Tunneling silicon thin film back-contact solar cell and preparation method therefor

Abstract

The present disclosure provides a method for preparing a tunneling silicon thin film back-contact solar cell, and a solar cell prepared by the method. The preparation method comprises using high-density plasma chemical vapor deposition to deposit a tunneling silicon thin film layer on a back surface of monocrystalline silicon.

Description

Tunneling silicon thin film back contact solar cell and preparation method thereof

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based on and claims priority to Chinese Patent Application No. 202411287757.3, filed on September 13, 2024, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates to the technical field of crystalline silicon solar cells, in particular to a preparation method of a tunneling silicon thin film back contact solar cell and a tunneling silicon thin film back contact solar cell obtained by the preparation method. BACKGROUND

[0004] In the technical field, the tunneling oxide layer is currently widely prepared by thermal oxidation and plasma enhancement technology. However, in the related art, the thermal oxidation technology generally adopts a processing temperature greater than 500 degrees Celsius, resulting in large energy loss and limited cost reduction space. Secondly, by using the method of plasma enhanced vapor deposition, the way of using laughing gas as a carrier gas, due to the influence of plasma bias, particle bombardment damage is easily caused, and film uniformity is not easy to control, which greatly affects the yield of the production line. The chemical nitric acid oxidation method is also one of the ways to prepare the tunneling layer, but it has the disadvantages of high raw material cost and high waste liquid treatment requirement, which is not conducive to cost reduction. Therefore, it is increasingly urgent to explore and apply a tunneling layer material technology that can reduce the preparation cost and improve the conversion efficiency of solar cells to meet the needs of photovoltaic efficiency and cost reduction. SUMMARY

[0005] The present disclosure provides a preparation method of a tunneling silicon thin film back contact solar cell, which comprises depositing a tunneling silicon thin film layer on the back surface of a single crystal silicon by high-density plasma chemical vapor deposition (HDPCVD), also known as inductively coupled plasma chemical vapor deposition (ICPCVD).

[0006] In some embodiments, the tunneling silicon thin film layer is selected from one or more of a silicon oxide thin film, a silicon carbide multilayer thin film, a silicon nitride multilayer thin film, and a C or N doped silicon oxide layer thin film.

[0007] In some embodiments, in the high-density plasma chemical vapor deposition process, silane (SiH4), laughing gas (N2O), hydrogen (H2), argon (Ar), nitrogen (N2), carbon dioxide (CO2), methane (CH4), and ammonia (NH3) are used as process gases to deposit silicon oxide, nanocrystalline silicon oxide, silicon carbide, and silicon nitride, and a tunneling silicon thin film layer comprising a single layer or a multilayer structure is formed by high-density plasma chemical vapor deposition. The thickness of the tunneling silicon thin film layer is 1-10 nm.

[0008] In some embodiments, in the high-density plasma chemical vapor deposition process, the volume ratio of other gas to silane in the process gas is in the range of 0.1-100, the process pressure is 0.2-10 mbar, the deposition temperature is between 30°C-500°C, the radio frequency power density is 1-500 mW / cm 2 .

[0009] In some embodiments, in the high-density plasma chemical vapor deposition process, the thickness of the tunneling silicon thin film layer is 1-5 nm.

[0010] In some embodiments, the high-density plasma chemical vapor deposition process can include the following operations: using a mixed gas of silane, laughing gas, and hydrogen to deposit a silicon oxide thin film on the back of the single crystal silicon, the volume ratio of N2O / SiH4 in the mixed gas is in the range of 0.1-100, the volume ratio of H2 / SiH4 is in the range of 0.1-100; the deposition temperature is between 30°C-500°C, the time is 1-10 minutes; the process pressure is 0.2-10 mbar, the radio frequency power density is 1-500 mW / cm 2 .

[0011] In some embodiments, the high-density plasma chemical vapor deposition process can include the following operations: using laughing gas to deposit a silicon oxide thin film on the back of the single crystal silicon, the laughing gas flow is in the range of 0-2000 sccm; the deposition temperature is between 30°C-500°C, the time is 1-10 minutes; the process pressure is 0.2-10 mbar, the radio frequency power density is 1-500 mW / cm 2 .

[0012] In some embodiments, the high-density plasma chemical vapor deposition process can include the following operations: using laughing gas to deposit a silicon oxide thin film on the back of the single crystal silicon, the laughing gas flow is in the range of 0-2000 sccm; the deposition temperature is between 30°C-500°C, the time is 1-10 minutes; the process pressure is 0.2-10 mbar, the radio frequency power density is 1-500 mW / cm 2 ; using a mixed gas of silane, methane, and hydrogen to deposit a tunneling silicon carbide thin film, the volume ratio of CH4 / SiH4 in the mixed gas is in the range of 0.1-100, the volume ratio of H2 / SiH4 is in the range of 0.1-100; the deposition temperature is between 30°C-500°C, the time is 1-10 minutes; the process pressure is 0.2-10 mbar, the radio frequency power density is 1-500 mW / cm 2 .

[0013] In some embodiments, the high-density plasma chemical vapor deposition process can include the following operations: depositing a silicon oxide film on the back surface of the single crystal silicon using nitrous oxide, the nitrous oxide flow rate being in the range of 0-2000 seem; the deposition temperature being between 30°C-500°C, the time being 1-10 minutes; the process pressure being 0.2-10 mbar, the radio frequency power density being 1-500 mW / cm 2 ; depositing a tunneling silicon nitride film using a mixed gas of silane, argon, and nitrogen, the mixed gas N2 / SiH4volume ratio being in the range of 0.1-100, the Ar / SiH4volume ratio being in the range of 0.1-100; the deposition temperature being between 30°C-500°C, the time being 1-10 minutes; the process pressure being 0.2-10 mbar, the radio frequency power density being 1-500 mW / cm 2 .

[0014] In some embodiments, the high-density plasma chemical vapor deposition process can include the following operations: depositing a silicon oxide film on the back surface of the single crystal silicon using nitrous oxide, the nitrous oxide flow rate being in the range of 0-2000 seem; the deposition temperature being between 30°C-500°C, the time being 1-10 minutes; the process pressure being 0.2-10 mbar, the radio frequency power density being 1-500 mW / cm 2 ; depositing a tunneling silicon nitride film using a mixed gas of silane, argon, and nitrogen, the mixed gas N2 / SiH4volume ratio being in the range of 0.1-100, the Ar / SiH4volume ratio being in the range of 0.1-100; the deposition temperature being between 30°C-500°C, the time being 1-10 minutes; the process pressure being 0.2-10 mbar, the radio frequency power density being 1-500 mW / cm 2 ; depositing a tunneling silicon nitride film using a mixed gas of silane, argon, and nitrogen, the mixed gas N2 / SiH4volume ratio being in the range of 0.1-100, the Ar / SiH4volume ratio being in the range of 0.1-100; the deposition temperature being between 30°C-500°C, the time being 1-10 minutes; the process pressure being 0.2-10 mbar, the radio frequency power density being 1-500 mW / cm 2 .

[0015] In some embodiments, the high-density plasma chemical vapor deposition process can include the following operations: depositing a silicon oxide film on the back surface of the single crystal silicon using nitrous oxide, the nitrous oxide flow rate being in the range of 0-2000 seem; the deposition temperature being between 30°C-500°C, the time being 1-10 minutes; the process pressure being 0.2-10 mbar, the radio frequency power density being 1-500 mW / cm 2; depositing a tunneling silicon carbide film using a mixed gas of silane, methane and hydrogen, the volume ratio of CH4 / SiH4 in the mixed gas being in the range of 0.1-100, the volume ratio of H2 / SiH4 being in the range of 0.1-100; the deposition temperature being in the range of 30-500°C, the time being 1-10 minutes; the process pressure being 0.2-10 mbar, the radio frequency power density being 1-500 mW / cm 2 ; depositing a tunneling silicon nitride film using a mixed gas of silane, carbon dioxide and nitrogen, the volume ratio of CO2 / SiH4 in the mixed gas being in the range of 0.1-100, the volume ratio of N2 / SiH4 being in the range of 0.1-100; the deposition temperature being in the range of 30-500°C, the time being 1-10 minutes; the process pressure being 0.2-10 mbar, the radio frequency power density being 1-500 mW / cm 2 .

[0016] In the method for preparing the tunneling silicon film back contact solar cell according to the present disclosure, the tunneling silicon film layer is deposited after the texturing, polishing and cleaning of the single crystal silicon wafer are completed.

[0017] In the method for preparing the tunneling silicon film back contact solar cell according to the present disclosure, the silicon film is deposited after the tunneling silicon film layer is deposited.

[0018] In the method for preparing the tunneling silicon film back contact solar cell according to the present disclosure, the post annealing treatment is performed after the silicon film layer is deposited.

[0019] In the method for preparing the tunneling silicon film back contact solar cell according to the present disclosure, the functional region patterning, the deposition of the recombination passivation film and the back surface metallization treatment are sequentially performed after the post annealing treatment.

[0020] The present disclosure provides a tunneling silicon film back contact solar cell having a tunneling silicon film layer deposited by using the high density plasma chemical vapor deposition technology. BRIEF DESCRIPTION OF DRAWINGS

[0021] Fig. 1 is a flow chart of the method for preparing the tunneling silicon film back contact solar cell according to the present disclosure.

[0022] Fig. 2 is a structural diagram of the tunneling silicon film back contact solar cell according to the present disclosure. DETAILED DESCRIPTION

[0023] In order to make the skilled in the art better understand the technical solutions of the present disclosure, the technical solutions of the present disclosure are described in detail below in combination with the drawings.

[0024] Example embodiments will be described more fully hereinafter with reference to the accompanying drawings, in which example embodiments are shown. The example embodiments may, however, be embodied in different forms, and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided as a full and enabling disclosure of the example embodiments, and to fully convey their scope to those skilled in the art. Numbered examples are provided as a full and enabling disclosure of the example embodiments, and to fully convey their scope to those skilled in the art.

[0025] The various embodiments in the present disclosure and the various features in the embodiments are combinable unless there is a conflict.

[0026] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0027] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0028] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an overly literal or overly formal sense unless expressly so defined herein.

[0029] The present disclosure provides a method for fabricating a tunneling silicon thin film back contact solar cell, which comprises depositing a tunneling silicon thin film layer on the back surface of a single crystal silicon wafer by high density plasma chemical vapor deposition (HDPCVD). HDPCVD is also known as inductively coupled plasma chemical vapor deposition (ICPCVD).

[0030] The tunneling silicon thin film layer is selected from one or more of a silicon oxide thin film, a silicon carbide multilayer thin film, a silicon nitride multilayer thin film, and a C or N doped silicon oxide thin film.

[0031] In the high density plasma chemical vapor deposition process, silane (SiH4), laughing gas (N2O), hydrogen (H2), argon (Ar), nitrogen (N2), carbon dioxide (CO2), methane (CH4), and ammonia (NH3) are used as process gases to deposit silicon oxide, nanocrystalline silicon oxide, silicon carbide, and silicon nitride to form a tunneling silicon thin film layer comprising a single layer or a multilayer structure. The thickness of the tunneling silicon thin film layer is 1-10 nm, and more preferably 1-5 nm.

[0032] In the high-density plasma chemical vapor deposition process, the volume ratio of other gas to silane in the process gas is in the range of 0.1-100, the process pressure is in the range of 0.2-10 mbar, the deposition temperature is in the range of 30°C-500°C, and the radio frequency power density is in the range of 1-500 mW / cm 2 .

[0033] Specifically, the volume ratio of process gas N2O, H2, CH4, N2, CO2 or Ar to SiH4 is in the range of 0.1-100, preferably 20-80, more preferably 30-70; for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, etc.

[0034] The process pressure is in the range of 0.2-10 mbar, preferably 1-8 mbar, more preferably 2-6 mbar; for example, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 mbar, etc.

[0035] The deposition temperature is in the range of 30°C-500°C, preferably 50°C-450°C, more preferably 100°C-400°C; for example, 50, 75, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 475°C, etc.

[0036] The radio frequency power density is in the range of 1-500 mW / cm 2 , preferably 50-400 W / cm 2 , more preferably 100-350 W / cm 2 ; for example, 25, 50, 75, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325, 350, 375, 400, 425, 450, 475 W / cm 2 , etc.

[0037] In one embodiment of the present disclosure, the high-density plasma chemical vapor deposition process can include the following operations: using a mixed gas of silane, laughing gas and hydrogen to deposit on the back of a single crystal silicon, the volume ratio of N2O / SiH4 in the mixed gas is in the range of 0.1-100, the volume ratio of H2 / SiH4 is in the range of 0.1-100; the deposition temperature is between 30°C-500°C, the time is 1-10 minutes; the process pressure is 0.2-10 mbar, and the radio frequency power density is 1-500 mW / cm 2 .

[0038] In another embodiment of the present disclosure, the high-density plasma chemical vapor deposition process can include the following operations: depositing a silicon oxide thin film on the back surface of a single crystal silicon using nitrous oxide, with a nitrous oxide flow rate in the range of 0-2000 seem; a deposition temperature between 30°C-500°C for a time period of 1-10 minutes; a process pressure of 0.2-10 mbar, and a radio frequency power density of 1-500 mW / cm 2 .

[0039] In another embodiment of the present disclosure, the high-density plasma chemical vapor deposition process can include the following operations: depositing a silicon oxide thin film on the back surface of a single crystal silicon using nitrous oxide, with a nitrous oxide flow rate in the range of 0-2000 seem; a deposition temperature between 30°C-500°C for a time period of 1-10 minutes; a process pressure of 0.2-10 mbar, and a radio frequency power density of 1-500 mW / cm 2 ;

[0040] depositing a tunneling silicon carbide thin film using a mixed gas of silane, methane, and hydrogen, with a mixed gas CH4 / SiH4 volume ratio in the range of 0.1-100, and a H2 / SiH4 volume ratio in the range of 0.1-100; a deposition temperature between 30°C-500°C for a time period of 1-10 minutes; a process pressure of 0.2-10 mbar, and a radio frequency power density of 1-500 mW / cm 2 .

[0041] In another embodiment of the present disclosure, the high-density plasma chemical vapor deposition process can include the following operations: depositing a silicon oxide thin film on the back surface of a single crystal silicon using nitrous oxide, with a nitrous oxide flow rate in the range of 0-2000 seem; a deposition temperature between 30°C-500°C for a time period of 1-10 minutes; a process pressure of 0.2-10 mbar, and a radio frequency power density of 1-500 mW / cm 2 ;

[0042] depositing a tunneling silicon nitride thin film using a mixed gas of silane, argon, and nitrogen, with a mixed gas N2 / SiH4 volume ratio in the range of 0.1-100, and an Ar / SiH4 volume ratio in the range of 0.1-100; a deposition temperature between 30°C-500°C for a time period of 1-10 minutes; a process pressure of 0.2-10 mbar, and a radio frequency power density of 1-500 mW / cm 2 .

[0043] In yet another embodiment of the present disclosure, the high-density plasma chemical vapor deposition process can include the following operations: depositing a silicon oxide film on the back surface of a single crystal silicon wafer using nitrous oxide, with a nitrous oxide flow rate in the range of 0-2000 seem; a deposition temperature between 30°C-500°C for a time period of 1-10 minutes; a process pressure of 0.2-10 mbar, and a radio frequency power density of 1-500 mW / cm 2 ;

[0044] depositing a tunneling silicon carbide film using a mixed gas of silane, methane, and hydrogen, with a mixed gas CH4 / SiH4 volume ratio in the range of 0.1-100 and a H2 / SiH4 volume ratio in the range of 0.1-100; a deposition temperature between 30°C-500°C for a time period of 1-10 minutes; a process pressure of 0.2-10 mbar, and a radio frequency power density of 1-500 mW / cm 2 ;

[0045] depositing a tunneling silicon nitride film using a mixed gas of silane, argon, and nitrogen, with a mixed gas N2 / SiH4 volume ratio in the range of 0.1-100 and a Ar / SiH4 volume ratio in the range of 0.1-100; a deposition temperature between 30°C-500°C for a time period of 1-10 minutes; a process pressure of 0.2-10 mbar, and a radio frequency power density of 1-500 mW / cm 2 .

[0046] In yet another embodiment of the present disclosure, the high-density plasma chemical vapor deposition process can include the following operations: depositing a silicon oxide film on the back surface of a single crystal silicon wafer using nitrous oxide, with a nitrous oxide flow rate in the range of 0-2000 seem; a deposition temperature between 30°C-500°C for a time period of 1-10 minutes; a process pressure of 0.2-10 mbar, and a radio frequency power density of 1-500 mW / cm 2 ;

[0047] depositing a tunneling silicon carbide film using a mixed gas of silane, methane, and hydrogen, with a mixed gas CH4 / SiH4 volume ratio in the range of 0.1-100 and a H2 / SiH4 volume ratio in the range of 0.1-100; a deposition temperature between 30°C-500°C for a time period of 1-10 minutes; a process pressure of 0.2-10 mbar, and a radio frequency power density of 1-500 mW / cm 2 ;

[0048] depositing a tunneling silicon nitride film using a mixed gas of silane, carbon dioxide, and nitrogen, with a mixed gas CO2 / SiH4 volume ratio in the range of 0.1-100 and a N2 / SiH4 volume ratio in the range of 0.1-100; a deposition temperature between 30°C-500°C for a time period of 1-10 minutes; a process pressure of 0.2-10 mbar, and a radio frequency power density of 1-500 mW / cm2 .

[0049] In the preparation method of the tunneling silicon thin film back contact solar cell, the tunneling silicon thin film layer is deposited after the texturing, polishing and cleaning of the single crystal silicon wafer are completed. The single crystal silicon can be P-type single crystal silicon or N-type single crystal silicon.

[0050] In the preparation method of the tunneling silicon thin film back contact solar cell, the silicon thin film is deposited after the tunneling silicon thin film layer is deposited.

[0051] The silicon thin film can include amorphous silicon, nanocrystalline silicon and microcrystalline silicon. The silicon thin film can be an intrinsic silicon thin film, a boron-doped silicon thin film and a phosphorus-doped silicon thin film. The silicon thin film can be a single layer film or a multi-layer film.

[0052] After the deposition of the tunneling silicon thin film layer is completed, the p+ silicon thin film or the n+ silicon thin film is deposited by plasma enhanced chemical vapor deposition (PECVD), low pressure chemical vapor deposition (LPCVD), magnetron sputtering and resistance thermal evaporation.

[0053] For example, when the p+ silicon thin film is deposited by plasma enhanced chemical vapor deposition, the polished and cleaned silicon wafer can be placed in a graphite boat, and SiH4, BH3 and H2 are introduced to deposit the p+ silicon thin film under the conditions of 2-80 MHz power and a temperature of 100-500°C. The flow rate of SiH4 can be 100-5000 sccm, the flow rate of BH3 can be 100-15000 sccm, and the flow rate of H2 can be 100-20000 sccm.

[0054] When the n+ silicon thin film is deposited by plasma enhanced chemical vapor deposition, the polished and cleaned silicon wafer can be placed in a graphite boat, and SiH4, PH3 and H2 are introduced to deposit the n+ silicon thin film under the conditions of 2-80 MHz power and a temperature of 100-500°C. The flow rate of SiH4 can be 100-5000 sccm, the flow rate of BH3 can be 100-15000 sccm, and the flow rate of H2 can be 100-20000 sccm.

[0055] In the preparation method of the tunneling silicon thin film back contact solar cell, the silicon thin film layer is deposited after the tunneling silicon thin film layer is deposited.

[0056] The annealing method can use rapid thermal annealing and tube high temperature annealing. For example, N2 is introduced at a temperature of 700-1080°C, and annealing is performed for 300-7200 s. The flow rate of N2 can be 2000-80000 sccm.

[0057] The preparation method of the tunneling silicon thin film back contact solar cell disclosed in the present disclosure comprises the following steps: after the post-annealing treatment, the functional region is patterned, the composite passivation film is deposited, and the back metalization treatment is performed in sequence.

[0058] After the annealing treatment, the silicon wafer can be patterned by laser, photolithography, screen printing, etc., and the p+ silicon thin film of the N region is removed.

[0059] In the photolithography process, a dry photoresist film can be used as a mask, extreme ultraviolet light can be used as an exposure light source, NaOH can be used as a developer, and a mixed solution of HNO3 and HF can be used as a wet etching solution to remove the p+ silicon thin film of the N region, and then acetone is used to remove the residual photoresist.

[0060] After the patterning process is completed, the front surface of the silicon wafer is textured by a wet process, and then the composite passivation film is deposited on the front and back surfaces of the silicon wafer.

[0061] The composite passivation film can be a laminated film or a multilayer film formed by SiOx, AlOx, SiNxOy, SiNx or MgFx. The composite passivation film can be deposited by resistance heating evaporation, electron beam evaporation, magnetron sputtering, PECVD and LPCVD, etc.

[0062] After the deposition of the composite passivation film, the silicon wafer is patterned by laser, photolithography, screen printing, etc., to form a Gap insulating region.

[0063] In the photolithography process, a dry photoresist film can be used as a mask, extreme ultraviolet light can be used as an exposure light source, NaOH can be used as a developer, and a mixed solution of HNO3 and HF can be used as a wet etching solution to remove the p+ silicon thin film of the N region, and then acetone is used to remove the residual photoresist.

[0064] Then, a metallization process can be used to form the metal electrode of the back contact solar cell. In the metallization process, techniques such as thermal evaporation, atomic layer deposition, magnetron sputtering, chemical plating, screen printing, laser pattern conversion, etc. can be used.

[0065] In the resistance heating evaporation process, the deposition pressure is 1E-2 to 1E-6 Pa, the deposition power is 1-2000 W, the deposition pressure is 1E-3 to 1E-5 Pa, the rotation speed of the carrier is 5 revolutions per minute, the substrate temperature is 25-300°C, the thermal evaporation temperature is 500-1200°C, and the deposited metal material is Cu, Al, Ag, Ti, Ni, Pd, Au, Cr and Pt, etc.

[0066] After the metallization process is completed, the photoresist and metal in the non-metallized area can be removed by ultrasonic technology. Acetone can be used as a solvent.

[0067] According to one embodiment of the present disclosure, referring to FIG. 1, the preparation method of the tunneling silicon thin film back contact solar cell comprises the following steps:

[0068] S1, texturing and polishing of N-type silicon wafer;

[0069] S2, deposition of tunneling silicon thin film layer;

[0070] S3, deposition of boron-doped silicon thin film layer;

[0071] S4, annealing, boron activation of the boron-doped silicon thin film layer deposition;

[0072] S5, photolithographic patterning to remove silicon thin film in N region;

[0073] S6, deposition of tunneling silicon thin film layer;

[0074] S7, deposition of phosphorus-doped silicon thin film layer;

[0075] S8, annealing, phosphorus activation of the phosphorus-doped silicon thin film layer deposition;

[0076] S9, deposition of composite passivation film on front and back surfaces;

[0077] S10, photolithographic patterning to form metal contact region; and

[0078] S11, metal evaporation, ultrasonic process to make solar cell wafer.

[0079] According to another embodiment of the present disclosure, the preparation method of the tunneling silicon thin film back contact solar cell comprises the following steps:

[0080] S1, texturing and polishing of N-type silicon wafer;

[0081] In the texturing step, an alkaline solution is used to remove the damaged layer on the surface of the silicon wafer and to smooth the surface.

[0082] S2, deposition of tunneling silicon thin film layer;

[0083] HDPCVD technology is adopted, N2O is introduced, tunneling silicon thin film layer SiOx is formed, and the thickness is 0.5-5 nm.

[0084] S3, deposition of boron-doped silicon thin film layer;

[0085] PECVD technology is adopted, SiH4, H2 and BH3 are introduced to deposit boron-doped amorphous silicon thin film.

[0086] S4, annealing, boron activation of the boron-doped silicon thin film layer deposition;

[0087] In a tube-type annealing furnace, a peak temperature of 850℃ is adopted to anneal the silicon wafer to form polysilicon.

[0088] S5, photolithographic patterning to remove silicon thin film in N region;

[0089] The patterned photoresist is formed by using ultraviolet exposure and photoresist technology, and the silicon film in the N region is removed by using a mixed solution of HNO3 and HF.

[0090] S6, deposition of a tunneling silicon film layer;

[0091] The tunneling silicon film layer SiOx is formed by using HDPCVD technology and by introducing N2O, and the thickness is 0.5-5 nm.

[0092] S7, deposition of a phosphorus-doped silicon film layer;

[0093] The phosphorus-doped amorphous silicon film is deposited by using PECVD technology and by introducing SiH4, H2 and PH3.

[0094] S8, annealing, phosphorus activation of the phosphorus-doped silicon film layer;

[0095] The silicon wafer is annealed in a tube furnace at a peak temperature of 850°C to form polysilicon.

[0096] S9, deposition of a composite passivation film on the front and back surfaces;

[0097] The SiNx and SiNxOy films are deposited by using PECVD technology and by introducing SiH4, CO2, NH3 and H2.

[0098] S10, photoetching to form a metal contact region;

[0099] The patterned photoresist is formed by using ultraviolet exposure and photoresist technology, and the insulating film in the metalized region is opened by using a BOE mixed solution.

[0100] S11, metal evaporation, ultrasonic process to form a solar cell wafer;

[0101] The 1-μm silver metal is formed by using resistance heating evaporation, and the silicon wafer is placed in an ultrasonic instrument, acetone solution is poured in, and ultrasonic treatment is performed for 30 minutes, and the silicon wafer is taken out and dried to form a tunneling silicon film back contact solar cell.

[0102] The present disclosure also provides a tunneling silicon film back contact solar cell having a tunneling silicon film layer deposited by using high-density plasma chemical vapor deposition technology.

[0103] Referring to FIG. 2, the cell includes the following structure:

[0104] 1: N-type silicon wafer, 2: n+poly-Si, 3: p+poly-Si, 4: anti-reflection film 1, 5: anti-reflection film 2, 6: tunneling silicon film layer, 7: N-region metal electrode, 8: P-region metal electrode.

[0105] The preparation method of the tunneling silicon thin film back contact solar cell disclosed by the present disclosure can fill gaps below 0.5 microns by using the high-density plasma chemical vapor deposition technology which can simultaneously perform deposition and etching processes in the same reaction cavity, so that the tunneling silicon thin film layer is more dense and uniform, thereby improving the photoelectric conversion efficiency of the crystalline silicon solar cell; in addition, the high-density plasma chemical vapor deposition technology does not need multiple process cycles and post-deposition treatment, so that the cost can be reduced.

[0106] In order for those skilled in the art to more clearly understand the technical solutions provided by the embodiments of the present disclosure, the technical solutions provided by the embodiments of the present disclosure are described in detail below through specific embodiments:

[0107] Embodiment 1

[0108] The N-type silicon wafer is textured and polished, and an alkaline solution is used in the texturing step to remove the damage layer on the surface of the silicon wafer and to smooth the morphology.

[0109] The HDPCVD technology is used to deposit a tunneling silicon thin film layer on the back surface of the single crystal silicon using a mixed gas of silane, laughing gas and hydrogen, the volume ratio of the mixed gas N2O / SiH4 is 80, the volume ratio of H2 / SiH4 is 60; the deposition temperature is 300℃, the time is 8 minutes; the pressure is 5mbar, the radio frequency power density is 300mW / cm 2 ; the thickness is 2nm.

[0110] The PECVD technology is used to deposit a boron-doped amorphous silicon thin film by passing in SiH4, H2 and BH3, under the conditions of a power of 50MHz and a temperature of 200℃, the flow rate of SiH4 can be 1000sccm, the flow rate of BH3 can be 8000sccm, and the flow rate of H2 can be 12000sccm.

[0111] In a tube-type annealing furnace, boron activation is performed on the boron-doped silicon thin film layer deposition, a peak temperature of 850℃ is used to anneal the silicon wafer to form polysilicon.

[0112] Ultraviolet exposure and photoresist technology are used to form a patterned photoresist; an N-zone silicon thin film is removed using a mixed solution of HNO3 and HF; and then the silicon wafer is cleaned.

[0113] The HDPCVD technology is used to deposit a tunneling silicon thin film layer on the back surface of the single crystal silicon using a mixed gas of silane, laughing gas and hydrogen, the volume ratio of the mixed gas N2O / SiH4 is 70, the volume ratio of H2 / SiH4 is 80; the deposition temperature is 250℃, the time is 5 minutes; the pressure is 4mbar, the radio frequency power density is 200mW / cm 2 ; the thickness is 3nm.

[0114] The PECVD technology is used to deposit the phosphorus-doped amorphous silicon film by inputting SiH4, H2 and PH3, the power is 60 MHz, the temperature is 250℃, the flow rate of SiH4 can be 2000sccm, the flow rate of BH3 can be 6000sccm, and the flow rate of H2 can be 10000sccm.

[0115] In a tube furnace, the silicon wafer is annealed to form polysilicon at a peak temperature of 850℃.

[0116] The PECVD technology is used to deposit SiNx and SiNxOy films by inputting SiH4, CO2, NH3 and H2, the deposition temperature is 400℃, the deposition time is 8 minutes, and the deposition pressure is 1.5mbar.

[0117] The patterned photoresist is formed by using ultraviolet exposure and photoresist technology, and the insulating film of the metallized area is opened by using a BOE mixed solution, the concentration ratio of the BOE is 1:7, and the process time is 2 minutes.

[0118] The resistance hot evaporation metal is used to form a 1μm silver metal, the silicon wafer is placed in an ultrasonic instrument, the acetone solution is poured, the ultrasonic power is 200W, the temperature is 50℃, the silicon wafer is taken out and dried, and a tunneling silicon thin film back contact solar cell is prepared.

[0119] Example 2

[0120] The tunneling silicon thin film back contact solar cell is prepared in the same manner as in Example 1, except that the deposition operation of the tunneling silicon thin film layer is as follows:

[0121] The nitrous oxide is used to deposit a silicon oxide film on the back of the single crystal silicon, the flow rate of the nitrous oxide is 1200sccm, the deposition temperature is 350℃, the time is 8 minutes, the pressure is 8mbar, and the radio frequency power density is 350mW / cm 2 ; the thickness is 5nm.

[0122] Example 3

[0123] The tunneling silicon thin film back contact solar cell is prepared in the same manner as in Example 1, except that the deposition operation of the tunneling silicon thin film layer is as follows:

[0124] The nitrous oxide is used to deposit a silicon oxide film on the back of the single crystal silicon, the flow rate of the nitrous oxide is 1500sccm, the deposition temperature is 400℃, the time is 6 minutes, the pressure is 5mbar, and the radio frequency power density is 250mW / cm 2 ; the thickness is 2nm;

[0125] Then, a tunneling silicon carbide film is deposited using a mixture of silane, methane and hydrogen, the volume ratio of CH4 / SiH4 being 60 and the volume ratio of H2 / SiH4 being 40; the deposition temperature is between 300°C, the time is 5 minutes; the pressure is 6 mbar and the radio frequency power density is 350 mW / cm 2 ; the thickness is 4 nm.

[0126] Example 4

[0127] A tunneling silicon film back contact solar cell is prepared in the same way as in Example 1, except that the deposition of the tunneling silicon film layer is performed as follows:

[0128] A silicon oxide film is deposited on the back of the single crystal silicon using nitrous oxide, the nitrous oxide flow being 1000 seem; the deposition temperature is 100°C, the time is 8 minutes; the pressure is 6 mbar and the radio frequency power density is 350 mW / cm 2 ; the thickness is 3 nm;

[0129] Then, a tunneling silicon nitride film is deposited using a mixture of silane, argon and nitrogen, the volume ratio of N2 / SiH4 being 50 and the volume ratio of Ar / SiH4 being 80; the deposition temperature is 400°C, the time is 6 minutes; the pressure is 5 mbar and the radio frequency power density is 250 mW / cm 2 ; the thickness is 3 nm.

[0130] Example 5

[0131] A tunneling silicon film back contact solar cell is prepared in the same way as in Example 1, except that the deposition of the tunneling silicon film layer is performed as follows:

[0132] A silicon oxide film is deposited on the back of the single crystal silicon using nitrous oxide, the nitrous oxide flow being 800 seem; the deposition temperature is 400°C, the time is 6 minutes; the pressure is 7 mbar and the radio frequency power density is 300 mW / cm 2 ; the thickness is 3 nm;

[0133] Then, a tunneling silicon carbide film is deposited using a mixture of silane, methane and hydrogen, the volume ratio of CH4 / SiH4 being 60 and the volume ratio of H2 / SiH4 being 80; the deposition temperature is 200°C, the time is 7 minutes; the process pressure is 9 mbar and the radio frequency power density is 400 mW / cm 2 ; the thickness is 2 nm;

[0134] Then, a tunneling silicon nitride film is deposited using a mixture of silane, argon and nitrogen, the volume ratio of N2 / SiH4 being 80 and the volume ratio of Ar / SiH4 being 60; the deposition temperature is 200°C, the time is 8 minutes; the pressure is 5 mbar and the radio frequency power density is 450 mW / cm2 ; thickness of 4 nm.

[0135] Example 6

[0136] A tunneling silicon thin film back contact solar cell was prepared in the same manner as in Example 1, except that the deposition operation of the tunneling silicon thin film layer was as follows:

[0137] A silicon oxide thin film was deposited on the back surface of the single crystal silicon using laughing gas at a flow rate of 1500 seem; the deposition temperature was 250°C, the time was 8 minutes; the pressure was 6 mbar, and the radio frequency power density was 400 mW / cm 2 ; thickness of 3 nm;

[0138] Then, a tunneling silicon carbide thin film was deposited using a mixed gas of silane, methane, and hydrogen, with a CH4 / SiH4volume ratio of 55 and a H2 / SiH4volume ratio of 75; the deposition temperature was 300°C, the time was 6 minutes; the pressure was 4 mbar, and the radio frequency power density was 300 mW / cm 2 ; thickness of 4 nm;

[0139] Then, a tunneling silicon nitride thin film was deposited using a mixed gas of silane, carbon dioxide, and nitrogen, with a CO2 / SiH4volume ratio of 85 and a N2 / SiH4volume ratio of 70; the deposition temperature was 250°C, the time was 8 minutes; the pressure was 8 mbar, and the radio frequency power density was 400 mW / cm 2 ; thickness of 2 nm.

[0140] Comparative Example 1

[0141] A tunneling silicon thin film back contact solar cell was prepared in the same manner as in Example 1, except that the deposition operation of the tunneling silicon thin film layer was as follows:

[0142] A thermal oxidation method was used, in which oxygen was introduced into a tube furnace, the temperature was set to 600-700°C, and the process treatment time was 5 minutes; the thickness of the tunneling silicon thin film layer was 5 nm.

[0143] Comparative Example 2

[0144] A tunneling silicon thin film back contact solar cell was prepared in the same manner as in Example 1, except that the deposition operation of the tunneling silicon thin film layer was as follows:

[0145] A plasma enhanced vapor phase chemical deposition method was used, in which N2O was introduced as the reaction gas, the power was 20 W, the temperature was set to 180°C, the working pressure was 2 mbar, and the reaction time was 4 minutes; the thickness of the tunneling silicon thin film layer was 5 nm.

[0146] The batteries prepared in the examples and comparative examples were subjected to performance tests, and the comparison of the performance of each battery is shown in Table 1 below.

[0147] Table 1: Comparison of the electrical performance of the solar cells prepared in the examples and comparative examples of the present application

[0148] It can be observed from Table 1 that the solar cells prepared using the present method have a significant advantage in energy conversion efficiency, with an increase of at least 0.2%, which can significantly improve efficiency and reduce costs.

[0149] The preparation method of the tunneling silicon thin film back contact solar cell described in the present disclosure can complete the preparation of the tunneling silicon thin film layer in one step and achieve atomic doping, which can improve the properties of the tunneling silicon thin film layer, improve the photoelectric conversion efficiency of the crystalline silicon solar cell, and reduce costs.

[0150] Example embodiments have been disclosed herein and, although the use of specific terms is exemplified throughout, they are used in this context only and should not be construed as limiting unless specifically stated otherwise. In some instances, it will be apparent to those skilled in the art that features, characteristics or / and elements described in connection with a particular embodiment can be used in conjunction with other embodiments unless otherwise explicitly stated. As such, those skilled in the art will appreciate that various changes can be made in form and detail without departing from the scope of the disclosure as set forth in the appended claims.

Claims

1. A method for preparing a tunneling silicon thin film back contact solar cell, comprising depositing a tunneling silicon thin film layer on the back surface of a single crystal silicon wafer by high density plasma chemical vapor deposition.

2. The method for preparing a tunneling silicon thin film back contact solar cell according to claim 1, wherein the tunneling silicon thin film layer is selected from one or more of a silicon oxide thin film, a silicon carbide multilayer thin film, a silicon nitride multilayer thin film, and a carbon or nitrogen doped silicon oxide thin film.

3. The method of making a tunneling silicon thin film back contact solar cell of claim 1, wherein, Silicon oxide, nanocrystalline silicon oxide, silicon carbide, and silicon nitride are deposited as process gases using silane (SiH4), nitrous oxide (N2O), hydrogen (H2), argon (Ar), nitrogen (N2), carbon dioxide (CO2), methane (CH4), and ammonia (NH3) to form a tunneling silicon thin film layer comprising a single layer or a multilayer structure by high density plasma chemical vapor deposition.

4. The method of making a tunneling silicon thin film back contact solar cell of claim 3, wherein, The volume ratio of other gas to SiH4 in the process gas is in the range of 0.1-100, the process pressure is 0.2-10 mbar, the deposition temperature is between 30℃-500℃, and the radio frequency power density is 1-500 mW / cm 2 .

5. The method of making a tunneling silicon thin film back contact solar cell of claim 1, wherein, The tunneling silicon thin film layer has a thickness of 1-5 nm.

6. The method of making a tunneling silicon thin film back contact solar cell of claim 3, wherein, A tunneling silicon thin film layer is deposited on the back surface of a single crystal silicon wafer by high-density plasma chemical vapor deposition, including: using a mixture of SiH4, N2O and H2 to deposit on the back surface of the single crystal silicon wafer, in the mixture, the volume ratio of N2O / SiH4 is in the range of 0.1-100, and the volume ratio of H2 / SiH4 is in the range of 0.1-100; the deposition temperature is between 30-500°C, the time is 1-10 minutes; the process pressure is 0.2-10 mbar, and the radio frequency power density is 1-500 mW / cm 2 .

7. The method of making a tunneling silicon thin film back contact solar cell of claim 3, wherein, A high-density plasma chemical vapor deposition is used to deposit a tunneling silicon thin film layer on the back surface of a single crystal silicon, including using N2O to deposit a silicon oxide thin film on the back surface of the single crystal silicon, the N2O flow being in the range of 0-2000 seem; the deposition temperature being in the range of 30-500°C, the time being 1-10 minutes; the process pressure being 0.2-10 mbar, and the radio frequency power density being 1-500 mW / cm 2 .

8. The method of fabricating a tunneling silicon thin film back contact solar cell of claim 3, wherein, Deposition of a tunneling silicon thin film layer on the backside of a single crystal silicon wafer using high-density plasma chemical vapor deposition, comprising: deposition of a silicon oxide thin film on the backside of a single crystal silicon wafer using N2O, the N2O flow being in the range of 0-2000 seem; the deposition temperature being in the range of 30°C-500°C, the time being 1-10 minutes; the process pressure being 0.2-10 mbar, the radio frequency power density being 1-500 mW / cm 2 ; A tunneling silicon carbide film is deposited using a mixed gas of SiH4, CH4 and H2, wherein the volume ratio of CH4 / SiH4 is in the range of 0.1 to 100, the volume ratio of H2 / SiH4 is in the range of 0.1 to 100; the deposition temperature is between 30°C and 500°C, the time is 1 to 10 minutes; the process pressure is 0.2 to 10 mbar, and the radio frequency power density is 1 to 500 mW / cm 2 .

9. The method of producing a tunneling silicon thin film back contact solar cell according to claim 3, wherein, Deposition of a tunneling silicon thin film layer on the backside of a single crystal silicon wafer using high-density plasma chemical vapor deposition, comprising: deposition of a silicon oxide thin film on the backside of a single crystal silicon wafer using N2O, the N2O flow rate being in the range of 0-2000 seem; the deposition temperature being in the range of 30°C-500°C, the time being 1-10 minutes; the process pressure being 0.2-10 mbar, the radio frequency power density being 1-500 mW / cm 2 ; The tunneling silicon nitride film is deposited by using a mixed gas of SiH4, Ar and N2, wherein the volume ratio of N2 / SiH4 is in the range of 0.1-100, the volume ratio of Ar / SiH4 is in the range of 0.1-100; the deposition temperature is in the range of 30-500℃, the time is 1-10 minutes; the process pressure is 0.2-10mbar, and the radio frequency power density is 1-500mW / cm 2 .

10. The method of producing a tunneling silicon thin film back contact solar cell according to claim 3, wherein, Deposition of a tunneling silicon thin film layer on the backside of a single crystal silicon wafer using high-density plasma chemical vapor deposition, comprising: deposition of a silicon oxide thin film on the backside of a single crystal silicon wafer using N2O, the N2O flow rate being in the range of 0-2000 seem; the deposition temperature being in the range of 30°C-500°C, the time being 1-10 minutes; the process pressure being 0.2-10 mbar, the radio frequency power density being 1-500 mW / cm 2 ; A tunneling silicon carbide film is deposited using a mixed gas of SiH4, CH4 and H2, wherein the volume ratio of CH4 / SiH4 is in the range of 0.1 to 100, the volume ratio of H2 / SiH4 is in the range of 0.1 to 100; the deposition temperature is between 30°C and 500°C, the time is 1 to 10 minutes; the process pressure is 0.2 to 10 mbar, and the radio frequency power density is 1 to 500 mW / cm 2 . The tunneling silicon nitride film is deposited using a mixed gas of SiH4, Ar and N2, wherein the volume ratio of N2 / SiH4 is in the range of 0.1-100, the volume ratio of Ar / SiH4 is in the range of 0.1-100; the deposition temperature is in the range of 30-500℃, the time is 1-10 minutes; the process pressure is 0.2-10 mbar, and the radio frequency power density is 1-500 mW / cm 2 .

11. The method of producing a tunneling silicon thin film back contact solar cell according to claim 3, wherein, Deposition of a tunneling silicon thin film layer on the backside of a single crystal silicon wafer using high-density plasma chemical vapor deposition, comprising: deposition of a silicon oxide thin film on the backside of a single crystal silicon wafer using N2O, the N2O flow rate being in the range of 0-2000 seem; the deposition temperature being in the range of 30°C-500°C, the time being 1-10 minutes; the process pressure being 0.2-10 mbar, the radio frequency power density being 1-500 mW / cm 2 ; A tunneling silicon carbide film is deposited using a mixed gas of SiH4, CH4 and H2, wherein the volume ratio of CH4 / SiH4 is in the range of 0.1 to 100, the volume ratio of H2 / SiH4 is in the range of 0.1 to 100; the deposition temperature is between 30°C and 500°C, the time is 1 to 10 minutes; the process pressure is 0.2 to 10 mbar, and the radio frequency power density is 1 to 500 mW / cm 2 . A tunneling silicon nitride film is deposited using a mixed gas of SiH4, CO2 and N2, wherein the volume ratio of CO2 / SiH4 is in the range of 0.1-100, the volume ratio of N2 / SiH4 is in the range of 0.1-100; the deposition temperature is between 30°C-500°C, the time is 1-10 minutes; the process pressure is 0.2-10 mbar, the radio frequency power density is 1-500 mW / cm 2 .

12. The method of producing a tunneling silicon thin film back contact solar cell according to claim 1, wherein, Before depositing the tunneling silicon thin film layer on the back surface of a single crystal silicon wafer by high density plasma chemical vapor deposition, the method further comprises: Texturing, polishing, and cleaning the single crystal silicon wafer.

13. The method of producing a tunneling silicon thin film back contact solar cell according to claim 1, wherein, After depositing the tunneling silicon thin film layer on the back surface of a single crystal silicon wafer by high density plasma chemical vapor deposition, the method further comprises depositing a silicon thin film.

14. The method of producing a tunneling silicon thin film back contact solar cell according to claim 13, wherein, After depositing the silicon thin film layer, the method further comprises performing a post annealing process.

15. The method of producing a tunneling silicon thin film back contact solar cell according to claim 14, wherein, After the post annealing process, the method further comprises sequentially performing functional region patterning, composite passivation film deposition, and back surface metallization processing.

16. A tunneling silicon thin film back contact solar cell obtained by the method for preparing a tunneling silicon thin film back contact solar cell according to any one of claims 1-15.

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