阅读说明：本技术 一种薄化晶硅电池及制备方法 (Thinned crystalline silicon battery and preparation method ) 是由 严文生 臧月 于 2021-06-30 设计创作，主要内容包括：本发明公开了一种薄化晶硅电池及制备方法,本发明一种薄化晶硅电池,从上到下依次包括第一SiO-(x)薄膜,第一SiN-(x)薄膜、第二SiN-(x)薄膜、SiO-(2)钝化薄膜、p型单晶硅片、Al-(2)O-(3)薄膜、第三SiN-(x)薄膜、第二SiO-(x)薄膜；所述的p型单晶硅片上表面织构化,且p型单晶硅形成n+发射极,得到p-n结,p型单晶硅片背面采用激光打孔,并在孔内形成p+局部背表面场,并设置金属触点；p型单晶硅片上表面设有选择性发射结,选择性发射结上设有金属电极；通过本发明,可以使晶硅电池在厚度减薄的情况下,有效解决电池的光吸收及效率损失。(The invention discloses a thinned crystalline silicon battery and a preparation method thereof x Film, first SiN x Thin film, second SiN x Film, SiO 2 Passivation film, p-type monocrystalline silicon wafer, and Al 2 O 3 Thin film, third SiN x Film, second SiO x A film; texturing the upper surface of the p-type monocrystalline silicon piece, forming an n + emitter by the p-type monocrystalline silicon to obtain a p-n junction, drilling holes on the back surface of the p-type monocrystalline silicon piece by using laser, forming a p + local back surface field in the holes, and arranging metal contacts; the upper surface of the p-type monocrystalline silicon piece is provided with a selective emitter junction, and the selective emitter junction is provided with a metal electrode; go through the bookThe invention can effectively solve the problems of light absorption and efficiency loss of the crystalline silicon battery under the condition of reducing the thickness of the crystalline silicon battery.)

1. A thinned crystalline silicon cell, characterized by: comprises a first SiO in sequence from top to bottom_xFilm, first SiN_xThin film, second SiN_xFilm, SiO₂Passivation film, p-type monocrystalline silicon wafer, and Al₂O₃Thin film, third SiN_xFilm, second SiO_xA film; texturing the upper surface of the p-type monocrystalline silicon piece, forming an n + emitter by the p-type monocrystalline silicon to obtain a p-n junction, wherein the doping concentration of the n + emitter is (1.2 +/-0.8) multiplied by 10¹⁹/cm³Laser drilling is adopted on the back surface of the p-type monocrystalline silicon piece, a p + local back surface field is formed in the hole, and a metal contact is arranged; the upper surface of the p-type monocrystalline silicon piece is provided with a selective emitter junction, and the selective emitter junction is provided with a metal electrode; wherein the refraction factor of the second SiNx film is higher than that of the first SiNx film;

the first SiO_xA film thickness of 10-15 nm, first SiN_xThe film thickness is 35-40 nm, and the second SiN_xThe thickness of the film is 20-25 nanometers and SiO₂The thickness of the passivation film is 8-12 nanometers, and the p-type single crystalThe thickness of the crystal silicon wafer is 100-140 microns and Al₂O₃The film thickness is 8-15 nm, and the third SiN_xThe film thickness is 30-45 nm, and the second SiO is_xThe thickness of the film is 200 nm and 250 nm.

2. The thinned crystalline silicon cell of claim 1, wherein: the p-type monocrystalline silicon wafer is obtained by a slicing method.

3. The method of claim 1, further comprising the steps of:

the method comprises the following steps: sequentially preparing Al on the back of a p-type monocrystalline silicon wafer with the thickness of 100-140 microns₂O₃Thin film, third SiN_xFilm and second SiO_xA film; the Al is₂O₃The film thickness is 8-15 nm, and the third SiN_xThe film thickness is 30-45 nm, and the second SiO is_xThe thickness of the film is 200-250 nm;

step two: laser drilling is carried out on the back surface of the p-type monocrystalline silicon wafer obtained in the first step, a p + local back surface field is formed in the hole, and an aluminum electrode is formed through a screen printing method;

step three: texturing the upper surface of the product obtained in the second step to form a pyramid with the characteristic size of 1-2um in random distribution;

step four: on the product obtained in step three, POCl is used at the temperature of 840-900 DEG C₃Forming n + emitter by diffusion method to obtain p-n junction, wherein the doping concentration of n + emitter is (1.2 + -0.8) × 10¹⁹/cm³；

Step five: sequentially preparing SiO on the upper surface of the product obtained in the step four from bottom to top₂Passivation film, second SiN_xThin film, first SiN_xFilm and first SiO_xA film; wherein the second SiN_xFilm refractive index higher than first SiN_xFilm, first SiO_xA film thickness of 10-15 nm, first SiN_xThe film thickness is 35-40 nm, and the second SiN_xThe thickness of the film is 20-25 nm,SiO₂The thickness of the passivation film is 8-12 nanometers;

step six: forming a local selective emitter junction on the upper surface of the product obtained in the step five by adopting local laser doping, wherein the width of the local selective emitter junction is 200-250 microns, and the sheet resistance is 55 +/-8/sq; and a metal electrode is disposed on the emitter junction.

4. The method of claim 3, wherein the step of forming the thin crystalline silicon cell comprises: the SiO₂The passivation film is formed by thermal growth at a temperature of 850-.

5. The method of claim 3, wherein the step of forming the thin crystalline silicon cell comprises: the first SiN_xThin film, second SiN_xFilm, first SiO_xThe thin film is prepared by a PECVD method.

6. The method of claim 3, wherein the step of forming the thin crystalline silicon cell comprises: the Al is₂O₃The film is prepared by an atomic layer deposition method.

7. The method of claim 3, wherein the step of forming the thin crystalline silicon cell comprises: the third SiN_xFilm, second SiO_xThe film is prepared by adopting a PECVD method.

8. The method of claim 3, wherein the step of forming the thin crystalline silicon cell comprises: and a metal electrode made of silver is arranged on the selective emitter junction.

9. The method of claim 3, wherein the step of forming the thin crystalline silicon cell comprises: the front surface is textured by treatment in NaOH solution at 82-85 deg.C.

10. The method of claim 3, wherein the step of forming the thin crystalline silicon cell comprises: the resistivity of the p-type monocrystalline silicon wafer substrate is 0.9 +/-0.2 omega cm.

Technical Field

The invention belongs to the technical field of photovoltaic new energy, and particularly relates to a preparation method of a thinned crystalline silicon battery. The battery preparation is carried out by adopting a proper method in the expected design, and the conversion efficiency of the crystalline silicon solar battery is improved under the condition of reducing the cost caused by battery thinning.

Background

As a sustainable clean new energy source, photovoltaic solar cells are being rapidly applied and popularized. In recent years, crystalline silicon solar cells have been dominant in the photovoltaic market due to their unique advantages. Currently, the typical thickness of industrial crystalline silicon cells is 170-180 microns. However, since the silicon material occupies 60% of the cost of the battery. In 2021, the cost of silicon wafers is dramatically increased by 150%. Therefore, the development of thinned crystalline silicon cells is one of the main approaches to significantly reduce cost. By reducing the thickness of the crystalline silicon, significant benefits in cost reduction can be realized. However, at present, thin-crystal silicon cells are not technically mature to be prepared. Reducing the thickness of the crystalline silicon cell introduces optical absorption loss, which reduces the conversion efficiency of the cell. The invention selects the PERC (passivated emitter back contact cell) cell as the basis of the current mainstream crystalline silicon cell structure, adopts the optical and electrical design schemes of the front surface and the back surface for the thinned crystalline silicon cell with the thickness of 100-140 microns, can obviously improve the conversion efficiency of the thinned cell with the thickness of 100-140 microns by adopting the process of the invention, and realizes higher cost performance of the cell.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a thinned crystalline silicon battery and a preparation method thereof.

The invention discloses a thinned crystalline silicon battery which sequentially comprises a first SiO from top to bottom_xFilm, first SiN_xThin film, second SiN_xFilm, SiO₂Passivation film, p-type monocrystalline silicon wafer, and Al₂O₃Thin film, third SiN_xFilm, second SiO_xA film; texturing the upper surface of the p-type monocrystalline silicon piece, forming an n + emitter by the p-type monocrystalline silicon to obtain a p-n junction, wherein the doping concentration of the n + emitter is (1.2 +/-0.8) multiplied by 10¹⁹/cm³Laser drilling is adopted on the back surface of the p-type monocrystalline silicon piece, a p + local back surface field is formed in the hole, and a metal contact is arranged; the upper surface of the p-type monocrystalline silicon piece is provided with a selective emitter junction, and the selective emitter junction is provided with a metal electrode; wherein the second SiN_xThe film has high refractive factorIn the first SiN_xA film;

the first SiO_xA film thickness of 10-15 nm, first SiN_xThe film thickness is 35-40 nm, and the second SiN_xThe thickness of the film is 20-25 nanometers and SiO₂The thickness of the passivation film is 8-12 nanometers, the thickness of the p-type monocrystalline silicon piece is 100-140 micrometers, and Al is₂O₃The film thickness is 8-15 nm, and the third SiN_xThe film thickness is 30-45 nm, and the second SiO is_xThe thickness of the film is 200 nm and 250 nm.

Preferably, the p-type monocrystalline silicon wafer is obtained by a slicing method.

A preparation method of a thinned crystalline silicon battery specifically comprises the following steps:

the method comprises the following steps: sequentially preparing Al on the back of a p-type monocrystalline silicon wafer with the thickness of 100-140 microns₂O₃Thin film, third SiN_xFilm and second SiO_xA film; the Al is₂O₃The film thickness is 8-15 nm, and the third SiN_xThe film thickness is 30-45 nm, and the second SiO is_xThe thickness of the film is 200-250 nm;

step two: laser drilling is carried out on the back surface of the p-type monocrystalline silicon wafer obtained in the first step, a p + local back surface field is formed in the hole, and an aluminum electrode is formed through a screen printing method;

step three: texturing the upper surface of the product obtained in the second step to form a pyramid with the characteristic size of 1-2um distributed randomly;

step four: on the product obtained in step three, POCl is used at the temperature of 840-900 DEG C₃Forming n + emitter by diffusion method to obtain p-n junction, wherein the doping concentration of n + emitter is (1.2 + -0.8) × 10¹⁹/cm³；

Step five: sequentially preparing SiO on the upper surface of the product obtained in the step four from bottom to top₂Passivation film, second SiN_xThin film, first SiN_xFilm and first SiO_xA film; wherein the second SiN_xFilm refractive index higher than first SiN_xFilm, first SiO_xThe film thickness is 10-15 nm, the first SiN_xThe film thickness is 35-40 nm, and the second SiN_xThe thickness of the film is 20-25 nanometers and SiO₂The thickness of the passivation film is 8-12 nanometers;

step six: forming a local selective emitter junction on the upper surface of the product obtained in the step five by adopting local laser doping, wherein the width of the local selective emitter junction is 200-250 microns, and the sheet resistance is 55 +/-8/sq; and a metal electrode is disposed on the emitter junction.

Preferably, the SiO₂The passivation film is formed by thermal growth at a temperature of 850-.

Preferably, the first SiN_xThin film, second SiN_xFilm, first SiO_xThe thin film is prepared by a PECVD method.

Preferably, the Al is₂O₃The film is prepared by an atomic layer deposition method.

Preferably, the third SiN_xFilm, second SiO_xThe film is prepared by adopting a PECVD method.

Preferably, the metal electrode arranged on the emitter junction is silver.

Preferably, the front surface is textured by treatment in a NaOH solution at a temperature of 82-85 ℃.

Preferably, the resistivity of the p-type monocrystalline silicon wafer substrate is 0.9 +/-0.2 omega-cm.

The invention has the beneficial effects that: by the method, the light absorption and efficiency loss of the crystalline silicon battery can be effectively solved under the condition that the thickness of the crystalline silicon battery is reduced. Thereby, a crystalline silicon battery with higher cost performance can be achieved. By adopting the method, the prepared battery efficiency at 100-140 microns is equivalent to the conversion efficiency of a crystalline silicon battery with the thickness of 180 microns in a commercial typical structure. The benefit comes from the front and back surface solution adopted in the invention, on one hand, the absorption of light in the crystal silicon can be improved, and the crystal silicon comprises a short wavelength region and a long wavelength region; on the other hand, SiO is formed by thermal oxidation previously employed₂The thin film ensures that the front surface of the crystalline silicon has better passivation, so that the open-circuit voltage of the battery can be improved; surface pyramid ruler prepared by the inventionThe size of the pyramid is 1-2 microns and is far smaller than the average size of a pyramid for texturing a commercial battery, so that the surface light trapping of the battery is more favorable, and higher short-circuit current density is favorably obtained; the superposition of these combined factors may result in improved conversion efficiency with reduced thickness of the crystalline silicon (i.e., reduced cost).

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a graph of front surface reflection and light absorption within a thinned crystalline silicon cell as a function of wavelength;

fig. 3 is a plot of measured current density versus voltage for a 140 micron, thinned crystalline silicon cell.

Detailed Description

In the first embodiment, as shown in fig. 1:

the method comprises the following steps: preparing Al on the back of a p-type monocrystalline silicon wafer with the thickness of 100 microns in sequence₂O₃Thin film, third SiN_xFilm and second SiO_xA film; the Al is₂O₃Film thickness of 8 nm, third SiN_xThe film thickness is 30 nm, the second SiO_xThe thickness of the film is 200 nm;

step two: laser drilling is carried out on the back surface of the p-type monocrystalline silicon wafer obtained in the first step, a p + local back surface field is formed in the hole, and an aluminum electrode is formed through a screen printing method; the resistivity of the p-type monocrystalline silicon wafer substrate is 0.9 omega cm.

Step three: texturing the upper surface of the product obtained in the second step to form a pyramid with the characteristic size of 1-2um distributed randomly;

step four: on the product obtained in step three, at a temperature of 840 ℃ with POCl₃Forming n + emitter with doping concentration of 1.2 × 10 by diffusion to obtain p-n junction¹⁹/cm³；

Step five: sequentially preparing SiO on the upper surface of the product obtained in the step four from bottom to top₂Passivation film, second SiN_xThin film, first SiN_xFilm and first SiO_xA film; wherein the second SiN_xFilm refractive factorHigher than the first SiN_xFilm, first SiO_xA film thickness of 10 nm, first SiN_xFilm thickness of 35 nm, second SiN_xThe thickness of the film is 20 nanometers and SiO₂The thickness of the passivation film is 8 nanometers;

step six: forming a local selective emitter junction on the upper surface of the product obtained in the fifth step by adopting local laser doping, wherein the width of the local selective emitter junction is 200 microns, and the sheet resistance is 55/sq; and a silver metal electrode is disposed on the selective emitter junction. A comparison of the standard thickness and photovoltaic parameter measurements of the example-thinned crystalline silicon cell is shown in table 1:

table 1 comparison of photovoltaic parameter measurements for standard thickness and example one thinned crystalline silicon cell (100 cells each) is shown in table 2:

TABLE 2

As shown in fig. 2, the front surface reflection and the light absorption in the cell are related to the wavelength in the silicon cell of the example.

As shown in fig. 3, a plot of current density versus voltage is shown for the 140 micron and first example cell.

Example two:

the method comprises the following steps: preparing Al on the back of a p-type monocrystalline silicon wafer with the thickness of 120 microns in sequence₂O₃Thin film, third SiN_xFilm and second SiO_xA film; the Al is₂O₃Film thickness of 10 nm, third SiN_xFilm thickness of 38 nm, second SiO_xThe film thickness is 220 nm;

step two: laser drilling is carried out on the back surface of the p-type monocrystalline silicon wafer obtained in the first step, a p + local back surface field is formed in the hole, and an aluminum electrode is formed through a screen printing method;

step three: texturing the upper surface of the product obtained in the second step to form a pyramid with the characteristic size of 1-2um distributed randomly;

step four: on the product obtained in step three, at a temperature of 880 ℃ with POCl₃Forming n + emitter with doping concentration of 1.2 × 10 by diffusion to obtain p-n junction¹⁹/cm³；

Step five: sequentially preparing SiO on the upper surface of the product obtained in the step four from bottom to top₂Passivation film, second SiN_xThin film, first SiN_xFilm and first SiO_xA film; wherein the second SiN_xFilm refractive index higher than first SiN_xFilm, first SiO_xA film thickness of 12 nm, first SiN_xFilm thickness of 38 nm, second SiN_xThe thickness of the film is 22 nanometers and SiO₂The thickness of the passivation film is 10 nanometers;

step six: forming a local selective emitter junction on the upper surface of the product obtained in the step five by adopting local laser doping, wherein the width of the local selective emitter junction is 230 microns, and the sheet resistance is 47/sq; and a silver electrode is disposed on the selective emitter junction.

Example three:

a preparation method of a thinned crystalline silicon battery specifically comprises the following steps:

the method comprises the following steps: preparing Al on the back of a p-type monocrystalline silicon wafer with the thickness of 140 microns in sequence₂O₃Thin film, third SiN_xFilm and second SiO_xA film; the Al is₂O₃Film thickness of 15 nm, third SiN_xFilm thickness of 45 nm, second SiO_xThe thickness of the film is 250 nanometers;

step two: laser drilling is carried out on the back surface of the p-type monocrystalline silicon wafer obtained in the first step, a p + local back surface field is formed in the hole, and an aluminum electrode is formed through a screen printing method;

step three: texturing the upper surface of the product obtained in the second step to form a pyramid with the characteristic size of 1-2um distributed randomly;

step (ii) ofFourthly, the method comprises the following steps: on the product obtained in step three, at a temperature of 900 ℃ with POCl₃Forming n + emitter with doping concentration of 2 × 10 by diffusion to obtain p-n junction¹⁹/cm³；

Step five: sequentially preparing SiO on the upper surface of the product obtained in the step four from bottom to top₂Passivation film, second SiN_xThin film, first SiN_xFilm and first SiO_xA film; wherein the second SiN_xFilm refractive index higher than first SiN_xFilm, first SiO_xA film thickness of 15 nm, first SiN_xFilm thickness of 40 nm, second SiN_xThe thickness of the film is 25 nanometers and SiO₂The thickness of the passivation film is 12 nanometers;

step six: forming a local selective emitter junction on the upper surface of the product obtained in the step five by adopting local laser doping, wherein the width of the local selective emitter junction is 250 microns, and the sheet resistance is 63/sq; and a metal electrode is disposed on the selective emitter junction.