Preparation method of local passivation contact structure of solar cell
By using patterned mask bonding and mechanical tearing methods in the local passivation contact structure of solar cells, the existing process flow is complicated and poor controllability is solved, and process simplification and electrical performance are achieved.
Patent Information
- Application Number
- CN202311454237.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-02
- Publication Date
- 2025-05-09
AI Technical Summary
The local amorphous silicon passivation contact structure process of existing solar cells is complex and has poor controllability, with residual masks on the surface, easy corrosion to the functional layer of the PN junction and lateral drilling.
The patterned mask is used to apply to the passivation layer, and the mask is mechanically tear off to form a hollow area, and the passivation layer is removed by chemical corrosion in the subsequent process, simplifying the process flow and improving controllability.
The process flow of local passivation contact structure is simplified, the controllability of the process is improved, mask residue and corrosion error are avoided, and electrical performance is enhanced.
Smart Images
Figure CN119967922A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of solar cells, and in particular relates to a method for preparing a local passivation contact structure of a solar cell. Background Art
[0002] In the field of solar photovoltaic technology, laser heavy doping has been widely used in SE (selective emitter) cells, including P-type phosphorus doping and N-type boron doping, and is currently widely used in PERC and Topcon cell production. Although the contact resistance is reduced to a certain extent, the contact recombination between the surface electrode and the heavily doped area is still high. For example, the gate line contact recombination J0-metal is 300-400fA / cm 2 , there is still room for improvement.
[0003] At present, the local amorphous silicon passivation on the front side mainly adopts PSG, BSG, SiNx, SiOx, ink and other methods, assisted by laser large-area film removal or photolithography, and then chemical etching to remove 95% of the mask area; or the metal mask plate type physical mask method. All the above methods have some problems: 1) Laser + chemical etching method: The surface residual mask and the amorphous silicon layer are chemically etched (acid, alkali) with poor controllability, which is easy to corrode the surface PN junction functional layer, affecting the electrical performance. At the same time, due to the characteristics of chemical isotropic corrosion, the reserved amorphous silicon layer has lateral drilling and forms an inverted trapezoid; 2) Metal physical mask plate method, due to the gap between the sample and the mask, it is easy to cause plating around. Summary of the invention
[0004] The technical problem to be solved by the present invention is to provide a method for preparing a local passivation contact structure of a solar cell, which can simplify the process flow of the local amorphous silicon passivation contact structure and improve process controllability.
[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a local passivation contact structure of a solar cell, wherein a passivation layer is first prepared on a side of the solar cell where the local passivation contact structure is to be prepared, and then a mask having a hollow area is attached to the passivation layer; the shape of the hollow area corresponds to the local passivation contact electrode area or the non-local passivation contact electrode area of the cell; the mask is obtained by patterning with a laser;
[0006] The mask is torn off mechanically in the subsequent process, so that the hollow area forms a desired structure; the passivation layer is removed by chemical etching in the subsequent process; finally, a front local passivation contact structure or a back local passivation contact structure is obtained.
[0007] According to the above method, the mask includes a polymer film layer and an adhesive layer that are bonded to each other, and the polymer film layer is bonded to the passivation layer through the adhesive layer.
[0008] According to the above method, the polymer film layer is prepared by a material with a temperature resistance greater than 350°C; the thickness of the polymer film layer is 5-100 μm, and the thickness of the adhesive layer is 3-10 μm.
[0009] According to the above method, when the mask is torn off mechanically, auxiliary heating is performed, and the heating temperature is 40-120°C.
[0010] According to the above method, the side of the solar cell that needs to be prepared with a local passivation contact structure is the front side of the solar cell. The method specifically includes:
[0011] Pre-treat the substrate, texturing the front side and polishing the back side;
[0012] Prepare a first passivation layer on the front side of the substrate;
[0013] The mask is attached to the first passivation layer; the shape of the hollowed-out area of the mask is the same as the pattern of the local passivation contact electrode to be prepared;
[0014] The first passivation layer of the mask hollowing area is removed by etching;
[0015] A tunneling oxide layer, an amorphous silicon layer and a second passivation layer are sequentially prepared on the front surface, wherein the amorphous silicon layer is an intrinsic amorphous silicon layer, a doped amorphous silicon layer, an intrinsic amorphous silicon plus a silicon oxide layer, or a doped amorphous silicon plus a silicon oxide layer; the thickness of the second passivation layer is greater than that of the first passivation layer;
[0016] The mask is mechanically torn off, so that the tunneling oxide layer, the amorphous silicon layer and the second passivation layer covering the mask are torn off together, exposing the first passivation layer under the mask, and the tunneling oxide layer, the amorphous silicon layer and the second passivation layer formed in the original hollowed-out area are left;
[0017] Corrosion removes the first passivation layer and part of the second passivation layer on the surface;
[0018] Annealing the amorphous silicon layer to form a polycrystalline silicon layer;
[0019] The remaining portion of the second passivation layer and any silicon oxide layer that may exist are removed by etching.
[0020] According to the above method, the thickness of the first passivation layer is 10-80 nm; the thickness of the second passivation layer is 20-90 nm.
[0021] According to the above method, the side of the solar cell that needs to be prepared with a local passivation contact structure is the back side of the solar cell. The method specifically includes:
[0022] Pre-treat the substrate, texturing the front side and polishing the back side;
[0023] A tunneling oxide layer, a first amorphous silicon layer and a first passivation layer are sequentially prepared on the back side, wherein the first amorphous silicon layer is an intrinsic amorphous silicon layer, a doped amorphous silicon layer, an intrinsic amorphous silicon plus a silicon oxide layer, or a doped amorphous silicon plus a silicon oxide layer;
[0024] The mask is attached to the back side; the shape of the hollowed-out area of the mask is the same as the pattern of the local passivation contact electrode to be prepared;
[0025] Corrosion removes the first passivation layer in the hollowed-out area;
[0026] Continue to sequentially prepare a second amorphous silicon layer and a second passivation layer on the back side; the second amorphous silicon layer is an intrinsic amorphous silicon layer, a doped amorphous silicon layer, an intrinsic amorphous silicon plus a silicon oxide layer, or a doped amorphous silicon plus a silicon oxide layer;
[0027] The mask is mechanically torn off, so that the second amorphous silicon layer and the second passivation layer covering the mask are torn off together, exposing the first passivation layer under the mask, and the second amorphous silicon layer and the second passivation layer formed in the original hollowed-out area are left;
[0028] Annealing the first amorphous silicon layer and the second amorphous silicon layer to form a polycrystalline silicon layer;
[0029] The first passivation layer and the second passivation layer are removed from the surface by etching.
[0030] According to the above method, the thickness of the first passivation layer and the second passivation layer are 40-90 nm respectively, and the thickness of the first amorphous silicon layer and the second amorphous silicon layer are 30-100 nm respectively.
[0031] According to the above method, the side of the solar cell that needs to be prepared with a local passivation contact structure is the back side of the solar cell. The method specifically includes:
[0032] Pre-treat the substrate, texturing the front side and polishing the back side;
[0033] A tunneling oxide layer, an amorphous silicon layer and a first passivation layer are sequentially prepared on the back side, wherein the amorphous silicon layer is an intrinsic amorphous silicon layer, a doped amorphous silicon layer, an intrinsic amorphous silicon plus a silicon oxide layer, or a doped amorphous silicon plus a silicon oxide layer;
[0034] Annealing the amorphous silicon layer to form a polycrystalline silicon layer;
[0035] The mask is attached to the back side; the shape of the mask is the same as the pattern of the local passivation contact electrode to be prepared;
[0036] Acid etching is used to remove the first passivation layer in the hollow region to expose the polysilicon layer in the hollow region;
[0037] Mechanically tearing off the mask to expose the first passivation layer under the mask;
[0038] Alkali-etching a portion of the exposed polysilicon layer to leave a thinned polysilicon layer; while the polysilicon layer covered by the first passivation layer retains its original thickness;
[0039] The acid etches the remaining first passivation layer, exposing the polysilicon layer which retains its original thickness.
[0040] According to the above method, the original thickness of the amorphous silicon layer is 120-200 nm, the thickness of the thinned polysilicon layer is 40-60 nm; and the thickness of the first passivation layer is 40-90 nm.
[0041] A solar cell with a local passivation contact structure, wherein the passivation contact structure is obtained by adopting the preparation method.
[0042] The beneficial effects of the present invention are:
[0043] 1. By adopting the process of laminating the patterned mask and utilizing the high temperature resistance of the mask material itself, the material is directly deposited after laminating and then the film is mechanically torn off. At this moment, the desired structure is formed in the hollow area, while the material deposited in the non-hollow area of the mask (if any) is on the mask surface and is naturally taken away by the mask when the film is torn off. This not only simplifies the mask preparation process, but also simplifies the process flow of the local passivation contact structure, thereby improving the controllability of the process. At the same time, a passivation layer is prepared in advance before laminating the mask. On the one hand, it serves as a passivation layer, and on the other hand, it can serve as a pollution barrier layer, which can effectively avoid the possibility that local glue may remain on the substrate surface when the mask material containing glue is torn off after high temperature coating, thereby isolating glue pollution.
[0044] 2. This method is also applicable to front and back local passivation contact structures.
[0045] 3. When this method is used to prepare a front local passivation contact structure, the outermost second passivation layer needs to be slightly thicker than the first passivation layer. When the first passivation layer is removed in the subsequent process, a portion of the second passivation layer can still be retained as a mask layer. There is no need to add a new process to set up a mask layer, which further simplifies the process. BRIEF DESCRIPTION OF THE DRAWINGS
[0046] Figure 1 This is a mask patterning device in an embodiment of the present invention.
[0047] Figure 2 is the patterned mask.
[0048] Figure 3 This is a schematic diagram of the battery structure corresponding to step three of embodiment one of the present invention.
[0049] Figure 4 This is a schematic diagram of the battery structure corresponding to step 4 of embodiment 1 of the present invention.
[0050] Figure 5 This is a schematic diagram of the battery structure corresponding to step five of embodiment one of the present invention.
[0051] Figure 6 This is a schematic diagram of the battery structure corresponding to step six of embodiment one of the present invention.
[0052] Figure 7 This is a schematic diagram of the battery structure corresponding to step seven of embodiment one of the present invention.
[0053] Figure 8 This is a schematic diagram of the battery structure corresponding to step eight of embodiment one of the present invention.
[0054] Fig. 9 This is a schematic diagram of the battery structure corresponding to step nine of embodiment one of the present invention.
[0055] Fig.10 This is a schematic diagram of the battery structure corresponding to step 2 of embodiment 2 of the present invention.
[0056] Fig.11 This is a schematic diagram of the battery structure corresponding to step three of embodiment two of the present invention.
[0057] Fig.12 This is a schematic diagram of the battery structure corresponding to step 4 of embodiment 2 of the present invention.
[0058] Fig.13 This is a schematic diagram of the battery structure corresponding to step five of embodiment two of the present invention.
[0059] Fig.14 This is a schematic diagram of the battery structure corresponding to step six of embodiment two of the present invention.
[0060] Fig.15 This is a schematic diagram of the battery structure corresponding to step seven of the second embodiment of the present invention.
[0061] Fig.16 This is a schematic diagram of the battery structure corresponding to step eight of embodiment two of the present invention.
[0062] Fig.17 This is a schematic diagram of the battery structure corresponding to step 2 of embodiment 3 of the present invention.
[0063] Fig.18 This is a schematic diagram of the battery structure corresponding to step three of embodiment three of the present invention.
[0064] Fig.19 This is a schematic diagram of the battery structure corresponding to step 4 of embodiment 3 of the present invention.
[0065] Fig. 20 This is a schematic diagram of the battery structure corresponding to step five of embodiment three of the present invention.
[0066] Fig.21 This is a schematic diagram of the battery structure corresponding to step six of embodiment three of the present invention.
[0067] Fig. 22 This is a schematic diagram of the battery structure corresponding to step seven of embodiment three of the present invention.
[0068] Fig.23 This is a schematic diagram of the battery structure corresponding to step eight of embodiment three of the present invention.
[0069] In the figure: 1-1 laser; 1-2 reflector; 1-3 beam expander; 1-4 galvanometer scanning module; 1-5 mask; 1-5-1 mask body; 1-5-2 mask corresponding to the main grid hollow area; 1-5-3 mask corresponding to the auxiliary grid hollow area; 1-6 table;
[0070] 2-1 substrate; 2-2 first front passivation layer; 2-3 front tunneling oxide layer; 2-4 front amorphous silicon layer; 2-4' front polysilicon layer; 2-5 second front passivation layer;
[0071] 3-1 substrate; 3-2 first back passivation layer; 3-3 back tunneling oxide layer; 3-4 first back amorphous silicon layer; 3-4' first back polysilicon layer; 3-5 second back passivation layer; 3-6 second back amorphous silicon layer; 3-6' second back polysilicon layer;
[0072] 4-1 substrate; 4-2 first back passivation layer; 4-3 back tunneling oxide layer; 4-4 back amorphous silicon layer; 4-4' back polysilicon layer; 4-4'-1 back thinned polysilicon layer. DETAILED DESCRIPTION
[0073] The present invention will be further described below in conjunction with specific examples and drawings.
[0074] The present invention provides a method for preparing a local passivation contact structure of a solar cell. In this method, a passivation layer is first prepared on the side of the solar cell where the local passivation contact structure needs to be prepared, and then a mask with a hollow area is attached to the passivation layer; the shape of the hollow area corresponds to the local passivation contact electrode area or the non-local passivation contact electrode area of the cell. The mask is torn off mechanically in a subsequent process, so that the hollow area forms a desired structure, and the material of the non-hollow area is taken away with the mask; the passivation layer is removed by chemical corrosion (such as acid corrosion) in a subsequent process; finally, a front local passivation contact structure or a back local passivation contact structure is obtained. Wherein, the front local passivation contact structure is as follows: Fig. 9As shown, it includes a front tunneling oxide layer 2-3 and a front polysilicon layer 2-4' formed locally on the front side of the substrate 2-1, wherein the shapes of the front tunneling oxide layer 2-3 and the front polysilicon layer 2-4' are the same as the later gate line pattern. Fig.16 or Fig.23 As shown, it includes a back tunneling oxide layer 3-3 / 4-3 and a thinner polysilicon layer (back first polysilicon layer 3-4' / back thinned polysilicon layer 4-4'-1) formed in sequence on the back side of the substrate 3-1 / 4-1, and a polysilicon layer (back second polysilicon layer 3-6' / back polysilicon layer 4-4') with the same electrode pattern as that formed locally on the thinner polysilicon layer (back first polysilicon layer 3-4' / back thinned polysilicon layer 4-4'-1).
[0075] The mask is a pre-obtained mask, which is mainly obtained by laser patterning. During laser patterning, a mask pattern is engraved on the mask surface, wherein the relevant feature points of the mask pattern include the main grid, main grid welding point, sub-grid, harpoon and other feature points. The laser method is used to prepare the mask, which has flexible patterning, a wide variety of mask materials, and low cost; the battery preparation process is short, and the process is relatively simple and controllable.
[0076] The present invention takes laser patterning as an example and adopts Figure 1 The mask patterning device shown includes an optical path module and a stage module, wherein the optical path module includes a laser 1-1, a reflector 1-2, a beam expander 1-3 and a galvanometer scanning module 1-4 which are arranged in sequence.
[0077] The laser wavelength generated by the laser is 0.3-12 μm; the light mode is pulse mode, quasi-continuous mode or continuous mode; the light pulse width is ps (picoseconds) or ns (nanoseconds); the laser energy distribution is Gaussian distribution or uniform distribution; the laser spot is circular or square; the laser spot size is 10-500 μm;
[0078] The specific patterning method is: adsorb the mask 1-5 on the table 1-6 with the glue surface facing upward; the laser emitted by the laser 1-1 passes through the reflector 1-2, the beam expander 1-3 and the galvanometer scanning module 1-4 in sequence and reaches the carrier, and the mask 1-5 on the table 1-6 is patterned under the scanning path of the galvanometer scanning module 1-4.
[0079] In some cases, the resulting masks 1-5 are as follows Figure 2As shown, the mask body 1-5-1 includes a mask body 1-5-1, on which a mask corresponding main grid hollow region 1-5-2 and a mask corresponding auxiliary grid hollow region 1-5-3 are provided, corresponding to the pattern of the future local passivation contact electrode. In other cases, the obtained mask 1-5 may have other types of hollow regions (such as the pattern corresponding to the future non-local passivation contact electrode), which is mainly determined according to process requirements and needs.
[0080] The mask 1-5 includes a polymer film layer and an adhesive layer that are bonded to each other. The polymer film layer is bonded to the passivation layer through the adhesive layer, which is equivalent to adding an adhesive layer to ensure that the effective structural layer of the mask and the passivation layer are tightly bonded. The effective structural layer of the mask is selected to be a polymer material film layer, and the polymer film layer is made of a material with a temperature resistance greater than 350°C. The thickness of the polymer film layer is between 5-100μm, and the thickness of the adhesive layer is between 3-10μm. Specifically, the upper surface of the mask 1-5 is a film with a thickness of 3 to 10μm, and the lower surface is a high temperature resistant (>350°C) material such as polyimide (PI) with a thickness of 5 to 50μm.
[0081] The polymer film layer is prepared from a material with a temperature resistance greater than 350°C to ensure that the film material will not be adversely affected during the laser processing patterning process, and to effectively improve the accuracy of patterning the first mask pattern layer 200. Specifically, the temperature resistance usually refers to the glass transition temperature of the polymer film layer. The thickness of the polymer film layer is set between 5-100μm, preferably between 5-50μm, and the thickness of the adhesive layer is between 3-10μm to ensure that the polymer film layer has sufficient thickness to form a mask pattern, to ensure the adhesion of the adhesive layer and to avoid the adverse effects of excessive thickness of the adhesive layer on the accuracy of the mask pattern. At the same time, the polymer film is made of a material with a temperature resistance greater than 350°C, which is also more friendly to the process of depositing the back amorphous silicon layer.
[0082] The passivation layer can function as a passivation layer on the one hand, and can also serve as a pollution barrier layer on the other hand, which can effectively avoid the possibility that local glue may remain on the substrate surface when the glue-containing mask material is mechanically torn off after high-temperature coating, thereby isolating glue contamination.
[0083] The present invention is applicable to both front and back local passivation contact structures.
[0084] Since the location and structure of the local passivation contact structure of different solar cells are slightly different, the present invention only provides the following embodiments to further illustrate the present invention.
[0085] Embodiment 1:
[0086] In the method for preparing a local passivation contact structure of a solar cell provided in this embodiment, the side of the solar cell on which the local passivation contact structure needs to be prepared is the front side of the solar cell.
[0087] This method specifically includes:
[0088] Step 1: Pre-treat the substrate 2-1, including necessary cleaning, front surface texturing, and back surface polishing.
[0089] Step 2: deposit a first front passivation layer 2-2 made of SiNx, SiOx or SiONx on the front side of the substrate 2-1, with a thickness of 10 to 80 nm.
[0090] Step 3: Attach the patterned mask 1-5 to the front first passivation layer 2-2, as shown in FIG. Figure 3 As shown. The hollowed-out area on the mask 1-5 in this embodiment is the same as the pattern of the local passivation contact electrode to be prepared in the future. The patterning of the mask 1-5 adopts the aforementioned laser patterning method, which will not be repeated here.
[0091] Step 4: Use HF solution to etch and remove the front first passivation layer 2-2 in the mask hollow area, and the obtained structure is as follows: Figure 4 As shown;
[0092] Step 5: sequentially prepare a front tunneling oxide layer 2-3, a front amorphous silicon layer 2-4 and a front second passivation layer 2-5 on the front surface, wherein the front amorphous silicon layer is an intrinsic amorphous silicon layer, a doped amorphous silicon layer, an intrinsic amorphous silicon plus a silicon oxide layer, or a doped amorphous silicon plus a silicon oxide layer; the thickness of the front second passivation layer 2-5 is greater than that of the front first passivation layer 2-2, such as Figure 5 shown.
[0093] In this embodiment, an in-situ doping method (LPCVD, PECVD, HWCVD, etc.) is adopted to deposit a tunneling oxide layer, a boron-containing amorphous silicon layer on the surface in sequence; or a tunneling oxide layer, an intrinsic amorphous silicon layer, a boron-containing amorphous silicon layer; or a tunneling oxide layer, an intrinsic amorphous silicon layer, a boron-containing silicon oxide layer (BSG); and then a front second passivation layer of SiNx or SiOx or SiONx is deposited on the outermost surface with a thickness of 20 to 90 nm [used for the P++ layer on one side].
[0094] Alternatively, an in-situ doping method (LPCVD, PECVD, HWCVD, etc.) is used to sequentially deposit a tunneling oxide layer, a phosphorus-containing amorphous silicon layer; or a tunneling oxide layer, an intrinsic amorphous silicon layer, a phosphorus-containing amorphous silicon layer; or a tunneling oxide layer, an intrinsic amorphous silicon layer, a phosphorus-containing silicon oxide layer (PSG); and then a front second passivation layer of SiNx or SiOx or SiONx is deposited on the outermost surface with a thickness of 20 to 90 nm.
[0095] Step 6: Mechanically tear off the mask 1-5, so that the front tunneling oxide layer 2-3, the front amorphous silicon layer 2-4 and the front second passivation layer 2-5 covering the mask 1-5 are torn off together, exposing the front first passivation layer 2-2 under the mask, and the front tunneling oxide layer 2-3, the front amorphous silicon layer 2-4 and the front second passivation layer 2-5 formed in the original hollow area are left, such as Figure 6 When the mask is torn off mechanically, auxiliary heating can be performed at a temperature of 40 to 120° C., which makes it easier to remove the mask 1-5.
[0096] Step 7: Use HF solution to corrode and remove the first front passivation layer 2-2 and part of the second front passivation layer 2-5 on the surface, such as Figure 7 As shown, since the thickness of the second front passivation layer 2-5 is relatively thick, a certain thickness will be left to serve as a mask layer.
[0097] Step eight: annealing treatment to form the front amorphous silicon layer 2-4 into a front polysilicon layer 2-4'. Figure 8 As shown; a furnace tube can be used for annealing, the annealing temperature is 800-950°C, and the time is 10-20 minutes; wherein the doped amorphous silicon layer forms a P++ or N++ polysilicon layer after annealing; or a laser annealing method can be used.
[0098] Step 9: Use HF solution to etch and remove the remaining second passivation layer 2-5 on the front side, as well as possible silicon oxide layers, such as PSG, BSG, etc. Fig. 9 As shown, the surface of the battery cell is cleaned.
[0099] Embodiment 2:
[0100] In this embodiment, the side of the solar cell on which the local passivation contact structure needs to be prepared is the back side of the solar cell, and the method specifically includes:
[0101] Step 1: pre-treating the substrate 3-1, including conventional cleaning, front surface texturing, and back surface polishing;
[0102] Step 2: If Fig.10 As shown, a back tunneling oxide layer 3-3, a back first amorphous silicon layer 3-4 and a back first passivation layer 3-2 are sequentially prepared on the back side, and the back first amorphous silicon layer 3-4 is an intrinsic amorphous silicon layer, a doped amorphous silicon layer, an intrinsic amorphous silicon plus a silicon oxide layer, or a doped amorphous silicon plus a silicon oxide layer.
[0103] In this embodiment, an in-situ doping method (LPCVD, PECVD, HWCVD, etc.) is adopted to sequentially deposit a tunneling oxide layer, a boron-containing amorphous silicon layer on the back surface (polished surface); or a tunneling oxide layer, an intrinsic amorphous silicon layer, a boron-containing amorphous silicon layer; or a tunneling oxide layer, an intrinsic amorphous silicon layer, a boron-containing silicon oxide layer (BSG); and then a back first passivation layer 3-2 of SiNx or SiOx or SiONx is deposited on the outermost surface, with a thickness of 40 to 90 nm [used for the P++ layer on one side];
[0104] Alternatively, an in-situ doping method (LPCVD, PECVD, HWCVD, etc.) is used to deposit a tunneling oxide layer, a phosphorus-containing amorphous silicon layer on the surface in sequence; or a tunneling oxide layer, an intrinsic amorphous silicon layer, a phosphorus-containing amorphous silicon layer; or a tunneling oxide layer, an intrinsic amorphous silicon layer, a phosphorus-containing silicon oxide layer (PSG); and then a back first passivation layer 3-2 of SiNx or SiOx or SiONx is deposited on the surface with a thickness of 40 to 90 nm [used for the N++ layer on one side].
[0105] The deposition thickness of the first amorphous silicon layer 3-4 on the back side is 30 to 100 nm, and optimally 40 to 60 nm.
[0106] Step 3: attach the patterned mask 1-5 to the back side, such as Fig.11 In this embodiment, the shape of the hollowed-out area of the mask 1-5 is the same as the pattern of the local passivation contact electrode to be prepared in the future. The mask 1-5 is obtained by the aforementioned laser patterning method.
[0107] Step 4: Use HF solution to etch and remove the first passivation layer 3-2 on the back of the hollow area. Fig.12 shown.
[0108] Step 5: Continue to sequentially prepare the back second amorphous silicon layer 3-6 and the back second passivation layer 3-5 on the back; the back second amorphous silicon layer 3-6 is an intrinsic amorphous silicon layer, a doped amorphous silicon layer, an intrinsic amorphous silicon plus a silicon oxide layer, or a doped amorphous silicon plus a silicon oxide layer, such as Fig.13 shown.
[0109] In this embodiment, an in-situ doping method (LPCVD, PECVD, HWCVD, etc.) is adopted to deposit a boron-containing amorphous silicon layer, or an intrinsic amorphous silicon layer, a boron-containing silicon oxide layer (BSG) on the back surface (polished surface); then a back second passivation layer 3-5 of SiNx or SiOx or SiONx is deposited on the outermost surface with a thickness of 40 to 90 nm [used for the polished side P++ layer].
[0110] Alternatively, an in-situ doping method (LPCVD, PECVD, HWCVD, etc.) is used to deposit a phosphorus-containing amorphous silicon layer, or an intrinsic amorphous silicon layer, or a phosphorus-containing silicon oxide layer (PSG) on the surface; then a back second passivation layer 3-5 of SiNx, SiOx or SiONx is deposited on the outermost surface with a thickness of 40 to 90 nm [used for the polishing side N++ layer].
[0111] The deposition thickness of the second amorphous silicon layer 3-6 on the back side is 30-100 nm, preferably 60-70 nm.
[0112] Step 6: Mechanically tear off the mask 1-5, so that the back second amorphous silicon layer 3-6 and the back second passivation layer 3-5 covering the mask 1-5 are torn off together, exposing the back first passivation layer 3-2 under the mask 1-5, and the back second amorphous silicon layer 3-6 and the back second passivation layer 3-5 formed in the original hollow area are left. Fig.14 As shown; auxiliary heating and the like can be used, and the heating temperature is 40 to 120°C, which makes it easier to remove the surface thin film mask.
[0113] Step 7: Annealing treatment is performed to form the first back amorphous silicon layer 3-4 and the second back amorphous silicon layer 3-6 into a first back polysilicon layer 3-4' and a second back polysilicon layer 3-6'. Fig.15 shown.
[0114] The annealing can be carried out in a furnace tube at a temperature of 800-950° C. for 10-20 minutes; wherein the doped amorphous silicon layer forms a P++ or N++ polysilicon layer after annealing; or laser annealing can be used.
[0115] Step 8: HF solution is used to corrode and remove the first back passivation layer 3-2 and the second back passivation layer 3-5 on the surface, that is, to remove the SiNx or SiOx or SiONx, PSG, BSG and other materials on the surface, and clean the surface of the cell to obtain the following: Fig.16 The structure shown.
[0116] In this embodiment, there is a difference in the thickness of the poly layer between the gate line area and the non-gate line area. The poly layer thickness at the gate line is about 100-150nm, and the poly layer thickness at the non-gate line is about 50-70nm; therefore, two passivation layer treatments are required.
[0117] Embodiment three:
[0118] In this embodiment, the side of the solar cell on which the local passivation contact structure needs to be prepared is the back side of the solar cell, and the method specifically includes:
[0119] Step 1: pre-treating the substrate 4-1, including conventional cleaning, front surface texturing, and back surface polishing;
[0120] Step 2: If Fig.17 As shown, a back tunneling oxide layer 4-3, a back amorphous silicon layer 4-4 and a back first passivation layer 4-2 are sequentially prepared on the back side, and the back amorphous silicon layer 4-4 is an intrinsic amorphous silicon layer, a doped amorphous silicon layer, an intrinsic amorphous silicon plus a silicon oxide layer, or a doped amorphous silicon plus a silicon oxide layer.
[0121] In this embodiment, an in-situ doping method (LPCVD, PECVD, HWCVD, etc.) is adopted to sequentially deposit a tunneling oxide layer, a boron-containing amorphous silicon layer on the back surface (polished surface); or a tunneling oxide layer, an intrinsic amorphous silicon layer, a boron-containing amorphous silicon layer; or a tunneling oxide layer, an intrinsic amorphous silicon layer, a boron-containing silicon oxide layer (BSG); and then a back first passivation layer 4-2 of SiNx or SiOx or SiONx is deposited on the outermost surface, with a thickness of 40 to 90 nm [used for the P++ layer on one side];
[0122] Alternatively, an in-situ doping method (LPCVD, PECVD, HWCVD, etc.) is used to deposit a tunneling oxide layer, a phosphorus-containing amorphous silicon layer on the surface in sequence; or a tunneling oxide layer, an intrinsic amorphous silicon layer, a phosphorus-containing amorphous silicon layer; or a tunneling oxide layer, an intrinsic amorphous silicon layer, a phosphorus-containing silicon oxide layer (PSG); and then a back first passivation layer 4-2 of SiNx or SiOx or SiONx is deposited on the outermost surface with a thickness of 40 to 90 nm [used for the N++ layer on one side].
[0123] The deposition thickness of the back amorphous silicon layer 4-4 is between 120 and 200 nm, and the optimal thickness is between 120 and 150 nm.
[0124] Step 3: Annealing treatment to form the back amorphous silicon layer 4-4 into a back polysilicon layer 4-4'. Fig.18 As shown; annealing treatment can be performed in a furnace tube, the annealing temperature is 800-950°C, and the time is 10-20 minutes; wherein the doped amorphous silicon layer forms a P++ or N++ polysilicon layer after annealing; or laser annealing can be used.
[0125] Step 4: attach the patterned mask 1-5 to the back side, such as Fig.19 In this embodiment, the pattern of the mask is the same as the pattern of the local passivation contact electrode to be prepared in the future, that is, the pattern of its hollowed-out area is opposite to the pattern of the local passivation contact electrode to be prepared in the future. Masks 1-5 are obtained by the aforementioned laser patterning method.
[0126] Step 5: Acid etching is used to remove the first back passivation layer 4-2 in the hollow region to expose the back polysilicon layer 4-4' in the hollow region. Fig. 20 shown.
[0127] In this embodiment, the back first passivation layer 4 - 2 of SiNx or SiOx or SiONx in the hollowed-out area of the mask material is removed in HF solution.
[0128] Step 6: mechanically tear off the mask 1-5 to expose the first back passivation layer 4-2 under the mask 1-5. Fig.21 As shown, auxiliary heating and the like can be used, and the heating temperature is 40 to 120° C., which makes it easier to remove the mask 1-5.
[0129] Step 7: Alkali-etch a portion of the exposed back polysilicon layer 4-4' to leave the back thinned polysilicon layer 4-4'-1; and the back polysilicon layer 4-4' covered by the back first passivation layer 4-2 retains the original thickness, such as Fig. 22 shown.
[0130] In this embodiment, an alkaline solution such as NaOH, KOH, TMAH or the like is used to etch and remove the exposed back polysilicon layer 4 - 4 ′; wherein the remaining thickness is controlled to be 40 to 60 nm.
[0131] Step 8: Acid etch the remaining back first passivation layer 4-2 to expose the back polysilicon layer 4-4' with the original thickness. Fig.23 This embodiment uses HF solution to remove SiNx or SiOx or SiONx, PSG, BSG and other materials on the surface, and cleans the surface of the battery cell.
[0132] The present invention adopts a simplified version of the method for preparing a solar cell with a local passivation contact structure, which is simple and easy to implement and convenient for subsequent processing; the obtained solar cell has high conversion efficiency.
[0133] The solar cell obtained by the above preparation method is also within the protection scope of the present invention.
[0134] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.
Claims
1. A method for preparing a local passivation contact structure of a solar cell, characterized in that: The method first prepares a passivation layer on the side of the solar cell where a local passivation contact structure is required, and then adheres a mask with a hollow area on the passivation layer; the shape of the hollow area corresponds to the local passivation contact electrode area or the non-local passivation contact electrode area of the solar cell; the mask is obtained by laser patterning; The mask is torn off mechanically in the subsequent process, so that the hollow area forms a desired structure; the passivation layer is removed by chemical etching in the subsequent process; finally, a front local passivation contact structure or a back local passivation contact structure is obtained.
2. The method for preparing a local passivation contact structure of a solar cell according to claim 1, characterized in that: The mask comprises a polymer film layer and an adhesive layer which are bonded to each other, and the polymer film layer is bonded to the passivation layer through the adhesive layer.
3. The method for preparing a local passivation contact structure of a solar cell according to claim 2, characterized in that: The polymer film layer is made of a material with a temperature resistance greater than 350° C. The thickness of the polymer film layer is 5-100 μm, and the thickness of the adhesive layer is 3-10 μm.
4. The method for preparing a local passivation contact structure of a solar cell according to claim 1, characterized in that: When the mask is torn off mechanically, auxiliary heating is performed, and the heating temperature is 40-120°C.
5. The method for preparing a local passivation contact structure of a solar cell according to any one of claims 1 to 4, characterized in that: The side of the solar cell that needs to be prepared with a local passivation contact structure is the front side of the solar cell. The method specifically includes: Pre-treat the substrate, texturing the front side and polishing the back side; Prepare a first passivation layer on the front side of the substrate; The mask is attached to the first passivation layer; the shape of the hollowed-out area of the mask is the same as the pattern of the local passivation contact electrode to be prepared; The first passivation layer of the mask hollowing area is removed by etching; A tunneling oxide layer, an amorphous silicon layer and a second passivation layer are sequentially prepared on the front surface, wherein the amorphous silicon layer is an intrinsic amorphous silicon layer, a doped amorphous silicon layer, an intrinsic amorphous silicon plus a silicon oxide layer, or a doped amorphous silicon plus a silicon oxide layer; the thickness of the second passivation layer is greater than that of the first passivation layer; The mask is mechanically torn off, so that the tunneling oxide layer, the amorphous silicon layer and the second passivation layer covering the mask are torn off together, exposing the first passivation layer under the mask, and the tunneling oxide layer, the amorphous silicon layer and the second passivation layer formed in the original hollowed-out area are left; Corrosion removes the first passivation layer and part of the second passivation layer on the surface; Annealing the amorphous silicon layer to form a polycrystalline silicon layer; The remaining portion of the second passivation layer and any silicon oxide layer that may exist are removed by etching.
6. The method for preparing a local passivation contact structure of a solar cell according to claim 5, characterized in that: The thickness of the first passivation layer is 10-80 nm; the thickness of the second passivation layer is 20-90 nm.
7. The method for preparing a local passivation contact structure of a solar cell according to any one of claims 1 to 4, characterized in that: The side of the solar cell that needs to be prepared with a local passivation contact structure is the back side of the solar cell. The method specifically includes: Pre-treat the substrate, texturing the front side and polishing the back side; A tunneling oxide layer, a first amorphous silicon layer and a first passivation layer are sequentially prepared on the back side, wherein the first amorphous silicon layer is an intrinsic amorphous silicon layer, a doped amorphous silicon layer, an intrinsic amorphous silicon plus a silicon oxide layer, or a doped amorphous silicon plus a silicon oxide layer; The mask is attached to the back side; the shape of the hollowed-out area of the mask is the same as the pattern of the local passivation contact electrode to be prepared; Corrosion removes the first passivation layer in the hollowed-out area; Continue to sequentially prepare a second amorphous silicon layer and a second passivation layer on the back side; the second amorphous silicon layer is an intrinsic amorphous silicon layer, a doped amorphous silicon layer, an intrinsic amorphous silicon plus a silicon oxide layer, or a doped amorphous silicon plus a silicon oxide layer; The mask is mechanically torn off, so that the second amorphous silicon layer and the second passivation layer covering the mask are torn off together, exposing the first passivation layer under the mask, and the second amorphous silicon layer and the second passivation layer formed in the original hollowed-out area are left; Annealing the first amorphous silicon layer and the second amorphous silicon layer to form a polycrystalline silicon layer; The first passivation layer and the second passivation layer are removed from the surface by etching.
8. The method for preparing a local passivation contact structure of a solar cell according to claim 7, characterized in that: The thickness of the first passivation layer and the second passivation layer are 40-90 nm respectively, and the thickness of the first amorphous silicon layer and the second amorphous silicon layer are 30-100 nm respectively.
9. The method for preparing a local passivation contact structure of a solar cell according to any one of claims 1 to 4, characterized in that: The side of the solar cell that needs to be prepared with a local passivation contact structure is the back side of the solar cell. The method specifically includes: Pre-treat the substrate, texturing the front side and polishing the back side; A tunneling oxide layer, an amorphous silicon layer and a first passivation layer are sequentially prepared on the back side, wherein the amorphous silicon layer is an intrinsic amorphous silicon layer, a doped amorphous silicon layer, an intrinsic amorphous silicon plus a silicon oxide layer, or a doped amorphous silicon plus a silicon oxide layer; Annealing the amorphous silicon layer to form a polycrystalline silicon layer; The mask is attached to the back side; the shape of the mask is the same as the pattern of the local passivation contact electrode to be prepared; Acid etching is used to remove the first passivation layer in the hollow region to expose the polysilicon layer in the hollow region; Mechanically tearing off the mask to expose the first passivation layer under the mask; Alkali-etching a portion of the exposed polysilicon layer to leave a thinned polysilicon layer; while the polysilicon layer covered by the first passivation layer retains its original thickness; The acid etches the remaining first passivation layer, exposing the polysilicon layer which retains its original thickness.
10. The method for preparing a local passivation contact structure of a solar cell according to claim 9, characterized in that: The original thickness of the amorphous silicon layer is 120-200 nm, the thickness of the thinned polysilicon layer is 40-60 nm; and the thickness of the first passivation layer is 40-90 nm.
11. A solar cell with a local passivation contact structure, characterized in that: The passivation contact structure is obtained by the preparation method described in any one of claims 1 to 10.