TBC battery and preparation method thereof

Abstract

According to the TBC battery and the preparation method thereof, boron-doped carrier selective contact areas and phosphorus-doped carrier selective contact areas are sequentially constructed on the back surface of a silicon wafer, and the synergistic effect of a tunneling oxide layer and a polycrystalline / amorphous silicon film is combined, so that efficient blocking of minority carriers and selective transmission of majority carriers are effectively realized; and the interface recombination loss is obviously inhibited, so that the open-circuit voltage and the filling factor of the battery are greatly improved. On the basis, strontium titanate is introduced as a passivation layer material, and after the strontium titanate is matched with an alkyl modification layer formed on the surface of the strontium titanate, the chemical stability and environmental durability of the passivation layer are improved, the interface energy band structure between the passivation layer and a subsequent metal electrode is optimized, the contact barrier and the contact resistance are remarkably reduced, and the service life of the solar cell is prolonged. And efficient extraction and transverse transportation of majority carriers are promoted. Therefore, excellent surface passivation performance can be achieved, and meanwhile good interface compatibility, low contact resistance and long-term operation stability are achieved.

Description

Technical Field

[0001] This application relates to the photovoltaic field, and more specifically, to a TBC cell and its preparation method. Background Technology

[0002] Tunneling Back Contact (TBC) solar cells, by integrating all electrodes on the back of the cell, effectively eliminate optical shading losses caused by front-side metal grid lines. Combined with high-quality surface passivation and carrier-selective contact structures, they have become one of the important technical routes for high-efficiency crystalline silicon photovoltaic devices.

[0003] In TBC (Total Burner Cell) structures, a high-quality surface passivation layer and carrier-selective contact structure play a crucial role in suppressing carrier recombination, improving open-circuit voltage, and increasing fill factor. Currently, silicon nitride (SiNx) and silicon dioxide (SiO2) are commonly used as passivation layers. However, these traditional passivation materials exhibit significant lattice mismatch with the crystalline silicon substrate, easily introducing a high density of interface states (Dit) at the interface, thereby weakening the surface passivation effect and limiting further improvements in cell performance. Furthermore, these passivation layers typically have high resistivity and form a large contact barrier with the subsequently deposited metal electrodes, leading to increased contact resistance and severely restricting the effective extraction and transport efficiency of majority carriers.

[0004] Therefore, there is an urgent need to develop a new type of passivation layer that can achieve excellent surface passivation performance while possessing good interfacial compatibility, low contact resistance, and long-term operational stability. Summary of the Invention

[0005] This application provides a TBC battery and a method for preparing the same, in order to achieve the above-mentioned objective.

[0006] The embodiments of this application are implemented as follows: In a first aspect, the present invention provides a method for preparing a TBC battery, comprising: Silicon wafer pretreatment: The silicon wafers are resistivity screened and their back sides are cleaned and surface pretreated; One-stage thin film deposition: depositing a polycrystalline silicon thin film or an amorphous silicon thin film on the back side of a silicon wafer; Boron diffusion and patterning: Boron diffusion, annealing, and patterning of silicon wafers; Tunneling oxide deposition: Depositing a tunneling oxide film on the back side of a silicon wafer; Secondary thin film deposition: depositing polycrystalline silicon thin films or amorphous silicon thin films on the back side of a silicon wafer; Phosphorus diffusion and patterning: Phosphorus diffusion, annealing, and patterning of silicon wafers; Surface treatment: Acid etching and texturing of silicon wafers; Passivation modification: A strontium titanate passivation layer is deposited on the back side of the silicon wafer and a hydrocarbon-based modification layer is generated on the surface of the strontium titanate passivation layer; Electrode fabrication: Depositing antireflective coatings and printing gate lines on silicon wafers.

[0007] In an optional embodiment, during the passivation modification step, a strontium titanate passivation layer is first deposited, followed by plasma treatment with a mixture of oxygen and water vapor to generate a hydrocarbon-based modification layer on the surface of the strontium titanate passivation layer.

[0008] In an optional implementation, a strontium titanate passivation layer is deposited on the back side of a silicon wafer using an ALD process at a deposition temperature of 200-350°C and a pressure of 1-10 mTorr.

[0009] In an optional implementation, the oxygen flow rate is 20-100 ccm and the water vapor flow rate is 5-60 ccm.

[0010] In an optional embodiment, the plasma treatment pressure is 10-50 Pa, the temperature is 25-100 °C, and the time is 20-200 s.

[0011] In an optional embodiment, the thickness of the hydrocarbon-based modification layer is 1-3 nm.

[0012] In an optional implementation, a protective gas is introduced during the plasma treatment process, with a volume ratio of protective gas to oxygen of 1-3.

[0013] In an optional implementation, in the first or second thin film deposition step, silane and methane are first deposited on the back side of the silicon wafer in HDPCVD using process gases; then hydrogen, silane, and borane are deposited on the carbon-doped layer in LPCVD using process gases.

[0014] In an optional embodiment, during HDPCVD, the volume ratio of methane to silane is 3-10, the reaction temperature is 30-500°C, the reaction time is 10-60 min, the reaction pressure is 0.2-50 mW / cm², and the radio frequency power density is 0.5-20 mW / cm². 2 ; In LPCVD, the volume ratio of hydrogen to silane is 0.1-500, the volume ratio of hydrogen to borane is 0.1-500, and the radio frequency power density is 0.5-20 mW / cm³. 2 The reaction pressure is 0.2-50 mbar, the reaction temperature is 200-500℃, and the reaction time is 10-100 min.

[0015] Secondly, this application provides a TBC battery, which is manufactured using the TBC battery preparation method of any of the above embodiments.

[0016] This application achieves efficient blocking of minority carriers and selective transport of majority carriers by sequentially constructing boron-doped and phosphorus-doped carrier-selective contact regions on the back side of a silicon wafer, combined with the synergistic effect of a tunneling oxide layer and a polycrystalline / amorphous silicon thin film. This significantly suppresses interfacial recombination losses, thereby greatly improving the open-circuit voltage and fill factor of the battery. Furthermore, strontium titanate (SrTiO3, STO) is introduced as a passivation layer material. The combination of SrTiO3 and its surface-formed hydrocarbon-based modification layer not only enhances the chemical stability and environmental durability of the passivation layer but also optimizes the interfacial band structure between the passivation layer and the subsequent metal electrode, significantly reducing the contact barrier and contact resistance, and promoting efficient extraction and lateral transport of majority carriers. In addition, by performing acid etching and texturing on the front side and integrating an antireflective film and a full back electrode structure on the back side, optical obstruction caused by the front metal grid lines is completely eliminated, increasing the short-circuit current density. Therefore, it achieves excellent surface passivation performance while possessing good interfacial compatibility, low contact resistance, and long-term operational stability. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of the preparation method of the TBC battery according to an embodiment of this application. Detailed Implementation

[0019] As used in this article: "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0020] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0021] In these embodiments, unless otherwise specified, the parts and amounts are all by weight.

[0022] The embodiments of this application will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of this application. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0023] refer to Figure 1 This application discloses a method for preparing a TBC battery, comprising: Silicon wafer pretreatment: The silicon wafers are resistivity screened and their back sides are cleaned and surface pretreated; One-stage thin film deposition: depositing a polycrystalline silicon thin film or an amorphous silicon thin film on the back side of a silicon wafer; Boron diffusion and patterning: Boron diffusion, annealing, and patterning of silicon wafers; Tunneling oxide deposition: Depositing a tunneling oxide film on the back side of a silicon wafer; Secondary thin film deposition: depositing polycrystalline silicon thin films or amorphous silicon thin films on the back side of a silicon wafer; Phosphorus diffusion and patterning: Phosphorus diffusion, annealing, and patterning of silicon wafers; Surface treatment: Acid etching and texturing of silicon wafers; Passivation modification: A strontium titanate passivation layer is deposited on the back side of the silicon wafer and a hydrocarbon-based modification layer is generated on the surface of the strontium titanate passivation layer; Electrode fabrication: Depositing antireflective coatings and printing gate lines on silicon wafers.

[0024] Thus, by sequentially constructing boron-doped and phosphorus-doped carrier-selective contact regions on the back side of the silicon wafer, and combining the synergistic effect of the tunneling oxide layer and the polycrystalline / amorphous silicon thin film, efficient blocking of minority carriers and selective transport of majority carriers are effectively achieved, significantly suppressing interface recombination losses, thereby greatly improving the open-circuit voltage and fill factor of the battery.

[0025] Building upon this, strontium titanate (SrTiO3, STO) is introduced as a passivation layer material. SrTiO3, a typical perovskite oxide, is frequently used as a passivation layer material in electronic devices due to its excellent dielectric properties, chemical stability, and compatibility with various semiconductors / metals. Its passivation mechanism mainly revolves around three core aspects: surface state modulation, interfacial charge buffering, and chemical / physical isolation. These can be analyzed in detail from the following dimensions: 1. Surface state passivation: suppressing carrier recombination Semiconductors (such as silicon, silicon carbide, and perovskite) have numerous dangling bonds and defect states (such as vacancies and impurity levels) on their surfaces. These surface states become recombination centers for charge carriers (electron-hole pairs), severely reducing the carrier mobility and lifetime of the device. Strontium titanate achieves surface state passivation through the following mechanisms: 1. Defect state saturation and chemical bonding Ti on the surface of strontium titanate 4+ Sr² + Ions can form stable chemical bonds (such as Si-O-Ti, Pb-O-Ti, etc.) with dangling bonds on the semiconductor surface, saturating surface dangling bonds and eliminating or reducing the surface defect state density. For example, in perovskite solar cells, STO can react with Pb²⁺ on the perovskite surface. + I - Coordination bonds are formed to fill surface vacancies in perovskites and suppress nonradiative recombination of charge carriers.

[0026] Furthermore, the oxygen atoms in its perovskite structure can form an oxide layer with the unsaturated metal atoms on the semiconductor surface, further stabilizing the surface chemical state and reducing the generation of defect states.

[0027] 2. Energy level matching to regulate charge trapping Strontium titanate has a band gap of approximately 3.2 eV (insulator characteristic), and its conduction band bottom (CBM) and valence band top (VBM) energy levels can be tuned through doping (such as La or Nb doping) or interface modification. When STO forms a heterojunction with a semiconductor, if its energy level positions match the Fermi level of the semiconductor, charge trapping traps can be avoided, or the transfer of charge carriers to surface states can be suppressed by energy level shifting, thereby reducing recombination losses.

[0028] II. Interface charge buffering and field effect modulation At semiconductor-metal or semiconductor-electrolyte interfaces, the high dielectric properties and polarization effect of strontium titanate can achieve charge buffering and interfacial electric field modulation, indirectly improving the passivation effect. 1. High dielectric properties suppress charge tunneling The relative permittivity (ε) of strontium titanate With a dielectric constant of approximately 200-300 (far higher than SiO2's 3.9), it can reduce the interfacial electric field strength and decrease the tunneling recombination probability of charge carriers when used as a passivation layer. Simultaneously, the high dielectric properties help reduce interfacial charge accumulation, avoiding local electric field distortion and defect state activation caused by charge accumulation.

[0029] 2. Polarization effect modulates interfacial charge distribution Strontium titanate (STO) exhibits spontaneous or field-induced polarization properties (especially under doping or stress modulation). Its polarization charge can form a stable electric field at the interface, regulating the carrier concentration and transport direction on the semiconductor surface. For example, in n-type silicon devices, the positive polarization charge of STO can induce a depletion layer on the silicon surface, reducing electron-hole recombination; in p-type semiconductors, it can form an accumulation layer, improving carrier mobility.

[0030] III. Chemical and Physical Isolation Protection The high chemical stability and dense structure of strontium titanate can form a physical barrier, blocking the erosion of the substrate material by the external environment or subsequent processes, reducing the generation of defect states at the source, and indirectly enhancing the passivation effect. 1. Chemical isolation to prevent oxidation / corrosion Strontium titanate exhibits excellent stability at high temperatures (above 800°C) and in harsh chemical environments (such as acids, alkalis, and plasma atmospheres), effectively protecting semiconductor substrates (such as silicon and perovskite) from oxidation, hydrolysis, or corrosion. For example, in perovskite solar cells, the STO passivation layer can block the contact between moisture and perovskite, inhibiting its decomposition; in semiconductor etching processes, it can protect specific areas from plasma erosion.

[0031] 2. A physically dense layer prevents impurity diffusion. When strontium titanate thin films are prepared using processes such as sputtering and sol-gel, they can form a dense crystalline structure that effectively blocks metal ions (such as Ag in electrodes). + Au + ) or external impurities (such as H) + O2 - The impurities diffuse into the semiconductor to prevent lattice distortion and the increase of defect states caused by the introduction of impurities, thus maintaining the intrinsic electrical properties of the semiconductor.

[0032] IV. Optimization of passivation mechanism by doping and interface modification By doping or modifying the interface of strontium titanate, its passivation effect can be further enhanced, expanding its application scenarios: 1. Doping modulates energy levels and conductivity Donor doping (such as Nb doping) can make STO exhibit n-type conductivity, shifting its conduction band bottom energy level downward, making it easier to form ohmic contacts or heterojunctions with energy level matching with semiconductors, thus improving charge transport efficiency; acceptor doping (such as Mg doping) can enhance its dielectric properties and optimize the effect of interface electric field modulation.

[0033] 2. Interface coupling agent modification enhances binding strength. Introducing coupling agents (such as silane coupling agents and titanate coupling agents) at the interface between STO and semiconductor can enhance the interfacial bonding force between the two, reduce interfacial defect states (such as voids and interfacial state energy levels), and further reduce the carrier recombination probability.

[0034] In summary, the passivation mechanism of strontium titanate is a synergistic effect of surface state saturation, interfacial charge regulation, and chemical-physical isolation: surface defect states are eliminated through chemical bonding, charge transport is optimized using high dielectric properties and polarization effects, and external erosion is blocked by the dense structure, ultimately achieving suppression of carrier recombination and improvement of stability in semiconductor devices. Its passivation effect can be further modulated through doping and process optimization, thus showing broad application potential in photovoltaic cells, field-effect transistors, and power devices.

[0035] Therefore, strontium titanate has excellent dielectric properties, low interface state density, and good lattice matching with crystalline silicon, which can effectively reduce the defect density at the silicon / passivation layer interface and further enhance the surface passivation effect.

[0036] The hydrocarbon-modified layer, as a functional capping layer on the surface of the strontium titanate (SrTiO3) passivation layer, plays the following key roles: 1. Reduce interface state density and enhance passivation effect Hydrocarbon groups (such as -CH3, -C2H5 and other alkyl functional groups) can saturate dangling bonds or active sites on the surface of strontium titanate through chemical bonding, effectively reducing the surface defect state density, thereby further suppressing nonradiative recombination of charge carriers at the passivation layer / metal electrode interface and improving the overall surface passivation quality.

[0037] 2. Modulate the interface band structure to reduce the contact barrier. Hydrocarbon groups possess a certain dipole moment, and their orderly arrangement on the strontium titanate surface can introduce an interfacial dipole layer, modulating the local work function and band bending, and optimizing the majority carriers (such as holes in p-type carriers). + Area, electron in n + The transport barrier from the silicon substrate to the metal electrode is reduced, thereby significantly reducing the contact resistance and improving the carrier extraction efficiency.

[0038] 3. Improve interfacial chemical stability and antifouling ability The hydrocarbon-based modification layer is hydrophobic and chemically inert, and can form a protective film that can effectively block the corrosion or contamination of the strontium titanate passivation layer by moisture, oxygen and metal ions in the environment. It can maintain the stability of passivation performance during long-term battery operation or subsequent high-temperature processes, delay battery performance degradation and extend service life.

[0039] 4. Improve the compatibility of metal electrode deposition In subsequent grid line printing or metal evaporation processes, the hydrocarbon substrate can act as a buffer interface to suppress the diffusion of metal atoms into the passivation layer or silicon substrate, avoid the formation of recombination centers, and at the same time promote good adhesion and ohmic contact between the metal and the passivation layer, reduce contact resistance, and accelerate the migration of charge carriers to the electrode.

[0040] Therefore, the hydrocarbon-based modification layer not only enhances the electrical and chemical properties of the strontium titanate passivation layer, but also plays a synergistic role in carrier selective transport, contact resistance control, and long-term device reliability.

[0041] When combined with the hydrocarbon-based modification layer formed on its surface, strontium titanate not only improves the chemical stability and environmental durability of the passivation layer, but also optimizes the interfacial band structure between it and the subsequent metal electrode, significantly reducing the contact barrier and contact resistance, and promoting the efficient extraction and lateral transport of majority carriers.

[0042] Furthermore, by performing acid etching and texturing on the front side and integrating an anti-reflective film and a full back electrode structure on the back side, optical obstruction caused by the front metal grid lines is completely eliminated, thereby improving the short-circuit current density.

[0043] In the passivation modification step, a strontium titanate passivation layer is first deposited, followed by plasma treatment with a mixture of oxygen and water vapor to generate a hydrocarbon-based modification layer on the surface of the strontium titanate passivation layer.

[0044] Thus, after the strontium titanate passivation layer is deposited, plasma treatment with a mixture of oxygen and water vapor is introduced. The high activity of plasma can induce a controllable plasma-assisted surface functionalization reaction on the surface of the strontium titanate passivation layer: on the one hand, plasma activates water molecules (H2O) and oxygen molecules (O2), generating active hydroxyl groups (-OH), oxygen free radicals, and hydrogen species; on the other hand, these active species coordinate or adsorb with titanium / strontium atoms in the strontium titanate surface layer, while promoting the directional recombination of trace carbon sources in the environment (such as residual organic matter or background hydrocarbons in the process chamber) on the surface, forming stable hydrocarbon terminal functional groups (such as -CH3, -CH2-).

[0045] The hydrocarbon-modified layer formed in this way has the following multiple advantages: (1) By controlling the surface work function of strontium titanate through the surface dipole effect, the band matching between it and the subsequent metal electrode is optimized, and the contact barrier is reduced. (2) The hydrophobic properties of hydrocarbon groups effectively block the diffusion of environmental moisture and impurity ions to the passivation / silicon interface, enhancing the long-term operational stability of the device. (3) The organic-inorganic hybrid interface can alleviate mechanical stress and lattice mismatch during the metal deposition process, improve electrode adhesion and interface uniformity, thereby significantly reducing contact resistance ((R_c)) and increasing the fill factor (FF). (4) Compared with traditional modification methods that rely on high-temperature annealing or complex self-assembled monolayers (SAMs), this plasma in-situ treatment process is compatible with existing production lines, has a mild temperature window, high repeatability, and has good industrialization prospects.

[0046] Therefore, by employing a synergistic strategy of "strontium titanate passivation + plasma-induced hydrocarbon modification", not only was high-quality passivation with ultra-low interface state density achieved, but also a low-resistivity, stable, and engineerable carrier-selective contact interface was constructed, providing key material and process support for further breakthroughs in the efficiency of back contact (TBC) solar cells.

[0047] Optionally, a strontium titanate passivation layer is deposited on the back of the silicon wafer using an ALD (Atomic Layer Deposition) process at a deposition temperature of 200-350℃ and a pressure of 1-10 mTorr.

[0048] Thus, firstly, the ALD process itself possesses excellent thin-film conformal properties and atomic-level thickness control capabilities, enabling the formation of a uniform, pinhole-free strontium titanate passivation layer on the surface of TBC cells with complex patterned structures (such as alternating p / n doped regions). This ensures effective passivation of all silicon / dielectric interfaces, preventing localized leakage or recombination hotspots. Moreover, ALD equipment is more common and has a lower cost.

[0049] Secondly, limiting the deposition temperature to the range of 200-350℃ is sufficient to activate the surface reaction of the precursor, ensuring the crystal quality and stoichiometry of the strontium titanate film, while avoiding excessive redistribution or degradation of the already formed doped polycrystalline silicon layer (especially the phosphorus diffusion region) due to high temperature, thereby maintaining the steep doping gradient and electrical integrity of the p / n selective contact region.

[0050] If the temperature is too high: excessive crystallinity can lead to coarse grains, cracks, or stress concentration in the film, reducing its density and causing a decrease in the corrosion resistance and barrier properties of the passivation layer. Excessive temperature can also exacerbate interfacial diffusion between the film and the substrate, forming undesirable interfacial phases, weakening interfacial adhesion, and making the film prone to peeling. Furthermore, it may cause an imbalance in the volatilization of Sr and Ti elements in strontium titanate, deviating from the stoichiometric ratio, which deteriorates the dielectric properties of the film (such as dielectric constant and leakage current), affecting the electrical stability of the device.

[0051] If the temperature is too low: the film crystallinity is insufficient, mostly amorphous or microcrystalline structures, with high porosity, failing to form an effective physical and chemical protective barrier, allowing external water vapor and ions to easily penetrate, thus losing its passivation effect. Insufficient kinetic energy of the deposited particles results in poor adhesion between the film and the substrate, making it prone to scratches and detachment during subsequent processes (such as photolithography and etching), affecting device yield. At low temperatures, the film growth rate is slow, and the thickness uniformity is poor, leading to significant differences in electrical properties across different regions, resulting in reduced device performance consistency.

[0052] Finally, ALD deposition under a low-pressure environment of 1-10 mTorr helps to increase the mean free path of precursor molecules, enhance their diffusion ability in patterned trenches or high aspect ratio structures, and further improve the step coverage and compositional uniformity of the film. In addition, the low-pressure conditions can also effectively suppress gas phase side reactions, reduce particle formation, and improve film purity and interface cleanliness.

[0053] Excessive pressure shortens the mean free path of precursor molecules, restricting gas-phase diffusion. This is particularly problematic on the back side of TBC cells with high aspect ratio patterns, making uniform coverage difficult and leading to poor step coverage or localized deposition gaps. Furthermore, uncontrolled gas-phase nucleation or polymerization may occur before the precursor reaches the substrate surface, generating microparticles or non-stoichiometric byproducts, reducing film purity and introducing defect states. Simultaneously, increased residual gas partial pressure may introduce water vapor, oxygen, or other impurities into the film, disrupting the stoichiometry of strontium titanate and degrading its dielectric properties and passivation capabilities. If the pressure is too low: Insufficient precursor flux reduces the number of reactant molecules reaching the silicon wafer surface per unit time, leading to a significant decrease in deposition rate and impacting production efficiency. Furthermore, inadequate surface reaction results in some active sites not being effectively saturated, causing insufficient film density, the presence of micropores or breaks, and weakening its passivation effect on charge carriers and its ability to block the environment.

[0054] Of course, it is understandable that the strontium titanate passivation layer can also be formed using other deposition processes, such as: Magnetron sputtering: This method deposits a strontium titanate thin film on the back side of a silicon wafer by sputtering a composite target containing strontium and titanium (such as a SrTiO3 ceramic target) using radio frequency (RF) or direct current (DC). This method offers advantages such as high deposition rate, dense film, and good compatibility with production lines; however, it requires precise control of the oxygen partial pressure to maintain the stoichiometry, and care must be taken to ensure that ion bombardment during sputtering can damage the formed doped layer.

[0055] Pulsed Laser Deposition (PLD): High-energy lasers ablate SrTiO3 targets to epitaxially or amorphously grow high-quality thin films on substrates. PLD can achieve excellent compositional fidelity and crystal quality, making it suitable for laboratory-scale high-performance device development. However, the equipment cost is high and the deposition area is limited, making industrial application difficult.

[0056] Metal-Organic Chemical Vapor Deposition (MOCVD): This method uses metal-organic precursors (such as Sr(C5H5)2, Ti(OiPr)4, etc.) to generate SrTiO3 thin films through pyrolysis at high temperatures. MOCVD offers good step coverage and large-area uniformity, making it suitable for film deposition on complex surface structures. However, it typically requires high deposition temperatures (>400℃), which may affect the pre-existing dopant distribution and interface characteristics in TBC solar cells.

[0057] The oxygen flow rate is 20-100ccm, and the water vapor flow rate is 5-60ccm.

[0058] Oxygen, as the main active component in plasma, can generate high concentrations of oxygen atoms (O) and oxygen ions (O2) during the discharge process. + It contains 1000 molecules and excited oxygen molecules (O2*), which effectively remove residual hydrocarbon contaminants on the surface of strontium titanate, improve surface cleanliness, and provide active sites for subsequent functionalization modifications.

[0059] Under plasma irradiation, O2 promotes the activation of lattice oxygen on the surface of strontium titanate and synergistically generates an appropriate amount of surface hydroxyl groups (-OH) with water vapor. These -OH groups are key anchoring sites for subsequent hydrocarbon grafting (such as -CH3) or self-assembly reactions. If the O2 flow rate is too low (<20ccm), the oxidation capacity is insufficient, and the surface activation is inadequate; if it is too high (>100ccm), it may lead to over-oxidation, forming a thick oxide layer or disrupting the stoichiometry of the strontium titanate surface, thus inhibiting the efficiency of hydrocarbon modification.

[0060] An oxygen flow rate of 20-100 ccm helps maintain a stable glow discharge state, avoids plasma extinction or local arcing caused by gas scarcity, and ensures uniform processing.

[0061] Water vapor decomposes into OH radicals and H atoms in plasma, which not only participate in the formation of surface -OH terminal functional groups, but the released hydrogen can also passivate the dangling bonds at the strontium titanate / silicon interface, further reducing the interface state density.

[0062] In the presence of trace carbon sources (such as background organic matter in the chamber, precursor residues, or intentionally introduced hydrocarbon gases), OH and H can regulate the surface reaction pathway, guiding the selective adsorption and recombination of hydrocarbon species into stable alkyl (such as -CH3, -CH2-) terminal functional groups, forming a hydrophobic hydrocarbon modification layer. When the water vapor flow rate is too low (<5ccm), hydroxyl groups are insufficiently generated, resulting in a low hydrocarbon grafting rate; when the flow rate is too high (>60ccm), it easily leads to excessive surface hydration, forming a physically adsorbed water film, which hinders hydrocarbon formation and may introduce interfacial defects. H2O molecules have high polarity and dissociation energy; their appropriate introduction can optimize the plasma electron energy distribution and avoid sputtering damage to the strontium titanate film caused by high-energy ions.

[0063] In summary, within the ratio range of O2:20-100ccm and H2O:5-60ccm, the synergistic effect of the two can achieve moderate surface activation and cleaning, controllable hydroxyl density, dense and stable hydrocarbon-modified layer with strong hydrophobicity, effective modulation of work function, significant reduction in contact resistance, and excellent passivation quality.

[0064] The plasma treatment pressure is 10-50 Pa, the temperature is 25-100℃, and the time is 20-200 s.

[0065] 10-50 Pa (approximately 75-375 mTorr) falls within the typical low-pressure plasma operating range, ensuring sufficient gas molecule density to maintain stable glow discharge while avoiding excessively high pressure that could lead to a short mean free path of electrons and rapid energy dissipation. Under this pressure, the O2 / H2O mixture can be efficiently dissociated into reactive oxygen atoms (O), hydroxyl radicals (·OH), hydrogen atoms (·H), etc., which are uniformly distributed on the sample surface.

[0066] Compared to high vacuum (<1Pa), 10-50Pa is more conducive to the diffusion of active species to the sidewalls and bottom of patterned back contact structures (such as p / n alternating trenches), improving the processing uniformity under complex morphologies; and compared to atmospheric pressure plasma, this low-pressure condition effectively suppresses gas phase side reactions and the formation of local hot spots, avoiding film damage.

[0067] Before plasma treatment, TBC cells have undergone boron / phosphorus diffusion and polycrystalline silicon deposition. High temperatures may cause redistribution of doped atoms or interface degradation. Limiting the processing temperature to 25-100℃ (close to room temperature to mild heating) can completely avoid exceeding the thermal budget and protect the integrity of the formed p / n selective contact structure.

[0068] Moderate heating (e.g., 60-100℃) helps improve surface atomic mobility and accelerates the reaction of ·OH with metal sites on the strontium titanate surface (Ti). 4+ Sr² +The coordination reaction of CO / CH promotes the directional adsorption of hydrocarbon precursors (such as hydrocarbons from the chamber background) and CO / CH bonding; however, the temperature should not be too high to prevent the thermal desorption or oxidative decomposition of the weakly bonded hydrocarbon groups (such as -CH3).

[0069] If the plasma treatment time is too short (<20s): the surface activation is insufficient, the hydroxyl density is insufficient, the hydrocarbon grafting rate is low, it is difficult to form a continuous hydrophobic layer, and the passivation and contact improvement effects are limited; if the time is too long (>200s): it may lead to excessive oxidation or plasma etching effect, damage the surface of strontium titanate, or even introduce defect states, which will degrade the passivation performance.

[0070] The time is between 20 and 200 seconds. Surface cleaning and activation can be completed in a few seconds, hydroxylation can be completed in tens of seconds, and the subsequent time is used for hydrocarbon self-assembly or hydrocarbon species recombination, ultimately forming a dense and stable organic-inorganic hybrid interface.

[0071] In summary, within a process window of 10-50 Pa pressure, 25-100 °C temperature, and 20-200 s time, plasma treatment can efficiently generate surface -OH terminal functional groups, induce the formation of a uniform, hydrophobic hydrocarbon-based modification layer in situ, regulate the surface dipole of strontium titanate, reduce the work function, decrease the Schottky barrier with the metal electrode, and reduce the contact resistance, while maintaining excellent surface passivation performance. The entire process is carried out at low temperature, without damage, and without the introduction of additional chemicals, meeting the requirements of green manufacturing.

[0072] The hydrocarbon-modified layer has a thickness of 1-3 nm, which corresponds to the length of about 1-3 hydrocarbon chains (such as -CH3, -C2H5 or long-chain alkyl), indicating the formation of a dense monolayer or thin oligolayer structure, sufficient to achieve surface functionalization without hindering carrier tunneling. Such an ultrathin organic layer has a very small transport barrier for electrons / holes, maintaining good passivation without significantly increasing series resistance. Even a hydrocarbon base layer only 1 nm thick can significantly modulate the surface work function of strontium titanate through its surface dipole moment, optimizing the band alignment with metal electrodes (such as Ag, Al). At the same time, the fully covered hydrocarbon base layer can effectively block environmental moisture and ionic contaminants from penetrating into the sensitive passivation / silicon interface, improving the long-term reliability of the device.

[0073] During plasma treatment, a protective gas is introduced, with a volume ratio of protective gas to oxygen of 1-3. In other words, by introducing a protective gas (such as nitrogen N2, argon Ar, or a mixture thereof) during plasma treatment, and controlling the volume ratio of protective gas to oxygen at 1:1 to 3:1 (i.e., protective gas: oxygen = 1-3), the hydrocarbon modification process on the surface of the strontium titanate (SrTiO3) passivation layer can be precisely controlled.

[0074] Because pure oxygen plasma has strong oxidizing properties, it can easily lead to excessive oxidation of the strontium titanate surface or escape of lattice oxygen, and even etch the formed thin film. Introducing an inert protective gas (such as Ar or N2) can effectively dilute the concentration of oxygen free radicals, maintaining sufficient surface activation capacity while avoiding surface structure damage or stoichiometric imbalance. Moreover, the addition of a protective gas can improve plasma impedance matching, making glow discharge more stable and uniform. Especially in the processing of large-area silicon wafers, it can reduce edge effects and local hot spots, ensuring the consistency of processing in the patterned back contact area.

[0075] When the ratio is too low (<1, i.e., oxygen is excessive): the concentration of oxygen free radicals is too high, which can easily cause excessive hydroxylation of the strontium titanate surface or even the formation of a non-stoichiometric oxide layer, damaging the surface integrity; at the same time, it may completely oxidize the trace carbon source in the environment into CO / CO2, inhibiting the formation of hydrocarbon groups, resulting in an incomplete modification layer.

[0076] When the ratio is too high (>3, i.e., excessive protective gas): there are insufficient oxygen-active species, the surface activation is insufficient, the density of -OH groups is too low, and it is impossible to provide enough anchoring sites for subsequent hydrocarbon grafting; the plasma energy distribution is too "cold", the reaction kinetics are limited, and the modification efficiency decreases.

[0077] If the ratio is within the preferred range of 1-3: Achieving a balance between "mild activation and selective functionalization": the surface is moderately cleaned and an appropriate amount of -OH is generated, while trace amounts of hydrocarbon species (such as pump oil vapor and residual organic matter) in the environment or chamber are retained for in-situ hydrocarbon recombination; It is conducive to the formation of a dense, hydrophobic, low-defect hydrocarbon terminal layer (with a thickness of about 1-3 nm). It effectively reduces the contact barrier between the metal electrode and the passivation layer, and the contact resistance ((R_c)) can be stably controlled within 10-50 mΩ·cm². At the same time, it maintains the original high passivation performance of strontium titanate (interfacial state density (D_{it}) < 1×10¹¹cm). - ²·eV - ¹).

[0078] Therefore, by introducing a protective gas into the plasma treatment process and controlling its volume ratio with oxygen at 1-3, the interfacial chemical state can be precisely controlled without sacrificing the surface passivation quality, thus efficiently constructing a "strontium titanate-hydrocarbon" hybrid interface that combines low contact resistance, high stability, and excellent carrier selectivity. Optionally, in the silicon wafer pretreatment step, the silicon wafer is screened by resistivity and then etched and alkaline polished on the back side. In this process, after screening silicon wafers by resistivity using a silicon wafer sorting machine, the silicon wafers are alkaline polished using a KOH solution with a concentration of 1-3wt% at a reaction temperature of 60-85℃ and a reaction time of 10-40min.

[0079] In the primary or secondary thin film deposition steps, a flexible combination of various vapor deposition techniques (including high-density plasma-chemical vapor deposition (HDPCVD), plasma-enhanced chemical vapor deposition (PECVD), low-pressure chemical vapor deposition (LPCVD), and physical vapor deposition (PVD)) can be used to construct a multilayer or composite film structure of polycrystalline silicon (poly-Si) and amorphous silicon (a-Si:H) on the back side of a silicon wafer. This multi-process synergistic strategy allows for precise control of materials and interfaces to meet different functional requirements.

[0080] For example, in HDPCVD, silane and methane are used as process gases to deposit a carbon-doped amorphous / microcrystalline silicon layer on the back of a silicon wafer; then in LPCVD, hydrogen, silane, and borane are used as process gases to deposit a boron-doped polycrystalline silicon layer on the carbon-doped layer.

[0081] Thus, during the HDPCVD stage, carbon atoms generated from the decomposition of CH4 partially replace silicon lattice sites, forming a Si:C alloy. Appropriate carbon doping can: widen the optical bandgap of the deposited layer, enhancing its ability to block minority carriers; suppress the lateral diffusion of dopant atoms (such as B and P) during subsequent high-temperature annealing, increasing the doping steepness of the p / n contact region; and lower the film crystallization temperature, which is beneficial for forming high-quality microcrystalline structures at low temperatures.

[0082] HDPCVD technology features high-density plasma providing strong dissociation capabilities, enabling dense, low-hydrogen-content thin film deposition at relatively low temperatures (<400℃); ion-assisted growth improves film adhesion and step coverage, adapting to the patterned surface of TBC cells; in-situ carbon doping avoids damage from subsequent ion implantation and maintains interface integrity.

[0083] The LPCVD stage involves depositing boron-doped polycrystalline silicon (p0.05) on a carbon-doped substrate. + -poly-Si), H2 acts as a carrier gas and reducing agent, promoting the pyrolysis of SiH4 and etching weakly bonded silicon, thus improving crystal quality; B2H6 provides a p-type doping source, achieving a high activation concentration (>1×10²). 0 cm - ³), ensuring a low-resistance ohmic contact with the metal electrode; the high conductivity of polysilicon effectively reduces lateral transport resistance and improves the fill factor (FF).

[0084] The Si:C layer formed by HDPCVD acts as a diffusion barrier layer, suppressing excessive penetration of boron into the crystalline silicon substrate during the high-temperature (typically 580-630℃) process of LPCVD, thus preventing uncontrolled junction depth. At the same time, it acts as a stress buffer layer, alleviating the mismatch in thermal expansion coefficients between polycrystalline silicon and monocrystalline silicon, and reducing the generation of interface defects.

[0085] Thus, by employing a composite deposition strategy of "HDPCVD carbon-doped silicon + LPCVD boron-doped polycrystalline silicon," a p-type (or n-type, if replaced with phosphine PH3) selective contact stack structure with the following characteristics can be constructed: Excellent carrier selectivity: Wide-bandgap Si:C layer blocks minority carriers, while highly doped poly-Si layer efficiently extracts majority carriers; Low recombination and high conductivity: interfacial recombination rate <10fA / cm², contact resistance <20mΩ·cm²; Thermal budget is controllable: the key passivation / doping interface is formed in low-temperature HDPCVD, while high-temperature LPCVD only affects the upper conductive layer; High process compatibility: The two-step method can be integrated into existing TBC production lines without the need for additional complex equipment.

[0086] In HDPCVD, the volume ratio of methane to silane is 3-10, the reaction temperature is 30-500℃, the reaction time is 10-60 min, the reaction pressure is 0.2-50 mar, and the radio frequency power density is 0.5-20 mW / cm³. 2 ， The thickness of the carbon-doped layer formed is 5-100 nm; In LPCVD, the volume ratio of hydrogen to silane is 0.1-500, the volume ratio of hydrogen to borane is 0.1-500, and the radio frequency power density is 0.5-20 mW / cm³. 2 The reaction pressure is 0.2-50 mbar, the reaction temperature is 200-500℃, the reaction time is 10-100 min, and the thickness of the boron doped layer formed is 10-300 nm.

[0087] In the boron or phosphorus diffusion and patterning steps, the silicon wafer is annealed and crystallized using an annealing furnace. The annealing method can be rapid thermal annealing or tubular high-temperature annealing. The annealing atmosphere is nitrogen or argon, with a flow rate of 2000-9000 ccm. The annealing temperature is 700-1080℃, and the time is 10-90 min. For example, N2 is introduced at a temperature of 700-900℃ and held for 500-7000 s for annealing.

[0088] Patterning distinguishes between etched and non-etched areas. Patterning processes include one or more of screen printing, laser etching, and photolithography. In laser etching, the laser power is 200-1000W and the laser spot size is 30×30-300×300μm. In photolithography, a dry photoresist film is used as a mask and infrared light is used as the exposure light source.

[0089] Following the boron diffusion and patterning steps, the preparation method further includes: RCA cleaning: KOH is used as the main etching solution, with an alkaline washing solution of 1.0wt%-2.5wt% and an alkaline washing additive of 0.05-0.10wt%. The reaction time is 600s-1200s, and the reaction temperature is 65-85℃. It can be carried out under ultrasonic conditions with an ultrasonic power of 600-1200W and a frequency of 20-80kHz. Bubbling conditions can also be added, and some surfactants can be added to the solution, such as K2SO4, SLS, DP, DBSA, SDS, or other surfactants, or Triton or OG additives can be compounded.

[0090] Tunneling oxide film deposition: HDPCVD is used, with oxygen and silane as process gases. The silane to oxygen flow ratio is 1:10 to 1:20, and the RF power density is 0.5-20 mW / cm². 2 The pressure is 0.2-50 mbar, the temperature is 200℃-500℃, and the time is 1-10 min. The thickness of the tunneling oxide film formed is 1-2 nm.

[0091] Following the phosphorus diffusion and patterning steps, the preparation method also includes: Acid etching: The silicon wafer is acid-etched together with a mixed solution of HF concentration of 3-6wt% and HNO3 to HF solution ratio of 6-8:1 and HCl concentration of 1-2wt%.

[0092] Texturing: The silicon wafer is texturized using a mixed solution of alkali and texturing additives. The alkali can be KOH or NaOH, with the alkali washing solution at 1.0wt%-2.5wt% and the alkali washing additive at 0.05-0.10wt%. The reaction time is 600-1200s, and the reaction temperature is 65-85℃. This process can be performed under ultrasonic conditions, with an ultrasonic power of 600-1200W and a frequency of 20-80kHz. Bubbling can also be added, and appropriate surfactants can be added to the solution, such as K2SO4, SLS, DP, DBSA, SDS, or other surfactants, or compounded Triton or OG additives. After cleaning and texturing, the textured surface size of the silicon wafer is 0.5μm-3.6μm.

[0093] In the electrode fabrication process, the antireflection coating uses silane, nitrogen, and ammonia as process gases. The volume ratio of silane to ammonia is 1:3 to 1:10, and the volume ratio of nitrogen to silane is 1:1 to 10:1. The temperature is 200℃-500℃, the time is 10-60 min, the pressure is 0.2-50 mbar, and the RF power density is 0.5-20 mW / cm². 2 The thickness of the formed silicon nitride passivation film is 50-140 nm, and the refractive index of silicon nitride is 2.00-2.10.

[0094] In addition to the silicon nitride passivation film, it may also include materials such as SiO2. x AlO x SiN x O y MgF x The same film layers are formed to create a composite passivation film.

[0095] The grid line printing includes forming metal electrodes by screen printing. The sintering temperature of the front side is 150-300℃, and the time is 20-30 min; the sintering temperature of the back side is 180-250℃, and the time is 20-30 min.

[0096] This embodiment also discloses a TBC battery, which is manufactured using the above-described TBC battery preparation method.

[0097] The preparation method of the TBC battery according to the present application is further described in detail below with reference to the embodiments.

[0098] Example 1 S1. The silicon wafer is screened by resistivity, and the back side is etched and alkaline polished. S2. Use HDPCVD, LPCVD or other CVD to form stacked or composite carbon-doped or oxygen-doped P-type polycrystalline silicon thin films or amorphous silicon thin films on the back side of a silicon wafer. S3. Boron diffusion and annealing are performed on the silicon wafer; S4. Perform laser patterning on the silicon wafer once (P1); S5, RCA alkaline bath ultrasonic cleaning S6. Use HDPCVD to create a tunnel oxide film on the back of the silicon wafer; S7. Use HDPCVD, LPCVD or other CVD to form a stacked or composite carbon-doped or oxygen-doped N-type polycrystalline silicon thin film or amorphous silicon thin film on the back of a silicon wafer. S8. Phosphorus diffusion and annealing of silicon wafers. S9. Perform laser secondary patterning on the silicon wafer (P2); S10. Acid etching is performed on the silicon wafer; S11. Texturing the silicon wafer; S12. Passivate the back of the battery with strontium titanate and generate a hydroxyl-modified layer; S13. Apply anti-reflective coatings to the front and back sides of the silicon wafer using HDPCVD. S14. Print grid lines on the back of the silicon wafer; In detail, in step S1, a silicon wafer sorting machine is used to screen the resistivity of silicon wafers; the KOH solution concentration is 1-3wt%, the reaction temperature is 60-85℃, and the reaction time is 10-40min.

[0099] In step S1, a silicon wafer sorting machine is used to screen the resistivity of the silicon wafers, and then the back side is polished using a KOH solution with a concentration of 1-3wt%, a reaction temperature of 60-85℃, and a reaction time of 10-40min.

[0100] In step S3, silane and methane are first used as process gases in HDPCVD, with a silane to methane volume ratio of 1:4, a temperature of 450°C, a time of 45 minutes, a pressure of 10 mbar, and an RF power density of 20 mW / cm². 2 The first carbon-doped poly layer, with a thickness of 50 nm, was formed. Subsequently, in LPCVD, a mixture of hydrogen, silane, and borane was used as the process gas, with a hydrogen to silane volume ratio (H2 / SiH4) of 10:1 and a hydrogen to borane volume ratio (H2 / PH3) of 8:1. The RF power density was 20 mW / cm². 2 The pressure was 20 mbar, the temperature was 350℃, and the time was 30 min. A second doped poly layer with a thickness of 150 nm was formed, at which point a composite P-type POLY was formed.

[0101] The annealing in steps S3 and S8 involves crystallizing the silicon wafer using a high-temperature annealing furnace. The annealing method can be rapid thermal annealing or tubular high-temperature annealing. The annealing atmosphere is nitrogen or argon, the annealing temperature is 850°C, and the annealing time is 50 minutes.

[0102] Step S4 involves patterning. Patterning processes include screen printing, laser processing, and photolithography. For example, laser etching can be used to complete the patterning process, with a laser power of 600W and a laser spot size of 30μm x 30μm to 300μm x 300μm. In photolithography, a dry photoresist film can be used as a mask, and infrared light can be used as the exposure light source.

[0103] In step S5, KOH is used as the main etching solution, the alkaline washing solution is 1.5 wt%, the alkaline washing additive is 0.08 wt%, the reaction time is 800 s, the reaction temperature is 75 ℃, and it can be carried out under ultrasonic conditions with an ultrasonic power of 900 W and a frequency of 70 kHz. Bubbling conditions can also be added, and some surfactants can be added to the solution, such as K2SO4, SLS, DP, DBSA, SDS, or other surfactants, or Triton or OG additives can be compounded.

[0104] In step S6, HDPCVD is used, with oxygen and silane as process gases. The flow ratio of silane to oxygen is 1:10, and the RF power density is 15 mW / cm². 2The pressure was 20 mbar, the temperature was 350℃, and the time was 8 min. The thickness of the resulting tunneling oxide film was 1-2 nm.

[0105] In step S7, silane and methane are first used as process gases in HDPCVD, with a silane to methane volume ratio of 1:5, a temperature of 400°C, a time of 40 minutes, a pressure of 15 mbar, and an RF power density of 15 mW / cm². 2 The first carbon-doped poly layer was formed at 30 nm. Subsequently, in LPCVD, a mixture of hydrogen, silane, and phosphine was used as the process gas, with a hydrogen to silane volume ratio (H2 / SiH4) of 10:1 and a hydrogen to phosphine volume ratio (H2 / PH3) of 8:1. The RF power density was 15 mW / cm². 2 The pressure was 20 mbar, the temperature was 350℃, and the time was 30 min. A second doped poly layer with a thickness of 170 nm was formed, at which point a composite N-type POLY was formed.

[0106] In step S9, the patterning method is laser removal, with a laser wavelength of 556 nm, a frequency of 20000 Hz, and an energy density of 80 mW / cm². 2 .

[0107] In step S10, the HF concentration is 5 wt%, the HNO3 to HF solution ratio is 6:1, and acid washing is performed at a 2 wt% HCl concentration. In step S11, the silicon wafer is texturized using a mixed solution of alkali and texturing additive. KOH is used as the main etching solution, the alkali washing solution is 1.2 wt%, the alkali washing additive is 0.1 wt%, the reaction time is 900 s, and the reaction temperature is 68°C. The process can be performed under ultrasonic conditions with a power of 900 W and a frequency of 70 kHz, and bubbling can also be added. After cleaning and texturing, the textured surface size of the silicon wafer is 0.5 μm-3.6 μm.

[0108] In step S12, a strontium titanate passivation layer is deposited using the ALD process at a temperature of 300°C for 120 cycles, resulting in a thickness of 15 nm. This is followed by plasma treatment using oxygen (60 ccm flow rate) and water vapor (20 ccm flow rate) as the treatment gases, at a temperature of 25°C, a reaction chamber pressure of 20 Pa, and a treatment time of 45 s, forming a 2 nm thick hydroxyl-modified layer. In step S13, silane, nitrogen, and ammonia are used as process gases. The volume ratio of silane to ammonia is 1:6, and the volume ratio of nitrogen to silane is 8:1. The temperature is 400℃, the time is 40 min, the pressure is 0.2-50 mbar, and the RF power density is 15 mW / cm². The resulting silicon nitride passivation film has a thickness of 80 nm and a refractive index of 2.00. According to one embodiment of this disclosure, in addition to the silicon nitride passivation film, it may also include materials such as SiO₂. x AlO x SiN x O y MgF x The same film layers are formed to create a composite passivation film.

[0109] In step S14, metal electrodes are formed by screen printing. The sintering temperature of the front side is 150-300℃, and the time is 20-30 min; the sintering temperature of the back side is 180-250℃, and the time is 20-30 min.

[0110] Example 2 In step S12, the deposition pressure of the strontium titanate passivation layer is 1 mTorr, the precursor is uniformly diffused, the impurity content is low, the surface roughness is small, the deposition temperature is 200℃, the precursor does not decompose but has low activity, and the film is a polycrystalline phase of Sr(OH)2.

[0111] During plasma treatment, the oxygen flow rate was 20 ccm, the water vapor flow rate was 5 ccm, the pressure was 10 Pa, the temperature was 25 °C, the time was 20 s, the surface hydrophilicity (contact angle) was 35-45°, the relative content of oxygen-containing functional groups (-OH / -COOH) was 40-45%, and the passivation effect (surface recombination efficiency) was 40-50 μs. -1 .

[0112] Example 3 In step S12, the strontium titanate passivation layer is deposited at a pressure of 10 mTorr, resulting in high nucleation density, no pinhole defects, and small thickness uniformity error. The deposition temperature is 350℃, which provides a precursor with moderate activity and good crystallinity, making it suitable for capacitor requirements.

[0113] During plasma treatment, the oxygen content was 100 ccm, the water vapor flow rate was 60 ccm, the pressure was 50 Pa, the temperature was 100℃, the time was 200 s, the surface hydrophilicity (contact angle) was 10-15°, the relative content of oxygen-containing functional groups (-OH / -COOH) was 85-90%, and the passivation effect (surface recombination efficiency) was 8-12 μs. -1 .

[0114] Example 4 In step S12, the strontium titanate passivation layer was deposited at a pressure of 0.5 mTorr, resulting in low nucleation density, local discontinuities in the film, and weak interfacial adhesion that made it easy to peel off. The deposition temperature was 150℃, leading to insufficient precursor adsorption, incomplete reaction, and an amorphous film that failed to meet the requirements of electrical devices.

[0115] During plasma treatment, the oxygen content was 10 ccm, the water vapor flow rate was 3 ccm, the pressure was 5 Pa, the temperature was 15℃, the time was 10 s, the surface hydrophilicity (contact angle) was 65-75°, the relative content of oxygen-containing functional groups (-OH / -COOH) was 15-20, and the passivation effect (surface recombination efficiency) was 80-100 μs. -1 .

[0116] Example 5 In step S12, the pressure for depositing the strontium titanate passivation layer is 30 mTorr, which disrupts the self-limiting property of the ALD, increases the edge thickness deviation, introduces the Sr(OH)2 impurity phase, results in high leakage current density, and degrades electrical performance. The deposition temperature is 370℃, leading to partial decomposition of the precursor and easy distortion of the crystalline phase.

[0117] During plasma treatment, the oxygen content was 120 ccm, the water vapor flow rate was 70 ccm, the pressure was 60 Pa, the temperature was 120 °C, the time was 250 s, the surface hydrophilicity (contact angle) was 8-12°, the relative content of oxygen-containing functional groups (-OH / -COOH) was 92-95%, and the passivation effect (surface recombination efficiency) was 15-20 μs. -1 .

[0118] Comparative Example 1 Step S12 is discarded.

[0119] The TBC batteries prepared in Examples 1-5 and Comparative Example 1 were subjected to performance tests, and the results are shown in Table 1 below: Table 1

[0120] As can be seen from the examples, comparative examples and Table 1 above, the "strontium titanate passivation + hydrocarbon group modification + optimized plasma treatment" technical route proposed in this application can achieve high efficiency (Eff≈24.7%), high fill factor (>80.25%), etc.

[0121] The above description is merely a specific embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a TBC battery, characterized in that, include: Silicon wafer pretreatment: The silicon wafers are resistivity screened and their back sides are cleaned and surface pretreated; One-stage thin film deposition: depositing a polycrystalline silicon thin film or an amorphous silicon thin film on the back side of a silicon wafer; Boron diffusion and patterning: Boron diffusion, annealing, and patterning of silicon wafers; Tunneling oxide deposition: Depositing a tunneling oxide film on the back side of a silicon wafer; Secondary thin film deposition: depositing polycrystalline silicon thin films or amorphous silicon thin films on the back side of a silicon wafer; Phosphorus diffusion and patterning: Phosphorus diffusion, annealing, and patterning of silicon wafers; Surface treatment: Acid etching and texturing of silicon wafers; Passivation modification: A strontium titanate passivation layer is deposited on the back side of the silicon wafer and a hydrocarbon-based modification layer is generated on the surface of the strontium titanate passivation layer; Electrode fabrication: Depositing antireflective coatings and printing gate lines on silicon wafers.

2. The method for preparing a TBC battery according to claim 1, characterized in that, In the passivation modification step, a strontium titanate passivation layer is first deposited, followed by plasma treatment with a mixture of oxygen and water vapor to generate a hydrocarbon-based modification layer on the surface of the strontium titanate passivation layer.

3. The method for preparing a TBC battery according to claim 2, characterized in that, A strontium titanate passivation layer is deposited on the back side of a silicon wafer using the ALD process at a temperature of 200-350℃ and a pressure of 1-10 mTorr.

4. The method for preparing a TBC battery according to claim 2, characterized in that, The oxygen flow rate is 20-100ccm, and the water vapor flow rate is 5-60ccm.

5. The method for preparing a TBC battery according to claim 2, characterized in that, The plasma treatment pressure is 10-50 Pa, the temperature is 25-100℃, and the time is 20-200 s.

6. The method for preparing a TBC battery according to claim 4 or 5, characterized in that, The thickness of the hydrocarbon-based modification layer is 1-3 nm.

7. The method for preparing a TBC battery according to claim 2, characterized in that, During plasma treatment, a protective gas is introduced, with a volume ratio of 1-3 between the protective gas and oxygen.

8. The method for preparing a TBC battery according to claim 1, characterized in that, In the first or second thin film deposition step, silane and methane are first deposited on the back side of the silicon wafer in HDPCVD using process gases; then hydrogen, silane and borane are deposited on the carbon-doped layer in LPCVD using process gases.

9. The method for preparing a TBC battery according to claim 8, characterized in that, In HDPCVD, the volume ratio of methane to silane is 3-10, the reaction temperature is 30-500℃, the reaction time is 10-60 min, the reaction pressure is 0.2-50 mar, and the radio frequency power density is 0.5-20 mW / cm³. 2 ; In LPCVD, the volume ratio of hydrogen to silane is 0.1-500, the volume ratio of hydrogen to borane is 0.1-500, and the radio frequency power density is 0.5-20 mW / cm³. 2 The reaction pressure is 0.2-50 mbar, the reaction temperature is 200-500℃, and the reaction time is 10-100 min.

10. A TBC battery, characterized in that, It is manufactured using the preparation method of the TBC battery according to any one of claims 1-9.

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