CN117766640B - Flexible silicon heterojunction solar cell with high photoelectric conversion efficiency and manufacturing method thereof - Google Patents

Abstract

The invention discloses a bendable silicon heterojunction solar cell with high photoelectric conversion efficiency, comprising a silicon substrate layer; a hydrogenated amorphous silicon oxygen layer, a hydrogenated amorphous silicon layer, an n-type hydrogenated nanocrystalline silicon oxygen layer and a transparent conductive oxide layer are sequentially deposited on the front side of the silicon substrate layer; a hydrogenated amorphous silicon oxygen layer, a hydrogenated amorphous silicon layer, a p-type hydrogenated nanocrystalline silicon layer and a transparent conductive oxide layer are sequentially deposited on the back side of the silicon substrate layer; and a metal electrode is printed on the transparent conductive oxide layer. The present invention also discloses a method for preparing the above-mentioned silicon heterojunction solar cell, which specifically comprises: thinning and texturing the silicon base layer; continuously depositing a hydrogenated amorphous silicon oxide layer and a hydrogenated amorphous silicon layer on the silicon base layer to form a passivation layer; using a mixture of carbon dioxide and hydrogen to perform plasma pretreatment on the passivation layers on both sides to achieve nanocrystal seeding on the shallow surface of the passivation layer; vertically growing a phosphorus-doped n-type nanocrystalline silicon oxide layer on the front passivation layer seeded with nanocrystals; vertically growing a boron-doped p-type nanocrystalline silicon layer on the back passivation layer seeded with nanocrystals; depositing cerium-doped indium oxide as a transparent conductive oxide layer, and then printing a metal electrode on the transparent conductive oxide layer.

Description

A bendable silicon heterojunction solar cell with high photoelectric conversion efficiency and its manufacturing method

Technical Field

The present invention relates to a bendable silicon heterojunction solar cell with high photoelectric conversion efficiency, and also relates to a method for preparing the silicon heterojunction solar cell.

Background Art

Solar energy has attracted much attention as a renewable energy source due to the growing demand for energy and the urgent need for environmentally friendly energy. However, traditional crystalline silicon solar cells are limited by their energy conversion efficiency, cost and inflexibility, which restricts their application areas.

In order to improve the efficiency of solar cells and reduce costs, researchers have begun to focus on the potential of crystalline silicon heterojunction solar cells. This type of solar cell uses crystalline silicon (c-Si) as the substrate material and introduces amorphous silicon on its surface or interface to form a heterojunction, thereby improving the light absorption and carrier separation efficiency of the cell.

Existing c-Si solar cells account for more than 95% of the solar cell market, and their wafer thickness is usually 150 to 180 μm. This thickness makes them unsuitable for use in some extreme environments (such as satellites, spacecraft and drones), so higher requirements are placed on the weight reduction and flexibility of solar cells. Currently, reducing the thickness of c-Si wafers to be much thinner than typical c-Si solar cells and incorporating the advantages of "thin-film solar cells" into c-Si solar cells is a hot topic. However, the power conversion efficiency of thin c-Si solar cells (55 to 130 μm) has been maintained in the range of 23.27 to 24.70% for decades.

Summary of the invention

Purpose of the invention: The purpose of the present invention is to provide a silicon heterojunction solar cell that is bendable (thickness less than 130 μm) and has high photoelectric conversion efficiency; another purpose of the present invention is to provide a method for preparing the above-mentioned silicon heterojunction solar cell.

Technical solution: The bendable silicon heterojunction solar cell with high photoelectric conversion efficiency described in the present invention includes a silicon base layer; a hydrogenated amorphous silicon oxygen layer, a hydrogenated amorphous silicon layer, an n-type hydrogenated nanocrystalline silicon oxygen layer and a transparent conductive oxide layer are sequentially deposited on the front side of the silicon base layer; a hydrogenated amorphous silicon oxygen layer, a hydrogenated amorphous silicon layer, a p-type hydrogenated nanocrystalline silicon layer and a transparent conductive oxide layer are sequentially deposited on the back side of the silicon base layer; and a metal electrode is printed on the transparent conductive oxide layer.

Among them, the metal electrodes silk-screened on the transparent conductive oxide layer on the front and back sides of the silicon substrate layer are all in the form of grid lines; or the metal electrodes silk-screened on the transparent conductive oxide layer on the front side of the silicon substrate layer are in the form of grid lines, and the metal electrodes on the transparent conductive oxide layer on the back side of the silicon substrate layer are metal electrodes that fully cover the entire surface.

The silicon base layer is n-type single crystal silicon, the surface adopts a texturing structure, and the thickness of the silicon base layer is less than 130 μm.

The thickness of the hydrogenated amorphous silicon oxygen layer is less than 0.5 nm, the oxygen atom content is 8-12 at.%, and the hydrogen content is 22-30 at.%; the thickness of the hydrogenated amorphous silicon layer is 4-5 nm, and the hydrogen content is 18-25 at.%.

The thickness of the n-type hydrogenated nanocrystalline silicon oxygen layer is 12-18 nm, and the volume fraction of the crystal is 40-46%; the thickness of the p-type hydrogenated nanocrystalline silicon layer is 20-25 nm, and the volume fraction of the crystal is 60-66%.

The transparent conductive oxide layer is cerium-doped indium oxide with a thickness of 70nm; the metal electrode is a silver electrode. For double-sided cells, both the front and back sides are in the form of grid lines with a width of 16 to 18μm. For single-sided cells, the front side is in the form of grid lines, and the back side of the cell is fully covered with metal electrodes, that is, the back side is covered with silver paste.

The method for preparing the above silicon heterojunction solar cell comprises the following steps:

(1) Thinning and texturing the silicon base layer;

(2) Continuously plasma-enhanced chemical vapor deposition of a hydrogenated amorphous silicon oxide layer and a hydrogenated amorphous silicon layer on the silicon substrate to form a passivation layer; the present invention uses an ultra-thin hydrogenated amorphous silicon oxide layer and a hydrogenated amorphous silicon layer to form a composite, which can effectively reduce the adverse effects of the passivation layer on the conductivity of the battery, and can effectively protect the integrity and flatness of the passivation layer through process control, so that it has a good passivation effect;

(3) Plasma pretreatment is performed on the passivation layer using a mixture of CO ₂ and H ₂ to achieve nanocrystal seeding on the shallow surface of the passivation layer. The use of a mixed gas for plasma pretreatment can, on the one hand, enable the nanocrystals to be seeded on the surface of the passivation layer, and the subsequent doped contact layer can grow vertically, thereby improving the conductivity of the battery; on the other hand, it can inhibit the reverse epitaxy of the seed layer, thereby ensuring the integrity of the passivation layer and avoiding damage to the passivation effect.

(4) under the gas flow ratio of high hydrogen silane, a phosphorus-doped n-type nanocrystalline silicon oxide layer is vertically grown on the nanocrystalline seeds of the passivation layer, and the volume fraction of the crystal is 40-46% (i.e., a specific proportion of amorphous silicon is converted into nanocrystalline silicon); further increasing the gas flow ratio of hydrogen silane, a boron-doped p-type nanocrystalline silicon layer is vertically grown on the nanocrystalline seeds of the back passivation layer, and the volume fraction of the crystal is 60-66%;

(5) Depositing cerium-doped indium oxide as a transparent conductive oxide layer, and then using non-contact laser transfer printing on the transparent conductive oxide layer.

Wherein, in step (2), during the continuous deposition of hydrogenated amorphous silicon oxide layer and hydrogenated amorphous silicon layer on the silicon substrate layer, the gas resistance in the working chamber is monitored in real time by a gas resistance sensor, and a diode with a density of 18 to 19/ ^cm2 is set on the surface of the sample stage (as a voltage sensor to feedback the bombardment intensity of the battery surface plasma) to detect the bombardment voltage on the battery surface. The resistance sensor transmits the collected gas resistance value and the voltage value of each point on the battery surface detected by the diode to the intelligent terminal of the system; the intelligent terminal switches the gas and adjusts the gas flow rate by controlling the opening of different types of gas inlet valves, so that the fluctuation value of the battery surface bombardment voltage is less than ±0.5% of the initial battery surface voltage value. Even during the gas switching or gas flow rate adjustment process, the gas resistance in the working chamber can be maintained constant, thereby achieving low damage to the surface of the passivation layer and avoiding damage to the passivation effect.

The specific process of continuously depositing the hydrogenated amorphous silicon oxide layer and the hydrogenated amorphous silicon layer is as follows: at 190°C, silane (SiH ₄ ) and CO ₂ are used as raw materials to grow an ultra-thin (<0.5nm) hydrogenated amorphous silicon oxide layer with a thickness of 2 to 3 atomic layers and anti-epitaxial growth on both sides (front and back) of the silicon substrate layer; the gas flow ratio of CO ₂ :SiH ₄ is 0.1 to 0.2:1; when transitioning from the hydrogenated amorphous silicon oxide layer to the hydrogenated amorphous silicon layer deposition, the CO ₂ is switched to the H ₂ inlet, and the H ₂ :SiH 4 ratio is adjusted. ₄ has a gas flow ratio of 18 to 20:1, so that the plasma fluctuation voltage is <±0.5%, and another non-epitaxial hydrogenated amorphous silicon layer is deposited on the hydrogenated amorphous silicon oxygen sub-monolayer; the present invention can realize the continuous deposition of hydrogenated amorphous silicon oxygen layer and hydrogenated amorphous silicon layer on the silicon substrate layer, that is, it can realize the natural interface transition from the first passivation layer to the second passivation layer, and the whole passivation process protects the fine amorphous layer from plasma damage, especially the damage of the ultra-thin hydrogenated amorphous silicon oxygen layer, thereby effectively improving its ability to prevent epitaxial growth; the surface of the passivation layer obtained by the method of the present invention is complete, as shown in Figure 3, and the photoelectric conversion efficiency of the battery of the present invention is greatly improved.

Wherein, in step (4), a phosphorus-doped n-type nanocrystalline silicon oxide layer is vertically grown on the nanocrystalline seeds of the passivation layer (hydrogenated amorphous silicon layer) when the gas flow ratio of _H2 : _SiH4 : _PH3 is 720-780:5:0.1 and the gas flow ratio of _CO2 : _SiH4 is 0.5±0.2; the _CO2 inlet is disconnected, and the gas flow ratio of hydrogen silane is further increased to a gas flow ratio of _H2 : _SiH4 : _B2H6 of 2500-2900:5:0.1, and a boron-doped p-type nanocrystalline silicon layer is vertically grown on the nanocrystalline _seeds of the back passivation layer.

Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the present invention can produce silicon heterojunction solar cells with a photoelectric conversion efficiency higher than 26% at a thickness of 55 to 130 μm, and obtains photoelectric conversion efficiencies of 26.06%, 26.19%, 26.50%, 26.56% and 26.79% at thicknesses of 57, 74, 84, 106 and 125 μm, respectively; among them, the open circuit voltage of a 57 μm thick battery reaches 761 mV, which is the highest value among current c-Si solar cells; the power-to-weight ratio of a 57 μm thick battery reaches 1.9 W·g ^-1 , which is the highest level of c-Si solar cells; at the same time, battery thinning also brings about a significant improvement in flexibility, so that the battery curvature radius can reach 19.6 mm (57 μm), which opens up new possibilities for drones, spacecraft and other applications that require extremely high weight and flexibility.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram of a double-sided silicon heterojunction solar cell according to the present invention;

FIG2 is a schematic structural diagram of a single-sided silicon heterojunction solar cell according to the present invention;

FIG3 is a high-resolution transmission electron microscope photograph of a cross section of a silicon heterojunction solar cell of Example 1;

FIG4 (a) is an atomic force microscope photograph and roughness of the passivation layer obtained by conventional discontinuous plasma enhanced chemical vapor deposition; FIG4 (b) is an atomic force microscope photograph and roughness of the passivation layer obtained by low-damage continuous plasma enhanced chemical vapor deposition adopted in Example 1;

FIG5 is a graph showing the relationship between the main performance of the silicon heterojunction solar cell according to the present invention and the thickness;

FIG6 shows the anti-potential induced degradation performance and anti-light induced degradation performance of the silicon heterojunction solar cell of the present invention.

DETAILED DESCRIPTION

Example 1

As shown in FIG1 , the bendable silicon heterojunction solar cell of the present invention with high photoelectric conversion efficiency comprises a silicon substrate layer 1; a hydrogenated amorphous silicon oxide layer 2, a hydrogenated amorphous silicon layer 3, an n-type hydrogenated nanocrystalline silicon oxide layer 4 and a transparent conductive oxide layer 6 are sequentially deposited on the front side of the silicon substrate layer 1; a hydrogenated amorphous silicon oxide layer 2, a hydrogenated amorphous silicon layer 3, a p-type hydrogenated nanocrystalline silicon layer 5 and a transparent conductive oxide layer 6 are sequentially deposited on the back side of the silicon substrate layer 1; a metal electrode 7 is printed on the transparent conductive oxide layer 6; wherein the metal electrodes 7 printed on the transparent conductive oxide layer 6 on the front and back sides of the silicon substrate layer 1 are both in the form of grid lines.

Among them, the silicon base layer 1 is n-type single crystal silicon, the surface adopts a texturing structure, and the thickness of the silicon base layer 1 is 57μm; the thickness of the hydrogenated amorphous silicon oxygen layer 2 is less than 0.5nm, wherein the oxygen atom content is 10at.%, and the hydrogen content is 26.3at.%; the thickness of the hydrogenated amorphous silicon layer 3 is 4.5nm, wherein the hydrogen content is 19.2at.%; the thickness of the n-type hydrogenated nanocrystalline silicon oxygen layer 4 is 15nm, and the volume fraction of the crystal is 43.7%; the thickness of the p-type hydrogenated nanocrystalline silicon layer 5 is 22nm, and the volume fraction of the crystal is 63.4%; the transparent conductive oxide layer 6 is cerium-doped indium oxide, and the thickness is 70nm; the metal electrode 7 is a silver electrode, and the width of the silver electrode in the form of a gate line is 18μm.

The method for preparing the above silicon heterojunction solar cell comprises the following steps:

(1) The silicon substrate layer is thinned and textured, specifically: the silicon wafer is selected as n-type Czochralski c-Si single crystal silicon with a thickness of 150 μm and a size of M6 (166×166 mm±0.25), with a (100) orientation and a resistivity of 1 to 3 Ω·cm; the silicon wafer is immersed in a KOH solution with a mass fraction of 10% for isotropic chemical etching, and the etching time is about 1200 s to reduce the thickness of the wafer; the silicon wafer is textured in a KOH solution with an additive added to form a tetrahedral pyramid with a size of 3 to 9 μm and an exposed (111) crystal plane on the wafer surface, and then chemically etched with a HF solution with a mass fraction of 1 to 2% to remove the natural SiO _x film on the wafer surface. The average thickness of each group of wafers is measured by weighing method with an accuracy of ±0.5 μm;

(2) continuously depositing a hydrogenated amorphous silicon oxide layer and a hydrogenated amorphous silicon layer on the silicon substrate layer to form a passivation layer, specifically: using a radio frequency enhanced plasma chemical vapor deposition (RF-PECVD) (13.56 MHz) system, at 190°C, using _SiH4 and _CO2 as raw materials to grow an ultra-thin (<0.5 nm) hydrogenated amorphous silicon oxide layer with a thickness of 2 to 3 atomic layers and capable of resisting epitaxial growth on both sides (front and back sides) of the silicon substrate layer; the gas flow ratio of _CO2 : _SiH4 is 0.15:1; when transitioning from the hydrogenated amorphous silicon oxide layer to the hydrogenated amorphous silicon layer deposition, _CO2 is switched to _H2 inlet gas, and the gas flow ratio of _H2 : _SiH4 is adjusted to 19:1, so that the plasma fluctuation voltage is <±0.5%, and another non-epitaxial hydrogenated amorphous silicon layer is deposited on the hydrogenated amorphous silicon oxide sub-monolayer;

During the continuous deposition of hydrogenated amorphous silicon oxide layer and hydrogenated amorphous silicon layer on the silicon substrate layer, the gas resistance in the working chamber is monitored in real time by a gas resistance sensor, and diodes (voltage sensors for feedback of the bombardment intensity (bombardment voltage) of the battery surface plasma) with a density of 18 to 19/ ^cm2 are arranged on the battery surface to detect the bombardment voltage on the battery surface; the resistance sensor transmits the collected gas resistance value and the bombardment voltage value of each point on the battery surface detected by the diode to the intelligent terminal of the system; the intelligent terminal switches the gas and adjusts the intake flow rate of each gas by controlling the opening of each gas intake pipe valve, so that the fluctuation value of the battery surface bombardment voltage is less than ±0.5% of the initial battery surface voltage value;

(3) Plasma pretreatment is performed on the passivation layer using a mixture of CO ₂ and H ₂ to achieve seeding of nanocrystals on the surface of the passivation layer, specifically: a doped contact layer is prepared by a self-recovering nanocrystal seeding and vertical growth induction (NSVGI) method, and the surface of the hydrogenated amorphous silicon layer is pretreated with a mixture of CO ₂ and H ₂ by a very high frequency plasma chemical vapor deposition (VHF-PECVD) method (40.68 MHz) (the flow ratio of CO ₂ :H ₂ is 1:20, and the treatment time is 20 to 50 s); nanocrystal seeds are seeded and the hydrogen content in the passivation layer is retained, so that the passivation layer maintains an optimal passivation effect, and the nanocrystal seeding can be limited to the surface of the passivation layer, which can, on the one hand, induce the vertical growth of the subsequent doped nanocrystal junction, and on the other hand, will not destroy the passivation effect of the passivation layer;

(4) Under the conditions of H ₂ :SiH ₄ :PH ₃ gas flow ratio of 750:5:0.1 and CO ₂ :SiH ₄ gas flow ratio of 0.5±0.2, a 15 nm thick phosphorus-doped n-type nanocrystalline silicon oxide layer (n ⁺ :nc-SiO _x :H) was vertically grown on the nanocrystal seeds of the passivation layer as an electron collection layer, with a crystal volume fraction of 43.7%, and the optical band gap was optimal at this crystallinity; for the back junction, the CO ₂ inlet was disconnected, and the gas flow ratio of hydrogen silane was further increased to H ₂ :SiH ₄ :B ₂ H ₆ gas flow ratio of 2700:5:0.1, and a 22 nm thick boron-doped p-type nanocrystalline silicon layer (p ⁺ :nc-Si:H) was vertically grown on the nanocrystal seeds of the back passivation layer, with a crystal volume fraction of 63.4%; n ⁺ :nc-SiO _x :H and p ⁺ :nc-Si:H contacts are grown in the same chamber with a substrate temperature of 170°C; optimization of the crystal volume fraction of the doped contact layer can improve the fill factor and conversion efficiency of the cell;

(5) Using an indium oxide (In ₂ O ₃ ) target doped with 2.8 wt.% Ce, a 70 nm cerium-doped indium oxide layer was deposited on both sides on a low-damage reactive plasma deposition (RPD) sputtering tool with high-purity argon (Ar) as the sputtering gas at a substrate temperature of 100°C. During the RPD process, the ion bombardment voltage was less than 30 eV to avoid damage to the nanocrystalline junction and the passivation layer; silver grid lines with a line width of 18 μm were printed by non-contact laser transfer, and the aspect ratio was optimized to 0.7;

(6) using a thermal evaporation device to cover the front of the battery with a 80 nm thick magnesium fluoride (MgF ₂ ) layer; or using a thermal evaporation device to cover both the front and back of the battery with a 80 nm thick MgF ₂ layer, either method is acceptable;

(7) The current-voltage (J-V) curve test was carried out under the AM 1.5 spectrum, and the photoelectric conversion efficiency was 26.06%.

Only the etching time is adjusted, and the other process parameters remain unchanged. The preparation process of Example 1 can also be used to obtain batteries with thicknesses of 74, 84, 106, and 125 μm. The J-V curve test of the batteries with thicknesses of 74, 84, 106, and 125 μm under the AM 1.5 spectrum shows that the photoelectric conversion efficiencies are 26.19%, 26.50%, 26.56%, and 26.79%, respectively.

FIG3 is a high-resolution transmission electron microscope photograph of a battery cross section, from which it can be observed that there is no epitaxial growth in the passivation layer and that the nanocrystals of the doped contact layer grow vertically; FIG4a shows that discontinuous plasma is used, and the passivation layer has multiple perforations and high damage; FIG4b shows that continuous plasma is used, and the passivation layer is intact and smooth with low damage; FIG5 shows the performance parameters of batteries of different thicknesses (57 to 125 μm) prepared by the method of the present invention, from which it can be seen that the battery obtained by the method of the present invention has good conversion efficiency, fill factor, open circuit voltage, and short circuit current.

FIG6 shows that batteries of different thicknesses (57 to 125 μm) prepared by the method of the present invention all have reliable weather resistance.

Example 2

As shown in FIG2 , the bendable silicon heterojunction solar cell with high photoelectric conversion efficiency of the present invention comprises a silicon substrate layer 1; a hydrogenated amorphous silicon oxide layer 2, a hydrogenated amorphous silicon layer 3, an n-type hydrogenated nanocrystalline silicon oxide layer 4 and a transparent conductive oxide layer 6 are sequentially deposited on the front side of the silicon substrate layer 1; a hydrogenated amorphous silicon oxide layer 2, a hydrogenated amorphous silicon layer 3, a p-type hydrogenated nanocrystalline silicon layer 5 and a transparent conductive oxide layer 6 are sequentially deposited on the back side of the silicon substrate layer 1; a metal electrode 7 is printed on the transparent conductive oxide layer 6; wherein the metal electrode 7 printed on the transparent conductive oxide layer 6 on the front side of the silicon substrate layer 1 is in the form of a grid line, and the transparent conductive oxide layer 6 on the back side of the silicon substrate layer 1 entirely covers the metal electrode.

Among them, the silicon base layer 1 is n-type single crystal silicon, the surface adopts a texturing structure, and the thickness of the silicon base layer 1 is 57μm; the thickness of the hydrogenated amorphous silicon oxygen layer 2 is less than 0.5nm, wherein the oxygen atom content is 10at.%, and the hydrogen content is 26.3at.%; the thickness of the hydrogenated amorphous silicon layer 3 is 4.5nm, wherein the hydrogen content is 19.2at.%; the thickness of the n-type hydrogenated nanocrystalline silicon oxygen layer 4 is 15nm, and the volume fraction of the crystal is 43.7%; the thickness of the p-type hydrogenated nanocrystalline silicon layer 5 is 22nm, and the volume fraction of the crystal is 63.4%; the transparent conductive oxide layer 6 is cerium-doped indium oxide, and the thickness is 70nm; the metal electrode 7 is a silver electrode, and the width of the silver electrode in the form of a grid line on the front of the battery is 18μm, and the back of the battery is fully covered, that is, the back is fully brushed with silver paste.

The method for preparing the above silicon heterojunction solar cell comprises the following steps:

(1) The silicon substrate layer is thinned and textured, specifically: the silicon wafer is selected as n-type Czochralski c-Si single crystal silicon with a thickness of 150 μm and a size of M6 (166×166 mm±0.25), with a (100) orientation and a resistivity of 1 to 3 Ω·cm; the silicon wafer is immersed in a KOH solution with a mass fraction of 10% for isotropic chemical etching, and the etching time is about 1200 s to reduce the thickness of the wafer; the silicon wafer is textured in a KOH solution with an additive added to form a tetrahedral pyramid with a size of 3 to 9 μm and an exposed (111) crystal plane on the wafer surface, and then chemically etched with a HF solution with a mass fraction of 1 to 2% to remove the natural SiO _x film on the wafer surface. The average thickness of each group of wafers is measured by weighing method with an accuracy of ±0.5 μm;

(2) continuously depositing a hydrogenated amorphous silicon oxide layer and a hydrogenated amorphous silicon layer on the silicon substrate layer to form a passivation layer, specifically: using an RF-PECVD (13.56 MHz) system, at 190°C, using _SiH4 and _CO2 as raw gas to grow an ultra-thin (<0.5 nm) hydrogenated amorphous silicon oxide layer with a thickness of 2 to 3 atomic layers and capable of resisting epitaxial growth on both sides (front and back sides) of the silicon substrate layer; the gas flow ratio of _CO2 : _SiH4 is 0.15:1; when transitioning from the hydrogenated amorphous silicon oxide layer to the hydrogenated amorphous silicon layer deposition, _CO2 is switched to _H2 inlet gas, and the gas flow ratio of _H2 : _SiH4 is adjusted to 19:1, so that the plasma fluctuation voltage is <±0.5%, and another non-epitaxial hydrogenated amorphous silicon layer is deposited on the hydrogenated amorphous silicon oxide sub-monolayer;

During the continuous deposition of hydrogenated amorphous silicon oxide layer and hydrogenated amorphous silicon layer on the silicon substrate layer, the gas resistance in the working chamber is monitored in real time by a gas resistance sensor, and diodes (voltage sensors for feedback of the bombardment intensity (bombardment voltage) of the battery surface plasma) with a density of 18 to 19/ ^cm2 are arranged on the battery surface to detect the bombardment voltage on the battery surface; the resistance sensor transmits the collected gas resistance value and the bombardment voltage value of each point on the battery surface detected by the diode to the intelligent terminal of the system; the intelligent terminal switches the gas and adjusts the intake flow rate of each gas by controlling the opening of each gas intake pipe valve, so that the fluctuation value of the battery surface bombardment voltage is less than ±0.5% of the initial battery surface voltage value;

(3) Plasma pretreatment is performed on the passivation layer using a mixture of CO ₂ and H ₂ to achieve seeding of nanocrystals on the surface of the passivation layer, specifically: a doped contact layer is prepared by an NSVGI method, and a surface of a hydrogenated amorphous silicon layer is pretreated by a mixture of CO ₂ and H ₂ using a VHF-PECVD method (40.68 MHz) (the flow ratio of CO ₂ :H ₂ is 1:20, and the treatment time is 20 to 50 s); nanocrystal seeds are seeded and the hydrogen content in the passivation layer is retained, so that the passivation layer maintains an optimal passivation effect, and the seeding of nanocrystals can be limited to the surface of the passivation layer, which can, on the one hand, induce the vertical growth of subsequent doped nanocrystal junctions, and on the other hand, will not destroy the passivation effect of the passivation layer;

(4) Under the conditions of H ₂ :SiH ₄ :PH ₃ gas flow ratio of 750:5:0.1 and CO ₂ :SiH ₄ gas flow ratio of 0.5±0.2, a 15 nm thick phosphorus-doped n ⁺ :nc-SiO _x :H layer was vertically grown on the nanocrystal seeds of the passivation layer as an electron collection layer, with a crystal volume fraction of 43.7%, and the optical band gap was optimal at this crystallinity; for the back junction, the CO ₂ gas inlet was disconnected, and the gas flow ratio of hydrogen silane was further increased to H ₂ :SiH ₄ :B ₂ H ₆ gas flow ratio of 2700:5:0.1, and a 22 nm thick boron-doped p ⁺ :nc-Si:H layer was vertically grown on the nanocrystal seeds of the back passivation layer, with a crystal volume fraction of 63.4%; n ⁺ :nc-SiO _x :H and p ⁺ :nc-Si:H contacts are grown in the same chamber with a substrate temperature of 170°C; optimization of the crystal volume fraction of the doped contact layer can improve the fill factor and conversion efficiency of the cell;

(5) Using an In ₂ O ₃ target doped with 2.8 wt.% Ce, on a low-damage RPD sputtering tool, with high-purity Ar as the sputtering gas, at a substrate temperature of 100°C, a 70 nm cerium-doped indium oxide layer was deposited on both sides. During the RPD process, the ion bombardment voltage was less than 30 eV to avoid damage to the nanocrystalline junction and the passivation layer; a silver grid line with a line width of 18 μm was printed on the front of the battery by non-contact laser transfer, and the aspect ratio was optimized to 0.7; and silver paste was applied to the back of the battery;

(6) Using a thermal evaporation device to cover the front of the battery with a 80 nm thick MgF2 _layer ; or using a thermal evaporation device to cover both the front and back of the battery with a 80 nm thick MgF2 _layer , either method is acceptable;

(7) The J-V curve test was carried out under the AM 1.5 spectrum, and the photoelectric conversion efficiency was 26.11%.

Claims (10)

1. A bendable silicon heterojunction solar cell with high photoelectric conversion efficiency, characterized in that: it comprises a silicon substrate layer (1); a hydrogenated amorphous silicon oxide layer (2), a hydrogenated amorphous silicon layer (3), an n-type hydrogenated nanocrystalline silicon oxide layer (4) and a transparent conductive oxide layer (6) are sequentially deposited on the front side of the silicon substrate layer (1); a hydrogenated amorphous silicon oxide layer (2), a hydrogenated amorphous silicon layer (3), a p-type hydrogenated nanocrystalline silicon layer (5) and a transparent conductive oxide layer (6) are sequentially deposited on the back side of the silicon substrate layer (1); and a metal electrode (7) is printed on the transparent conductive oxide layer (6). 2. The bendable silicon heterojunction solar cell with high photoelectric conversion efficiency according to claim 1 is characterized in that: the metal electrodes (7) printed by contactless laser transfer printing on both the front and back transparent conductive oxide layers (6) of the silicon substrate layer (1) are in the form of grid lines; or the metal electrodes (7) printed by contactless laser transfer printing on the front transparent conductive oxide layer (6) of the silicon substrate layer (1) are in the form of grid lines, and the transparent conductive oxide layer (6) on the back of the silicon substrate layer (1) is fully covered with metal electrodes. 3. According to claim 1, the bendable silicon heterojunction solar cell with high photoelectric conversion efficiency is characterized in that the silicon base layer (1) is n-type single crystal silicon, the surface adopts a texturing structure, and the thickness of the silicon base layer (1) is less than 130 μm. 4. The bendable silicon heterojunction solar cell with high photoelectric conversion efficiency according to claim 1 is characterized in that: the thickness of the hydrogenated amorphous silicon oxygen layer (2) is less than 0.5 nm, wherein the oxygen atom content is 8 to 12 at.%, and the hydrogen content is 22 to 30 at.%; the thickness of the hydrogenated amorphous silicon layer (3) is 4 to 5 nm, wherein the hydrogen content is 18 to 25 at.%. 5. The bendable silicon heterojunction solar cell with high photoelectric conversion efficiency according to claim 1 is characterized in that: the thickness of the n-type hydrogenated nanocrystalline silicon oxide layer (4) is 12 to 18 nm, and the volume fraction of the crystal is 40 to 46%; the thickness of the p-type hydrogenated nanocrystalline silicon layer (5) is 20 to 25 nm, and the volume fraction of the crystal is 60 to 66%. 6. The bendable silicon heterojunction solar cell with high photoelectric conversion efficiency according to claim 1 is characterized in that: the transparent conductive oxide layer (6) is cerium-doped indium oxide; the metal electrode (7) is a silver electrode, and the width of the silver electrode in the form of a grid line is 16 to 18 μm. 7. The method for preparing a silicon heterojunction solar cell according to claim 1, characterized in that it comprises the following steps: (1) Thinning and texturing the silicon base layer; (2) continuously depositing a hydrogenated amorphous silicon oxide layer and a hydrogenated amorphous silicon layer on the silicon base layer to form a composite passivation layer; (3) using a mixture of carbon dioxide (CO ₂ ) and hydrogen (H ₂ ) to perform plasma pretreatment on the passivation layers on both sides to achieve nanocrystal seeding on the shallow surface of the passivation layer; (4) under a high hydrogen silane gas flow ratio, a phosphorus-doped n-type nanocrystalline silicon oxide layer is vertically grown on the front passivation layer seeded with nanocrystals, and the volume fraction of the crystal is 40-46%; further increasing the hydrogen silane gas flow ratio, a boron-doped p-type nanocrystalline silicon layer is vertically grown on the back passivation layer seeded with nanocrystals, and the volume fraction of the crystal is 60-66%; (5) Depositing cerium-doped indium oxide as a transparent conductive oxide layer, and then using non-contact laser transfer printing on the transparent conductive oxide layer. 8. The method for preparing a silicon heterojunction solar cell according to claim 7 is characterized in that, in step (2), during the continuous deposition of the hydrogenated amorphous silicon oxide layer and the hydrogenated amorphous silicon layer on the silicon substrate layer, the gas resistance in the working chamber is monitored in real time by a gas resistance sensor, and diodes with a density of 18 to 19 per ^cm2 are arranged on the surface of the sample stage to detect the plasma bombardment voltage on the battery surface; the resistance sensor transmits the collected gas resistance value and the voltage value of each point on the battery surface detected by the diode to the intelligent terminal of the system; the intelligent terminal switches the gas and adjusts the gas flow rate by controlling the opening of different types of gas inlet valves, so that the fluctuation value of the battery surface bombardment voltage is less than ±0.5% of the initial battery surface voltage value. 9. The method for preparing a silicon heterojunction solar cell according to claim 8 is characterized in that the specific process of continuously depositing a hydrogenated amorphous silicon oxide layer and a hydrogenated amorphous silicon layer is as follows: at 190-200° C., firstly, using silane and CO ₂ as raw material gases, a hydrogenated amorphous silicon oxide layer with a thickness of 2-3 atomic layers and resistant to epitaxial growth is grown on both sides of the silicon substrate layer; the gas flow ratio of CO ₂ :SiH ₄ is 0.1-0.2:1; when transitioning from the hydrogenated amorphous silicon oxide layer to the hydrogenated amorphous silicon layer deposition, CO ₂ is switched to H ₂ inlet gas, and the gas flow ratio of H ₂ :SiH ₄ is adjusted to 18-20:1, so that the plasma voltage fluctuation on the battery surface is <±0.5%, and another non-epitaxial hydrogenated amorphous silicon layer is deposited on the hydrogenated amorphous silicon oxide layer. 10. The method for preparing a silicon heterojunction solar cell according to claim 7, characterized in that, in step (4), a phosphorus-doped n-type nanocrystalline silicon oxide layer is vertically grown on the passivation layer nanocrystal seeds on the front side of the cell under a gas flow ratio of _H2 : _SiH4 : _PH3 of 720-780:5:0.1 and a _CO2 : _SiH4 gas flow ratio of 0.5±0.2; the gas flow ratio of hydrogen silane is further increased to a gas flow ratio of _H2 : _SiH4 : _B2H6 of 2500-2900:5 _: 0.1, and a boron-doped p-type nanocrystalline silicon layer is vertically grown on the passivation layer nanocrystal seeds on the back side of the cell.