A kind of method of making crystalline silicon high-efficiency solar cell
Technical field
The present invention relates to a kind of method of making crystalline silicon high-efficiency solar cell, utilize the light of the nanocrystalline quantum limitation effect modulated photonic-energy of surface silicon greater than body silicon energy gap (1.1eV), short wavelength's light particularly, it is fully absorbed by crystal silicon battery, to reach the raising conversion efficiency, the purpose that reduces cost.
Background technology
In recent years, problem of environmental pollutions such as rise in oil price equal energy source shortage problem and global warming are increasingly serious, and people are unprecedentedly urgent to the regenerative resource demand of cleaning.Solar energy is inexhaustible, is expected to substitute traditional energy, and the important form of using as solar energy, solar cell receives much attention.
Propose first with silica-based PN junction structure applications in solar cell so far from Chapin in 1954 etc., solar cell is through the development of over half a century, and kind is on the increase.From the thin-film solar cells of the monocrystaline silicon solar cell of the first generation, the second generation high performance solar batteries of the third generation till now, its cost of manufacture progressively reduces, and conversion efficiency improves constantly.
At present, the subject matter that faces of crystal silicon battery has: conversion efficiency is not very high (large-scale production can be accomplished on average 17%), costs an arm and a leg etc.Yet these problems all are not enough to influence crystal silicon (monocrystalline and polycrystalline) the battery leading position in solar cell market at present, and therefore how improving the conversion efficiency of battery and then reduce cost becomes the focus of concern.From the light absorption angle, energy is greater than the above photon of silicon energy gap (1.1eV), and particularly high-octane short wavelength photons is lost with the form of heat energy greatly.Pertinent literature points out, the only above-mentioned loss that causes aspect the short wavelength is up to 33% of all losses, if the light of these spectral regions effectively can be used, and raising that then can very high realization battery efficiency.
The present invention is applied in this nanostructure of silicon nanocrystal on the crystal silicon solar batteries sheet, thereby but short wavelength's light is converted in the absorption region, finally fully absorbed by the crystal silicon PN junction, realize higher conversion efficiency.Simultaneously this silicon nanocrystal technology of preparing can with the large-scale production compatibility, do not influence existing crystal silicon battery technology, can farthest reduce cost and realize industrialization.
Summary of the invention
(1) technical problem that will solve
The purpose of this invention is to provide a kind of method of making crystalline silicon high-efficiency solar cell, the light with application surface silicon nanocrystal structure modulation short wavelength is fully absorbed it by crystal silicon battery itself, improve existing crystal silicon battery conversion efficiency with this.
(2) technical scheme
In order to achieve the above object, the invention provides a kind of method of making crystalline silicon high-efficiency solar cell, comprise the steps:
Step 1, at crystalline silicon substrate surface preparation suede structure;
Step 2, employing diffusion method form the PN junction structure on crystalline silicon substrate;
Step 3, utilize film deposition techniques and heat treatment to form the silicon nanocrystal structure on the surface;
Step 4, utilize the plasma-reinforced chemical vapor deposition method at substrate surface deposit silicon nitride antireflective film;
The making of positive and negative electrode is finished in step 5, silk screen printing;
Step 6, alloying finally form the solar cell of the nanocrystalline modulation of surface silicon.
In the such scheme, crystalline silicon substrate described in the step 1 is employed P type standard film in producing, and monocrystalline silicon piece is of a size of 125 * 125cm
2(rescinded angle), polysilicon chip is of a size of 156 * 156cm
2, adopt the chemical solution wet etching to go out pyramidal suede structure.
In the such scheme, diffusion method described in the step 2 is to utilize liquid phosphorus oxychloride to form PN junction for diffuse source, and junction depth is controlled at 200~500nm, diffusion back trimming.
In the such scheme, form the silicon nanocrystal structure on the surface described in the step 3, be to utilize magnetron sputtering or electron beam evaporation technique, and form the silicon nanocrystal of size, controllable density by the mode of rapid thermal annealing at crystalline silicon substrate surface deposition one deck silicon thin film.
In the such scheme, the method for plasma-reinforced chemical vapor deposition described in the step 4 is the substrate surface deposit silicon nitride antireflective film after forming the silicon nanocrystal structure, and the thickness of silicon nitride antireflective film is between 70nm~120nm.
In the such scheme, the making of electrode described in the step 5 is that the aluminum paste material is printed at the back side, at positive silk screen printing silver paste, forms the positive and negative electrode of battery.
In the such scheme, alloying process described in the step 6 is through high temperature sintering, and no special atmosphere protection finally forms the nanocrystalline modulation crystalline silicon high-efficiency solar cell of surface silicon.
(3) beneficial effect
1, the method for this making crystalline silicon high-efficiency solar cell provided by the invention, application surface silicon nanocrystal structure modulation short wavelength's light is fully absorbed it by crystal silicon battery itself, improved existing crystal silicon battery conversion efficiency with this.The technology of preparing that the present invention relates to simultaneously is simple, with existing crystal silicon battery large-scale production process compatibility, needs the equipment and the processing step of increase few, is easy to large-scale production and industrialization, finally can reach the purpose that reduces cost.
2, the method for this making crystalline silicon high-efficiency solar cell provided by the invention, the PN junction crystal silicon solar batteries that utilization is prepared by the process means on the big production line, at its surface preparation silicon nanocrystal, can be with regulating action by silicon nanocrystal, make crystal silicon battery can more effectively utilize sunlight wavelength, and then improve the efficient of crystal silicon battery.
3, the method for this making crystalline silicon high-efficiency solar cell provided by the invention, be a kind of based on existing mass production procedure, the technology of developing in conjunction with new structure, solar cell by this technology preparation can effectively utilize the light wave that lost originally, has the advantage that short circuit current is big, efficient is high.The technology of the efficient crystal silicon solar batteries of this preparation is compatible mutually with existing ripe mass production techniques, and it is simple to have production technology, is easy to characteristics such as industrialization, can reduce cost effectively, obtains efficient crystal silicon solar batteries.
Description of drawings
Fig. 1 is nanocrystalline for surperficial Si among the present invention, the flow chart of metallic nano crystal hybrid modulation crystal silicon high performance solar batteries.
Fig. 2 is a P type crystalline silicon substrate schematic diagram.
Fig. 3 is for to prepare the matte schematic diagram at the substrate positive and negative.
Fig. 4 forms the PN junction structural representation for the diffusion back.
Fig. 5 forms the silicon nanocrystal schematic diagram through Overheating Treatment again for after utilizing magnetron sputtering or electron beam evaporation equipment formation silicon thin film.
Fig. 6 is for utilizing plasma enhanced chemical vapor deposition (PECVD) equipment grown silicon nitride antireflective film schematic diagram
Fig. 7 is for utilizing screen printing technique at the positive and negative schematic diagram that prints electrode respectively.
Embodiment
Reach technological means and the effect that predetermined goal of the invention is taked for further setting forth the present invention, embodiment be illustrated, be described in detail as follows:
As shown in Figure 1, Fig. 1 is the method flow diagram of the nanocrystalline modulation crystalline silicon high-efficiency solar cell of preparation surface silicon provided by the invention, and this method may further comprise the steps:
Step 101: at crystalline silicon substrate surface preparation suede structure;
Step 102: diffuse to form the PN junction structure on the crystalline silicon substrate of suede structure having;
Step 103: front face surface forms the silicon nanocrystal structure;
Step 104: surface deposition silicon nitride antireflective film;
Step 105: the making of positive and negative electrode is finished in silk screen printing;
Step 106: alloying finally forms the solar cell of the nanocrystalline modulation of surface silicon.
The processing step that the present invention takes is as follows:
1), utilize the method for preparing matte on the large-scale production line, be that crystalline silicon substrate between 180 microns to 250 microns is positioned over and carries out anisotropic etch (step of polysilicon is slightly different) in the sodium hydroxide solution with thickness; The front of substrate and reverse side all place corrosive liquid in preparation process, the matte each side characteristic basically identical of the positive and negative of preparing.Suede structure presents the pyramid of mean depth about 10 microns.
2), all have the crystal silicon substrate of suede structure to be placed in the diffusion furnace tow sides, spread.Diffuse source is liquid POCl
3, diffusion technology is realized in the gasification back.Its junction depth of the double-sided PN junction that diffuses out is between 200~500 microns.Utilize pickling to remove the phosphorosilicate glass of positive and negative after having spread, and carry out trimming with edge-engraving machine and handle.
3), utilize magnetron sputtering or electron beam evaporation equipment at crystalline silicon substrate surface deposition one deck silicon thin film, film thickness is between 2~10nm.Form the silicon nanocrystal of size, controllable density afterwards by the mode of rapid thermal annealing.
4), crystalline silicon substrate that the surface has been formed the silicon nanocrystal structure is positioned in plasma enhanced chemical vapor deposition (PECVD) equipment, at the positive grown silicon nitride antireflective film of substrate, thickness is 70~120nm.
5), utilize screen printing technique, carry out silk screen printing, low-temperature setting heat treatment respectively at substrate reverse side and front, form electrode pattern.
6), adopt the staged heating mode to carry out alloying to carrying out electrode, no special atmosphere is protected, available compressed air cools off.The final complete efficient crystal silicon solar batteries of the nanocrystalline modulation of surface silicon of preparing.
Fig. 2 to Fig. 7 is the schematic diagram that is used for illustrating a specific embodiment of the present invention.
As shown in Figure 2, the crystalline silicon substrate of choosing is commercial monocrystalline or polysilicon chip, and monocrystalline silicon piece is of a size of 125 * 125cm
2(rescinded angle), polysilicon chip is of a size of 156 * 156Gm
2, substrate type is a P type substrate, among the figure 201; Monocrystalline resistivity is 0.5~3 Ω cm, and polycrystalline resistivity is 0.5~6 Ω cm.
As shown in Figure 3, utilizing large-scale production to prepare the method for matte, is that crystal silicon substrate between 180 microns to 250 microns is positioned over prepared NaOH, Na by a certain percentage with thickness
2SiO
3In the Woolen-making liquid that mixes with absolute ethyl alcohol, crystal silicon is carried out anisotropic wet etching and forms and be pyramidal suede structure, average height is about 10 microns, and wherein to prepare the mode of matte slightly different for polysilicon.The front of substrate and reverse side all place corrosive liquid in preparation process, and the matte each side characteristic basically identical of the positive and negative of preparing is shown among the figure 301.
As shown in Figure 4, the crystal silicon substrate that tow sides is prepared suede structure is placed in the diffusion furnace, spreads.The diffusion furnace temperature can be 300 ℃ to 1300 ℃ variations.In this example, we choose diffusion temperature between 850~950 ℃, and diffuse source is liquid POCl
3, single face diffusion obtains the PN junction structure of junction depth between 200~500nm by control diffusion time, and the square resistance of formation changes about between 20~50 Ω/, as among the figure 401.Then remove in the diffusion process at the phosphorosilicate glass of battery surface formation, clean up and dry with deionized water after having removed phosphorosilicate glass with the hybrid corrosion liquid of hydrofluoric acid, nitric acid and water.Adopt edge-engraving machine equipment with battery sheet trimming then.
Be illustrated in figure 5 as process in surface preparation silicon nanocrystal structure.Before preparation, clean the substrate of having finished the every technology in front with hydrofluoric acid solution, remove surface oxide layer.Afterwards substrate is put in the cavity of magnetron sputtering or electron beam evaporation equipment and rapid vacuumizing,, evaporated the silicon thin film of a layer thickness at 2~10nm to reduce the oxidation on crystal silicon surface.Utilize the rapid thermal annealing method to form silicon nanocrystal after evaporating, among the figure shown in 501.In this step process process, the temperature and time when thickness that can be by the silicon thin film that evaporated of control, rapid thermal annealing obtains size, silicon nanocrystal structure that density is different.
Be illustrated in figure 6 as the process of preparation antireflective film.The substrate of finishing the every technology in front is put in the plasma enhanced chemical vapor deposition equipment (PECVD), the grown silicon nitride film, film thickness monitoring is between 70~120nm, and for the individual layer antireflective film situation of crystal silicon battery, it is best that its anti-reflection effect to light can reach.The antireflective film of this thickness can cover the silicon nanocrystal layer, as among the figure 601.
As shown in Figure 7, utilize silk screen printing that aluminum slurry is printed in cell backside, form aluminium back of the body field plate, finish printing the back and also solidified 200 ℃ of heat treatments.At front surface coated negative electrode silver paste, form grid line and busbar with screen process press, finish printing the back and also solidified 200 ℃ of heat treatments.The electrode structure of battery front side, reverse side is respectively as 701,702 signals among the figure.
At last according to the mode of large-scale production line electrode positive, reverse side is carried out staged thermal anneal process from 300 ℃ to 900 ℃, so far, alloying process is finished.Finally prepare the preparation of the nanocrystalline modulation crystalline silicon high-efficiency solar cell of surface silicon.
Above-described specific embodiment; purpose of the present invention, technical scheme and beneficial effect are further described; institute is understood that; the above only is specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any modification of being made, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.