Heterojunction battery and preparation method thereof

Abstract

The present invention provides a heterojunction battery and a preparation method thereof, comprising a substrate; a back-doped amorphous silicon layer located on the backlight side of the substrate; and a back passivation layer located between the back-doped amorphous silicon layer and the substrate, wherein the back passivation layer comprises an oxygen-doped material, and the back passivation layer has a contact portion and a non-contact portion with the back-doped amorphous silicon layer, and the oxygen doping concentration of the contact portion is less than the oxygen doping concentration of at least a part of the non-contact portion. In this way, the optical band gap of the back passivation layer can be made larger, and a large valence band offset can be avoided, the absorption of light can be reduced, the short-circuit current density can be increased, and the passivation effect can be further improved. At the same time, the influence on the transmission and collection of holes can be reduced, so that the performance of the heterojunction battery is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of heterojunction batteries, and in particular to a heterojunction battery and a preparation method thereof. Background Art

[0002] Heterojunction (HJT) cell technology has become a hot topic in current research, with efficiency improvement and cost reduction being important optimization guidelines for researchers and scholars. Hydrogenated amorphous silicon (ia-Si:H) is often used as a passivation layer material for HJT cells. It can provide abundant hydrogen, thereby passivating dangling bonds, reducing defects, and reducing carrier recombination. However, due to its lower optical band gap, hydrogenated amorphous silicon absorbs some light, resulting in a decrease in the short-circuit current density of solar cells.

[0003] Typically, hydrogenated amorphous silicon oxide can be used instead of hydrogenated amorphous silicon to form the passivation layer of the HJT cell. Due to the incorporation of oxygen, the optical band gap increases, the absorption of light is reduced, the short-circuit current density is increased, and the passivation effect can be further improved.

[0004] However, research has found that this method is not conducive to the transmission and collection of holes, and has some adverse effects on the performance of HJT batteries. Summary of the invention

[0005] In order to solve the above problems, the inventors found the causes of the problems through research and development and formed solutions.

[0006] In a first aspect, the present invention provides a heterojunction battery, the heterojunction battery comprising:

[0007] substrate;

[0008] A doped amorphous silicon layer located on the back side of the backlight surface of the substrate;

[0009] a back passivation layer located between the back doped amorphous silicon layer and the substrate,

[0010] The back passivation layer includes an oxygen-doped material, and has a contact portion and a non-contact portion with the back doped amorphous silicon layer, and the oxygen doping concentration of the contact portion is lower than the oxygen doping concentration of at least a part of the non-contact portion.

[0011] Furthermore, in the above-mentioned heterojunction battery, the non-contact portion includes a first passivation layer and a second passivation layer, and the contact portion is a third passivation layer;

[0012] The oxygen doping concentration of the first passivation layer and the oxygen doping concentration of the third passivation layer are both lower than the oxygen doping concentration of the second passivation layer.

[0013] Furthermore, in the above-mentioned heterojunction battery, the oxygen doping concentration of the first passivation layer is less than or equal to the oxygen doping concentration of the third passivation layer.

[0014] Furthermore, in the above-mentioned heterojunction battery, the oxygen doping concentration of the first passivation layer gradually increases, and the oxygen doping concentration of a surface of the first passivation layer close to the second passivation layer is lower than the oxygen doping concentration of the second passivation layer.

[0015] Furthermore, in the above-mentioned heterojunction battery, the oxygen doping concentration of the third passivation layer gradually decreases, and the oxygen doping concentration of a surface of the third passivation layer close to the second passivation layer is less than the oxygen doping concentration of the second passivation layer.

[0016] Furthermore, in the heterojunction battery described above, the oxygen doping concentration of the first passivation layer gradually increases, the oxygen doping concentration of the second passivation layer gradually increases, and the oxygen doping concentration of the third passivation layer gradually decreases;

[0017] Wherein, the oxygen doping concentration of a surface of the first passivation layer close to the second passivation layer is less than the oxygen doping concentration of a surface of the second passivation layer close to the first passivation layer;

[0018] The oxygen doping concentration of a surface of the third passivation layer close to the second passivation layer is lower than the oxygen doping concentration of a surface of the second passivation layer close to the third passivation layer.

[0019] Furthermore, in the above-mentioned heterojunction battery, the non-contact portion includes a first passivation layer and a second passivation layer, and the contact portion is a third passivation layer;

[0020] The oxygen doping concentration of the first passivation layer gradually increases, the oxygen doping concentration of the second passivation layer gradually increases, and the oxygen doping concentration of the third passivation layer gradually decreases;

[0021] The oxygen-doping concentration of the first passivation layer on the side close to the second passivation layer is greater than or equal to the oxygen-doping concentration of the second passivation layer on the side close to the first passivation layer, and the oxygen-doping concentration of the second passivation layer on the side away from the first passivation layer is greater than the oxygen-doping concentration of the first passivation layer on the side close to the second passivation layer;

[0022] The oxygen-doping concentration of the third passivation layer on a side close to the second passivation layer is less than or equal to the oxygen-doping concentration of the second passivation layer on a side away from the first passivation layer, and the oxygen-doping concentration of the second passivation layer on a side close to the first passivation layer is greater than the oxygen-doping concentration of the third passivation layer on a side away from the second passivation layer.

[0023] In a second aspect, the present invention provides a method for preparing a heterojunction battery, the method for preparing a heterojunction battery comprising:

[0024] forming a back passivation layer and a back doped amorphous silicon layer in sequence on the backlight side of the substrate;

[0025] The back passivation layer includes an oxygen-doped material, and has a contact portion and a non-contact portion with the back doped amorphous silicon layer, and the oxygen doping concentration of the contact portion is lower than the oxygen doping concentration of at least a part of the non-contact portion.

[0026] Furthermore, in the above-mentioned method for preparing a heterojunction battery, the process of forming the back passivation layer includes:

[0027] Passing an oxygen-doped gas source, sequentially depositing the first passivation layer, the second passivation layer and the third passivation layer on the backlight surface of the substrate;

[0028] The first passivation layer and the second passivation layer constitute the non-contact portion, the third passivation layer constitutes the contact portion, and the oxygen doping concentration of the first passivation layer and the oxygen doping concentration of the third passivation layer are both lower than the oxygen doping concentration of the second passivation layer.

[0029] Furthermore, in the above-mentioned method for preparing a heterojunction battery, depositing the first passivation layer comprises:

[0030] The first passivation layer with gradually increasing oxygen doping concentration is formed by adjusting the ratio of the oxygen-doped gas source, wherein the oxygen doping concentration of a surface of the first passivation layer close to the second passivation layer is lower than the oxygen doping concentration of the second passivation layer.

[0031] Furthermore, in the above-mentioned method for preparing a heterojunction battery, depositing the third passivation layer comprises:

[0032] The third passivation layer with gradually decreasing oxygen doping concentration is formed by adjusting the ratio of the oxygen doping gas source, wherein the oxygen doping concentration of a surface of the third passivation layer close to the second passivation layer is lower than the oxygen doping concentration of the second passivation layer.

[0033] Furthermore, in the above-mentioned method for preparing the heterojunction battery, depositing the first passivation layer, the second passivation layer and the third passivation layer comprises:

[0034] By adjusting the ratio of the oxygen-doped gas source, the first passivation layer with gradually increasing oxygen doping concentration, the second passivation layer with gradually increasing concentration, and the third passivation layer with gradually decreasing concentration and gradually decreasing oxygen doping concentration are formed;

[0035] Wherein, the oxygen doping concentration of a surface of the first passivation layer close to the second passivation layer is less than the oxygen doping concentration of a surface of the second passivation layer close to the first passivation layer;

[0036] The oxygen doping concentration of a surface of the third passivation layer close to the second passivation layer is lower than the oxygen doping concentration of a surface of the second passivation layer close to the third passivation layer.

[0037] Furthermore, in the above-mentioned method for preparing a heterojunction battery, the formation process of the back passivation layer is:

[0038] By adjusting the ratio of the oxygen-doped gas source, the first passivation layer with gradually increasing concentration, the second passivation layer with gradually increasing concentration, and the third passivation layer with gradually decreasing concentration and gradually decreasing oxygen doping concentration are formed;

[0039] Wherein, the first passivation layer and the second passivation layer constitute the non-contact portion, and the third passivation layer constitutes the contact portion;

[0040] The oxygen doping concentration of the first passivation layer on a side close to the second passivation layer is greater than or equal to the oxygen doping concentration of the second passivation layer on a side close to the first passivation layer, and the oxygen doping concentration of the second passivation layer on a side away from the first passivation layer is greater than the oxygen doping concentration of the first passivation layer on a side close to the second passivation layer;

[0041] The oxygen-doping concentration of the third passivation layer on a side close to the second passivation layer is less than or equal to the oxygen-doping concentration of the second passivation layer on a side away from the first passivation layer, and the oxygen-doping concentration of the second passivation layer on a side close to the first passivation layer is greater than the oxygen-doping concentration of the third passivation layer on a side away from the second passivation layer.

[0042] The above one or more technical solutions of the present invention have at least one or more of the following beneficial effects:

[0043] When implementing the technical solution of the present invention, a back passivation layer of an oxide-doped material is arranged on the backlight surface of the substrate, and the back passivation layer is utilized and configured to be at least in a high-concentration and low-concentration distribution state in a direction perpendicular to the substrate and from the inside to the outside, so that the optical band gap of the back passivation layer is larger, and the valence band shift can be avoided, the absorption of light is reduced, the short-circuit current density is increased, and the passivation effect can be further improved. At the same time, the influence on the transmission and collection of holes can be reduced, so that the performance of the HJT battery is better. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The disclosure of the present invention will become more easily understood with reference to the accompanying drawings. It is easy for those skilled in the art to understand that these drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. In addition, similar numbers in the drawings are used to represent similar components, wherein:

[0045] Figure 1 It is a schematic diagram of the structure of a HJT battery;

[0046] Figure 2 is a schematic flow chart of a method for preparing a HJT battery according to an embodiment of the present invention;

[0047] Figure 3 This is a schematic diagram of a process flow for preparing HJT batteries. DETAILED DESCRIPTION

[0048] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0049] In the description of the present invention, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, in the present invention, unless otherwise clearly specified and defined, the terms "connected", "connected", and the like should be understood in a broad sense. For example, it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0050] In the present invention, the term "and / or" used includes any and all combinations of one or more related listed items. The "multiple" used herein includes two and more than two items. The "above a certain number" used herein should be understood as a certain number and a range greater than a certain number.

[0051] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0052] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0053] HJT cell technology has become a hot topic in current research, with efficiency improvement and cost reduction being important optimization guidelines for researchers and scholars. Hydrogenated amorphous silicon (ia-Si:H) is often used as a passivation layer material for HJT cells. It can provide abundant hydrogen, thereby passivating dangling bonds, reducing defects, and reducing carrier recombination. However, due to its lower optical band gap, hydrogenated amorphous silicon absorbs some light, resulting in a decrease in the short-circuit current density of solar cells.

[0054] Compared with hydrogenated amorphous silicon, hydrogenated amorphous silicon oxide has a larger optical band gap due to the incorporation of oxygen elements, thereby reducing the absorption of light, allowing more photons to reach the absorption layer of the solar cell (laser electron-hole pairs), thereby increasing the short-circuit current density of the HJT cell.

[0055] In addition, the Si-O bonds formed during the growth and deposition of hydrogenated amorphous silicon oxide can also effectively inhibit the epitaxial growth of crystalline silicon, thereby further improving the passivation quality and obtaining a higher open circuit voltage.

[0056] However, HJT cells based on hydrogenated amorphous silicon oxide to form a passivation layer have good passivation effect and high short-circuit current density, but are often accompanied by phenomena that are not conducive to the transmission and collection of holes. Therefore, in response to this technical problem, HJT cells were studied and the reasons that affect the transmission and collection of holes were found to be as follows:

[0057] The passivation layer formed by hydrogenated amorphous silicon oxide is in direct contact with the P-type doped amorphous silicon layer. In this way, due to the high oxygen concentration in the hydrogenated amorphous silicon oxide, the increase in the optical band gap will cause a large valence band offset to be formed on the valence band when the passivation layer contacts the P-type doped layer, forming a new transmission barrier, which is not conducive to the transmission and collection of holes.

[0058] For this reason, attempts were made to adjust the oxygen doping concentration in the passivation layer, and it was finally discovered that when the oxygen doping concentration of the passivation layer is distributed perpendicular to the substrate and from the inside to the outside of the substrate at least in a high concentration and low concentration distribution state, it is beneficial to the transmission and collection of holes in the HJT battery. In other words, the back passivation layer has a contact portion and a non-contact portion with the back doped amorphous silicon layer. At least a portion of the portion (non-contact portion) of the back passivation layer that is not in contact with the back doped amorphous silicon layer can be doped with a higher concentration of oxygen to increase the band gap, while the portion (contact portion) that is in direct contact with the back doped amorphous silicon layer can be doped with a lower concentration of oxygen to reduce the valence band offset, thereby satisfying both the increase in the band gap and the transmission and collection of holes.

[0059] Specifically, Figure 1 This is a schematic diagram of the structure of a HJT battery. Figure 1 As shown, the HJT cell is described by taking the non-contact portion of the back passivation layer including the first passivation layer 121 and the second passivation layer 122, and the contact portion being the third passivation layer 123 as an example. Specifically, the HJT cell includes a substrate 11, a back passivation layer 12, and a back doped amorphous silicon layer 13. Among them, the back passivation layer 12 and the back doped amorphous silicon layer 13 are both located on the backlight side of the substrate 11, and the back passivation layer 12 is located between the substrate 11 and the back doped amorphous silicon layer 13, and the back passivation layer 12 is in direct contact with the back doped amorphous silicon layer 13. In a specific implementation process, the back passivation layer 12 includes an oxygen-doped material, such as hydrogenated amorphous silicon oxide. In this way, due to the incorporation of oxygen elements, the optical band gap will be increased, so that the absorption of light can be reduced, so that more photons can reach the absorption layer of the HJT cell, thereby increasing the short-circuit current density of the HJT cell.

[0060] However, when the oxygen doping concentration in the oxygen-doped material is low, the band gap increases to a limited extent, and when the oxygen doping concentration in the oxygen-doped material is high, the valence band of the passivation layer will be greatly offset. Therefore, in this embodiment, the passivation layer can be divided into a first passivation layer 121, a second passivation layer 122, and a third passivation layer 123, and the oxygen doping concentration of the first passivation layer 121, the second passivation layer 122, and the third passivation layer 123 as a whole is distributed in a low concentration, a high concentration, and a low concentration, that is, the oxygen doping concentration of the contact portion is less than the oxygen doping concentration of at least a portion of the non-contact portion, for example, the oxygen doping concentration of the third passivation layer 123 is less than the oxygen doping concentration of the second passivation layer 122, but the oxygen doping concentration of the first passivation layer 121 can be less than or equal to the oxygen doping concentration of the third passivation layer 123.

[0061] It should be noted that the distribution states of low concentration, high concentration and low concentration here refer to: the approximate change trend of the oxygen doping concentration in the three passivation layers. For example, the oxygen doping concentration of the first passivation layer 121 and the oxygen doping concentration of the third passivation layer 123 may be less than the oxygen doping concentration of the second passivation layer 122, or the oxygen doping concentration of the first passivation layer 121 and the oxygen doping concentration of the second passivation layer 122 may overlap, and / or the oxygen doping concentration of the third passivation layer 123 and the oxygen doping concentration of the second passivation layer 122 may overlap, but the overall change is low concentration, high concentration and low concentration.

[0062] In a specific implementation process, a three-layer passivation layer structure is adopted, the oxygen doping concentration of the first passivation layer 121 is low, and the oxygen doping concentration of the second passivation layer 122 is high. In this way, by setting the oxygen doping concentration gradient, the HJT battery has a higher CTM value and can make the optical band gap larger. Among them, the CTM value represents the ratio of the output power of the component to the total power of the battery cell. However, the increase in the optical band gap will cause the conduction band of the entire passivation layer to bend upward, while the valence band bends downward. At this time, the upward-bending conduction band will be more conducive to blocking the transmission of electrons, while the transmission of holes will be less affected; the downward-bending valence band will form a new potential barrier, which is not conducive to the transmission and collection of holes. Therefore, a third passivation layer 123 with a lower oxygen doping concentration is used to contact the back-doped amorphous silicon layer 13, so that the degree of downward bending of the entire valence band is reduced, so that when in contact with P-type doped silicon, the change of the valence band can be more slowly transitioned, which is conducive to the transmission and collection of holes, thereby improving the fill factor of the battery.

[0063] In a specific implementation process, when the oxygen doping concentration of the first passivation layer 121 and the oxygen doping concentration of the third passivation layer 123 are both less than the oxygen doping concentration of the second passivation layer 122, the following two situations may be included:

[0064] The first type: the oxygen doping concentration of the first passivation layer 121, the oxygen doping concentration of the second passivation layer 122, and the oxygen doping concentration of the third passivation layer 123 are fixed values. In this case, the oxygen doping concentration of the first passivation layer 121 and the oxygen doping concentration of the third passivation layer 123 are both less than the oxygen doping concentration of the second passivation layer 122, so that the oxygen doping concentration of the back passivation layer 12 is configured to be distributed in low concentration, high concentration, and low concentration.

[0065] The second type: at least one of the oxygen doping concentration of the first passivation layer 121, the oxygen doping concentration of the second passivation layer 122, and the oxygen doping concentration of the third passivation layer 123 is a gradient value. This case can be divided into the following cases:

[0066] a. The oxygen doping concentration of the first passivation layer 121 gradually increases, and the oxygen doping concentration of the first passivation layer 121 on the side close to the second passivation layer 122 is less than the oxygen doping concentration of the second passivation layer 122. In other words, the oxygen doping concentration of the first passivation layer 121 gradually increases, but its maximum value is less than the oxygen doping concentration of the second passivation layer 122. For example, the oxygen doping concentration of the first passivation layer 121 increases from a1 to b1, and the oxygen doping concentration of the second passivation layer 122 is a2, then b1 is less than a2.

[0067] b. The oxygen doping concentration of the third passivation layer 123 gradually decreases, and the oxygen doping concentration of the side of the third passivation layer 123 close to the second passivation layer 122 is less than the oxygen doping concentration of the second passivation layer 122. In other words, the maximum value of the oxygen doping concentration of the third passivation layer 123 is less than the oxygen doping concentration of the second passivation layer 122. For example, the oxygen doping concentration of the third passivation layer 123 decreases from b3 to a3, and the oxygen doping concentration of the second passivation layer 122 is a2, then b3<a2.

[0068] c. The oxygen doping concentration of the first passivation layer 121 gradually increases, the oxygen doping concentration of the second passivation layer 122 gradually increases, and the oxygen doping concentration of the third passivation layer 123 gradually decreases; the oxygen doping concentration of the first passivation layer 121 close to the second passivation layer 122 is less than the oxygen doping concentration of the second passivation layer 122 close to the first passivation layer 121; the oxygen doping concentration of the third passivation layer 123 close to the second passivation layer 122 is less than the oxygen doping concentration of the second passivation layer 122 close to the third passivation layer 123. In other words, the maximum value of the oxygen doping concentration of the first passivation layer 121 and the maximum value of the oxygen doping concentration of the third passivation layer 123 are both less than the minimum value of the oxygen doping concentration of the second passivation layer 122. For example, the oxygen doping concentration of the first passivation layer 121 increases from a1 to b1, the oxygen doping concentration of the second passivation layer 122 increases from a2 to b2, and the oxygen doping concentration of the third passivation layer 123 decreases from b3 to a3, then b1<a2, b2<a2.

[0069] In a specific implementation process, when only some values ​​of the oxygen-doping concentration of the first passivation layer 121 and the oxygen-doping concentration of the third passivation layer 123 are less than the oxygen-doping concentration of the second passivation layer 122, that is, the oxygen-doping concentration of the first passivation layer 121 can overlap with the oxygen-doping concentration of the second passivation layer 122, and the oxygen-doping concentration of the third passivation layer 123 can overlap with the oxygen-doping concentration of the second passivation layer 122, the concentrations of the first passivation layer 121 to the third passivation layer 123 are set according to the following principles:

[0070] The oxygen-doping concentration of the first passivation layer 121 gradually increases, the oxygen-doping concentration of the second passivation layer 122 gradually increases, and the oxygen-doping concentration of the third passivation layer 123 gradually decreases; wherein, the oxygen-doping concentration of the first passivation layer 121 close to the second passivation layer 122 is greater than or equal to the oxygen-doping concentration of the second passivation layer 122 close to the first passivation layer 121, and the oxygen-doping concentration of the second passivation layer 122 away from the first passivation layer 121 is greater than the oxygen-doping concentration of the first passivation layer 121 close to the second passivation layer 122; the oxygen-doping concentration of the third passivation layer 123 close to the second passivation layer 122 is less than or equal to the oxygen-doping concentration of the second passivation layer 122 away from the first passivation layer 121, and the oxygen-doping concentration of the second passivation layer 122 close to the first passivation layer 121 is greater than the oxygen-doping concentration of the third passivation layer 123 away from the second passivation layer 122. That is to say, there is an intersection between the oxygen doping concentration of the first passivation layer 121 and the oxygen doping concentration of the second passivation layer 122. There is an intersection between the oxygen doping concentration of the third passivation layer 123 and the oxygen doping concentration of the second passivation layer 122. For example, the oxygen doping concentration of the first passivation layer 121 increases from a1 to b1, the oxygen doping concentration of the second passivation layer 122 increases from a2 to b2, and the oxygen doping concentration of the third passivation layer 123 decreases from b3 to a3, then a1<a2<b1<b2, a2<b3<b2, a3<a2.

[0071] Those skilled in the art can understand that, on the side of the back doped amorphous silicon layer 13 facing away from the substrate 11, a back transparent conductive layer 14 and a back electrode 15 are sequentially arranged. On the light incident surface of the substrate 11, a front passivation layer 16, a front doped layer 17, a front transparent conductive layer 18 and a front electrode 19 are sequentially arranged from the inside to the outside. These film layers can refer to the records of the existing related technologies and will not be repeated here.

[0072] The HJT battery of this embodiment is provided with a back passivation layer 12 of an oxide-doped material on the backlight surface of the substrate 11, and the back passivation layer 12 is configured to be at least distributed in a high concentration and a low concentration in a direction perpendicular to the substrate 11 and from the inside to the outside, so that the optical band gap of the back passivation layer 12 is larger, and the valence band shift can be avoided, the absorption of light can be reduced, the short-circuit current density can be increased, and the passivation effect can be further improved. At the same time, the influence on the transmission and collection of holes can be reduced, so that the performance of the HJT battery is better.

[0073] Furthermore, the present invention also provides a method for preparing a HJT battery.

[0074] Figure 2 is a schematic diagram of a process for preparing a HJT battery according to an embodiment of the present invention; Figure 2As shown, the preparation method of the HJT battery of this embodiment mainly includes the following steps:

[0075] Step 201, forming a back passivation layer 12 on the backlight surface of the substrate;

[0076] In a specific implementation process, the back passivation layer 12 includes an oxygen-doped material, and the back passivation layer 12 has a contact portion and a non-contact portion with the back doped amorphous silicon layer 13, and the oxygen doping concentration of the contact portion is lower than the oxygen doping concentration of at least part of the non-contact portion.

[0077] Specifically, an oxygen-doped gas source can be introduced to deposit the first passivation layer 121, the second passivation layer 122 and the third passivation layer 123 in sequence on the backlight surface of the substrate; wherein the first passivation layer 121 and the second passivation layer 122 constitute the non-contact portion, the third passivation layer 123 constitutes the contact portion, and the oxygen-doping concentration of the first passivation layer 121 and the oxygen-doping concentration of the third passivation layer 123 are both less than the oxygen-doping concentration of the second passivation layer 122.

[0078] In a specific implementation process, when depositing the first passivation layer 121, the ratio of the oxygen-doped gas source can be adjusted to form the first passivation layer 121 with a gradually increasing oxygen-doping concentration, wherein the oxygen-doping concentration of a side of the first passivation layer 121 close to the second passivation layer 122 is less than the oxygen-doping concentration of the second passivation layer 122.

[0079] In a specific implementation process, when depositing the third passivation layer 123, the ratio of the oxygen-doped gas source can be adjusted to form the third passivation layer 123 with a gradually decreasing oxygen-doping concentration, wherein the oxygen-doping concentration of a side of the third passivation layer 123 close to the second passivation layer 122 is less than the oxygen-doping concentration of the second passivation layer 122.

[0080] In a specific implementation process, when depositing the first passivation layer 121, the second passivation layer 122 and the third passivation layer 123, by adjusting the ratio of the oxygen-doped gas source, the first passivation layer 121 with gradually increasing oxygen doping concentration, the second passivation layer 122 with gradually increasing concentration, and the third passivation layer 123 with gradually decreasing concentration are formed; wherein the oxygen doping concentration of the first passivation layer 121 close to the second passivation layer 122 is less than the oxygen doping concentration of the second passivation layer 122 close to the first passivation layer 121; the oxygen doping concentration of the third passivation layer 123 close to the second passivation layer 122 is less than the oxygen doping concentration of the second passivation layer 122 close to the third passivation layer 123.

[0081] Step 202: forming a back-doped amorphous silicon layer 13 on a side of the back passivation layer 12 away from the substrate.

[0082] The preparation method of the HJT battery in the above-mentioned embodiment and the embodiment of the HJT battery in the above-mentioned embodiment are similar in technical principles, technical problems solved and technical effects produced. Those skilled in the art can clearly understand that for the convenience and conciseness of description, the specific working process and related instructions of the work order generation device can refer to the contents described in the embodiment of the work order generation method, and will not be repeated here.

[0083] The following is an example of a specific process for preparing HJT batteries:

[0084] Figure 3 This is a schematic diagram of a process flow for preparing HJT batteries. Figure 3 As shown, the process flow of preparing the HJT battery may specifically include the following steps 301 to 308:

[0085] Step 301, providing an N-type single crystal silicon substrate 11, cleaning it, double-sided texturing it, and drying it;

[0086] First, before preparing the above-mentioned films, the substrate needs to be cleaned and a pyramid velvet surface needs to be prepared on the front and back sides by etching, in order to reduce the reflection on the substrate surface.

[0087] Step 302, depositing a front passivation layer 16 on the light incident surface of the substrate 11;

[0088] The front passivation layer 16 can be deposited on the incident surface of the substrate, and its film thickness is about 5-15nm. It can be prepared by PECVD, HWCVD and other processes. Common passivation layer materials are ia-Si:H, ia-SiOx:H, and the process gases required are hydrogen, silane and carbon dioxide. The preparation conditions include: in the reaction gas of SiH4 and CO2 with a molar volume ratio of 80:3, the pressure is 1mbar, and the front passivation layer 16 is prepared with a thickness of about 8nm.

[0089] Step 303, depositing a back passivation layer 12 having a "sandwich" structure on the backlight surface of the substrate 11;

[0090] The back passivation layer 12 that can be deposited on the backlight side of the substrate can be prepared using processes such as PECVD and HWCVD. Commonly used passivation layer materials are ia-Si:H and ia-SiOx:H, and the process gases required are hydrogen, silane and carbon dioxide.

[0091] Among them, it is necessary to deposit in three steps. First, a layer of low-oxygen doped hydrogenated amorphous silicon oxide film is deposited. During the deposition, the gas flow ratio of carbon dioxide gas to silane is 0-20%, and the thickness is about 1-5nm; then a high-oxygen doped hydrogenated amorphous silicon oxide layer is deposited. At this time, it is necessary to control the flow ratio of carbon dioxide and silane to be between 30-70% to form a high-oxygen doped amorphous silicon oxide layer with a thickness of about 1-5nm; finally, low-oxygen doped hydrogenated oxide amorphous silicon is deposited. At this time, the flow ratio of carbon dioxide and silane is controlled to be between 10-30%, and the thickness is about 1-5nm. Thus, a special back passivation layer 12 with a low-high-low sandwich structure is formed.

[0092] Step 304, depositing a front doping layer 17 on the light incident surface of the substrate 11;

[0093] A front doping layer 17 is deposited on the surface of the front passivation layer 16. The front doping layer 17 may be an N-type doping layer. Specific conditions include: in a reaction gas of H2, SiH4, CO2 and CO2 with a molar volume ratio of 400:1:0.6:0.3, the pressure is 3 mbar, and an N-type contact layer is prepared as the front doping layer 17.

[0094] Step 305 , depositing a back doping layer 13 on the light incident surface of the substrate 11 ;

[0095] A back doping layer, which may be a P-type doping layer, is deposited on the surface of the back passivation layer 12. Specific conditions include: in a reaction gas of H2, SiH4 and B2H6 with a molar volume ratio of 400:1:0.3, the pressure is 3 mbar, and a P-type contact layer is prepared as the back doping layer.

[0096] Step 306, depositing a front transparent conductive layer 18 and a back transparent conductive layer 14 on the doped layers on both sides of the substrate 11 respectively;

[0097] The specific conditions include: preparing a P-type contact layer in a reaction gas of H2, SiH4 and B2H6 with a molar volume ratio of 400:1:0.3 and a pressure of 3 mbar;

[0098] Step 307 : depositing the front electrode 19 and the back electrode 15 on the transparent conductive layers on both sides.

[0099] In a specific implementation process, when the back passivation layer 12 having a "sandwich" structure is deposited on the backlight side of the substrate in step 303, the three passivation layers can also be prepared into passivation layers with a gradient oxygen-doped concentration according to the following three preparation conditions:

[0100] The first condition for preparing the back passivation layer 12 includes: in the reaction gas of SiH4 and CO2 with a molar volume ratio of 20:1, the pressure is 1 mbar, and the first passivation layer 121 with a thickness of about 4 nm is prepared on the back; during the deposition process, the molar volume ratio of SH4 and CO2 gas is gradually increased to 20:3, so that a gradually increasing oxygen concentration can be formed inside the first passivation layer 121; in the reaction gas of SiH4 and CO2 with a molar volume ratio of 20:6, the pressure is 1 mbar, and the first passivation layer 121 with a thickness of about 4 nm is prepared on the back. The second passivation layer 122 has a thickness of about 3 nm. During the deposition process, the molar volume ratio of SH4 and CO2 gases gradually increases to 20:8. In the reaction gas of H2, SiH4 and CO2 with a molar volume ratio of 200:20:4, the pressure is 1 mbar, and the third passivation layer 123 on the back side is prepared with a thickness of about 3 nm. During the deposition process, the molar volume ratio of H2, SH4 and CO2 gases gradually decreases to 200:20:2, so that a gradually decreasing oxygen doping concentration can be formed in the third passivation layer 123.

[0101] In a specific implementation process, the back passivation layer 12 can also be prepared according to condition 2. The main difference between condition 2 and condition 1 is that when depositing the third passivation layer 123, oxygen is not doped, and the molar volume ratio of H2 and SH4 gas is 200:20 during the deposition process to prepare the third passivation layer 123. In this way, the valence band offset can still be reduced.

[0102] In a specific implementation process, the back passivation layer 12 can also be prepared according to condition three. The main difference between condition three and condition one is that when depositing the first passivation layer 121, the initial oxygen doping concentration of the first passivation layer 121 can also be increased. In the reaction gas of SiH4 and CO2 with a molar volume ratio of 20:3, the pressure is 1 mbar, and the back first passivation layer 121 with a thickness of about 4 nm is prepared; during the deposition process, the molar volume ratio of SH4 to CO2 gas gradually increases to 20:5, so that the band gap of the entire passivation layer can be made larger.

[0103] The performance comparison of the HJT battery whose back passivation layer 12 is prepared as described above and whose back passivation layer 12 is not made of the base-doped material is shown in Table 1.

[0104] Table 1

[0105]

[0106]

[0107] It can be seen from Table 1 that the HJT battery with the above-mentioned "sandwich" structure passivation layer has higher open circuit voltage, short circuit current and conversion efficiency than the conventional undoped HJT battery. In other words, the HJT battery with the above-mentioned "sandwich" structure passivation layer has better performance.

[0108] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A heterojunction battery, characterized in that: include: substrate; A doped amorphous silicon layer located on the back side of the backlight surface of the substrate; a back passivation layer located between the back doped amorphous silicon layer and the substrate, Wherein, the back passivation layer comprises an oxygen-doped material, and the back passivation layer has a contact portion and a non-contact portion with the back doped amorphous silicon layer; The non-contact portion includes a first passivation layer and a second passivation layer, and the contact portion is a third passivation layer; the oxygen doping concentration of the first passivation layer gradually increases from the substrate to the doped amorphous silicon layer, the oxygen doping concentration of the second passivation layer gradually increases from the substrate to the doped amorphous silicon layer, and the oxygen doping concentration of the third passivation layer gradually decreases from the substrate to the doped amorphous silicon layer; Among them, the oxygen-doping concentration of the first passivation layer and the oxygen-doping concentration of the third passivation layer are both lower than the oxygen-doping concentration of the second passivation layer, or the oxygen-doping concentration of the first passivation layer and the oxygen-doping concentration of the second passivation layer have overlapping concentrations, and the oxygen-doping concentration of the third passivation layer and the oxygen-doping concentration of the second passivation layer have overlapping concentrations, so that the oxygen-doping concentrations of the first passivation layer, the second passivation layer and the third passivation layer change to low concentration, high concentration and low concentration as a whole.

2. The heterojunction battery according to claim 1, characterized in that: The oxygen doping concentration of a surface of the first passivation layer close to the second passivation layer is lower than the oxygen doping concentration of a surface of the second passivation layer close to the first passivation layer; The oxygen doping concentration of a surface of the third passivation layer close to the second passivation layer is lower than the oxygen doping concentration of a surface of the second passivation layer close to the third passivation layer.

3. The heterojunction battery according to claim 1, characterized in that: The oxygen doping concentration of the first passivation layer on a side close to the second passivation layer is greater than or equal to the oxygen doping concentration of the second passivation layer on a side close to the first passivation layer, and the oxygen doping concentration of the second passivation layer on a side away from the first passivation layer is greater than the oxygen doping concentration of the first passivation layer on a side close to the second passivation layer; The oxygen-doping concentration of the third passivation layer on a side close to the second passivation layer is less than or equal to the oxygen-doping concentration of the second passivation layer on a side away from the first passivation layer, and the oxygen-doping concentration of the second passivation layer on a side close to the first passivation layer is greater than the oxygen-doping concentration of the third passivation layer on a side away from the second passivation layer.

4. A method for preparing a heterojunction battery, characterized in that: include: forming a back passivation layer and a back doped amorphous silicon layer in sequence on the backlight side of the substrate; The back passivation layer includes an oxygen-doped material, and the back passivation layer has a contact portion and a non-contact portion with the back doped amorphous silicon layer, the non-contact portion includes a first passivation layer and a second passivation layer, and the contact portion is a third passivation layer; the oxygen-doping concentration of the first passivation layer gradually increases from the substrate to the doped amorphous silicon layer, the oxygen-doping concentration of the second passivation layer gradually increases from the substrate to the doped amorphous silicon layer, and the oxygen-doping concentration of the third passivation layer gradually decreases from the substrate to the doped amorphous silicon layer; Among them, the oxygen-doping concentration of the first passivation layer and the oxygen-doping concentration of the third passivation layer are both lower than the oxygen-doping concentration of the second passivation layer, or the oxygen-doping concentration of the first passivation layer and the oxygen-doping concentration of the second passivation layer have overlapping concentrations, and the oxygen-doping concentration of the third passivation layer and the oxygen-doping concentration of the second passivation layer have overlapping concentrations, so that the oxygen-doping concentrations of the first passivation layer, the second passivation layer and the third passivation layer change to low concentration, high concentration and low concentration as a whole.

5. The method for preparing a heterojunction battery according to claim 4, characterized in that: The process of forming the back passivation layer includes: By adjusting the ratio of the oxygen-doped gas source, the first passivation layer with gradually increasing oxygen doping concentration, the second passivation layer with gradually increasing concentration, and the third passivation layer with gradually decreasing concentration and gradually decreasing oxygen doping concentration are formed; Wherein, the oxygen doping concentration of a surface of the first passivation layer close to the second passivation layer is less than the oxygen doping concentration of a surface of the second passivation layer close to the first passivation layer; The oxygen doping concentration of a surface of the third passivation layer close to the second passivation layer is lower than the oxygen doping concentration of a surface of the second passivation layer close to the third passivation layer.

6. The method for preparing a heterojunction battery according to claim 4, characterized in that: The formation process of the back passivation layer, By adjusting the ratio of the oxygen-doped gas source, the first passivation layer with gradually increasing concentration, the second passivation layer with gradually increasing concentration, and the third passivation layer with gradually decreasing concentration and gradually decreasing oxygen doping concentration are formed; The oxygen-doping concentration of the first passivation layer on the side close to the second passivation layer is greater than or equal to the oxygen-doping concentration of the second passivation layer on the side close to the first passivation layer, and the oxygen-doping concentration of the second passivation layer on the side away from the first passivation layer is greater than the oxygen-doping concentration of the first passivation layer on the side close to the second passivation layer; The oxygen-doping concentration of the third passivation layer on a side close to the second passivation layer is less than or equal to the oxygen-doping concentration of the second passivation layer on a side away from the first passivation layer, and the oxygen-doping concentration of the second passivation layer on a side close to the first passivation layer is greater than the oxygen-doping concentration of the third passivation layer on a side away from the second passivation layer.

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