A method for depositing an ALD film layer for passivating the entire film layer of a solar cell

Abstract

The present invention is an ALD film deposition method for passivating the entire film layer of a solar cell, comprising the following steps: S1, pulse-feeding H2O so that part of the H in the H2O enters the silicon wafer; S2, pulse-feeding TMA and H2O alternately to form a first layer of aluminum oxide film; S3, pulse-feeding H2O so that part of the H in the H2O enters the first layer of aluminum oxide film; S4, pulse-feeding TMA and H2O alternately to form a second layer of aluminum oxide film. Since a certain amount of H will enter the surface of the silicon wafer when water is treated, a certain degree of passivation is achieved, and saturated adsorption of the silicon wafer surface is achieved before TMA is introduced. When TMA is introduced, H atoms in MTA will not enter the silicon wafer, so that multiple water pretreatments and depositions can achieve passivation excellence and consistency for the entire film layer.

Description

Technical Field

[0001] The invention relates to the technical field of solar cells, and in particular to an ALD film deposition method for full-film passivation of a solar cell. Background Art

[0002] In the preparation of solar cells, various composite defects affect the minority carrier lifetime of the cell and thus reduce the efficiency of the solar cell. Therefore, thin films of different properties are generally deposited on the surface of the silicon wafer for passivation to improve the cell efficiency.

[0003] Due to the excellent chemical passivation and field passivation effects of aluminum oxide, it is widely used in various solar cells such as perc and TOPCon. Generally, tubular ALD (atomic layer deposition) or PECVD is used to prepare the aluminum oxide film.

[0004] The ALD passivation process refers to the use of reactive stabilizers (such as water molecules) to make surface atoms non-reactive before depositing a single layer to prevent further interaction with the atomic layer. During the ALD deposition process, water molecules adsorb on active centers (such as -OH) to form a stable surface component (such as -OH2), blocking continued reaction with the atomic layer. The current mainstream ALD aluminum oxide film deposition scheme is to alternately introduce H2O and TMA (trimethylaluminum) gas to deposit aluminum oxide films. When TMA is introduced, the hydrogen atoms in TMA will enter the silicon wafer, thereby affecting the passivation effect of the aluminum oxide film. Summary of the invention

[0005] In order to solve the technical problems in the background technology, the present invention discloses an ALD film deposition method for full film passivation of a solar cell.

[0006] The present invention provides an ALD film deposition method for full-film passivation of a solar cell, comprising the following steps:

[0007] S1, pulse H2O is introduced so that part of the H in H2O enters the silicon wafer;

[0008] S2, TMA and H2O are introduced alternately in pulses to form the first layer of aluminum oxide film;

[0009] S3, introducing H2O in a pulsed manner, so that part of the H in the H2O enters the first layer of aluminum oxide film;

[0010] S4. TMA and H2O are introduced alternately in pulses to form a second layer of aluminum oxide film.

[0011] In step S1, the pulse time is 6 s, the purge time is 12 s, the process flow rate is 20 slm, and the number of cycles is 5, so that the silicon wafer adsorbs H to a saturated state.

[0012] In step S2, the temperature is 290°C, the TMA pulse time is 6.5s, the purge time is 12s, the process flow rate is 20slm; the H2O pulse time is 5.5s, the purge time is 12s, the process flow rate is 20slm, and the number of cycles is 10, so that the thickness of the first layer of aluminum oxide film accounts for 50-75% of the total thickness of the aluminum oxide film.

[0013] In step S3, the temperature is 290°C, the pulse time of H2O is 6s, the purge time is 12s, the process flow rate is 20slm, and the number of cycles is 5, so that the first aluminum oxide film adsorbs H to a saturated state.

[0014] In step S4, the temperature is 290°C, the pulse time of TMA is 6.5s, the purge time is 12s, the process flow rate is 20slm, the H2O pulse time is 5.5s, the purge time is 12s, the process flow rate is 20slm, and the number of cycles is 18 times, so that the thickness of the second layer of aluminum oxide film accounts for 25-50% of the total thickness of the aluminum oxide film.

[0015] The beneficial effects of the present invention are: 1. Since a certain amount of H will enter the surface of the silicon wafer during water treatment, a certain degree of passivation is achieved, and saturated adsorption of the silicon wafer surface is achieved before TMA is introduced. When TMA is introduced, the H atoms in MTA will not enter the silicon wafer, so that multiple water pretreatments and depositions can achieve excellent passivation and consistency of the entire film layer; 2. In the subsequent sintering process, the H in step S3 will enter the silicon substrate, which can increase the open circuit voltage of the battery. DETAILED DESCRIPTION

[0016] The present invention provides an ALD film deposition method for full film passivation of a solar cell, characterized in that it comprises the following steps:

[0017] Embodiment 1:

[0018] The present invention discloses an ALD film deposition method for full-film passivation of a solar cell, comprising the following steps:

[0019] S1, pulse H2O is introduced to allow part of the H in the H2O to enter the silicon wafer; the pulse time is 6s, the purge time is 12s, the process flow rate is 20slm, and the number of cycles is 5, so that the silicon wafer adsorbs H to a saturated state;

[0020] S2, TMA and H2O are alternately introduced in pulses to form a first layer of aluminum oxide film; the temperature is 290°C, the TMA pulse time is 6.5s, the purge time is 12s, and the process flow rate is 20slm; the H2O pulse time is 5.5s, the purge time is 12s, and the process flow rate is 20slm, and the number of cycles is 10, so that the thickness of the first layer of aluminum oxide film accounts for 50% of the total thickness of the aluminum oxide film;

[0021] S3, pulse H2O is introduced so that part of the H in the H2O enters the first aluminum oxide film; the temperature is 290°C, the pulse time of H2O is 6s, the purge time is 12s, the process flow rate is 20slm, and the number of cycles is 5, so that the first aluminum oxide film adsorbs H to a saturated state;

[0022] S4. TMA and H2O are introduced alternately in pulses to form a second layer of aluminum oxide film; the temperature is 290°C, the pulse time of TMA is 6.5s, the purge time is 12s, the process flow rate is 20slm, the pulse time of H2O is 5.5s, the purge time is 12s, the process flow rate is 20slm, and the number of cycles is 18 times, so that the thickness of the second layer of aluminum oxide film accounts for 50% of the total thickness of the aluminum oxide film.

[0023] The beneficial effects of the present invention are: 1. Since a certain amount of H will enter the surface of the silicon wafer during water treatment, a certain degree of passivation is achieved, and saturated adsorption of the silicon wafer surface is achieved before TMA is introduced. When TMA is introduced, the H atoms in MTA will not enter the silicon wafer, so that multiple water pretreatments and depositions can achieve excellent passivation and consistency of the entire film layer; 2. In the subsequent sintering process, the H in step S3 will enter the silicon substrate, which can increase the open circuit voltage of the battery.

[0024] Embodiment 2:

[0025] Compared with the first embodiment, the difference is that the thickness of the first aluminum oxide film accounts for 75% of the total thickness of the aluminum oxide film; the thickness of the second aluminum oxide film accounts for 25% of the total thickness of the aluminum oxide film.

[0026] Comparative Example 1:

[0027] The invention discloses an ALD film deposition method for full-film passivation of a solar cell, and the operation steps are as follows: TMA and H2O are alternately introduced in a pulsed manner to form a second aluminum oxide film; the temperature is 290° C., the pulse time of TMA is 6.5 s, the purge time is 12 s, the process flow rate is 20 slm, the pulse time of H2O is 5.5 s, the purge time is 12 s, the process flow rate is 20 slm, and the number of cycles is 28 times.

[0028] The comparison data is as follows:

[0029]

[0030] Where Pmpp: power; Uoc: open circuit voltage; Isc: short circuit current; Rser: series resistance; Rshunt: parallel resistance; FF: fill factor; Eta: conversion efficiency.

[0031] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. An ALD film deposition method for full-film passivation of a solar cell, characterized in that: The following steps are involved: S1, pulse H2O is introduced so that part of the H in H2O enters the silicon wafer; S2, TMA and H2O are introduced alternately in pulses to form the first layer of aluminum oxide film; S3, introducing H2O in a pulsed manner, so that part of the H in the H2O enters the first layer of aluminum oxide film; in the subsequent sintering process, these H can enter the silicon substrate; S4. TMA and H2O are introduced alternately in pulses to form a second layer of aluminum oxide film.

2. The ALD film deposition method for full-film passivation of a solar cell according to claim 1, characterized in that: In step S1, the pulse time is 6 s, the purge time is 12 s, the process flow rate is 20 slm, and the number of cycles is 5, so that the silicon wafer adsorbs H to a saturated state.

3. The ALD film deposition method for full-film passivation of a solar cell according to claim 2, characterized in that: In step S2, the temperature is 290°C, the TMA pulse time is 6.5s, the purge time is 12s, and the process flow rate is 20slm; the H2O pulse time is 5.5s, the purge time is 12s, the process flow rate is 20slm, and the number of cycles is 10 times.

4. The ALD film deposition method for full-film passivation of a solar cell according to claim 3, characterized in that: In step S3, the temperature is 290°C, the pulse time of H2O is 6s, the purge time is 12s, the process flow rate is 20slm, and the number of cycles is 5, so that the first aluminum oxide film adsorbs H to a saturated state.

5. The ALD film deposition method for full-film passivation of a solar cell according to claim 4, characterized in that: In step S4, the temperature is 290°C, the pulse time of TMA is 6.5s, the purge time is 12s, the process flow rate is 20slm, the pulse time of H2O is 5.5s, the purge time is 12s, the process flow rate is 20slm, and the number of cycles is 18 times.

6. The ALD film deposition method for full-film passivation of a solar cell according to claim 3, characterized in that: The thickness of the first aluminum oxide film accounts for 50-75% of the total thickness of the aluminum oxide film.

7. The ALD film deposition method for full-film passivation of a solar cell according to claim 4, characterized in that: The thickness of the second aluminum oxide film accounts for 25-50% of the total thickness of the aluminum oxide film.

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