RU2815653C1 - Method of forming solar battery cell - Google Patents

Abstract

FIELD: laser physics; optoelectronics.

SUBSTANCE: invention relates to laser physics and optoelectronics and is used to form a solar battery cell from monocrystalline silicon super-doped with impurities. Disclosed is a method of forming a solar battery cell, including obtaining a p-type monocrystalline silicon plate, texturing of both its surfaces and formation of current-conducting contacts on them, characterized in that texturing is carried out by chemical etching in 2% potassium hydroxide solution at temperature of 80 °C for 25 minutes, and then on the back surface of said plate in an inert atmosphere, aluminium is deposited to form a layer with thickness of 5 nm, after which it is exposed to a beam of laser radiation with a pulse duration of 120 ns and a power density of 8 J/cm², and the front surface of said plate is annealed as a result of exposure to a beam of laser radiation with pulse duration of 120 ns and power density of 2.2 J/cm² in an inert atmosphere to form an n-type region.

EFFECT: providing high absorption capacity in the range of the entire solar spectrum (250–2,500 nm).

1 cl, 2 dwg

Description

The invention relates to laser physics and optoelectronics and can be used to form a solar battery cell from monocrystalline silicon superdoped with impurities.

There is a known method for forming a solar battery cell, which includes obtaining a p-type monocrystalline silicon wafer, texturing both of its surfaces and forming conductive contacts on them (see, in particular, S. Wen, Y. J. Yang, Y. J. Ma et al. Sulfur-hyperdoped silicon nanocrystalline layer prepared on polycrystalline silicon solar cell substrate by thin film deposition and nanosecond-pulsed laser irradiation, Applied Surface Science 476 (2019), pp. 49-60 [1]). In the known method, texturing of the rear (relative to the incidence of sunlight) surface of the wafer is carried out simultaneously with superalloying of silicon with sulfur, and then the rear surface of the wafer is coated with aluminum paste.

The disadvantage of this known method is that the operating range of the cell formed by it is limited to 1.1 microns, which reduces its efficiency, because The wavelength of solar radiation reaches 2.5 microns.

The method known from [1] is accepted as the closest analogue of the claimed method.

The technical problem solved by the claimed invention is to create a method for forming a solar battery cell from monocrystalline silicon, which has increased efficiency over a wide range of wavelengths.

In this case, a technical result is achieved, which consists in the possibility of forming a solar battery cell from monocrystalline silicon with high absorption capacity in the range of the entire solar spectrum (250-2500 nm) while simultaneously simplifying the technological process of its formation and reducing its duration.

The technical problem is solved, and the specified technical result is achieved as a result of creating a method for forming a solar battery cell, in which a p-type monocrystalline silicon wafer is obtained and both of its surfaces are textured and conductive contacts are formed on them. Texturing is carried out by chemical etching in a 2% solution of potassium hydroxide at a temperature of 80°C for 25 minutes. Then, aluminum is applied to one of the surfaces of the said plate in an inert atmosphere to form a layer 5 nm thick, after which it is exposed to a laser beam with a pulse duration of 120 ns and a power density of 8 J/cm ² , and the opposite surface of the said plate is annealed as a result exposure of it to a laser beam with a pulse duration of 120 ns and a power density of 2.2 J/cm ² in an inert atmosphere with the formation of an n-type region.

In fig. Figure 1 shows a schematic representation of a solar battery cell obtained by the claimed method.

In fig. Figure 2 shows the dependence of the absorption capacity of solar cell cells formed in various ways on the wavelength (1 - p-type monocrystalline silicon wafer without texturing, 2 - p-type monocrystalline silicon wafer with texturing of its surfaces without laser treatment, 3 - p-type monocrystalline silicon wafer -type, processed according to the stated method).

The claimed method is implemented by performing the following sequence of actions (see Fig. 1).

1. A p-type monocrystalline silicon wafer is obtained (1) (see GOST 19658-81 [2]).

2. Texturing of both surfaces of the plate (1) is carried out by chemical etching in a 2% solution of potassium hydroxide (KOH) at a temperature of 80°C for 25 minutes. As a result of etching, pyramidal structures (2) and (3) are formed over the entire surface area.

3. Aluminum is applied to one of the surfaces of the plate (1) (in the working position of the cell relative to the incidence of sunlight) in an inert atmosphere (any inert gas or a mixture of inert gases) to form a layer (4) 5 nm thick, and then subjected to exposed to a laser beam with a pulse duration of 120 ns and a power density of 8 J/cm ² .

4. The opposite surface of the plate (1) is subjected to annealing as a result of exposure to a laser beam with a pulse duration of 120 ns and a power density of 2.2 J/cm ² in an inert atmosphere (any inert gas or mixture of inert gases) with the formation of the n- region type.

5. Formed (in a typical manner, disclosed, for example, in A.S. Abramov, D.A. Andronikov, S.N. Abolmasov, E.I. Terukov. Silicon Heterojunction Technology: A Key to High Efficiency Solar Cells at Low Cost, High-Efficient Low-Cost Photovoltaics, pp.113 -132 [3]) on both surfaces of the plate (1) there are conductive contacts (5) and (6).

The possibility of implementing the claimed method is confirmed by the following experiment, taken as an example.

A wafer of monocrystalline silicon (boron-doped) grown by the Czochralski method was used. The plate had a crystallographic orientation <100>, the resistivity was 1-3 Ohm⋅cm, the thickness was 120 μm, and the dimensions were 157×157 mm ² .

Further processing of the plate was carried out as follows.

First, chemical etching of both surfaces of the plate was carried out in a 2% KOH solution at a temperature of 80°C for 25 minutes. Then aluminum was deposited onto one of the surfaces of the plate to form a 5 nm thick film using a magnetron sputtering setup in an inert atmosphere (argon).

After this, this surface was exposed to a laser beam with a pulse duration of 120 ns and a power of 0.1 mJ, focused on the surface of the plate into a spot with a radius of ≈20 μm, which corresponded to a peak laser power density of 8 J/cm ² .

The opposite surface of the plate was subjected to laser annealing in an inert atmosphere (argon) as a result of exposure to a laser beam with a pulse duration of 120 ns and a power density of 2.2 J/cm ² . The laser beam was focused on the surface of the plate into a spot with a radius of ≈0.5 mm, which corresponded to a peak laser power density of 2.2 J/cm ² .

In both cases, a nanosecond ytterbium-based fiber laser HTF Mark, developed by the Bulat Design Bureau (Moscow, Russia), was used. The laser had a central wavelength λ = 1064 nm, a maximum pulse energy E _max of up to 1 mJ. The pulse repetition rate was 20-80 kHz.

The claimed method makes it possible to create a solar battery cell with increased efficiency as a result of an increase in the absorption capacity of such a cell in a wide range of the solar spectrum (250-2500 nm) (see Fig. 2).

Claims (1)

A method for forming a solar battery cell, including producing a wafer of monocrystalline p-type silicon, texturing both of its surfaces and forming current-conducting contacts on them, characterized in that texturing is carried out by chemical etching in a 2% solution of potassium hydroxide at a temperature of 80°C for 25 minutes, and then aluminum is applied to the back surface of the said plate in an inert atmosphere to form a layer 5 nm thick, after which it is exposed to a laser beam with a pulse duration of 120 ns and a power density of 8 J/cm ² , and the front surface of the said plate is annealed as a result of exposure to a laser beam with a pulse duration of 120 ns and a power density of 2.2 J/cm ² in an inert atmosphere with the formation of an n-type region.