Diamond conductive substrate and perovskite photovoltaic cell

Abstract

This invention discloses a diamond conductive substrate and a perovskite photovoltaic cell based on the substrate. The substrate comprises an integrated graphite-like conductive layer formed in one step by MPCVD and a polycrystalline diamond insulating support layer. The conductive layer has a thickness of 10 nm to 10 μm and a sheet resistance of 10 to 1000 Ω / sq. The insulating support layer has a thickness of 10 nm to 1000 μm, a light transmittance of ≥50%, and a thermal conductivity of ≥1000 W / (mK). The perovskite photovoltaic cell is composed of a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, and a back electrode sequentially arranged on the substrate, with an effective area of ​​≤50 mm50 mm. The substrate of this invention is radiation-resistant, has high thermal conductivity, excellent interface stability, and a cell irradiation efficiency retention rate of over 94%, solving the problem of easy degradation of traditional photovoltaic substrates in space environments and providing a reliable photovoltaic energy solution for space equipment such as computing satellites.

Description

Technical Field

[0001] This invention relates to the field of perovskite photovoltaic cell technology, and in particular to a diamond conductive substrate, a photovoltaic cell, and a method for preparing the photovoltaic cell. Background Technology

[0002] With the rapid development and technological advancements in artificial intelligence computing power and chip hardware manufacturing processes, the exponentially increasing chip power consumption places extremely high demands on power consumption and heat dissipation. Therefore, constructing computing centers in space, where the environment is cold and rich in solar energy, effectively solves the key problems of power and heat dissipation: the space environment provides uninterrupted and stronger sunlight, ensuring a continuous power supply for computing chips; simultaneously, the lower ambient temperature facilitates heat dissipation from high-power chips, improving their performance and durability. Currently, perovskite photovoltaic cells, as a new generation of photovoltaic technology, possess advantages such as high efficiency, low cost, and high energy-quality ratio, making them particularly suitable for space photovoltaic applications and a popular candidate for photovoltaic technology mounted on computing satellites.

[0003] However, due to the presence of numerous high-energy particles in the space environment, such as X-rays, protons, and neutrons, the transparent conductive substrates commonly used in perovskite photovoltaic cells cannot withstand the impact of high-energy particle radiation. Furthermore, the transport layers commonly used in the cells will degrade under radiation conditions. Therefore, the operational stability results of perovskite photovoltaic cells under both simulated and space-based experimental conditions are unsatisfactory. Diamond materials exhibit excellent radiation resistance, but they are rarely used as radiation-resistant substrates for photovoltaic cells. This may be because diamond materials have poor contact with common transparent conductive materials, and conventional deposition methods cannot obtain stable "diamond / transparent conductive material" radiation-resistant conductive substrates. Moreover, traditional post-deposition conductive layer processes easily lead to weak interfacial bonding, thermal expansion mismatch, and poor process compatibility, severely affecting the structural stability and long-term reliability of the substrate. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a diamond conductive substrate and a perovskite photovoltaic cell based on the substrate. This invention utilizes the good conductivity of the graphite-like phase through a one-step forming method to grow the conductive layer and the diamond insulating support layer simultaneously, overcoming the problems of poor post-deposition contact of the conductive layer and substrate instability. This substrate is used to prepare perovskite photovoltaic cells, which significantly improves the irradiation stability of perovskite photovoltaic cells.

[0005] To achieve the above objectives, the present invention provides a diamond conductive substrate comprising an integrated stacked conductive layer and an insulating support layer; the conductive layer is a graphite-like carbon material with a thickness of 10 nm to 10 μm and a sheet resistance of 10 to 1000 Ω / sq, exhibiting good in-plane conductivity and capable of replacing traditional transparent conductive oxides as the conductive substrate for photovoltaic devices; the insulating support layer is a polycrystalline diamond material with a thickness of 10 nm to 1000 μm, exhibiting an average transmittance ≥50% in the visible to near-infrared band (400–800 nm) and a thermal conductivity ≥1000 W / (m²). K) provides the substrate with high thermal conductivity, high mechanical strength and excellent radiation resistance.

[0006] The conductive layer and the insulating support layer are formed by in-situ continuous growth using a one-step microwave plasma chemical vapor deposition (MPCVD) process. The growth sequence is to first grow the conductive layer, and then grow the insulating support layer on the surface of the conductive layer. The two layers are grown in steps by precisely controlling parameters such as gas composition, microwave power, reaction pressure, and growth time of the MPCVD process. This eliminates the need for cavity replacement or secondary processing and avoids the interface defects of traditional post-deposition processes.

[0007] MPCVD fabrication process for conductive layer:

[0008] Using silicon, molybdenum, or other materials as the original growth substrate, a mixed gas containing CH4, N2, and H2 is introduced, wherein the volume percentage of CH4 is 1%–3%, the concentration of N2 is 0–800 ppm (diluted with H2 as the carrier gas), the microwave power is set to 1.5–2.0 kW, the reaction gas pressure is 100–150 Torr, and the growth time is 10–120 min. Preferably, the volume percentage of CH4 in H2 is 2%, and the N2 concentration is 500-600 ppm. This parameter range can ensure the crystallinity and conductivity of the graphite-like carbon material, while controlling the thickness of the conductive layer within the target range to avoid excessive thickness leading to a decrease in light transmittance.

[0009] MPCVD fabrication process for insulating support layer: After the conductive layer is grown, the process parameters are adjusted and the growth continues directly in the same MPCVD reaction chamber. The N2 channel is closed and a mixed gas containing CH4 and H2 is introduced, in which the volume percentage of CH4 is 0.5% to 2%. The microwave power is set to 2.0 to 10 kW, the reaction gas pressure is 100 to 150 Torr, and the growth time is 2 to 1000 h. Preferably, the volume percentage of CH4 in H2 is 1% to 1.2%. This parameter range can ensure the purity and crystal quality of polycrystalline diamond, achieve the performance requirements of high thermal conductivity and high light transmittance, and at the same time achieve lattice matching with the conductive layer to reduce stress mismatch.

[0010] The diamond conductive substrate is heteroepitaxially grown on a silicon or molybdenum original growth substrate and is peeled off from the original growth substrate to form a self-supporting structure by an edge exposure peeling method. The edge exposure peeling method involves mechanically scribing to create microcracks at the edge of the substrate and then peeling off with thermal stress assistance. After peeling, the conductive layer is exposed as the front side of the device and can be used for the subsequent fabrication of photovoltaic devices.

[0011] The present invention also provides a perovskite photovoltaic cell based on the aforementioned diamond conductive substrate, comprising, in sequence: an insulating support layer and a conductive layer of the diamond conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, and a back electrode; the effective area of ​​the perovskite photovoltaic cell is ≤50mm². 50mm, suitable for micro-computing satellites or space-based distributed energy systems.

[0012] The hole transport layer is made of a P-type semiconductor material with a thickness of no more than 100 nm. The P-type semiconductor material is Spiro-OMeTAD, PEDOT:PSS, TPD, PTAA, P3HT, PCPDTBT, or NiO. x It contains at least one of V2O5, CuI, MoO3, CuO, and Cu2O, which mainly enables hole transport and electron blocking.

[0013] The perovskite light-absorbing layer is made of a material with the general chemical formula ABX3, and has a thickness of 500–2000 nm; wherein, A is CH3NH3. + (MA + ), NH2=CHNH2 + (FA + C4H9NH3 + Cs + 、Rb + At least one of them; B is Pb 2+ Sn 2+ 、Ge 2+ Sb 3+ Bi 3+ Ag + Au 3+ Ti 4+ At least one of them; X is Cl - , Br - I - Or at least one of halogens, serving as the core photoelectric conversion layer of the battery to achieve the absorption of sunlight and the separation of charge carriers.

[0014] The electron transport layer is an N-type semiconductor material with a thickness of no more than 100 nm. The N-type semiconductor material includes titanium oxide (TiO2), zinc oxide (ZnO), tin oxide (SnO2), nickel oxide, magnesium oxide, copper oxide, cuprous oxide, tungsten oxide, C60 fullerene, and their derivatives (such as PC). 61 BM, PC 71 At least one of BM), which mainly realizes the transmission of electrons and the blocking of holes; Preferably, after the electron transport layer is deposited, a BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) modification layer is spin-coated, and the thickness of the BCP modification layer is 3-8 nm to improve the electron transport efficiency.

[0015] The back electrode is made of one of Au, Ag, Cu, C, or ITO, and its thickness is 80–150 nm. It serves as a carrier collection electrode to complete the circuit closure.

[0016] The present invention also provides a method for preparing the above-mentioned perovskite photovoltaic cell, comprising the following steps: The surface of the conductive layer of the stripped diamond conductive substrate is treated with ultraviolet ozone or oxygen plasma. The ultraviolet ozone treatment time is 5 to 15 minutes, and the oxygen plasma treatment power is 40 to 60 W and the treatment time is 3 to 8 minutes. This improves the surface energy and wettability, and enhances the interfacial bonding force between the conductive layer and the subsequent charge carrier transport layer. A hole transport layer is deposited on the surface of the conductive layer using physical sputtering, vapor deposition, or coating processes. Perovskite light-absorbing layers are prepared on the surface of the hole transport layer using methods such as slot coating, blade coating, screen printing, vacuum evaporation, or inkjet printing. An electron transport layer is deposited on the surface of the perovskite light-absorbing layer using physical sputtering, vapor deposition, or coating processes. The back electrode is prepared by vacuum thermal evaporation or magnetron sputtering on the surface of the electron transport layer, and the device is packaged to obtain a perovskite photovoltaic cell.

[0017] The beneficial effects of this invention are: The insulating support layer is made of polycrystalline diamond material and can withstand >10 16 n / cm 2 High-energy proton / neutron irradiation of a certain magnitude can effectively shield the perovskite active layer and its functional layers from high-energy particle radiation in the space environment. After 10 MeV proton irradiation (flux 1 × 10⁻⁶), 15 p / cm 2 After that, the photoelectric conversion efficiency of perovskite photovoltaic cells can be maintained at over 94%, which is much higher than the 56.9% of traditional ITO / glass-based devices; The thermal conductivity of the diamond insulating support layer is ≥1000 W / (m). K), which is much higher than that of traditional glass substrates (~1W / (m)). K)) and sapphire substrate (~30W / (m)) K)) can promptly dissipate the heat generated during battery operation. Under 1 Sun irradiation, the operating temperature of the perovskite photovoltaic cell of the present invention is 18°C ​​lower than that of ITO-based devices, effectively avoiding device performance degradation caused by heat accumulation. The in-situ continuous growth of the conductive layer and the diamond insulating support layer is achieved by one-step MPCVD molding process with precise matching of process parameters. The two layers have high lattice matching degree and small stress mismatch, forming an integrated self-supporting structure. There is no risk of interface contamination or adhesion failure, which significantly improves the structural stability and long-term reliability of the substrate and battery device. By defining the range of MPCVD process parameters, the sheet resistance of the graphite-like conductive layer is precisely controlled within the range of 10 to 1000 Ω / sq, exhibiting excellent in-plane conductivity. This layer can replace traditional transparent conductive oxides such as ITO and FTO. The diamond insulating support layer has an average transmittance of ≥50% in the visible to near-infrared band, and the balance between transmittance and conductivity can be achieved by adjusting the growth time of the conductive layer, thus meeting the photoelectric conversion requirements of photovoltaic devices. The diamond conductive substrate has a self-supporting structure, is lightweight and has high mechanical strength, and the effective area of ​​the perovskite photovoltaic cell is ≤50mm². With a thickness of 50mm, it meets the miniaturization and integration needs of space devices such as micro-computing satellites and deep space probes. At the same time, it has four core properties: high conductivity, high light transmittance, ultra-high thermal conductivity, and strong radiation resistance, providing a reliable energy solution for the field of space photovoltaics. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the perovskite photovoltaic cell of the present invention.

[0019] In the figure: 1-Insulating support layer, 2-Conductive layer, 3-Hole transport layer, 4-Perovskite light-absorbing layer, 5-Electron transport layer, 6-Back electrode. Detailed Implementation

[0020] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0021] Example 1 Fabrication of thin conductive layer diamond substrates (suitable for high light transmittance requirements): A single-crystal silicon wafer is used as the original growth substrate and placed in the MPCVD reaction chamber; A mixed gas of CH4 (2% in H2), N2 (500ppm in H2), and H2 was introduced, and the microwave power was set to 1.8kW, the reaction pressure to 120Torr, and the growth time was 30 minutes to form a 50nm thick graphite-like conductive layer on the surface of a single crystal silicon wafer. In the same reaction chamber, the process parameters were directly adjusted, N2 was turned off, and a mixed gas of high-purity H2+CH4 (1% in H2) was switched to. The microwave power was increased to 10kW, the reaction gas pressure was kept at 120Torr, and the growth continued for 200 hours to form a 200μm thick polycrystalline diamond insulating support layer on the surface of the conductive layer. After the reaction is completed and cooled to room temperature, microcracks are created at the edge of the substrate using mechanical scribing. The original growth substrate of the single crystal silicon wafer is peeled off using a thermal stress-assisted edge exposure peeling method to form a self-supporting diamond conductive substrate. The graphite-like conductive layer is then exposed as the front side of the device.

[0022] The performance of the prepared diamond conductive substrate was tested: the sheet resistance of the conductive layer was measured to be 85 Ω / sq using the four-probe method; the average transmittance in the visible to near-infrared band (400–800 nm) was measured to be 62% using a UV-Vis spectrophotometer; and the thermal conductivity was measured to be 1150 W / (m²) using the laser scintillation method. K); The bending strength was measured using the three-point bending method and was >800MPa.

[0023] Perovskite photovoltaic cell fabrication: The surface of the conductive layer of the self-supporting diamond conductive substrate was treated with oxygen plasma with process parameters of 50W and 5min to improve the surface energy and wettability of the conductive layer. A NiOx thin film with a thickness of 30 nm was deposited on the surface of the conductive layer using a spin coating process, serving as a hole transport layer. A Cs0.1FA0.9PbI3 perovskite precursor solution (a mixed solvent of DMF:DMSO = 4:1 (V:V) with a concentration of 1.4 mol / L) was coated on the surface of a NiOx thin film using a slit coating method. After annealing at 100℃ for 15 min, a perovskite light-absorbing layer with a thickness of 550 nm was formed. A C60 thin film with a thickness of 40 nm was deposited on the surface of the perovskite light-absorbing layer using a vapor deposition process as an electron transport layer. Subsequently, a BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) modification layer with a thickness of 5 nm was spin-coated. Ag electrodes were deposited on the surface of the BCP-modified layer using a vacuum thermal evaporation process, with a film thickness of 100 nm. Device encapsulation was then completed to obtain a perovskite photovoltaic cell with an effective area of ​​16 mm² (4 mm²). 4mm).

[0024] Performance testing Irradiation stability tests were conducted on the prepared perovskite photovoltaic cells: 10 MeV proton irradiation was performed on a ground-based simulation platform, with a flux of 1 × 10¹. 5 p / cm² (equivalent to a 1-year dose in low Earth orbit); Before irradiation, the photoelectric conversion efficiency (PCE) of the cell was 22.3%, and after irradiation, the PCE was 21.1%, with an efficiency retention rate of 94.6%. Comparative example (ITO / glass-based device): After irradiation, the PCE decreased from 21.8% to 12.4% (retention rate of only 56.9%). Example 2 Fabrication of thick conductive layer diamond substrates (suitable for low sheet resistance requirements): A molybdenum sheet was used as the original growth substrate and placed in the MPCVD reaction chamber. A mixed gas of CH4 (2% in H2), N2 (500ppm) and H2 was introduced, and the microwave power was set to 1.8kW, the reaction pressure to 120Torr, and the growth time was 90 minutes to form a 2μm thick graphite-like conductive layer on the surface of the molybdenum sheet. In the same reaction chamber, the process parameters were directly adjusted, N2 was turned off, and a mixed gas of high-purity H2+CH4 (1% in H2) was switched to. The microwave power was increased to 10kW, the reaction gas pressure was kept at 120Torr, and the growth continued for 500 hours to form a 500μm thick polycrystalline diamond insulating support layer on the surface of the conductive layer. After the reaction is completed and cooled to room temperature, the original growth substrate of the molybdenum sheet is peeled off using the same peeling method as in Example 1, through edge exposure peeling (mechanical scribing + thermal stress assistance), forming a flexible and bendable self-supporting diamond conductive substrate. The graphite-like conductive layer is then exposed as the front side of the device.

[0025] The performance of the prepared diamond conductive substrate was tested: the sheet resistance of the conductive layer was measured to be 18 Ω / sq using the four-probe method; the average transmittance in the visible to near-infrared band (400–800 nm) was measured to be 51% using a UV-Vis spectrophotometer; and the thermal conductivity was measured to be 1020 W / (m²) using the laser scintillation method. K); Bending tests show that the substrate can withstand 1000 repeated bends with a curvature radius of 10mm without cracking.

[0026] The fabrication process of the perovskite photovoltaic cell is the same as in Example 1, and the effective area of ​​the device is 2500 mm² (50 mm²). 50mm).

[0027] Performance testing Irradiation stability tests were conducted on the prepared perovskite photovoltaic cells: fast neutron irradiation with a flux of 1 × 10¹ was performed on a ground-based simulation platform. 6 n / cm²; the photoelectric conversion efficiency (PCE) of the cell before irradiation is 20.7%, and the PCE after irradiation is 19.5%, with an efficiency retention rate of 94.2%; under 1 Sun irradiation, the operating temperature of this cell is 18℃ lower than that of traditional ITO / glass-based perovskite photovoltaic cells.

[0028] Comparative example of conventional ITO / glass-based perovskite photovoltaic cells Perovskite photovoltaic cells were fabricated using a conventional ITO / glass transparent conductive substrate, following the same process as in Example 1, with an effective device area of ​​16 mm².

[0029] Performance tests show that the ITO / glass substrate has a sheet resistance of 15 Ω / sq and a light transmittance of 85%, but a thermal conductivity of <1.5 W / (m²). K); Irradiated with 10 MeV protons as in Example 1 (flux 1 × 10¹) 5 After the p / cm², obvious microcracks appeared in the ITO layer, the sheet resistance increased by 300%, the perovskite light-absorbing layer was severely decomposed, and the photoelectric conversion efficiency of the cell dropped from 21.8% to 12.4%, with an efficiency retention rate of only 56.9%.

[0030] As can be seen from the above embodiments and comparative examples, by defining the precise parameter range of the MPCVD process, the present invention achieves one-step in-situ continuous growth of the conductive layer and the insulating support layer. The prepared diamond conductive substrate has high conductivity, high light transmittance, ultra-high thermal conductivity and strong radiation resistance. The perovskite photovoltaic cells prepared based on this substrate have extremely high stability in the space simulated radiation environment and excellent heat dissipation capacity. Compared with traditional ITO / glass-based devices, they have significant performance advantages and are fully adapted to the photovoltaic application requirements of the extreme space environment.

[0031] Based on the disclosure in the foregoing specification, those skilled in the art can make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A diamond conductive substrate, characterized in that: It includes a stacked conductive layer and an insulating support layer. The conductive layer is a graphite-phase carbon material layer, and the insulating support layer is a polycrystalline diamond material layer. The thickness of the graphite-phase carbon material layer is 10 nm to 10 μm, and the sheet resistance is 10 to 1000 Ω / sq. The thickness of the polycrystalline diamond material layer is 10 nm to 1000 μm, with an average light transmittance of ≥50% in the 400–800 nm wavelength band and a thermal conductivity of ≥1000 W / (m²). K).

2. The diamond conductive substrate according to claim 1, characterized in that: The diamond conductive substrate is formed by in-situ continuous growth using a one-step MPCVD process, with the growth sequence being: first, a conductive layer is grown, and then an insulating support layer is grown on the surface of the conductive layer.

3. The diamond conductive substrate according to claim 2, characterized in that: The conductive layer is grown by MPCVD process, with the following growth conditions: a mixed gas containing CH4, N2, and H2 is introduced, with CH4 accounting for 1% to 3% of the volume of H2; H2 is used as the carrier gas for dilution, and the N2 concentration is 0 to 800 ppm; microwave power is 1.5 to 2.0 kW, reaction gas pressure is 100 to 150 Torr, and growth time is 10 to 120 min.

4. The diamond conductive substrate according to claim 2, characterized in that: The insulating support layer is continuously grown on the surface of the conductive layer by MPCVD process. The growth process conditions are as follows: the N2 channel is closed, a mixed gas containing CH4 and H2 is introduced, the volume percentage of CH4 in H2 is 0.5% to 2%, the microwave power is 2.0 to 10 kW, the reaction gas pressure is 100 to 150 Torr, and the growth time is 2 to 1000 h.

5. The diamond conductive substrate according to claim 1, characterized in that: The diamond conductive substrate is heteroepitaxially grown on the original growth substrates of silicon and molybdenum, and is peeled off from the original growth substrates by an edge exposure peeling method to form a self-supporting structure. The peeled conductive layer is exposed as the front side of the device.

6. A perovskite photovoltaic cell based on any one of the diamond conductive substrates described in claims 1 to 5, characterized in that: It consists of, in sequence, an insulating support layer, a conductive layer, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, and a back electrode; The thickness of the hole transport layer is ≤100nm; The thickness of the perovskite light-absorbing layer is 500–2000 nm; The thickness of the electron transport layer is ≤100nm; The thickness of the back electrode is 80–150 nm; The effective area of ​​the perovskite photovoltaic cell is ≤50mm². 50mm.

7. The perovskite photovoltaic cell according to claim 6, characterized in that: The hole transport layer is made of a P-type semiconductor material, such as Spiro-OMeTAD, PEDOT:PSS, TPD, PTAA, P3HT, PCPDTBT, or NiO. x At least one of V2O5, CuI, MoO3, CuO, and Cu2O.

8. The perovskite photovoltaic cell according to claim 6, characterized in that: The perovskite light-absorbing layer is made of a material with the general chemical formula ABX3, where A is CH3NH3. + NH2=CHNH2 + C4H9NH3 + Cs + 、Rb + At least one of them; B is Pb 2 + Sn 2+ 、Ge 2+ Sb 3+ Bi 3+ Ag + Au 3+ Ti 4+ At least one of them; X is Cl - , Br - I - Or at least one of the halogens.

9. The perovskite photovoltaic cell according to claim 6, characterized in that: The electron transport layer is made of an N-type semiconductor material, which is at least one of titanium oxide, zinc oxide, tin oxide, nickel oxide, magnesium oxide, copper oxide, cuprous oxide, tungsten oxide, C60 fullerene, and their derivatives.

10. The perovskite photovoltaic cell according to claim 4, characterized in that: The back electrode is made of one of Au, Ag, Cu, C, or ITO and is prepared using vacuum thermal evaporation or magnetron sputtering processes.

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