Manufacturing method of heterojunction solar cell and heterojunction solar cell

Abstract

The invention relates to the technical field of solar cells. The invention particularly relates to a manufacturing method of a heterojunction solar cell and the heterojunction solar cell. The method comprises the steps of providing a semiconductor substrate; forming an intrinsic passivation layer on the surface of the semiconductor substrate; forming a doping layer on the surface of the intrinsic passivation layer; wherein the step of forming the doping layer adopts a CVD (Chemical Vapor Deposition) process and comprises the following steps of: fully mixing a silicon source gas, an oxygen source gas and a doping source gas, and introducing the mixture into a process cavity; adjusting the power of a power supply, the temperature of a process cavity and the flow of gas, and depositing on the surface of the intrinsic passivation layer; the flow of the silicon source gas and the oxygen source gas is controlled to change in a gradient manner along with the process time, so that the oxygen content in the doped layer formed by deposition is reduced in a gradient manner from one side close to the semiconductor substrate to one side far away from the semiconductor substrate; the oxygen source gas comprises first oxygen source gas CO2 or N2O and further comprises second oxygen source gas O3 or O2. According to the invention, parasitic absorption and electrical property loss of the front structure of the heterojunction cell can be effectively balanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar cells. Specifically, it relates to a manufacturing method of a heterojunction solar cell and a heterojunction solar cell. BACKGROUND

[0002] In the technical field of solar cells, heterojunction cells have attracted much attention due to their high efficiency, low cost and good stability. They are formed by depositing two or more different semiconductor material films on the same substrate in sequence, and these materials have different energy band gaps, forming a semiconductor heterojunction, which is a special PN junction. In a heterojunction solar cell, the commonly used base materials are hydrogenated amorphous silicon and doped hydrogenated amorphous / microcrystalline silicon. However, the efficiency of heterojunction cells is still limited by some factors, one of which is parasitic absorption. In a heterojunction cell, parasitic absorption mainly exists in the TCO layer, the doped layer and the intrinsic layer of the light-receiving surface.

[0003] In order to reduce the parasitic absorption of hydrogenated amorphous intrinsic silicon and hydrogenated amorphous / microcrystalline doped silicon on the front surface of a heterojunction cell, a method of doping oxygen during film plating is usually used to increase the band gap and thus reduce the light absorption in the medium and long wave range. This method can reduce parasitic absorption to some extent, increase the short-circuit current of the cell and thus improve the efficiency of the cell.

[0004] However, doping oxygen also has some problems. First, doping oxygen increases the band gap of the film layer, thereby increasing the potential barrier for interface transmission and reducing the electrical conductivity of the film layer, which affects the electrical performance of the cell. Electrical conductivity is a key factor affecting the internal resistance and current output of the cell, and a decrease in electrical conductivity will lead to a decrease in the electrical performance of the cell. Second, excessive doping of oxygen will cause more serious dark decay and other reliability problems, which will affect the long-term performance of the cell.

[0005] Therefore, a solution is needed to balance the parasitic absorption and electrical performance loss of the front surface structure of a heterojunction cell. SUMMARY

[0006] Therefore, the present application provides a manufacturing method of a heterojunction solar cell and a heterojunction solar cell to solve the problem of balancing the parasitic absorption and electrical performance loss of the front surface structure of a heterojunction cell.

[0007] In one aspect of the present application, the present application provides a manufacturing method of a heterojunction solar cell, comprising the following steps:

[0008] providing a semiconductor substrate;

[0009] forming an intrinsic passivation layer on the surface of the semiconductor substrate;

[0010] forming a doped layer on the surface of the intrinsic passivation layer;

[0011] forming a transparent conductive layer on the back side of the doped layer opposite to the semiconductor substrate;

[0012] In the step of forming the doped layer on at least one side, a CVD process is adopted, comprising:

[0013] The silicon source gas, the oxygen source gas and the doping source gas are mixed sufficiently and then introduced into the process cavity;

[0014] The power of the power source, the temperature of the process cavity and the flow rate of the gas are adjusted to deposit on the surface of the intrinsic passivation layer;

[0015] The flow rate of the silicon source gas and the oxygen source gas is controlled to change with the process time gradient, so that the oxygen content in the doped layer formed by deposition is increased from the side close to the semiconductor substrate to the side away from the semiconductor substrate;

[0016] The oxygen source gas comprises a first oxygen source gas CO2 or N2O, and further comprises a second oxygen source gas O3 or O2.

[0017] The manufacturing method of the heterojunction solar cell provided in the application realizes the gradient change of the oxygen doping amount by the joint control of the process gas, the power of the power source and the temperature of the process cavity in the process of preparing the doped layer, so that the oxygen content in the doped layer of the finally formed heterojunction solar cell can change from the side close to the semiconductor substrate to the side away from the semiconductor substrate, and then the refractive index from the side close to the light-receiving surface to the side away from the light-receiving surface can have a stepped change, the parasitic absorption is reduced, and the reflection is reduced. At the same time, the band gap is gradually changed, the carrier transport barrier is reduced, and the conductivity is improved. That is, the parasitic absorption is reduced while the conductivity is improved, and the balance between the oxygen doping amount of the doped layer and the high conductivity and the low parasitic absorption does not need to be considered. In addition, the oxygen doping concentration of the doped layer on one side is increased, and when the doped layer is used as the side of the light-receiving surface, the oxygen-doped doped layer can reduce the refractive index to obtain good light transmittance. Due to the gradient change of the oxygen content, the refractive index gradually increases in the direction close to the substrate layer, so that the high conductivity can be ensured. In the direction away from the substrate layer, the concentration of oxygen elements is gradually increased, so that the good electrical performance can be ensured. This design can improve the efficiency of the battery without causing more serious reliability problems such as dark decay of the battery. Further, the gradient oxygen doping method has a unique synergistic effect. While adjusting the light transmittance and electrical performance of the doped layer, the surface morphology and interface characteristics of the battery are also improved. For example, the gradient distribution of oxygen elements can optimize the interface bonding between the doped layer and other layers, reduce interface defects, and further improve the stability and reliability of the battery. Active oxygen atoms combine with silicon dangling bonds to form a Si-O-Si network, and the interface state density is reduced to 10 10 cm -2 ·eV -1The following simultaneously inhibits the problem of dark decay caused by hydrogen escape (efficiency decay after boiling <1%). In addition, by adding ozone or oxygen to the oxygen source gas, the high reactivity and controllable reaction of ozone or oxygen can achieve more precise control of the gradient distribution of oxygen doping, and can overcome the limitations of existing oxygen sources. Specifically, the high reactivity has two main reasons: (1) Ozone (O) can be decomposed into O and active oxygen atom (O*) at 80-120°C, which can significantly reduce the thermodynamic barrier compared to traditional CO (which needs to be decomposed at >300°C), and can achieve high-density active oxygen supply within the low-temperature process window (150-250°C) of heterojunction cells. (2) Using VHF power sources (such as 40.68 MHz) to excite ozone plasma, O - , O2 + and other high-activity oxygen species are produced, which have a reaction cross-section that is 2-3 orders of magnitude larger than that of neutral oxygen molecules, increasing the oxygen doping efficiency on the silicon surface to more than 95%. The controllable reaction mainly reflects in that the oxygen doping rate equation can be established:

[0018]

[0019] The above equation is a gas-temperature-power linkage function, where R O is the oxygen doping rate, k0 is the process constant, P O3 / PSiH4 is the flow ratio of ozone and silane, E a is the film layer activation energy, T is the temperature, and f RF is the radio frequency. According to the above equation, the oxygen concentration can be precisely controlled by adjusting the flow ratio of ozone and silane, the radio frequency, and the temperature in real time, so that the deviation of oxygen concentration control is less than 5%.

[0020] The present application breaks through the precision limit of traditional oxygen doping (from micron-level to nanometer-level gradient control) through ozone activation kinetics optimization (low temperature and high activity), multi-physical field coupling control (gas-heat-electricity cooperation), and standing wave elimination technology (double power interference suppression), and provides a theoretical and technical basis for the carrier transport-light absorption synergistic optimization of heterojunction cells.

[0021] Through synchronous gradient variation, fine adjustment of the distribution of oxygen elements can be achieved. The present application innovatively uses CO2 or N2O with a certain proportion of ozone or oxygen (proportion 1%-100%) as the oxygen source, and by precisely controlling the gas flow ratio of the silicon source and the oxygen source with time and space variation (for example, ozone flow 10 sccm, CO2 flow 200 sccm, Si2H6 flow 150 sccm), the gradient control bottleneck caused by the reaction inertness of traditional CO / NO is broken through, and nanometer-level oxygen concentration gradient control is achieved. And according to the specific needs of different positions of heterojunction cells for light transmission and electrical performance, the distribution of oxygen elements can be precisely adjusted. This fine adjustment is lacking in existing technologies, which further improves the performance of the cell.

[0022] In some embodiments of the present application, the step of forming the doped layer is performed by:

[0023] The process cavity temperature, power, flow rate of silicon source gas, flow rate of first oxygen source gas, and flow rate of second oxygen source gas are controlled to change synchronously and gradiently.

[0024] In some embodiments of the present application, the process cavity temperature, power, and pulse frequency, flow rate of silicon source gas, flow rate of first oxygen source gas, and flow rate of second oxygen source gas are controlled to change synchronously and gradiently in the following process:

[0025] The temperature gradient is positively correlated with the flow rate gradient of the oxygen source gas. For every 1% increase in the flow rate of the oxygen source gas, the process cavity temperature is increased by 0.5-1.5°C synchronously.

[0026] In the process of gradiently changing the power:

[0027] When the flow rate of the oxygen source gas accounts for less than 30% of the total flow rate of the gases, the power increase rate is 0.8 times the flow rate increase rate of the oxygen source gas.

[0028] When the flow rate of the oxygen source gas accounts for 30-60% of the total flow rate of the gases, the power increase rate is 1.2 times the flow rate increase rate of the oxygen source gas.

[0029] When the flow rate of the oxygen source gas accounts for more than 60% of the total flow rate of the gases, the power increase rate is reduced to 0.5 times. The flow rate gradient of the silicon source gas is negatively correlated with the flow rate gradient of the oxygen source gas. For every 1% increase in the flow rate of the oxygen source gas, the flow rate of the silicon source gas is decreased by 0.3-0.8%.

[0030] The method for manufacturing a heterojunction solar cell provided in the present application has multiple preparation process parameters changing gradiently, so as to achieve fine balance and precise control of the deposition rate and effective oxygen doping concentration. For example, when the flow rate of the oxygen source gas is increased, the power is increased synchronously, and the reaction temperature is increased to increase the reaction rate.

[0031] In some embodiments of the present application, the process cavity temperature, power, and pulse frequency, flow rate of silicon source gas, flow rate of first oxygen source gas, and flow rate of second oxygen source gas are controlled to change synchronously and gradiently in the following process: in the stage of 0-30% of the process time, a high-frequency pulse mode is adopted, the pulse frequency is 50-100 kHz, and the pulse time accounts for 60%; in the stage of 30-70% of the process time, a low-frequency long pulse mode is switched to, the pulse frequency is 10-30 kHz, and the pulse time accounts for 75%; in the stage of 70-100% of the process time, a pulse duty cycle dynamic adjustment mode is adopted, and the pulse time is adjusted according to the oxygen gradient distribution data monitored in real time, with 1% duty cycle adjustment corresponding to every 5% oxygen concentration change.

[0032] The method for manufacturing the heterojunction solar cell provided in the application is performed through multi-stage pulse variation, process conditions are adjusted, and gradient parameters are controlled.

[0033] In some embodiments of the application, in the step of forming the doped layer, a double power supply joint control is used, which comprises:

[0034] The first power supply is a radio frequency power supply, serving as a main power supply, with a working frequency of 13.56 MHz, suitable for maintaining a basic plasma density, and a power range of 50 W to 200 W;

[0035] The second power supply is a very high frequency power supply, serving as an auxiliary power supply, with a working frequency of 40 MHz to 60 MHz, suitable for enhancing excitation efficiency in the interface region of the doped layer, and a power range of 20 W to 80 W;

[0036] The first power supply and the second power supply adopt an alternating pulse working mode, the first power supply pulse phase leads the second power supply by 15° to 30°, and through standing wave phase difference cancellation effect, energy fluctuation is reduced to within ±3%.

[0037] The method for manufacturing the heterojunction solar cell provided in the application can reduce standing wave effect through double power supply joint control, and optimize activity of a reaction process through regulation and control of a double power supply power ratio.

[0038] In some embodiments of the application, the CVD process comprises a PECVD process or an LPCVD process.

[0039] In some embodiments of the application, the semiconductor substrate is an N-type single crystal silicon substrate;

[0040] The intrinsic passivation layer is a hydrogenated amorphous silicon layer;

[0041] The silicon source gas comprises Si2H6 or SiH4;

[0042] The doping source gas comprises B2H6 or PH3;

[0043] The ratio of the flow rate of the first oxygen source gas to the flow rate of the second oxygen source gas is 1:1 to 100:1;

[0044] The flow rate of the first oxygen source gas is 100 sccm to 1000 sccm;

[0045] The flow rate of the second oxygen source gas is 10 sccm to 100 sccm;

[0046] The power supply power is 5 KW to 9 KW;

[0047] The process cavity temperature is 80°C to 250°C.

[0048] In another aspect of the present application, the present application also provides a heterojunction solar cell manufactured by the method for manufacturing a heterojunction solar cell provided by the present application, comprising:

[0049] a semiconductor substrate layer;

[0050] an intrinsic passivation layer on the opposite side surface of the semiconductor substrate layer;

[0051] a doped layer on the side of the intrinsic passivation layer opposite to the semiconductor substrate layer;

[0052] a transparent conductive layer on the side of the doped layer opposite to the semiconductor substrate layer;

[0053] wherein the doped layer on at least one side comprises a plurality of regions with gradiently increased oxygen content from the side close to the semiconductor substrate layer to the side away from the semiconductor substrate layer.

[0054] The heterojunction solar cell provided by the present application is manufactured by the method for manufacturing a heterojunction solar cell provided by the present application. By jointly controlling the process gas, power supply power and process cavity temperature during the preparation of the doped layer, the gradient change of the oxygen content of the doped layer is realized, so that the oxygen content of the doped layer in the finally formed heterojunction solar cell can be gradiently changed from the side close to the semiconductor substrate to the side away from the semiconductor substrate, and then the refractive index from the side close to the light-receiving surface to the side away from the light-receiving surface can be stepped, the parasitic absorption is reduced, and the reflection is also reduced. At the same time, the band gap is gradually changed, the carrier transport barrier is reduced, and the conductivity is improved. That is, the parasitic absorption is reduced while the conductivity is improved, and the balance between the oxygen content of the doped layer and the high conductivity and the low parasitic absorption does not need to be considered. In addition, the oxygen content of the doped layer on one side is increased, and when it is used as the side of the light-receiving surface, the doped layer with oxygen can reduce the refractive index to obtain good light transmittance; due to the gradient change of the oxygen content, the refractive index gradually increases in the direction close to the substrate layer, which can ensure high conductivity; and in the direction away from the substrate layer, the concentration of oxygen elements gradually increases, which can ensure good electrical performance. This design can improve the efficiency of the battery without causing more serious reliability problems such as dark decay of the battery. Further, the gradient oxygen doping method has a unique synergistic effect. While adjusting the light transmittance and electrical performance of the doped layer, the surface morphology and interface characteristics of the battery are also improved. For example, the gradient distribution of oxygen elements can optimize the interface bonding between the doped layer and other layers, reduce interface defects, and further improve the stability and reliability of the battery.

[0055] In some embodiments of the present application, the oxygen content of the doped layer with gradiently changed oxygen content is 20at%-6at%, and the gradient change of each region is 2at%-4at% from the side close to the semiconductor substrate layer to the side away from the semiconductor substrate layer. BRIEF DESCRIPTION OF DRAWINGS

[0056] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced. Obviously, the accompanying drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort.

[0057] Figure 1 For an embodiment of the present application, the flow chart of the manufacturing method of the heterojunction solar cell is shown in the figure.

[0058] Figure 2 For an embodiment of the present application, the schematic diagram of the principle of forming a band gap gradient layer by gradient oxygen doping to reduce the carrier transport barrier and improve the conductivity is shown in the figure.

[0059] Figure 3 For an embodiment of the present application, the schematic diagram of the structure of the solar cell manufactured by the manufacturing method of the heterojunction solar cell is shown in the figure.

[0060] Figure 4 For an embodiment of the present application, the schematic diagram of the refractive index gradient change of the doped layer due to the oxygen content gradient change is shown in the figure. EMBODIMENT

[0061] The present application provides a manufacturing method of a heterojunction solar cell and a heterojunction solar cell to solve the problem of balancing the parasitic absorption of the front structure of the heterojunction solar cell and the loss of electrical performance.

[0062] The present application provides a manufacturing method of a heterojunction solar cell, comprising the following steps: providing a semiconductor substrate; forming an intrinsic passivation layer on the surface of the semiconductor substrate; forming a doped layer on the surface of the intrinsic passivation layer; forming a transparent conductive layer on the side of the doped layer away from the substrate; wherein in the step of forming the doped layer on at least one side, a CVD process is used, comprising: mixing a silicon source gas, an oxygen source gas and a doping source gas, and then introducing them into a process chamber; adjusting the power of the power source, the temperature of the process chamber and the flow rate of the gas to deposit on the surface of the intrinsic passivation layer; in the process, the flow rates of the silicon source gas and the oxygen source gas are controlled to change with the process time gradient, so that the oxygen content in the deposited doped layer decreases from the side close to the semiconductor substrate to the side away from the semiconductor substrate; the oxygen source gas comprises a first oxygen source gas CO2 or N2O, and also comprises a second oxygen source gas O3 or O2.

[0063] The application also provides a heterojunction solar cell manufactured by the manufacturing method of the heterojunction solar cell provided in Embodiment 1, comprising: a semiconductor substrate layer; an intrinsic passivation layer on the opposite two sides of the semiconductor substrate layer; a doped layer on the side of the intrinsic passivation layer away from the semiconductor substrate layer; and a transparent conductive layer on the side of the doped layer away from the semiconductor substrate layer; wherein the doped layer on at least one side comprises a plurality of regions with gradiently increased oxygen content from the side close to the semiconductor substrate layer to the side away from the semiconductor substrate layer.

[0064] The application will be further described below in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are merely intended for explaining the application, but not limiting the application. In addition, it should be noted that only the parts related to the application are shown in the drawings for the convenience of description, but not all the structures.

[0065] In the following description, the description of well-known structures and techniques is omitted to avoid unnecessary confusion of the concept of the application. In the drawings, various structural diagrams according to the embodiments of the application are shown. These diagrams are not drawn to scale, in which some details are exaggerated for the purpose of clear expression, and some details can be omitted. The shapes of various regions, layers, and the relative size and position relationship between them shown in the drawings are only exemplary, and in actuality, they can be deviated due to manufacturing tolerance or technical limitation, and a person skilled in the art can additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs. In the context of the application, when a layer / element is referred to as being located "on" another layer / element, the layer / element can be directly located on the other layer / element, or there can be an intermediate layer / element between them. In addition, if a layer / element is located "on" another layer / element in one orientation, the layer / element can be located "under" the other layer / element when the orientation is reversed.

[0066] Embodiment 1

[0067] Reference Figure 1 The embodiment provides a manufacturing method of a heterojunction solar cell, comprising the following steps:

[0068] providing a semiconductor substrate;

[0069] forming an intrinsic passivation layer on the surface of the semiconductor substrate;

[0070] forming a doped layer on the surface of the intrinsic passivation layer;

[0071] forming a transparent conductive layer on the side of the doped layer away from the substrate;

[0072] wherein in the step of forming the doped layer on at least one side, a CVD process is adopted, comprising:

[0073] The silicon source gas, the oxygen source gas and the doping source gas are mixed sufficiently and then introduced into the process cavity;

[0074] The power of the power supply, the temperature of the process cavity and the flow rate of the gas are adjusted to deposit on the surface of the intrinsic passivation layer;

[0075] The flow rates of the silicon source gas and the oxygen source gas are controlled to change with the process time gradient, so that the oxygen content in the doping layer formed by deposition is increased from the side close to the semiconductor substrate to the side away from the semiconductor substrate;

[0076] The oxygen source gas includes a first oxygen source gas CO2 or N2O, and also includes a second oxygen source gas O3 or O2.

[0077] The manufacturing method of the heterojunction solar cell provided in the embodiment realizes the gradient change of the oxygen doping amount by the joint control of the process gas, the power of the power supply and the temperature of the process cavity in the doping layer preparation process, so that the oxygen content in the doping layer of the finally formed heterojunction solar cell can change from the side close to the semiconductor substrate to the side away from the semiconductor substrate, and then the refractive index from the side close to the light-receiving surface to the side away from the light-receiving surface can have a stepped change, thereby reducing the parasitic absorption and the reflection. At the same time, the band gap is gradually changed, the carrier transport barrier is reduced, and the conductivity is improved. That is, the parasitic absorption is reduced while the conductivity is improved, and the balance between the oxygen doping amount of the doping layer and the high conductivity and the low parasitic absorption does not need to be considered. In addition, the oxygen doping concentration of the doping layer on one side is improved, and when it is used as the side of the light-receiving surface, the oxygen-doped doping layer can reduce the refractive index to obtain good light transmittance. Due to the gradient change of the oxygen content, the refractive index gradually increases in the direction close to the substrate layer, which can ensure high conductivity. In the direction away from the substrate layer, the concentration of oxygen elements gradually increases, which can ensure good electrical performance. This design can improve the efficiency of the battery without causing more serious reliability problems such as dark decay of the battery. Further, the gradient oxygen doping method has a unique synergistic effect. While adjusting the light transmittance and electrical performance of the doping layer, the surface morphology and interface characteristics of the battery are also improved. For example, the gradient distribution of oxygen elements can optimize the interface bonding between the doping layer and other layers, reduce interface defects, and further improve the stability and reliability of the battery. Active oxygen atoms combine with silicon dangling bonds to form a Si-O-Si network, reducing the interface state density to 10 10 cm -2 ·eV -1The following simultaneously inhibits the problem of dark decay caused by hydrogen escape (efficiency decay after boiling <1%). In addition, by adding ozone or oxygen to the oxygen source gas, the high reactivity and controllable reaction of ozone or oxygen can achieve more precise control of the gradient distribution of oxygen doping, and can overcome the limitations of existing oxygen sources. Specifically, the high reactivity has two main reasons: (1) ozone (O) can be decomposed into O and active oxygen atoms (O*) at 80-120°C, which can significantly reduce the thermodynamic barrier compared to traditional CO (which needs to be decomposed at >300°C), and can provide high-density active oxygen in the low-temperature process window (150-250°C) of heterojunction cells. (2) Using VHF power sources (such as 40.68 MHz) to excite ozone plasma, O - , O2 + and other high-activity oxygen species are produced, which have a reaction cross section 2-3 orders of magnitude larger than neutral oxygen molecules, and can improve the oxygen doping efficiency on the silicon surface to more than 95%. The controllable reaction mainly reflects that the oxygen doping rate equation can be established:

[0078]

[0079] The above equation is a gas-temperature-power linkage function, where R O is the oxygen doping rate, k0 is the process constant, P O3 / PSiH4 is the flow ratio of ozone and silane, E a is the film layer activation energy, T is the temperature, and f RF is the radio frequency. According to the above equation, the oxygen concentration can be precisely controlled by adjusting the flow ratio of ozone and silane, the radio frequency, and the temperature in real time, so that the deviation of oxygen concentration control is <5%.

[0080] The present application breaks through the precision limit of traditional oxygen doping (from single micron-level control to nanometer-level gradient control) through ozone activation kinetics optimization (low temperature and high activity), multi-physical field coupling control (gas-heat-electricity cooperation), and standing wave elimination technology (double power interference suppression), and provides a theoretical and technical basis for the carrier transport-light absorption synergistic optimization of heterojunction cells.

[0081] By synchronizing gradient changes, precise control of oxygen distribution can be achieved. This invention innovatively uses CO2 or N2O with a certain proportion of ozone or oxygen (1%–100%) as the oxygen source. By precisely controlling the change in the gas flow ratio of silicon and oxygen sources over time and space during the coating process (e.g., ozone flow rate 10 sccm, CO2 flow rate 200 sccm, Si2H6 flow rate 150 sccm), it overcomes the bottleneck of traditional CO / NO gradient control due to reaction inertia, achieving nanoscale oxygen concentration gradient control. Furthermore, it can precisely adjust the oxygen distribution according to the specific requirements of light transmittance and electrical performance at different locations in the heterojunction cell. This precise control is lacking in existing technologies, further improving cell performance.

[0082] For example, such as Figure 2 As shown: Figure 2 This is a schematic diagram illustrating how gradient oxygen doping forms a bandgap gradient layer in one embodiment of this application, reducing the carrier transport barrier and improving conductivity. The left side of the diagram shows the energy band structure formed by the gradient oxygen doping in the doped layer, while the right side shows the energy band structure of the intrinsic layer. Under illumination, the electron gradient oxygen doping of the intrinsic layer achieves a gradient change in the doped layer's energy bands, lowering the barrier for electron conduction in single-crystal silicon after illumination, while simultaneously increasing the barrier for photogenerated holes in single-crystal silicon. Gradient oxygen doping enhances the selectivity of carrier transport, thus improving the electrical performance of the doped layer.

[0083] Furthermore, in some embodiments of this application, in the step of forming the doped layer:

[0084] The temperature of the control chamber, power supply, flow rate of silicon source gas, flow rate of the first oxygen source gas, and flow rate of the second oxygen source gas are synchronously varied in a gradient.

[0085] Furthermore, in some embodiments of this application, during the process of synchronously gradient changing the process chamber temperature, power supply and pulse frequency, silicon source gas flow rate, first oxygen source gas flow rate, and second oxygen source gas flow rate:

[0086] The temperature gradient is positively correlated with the flow rate gradient of the oxygen source gas. For every 1% increase in the flow rate ratio of the oxygen source gas, the temperature of the process chamber increases by 0.5℃ to 1.5℃.

[0087] During the process of power gradient change:

[0088] When the flow rate of the oxygen source gas accounts for less than 30% of the total gas flow rate, the power increase rate is 0.8 times the flow rate increase rate of the oxygen source gas.

[0089] When the flow rate of the oxygen source gas accounts for 30% to 60% of the total gas flow rate, the power increase rate is 1.2 times that of the oxygen source gas flow rate increase rate.

[0090] When the flow rate of the oxygen source gas accounts for more than 60% of the total flow rate, the power increase rate is reduced to 0.5 times; the flow rate gradient of the silicon source gas is negatively correlated with the flow rate gradient of the oxygen source gas, and when the flow rate proportion of the oxygen source gas is increased by 1%, the flow rate of the silicon source gas is reduced by 0.3%-0.8%.

[0091] The manufacturing method of the heterojunction solar cell provided in the application has gradient changes in multiple preparation process parameters, so that the deposition rate and the effective oxygen doping concentration are finely balanced and accurately controlled. For example, when the flow rate proportion of the oxygen source gas is increased, the power supply power is simultaneously increased, and the reaction temperature is increased to increase the reaction rate.

[0092] Further, in some embodiments of the application, during the process of synchronously gradient changing the process cavity temperature, the power supply power and the pulse frequency, the flow rate of the silicon source gas, the flow rate of the first oxygen source gas and the flow rate of the second oxygen source gas, in the stage of 0-30% of the process time, a high-frequency pulse mode is adopted, the pulse frequency is 50 kHz-100 kHz, and the pulse time proportion is 60%; in the stage of 30%-70% of the process time, a low-frequency long pulse mode is switched to, the pulse frequency is 10 kHz-30 kHz, and the pulse time proportion is increased to 75%; in the stage of 70%-100% of the process time, a pulse duty cycle dynamic adjustment mode is adopted, and the pulse time is adjusted according to 1% of the duty cycle corresponding to 5% of the oxygen concentration change based on the real-time monitoring of the oxygen gradient distribution data.

[0093] The manufacturing method of the heterojunction solar cell provided in the application is performed through multi-stage pulse changes, the process conditions are adjusted, and the gradient parameters are controlled.

[0094] Further, in some embodiments of the application, in the step of forming the doped layer, a double power supply joint control is used, which includes:

[0095] The first power supply is a radio frequency power supply, which is used as a main power supply, has a working frequency of 13.56 MHz, is suitable for maintaining a basic plasma density, and has a power range of 50 W-200 W;

[0096] The second power supply is a very high frequency power supply, which is used as an auxiliary power supply, has a working frequency of 40 MHz-60 MHz, is suitable for enhancing excitation efficiency in the interface region of the doped layer, and has a power range of 20 W-80 W;

[0097] The first power supply and the second power supply adopt an alternating pulse working mode, the first power supply pulse phase leads the second power supply pulse phase by 15°-30°, and the standing wave phase difference offset effect is used to reduce the energy fluctuation to within ±3%.

[0098] The manufacturing method of the heterojunction solar cell provided in the application can reduce the standing wave effect through the double power supply joint control, and the activity of the reaction process can be optimized through the regulation and control of the power proportion of the double power supplies.

[0099] Further, in some embodiments of the present application, the CVD process includes a PECVD process or a LPCVD process.

[0100] Further, in some embodiments of the present application, the semiconductor substrate is an N-type monocrystalline silicon substrate.

[0101] The intrinsic passivation layer is a hydrogenated amorphous silicon layer.

[0102] The silicon source gas includes Si2H6 or SiH4.

[0103] The dopant source gas includes B2H6 or PH3.

[0104] The ratio of the flow rate of the first oxygen source gas to the flow rate of the second oxygen source gas is 1:1-100:1.

[0105] The flow rate of the first oxygen source gas is 100sccm-1000sccm.

[0106] The flow rate of the second oxygen source gas is 10sccm-100sccm.

[0107] The power of the power source is 5KW-9KW.

[0108] The temperature of the process cavity is 80℃-250℃.

[0109] One specific implementation process of the gradient variation doping is as follows:

[0110] First stage (close to the substrate): ozone flow rate <5sccm, temperature 250℃, oxygen concentration <2at.%, conductivity increased to 10 3 S / cm, interface potential barrier reduced by 0.3eV.

[0111] Second stage (intermediate transition layer): ozone flow rate increased to 10sccm-20sccm, temperature increased to 220℃, oxygen concentration gradient reduced to 4at.%-6at.%, forming a gradual band gap structure (1.8eV-1.5eV), carrier mobility increased to 25cm 2 / V·s.

[0112] Third stage (far from the substrate): ozone flow rate 30sccm-50sccm, temperature 180℃, generating a high oxygen concentration (8at.%-12at.%) amorphous silicon oxygen layer, refractive index as low as 1.8, light transmittance increased by 15%.

[0113] Embodiment 2

[0114] This embodiment provides a heterojunction solar cell, which is manufactured using the manufacturing method of the heterojunction solar cell provided in Embodiment 1, and refers to Figure 3 , and includes:

[0115] semiconductor substrate layer 100;

[0116] intrinsic passivation layer 200 on both sides of the semiconductor substrate layer;

[0117] doped layer 300 on the side of the intrinsic passivation layer away from the semiconductor substrate layer;

[0118] transparent conductive layer 400 on the side of the doped layer away from the semiconductor substrate layer;

[0119] In one embodiment, the doped layer on at least one side comprises a plurality of regions with gradiently increasing oxygen content from the side close to the semiconductor substrate layer to the side away from the semiconductor substrate layer. For example, as shown in FIG. 3, the doped layer comprises regions 310, 320, 330, 340, and 350 with gradiently increasing oxygen content. Figure 3 As shown in FIG. 4, the refractive index n gradually increases from the side close to the substrate to the side away from the substrate. Figure 4 As shown in FIG. 4, the refractive index n gradually increases from the side close to the substrate to the side away from the substrate.

[0120] The heterojunction solar cell provided in the embodiment is manufactured using the manufacturing method of the heterojunction solar cell provided in Embodiment 1. Through joint control of the process gas, power supply power, and process cavity temperature during the preparation of the doped layer, gradient variation of the oxygen doping amount is achieved, so that the oxygen content of the doped layer in the finally formed heterojunction solar cell can vary gradiently from the side close to the semiconductor substrate to the side away from the semiconductor substrate, and thus the refractive index can have a stepped change from the side close to the light-receiving surface to the side away from the light-receiving surface, reducing parasitic absorption and reflection. At the same time, a gradually changing band gap is achieved, which can reduce the carrier transport barrier and improve the electrical conductivity. That is, the parasitic absorption is reduced while the electrical conductivity is improved, and the balance between the oxygen doping amount of the doped layer and the high electrical conductivity and low parasitic absorption does not need to be considered. In addition, the oxygen doping concentration of the doped layer on one side is increased, and when it is used as the side of the light-receiving surface, the oxygen-doped doped layer can reduce the refractive index to obtain good light transmittance. Due to the gradient variation of the oxygen content, the refractive index gradually increases in the direction close to the substrate layer, which can ensure high electrical conductivity. In the direction away from the substrate layer, the concentration of oxygen elements gradually increases, which can ensure good electrical performance. This design can improve the efficiency of the battery without causing more serious reliability problems such as dark decay of the battery. Further, the gradient oxygen doping method has a unique synergistic effect. While adjusting the light transmittance and electrical performance of the doped layer, it can also improve the surface morphology and interface characteristics of the battery. For example, the gradient distribution of oxygen elements can optimize the interface bonding between the doped layer and other layers, reduce interface defects, and further improve the stability and reliability of the battery.

[0121] Further, in some embodiments of the present application, the oxygen content in the oxygen content gradient-doped layer is 20 at% to 6 at%, and the oxygen content in each region changes by 2 at% to 4 at% from the semiconductor substrate layer to the direction away from the semiconductor substrate layer.

[0122] In the description of the present specification, the description of the terms "the present embodiment", "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples, without contradiction. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically limited.

[0123] In the above description, the technical details such as the patterning, etching, etc. of each layer are not described in detail. However, those skilled in the art should understand that the layers, regions, etc. of the required shape can be formed by various technical means. In addition, those skilled in the art can also design methods that are not exactly the same as the methods described above in order to form the same structure. In addition, although each embodiment is described above, this does not mean that the measures in each embodiment cannot be used advantageously in combination.

[0124] The above are only the preferred embodiments of the present application and the technical principles applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described above, and those skilled in the art can make various obvious changes, re-adjustments, mutual combinations and replacements without departing from the scope of protection of the present application. Therefore, although the present application has been described in more detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application. The scope of protection of the present application is determined by the scope of the appended claims.

Claims

1. A method for manufacturing a heterojunction solar cell, characterized by, The method comprises the following steps: providing a semiconductor substrate; forming an intrinsic passivation layer on the surface of the semiconductor substrate; forming a doped layer on the surface of the intrinsic passivation layer; forming a transparent conductive layer on the side of the doped layer away from the substrate; wherein, in the step of forming the doped layer on at least one side, a CVD process is adopted, comprising: mixing a silicon source gas, an oxygen source gas and a doping source gas, and then introducing them into a process chamber; adjusting the power of the power source, the temperature of the process chamber and the flow rate of the gases to deposit on the surface of the intrinsic passivation layer; in the process, the flow rates of the silicon source gas and the oxygen source gas are controlled to change with the process time gradient, so that the oxygen content in the deposited doped layer is increased from the side close to the semiconductor substrate to the side away from the semiconductor substrate; the oxygen source gas comprises a first oxygen source gas CO2 or N2O, and a second oxygen source gas O3 or O2.

2. The method according to claim 1, wherein, in the step of forming the doped layer: the temperature of the process chamber, the power of the power source and the pulse frequency, the flow rate of the silicon source gas, the flow rate of the first oxygen source gas and the flow rate of the second oxygen source gas are controlled to change synchronously with the process time gradient.

3. The method according to claim 2, wherein, in the process of controlling the temperature of the process chamber, the power of the power source and the pulse frequency, the flow rate of the silicon source gas, the flow rate of the first oxygen source gas and the flow rate of the second oxygen source gas to change synchronously with the process time gradient: the temperature gradient is positively correlated with the flow rate gradient of the oxygen source gas, and for every 1% increase in the flow rate of the oxygen source gas, the temperature of the process chamber is increased by 0.5-1.5°C synchronously; in the process of changing the power gradient: when the flow rate of the oxygen source gas accounts for less than 30% of the total flow rate of the gases, the power increase rate is 0.8 times the flow rate increase rate of the oxygen source gas; when the flow rate of the oxygen source gas accounts for 30-60% of the total flow rate of the gases, the power increase rate is 1.2 times the flow rate increase rate of the oxygen source gas; when the flow rate of the oxygen source gas accounts for more than 60% of the total flow rate of the gases, the power increase rate is reduced to 0.5 times; the flow rate gradient of the silicon source gas is negatively correlated with the flow rate gradient of the oxygen source gas, and for every 1% increase in the flow rate of the oxygen source gas, the flow rate of the silicon source gas is reduced by 0.3-0.8%.

4. The method according to claim 2, wherein, in the process of controlling the temperature of the process chamber, the power of the power source and the pulse frequency, the flow rate of the silicon source gas, the flow rate of the first oxygen source gas and the flow rate of the second oxygen source gas to change synchronously with the process time gradient: in the stage of 0-30% of the process time, a high-frequency pulse mode is adopted, the pulse frequency is 50-100 kHz, and the pulse time accounts for 60%; in the stage of 30-70% of the process time, a low-frequency long pulse mode is switched to, the pulse frequency is 10-30 kHz, and the pulse time accounts for 75%. ​ ​ ​ In the stage of 70%~100% of the process time, the pulse duty cycle dynamic adjustment mode is adopted, and the pulse time is adjusted by 1% duty cycle corresponding to every 5% oxygen concentration change according to the real-time monitoring oxygen gradient distribution data.

5. The method according to claim 2, wherein, In the step of forming the doped layer, a double power supply joint control is used, including: The first power supply is a radio frequency power supply, which is used as a main power supply, has a working frequency of 13.56 MHz, and is suitable for maintaining a basic plasma density and has a power range of 50 W to 200 W; The second power supply is a very high frequency power supply, which is used as an auxiliary power supply, has a working frequency of 40 MHz to 60 MHz, is suitable for enhancing excitation efficiency in the interface region of the doped layer, and has a power range of 20 W to 80 W; The first power supply and the second power supply adopt an alternating pulse working mode, the first power supply pulse phase leads the second power supply by 15° to 30°, and the standing wave phase difference offset effect reduces energy fluctuation to within ±3%.

6. The method according to claim 1, wherein, The CVD process includes a PECVD process or an LPCVD process.

7. The method according to claim 1, wherein, The semiconductor substrate is an N-type single crystal silicon substrate; The intrinsic passivation layer is a hydrogenated amorphous silicon layer; The silicon source gas includes Si2H6 or SiH4; The doping source gas includes B2H6 or PH3; The ratio of the flow rate of the first oxygen source gas to the flow rate of the second oxygen source gas is 1:1 to 100:1; The flow rate of the first oxygen source gas is 100 sccm to 1000 sccm; The flow rate of the second oxygen source gas is 10 sccm to 100 sccm; The power supply power is 5 KW to 9 KW; The process cavity temperature is 80°C to 250°C.

8. A method for manufacturing a heterojunction solar cell, characterized by ， The method for manufacturing a heterojunction solar cell according to any one of claims 1-7, comprising: a semiconductor substrate layer; intrinsic passivation layers on the opposite two sides of the semiconductor substrate layer; a doped layer on the side of the intrinsic passivation layer away from the semiconductor substrate layer; a transparent conductive layer on the side of the doped layer away from the semiconductor substrate layer; wherein the doped layer on at least one side comprises a plurality of regions with gradiently increased oxygen content from the side close to the semiconductor substrate layer to the side away from the semiconductor substrate layer.

9. The method according to claim 8, wherein the oxygen content in the doped layer with gradiently changed oxygen content is 20 at% to 6 at%, and the gradient change of each region is 2 at% to 4 at% from the side close to the semiconductor substrate layer to the side away from the semiconductor substrate layer.

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