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CN-122002960-A - Solar cell and preparation method thereof

CN122002960ACN 122002960 ACN122002960 ACN 122002960ACN-122002960-A

Abstract

The invention provides a solar cell and a preparation method thereof. The solar cell comprises a silicon substrate, wherein the silicon substrate is provided with a first conductive type doping element, the first surface of the silicon substrate comprises a first carrier collecting layer, a first passivation layer and a first electrode, the first carrier collecting layer, the first passivation layer and the first electrode are sequentially arranged far away from the silicon substrate, the first carrier collecting layer is provided with a second conductive type doping element, the first conductive type is opposite to the second conductive type, the first carrier collecting layer is provided with a wavy section in the thickness direction of the solar cell, the concentration of the second conductive type doping element in the first carrier collecting layer is increased in the advancing direction from the position of a trough to the position of a crest in each wavy section period, and the first electrode covers the crest of the first carrier collecting layer. The solar cell structure improves the balance between the surface passivation effect and the efficient carrier transmission.

Inventors

  • LI YA
  • SUN ZIQIANG
  • ZHANG JUNBING

Assignees

  • 晶澳（扬州）太阳能科技有限公司

Dates

Publication Date
20260508
Application Date
20260209

Claims (20)

  1. 1. A solar cell comprising a silicon substrate having a doping element of a first conductivity type, a first surface of the silicon substrate comprising a first carrier-collecting layer, a first passivation layer and a first electrode disposed in sequence away from the silicon substrate, the first carrier-collecting layer having a doping element of a second conductivity type, the first conductivity type being opposite to the second conductivity type, wherein, The first carrier collecting layer is provided with a wave-shaped section along the thickness direction of the solar cell, the concentration of the second conductive type doping element in the first carrier collecting layer is increased along the advancing direction from the position of the trough to the position of the crest in each wave-shaped section period, and the first electrode covers the crest of the first carrier collecting layer.
  2. 2. The solar cell of claim 1, wherein the concentration of the second conductivity-type doping element in the first carrier-collecting layer is 1 x 10 18 atoms/cm 3 - 5×10 19 atoms/cm 3 , optionally the second conductivity-type doping element is an element B.
  3. 3. The solar cell according to claim 1 or 2, wherein the wave line in each period in the wave-shaped cross section is a gaussian curve.
  4. 4. A solar cell according to any one of claims 1 to 3, wherein the wavelength of the wavy cross-section is 100-1200 μm.
  5. 5. The solar cell of any one of claims 1 to 4, wherein the sheet resistance of the first carrier collection layer is 100 Ω/sqr-500 Ω/sqr.
  6. 6. The solar cell of any one of claims 1 to 5, wherein the first surface of the silicon substrate is textured.
  7. 7. The solar cell according to any one of claims 1 to 6, wherein the silicon substrate is an N-type silicon substrate, Optionally, the silicon substrate is a phosphorus atom doped monocrystalline silicon wafer; optionally, the silicon substrate has a resistivity of 0.1 Ω -cm to 100 Ω -cm, and/or the silicon substrate has a thickness of 100 μm to 500 μm.
  8. 8. The solar cell of any one of claims 1 to 7, wherein a second surface of the silicon substrate opposite the first surface comprises a second carrier-collection layer, a second passivation layer, and a second electrode disposed sequentially away from the silicon substrate.
  9. 9. The solar cell of claim 8, wherein the second carrier-collection layer comprises a tunneling oxide layer and a first conductivity type doped polysilicon layer disposed along a stack away from the silicon substrate.
  10. 10. The solar cell according to any one of claims 1 to 9, wherein the first electrode is a thin-gate line electrode, the thin-gate line having a width of 5-50 μm.
  11. 11. A method of fabricating a solar cell, comprising the steps of: s1, providing a silicon substrate, wherein the silicon substrate is provided with a first conductive type doping element; s2, depositing a second conductive type doping element on the first surface of the silicon substrate to form a first diffusion layer; S3, etching the first diffusion layer by using Gaussian light spots to form a diffusion layer with a wavy section; S4, performing heat treatment in an oxidizing atmosphere to form a first carrier collecting layer, wherein the concentration of the doping elements of the second conductivity type in the first carrier collecting layer is increased along the advancing direction from the position of the trough to the position of the crest in each wave-shaped period; s5, a first passivation layer and a first electrode are arranged on the surface of the first carrier collecting layer, and the first electrode covers the wave crest of the wave shape.
  12. 12. The method of manufacturing of claim 11, wherein the gaussian spot meets any one or more of the following conditions: The wavelength of the Gaussian light spot is 266+/-5 nm, 355+/-5 nm or 532+/-5 nm; The energy density of the center of the Gaussian light spot is 50mJ/cm 2 -300mJ/cm 2 ; The half peak width of the Gaussian light spot is 50-600 mu m; the etching time of the Gaussian light spot is 5ps-20ps.
  13. 13. The preparation method according to any one of claims 11 to 12, wherein the conditions of step S4 include one or more of the following: the oxygen flow rate of the heat treatment is 1000 sccm-20000 sccm; The temperature of the heat treatment is 1000-1050 ℃; The heat treatment time is 20min-100min.
  14. 14. The production method according to any one of claims 11 to 13, wherein the wave-shaped peaks formed in the step S3 are spaced apart from the silicon substrate by h1, the wave-trough is spaced apart from the silicon substrate by h2, the relative difference of each of the h1 is within a range of 5%, and the relative difference of each of the h2 is within a range of 5%.
  15. 15. The process according to claim 14, wherein 0.2 μm≤h1-h2≤1.5 μm, Alternatively, the process may be carried out in a single-stage, h1 is more than or equal to 0.5 mu m and less than or equal to 2 mu m, and/or 0.3 μm≤h2≤1 μm.
  16. 16. The method of any one of claims 11 to 15, wherein the first surface of the silicon substrate is textured.
  17. 17. The production method according to any one of claims 11 to 16, wherein the second conductivity type doping element in the step S2 is a B element, and/or The deposition temperature of the second conductivity type doping element is 830-950 ℃.
  18. 18. The production process according to any one of claims 11 to 17, wherein, The step S4 is to form a first carrier-collecting layer simultaneously with the formation of a first doped glass on a surface of the first carrier-collecting layer and on a second surface of the silicon substrate, the first surface being disposed opposite to the second surface, The step S5 includes: Removing the first doped glass on the second surface and polishing to obtain a polished second surface; Providing a second carrier doped layer on the polished second surface, simultaneously concomitantly forming a second doped glass on the second carrier doped layer surface and concomitantly forming a cladding layer on the first surface; Removing the wrapping layer, the rest of the first doped glass and the second doped glass to expose the first carrier collecting layer and the second carrier collecting layer; a first passivation layer is arranged on the surface of the first carrier collecting layer, and a second passivation layer is arranged on the surface of the second carrier doping layer; and a first electrode is arranged on the first passivation layer, a second electrode is arranged on the second passivation layer, and the first electrode covers the wave crest position of the wave shape.
  19. 19. The production method according to any one of claims 11 to 18, wherein the silicon substrate is an N-type silicon substrate, Optionally, the silicon substrate is a phosphorus atom doped monocrystalline silicon wafer; optionally, the silicon substrate has a resistivity of 0.1 Ω -cm to 100 Ω -cm, and/or the silicon substrate has a thickness of 100 μm to 500 μm.
  20. 20. The solar cell of claim 18 or 19, wherein the second carrier-collection layer comprises a tunneling oxide layer and a first conductivity type doped polysilicon layer disposed along a stack away from the silicon substrate.

Description

Solar cell and preparation method thereof Technical Field The invention relates to the technical field of solar cells, in particular to a solar cell and a preparation method thereof. Background Currently, solar cells based on tunnel oxide passivation contact (TOPCon, tunnel Oxide Passivated Contact) technology have become one of the main technological routes to achieve high conversion efficiency due to their excellent surface passivation properties on the back side. Along with rapid maturation and popularization of TOPCon mass production technologies, further improvement of conversion efficiency and reduction of manufacturing cost become core focus of industrial competition. In one existing TOPCon cell structure, the back side is the passivation contact structure of the tunnel oxide layer/doped polysilicon layer stack and the front side is the p+ emitter formed by boron diffusion. A passivation layer is arranged on the emitter, and the metal grid line passes through the passivation layer to form ohmic contact with the P+ emitter. The P+ emitter is a selective emitter (SELECTIVE EMITTER, SE) structure, and particularly comprises a heavy doped region with lower resistance corresponding to the metal grid line and a light doped region with higher resistance outside the heavy doped region, and carriers are guided to directionally transmit to a low-resistance region below the metal grid line by utilizing the potential difference between the heavy doped region and the surrounding light doped region, so that the transverse resistance loss is reduced. The selective emitter structure is secondarily doped in the area below the metal grid line by utilizing laser (such as a common red nanosecond laser) to form the heavily doped area. However, in the existing selective emitter preparation process, when the nanosecond laser is used for forming a local heavily doped region, high-energy pulse of the nanosecond laser can cause thermal damage to a silicon substrate and a surface passivation layer, the original passivation effect is destroyed, and a new composite center is introduced. Disclosure of Invention Aiming at the problem that the silicon matrix and the passivation layer are damaged in the process of preparing the selective emitter in the prior art, the invention provides a solar cell and a preparation method thereof. The first aspect of the application provides a solar cell, which comprises a silicon substrate, wherein the silicon substrate is provided with a first conductive type doping element, a first surface of the silicon substrate comprises a first carrier collecting layer, a first passivation layer and a first electrode, the first carrier collecting layer, the first passivation layer and the first electrode are sequentially arranged far away from the silicon substrate, the first carrier collecting layer is provided with a second conductive type doping element, the first conductive type doping element is opposite to the second conductive type doping element, the first carrier collecting layer is provided with a wave-shaped section in the thickness direction of the solar cell, the concentration of the second conductive type doping element in the first carrier collecting layer increases along the advancing direction from the position of a trough to the position of a crest in each wave-shaped section period, and the first electrode covers the crest of the first carrier collecting layer. In the solar cell with the structure, the first carrier collecting layer is provided with the wavy cross section along the thickness direction of the solar cell, so that the periodically distributed first surface emitter structure is formed, the concentration of the second conductive type doping element is increased along the advancing direction of the position of the trough to the position of the peak in each wavy cross section period, the auger recombination is restrained by the low doping concentration of the trough so as to improve the open circuit voltage, and the change of the concentration of the second conductive type doping element promotes the photo-generated carriers to be transversely transmitted from the trough region with lower doping concentration to the peak region with high concentration under the gradient drive of the concentration of the second conductive type doping element, so that the first electrode covered on the peak can efficiently collect the carriers transmitted to the peak. The first carrier collecting layer in the wave form does not depend on nanosecond laser, so that thermal damage of the laser to the passivation layer can be effectively controlled. Thus, the solar cell of the application achieves a balance between passivation effect and charge transport efficiency. In any embodiment of the first aspect, the concentration of the second conductivity-type doping element in the first carrier-collecting layer is 1×10 18 atoms/cm3- 5×1019 atoms/cm3. Optionally, the second conductivity type doped element is