TOPCON-based batteries

Abstract

The utility model discloses a battery based on TOPCON, which relates to the field of batteries. The battery includes a silicon substrate, a natural oxide layer, a pre-doped layer, a tunneling oxide layer, a hydrogen lock passivation layer, a tunneling enhancement barrier layer, an electron transport layer, a silicon nitride anti-reflection layer and a silver electrode; the interaction between the pre-doped layer and the hydrogen lock passivation layer is used to achieve the functional separation of passivation and field effect, and the passivation and field effect are obtained at the same time, thereby improving the open circuit voltage Uoc. At the same time, because the passivation and field effect are functionally separated, the nitrogen-doped N hydrogen lock passivation layer can be annealed at a low temperature to avoid the hole effect caused by the annealing temperature being too high, thereby resulting in a reduction in the filling factor FF; the introduction of the tunneling enhancement barrier layer can not only prevent nitrogen N from diffusing into the electron transport layer, resulting in the middle region increasing the resistance of the electron transport layer and reducing the filling factor FF, but also prevent phosphorus P from diffusing into the hydrogen lock passivation layer, thereby preventing the electron transport layer from having a low phosphorus P content, thereby increasing the contact barrier of the Ag-Si alloy and reducing the filling factor FF.

Description

Technical Field

[0001] The utility model relates to the field of batteries, in particular to a battery based on TOPCON. Background Art

[0002] Topcon (tunneling oxide passivation contact) realizes its function by preparing an ultra-thin oxide layer (1-2nm) and a doped amorphous silicon layer (60-150nm, after high-temperature annealing) on ​​the back of the battery. The tunneling oxide layer has three main functions: 1. Interface passivation, effectively reducing surface recombination; 2. Selective carrier transmission, electrons easily tunnel through, while holes are blocked, further reducing the carrier recombination effect; 3. Blocking excessive internal expansion of P atoms to form new recombination centers (appropriate amount of P atoms can enhance the field effect). The polysilicon layer also has three main functions: 1. Increase electron mobility and inhibit hole mobility; 2. When amorphous silicon contacts metal, it acts as an electron transmission bridge; 3. Chemical passivation: Amorphous silicon is rich in hydrogen atoms, which can chemically passivate defects on the surface and in the body during heat treatment, thereby reducing the recombination of surface electrons.

[0003] However, in the actual mass production process, the silicon wafer will not be immediately processed for the next Poly after cleaning. During the waiting process, an uneven natural oxide layer will be produced on the surface, introducing more defects, and the passivation effect will be further affected. Because of the unevenness of the natural oxide layer, the thickness of the tunnel oxide layer grown on it will also be uneven, resulting in inconsistent phosphorus concentration after internal expansion, which will not only affect efficiency improvement, but also easily form light and dark inside the chip. At the same time, there are a large number of H atoms in the poly. If the stress is not released in time, the film will explode in the subsequent links, which will greatly reduce the efficiency.

[0004] One solution is to dope N into amorphous silicon, which can further improve the passivation quality and inhibit film explosion. However, N doping will inhibit the activation of P atoms (the P activation concentration can be reduced from 70% to below 5%), which brings two new problems: 1. The transmission resistance of N-doped amorphous silicon is large, which can be alleviated by stacking, but N will diffuse to a certain extent in the stacking, reducing the effect of the stacking design. 2. Under the same annealing conditions, it is difficult for P to diffuse into C-Si through SiO2, resulting in the loss of the field effect gain of the internally expanded P, and iVoc decreases instead of increases. Increasing the annealing temperature will increase the number of pinholes in silicon dioxide, which will also lead to a decrease in iVOC. Because of these two problems, it is difficult to obtain industrial efficiency gains. Utility Model Content

[0005] The purpose of the utility model is to design a battery based on TOPCON in order to solve the above problems.

[0006] The utility model achieves the above-mentioned purpose through the following technical solutions:

[0007] The TOPCON-based battery includes, from top to bottom or from bottom to top: a silicon substrate, a natural oxide layer, a pre-doped layer, a tunneling oxide layer, a hydrogen-locking passivation layer, a tunneling enhancement barrier layer, an electron transport layer, a silicon nitride anti-reflection layer and a silver electrode. The pre-doped layer is doped with phosphorus, the hydrogen-locking passivation layer is provided with nitrogen, and the natural oxide layer is located on the back of the silicon substrate.

[0008] The beneficial effect of the utility model is that the interaction between the pre-doped layer and the hydrogen lock passivation layer is utilized to realize the functional separation of passivation and field effect, thereby simultaneously obtaining passivation and field effect, thereby further improving the open circuit voltage Uoc. At the same time, because the passivation and field effect are functionally separated, the nitrogen-doped hydrogen lock passivation layer can be annealed at a low temperature, avoiding the hole effect caused by the annealing temperature being too high, thereby causing a decrease in the filling factor FF; the introduction of the tunneling enhancement barrier layer can not only prevent nitrogen N from diffusing into the electron transport layer, resulting in the increase of the electron transport layer resistance in the middle region and the decrease in the filling factor FF, but also prevent phosphorus P from diffusing into the hydrogen lock passivation layer, avoiding the low phosphorus P content in the electron transport layer, causing the contact barrier of the Ag-Si alloy to increase and causing the filling factor FF to decrease, and finally the tunneling enhancement barrier layer can also inhibit the diffusion of silver, avoiding a large amount of silver from passing through the hydrogen lock passivation layer to the surface or inside of the tunneling oxide layer, causing a decrease in the open circuit voltage Uoc. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic diagram of the battery based on TOPCON of the utility model;

[0010] The corresponding figures are as follows:

[0011] 1-silicon substrate, 2-natural oxide layer, 3-pre-doped layer, 4-tunneling oxide layer, 5-hydrogen lock passivation layer, 6-tunneling enhancement barrier layer, 7-electron transport layer, 8-Mask protection layer. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0013] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the present invention to be protected, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0015] In the description of the present utility model, it should be understood that the terms "upper", "lower", "inside", "outside", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the utility model product is usually placed when in use, or are directions or positional relationships that are usually understood by those skilled in the art. These directions or positional relationships are only for the convenience of describing the present utility model and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present utility model.

[0016] Furthermore, the terms “first”, “second”, etc. are merely used for distinguishing descriptions and should not be understood as indicating or implying relative importance.

[0017] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms such as "setting" and "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0018] The specific implementation of the utility model is described in detail below in conjunction with the accompanying drawings.

[0019] like Figure 1 As shown, the TOPCON-based battery includes, from top to bottom or from bottom to top, a silicon substrate 1, a natural oxide layer 2, a pre-doped layer 3, a tunneling oxide layer 4, a hydrogen lock passivation layer 5, a tunneling enhancement barrier layer 6, an electron transport layer 7, a silicon nitride anti-reflection layer and a silver electrode, the pre-doped layer 3 is doped with phosphorus, the hydrogen lock passivation layer 5 is provided with nitrogen, and the natural oxide layer 2 is located on the back of the silicon substrate 1.

[0020] The thickness of the pre-doped layer 3 is in the range of 5-10 nm, the thickness of the tunneling oxide layer 4 is in the range of 1-2 nm, the thickness of the hydrogen lock passivation layer 5 is in the range of 10-20 nm, the thickness of the tunneling enhancement barrier layer 6 is in the range of 0.5-0.99 nm, and the thickness of the electron transport layer 7 is in the range of 40-60 nm.

[0021] The natural oxide layer 2 is naturally generated when the product is waiting for production. Defects will be introduced during the production process. At the same time, due to its uneven production, the thickness of the tunnel oxide layer 4 grown subsequently will be different. The pre-doped layer 3 mainly provides sufficient activatable phosphorus atoms to provide field effect and electron transmission. The tunnel oxide layer 4 mainly plays the role of passivation and carrier separation. The hydrogen lock passivation layer 5 mainly plays the role of limiting film explosion and improving the passivation effect. The tunneling enhancement barrier layer 6 mainly plays the role of assisting in the separation of carriers, isolating the mutual diffusion on both sides of N and P, and blocking the further penetration of silver. The electron transport layer 7 is mainly used to transmit electrons and form a better ohmic contact with Ag. The Mask protective layer 8 protects the lower film layer from damage and is removed in the subsequent process.

[0022] A method for preparing a TOPCON-based battery, for preparing the above-mentioned TOPCON-based battery, comprises:

[0023] S0, at 420-510°C, increase the nitrogen N25000-50000sccm range to remove the air in the furnace tube;

[0024] S1, the temperature range of the furnace tube is 420-510°C, the power range is 10000-15000W, silane, phosphine and hydrogen are introduced into the furnace tube for deposition, the deposition reaction time is 100-300s, the flow volume range of silane is 2000-5000sccm, the flow volume range of phosphine is 20-50sccm, the flow volume range of hydrogen is 8000-12000sccm, and a pre-doped layer 3 with a thickness of 5-10nm is formed on the natural oxide layer 2;

[0025] S2, when the temperature in the furnace tube is in the range of 420-510°C and the power is in the range of 10000-15000W, nitrous oxide is introduced into the furnace tube, the flow volume of nitrous oxide is in the range of 5000-20000sccm, and oxidation is performed at a duty ratio of NO:OFF=20:2000, the oxidation time is 80s-120s, and a tunneling oxide layer 4 with a thickness of 1-2nm is oxidized on the pre-doped layer 3;

[0026] S3, the temperature range of the furnace tube is 420-510°C, the power range is 10000-15000W, silane, phosphine, hydrogen and ammonia are introduced into the furnace tube for deposition, the deposition reaction time is 60-150s, the flow volume range of silane is 2000-5000sccm, the flow volume range of phosphine is 600-900sccm, the flow volume range of hydrogen is 8000-12000sccm, the ratio of ammonia to silane is controlled within 2%-5%, and a 10-mm thick layer is formed on the tunneling oxide layer 4. The hydrogen lock passivation layer 5 is 20nm thick, and the hydrogen lock passivation layer 5 is also the first amorphous silicon layer; nitrogen is added to suppress the purification rate of amorphous silicon. Since the lower the purification rate, the better the animation effect, the animation effect can be enhanced, but at the same time, the lower the purification rate, the smaller the phosphorus penetration effect, which also causes the phosphorus in the hydrogen lock passivation layer 5 to be unable to enter the silicon substrate 1, and the field effect cannot be guaranteed. Therefore, a phosphorus pre-doped layer 3 is provided between the silicon substrate 1 and the hydrogen lock passivation layer 5. Phosphorus-containing amorphous silicon absorbs light, and nitrogen doping N can reduce or even avoid light absorption, thereby improving the propagation response of amorphous silicon.

[0027] S4, when the temperature in the furnace tube is in the range of 420-510° C. and the power is in the range of 10000-15000 W, nitrous oxide is introduced into the furnace tube, the flow volume of nitrous oxide is in the range of 5000-20000 sccm, and oxidation is performed at a duty ratio of NO:OFF=20:2000, the oxidation time is 20s-40s, and a tunneling enhancement barrier layer 6 with a thickness of 0.5-0.99 nm is formed on the hydrogen lock passivation layer 5;

[0028] S5, the temperature range of the furnace tube is 420-510° C., the power range is 10000-15000 W, silane, phosphine and hydrogen are introduced into the furnace tube for deposition, the deposition reaction time is 250-450 s, the flow volume range of silane is 2000-5000 sccm, the flow volume range of phosphine is 800-900 sccm, the flow volume range of hydrogen is 8000-12000 sccm, and an electron transport layer 7 with a thickness of 40-60 nm is formed on the tunneling enhancement barrier layer 6;

[0029] S6, the temperature range of the furnace tube is 420-510° C., the power range is 10000-15000W, silane and nitrous oxide are introduced into the furnace tube for reaction, the reaction time is 30-70s, the flow volume range of silane is 1000-2000sccm, the flow volume range of nitrous oxide is 7000-9000sccm, and a mask protection layer 8 with a thickness of 10-50nm is formed on the electron transport layer 7;

[0030] S7, performing high temperature annealing treatment at a temperature of 880-920° C. for 25-35 min, and removing the mask protection layer 8;

[0031] S8, depositing a silicon nitride anti-reflection layer on the electron transport layer 7 by using a PECVD method;

[0032] S9. Print silver paste on the silicon nitride anti-reflection layer, perform light injection treatment after drying and sintering, and complete the production of the poly stacking optimization structure on the back of the TOPCON-based battery.

[0033] The preparation method of the utility model is highly compatible with the production line. The interaction between the pre-doped layer 3 and the hydrogen lock passivation layer 5 is used to achieve the functional separation of passivation and field effect, thereby obtaining passivation and field effect at the same time, thereby further improving the open circuit voltage Uoc. At the same time, because the passivation and field effect are functionally separated, the nitrogen-doped hydrogen lock passivation layer 5 can be annealed at low temperature to avoid the hole effect caused by the annealing temperature being too high, thereby reducing the filling factor FF. The introduction of the tunneling enhancement barrier layer 6 can not only prevent nitrogen N from diffusing into the middle area of ​​the electron transport layer 7, which will increase the resistance of the electron transport layer 7 and reduce the filling factor FF, but also prevent phosphorus P from diffusing into the hydrogen lock passivation layer 5, thereby avoiding the situation where the phosphorus P content of the electron transport layer 7 is too low, causing the contact barrier of the Ag-Si alloy to increase and causing the filling factor FF to decrease. Finally, the tunneling enhancement barrier layer 6 can also inhibit the diffusion of silver, preventing a large amount of silver from passing through amorphous silicon to the surface or inside of the tunneling layer, causing the open circuit voltage Uoc to decrease.

[0034] The nitrogen-doped N-doped hydrogen lock passivation layer 5 only needs 10-20nm to form a very good passivation effect. Based on experiments, under the premise of silicon dioxide cutting off silver diffusion, amorphous silicon of about 30-40nm can form a good contact with silver and achieve good electron transmission function. Therefore, the thickness of the entire effective poly layer can be reduced from the current 90-150nm to about 60nm, and the reduction of the transmission path will further increase the fill factor FF. At the same time, the thinner the amorphous silicon thickness, the less long waves are absorbed, and the higher the short-circuit current Isc. It can be concluded that the open-circuit voltage Uoc, fill factor FF, and short-circuit current Isc are all improved to a certain extent by using new technology and process, and the bifaciality of the battery cell can also be increased to more than 85%.

[0035] To achieve the above effect, no new equipment is needed, only an additional NH3 pipeline is needed. At the same time, after the introduction of this process, the poly layer is greatly reduced, achieving the goal of both reducing consumption and improving efficiency.

[0036] Adding a pre-doped layer 3 to separate the passivation layer from the field effect can achieve good efficiency gains when annealing the nitrogen-doped phosphorus P diffusion process at temperatures below 920 degrees. The total thickness of the poly layer can be limited to 50-70nm. The current industry poly layer thickness is 90-150nm, thereby achieving better efficiency gains and further improving the battery's 90-150 bifaciality.

[0037] The technical solution of the present utility model is not limited to the above-mentioned specific embodiments, and all technical variations made according to the technical solution of the present utility model fall within the protection scope of the present utility model.

Claims

1. TOPCON-based battery, characterized in that: From top to bottom or from bottom to top, it includes: a silicon substrate, a natural oxide layer, a pre-doped layer, a tunneling oxide layer, a hydrogen locking passivation layer, a tunneling enhancement barrier layer, an electron transport layer, a silicon nitride anti-reflection layer and a silver electrode. The pre-doped layer is doped with phosphorus, the hydrogen locking passivation layer is provided with nitrogen, and the natural oxide layer is located on the back of the silicon substrate.

2. The TOPCON-based battery according to claim 1, characterized in that: The thickness of the pre-doped layer ranges from 5 to 10 nm.

3. The TOPCON-based battery according to claim 1, characterized in that: The thickness of the hydrogen lock passivation layer ranges from 10 to 20 nm.

4. The TOPCON-based battery according to claim 1, characterized in that The thickness of the tunnel oxide layer is in the range of 1-2 nm.

5. The TOPCON-based battery according to claim 1, characterized in that: The thickness of the tunneling enhancement barrier layer ranges from 0.5 to 0.99 nm.

6. The TOPCON-based battery according to claim 1, characterized in that: The thickness of the electron transport layer ranges from 40 to 60 nm.

Images