Heterojunction solar cell and method for manufacturing the same

Abstract

The application provides a heterojunction solar cell and a preparation method thereof. The heterojunction solar cell comprises a single crystal silicon substrate, an intrinsic amorphous silicon thin film layer prepared on the front surface and the back surface of the single crystal silicon substrate, an N-type amorphous silicon doped layer or an N-type microcrystalline silicon doped layer arranged on the top surface of the intrinsic amorphous silicon thin film layer on the front surface of the single crystal silicon substrate, a P-type microcrystalline silicon doped layer arranged on the bottom surface of the intrinsic amorphous silicon thin film layer on the back surface of the single crystal silicon substrate, a light-transmitting conductive layer arranged on the top surface of the N-type amorphous silicon doped layer or the N-type microcrystalline silicon doped layer and the bottom surface of the P-type microcrystalline silicon doped layer, and an electrode arranged on the surface of the light-transmitting conductive layer. The P-type microcrystalline silicon doped layer is a layered structure deposited by at least a mixed gas of silane and trimethyl boron, the damage of boron atoms to Si-H bonds is reduced, the crystallization rate of microcrystalline silicon is improved, and thus the conversion efficiency of the cell is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of heterojunction solar cells, in particular to a heterojunction solar cell and a preparation method thereof. BACKGROUND

[0002] The crystalline silicon / amorphous silicon heterojunction solar cell (HJT) has the advantages of high conversion efficiency and simple process flow. The conventional preparation method is to use an N-type crystalline silicon wafer as a substrate, perform etching and cleaning, deposit double-sided amorphous silicon (a-Si:H) films, deposit double-sided transparent conductive films (TCO), screen print low-temperature paste, and solidify, etc. The microcrystalline silicon film (uc-Si:H) has the characteristics of good light transmittance and high conductivity, and can replace the amorphous silicon (a-Si:H) film as the doped layer of the HJT cell, thereby significantly improving the short-circuit current (Jsc) and the fill factor (FF) of the HJT cell. Therefore, how to combine the microcrystalline silicon film (uc-Si:H) with the crystalline silicon / amorphous silicon heterojunction solar cell (HJT) is a problem that needs to be considered. SUMMARY

[0003] The present application aims to provide a heterojunction solar cell and a preparation method thereof.

[0004] To solve the above technical problems, the present application provides a heterojunction solar cell, comprising:

[0005] a single crystal silicon substrate;

[0006] an intrinsic amorphous silicon film layer prepared on the front and back surfaces of the single crystal silicon substrate;

[0007] an N-type amorphous silicon doped layer or an N-type microcrystalline silicon doped layer arranged on the top surface of the intrinsic amorphous silicon film layer on the front surface of the single crystal silicon substrate;

[0008] a P-type microcrystalline silicon doped layer arranged on the bottom surface of the intrinsic amorphous silicon film layer on the back surface of the single crystal silicon substrate;

[0009] a light-transmitting conductive layer arranged on the top surface of the N-type amorphous silicon doped layer or the N-type microcrystalline silicon doped layer and the bottom surface of the P-type microcrystalline silicon doped layer, respectively;

[0010] an electrode arranged on the surface of the light-transmitting conductive layer.

[0011] Further, the P-type microcrystalline silicon doped layer is a layered structure deposited by at least a mixed gas of silane and trimethylboron doping.

[0012] Further, the P-type microcrystalline silicon doped layer is prepared by a coating equipment, and process parameters of the coating equipment are as follows: power of 1000-20000 W, and pressure of 50-1000 Pa; the coating equipment is a plasma vapor deposition equipment or a catalytic chemical vapor deposition equipment.

[0013] Further, the P-type microcrystalline silicon doped layer has a thickness of 5-50 nm.

[0014] Further, the intrinsic amorphous silicon thin film layer has three layers, i.e., a first intrinsic amorphous silicon thin film layer with a thickness of 0.5-2 nm, a second intrinsic amorphous silicon thin film layer with a thickness of 1-3 nm, and a third intrinsic amorphous silicon thin film layer with a thickness of 1-6 nm.

[0015] Further, when the doped layer on the top surface of the intrinsic amorphous silicon thin film layer on the front surface of the single crystal silicon substrate is the N-type microcrystalline silicon doped layer, the N-type microcrystalline silicon doped layer is a layered structure deposited by at least a mixed gas of silane and trimethylboron.

[0016] The application further provides a preparation method of the heterojunction solar cell piece.

[0017] 002: selecting a single crystal silicon piece, and cleaning and texturing the single crystal silicon piece;

[0018] 004: preparing an intrinsic amorphous silicon thin film layer on the front surface and the back surface of the single crystal silicon piece;

[0019] 006: preparing an N-type doped layer on the top surface of the intrinsic amorphous silicon thin film layer on the front surface;

[0020] 008: preparing a P-type microcrystalline silicon doped layer on the intrinsic amorphous silicon thin film layer on the back surface;

[0021] 010: preparing a light-transmitting conductive layer on the top surface of the N-type doped layer and the bottom surface of the P-type microcrystalline silicon doped layer, respectively;

[0022] 012: printing an electrode on the surface of the light-transmitting conductive layer.

[0023] Further, the N-type doped layer is an N-type amorphous silicon doped layer or an N-type microcrystalline silicon doped layer.

[0024] Further, in step 008, the P-type microcrystalline silicon doped layer is deposited by introducing at least a mixed gas of hydrogen, silane and trimethylboron into a coating equipment.

[0025] Further, the flow rate of hydrogen is 20-500 times the flow rate of silane, and the flow rate of trimethylboron is 0.1-10% of the flow rate of silane.

[0026] Microcrystalline silicon (μc-Si:H) is a mixed phase of microcrystalline grains, amorphous, grain boundaries and cavities, so that microcrystalline silicon has different properties from amorphous silicon and single crystal silicon. Microcrystalline silicon has a high degree of crystallization, and has a higher order than amorphous silicon material. The light transmittance of microcrystalline silicon is better than that of amorphous silicon.

[0027] In the present application, the heterojunction solar cell, i.e. microcrystalline silicon heterojunction cell, uses doped microcrystalline silicon as a doped layer (n-uc-Si:H, p-uc-Si:H) deposited on an intrinsic amorphous silicon thin film layer (i-layer), instead of a conventional amorphous silicon doped layer (n-a-Si:H, p-a-Si:H). The preparation process is as follows: N-type single crystal silicon (which can be P-type silicon, polycrystalline silicon, etc.) is used as a substrate, which is subjected to wet chemical (which can be other texturing methods) treatment such as texturing cleaning to form a pyramid textured structure (which can be other textured structures). A film coating device (which can be RF-PECVD, VHF-PECVD, CAT-CVD, or other film coating methods) is used to deposit an intrinsic amorphous silicon thin film layer (i-layer) as a passivation layer on the front and back surfaces of the textured silicon wafer. An N-type microcrystalline silicon doped layer (n-uc-Si:H, three-layer structure) is further deposited on the front surface of the intrinsic amorphous silicon thin film layer. Further, a P-type microcrystalline silicon doped layer (p-uc-Si:H) is deposited on the back surface of the intrinsic amorphous silicon thin film layer as an emitter layer. After the deposition of the double-sided microcrystalline silicon film, TCO thin film is further deposited on the front and back surfaces by PVD (which can be RPD, PAR, or other methods). Low-temperature silver paste (which can be inkjet printing, electroplating, or other methods) is printed on the front and back surfaces of the cell by screen printing. After drying and curing, the metallization of the cell is completed.

[0028] In the present application, the heterojunction solar cell, i.e. microcrystalline silicon heterojunction cell, uses doped microcrystalline silicon as a doped layer (n-uc-Si:H, p-uc-Si:H) deposited on an intrinsic amorphous silicon thin film layer (i-layer), instead of a conventional amorphous silicon doped layer (n-a-Si:H, p-a-Si:H). The preparation process is as follows: N-type single crystal silicon (which can be P-type silicon, polycrystalline silicon, etc.) is used as a substrate, which is subjected to wet chemical (which can be other texturing methods) treatment such as texturing cleaning to form a pyramid textured structure (which can be other textured structures). A film coating device (which can be RF-PECVD, VHF-PECVD, CAT-CVD, or other film coating methods) is used to deposit an intrinsic amorphous silicon thin film layer (i-layer) as a passivation layer on the front and back surfaces of the textured silicon wafer. An N-type microcrystalline silicon doped layer (n-uc-Si:H, three-layer structure) is further deposited on the front surface of the intrinsic amorphous silicon thin film layer. Further, a P-type microcrystalline silicon doped layer (p-uc-Si:H) is deposited on the back surface of the intrinsic amorphous silicon thin film layer as an emitter layer. After the deposition of the double-sided microcrystalline silicon film, TCO thin film is further deposited on the front and back surfaces by PVD (which can be RPD, PAR, or other methods). Low-temperature silver paste (which can be inkjet printing, electroplating, or other methods) is printed on the front and back surfaces of the cell by screen printing. After drying and curing, the metallization of the cell is completed.

[0029] The present application has the following advantages:

[0030] (1) The main function of the intrinsic amorphous silicon thin film layer is to passivate the surface of the single crystal silicon substrate, reduce the surface defect state, and reduce the surface recombination of carriers. On the back surface of the single crystal silicon substrate, a microcrystalline silicon thin film doped with trimethylboron is directly deposited on the intrinsic amorphous silicon thin film, which is beneficial to improve the crystallization rate of the microcrystalline silicon layer. The use of multiple intrinsic amorphous silicon thin films can improve the passivation effect and further improve the crystallization rate.

[0031] (2) In the process of manufacturing microcrystalline silicon heterojunction solar cell, trimethylboron (TMB) is used as B dopant to dope microcrystalline silicon on the back of the cell (i.e. the back of the single crystal silicon substrate), as the P-type doped layer of the HJT cell. In the molecular structure of TMB, the boron atom is connected with three methyl groups, and the valence bond between them is exactly the same, the chemical bond is relatively tight, there is no B-B, B-H weak bond, and the thermal stability is relatively high. Therefore, using trimethylboron as boron (B) dopant to dope microcrystalline silicon thin film can reduce the damage of B atoms to Si-H bond, and the doped microcrystalline silicon has a higher crystallization rate, and it is easier to prepare a microcrystalline P-type doped layer with high crystallization rate.

[0032] (3) The microcrystalline silicon thin film is prepared by using a coating equipment, and the production process adopts high power, high pressure and high hydrogen dilution ratio, which can improve the density of the reaction precursor in the plasma, and prepare a microcrystalline silicon thin film containing a large amount of hydrogen. BRIEF DESCRIPTION OF DRAWINGS

[0033] The application will be further described below in combination with the drawings and examples.

[0034] Figure 1 is a structure diagram of a heterojunction solar cell provided in an embodiment of the application.

[0035] Figure 2 is a structure diagram of another heterojunction solar cell provided in an embodiment of the application.

[0036] Figure 3 is a preparation flowchart of a heterojunction solar cell provided in an embodiment of the application.

[0037] Figure 4 is a molecular structure diagram of diborane provided in an embodiment of the application.

[0038] Figure 5 is a molecular structure diagram of trimethylboron provided in an embodiment of the application.

[0039] In the figure: 110-single crystal silicon substrate; 120-intrinsic amorphous silicon thin film layer; 121-first intrinsic amorphous silicon thin film layer; 122-second intrinsic amorphous silicon thin film layer; 123-third intrinsic amorphous silicon thin film layer; 130-N-type doped layer; 131-first N-type amorphous silicon doped layer; 132-second N-type amorphous silicon doped layer; 133-third N-type amorphous silicon doped layer; 140-P-type microcrystalline silicon doped layer; 150-light-transmitting conductive layer; 160-electrode; 170-type microcrystalline silicon doped layer. DETAILED DESCRIPTION

[0040] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0041] Example 1

[0042] like Figure 1 As shown, a heterojunction solar cell is provided, comprising: a monocrystalline silicon substrate 110 (nc-si), an intrinsic amorphous silicon thin film layer 120 (i-layer), an N-type amorphous silicon doped layer 130 (n-uc-si-layer), a P-type microcrystalline silicon doped layer 140 (p-uc-si-layer), a light-transmitting conductive layer 150 (TCO), and an electrode 160. The N-type amorphous silicon doped layer 130 (n-uc-si-layer) has a three-layer structure, including a first N-type amorphous silicon doped layer 131, a second N-type amorphous silicon doped layer 132, and a third N-type amorphous silicon doped layer 133.

[0043] An intrinsic amorphous silicon thin film layer 120 is located above the monocrystalline silicon substrate 110 on the front side of the monocrystalline silicon substrate 110. The intrinsic amorphous silicon thin film layer 120, an N-type amorphous silicon doped layer 130, a light-transmitting conductive layer 150, and an electrode 160 are sequentially arranged to form the front side of the solar cell. An intrinsic amorphous silicon thin film layer 120 is located below the monocrystalline silicon substrate 110 on the back side of the monocrystalline silicon substrate 110. The intrinsic amorphous silicon thin film layer 120, a P-type microcrystalline silicon doped layer 140, a light-transmitting conductive layer 150, and an electrode 160 are sequentially arranged to form the back side of the solar cell.

[0044] like Figure 2 As shown, another heterojunction solar cell is provided, comprising: a monocrystalline silicon substrate 110, an intrinsic amorphous silicon thin film layer 120, an N-type microcrystalline silicon doped layer 170, a P-type microcrystalline silicon doped layer 140, a light-transmitting conductive layer 150, and an electrode 160. The intrinsic amorphous silicon thin film layer 120, located above the monocrystalline silicon substrate 110, is on the front side of the monocrystalline silicon substrate 110. The intrinsic amorphous silicon thin film layer 120, the N-type microcrystalline silicon doped layer 170, the light-transmitting conductive layer 150, and the electrode 160 are sequentially arranged to form the front side of the solar cell. The intrinsic amorphous silicon thin film layer 120, located below the monocrystalline silicon substrate 110, is on the back side of the monocrystalline silicon substrate 110. The intrinsic amorphous silicon thin film layer 120, the P-type microcrystalline silicon doped layer 140, the light-transmitting conductive layer 150, and the electrode 160 are sequentially arranged to form the back side of the solar cell.

[0045] In the above two heterojunction solar cell structures, the intrinsic amorphous silicon thin film layer includes three layers, i.e., a first intrinsic amorphous silicon thin film layer 121 (i1-layer) with a thickness of 0.5 nm-2 nm, a second intrinsic amorphous silicon thin film layer 122 (i2-layer) with a thickness of 1 nm-3 nm, and a third intrinsic amorphous silicon thin film layer 123 (i3-layer) with a thickness of 1 nm-6 nm. The first, second, and third intrinsic amorphous silicon thin film layers are arranged in sequence, and the first intrinsic amorphous silicon thin film layer is arranged on the front surface or the back surface of the single crystal silicon substrate 110.

[0046] The main function of the intrinsic amorphous silicon thin film layer is to passivate the surface of the single crystal silicon substrate, reduce the surface defect state, and reduce the surface recombination of carriers. On the back surface of the single crystal silicon substrate, a microcrystalline silicon thin film doped with trimethylboron is plated directly on the intrinsic amorphous silicon thin film, which is beneficial to improving the crystallization rate of the microcrystalline silicon layer. The use of a multi-layer intrinsic amorphous silicon thin film can improve the passivation effect and is more beneficial to the improvement of the crystallization rate.

[0047] In the above two heterojunction solar cell structures, the P-type microcrystalline silicon doped layer 140 is located below the intrinsic amorphous silicon thin film layer on the back surface of the single crystal silicon substrate. The P-type microcrystalline silicon doped layer 140 is a layered structure deposited from at least a mixed gas of silane and trimethylboron. In preparation, the P-type microcrystalline silicon doped layer is prepared by using a plating equipment, and the process parameters of the plating equipment are as follows: the power of the power supply is 1000-20000 W, and the pressure is 50-1000 Pa. The plating equipment is a plasma enhanced chemical vapor deposition (PECVD) or a catalytic chemical vapor deposition (CAT-CVD). The PECVD equipment is assisted by microwaves or radio frequency to ionize the gas containing film composition atoms, to form a local plasma, and the plasma has strong chemical activity and can easily react to deposit the desired thin film on the substrate. The PECVD equipment includes radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) and very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD). The working principle of CAT-CVD is similar to that of PECVD, and both of them introduce chemical reactions in the gas phase. The high-temperature catalyst is used to trigger the gas phase reaction in CAT-CVD, and the silane molecules are rapidly decomposed under high-temperature catalysis.

[0048] Specifically, the process of preparing the P-type microcrystalline silicon doped layer 140 is as follows:

[0049] The P-type microcrystalline silicon doped layer 140 is prepared on the back surface of the intrinsic amorphous silicon thin film layer by using a plasma vapor deposition device, and the process parameters of the plasma vapor deposition device are as follows: power of 1000-20000 W, pressure of 50-1000 Pa, ratio of hydrogen flow to silane flow (H2 / SiH4) of 20-500 times, and ratio of trimethylboron flow to silane flow (TMB / SiH4) of 0.1-10%.

[0050] The microstructure factor R of the prepared P-type microcrystalline silicon doped layer 140 is 40-90%, the resistance is 10-1000 MΩ, and the crystallization rate is 10-90%.

[0051] The preparation method of the N-type microcrystalline silicon doped layer 170 is the same as that of the P-type microcrystalline silicon doped layer 140.

[0052] In this embodiment, the transparent conductive layer is arranged on the top surface of the N-type amorphous silicon doped layer or the N-type microcrystalline silicon doped layer and the bottom surface of the P-type microcrystalline silicon doped layer, respectively, and the transparent conductive layer is prepared by using PAR / PVD / RPD. The square resistance of the transparent conductive layer is 20-150 Ω / □, the mobility is 20-150 cm 2 / V-s, and the transmittance is 90-98%.

[0053] The transparent conductive layer (TCO) refers to a transparent conductive oxide. TCO is a general term for a series of semiconductor materials with both light transmission and conductivity, mainly including ITO (indium tin oxide), IWO (indium oxide doped with tungsten), and AZO (aluminum-doped zinc oxide). Among the TCO materials mentioned, all those with I contain the rare metal indium (In).

[0054] The preparation method of the transparent conductive layer includes a magnetron sputtering device (PVD) and a reactive plasma deposition device (RPD). The magnetron sputtering device (PVD) is a device that uses high-energy particles to bombard the surface of a target in a vacuum chamber, so that the particles bombarded out form a thin film on the substrate surface. The reactive plasma deposition device (RPD) uses an ion source to bombard the target after being deflected by a magnetic field, so that the target atoms are bombarded and deposited on the sample, reducing the bombardment and etching of ions on the substrate surface.

[0055] In the embodiment, electrodes are set on the surface of the light-transmitting conductive layer by screen printing low-temperature silver paste on the front and back surfaces of the light-transmitting conductive layer, the grid line is 10-30 microns high and 20-80 microns wide, and after drying and curing, the electrodes are formed, the metallization of the microcrystalline silicon heterojunction battery is completed, and the preparation of the microcrystalline silicon heterojunction battery piece is completed.

[0056] In the process of manufacturing the microcrystalline silicon heterojunction HJT battery, trimethylboron (TMB) is used as a B dopant to dope the microcrystalline silicon on the back surface of the battery piece, serving as a P-type doped layer of the HJT battery. In the molecular structure of TMB, the boron atom is connected to three methyl groups, and the valence bonds between them are completely the same, the chemical bond is relatively tight, there are no weak bonds such as B-B and B-H, and the thermal stability is relatively high. Therefore, the doped microcrystalline silicon has a high crystallization rate, and it is easier to prepare a microcrystalline P with a high crystallization rate.

[0057] Embodiment 2

[0058] To prepare the battery piece in Embodiment 1, refer to Figure 2 The present application also provides a preparation method of a heterojunction solar cell piece, and the steps of the method include:

[0059] 002: Select a single crystal silicon piece, clean and texturize the single crystal silicon piece.

[0060] 004: Prepare an intrinsic amorphous silicon film layer on the front and back surfaces of the single crystal silicon piece.

[0061] 006: Prepare an N-type doped layer on the top surface of the intrinsic amorphous silicon film layer on the front surface, wherein the N-type doped layer is an N-type amorphous silicon doped layer or an N-type microcrystalline silicon doped layer.

[0062] 008: Prepare a P-type microcrystalline silicon doped layer on the intrinsic amorphous silicon film layer on the back surface, the P-type microcrystalline silicon doped layer is deposited by introducing a mixed gas containing at least trimethylboron doped hydrogen and silane into a plasma vapor deposition device, wherein the flow rate ratio of hydrogen to silane is 20-500 times, the flow rate ratio of trimethylboron to silane is 0.1-10%, and the process parameters of the plasma vapor deposition device are: power of 1000-20000 W and pressure of 50-1000 Pa.

[0063] 010: Prepare a light-transmitting conductive layer on the top surface of the N-type doped layer and the bottom surface of the P-type microcrystalline silicon doped layer, respectively.

[0064] 012: Set electrodes on the surface of the light-transmitting conductive layer.

[0065] Specifically:

[0066] In step 002, a single crystal silicon substrate, using an N-type single crystal silicon wafer, after completing the texturing cleaning, the thickness of the silicon wafer is 50-150 μm, the height of the pyramids on the textured surface is 0.5-5 μm, and the width is 1-10 μm.

[0067] In step 004, using a coating equipment, an intrinsic amorphous silicon thin film layer 120 is prepared on the front and back surfaces of the single crystal silicon substrate, the intrinsic amorphous silicon thin film layer is three layers, respectively, a first intrinsic amorphous silicon thin film layer with a thickness of 0.5 nm-2 nm, a second intrinsic amorphous silicon thin film layer with a thickness of 1 nm-3 nm, and a third intrinsic amorphous silicon thin film layer with a thickness of 1 nm-6 nm.

[0068] In step 006, using a coating equipment, an N-type doped layer is plated on the front surface of the intrinsic amorphous silicon thin film layer, the N-type doped layer is an N-type amorphous silicon doped layer with a thickness of 2 nm-10 nm; or the N-type doped layer is an N-type microcrystalline silicon doped layer with a thickness of 10 nm-30 nm.

[0069] In step 008, using a coating equipment, a P-type microcrystalline silicon doped layer is plated on the back surface of the intrinsic amorphous silicon thin film layer, the power supply power is 1000-20000 W, the pressure is 50-1000 Pa, the ratio of hydrogen flow to silane flow (H2 / SiH4) is 20-500 times, and the ratio of TMB flow to silane flow (TMB / SiH4) is 0.1-10%.

[0070] The prepared P-type microcrystalline silicon doped layer has a thickness of 5 nm-50 nm, a microstructure factor R of 40-90%, a resistance of 10-1000 MΩ, and a crystallization rate of 10-90%.

[0071] In step 0010, a PAR / PVD / RPD is used to plate a light-transmitting conductive layer with a square resistance of 20-150 Ω / □ and a mobility of 20-150 cm 2 / V-s, a transmittance of 90-98%; and

[0072] In step 012, a screen printing low-temperature silver paste is used to print on the transparent conductive layer on the front and back surfaces, the grid line is 10 μm-30 μm high and 20 μm-80 μm wide, after drying and curing, an electrode is formed, i.e. the metallization of the microcrystalline silicon heterojunction solar cell is completed, and the preparation of the microcrystalline silicon heterojunction solar cell wafer is completed.

[0073] Example 3

[0074] The P-type microcrystalline silicon doped layer in the heterojunction solar cell wafer in Example 1 or Example 2 is a layered structure deposited from a mixed gas of silane and trimethylboron doping. On the basis of Example 1 or Example 2, a heterojunction solar cell wafer doped with trimethylboron and a heterojunction solar cell wafer doped with diborane are prepared, and the preparation process is as follows:

[0075] 1. After texturing and cleaning, the thickness of the N-type monocrystalline silicon wafer is 140 μm, the height of the pyramids on the textured surface is 3 μm, and the width is 5 μm.

[0076] 2. The intrinsic amorphous silicon thin film layers on the front and back surfaces of the N-type monocrystalline silicon wafer are prepared by using a plasma vapor deposition device, the thickness of the first intrinsic amorphous silicon thin film layer is 1 nm, the thickness of the second intrinsic amorphous silicon thin film layer is 2.5 nm, and the thickness of the third intrinsic amorphous silicon thin film layer is 4 nm.

[0077] 3. An N-type amorphous silicon doped layer is plated on the intrinsic amorphous silicon thin film layer on the front surface by using a plasma vapor deposition device, and the thickness is 5 nm.

[0078] 4. A P-type microcrystalline silicon doped layer is plated on the intrinsic amorphous silicon thin film layer on the back surface by using a radio frequency-plasma enhanced chemical vapor deposition (RF-PECVD) device, and borine and trimethylboron are used as control experiments, and the specific data are shown in Table 1.

[0079]

[0080] 5. Crystallization rate test

[0081] The crystallization rate of a material can be obtained by analyzing the Raman scattering spectrum. The frequency of the light photons after Raman scattering changes relative to the incident light, and this change is called Raman shift. The Raman shift is related to the atomic vibration energy and arrangement. For microcrystalline silicon thin film materials, microcrystalline silicon thin films with different crystallization degrees have different peak values in the Raman spectrum. Specifically, after multiple single-point tests on a single P-type microcrystalline silicon film layer, peak fitting can be performed by using OMNIC and origin software, and the crystallization rate can be calculated from the peak area. The results are shown in Table 2.

[0082] Experimental group Crystallization rate 1 Crystallization rate 2 Crystallization rate 3 Crystallization rate average Group 1 0.302 0.300 0.298 0.300 Group 2 0.589 0.607 0.604 0.600

[0083] The above preparation process of the N-type monocrystalline silicon wafer, the preparation of the intrinsic amorphous silicon thin film layer, and the preparation of the amorphous silicon doped layer are the same, and the only variable is the different doping substances. Group 1 prepared a P-type microcrystalline silicon doped layer doped with borine, and the average crystallization rate value was 0.300. Group 2 prepared a P-type microcrystalline silicon doped layer doped with trimethylboron, and the average crystallization rate value was 0.600. It can be seen that the crystallization rate of the P-type microcrystalline silicon doped layer doped with trimethylboron is significantly higher than that of the P-type microcrystalline silicon doped layer doped with borine.

[0084] In addition, through repeated experiments, it can be verified from the comparison results that the crystallization rate of the P-type microcrystalline silicon doped layer doped with trimethylboron is significantly higher than that of the P-type microcrystalline silicon doped layer doped with borine.

[0085] The theoretical basis for significantly improving the crystallization rate by using trimethylboron as a microcrystalline doping substance is as follows:

[0086] Diborane (B2H6) is a commonly used boron dopant for heterojunction solar cells, and its molecular structure is shown in Figure 3 It contains a large number of B-B and B-H weak bonds. In the preparation of a P-type microcrystalline silicon doped layer, the incorporation of diborane (B2H6) easily introduces these B-B and B-H weak bonds, resulting in a large number of high-density defect states and reducing the crystallization rate of the thin film.

[0087] The hydrogen content in a P-type microcrystalline silicon doped layer is relatively high, and a microstructure factor R is often used to characterize it (R = [I2100] / [I2100+I2000]), where I is the ratio of the absorption peak intensities of different Si-Hx bonds in a Fourier transform infrared spectrum (FT-IR). The use of diborane (B2H6) doping leads to a large number of silicon-hydrogen bond (Si-H) breakage and hydrogen overflow, resulting in a low microstructure factor R and a reduced crystallization rate of the microcrystalline silicon thin film.

[0088] In addition, the boron in the P-type microcrystalline silicon doped layer is unstable when diborane (B2H6) is used for doping, and is easily detached from the bonding position, generating new dangling bonds, causing a decrease in atomic order and an increase in defect state density, so the crystallization rate of the microcrystalline silicon thin film decreases after the incorporation of B2H6.

[0089] On the other hand, diborane (B2H6) is easily decomposed, and in the plasma, it is first decomposed into BHx (x = 0, 1, 2) and H+, etc. These ions react with silane (SiH4) and H2 in molecular collisions, promoting the decomposition of silane (SiH4) and H2, increasing the plasma density, leading to an accelerated growth rate of the thin film, and making the deposited thin film more loose, thus reducing the crystallization rate of the thin film.

[0090] Taking an N-type crystalline silicon wafer as an example, N-type crystalline silicon is formed by doping a small amount of pentavalent element phosphorus into intrinsic semiconductor silicon. In the manufacturing process of a microcrystalline silicon heterojunction HJT cell, trimethylboron (TMB) is used as a boron (B) dopant to dope microcrystalline silicon on the back surface of the cell wafer, serving as a P-type doped layer of the HJT cell.

[0091] However, trimethylboron is used for doping, and its molecular structure is shown in Figure 4 The boron atom is connected to three methyl groups, and the valence bonds between them are completely the same, the chemical bonds are relatively tight, and there are no B-B and B-H weak bonds, and the thermal stability is good. Compared with p-uc-Si:H doped with diborane (B2H6), the crystallization rate of microcrystalline silicon doped with trimethylboron is higher, and it is easier to prepare a P-type microcrystalline silicon doped layer with a high crystallization rate.

[0092] 6. PAR IWO film (a kind of transparent conductive layer) is used, sheet resistance is 30 Ω / D, mobility is 100 cm 2 / V-s, transmittance is 98%;

[0093] 7. Screen printing low-temperature silver paste is used to print grid lines on the IWO film on the front and back surfaces, the grid line height is 15 μm, the grid line width is 60 μm, after drying and curing, electrodes are formed, that is, the metallization of the microcrystalline silicon heterojunction cell is completed, and the preparation of the microcrystalline silicon heterojunction cell is completed.

[0094] 8. Cell conversion efficiency detection results

[0095] Group 1: Compared with the HJT cell using an amorphous P-type doped layer, the fill factor (FF) is increased by about 0.15%, and the cell conversion efficiency is increased by about 0.05%.

[0096] Group 2: Compared with the HJT cell using an amorphous P-type doped layer, the fill factor (FF) is increased by about 0.5%, and the cell conversion efficiency is increased by about 0.15%.

[0097] Example 4

[0098] On the basis of Example 1 or Example 2, a heterojunction solar cell sheet doped with trimethylboron is prepared, wherein a very high frequency plasma enhanced chemical vapor deposition device (VHF-PECVD) is used to perform the plating of the P-type microcrystalline silicon doped layer, and the process is as follows:

[0099] 1. After completing the texturing and cleaning of the N-type monocrystalline silicon sheet, the thickness is 120 μm, the pyramidal height of the textured surface is 1.5 μm, and the width is 2 μm;

[0100] 2. An intrinsic amorphous silicon film layer is prepared by using a plasma vapor deposition device, the first intrinsic amorphous silicon film layer has a thickness of 1.5 nm, the second intrinsic amorphous silicon film layer has a thickness of 2 nm, and the third intrinsic amorphous silicon film layer has a thickness of 4.5 nm; 3. An N-type microcrystalline silicon doped layer is plated on the intrinsic amorphous silicon film layer on the front surface by using a plasma vapor deposition device, and the thickness is 20 nm;

[0101] 4. A P-type microcrystalline silicon doped layer is prepared by using a very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD), and the microcrystalline doping of trimethylboron is performed, and the relevant data are shown in Table 3:

[0102]

[0103] 5. Crystallization rate test

[0104] The crystallization rate of the material can be obtained by Raman scattering spectrum analysis. The frequency of the photons after Raman scattering changes relative to the incident light, which is called Raman shift. The Raman shift is related to the atomic vibration energy and arrangement. For microcrystalline silicon thin film material, microcrystalline silicon thin films with different crystallization degrees have different peak values in the Raman spectrum. Specifically, after multiple single-point tests on a single P-type microcrystalline silicon film layer, peak fitting can be performed using OMNIC and origin software, and the crystallization rate can be calculated from the peak area. The results are as shown in Table 4:

[0105] Experimental group Crystallization rate 1 Crystallization rate 2 Crystallization rate 3 Crystallization rate average Group 3 0.752 0.755 0.743 0.750

[0106] Group 3 is to prepare a P-type microcrystalline silicon doped layer by using very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD), and to test the crystallization rate of the P-type microcrystalline silicon doped layer at multiple points. The average value obtained is 0.750, which is a relatively high crystallization rate.

[0107] It can be seen that by using different equipment and selecting appropriate process parameters, a P-type microcrystalline silicon doped layer with a relatively high crystallization rate can also be prepared.

[0108] 5. PAR IWO thin film (a kind of light-transmitting conductive layer) is used, the sheet resistance is 20 Ω / D, and the mobility is 120 cm 2 / V-s, and the transmittance is 98%;

[0109] 6. The IWO thin film on the front and back surfaces is printed with a grid line by using a screen printing low-temperature silver paste. The grid line is 20 μm high and 55 μm wide. After drying and curing, the electrode is formed, and the metallization of the microcrystalline silicon heterojunction cell is completed, and the preparation of the microcrystalline silicon heterojunction cell is completed.

[0110] 7. Test results of cell conversion efficiency

[0111] Group 3: Compared with the HJT cell using an amorphous P-type doped layer, the fill factor (FF) is increased by about 0.5%, and the cell conversion efficiency (Efficiency) is increased by about 0.15%.

[0112] Based on the above ideal embodiments according to the present application, through the above description, relevant personnel can make various changes and modifications without deviating from the technical idea of the present application. The technical scope of the present application is not limited to the contents of the specification, and must be determined by the scope of the claims.

Claims

1. A heterojunction solar cell, characterized by, It comprises: a single crystal silicon substrate; an intrinsic amorphous silicon thin film layer is prepared on the front and back of the single crystal silicon substrate respectively; an N-type amorphous silicon doped layer or an N-type microcrystalline silicon doped layer is arranged on the top surface of the intrinsic amorphous silicon thin film layer on the front of the single crystal silicon substrate; a P-type microcrystalline silicon doped layer is arranged on the bottom surface of the intrinsic amorphous silicon thin film layer on the back of the single crystal silicon substrate; a light-transmitting conductive layer is arranged on the top surface of the N-type amorphous silicon doped layer or the N-type microcrystalline silicon doped layer and the bottom surface of the P-type microcrystalline silicon doped layer respectively; an electrode is arranged on the surface of the light-transmitting conductive layer; The P-type microcrystalline silicon doped layer is a layered structure deposited by at least a mixed gas of silane and trimethyl boron.

2. A heterojunction solar cell as claimed in claim 1, wherein, The P-type microcrystalline silicon doped layer is prepared by a coating equipment, and the process parameters of the coating equipment are: the power of the power supply is 1000-20000 W, and the pressure is 50-1000 Pa; the coating equipment is a plasma vapor deposition equipment or a catalytic chemical vapor deposition equipment.

3. A heterojunction solar cell as described in claim 1, characterized in that, The thickness of the P-type microcrystalline silicon doped layer is 5-50 nm.

4. A heterojunction solar cell as described in claim 1, characterized in that, The intrinsic amorphous silicon thin film layer is three layers, which are a first intrinsic amorphous silicon thin film layer with a thickness of 0.5-2 nm, a second intrinsic amorphous silicon thin film layer with a thickness of 1-3 nm, and a third intrinsic amorphous silicon thin film layer with a thickness of 1-6 nm.

5. The heterojunction solar cell of claim 1, wherein the transparent conductive oxide layer is formed of a transparent conductive oxide material selected from the group consisting of ITO, FTO, ATO, Sn02, ZnO, and AZO. When the doped layer arranged on the top surface of the intrinsic amorphous silicon thin film layer on the front of the single crystal silicon substrate is the N-type microcrystalline silicon doped layer, the N-type microcrystalline silicon doped layer is a layered structure deposited by at least a mixed gas of silane and trimethyl boron.

6. A method for manufacturing a heterojunction solar cell, characterized by, The method steps comprise: 002: selecting a single crystal silicon wafer, cleaning and texturing the single crystal silicon wafer; 004: preparing an intrinsic amorphous silicon thin film layer on the front and back of the single crystal silicon wafer; 006: preparing an N-type doped layer on the top surface of the intrinsic amorphous silicon thin film layer on the front; 008: preparing a P-type microcrystalline silicon doped layer on the intrinsic amorphous silicon thin film layer on the back; 010: preparing a light-transmitting conductive layer on the top surface of the N-type doped layer and the bottom surface of the P-type microcrystalline silicon doped layer respectively; 012: printing an electrode on the surface of the light-transmitting conductive layer.

7. The preparation method of the heterojunction solar cell wafer according to claim 6, wherein The N-type doped layer is an N-type amorphous silicon doped layer or an N-type microcrystalline silicon doped layer.

8. The method of claim 6, wherein the method further comprises: depositing a transparent conductive layer on the transparent substrate; and depositing a transparent conductive layer on the transparent substrate. In step 008, the P-type microcrystalline silicon doped layer is deposited by at least a mixed gas of hydrogen, silane and trimethyl boron in a coating equipment.

9. The preparation method of the heterojunction solar cell wafer according to claim 8, wherein The flow rate ratio of hydrogen to silane is 20-500 times, the flow rate ratio of trimethyl boron to silane is 0.1-10%, and the process parameters of the coating equipment are: the power of the power supply is 1000-20000 W, and the pressure is 50-1000 Pa.

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