Tunneling layer based on gradient control silicon nitride and full-perovskite laminated solar cell

Abstract

The invention discloses a tunneling layer based on gradient regulation and control silicon nitride and a full-perovskite laminated solar cell. The tunneling layer comprises a gradient regulation and control silicon nitride layer, an organic layer and a metal layer which are sequentially laminated from bottom to top, the metal layer is close to the upper perovskite layer, and the gradient regulation silicon nitride layer is close to the lower perovskite layer; the nitrogen content of the silicon nitride layer is gradually increased from one side close to the organic layer to one side close to the lower perovskite layer through gradient regulation and control; the full-perovskite laminated solar cell comprises a conductive substrate, a wide-band-gap perovskite solar cell, a tunneling layer based on gradient regulation and control silicon nitride, a narrow-band-gap perovskite solar cell and an interface top electrode which are sequentially laminated from bottom to top. According to the full-perovskite laminated solar cell, the tunneling layer optimizes an energy band structure at an interface, the charge transmission capability is improved, the protection effect on a bottom layer device is optimized, and the full-perovskite laminated solar cell has excellent electrical characteristics and high charge transmission efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor devices, and relates to a tunneling layer based on gradient-regulated silicon nitride and a perovskite tandem solar cell. Background Art

[0002] Perovskite solar cells have attracted much attention due to their high potential for photovoltaic conversion efficiency and low cost. In the structure of perovskite solar cells, the tunneling layer plays a key role in the effective transport of charges and the reduction of charge recombination. As a potential tunneling layer material, the performance of silicon nitride depends to a large extent on its composition and structure. However, traditional preparation methods of silicon nitride often make it difficult to achieve precise control of the composition, resulting in limited applications in perovskite cells.

[0003] Currently, methods for preparing the tunneling layer include sputtering indium tin oxide (ITO) as the tunneling layer and using atomic layer deposition (ALD) SnO x as a buffer layer to protect the underlying device from sputtering damage. MoO can also be thermally evaporated x as a buffer layer, which prevents damage to the bathocuproine (BCP) / Ag layer during the sputtering of ITO and ensures good contact between Ag and ITO. To prevent solvents from penetrating into the top cell during the processing of the bottom cell, the typical thickness of ITO exceeds 100 nm. In addition, a 5-nm aluminum-doped zinc oxide (AZO) layer deposited by solution treatment of a polyethyleneimine (PEIE) layer is sufficient to protect the bottom cell from solution treatment. However, the cells prepared by these treatment methods are difficult to maintain stable photovoltaic output for a long time and are easily affected by changes in external factors such as light and temperature. Once the external environment changes, damage or defects to the cell will greatly affect the service life of the cell. Therefore, a more concise and effective combination strategy is needed to overcome the above problems to prepare a tunneling layer with higher stability, thereby improving the photovoltaic performance of the perovskite tandem solar cell.

[0004] Currently, the method of using sputtering-assisted atomic layer deposition (ALD) SnOx as a buffer layer can effectively protect the underlying device from damage, or using thermally evaporated MoOx as a buffer layer can prevent damage to the bathocuproine (BCP) / Ag layer during the sputtering of ITO and ensure good contact between Ag and ITO. However, when using these methods to prepare the tunneling layer, it is required that the typical thickness of ITO exceeds 100 nm to prevent solvents from penetrating into the top cell during the processing of the bottom cell. In addition, a 5-nm aluminum-doped zinc oxide (AZO) layer deposited by solution treatment of a polyethyleneimine (PEIE) layer is sufficient to protect the bottom cell from solution treatment. This makes it difficult for the tunneling layer to achieve the best compromise between protection and transport. Summary of the Invention

[0005] To solve the technical problems in the prior art that the tunneling layer is prone to damage the underlying device and it is difficult for the tunneling layer to be compatible with the sub-cell, the present invention provides a tunneling layer based on gradient-regulated silicon nitride and a perovskite tandem solar cell. The technical solution adopted by the present invention is as follows:

[0006] A tunneling layer based on gradient-regulated silicon nitride, comprising a gradient-regulated silicon nitride layer, an organic layer, and a metal layer stacked in sequence from bottom to top;

[0007] The metal layer is close to the upper perovskite layer, and the gradient-regulated silicon nitride layer is close to the lower perovskite layer;

[0008] The nitrogen content of the gradient-regulated silicon nitride layer gradually increases from the side close to the organic layer to the side close to the lower perovskite layer.

[0009] In an embodiment of the present invention, the thickness of the gradient-regulated silicon nitride layer is 5-10 nm, the thickness of the organic layer is 10-20 nm, and the thickness of the metal layer is 20-30 nm.

[0010] A preparation method of a tunneling layer based on gradient-regulated silicon nitride, comprising the following steps:

[0011] S1. React SiH4 and NH3 mixed gas, and prepare a gradient-regulated silicon nitride layer on the lower perovskite layer by inductively coupled plasma chemical vapor deposition;

[0012] S2. Use copper phthalocyanine derivative or porphyrin compound as raw material, and prepare an organic layer on the gradient-regulated silicon nitride layer by spin coating;

[0013] S3. Use Ag or Au as raw material, and prepare a metal layer on the organic layer by thermal evaporation.

[0014] In an embodiment of the present invention, the step S1 includes:

[0015] S11. Use inductively coupled plasma chemical vapor deposition equipment, set the radio frequency power to 800-1000 W, set the reaction chamber pressure to 1-2 Torr, set the temperature to 250-300 °C, control the SiH4 flow rate to 10-15 sccm, control the NH3 flow rate to 80-100 sccm, and the deposition time is 2-5 minutes;

[0016] S12. Gradually reduce the NH3 flow rate to 40-60 sccm, and at the same time gradually increase the SiH4 flow rate to 25-35 sccm, and continue to deposit for 3-5 minutes;

[0017] S13. React SiH4 and NH3 mixed gas to prepare a gradient-regulated silicon nitride layer.

[0018] In one embodiment of the present invention, step S2 includes:

[0019] S21. Prepare a solution of copper phthalocyanine derivative or porphyrin compound;

[0020] S22. Spin-coat the solution on the gradient-regulated silicon nitride layer at a rotation speed of 2000 - 3000 rpm for 30 - 60 s;

[0021] S23. Anneal the gradient-regulated silicon nitride layer after spin-coating the solution in a vacuum oven at 80 - 100 °C for 10 - 15 min to form an organic layer.

[0022] In one embodiment of the present invention, step S3 includes: In a vacuum thermal evaporation device, using Ag or Au as raw materials, and controlling the deposition rate at Prepare a metal layer on the organic layer by thermal evaporation.

[0023] A perovskite tandem solar cell based on a gradient-regulated silicon nitride tunneling layer, comprising: a conductive substrate, a wide-bandgap perovskite solar cell, the tunneling layer based on gradient-regulated silicon nitride, a narrow-bandgap perovskite solar cell, and an interface top electrode, which are stacked in sequence from bottom to top.

[0024] In one embodiment of the present invention, the top of the metal layer is close to the narrow-bandgap perovskite solar cell, and the bottom of the gradient-regulated silicon nitride layer is close to the wide-bandgap perovskite solar cell;

[0025] The nitrogen content of the gradient-regulated silicon nitride layer gradually increases from the side close to the organic layer to the side close to the wide-bandgap perovskite solar cell.

[0026] In one embodiment of the present invention, the wide-bandgap perovskite solar cell is stacked in sequence from bottom to top: NiO x or PTAA thin film hole transport layer, crystalline Cs 0.2 FA 0.8 PbI 1.8 Br 1.2 conductive active layer and PCBM thin film electron transport layer;

[0027] The narrow-bandgap perovskite solar cell is stacked in sequence from bottom to top: PEDOT:PSS thin film hole transport layer, crystalline FA 0.7 MA 0.3 Pb 0.5 Sn 0.5 I3 conductive active layer and C60 and BCP electron transport layer;

[0028] The material of the conductive substrate is ITO or FTO conductive glass;

[0029] The material of the top electrode of the interface is Ag, and the thickness is 80 - 120 nm.

[0030] A preparation method of a perovskite tandem solar cell based on gradient-regulated silicon nitride tunneling layer includes the following steps:

[0031] 1) Prepare a wide-bandgap perovskite solar cell on a conductive substrate;

[0032] 2) On the wide-bandgap perovskite solar cell, prepare a tunneling layer based on gradient-regulated silicon nitride through the described preparation method;

[0033] 3) Prepare a narrow-bandgap perovskite solar cell on the tunneling layer based on gradient-regulated silicon nitride;

[0034] 4) Prepare a top electrode of the interface on the narrow-bandgap perovskite solar cell.

[0035] Advantages of the present invention:

[0036] 1. The tunneling layer of the present invention uses a gradient-regulated silicon nitride layer in combination with an organic layer and a metal layer as the tunneling layer to optimize the interface performance, improve the charge transport ability and optimize the protection of the underlying device. At the perovskite / silicon nitride interface, silicon nitride rich in nitrogen has a high bandgap, which can effectively block the hole transfer to the electron transport layer and reduce charge recombination. While on the side close to the adjacent transport layer, the gradually increasing silicon content makes the bandgap gradually decrease, which is beneficial to the smooth injection and transport of charges. Moreover, the gradient-regulated silicon nitride layer works synergistically with the organic layer and the metal layer to optimize the charge transport path, reduce charge recombination, and improve the short-circuit current and fill factor;

[0037] 2. The preparation method of the tunneling layer of the present invention uses the inductively coupled plasma chemical vapor deposition (ICPCVD) method to adjust the silicon nitride concentration gradient, which can regulate the energy band structure of silicon nitride, make it form an ideal energy level alignment with the upper and lower layer materials. The existence of the gradient component can gradually transition the energy band difference between the perovskite and the transport layer, reduce the interface energy barrier, promote the efficient transport of charges, improve the open-circuit voltage and short-circuit current of the battery, promote the effective transport of electrons or holes, and prevent the unexpected carrier flow. Moreover, it can effectively improve the carrier transport and reduce the parasitic absorption;

[0038] 3. The all-perovskite tandem solar cell of the present invention uses a tunneling layer based on gradient-regulated silicon nitride. In the tunneling layer, as the composition of the gradient-regulated silicon nitride layer gradually changes, the physical properties of the material also gradually change, which can alleviate the accumulation of internal stress caused by abrupt composition changes. The organic layer and the metal layer enhance the structural stability of the intermediate composite layer, reduce the influence of environmental factors on the battery performance, improve the long-term stability of the battery, and the introduction of the organic layer endows the battery with a certain flexibility, broadening the application scope of the battery in flexible electronic devices;

[0039] 4. The preparation method of the all-perovskite tandem solar cell of the present invention is simpler, more efficient, and easier to mass-produce, which helps to promote the industrialization process of perovskite solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic structural diagram of a tunneling layer based on gradient-regulated silicon nitride provided by an embodiment of the present invention;

[0041] Figure 2 It is a flowchart of a preparation method of a tunneling layer based on silicon nitride gradient regulation provided by an embodiment of the present invention;

[0042] Figure 3 It is a schematic structural diagram of an all-perovskite tandem solar cell provided by an embodiment of the present invention;

[0043] Figure 4 It is a flowchart of a preparation method of an all-perovskite tandem solar cell provided by an embodiment of the present invention;

[0044] Figure 5 It is a J-V curve diagram of an all-perovskite tandem solar cell provided by an embodiment of the present invention;

[0045] Figure 6 It is a J-V curve diagram of an all-perovskite tandem solar cell with a tunneling layer using tin oxide and a metal layer provided by an embodiment of the present invention.

[0046] In the drawings: 1, conductive substrate; 2, wide-bandgap perovskite solar cell; 3, tunneling layer based on gradient-regulated silicon nitride; 31, gradient-regulated silicon nitride layer; 32, organic layer; 33, metal layer; 4, narrow-bandgap perovskite solar cell; 5, interface top electrode. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0048] Example 1:

[0049] In view of the problems such as damage to the underlying device caused by the traditional tunneling layer and the incompatibility between the tunneling layer and the sub-cell, this embodiment provides a tunneling layer based on gradient-regulated silicon nitride. Refer to the attachedFigure 1 The tunneling layer based on gradient-regulated silicon nitride includes a gradient-regulated silicon nitride layer 31, an organic layer 32, and a metal layer 33 that are stacked from bottom to top; the metal layer 33 is close to the upper perovskite layer, and the gradient-regulated silicon nitride layer 31 is close to the lower perovskite layer; the nitrogen content of the gradient-regulated silicon nitride layer 31 gradually increases from the side close to the organic layer 32 to the side close to the lower perovskite layer.

[0050] The present invention selects silicon nitride because silicon nitride has better long-term stability and corrosion resistance, especially under humid and high-temperature conditions, and the energy level matching with perovskite materials is also more ideal. Atomic layer deposition (ALD) SnO x Compared with mature silicon nitride technology, more challenges may be faced in terms of cost-effectiveness, stability, interface matching degree, and process compatibility.

[0051] In the present invention, the nitrogen content of the gradient-regulated silicon nitride layer is low on the side close to the hybrid metal layer and high on the side close to the lower perovskite layer, and the nitrogen content gradually increases from the side close to the hybrid metal layer to the side close to the lower perovskite layer. As the composition of silicon nitride gradually changes, the physical properties of the material also gradually change, which can relieve the accumulation of internal stress caused by abrupt composition changes, enhance the bonding strength and stability of the interface, and improve the long-term reliability of the battery.

[0052] The gradient-regulated silicon nitride layer has unique properties. As the silicon-nitrogen ratio in the silicon nitride layer changes in a gradient manner, its energy band structure also shows a gradient change. This gradient energy band structure forms a built-in electric field, and electrons generated from the perovskite layer can be rapidly transported along the gradient direction under the action of this built-in electric field. For example, after electrons are injected from the perovskite layer into the silicon nitride layer, they move away from the perovskite layer under the drive of the built-in electric field, reducing the recombination probability of electrons and holes in the perovskite layer and at the interface, improving the electron transport efficiency, and finally being transported to the cathode of the battery.

[0053] The thickness of the gradient-regulated silicon nitride layer 31 in the present invention is 5-10 nm. If the silicon nitride layer is too thick, it may hinder the charge transport of the organic layer and affect the energy level matching between the two; if it is too thin, it cannot provide a stable charge transport environment for the organic layer. The thickness of the organic layer 32 is 10-20 nm. A thinner organic layer has a shorter charge transport path, which is beneficial for holes to quickly pass through the organic layer and be transported to the metal layer, reducing charge recombination and improving charge transport efficiency. When the thickness of the organic layer is less than 10 nm, defects such as pinholes may occur, resulting in charge leakage. The thickness of the metal layer 33 is 20-30 nm. If it is too thin, the resistance is easily too large; if it is too thick, it will enhance the absorption and reflection of light, which is not conducive to the generation of photo-generated carriers.

[0054] Gradient regulation of the nanoscale thickness of the silicon nitride layer and the change of the energy band structure inside it create conditions for the quantum tunneling effect. During the electron transport process, when encountering a potential barrier formed by the microscopic structure and energy level difference of the material, at the nanoscale, there is a certain probability for electrons to pass through the potential barrier through the quantum tunneling effect, further improving the charge transport efficiency. The synergistic effect of this tunneling effect and the built-in electric field enables charges to be quickly and effectively transported from the top sub-cell to the intermediate region to interact with the organic-inorganic hybrid metal layer, and then transported to the bottom sub-cell.

[0055] In addition, the gradient-regulated silicon nitride layer in this embodiment has a certain light regulation effect. The gradient change of its refractive index can optimize the light propagation path inside the battery, reduce the reflection and scattering losses of light, enable more light to be absorbed by the perovskite absorption layer, and indirectly improve the charge generation efficiency, providing more carriers for charge transport.

[0056] In the present invention, the role of the organic layer: The organic layer usually selects organic materials with a suitable energy level structure, such as polymers or small molecule organic compounds containing conjugated structures. Taking copper phthalocyanine derivatives as an example, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels match those of the perovskite layer and the metal electrode. The holes generated from the perovskite layer can be injected into the HOMO energy level of the organic layer through energy level matching and transported along the conjugated structure of the organic molecules. Through mechanisms such as π-π stacking or intermolecular charge transfer between organic molecules, long-distance hole transport is achieved, and finally transported to the metal electrode.

[0057] Synergy of the gradient-regulated silicon nitride layer and the metal layer: The gradient-regulated silicon nitride layer and the metal layer together form a hybrid structure. On the one hand, the gradient-regulated silicon nitride layer can enhance the stability and mechanical properties of the metal layer. On the other hand, its energy band structure is conducive to electron transport and regulation. The metal, as a good conductor, collects the holes transported from the organic layer and exports them to the external circuit. At the same time, the interface between the metal layer and the gradient-regulated silicon nitride layer also affects the charge transport efficiency. By optimizing the interface structure and properties, the charge recombination at the interface can be reduced.

[0058] The metal layer (Ag or Au) has excellent electrical conductivity and can provide a fast conduction path for charges. Taking Ag as an example, it has a high free electron concentration, and under the action of an electric field, electrons can move rapidly in the metal lattice. The organic part (such as copper phthalocyanine derivative TB-CuPc) forms a channel conducive to charge transport through intermolecular π-π stacking and other interactions. Holes can be transported through the charge transfer mechanism in the conjugated structure of organic molecules. The metal layer and the organic layer are tightly combined, enabling charges to be efficiently transferred between the two, realizing the transport from the top sub-cell to the intermediate region and then to the bottom sub-cell.

[0059] Example 2:

[0060] Traditional methods for preparing silicon nitride often have problems such as difficulty in precisely controlling the composition. This example provides a method for preparing a tunneling layer based on gradient regulation of silicon nitride. Referring to the attached Figure 2 , the method for preparing a tunneling layer based on gradient regulation of silicon nitride includes the following steps:

[0061] S1: Prepare silane (SiH4) as the silicon source gas and ammonia (NH3) as the nitrogen source gas. React the SiH4 and NH3 mixed gas, and prepare a gradient-regulated silicon nitride layer on the lower perovskite layer by inductively coupled plasma chemical vapor deposition method;

[0062] S2. Use copper phthalocyanine derivatives or porphyrin compounds as raw materials, and prepare an organic layer on the gradient-regulated silicon nitride layer by spin coating method;

[0063] S3. Use Ag or Au as the raw material for the metal layer, and prepare a metal layer on the organic layer by thermal evaporation method.

[0064] In this example, step S1 includes:

[0065] S11: Use inductively coupled plasma chemical vapor deposition equipment, set the radio frequency power to 800 - 1000W, the reaction chamber pressure to 1 - 2 Torr, the temperature to 250 - 300 °C, control the SiH4 flow rate to 10 - 15 sccm, control the NH3 flow rate to 80 - 100 sccm, and the deposition time to 2 - 5 minutes;

[0066] S12: Gradually reduce the NH3 flow rate until it reaches 40 - 60 sccm, and at the same time gradually increase the SiH4 flow rate until it reaches 25 - 35 sccm, and continue deposition for 3 - 5 minutes;

[0067] S13: React the SiH4 and NH3 mixed gas to prepare a gradient-regulated silicon nitride layer.

[0068] In this example, step S2 includes:

[0069] S21: Dissolve copper phthalocyanine derivatives or porphyrin compounds in chloroform to prepare a solution;

[0070] S22: Spin coat the solution on the gradient-regulated silicon nitride layer at a speed of 2000 - 3000 rpm for 30 - 60 s;

[0071] S23: Anneal the gradient-regulated silicon nitride layer after spin coating the solution in a vacuum oven at 80 - 100 °C for 10 - 15 min to form an organic layer.

[0072] In this embodiment, step S3 includes: in a vacuum thermal evaporation device, using Ag or Au as raw materials, and controlling the deposition rate at A metal layer is prepared on the organic layer by thermal evaporation.

[0073] Specifically, S31: Put Ag or Au with a purity of 99.99% into the evaporation source crucible, and close the vacuum chamber; S32: Start the vacuum pump and pump the vacuum degree in the vacuum chamber to the order of 10-4 to 10-6 Pa; S33: Heat the evaporation source to gradually sublime Ag or Au, and use a thickness monitoring system to monitor the film growth thickness in real time, and control the deposition rate at When the thickness reaches 3 to 7 nm, stop heating the evaporation source; S34: Turn off the heating power supply. After the sample cools to room temperature, slowly introduce nitrogen to restore the air pressure in the vacuum chamber to normal pressure, and take it out to obtain a tunneling layer based on silicon nitride gradient regulation.

[0074] In the present invention, by adjusting the ICPCVD process for silicon nitride concentration gradient regulation, the energy band structure of silicon nitride can be adjusted to form an ideal energy level alignment with the upper and lower layer materials. The existence of the gradient component can gradually transition the energy band difference between the perovskite and the transport layer, reduce the interface energy barrier, promote the efficient transport of charges, increase the open circuit voltage and short circuit current of the battery, promote the effective transport of electrons or holes, and prevent unexpected carrier flow (energy band engineering).

[0075] Example 3:

[0076] This embodiment provides a perovskite tandem solar cell based on a gradient-regulated silicon nitride tunneling layer. Referring to the attached Figure 3 , this perovskite tandem solar cell includes: a conductive substrate 1, a wide-bandgap perovskite solar cell 2, a tunneling layer 3 based on gradient-regulated silicon nitride, a narrow-bandgap perovskite solar cell 4, and an interface top electrode 5, which are stacked in sequence from bottom to top. By adopting a tunneling layer based on gradient-regulated silicon nitride, this perovskite tandem solar cell improves light absorption and enhances the protection of the wide-bandgap perovskite solar cell, further improving the performance of the perovskite tandem solar cell.

[0077] In this embodiment, the top of the metal layer is close to the narrow-bandgap perovskite solar cell, and the bottom of the gradient-regulated silicon nitride layer is close to the wide-bandgap perovskite solar cell; the nitrogen content of the gradient-regulated silicon nitride layer gradually increases from the side close to the organic layer to the side close to the wide-bandgap perovskite solar cell.

[0078] In the all-perovskite tandem solar cell of the present invention, at the perovskite / silicon nitride interface, the silicon nitride rich in nitrogen has a relatively high bandgap, which can effectively block the hole transfer to the electron transport layer and reduce charge recombination. On the side close to the narrow-bandgap perovskite solar cell, the gradually increasing silicon content makes the bandgap gradually decrease, which is beneficial to the smooth injection and transfer of charges from the perovskite layer to the transport layer of the narrow-bandgap perovskite solar cell.

[0079] In this embodiment, the wide-bandgap perovskite solar cell is stacked layer by layer from bottom to top: NiO x or a PTAA thin film hole transport layer, crystalline Cs 0.2 FA 0.8 PbI 1.8 Br 1.2 conductive active layer and a PCBM thin film electron transport layer. The narrow-bandgap perovskite solar cell is stacked layer by layer from bottom to top: a PEDOT:PSS thin film hole transport layer, crystalline FA 0.7 MA 0.3 Pb 0.5 Sn 0.5 I3 conductive active layer and a C60 and BCP electron transport layer. The material of the conductive substrate is ITO or FTO conductive glass; the material of the interface top electrode is Ag, and the thickness is 80 - 120 nm.

[0080] The all-perovskite tandem solar cell of the present invention adopts a tunneling layer based on gradient-regulated silicon nitride. In the tunneling layer, as the composition of the gradient-regulated silicon nitride layer gradually changes, the physical properties of the material also gradually change, which can relieve the accumulation of internal stress caused by abrupt composition changes, enhance the bonding strength and stability of the interface, and improve the long-term reliability of the battery.

[0081] Example 4:

[0082] This embodiment provides a preparation method of an all-perovskite tandem solar cell based on a gradient-regulated silicon nitride tunneling layer. Referring to the attached Figure 4 , the preparation method of the all-perovskite tandem solar cell with the silicon nitride gradient-regulated tunneling layer includes the following steps:

[0083] 1) Prepare a wide-bandgap perovskite solar cell on a conductive substrate;

[0084] 2) Prepare a tunneling layer based on gradient-regulated silicon nitride on the wide-bandgap perovskite solar cell by the preparation method of Example 2;

[0085] 3) Prepare a narrow-bandgap perovskite solar cell on the tunneling layer based on gradient-regulated silicon nitride;

[0086] 4) Prepare an interface top electrode on the narrow-bandgap perovskite solar cell.

[0087] In this embodiment, step 1) can be carried out by the following method:

[0088] First, pre-treat the conductive substrate.

[0089] The pre-treatment method adopted in this embodiment is as follows: successively ultrasonically clean the ITO or FTO conductive glass substrate with detergent, deionized water, acetone, and absolute ethanol for 15 minutes each, and blow dry with a high-purity nitrogen gun; then perform UV-ozone ultraviolet ozone treatment on the surface of the cleaned conductive glass substrate for 30 minutes.

[0090] Then, perform UV-ozone treatment on the surface of the pre-treated conductive substrate for 20 - 25 minutes, and spin-coat a 10 mg / mL precursor solution of NiO x or PTAA on the surface of the conductive substrate after UV-ozone treatment, anneal at 120 - 150 °C for 20 - 30 minutes to obtain a NiO x or PTAA thin film hole transport layer with a thickness of 60 - 70 nm;

[0091] Next, spin-coat a precursor solution of the wide-bandgap perovskite Cs x or PTAA thin film hole transport layer on the surface of the stabilized NiO 0.2 FA 0.8 PbI 1.8 Br 1.2 at a rotation speed of 1000 rpm for 10 s, then set the rotation speed to 4000 rpm and spin-coat for 50 s. At the 30th second of spin-coating, add 200 μL of anti-solvent CB (chlorobenzene) for extraction, and anneal at 100 - 110 °C for 10 - 15 minutes to obtain a crystalline Cs 0.2 FA 0.8 PbI 1.8 Br 1.2 thin film conductive active layer;

[0092] Finally, spin-coat a precursor suspension of PCBM material on the crystalline Cs 0.2 FA 0.8 PbI 1.8 Br 1.2 thin film conductive active layer. The concentration of PCBM is 20 mg / ml, the rotation speed is 4000 rpm, and the time is 40 s to grow a PCBM thin film electron transport layer with a thickness of 70 - 80 nm.

[0093] In this embodiment, in step 2), the preparation method of the silicon nitride gradient-regulated tunneling layer includes the following steps:

[0094] S1: React SiH4 with NH3 mixed gas, and prepare a gradient-regulated silicon nitride layer on the lower perovskite layer by inductively coupled plasma chemical vapor deposition.

[0095] Specifically, step S1 includes:

[0096] S11: Using an inductively coupled plasma chemical vapor deposition equipment, set the radio frequency power to 800 - 1000 W, the reaction chamber pressure to 1 - 2 Torr, the temperature to 250 - 300 °C, control the SiH4 flow rate to 10 - 15 sccm, control the NH3 flow rate to 80 - 100 sccm, and the deposition time to 2 - 5 minutes;

[0097] S12: Gradually reduce the NH3 flow rate until it reaches 40 - 60 sccm, and at the same time gradually increase the SiH4 flow rate until it reaches 25 - 35 sccm, and continue deposition for 3 - 5 minutes;

[0098] S13: React with the SiH4 and NH3 mixed gas to prepare a tunneling layer based on gradient - regulated silicon nitride. S2: Use Au material to prepare a hybrid metal layer on the gradient - regulated silicon nitride layer by thermal evaporation.

[0099] In this embodiment, step 3) can be carried out by the following method:

[0100] First, spin - coat the precursor solution of PEDOT:PSS on the first layer and anneal it at 100 - 120 °C for 10 - 15 min to obtain a PEDOT:PSS thin - film hole - transporting layer with a thickness of 60 - 80 nm;

[0101] Then, spin - coat the precursor solution of narrow - bandgap perovskite FA 0.7 MA 0.3 Pb 0.5 Sn 0.5 I3 on the surface of the stabilized PEDOT:PSS thin - film hole - transporting layer and anneal it to obtain a crystalline FA 0.7 MA 0.3 Pb 0.5 Sn 0.5 I3 thin - film conductive active layer;

[0102] Finally, on the FA 0.7 MA 0.3 Pb 0.5 Sn 0.5 I3 thin - film conductive active layer, use thermal evaporation to sequentially prepare a C60 layer with a thickness of 10 - 20 nm and a BCP layer with a thickness of 5 - 10 nm, which are combined into a C60 and BCP electron - transporting layer.

[0103] Use the all - perovskite solar cell prepared in Example 4 for detection. The J - V curve diagram of the all - perovskite tandem solar cell is shown in the appendix Figure 5, NBG represents narrow-bandgap perovskite solar cells, WBG represents wide-bandgap perovskite solar cells, and Tanderm represents the entire all-perovskite tandem solar cell.

[0104] The J-V curve of a solar cell with a tunneling layer composed of tin oxide and a metal layer is shown in the appendix Figure 6 . NBG represents narrow-bandgap perovskite solar cells, WBG represents wide-bandgap perovskite solar cells, and Tandem represents the entire all-perovskite tandem solar cell with a tunneling layer composed of tin oxide and a metal layer.

[0105] Appendix Figure 5 and appendix Figure 6 In which, the abscissa is voltage and the ordinate is current density.

[0106] From appendix Figure 5 and appendix Figure 6 It can be seen that: 1) Open-circuit voltage (Voc) comparison: The open-circuit voltage (Voc) of the all-perovskite tandem solar cell using the tunneling layer in this scheme is slightly higher than that of the all-perovskite tandem solar cell with a tunneling layer composed of tin oxide and a metal layer, indicating that the tunneling layer designed in this scheme helps to reduce charge recombination and enables the battery to accumulate a higher potential difference. 2) Short-circuit current density (Jsc) comparison: It can be clearly seen from the experimental data that the current density (Jsc) of the all-perovskite tandem solar cell using the tunneling layer of the present invention is significantly increased. A higher short-circuit current density means that the tunneling layer can more effectively promote the transport and collection of photo-generated carriers, enabling more photo-generated charges to participate in the current output. 3) Fill factor (FF) comparison: The curve of the all-perovskite tandem solar cell using the tunneling layer of the present invention is stable, and the fill factor increases, indicating that its internal resistance decreases, the charge transport efficiency increases, and charge recombination decreases.

[0107] The present invention controls the deposition process and composition of the silicon nitride layer to enable the silicon nitride layer to form a good interface contact with the perovskite layer. On the one hand, a suitable interface structure can reduce lattice mismatch, lower interface stress, and improve the stability of the battery structure. On the other hand, by adjusting the composition and energy band structure of the side of the silicon nitride layer close to the perovskite layer, it can better match the conduction band energy level of the perovskite layer, promote the injection of electrons from the perovskite layer to the silicon nitride layer, and at the same time inhibit the reverse transport of electrons, improving the directionality and efficiency of charge transport.

[0108] In the organic layer of the present invention, long-distance hole transport is achieved through mechanisms such as π-π stacking or intermolecular charge transfer between molecules, and finally the holes are transported to the metal electrode. The metal layer is tightly combined with the organic layer, enabling efficient charge transfer between the two and realizing the transfer from the top sub-cell to the middle region and then to the bottom sub-cell. At the same time, the interface between the metal layer and the inorganic layer also affects the charge transfer efficiency. By optimizing the interface structure and properties, the charge recombination at the interface can be reduced.

[0109] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. All contents that do not depart from the technical solutions of the present invention should be included within the protection scope of the present invention.

Claims

1. A tunneling layer based on gradient-controlled silicon nitride, characterized in that: It includes a gradient-controlled silicon nitride layer, an organic layer and a metal layer stacked in sequence from bottom to top; The metal layer is close to the upper perovskite layer, and the gradient-controlled silicon nitride layer is close to the lower perovskite layer; The nitrogen content of the gradient-regulated silicon nitride layer gradually increases from a side close to the organic layer to a side close to the underlying perovskite layer.

2. The tunneling layer based on gradient-controlled silicon nitride according to claim 1, characterized in that: The thickness of the gradient-controlled silicon nitride layer is 5 to 10 nm, the thickness of the organic layer is 10 to 20 nm, and the thickness of the metal layer is 20 to 30 nm.

3. A method for preparing a tunneling layer of silicon nitride based on gradient control, characterized in that: The steps include: S1. Using a mixed gas of SiH4 and NH3 to react, a gradient-controlled silicon nitride layer is prepared on the lower perovskite layer by an inductively coupled plasma chemical vapor deposition method; S2, using copper phthalocyanine derivatives or porphyrin compounds as raw materials, and preparing an organic layer on the gradient-controlled silicon nitride layer by spin coating; S3. Using Ag or Au as a raw material, a metal layer is prepared on the organic layer by a thermal evaporation method.

4. The method for preparing a tunneling layer based on gradient-controlled silicon nitride according to claim 3, characterized in that: The step S1 comprises: S11, using inductively coupled plasma chemical vapor deposition equipment, the RF power is set to 800-1000W, the reaction chamber pressure is set to 1-2Torr, the temperature is set to 250-300°C, the SiH4 flow rate is controlled to 10-15sccm, the NH3 flow rate is controlled to 80-100sccm, and the deposition time is 2-5 minutes; S12, gradually reduce the NH3 flow rate to 40-60 sccm, and gradually increase the SiH4 flow rate to 25-35 sccm, and continue deposition for 3-5 minutes; S13, preparing a gradient-controlled silicon nitride layer by reacting a mixed gas of SiH4 and NH3.

5. The method for preparing a tunneling layer based on gradient-controlled silicon nitride according to claim 3, characterized in that: The step S2 comprises: S21, preparing a solution of a copper phthalocyanine derivative or a porphyrin compound; S22, spin coating the solution on the gradient-controlled silicon nitride layer at a rotation speed of 2000-3000 rpm for 30-60 seconds; S23, annealing the gradient-controlled silicon nitride layer after spin coating the solution in a vacuum oven at 80-100° C. for 10-15 min to form an organic layer.

6. The method for preparing a tunneling layer based on gradient-controlled silicon nitride according to claim 5, characterized in that: The step S3 comprises: using Ag or Au as raw material in a vacuum thermal evaporation device, and controlling the deposition rate at A metal layer is prepared on the organic layer by a thermal evaporation method.

7. A full perovskite tandem solar cell based on gradient-controlled silicon nitride tunneling layer, characterized in that: include: A conductive substrate, a wide bandgap perovskite solar cell, a tunneling layer based on gradient-controlled silicon nitride as claimed in claim 1 or 2, a narrow bandgap perovskite solar cell and an interface top electrode are stacked in sequence from bottom to top.

8. The all-perovskite tandem solar cell based on gradient-controlled silicon nitride tunneling layer according to claim 7, characterized in that: The top of the metal layer is close to the narrow-bandgap perovskite solar cell, and the bottom of the gradient-controlled silicon nitride layer is close to the wide-bandgap perovskite solar cell; The nitrogen content of the gradient-regulated silicon nitride layer gradually increases from a side close to the organic layer to a side close to the wide bandgap perovskite solar cell.

9. The all-perovskite tandem solar cell based on gradient-controlled silicon nitride tunneling layer according to claim 8, characterized in that: The wide bandgap perovskite solar cell is stacked in sequence from bottom to top: NiO x Or PTAA thin film hole transport layer, crystalline Cs 0.2 FA 0.8 PbI 1.8 Br 1.2 Conductive active layer and PCBM thin film electron transport layer; The narrow bandgap perovskite solar cell is stacked in sequence from bottom to top: a PEDOT:PSS thin film hole transport layer, a crystalline FA 0.7 MA 0.3 Pb 0.5 Sn 0.5 I3 conductive active layer and C60 and BCP electron transport layers; The material of the conductive substrate is ITO or FTO conductive glass; The material of the interface top electrode is Ag, and the thickness is 80-120 nm.

10. A method for preparing a full perovskite tandem solar cell based on gradient-controlled silicon nitride tunneling layer, characterized in that: The steps include: 1) Fabrication of wide bandgap perovskite solar cells on conductive substrates; 2) On the wide bandgap perovskite solar cell, a tunneling layer based on gradient-controlled silicon nitride is prepared by the preparation method according to any one of claims 3 to 6; 3) Preparing a narrow bandgap perovskite solar cell on the gradient-controlled silicon nitride tunneling layer; 4) Preparing an interfacial top electrode on the narrow bandgap perovskite solar cell.

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