Disclosure of Invention
In order to solve the defects of the prior art, the invention provides a preparation method of a solar cell, which comprises the following steps: depositing a nano silicon boron slurry grid line for local laser doping on the front side or the back side of a silicon wafer, depositing a back metal grid line electrode on the back side of the silicon wafer, and depositing a front metal grid line electrode on the front side of the silicon wafer; the deposition adopts a non-contact laser transfer printing mode.
Preferably, the laser transfer printing comprises the following specific steps: placing a silicon wafer on a bearing table, arranging a transfer printing substrate above the silicon wafer, and coating a material to be transferred on the bottom surface of the transfer printing substrate; arranging a laser above the transfer printing substrate, and scanning and transferring the material to be transferred on the bottom surface of the transfer printing substrate onto a silicon wafer by using laser (high-energy linear light beams or Gaussian light beams) generated by the laser;
the transfer printing substrate is made of a material which meets the requirements of light transmission, high temperature resistance, corrosion resistance and stable chemical property;
when the laser transfer printing is adopted to deposit the nano silicon boron slurry grid line for laser local doping on the front side or the back side of the silicon wafer, the used material to be transferred is nano silicon boron slurry;
and when the back metal grid line electrode is deposited on the back surface of the silicon wafer by adopting laser transfer printing and the front metal grid line electrode is deposited on the front surface of the silicon wafer by adopting laser transfer printing, the used material to be transferred is a metal conductive material.
Preferably, the metal conductive material is aluminum paste or silver paste.
Preferably, the bearing table has a heating function, and before laser transfer printing, the bearing table heats the silicon wafer to enable the silicon wafer to reach a preset temperature.
Preferably, in the laser transfer process, the diameter of a laser line (the size of a focused beam) is controlled to be 1-20 μm, and the laser pulse is controlled to be 1-100 ns.
Preferably, in the laser transfer process, the distance between the bottom surface of the transfer substrate and the silicon wafer is controlled to be 1-50 μm.
Preferably, in the laser transfer process, the number of main grid lines of the transfer pattern is 1-10, the width of the grid line of the nano silicon boron paste is 1-180 μm, the width of the front side auxiliary grid line is 1-50 μm, and the width of the back side auxiliary grid line is 1-200 μm.
Preferably, the solar cell is a PERL cell, and the preparation method comprises the following specific steps:
1) cleaning a silicon wafer and texturing;
2) phosphorus diffusion;
3) locally re-doping by laser on the front surface;
4) chain oxidation;
5) removing PSG and back polishing;
6) back oxidation;
7) depositing a passivation film on the back;
8) depositing an anti-reflection film on the front surface;
9) depositing nano silicon boron slurry for laser local doping on the back of the silicon wafer;
10) laser local doping on the back;
11) depositing a back metal grid line electrode;
12) depositing a front metal grid line electrode;
13) and (5) sintering.
Preferably, the process parameters of the front laser local heavy doping are as follows: the laser wavelength is 300-780 nm, the laser power is 1-50 w, the frequency is 1-50 MHz, the scanning speed is 1-50 m/s, and the spot size is 1-100 um.
Preferably, the solar cell is a Topcon cell, and the preparation method comprises the following specific steps:
1) cleaning a silicon wafer and texturing;
2) front side boron diffusion;
3) BSG etching;
4) oxidizing the tunneling layer;
5) depositing polysilicon on the back;
6) back phosphorus diffusion;
7) cleaning;
8) depositing a passivation film on the front surface;
9) depositing an anti-reflection film on the back;
10) depositing nano silicon boron slurry for laser local doping on the front surface of the silicon wafer;
11) locally doping laser on the front surface;
12) cleaning to remove the boron slurry on the front surface;
13) depositing a back metal grid line electrode;
14) depositing a front metal grid line electrode;
15) and (5) sintering.
The invention has the advantages and beneficial effects that: the preparation method of the solar cell is provided, the non-contact deposition of the nano silicon boron slurry and the electrode is realized by utilizing laser transfer printing, and the subfissure and fragmentation rate of a silicon wafer are reduced; the method is favorable for optimizing the specification size and the appearance of the electrode, increasing the light absorption and improving the cell efficiency, simultaneously improves the cleanliness of the silicon wafer, eliminates a pollution source, and is suitable for application of large-scale production.
Detailed Description
The following description of the embodiments of the present invention will be made with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
Example 1
The invention provides a preparation method of a PERL solar cell, which comprises the following steps:
1) cleaning and texturing silicon wafers: using an alkaline solution for texturing, performing surface texture on a monocrystalline silicon wafer to form a pyramid shape, reducing surface reflection, cleaning the surface to remove impurities and metal ions, wherein the process temperature is 60-80 ℃, and the corrosion time is 20 min;
2) phosphorus diffusion: preparing a suede phosphorus diffusion layer to form a pn junction, wherein the diffusion temperature is 850 ℃, and the sheet resistance after diffusion is about 150 ohm/sq;
3) front laser local heavy doping: (532 nm, green light) and phosphorus silicon glass are used as doping sources to realize selective emission junctions, and the sheet resistance of the front laser doping area is 70 ohm/sq;
4) chain oxidation: oxidizing the silicon wafer in chain equipment to form a layer of silicon oxide on the surface of the front laser doping area, so as to protect the silicon oxide from being influenced in the alkali polishing process, wherein the thickness of the silicon oxide is about 10 nm;
5) PSG removal and back polishing: removing PSG on the back surface of a silicon wafer by water film protection, then realizing back polishing by adopting an alkali polishing process, removing phosphorosilicate glass and edge pn junctions on the front surface of the silicon wafer, wherein the process temperature is about 60-80 ℃, and the process time is about 20 min;
6) back oxidation: oxidizing the back of the silicon wafer to form a layer of silicon oxide with the thickness of about 10 nm;
7) depositing a passivation film on the back: growing a silicon oxynitride/silicon nitride laminated film on the back of the silicon wafer by using a PECVD method, wherein the thickness of the laminated film is 150 nm;
8) front side deposition of an antireflection film: growing a silicon nitride anti-reflection film on the front surface of the silicon wafer by using a PECVD method, wherein the thickness of the silicon nitride anti-reflection film is 75 nm;
9) depositing nano silicon boron slurry for laser local doping on the back of the silicon wafer: depositing a nano silicon boron slurry grid line for laser local doping on the back of a silicon wafer by adopting a non-contact laser transfer printing mode, accurately controlling the size and the shape of the nano silicon boron slurry grid line, controlling the laser pulse to be 10 ns-20 ns, controlling the diameter (the size of a focused light beam) of a laser line to be 15 mu m-20 mu m, controlling the distance between the bottom surface of a transfer printing substrate and the silicon wafer to be 20 mu m-40 mu m, and controlling the width of the nano silicon boron slurry grid line to be 60 mu m-100 mu m;
10) back laser local doping: doping the grid line of the nano silicon boron slurry by adopting nano laser (532 nm, green light), forming a heavily doped region at the position of the boron slurry, wherein the doping concentration is about 1E +20, and the depth is 0.8-1.2 um;
11) depositing a back metal grid line electrode: depositing a back metal grid line electrode (back aluminum grid line) on the back of the silicon wafer in a non-contact laser transfer printing mode, so that the back metal grid line electrode completely covers the boron paste grid line;
12) depositing a front metal grid line electrode: depositing a front metal grid line electrode on the front surface of the silicon wafer in a non-contact laser transfer printing mode;
13) and (5) sintering.
Example 2
The invention also provides a preparation method of the Topcon solar cell, which comprises the following steps:
1) cleaning and texturing by taking an N-type silicon wafer as a substrate: using an alkaline solution for texturing, forming a pyramid shape on a monocrystalline silicon wafer through surface texture, reducing surface reflection, cleaning the surface to remove impurities and metal ions, wherein the process temperature is 60-80 ℃, and the corrosion time is about 20 min;
2) front side boron diffusion: BCl used on suede surface3Forming a PN junction by diffusion, wherein the process temperature is 1025 ℃, and the sheet resistance is between 100 and 120 omega;
3) BSG etching: washing BSG with acid on the back, and etching and polishing the back with alkali solution;
4) oxidizing the tunneling layer: forming a silicon oxide tunneling layer on the back surface by using dry oxidation, wherein the process temperature is about 650 ℃, and the thickness of the tunneling layer is about 1-2 nm;
5) back polysilicon deposition: depositing a layer of poly-silicon on the back tunneling layer by using PECVD; introducing SiH4, depositing a layer of thinner poly silicon with the thickness of 20nm at the process temperature of 400-500 ℃; then heating to 650 ℃, and depositing secondary polysilicon with the thickness of about 110 nm, wherein the total thickness of the deposited polysilicon is 120-140 nm;
6) back side phosphorus diffusion: the back surface adopts POCl3Phosphorus diffusion is carried out to dope poly silicon to form P-type silicon, the diffusion temperature is 850 ℃, and the sheet resistance after diffusion is about 30-150 omega;
7) cleaning: washing PSG and BSG with acid, wherein the concentration of HF is 5%, the temperature is 70 ℃, and the total time is 10 min;
8) depositing AlOx and SiNx passivation films on the front side: growing an AlOx and SiNx laminated film on the front surface of the silicon wafer by a PECVD method, wherein the thickness of the laminated film is 85 nm;
9) depositing a SiNx anti-reflection film on the back: growing a silicon nitride anti-reflection film on the back of the silicon wafer by using a PECVD method, wherein the thickness of the silicon nitride anti-reflection film is 75 nm;
10) depositing nano silicon boron slurry for laser local doping on the front side of a silicon wafer: depositing a nano silicon boron slurry grid line for laser local doping on the front surface of a silicon wafer by adopting a non-contact laser transfer printing mode, accurately controlling the size and the appearance of the nano silicon boron slurry grid line, controlling the distance between the bottom surface of a transfer printing substrate and the silicon wafer to be 20-40 mu m, and controlling the width of the nano silicon boron slurry grid line to be 60-100 mu m;
11) front laser local doping: doping the nano silicon boron paste grid line by adopting laser, forming a heavily doped region at the boron paste position, and having no obvious damage to the texture;
12) cleaning to remove the boron slurry on the front surface;
13) depositing a back metal grid line electrode: depositing a back metal grid line electrode on the back of the silicon wafer by adopting a non-contact laser transfer printing mode;
14) depositing a front metal grid line electrode: depositing a front metal grid line electrode on the front surface of the silicon wafer by adopting a non-contact laser transfer printing mode, and accurately controlling to enable the front metal grid line electrode to be completely positioned in a boron slurry laser heavily-doped region;
15) and (5) sintering.
Step 9) of embodiment 1, depositing nano silicon boron slurry for laser local doping on the back surface of a silicon wafer, step 11) of depositing a back metal grid line electrode, and step 12) of depositing a front metal grid line electrode all adopt a non-contact laser transfer printing mode;
step 10) of embodiment 2, depositing nano silicon boron slurry for laser local doping on the front surface of a silicon wafer, step 13) depositing a back metal grid line electrode, and step 14) depositing a front metal grid line electrode also adopt a non-contact laser transfer printing mode;
specifically, as shown in fig. 1, the non-contact laser transfer method includes the following specific steps: placing a silicon wafer 4 on a bearing table 5, arranging a transfer printing substrate 2 above the silicon wafer 4, and coating a material 3 to be transferred on the bottom surface of the transfer printing substrate 2; a laser 1 is arranged above the transfer printing substrate 2, and the laser 6 (high-energy linear beam or Gaussian beam) generated by the laser 1 is used for scanning and transferring the material 3 to be transferred on the bottom surface of the transfer printing substrate 2 onto a silicon chip 4;
the transfer printing substrate 2 is made of a material which meets the requirements of light transmission, high temperature resistance, corrosion resistance and stable chemical property;
when the laser transfer printing is adopted to deposit the nano silicon boron slurry grid line for laser local doping on the back surface of the silicon chip 4, the used material 3 to be transferred is nano silicon boron slurry;
depositing a back metal grid line electrode on the back of a silicon wafer 4 by laser transfer printing, wherein the used material 3 to be transferred is aluminum paste;
when the front metal grid line electrode is deposited on the front surface of the silicon chip 4 by laser transfer printing, the material 3 to be transferred is silver paste;
the bearing table 5 has a heating function, and before laser transfer printing, the bearing table 5 heats the silicon wafer 4 to enable the silicon wafer 4 to reach a preset temperature;
in the laser transfer process:
the diameter of the laser line (the size of the focused beam) is controlled to be 15-20 μm, and the laser pulse is controlled to be 10-20 ns.
The distance between the bottom surface of the transfer substrate 2 and the silicon chip 4 is controlled to be 20-40 mu m;
the number of main grid lines of the transfer printing graph is 9, the width of the nanometer silicon boron slurry grid lines is 60-100 mu m, the width of the front side auxiliary grid lines is 10-40 mu m, and the width of the back side auxiliary grid lines is 100-120 mu m.
Example 1 a PERL solar cell was prepared having a structure as shown in fig. 2, in which a layered structure from one side of the cell to the other side thereof includes: the structure comprises a positive electrode 11, a positive electrode fine grid heavily-doped region 12, a front silicon nitride antireflection film 13, a phosphorus diffusion layer 14, a silicon substrate 10, a passivation layer 16, a silicon nitride layer 17, a nano silicon boron slurry heavily-doped region 15, a nano silicon boron slurry grid line 18 and a back electrode 19.
Example 2 a Topcon solar cell was prepared having the structure shown in fig. 3, the layered structure from one side of the cell to the other comprising: the solar cell comprises a positive electrode 21, a front SiNx antireflection film 22, an AlOx passivation layer 23, a boron diffusion layer 24, a nano silicon boron slurry heavily-doped region 25, an N-type silicon substrate 20, an SiOx tunneling layer 26, phosphorus-extended p-type poly-silicon 27, a back SiNx layer 28 and a back electrode 29.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the technical principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.