A heterojunction solar cell
By employing a multilayer transparent conductive oxide layer structure in heterojunction solar cells and optimizing the TCO thin film in both the grid region and the non-grid region, the performance mismatch of the TCO thin film was solved, resulting in higher carrier concentration and conductivity, and improved photoelectric conversion efficiency and output power of the cell.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 华能(嘉峪关)新能源有限公司
- Filing Date
- 2024-11-29
- Publication Date
- 2026-05-29
AI Technical Summary
In existing heterojunction solar cells, the performance requirements of TCO thin films in the grid line region and non-grid line region are mismatched, resulting in insufficient conductivity and transmittance, making it difficult to simultaneously meet the requirements of electrical and optical performance.
A multi-layered transparent conductive oxide layer structure is adopted, including a TCO thin film combination with metal gate lines in the gate line region and a separate TCO thin film combination in the non-gate line region, and their performance is optimized to meet the needs of different regions.
It increases carrier concentration and conductivity, maintains high transmittance, and improves the photoelectric conversion efficiency and output power of the battery.
Smart Images
Figure CN122121327A_ABST
Abstract
Description
Technical Field
[0001] This disclosure belongs to the field of solar cell technology, specifically relating to a heterojunction solar cell. Background Technology
[0002] In silicon heterojunction (HJT) solar cells, the emitter junction is an amorphous silicon thin film doped with phosphorus or boron, exhibiting high resistivity. A transparent conductive oxide (TCO) film needs to be deposited on its surface to collect photogenerated carriers and simultaneously serve as an antireflection layer to reduce surface light reflection losses. Furthermore, the TCO also acts as a barrier layer to prevent the diffusion of metals such as silver electrodes into the silicon layer. During the optimization of HJT solar cell fabrication, the TCO must possess both high carrier mobility and transmittance, while simultaneously controlling the work function to achieve good interfacial contact.
[0003] TCO films play a role in both electrical conductivity and light transmission, so good electrical and optical properties must be guaranteed. However, the electrical and optical properties of the film are interdependent, and it is actually very difficult to achieve both optical and electrical properties simultaneously and make both as high as possible.
[0004] The TCOs in the grid region and non-grid region of a battery have different functions due to their different locations, and therefore their performance requirements also differ. Taking the front surface of the battery as an example, the grid region requires the contact resistance between the TCO and the amorphous silicon and metal electrodes to be as low as possible to obtain a high fill factor, focusing on electrical aspects; while the non-grid region aims to improve transmittance and anti-reflection effect to obtain high short-circuit current while ensuring that the lateral conductivity of the TCO meets certain requirements, focusing on optical aspects. However, the current TCOs in the grid region and non-grid region of batteries have the same structure, especially since most are single-layer structures, resulting in low conductivity, low carrier mobility, and poor transmittance. Summary of the Invention
[0005] This disclosure aims to at least address one of the technical problems existing in the prior art by providing a heterojunction solar cell.
[0006] One aspect of this disclosure provides a heterojunction solar cell, comprising: an n-type monocrystalline silicon substrate; a first intrinsic amorphous silicon layer, a p-type amorphous silicon layer, a first transparent conductive oxide layer, and a first electrode sequentially stacked on the upper surface of the n-type monocrystalline silicon substrate; and a second intrinsic amorphous silicon layer, an n-type amorphous silicon layer, a second transparent conductive oxide layer, and a second electrode sequentially stacked on the lower surface of the n-type monocrystalline silicon substrate; wherein...
[0007] The first transparent conductive oxide layer includes a first TCO film, a metal gate line, and a second TCO film;
[0008] The second transparent conductive oxide layer includes a first TCO film and a second TCO film.
[0009] Optionally, the first TCO film and the second TCO film are indium oxide system, tin oxide system or zinc oxide system.
[0010] Optionally, the indium oxide system is In2O3 / ZnO, In2O3 / WO3; and / or,
[0011] The tin oxide system is SnO2 / Ta or SnO2 / F; and / or,
[0012] The zinc oxide system is ZnO / Al or ZnO / Ga.
[0013] Optionally, the first transparent conductive oxide layer is AZO / metal gate / AZO or ITO / metal gate / ITO.
[0014] Optionally, the thickness of the first TCO film is 90-130 nm;
[0015] The thickness of the second TCO film is 70-160 nm.
[0016] Optionally, the carrier concentration of the first TCO film is (0.5-1.5).
[0017] *10 20 cm -3 .
[0018] Optionally, the carrier concentration of the second TCO film is greater than 70 cm⁻¹. 2 / V·s.
[0019] Optionally, the resistivity of the first TCO thin film and the second TCO thin film is 2.
[0020] ×10 -5 -3×10 -2 Ω·cm.
[0021] Optionally, the metal grid lines are Ag, Au, Cu, Mg, or Pt.
[0022] Optionally, the thickness of the n-type single-crystal silicon substrate is 10-50 nm; and / or,
[0023] The thicknesses of the first intrinsic amorphous silicon layer and the second intrinsic amorphous silicon layer are preferably 5-12 nm; and / or,
[0024] The thickness of the p-type amorphous silicon layer and the n-type amorphous silicon layer is 10-30 nm.
[0025] This disclosure proposes a heterojunction solar cell, comprising: an n-type monocrystalline silicon substrate; a first intrinsic amorphous silicon layer, a p-type amorphous silicon layer, a first transparent conductive oxide layer, and a first electrode, sequentially stacked on the upper surface of the n-type monocrystalline silicon substrate; and a second intrinsic amorphous silicon layer, an n-type amorphous silicon layer, a second transparent conductive oxide layer, and a second electrode, sequentially stacked on the lower surface of the n-type monocrystalline silicon substrate; wherein the first transparent conductive oxide layer comprises a first TCO thin film, metal grid lines, and a second TCO thin film; and the second transparent conductive oxide layer comprises a first TCO thin film and a second TCO thin film. By employing transparent conductive oxide layers with different structures, different requirements in the grid line region and non-grid line region can be met, better matching the cell performance, effectively improving carrier concentration and conductivity, while maintaining high transmittance. Attached Figure Description
[0026] Figure 1 This is a schematic diagram of the structure of a heterojunction solar cell according to an embodiment of the present disclosure. Detailed Implementation
[0027] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this disclosure and represent a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.
[0028] like Figure 1 As shown, this disclosure proposes a heterojunction solar cell 100, comprising:
[0029] An n-type monocrystalline silicon substrate 110 includes a first intrinsic amorphous silicon layer 120, a p-type amorphous silicon layer 130, a first transparent conductive oxide layer 140, and a first electrode 150, which are sequentially stacked on the upper surface of the n-type monocrystalline silicon substrate 110. A second intrinsic amorphous silicon layer 160, an n-type amorphous silicon layer 170, a second transparent conductive oxide layer 180, and a second electrode 190 are sequentially stacked on the lower surface of the n-type monocrystalline silicon substrate 110. The first transparent conductive oxide layer 140 includes a first TCO thin film, a metal gate line, and a second TCO thin film; the second transparent conductive oxide layer includes both a first TCO thin film and a second TCO thin film.
[0030] In this embodiment, the first transparent conductive oxide layer located on the upper surface of the n-type single-crystal silicon substrate belongs to the gate line region. This embodiment adopts a sandwich structure with multiple layers stacked together, with metal gate lines disposed between the two TCO films for collecting and transporting charge carriers, thereby improving the photoelectric performance of the stacked films. The second transparent conductive oxide layer located on the lower surface of the n-type single-crystal silicon substrate belongs to the non-gate line region. The combination of the first and second TCO films achieves better conductivity. At the same time, the two TCO films can better balance the transport of charge carriers at different positions and directions. In other words, this embodiment can meet the different needs of the gate line region and the non-gate line region by using transparent conductive oxide layers with different structures, thus better matching the battery performance.
[0031] In some preferred embodiments, the first TCO film and the second TCO film are indium oxide system, tin oxide system or zinc oxide system.
[0032] As a further preferred option, the indium oxide system is In2O3 / ZnO or In2O3 / WO3.
[0033] As a further preferred option, the tin oxide system is SnO2 / Ta or SnO2 / F.
[0034] As a further preferred option, the zinc oxide system is ZnO / Al or ZnO / Ga.
[0035] In some other preferred embodiments, the first transparent conductive oxide layer is AZO / metal gate / AZO, that is, the aluminum-doped zinc oxide thin film is a transparent conductive film with good conductivity and light transmittance, effectively increasing transmittance and realizing current conduction. At the same time, aluminum doping can improve the conductivity of zinc oxide. That is, the AZO thin film can be used as an anti-reflection layer and a transparent electrode to improve the conversion efficiency of solar energy.
[0036] It should be understood that metal gates are typically made of metallic materials and their function is to collect and transmit current, helping to improve current collection efficiency and transmission speed. The metal gate sandwiched in the middle, combined with the AZO layers on both sides, can potentially form a structure with specific electrical and optical properties to meet the needs of heterojunction solar cells.
[0037] In some preferred embodiments, the first transparent conductive oxide layer is ITO / metal gate / ITO. ITO (indium tin oxide) itself has a certain degree of conductivity, while the metal gate is typically made of a highly conductive metal material, such as gold, silver, or copper. This combination provides lower resistance, facilitating more efficient current collection and transmission, and reducing energy loss. Furthermore, ITO is a transparent conductive material with high transmittance in the visible light range. Sandwiching the metal gate between two ITO layers enhances conductivity while maintaining the overall structural transparency.
[0038] It should be noted that this embodiment does not specifically limit the manufacturing method of the first transparent conductive oxide layer and the second transparent conductive oxide layer. For example, a DC magnetron sputtering method can be used, wherein the metal gate can be prepared using a metal mask and a sputtering method.
[0039] It should be further noted that this embodiment does not specifically limit the material of the metal gate. For example, the metal gate line can be Ag, Au, Cu, Mg or Pt.
[0040] Furthermore, in other preferred embodiments, the thickness of the first TCO film is 90-130 nm, for example, preferably 90 nm, 100 nm, 120 nm, 130 nm, etc., and the thickness of the second TCO film is 70-160 nm, for example, preferably 70 nm, 100 nm, 120 nm, 140 nm, 160 nm, etc. The two TCO films within this range can work synergistically, allowing more light to pass through to key areas inside the battery, such as the silicon heterojunction, thus improving the solar cell's light absorption efficiency and thereby enhancing the photoelectric conversion efficiency. In addition, two TCO films of suitable thickness can work together to achieve a good anti-reflection effect. Moreover, TCO films within the aforementioned thickness range can work better with metal grid lines, providing an efficient channel for carrier transport.
[0041] Furthermore, in other preferred embodiments, the thickness of the metal grid lines is relatively thin, for example, 10-90 nm, which can be specifically set according to the fabrication process and the performance of the battery, and is not specifically limited thereto.
[0042] Furthermore, the carrier concentration of the first TCO thin film is (0.5-1.5)*10 20 cm -3Higher carrier concentrations provide better conductivity, which helps reduce the series resistance of the cell, improves current collection efficiency, and thus increases the cell's output power. In heterojunction solar cells, the first TCO thin film, as a transparent conductive layer, needs to effectively transport photogenerated carriers. A suitable carrier concentration ensures rapid current transport and reduces energy loss. Furthermore, first TCO thin films with carrier concentrations within this range can better integrate with metal grid lines. The metal grid lines are responsible for collecting current and discharging it from the cell; combined with a TCO thin film of appropriate carrier concentration, efficient carrier collection and transport can be achieved, improving the overall performance of the cell. In other words, first TCO thin films within the aforementioned thickness range can achieve good conductivity while maintaining a certain level of light transmittance, generating photogenerated carriers.
[0043] Furthermore, the carrier concentration of the second TCO film is greater than 70 cm⁻¹. 2 A higher carrier mobility ( / V·s) means that carriers can move more quickly under the influence of an electric field, enabling the battery to more effectively transport photogenerated carriers to the electrodes, thereby improving the battery's output performance. Furthermore, rapid carrier transport reduces energy loss during transport, improving the battery's energy conversion efficiency and reducing recombination losses. In other words, the second TCO film of this embodiment, while maintaining good conductivity, can reduce the absorption of incident light and increase light transmittance, thereby increasing the amount of light reaching the battery's active layer and improving photoelectric conversion efficiency.
[0044] Furthermore, the resistivity of the first TCO film and the second TCO film is 2×10⁻⁶. -5 -3×10 -2 Ω·cm, for example, 2×10 -5 Ω·cm, 5×10 -4 Ω·cm, 3×10 -3 Ω·cm, 3×10 -2 A low resistivity, such as Ω·cm, indicates that the TCO thin film possesses excellent conductivity. This allows for the effective collection and transport of photogenerated carriers, reducing the series resistance of the cell and improving current collection efficiency, thereby enhancing the cell's output power and photoelectric conversion efficiency. A suitable resistivity allows for better integration of the TCO thin film with metal grid lines. The metal grid lines, responsible for collecting and discharging current from the cell, combined with the low-resistivity TCO thin film, enable highly efficient carrier collection and transport.
[0045] Furthermore, the thickness of the n-type single-crystal silicon substrate is preferably 10-50 nm, for example, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, etc. In addition, the substrate can be phosphorus (P) doped amorphous silicon.
[0046] Furthermore, the thickness of the first intrinsic amorphous silicon layer and the second intrinsic amorphous silicon layer is preferably 5-12 nm, for example, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, etc. In addition, the intrinsic amorphous silicon layer can preferably be made of high-purity amorphous silicon to reduce the influence of impurities on carrier recombination.
[0047] Furthermore, the thickness of the p-type amorphous silicon layer is preferably 10-30 nm, for example, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, etc., and boron (B) doped amorphous silicon can be used. Boron doping can provide holes to form a p-type semiconductor.
[0048] Furthermore, the thickness of the n-type amorphous silicon layer is preferably 10-30 nm, for example, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, etc., and phosphorus (P)-doped amorphous silicon can be used. Phosphorus doping can provide electrons to form an n-type semiconductor.
[0049] Furthermore, the first and second electrodes can preferably be made of materials with good conductivity and high chemical stability, such as silver (Ag), copper (Cu), and aluminum (Al). Silver has high conductivity and reflectivity, but is expensive; copper also has good conductivity, but is easily oxidized; aluminum is less expensive and has good conductivity and oxidation resistance. Of course, the transparent electrode can be made of the same material as the TCO layer, or a combination of other materials with good conductivity and light transmittance.
[0050] This embodiment improves the conductivity of the TCO film by inserting an ultrathin metal layer into the TCO film, thereby reducing the sheet resistance of the TCO film while maintaining high light transmittance.
[0051] The heterojunction solar cell will be further explained below with reference to specific embodiments:
[0052] Example 1
[0053] The heterojunction solar cell includes: an n-type monocrystalline silicon substrate, a first intrinsic amorphous silicon layer, a p-type amorphous silicon layer, a first transparent conductive oxide layer and a first electrode stacked sequentially on the upper surface of the n-type monocrystalline silicon substrate, and a second intrinsic amorphous silicon layer, an n-type amorphous silicon layer and a second transparent conductive oxide layer and a second electrode stacked sequentially on the lower surface of the n-type monocrystalline silicon substrate.
[0054] The first transparent conductive oxide layer is AZO / Mg / AZO; the second transparent conductive oxide layer is AZO / AZO. The thickness of the first TCO film is 100 nm, the thickness of the second TCO film is 120 nm, and the resistivity is 2 × 10⁻⁶. -5 The carrier concentration of the first TCO thin film is 1.0 × 10⁻⁶ Ω·cm. 20 cm-3 The carrier concentration of the second TCO film is 75 cm⁻¹. 2 / V·s.
[0055] Secondly, the n-type single-crystal silicon substrate is 30 nm thick, the first and second intrinsic amorphous silicon layers are 8 nm thick, and the p-type and n-type amorphous silicon layers are both 20 nm thick. The first and second electrodes are silver electrodes.
[0056] The battery performance obtained in Example 1 is shown in Table 1, with a conversion efficiency of 22.69%, an open-circuit voltage of 0.739V, a short-circuit current of 9.320A, and a fill factor of 80.14%.
[0057] Example 2
[0058] The heterojunction solar cell includes: an n-type monocrystalline silicon substrate, a first intrinsic amorphous silicon layer, a p-type amorphous silicon layer, a first transparent conductive oxide layer and a first electrode stacked sequentially on the upper surface of the n-type monocrystalline silicon substrate, and a second intrinsic amorphous silicon layer, an n-type amorphous silicon layer and a second transparent conductive oxide layer and a second electrode stacked sequentially on the lower surface of the n-type monocrystalline silicon substrate.
[0059] The first transparent conductive oxide layer is ITO / Ag / ITO; the second transparent conductive oxide layer is ITO / ITO. The thickness of the first TCO film is 100 nm, the thickness of the second TCO film is 120 nm, and the resistivity is 3 × 10⁻⁶. -3 The carrier concentration of the first TCO thin film is 1.5 × 10⁻⁶ Ω·cm. 20 cm -3 The carrier concentration of the second TCO film is 78 cm⁻¹. 2 / V·s.
[0060] Secondly, the n-type single-crystal silicon substrate is 30 nm thick, the first and second intrinsic amorphous silicon layers are 8 nm thick, and the p-type and n-type amorphous silicon layers are both 20 nm thick. The first and second electrodes are silver electrodes.
[0061] The battery performance obtained in Example 2 is shown in Table 1. The conversion efficiency is 23.06%, the open circuit voltage is 0.737V, the short circuit current is 9.358A, and the fill factor is 80.84%.
[0062] Comparative Example 1
[0063] The heterojunction solar cell includes: an n-type monocrystalline silicon substrate, a first intrinsic amorphous silicon layer, a p-type amorphous silicon layer, a first transparent conductive oxide layer and a first electrode stacked sequentially on the upper surface of the n-type monocrystalline silicon substrate, and a second intrinsic amorphous silicon layer, an n-type amorphous silicon layer and a second transparent conductive oxide layer and a second electrode stacked sequentially on the lower surface of the n-type monocrystalline silicon substrate.
[0064] The first transparent conductive oxide layer is an ITO thin film; the second transparent conductive oxide layer is also an ITO thin film. The TCO thin film has a thickness of 220 nm, a resistivity of 0.6 Ω·cm, and a carrier concentration of 0.1 × 10⁻⁶. 15 cm -3 .
[0065] Secondly, the n-type single-crystal silicon substrate is 30 nm thick, the first and second intrinsic amorphous silicon layers are 8 nm thick, and the p-type and n-type amorphous silicon layers are both 20 nm thick. The first and second electrodes are silver electrodes.
[0066] The battery performance obtained in Comparative Example 1 is shown in Table 1. The conversion efficiency is 23.06%, the open-circuit voltage is 0.737V, the short-circuit current is 9.358A, and the fill factor is 80.84%.
[0067] Table 1 Performance of Heterojunction Cells
[0068]
[0069] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.
Claims
1. A heterojunction solar cell, characterized in that, include: An n-type monocrystalline silicon substrate, comprising a first intrinsic amorphous silicon layer, a p-type amorphous silicon layer, a first transparent conductive oxide layer, and a first electrode, sequentially stacked on the upper surface of the n-type monocrystalline silicon substrate; and a second intrinsic amorphous silicon layer, an n-type amorphous silicon layer, a second transparent conductive oxide layer, and a second electrode, sequentially stacked on the lower surface of the n-type monocrystalline silicon substrate; wherein... The first transparent conductive oxide layer includes a first TCO film, a metal gate line, and a second TCO film; The second transparent conductive oxide layer includes a first TCO film and a second TCO film.
2. The heterojunction solar cell according to claim 1, characterized in that, The first TCO film and the second TCO film are indium oxide system, tin oxide system or zinc oxide system.
3. The heterojunction solar cell according to claim 2, characterized in that, The indium oxide system is In₂O₃ / ZnO, In₂O₃ / WO₃; and / or, The tin oxide system is SnO2 / Ta or SnO2 / F; and / or, The zinc oxide system is ZnO / Al or ZnO / Ga.
4. The heterojunction solar cell according to claim 3, characterized in that, The first transparent conductive oxide layer is either AZO / metal gate / AZO or ITO / metal gate / ITO.
5. The heterojunction solar cell according to claim 4, characterized in that, The thickness of the first TCO film is 90-130 nm; The thickness of the second TCO film is 70-160 nm.
6. The heterojunction solar cell according to claim 5, characterized in that, The carrier concentration of the first TCO film is (0.5-1.5)*10 20 cm -3 .
7. The heterojunction solar cell according to claim 5, characterized in that, The carrier concentration of the second TCO film is greater than 70 cm⁻¹ 2 / V·s.
8. The heterojunction solar cell according to any one of claims 1 to 7, characterized in that, The resistivity of the first TCO film and the second TCO film is 2×10⁻⁶. -5 -3×10 -2 Ω·cm.
9. The heterojunction solar cell according to any one of claims 1 to 7, characterized in that, The metal grid lines are Ag, Au, Cu, Mg, or Pt.
10. The heterojunction solar cell according to any one of claims 1 to 7, characterized in that, The thickness of the n-type single-crystal silicon substrate is 10-50 nm; and / or, The thicknesses of the first intrinsic amorphous silicon layer and the second intrinsic amorphous silicon layer are preferably 5-12 nm; and / or, The thickness of the p-type amorphous silicon layer and the n-type amorphous silicon layer is 10-30 nm.