Electronic passivation contact structure, preparation method and solar cell

Abstract

The present invention relates to the field of semiconductor manufacturing, and more specifically, to an electronically passivated contact structure, a preparation method, and a solar cell. The electronically passivated contact structure comprises a silicon substrate, a tunneling layer, and a titanium dioxide layer stacked in sequence. The titanium dioxide layer comprises a first titanium dioxide sublayer and a second titanium dioxide sublayer disposed along the thickness direction. The titanium dioxide layer is continuously deposited by an atomic layer deposition process to form the first and second titanium dioxide sublayers, wherein the first titanium dioxide sublayer has an amorphous structure and the second titanium dioxide sublayer has a crystalline structure.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing, and in particular to an electronic passivation contact structure, a preparation method and a solar cell. Background Art

[0002] As the core device for converting solar energy into electrical energy, the performance optimization and improvement of solar cells is an important research direction in the global photovoltaic industry and scientific research field. In high-efficiency crystalline silicon solar cells, the design of electronic passivation contact structure is crucial for improving the open circuit voltage (V OC ), fill factor (FF) and photoelectric conversion efficiency (η) are crucial.

[0003] In existing technologies, passivation contact structures typically consist of multiple thin films, including a passivation layer, a carrier selection layer, and a transparent conductive oxide (TCO). The synergistic effect of these films effectively prevents recombination losses at the metal-silicon interface, thereby improving device efficiency. However, due to the optical absorption characteristics of the TCO and the design limitations of the composite film, parasitic absorption is difficult to avoid, limiting further improvements in photoelectric conversion efficiency.

[0004] To solve the above problems, titanium dioxide is widely used in electron transport layers due to its high dielectric constant, low resistivity, and good match with the silicon conduction band position. The low work function of titanium dioxide facilitates the extraction and transmission of electrons, while its chemical stability also provides advantages for the long-term maintenance of device performance. However, the passivation effect and conductivity of existing titanium dioxide films are limited, and only a maximum conversion efficiency of 22.1% is achieved in specific applications, and the open circuit voltage (V OC ) is only 674mV, which is much lower than the theoretical value. Summary of the Invention

[0005] The object of the present invention is to provide an electronic passivation contact structure that can simultaneously enhance the passivation effect and improve the electron transmission performance.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solutions: an electronically passivated contact structure, comprising a silicon substrate, a tunneling layer and a titanium dioxide layer stacked in sequence, the titanium dioxide layer comprising a first titanium dioxide sublayer and a second titanium dioxide sublayer arranged along the thickness direction; the titanium dioxide layer is continuously deposited by an atomic layer deposition process to form a first titanium dioxide sublayer and a second titanium dioxide sublayer, wherein the first titanium dioxide sublayer is an amorphous structure and the second titanium dioxide sublayer is a crystalline structure.

[0007] Furthermore, the first titanium dioxide sublayer is an amorphous titanium dioxide layer formed by doping a precursor with magnesium and / or aluminum, and the doping concentration of magnesium and / or aluminum is 1 wt%-10 wt%;

[0008] The second titanium dioxide sub-layer is a crystalline titanium dioxide layer formed by doping a precursor with zinc and / or gallium, wherein the doping concentration of zinc and / or gallium is 5 wt % to 20 wt %.

[0009] Furthermore, the mass ratio of magnesium and aluminum doped by the precursor in the first titanium dioxide sublayer ranges from 80:20 to 20:80;

[0010] The mass ratio of zinc to gallium doped in the second titanium dioxide sub-layer by a precursor ranges from 70:30 to 30:70.

[0011] Furthermore, the thickness of the first titanium dioxide sublayer is 1 nm-5 nm, and the thickness of the second titanium dioxide sublayer is 5 nm-50 nm.

[0012] Furthermore, the first titanium dioxide sublayer is formed by a single cycle mode in an atomic layer deposition process, wherein the cycle ratio of the main deposition cycle to the doping cycle is (20-100):1;

[0013] The second titanium dioxide sublayer is formed by a super-cyclic mode in an atomic layer deposition process, wherein the cycle ratio of the main deposition cycle to the doping cycle is (10-50):1.

[0014] Furthermore, the electronic passivation contact structure further includes a hydrogen-containing capping layer stacked on the titanium dioxide layer.

[0015] The present application also provides a method for preparing an electronically passivated contact structure, comprising:

[0016] providing a silicon substrate;

[0017] forming a tunneling layer on the silicon substrate;

[0018] A first titanium dioxide sublayer and a second titanium dioxide sublayer are continuously deposited by an atomic layer deposition process to ultimately form an overall titanium dioxide layer; wherein: the first titanium dioxide sublayer is doped with a magnesium and / or aluminum precursor in a single-cycle mode, with the doping concentration controlled to be 1wt%-10wt% to form an amorphous structure; and the second titanium dioxide sublayer is doped with a zinc and / or gallium precursor in a super-cycle mode, with the doping concentration controlled to be 5wt%-20wt% to form a crystalline structure;

[0019] A hydrogen-containing capping layer is deposited on the titanium dioxide layer.

[0020] Furthermore, the method for preparing the electronic passivation contact structure further includes removing the hydrogen-containing capping layer.

[0021] The present application also provides a solar cell, comprising the above-mentioned electron passivation contact structure, wherein the electron passivation contact structure is located on the light-receiving surface and / or the backlight surface of the solar cell.

[0022] The beneficial effects of the present invention are as follows: the electronic passivation contact structure of the present application utilizes the titanium dioxide layer to simultaneously achieve enhanced passivation effect and improved electron transmission performance. Specifically, by dividing the titanium dioxide layer into two layers along the thickness direction, wherein the first titanium dioxide sublayer is an amorphous structure, which can effectively reduce interface defect states and significantly reduce the interface recombination rate, thereby providing excellent interface passivation performance; the second titanium dioxide sublayer is a crystalline structure, which can increase the electron concentration and reduce the film work function, significantly improve the electron transmission performance and mobility, and it has higher conductivity, further optimizes the electron selective transmission function, and enhances the efficiency of the overall device. Compared with existing transparent conductive oxides (TCOs), the electronic passivation contact structure of the present application has lower parasitic absorption characteristics in the light absorption band, thereby improving the short-circuit current density (J SC ) and ultimately improve the photoelectric conversion efficiency.

[0023] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 shows a schematic structural diagram of an electronic passivation contact structure according to one embodiment of the present application;

[0025] Figure 2-1 to Figure 2-3 A comparison of carrier lifetime, electron mobility and work function of titanium dioxide layer under different doping conditions is shown;

[0026] Figure 3 A schematic flow chart showing a method for preparing an electronically passivated contact structure according to an embodiment of the present invention is shown;

[0027] Figure 4 shows a schematic structural diagram of a solar cell shown in an embodiment of the present application;

[0028] Figure 5 A schematic structural diagram of a solar cell according to another embodiment of the present application is shown. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0030] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0031] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0032] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] Figure 1 FIG. 1 shows a schematic structural diagram of an electronically passivated contact structure according to an embodiment of the present invention. Figure 1 As shown, the electron passivation contact structure includes a silicon substrate 10, a tunneling layer 20, a titanium dioxide layer 30 and a hydrogen-containing capping layer 40 stacked in sequence, wherein the titanium dioxide layer 30 includes a first titanium dioxide sublayer and a second titanium dioxide sublayer arranged along the thickness direction; the titanium dioxide layer 30 is continuously deposited by an atomic layer deposition process to form a first titanium dioxide sublayer and a second titanium dioxide sublayer, wherein the first titanium dioxide sublayer is an amorphous structure for interface passivation; the second titanium dioxide sublayer is a crystalline structure for improving electron concentration, mobility and reducing work function.

[0034] The electronic passivation contact structure of the present application utilizes the titanium dioxide layer 30 to simultaneously achieve enhanced passivation effect and improved electron transmission performance. Specifically, the titanium dioxide layer 30 is divided into two layers along the thickness direction, wherein the first titanium dioxide sublayer 31 is an amorphous structure, which can effectively reduce interface defect states and significantly reduce the interface recombination rate, thereby providing excellent interface passivation performance; the second titanium dioxide sublayer 32 is a crystalline structure, which can increase electron concentration and reduce film work function, significantly improve electron transmission performance and mobility, and has higher conductivity, further optimizes the electron selective transmission function, and enhances the efficiency of the overall device. Compared with existing transparent conductive oxides (TCOs), the electronic passivation contact structure of the present application has lower parasitic absorption characteristics in the light absorption band, thereby improving the short-circuit current density (J SC ) and ultimately improve the photoelectric conversion efficiency.

[0035] It should be noted that existing studies have shown that titanium dioxide can achieve interface passivation and selective electron transport performance. The inventors took advantage of this property of titanium dioxide and initially attempted to uniformly dope a single component (such as magnesium, aluminum, zinc, gallium, hydrogen, and boron) in the titanium dioxide layer 30, hoping to optimize the interface passivation effect and electron transport performance by adjusting the overall doping concentration. However, as is known in the art, it is difficult to achieve both interface passivation and electron transport performance. Low doping concentrations are conducive to interface passivation, but the electron concentration and mobility are insufficient, and the open circuit voltage (V OC ) and fill factor (FF). While high doping concentrations can improve electron transport performance, they also increase interface defects and the interface recombination rate, leading to an overall decrease in device efficiency. Furthermore, when the thickness of the doped layer exceeds a certain value, the accumulation of interface defects and the reduction in material conductivity lead to a significant decrease in transmission efficiency.

[0036] In order to break through the limitations of single doping, the inventors further attempted to use a single-layer titanium dioxide layer with gradient doping or composite doping. In the gradient doping scheme, the inventors achieved a balance between interface passivation and electron transport performance by gradually changing the doping concentration in the titanium dioxide layer (such as from low doping to high doping). However, the preparation process window of gradient doping is narrow, the doping concentration distribution is difficult to control uniformly, and the experiment showed poor reproducibility. In the combined doping scheme, by simultaneously doping multiple elements (such as magnesium, aluminum, zinc, gallium, hydrogen, and boron) into the titanium dioxide layer, it is hoped that the overall performance will be optimized through the synergistic effect between the doping components. However, multiple doping components are prone to diffusion during high-temperature deposition or annealing, resulting in uneven doping distribution, increased interface state density, and reduced device performance.

[0037] Due to the above problems, the inventors gave up the idea of continuing to rely on the doping optimization or gradient adjustment of single-layer materials. However, through the above experiments and comparison of the experimental results, it was found that the low-doped amorphous structure can provide excellent interface passivation effect, reduce the interface defect density and carrier recombination rate, and the highly doped crystalline structure can increase the electron concentration and mobility, reduce the work function and enhance the electron selective transmission performance. On this basis, the inventors changed their ideas and first tried to deposit the first titanium dioxide layer and the second titanium dioxide layer in sequence. However, this structure has the following problems: Since the first titanium dioxide layer and the second titanium dioxide layer are two independent structures, there are many interface defects and there is a large stress at the interface, resulting in poor interface stability; and due to the stress and interface defects, the electron transmission performance is poor.

[0038] On this basis, attempts were made to divide the titanium dioxide layer into two layers, and to dope different elements into the two titanium dioxide layers to form an amorphous structure in the lower layer and a crystalline structure in the upper layer. At the same time, by trying various processes and data analysis, it was finally confirmed that the use of atomic layer deposition process to continuously deposit the first titanium dioxide sublayer 31 and the second titanium dioxide sublayer 32 can avoid the problem of inconsistent performance caused by edge effects, thereby obtaining an electronic passivation contact structure that can simultaneously achieve enhanced passivation effect and improved electron transmission performance.

[0039] In this solution, the atomic layer deposition process may create a transition zone, which can cause uneven performance or interface issues. To enhance the independence of the passivation effect and electron transport performance, this solution forms a clear interface between the first titanium dioxide sublayer 31 and the second titanium dioxide sublayer 32, without a transition zone. To achieve this goal, during the preparation process, a purge gas (such as nitrogen and / or hydrogen) is introduced when switching precursors to remove precursor residues on the surface of the first sublayer. Of course, the absence of a transition zone may lead to lattice mismatch issues.

[0040] In order to ensure the stability of the layer structure and functional optimization while reducing the lattice mismatch problem, in one embodiment, the first titanium dioxide sublayer 31 is an amorphous titanium dioxide layer 30 formed by doping magnesium and / or aluminum by a precursor, and the doping concentration of magnesium and / or aluminum is 1wt%-10wt%, for example, 1wt%, 5wt% or 10wt%; the second titanium dioxide sublayer 32 is a crystalline titanium dioxide layer 30 formed by doping zinc and / or gallium by a precursor, wherein the doping concentration of zinc and / or gallium is 5wt%-20wt%, for example: 5wt%, 10wt%, 13wt%, 15wt% or 20wt%.

[0041] It should be noted that in this application, the first titanium dioxide sublayer 31 and the second titanium dioxide sublayer 32 are formed by doping with a precursor to form the amorphous titanium dioxide layer 30 and the crystalline titanium dioxide layer 30, respectively. However, the inventors have also attempted to use ion doping solutions (for example, doping with magnesium ions, aluminum ions, zinc ions, and gallium ions). Although similar interface passivation effects can be achieved by adjusting the doping amount and changing the manufacturing process, when using ion doping, the doping amount is generally high, and the doping concentration needs to be increased accordingly to ensure an effect similar to that of precursor doping. In actual operation, the doping amount is difficult to accurately control, and problems such as uneven doping and greater control difficulty may occur.

[0042] The present application adopts a precursor doping solution. Compared with the ion doping solution, the precursor can usually achieve better doping effects at low doping concentrations and has better uniformity. In addition, by adopting atomic layer deposition (ALD), the doping concentration can be precisely controlled, and the operation difficulty is relatively low. In the precursor doping solution, annealing can remove possible doping source residues and ensure the quality and doping effect of the titanium dioxide layer 30, thereby optimizing the electronic structure and interface properties of the film. Unlike the ion doping solution, the deposition of the precursor is usually carried out at a lower temperature (such as 100-200°C), which is conducive to the formation of a thin and uniform titanium dioxide layer 30 on the surface of the silicon substrate without causing excessive thermal impact on the silicon substrate 10.

[0043] In an electronically passivated contact structure, an appropriate thickness helps balance the interface passivation effect and electron transport performance. The thickness of the first titanium dioxide sublayer 31 must be thin enough to maintain good interface passivation while avoiding the obstruction of the electron tunneling effect caused by excessive thickness. The thickness of the second titanium dioxide sublayer 32 needs to ensure that the interface resistance is not increased too much while improving the electron concentration and mobility. However, if the first titanium dioxide sublayer 31 is too thin, the passivation will be incomplete and the interface defect states will increase; if the second titanium dioxide sublayer 32 is too thick, the work function control will fail and the electron injection efficiency will decrease. In order to obtain the appropriate thickness, the inventors finally obtained the preferred solution through a large number of experimental adjustments: the thickness of the first titanium dioxide sublayer 31 is 1nm-5nm, for example, the thickness can be 1nm, 3nm, 4nm or 5nm, and the thickness of the second titanium dioxide sublayer 32 is 5nm-50nm, for example, the thickness can be 5nm, 10nm, 25nm, 40nm or 50nm. It should be noted that the above thickness setting can also further reduce the lattice mismatch.

[0044] As mentioned above, in the first titanium dioxide sublayer 31, the doping element can be either single magnesium or aluminum, or a combination of magnesium and aluminum; correspondingly, in the second titanium dioxide sublayer 32, the doping element can be either single zinc or gallium, or a combination of zinc and gallium.

[0045] Figure 2-1 、 Figure 2-2 、 Figure 2-3 A comparison diagram of the carrier lifetime, electron mobility and work function of the titanium dioxide layer 30 in the present application under different doping conditions is shown. In the above embodiment, the magnesium and / or aluminum doping concentration in the first titanium dioxide sublayer 31 is: 5wt%, and the mass ratio is 50:50; the zinc and / or gallium doping concentration in the second titanium dioxide sublayer 32 is: 10wt%, and the mass ratio is 70:30. Figure 2-1 This is a comparison chart of carrier lifetimes obtained through μ-PCD testing. It can be seen from the figure that the passivation effect of Mg+Al combined doping is better than that of single element doping; Figure 2-2 This is a comparison chart of electron mobility obtained through Hall effect testing. It can be seen from the figure that the conductive performance of Mg+Al combined doping is better than that of single element doping; Figure 2-3 This is a comparison diagram of the work function obtained through UPS testing. It can be seen from the figure that the work function of Mg+Al combination doping is lower than that of single element doping.

[0046] Based on experimental results, the present application ultimately selected a combination of magnesium and aluminum for doping the first titanium dioxide sublayer 31, and a combination of zinc and gallium for doping the second titanium dioxide sublayer 32. In one embodiment, the mass ratio of magnesium to aluminum introduced by the precursor for the first titanium dioxide sublayer 31 is preferably set in the range of 80:20 to 20:80, for example, 80:20, 50:50, or 20:80; and the mass ratio of zinc to gallium introduced by the precursor for the second titanium dioxide sublayer 32 is preferably set in the range of 70:30 to 30:70, for example, 70:30, 50:50, or 30:70.

[0047] In this embodiment, the first titanium dioxide sublayer 31 is formed by a single cycle mode in an atomic layer deposition process, each single cycle includes several main deposition cycles and doping cycles, wherein the cycle ratio of the main deposition cycle to the doping cycle is (20~100):1, for example, the cycle ratio can be 20:1, 30:1, 50:1, 60:1, 80:1 or 100:1; the second titanium dioxide sublayer 32 is formed by a super cycle mode in an atomic layer deposition (ALD) process, each super cycle includes several main deposition cycles and doping cycles, wherein the cycle ratio of the main deposition cycle to the doping cycle is (10-50):1, for example, the cycle ratio can be 10:1, 20:1, 30:1, 35:1, 40:1 or 50:1. The first titanium dioxide sublayer 31 deposited by adopting a single cycle mode has good passivation performance, can effectively reduce the interface defect density, and provide sufficient electrical uniformity. By adjusting the cycle ratio of the main deposition cycle and the doping cycle by the super cycle mode, it is possible to achieve precise control of the zinc and / or gallium doping concentration, avoiding excessive doping or uneven distribution. Among them, the high cycle ratio of the main deposition cycle helps to form a high-quality crystalline titanium dioxide substrate structure, while the doping cycle introduces zinc and / or gallium at an appropriate ratio, improving electron mobility and reducing work function while ensuring the integrity of the crystal structure. By setting the cycle ratio, it is possible to avoid the problem of doping ion aggregation due to too high a doping cycle ratio, introducing additional defects, and reducing interface performance.

[0048] The tunneling layer 20 is used to provide an efficient tunneling channel for electrons while passivating interface defects to reduce carrier recombination. In this embodiment, the tunneling layer 20 is silicon dioxide with a thickness of 0.5nm-2nm. For example, the thickness can be 0.5nm, 1nm, 1.5nm or 2nm. In other embodiments, the tunneling layer 20 can also be aluminum oxide or hafnium dioxide, and the corresponding thickness can be 1nm-3nm or 0.3nm-1.5nm, respectively. By setting the thickness of the tunneling layer 20, the carrier passivation effect and tunneling efficiency can be balanced.

[0049] In this embodiment, the thickness of the hydrogen-containing cap layer 40 is set to be 3 nm-10 nm, for example, the thickness can be 3 nm, 7 nm or 10 nm. In other embodiments, the hydrogen-containing cap layer 40 can also be removed.

[0050] Figure 3 A schematic flow chart of a method for preparing an electronically passivated contact structure according to a first embodiment of the present invention is shown. The steps for preparing the electronically passivated contact structure are as follows:

[0051] Step S10: providing a silicon substrate 10;

[0052] The silicon substrate 10 is cleaned to remove surface contaminants and a natural oxide layer to ensure uniformity of subsequent deposition.

[0053] Step S20: forming a tunneling layer 20 on the silicon substrate 10;

[0054] An atomic layer deposition (ALD) process is used, using silicon tetrachloride as a silicon source precursor and water as an oxidant, to deposit silicon dioxide on a silicon substrate 10 to form a tunneling layer 20. The thickness is controlled to be 0.5 nm to 2 nm, for example, 0.5 nm, 1.5 nm, or 2 nm. In this embodiment, the thickness is 1 nm. The deposition temperature is controlled to be 250° C. to 300° C., for example, 260° C., 275° C., or 300° C. In this embodiment, the deposition temperature is controlled to be 250° C. The specific number of cycles is determined by the deposition rate of the equipment, and is generally 50 to 100 cycles, for example, 50 cycles, 80 cycles, or 100 cycles.

[0055] Step S30: A first titanium dioxide sub-layer 31 and a second titanium dioxide sub-layer 32 are continuously deposited by an atomic layer deposition (ALD) process, and finally a whole titanium dioxide layer 30 is formed.

[0056] Step S31: depositing a first titanium dioxide sublayer 31;

[0057] Atomic layer deposition (ALD) is used with titanium tetrachloride as a titanium source precursor, while magnesium acetylacetonate and trimethylaluminum are introduced as dopant agents to achieve magnesium and aluminum co-doping of the titanium dioxide-based film through a co-deposition process. The doping concentration is controlled within a range of 1wt% to 10wt%, for example, 1wt%, 5wt%, or 10wt%. In this embodiment, the doping concentration is controlled within a range of 5wt%. The mass ratio of magnesium to aluminum is set to 80:20 to 20:80, for example, 80:20, 40:60, 60:40, or 20:80. In this embodiment, the mass ratio is set to 50:50. The deposition temperature is set to 100° C.-200° C., for example, 100° C., 130° C., 170° C., or 200° C. In this embodiment, the deposition temperature is set to 150° C. Within this temperature range, by regulating the number of reaction cycles, a first titanium dioxide sublayer 31 with an amorphous structure is formed, and its thickness is controlled within the range of 1 nm-5 nm, for example, 1 nm, 2 nm, 3 nm, 4 nm, or 5 nm. A single-cycle mode is adopted, and the cycle ratio of the main deposition cycle to the doping cycle is (20-100):1, for example, 10:1, 30:1, 50:1, 70:1, or 100:1.

[0058] Step S32: In the same reaction chamber, atomic layer deposition (ALD) is continued. Based on titanium tetrachloride as a titanium source precursor, dimethyl zinc and trimethyl gallium are introduced as co-doping precursors. Simultaneous doping of zinc and gallium is achieved by alternating pulsed precursors. The doping concentration range is set to 5wt%-20wt%, for example, 5wt%, 13wt%, 15wt%, or 20wt%. In this embodiment, the doping concentration range is set to 10wt%. The mass ratio of zinc to gallium is set to 70:30 to 30:70, for example, 60:40, 50:50, 40:60, or 30:70. In this embodiment, the mass ratio is set to 70:30. The deposition temperature is set to 100°C-200°C, for example, 100°C, 130°C, or 170°C. In this embodiment, the deposition temperature is set to 200°C. Within this temperature range, by regulating the number of reaction cycles, a second titanium dioxide sublayer 32 with a crystalline structure is formed, and its thickness is controlled within the range of 5nm-50nm, for example, 5nm, 15nm, 25nm, 40nm or 50nm. In this embodiment, the thickness is 10nm; using the super cycle mode, the cycle ratio of the main deposition cycle to the doping cycle is (10-50):1, for example, 10:1, 20:1, 40:1 or 50:1. In this embodiment, the cycle ratio is set to 30:1.

[0059] In the above scheme, in order to form a clear interface between the first titanium dioxide sublayer 31 and the second titanium dioxide sublayer 32 and no transition zone is formed between the two, this embodiment also adopts: before step S32, a cleaning gas (such as nitrogen and / or hydrogen) is introduced when switching the precursor to remove the precursor residue on the surface of the first titanium dioxide sublayer 31. Specifically: a mixed gas of 95% nitrogen + 5% hydrogen is used to remove part of the precursor in step S32, and the cleaning time is set to 3-10 seconds, for example, 3 seconds, 6 seconds, 10 seconds. In this embodiment, the cleaning time is set to 5 seconds.

[0060] Step S40: depositing a hydrogen-containing capping layer on the titanium dioxide layer;

[0061] A low-temperature atomic layer deposition (ALD) process is used to react dimethylsilane or triethylborane or a silane hydrogen-containing precursor with water or ozone to form a silicon hydroxide-doped or boron hydroxide-doped silicon film, wherein the deposition temperature is set to 100°C-200°C, for example, 100°C, 130°C, 170°C or 200°C. In this embodiment, the deposition temperature is set to 200°C, and the film thickness is controlled between 3nm and 10nm, for example, 3nm, 4nm, 8nm or 10nm. In this embodiment, the film thickness is controlled to be 5nm.

[0062] Step S50: annealing treatment;

[0063] Low-temperature annealing is performed in an inert atmosphere (nitrogen or argon) to improve interface bonding and doping uniformity. The annealing temperature is 300°C-400°C, for example, 350°C or 400°C. In this embodiment, the temperature is controlled at 300°C, the annealing time is set to 10 minutes, and the gas flow rate is set to 100 sccm.

[0064] The electron-passivating contact structure formed by the above-mentioned preparation method can simultaneously enhance the passivation effect and improve electron transport performance, while effectively alleviating lattice mismatch issues. Furthermore, in this preparation method, by limiting the deposition temperature, doping mass ratio, and deposition pattern, a distinct transition interface is formed, eliminating the need for additional transition layers and reducing manufacturing complexity.

[0065] In another embodiment, the magnesium precursor can also be magnesium dimethylcarbamate. It should be noted that in addition to using the above precursors, the inventors also attempted to use other precursors as substitutes, such as titanium tetraisobutoxide or titanium tetraacetylacetonate, magnesium ethoxy compounds or magnesium methyl compounds, diethylaluminum hydride, zinc chloride, triethylgallium, etc. However, these were ultimately abandoned due to less than ideal results (e.g., low volatility). The above precursors exhibit relatively excellent volatility, reactivity, stability, and byproducts. For example, most byproducts are gaseous (e.g., hydrogen chloride, methane), which reduces contamination of the film and facilitates removal.

[0066] An embodiment of the present invention provides an electronically passivated contact structure. This electronically passivated contact structure can be applied to a solar cell, with the electronically passivated contact structure located on the light-receiving and / or backlight-receiving sides of the solar cell. The following describes the specific structures of two exemplary solar cells in detail.

[0067] Example 1

[0068] Ginseng Figure 4 The figure shows a schematic diagram of an electronic passivation contact structure applied to a BC battery, which includes a silicon substrate 101, an n-type heavily doped layer 102 (i.e., a tunneling layer), a titanium dioxide layer 103, and a silicon nitride anti-reflection layer 104 (hydrogen-containing cap layer) deposited in sequence on the front side of the silicon substrate 101, and a P+ emitter layer 105, an n+ BSF layer 106, a passivation layer 107, and a metal electrode 108 deposited in sequence on the back side of the silicon substrate 101.

[0069] In other embodiments, the electronically passivated contact structure may also be formed after removing the hydrogen-containing capping layer. In this case, the titanium dioxide layer serves as the front passivation layer structure in the current BC solar cell structure.

[0070] Example 2

[0071] Ginseng Figure 5The figure shows a schematic diagram of an electronic passivation contact structure applied to a BC / perovskite stacked cell, which includes a silicon substrate 201, an n-type heavily doped layer 202 (i.e., a tunneling layer), a titanium dioxide layer 203, a silicon nitride anti-reflection layer 204 (i.e., a hydrogen-containing capping layer) deposited in sequence on the front side of the silicon substrate 201, a composite layer 209, a perovskite hole transport layer 210, a perovskite layer 211, a fullerene C60 layer 212, a tin dioxide layer 213, a transparent conductive layer 214, an anti-reflection layer 215, and a silver electrode 216, and a P+ emitter layer 205, an n+ BSF layer 206, a passivation layer 207, and a metal electrode 208 deposited in sequence on the back side of the silicon substrate 201.

[0072] In other embodiments, the electronically passivated contact structure may also be formed after removing the hydrogen-containing capping layer. In this case, the titanium dioxide layer serves as the front passivation layer structure in the current BC solar cell structure.

[0073] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0074] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing an electronically passivated contact structure, characterized in that: include: providing a silicon substrate; forming a tunneling layer on the silicon substrate; forming a first titanium dioxide sublayer and a second titanium dioxide sublayer by continuous deposition through an atomic layer deposition process, so as to ultimately form an overall titanium dioxide layer; the first titanium dioxide sublayer is an amorphous structure, and the second titanium dioxide sublayer is a crystalline structure; Specifically, the atomic layer deposition process is used, titanium tetrachloride is used as a titanium source precursor, and magnesium acetylacetonate and trimethylaluminum are introduced as dopant drivers. The magnesium and aluminum co-doping of the titanium dioxide-based film is achieved through a co-deposition process. The deposition temperature is set at 100°C-200°C. Within this temperature range, the number of reaction cycles is controlled to form a first titanium dioxide sublayer with an amorphous structure. In the same reaction chamber, atomic layer deposition (ALD) was continued. Using titanium tetrachloride as a titanium source precursor, dimethylzinc and trimethylgallium were introduced as co-doping precursors. Simultaneous doping of zinc and gallium was achieved by alternating pulses of the precursors. The deposition temperature was set between 100°C and 200°C. Within this temperature range, the number of reaction cycles was controlled to form a second crystalline titanium dioxide sublayer. A hydrogen-containing capping layer is deposited on the titanium dioxide layer.

2. The preparation method according to claim 1, wherein: The first titanium dioxide sublayer is doped with magnesium and aluminum precursors in a single-cycle mode at a controlled doping concentration of 1wt%-10wt% to form an amorphous structure; the second titanium dioxide sublayer is doped with zinc and gallium precursors in a super-cycle mode at a controlled doping concentration of 5wt%-20wt% to form a crystalline structure.

3. The preparation method according to claim 1, wherein: The method for preparing the electronic passivation contact structure further includes removing the hydrogen-containing capping layer.

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