Perovskite reflector laminated solar cell and band gap regulation and control method thereof

Abstract

According to the perovskite reflector laminated solar cell and the band gap regulation and control method thereof provided by the invention, during preparation, a multi-element perovskite composite system is introduced to regulate and control the band gap of a perovskite material and inhibit ion migration and phase separation, so that the stability and the photoelectric conversion efficiency of the material are improved, the multi-element perovskite composite system comprises Cs3Bi2I9 and Cs2AgBiI6, and therefore, the stability and the photoelectric conversion efficiency of the material are improved. The doping concentration of the Cs3Bi2I9 is 3 to 12 mol percent, and the doping concentration of the Cs2AgBiI6 is 5 to 15 mol percent. By introducing Cs3Bi2I9 and Cs2AgBiI6, X-site ion migration of the perovskite material is reduced, so that ion aggregation and phase separation are inhibited. After Cs3Bi2I9 and Cs2AgBiI6 are doped, the photoelectric conversion efficiency of the cell is remarkably improved, and the long-term stability of the device is improved. By controlling the doping proportion of Cs3Bi2I9 and Cs2AgBiI6, the energy band matching and carrier diffusion performance is optimized, and the fill factor of the device is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic cells, and in particular to a perovskite reflector stacked solar cell and a band gap control method thereof. Background Art

[0002] Perovskite solar cells have attracted widespread attention in the photovoltaic field due to their high photoelectric conversion efficiency and low cost. In particular, wide-bandgap perovskite materials, due to their good light absorption capacity, are particularly suitable for high-efficiency photovoltaic devices such as stacked solar cells. However, the application of wide-bandgap perovskite materials also faces certain technical challenges, especially due to the X-site ion (I - / Br - ) migration, leading to ion aggregation during long-term use and, in turn, phase separation. These issues not only reduce the stability of the perovskite material but also significantly affect the photovoltaic efficiency of solar cells. Furthermore, existing bandgap adjustment methods rely primarily on varying the ratio of X-site ions (e.g., increasing the Br content), but excessive Br content often leads to phase separation and reduces material stability.

[0003] To address these issues, researchers have proposed optimizing the perovskite band gap by doping it with other elements or composite materials, thereby inhibiting ion migration and improving device stability. Materials such as Cs3Bi2I9 and Cs2AgBiI6, due to their excellent stability and tunable band gap, are considered effective options for improving the stability and photoelectric conversion efficiency of perovskite solar cells. Summary of the Invention

[0004] The purpose of the present invention is to provide a perovskite reflector stacked solar cell and a band gap control method thereof, aiming to optimize the optical and electrical properties of wide band gap perovskite by rationally doping materials such as Cs3Bi2I9 and Cs2AgBiI6, while inhibiting ion migration and phase separation, thereby significantly improving the stability, photoelectric conversion efficiency and environmental tolerance of the perovskite / reflector stacked solar cell.

[0005] According to the purpose of the present invention, the present invention provides a band gap regulation method for perovskite reflector stacked solar cells. During the preparation, a multi-element perovskite composite system is introduced to regulate the band gap of the perovskite material, and ion migration and phase separation are inhibited, thereby improving the stability of the material and the photoelectric conversion efficiency.

[0006] Furthermore, the multi-element perovskite composite system includes Cs3Bi2I9 and Cs2AgBiI6.

[0007] Furthermore, the doping concentration of Cs3Bi2I9 is 3-12 mol%, and the doping concentration of Cs2AgBiI6 is 5-15 mol%.

[0008] Furthermore, the doping ratio of the perovskite composite system is 8% Cs3Bi2I9 and 10% Cs2AgBiI6.

[0009] Furthermore, the band gap of the perovskite material is 1.65 eV to 2.0 eV.

[0010] Furthermore, the photoelectric conversion efficiency of the stacked solar cell is greater than 20%.

[0011] Furthermore, after 500 hours of illumination, the remaining PCE of the stacked solar cell accounts for more than 90% of the initial PCE.

[0012] Furthermore, the octahedral unit structure of Cs3Bi2I9 improves the lattice rigidity of the material, reduces the migration channels of X-site ions, reduces the risk of phase separation, and at the same time improves the energy band matching and enhances interfacial charge transport.

[0013] Furthermore, Cs2AgBiI6 has excellent chemical stability, which reduces the degradation of the perovskite layer in humidity and thermal environments.

[0014] According to another object of the present invention, the present invention provides a stacked solar cell prepared by the above-mentioned control method, wherein the stacked solar cell includes, from bottom to top, a reflector, a transparent electrode, an electron transport layer or a hole transport layer, a perovskite light absorption layer, a hole transport layer or an electron transport layer, a transparent electrode and an encapsulation layer.

[0015] The technical solution of the present invention reduces X-site ion migration in the perovskite material by introducing Cs3Bi2I9 and Cs2AgBiI6, thereby suppressing ion aggregation and phase separation. After doping with Cs3Bi2I9 and Cs2AgBiI6, the photoelectric conversion efficiency of the battery is significantly improved, and the long-term stability of the device is also enhanced. By controlling the doping ratio of Cs3Bi2I9 and Cs2AgBiI6, the band matching and carrier diffusion performance are optimized, and the fill factor of the device is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 This is a diagram showing the battery efficiency test results of an embodiment of the present invention;

[0018] Figure 2 This is a diagram showing the battery stability test results of an embodiment of the present invention;

[0019] Figure 3 Schematic diagram of the structure of the laminated solar cell according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore should not be understood as limiting the present invention.

[0022] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a communication between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0023] Example 1

[0024] A method for bandgap regulation of perovskite reflector-laminated solar cells is disclosed. During preparation, a multi-component perovskite composite system (including Cs3Bi2I9 and Cs2AgBiI6) is introduced to optimize the bandgap and inhibit ion migration and phase separation, thereby improving material stability and photoelectric conversion efficiency. The multi-component perovskite composite system includes Cs3Bi2I9 and Cs2AgBiI6. The doping concentration of Cs3Bi2I9 is 3-12 mol%, and the doping concentration of Cs2AgBiI6 is 5-15 mol%.

[0025] Cs3Bi2I9 improves the stability of the perovskite material through its larger band gap and better lattice stability. The introduction of Cs2AgBiI6 improves the chemical stability of the perovskite material and reduces degradation in humidity and thermal environments. After doping with Cs3Bi2I9 and Cs2AgBiI6, the band gap of the perovskite material can be adjusted between 1.65eV and 2.0eV.

[0026] Conventional wide bandgap perovskites (such as FA 1-x Cs x Pb(I 1-x Br x )3) Usually use X position (I - / Br - ) ions to regulate the band gap. However, high Br - The content (>20%) will lead to a wider band gap but a lower material stability due to the Br - The local enrichment of will induce phase separation. The present invention proposes to optimize the band gap by multi-element perovskite doping:

[0027] The introduction of Cs3Bi2I9, whose octahedral unit structure can improve the material lattice rigidity, reduce the migration channel of X-site ions, and reduce the risk of phase separation. 3+ Can partially replace Pb 2+ , reducing the toxicity of the material while improving the energy band matching and enhancing the interfacial charge transport. Controlling the doping ratio (3-12mol%) ensures the stability of the material and the carrier diffusion performance.

[0028] The introduction of double perovskite Cs2AgBiI6 has stronger chemical stability and can reduce the degradation of the perovskite layer in humidity and heat environments. + Can partially replace Pb 2+ , causing a slight energy level rearrangement, making the band gap adjustable in the range of 1.65eV-2.0eV. The doping concentration is controlled at 5-15mol% to prevent carrier transport from being blocked.

[0029] Impact of band gap after doping: See Table 1:

[0030] Table 1 Comparison of band gap calculated by doping ratio

[0031]

[0032] Ion migration is one of the main factors that lead to the degradation of perovskite solar cells, especially the migration of X-position (I- / Br-), which can destroy the uniformity of the material. The present invention inhibits ion migration by the following means:

[0033] Introducing Bi 3+ ions (from Cs3Bi2I9 and Cs2AgBiI6): due to Bi 3 The radius of Bi is larger, and its existence can enhance the lattice energy and improve the thermal stability of the material. 3 +Can partially replace Pb 2 +, reduce vacancy defects and increase the lifetime of photogenerated carriers.

[0034] like Figure 1 As shown in the figure, under standard illumination conditions, the stability of the undoped composite cell decayed to 15% of its original efficiency after 300 hours. As shown in Table 2, the efficiency of the composite cell doped with 8% Cs3Bi2I9 and 10% Cs2AgBiI6 after illumination can be significantly improved to 92%, while excessive doping (12% Cs3Bi2I9 and 15% Cs2AgBiI6) causes the composite cell's stability to begin to decline (the efficiency after illumination is 76% of the initial efficiency). Therefore, doping with 8% Cs3Bi2I9 and 10% Cs2AgBiI6 is the optimal combination for improving the stability of the composite cell.

[0035] Table 2 Comparison of the efficiency of Cs3Bi2I9 and Cs2AgBiI6 doped composite cells after illumination

[0036]

[0037] The present invention improves the photoelectric conversion efficiency, optimizes the energy band matching, reduces the interface energy barrier, adjusts the energy band structure by controlling the doping ratio of Cs3Bi2I9 and Cs2AgBiI6, matches the work function of the perovskite layer with that of the ETL / HTL, and reduces carrier recombination.

[0038] This invention optimizes the carrier diffusion length and increases the photogenerated current. Because the introduction of Cs2AgBiI6 reduces electron-hole recombination, the carrier diffusion length of the doped system can be increased. A gradient doping design makes the electric field distribution more uniform, reduces interfacial charge accumulation, and improves the device's fill factor (FF).

[0039] By introducing Cs3Bi2I9 and Cs2AgBiI6, the present invention reduces X-site ion migration in perovskite materials, thereby suppressing ion aggregation and phase separation. Doping with Cs3Bi2I9 and Cs2AgBiI6 significantly improves the photoelectric conversion efficiency of the battery and enhances the long-term stability of the device. By controlling the doping ratio of Cs3Bi2I9 and Cs2AgBiI6, the energy band matching and carrier diffusion performance are optimized, thereby increasing the device's fill factor.

[0040] The method for preparing the above-mentioned laminated solar cell comprises the following steps:

[0041] Steps include preparing precursor solution, processing reflector substrate, depositing electron transport layer, preparing multi-element perovskite active layer, depositing hole transport layer and preparing electrode.

[0042] Specifically, the above steps include:

[0043] S1. Preparation of precursor solution: Dissolve PbI2, PbBr2, FAI, MABr, CsI, Cs3Bi2I9 and Cs2AgBiI6 in DMF / DMSO solvent system, and add a small amount of additives (such as KI or PEAI) to improve solution stability.

[0044] S2. Reflector substrate processing:

[0045] The reflector substrate is ITO glass, which is first ultrasonically cleaned with acetone, isopropyl alcohol and deionized water for 15 minutes and then blown dry with nitrogen.

[0046] The mirror was fabricated by depositing a 150nm Ag layer on the reverse side of the ITO glass using magnetron sputtering. A 15nm Al2O3 protective layer was then grown by atomic layer deposition (ALD). The sputtering power was 100W, the atmosphere was Ar, and the substrate temperature was 80°C. The ALD temperature was 120°C.

[0047] S3, electron transport layer (ETL) deposition:

[0048] SnCl4·5H2O was dissolved in ethanol and stabilized with acetylacetone. Spin coating was performed at 3000 rpm for 30 seconds and annealed at 150°C for 30 minutes to form a dense SnO2 layer (approximately 30 nm).

[0049] S4. Preparation of multi-element perovskite active layer:

[0050] The perovskite layer was deposited using a two-step spin coating method, first spinning at 1000 rpm (10 seconds) and then increasing the speed to 6000 rpm (30 seconds). In the second step, 200 μL of chlorobenzene was added as an antisolvent.

[0051] Then annealing: 100°C for 10 minutes, followed by 150°C for 20 minutes (N2 atmosphere).

[0052] S5. Hole transport layer (HTL) deposition:

[0053] Spin coat the Spiro-OMeTAD solution and age at room temperature for 12 hours (humidity <30%). Dissolve 72.3 mg of Spiro-OMeTAD in 1 mL of chlorobenzene, add 17.5 μL of Li-TFSI (520 mg / mL in acetonitrile) and 28.8 μL of 4-tert-butylpyridine. Spin coat at 4000 rpm for 30 seconds and age at room temperature for 12 hours (humidity <30%).

[0054] S6. Electrode preparation:

[0055] To achieve optical coupling of perovskite / mirror hybrid solar cells, the top electrode needs to be changed to a semi-transparent electrode so that unabsorbed photons can be transmitted to the mirror.

[0056] The following is the specific preparation method:

[0057] S601, Material Selection

[0058] Transparent Conductive Oxide (TCO):

[0059] ITO (Indium Tin Oxide): Sputtering deposition, visible light transmittance >85%, square resistance <15Ω / sq.

[0060] IZO (Indium Zinc Oxide): Suitable for low-temperature processes (<100°C).

[0061] Ultra-thin metal electrodes:

[0062] Ag nanowire network: solution spin coating, thickness <20nm, transmittance ~80%, square resistance ~10Ω / sq.

[0063] Au / Ag ultra-thin layer: thermal evaporation deposition (1-2nm Au as adhesion layer + 8-10nm Ag), transmittance ~70%.

[0064] Two-dimensional material composite electrodes:

[0065] Graphene / Au grid: CVD graphene is transferred and covered with a micron-scale Au grid, which takes into account both conductivity and light transmittance.

[0066] S602, Preparation process (taking ITO sputtering as an example)

[0067] S6021: Hole Transport Layer (HTL) Surface Treatment

[0068] Plasma treatment: O2 plasma treatment (power 50 W, time 30 seconds) was performed on the Spiro-OMeTAD surface to enhance the ITO adhesion.

[0069] Interface modification: Spin coating of MoO3 nanoparticle solution (0.5 wt% in IPA, 3000 rpm, 30 s) to reduce energy level mismatch.

[0070] S6022: ITO sputtering deposition

[0071] Sputtering parameters:

[0072] Target material: In2O3:SnO2 (90:10wt%).

[0073] Substrate temperature: room temperature to 80°C (to avoid damaging the perovskite layer).

[0074] Sputtering gas: Ar (20 sccm) + 1% O2 (to suppress oxygen vacancies).

[0075] Power: DC 100W, deposition rate

[0076] Thickness control:

[0077] Target thickness: 80-100nm (transmittance >85%, square resistance ~10-15Ω / sq).

[0078] Real-time monitoring: Calibrate thickness using a quartz crystal microbalance (QCM) or ellipsometer.

[0079] S6023: Post-annealing and passivation

[0080] Low temperature annealing: 120℃, annealing in N2 atmosphere for 15 minutes to improve crystallinity.

[0081] Surface passivation:

[0082] ALD deposition of Al2O3 (2-3 nm) or spin coating of PFN-Br (0.1 mg / mL in methanol) was used to reduce interfacial recombination.

[0083] The electrode preparation of this embodiment can also adopt the solution method ultra-thin metal electrode, such as:

[0084] Preparation of Ag nanowire electrodes, including the following steps:

[0085] 1. Solution preparation:

[0086] Ag nanowires (diameter ∼30 nm, length ∼20 μm) were dispersed in ethanol (0.5 mg / mL) and stabilized with 0.1% PVP.

[0087] 2. Spin coating process:

[0088] 1500 rpm, 60 seconds, dry at room temperature.

[0089] 3. Annealing optimization:

[0090] Hot pressing annealing was performed at 120°C for 5 minutes (pressure 0.5 MPa) to reduce the contact resistance of the nanowires.

[0091] like Figure 2As shown, the present invention successfully reduces the migration channels of X-site ions by introducing Cs3Bi2I9, Cs2AgBiI6, and Ag- ions, thereby effectively suppressing ion migration. Experimental results show that in light stability tests, the efficiency of an undoped perovskite hybrid cell decays to 15% of its original efficiency after 300 hours, while the efficiency of a cell doped with 8% Cs3Bi2I9 and 10% Cs2AgBiI6 increases to 92% after exposure to light. This significantly enhances the device's stability under long-term light exposure and extends the solar cell's service life.

[0092] By constructing a multi-element perovskite composite system, the present invention enables precise control of the band gap, maintaining it between 1.65eV and 2.0eV. This not only avoids the decrease in light absorption efficiency caused by an excessively wide band gap, but also fully utilizes high-energy photons, improving photoelectric conversion efficiency. Experimental data shows that after doping with Cs3Bi2I9 and Cs2AgBiI6, the photoelectric conversion efficiency of the cell can be increased to 20.2%, significantly better than the undoped material (18.92%), and the cell's efficiency decays slowly under different lighting conditions.

[0093] like Figure 3 As shown, a perovskite reflector stacked solar cell comprises, from bottom to top, a reflector, a transparent electrode, a transmission layer, a perovskite light-absorbing layer, a transmission layer, a transparent electrode, and an encapsulation layer. Cs3Bi2I9 and Cs2AgBiI6 are added to the perovskite light-absorbing layer. The stacked solar cell of the present invention uses a multi-element perovskite composite system to adjust the band gap of the stacked solar cell. By introducing perovskite materials such as Cs3Bi2I9 and Cs2AgBiI6, the band gap of the material is optimized and ion migration is suppressed, significantly improving the stability and photoelectric conversion efficiency of the perovskite solar cell. The solar cell of the present invention is suitable for high-efficiency perovskite / reflector stacked solar cells and photovoltaic-thermal coupling systems, and provides a new technical solution for long-term stability and high efficiency in the photovoltaic field.

[0094] The present invention proposes a perovskite-mirror hybrid solar cell designed to optimize the optical and electrical properties of wide-bandgap perovskite materials while simultaneously reducing ion migration effects and improving the long-term stability of the device. This method, through the construction of a multi-element perovskite composite system, suppresses phase separation, reduces defect density, and enhances the device's environmental tolerance while maintaining high photoelectric conversion efficiency, making it suitable for high-efficiency perovskite / mirror hybrid solar cells and photovoltaic-thermal coupled systems.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A bandgap control method for a perovskite reflector stacked solar cell, characterized in that: During the preparation, a multi-perovskite composite system is introduced to regulate the band gap of the perovskite material and inhibit ion migration and phase separation, thereby improving the stability and photoelectric conversion efficiency of the material.

2. The bandgap control method of the perovskite reflector stacked solar cell according to claim 1, characterized in that: The multi-element perovskite composite system includes Cs3Bi2I9 and Cs2AgBiI6.

3. The bandgap control method of the perovskite reflector stacked solar cell according to claim 2, characterized in that: The doping concentration of Cs3Bi2I9 is 3-12 mol%, and the doping concentration of Cs2AgBiI6 is 5-15 mol%.

4. The bandgap control method of the perovskite reflector stacked solar cell according to claim 2, characterized in that: The doping ratio of the perovskite composite system is 8% Cs3Bi2I9 and 10% Cs2AgBiI6.

5. The bandgap control method of the perovskite reflector stacked solar cell according to claim 2, characterized in that: After doping with Cs3Bi2I9 and Cs2AgBiI6, the band gap of the perovskite material can be regulated between 1.65eV and 2.0eV.

6. The bandgap control method of the perovskite reflector stacked solar cell according to claim 2, characterized in that: The photoelectric conversion efficiency of the stacked solar cell is greater than 20%.

7. The bandgap control method of the perovskite reflector stacked solar cell according to claim 2, characterized in that: After 500 hours of illumination, the remaining PCE of the stacked solar cell accounts for more than 90% of the initial PCE.

8. The bandgap control method of a perovskite reflector-stacked solar cell according to claim 2, characterized in that: The octahedral unit structure of Cs3Bi2I9 improves the lattice rigidity of the material, reduces the migration channels of X-site ions, reduces the risk of phase separation, and at the same time improves the energy band matching and enhances interfacial charge transport.

9. The bandgap control method of a perovskite reflector-stacked solar cell according to claim 2, characterized in that: Cs2AgBiI6 has excellent chemical stability, which reduces the degradation of the perovskite layer in humidity and thermal environments.

10. A perovskite reflector stacked solar cell, characterized in that: The laminated solar cell is prepared by the band gap control method according to any one of claims 1 to 9, and comprises, from bottom to top, a reflector, a transparent electrode, an electron transport layer or a hole transport layer, a perovskite light absorption layer, a hole transport layer or an electron transport layer, a transparent electrode and an encapsulation layer.

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