive surface paste for use in electrode under 25 (DEG C)-20 (rpm) be 150 ~ 250 (Pas) scope in, ratio of viscosities (i.e. [viscosity under 10 (rpm)]/[viscosity under 100 (rpm)]) is 3 ~ 8.By using the paste with such viscosity characteristics, the lowering viscousity and through screen cloth well when nip drum, its through after return to high viscosity, the expansion of printing width can be suppressed, therefore can easy through sieve, do not occur block etc. guarantee printing state under easily obtain thread pattern.The scope of the viscosity of electrode paste more preferably 180 ~ 240 (Pas), ratio of viscosities more preferably 4.5 ~ 7.5 scope.In addition, want design live width to be 100 (μm) graph thinning below, preferred viscosities ratio is 5 ~ 7.
Moreover, even if also to improve by such as the emulsion thickness of plate making being thickened, by tension force, wire diameter to be attenuated thus film thickness is thickened to make live width attenuate by enlarged openings footpath etc. also can guarantee sectional area.But if thickened by emulsion thickness, version separation property is deteriorated, and therefore can not get the stability of printed patterns shape.In addition, if improve tension force or make wire diameter attenuate, then screen cloth easily extends, and therefore exists and is difficult to guarantee size and dimension precision and the problem of the durability of plate making reduction.And owing to arranging with thick width, therefore thickened by thickness and unnecessary bus (busbar: busbar) also can be made thickening, the waste that therefore also there is material becomes many problems.
In addition, preferred described solar cell sensitive surface paste for use in electrode contains described electroconductive powder with the ratio in the scope of 64 ~ 90 weight portions, contains described vehicle with the ratio in the scope of 3 ~ 20 weight portions.If so, then the electrode paste that easily can form the electrode that printing is good, line width is thin, conductivity is high can be obtained.
In addition, to be 0.1 ~ 10 weight portion relative to the described electroconductive powder of 100 weight portions, scope contains described frit to preferred described solar cell sensitive surface paste for use in electrode.If containing more than 0.1 weight portion, sufficient aggressivity (burning till connectivity) can be obtained, therefore can obtain good ohmic contact.In addition, if control below 10 weight portions, be difficult to form insulating barrier, therefore can obtain sufficient conductivity.0.5 ~ 8 weight portion is more preferably, more preferably 0.5 ~ 7 weight portion relative to the amount of glass of the electroconductive powder of 100 weight portions.
In addition, the paste for use in electrode of the present application also can be used for backplate and is formed, such as, when be applied to silver be the paste for use in electrode of conductive compositions, the effect of the bond strength that can be improved by rodent inequality as described above.In addition, when be applied to aluminium be the paste for use in electrode of conductive compositions, because the additive that softening point is low and leaded supports around glass, therefore just moderately react with Al powder from low firing temperature, the uniformity of BSF layer improves, and therefore electrical characteristics improve.But, the paste for use in electrode of the present application, due to can control well as mentioned above by burn till through form electrode time the precipitation of silver, therefore can be particularly suitable for for sensitive surface electrode.
Accompanying drawing explanation
Fig. 1 represents that the paste for use in electrode of one embodiment of the invention is applied to the schematic diagram of the cross section structure of the solar cell of the formation of sensitive surface electrode.
Fig. 2 is the figure of an example of the sensitive surface electrode pattern of the solar cell representing Fig. 1.
Description of reference numerals
10: solar cell, 12: solar module, 14: encapsulant, 16: watch crystal, 18: diaphragm, 20: silicon substrate, 22:n layers, 24:p +layer, 26: antireflection film, 28: sensitive surface electrode, 30: backplate, 32: sensitive surface, 34: whole electrode, 36: band electrode, 38: solder band
Embodiment
Below, with reference to accompanying drawing, one embodiment of the invention are described in detail.Moreover accompanying drawing is suitably simplified or is out of shape below in an example, the size ratio of each several part and shape etc. are not necessarily correctly described.
Fig. 1 is the figure of the cross section structure of the solar module 12 schematically showing the silicon system solar cell 10 possessing the conductive composition applying one embodiment of the invention.In FIG, solar module 12 possess above-mentioned solar cell 10, the encapsulant 14 sealed, be arranged at the watch crystal 16 on encapsulant 14 and the diaphragm (i.e. backboard) 18 in order to arrange from rear side protection solar cell 10 and encapsulant 14 in sensitive surface side.Above-mentioned encapsulant 14 is such as the encapsulant formed by EVA, is suitably combined with crosslinking agent, ultra-violet absorber, splice protection agent etc. to make having sufficient weatherability.In addition; said protection film 18 is formed by such as fluororesin, PETG (PET) resin or is formed by following film etc.; described film is fitted by the resin molding formed by PET, EVA etc. of multi-disc, and this diaphragm possesses high weatherability, water vapor barrier property etc.
In addition, above-mentioned solar cell 10 possesses such as the silicon substrate 20 of p-type poly semiconductor, the n layer 22 being formed at the top and bottom of this substrate respectively and p +layer 24, be formed at antireflection film 26 and the sensitive surface electrode 28 on this n layer 22 and be formed at this p +backplate 30 on layer 24.The gauge of above-mentioned silicon substrate 20 is such as 100 ~ 200 (μm) left and right.
Above-mentioned n layer 22 and p +layer 24, is arranged by the layer forming impurity concentration high in the top and bottom of silicon substrate 20, the gauge of this high concentration layer, and n layer 22 is such as 70 ~ 100 (nm) left and right, p +layer 24 is such as 500 (nm) left and right.N layer 22 is 100 ~ 200 (nm) left and right in general silicon system solar cell, but employs the LDE substrate thinner than it in the present embodiment, forms the structure being called as shallow emitter.Moreover impurity contained in n layer 22 is alloy, the such as phosphorus (P) of N-shaped, p +impurity contained in layer 24 is alloy, such as aluminium (Al), the boron (B) of p-type.
In addition, described antireflection film 26 is by such as silicon nitride Si 3n 4deng formed film, by with about 1/4 of such as visible wavelength optical thickness, such as 80 (nm) left and right arrange, be configured to 10 (%) below, such as 2 (%) left and right extremely low reflectivity.
In addition, described sensitive surface electrode 28 is formed by the thick film conductor of such as the same gauge, as shown in Figure 2, at roughly whole of sensitive surface 32, arranges to form the flat shape of the pectination with many thin thread parts.
Above-mentioned thick film conductor, formed by thick film silver, described thick film silver comprises Ag, glass, leaded additive (plumbous or lead compound) and the additive (simple substance of W, Mo, Cr or its compound) containing refractory metal, relative to the Ag of 100 weight portions, glass is contained with the ratio in the scope in 0.1 ~ 10 weight portion, about such as 1.6 weight portions, contain leaded additive with the ratio in the scope of 0.1 ~ 10 weight portion, about such as 1.1 weight portions, containing refractory metal additive when for when W to press WO 3ratio in the scope being scaled 0.005 ~ 4 weight portion, about such as 0.2 weight portion contains, when for containing with the ratio be scaled in MoO in the scope of 0.002 ~ 2 weight portion, about such as 0.1 weight portion when Mo, when for when Cr to press Cr 2o 3the ratio be scaled in the scope of 0.001 ~ 1 weight portion, about such as 0.05 weight portion contains.In addition, leaded additive and containing the additive of refractory metal relative to the ratio of glass, press oxide conversion respectively, in the scope for PbO/ glass=0.5 ~ 1.0, about such as 1.1/1.6=0.7, WO 3the scope of/glass=0.04 ~ 0.35 is interior, about such as 0.18/1.6=0.11, MoO 3the scope of/glass=0.02 ~ 0.2 is interior, about such as 0.1/1.6=0.06, Cr 2o 3the scope of/glass=0.01 ~ 0.09 is interior, about such as 0.07/1.6=0.04.
Above-mentioned leaded additive is with glass dividually by the material contained, such as, according to the simple substance added when forming electrode or compound containing Pb, Pb 3o 4, Pb (NO 3) 2, PbO, PbCO 3deng.
In addition, the described additive containing refractory metal is also with glass dividually by the material contained, such as, according to the simple substance added when forming electrode or compound containing WO 3, MoO 3, Cr 2o 3, (NH 4) 10w 12o 4, H 2wO 4deng.
In addition, described glass is that such as Te plays a role as network former and do not contain unleaded tellurium glass, the such as TeO of Pb 2-Li 2o-Bi 2o 3system lead-free glass.Its composition without particular limitation of, the glass of the suitable composition of the electrode of general solar cell can be used.This crown glass, preferably comprises CuO and SiO except above-mentioned main component 2, can ZnO, MgO, Fe be comprised 2o 3, NiO.In addition, described refractory metal (WO 3, MoO 3, Cr 2o 3) also can be contained in glass.B can be comprised further 2o 3, Al 2o 3, TiO 2, P 2o 5, V 2o 5, BaO etc.
In addition, the gauge of above-mentioned conductive layer be such as 10 ~ 25 (μm) scope in, such as 15 (μm) left and right, each width dimensions of thin thread part be such as 35 ~ 80 (μm) scope in, such as 45 (μm) left and right, possess fully high conductivity.
In addition, described backplate 30 is made up of whole electrode 34 and band electrode 36, and described whole electrode 34 is at p +on layer 24, roughly whole ground coating take aluminium as the electrode that the thick-film material of conductor composition is formed, and described band electrode 36 is the electrodes be made up of thick film silver formed with band shape coating on this whole electrode 34.This band electrode 36 is in order to arrange in the solderings such as solder band 38, wire overleaf electrode 30.Described sensitive surface electrode 28 is deposited with solder band 38 in the same manner as rear side.
Sensitive surface electrode 28 as described above, is use the paste for use in electrode comprising such as conductor powder, frit, leaded additive, additive, vehicle and solvent containing refractory metal, and adopts the through method of burning till known to be formed.Leaded additive and can former state mixing with powder containing the additive of refractory metal, but also can be mixed by the state supported on frit with part or all.Below an example of the manufacture method comprising the solar cell 10 forming sensitive surface electrode is described.
First, above-mentioned frit is made.Prepare the lithium carbonate Li as Li source respectively 2cO 3, as the silicon dioxide SiO in Si source 2, the CuO as Cu source, the ZnO as Zn source, Bi as Bi source 2o 3, as the TeO in Te source 2, carry out weighing, concocting the glass composition making to become desired.Dropped in crucible, melting 30 minutes ~ 1 hours at the temperature in the scope of 900 ~ 1200 (DEG C) corresponding to composition, makes its vitrifying by chilling.The suitable reducing mechanism such as planetary mill, ball mill is used to pulverize this glass.Grinding time is 1 ~ 8 hours, and the average grain diameter (D50) after pulverizing is such as 0.3 ~ 10 (μm) left and right.Moreover the average grain diameter of above-mentioned glass powder adopts air permeability method to calculate.
In addition, such as Pb is prepared as leaded additive 3o 4powder.Pb 3o 4powder use such as average grain diameter be 2 (μm) left and right commercially available powder.
In addition, as the additive containing refractory metal, such as WO is prepared 3powder, MoO 3powder, Cr 2o 3powder, (NH 4) 10w 12o 4powder, H 2wO 4powder, (NH 4) 2moO 4powder, Cr 3(OH) 2(OCOCH 3) 7powder etc.These substance migration such as average grain diameter is the commercially available powder of 0.5 (μm) left and right.In the following description, to use WO 3situation as the additive containing refractory metal is example.
Then, ready glass powder, Pb will be distinguished like this 3o 4powder and WO 3powder mixes, and is placed in such as setter (setter) etc., implements falsely to burn process in oxidizing atmosphere at the temperature of 300 ~ 500 (DEG C) left and right.False treatment temperature of burning is set to than glass powder and Pb 3o 4powder and/or WO 3the temperature that powder sintered temperature is fully low, can make unreacted Pb thus 3o 4and WO 3part or all is supported the powder on glass powder to obtain it under residual state.
Moreover, above-mentionedly support process, also can adopt mechanochemical reaction to replace and falsely burn process.For the processing unit of mechanochemical reaction, the ノ PVC Le タ NOB-130 etc. having such as ホ ソ カ ワ ミ Network ロ Application (strain) to make, but without particular limitation of, suitable device can be used.The operating condition of composited processing when use NOB-130, such as blade rotational speed is set to 2500 (rpm), processing time to be set in the scope of 10 ~ 20 minutes, such as 10 minutes, living load is set in the scope of 4.5 ~ 5.0 (kW), such as 4.7 (kW).The gap of 3 (mm) left and right is provided with between blade and inner surface of container, operate if material is put in container, then glass powder, leaded additive powder and the additive powder containing refractory metal are mixed, and be applied in mechanicals efforts, additive powder leaded thus and be securely fixed in glass powder surface with the thickness of monolayer containing the additive powder of refractory metal, obtains compound particle.The compound particle produced like this can be used to replace frit.
In addition, as conductor powder, prepare the commercially available spherical silver powder that scope is interior, such as average grain diameter is 1.6 (μm) left and right that such as average grain diameter (D50) is 0.3 ~ 3.0 (μm).By using the silver powder that such average grain diameter is fully little, the filling rate of the silver powder in coated film can be improved and then improve the conductance of conductor.In addition, described vehicle makes organic bond be dissolved in organic solvent and modulate, and can use such as butyl carbitol acetate, can use such as ethyl cellulose as organic bond as organic solvent.The ratio of the ethyl cellulose in vehicle is such as about 15 (% by weight).In addition, the solvent added dividually with vehicle is such as butyl carbitol acetate.That is, although be not limited thereto, can be with for the identical solvent of the solvent in vehicle.This solvent is added for the object of the viscosity adjustment of sticking with paste.
Prepare above paste raw material respectively, such as interior with the scope of 77 ~ 90 (% by weight), such as 89 (% by weight) ratio weighs conductor powder, interior, such as 1.4 (% by weight) the ratio of scope with 0.1 ~ 10 (% by weight) weighs frit, interior, such as 1.0 (% by weight) the ratio of scope with 0.1 ~ 10 (% by weight) weighs leaded additive, and interior, such as 0.15 (% by weight) the ratio of the scope with 0.004 ~ 3.5 (% by weight) weighs additive, such as WO containing refractory metal 3interior, such as 5.0 (% by weight) the ratio of scope with 3 ~ 14 (% by weight) weighs vehicle, interior, such as 3.6 (% by weight) the ratio of scope with 2 ~ 5 (% by weight) weighs solvent, after using the mixing such as mixer, such as three-roll mill is utilized to carry out dispersion treatment.Obtain described paste for use in electrode thus.In this embodiment, PbO/ glass=0.7, WO 3/ glass=0.11.
Modulator electrode is stuck with paste as described above, on the other hand, on suitable silicon substrate, and the method diffusion adopting such as thermal diffusion method, ion implantation etc. to know or implanted dopant and form described n layer 22 and p +layer 24, produces described silicon substrate 20 thus.Then, thereon, the suitable methods such as such as PE-CVD (plasma CVD) are adopted to form silicon nitride film to arrange described antireflection film 26.
Then, with the pattern shown in described Fig. 2 by described paste for use in electrode silk screen printing on above-mentioned antireflection film 26.It is dry under such as 150 (DEG C), and then implement to burn till process at temperature in near-infrared stove in the scope of 700 ~ 900 (DEG C).Thus, in this sintering process, antireflection film 26 melts by the glass ingredient in paste for use in electrode, this paste for use in electrode destroys antireflection film 26, therefore can obtain the electrical contact of conductor composition in paste for use in electrode i.e. silver and n layer 22, as described in obtain the ohmic contact of silicon substrate 20 and sensitive surface electrode 28 as shown in Figure 1.Sensitive surface electrode 28 is formed in this wise.
Moreover described backplate 30 can be formed after above-mentioned operation, but also can side by side burn till with sensitive surface electrode 28 and be formed.When forming backplate 30, at the whole back side of above-mentioned silicon substrate 20, adopting silk screen print method etc. to be coated with such as aluminium and sticking with paste, and implementing to burn till process, forming described whole the electrode 34 be made up of aluminium thick film thus.And then, be zonally coated with described paste for use in electrode by adopting silk screen print method on the surface of this whole electrode 34 and implement to burn till process, forming described band electrode 36.Thus, formed by cover the whole back side whole electrode 34 and in the part on its surface with the backplate 30 that formed of band electrode 36 that band shape is arranged, obtain described solar cell 10.In above-mentioned operation, when manufacturing by burning till simultaneously, before the burning till of sensitive surface electrode 28, implement printing treatment.
The solar cell 10 of the present embodiment, employing is burnt till through method and is provided with sensitive surface electrode 28 as described above, but comprises unleaded tellurium glass, leaded additive and additive (the such as WO containing refractory metal because this sensitive surface electrode 28 uses 3) thick film silver stick with paste and formed by burning till through, therefore due to the existence of Te, Ag increases to the meltage in glass, and Pb and W and glass are added dividually, the moderately irregular erosion surface of tool can be obtained thus, therefore can obtain ohmic contact well, electrical characteristics excellence and the high solar cell 10 of bond strength can be obtained.
Below, illustrate glass composition, leaded additive amount, the result of carrying out various change containing kind and amount, the Composite method etc. of the additive of refractory metal and evaluating.In following table 1, table 2, employ following glass, described glass is for TeO 2-Li 2o-Bi 2o 3-CuO-SiO 2be glass, the ratio of each composition is carried out various change, and comprise PbO, WO as the glass ingredient added 3, MoO 3, Cr 2o 3, ZnO, MgO, Fe 2o 3, the glass of 1 ~ 2 kind among NiO.In the evaluation shown in table 1, table 2, except illustrating especially, PbO/ tellurium glass ratio is set to 0.7, by glass and leaded additive and burn temperature containing the vacation of the additive of refractory metal and be set to 360 (DEG C), implement to support process, modulated paste.Other condition do not expressed is all identical, as illustrated in previous building methods.Each sample is all stick with paste according to the modulation of above-mentioned manufacturing process, forms sensitive surface electrode 28 and manufactures solar cell 10, measuring it and export and obtained FF value.In addition, solder band is engaged with sensitive surface electrode 28, have rated bond strength.The output of solar cell measures based on the commercially available solar simulator of use the FF value obtained and evaluates, and bond strength uses commercially available cupping machine to evaluate." non-LDE " is the use of the sample of the thick substrate in the past of n layer 22, " LDE " is the use of the sample of the LDE substrate same with the substrate 20 of embodiment, evaluation result FF value being shown respectively and determining based on this value, by FF value be more than 76 be designated as "○" (i.e. embodiment), be less than 75 be designated as "×" (i.e. comparative example) by FF value.FF value is the judgement whether obtaining good ohmic contact, if usually the FF value of solar cell is more than 70, is believed to use, but certainly more high better, in the present embodiment, by FF value be more than 76 be judged to qualified.The evaluation of non-LDE substrate is carried out for following object: confirm if the paste of the present embodiment, even if be then applied to LDE substrate also can obtain good characteristic in the same manner as the situation of non-LDE substrate.In addition, in " bond strength " hurdle, show the intensity determined and the result judged based on this intensity, be designated as " △ " (slightly poor but still qualified) by being designated as "○" (namely good) more than 3 (N), by more than 2 (N) lower than 2.8 (N), "×" (i.e. undercapacity) will be designated as lower than 2 (N).
Table 1
Table 2
In table 1 above, No.1 ~ 29 are at SiO 2be 14.0 (mol%), Li 2o is 11.4 (mol%), TeO 2be 68.9 (mol%), Bi 2o 3under the glass composition of to be 4.4 (mol%), CuO be 1.3 (mol%), have studied the example of the weight ratio of additive and glass.No.1 ~ 6 are WO 3/ amount of glass is that the scope of 0 ~ 0.45 is have rated the example of characteristic, WO 3/ amount of glass is No.2 ~ 5 of the scope of 0.04 ~ 0.35, even obtain LDE also in the same manner as non-LDE, FF value is high, be 78 ~ 79, and bond strength is also high is the result of 3.1 ~ 3.3 (N).On the other hand, WO is not added 3no.1, although being 77 for FF value during non-LDE is high, being 75 for FF value during LDE.Moreover bond strength is 2.3 (N), in allowed band.In addition, WO 3/ amount of glass is the No.6 of 0.45, and FF value when non-LDE, LDE is all less than 75, and bond strength is also the low value of 1.5 (N).
In addition, No.7 ~ 11 are by WO 3/ amount of glass is set to the steady state value of 0.11, PbO/ amount of glass is that the scope of 0.40 ~ 1.10 is have rated the example of characteristic, PbO/ amount of glass is No.8 ~ 10 of the scope of 0.50 ~ 1.00, FF value when obtaining non-LDE, LDE is all high, be 77 ~ 79, bond strength is also high is the result of 3.2 ~ 3.4 (N).On the other hand, PbO/ amount of glass be 0.40 No.7 and be 1.10 No.11, FF value when non-LDE, LDE is all less than 75.
In addition, No.12 ~ 16 are MoO 3/ amount of glass is that the scope of 0.02 ~ 0.35 is have rated the example of characteristic, MoO 3/ amount of glass is 0.02 ~ 0.20 ([2 × MoO 3/ amount of glass] be 0.04 ~ 0.40) No.12 ~ 15 of the scope of (same scaled value being called " 2 times of values " below), FF value when obtaining non-LDE, LDE is all high, be 78 ~ 79, bond strength is also high is the result of 3.0 ~ 3.2 (N).On the other hand, MoO 3/ amount of glass is the No.16 of 0.35 (2 times of values are 0.70), and FF value when non-LDE, LDE is all 75, and bond strength is 1.4 (N), also insufficient.
In addition, No.17 ~ 21 are Cr 2o 3/ amount of glass is that the scope of 0.01 ~ 0.17 is have rated the example of characteristic, Cr 2o 3/ amount of glass is 0.01 ~ 0.09 ([4 × Cr 2o 3/ amount of glass] be 0.04 ~ 0.36) No.17 ~ 20 of the scope of (same scaled value being called " 4 times of values " below), FF value when obtaining non-LDE, LDE is all high, be 78 ~ 79, bond strength is also high is the result of 2.8 ~ 3.2 (N).On the other hand, Cr 2o 3/ amount of glass is the No.21 of 0.17 (4 times of values are 0.68), and FF value when non-LDE, LDE is all less than 75, and bond strength is 1.3 (N), also insufficient.
In addition, simultaneously No.22 ~ 29 with the addition of 2 ~ 3 kinds of examples containing the additive powder of refractory metal.The refractory metal of each data relative to the weight ratio of glass, the WO of No.22 3, Cr 2o 3be respectively 0.03,0.005 (WO 3/ amount of glass+[4 × Cr 2o 3/ amount of glass]=0.05), the WO of No.23 3, Cr 2o 3be respectively 0.11,0.03 (WO 3/ amount of glass+[4 × Cr 2o 3/ amount of glass]=0.23), the WO of No.24 3, Cr 2o 3be respectively 0.15,0.05 (WO 3/ amount of glass+[4 × Cr 2o 3/ amount of glass]=0.35), the WO of No.25 3, Cr 2o 3be respectively 0.22,0.08 (WO 3/ amount of glass+[4 × Cr 2o 3/ amount of glass]=0.54), the WO of No.26 3, MoO 3, Cr 2o 3be respectively 0.02,0.01,0.005 (WO 3/ amount of glass+[2 × MoO 3/ amount of glass]+[4 × Cr 2o 3/ amount of glass]=0.06), the WO of No.27 3, MoO 3, Cr 2o 3be respectively 0.11,0.02,0.01 (WO 3/ amount of glass+[2 × MoO 3/ amount of glass]+[4 × Cr 2o 3/ amount of glass]=0.19), the WO of No.28 3, MoO 3, Cr 2o 3be respectively 0.11,0.06,0.03 (WO 3/ amount of glass+[2 × MoO 3/ amount of glass]+[4 × Cr 2o 3/ amount of glass]=0.35), the WO of No.29 3, MoO 3, Cr 2o 3be respectively 0.12,0.08,0.04 (WO 3/ amount of glass+[2 × MoO 3/ amount of glass]+[4 × Cr 2o 3/ amount of glass]=0.44).
As above state shown in evaluation result, WO 3/ amount of glass+[2 × MoO 3/ amount of glass]+[4 × Cr 2o 3/ amount of glass] No.22 ~ 24 of value in the scope of 0.05 ~ 0.35,26 ~ 28, FF value when obtaining non-LDE, LDE is all high, be 78 ~ 79, bond strength also fully high, be the result of 3.1 ~ 3.3 (N).Above-mentioned calculated value be 0.54 No.25, be 0.44 No.29, FF value when being non-LDE, LDE is all low, be 72 ~ 74, bond strength also low, be the result of 1.3 ~ 1.4 (N).According to this evaluation result, when comprising multiple kind at the same time, even if WO 3, MoO 3, Cr 2o 3each weight ratio relative to glass, WO 3low is about 0.02, MoO 3low is about 0.01, Cr 2o 3low when being about 0.005, as long as above-mentioned calculated value is more than 0.05, output characteristic and all excellent solar cell 10 of bond strength just can be obtained.Moreover, in the data shown by No.22 ~ 29, the scope obtaining the calculated value of good result is 0.05 ~ 0.35, but only comprising the described No.2 of a kind of refractory metal, No.12, in No.17 etc., above-mentioned calculated value is 0.04, obtain good result, at No.15, in No.20, above-mentioned calculated value is 0.36 ~ 0.40, obtain good result, that obtain insufficient result is No.6, the calculated value of No.16 etc. is the example of more than 0.45, if contrasted with this situation, then think that it is appropriate for can obtaining good result when calculated value is the scope of 0.04 ~ 0.40.
According to the evaluation result of above-mentioned No.1 ~ 29, be scope, the WO of 0.50 ~ 1.00 in PbO/ amount of glass 3/ amount of glass is scope, the MoO of 0.04 ~ 0.35 3/ amount of glass is scope, the Cr of 0.02 ~ 0.20 2o 3/ amount of glass is scope, the WO of 0.01 ~ 0.09 3/ amount of glass+[2 × MoO 3/ amount of glass]+[4 × Cr 2o 3/ amount of glass] following paste for use in electrode can be obtained when being the scope of 0.04 ~ 0.40, described paste for use in electrode is the paste for use in electrode that can obtain all excellent solar cell 10 of output characteristic and bond strength, confirm in addition: if at least total amount relative to the weight ratio of glass be until 0.14 scope, even if also obtain same effect when then adding the multiple additive powder containing refractory metal at the same time.
In addition, No.30 ~ 44 are the use of the example that the glass comprising refractory metal replaces the additive powder added containing refractory metal.Moreover, when comprising refractory metal in glass, " weight ratio relative to glass " represents the value obtained by [quality of the refractory metal oxide in glass]/[the total quality of the composition except refractory metal oxide in glass].In addition, glass forms, and based on the glass used in described No.1 ~ 29, for obtaining the glass of same proterties, have adjusted SiO according to the component amount added 2, Li 2o, TeO 2, Bi 2o 3, CuO each component amount.No.30 ~ 33 are for employing containing WO 3the evaluation result of glass.WO is contained in glass with the scope of 2.3 ~ 17.8 (mol%) (with the mass ratio range relative to glass, being 0.04 ~ 0.35) 3no.30 ~ 32, FF value when obtaining non-LDE, LDE is all high, be 78 ~ 79, bond strength is fully high, be the result of 2.4 ~ 2.5 (N).On the other hand, with 21.6 (mol%) (with the mass ratio range relative to glass, being 0.45) containing WO 3no.33 in, make FF value when non-LDE, LDE be all less than 75, bond strength is also low is the result of 1.3 (N).
In addition, No.34 ~ 37 are for employing containing MoO 3the evaluation result of glass.(with the mass ratio range relative to glass, be 0.02 ~ 0.20 with 2.3 ~ 15.6 (mol%) in glass; 2 times of values are 0.04 ~ 0.40) scope contain MoO 3no.34 ~ 36, FF value when obtaining non-LDE, LDE is all high, be 78 ~ 79, bond strength is fully high, be the result of 2.3 ~ 2.5 (N).On the other hand, (with the mass ratio range relative to glass, be 0.35 with 22.9 (mol%); 2 times of values are 0.70) containing MoO 3no.37, FF value when being non-LDE, LDE is all less than 75, and bond strength is also low is the result of 1.3 (N).
In addition, No.38 ~ 41 are for employing containing Cr 2o 3the evaluation result of glass.(with the mass ratio range relative to glass, be 0.01 ~ 0.09 with 0.8 ~ 7.3 (mol%) in glass; 4 times of values are 0.04 ~ 0.36) scope contain Cr 2o 3no.38 ~ 40, FF value when obtaining non-LDE, LDE is all high, be 77 ~ 78, bond strength is fully high, be the result of 2.3 ~ 2.4 (N).On the other hand, (with the mass ratio range relative to glass, be 0.17 with 13.0 (mol%); 4 times of values are 0.68) containing Cr 2o 3no.41, FF value when being non-LDE, LDE is all 75, and bond strength is also low is the result of 1.4 (N).
In addition, No.42 ~ 44 are for employing the evaluation result of the glass containing any one metal in PbO and refractory metal.Evaluate in the scope that PbO amount is 29.6 ~ 30.6 (mol%), although FF value when being obtained for non-LDE, LDE is all high, be the result of 78 ~ 79, the result of bond strength to be low be 1.7 ~ 1.8 (N).
According to the results verification of above-mentioned No.30 ~ 44 to following situation: if use the glass containing refractory metal, namely use and contain WO with 17.8 (mol%) scope below respectively 3, contain MoO with 15.6 (mol%) scope below 3, contain Cr with 7.3 (mol%) scope below 2o 3(separately with the mass ratio range relative to glass, be less than 0.35, less than 0.20, less than 0.09) glass, and leaded additive is added in paste, even if then do not add the additive containing refractory metal, also the solar cell exported and bond strength is all excellent can be obtained, but when replacing when using the glass containing lead adding leaded additive in paste, though high output can be obtained, can not bond strength be obtained.That is, unleaded tellurium glass must be used and add leaded additive in paste.In addition, if with the Comparative result of No.1 ~ 29, then can say: compared with being contained in glass with refractory metal, refractory metal adds in paste can improve bond strength, therefore preferably.
In addition, No.45 ~ 69 of table 2 are adding leaded additive and the additive (WO containing refractory metal in sticking with paste 3) make PbO/ amount of glass become 0.70, WO 3under/amount of glass becomes the mediation specification of 0.11, have studied the example of glass composition.No.45 ~ 50 have studied SiO 2amount and TeO 2the example of amount, at SiO 2be 0 ~ 22.5 (mol%), Li 2o is 10.3 ~ 15.6 (mol%), TeO 2be 57.4 ~ 82.0 (mol%), Bi 2o 3be 4.0 ~ 6.0 (mol%), CuO be in the scope of 1.2 ~ 1.8 (mol%), at SiO 2be 0 ~ 19.6 (mol%) and TeO 2be 60.6 ~ 80.1 (mol%) scope in FF value when obtaining non-LDE, LDE be all 77 ~ 78, bond strength is the good result of 3.1 ~ 3.3 (N).On the other hand, at SiO 2be No.48, TeO of 22.5 (mol%) 2be in the No.45,50 of 82.0 (mol%), 57.4 (mol%), although bond strength fully, be 3.1 ~ 3.3 (N), FF value when non-LDE, LDE is all less than 75, is insufficient result.
In addition, No.51 ~ 54 are for have studied Li 2the evaluation result of O amount.At SiO 2be 12.4 ~ 15.9 (mol%), Li 2o is 0 ~ 22.0 (mol%), TeO 2be 60.6 ~ 77.7 (mol%), Bi 2o 3be 3.9 ~ 4.9 (mol%), CuO be in the scope of 1.2 ~ 1.5 (mol%), at Li 2o amount is in the No.52,53 of 0.4 ~ 18.0 (mol%), the good result that FF value when obtaining non-LDE, LDE is all 76 ~ 78, bond strength is 3.3 ~ 3.4 (N).On the other hand, at Li 2o amount is in the No.51 of 0, and FF value when non-LDE, LDE is all 75, and in the No.54 of 22.0 (mol%), FF value when non-LDE, LDE is all less than 75, is all insufficient result.
In addition, No.55 ~ 58 are for have studied Bi 2o 3the evaluation result of amount.At SiO 2be 10.7 ~ 14.7 (mol%), Li 2o is 8.7 ~ 11.9 (mol%), TeO 2be 52.3 ~ 72.0 (mol%), Bi 2o 3be 0 ~ 27.4 (mol%), CuO be in the scope of 1.0 ~ 1.4 (mol%), at Bi 2o 3amount is in No.55 ~ 57 of 0 ~ 25.1 (mol%), the good result that FF value when obtaining non-LDE, LDE is all 76 ~ 78, bond strength is 3.2 ~ 3.4 (N).On the other hand, at Bi 2o 3amount is in the No.58 of 27.4 (mol%), and FF value when non-LDE, LDE is all less than 75, is insufficient result.
In addition, No.59 ~ 61 are for have studied the evaluation result of CuO amount.At SiO 2be 13.2 ~ 14.2 (mol%), Li 2o is 10.7 ~ 11.5 (mol%), TeO 2be 64.5 ~ 69.8 (mol%), Bi 2o 3be 4.1 ~ 4.4 (mol%), CuO be in the scope of 0 ~ 7.5 (mol%), measuring at CuO is in the No.59,60 of 0 ~ 4.8 (mol%), the good result that FF value when obtaining non-LDE, LDE is all 77 ~ 78, bond strength is 3.2 ~ 3.4 (N).On the other hand, be in the No.61 of 7.5 (mol%) in CuO amount, FF value when non-LDE, LDE is all less than 75, is insufficient result.
In addition, No.62 ~ 69 are containing ZnO, MgO, Fe 2o 3, have studied the evaluation result of their allowed band (upper limit) in the glass of any one in NiO.At SiO 2be 12.9 ~ 13.4 (mol%), Li 2o is 10.5 ~ 10.8 (mol%), TeO 2be 63.2 ~ 65.6 (mol%), Bi 2o 3be 4.0 ~ 4.2 (mol%), CuO being in the scope of 1.2 ~ 1.3 (mol%), is No.64, Fe of 5.9 (mol%) in ZnO amount No.62, MgO amount that is 5.9 (mol%) 2o 3amount is No.66, NiO amount of 4.8 (mol%) is in the No.68 of 4.8 (mol%), the good result that FF value when obtaining non-LDE, LDE is all 77 ~ 78, bond strength is 3.2 ~ 3.4 (N).On the other hand, No.63, MgO amount being 8.3 (mol%) in ZnO amount is No.65, Fe of 8.3 (mol%) 2o 3amount is No.67, NiO amount of 7.4 (mol%) is in the No.69 of 7.4 (mol%), and FF value when non-LDE, LDE is all less than 75, is insufficient result.
Following situation has been understood fully: by using SiO according to the evaluation result of above-mentioned No.45 ~ 69 2be 0 ~ 19.6 (mol%), Li 2o is 0.4 ~ 18.0 (mol%), TeO 2be 54.0 ~ 80.1 (mol%), Bi 2o 3be 0 ~ 25.1 (mol%), CuO to be 0 ~ 4.8 (mol%), ZnO be 5.9 (mol%) below, MgO amount be 5.9 (mol%) below, Fe 2o 3amount be 4.8 (mol%) below, NiO amount is the glass of 4.8 (mol%) composition below, FF value can be obtained and be more than 76 and bond strength is the solar cell of the excellence of more than 3.1 (N).
Following situation has been understood fully: in unleaded tellurium glass, with the addition of leaded additive and containing the additive of refractory metal or to containing the conductive paste that with the addition of leaded additive in the unleaded tellurium glass of refractory metal according to above evaluation result, do not limit composition especially, for the glass of various composition, by adding leaded additive and just can obtaining the effect of FF value improvement containing the additive of refractory metal.
Following table 3, to supporting leaded additive on the frit and carrying out various change to modulate paste containing the Composite process (Composite operation) of additive of refractory metal and the kind of additive, form sensitive surface electrode, evaluate the summary sheet of the result of its characteristic.In this evaluation, glass all uses the glass identical with embodiment No.2 of above-mentioned table 1 etc., leaded additive, is all set to constant containing the additive of refractory metal relative to the weight ratio of glass.In addition, FF value is identical with the evaluation shown in above-mentioned table 1, table 2 with the judgment standard of bond strength.
No.P01 ~ the P06 of above-mentioned table 3 is the use of WO 3as the example of the additive containing refractory metal.When modulating paste, be the No.P01 by leaded additive and the additives mixed containing refractory metal without Composite process, FF value when have also been obtained non-LDE, LDE is all the good result of more than 77.Moreover in the scope of the evaluation shown in this table 3, bond strength is all the good result of more than 2.9 (N).In addition, implementing the false No.P02 ~ P04 burnt in the scope of 350 ~ 500 (DEG C) has carried out in the No.P06 of Composite with employing mechanochemical reaction, FF value when obtaining non-LDE, LDE is all high, be the result of 77 ~ 79, but be set in the No.P05 of 550 (DEG C) vacation being burnt temperature, although being 76 for FF value during non-LDE, but when for LDE, FF value is 75, it is insufficient result.Can this is presumably because because the too high cause thus generating compound as shown in " precipitate after compound " hurdle of temperature is burnt in vacation.
In addition, the No.P07 ~ P11 of table 3 is the use of MoO 3as the example of the additive containing refractory metal.When modulating paste, be the No.P07 by leaded additive and the additives mixed containing refractory metal without Composite process, FF value when have also been obtained non-LDE, LDE is all the good result of more than 77.In addition, implement No.P08, P09 of false burning in the scope of 400 ~ 500 (DEG C) and adopt mechanochemical reaction to carry out in the No.P11 of Composite, FF value when obtaining non-LDE, LDE is all high, be the result of 78 ~ 79, but be set in the No.P10 of 550 (DEG C) vacation being burnt temperature, although being 76 for FF value during non-LDE, but when for LDE, FF value is 74, it is insufficient result.Can think that this is also owing to burning the too high cause thus generating compound as shown in " precipitate after compound " hurdle of temperature because of vacation.
In addition, the No.P12 ~ P16 of table 3 is the use of Cr 2o 3as the example of the additive containing refractory metal.When modulating paste, be the No.P12 by leaded additive and the additives mixed containing refractory metal without Composite process, FF value when have also been obtained non-LDE, LDE is all the good result of more than 77.In addition, implement No.P13, P14 of false burning in the scope of 400 ~ 500 (DEG C) and adopt mechanochemical reaction to carry out in the No.P16 of Composite, FF value when obtaining non-LDE, LDE is all high, be the result of 77 ~ 79, but be set in the No.P15 of 550 (DEG C) vacation being burnt temperature, although being 76 for FF value during non-LDE, but when for LDE, FF value is 74, it is insufficient result.Can think that this is also owing to burning the too high cause thus generating compound as shown in " precipitate after compound " hurdle of temperature because of vacation.
In addition, the No.P17 ~ P24 of table 3 is the use of and above-mentioned different other compound, i.e. (NH 4) 10w 12o 4, H 2wO 4, (NH 4) 2moO 4, Cr 3(OH) 2(OCOCH 3) 7as the example of the additive containing refractory metal.Even if adopt such compound to add, even if use the either method in the method only mixed, false burning method, mechanochemical reaction, FF value when all can obtain non-LDE, LDE is all the good result of 77 ~ 79.
In addition, No.P25 ~ 27 are that the kind of leaded additive is changed to Pb (NO 3) 2, PbCO 3, Pb example.Evaluate the situation that only vacation is burnt, FF value when have also been obtained non-LDE, LDE is in these cases all the extremely good result of 78 ~ 79.
In addition, No.P28 ~ 30 are mixed in frit by refractory metal oxide, after the false burning of enforcement supports, with the addition of Pb when modulating and sticking with paste 3o 4example.FF value when have also been obtained non-LDE, LDE is in these cases all the extremely good result of 77 ~ 78.
Distinguish according to above evaluation result: Composite process is not specially limited, but when carrying out vacation and burning, preferably control at 500 (DEG C) below, to make not occur glass, reaction with plumbous and refractory metal.
Following table 4, for various glass, the result summarizing the presence or absence of additive and kind and the output of the solar cell (non-LDE) of the structure in the past when being defined sensitive surface electrode by the paste employing this additive, the output employed in the solar cell of the LDE substrate same with the above embodiments, bond strength are evaluated.This evaluation, be for each of the combination of the frit shown in table 4 and additive, glass is formed, stick with paste composition etc. and carry out various change, under each combination, being considered to have rated characteristic under optimal conditions, illustrate only the evaluation result of optimum condition in table 4.The solar cell of above-mentioned structure in the past, except using the surperficial phosphorus concentration of sensitive surface side high and except the substrate of n thickness, producing in the same manner as above-mentioned solar cell 10.In addition, LDE substrate employs the substrate that film resistor is 110 ~ 120 (Ω/).This sheet resistance is the value determined by commercially available four probe method film resistor analyzer.In addition, in table 4, " frit " " the supporting " on hurdle implements as described above falsely burn process and support on frit by PbO, WO etc., " additive " one hurdle be modulate stick with paste time and the additive that adds dividually of glass.To export and same with shown in table 1 of the assay method of bond strength and judgment standard, but about exporting evaluation result, FF value more than 78 being designated as "○", 76 ~ 77 and being designated as " △ ", less than 75 and being designated as "×".
Table 4
[Property comparison gathers]
Shown in table 4 described above, when for using Pb-Te glass and not containing the formation of refractory metal, can not get LDE and export ("×" evaluation), the interpolation of ZnO is limited to the improvement of bond strength.In addition, when the additive or use for containing refractory metal to the interpolation of Pb-Te glass comprises the formation of Pb-Te glass of refractory metal, export though obtain LDE, bond strength insufficient ("×" evaluation).In addition, even support PbO or with the addition of the formation of leaded additive to this glass on Te glass, when not containing refractory metal, also can not get LDE and export.On the other hand, distinguished: when on Te glass, support PbO or add leaded additive to this glass and support in WO, CrO, MoO any one or with the addition of containing the additive of refractory metal formation and on the Te glass comprising refractory metal, supported the formation of PbO time, LDE exports and bond strength all improves.When particularly having supported the situation of PbO and supported PbO and refractory metal on the Te glass comprising refractory metal on Te glass, LDE exports high ("○" evaluation), and, Te glass has supported PbO and refractory metal, obtain the result of bond strength also high ("○" evaluation).
According to above-mentioned result, export to improve LDE, preferably supported on Te glass refractory metal or use comprise refractory metal Te glass and supported Pb, in order to improve bond strength, the additive preferably having supported refractory metal or with the addition of containing refractory metal.Therefore, in the scope evaluated, think that the mode supporting PbO and refractory metal on Te glass is best.Moreover, even the combination identical with exporting the combination that is evaluated as zero in above-mentioned table 4, in described table 1, table 3, also have FF value to be limited to the situation of 76 ~ 77, but as mentioned above, the result shown in table 4 is the result based on the optimum condition under each combination.The situation that FF value is low in table 1, table 3 is not had caused by the reasons such as optimization by glass combination.
As mentioned above, according to the present embodiment, for the paste for use in electrode of the formation of sensitive surface electrode 28, use the unleaded tellurium glass of various compositions as described above, mix various leaded additive and the additive containing refractory metal wherein, or leaded additive is mixed in the unleaded tellurium glass comprising refractory metal, preferred employing vacation is burnt, the method that mechanochemical reaction etc. are suitable for supports, therefore when by burn till through form sensitive surface electrode 28 time, the moderately irregular erosion surface of tool can be obtained, therefore the solar cell 10 that simultaneously can meet electrical characteristics and bond strength can be obtained.And, as the result forming paste as described above, owing to comprising refractory metal and lead in sensitive surface electrode 28, therefore again in conjunction with suppressed, even therefore there is LDE substrate also can obtain the high advantage exported.
Reference accompanying drawing is to invention has been detailed description above, but the present invention also can implement in other manners, can impose various change in the scope not departing from its purport.

Claims (16)

1. a solar cell sensitive surface paste for use in electrode, it is characterized in that, comprise electroconductive powder, frit and vehicle, described frit is made up of unleaded tellurium glass, this paste is on the face of by coating silicon substrate and process is burnt till in enforcement, through burning till through and forming the sensitive surface electrode of solar cell
This paste comprises:
At least a kind of refractory metal among tungsten, molybdenum and chromium; With
Leaded additive.
2. solar cell sensitive surface paste for use in electrode according to claim 1, described refractory metal is added dividually with the form of the additive containing refractory metal and described unleaded tellurium glass, and the described additive containing refractory metal comprises at least a kind among these refractory metals of tungsten, molybdenum and chromium.
3. solar cell sensitive surface paste for use in electrode according to claim 2, part or all of the described additive containing refractory metal is supported on described frit.
4. the solar cell sensitive surface paste for use in electrode according to any one of claims 1 to 3, part or all of described leaded additive is supported on described frit.
5. solar cell sensitive surface paste for use in electrode according to claim 4, described leaded additive processes by implementing false burning under mixing with described frit the temperature be incorporated in oxidizing atmosphere below 500 DEG C and is supported on this frit.
6. solar cell sensitive surface paste for use in electrode according to claim 5, a part for described leaded additive is remaining in the form of an oxide.
7. the solar cell sensitive surface paste for use in electrode according to any one of claim 1 ~ 6, described leaded additive, with the PbO/ frit weight ratio converted in oxide be 0.5 ~ 1.0 scope in ratio contained.
8. the solar cell sensitive surface paste for use in electrode according to any one of claim 1 ~ 7, described refractory metal, by being converted into the value after oxide separately, with relative to frit except WO 3, MoO, Cr 2o 3the total quality G of composition in addition, (WO 3/ G)+2 (MoO 3/ G)+4Cr 2o 3/ G be 0.04 ~ 0.40 scope in ratio by containing at least a kind.
9. the solar cell sensitive surface paste for use in electrode according to any one of claim 1 ~ 8, described unleaded tellurium glass, containing the TeO being scaled 54 ~ 80mol% by oxide 2, and the Li of 0.4 ~ 18mol% 2o.
10. the solar cell sensitive surface paste for use in electrode according to any one of claim 1 ~ 9, described unleaded tellurium glass, containing the Bi being scaled below 25mol% by oxide 2o 3, the CuO of below 5mol% and the SiO of below 20mol% 2.
The manufacture method of 11. 1 kinds of solar cell sensitive surface paste for use in electrode, is characterized in that, comprising:
Leaded additive supporting procedures, this operation make leaded additive part or all support on the frit be made up of unleaded tellurium glass, described unleaded tellurium glass contains at least a kind of refractory metal among tungsten, molybdenum and chromium; With
Mixed processes, electroconductive powder, described frit, described leaded additive and vehicle mix by this operation.
The manufacture method of 12. solar cell sensitive surface paste for use in electrode according to claim 11, described leaded additive supporting procedures, be that the powder of described frit with described leaded additive is mixed, and at temperature in oxidizing atmosphere below 500 DEG C, implement false operation of burning process.
The manufacture method of 13. 1 kinds of solar cell sensitive surface paste for use in electrode, is characterized in that, comprising:
Containing the additive supporting procedures of refractory metal, this operation make the additive of at least a kind of refractory metal among containing tungsten, molybdenum and chromium part or all support on the frit be made up of unleaded tellurium glass; With
Mixed processes, this operation is by electroconductive powder, described frit, the described additive containing refractory metal, leaded additive and vehicle mixing.
The manufacture method of 14. solar cell sensitive surface paste for use in electrode according to claim 13, comprises leaded additive supporting procedures, this operation make described leaded additive part or all support on described frit.
15. solar cell sensitive surface paste for use in electrode according to claim 14, described leaded additive supporting procedures, be that the powder of described frit with described leaded additive is mixed, and at temperature in oxidizing atmosphere below 500 DEG C, implement false operation of burning process.
16. 1 kinds of solar battery cells, the n on the face being formed at p-type silicon substrate +layer possesses antireflection film, and is provided with sensitive surface electrode by burning till through,
The feature of this solar battery cell is, described sensitive surface electrode is generated by the solar cell sensitive surface paste for use in electrode described in any one of claim 1 ~ 10.
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