CN101373801A - Technique for preparing ultra-thin solar battery slice - Google Patents
Technique for preparing ultra-thin solar battery slice Download PDFInfo
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- CN101373801A CN101373801A CNA2007101206069A CN200710120606A CN101373801A CN 101373801 A CN101373801 A CN 101373801A CN A2007101206069 A CNA2007101206069 A CN A2007101206069A CN 200710120606 A CN200710120606 A CN 200710120606A CN 101373801 A CN101373801 A CN 101373801A
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Abstract
The invention discloses a production method for a solar cell piece, in particular to a production method for an ultra-thin cell piece. The method comprises the following steps: the positive surface of the cell piece is processed on a silicon slice of conventional thickness, and then a transparent glass base plate is adhered to the positive surface of the processed cell piece. The body layer of the silicon slice is subjected to thinning processing to achieve the anticipated thickness. An amorphous dopant material is applied to the back surface of the thin silicon slice, and exposed in pulse laser energy with appropriate duration and intensity, so that the amorphous material can be molten, but thermal damage can not be caused to the cementing line. After the production of dielectric medium on the back surface, a back contact mask and a back surface reflector, the processing of the cell piece is finished.
Description
Technical field
The present invention system belongs to the Application of Solar Energy field about the production method of ultra-thin solar battery sheet.
Background technology
A key factor that causes solar cell industry development to slow down at present is the contention for silicon materials of solar cell industry and chip manufacturing industry, and the shortage of solar level crystalline silicon material causes the HIGH-PURITY SILICON price to sharp rise.From photovoltaic industry long-run development trend, the decisive factor of decision whole industry and company development prospect is the improvement of company's technology and the raising of technology, for example, the attenuation of silicon chip cutting thickness improves the conversion efficiency of battery sheet on the other hand to reduce the silicon materials consumption of every battery sheet.At present, the used silicon wafer thickness of industry will drop to 150um at 200～220um by 2010, and the following general who has surrendered of thickness causes photovoltaic generation battery cost to reduce about 40%.The production technology of current battery sheet mainly comprises cleaning and texturing, POCL
3Technologies such as diffusion system knot, edge etching, antireflective coating deposition, screen printing electrode and sintering are formed, but attenuate along with the battery sheet, on current production technology, bring a lot of problems, as easy fragmentation of battery sheet in the operating process etc., this problem has seriously restricted the development of solar cell industry.
This patent relates to the production of slimline battery sheet, and the battery sheet of producing has gratifying electrical property.The critical design parameters of solar battery sheet is a diffusion length and the ratio of battery sheet thickness.In traditional battery sheet is produced, will be diffused into the silicon chip front with the doping agent that the silicon chip body mixes up type opposite, so just produced charge carrier to (electronics and hole), and charge carrier must be diffused into the front and rear surfaces of silicon chip to be collected.Any compound (comprising compound and surface recombination in the body) in the silicon chip all can reduce collected current and output voltage, thereby causes the decline of conversion efficiency.Theoretical prediction is as ratio L
p/ t is obviously greater than 1 o'clock, compound and damaged will minimizing.So this battery sheet can be collected the charge carrier of very most of generation.Suppose that the thin silicon sheet has the charge carrier identical with thick silicon chip to produce, under the then identical diffusion length, thin slice will increase the charge carrier number of collecting greatly, and compound reduction directly causes the raising of efficient.
The battery sheet also is subject to the influence of radiation damage.Improved radiation resistance can prolong the Acceptable life of battery sheet., can improve radiation resistance characteristics according to this point because thereby radiation resistance tends to reduce the diffusion length reduction battery sheet efficient of battery sheet.So under the situation of identical initial efficient, thin slice has better own radiation resistance than sheet.
Summary of the invention
Usually, the following process of thin solar battery sheet process: wafer thinning utilizes production technology that silicon chip is processed as the battery sheet to suitable thickness, at last the battery sheet that is shaped is welded to in its protective glass that provides support.This manufacture method has several shortcomings: at first, under relatively thinner state silicon chip is processed, silicon chip is more fragile than standard silicon chip, needs special operation, and very easily produces fragment.With monocrystalline silicon is example, and thickness is difficult to carrying less than 50 microns silicon chip after the manufacturing process neutralization completes, very easily broken.And the production cost of this silicon chip is very high, be above standard 10 times of silicon chip of its cost.The another one shortcoming of thin battery sheet is that the thickness of the absorption of light and battery sheet is closely bound up.For silicon materials, it is a kind of indirect energy carrying material, and in order to absorb all effective incident lights, it generally needs the thickness of hundreds of micron.So be necessary at silicon chip back making one deck antireflective coating.
The target of this patent is: 1) making for ultra-thin solar battery slice provides a kind of method, and it is broken to guarantee that it is difficult for after the manufacturing process neutralization completes; 2) manufacture method of the battery sheet that a kind of radiation resistance and efficient improves is to some extent proposed.
In order to reach above target, provided a kind of method of making solar cell by the thin silicon sheet.At first at front treatment process common, the enterprising column criterion of thick silicon chip (250um).After handle in the silicon chip front, the front surface of silicon chip is attached on the transparent substrate, connect thereby between substrate and silicon chip, form.Next, silicon chip is carried out reduction processing.Subsequently PROCESS FOR TREATMENT is carried out at the silicon chip back side, thereby form good Ohmic contact, reduce back of the body surface recombination, and form the back reflectance coating.
The technical process on silicon chip back of the body surface is included in and deposits the amorphous materials that one deck comprises doping agent on the thin silicon sheet bottom surface, to form ohmic contact and back of the body surface field.Amorphous layer is exposed to the open air in pulse laser, and energy pulse is enough high, thereby makes amorphous materials and very thin one deck silicon chip fusing below it, but joint lines is not had fire damage.To carry on the back the residue on surface subsequently removes.The back of the body surface treatment method of better method also comprises the interpolation dielectric, passes dielectric opening mask, and the interpolation of a metal level that back of the body surface reflection device is connected with wiring.
This patent and target thereof, advantage can better be understood by following figure.
Fig. 1 is the sectional view of front with the solar battery sheet of standard technology making.
Fig. 2 is the sectional view after Fig. 1 battery sheet adds protective glass.
Fig. 3 protects the perspective view of the hookup of protective glass and silicon chip for suitable being used to.
Fig. 4 is the sectional view of the solar battery sheet of patent that utilization proposes making.
Fig. 5 is the exploded perspective view that comprises the solar battery sheet of protective glass.
Fig. 6 is the schematic diagram of laser anneal device.
The battery sheet manufacture method that the patent of utilizing this paper to propose is said is to carry out PROCESS FOR TREATMENT on the silicon chip 10 of 220um at existing thickness.After silicon chip 10 processes, it is attached on the transparency carrier shown in Figure 2.Next by grinding, perhaps back etched is thinned to silicon chip 10 thickness of expectation.In thinning process, substrate provides support for the battery sheet.Subsequently, reduce surface damage by polishing or etching.
When polish or after etching gets rid of residual impairment at the back side, at the amorphous doped semiconductor material of its surface applied one deck, it has realized the formation of cell back surface field and ohmic contact with the laser processing technique of back.In such process, there is an important problem to need to consider that is exactly to prevent that some composition of battery sheet such as base plate bonding agent 19 from exposing to the open air under too high temperature (greater than 150 ℃), even the very short time.So the amorphous materials that comprises doping agent is coated onto the back of the body surface of thin silicon sheet at low temperatures.Utilize the energy of pulsed laser source to make amorphous materials and part back of the body surface melting subsequently.In fusing and crystal recrystallization process, doping agent has injected the bottom surface of silicon chip.The intensity of paired pulses lasing light emitter is selected, and has guaranteed that the silicon chip back side has only a more shallow zone melting, and can not burn silicon chip.After the laser treatment, at the backside deposition one deck dielectric layer and the back side antireflective coating of battery sheet.
Fig. 1 has represented the sectional view of the battery sheet after phase I technology is finished.The phase I process using be standard solar cells sheet manufacture craft.Concrete what adopt is that existing thickness is that the P type silicon chip 10 of 220um can not cause extra fragmentation to guarantee operation, on this basis silicon chip is carried out attenuate.In front growth or deposition layer of oxide layer.Opening on the oxide layer 11 is used to realize the generation (adopting the technology of mixing up of standard) of N type positive layer 12.Formed P-N knot 30 at positive layer 12 and body layer 13 joints.Next utilize photoetching process on this layer oxide, to open contact point.Metal interconnecting layer 15 is applied to the front of silicon chip 10 thereupon, electrically contacts thereby form.By etch process, can form the contact grid line that is positioned on the oxide layer 11 on the interconnection layer, and, see Fig. 5 for positive layer 12 provides the contact openings of ohmic contact.The stratification structure that antireflection layer 16 can be made up of Ta2O5, Al2O3 etc.When needing to detect quality, metal level 17 can be used for the body layer bottom provides the secondary contact.The concrete contact detection material that adopts is the Al behind the sintering.
Fig. 2 has described the device profile map after the second stage technology.In second stage technology, bonding agent 19 is used for the front surface of bonding protective glass 18 and battery sheet.Can select for use different conventional coating to be coated in a side or the both sides of protective glass 18, improve its transmission characteristic and the harmful ultraviolet radiation of reflection.Bonding agent 19 has formed bonding wire between protective glass 18 and silicon chip front 14, it should select not to be subject to ultraviolet irradiation and the material of decaying.Bonding way can select static to connect or chemical vapor deposition wherein a kind of.
Fig. 3 has provided a kind of method that might realize that connects protective glass 18 and battery sheet.Battery sheet 24 is placed on the vacuum cup 27 that possesses accurate flatness.On implementation method, battery sheet 24 must be smooth and suitable with the final permissible accuracy of device at least.For example, select silica gel as bonding agent, protective glass 18 is placed on the similar vacuum cup 25, next bonding agent 19 is coated on the battery sheet 24, utilizes micrometer 26 that vacuum cup 25 and 27 is accurately screwed.Next bonding agent solidifies, and the silicon chip that connects is removed from vacuum cup 25 and 27.After the protective glass 18 that supports usefulness installed, cell back portion is carried out thinning handle, processing method can be combinations chemical, machinery or two kinds of technology.What use always in the monocrystalline silicon battery blade technolgy is the combination of the two, for example, utilizes traditional silicon chip grinding technology and glossing, the thickness of silicon chip can be thinned to 100um by 300-400um.Glossing need carry out strictness control to uniformity.Obtaining inhomogeneity a kind of possible approach is to adopt the vacuum installation and design.Pottery can be not crooked under the thermal stress effect, so used vacuum cup can utilize processable ceramic manufacturing in the polishing process.The use of vacuum cup makes and can obtain on 3 inches silicon chip ± uniformity of 0.3um.Next utilize chemical etchant further with wafer thinning to 20-50um, etching is up to the thickness that obtains expectation in 80 ℃ NaOH solution (mass percent 30%).In this solution, the etch-rate of silicon chip is about 1.5 microns/minute.Next put into HF:HNO3 than being etched with the acquisition clean Surface for the solution of 1:100.
Fig. 4 has provided the side cutaway view of device after phase III technology and the final stage technology.The 3rd operation stage comprises wafer thinning back surface treatment.For ohmic contact is provided, it is compound to reduce effective back side charge carrier, and back of the body surface antireflection film is provided, and back of the body surface treatment comprises several steps.Ohmic contact doped region 20 utilizes the pulse laser process sequence to form, and back side antireflective coating forms by the deposition of the deposition of dielectric substance under the low temperature 21 and reflection-reducing material subsequently (as Al) 22.Contact hole 23 passes dielectric substance 21, thereby makes that antireflective metal 22 also can electrically contacting as the battery sheet.The problem of a needs consideration is some composition of battery sheet, can not expose to the open air in the high temperature more than 150 ℃ such as the protective glass bonding agent, even the very short time.Do not damage battery sheet composition in order to finish this technology, proposed a kind of new method of introducing doping agent.
Next a step is that the etching silicon chip is to obtain being connected of back of the body field and positive contact.Usually select for use the KOH etchant to finish.The KOH solution concentration is 30%, and temperature is 80 ℃.Etch-rate is approximately 1.5 microns/minute, and etching period depends on the thickness of battery sheet.
Opening contact hole on the dielectric 21 overleaf at last, deposition antireflective metal 22 also forms pattern and forms an ohmic contact and a back of the body anti-reflection beam.Because when contacting with dielectric 21, AL has higher relatively reflection coefficient, it can provide good Ohmic contact simultaneously, selects for use AL as antireflective metal 22 usually.Fig. 5 is the perspective view that utilizes the battery sheet that said method makes.
Though the battery sheet production technology in this patent is not to adopt on the current industrial, because so specific production technology is carried out in the thinning day by day of silicon chip, wherein many contents can be used for reference and be applied to the production of battery sheet and other aspects.Especially wherein selected special material, size and intensity can change the validity of verifying patent.In addition, this patent has only related to silicon materials and monocrystalline silicon battery sheet, but method wherein can be used for other semi-conducting materials equally.So the specific example of listing can be thought illustrative, patent not only is confined to wherein given aspect.For persons skilled in the art, any conspicuous change of under the prerequisite that does not deviate from the utility model spirit it being done all constitutes the infringement to this patent, with corresponding legal responsibilities.
Claims (9)
1. solar battery sheet has upper surface and lower surface, silicon chip comprise the oxide layer that forms upper surface, the PN junction layer that closes on oxide layer, first conduction type PN junction layer, with the bulk material of second conduction type of first conductivity type opposite.This kind battery sheet production method comprises following flow process:
Utilize bonding agent that support unit is adhered to the silicon chip upper surface, form bonding wire between the two;
Form the process of mixing up with ohmic contact back of the body field at the silicon chip back side and be included in the amorphous materials that silicon chip backside deposition one deck comprises required doping agent, utilize pulsed laser source that amorphous material layer melt, assurance does not simultaneously cause fire damage to bonding wire.
2. after requiring the method described in 1 to be included in silicon chip bonded to support unit the bulk silicon lamella is thinned to thickness less than 50 microns processes.
3. as requiring 2 described silicon chips to be fabricated from a silicon.
4. be boron as requiring the doping agent of 3 described selections.
5. as require 1 described method also to be included in after the pulse laser processing at silicon chip back side coating dielectric layer.
6. as require the said support unit of 1 described production method can be fully by electromagnetic radiation.
7. the formation of cell back superficial layer comprises following a few step: support unit is bonded on the silicon chip so that support structure to be provided; Form bonding wire between the two; Silicon chip thinning after supporting is handled below 100 micron thickness; Deposition one deck comprises the amorphous materials of doping agent on the back of the body surface of the silicon chip after the thinning; Amorphous materials is exposed to the open air under pulsed laser energy,, bonding wire is not caused fire damage again simultaneously amorphous materials and the very thin one deck silicon fusing that closes on.
8. be cover glass as requiring the support unit described in 7.
9. be after-applied to silicon chip back of the body surface as requiring the dielectric layer described in 8 in pulse laser processing.
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| Application Number | Priority Date | Filing Date | Title |
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| CNA2007101206069A CN101373801A (en) | 2007-08-22 | 2007-08-22 | Technique for preparing ultra-thin solar battery slice |
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| CNA2007101206069A CN101373801A (en) | 2007-08-22 | 2007-08-22 | Technique for preparing ultra-thin solar battery slice |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103943724A (en) * | 2014-04-17 | 2014-07-23 | 南京大学 | Flexible and efficient crystalline silicon solar cell and manufacturing method thereof |
| CN104009120A (en) * | 2014-05-22 | 2014-08-27 | 奥特斯维能源（太仓）有限公司 | Preparation method of N-type crystalline silicon grooved buried contact cell |
| CN104037262A (en) * | 2014-05-08 | 2014-09-10 | 中国电子科技集团公司第四十八研究所 | Manufacturing process of ultrathin crystal silicon flexible solar cell |
| CN104201234A (en) * | 2014-06-26 | 2014-12-10 | 余林蔚 | Flexible high-light-trapping-property radial-junction heterojunction efficient crystalline silicon solar cell and manufacturing method thereof |
-
2007
- 2007-08-22 CN CNA2007101206069A patent/CN101373801A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103943724A (en) * | 2014-04-17 | 2014-07-23 | 南京大学 | Flexible and efficient crystalline silicon solar cell and manufacturing method thereof |
| CN104037262A (en) * | 2014-05-08 | 2014-09-10 | 中国电子科技集团公司第四十八研究所 | Manufacturing process of ultrathin crystal silicon flexible solar cell |
| CN104009120A (en) * | 2014-05-22 | 2014-08-27 | 奥特斯维能源（太仓）有限公司 | Preparation method of N-type crystalline silicon grooved buried contact cell |
| CN104201234A (en) * | 2014-06-26 | 2014-12-10 | 余林蔚 | Flexible high-light-trapping-property radial-junction heterojunction efficient crystalline silicon solar cell and manufacturing method thereof |
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Open date: 20090225 |