Backlight-preventing total reflection passivation buffer structure and preparation method and application thereof

Abstract

The invention provides an anti-backlight total reflection passivation buffer structure and a preparation method and application thereof.The anti-backlight total reflection passivation buffer structure comprises an Al3O2 film layer rich in OH bonds and an AlNx buffer film layer which are sequentially deposited on the surface of an activated crystalline silicon substrate, and the activated crystalline silicon substrate is obtained after a crystalline silicon substrate is subjected to primary plasma treatment; the Al3O2 film layer rich in OH bonds is obtained by carrying out secondary plasma treatment on an aluminum oxide film layer; the refractive index of the Al3O2 film layer rich in OH bonds is smaller than 1.7, and the refractive index of the AlNx buffer film layer ranges from 1.7 to 1.9. The Al3O2 film layer rich in OH bonds can adsorb more OH bonds and H bonds with higher binding energy, the AlNx buffer film layer serves as a light absorption buffer layer, the good passivation effect is guaranteed, meanwhile, the adverse phenomenon of backlight total reflection caused by mismatching of the refractive index of the film layer on the surface of the solar cell is reduced, and the conversion efficiency of the solar cell is improved.

Description

Technical Field

[0001] The invention relates to the technical field of solar cells, and in particular to an anti-backlight total reflection passivation buffer structure and a preparation method and application thereof. Background Art

[0002] Tunnel Oxide Passivating Contacts (TOPCon) is a passivation structure used for crystalline silicon solar cells. It consists of an ultra-thin layer of silicon oxide and a layer of heavily doped polysilicon. It effectively reduces surface recombination and metal contact recombination, thereby improving energy conversion efficiency. It is mainly used for passivation of the back surface of the cell, and can achieve excellent surface passivation and selective collection of carriers. The conversion efficiency of TOPCon solar cells prepared with it has exceeded 25.7%. However, compared with the theoretical limit efficiency, there is still a lot of room for improvement. Among them, because the tunnel oxide passivation contact structure mainly uses silicon material, its light absorption rate is not high, and it cannot take into account good passivation and transmission effects, which has become one of the factors restricting its conversion efficiency.

[0003] In addition, the existing TOPCon solar cell preparation process inevitably requires the process of selectively depositing doped silicon films and selectively removing silicon films, which is complex and has high production costs.

[0004] The Chinese patent document discloses "a solar cell laminated passivation structure and laminated passivation contact solar cell", and its publication number is CN 210167363U. The patent has a first passivation film layer and a second passivation film layer on the back of the silicon wafer; the first passivation film layer is made of aluminum oxide material; the second passivation film layer is made of silicon nitride material, and the first N is formed by in-situ doping and high temperature treatment. + Type polysilicon layer, so that the N + The uniform sheet resistance of the layers helps to improve the open circuit voltage of the passivation structure. However, the solar cell stacked passivation structure still cannot improve the light absorption rate of the solar cell. Summary of the invention

[0005] In view of the shortcomings of the prior art mentioned above, the purpose of the present invention is to provide an anti-backlight total reflection passivation buffer structure and a preparation method and application thereof, which are used to solve the problems that the tunneling oxide layer passivation contact structure of the existing TOPCon solar cell mainly uses silicon material, has a low light absorption rate, cannot take into account good passivation and transmission effects, and has a complex preparation process and high production cost.

[0006] To achieve the above objectives and other related objectives, the present invention is obtained by including the following technical solutions.

[0007] The present invention provides an anti-backlight total reflection passivation buffer structure, comprising an Al3O2 film layer rich in OH bonds and an AlN x The buffer film layer, the activated substrate is obtained by subjecting the substrate to a plasma treatment, the OH-rich Al3O2 film layer is prepared by subjecting the aluminum oxide film layer to a plasma treatment; the refractive index of the OH-rich Al3O2 film layer is less than 1.7, the AlN x The refractive index of the buffer film layer is 1.7~1.9.

[0008] The present application uses an activated substrate obtained by a crystalline silicon substrate after a plasma treatment as a substrate, which can make the dangling bonds of silicon atoms and dopant atoms more easily form chemical passivation with the oxygen elements in alumina, which is beneficial to the subsequent deposition of an OH bond-rich Al3O2 film layer; the OH bond-rich Al3O2 film layer of the present application is obtained based on the ionization and electric field acceleration of a secondary plasma, and can adsorb more OH bonds and H bonds with stronger binding energy, but at this time, the single OH bond-rich Al3O2 film layer does not have excellent passivation effect and light absorption effect, because the fixed charges therein are not activated.

[0009] The present invention creatively deposits AlN on the surface of the OH-bond-rich Al3O2 film layer. x The buffer film layer forms an anti-reflection total reflection passivation buffer structure, AlN x The role of the buffer film layer has the following two aspects: (1) Promoting the movement of OH bonds and H bonds in the OH-bond-rich Al3O2 film layer, activating the fixed charges in the OH-bond-rich Al3O2 film layer, causing it to carry a large amount of negative fixed charges, thereby improving the passivation effect of the anti-backlight total reflection passivation buffer structure; (2) Combined with the structural characteristics of the existing solar cells with passivation contact structure, in order to ensure the perfect passivation effect, the passivation contact structure is usually an intrinsic amorphous silicon and doped amorphous silicon stacked structure or an ultra-thin silicon dioxide and doped polycrystalline silicon film structure. Due to the high light absorption characteristics of the silicon film layer itself, the disadvantage of the current solar cells with passivation contact structure is that the photoelectric conversion efficiency is relatively low, that is, part of the light is absorbed by the passivation contact structure instead of being absorbed by the solar cell itself and converted into photogenerated carriers. This application deposits AlN with a refractive index of 1.7~1.9 on the surface of the OH bond-rich Al3O2 film layer. x The buffer film layer effectively solves the passivation of solar cells. At the same time, it is combined with the transparent conductive film layer to solve the above technical problems. x The refractive index of the buffer film is between the OH-rich Al3O2 film and the transparent conductive film. xThe buffer film layer can be used as a light absorption buffer layer to reduce the disadvantages of backlight total reflection caused by the mismatch of the film refractive index, greatly improving the light absorption function of the solar cell, thereby improving the conversion efficiency of the solar cell.

[0010] Preferably, the thickness of the OH-rich Al3O2 film layer is 7-16 nm, and the AlN x The thickness of the buffer film layer is 2~10nm.

[0011] The present invention also provides a method for preparing an anti-backlight total reflection passivation buffer structure, comprising the following steps: S1: performing a plasma treatment on the surface of the crystalline silicon substrate to obtain an activated crystalline silicon substrate; S2: depositing an aluminum oxide film layer on the surface of an activated crystalline silicon substrate, and performing a secondary plasma treatment on the aluminum oxide film layer to obtain an Al3O2 film layer rich in OH bonds; S3: Deposition of AlN on the surface of the OH-rich Al3O2 film x A buffer film layer is provided to form a laminated structure; S4: annealing the stacked structure to form an anti-backlight total reflection passivation buffer structure; the annealing process can cause the OH bonds and H bonds in the OH bond-rich Al3O2 film layer to move, activate the fixed charges in the OH bond-rich Al3O2 film layer, and make it carry a large amount of negative fixed charges, thereby improving the passivation effect of the anti-backlight total reflection passivation buffer structure.

[0012] Preferably, the plasma precursor gas used in the primary plasma treatment and the secondary plasma treatment is selected from one or more of nitrous oxide, ammonia and hydrogen.

[0013] More preferably, the flow rate of the laughing gas is 1000-3000 sccm, the flow rate of the ammonia is 2000-5000 sccm, and the flow rate of the hydrogen is 4000-5000 sccm.

[0014] More preferably, the temperature of the primary plasma treatment and the secondary plasma treatment are both 110-320°C.

[0015] Preferably, in S2, the PE-ALD deposition chamber is heated to 110-310°C, TMA is introduced first, then nitrogen is introduced for purging, then water vapor is introduced, and finally nitrogen is introduced for purging, and this cycle is repeated to deposit an aluminum oxide film layer on the surface of the activated crystalline silicon substrate.

[0016] More preferably, in S2, in a single cycle, the flow rate of TMA is 1000-3000 sccm, the flow rate of water vapor is 1000-3000 sccm, and the N2 purge flow rate is 4000-6000 sccm.

[0017] More preferably, in S2, after each cycle, each deposited aluminum oxide film layer is subjected to a secondary plasma treatment, and this cycle is repeated to obtain an Al3O2 film layer rich in OH bonds.

[0018] More preferably, in S2, after all cycles are completed, the finally obtained aluminum oxide film layer is subjected to a secondary plasma treatment to obtain an Al3O2 film layer rich in OH bonds.

[0019] More preferably, in S3, AlN is deposited by plasma-assisted atomic layer deposition or plasma-enhanced chemical vapor deposition. x The buffer film layer, the gas source includes one or more of ammonia, hydrogen and TMA, and at least includes ammonia.

[0020] The above deposition method of the present application can not only make AlN x The refractive index of the buffer film layer is low and controllable, which promotes the light absorption of the solar cell. The gas source during the deposition process includes at least ammonia gas, which can be x The introduction of more H into the buffer film layer is conducive to H transfer during the annealing process, further promoting the movement of OH bonds and H bonds in the OH-rich Al3O2 film layer, activating the fixed charges in the OH-rich Al3O2 film layer, and improving the passivation effect.

[0021] More preferably, in S3, the deposition temperature is 110-310°C.

[0022] More preferably, in S3, the flow rate of ammonia is controlled to be 3000-5000 sccm, the flow rate of hydrogen is controlled to be 3000-4000 sccm, and the flow rate of TMA is controlled to be 2000-3000 sccm.

[0023] Preferably, in S4, the annealing treatment is performed under a protective atmosphere, the annealing temperature is 290-550° C., and the annealing time is 10-60 min.

[0024] More preferably, the protective atmosphere is nitrogen or argon, and the flow rate of the nitrogen or argon is controlled to be 4000-5000 sccm.

[0025] The present application also provides an application of the above-mentioned anti-backlight total reflection passivation buffer structure in the preparation of solar cells, combining the anti-backlight total reflection passivation buffer structure with a transparent conductive film, and the refractive index of the transparent conductive film is 1.9~2.0.

[0026] The anti-backlight total reflection passivation buffer structure of the present application is combined with a transparent conductive film and applied to the preparation of solar cells. Since the insulation of the anti-backlight total reflection passivation buffer structure has no polarity influence, and both the anti-backlight total reflection passivation buffer structure and the transparent conductive film have the characteristics of light conduction, refraction, and absorption, the combination of the two not only takes into account good passivation effect and excellent transmission effect, but also greatly simplifies the solar cell preparation process while achieving the conversion efficiency of TOPCon solar cells and heterojunction structure solar cells, eliminating the process troubles of selectively depositing doped silicon thin films and selectively removing silicon thin films, which can achieve efficient photoelectric conversion efficiency and greatly reduce process control and production costs. The anti-backlight total reflection passivation buffer structure of the present application has high light transmittance and excellent passivation effect, so that it can replace the tunneling passivation structure in the TOPCon solar cell structure as the passivation layer of the solar cell.

[0027] The preparation method of the solar cell using the anti-backlight total reflection passivation buffer structure of the present application is different from the preparation process of the TOPCon cell. Through the introduction of passivation film deposition equipment and transparent conductive film deposition equipment, the polysilicon film deposition equipment, conventional aluminum oxide deposition equipment, and front and back silicon nitride equipment are eliminated. Combined with the optimization of the junction depth of the pn junction and the heavily doped area, the energy loss is greatly reduced.

[0028] As described above, the present invention has the following beneficial effects: (1) The present invention uses an activated substrate obtained by a plasma treatment of a crystalline silicon substrate as a substrate, which can make the dangling bonds of silicon atoms and dopant atoms more easily chemically passivated with the oxygen element in alumina, which is beneficial to the subsequent deposition of an Al3O2 film layer rich in OH bonds; (2) The OH bond-rich Al3O2 film of the present invention is obtained based on the ionization of secondary plasma and the electric field acceleration, and can adsorb more OH bonds and H bonds with stronger binding energy. By depositing AlN with a refractive index of 1.7 to 1.9 on the surface of the OH bond-rich Al3O2 film, x The buffer film layer acts as a light absorption buffer layer, which reduces the backlight total reflection phenomenon of the film layer, greatly improving the light absorption function of the solar cell, thereby improving the conversion efficiency of the solar cell; (3) AlN x During the deposition of the buffer film, the gas source includes at least ammonia gas, which can be x The introduction of more H into the buffer film layer is conducive to H transfer during the annealing process, further promoting the movement of OH bonds and H bonds in the OH-rich Al3O2 film layer, activating the fixed charges in the OH-rich Al3O2 film layer, and improving the passivation effect. DETAILED DESCRIPTION

[0029] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0030] It should be noted that the process equipment or devices not specifically specified in the following embodiments are all conventional equipment or devices in the art.

[0031] In addition, it should be understood that one or more method steps mentioned in the present invention do not exclude the existence of other method steps before or after the combination step or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified; it should also be understood that the combination connection relationship between one or more devices / apparatuses mentioned in the present invention does not exclude the existence of other devices / apparatuses before or after the combination device / apparatus or the insertion of other devices / apparatuses between these explicitly mentioned two devices / apparatuses, unless otherwise specified. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or the scope of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the present invention without substantially changing the technical content.

[0032] Example 1 The present application embodiment provides a method for preparing an anti-backlight total reflection passivation buffer structure, which is prepared by using a one-plate time-type plasma enhanced atomic layer deposition (PE-ALD) device, including the following steps: S1: Place the crystalline silicon substrate in the reactor of the PE-ALD equipment, evacuate the reactor, heat the reactor to 110°C, introduce nitrous oxide at a flow rate of 2000sccm, introduce hydrogen at a flow rate of 4000sccm, control the reaction pressure to be 180Pa, the discharge power supply to be 40kHz, the discharge power to be 3000W, the switch ratio to be 1 / 10, the treatment time to be 2min, perform a plasma treatment on the surface of the crystalline silicon substrate, and obtain an activated crystalline silicon substrate; S2: Keep the reaction furnace at 110°C, introduce TMA at a flow rate of 2000sccm, then introduce nitrogen at a flow rate of 5000sccm for purging, then introduce water vapor at a flow rate of 2000sccm, and finally introduce nitrogen at a flow rate of 5000sccm for purging. The source pressure is 50Pa, and an aluminum oxide film with a thickness of 3nm is deposited on the surface of the activated crystalline silicon substrate; After depositing a layer of aluminum oxide, the reaction furnace was kept at 110° C., nitrous oxide was introduced at a flow rate of 2000 sccm, ammonia was introduced at a flow rate of 4000 sccm, the reaction pressure was 180 Pa, the power supply used was 40 kHz, the discharge power was 4000 W, the on-off ratio was 1 / 20, the treatment time was 2 min, and the aluminum oxide film layer was subjected to secondary plasma treatment; Then, the reaction furnace was kept at 110° C., TMA was introduced again at a flow rate of 2000 sccm, nitrogen was introduced at a flow rate of 5000 sccm for purging, water vapor was introduced at a flow rate of 2000 sccm, and finally nitrogen was introduced at a flow rate of 5000 sccm for purging at a source pressure of 50 Pa, and an aluminum oxide film layer with a thickness of 4 nm was deposited on the surface of the activated crystalline silicon substrate; Afterwards, the reaction furnace was kept at 110° C., nitrous oxide was introduced at a flow rate of 2000 sccm, ammonia was introduced at a flow rate of 4000 sccm, the reaction pressure was 180 Pa, the power supply used was 40 kHz, the discharge power was 4000 W, the switch ratio was 1 / 20, the treatment time was 2 min, and the newly deposited aluminum oxide film layer was subjected to secondary plasma treatment; finally, an Al3O2 film layer rich in OH bonds with a thickness of 7 nm was obtained on the surface of the activated crystalline silicon substrate; S3: The reaction furnace is maintained at 110°C, ammonia is introduced at a flow rate of 5000sccm, TMA is introduced at a flow rate of 2000sccm, nitrogen is introduced at a flow rate of 5000sccm for purging, the discharge power is 40kHz, the discharge power is 4000W, the switch ratio is 1 / 20, the pressure is 180Pa, the TMA introduction step pressure is 50Pa, and AlN with a refractive index of 1.7 and a thickness of 2nm is deposited on the surface of the OH-rich Al3O2 film layer. x A buffer film layer is provided to form a laminated structure; S4: annealing the laminated structure in a nitrogen protective atmosphere at a temperature of 290° C., a nitrogen flow rate of 5000 sccm, a pressure of 800 Pa, and an annealing time of 60 min, thereby obtaining an anti-backlight total reflection passivation buffer structure.

[0033] The present application also provides an anti-backlight total reflection passivation buffer structure prepared by the above preparation method, comprising an Al3O2 film layer rich in OH bonds and an AlN x The buffer film layer, the activated crystalline silicon substrate is obtained by subjecting the crystalline silicon substrate to a plasma treatment, the OH bond-rich Al3O2 film layer is obtained by subjecting the aluminum oxide film layer to a secondary plasma treatment; the OH bond-rich Al3O2 film layer has a refractive index of less than 1.7 and a thickness of 7nm; the AlN x The refractive index of the buffer film layer is 1.7 and the thickness is 2 nm.

[0034] Example 2 The present application provides a method for preparing an anti-backlight total reflection passivation buffer structure, which is prepared by using a one-plate time-type PE-ALD device, including the following steps: S1: Place a crystalline silicon substrate into a reaction furnace of a plate-type time-type PE-ALD device, evacuate the furnace, heat the reaction furnace to 210°C, introduce nitrous oxide at a flow rate of 2000sccm, introduce ammonia at a flow rate of 3000sccm, the reaction pressure is 180Pa, the discharge power is 40kHz, the discharge power is 3000W, the switch ratio is 1 / 15, the treatment time is 2min, and the surface of the crystalline silicon substrate is subjected to a plasma treatment to obtain an activated crystalline silicon substrate; S2: Keep the reaction furnace at 210°C, introduce TMA at a flow rate of 2000sccm, introduce water vapor at a flow rate of 2000sccm, introduce nitrogen purge at a flow rate of 5000sccm, and the source pressure is 50Pa. In this cycle, an aluminum oxide film with a thickness of 11.5nm is deposited on the surface of the activated crystalline silicon substrate; After the aluminum oxide film layer is deposited, the reaction furnace is maintained at 210° C., nitrous oxide is introduced at a flow rate of 2000 sccm, hydrogen is introduced at a flow rate of 4000 sccm, the reaction pressure is 180 Pa, the discharge power is 40 kHz, the discharge power is 4000 W, the switch ratio is 1 / 10, and the processing time is 3 min. The aluminum oxide film layer is subjected to secondary plasma treatment to obtain an Al3O2 film layer rich in OH bonds with a thickness of 11.5 nm; S3: The reactor is kept at 210°C, ammonia is introduced at a flow rate of 3000sccm, hydrogen is introduced at a flow rate of 4000sccm, TMA is introduced at a flow rate of 2000sccm, nitrogen is introduced at a flow rate of 5000sccm for purging, the discharge power is 40kHz, the discharge power is 4000W, the switching ratio is 1 / 15, the pressure is 180Pa, the TMA introduction step pressure is 50Pa, and AlN with a refractive index of 1.8 and a thickness of 6nm is deposited on the surface of the OH-rich Al3O2 film layer. x A buffer film layer is provided to form a laminated structure; S4: annealing the stacked structure in a nitrogen protective atmosphere at a temperature of 450° C., a nitrogen flow rate of 5000 sccm, a pressure of 800 Pa, and an annealing time of 25 min, thereby obtaining an anti-backlight total reflection passivation buffer structure.

[0035] The present application also provides an anti-backlight total reflection passivation buffer structure prepared by the above preparation method, comprising an Al3O2 film layer rich in OH bonds and an AlN xThe buffer film layer, the activated crystalline silicon substrate is obtained by subjecting the crystalline silicon substrate to a plasma treatment, the OH bond-rich Al3O2 film layer is obtained by subjecting the aluminum oxide film layer to a secondary plasma treatment; the refractive index of the OH bond-rich Al3O2 film layer is less than 1.7, the thickness is 11.5nm, the AlN x The refractive index of the buffer film layer is 1.8 and the thickness is 6 nm.

[0036] Example 3 The present application provides a method for preparing an anti-backlight total reflection passivation buffer structure, which is prepared by using a one-plate time-type PE-ALD device, including the following steps: S1: Place the crystalline silicon substrate into a reactor of a plate-type time-type PE-ALD device, evacuate the reactor, heat the reactor to 310°C, introduce hydrogen at a flow rate of 2000sccm, introduce ammonia at a flow rate of 4000sccm, the reaction pressure is 220pa, the discharge power is 40kHz, the discharge power is 6000W, the switch ratio is 1 / 15, and the treatment time is 2min. Perform a plasma treatment on the surface of the crystalline silicon substrate to obtain an activated crystalline silicon substrate; S2: Keep the reaction furnace at 310°C, introduce TMA at a flow rate of 3000sccm, then introduce nitrogen at a flow rate of 6000sccm for purging, then introduce water vapor at a flow rate of 3000sccm, and finally introduce nitrogen at a flow rate of 6000sccm for purging. The source pressure is 50Pa, and the source pressure is 50Pa. Deposit an aluminum oxide film with a thickness of 16nm on the surface of the activated crystalline silicon substrate; After the aluminum oxide film layer is deposited, the reaction furnace is maintained at 310° C., laughing gas is introduced at a flow rate of 1000 sccm, hydrogen is introduced at a flow rate of 3000 sccm, ammonia is introduced at a flow rate of 3000 sccm, the reaction pressure is 220 Pa, the discharge power is 40 kHz, the discharge power is 4000 W, the switch ratio is 1 / 10, the processing time is 3 min, and the aluminum oxide film layer is subjected to secondary plasma to obtain an Al3O2 film layer rich in OH bonds with a thickness of 15 nm; S3: The reactor is kept at 310°C, hydrogen is introduced at a flow rate of 3000sccm, ammonia is introduced at a flow rate of 4000sccm, TMA is introduced at a flow rate of 3000sccm, nitrogen is purged at a flow rate of 5000sccm, the discharge power is 40kHz, the discharge power is 4000W, the switch ratio is 1 / 15, the pressure is 180Pa, and AlN with a refractive index of 1.9 and a thickness of 10nm is deposited on the surface of the OH-rich Al3O2 film layer. x A buffer film layer is provided to form a laminated structure; S4: annealing the stacked structure in an argon protective atmosphere, with an annealing temperature of 550° C., a nitrogen flow rate of 5000 sccm, a pressure of 800 Pa, and an annealing time of 10 min, thereby obtaining an anti-backlight total reflection passivation buffer structure.

[0037] The present application also provides an anti-backlight total reflection passivation buffer structure prepared by the above preparation method, comprising an Al3O2 film layer rich in OH bonds and an AlN x The buffer film layer, the activated crystalline silicon substrate is obtained by subjecting the crystalline silicon substrate to a plasma treatment, and the OH-rich Al3O2 film layer is obtained by subjecting the aluminum oxide film layer to a secondary plasma treatment; the OH-rich Al3O2 film layer has a refractive index of less than 1.7 and a thickness of 16 nm. x The refractive index of the buffer film layer is 1.9 and the thickness is 10 nm.

[0038] Comparative Example 1 Comparative Example 1 uses a conventional thermal atomic layer deposition process to deposit an aluminum oxide film on the surface of a substrate, and the preparation method is as follows: The surface of the cleaned n-type crystalline silicon substrate was pretreated with O3, and a thin layer of silicon oxide with a thickness of about 1 nm was deposited on the surface of the n-type crystalline silicon substrate to assist in increasing the chemical passivation of aluminum oxide; then, an aluminum oxide film layer with a thickness of 10 nm was deposited on the silicon oxide surface using water and TMA, and annealed at 500°C for 30 minutes to obtain an aluminum oxide film passivation structure.

[0039] The passivation effects of the anti-backlight total reflection passivation buffer structures prepared in Examples 1 to 3 and the aluminum oxide film layer of Comparative Example 1 were tested. Double-sided polished and textured silicon wafers were used for testing. The testing instrument used was a Sintion WCT 120 minority carrier lifetime tester. The results are shown in Table 1: Table 1. Passivation effect of the anti-backlight total reflection passivation buffer structure prepared in Examples 1 to 3 and the aluminum oxide film layer of Comparative Example 1 Grouping Number of pieces Average silicon wafer resistivity (ohm cm) Average silicon wafer thickness (micrometers) Average iVoc(mV) Example 1 50 0.8 130 738 Example 2 50 0.8 129 743 Example 3 50 0.9 130 745 Comparative Example 1 50 1 130 706 In Table 1: iVoc is the ideal open circuit voltage, which is used to characterize the passivation effect of the solar cell. The larger the iVoc is, the better the passivation effect is.

[0040] The anti-backlight total reflection passivation buffer structure prepared in Example 1 is combined with a transparent conductive film to prepare a solar cell structure: cleaning and texturing, depositing a BSG film layer on the back, selective shallow junction heavy doping with laser, removing the BSG film layer, depositing a PSG film layer, selective shallow junction doping, removing the PSG film layer at the side edges, removing the PSG film layer and BSG film layer on the front and back sides, double-sided deposition of the anti-backlight total reflection passivation buffer structure (total thickness 9nm) prepared in Example 1, double-sided selective laser opening, deposition of an indium-doped tin oxide film layer, preparation of a low-temperature electrode, light injection and laser-assisted passivation contact to obtain a solar cell.

[0041] The aluminum oxide film layer of Comparative Example 1 was used to prepare TOPCon solar cells according to the preparation process of mass-produced TOPCon solar cells: cleaning and texturing, depositing a BSG film layer on the back, removing the BSG film layer on the edge and the back, depositing a tunneling oxide layer and a poly-Si film layer on the back, and depositing a PSG film layer, annealing, cleaning and removing the edge and front PSG film layer, removing the front and side phosphorus-doped poly-Si wrapping, removing the front BSG film layer and the back PSG film layer, depositing an aluminum oxide film layer on the front, depositing a silicon oxynitride stacked film on the front, depositing a silicon nitride stacked film on the back, printing high-temperature electrodes on the front and back,) light injection and laser-assisted sintering to prepare TOPCon solar cells.

[0042] The performance of the solar cell using the anti-backlight total reflection passivation buffer structure of Example 1 and the TOPCon solar cell using the aluminum oxide film layer of Comparative Example 1 were tested respectively, and the results are shown in Table 2: Table 2. Performance data of solar cells prepared in Example 1 and Comparative Example 1 Grouping Number of pieces Voc (V) Isc (A) FF (%) Eff (%) Example 1 10000 0.745 14.433 83.201 27.097 Comparative Example 1 10000 0.738 13.906 84.901 26.391 In Table 2: Voc is the open circuit voltage, Isc is the short circuit current, FF is the fill factor, and Eff is the photoelectric conversion efficiency.

[0043] It can be seen from Table 2 that the solar cell prepared by using the anti-backlight total reflection passivation buffer structure of the present application has a higher open circuit voltage and short-circuit current, indicating that the anti-backlight total reflection passivation buffer structure of the present application is combined with the transparent conductive film, and has the characteristics of light conduction, refraction and absorption, taking into account good passivation effect and excellent transmission effect, and the passivation property is not weaker than the passivation effect of the passivation tunneling layer structure in TOPCon, and can replace the tunneling passivation structure in the TOPCon solar cell structure as the passivation layer of the solar cell.

[0044] The above is only a preferred embodiment of the present invention, and is not any formal or substantial limitation of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention, and these improvements and supplements should also be regarded as the protection scope of the present invention. Any technician familiar with this profession, without departing from the spirit and scope of the present invention, can make some changes, modifications and evolutions of the technical content disclosed above, which are equivalent embodiments of the present invention; at the same time, any changes, modifications and evolutions of any equivalent changes made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. An anti-backlight total reflection passivation buffer structure, characterized in that: The invention comprises an Al3O2 film layer rich in OH bonds and an AlN film layer sequentially deposited on the surface of an activated crystalline silicon substrate. x The buffer film layer, the activated crystalline silicon substrate is obtained by subjecting the crystalline silicon substrate to a plasma treatment, the OH bond-rich Al3O2 film layer is obtained by subjecting the aluminum oxide film layer to a secondary plasma treatment; the refractive index of the OH bond-rich Al3O2 film layer is less than 1.7, the AlN x The refractive index of the buffer film layer is 1.7~1.

9.

2. The anti-backlight total reflection passivation buffer structure according to claim 1, characterized in that: The thickness of the OH-rich Al3O2 film layer is 7-16 nm. x The thickness of the buffer film layer is 2~10nm.

3. A method for preparing the anti-backlight total reflection passivation buffer structure according to claim 1 or 2, characterized in that: The following steps are involved: S1: performing a plasma treatment on the surface of the crystalline silicon substrate to obtain an activated crystalline silicon substrate; S2: depositing an aluminum oxide film layer on the surface of an activated crystalline silicon substrate, and performing a secondary plasma treatment on the aluminum oxide film layer to obtain an Al3O2 film layer rich in OH bonds; S3: Deposition of AlN on the surface of the OH-rich Al3O2 film x A buffer film layer is provided to form a laminated structure; S4: annealing the stacked structure to form an anti-backlight total reflection passivation buffer structure.

4. The preparation method according to claim 3, characterized in that: The plasma precursor gas used in the primary plasma treatment and the secondary plasma treatment is selected from one or more of nitrous oxide, ammonia and hydrogen, and the temperature of the primary plasma treatment and the secondary plasma treatment is 110-320°C.

5. The preparation method according to claim 3, characterized in that: In S2, the PE-ALD deposition chamber is heated to 110-310°C, TMA is introduced first, then nitrogen is introduced for purging, then water vapor is introduced, and finally nitrogen is introduced for purging, and this cycle is repeated to deposit an aluminum oxide film layer on the surface of the activated crystalline silicon substrate.

6. The preparation method according to claim 5, characterized in that: In S2, after each cycle, each deposited aluminum oxide film layer is subjected to a secondary plasma treatment, and this cycle is repeated to obtain an Al3O2 film layer rich in OH bonds.

7. The preparation method according to claim 5, characterized in that: In S2, after all cycles are completed, the finally obtained aluminum oxide film layer is subjected to a secondary plasma treatment to obtain an Al3O2 film layer rich in OH bonds.

8. The preparation method according to claim 3, characterized in that: In S3, AlN is deposited by plasma-assisted atomic layer deposition or plasma-enhanced chemical vapor deposition. x The buffer film layer, the gas source includes one or more of ammonia, hydrogen and TMA, and at least includes ammonia; the deposition temperature is 110~310℃.

9. The preparation method according to claim 3, characterized in that: In S4, annealing treatment is performed under a protective atmosphere, the annealing temperature is 290-550° C., and the annealing time is 10-60 min.

10. An application of the anti-backlight total reflection passivation buffer structure as claimed in claim 1 or 2 in the preparation of solar cells, characterized in that: The anti-backlight total reflection passivation buffer structure is combined with a transparent conductive film, and the refractive index of the transparent conductive film is 1.9-2.0.