CN105261665A - A kind of crystalline silicon solar cell with high-efficiency light-trapping structure and its preparation method - Google Patents

Abstract

The invention discloses a crystalline silicon solar cell with a high-efficiency light tripping structure and a preparation method of the crystalline silicon solar cell. The cell comprises a front electrode layer, a transparent conductive antireflection layer, a light tripping P-type emission layer, an N-type absorption layer, an N+ doping layer and a back electrode layer in a light irradiation direction in sequence. A backlight surface of the N-type absorption layer is provided with the back electrode layer which forms ohmic contact with the N-type absorption layer. A sensitive surface of the N-type absorption layer is provided with blind holes which are of an inverted quadrangular frustum structure and which are distributed in a matrix. The method uses micromachining technologies such as photoetching for preparing a periodic ordered inverted quadrangular frustum-structured blind hole matrix array; a magnetron sputtering method is used for preparing the conductive antireflection layer; a screen printing technology is used for preparing a theta-shaped front electrode; and the sensitive surface of the electrode is a periodic ordered inverted quadrangular frustum-structured blind hole matrix which is special and which enables the cell to absorb more than 90% visible light.

Description

A kind of crystalline silicon solar cell with high-efficiency light-trapping structure and its preparation method

technical field

The invention belongs to the field of solar cells, and relates to a crystalline silicon solar cell with a high-efficiency light-trapping structure and a preparation method thereof, in particular to a novel monocrystalline silicon photovoltaic cell structure with a high absorption rate in visible light and a preparation method thereof.

Background technique

Solar cells are currently the most promising type of cells in the new energy industry, including monocrystalline silicon cells, polycrystalline silicon cells and thin-film cells. However, in the current solar cell market, monocrystalline silicon cells are still the main product. Improving the absorption of light by monocrystalline silicon solar cells is a major means to further improve monocrystalline silicon solar cells. Technicians in the field of photovoltaic cells have made a lot of technological innovations and improvements in improving the light absorption of crystalline silicon cells. Using the plasmon resonance absorption effect of metal nanoparticles to improve the light absorption of single crystal silicon solar cells, there are also literature reports (NanoLett. Absorption of light by crystalline silicon solar cells. However, these process methods are complicated and costly. Not only that, these several process methods can not play a very good role in enhancing the light absorption of monocrystalline silicon solar cells in the long-wave range.

Contents of the invention

The object of the present invention is to provide a crystalline silicon solar cell with an efficient light-trapping structure to address the deficiencies of the prior art. The monocrystalline silicon battery is because a periodic and ordered array of blind hole structures of inverted quadrangular prisms is prepared on the monocrystalline silicon wafer, so that it has a high absorption rate for light.

The monocrystalline silicon photovoltaic cell with high light-trapping effect of the present invention comprises a front electrode layer, a transparent conductive anti-reflection layer, a light-trapping P-type emission layer, an N-type absorption layer, an N ⁺ doped layer, and a back electrode layer sequentially from the direction of light irradiation Wherein the transparent conductive anti-reflection layer is a TCO layer, the P-type emission layer is used as the light-receiving surface of the monocrystalline silicon photovoltaic cell of the present invention, and the N-type absorbing layer is a monocrystalline silicon wafer as the backlight surface of the monocrystalline silicon photovoltaic cell of the present invention;

The backlight surface of the N-type absorbing layer is provided with a back electrode layer forming an ohmic contact with the N-type absorbing layer; the light-receiving surface of the N-type absorbing layer is provided with a number of blind holes with an inverted truss structure arranged in a matrix through a micromachining process. holes, and then through the diffusion and coating process, a P-type emitting layer and a TCO layer are sequentially arranged on the light-receiving surface of the N-type absorbing layer. This design makes the matrix array of periodic and ordered blind holes use light concentrating to enhance the absorption of sunlight by the battery; The distance between adjacent blind holes is 1-2um, preferably 1um; the top surface of the blind hole is a rectangle with a side length of 10-13um, the bottom surface is a rectangle with a side length of less than 1um, and the four side walls are inverted Isosceles trapezoid.

The front electrode is a sun-shaped aluminum electrode with a line width of 1-2mm. The sun-shaped design reduces the reflection of the front electrode to sunlight;

The TCO layer can be all transparent conductive films, such as ZnO, SnO2, ITO, etc. and their doped films;

The thickness of the P-type emission layer is within 500nm;

The N-type absorbing layer is a single crystal silicon wafer with a doping concentration of 1.0×10 ¹⁸ to 1.0×10 ¹⁹ , and a thickness of 100 to 300 μm;

The N ⁺ doped layer is heavily doped with a concentration above 1.0×10 ²⁰ , and any doping method can be used;

The back electrode is an aluminum electrode plate with a thickness of more than 100 nm;

Another object of the present invention is to provide a method for preparing the above-mentioned high-efficiency light-trapping monocrystalline silicon solar cell, the method comprising the following steps:

The monocrystalline silicon wafer is used as the N-type absorbing layer, and then a number of blind holes with inverted quadrangular truss structure are opened on the light-receiving surface by micro-processing technology, and these blind holes are distributed in a matrix periodic order array;

Preparing a P-type emission layer on the above-mentioned blind hole by a diffusion process;

Prepare N ⁺ doped layer on the backlight surface of N-type single wafer by diffusion process;

On the light-receiving surface of the P-type emission layer, the TCO layer is prepared by magnetron sputtering and other coating processes;

Use the screen printing process to print a Japanese-shaped aluminum electrode on the light-receiving surface of the TCO layer as the front electrode layer;

An aluminum electrode is printed on the backlight side of the N ⁺ doped layer as a back electrode layer by a screen printing process.

The beneficial effects of the present invention are: the present invention provides a monocrystalline silicon solar cell with a high-efficiency light-trapping structure and its preparation method, and combines the micromachining process to prepare an ordered array of blind hole matrix, and utilizes the light concentrating effect of the blind hole matrix, which is very The light absorption of the single crystal silicon solar cell in the visible light band is greatly improved, and the absorption rate of the single crystal silicon solar cell to light in the wavelength range of 550 to 1000nm can be realized to be over 90%.

Description of drawings

Fig. 1 is a schematic structural view of a periodic ordered blind hole matrix array of the present invention;

Fig. 2 is the sectional view of battery of the present invention;

Fig. 3 is the structural representation of front electrode of the present invention;

Fig. 4 is a scanning electron microscope picture of a periodic ordered blind hole matrix array formed on the light-receiving surface of the N-type absorbing layer through a three-dimensional processing process;

Fig. 5 is a scanning electron microscope picture of a blind hole with a single inverted quadrangular prism structure;

Fig. 6 is a scanning electron microscope picture of the cross-sectional structure of a blind hole with a single inverted quadrangular truss structure;

Figure 7 is the light absorption spectrum of a single crystal silicon photovoltaic cell with high light trapping effect in the wavelength range of 400-1000nm;

Among them, 1 is a periodic ordered blind hole matrix array, 2 is a conductive anti-reflection layer (TCO layer), 3 is a P-type emission layer, 4 is an N-type absorption layer, 5 is an N ⁺ doped layer, and 6 is a back electrode layer .

detailed description

The embodiments of the present invention are described in detail below. This embodiment is implemented under the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are provided, but the protection scope of the present invention is not limited to the following embodiments. .

The invention discloses a monocrystalline silicon photovoltaic cell with high light-trapping effect. The structure of the battery is: from the order of light irradiation, it includes a front electrode layer, a transparent conductive anti-reflection layer, a P-type emission layer, an N-type absorption layer, an N ⁺ doped layer, and a back electrode layer; the transparent conductive anti-reflection layer is a TCO layer, The P-type emission layer is used as the light-receiving surface of the monocrystalline silicon photovoltaic cell, and the N-type absorption layer is the monocrystalline silicon substrate, which is used as the backlight surface of the monocrystalline silicon photovoltaic cell;

The backlight surface of the N-type absorbing layer is provided with a back electrode layer forming an ohmic contact with the N-type absorbing layer; the light-receiving surface of the N-type absorbing layer is provided with a number of blind holes with an inverted truss structure arranged in a matrix through a micromachining process. holes, and then through the diffusion and coating process, a P-type emitting layer and a TCO layer are sequentially arranged on the light-receiving surface of the N-type absorbing layer. This design makes the matrix array of periodic and ordered blind holes use light concentrating to enhance the absorption of sunlight by the battery; The distance between adjacent blind holes is 1-2um, preferably 1um; the top surface of the blind hole is a rectangle with a side length of 10-13um, the bottom surface is a rectangle with a side length of less than 1um, and the four side walls are inverted Isosceles trapezoid.

The front electrode is a sun-shaped aluminum electrode with a line width of 1-2 mm. The sun-shaped design reduces the reflection of the front electrode to sunlight.

Example 1:

This embodiment includes the following steps:

Step (1), as shown in FIG. 1 , select an N-type single crystal silicon substrate 4 with a crystal plane of 001, and clean the surface of the single crystal silicon through a standard semiconductor cleaning process. A dense silicon nitride layer is deposited on the single crystal silicon wafer by plasma enhanced chemical vapor deposition (PECVD). The preparation conditions are: silane (SiH ₄ ) and ammonia gas diluted to 10% with nitrogen are used as reaction gases, the flow rate of silane gas is 30 sccm, the flow rate of ammonia gas is 60 sccm, and the vacuum degree of the back and bottom of the vacuum chamber is 3×10 ^-4 Pa , the working pressure is 20Pa, the substrate temperature is 300°C, and the plasma RF power is 80W. A silicon nitride layer was grown to a thickness of 0.25 µm under the above conditions. Then a layer of SiO ₂ is deposited on the single crystal silicon wafer coated with silicon nitride by magnetron sputtering. The preparation conditions are as follows: Ar is used as the sputtering gas, the flow rate is 20 sccm, the silicon target is used as the sputtering target, the sputtering pressure is 1Pa, and the radio frequency power is 100W. Then, through the photolithography process, combined with the etching process of silicon dioxide and silicon nitride with HF acid and phosphoric acid respectively, a periodic and ordered square window array with a side length of 10um is carved on the light-receiving surface of the single crystal silicon substrate; then there will be The N-type single crystal silicon substrate with a periodic ordered window array is placed in a high-concentration KOH solution for anisotropic etching, and finally a periodic and ordered inverted quadrangular blind hole array is formed on the light-receiving surface of the single crystal silicon substrate. 1. The actual single inverted quadrangular truss blind hole structure obtained by the process of step (1) is shown in Figure 5, and its cross-sectional view is shown in Figure 6. The actual periodic and ordered inverted quadrangular truss blind hole matrix array is shown in Figure 5. Shown in accompanying drawing 4.

Step (2), as shown in FIG. 2 , performs P-type diffusion on the light-receiving surface of the N-type single crystal silicon substrate by a gaseous source diffusion process to form a P-type diffusion layer 3 .

Step (3), as shown in Figure 2, utilizes the magnetron sputtering coating process, carries out sputter plating conductive anti-reflection layer 2 on the surface of the periodic and orderly inverted square blind hole matrix array obtained in step (2) (TCO membrane). The target material can be a ceramic target such as ITO, FTO, AZO, etc. The sputtering pressure is 0.5Pa, and O ₂ and Ar are fed into the sputtering process at the same time. The thickness of the TCO layer is 50-100 nm.

Step (3), as shown in accompanying drawing 2, carry out N ⁺ doping on the backlight surface of N-type substrate, form N ⁺ doped layer 5; To the realization of preparing N ⁺ doped layer, adopt rapid annealing process scheme, in The backlight surface of the N-type absorbing layer is coated with 50% phosphoric acid, and then placed in a rapid annealing furnace for annealing.

In step (4), the aluminum electrode 6 plate is printed on the backlight surface of the N ⁺ doped layer by screen printing technology.

Step (5), screen printing aluminum electrodes 7 on the TCO film obtained in step 4. The aluminum electrode is a zigzag electrode with a width of 2 mm, as shown in Figure 3.

Step (6), sintering the N-type monocrystalline silicon substrate at a temperature of 400 degrees, so that the aluminum electrode and the N ⁺ doped layer form an ohmic contact.

Step (7), sintering the N-type monocrystalline silicon substrate at a temperature of 400 degrees to crystallize the TCO thin film obtained in step 5 to enhance conductivity.

Step (8), using an ultraviolet-visible spectrometer to test the light absorption spectrum of the prepared monocrystalline silicon solar cell with a periodic inverted quadrangular blind hole matrix structure, the obtained light absorption in the wavelength range of 400-1000nm The spectrum is shown in Figure 7.

Example 2:

This embodiment includes the following steps:

Step (1), as shown in FIG. 1 , select an N-type single crystal silicon substrate 4 with a crystal plane of 001, and clean the surface of the single crystal silicon through a standard semiconductor cleaning process. Put the cleaned substrate into an atmosphere furnace filled with high-purity nitrogen to grow a silicon nitride film at a temperature of 1000°C. Then a layer of SiO2 is deposited on the single crystal silicon wafer coated with silicon nitride by plasma enhanced chemical vapor deposition (PECVD) process. The preparation conditions are: silane (SiH ₄ ) and N ₂ O diluted to 10% by nitrogen gas are used as reaction gases, the flow rate of silane gas is 30 sccm, the flow rate of N ₂ O gas is 25 sccm, and the vacuum degree of the back of the vacuum chamber is 3×10 ^{− 4} Pa, the working pressure is 10Pa, the substrate temperature is 300°C, and the RF power is 200W. A silicon oxide layer was grown to a thickness of 0.1 µm under the above conditions. Then, through the photolithography process, combined with the etching process of silicon dioxide and silicon nitride with HF acid and phosphoric acid respectively, a periodic and ordered square window array with a side length of 10um is carved on the light-receiving surface of the single crystal silicon substrate; then there will be The N-type single crystal silicon substrate of the periodic ordered window array is placed in a high concentration KOH solution for anisotropic etching, and finally a periodic ordered inverted quadrangular truss blind hole matrix is formed on the light receiving surface of the single crystal silicon substrate array1. The actual single inverted quadrangular truss blind hole structure obtained by the process of step (1) is shown in Figure 5, and its cross-sectional view is shown in Figure 6. The actual periodic and ordered inverted quadrangular truss blind hole matrix array is shown in Figure 5. Shown in accompanying drawing 4.

Step (2), as shown in accompanying drawing 2, utilize diffusion process to the N-type monocrystalline silicon substrate that has periodic ordered inverted quadrangular truss blind hole matrix array surface obtained in step (1) to carry out P-type diffused type layer Launch 3: Perform P-type rapid annealing process on N-type single crystal silicon substrates, coat the P-type light-receiving surface with 50% boric acid, and then put it into a rapid annealing furnace for annealing at a temperature of 950°C.

Step (3), as shown in Figure 2, utilizes the magnetron sputtering coating process, carries out sputter plating conductive anti-reflection layer 2 on the surface of the periodic and orderly inverted square blind hole matrix array obtained in step (2) (TCO membrane). The target material can be a ceramic target such as ITO, FTO, AZO, etc. The sputtering pressure is 0.5Pa, and O ₂ and Ar are fed into the sputtering process at the same time. The thickness of the TCO layer is 50-100 nm.

Step (3), as shown in accompanying drawing 2, carry out N ⁺ doping on the backlight surface of N-type substrate, form N ⁺ doped layer 5; To the realization of preparing N ⁺ doped layer, adopt rapid annealing process scheme, in The N-type backlight is coated with 50% phosphoric acid, and then placed in a rapid annealing furnace for annealing.

In step (4), the electrode 6 plate is sputtered and deposited on the N ⁺ doped layer through a magnetron sputtering coating process.

Step (5), screen printing aluminum electrodes 7 on the TCO film obtained in step 4. The aluminum electrode is a zigzag electrode with a width of 2 mm, as shown in Figure 3 .

Step (6), sintering the N-type monocrystalline silicon substrate at a temperature of 400 degrees, so that the aluminum electrode and the N ⁺ doped layer form an ohmic contact

Step (7), sintering the N-type monocrystalline silicon substrate at a temperature of 400 degrees to crystallize the TCO thin film obtained in step 5 to enhance conductivity.

Step (8), using a UV-visible spectrometer to test the light absorption spectrum of the prepared monocrystalline silicon solar cell with a periodic and ordered inverted quadrangular blind hole matrix array structure, the obtained light is in the range of 400-1000nm The light absorption spectrum of is shown in accompanying drawing 7.

Example 3:

This embodiment includes the following steps:

Step (1), as shown in FIG. 1 , select an N-type single crystal silicon substrate 4 with a crystal plane of 001, and clean the surface of the single crystal silicon through a standard semiconductor cleaning process. Then a layer of silicon nitride is deposited on the single crystal silicon wafer coated with silicon nitride by magnetron sputtering process. The preparation conditions are: argon is used as the sputtering gas, the gas flow rate is 20 sccm, nitrogen is used as the reaction gas, the flow rate is 10 sccm, the vacuum degree of the back and bottom of the vacuum chamber is 3×10 ^-4 Pa, the sputtering pressure is 1 Pa, and the sputtering target The material is a high-purity silicon target, and the RF power is 100W. A silicon nitride layer was grown to a thickness of 0.2 µm under the above conditions. Then, a layer of silicon dioxide is deposited on the single crystal silicon wafer coated with silicon nitride by magnetron sputtering process. The preparation conditions are: argon is used as the sputtering gas, the gas flow rate is 20 sccm, the vacuum degree of the back and bottom of the vacuum chamber is 3×10 ^-4 Pa, the sputtering pressure is 1 Pa, and the sputtering target is a high-purity silicon dioxide target. The RF power is 200W. A silicon dioxide layer was grown to a thickness of 0.2 µm under the above conditions. Then, through the photolithography process, combined with the etching process of silicon dioxide and silicon nitride with HF acid and phosphoric acid respectively, a periodic and ordered square window array with a side length of 10um is carved on the light-receiving surface of the single crystal silicon substrate; then there will be The N-type single crystal silicon substrate of the periodic ordered window array is placed in a high concentration KOH solution for anisotropic etching, and finally a periodic ordered inverted quadrangular truss blind hole matrix is formed on the light receiving surface of the single crystal silicon substrate array1. The actual single inverted pyramid structure obtained by using the step (1) process is shown in Figure 5, its cross-sectional view is shown in Figure 6, and the actual periodic and ordered inverted quadrangular truss blind hole matrix array is shown in Figure 4 shown.

Step (2), as shown in accompanying drawing 2, utilize diffusion process to the N-type monocrystalline silicon substrate that has periodic ordered inverted quadrangular truss blind hole matrix array surface obtained in step (1) to carry out P-type diffused type layer Launch 3: Perform P-type rapid annealing process on N-type single crystal silicon substrates, coat the P-type light-receiving surface with 50% boric acid, and then put it into a rapid annealing furnace for annealing at a temperature of 950°C.

Step (3), as shown in Figure 2, utilizes the magnetron sputtering coating process, carries out sputter plating conductive anti-reflection layer 2 on the surface of the periodic and orderly inverted square blind hole matrix array obtained in step (2) (TCO membrane). The target material can be a ceramic target such as ITO, FTO, AZO, etc. The sputtering pressure is 0.5Pa, and O ₂ and Ar are fed into the sputtering process at the same time. The thickness of the TCO layer is 50-100 nm.

Step (3), as shown in accompanying drawing 2, carry out N ⁺ doping on the backlight surface of N-type substrate, form N ⁺ doped layer 5; The realization of preparing N ⁺ doped layer is diffused by gaseous source diffusion process .

In step (4), the electrode 6 plate is sputtered and deposited on the N ⁺ doped layer through a magnetron sputtering coating process.

Step (5), screen printing aluminum electrodes 7 on the TCO film obtained in step 4. The aluminum electrode is a zigzag electrode with a width of 2 mm, as shown in Figure 3 .

Step (6), sintering the N-type monocrystalline silicon substrate at a temperature of 400 degrees, so that the aluminum electrode and the N ⁺ doped layer form an ohmic contact.

Step (7), sintering the N-type monocrystalline silicon substrate at a temperature of 400 degrees to crystallize the TCO thin film obtained in step 5 to enhance conductivity.

Step (8), using an ultraviolet-visible spectrometer to test the light absorption spectrum of the prepared monocrystalline silicon solar cell with a periodic inverted quadrangular blind hole matrix structure, the obtained light absorption in the wavelength range of 400-1000nm The spectrum is shown in Figure 7.

The contents not described in detail in the description of the present invention belong to the prior art known to those skilled in the art. The above embodiments do not limit the present invention, and the present invention is not limited to the above embodiments, as long as the requirements of the present invention are met, they all belong to the protection scope of the present invention.

Claims (10)

1. there is a crystal silicon solar energy battery for efficient light trapping structure, it is characterized in that comprising front electrode layer, electrically conducting transparent antireflection layer successively from light direction of illumination, falling into light P type emission layer, N-type absorbed layer, N ⁺doped layer, dorsum electrode layer;

The shady face of described N-type absorbed layer is provided with the dorsum electrode layer forming ohmic contact with N-type absorbed layer; The sensitive surface of N-type absorbed layer has the blind hole of some inversion truncated rectangular pyramids structures in matrix distribution.

2. there is a preparation method for the crystal silicon solar energy battery of efficient light trapping structure, it is characterized in that the method is as follows:

Using monocrystalline silicon piece as N-type absorbed layer, then utilize micro fabrication to have the blind hole of some inversion truncated rectangular pyramids structures at its sensitive surface, these blind holes are the distribution of matrix periodic ordered array;

Adopt diffusion technology in above-mentioned blind hole, prepare P type emission layer;

Diffusion technology is adopted to prepare N at N-type single-chip shady face ⁺doped layer;

The coating process such as magnetron sputtering are utilized to prepare tco layer at the sensitive surface of P type emission layer;

Electrode layer before utilizing silk-screen printing technique to print on the sensitive surface of tco layer;

Utilize silk-screen printing technique at N ⁺the shady face printing of doped layer and N-type absorbed layer form the dorsum electrode layer of ohmic contact.

3. as claimed in claim 1 a kind of there is efficient light trapping structure crystal silicon solar energy battery or a kind of preparation method with the crystal silicon solar energy battery of efficient light trapping structure as claimed in claim 2, it is characterized in that the spacing distance in blind hole matrix array between adjacent blind hole is 1 ~ 2um.

4. as claimed in claim 1 a kind of there is efficient light trapping structure crystal silicon solar energy battery or a kind of preparation method with the crystal silicon solar energy battery of efficient light trapping structure as claimed in claim 2, it is characterized in that the spacing distance in blind hole matrix array between adjacent blind hole is 1um.

5. as claimed in claim 1 a kind of there is efficient light trapping structure crystal silicon solar energy battery or a kind of preparation method with the crystal silicon solar energy battery of efficient light trapping structure as claimed in claim 2, it is characterized in that the end face of blind hole in blind hole matrix array to be the length of side be the rectangle of 10 ~ 13um, bottom surface is the rectangle that the length of side is less than 1um, and four sidewalls are inverted isosceles trapezoid.

6. as claimed in claim 1 a kind of there is efficient light trapping structure crystal silicon solar energy battery or a kind of preparation method with the crystal silicon solar energy battery of efficient light trapping structure as claimed in claim 2, it is characterized in that described front electrode is day font aluminium electrode, live width is 1 ~ 2mm.

7. as claimed in claim 1 a kind of there is efficient light trapping structure crystal silicon solar energy battery or a kind of preparation method with the crystal silicon solar energy battery of efficient light trapping structure as claimed in claim 2, it is characterized in that the thickness of described P type emission layer is within 500nm.

8. as claimed in claim 1 a kind of there is efficient light trapping structure crystal silicon solar energy battery or a kind of preparation method with the crystal silicon solar energy battery of efficient light trapping structure as claimed in claim 2, it is characterized in that described N-type absorbed layer be doping content is 1.0 × 10 ¹⁸~ 1.0 × 10 ¹⁹monocrystalline silicon piece, thickness is 100 ~ 300um.

9. as claimed in claim 1 a kind of there is efficient light trapping structure crystal silicon solar energy battery or a kind of preparation method with the crystal silicon solar energy battery of efficient light trapping structure as claimed in claim 2, it is characterized in that described N ⁺doped layer is heavy doping, and concentration is 1.0 × 10 ²⁰above.

10. as claimed in claim 1 a kind of there is efficient light trapping structure crystal silicon solar energy battery or a kind of preparation method with the crystal silicon solar energy battery of efficient light trapping structure as claimed in claim 2, it is characterized in that described back electrode to be thickness be the aluminium electrode plate of more than 100nm.