CN110718597A - N-type local high-low junction back surface field double-sided solar cell and preparation process thereof - Google Patents

Abstract

The invention discloses an n-type local high-low junction back surface field double-sided solar cell and a preparation process thereof, and relates to the technical field of solar cells. The invention comprises an n-type silicon substrate, and the bottom of the n-type silicon substrate is provided with The silicon oxide passivation layer, the intrinsic amorphous silicon layer and the backside silicon nitride anti-reflection layer, a number of phosphorus source doped layers are embedded at the bottom of the n-type silicon substrate, and the bottom of the phosphorus source doped layer is connected to the bottom of the silicon oxide. The backside metal electrode layer of the passivation layer, the intrinsic amorphous silicon layer and the backside silicon nitride anti-reflection layer, during preparation, several partial grooves are opened on the lower surface of the backside silicon nitride anti-reflection layer by laser, and the partial grooves are all opened to At the bottom of the n-type silicon substrate, the phosphorus source paste is printed in the slotted area to form a high-low junction structure, which improves the open circuit voltage of the back cell of the double-sided solar cell. The heavily doped area of the slotted phosphorus source paste contacts the metal electrode to form an ohmic contact Lowering the series resistance increases the fill factor and increases the bifacial ratio of the cell without reducing the front-side efficiency.

Description

An n-type local high-low junction back surface field bifacial solar cell and its fabrication process

technical field

The invention relates to the technical field of solar cells, in particular to an n-type local high-low junction back surface field double-sided solar cell and a preparation process thereof.

Background technique

In recent years, the vigorous development of renewable energy has been increasing, and the more popular renewable energy fields include solar energy, wind energy, and tidal energy. Compared with traditional energy, solar energy has the characteristics of simple utilization, safety, and no pollution, and has become the focus of research in the field of renewable new energy. The basic principle of solar cell power generation is the photovoltaic effect. Solar cells are new energy devices that convert sunlight into electrical energy. With the increase in the application field of solar power generation, new policies and other preferential issues, the cost of photovoltaic power generation needs to be greatly reduced. The cost reduction of photovoltaic power generation needs to improve efficiency and reduce costs in the field of battery manufacturing. The problems of low conversion efficiency and low power generation of traditional single-sided power generation cells require researchers engaged in solar cell research to study double-sided solar cells to save silicon substrate materials and increase power generation. Bifacial cells can be used in lakes to form complementary fishing and light, and can also be used in highways, photovoltaic building integration, snow, etc. The back of the solar cell makes full use of diffuse reflected light to increase the power generation of bifacial solar cells.

For the existing n-type silicon substrate double-sided solar cell, the lower surface of the double-sided solar cell is made of a laminated film of Al2O3 and silicon nitride. Bifacial solar cells have low back cell efficiency and low bifacial ratio.

Therefore, how to solve the above-mentioned technical problems has practical significance for those skilled in the art.

SUMMARY OF THE INVENTION

The purpose of the present invention is: in order to solve the technical problem that the filling factor and open circuit voltage of the existing n-type silicon substrate double-sided solar cells are relatively low, resulting in low efficiency of the double-sided solar cells on the back of the solar cells, and the double-sided ratio is also relatively low, the present invention Provided are an n-type local high-low junction back surface field double-sided solar cell and a preparation process thereof.

The present invention specifically adopts the following technical solutions in order to achieve the above object:

An n-type local high-low junction back surface field double-sided solar cell includes an n-type silicon substrate, and the bottom of the n-type silicon substrate is provided with a silicon oxide passivation layer, an intrinsic amorphous silicon layer and a backside nitride from top to bottom Silicon anti-reflection layer, a number of phosphorus source doped layers are embedded at the bottom of the n-type silicon substrate, and the bottom of the phosphorus source doped layer is connected with the passivation layer of silicon oxide, the intrinsic amorphous silicon layer and the backside silicon nitride anti-reflection layer. The backside metal electrode layer of the reverse layer.

Further, the top of the n-type silicon substrate is provided with a boron source doped layer and a front silicon nitride antireflection layer in sequence from bottom to top, and the upper surface of the boron source doped layer is provided with a number of corresponding phosphorus source doped layers. The front-side metal electrode layer of the front-side metal electrode layer penetrates the front-side silicon nitride anti-reflection layer.

Further, the front metal electrode layer and the back metal electrode layer are Ag or Ag alloy or alloy formed by Cu or Cu and at least one of Mo, W, Ti, Ni, Al, Mg, Ta, Sn.

Further, the thickness of the n-type silicon substrate is 100-160um, the thickness of the boron source doping layer is 300-500nm, the thickness of the front silicon nitride antireflection layer is 80-100nm, and the thickness of the silicon oxide passivation layer is 1-10nm. The thickness of the amorphous silicon layer is 2-10 nm, the thickness of the silicon nitride antireflection layer on the back is 100-150 nm, and the thickness of the phosphorus source doped layer is 300-500 nm.

Further, the width of the electrode grid lines of the back metal electrode layer and the front metal electrode layer are both 40-80um, and the heights are both 25-50um.

A preparation process of an n-type local high-low junction back surface field double-sided solar cell, comprising the following steps:

S1: select an n-type silicon substrate, clean the n-type silicon substrate, and perform surface polishing;

S2: perform low-pressure thermal diffusion on the upper surface of the n-type silicon substrate to prepare a boron source doped layer;

S3: Ozone oxidation is performed on the lower surface of the n-type silicon substrate to grow a silicon oxide passivation layer;

S4: preparing a front silicon nitride antireflection layer on the upper surface of the boron source doped layer;

S5: preparing an intrinsic amorphous silicon layer on the lower surface of the silicon oxide passivation layer;

S6: preparing a backside silicon nitride antireflection layer on the lower surface of the intrinsic amorphous silicon layer;

S7: Use laser to cut a number of local grooves on the lower surface of the backside silicon nitride antireflection layer. The local grooves are all opened to the bottom of the n-type silicon substrate. The depth of the grooves at the bottom of the n-type silicon substrate is 300-500nm. The distance between them is 3-5um, and then the phosphorus source doped layer is prepared by screen printing the phosphorus source paste in the partial groove until the lower surface of the phosphorus source doped layer is flush with the lower surface of the n-type silicon substrate, and the phosphorus source paste The main components include phosphoric acid with a concentration of 50%-70% and epoxy phosphate with a purity of 20%-50%;

S8: Perform screen printing on the lower surface of the phosphorus source doped layer in the partial groove to prepare the back metal electrode layer, and the back metal electrode layer passes through the silicon oxide passivation layer, the intrinsic amorphous silicon layer and the back silicon nitride anti-reflection layer in turn. Floor;

S9: Finally, screen printing is performed on the upper surface of the front-side silicon nitride antireflection layer to prepare a front-side metal electrode layer.

Further, in step S2, the doping concentration of the boron source doped layer is 10 ¹⁶ -10 ²⁰ /cm ³ .

Further, in step S3, the concentration of ozone during ozone oxidation is 5-20 g/m ³ .

Further, in step S4, the PECVD method is used to prepare the front side silicon nitride anti-reflection layer, the nitrogen source is nitrogen monoxide, and the plasma power density is 100-250mW/cm ² , and in step S6, the back side silicon nitride is prepared For the antireflection layer, the PECVD method is used, the nitrogen source is nitrogen monoxide, and the plasma power density is 100-250 mW/cm ² .

Further, in step S7, a green light source is used for laser grooving, the spot of the laser is 10-30 nm, and the scribing speed of the laser grooving is 20-30 m/s.

The beneficial effects of the present invention are as follows:

1. The present invention uses a laser to open a number of partial grooves, and the partial grooves pass through the silicon nitride antireflection layer on the back side, the intrinsic amorphous silicon layer and the silicon oxide passivation layer in turn, open to the bottom of the n-type silicon substrate, and then open the grooves at the bottom of the n-type silicon substrate. Phosphorus source paste is filled in the area of the solar cell to form a back-field high-low junction structure, and the composition ratio of the phosphorus source paste is reasonably prepared to improve the open circuit voltage of the back cell of the double-sided solar cell. The heavily doped area of the paste forms an ohmic contact, which reduces the series resistance of the battery, improves the photoelectric conversion efficiency and bifacial ratio of the back side of the double-sided solar cell without reducing the front-side efficiency, and increases the power generation of the battery module. It reduces the floor space of the power station, makes full use of the limited space resources, and saves the silicon substrate material. Tests show that the front efficiency of the battery prepared by the invention is over 22.38%, the double-sided ratio is over 78.4%, and the power generation gain is 5%-15%.

Description of drawings

1 is a schematic structural diagram of an n-type local high-low junction back surface field double-sided solar cell of the present invention;

FIG. 2 is a schematic structural diagram of an n-type local high-low junction back surface field single-sided solar cell in Example 2. FIG.

Reference numerals: 1- front metal electrode layer, 2- front silicon nitride anti-reflection layer, 3- boron source doped layer, 4- n-type silicon substrate, 5- phosphorus source doped layer, 6- silicon oxide passivation Chemical layer, 7-intrinsic amorphous silicon layer, 8-backside silicon nitride antireflection layer, 9-backside metal electrode layer, 10-aluminum backside field layer.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", The orientation or positional relationship indicated by "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying The device or element referred to must have a particular orientation, be constructed and operate in a particular orientation, and therefore should not be construed as a limitation of the present application.

The features and performances of the present invention will be further described in detail below in conjunction with the embodiments.

Example 1

As shown in FIG. 1 , this embodiment provides an n-type local high-low junction back surface field double-sided solar cell, including an n-type silicon substrate 4, and the bottom of the n-type silicon substrate 4 is provided with silicon oxide passivation from top to bottom Layer 6, intrinsic amorphous silicon layer 7 and backside silicon nitride anti-reflection layer 8, a number of phosphorus source doped layers 5 are embedded at the bottom of the n-type silicon substrate 4, and the bottom of the phosphorus source doped layer 5 is connected with simultaneous penetrations. The silicon oxide passivation layer 6 , the intrinsic amorphous silicon layer 7 and the backside metal electrode layer 9 of the backside silicon nitride antireflection layer 8 .

Several phosphorus source doped layers 5 are embedded at the bottom of the n-type silicon substrate 4 to form a back field high-low junction structure, which improves the open circuit voltage of the back side of the double-sided solar cell, and the back side metal electrode layer 9 is doped with the phosphorus source. The miscellaneous layer 5 forms an ohmic contact, which reduces the series resistance of the battery, improves the photoelectric conversion efficiency and bifacial ratio of the back side of the double-sided solar cell without reducing the front efficiency, increases the power generation of the battery module, and reduces the The power station covers an area and makes full use of the limited space resources, saving silicon substrate materials. Tests show that the front efficiency of the battery prepared by the invention is over 22.38%, the double-sided ratio is over 78.4%, and the power generation gain is 5%-15%.

As a preferred technical solution of the present embodiment:

The top of the n-type silicon substrate 4 is provided with a boron source doped layer 3 and a front silicon nitride antireflection layer 2 in sequence from bottom to top. A corresponding front-side metal electrode layer 1 , and the front-side metal electrode layer 1 penetrates the front-side silicon nitride anti-reflection layer 2 .

As a preferred technical solution of the present embodiment:

The front metal electrode layer 1 and the back metal electrode layer 9 are both Ag or Ag alloys or alloys formed by Cu or Cu and at least one of Mo, W, Ti, Ni, Al, Mg, Ta, and Sn, all of which meet the application requirements.

As a preferred technical solution of the present embodiment:

The thickness of the n-type silicon substrate 4 is 100-160um, the thickness of the boron source doped layer 3 is 300-500nm, the thickness of the front silicon nitride anti-reflection layer 2 is 80-100nm, the thickness of the silicon oxide passivation layer 6 is 1-10nm, The thickness of the intrinsic amorphous silicon layer 7 is 2-10 nm, the thickness of the backside silicon nitride antireflection layer 8 is 100-150nm, the thickness of the phosphorus source doped layer 5 is 300-500nm, the backside metal electrode layer 9 and the frontside metal electrode layer are The width of the electrode grid line of 1 is 40-80um, and its height is 25-50um, and the thickness of each layer is optimized to improve the battery performance.

The principles of the present invention can also be applied to single-sided solar cells, as shown in Example 2 below:

Example 2

As shown in FIG. 2 , this embodiment provides an n-type local high-low junction back surface field single-sided solar cell, including an n-type silicon substrate 4, and the bottom of the n-type silicon substrate 4 is provided with silicon oxide passivation from top to bottom Layer 6 and the backside silicon nitride antireflection layer 8, several phosphorus source doped layers 5 are embedded at the bottom of the n-type silicon substrate 4, and the bottom of the phosphorus source doped layer 5 is connected with the passivation layer 6 and the backside through the silicon oxide. The aluminum back field layer 10 of the silicon nitride anti-reflection layer 8, and the aluminum back field layer 10 extends out to cover the lower surface of the back silicon nitride anti-reflection layer 8, and the top of the n-type silicon substrate 4 is sequentially provided with a boron source from bottom to top The doped layer 3 and the front side silicon nitride antireflection layer 2, the upper surface of the boron source doped layer 3 is provided with a number of front side metal electrode layers 1 corresponding to the positions of the phosphorus source doped layer 5, and the front side metal electrode layers 1 all penetrate Front side silicon nitride anti-reflection layer 2.

Example 3

As shown in FIG. 1 , this embodiment provides a preparation process of an n-type local high-low junction back surface field double-sided solar cell, including the following steps:

S1: select an n-type silicon substrate 4, clean the n-type silicon substrate 4, and perform surface polishing;

S2: low-pressure thermal diffusion is performed on the upper surface of the n-type silicon substrate 4 to prepare the boron source doped layer 3;

S3: Ozone oxidation is performed on the lower surface of the n-type silicon substrate 4 to grow a silicon oxide passivation layer 6;

S4: preparing the front silicon nitride anti-reflection layer 2 on the upper surface of the boron source doped layer 3;

S5: preparing an intrinsic amorphous silicon layer 7 on the lower surface of the silicon oxide passivation layer 6;

S6: preparing a backside silicon nitride antireflection layer 8 on the lower surface of the intrinsic amorphous silicon layer 7;

S7: using a laser to cut a number of local grooves on the lower surface of the backside silicon nitride antireflection layer 8, the local grooves are all opened to the bottom of the n-type silicon substrate 4, and the depth of the grooves at the bottom of the n-type silicon substrate 4 is 300-500nm, The spacing between the local grooves is 3-5um, and then the phosphorus source doped layer 5 is prepared by screen printing the phosphorus source paste in the local groove until the lower surface of the phosphorus source doped layer 5 and the lower surface of the n-type silicon substrate 4 Flush, the main components of the phosphorus source slurry include phosphoric acid with a concentration of 50%-70% and epoxy phosphate with a purity of 20%-50%;

S8: Perform screen printing on the lower surface of the phosphorus source doped layer 5 in the partial groove to prepare the back metal electrode layer 9, and the back metal electrode layer 9 passes through the silicon oxide passivation layer 6, the intrinsic amorphous silicon layer 7 and the back surface in sequence Silicon nitride anti-reflection layer 8;

S9: Finally, screen printing is performed on the upper surface of the front silicon nitride anti-reflection layer 2 to prepare the front metal electrode layer 1 .

Further, in step S2, the doping concentration of the boron source doped layer 3 is 10 ¹⁶ -10 ²⁰ /cm ³ .

Further, in step S3, the concentration of ozone during ozone oxidation is 5-20 g/m ³ .

Further, in step S4, the PECVD method is used to prepare the front side silicon nitride anti-reflection layer 2, the nitrogen source is nitrogen monoxide, and the plasma power density is 100-250mW/cm ² , and in step S6, the backside nitridation is prepared The silicon anti-reflection layer 8 adopts the PECVD method, the nitrogen source is nitrogen monoxide, and the plasma power density is 100-250 mW/cm ² .

Further, in step S7, a green light source is used for laser grooving, the spot of the laser is 10-30 nm, and the scribing speed of the laser grooving is 20-30 m/s.

In this embodiment, a number of local grooves are formed by laser, and the local grooves pass through the silicon nitride antireflection layer 8 on the back side, the intrinsic amorphous silicon layer 7 and the silicon oxide passivation layer 6 in sequence, and are opened to the bottom of the n-type silicon substrate 4 , and then fill the grooved area with phosphorus source paste to form a back-field high-low junction structure, and rationally prepare the composition ratio of phosphorus source paste to improve the open circuit voltage of the back cell of the double-sided solar cell, and the back metal electrode layer 9 It forms ohmic contact with the heavily doped area of the laser grooved printed phosphorous paste, which reduces the series resistance of the cell, and improves the photoelectric conversion efficiency and bifacial ratio of the back cell of the double-sided solar cell without reducing the front-side efficiency.

The preparation process of the n-type local high-low junction back surface field single-sided solar cell in Example 2 is the same as that of Example 3 above.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. The scope of patent protection of the present invention is subject to the claims. Any equivalent structural changes made by using the contents of the description and drawings of the present invention, Similarly, all should be included in the protection scope of the present invention.

Claims (10)

1. An n-type local high-low junction back surface field double-sided solar cell, comprising an n-type silicon substrate (4), and the bottom of the n-type silicon substrate (4) is provided with a silicon oxide passivation layer (6) from top to bottom , an intrinsic amorphous silicon layer (7) and a backside silicon nitride antireflection layer (8), characterized in that a number of phosphorus source doped layers (5) are embedded at the bottom of the n-type silicon substrate (4), and the phosphorus source The bottom of the source doped layer (5) is connected with a backside metal electrode layer (9) penetrating the silicon oxide passivation layer (6), the intrinsic amorphous silicon layer (7) and the backside silicon nitride antireflection layer (8) at the same time. 2. A kind of n-type local high-low junction back surface field double-sided solar cell according to claim 1, characterized in that, the top of the n-type silicon substrate (4) is sequentially provided with a boron source doped layer ( 3) and the front side silicon nitride antireflection layer (2), the upper surface of the boron source doped layer (3) is provided with a number of front side metal electrode layers (1) corresponding to the positions of the phosphorus source doped layer (5) one-to-one. The metal electrode layers (1) all penetrate the front silicon nitride antireflection layer (2). 3. a kind of n-type local high-low junction back surface field double-sided solar cell according to claim 2, is characterized in that, front metal electrode layer (1) and back metal electrode layer (9) are Ag or Ag alloy or An alloy of Cu or Cu and at least one of Mo, W, Ti, Ni, Al, Mg, Ta, Sn. 4. A kind of n-type local high-low junction back surface field double-sided solar cell according to claim 2, characterized in that, the thickness of the n-type silicon substrate (4) is 100-160um, and the boron source doped layer (3) The thickness is 300-500nm, the thickness of the front silicon nitride antireflection layer (2) is 80-100nm, the thickness of the silicon oxide passivation layer (6) is 1-10nm, and the thickness of the intrinsic amorphous silicon layer (7) is 2-10nm , the thickness of the backside silicon nitride antireflection layer (8) is 100-150nm, and the thickness of the phosphorus source doped layer (5) is 300-500nm. 5. A kind of n-type local high-low junction back surface field double-sided solar cell according to any one of claims 2 to 4, characterized in that the back metal electrode layer (9) and the front metal electrode layer (1) The width of the electrode grid lines is 40-80um, and the height is 25-50um. 6. A preparation process for an n-type local high-low junction back surface field double-sided solar cell, characterized in that, comprising the following steps: S1: select an n-type silicon substrate (4), clean the n-type silicon substrate (4), and perform surface polishing; S2: performing low-pressure thermal diffusion on the upper surface of the n-type silicon substrate (4) to prepare a boron source doped layer (3); S3: Ozone oxidation is performed on the lower surface of the n-type silicon substrate (4) to grow a silicon oxide passivation layer (6); S4: preparing a front silicon nitride antireflection layer (2) on the upper surface of the boron source doped layer (3); S5: preparing an intrinsic amorphous silicon layer (7) on the lower surface of the silicon oxide passivation layer (6); S6: preparing a backside silicon nitride antireflection layer (8) on the lower surface of the intrinsic amorphous silicon layer (7); S7: using a laser to cut a number of local grooves on the lower surface of the backside silicon nitride antireflection layer (8), the local grooves are all opened to the bottom of the n-type silicon substrate (4), and the bottom of the n-type silicon substrate (4) is grooved The depth is 300-500nm, the spacing between the partial grooves is 3-5um, and then the phosphorous source doped layer (5) is prepared by screen printing the phosphorous source paste in the partial grooves until under the phosphorous source doped layer (5) The surface is flush with the lower surface of the n-type silicon substrate (4), and the main components of the phosphorus source slurry include phosphoric acid with a concentration of 50%-70% and epoxy phosphate with a purity of 20%-50%; S8: screen printing is performed on the lower surface of the phosphorus source doped layer (5) in the partial groove to prepare the back metal electrode layer (9), and the back metal electrode layer (9) passes through the silicon oxide passivation layer (6), the an amorphous silicon layer (7) and a backside silicon nitride antireflection layer (8); S9: Finally, screen printing is performed on the upper surface of the front-side silicon nitride antireflection layer (2) to prepare a front-side metal electrode layer (1). 7 . The preparation process of an n-type local high-low junction back surface field double-sided solar cell according to claim 6 , wherein in step S2 , the doping concentration of the boron source doped layer ( 3 ) is 10 ¹⁶ . 10 ²⁰ /cm ³ . 8 . The preparation process of an n-type local high-low junction back surface field double-sided solar cell according to claim 6 , wherein, in step S3 , the concentration of ozone during ozone oxidation is 5-20 g/m ³ . 9. The preparation technology of a kind of n-type local high-low junction back surface field double-sided solar cell according to claim 6, wherein in step S4, PECVD is adopted when preparing the front silicon nitride antireflection layer (2). method, the nitrogen source is nitrogen monoxide, the plasma power density is 100-250 mW/cm ² , in step S6, the PECVD method is used when preparing the backside silicon nitride anti-reflection layer (8), the nitrogen source is nitrogen monoxide, and the plasma The bulk power density is 100-250 mW/cm ² . 10. The preparation process of an n-type local high-low junction back surface field double-sided solar cell according to claim 6, wherein in step S7, a green light source is used when the laser is slotted, and the laser spot is 10 -30nm, the scribing speed of laser grooving is 20-30m/s.

Images