Solar cell containing PECVD (Plasma Enhanced Chemical Vapor Deposition) deposited silicon oxynitride film layer and preparation method

Abstract

The invention discloses a PECVD (Plasma Enhanced Chemical Vapor Deposition)-containing silicon oxynitride film layer solar cell and a preparation method, and belongs to the technical field of solar cell manufacturing, and the technical scheme is as follows: S1, boat entering, and S2, temperature control. S3, vacuumizing for the first time; s4, pre-inflation is carried out; s5, deposition is carried out; s6, vacuumizing for the second time; s7, cleaning is conducted; s8, vacuumizing for the third time; s9, pressure returning; s10, the boat is taken out; according to the PECVD-containing silicon oxynitride film layer solar cell and the preparation method thereof provided by the invention, the silicon oxynitride is deposited on the back surface, so that the back surface passivation effect of the solar cell is enhanced, and the recombination of current carriers is reduced; the silicon oxynitride thin film is deposited on the surface layer of the front surface of the solar cell, so that the short-wave light reflectivity of the solar cell within 300-500nm is reduced, the absorption of the short-wave light is enhanced, and the photoelectric conversion efficiency of the solar cell is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solar cell manufacturing, and particularly relates to a solar cell containing a PECVD deposited silicon oxynitride film layer and a preparation method. BACKGROUND

[0002] Solar cell back surface passivation and enhanced front light absorption are important means to improve its performance and increase photoelectric conversion efficiency. Generally, a passivation medium film is introduced to reduce the recombination rate of the solar cell surface and change the refractive index of the medium film by passivating the dangling bonds on the silicon surface, thereby improving the photoelectric conversion efficiency of the solar cell. Common passivation medium films include silicon oxide film, silicon nitride film and aluminum oxide film.

[0003] At present, PECVD deposited silicon nitride film is commonly used as the front surface anti-reflection film of the crystalline silicon solar cell in industrial production. Since silicon nitride contains a large number of positive charges, the deposition on the front surface N-type emitter generates an inversion layer, which is more conducive to the passivation of the N+ layer surface. However, due to the positive charges, when used for back surface passivation of the solar cell, the fixed positive charges in the film form an inversion layer, resulting in increased current leakage of the solar cell, and the cell efficiency is not ideal.

[0004] In addition, silicon nitride has a strong tensile stress on the Si surface. Although hydrogen can diffuse to the Si-SiNx interface to effectively passivate the interface state, the interface quality is not as good as Si-SiO2. The amorphous aluminum oxide medium film has a high concentration of negative charges at the Si interface, and has good passivation effect on both P and N type surfaces. The back surface passivation medium film generally uses an aluminum oxide film layer.

[0005] Therefore, it is urgent to develop a solar cell containing a PECVD deposited silicon oxynitride film layer and a preparation method to further enhance the passivation of the back surface of the solar cell and the absorption of the front light. SUMMARY

[0006] The first object of the present application is to provide a preparation method of a solar cell containing a PECVD deposited silicon oxynitride film layer. The deposition of silicon oxynitride on the back surface enhances the passivation effect of the back surface of the solar cell and reduces the recombination of carriers. The deposition of silicon oxynitride thin film on the front surface layer reduces the reflectivity of short wave light between 300-500 nm of the solar cell, enhances the absorption of short wave light, and improves the photoelectric conversion efficiency of the solar cell.

[0007] The second object of the present application is to provide a solar cell containing a PECVD deposited silicon oxynitride film layer, which improves the absorption of corresponding light, thereby improving the photoelectric conversion efficiency of the solar cell, enhancing the passivation of the back surface of the solar cell and the absorption of the front light.

[0008] The application aims at achieving a preparation method of a solar cell containing a PECVD deposited silicon oxynitride film layer, comprising the following steps: S1, boat loading, a graphite boat filled with silicon wafers is sent into a deposition tube by a paddle, and the temperature in the deposition tube is controlled to be 490-530 DEG C; S2, temperature control, the temperature in the deposition tube is controlled to be constant by sequentially operating temperature rising and constant temperature, the highest temperature of the temperature rising is 600 DEG C, and the temperature in the deposition tube is controlled to be 490-530 DEG C by stopping heating; S3, first vacuumizing, the deposition tube after S2 is operated to be vacuumized and leak detection is performed; S4, pre-gas filling, reaction gas is introduced to be excited with plasma, the reaction gas NH3, N2O and SiH4 are introduced, the gas flow is controlled by a mass flow meter, the mixing ratio is adjusted according to the film type, the radio frequency power is applied to be 13.56 MHz, 200-1000 W, and the glow discharge is triggered to generate plasma, and the impedance is adjusted by a matching network to maintain the stability of the plasma; S5, deposition, the film deposition and process monitoring, the high-energy electrons in the plasma decompose gas molecules to generate active groups, which are transported to the substrate surface by diffusion or ion acceleration to occur adsorption-reaction-film forming process; S6, second vacuumizing, the deposition tube after S5 is operated to be vacuumized for the second time; S7, cleaning, the substrate in the deposition tube is cleaned to remove the residues in the deposition process; S8, third vacuumizing, the deposition tube after S7 is operated to be vacuumized for the third time; S9, back pressure, the deposition tube after S8 is operated to be filled with nitrogen back pressure; S10, boat unloading, the graphite boat after S9 is sent out from the deposition tube to complete the deposition operation.

[0009] Further, before S1 operation, the substrate in the deposition tube is pretreated and cleaned, and the substrate is loaded on a heated base in the reaction cavity.

[0010] Further, the cleaning operation adopts wet cleaning or plasma etching pretreatment.

[0011] Further, the gas flow is controlled by a mass flow meter, and the precision is controlled to be ±1%.

[0012] Further, after the deposition of S5 is completed, the radio frequency power is turned off, inert gas is introduced, and the chamber is cooled to room temperature.

[0013] Further, the pressure in the deposition tube during the deposition process of S5 is 0.1-5 Torr.

[0014] Further, the ratio of the reacted gases NH3, N2O and SiH4 is 1:1:1.

[0015] Further, the flow rate of SiH4 is 100-200 sccm, the flow rate of N2O is 1000-2000 sccm, and the flow rate of NH3 during the thin film deposition process is 2000-4000 sccm to keep the pressure in the reaction chamber stable, and the deposition time is 10-60 seconds.

[0016] A solar cell containing a PECVD-deposited silicon oxynitride film layer is deposited by the above method.

[0017] Further, the SiON layer, SiNx layer, AlOx layer, N-type silicon layer, AlOx layer and SiNx layer are sequentially arranged from top to bottom.

[0018] The beneficial effects of the present application are embodied in: 1. In the present application, silicon oxynitride is an intermediate phase of silicon oxide and silicon nitride, and the silicon oxynitride film has excellent passivation and antireflection properties. By changing the component ratio, the refractive index can be adjusted within a certain range, i.e. 1.4-2.2, so that the silicon oxynitride film has good antireflection performance. At the same time, the silicon oxynitride also contains a large number of hydrogen atoms, which can also achieve good passivation effect.

[0019] 2. In the present application, the silicon oxynitride thin film is deposited by the PECVD method, which enhances the back passivation effect of the solar cell and reduces the recombination of carriers by depositing silicon oxynitride on the back surface. By depositing a silicon oxynitride thin film on the front surface layer, the solar cell reduces the reflectivity of short-wave light between 300-500 nm, enhances the absorption of short-wave light, and improves the absorption of corresponding light, thereby improving the photoelectric conversion efficiency of the solar cell.

[0020] 3. In the present application, after adding a silicon oxynitride film layer on the back surface of the solar cell, the stress of the silicon oxynitride thin film in the silicon oxynitride / silicon nitride stacked film is low, and the Si-O bond can be used to ensure the stability of the interface properties on the silicon interface. Secondly, the hydrogen atoms in the outer silicon nitride layer diffuse into the solar cell body during heat treatment and are bound by the silicon oxynitride layer, further enhancing the bulk passivation effect and thereby improving the minority carrier lifetime.

[0021] 4、In the application, with the increase of NH3 flow, the main component of the generated film changes from SiOx to silicon oxynitride, which makes the refractive index of the solar cell increase. N-H bond energy is much lower than N-N bond energy, so NH3 is the main source of N in the silicon oxynitride film; O has strong negative charge, and the binding energy of Si and O is lower than that of Si and N, so that the combination probability of Si and O atoms is higher. Increasing the flow of NH3 inhibits the combination of Si and O atoms, increases the proportion of N atoms, and thus leads to the decrease of the film deposition rate and the increase of the refractive index. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or prior art description will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, each element or part is not necessarily drawn according to the actual proportion.

[0023] Figure 1 The structure of the solar cell of the present application; Figure 2 The reflectivity comparison chart of different film layer structures; Figure 3 The process flow step schematic diagram of the method of the present application. DETAILED DESCRIPTION

[0024] The embodiments of the technical solutions of the present application will be described in detail below in combination with the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, but cannot limit the protection scope of the present application.

[0025] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should be understood as the usual meaning understood by the skilled person in the field to which the present application belongs.

[0026] A preparation method of a solar cell containing a PECVD deposited silicon oxynitride film layer, comprising the following steps: S1, loading, a graphite boat filled with silicon wafers is sent into the deposition tube by paddle, and the temperature in the deposition tube is controlled to be 490-530℃; S2, temperature control, the temperature in the deposition tube is controlled to be constant by sequential operation of temperature rising and constant temperature, the highest temperature of temperature rising is 600℃, and the temperature in the deposition tube is controlled to be 490-530℃ by stopping heating; S3, first vacuumizing, after the deposition tube after S2 is vacuumized and leak detection is performed; S4, pre-charge, the reaction gas is introduced into the plasma excitation, the gas NH3, N2O and SiH4 is introduced into the reaction, the gas flow is controlled by the mass flow meter, the mixing ratio is adjusted according to the film type, the radio frequency power is applied, 13.56 MHz, 200-1000 W, and the glow discharge is triggered to generate plasma, and the impedance is adjusted by the matching network to maintain the stability of the plasma; S5, deposition, the film deposition is decomposed by the high-energy electrons in the plasma to generate active groups, which are transported to the substrate surface by diffusion or ion acceleration to occur the adsorption-reaction-film forming process; S6, second vacuumizing, the deposition tube after S5 is operated for the second time; S7, cleaning, the substrate in the deposition tube is cleaned to remove the residues in the deposition process; S8, third vacuumizing, the deposition tube after S7 is operated for the third time; S9, back pressure, the deposition tube after S8 is filled with nitrogen and back pressure is operated; S10, boat, the graphite boat after S9 is sent out from the deposition tube to complete the deposition operation.

[0027] As preferred, before S1 operation, the substrate in the deposition tube is pretreated and cleaned, and the substrate is loaded on the heating base in the reaction chamber.

[0028] As preferred, the cleaning operation adopts the wet cleaning or the plasma etching pretreatment.

[0029] As preferred, the gas flow is controlled by the mass flow meter, and the precision is controlled at ±1%.

[0030] As preferred, after the deposition of S5 is completed, the radio frequency power is turned off, the inert gas is introduced, and the chamber is cooled to room temperature.

[0031] As preferred, during the deposition of S5, the pressure in the deposition tube is 0.1-5 Torr.

[0032] As preferred, the ratio of the reaction gas NH3, N2O and SiH4 is 1:1:1.

[0033] As preferred, the flow of SiH4 is 100-200 sccm, the flow of N2O is 1000-2000 sccm, the flow of NH3 introduced during the film deposition process is 2000-4000 sccm to keep the pressure in the reaction chamber stable, and the deposition time is 10 s-1 min.

[0034] A solar cell containing a PECVD deposited silicon oxynitride film layer adopts the above method for deposition.

[0035] Preferably, the layers are arranged in order from top to bottom as follows: a SiON layer, a SiNx layer, an AlOx layer, an N-type silicon layer, an AlOx layer, and a SiNx layer.

[0036] Embodiment 1 A method for manufacturing a solar cell comprising a PECVD-deposited silicon oxynitride film layer, comprising the following steps: S1, pretreating and cleaning the substrate in the deposition tube, and loading the substrate onto a heated base in the reaction chamber, the cleaning operation using wet cleaning or plasma etching pretreatment; boat loading, a graphite boat filled with silicon wafers is sent into the deposition tube by a paddle, and the temperature in the deposition tube is controlled at 490°C; S2, temperature control, the temperature in the deposition tube is controlled by sequentially operating the temperature rising and constant temperature, the highest temperature of the temperature rising is 600°C, and the temperature in the deposition tube is controlled within 490°C by stopping heating; S3, first vacuumizing, the deposition tube after S2 is vacuumized and leak detection is performed; S4, pre-charging, introducing the reaction gas into plasma excitation, introducing the reaction gases NH3, N2O and SiH4, the gas flow is controlled by a mass flow meter, the gas flow is controlled by a mass flow meter, and the accuracy is controlled at ±1%, the mixing ratio is adjusted according to the type of thin film, the ratio of the reaction gases NH3, N2O and SiH4 is 1:1:1, the flow rate of SiH4 is 200sccm, the flow rate of N2O is 1000sccm, the flow rate of NH3 introduced during the thin film deposition process is 2000sccm to keep the pressure in the reaction chamber stable, the deposition time is 12s, the radio frequency power applied is 13.56MHz, 200W, and the glow discharge is triggered to generate plasma, the impedance is adjusted by a matching network to maintain the stability of the plasma; S5, deposition, the pressure in the deposition tube is 0.1Torr, the thin film deposition process is monitored, the high-energy electrons in the plasma decompose the gas molecules to generate active groups, which are transported to the substrate surface by diffusion or ion acceleration to undergo adsorption-reaction-film formation process, the radio frequency power is turned off, the inert gas is introduced, and the chamber is cooled to room temperature; S6, second vacuumizing, the deposition tube after S5 is vacuumized for the second time; S7, cleaning, the substrate in the deposition tube is cleaned by wet cleaning or plasma etching pretreatment to remove the residues in the deposition process; S8, third vacuumizing, the deposition tube after S7 is vacuumized for the third time; S9, back pressure, the deposition tube after S8 is filled with nitrogen back pressure operation; S10, the graphite boat after S9 is sent out from the deposition tube, and the deposition operation is completed.

[0037] Preferably, before S1, the substrate in the deposition tube is pretreated and cleaned, and the substrate is loaded onto the heating base in the reaction chamber.

[0038] Example 2 A method for preparing a solar cell containing a PECVD deposited silicon oxynitride film layer, comprising the following steps: S1, the substrate in the deposition tube is pretreated and cleaned, and the substrate is loaded onto the heating base in the reaction chamber, the cleaning operation uses wet cleaning or plasma etching pretreatment; the graphite boat filled with silicon wafers is sent into the deposition tube through the paddle, and the temperature in the deposition tube is controlled at 520℃; S2, temperature control, the temperature in the deposition tube is controlled by temperature rising and constant temperature in sequence, the highest temperature of the temperature rising is 600℃, and the temperature in the deposition tube is controlled in 520℃ by stopping heating; S3, first vacuumizing, after the deposition tube after S2 is vacuumized and leak detection is performed; S4, pre-charging, the reaction gas is introduced and excited by plasma, the reaction gases NH3, N2O and SiH4 are introduced, the gas flow is controlled by a mass flow meter, the gas flow is controlled by a mass flow meter, and the precision is controlled at ±1%, the mixing ratio is adjusted according to the film type, the ratio of the reaction gases NH3, N2O and SiH4 is 1:1:1, the flow of SiH4 is 180sccm, the flow of N2O is 1650sccm, the flow of NH3 introduced during the film deposition process is 3600sccm to keep the pressure in the reaction chamber stable, the deposition time is 50s, the radio frequency power is 13.56MHz, 800W, the glow discharge is triggered to generate plasma, the impedance is adjusted by a matching network to maintain the stability of the plasma; S5, deposition, the pressure in the deposition tube is 1.5Torr, the film deposition and process monitoring, the active groups are generated by the high-energy electrons in the plasma decomposing the gas molecules, the adsorption-reaction-film forming process occurs on the substrate surface by diffusion or ion acceleration transport, the radio frequency power is turned off, the inert gas is introduced, and the chamber is cooled to room temperature; S6, second vacuumizing, the deposition tube after S5 is vacuumized for the second time; S7, cleaning, the substrate in the deposition tube is cleaned by wet cleaning or plasma etching pretreatment to remove the residues in the deposition process; S8, third vacuumizing, the deposition tube after S7 is vacuumized for the third time; S9, back pressure, nitrogen back pressure operation is performed on the deposition tube after S8 is completed; S10, boat, the graphite boat after S9 is completed is sent out from the deposition tube, and the deposition operation is completed.

[0039] Comparative Example 1 One of the key differences between Comparative Example 1 and Example 1 is that the conventional preparation process of Comparative Example 1 lacks step S4, and the rest of the process is exactly the same except for the lack of this process.

[0040] Comparative Example 2 The key difference between Comparative Example 2 and Example 2 is that the conventional preparation process of Comparative Example 1 lacks steps S4 and S9, and the rest of the process is exactly the same except for the lack of these two processes.

[0041] Test Results Table

[0042] In performance improvement: battery conversion efficiency is improved by 0.12%-0.25%; in compatibility: adapt to PERC, TOPCon, HJT and other mainstream technology routes.

[0043] It should be explained that Eta is the conversion efficiency (%), Uoc is the open circuit voltage (mV), Isc is the short circuit current (A), FF is the fill factor, Rser is the series resistance (Ω), Rsh is the parallel resistance (Ω), IRev2 is the reverse current (A).

[0044] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the specification of the present application.

Claims

1. A method for fabricating a silicon oxynitride film solar cell with PECVD deposition, characterized in that, Includes the following steps: S1. Entering the boat: The graphite boat filled with silicon wafers is fed into the deposition tube by a paddle. The temperature inside the deposition tube is controlled at 490-530℃. S2. Temperature control: The temperature inside the deposition tube is kept constant by sequentially heating and holding the temperature. The maximum temperature for heating is 600℃, and the temperature is held constant by stopping heating, keeping the temperature inside the deposition tube between 490-530℃. S3. First vacuuming: Vacuuming and leak detection are performed on the deposition tube after S2. S4. Pre-charge: Introduce the reaction gas into the plasma for excitation. Introduce the reaction gases NH3, N2O and SiH4. The gas flow rate is controlled by a mass flow meter. Adjust the mixing ratio according to the thin film type. Apply radio frequency power of 13.56MHz, 200-1000W, and trigger glow discharge to generate plasma. Adjust the impedance through a matching network to maintain plasma stability. S5. Deposition, Thin Film Deposition and Process Monitoring: High-energy electrons in plasma decompose gas molecules to generate active groups, which are then transported to the substrate surface via diffusion or accelerated ion transport to undergo an adsorption-reaction-film formation process. S6. Second vacuuming: Perform a second vacuuming operation on the deposition tube after completing S5. S7. Cleaning: Clean the substrate in the deposition tube to remove residues from the deposition process. S8. Third vacuuming: Perform a third vacuuming operation on the deposition tube after completing S7. S9, backpressure: Nitrogen backpressure is performed on the deposition tube after S8. S10, Unloading: After completing S9, the graphite boat will be unloaded from the deposition tube to complete the deposition operation.

2. The method for preparing a silicon oxynitride film solar cell with PECVD deposition according to claim 1, characterized in that, Before the S1 operation, the substrate inside the deposition tube is pretreated and cleaned, and then the substrate is loaded onto the heated base in the reaction chamber.

3. The method for preparing a silicon oxynitride film solar cell with PECVD deposition according to claim 2, characterized in that, The cleaning process employs either wet cleaning or plasma etching pretreatment.

4. The method for preparing a silicon oxynitride film solar cell with PECVD deposition according to claim 1, characterized in that, The gas flow rate is controlled by a mass flow meter with an accuracy of ±1%.

5. The method for preparing a silicon oxynitride film solar cell with PECVD deposition according to claim 1, characterized in that, After the S5 deposition is completed, the RF power is turned off, inert gas is introduced, and the chamber is cooled to room temperature.

6. The method for preparing a silicon oxynitride film solar cell with PECVD deposition according to claim 1, characterized in that, During the deposition process in S5, the pressure inside the deposition tube is 0.1-5 Torr.

7. The method for preparing a silicon oxynitride film solar cell with PECVD deposition according to claim 1, characterized in that, The ratio of the reacting gases NH3, N2O and SiH4 is 1:1:

1.

8. The method for preparing a silicon oxynitride film solar cell with PECVD deposition according to claim 1, characterized in that, The flow rate of SiH4 is 100-200 sccm, the flow rate of N2O is 1000-2000 sccm, and NH3 with a flow rate of 2000-4000 sccm is introduced during the thin film deposition process to maintain stable pressure in the reaction chamber. The deposition time is 10 s-1 min.

9. A solar cell containing a silicon oxynitride film layer deposited by PECVD, characterized in that, Deposition is performed using the method of any one of claims 1-8.

10. The solar cell with a silicon oxynitride film layer deposited by PECVD according to claim 9, characterized in that, It includes, from top to bottom, a SiON layer, a SiNx layer, an AlOx layer, an N-type silicon layer, an AlOx layer, and a SiNx layer.

Images