Background technology
Crystal silicon solar batteries is that one effectively absorbs solar radiant energy, utilize photovoltaic effect that transform light energy is become the device of electric energy, when solar irradiation is in semiconductor P-N junction, form new hole-electron pair, under the effect of P-N junction electric field, hole flows to P district by N district, and electronics flows to N district by P district, just forms electric current after connecting circuit.
Conventional crystalline silicon solar cell only adopts front passivating technique substantially, one deck silicon nitride is deposited in the mode of front side of silicon wafer PECVD, reduce the recombination rate of few son at front surface, significantly can promote open circuit voltage and the short circuit current of crystal silicon battery, thus promote the photoelectric conversion efficiency of crystal silicon solar battery.
Along with the requirement of the photoelectric conversion efficiency to crystal silicon battery is more and more higher, people begin one's study and carry on the back passivating solar battery technology.The way of current main flow is at silicon chip back side deposition alundum (Al2O3) or silicon dioxide, and then deposits one deck silicon nitride, then lbg overleaf, removes the backside passivation layer in fraction region.Then print aluminium paste overleaf, dry sintering.Aluminium paste is directly contacted with silicon by the above region, is derived by electric current.But lbg on passivation layer overleaf, easily bring the problem that silicon back surface damages.
For this reason, those skilled in the art start to adopt a kind of new method back side to slot, disclosed in Chinese patent CN103996743A, a kind of aluminium paste burns the preparation method of the back of the body annealing point contact solar cell of partial thin film, cell backside point cantact adopts the aluminium paste burning type to realize film perforate simultaneously, aluminium silicon contacts and contact position forms local aluminium back surface field, by perforate, aluminium paste contacts two steps and is condensed to a step with silicon, avoid the problem that laser beam drilling brings silicon back surface to damage.But owing to adopting point cantact mode to arrange as shown in Figure 1, the contact resistance of aluminium paste and silicon is higher, and therefore need ohmic contact ability well to corrode aluminium paste slurry, otherwise cannot mate with backside passivation layer, production cost is higher.In addition, because aluminium paste is liquid, pearl drop is formed on the capillary backside passivation layer surface that acts on, but owing to having mobility, easy diffusion thus increase the contact area of drop and backside passivation layer, perforate becomes greatly, compared with slotting with straight line, be difficult to the percentage that accurate controls local aluminium back surface field accounts for described backside passivation layer area, cause the reduction of open circuit voltage and short circuit current.And because drop spreads, the aluminium paste in the unit are in drop contact face is tailed off, easily occur that aluminium paste deficiency causes burning backside passivation layer, make local aluminum back surface field and P-type silicon can not form good ohmic contact.
Prior art is owing to adopting the mode of printing of lattice array, and the diameter of point is little, and just can mate with backside passivation layer the requirement of corrosion aluminium paste is very high, production cost is high.And the aluminium paste drop be printed in backside passivation layer easily spreads, the contact area of aluminium paste and backside passivation layer is difficult to control, and causes guaranteeing the accounting of local aluminum back surface field and accurately cannot improve photoelectric conversion efficiency.
The embodiment of the present invention adopts vertical bar parallel arrangement mode printing corrosion aluminium paste, and because aluminium paste is flowable on every bar straight line, there will not be the not flowable situation of point-like printing, therefore not easily spread, the controllability of operation is strong.Local aluminum back surface field area accounts for the 1%-10% of described backside passivation layer area, and preferred local aluminum back surface field vertical bar width is 20-30 μm, and number is 80-150 bar, and the photoelectric conversion efficiency of battery can be made at least to improve 0.3%.And adopting the corrosion aluminium paste of general performance just can mate well with back aluminium back surface field, cost of material reduces.The present invention is without the need to laser equipment, and full aluminum back electric field is connected with P-type silicon by the mode by printing corrosion aluminium paste.Screen printing apparatus is the mature technology producing the current use of line, that is the present invention can import large-scale industrial production fast.
Preferably, local aluminum back surface field vertical bar width is 25-30 μm, and number is 100-120 bar.
S108, at the full aluminum back electric field slurry of described silicon chip back side printing, covers corrosion aluminium paste, forms full aluminum back electric field, dries.
S109 is at described front side of silicon wafer print positive electrode slurry.
Described positive electrode slurry is preferably containing Ag slurry.
Silicon chip is carried out high temperature sintering by S110, corrodes aluminium paste corrosion backside passivation layer, form the local aluminum back surface field connecting full aluminum back electric field and P-type silicon in sintering process.
It should be noted that, be 3 ~ 15:80 at oxygen and nitrogen volume ratio, sinter in the atmosphere of 750 ~ 850 DEG C of temperature, obtain described polished backside crystal silicon solar batteries.
The present invention is set forth further below with specific embodiment:
Summary of the invention
Technical problem to be solved by this invention is, provides a kind of passivating back solar cell that significantly can improve cell photoelectric conversion efficiency.
Technical problem to be solved by this invention is also, provides a kind of preparation method of passivating back solar cell, and can significantly improve cell photoelectric conversion efficiency, equipment investment cost is low, and technique is simple, and good with current production line compatibility.
In order to solve the problems of the technologies described above, the invention provides a kind of passivating back solar cell, comprise backplate, full aluminum back electric field, backside passivation layer, local aluminum back surface field, P-type silicon, N-type emitter, passivating film and front electrode; Described backplate, full aluminum back electric field, backside passivation layer, P-type silicon, N-type emitter, passivating film are connected from bottom to up successively with front electrode, described local aluminum back surface field is formed by corroding after aluminium paste corrodes described backside passivation layer sintering, is connected respectively with described full aluminum back electric field and described P-type silicon;
Described local aluminum back surface field is one group of vertical bar group arranged in parallel, is evenly distributed in backside passivation layer.
As the improvement of such scheme, described local aluminum back surface field area accounts for the 1%-10% of described backside passivation layer area.
As the improvement of such scheme, the vertical bar width of described local aluminum back surface field is 20-30 μm, and number is 80-150 bar.
As the improvement of such scheme, described local aluminum back surface field is formed after printing corrosion aluminium paste sintering by silk screen printing or ink-jetting style in described backside passivation layer.
As the improvement of such scheme, described backside passivation layer is Al
2o
3/ SiN
xcomposite bed or SiO
2/ SiN
xcomposite bed.
Correspondingly, present invention also offers a kind of preparation method of passivating back solar cell, comprise the following steps:
(1) form matte at front side of silicon wafer, described silicon chip is P-type silicon;
(2) spread at described front side of silicon wafer, form N-type emitter;
(3) phosphorosilicate glass that diffusion process is formed is removed;
(4) at silicon chip back side deposition alundum (Al2O3) or silicon dioxide;
(5) deposited silicon nitride on alundum (Al2O3) layer or silicon dioxide layer, forms backside passivation layer;
(6) the antireflecting passivating film of silicon nitride is formed at described front side of silicon wafer;
(7) at described silicon chip back side printing back electrode slurry, dry;
(8) adopt silk screen printing or ink-jetting style printing corrosion aluminium paste at described silicon chip back side, dry;
(9) at the full aluminum back electric field slurry of described silicon chip back side printing, cover corrosion aluminium paste, form full aluminum back electric field, dry;
(10) at described front side of silicon wafer print positive electrode slurry;
(11) silicon chip is carried out high temperature sintering, corrode aluminium paste corrosion backside passivation layer in sintering process, form the local aluminum back surface field connecting full aluminum back electric field and P-type silicon;
Vertical bar parallel arrangement mode printing corrosion aluminium paste is adopted in described step (8).
As the improved scheme of above-mentioned preparation method, described local aluminum back surface field area accounts for the 1%-10% of described backside passivation layer area.
As the improved scheme of above-mentioned preparation method, the vertical bar width of described local aluminum back surface field is 20-30 μm, and number is 80-150 bar.
As the improved scheme of above-mentioned preparation method, described backside passivation layer is Al
2o
3/ SiN
xcomposite bed or SiO
2/ SiN
xcomposite bed;
As the improved scheme of above-mentioned preparation method, Al in described backside passivation layer
2o
3or SiO
2deposit thickness is 5-50nm, SiN
xdeposit thickness is 50-200nm.
Implement the embodiment of the present invention, there is following beneficial effect:
The local aluminum back surface field that the present invention adopts one group of vertical bar arranged in parallel is evenly distributed on backside passivation layer, make full aluminum back electric field and silicon can form good ohmic contact, avoid conventional laser to slot and damage silicon chip back surface, thus significantly improve the photoelectric conversion efficiency of battery.
The present invention adopts the printing of vertical bar parallel arrangement mode to corrode aluminium paste, because aluminium paste is flowable on every bar straight line, there will not be the not flowable situation of point-like printing, therefore not easily spread, the controllability of operation is strong, when avoiding prior art to adopt dot matrix to print, the contact area of aluminium paste and backside passivation layer is difficult to control, the situations such as production cost is high.
The present invention is without the need to laser equipment, and full aluminum back electric field is connected with P-type silicon by the mode by printing corrosion aluminium paste.Screen printing apparatus is the mature technology producing the current use of line, that is the present invention can import large-scale industrial production fast, and equipment investment cost is low, and technique is simple, and production efficiency is high, good with current production line compatibility.
Embodiment
For making the object, technical solutions and advantages of the present invention clearly, below in conjunction with accompanying drawing, the present invention is described in further detail.
As shown in Figure 2, a kind of passivating back solar cell of the embodiment of the present invention, comprises backplate 1, full aluminum back electric field 2, backside passivation layer 3, local aluminum back surface field 4, P-type silicon 5, N-type emitter 6, passivating film 7 and front electrode 8; Described backplate 1, full aluminum back electric field 2, backside passivation layer 3, P-type silicon 5, N-type emitter 6, passivating film 7 are connected from bottom to up successively with front electrode 8, described local aluminum back surface field 4 is corroded described backside passivation layer 3 by corrosion aluminium paste and is sintered rear formation, is connected respectively with described full aluminum back electric field 2 and described P-type silicon 5;
Described local aluminum back surface field 4 is one group of vertical bar group arranged in parallel, is evenly distributed in backside passivation layer 3.
It should be noted that, P-type silicon 5 described in the embodiment of the present invention is the methods by the crystal growth of P-type silicon raw material, after forming crystal bar, is sliced into the size of 156mm x 156mm, but is not limited to this size.
The local aluminum back surface field 4 of the embodiment of the present invention prints the rear formation of corrosion aluminium paste sintering by silk screen printing or ink-jetting style in described backside passivation layer 3.Described local aluminum back surface field 4 is embedded in described backside passivation layer 3, and two ends connect P-type silicon 5 and full aluminum back electric field 2, thus makes full aluminum back electric field 2 can form good ohmic contact with silicon.Backside passivation layer 3 reduces the few sub-recombination rate of back surface, improves open circuit voltage and the short circuit current of battery, and electric current derives from inside battery by local aluminum back surface field 4, thus significantly improves the photoelectric conversion efficiency of battery.The mode of aluminium paste is printed after adopting first lbg relative to prior art, the present embodiment becomes a step printing corrosion aluminium paste from the shaping local aluminum back surface field 4 of original two steps, optimization technological process, enhance productivity, and silk screen printing or ink-jet technology are all ripe equipment, good with current production line compatibility.
As shown in Figure 3, the local aluminum back surface field 4 of the embodiment of the present invention is one group of vertical bar group arranged in parallel, and be evenly distributed in backside passivation layer 3, wherein, local aluminum back surface field 4 vertical bar width is 20-30 μm, and number is 80-150 bar.Preferably, local aluminum back surface field 4 vertical bar width is 25-30 μm, and number is 100-120 bar.
The photoelectric conversion efficiency affecting solar cell comprises three factors: open circuit voltage (Voc), short circuit current (Isc) and fill factor, curve factor (FF).Backside passivation layer 3 described in the present embodiment is Al
2o
3/ SiN
xcomposite bed or SiO
2/ SiN
xcomposite bed, this backside passivation layer 3 effectively can improve open circuit voltage and the short circuit current of battery, and silicon chip contacts the fill factor, curve factor that can promote battery with the good ohmic of aluminium back surface field.When local aluminum back surface field 4 accounting is greater than 10%, namely local aluminum back surface field 4 is larger with the contact area of P-type silicon 5, the area of backside passivation layer 3 certainly will be caused less, open circuit voltage and short circuit current is reduced while the fill factor, curve factor promoting battery, in fact photoelectric conversion efficiency does not improve, on the contrary, when local aluminum back surface field 4 accounting is less than 1%, then cause local aluminum back surface field 4 not enough with the contact area of P-type silicon 5, although ensure that enough backside passivation layer 3 area coverages, but cause fill factor, curve factor to reduce, the photoelectric conversion efficiency of battery is also undesirable.Thus, local aluminum back surface field 4 directly affects photoelectric conversion efficiency with the accounting of backside passivation layer 3.The present inventor finds, when described local aluminum back surface field 4 area accounts for the 1%-10% of described backside passivation layer 3 area, the photoelectric conversion efficiency of battery at least can improve 0.3%.Preferably, when local aluminum back surface field 4 vertical bar width is 20-30 μm, when number is 80-150 bar, local aluminum back surface field 4 area described in it accounts for the 1%-3% of described backside passivation layer 3 area.
In order to show that the local aluminum back surface field 4 of embodiment of the present invention vertical bar distribution mode is on the impact of each performance of battery, by the battery performance of following each experimental subjects of experiment measuring further.
Experimental subjects: reference example 1 is not for having the conventional solar cells of local aluminum back surface field;
Reference example 2 adopts lbg and screen printing mode to prepare the solar cell of local aluminum back surface field;
The lattice array mode that reference example 3 adopts prior art to carry prints corrosion aluminium paste to prepare the solar cell of local aluminum back surface field;
Embodiment adopts vertical bar parallel arrangement mode printing corrosion aluminium paste to prepare the solar cell of local aluminum back surface field, and except the step difference of preparation local aluminum back surface field, the manufacture method of all the other each layers is all identical.
Experimental result is as follows:
As shown in Figure 4, the invention provides a kind of preparation method of passivating back solar cell, comprise the following steps:
S100 forms matte at front side of silicon wafer, and described silicon chip is P-type silicon.
Select wet method or dry etching technology, form matte on P-type silicon sheet surface, reflectivity controls at 1%-30%.
S101 spreads at described front side of silicon wafer, forms N-type emitter.
N-type emitter is formed by the method such as thermal diffusion or ion implantation, and wherein, the diffusion of described silicon chip preferably adopts phosphorus oxychloride, need control square resistance in 75-100 ohm/sq scope when spreading.
S102 removes the phosphorosilicate glass that diffusion process is formed.
Use the phosphorosilicate glass layer formed in N-type emitter front described in HF solution removal and described P-type silicon sheet back side diffusion process.
S103 is at silicon chip back side deposition alundum (Al2O3) or silicon dioxide.
S104 is deposited silicon nitride on alundum (Al2O3) layer or silicon dioxide layer, forms backside passivation layer.
It should be noted that, in the embodiment of the present invention, S103 and S104 step is all adopt PVECD equipment to deposit, and first forming thickness by S103 step at silicon chip back side is 5-50nmAl
2o
3layer or SiO
2layer.Pass through S104 step again at Al
2o
3layer or SiO
2it is the SiN of 50-200nm that layer deposits a layer thickness
x, finally form Al
2o
3/ SiN
xcomposite bed or SiO
2/ SiN
xcomposite bed.
It should be noted that, PECVD (Plasma Enhanced Chemical Vapor Deposition) refers to plasma enhanced chemical vapor deposition.PECVD is the gas ionization making containing film composed atom by microwave or radio frequency etc., is being partially formed plasma, and plasma chemistry activity is very strong, is easy to react, goes out desired film at deposition on substrate.
S105 forms the antireflecting passivating film of silicon nitride at described front side of silicon wafer.
S106, at described silicon chip back side printing back electrode slurry, is dried.
Described back electrode slurry is preferably containing Ag slurry.
S107 adopts silk screen printing or ink-jetting style printing corrosion aluminium paste at described silicon chip back side, dries.
It should be noted that, in S107 step, adopt the printing of vertical bar parallel arrangement mode to corrode aluminium paste.Corrosion aluminium paste can corrode backside passivation layer in sintering process, and this aluminium paste fills vertical bar groove, forms the local aluminum back surface field connecting full aluminum back electric field and P-type silicon.
Embodiment 1
(1) select 156mmP type silicon as basis material, form matte at front side of silicon wafer, described silicon chip is P-type silicon, and reflectivity controls 10%;
(2) spreading at described front side of silicon wafer, form N-type emitter, square resistance need be controlled in 75 ohm/sq scopes when spreading;
(3) phosphorosilicate glass that diffusion process is formed is removed;
(4) at silicon chip back side deposition alundum (Al2O3), thickness is 35nm;
(5) on alundum (Al2O3) layer, deposit thickness is the silicon nitride of 120nm, forms the backside passivation layer of compound;
(6) the antireflecting passivating film of silicon nitride is formed at described front side of silicon wafer;
(7) at described silicon chip back side printing back electrode slurry, dry;
(8) adopt silk screen printing or ink-jetting style to adopt vertical bar parallel arrangement mode printing corrosion aluminium paste at described silicon chip back side, dry, the vertical bar width of described local aluminum back surface field is 20 μm, and number is 100;
(9) at the full aluminum back electric field slurry of described silicon chip back side printing, cover corrosion aluminium paste, form full aluminum back electric field, dry;
(10) at described front side of silicon wafer print positive electrode slurry;
(11) be 5:80 at oxygen and nitrogen volume ratio, sinter in the atmosphere of 750 DEG C of temperature, obtain described passivating back solar cell.
Embodiment 2
(1) select 156mmP type silicon as basis material, form matte at front side of silicon wafer, described silicon chip is P-type silicon, and reflectivity controls 15%;
(2) spreading at described front side of silicon wafer, form N-type emitter, square resistance need be controlled in 85 ohm/sq scopes when spreading;
(3) phosphorosilicate glass that diffusion process is formed is removed;
(4) at silicon chip back side deposition of silica, thickness is 40nm;
(5) on silicon dioxide layer, deposit thickness is the silicon nitride of 130nm, forms the backside passivation layer of compound;
(6) the antireflecting passivating film of silicon nitride is formed at described front side of silicon wafer;
(7) at described silicon chip back side printing back electrode slurry, dry;
(8) adopt silk screen printing or ink-jetting style to adopt vertical bar parallel arrangement mode printing corrosion aluminium paste at described silicon chip back side, dry, the vertical bar width of described local aluminum back surface field is 25 μm, and number is 120;
(9) at the full aluminum back electric field slurry of described silicon chip back side printing, cover corrosion aluminium paste, form full aluminum back electric field, dry;
(10) at described front side of silicon wafer print positive electrode slurry;
(11) be 7:80 at oxygen and nitrogen volume ratio, sinter in the atmosphere of 780 DEG C of temperature, obtain described passivating back solar cell.
Embodiment 3
(1) select 156mmP type silicon as basis material, form matte at front side of silicon wafer, described silicon chip is P-type silicon, and reflectivity controls 20%;
(2) spreading at described front side of silicon wafer, form N-type emitter, square resistance need be controlled in 95ohm/sq scope when spreading;
(3) phosphorosilicate glass that diffusion process is formed is removed;
(4) at silicon chip back side deposition of silica, thickness is 50nm;
(5) on silicon dioxide layer, deposit thickness is the silicon nitride of 180nm, forms the backside passivation layer of compound;
(6) the antireflecting passivating film of silicon nitride is formed at described front side of silicon wafer;
(7) at described silicon chip back side printing back electrode slurry, dry;
(8) adopt silk screen printing or ink-jetting style to adopt vertical bar parallel arrangement mode printing corrosion aluminium paste at described silicon chip back side, dry, the vertical bar width of described local aluminum back surface field is 30 μm, and number is 130;
(9) at the full aluminum back electric field slurry of described silicon chip back side printing, cover corrosion aluminium paste, form full aluminum back electric field, dry;
(10) at described front side of silicon wafer print positive electrode slurry;
(11) be 1:10 at oxygen and nitrogen volume ratio, sinter in the atmosphere of 800 DEG C of temperature, obtain described passivating back solar cell.
Embodiment 4
(1) select 156mmP type silicon as basis material, form matte at front side of silicon wafer, described silicon chip is P-type silicon, and reflectivity controls 25%;
(2) spreading at described front side of silicon wafer, form N-type emitter, square resistance need be controlled in 100 ohm/sq scopes when spreading;
(3) phosphorosilicate glass that diffusion process is formed is removed;
(4) at silicon chip back side deposition alundum (Al2O3), thickness is 20nm;
(5) on alundum (Al2O3) layer, deposit thickness is the silicon nitride of 100nm, forms the backside passivation layer of compound;
(6) the antireflecting passivating film of silicon nitride is formed at described front side of silicon wafer;
(7) at described silicon chip back side printing back electrode slurry, dry;
(8) adopt silk screen printing or ink-jetting style to adopt vertical bar parallel arrangement mode printing corrosion aluminium paste at described silicon chip back side, dry, described local aluminum back surface field area accounts for 7% of described backside passivation layer area;
(9) at the full aluminum back electric field slurry of described silicon chip back side printing, cover corrosion aluminium paste, form full aluminum back electric field, dry;
(10) at described front side of silicon wafer print positive electrode slurry;
(11) be 9:80 at oxygen and nitrogen volume ratio, sinter in the atmosphere of 820 DEG C of temperature, obtain described passivating back solar cell.
Embodiment 5
(1) select 156mmP type silicon as basis material, form matte at front side of silicon wafer, described silicon chip is P-type silicon, and reflectivity controls 30%;
(2) spreading at described front side of silicon wafer, form N-type emitter, square resistance need be controlled in 80 ohm/sq scopes when spreading;
(3) phosphorosilicate glass that diffusion process is formed is removed;
(4) at silicon chip back side deposition of silica, thickness is 15nm;
(5) on silicon dioxide layer, deposit thickness is the silicon nitride of 145nm, forms the backside passivation layer of compound;
(6) the antireflecting passivating film of silicon nitride is formed at described front side of silicon wafer;
(7) at described silicon chip back side printing back electrode slurry, dry;
(8) adopt silk screen printing or ink-jetting style to adopt vertical bar parallel arrangement mode printing corrosion aluminium paste at described silicon chip back side, dry, described local aluminum back surface field area accounts for 9% of described backside passivation layer area;
(9) at the full aluminum back electric field slurry of described silicon chip back side printing, cover corrosion aluminium paste, form full aluminum back electric field, dry;
(10) at described front side of silicon wafer print positive electrode slurry;
(11) be 13:80 at oxygen and nitrogen volume ratio, sinter in the atmosphere of 850 DEG C of temperature, obtain described passivating back solar cell.
Finally to should be noted that; above embodiment is only in order to illustrate technical scheme of the present invention but not limiting the scope of the invention; although be explained in detail the present invention with reference to preferred embodiment; those of ordinary skill in the art is to be understood that; can modify to technical scheme of the present invention or equivalent replacement, and not depart from essence and the scope of technical solution of the present invention.