A method for manufacturing high-efficiency heterojunction microcrystalline cells

Abstract

The application relates to a high-efficiency heterojunction microcrystal cell manufacturing method, which comprises the following steps: depositing microcrystal silicon film layers on a semiconductor substrate after passivation, and controlling the deposition by gradually increasing the ratio between hydrogen and silane in the reaction gas in stages. The application aims to provide a high-efficiency heterojunction microcrystal cell manufacturing method, which can form microcrystal silicon film layers meeting the needs of the heterojunction cell by controlling the hydrogen-silicon ratio, can simultaneously improve the short-circuit current, open-circuit voltage and fill factor of the cell, and can greatly improve the conversion efficiency of the cell.

Description

TECHNICAL FIELD

[0001] The present application relates to a high-efficiency microcrystalline heterojunction cell manufacturing method. BACKGROUND

[0002] At present, the heterojunction solar cell usually takes silicon wafer as substrate, intrinsic amorphous silicon layer is deposited on the surface of the silicon wafer to passivate the surface, P-type semiconductor thin film is deposited on the front surface as the emitter layer, and N-type semiconductor thin film is deposited on the back surface as the back field. The semiconductor thin film is usually doped amorphous silicon thin film or doped microcrystalline silicon thin film. Compared with the doped amorphous silicon thin film, the doped microcrystalline silicon thin film has the advantages of higher doping efficiency, higher conductivity and lower light absorption, and its application in the heterojunction cell is expected to further improve the cell efficiency. However, the deposition conditions of the doped microcrystalline silicon thin film need to meet the requirements of high hydrogen flow, high gas pressure and high deposition power. If the deposition conditions are not controlled well, the formed doped microcrystalline silicon thin film will be non-uniform and will have adverse effects on the passivation of the silicon wafer, thereby damaging the cell performance and affecting the cell efficiency. SUMMARY

[0003] The present application aims to provide a high-efficiency microcrystalline heterojunction cell manufacturing method, which can form a microcrystalline silicon film layer that meets the needs of the heterojunction cell by controlling the hydrogen-silicon ratio, thereby improving the short-circuit current, open-circuit voltage and fill factor of the cell, and greatly improving the cell conversion efficiency.

[0004] The present application achieves the above-mentioned purpose by the following technical solutions:

[0005] A high-efficiency microcrystalline heterojunction cell manufacturing method, which comprises the following steps: depositing a microcrystalline silicon film layer on a passivated semiconductor substrate in stages, and gradually increasing the ratio of hydrogen to silane in the reaction gas for deposition control.

[0006] Compared with the prior art, the present application has the following advantages:

[0007] (1) By gradually increasing the hydrogen-silicon ratio, a microcrystalline silicon film layer with good crystallization effect can be formed, ensuring that the formed microcrystalline silicon film layer has uniform and consistent crystallization effect from the initial to the final film formation stage, thereby effectively improving the optical absorption and electrical performance of the heterojunction cell;

[0008] (2) The relatively low hydrogen-silicon ratio in the initial film formation stage of the microcrystalline thin film can reduce the influence on the amorphous passivation film interface; the gradually increasing hydrogen-silicon ratio is conducive to the growth of the microcrystalline silicon film layer, promotes the crystallization of the microcrystalline silicon film layer, forms relatively uniform microcrystalline grains, the thin film surface is relatively smooth, and a high crystallization rate and a low porosity are maintained, thereby improving the conductivity and reducing the contact resistance Rs, so that a high fill factor can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 is a structural diagram of an embodiment of a high-efficiency heterojunction microcrystalline cell. DETAILED DESCRIPTION

[0010] A method for manufacturing a high-efficiency heterojunction microcrystalline cell, which comprises depositing microcrystalline silicon film layers on a passivated semiconductor substrate in stages, and controlling the deposition by gradually increasing the ratio between hydrogen and silane in the reaction gas in stages.

[0011] In the deposition of the microcrystalline silicon film layers in stages, the ratio between hydrogen and silane, i.e. the hydrogen-silane ratio, is increased by an equal or unequal amount in each stage, and the hydrogen-silane ratio in the final stage is increased by more than 20% compared with the hydrogen-silane ratio in the initial stage; the hydrogen-silane ratio is a ratio by volume fraction.

[0012] The microcrystalline silicon film layers are doped microcrystalline silicon film layers; in the deposition of the microcrystalline silicon film layers in stages, the reaction gas comprises hydrogen, silane and a doping gas, and the hydrogen-silane ratio is (100-500):1.

[0013] The microcrystalline silicon film layers are N-type microcrystalline silicon film layers, in the deposition of the microcrystalline silicon film layers in stages, the hydrogen-silane ratio is (100-300):1, the pressure of the reaction gas is 150-400 Pa, and the deposition power density is 0.08-0.3 W / cm 2 ; or, the microcrystalline silicon film layers are P-type microcrystalline silicon film layers, in the deposition of the microcrystalline silicon film layers in stages, the hydrogen-silane ratio is (200-500):1, the pressure of the reaction gas is 150-400 Pa, and the deposition power density is 0.1-0.4 W / cm 2 .

[0014] The deposition of the microcrystalline silicon film layers in stages is divided into more than 5 stages in total.

[0015] In the deposition of N-type microcrystalline silicon film layers, the doping gas comprises phosphine, and the volume fraction ratio between phosphine and silane is (1-8):100; in the deposition of P-type microcrystalline silicon film layers, the doping gas comprises diborane or TMB, and the volume fraction ratio between diborane or TMB and silane is (0.5-4):100.

[0016] Before the deposition of the microcrystalline silicon film layers in stages, a microcrystalline silicon seed layer is deposited on the passivated semiconductor substrate using a mixed gas of hydrogen and silane.

[0017] The thickness of the microcrystalline silicon seed layer is 1-4 nm.

[0018] Before the deposition of the microcrystalline silicon film layers in stages, a microcrystalline silicon oxide layer is deposited on the passivated semiconductor substrate or on the semiconductor substrate on which the microcrystalline silicon seed layer is deposited using hydrogen, silane and a doping gas. The doping gas comprises carbon dioxide, and the volume fraction ratio between carbon dioxide and silane is (3-10):10.

[0019] The microcrystalline silicon oxide layer is an N-type microcrystalline silicon oxide layer or a P-type microcrystalline silicon oxide layer; when depositing the N-type microcrystalline silicon oxide layer, the doping gas includes phosphine, the volume ratio of phosphine to silane is (1-8):100, the volume ratio of carbon dioxide to silane is (30-100):100, and the reaction gas pressure is 150-400 Pa; when depositing the P-type microcrystalline silicon oxide layer, the doping gas includes diborane or TMB, the volume ratio of diborane or TMB to silane is (0.5-4):100, the reaction gas pressure is 150-400 Pa, and the ratio of hydrogen to silane, i.e. the hydrogen-silicon ratio, is (200-500):1.

[0020] The microcrystalline silicon oxide layer is deposited by stage-by-stage deposition, and the ratio of hydrogen to silane in the reaction gas is increased stage by stage to control the deposition.

[0021] In the stage-by-stage deposition of the microcrystalline silicon oxide layer, the ratio of hydrogen to silane, i.e. the hydrogen-silicon ratio, is increased by an equal or unequal amount in each stage, and the hydrogen-silicon ratio in the final stage is increased by more than 20% compared with the hydrogen-silicon ratio in the initial stage; the hydrogen-silicon ratio is a volume ratio.

[0022] The hydrogen-silicon ratio is (100-500):1. When depositing the N-type microcrystalline silicon oxide layer, the hydrogen-silicon ratio is (100-300):1; when depositing the P-type microcrystalline silicon oxide layer, the hydrogen-silicon ratio is (200-500):1.

[0023] The above are all processes for depositing a semiconductor film layer on a passivated semiconductor substrate. The semiconductor film layer prepared by the above process is composed of a microcrystalline silicon film layer, or composed of a microcrystalline silicon seed layer and a microcrystalline silicon film layer deposited in sequence from the bottom to the surface, or composed of a microcrystalline silicon oxide layer and a microcrystalline silicon film layer deposited in sequence from the bottom to the surface, or composed of a microcrystalline silicon seed layer, a microcrystalline silicon oxide layer and a microcrystalline silicon film layer deposited in sequence from the bottom to the surface. The deposition thickness of the semiconductor film layer is 7-20 nm.

[0024] The content of the present application will be described in detail below in combination with the drawings and examples in the specification:

[0025] As shown in Figure 1 The present application provides an embodiment of a high-efficiency heterojunction microcrystalline cell, which comprises an N-type silicon wafer 10, a first intrinsic amorphous silicon layer 20, an N-type semiconductor film layer 30 and a front transparent conductive layer 60-1 and a front metal grid layer 70-1 arranged in sequence on the front surface of the silicon wafer 10, and a second intrinsic amorphous silicon layer 40, a P-type semiconductor film layer 50 and a back transparent conductive layer 60-2 and a back metal grid layer 70-2 arranged in sequence on the back surface of the silicon wafer 10.

[0026] The N-type silicon wafer 10 is a single-crystal silicon wafer or a polycrystalline silicon wafer.

[0027] The thickness of the N-type semiconductor film layer is 7-16nm. The N-type semiconductor film layer is composed of a microcrystalline silicon seed layer, an N-type microcrystalline silicon oxide layer and an N-type microcrystalline silicon film layer deposited in sequence from bottom to surface.

[0028] The thickness of the P-type semiconductor film layer is 8-20nm. The P-type semiconductor film layer is composed of a microcrystalline silicon seed layer, a P-type microcrystalline silicon oxide layer and a P-type microcrystalline silicon film layer deposited in sequence from bottom to surface.

[0029] The method for manufacturing the high-efficiency heterojunction microcrystalline cell comprises the following steps:

[0030] S01, providing an N-type silicon wafer cleaned by texturing and washing;

[0031] S02, depositing a second intrinsic amorphous silicon layer on the back surface of the silicon wafer in S01 by PECVD;

[0032] S03, depositing a first intrinsic amorphous silicon layer on the front surface of the silicon wafer in S02 by PECVD;

[0033] S04, depositing an N-type semiconductor film layer on the second intrinsic amorphous silicon layer on the front surface of the silicon wafer in S03 by PECVD;

[0034] S05, depositing a P-type semiconductor film layer on the first intrinsic amorphous silicon layer on the back surface of the silicon wafer in S04 by PECVD;

[0035] S06, depositing a front transparent conductive layer and a back transparent conductive layer on the N-type semiconductor film layer on the front surface and the P-type semiconductor film layer on the back surface of the silicon wafer in S05 respectively by PVD magnetic sputtering;

[0036] S07, manufacturing a front metal grid layer and a back metal grid layer on the transparent conductive layers on the front surface and the back surface of the silicon wafer in S06 respectively.

[0037] Embodiment

[0038] A method for manufacturing a high-efficiency heterojunction microcrystalline cell, and the specific process is as follows:

[0039] S01, providing an N-type silicon wafer cleaned by texturing and washing; the specific process is to form a pyramid texture on the surface of the N-type silicon wafer by texturing and washing, and keep it clean; the N-type silicon wafer is a single crystal silicon wafer.

[0040] S02, depositing a second intrinsic amorphous silicon layer on the back surface of the silicon wafer in S01 by PECVD; the specific process is to introduce silane and hydrogen into a reaction cavity, preset the film forming temperature to be 150-250℃, the reaction gas pressure to be 30-150Pa, and the deposition thickness to be 5-10nm.

[0041] S03, depositing a first intrinsic amorphous silicon layer on the front side of the silicon wafer in S02 by PECVD; the specific process is to introduce silane and hydrogen into the reaction cavity, the preset film forming temperature is 150-250°C, the reaction gas pressure is 30-150Pa, and the deposition thickness is 4-7nm.

[0042] S04, depositing an N-type semiconductor film layer on the second intrinsic amorphous silicon layer on the front side of the silicon wafer in S03 by PECVD; the specific process is that the PECVD preset film forming temperature is 150-250°C; first, introduce a mixture of hydrogen and silane into the reaction cavity to form a 1-4nm microcrystalline silicon seed layer; then introduce a mixture of silane, phosphine, hydrogen and carbon dioxide to form a phosphorus-doped microcrystalline silicon oxide layer, wherein the ratio of phosphine to silane is (1-8):100, the ratio of carbon dioxide to silane is (30-100):100, the reaction gas pressure is 150-400Pa, and the ratio of hydrogen to silane, i.e. the hydrogen-silicon ratio, is (100-300):1; finally, introduce a mixture of silane, phosphine and hydrogen to form a phosphorus-doped microcrystalline silicon film layer, wherein the ratio of phosphine to silane is (1-8):100, the reaction gas pressure is 150-400Pa, and the hydrogen-silicon ratio is (100-300):1; during the deposition process, the hydrogen-silicon ratio is gradually increased in five stages, and the final hydrogen-silicon ratio is at least 20% higher than the initial hydrogen-silicon ratio; in this embodiment, the linear incremental method is used, but in other embodiments, the slow incremental method followed by the fast incremental method can also be used. The deposition power density of the N-type semiconductor film layer is 0.08-0.3W / cm 2 , and the deposition thickness is 7-16nm.

[0043] S05, depositing a P-type semiconductor film layer on the first intrinsic amorphous silicon layer on the back surface of the silicon wafer of S04 by PECVD; the specific process is that the preset film forming temperature of PECVD is 150-250 DEG C; firstly, a mixture gas of hydrogen and silane is introduced into the reaction cavity to form a 1-4 nm microcrystalline silicon seed layer; then a mixture gas of silane, diborane or TMB, hydrogen and carbon dioxide is introduced into the reaction cavity to form a boron-doped microcrystalline silicon oxide layer, wherein the ratio of diborane or TMB to silane is (0.5-4):100, the ratio of carbon dioxide to silane is (30-100):100, the reaction gas pressure is 150-400 Pa, and the ratio of hydrogen to silane, i.e., the hydrogen-silicon ratio, is (200-500):1; finally, a mixture gas of silane, diborane or TMB and hydrogen is introduced into the reaction cavity to form a boron-doped microcrystalline silicon film layer, wherein the ratio of diborane or TMB to silane is (0.5-4):100, the reaction gas pressure is 150-400 Pa, and the hydrogen-silicon ratio is (200-500):1; the hydrogen-silicon ratio is gradually increased in five stages during the deposition process, and the final hydrogen-silicon ratio is at least 20% higher than the initial hydrogen-silicon ratio; in the embodiment, the linear increasing mode is adopted, and in other embodiments, the slow increasing mode followed by the fast increasing mode can also be adopted. The deposition power density of the P-type semiconductor film layer is 0.1-0.4 W / cm 2 , and the deposition thickness is 8-20 nm.

[0044] S06, depositing ITO transparent conductive layers on the N-type semiconductor film layer on the front surface and the P-type semiconductor film layer on the back surface of the silicon wafer of S05 by PVD magnetic control sputtering, and the deposition thickness is 90-110 nm.

[0045] S07, making silver grid line electrodes on the ITO transparent conductive layers on the front surface and the back surface of the silicon wafer of S06 by screen printing.

[0046] Table 1 lists the efficiency comparison between the high-efficiency heterojunction microcrystalline cell and the conventional heterojunction solar cell, and the high-efficiency heterojunction microcrystalline cell has better electrical performance;

[0047]

[0048] In summary, the manufacturing method of the high-efficiency heterojunction microcrystalline cell provided by the application adopts a doped microcrystalline thin film to replace the existing doped amorphous layer, and the hydrogen-silicon gas ratio is increased in stages to make the microcrystalline film layer structure have good crystallization effect, and at the same time, the passivation effect of the amorphous film is not affected, so that the cell efficiency is greatly improved.

[0049] The above only describes the preferred embodiments of the application and is not intended to limit the application, and any modifications, equivalent replacements and improvements made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A method for fabricating high efficiency heterojunction microcrystalline solar cells, comprising: The microcrystalline silicon film layer is deposited on the semiconductor substrate which is passivated by the intrinsic amorphous silicon layer, and the deposition is controlled by increasing the ratio of hydrogen to silane in the reaction gas in each stage, wherein the ratio of hydrogen to silane, i.e. the hydrogen-silicon ratio, is increased by the same or different amount in each stage, and the hydrogen-silicon ratio in the final stage is increased by more than 20% compared with that in the initial stage; the hydrogen-silicon ratio is the ratio of volume fractions; the reaction gas in the deposition of the microcrystalline silicon film layer comprises hydrogen, silane and a doping gas; ​ The microcrystalline silicon film layer is an N-type microcrystalline silicon film layer, and in the stage-by-stage deposition of the microcrystalline silicon film layer, the hydrogen-silicon ratio is (100-300):1, the reaction gas pressure is 150-400 Pa, and the deposition power density is 0.08-0.3 W / cm 2 ; or the microcrystalline silicon film layer is a P-type microcrystalline silicon film layer, and in the stage-by-stage deposition of the microcrystalline silicon film layer, the hydrogen-silicon ratio is (200-500):1, the reaction gas pressure is 150-400 Pa, and the deposition power density is 0.1-0.4 W / cm 2 .

2. The method of claim 1, wherein: When the N-type microcrystalline silicon film layer is deposited, the doping gas comprises phosphine, and the volume fraction ratio of phosphine to silane is (1-8):100; when the P-type microcrystalline silicon film layer is deposited, the doping gas comprises diborane or TMB, and the volume fraction ratio of diborane or TMB to silane is (0.5-4):

100.

3. The method of producing a high-efficiency heterojunction microcrystalline solar cell according to claim 1 or 2, wherein: Before the deposition of the microcrystalline silicon film layer, a microcrystalline silicon seed layer is deposited on the passivated semiconductor substrate using a mixed gas of hydrogen and silane.

4. The method of claim 3, wherein the method further comprises: A microcrystalline silicon oxide layer is deposited on the microcrystalline silicon seed layer using hydrogen, silane and a doping gas.

5. The method of claim 4, wherein: The microcrystalline silicon oxide layer is deposited on the microcrystalline silicon seed layer, and the deposition is controlled by increasing the ratio of hydrogen to silane in the reaction gas in each stage.

6. The method of making a high-efficiency heterojunction microcrystalline solar cell of claim 1 or 2, wherein: Before the deposition of the microcrystalline silicon film layer, a microcrystalline silicon oxide layer is deposited on the passivated semiconductor substrate using hydrogen, silane and a doping gas.

7. The method of claim 6, wherein the method further comprises: The deposition of the microcrystalline silicon oxide layer is microcrystalline silicon oxide layer deposition, and the deposition is controlled by increasing the ratio of hydrogen to silane in the reaction gas in each stage.

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