A method for testing crystalline silicon bulk recombination

Abstract

The present invention relates to the technical field of crystalline silicon solar cells and discloses a method for testing bulk recombination in crystalline silicon. The method uses the bulk dark saturation current density values ​​of the crystalline silicon at different carrier injection concentrations to represent the bulk recombination value of the crystalline silicon. The method comprises: preparing a crystalline silicon sample; testing the hidden open circuit voltage values ​​and surface dark saturation current density values ​​of the crystalline silicon sample at different carrier injection concentrations; obtaining the total dark saturation current density values ​​of the crystalline silicon sample at different carrier injection concentrations based on the hidden open circuit voltage values; and obtaining the bulk recombination value of the crystalline silicon sample based on the surface dark saturation current density values ​​and total dark saturation current density values ​​at different carrier injection concentrations. The method accurately characterizes the bulk recombination magnitude of the crystalline silicon through the bulk dark saturation current density value, establishes a relationship with the open circuit voltage, and quantitatively calculates the bulk recombination value of the crystalline silicon at different carrier injection concentrations.

Description

Technical Field

[0001] The present invention relates to the technical field of crystalline silicon solar cells, and in particular to a method for testing recombination of a crystalline silicon body region. Background Art

[0002] In crystalline silicon solar cells, the open-circuit voltage is primarily determined by the recombination of the cell, which primarily originates from three sources: the bulk region of the silicon wafer, the passivation regions on the front and back surfaces, and the metal contact regions. In recent years, thanks to advances in passivation film technology and the introduction of passivating contact structures, recombination in the passivation regions and metal contact regions on the front and back surfaces of crystalline silicon solar cells has gradually decreased. Consequently, recombination in the bulk region has become increasingly significant, becoming a significant factor limiting the efficiency of crystalline silicon solar cells. Reclamation in the bulk region of the silicon wafer varies with different solar cell fabrication processes. For example, high-temperature processes (boron diffusion and annealing) can cause oxygen atoms in the silicon wafer to aggregate, forming oxygen precipitates, enhancing recombination in the bulk region. Similarly, phosphorus doping can extract impurities from the silicon wafer, reducing recombination in the bulk region.

[0003] In the past few years, the average conversion efficiency of crystalline silicon solar cells was generally low (≤22%). The recombination of the passivation area and the metal contact area on the front and back surfaces of crystalline silicon solar cells dominated, and the recombination of the silicon wafer body was not taken seriously. For example, a test method for the crystalline silicon body minority carrier lifetime provided by publication number CN104359737B generally uses the body minority carrier lifetime to compare the size of the silicon wafer body recombination. The body minority carrier lifetime (τ Bulk ) Usually the formula is: 1 / τ eff =1 / τ Bulk +2S / W to calculate, where τ eff The silicon wafer is implanted at a specific concentration (usually 1E15cm -3 ), S is the effective minority carrier lifetime of the silicon wafer surface, and W is the thickness of the silicon wafer. Therefore, the minority carrier lifetime of the silicon wafer obtained according to the above formula is also the value under a specific implantation concentration.

[0004] However, as bulk recombination in silicon wafers increasingly restricts the efficiency of crystalline silicon solar cells, there are many drawbacks in using the bulk minority carrier lifetime at a specific carrier injection concentration to describe the recombination performance in the bulk region of silicon wafers:

[0005] 1) When the silicon wafer has a long bulk lifetime and good surface passivation, there is a large error in the bulk lifetime test (this can be seen from the crystalline silicon bulk minority carrier lifetime test method in CN104359737B, which requires surface treatment in step S100 to increase the recombination velocity of the crystalline silicon surface, thereby improving the accuracy of the test results after steps S200 and S300). Moreover, N-type silicon wafers have a longer minority carrier lifetime than P-type silicon wafers. Taking a passivated high-resistivity (5Ω·cm) N-type single crystal silicon wafer as an example: the silicon wafer surface recombination velocity S corresponding to the passivated contact structure is 1.0cm / s, and the effective minority carrier lifetime of the silicon wafer at a specific implantation concentration is τ eff The minority carrier lifetime τ in the bulk region of the silicon wafer can be calculated to be 6ms and the thickness of the silicon wafer is 160μm. Bulk is 24ms; when τ eff When the fluctuation is 10%, τ eff The fluctuation is 6.6ms. The passivated contact structure can control the recombination rate on the silicon wafer surface to 1cm / s. The calculated bulk minority carrier lifetime τ of the N-type silicon wafer with a resistance of 5Ω·cm is Bulk is 37.68ms, τ Bulk The fluctuation is as high as 57%. It can be seen that when the silicon wafer has a higher body life and better surface passivation, τ eff Slight fluctuations in the test will affect τ Bulk The calculations lead to huge errors.

[0006] 2) Only the bulk minority carrier lifetime under a specific carrier injection concentration can be obtained; as mentioned above, τ eff The silicon wafer is injected at a specific carrier concentration (usually 1E15cm -3 ) effective minority carrier lifetime, so the obtained τ Bulk The bulk minority carrier lifetime at the same specific injection concentration is a single value and cannot be obtained at different injection concentrations. In crystalline silicon solar cells, the recombination in the silicon wafer bulk region varies with the injection concentration. The open circuit voltage of current large-scale industrial solar cells is generally between 650 and 750 mV, corresponding to a carrier injection concentration of 1.0x10 15 ~2.0x10 16 cm -3 Therefore, for different open circuit voltages and different carrier injection concentrations, the existing method cannot obtain the corresponding silicon wafer body region recombination value under different carrier injection concentrations.

[0007] 3) Bulk minority carrier lifetime cannot be directly correlated with the open-circuit voltage of a solar cell. Bulk minority carrier lifetime can only be used to qualitatively compare the performance of bulk recombination in silicon wafers, but not quantitatively. Therefore, improvements to existing bulk recombination testing methods are urgently needed. Summary of the Invention

[0008] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a method for testing the body region recombination of crystalline silicon, which accurately characterizes the body region recombination size of crystalline silicon through the dark state saturation current density value of the body region, can establish a relationship with the open circuit voltage, and can quantitatively calculate the body region recombination value of crystalline silicon under different carrier injection concentrations.

[0009] Based on this, the present invention discloses a method for testing the recombination of the body region of crystalline silicon, which uses the dark state saturation current density value of the body region of crystalline silicon under different carrier injection concentrations to represent the body region recombination value of crystalline silicon, and includes the following steps:

[0010] S1. Preparing a crystalline silicon sample to be tested: sequentially forming a carrier selective layer and an anti-reflection film on the front surface of a crystalline silicon substrate, and sequentially forming a carrier selective layer and an anti-reflection film on the back surface of the crystalline silicon substrate; wherein the carrier selective layer has a homogeneous structure or a passivated contact structure;

[0011] S2. Testing the hidden open circuit voltage and surface dark state saturation current density of the crystalline silicon sample at different carrier injection concentrations;

[0012] S3. Obtaining the total dark state saturation current density value of the crystalline silicon sample at different carrier injection concentrations according to the hidden open circuit voltage values ​​at different carrier injection concentrations;

[0013] S4. Obtaining a body region recombination value of the crystalline silicon sample according to the surface dark state saturation current density value and the total dark state saturation current density value under different carrier injection concentrations.

[0014] Preferably, in step S1, the homogeneous structure is a P-type or N-type single crystal doped layer, the sheet resistance of the homogeneous structure is 10 to 500 Ω / sq, and the junction depth is 0.3 to 3 μm.

[0015] Preferably, in step S1, the homogeneous structure is manufactured by thermal diffusion or ion implantation.

[0016] Preferably, in step S1, the passivation contact structure includes a tunneling oxide layer and a heavily doped polysilicon layer stacked on a surface of the tunneling oxide layer.

[0017] Further preferably, the tunnel oxide layer is made of silicon oxide, titanium oxide or aluminum oxide, and has a thickness of 0.5 to 3.0 nm.

[0018] Further preferably, the conductivity type of the heavily doped polysilicon layer is N-type or P-type, the thickness of the heavily doped polysilicon layer is 30 to 600 nm, and the doping concentration is 0.1 to 8.0E+20 cm -3 .

[0019] Preferably, in step S1, the anti-reflection film is a stacked structure formed by one or more films selected from the group consisting of aluminum oxide film, silicon dioxide film, silicon nitride film and silicon oxynitride film; and the thickness of the anti-reflection film is 50 to 150 nm.

[0020] Further preferably, in step S2, a minority carrier lifetime tester is used to test the hidden open circuit voltage value and the surface dark state saturation current density value of the crystalline silicon sample under different carrier injection concentrations.

[0021] Further preferably, in step S3, the total dark state saturation current density value of the crystalline silicon sample at different carrier injection concentrations is calculated by the following formula:

[0022]

[0023] Where, J G is the photocurrent value under different carrier injection concentrations Δn, iV oc is the hidden open circuit voltage value of crystalline silicon sample under different carrier injection concentration Δn, J 0,T is the total dark state saturation current density under different carrier injection concentrations Δn, V T is the thermal voltage, V T The magnitude is 0.0259V.

[0024] Further preferably, in step S4, the difference between the surface dark state saturation current density value and the total dark state saturation current density value under different carrier injection concentrations is the body region dark state saturation current density value of the crystalline silicon under different carrier injection concentrations, and its calculation formula is:

[0025] J 0,B =J 0,T -J 0,S

[0026] Where, J 0,T is the total dark state saturation current density value under different carrier injection concentrations Δn, J 0,S is the surface dark state saturation current density under different carrier injection concentrations Δn, J 0,B is the dark state saturation current density value of the body region of the crystalline silicon sample under different carrier injection concentrations Δn.

[0027] Compared with the prior art, the present invention has at least the following beneficial effects:

[0028] The present invention develops a method for testing crystalline silicon bulk recombination, creatively characterizing bulk recombination in the form of crystalline silicon's dark-state saturation current. This method accurately represents the bulk recombination magnitude of crystalline silicon using the bulk dark-state saturation current density of crystalline silicon, effectively avoiding test errors. It also establishes a relationship between bulk recombination and open-circuit voltage. This is because the open-circuit voltage of a crystalline silicon solar cell is directly correlated with the dark-state saturation current density (J0), with the magnitude of the dark-state saturation current density J0 directly determining the open-circuit voltage of the crystalline silicon solar cell. Furthermore, through the coordination of steps S1 to S4, the bulk recombination value of crystalline silicon at different carrier injection concentrations can be quantitatively obtained. Furthermore, the method can test crystalline silicon with homogeneous structures and / or passivated contact structures, has a wide test range, and is simple, time-efficient, and cost-effective. Therefore, the present invention's testing method can quickly and accurately measure bulk recombination magnitude in crystalline silicon, which is of great significance for monitoring and optimizing crystalline silicon manufacturing processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a flow chart of a method for testing crystalline silicon body region recombination.

[0030] Figure 2 Schematic diagram of the cross-sectional structure of the crystalline silicon sample of Example 1.

[0031] Figure 3 The IV values ​​of the crystalline silicon sample of Example 1 at different carrier injection concentrations obtained in step 2 are as follows: oc Data chart.

[0032] Figure 4 J under different carrier injection concentrations obtained from step 2 of the crystalline silicon sample in Example 1 0,S Data chart.

[0033] Figure 5 This is a diagram of body region recombination data at different carrier injection concentrations calculated in step 4 for the crystalline silicon sample of Example 1.

[0034] Figure 6 Schematic diagram of the cross-sectional structure of the crystalline silicon sample of Example 2.

[0035] Figure 7 The IV values ​​of the crystalline silicon sample of Example 2 under different carrier injection concentrations obtained in step 2 are as follows: oc Data chart.

[0036] Figure 8 J under different carrier injection concentrations obtained from step 2 of the crystalline silicon sample of Example 2 0,S Data chart.

[0037] Figure 9 This is a diagram of body region recombination data at different carrier injection concentrations calculated in step 4 for the crystalline silicon sample of Example 2.

[0038] Figure 10 Schematic diagram of the cross-sectional structure of the crystalline silicon sample of Example 3.

[0039] Figure 11 The IV values ​​of the crystalline silicon sample of Example 3 under different carrier injection concentrations obtained in step 2 are as follows: oc Data chart.

[0040] Figure 12 J under different carrier injection concentrations obtained from step 2 of the crystalline silicon sample in Example 3 0,S Data chart.

[0041] Figure 13 This is a diagram of body region recombination data at different carrier injection concentrations calculated in step 4 for the crystalline silicon sample of Example 3.

[0042] Description of the reference numerals: silicon substrate 11 , first carrier selective layer 12 , second carrier selective layer 13 , tunneling oxide layer 131 , doped polysilicon layer 132 , first anti-reflection film 14 , second anti-reflection film 15 . DETAILED DESCRIPTION

[0043] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] Example 1

[0045] A method for testing the recombination of the crystalline silicon body region in this embodiment is shown in FIG. Figure 1 , the test steps are as follows:

[0046] Step 1: Prepare the crystalline silicon sample to be tested:

[0047] a) Preparing a first carrier selection layer on both the front and rear surfaces of a crystalline silicon substrate 11: Select an N-type single crystal silicon substrate 11 with a resistivity of 0.3 to 5.0 Ω·cm and a thickness of 160 μm, perform a damage layer removal treatment and a texturing treatment on the silicon substrate 11, and then place the silicon substrate 11 in a thermal diffusion furnace for boron diffusion doping to form a first carrier selection layer on both the front and rear surfaces of the silicon substrate 11.

[0048] The first carrier selective layer 12 is a homogeneous structure, specifically a P-type or N-type single crystal doped layer prepared by thermal diffusion or ion implantation, and has a square resistance of 10-500Ω / sq and a junction depth of 0.3-3μm.

[0049] In this embodiment, the first carrier selective layer 12 is a P-type single crystal doped layer made by thermal diffusion, and the sheet resistance of the first carrier selective layer 12 is 100-150Ω / sq.

[0050] b) depositing a first anti-reflection film 14 on the front surface of the first carrier selective layer 12 located on the front surface of the silicon substrate 11, and depositing a first anti-reflection film 14 on the rear surface of the first carrier selective layer 12 located on the rear surface of the silicon substrate 11.

[0051] The first anti-reflection film 14 is a stacked structure formed by one or more films selected from the group consisting of aluminum oxide film, silicon dioxide film, silicon nitride film and silicon oxynitride film. The total thickness of the first anti-reflection film 14 is 50 to 150 nm.

[0052] Specifically, the first anti-reflection film 14 is a stacked structure formed by an aluminum oxide film and a silicon nitride film. The preparation method is as follows: an aluminum oxide film with a thickness of 0.5 to 5.0 nm is deposited on the first carrier selective layer 12 by the ALD method, and then a silicon nitride film with a thickness of 60 to 85 nm is deposited on the aluminum oxide film by the PECVD method to obtain the first anti-reflection film 14. The structure of the crystalline silicon sample prepared in step 1 of this embodiment is as follows: Figure 2 shown.

[0053] Step 2: Test the hidden open circuit voltage i-Voc and surface dark state saturation current density J of crystalline silicon samples under different carrier injection concentrations Δn. 0,S For example, the carrier injection concentration of the crystalline silicon sample is increased in sequence to obtain the hidden open circuit voltage value i-Voc and the surface dark state saturation current density value J of the crystalline silicon sample under different carrier injection concentrations Δn through testing. 0,S :

[0054] The crystalline silicon sample to be tested is placed on the platform of the Sinton WCT-120 minority carrier lifetime tester. The center area of ​​the crystalline silicon sample to be tested coincides with the center of the coil of the minority carrier lifetime tester. The iV of the crystalline silicon sample under different carrier injection concentrations Δn is measured. oc and J 0,S .

[0055] In this embodiment, the iV of the crystalline silicon sample under different carrier injection concentrations Δn oc The range is 598~740mV (the data is as follows Figure 3 As shown), the J of the crystalline silicon sample under different carrier injection concentrations Δn 0,S The range is 25~36fA / cm 2 (The data is as follows Figure 4 shown).

[0056] Step 3: Obscure open circuit voltage iV under different carrier injection concentrations Δn oc , and obtain the total dark state saturation current density J of the crystalline silicon sample at different carrier injection concentrations Δn 0,T :

[0057] Combined with the hidden open circuit voltage value iV under different carrier injection concentrations Δn obtained in step 2 oc The total dark state saturation current density J of the crystalline silicon sample under different carrier injection concentrations Δn is calculated by the following formula (3): 0,T ;

[0058] According to formulas (1) and (2), after simple transformation, we can get the following formula (3):

[0059] J G =C*N (1)

[0060]

[0061]

[0062] In formulas (1)-(3), J G is the photocurrent value under different carrier injection concentrations Δn, C is the current density value under 1 sun intensity, and the C value is 41.8mA / cm 2 , N is the number of suns under different carrier injection concentrations Δn, iV oc is the hidden open circuit voltage of crystalline silicon samples at different carrier injection concentrations Δn, J 0,T is the total dark state saturation current density under different carrier injection concentrations Δn, V T is the thermal voltage, V T The magnitude is 0.0259V.

[0063] In this embodiment, the J of the crystalline silicon sample under different carrier injection concentrations Δn 0,T The range is 51~80fA / cm 2 .

[0064] Step 4: Calculate the surface dark state saturation current density J under different carrier injection concentrations Δn 0,S and the total dark state saturation current density J 0,T , and obtain the dark state saturation current density value J of the body region of the crystalline silicon sample at different carrier injection concentrations Δn 0,B , that is, the body region recombination size of crystalline silicon samples under different carrier injection concentrations Δn:

[0065] Combined with the surface dark state saturation current density J under different carrier injection concentrations Δn tested in step 2 0,S, and the total dark state saturation current density J under different carrier injection concentrations Δn calculated in step 3 0,T , through J 0,S and J 0,T The dark state saturation current density J of the crystalline silicon sample at different carrier injection concentrations Δn was calculated. 0,B ;

[0066] The above J 0,S and J 0,T The difference calculation formula is shown in the following formula (4):

[0067] J 0,B =J 0,T -J 0,S (4)

[0068] In formula (4), J 0,T is the total dark state saturation current density value under different carrier injection concentrations Δn, J 0,S is the surface dark state saturation current density under different carrier injection concentrations Δn, J 0,B is the dark state saturation current density value of the body region of the crystalline silicon sample under different carrier injection concentrations Δn.

[0069] In this embodiment, the dark state saturation current density value J of the body region of the crystalline silicon sample under different carrier injection concentrations Δn is 0,B The range is 15~55fA / cm 2 , its data is as follows Figure 5 As shown, the body region recombination size of the crystalline silicon sample in this embodiment under different carrier injection concentrations Δn is obtained.

[0070] Example 2

[0071] A method for testing the recombination of the crystalline silicon body region in this embodiment is shown in FIG. Figure 1 , the test steps are as follows:

[0072] Step 1: Prepare the crystalline silicon sample to be tested:

[0073] a) Preparing a second carrier selective layer 13 on both the front and rear surfaces of a crystalline silicon substrate 11: Select an N-type single crystal silicon substrate 11 with a resistivity of 0.3 to 5.0 Ω·cm and a thickness of 160 μm, perform a damage layer removal treatment and a texturing treatment on the silicon substrate 11, and then form a second carrier selective layer 13 on both the front and rear surfaces of the treated silicon substrate 11.

[0074] The second carrier selective layer 13 is an N-type or P-type passivation contact structure, which is composed of a tunneling oxide layer 131 and a phosphorus-doped polysilicon layer 132 stacked on the surface of the tunneling oxide layer 131. The material of the tunneling oxide layer 131 is silicon oxide, titanium oxide or aluminum oxide, and the thickness of the tunneling oxide layer 131 is 0.5 to 3.0 nm. The conductivity type of the heavily doped polysilicon layer 132 is N-type or P-type, and the thickness of the heavily doped polysilicon layer 132 is 30 to 600 nm and the doping concentration is 0.1 to 8.0E+20 cm -3 .

[0075] In this embodiment, the second carrier selective layer 13 is an N-type passivation contact structure, the tunneling oxide layer 131 is a silicon oxide layer, the thickness of the tunneling oxide layer 131 is 1.0 to 2.0 nm, the thickness of the phosphorus-doped polysilicon layer 132 is 100 to 150 nm, and the doping concentration is 2.0 to 3.0E+20 cm -3 .

[0076] b) depositing a second anti-reflection film 15 on the front surface of the second carrier selective layer 13 located on the front surface of the silicon substrate 11, and depositing a second anti-reflection film 15 on the rear surface of the second carrier selective layer 13 located on the rear surface of the silicon substrate 11.

[0077] The second anti-reflection film 15 is a stacked structure formed by one or more films selected from the group consisting of aluminum oxide film, silicon dioxide film, silicon nitride film and silicon oxynitride film. The total thickness of the second anti-reflection film 15 is 50 to 150 nm.

[0078] Specifically, the second anti-reflection film 15 is a silicon nitride film, and its preparation method is: using the PECVD method to deposit a silicon nitride film with a thickness of 60 to 85 nm on the second carrier selective layer 13, so as to obtain the second anti-reflection film 15. The structure of the crystalline silicon sample prepared in step 1 of this embodiment is as follows: Figure 6 shown.

[0079] Step 2: Test the hidden open circuit voltage iV of the crystalline silicon sample under different carrier injection concentrations Δn oc and the surface dark state saturation current density J 0,S For the specific testing process of this step, please refer to step 2 of Example 1.

[0080] In this embodiment, the iV of the crystalline silicon sample under different carrier injection concentrations Δn oc The range is 593~710mV (the data is as follows Figure 7 As shown), the J of the crystalline silicon sample under different carrier injection concentrations Δn 0,S The range is 8~17fA / cm 2 (The data is as follows Figure 8 shown).

[0081] Step 3: Obscure open circuit voltage iV under different carrier injection concentrations Δn oc , and obtain the total dark state saturation current density J of the crystalline silicon sample at different carrier injection concentrations Δn 0,T For the specific calculation process of this step, please refer to step 3 of Example 1.

[0082] In this embodiment, the J of the crystalline silicon sample under different carrier injection concentrations Δn 0,T The range is 18~20fA / cm 2 .

[0083] Step 4: Calculate the surface dark state saturation current density J under different carrier injection concentrations Δn 0,S and the total dark state saturation current density J 0,T , and obtain the dark state saturation current density value J of the body region of the crystalline silicon sample at different carrier injection concentrations Δn 0,B , that is, the body region recombination size of the crystalline silicon sample under different carrier injection concentrations Δn. The specific calculation process of this step refers to step 4 of Example 1.

[0084] In this embodiment, the dark state saturation current density value J of the body region of the crystalline silicon sample under different carrier injection concentrations Δn is 0,B The range is 3~9fA / cm 2 , its data is as follows Figure 9 As shown, the body region recombination size of the crystalline silicon sample in this embodiment under different carrier injection concentrations Δn is obtained.

[0085] Example 3

[0086] A method for testing the recombination of the crystalline silicon body region in this embodiment is shown in FIG. Figure 1 , the test steps are as follows:

[0087] Step 1: Prepare the crystalline silicon sample to be tested:

[0088] a) Preparing a first carrier selective layer 12 on the front surface of a crystalline silicon substrate 11, and preparing a second carrier selective layer 13 on the back surface of the crystalline silicon substrate 11: selecting an N-type single crystal silicon substrate 11 with a resistivity of 0.3 to 5.0 Ω·cm and a thickness of 160 μm, performing a damage layer removal treatment and a texturing treatment on the silicon substrate 11, and then placing the silicon substrate 11 in a thermal diffusion furnace for boron diffusion doping to form a first carrier selective layer 12 on the front and back surfaces of the silicon substrate 11; then removing the first carrier selective layer 12 on the back surface of the silicon substrate 11 by etching, and then preparing a second carrier selective layer 13 on the back surface of the silicon substrate 11.

[0089] The first carrier selective layer 12 is a homogeneous structure, specifically a P-type or N-type single crystal doped layer prepared by thermal diffusion or ion implantation, and has a square resistance of 10-500Ω / sq and a junction depth of 0.3-3μm.

[0090] In this embodiment, the first carrier selective layer 12 is a P-type single crystal doped layer made by thermal diffusion, and the sheet resistance of the first carrier selective layer 12 is 100-150Ω / sq.

[0091] The second carrier selective layer 13 is an N-type or P-type passivation contact structure, which is composed of a tunneling oxide layer 131 and a phosphorus-doped polysilicon layer 132 stacked on the surface of the tunneling oxide layer 131. The material of the tunneling oxide layer 131 is silicon oxide, titanium oxide or aluminum oxide, and the thickness of the tunneling oxide layer 131 is 0.5 to 3.0 nm. The conductivity type of the heavily doped polysilicon layer 132 is N-type or P-type, and the thickness of the heavily doped polysilicon layer 132 is 30 to 600 nm and the doping concentration is 0.1 to 8.0E+20 cm -3 .

[0092] In this embodiment, the second carrier selective layer 13 is an N-type passivation contact structure, the tunneling oxide layer 131 is a silicon oxide layer, the thickness of the tunneling oxide layer 131 is 1.0 to 2.0 nm, the thickness of the phosphorus-doped polysilicon layer 132 is 100 to 150 nm, and the doping concentration is 2.0 to 3.0E+20 cm -3 .

[0093] b) depositing a first anti-reflection film 14 on the front surface of the first carrier selective layer 12 , and depositing a second anti-reflection film 15 on the rear surface of the second carrier selective layer 13 .

[0094] Among them, the first anti-reflection film 14 and the second anti-reflection film 15 are a stacked structure formed by one or more films selected from the group consisting of aluminum oxide film, silicon dioxide film, silicon nitride film and silicon oxynitride film, and the total thickness of the first anti-reflection film 14 and the second anti-reflection film 15 is 50 to 150 nm.

[0095] Specifically, the first anti-reflection film 14 is a stacked structure formed by an aluminum oxide film and a silicon nitride film, and its preparation method is: an aluminum oxide film with a thickness of 0.5 to 5.0 nm is deposited on the front surface of the first carrier selective layer 12 by the ALD method, and then a silicon nitride film with a thickness of 60 to 85 nm is deposited on the front surface of the aluminum oxide film by the PECVD method to obtain the first anti-reflection film 14.

[0096] Specifically, the second anti-reflection film 15 is a silicon nitride film, and its preparation method is as follows: a silicon nitride film with a thickness of 60 to 85 nm is deposited on the rear surface of the second carrier selective layer 13 by PECVD method, thereby obtaining the second anti-reflection film 15. The structure of the crystalline silicon sample prepared in step 1 of this embodiment is as follows: Figure 10 shown.

[0097] Step 2: Test the hidden open circuit voltage iV of the crystalline silicon sample under different carrier injection concentrations Δn oc and the surface dark state saturation current density J 0,S For the specific testing process of this step, please refer to step 2 of Example 1.

[0098] In this embodiment, the iV of the crystalline silicon sample under different carrier injection concentrations Δn oc The range is 626~748mV (the data is as follows Figure 11 As shown), the J of the crystalline silicon sample under different carrier injection concentrations Δn 0,S The range is 18 to 28 fA / cm 2 (The data is as follows Figure 12 shown).

[0099] Step 3: Obscure open circuit voltage iV under different carrier injection concentrations Δn oc , and obtain the total dark state saturation current density J of the crystalline silicon sample at different carrier injection concentrations Δn 0,T For the specific calculation process of this step, please refer to step 3 of Example 1.

[0100] In this embodiment, the J of the crystalline silicon sample under different carrier injection concentrations Δn 0,T The range is 28~32fA / cm 2 .

[0101] Step 4: Calculate the surface dark state saturation current density J under different carrier injection concentrations Δn 0,S and the total dark state saturation current density J 0,T , and obtain the dark state saturation current density value J of the body region of the crystalline silicon sample at different carrier injection concentrations Δn 0,B , that is, the body region recombination size of the crystalline silicon sample under different carrier injection concentrations Δn. The specific calculation process of this step refers to step 4 of Example 1.

[0102] In this embodiment, the dark state saturation current density value J of the body region of the crystalline silicon sample under different carrier injection concentrations Δn is 0,B The range is 3~9fA / cm 2 , its data is as follows Figure 13 As shown, the body region recombination size of the crystalline silicon sample in this embodiment under different carrier injection concentrations Δn is obtained.

[0103] A method for testing crystalline silicon bulk recombination, developed in Examples 1-3 of the present invention, creatively characterizes bulk recombination in crystalline silicon using its dark-state saturation current. This method not only accurately represents the magnitude of bulk recombination using the dark-state saturation current density of the crystalline silicon body, effectively avoiding testing errors, but also establishes a relationship between bulk recombination and open-circuit voltage. This is because the open-circuit voltage of a crystalline silicon solar cell is directly correlated with the dark-state saturation current density (J0), with the magnitude of the dark-state saturation current density J0 directly determining the open-circuit voltage of the crystalline silicon solar cell. Furthermore, through the coordination of steps S1 to S4, this method can quantitatively obtain bulk recombination values ​​for crystalline silicon at different carrier injection concentrations. Furthermore, because this testing method effectively avoids testing errors associated with existing methods (i.e., methods that use the bulk minority carrier lifetime to compare the magnitude of bulk recombination in silicon wafers) and can quantitatively characterize the magnitude of bulk recombination in crystalline silicon at different carrier injection concentrations, it offers greater accuracy and precision than existing methods.

[0104] In summary, the advantages of the testing methods of Examples 1-3 of the present invention include: 1) a wide testing range, capable of testing crystalline silicon with homogeneous structures and / or passivated contact structures; 2) the body region recombination value of crystalline silicon at different injection concentrations can be obtained, directly linked to the open-circuit voltage, and quantitatively obtained at different carrier injection concentrations; 3) the testing method is simple, time-efficient, and low-cost. Therefore, the testing methods of Examples 1-3 of the present invention can quickly and accurately test the body region recombination size of crystalline silicon, which is of great significance for monitoring the manufacturing process of crystalline silicon, optimizing the process, developing new structures, and optimizing efficiency.

[0105] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they become aware of the basic creative concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0106] The technical solution provided by the present invention is introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for testing crystalline silicon bulk recombination, characterized in that: The method of expressing the body region recombination value of crystalline silicon by using the body region dark state saturation current density value of crystalline silicon under different carrier injection concentrations includes the following steps: S1. Preparing a crystalline silicon sample to be tested: sequentially forming a carrier selective layer and an anti-reflection film on the front surface of a crystalline silicon substrate, and sequentially forming a carrier selective layer and an anti-reflection film on the back surface of the crystalline silicon substrate; wherein the carrier selective layer has a homogeneous structure or a passivated contact structure; S2. Testing the hidden open circuit voltage and surface dark state saturation current density of the crystalline silicon sample at different carrier injection concentrations; S3. Obtaining the total dark state saturation current density value of the crystalline silicon sample at different carrier injection concentrations according to the hidden open circuit voltage values ​​at different carrier injection concentrations; S4. Obtaining a body region recombination value of the crystalline silicon sample according to the surface dark state saturation current density values ​​and the total dark state saturation current density values ​​under different carrier injection concentrations; In step S4, the difference between the surface dark state saturation current density value and the total dark state saturation current density value under different carrier injection concentrations is the body region dark state saturation current density value of the crystalline silicon under different carrier injection concentrations, and its calculation formula is: I 0，B =J 0，T -J 0，S Where, J 0，T is the total dark state saturation current density value under different carrier injection concentrations Δn, J 0，S is the surface dark state saturation current density under different carrier injection concentrations Δn, J 0，B is the dark state saturation current density value of the body region of the crystalline silicon sample under different carrier injection concentrations Δn.

2. A method for testing crystalline silicon bulk recombination according to claim 1, characterized in that: In step S1 , the homogeneous structure is a P-type or N-type single crystal doped layer, the sheet resistance of the homogeneous structure is 10 to 500 Ω / sq, and the junction depth is 0.3 to 3 μm.

3. The method for testing crystalline silicon bulk recombination according to claim 1, wherein: In step S1, the homogeneous structure is manufactured by thermal diffusion or ion implantation.

4. The method for testing crystalline silicon bulk recombination according to claim 1, wherein: In step S1 , the passivation contact structure includes a tunneling oxide layer and a heavily doped polysilicon layer stacked on the surface of the tunneling oxide layer.

5. The method for testing crystalline silicon bulk recombination according to claim 4, characterized in that: The tunnel oxide layer is made of silicon oxide, titanium oxide or aluminum oxide, and has a thickness of 0.5 to 3.0 nm.

6. The method for testing crystalline silicon bulk recombination according to claim 4, characterized in that: The conductivity type of the heavily doped polysilicon layer is N-type or P-type, the thickness of the heavily doped polysilicon layer is 30 to 600 nm, and the doping concentration is 0.1 to 8.0E+20 cm -3 .

7. The method for testing crystalline silicon bulk recombination according to claim 1, characterized in that: In step S1, the anti-reflection film is a stacked structure formed by one or more films selected from the group consisting of aluminum oxide film, silicon dioxide film, silicon nitride film and silicon oxynitride film; and the thickness of the anti-reflection film is 50 to 150 nm.

8. A method for testing crystalline silicon bulk recombination according to any one of claims 1 to 7, characterized in that: In step S2, a minority carrier lifetime tester is used to test the hidden open circuit voltage value and the surface dark state saturation current density value of the crystalline silicon sample under different carrier injection concentrations.

9. A method for testing crystalline silicon bulk recombination according to any one of claims 1 to 7, characterized in that: In step S3, the total dark state saturation current density value of the crystalline silicon sample at different carrier injection concentrations is calculated by the following formula: Where, J G is the photocurrent value under different carrier injection concentrations Δn, iV oc is the hidden open circuit voltage value of crystalline silicon sample under different carrier injection concentration Δn, J 0，T is the total dark state saturation current density under different carrier injection concentrations Δn, V T is the thermal voltage, V T The magnitude is 0.0259V.

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