Post-doped N-type contact passivation battery
Technical Field
The invention relates to the field of solar cells, in particular to a rear-doped N-type contact passivation cell.
Background
Referring to fig. 1, the prior art N-type contact passivation cell includes an N-type silicon wafer 11, a front structure disposed on one side of the front surface of the N-type silicon wafer 11, and a back structure disposed on one side of the back surface of the N-type silicon wafer 11, wherein the front structure includes a p + doping layer 12, a front passivation layer 13, and a front metal electrode 14, the p + doping layer 12 and the front passivation layer 13 are sequentially disposed along a direction gradually away from the N-type silicon wafer 11, the front metal electrode 14 penetrates through the front passivation layer 13, an inner end of the front metal electrode 14 contacts with the p + doping layer 12, the back structure includes a tunneling layer 15, the N + polysilicon layer 16, the back passivation layer 17 and the back metal electrode 18 are sequentially arranged along the direction away from the N-type silicon wafer 11, the tunneling layer 15, the N + polysilicon layer 16 and the back passivation layer 17 are sequentially arranged, the back metal electrode 18 penetrates through the back passivation layer 17, and the inner end of the back metal electrode 18 is in contact with the outer end of the N + polysilicon layer 16. During manufacturing, a 1-2nm tunneling layer is deposited firstly, then an n + polycrystalline silicon layer with uniform thickness is deposited, in order to ensure that metal slurry does not burn through the n + polycrystalline silicon layer in the subsequent metallization process, the thickness of the n + polycrystalline silicon layer must be larger than 100nm, but the larger the thickness of the n + polycrystalline silicon layer is, the more serious the free carrier absorption of the back side is.
Disclosure of Invention
The invention aims to provide a post-doped N-type contact passivation battery, which can reduce the free carrier absorption of the back, improve the double-sided rate of a double-sided battery, eliminate the metal recombination of a metalized region and further improve the conversion efficiency of the N-type contact passivation battery.
In order to achieve the purpose, the invention adopts the technical scheme that: the utility model provides a back doping formula N type contact passivation battery, includes N type silicon chip, locates the positive structure of the positive one side of N type silicon chip and locates the back structure of the back one side of N type silicon chip, the back structure includes tunnel layer, N + polycrystalline silicon layer, back passivation layer and back metal electrode, the tunnel layer, N + polycrystalline silicon layer and back passivation layer set gradually along the direction of N type silicon chip far away, N type contact passivation battery still includes intrinsic polycrystalline silicon layer and N + + heavily doped region, intrinsic polycrystalline silicon layer locate N + polycrystalline silicon layer with between the back passivation layer, N + + heavily doped region runs through intrinsic polycrystalline silicon layer, the inner of N + + heavily doped region with N + polycrystalline silicon layer contact, back metal electrode runs through the back passivation layer, the inner of back metal electrode with the outer end contact of N + + heavily doped region, wherein, the thickness of the n + polycrystalline silicon layer is 10-50nm, and the thickness of the intrinsic polycrystalline silicon layer is 50-250 nm.
Further, the dopant of the n + + heavily doped region is phosphorus.
Further, the n + + heavily doped region is an n + + heavily doped region formed by a laser doping process.
Further, the tunneling layer is formed by deposition.
Further, the n + polysilicon layer is a deposited n + polysilicon layer.
Further, the intrinsic polycrystalline silicon layer is an intrinsic polycrystalline silicon layer formed by deposition.
Furthermore, the front structure comprises a p + doping layer, a front passivation layer and a front metal electrode, the p + doping layer and the front passivation layer are sequentially arranged along the direction away from the N-type silicon wafer, the front metal electrode penetrates through the front passivation layer, and the inner end of the front metal electrode is in contact with the p + doping layer.
Further, the dopant of the p + doped layer is boron tribromide.
Further, the p + doped layer is formed by means of airborne dopants.
Further, the front passivation layer and the back passivation layer are both antireflection passivation films.
Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages: the back surface of the back-doped N-type contact passivated cell disclosed by the invention is limited by the burnthrough property of metal slurry aiming at an N-type contact passivated double-sided cell, the photoelectric conversion efficiency of an industrialized cell is still lower, and through the design of combining back surface N + doping and intrinsic polycrystalline silicon, the absorption of free carriers on the back surface is reduced, the metal contact and metal area recombination is ensured, and the efficiency of the N-type contact passivated double-sided cell is further improved.
Drawings
Fig. 1 is a schematic diagram of a prior art N-contact passivated cell;
fig. 2 is a schematic diagram of the structure of an N-contact passivated cell in accordance with the present invention.
Wherein: 11, 21, N-type silicon chip; 12, 22, p + doped layer; 13, 23, front passivation layer; 14, 24, front metal electrodes; 15, 25, a tunneling layer; a 16, 26, n + polysilicon layer; 17, 27, back passivation layer; 18. 28, a back metal electrode; 291. an intrinsic polycrystalline silicon layer; 292. a heavily n + + doped region.
Detailed Description
The invention is further described with reference to the accompanying drawings and examples:
example one
Referring to fig. 2, as shown in the figure, a back-doped N-type contact passivation cell comprises an N-type silicon wafer 21, a front structure disposed on the front side of the N-type silicon wafer, and a back structure disposed on the back side of the N-type silicon wafer,
the front structure comprises a p + doping layer 22, a front passivation layer 23 and a front metal electrode 24, wherein the p + doping layer 22 and the front passivation layer 23 are sequentially arranged along the direction gradually far away from the N-type silicon wafer 21, the front metal electrode 24 penetrates through the front passivation layer 23, and the inner end of the front metal electrode 24 is in contact with the p + doping layer 22.
The back structure comprises a tunneling layer 25, an N + polycrystalline silicon layer 26, a back passivation layer 27 and a back metal electrode 28, the tunneling layer 25, the N + polycrystalline silicon layer 26 and the back passivation layer 27 are sequentially arranged along the direction gradually far away from the N-type silicon wafer 21, the N-type contact passivation cell further comprises an intrinsic polycrystalline silicon layer 291 and an N + + heavily doped region 292, the intrinsic polycrystalline silicon layer 291 is arranged between the N + polycrystalline silicon layer 26 and the back passivation layer 27, the N + + heavily doped region 292 penetrates through the intrinsic polycrystalline silicon layer 291, the inner end of the N + + heavily doped region 292 is in contact with the N + polycrystalline silicon layer 26, the back metal electrode 28 penetrates through the back passivation layer 27, the inner end of the back metal electrode 28 is in contact with the outer end of the N + + heavily doped region 292, wherein the thickness of the N + polycrystalline silicon layer 26 is 10-.
In a preferred embodiment of this embodiment, the dopant of the heavily n + + doped region 292 is phosphorus.
In a preferred embodiment of this embodiment, the n + + heavily doped region 292 is an n + + heavily doped region formed by a laser doping process.
In the preferred embodiment of the present invention, the tunneling layer 25 is a deposited tunneling layer.
In the preferred embodiment of this embodiment, the n + polysilicon layer 26 is a deposited n + polysilicon layer.
In the preferred embodiment of the present embodiment, the intrinsic polysilicon layer 291 is an intrinsic polysilicon layer formed by deposition.
In a preferred embodiment of this embodiment, the dopant of the p + doped layer 22 is boron tribromide.
In a preferred embodiment of this embodiment, the p + doped layer 22 is a p + doped layer formed by means of airborne dopants.
In a preferred embodiment of the present embodiment, the front passivation layer 23 and the back passivation layer 27 are both antireflective passivation films.
The method for manufacturing the N-type contact passivation battery comprises the following steps:
step1, carrying out double-sided alkali texturing on an N-type silicon wafer;
step2, adopting BBr3 to diffuse the N-type silicon wafer after alkali texturing to form a P + layer;
step3, etching the single surface to remove the back P + layer;
step4 back side deposition tunneling layer (SiO2/a-Si: H, etc.);
step5, depositing an n + polysilicon layer with the thickness of 10-50nm on the back in situ;
step 6: the method is the same as that of Step5, except that a phosphorus source is not connected, an intrinsic polycrystalline silicon layer with the thickness of 50-250nm is continuously deposited, and finally a layer of phosphorus source is deposited;
step 7: adopting a laser doping process to form an n + + region by local re-doping in a region needing metallization subsequently;
step 8: cleaning two sides, and annealing to activate in-situ doped phosphorus and eliminate laser damage;
step 9: depositing antireflection passive films on two sides respectively;
step 10: metallization is carried out on the back surface, and the metal paste printing area corresponds to the Step7 laser doping area;
step 11: and sintering to finish the preparation of the N-type contact passivation double-sided battery.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.