CN105826405A - Mono-crystalline silicon double-sided solar cell and preparation method thereof - Google Patents

Abstract

The invention discloses a monocrystalline silicon double-sided solar cell, which belongs to the technical field of solar cells. A front pyramid-shaped suede surface, a front doped emitter junction, a front passivation antireflection medium layer and a front surface of a single crystal silicon substrate are sequentially formed. The front electrode, on the back of the single crystal silicon substrate, forms the back pyramid-shaped suede, the back surface field, the back passivation anti-reflection medium layer and the back electrode in sequence, and it is characterized in that: the back pyramid-shaped suede is a separated pyramid shape On the suede surface, the pyramid structure only partially covers the single crystal silicon substrate, and the pyramid structure is scattered on the silicon substrate, and the area covered by the pyramid structure accounts for 20%-90% of the silicon substrate on the back side. At the same time, the invention also discloses a preparation method of a single-crystal silicon double-sided solar cell. The invention can optimize the minority carrier surface recombination and optical absorption characteristics of the double-sided solar cell, and improve the quantum conversion efficiency.

Description

A kind of monocrystalline silicon double-sided solar cell and its preparation method

technical field

The invention relates to a solar cell and a preparation method thereof, in particular to a single crystal silicon double-sided solar cell and a preparation method thereof, belonging to the technical field of solar cells.

Background technique

The pursuit of improving battery conversion efficiency while reducing or even maintaining manufacturing costs is the goal that the industry is constantly pursuing and where it can improve its own competitiveness. Compared with traditional crystalline silicon solar cells that receive light on one side, double-sided solar cells use two light-receiving surfaces, the front and the back, to obtain higher photocurrent densities and greatly increase power generation. Depending on the installation ground and environment, a photovoltaic power generation system based on bifacial solar cells can achieve a power gain of 10 to 30%.

The structure of double-sided solar cells includes: front and back textured surface structures, pn junction emitters, passivation anti-reflection dielectric layers, front and back electrodes, etc. Among them, the suede on the back can effectively improve the absorption of ground and ambient reflected light on the back of the double-sided solar cell, which is an important structure of the double-sided solar cell. At present, the back of the double-sided solar cell adopts a texture structure similar to that of the front, that is, the pyramids obtained by texture are closely distributed and overlap each other. Although such densely distributed pyramids are good for maximizing the absorption of direct light, they are not necessarily the optimal light-absorbing structure for diffuse reflection light, and the higher surface area will bring minority carrier recombination. Therefore, the back structure of double-sided solar cells needs to be further optimized.

Contents of the invention

The present invention aims at the above-mentioned technical problems existing in the prior art, and provides a monocrystalline silicon double-sided solar cell, which optimizes the minority carrier surface load and optical absorption characteristics of the solar cell, and improves the quantum conversion efficiency.

Another aspect of the present invention provides a method for preparing a monocrystalline silicon double-sided solar cell, which improves the conversion efficiency and production efficiency of the solar cell.

For this reason, the present invention adopts following technical scheme:

A monocrystalline silicon double-sided solar cell, in which a front pyramid-shaped suede surface (101), a front doped emitter junction (102), and a front passivation anti-reflection dielectric layer (103) are sequentially formed on the front surface of a single crystal silicon substrate (100). ) and the front electrode (104), on the back of the single crystal silicon substrate sequentially form the back pyramid-shaped suede (105), the back surface field (106), the back passivation anti-reflection dielectric layer (107) and the back electrode (108) , characterized in that: the back pyramid-shaped suede (105) is a separated pyramid-shaped suede, the pyramid structure (105a) only partially covers the monocrystalline silicon substrate, and the pyramid structure (105a) is dispersedly distributed on the silicon substrate On the top, the area covered by the pyramid structure (105a) accounts for 20%-90% of the back silicon substrate.

Further, the base length of a single pyramid structure (105a) is 1-7 μm.

Further, the front passivation anti-reflection dielectric layer (103) and the back passivation anti-reflection dielectric layer (107) are respectively made of silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, silicon carbide, amorphous silicon, Microcrystalline silicon, indium tin oxide or titanium oxide is a single-layer film or multi-layer film composed of materials.

Further, the front electrode (104) and the back electrode (108) are one or more metals of silver, aluminum, copper, nickel, titanium, tin, lead, cadmium, gold, zinc or alloys thereof.

Another aspect of the present invention provides a method for preparing a single-crystal silicon double-sided solar cell, which is used to prepare the single-crystal silicon double-sided solar cell, comprising the following steps:

S1: Texturing on the surface of a single crystal silicon substrate;

S2: The front side is doped to form an emitter junction;

S3: removing the impurity-containing glass layer on the back;

S4: Wet chemical method to prepare the back separation pyramid structure, and remove the doping layer on the back;

S5: Back doping forms a back surface field;

S6: preparing front and back passivation anti-reflection medium layers;

S7: preparing front and back electrodes.

In step S4, the chemical agents used to prepare the rear separation pyramid structure by wet chemical method include sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, nitric acid, phosphoric acid, hydrofluoric acid, ethanol, isopropanol or One or two or more mixed aqueous solutions of ethylene glycol; the preparation temperature is 60 to 80°C, and the time is 10-900 seconds.

Further, between steps S2 and S3, the following steps may also be included: S2-1: depositing a barrier layer on the front side.

Further, between steps S5 and S6, the following steps are also included: S5-1: using hydrofluoric acid to remove silicon oxide, phosphosilicate glass on the front and borosilicate glass on the back.

The monocrystalline silicon double-sided solar cell of the present invention reduces the surface area of the back surface of the solar cell by arranging a separate pyramid-shaped textured surface on the back side of the battery, and significantly reduces the recombination of photogenerated minority carriers on the back surface; The reflection of long-wavelength light on the back surface increases, the transmission decreases, and is absorbed by the solar cell again; at the same time, the back is covered with an anti-reflection medium layer, and the optical reflection on the back does not increase significantly, ensuring the optical absorption characteristics of the back. Therefore, the minority carrier surface recombination and optical absorption properties of double-sided solar cells can be optimized to improve the quantum conversion efficiency by separating the pyramidal topography on the back side.

The preparation method of the monocrystalline silicon double-sided solar cell of the present invention only needs to add a wet chemical method to prepare the rear separation pyramid structure, the process is relatively simple, and it is suitable for low-cost, large-volume, and stable industrial manufacturing.

Description of drawings

Fig. 1 is the structural representation of monocrystalline silicon double-sided solar cell of the present invention;

Fig. 2 is the micrograph of separation type pyramidal suede of the present invention;

Among them, 100 is a single crystal silicon substrate, 101 is a pyramid-shaped suede surface on the front side, 102 is a doped emitter junction on the front side, 103 is a passivation anti-reflection dielectric layer on the front side, 104 is a front electrode, 105 is a pyramid-shaped suede surface on the back side, 105a 106 is the back surface field, 107 is the passivation anti-reflection dielectric layer on the back, 108 is the back electrode, and 109 is the area not covered by the pyramid structure; the corresponding product structure in the figure is only a schematic diagram and is not drawn to scale.

detailed description

In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention.

Example 1:

This embodiment is the case where the present invention is applied to P-type single crystal silicon. As shown in FIG. 1 , a front pyramid-shaped textured surface 101, a front phosphorus-doped emitter junction 102, a front passivation anti-reflection dielectric layer 103, and a front electrode 104 are sequentially formed on the front surface of a P-type single crystal silicon substrate 100. The rear side of the single crystal silicon substrate is sequentially formed with a back separated pyramid-shaped textured surface 105, a boron-doped back surface field 106 formed by boron doping on the back side, a back passivation anti-reflection dielectric layer 107, and a back electrode 108, wherein, as shown in FIG. 2 As shown, in the back separation type pyramid-shaped suede 105, the pyramid structure 105a only partially covers the single crystal silicon substrate, and the pyramid structure 105a is scatteredly distributed on the back side of the single crystal silicon substrate, leaving some not covered by the pyramid structure. Area 109.

In this embodiment, the area covered by the pyramid structure 105a accounts for 85% of the entire backside silicon substrate, and the base length of a single pyramid structure 105a is 5 μm; the front passivation anti-reflection dielectric layer 103 is made of silicon nitride Single-layer film with a film thickness of 70 to 80 nm; the back passivation anti-reflection dielectric layer 107 is a double-layer film made of aluminum oxide and silicon nitride, wherein the film thickness of aluminum oxide is 20 to 30 nm and the film thickness of silicon nitride is 50 to 50 nm. 70nm. Both the front electrode 104 and the back electrode 108 are silver grid electrodes.

Example 2:

The difference between this embodiment and Embodiment 1 is: in the back separated pyramid-shaped suede 105, the area covered by the pyramid structure 105a accounts for 50% of the entire back silicon substrate, and the base length of a single pyramid structure 105a is 7 μm . The front passivation anti-reflection medium layer 103 is a single-layer film made of silicon oxynitride with a film thickness of 70 to 80 nm; the back passivation anti-reflection medium layer 107 is a double-layer film made of titanium oxide and silicon oxide, wherein, The titanium oxide film has a thickness of 20 to 30 nm and the silicon oxide film has a thickness of 50 to 70 nm. Both the front electrode 104 and the back electrode 108 are copper electrodes.

Example 3:

This embodiment is a case where the present invention is applied to N-type single crystal silicon. As shown in FIG. 1, a front pyramid-shaped textured surface 101, a front boron-doped emitter junction 102, a front passivation anti-reflection dielectric layer 103, and a front electrode 104 are sequentially formed on the front surface of an N-type single crystal silicon substrate 100. The rear side of the monocrystalline silicon substrate is sequentially formed with a rear separated pyramid-shaped textured surface 105, a phosphorus-doped rear surface field 106 formed by doping the rear phosphorus, a rear passivation anti-reflection dielectric layer 107, and a rear electrode 108, wherein the rear separation In the type pyramid-shaped suede surface 105, the pyramid structure 105a only partially covers the single crystal silicon substrate, and the pyramid structures 105a are scatteredly distributed on the back side of the single crystal silicon substrate, and the area covered by the pyramid structure 105a accounts for the whole back side of the silicon substrate. 30%, the base length of a single pyramid structure 105a is 2 μm.

In this embodiment, the front passivation anti-reflection dielectric layer 103 is a double-layer film made of aluminum oxide and silicon nitride, wherein the thickness of the aluminum oxide film is 20 to 30 nm and the thickness of the silicon nitride film is 50 to 70 nm; The passivation anti-reflection medium layer 107 is a single-layer film made of silicon nitride with a film thickness of 70 to 80 nm; both the front electrode 104 and the back electrode 108 are silver grid electrodes.

Example 4:

The difference between this embodiment and Embodiment 3 is: in the back separated pyramid-shaped suede 105, the area covered by the pyramid structure 105a accounts for 65% of the entire back silicon substrate, and the base length of a single pyramid structure 105a is 4 μm . The front passivation anti-reflection dielectric layer 103 is a double-layer film made of indium tin oxide and amorphous silicon, wherein the thickness of the indium tin oxide film is 60 to 80 nm and the thickness of the amorphous silicon film is 5 to 20 nm; The dielectric layer 107 is a double-layer film made of indium tin oxide and amorphous silicon, wherein the film thickness of indium tin oxide is 60-80 nm and the film thickness of amorphous silicon is 5-20 nm; the front electrode 104 and the back electrode 108 are both silver electrodes.

Example 5:

A method for preparing a monocrystalline silicon double-sided solar cell, for preparing the P single-crystalline silicon double-sided solar cell described in Example 1, comprising the steps of:

S1: Texturing on the surface of a single crystal silicon substrate: Use an alkaline texturing solution containing sodium hydroxide and isopropanol at a temperature of 80°C to texture the surface of the p-type single crystal silicon substrate 100 to form a front pyramid Shape the suede 101, and remove the silicon wafer cutting damage layer at the same time;

S2: Front doping to form an emitter junction: Phosphorus doping is performed to form a front doped emitter junction 102. Phosphorus doping can be diffused in a tube furnace with a phosphorus oxychloride source, ion implantation, or diffusion by coating a phosphorus-containing impurity layer. Square resistance is 40 to 200Ω/□;

S2-1: Deposition barrier layer on the front side: use PECVD to deposit a process barrier layer of silicon oxide film on the front side, with a thickness of 50 to 300 nm;

S3: Removing the impurity-containing glass layer on the back: using hydrofluoric acid to remove the phosphosilicate glass layer on the back;

S4: Preparation of back-separated pyramid-shaped suede by wet chemical method, and removal of doping on the back: using an alkaline solution containing tetramethylammonium hydroxide and isopropanol, the temperature is 80°C, and the time is 10 to 900s. Forming the rear separated pyramid-shaped suede 105, while removing the phosphorus-doped layer on the rear;

S5: back surface doping to form back surface field: perform boron doping to form back surface field 106, boron doping can adopt tube furnace diffusion of boron tribromide source, ion implantation or diffusion of coating boron-containing impurity layer, the diffusion method Resistance is 60 to 200Ω/□;

S5-1: Use hydrofluoric acid to remove silicon oxide, phosphosilicate glass on the front and borosilicate glass on the back;

S6: Preparation of front and back passivation anti-reflection dielectric layers: PECVD is used to prepare front-side silicon nitride 103 and rear-side aluminum oxide/silicon nitride passivation anti-reflection dielectric layer 107; Aluminum thickness is 20 to 30nm, silicon nitride thickness is 50 to 70nm;

S7: Preparing front and back electrodes: using screen printing to prepare silver-containing grid wire electrodes 104 and 108 on the front and back sides, respectively, and sintering at a high temperature at a temperature of 850 to 900°C.

Certainly, in step S4, an acid solution containing nitric acid and hydrofluoric acid may also be used to prepare the back-separated pyramid-shaped suede.

The preparation method of embodiment 2 refers to the preparation method of embodiment 1.

Embodiment 6:

A method for preparing a monocrystalline silicon double-sided solar cell, which is used to prepare the N single-crystalline silicon double-sided solar cell described in Example 3, comprising the steps of:

S1: Texturing on the surface of the single crystal silicon substrate: use an alkaline texturing solution containing sodium hydroxide and isopropanol at a temperature of 80°C to make texturing on the surface of the n-type single crystal silicon substrate 100 to form a front texture Surface morphology 101, while removing the silicon wafer cutting damage layer;

S2: front-side doping to form an emitter junction: perform boron doping to form a front-side boron-doped emitter junction 102, phosphorus doping can be diffused in a tube furnace with a boron tribromide source, ion implantation or diffusion coated with a boron-containing impurity layer, Diffusion square resistance is 60 to 200Ω/□;

S2-1: Deposition barrier layer on the front side: use PECVD to deposit a process barrier layer of silicon oxide film on the front side, with a thickness of 50 to 300 nm;

S3: remove the impurity glass layer on the back: use hydrofluoric acid to remove the borosilicate glass layer on the back;

S4: Preparation of back-separated pyramid-shaped suede by wet chemical method, and removal of doping on the back: using an alkaline solution containing tetramethylammonium hydroxide and isopropanol, the temperature is 80°C, and the time is 10 to 900s. Pyramidal suede 105 on the back side, while removing the boron doped layer on the back side;

S5: Doping on the back to form a back surface field: Phosphorus doping is performed to form a back surface field 106. The phosphorus doping can be diffused in a tube furnace with phosphorus oxychloride source, ion implantation or diffusion coated with a phosphorus-containing impurity layer. The diffusion method Resistance is 40 to 200Ω/□;

S5-1: Use hydrofluoric acid to remove silicon oxide, borosilicate glass on the front and phosphosilicate glass on the back;

S6: Preparation of the front and back passivation anti-reflection dielectric layers: PECVD is used to prepare the passivation anti-reflection dielectric layer 107 of the front aluminum oxide/silicon nitride, 103 and the back silicon nitride; the thickness of the front aluminum oxide is 20 to 30 nm, The thickness of silicon is 50 to 70nm; the thickness of silicon nitride on the back is 70 to 80nm;

S7: Preparing front and back electrodes: using screen printing to prepare silver-containing grid wire electrodes 104 and 108 on the front and back sides, respectively, and sintering at a high temperature at a temperature of 850 to 900°C.

The preparation method of embodiment 4 refers to the preparation method of embodiment 3.

Apparently, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

Claims (8)

1. a monocrystal silicon double-side solar cell, front pyramid matte (101) is sequentially formed in the front of monocrystalline substrate (100), front doping emitter junction (102), front passivated reflection reducing dielectric layer (103) and front electrode (104), back side pyramid matte (105) is sequentially formed at the back side of monocrystalline substrate, back surface field (106), passivating back anti-reflection dielectric layer (107) and backplate (108), it is characterized in that: described back side pyramid matte (105) is divergence type pyramid floss face, pyramid structure (105a) only partially covers monocrystalline substrate, pyramid structure (105a) is distributed on a silicon substrate dispersedly, the region covered by pyramid structure (105a) accounts for the 20%-90% of back side silicon substrate.

Monocrystal silicon double-side solar cell the most according to claim 1, it is characterised in that: the bottom side length of single pyramid structure (105a) is 1-7 μm.

Monocrystal silicon double-side solar cell the most according to claim 1, it is characterised in that: it is the monofilm that forms of material or multilayer film that described front passivated reflection reducing dielectric layer (103) and passivating back anti-reflection dielectric layer (107) are respectively by silicon oxide, silicon nitride, silicon oxynitride, aluminium oxide, carborundum, non-crystalline silicon, microcrystal silicon, tin indium oxide or titanium oxide.

Monocrystal silicon double-side solar cell the most according to claim 1, it is characterised in that: described front electrode (104), backplate (108) they are silver, aluminum, copper, nickel, titanium, stannum, lead, cadmium, gold, one or more metals of zinc or its alloy.

5. a preparation method for monocrystal silicon double-side solar cell, is used for preparing the arbitrary described monocrystal silicon double-side solar cell of claim 1-4, comprises the steps:

S1: at monocrystalline substrate surface wool manufacturing；

The doping of S2: front forms emitter junction；

S3: remove the impure glassy layer in the back side；

S4: wet chemistry method prepares back side separation pyramid appearance structure, and removes back side doped layer；

The doping of S5: the back side forms back surface field；

S6: preparation front, passivating back anti-reflection dielectric layer；

S7: preparation front, backplate.

The preparation method of monocrystal silicon double-side solar cell the most according to claim 5, it is characterized in that: in step s 4, wet chemistry method prepares the chemical agent that separation pyramid appearance structure in the back side used aqueous solutions of one or more mixing in sodium hydroxide, potassium hydroxide, Tetramethylammonium hydroxide, nitric acid, phosphoric acid, Fluohydric acid., ethanol, isopropanol or ethylene glycol；Preparation temperature is 60 to 80 DEG C, and the time is the 10-900 second.

The preparation method of monocrystal silicon double-side solar cell the most according to claim 5, it is characterised in that: between step S2 and S3, also comprise the steps

S2-1: deposition barrier layer, front: using PECVD is 50 to 300nm at the technique barrier layer of front precipitated silica thin film, thickness.

The preparation method of monocrystal silicon double-side solar cell the most according to claim 5, it is characterised in that: between step S5 and S6, also comprise the steps

S5-1: use Fluohydric acid. to remove the silicon oxide in front, phosphorosilicate glass and the Pyrex at the back side.