Perovskite crystalline silicon laminated solar cell and preparation method thereof

Abstract

The invention discloses a perovskite crystalline silicon laminated solar cell and a preparation method thereof, and the perovskite crystalline silicon laminated solar cell comprises a crystalline silicon bottom cell, a middle connection layer and a perovskite top cell which are laminated from bottom to top. The perovskite top cell comprises a hole transport layer, a perovskite absorption layer, an electron transport layer, a buffer layer and a transparent top electrode layer which are stacked from bottom to top, and the buffer layer is composed of a Cr thin film and a CrOx thin film which are stacked from bottom to top. The invention develops a novel buffer layer material, and the problems of interface damage, optical loss and mechanical stability can be synchronously solved by utilizing the unique physicochemical properties of a Cr / CrOx composite structure.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to a perovskite-silicon tandem solar cell and its preparation method. Background Technology

[0002] Perovskite-silicon tandem solar cells combine the advantages of perovskite's broad-spectrum absorption and crystalline silicon's high stability, and are considered an effective way to break through the Shockley-Quisser theoretical efficiency limit of single-junction solar cells, showing great promise for development. In the fabrication of the perovskite top cell in a tandem solar cell, a transparent top electrode (TCO) needs to be deposited on top. Magnetron sputtering is the mainstream technology for preparing high-performance TCO thin films, but the bombardment of high-energy particles during this process can damage the underlying functional layers (such as the electron transport layer and the perovskite absorber layer), leading to performance degradation of the device.

[0003] To address this issue, existing technologies generally employ the introduction of a buffer layer between the electron transport layer and the TCO electrode to mitigate sputtering damage. Among these, tin oxide (ALD-SnO) prepared by atomic layer deposition is commonly used. x Thin films are widely studied and applied due to their high stability, low parasitic absorption, and good resistance to sputtering damage. Typical ALD-SnO... x The preparation process involves introducing tin and water sources into the reaction chamber in a cross-pulse manner, and depositing a dense and uniform SnO on the substrate surface through a chemical reaction. x film.

[0004] However, this method of preparing SnOx buffer layers based on ALD technology has the following technical drawbacks: (1) Interfacial chemical damage and defect state formation: The water source used in the ALD process comes into direct contact with the electron transport layer. The oxygen adsorbed on the surface can quickly penetrate into the electron transport layer, leading to the formation of deep-level defect states, reducing the conductivity of the electron transport layer and changing the carrier balance, thereby intensifying nonradiative recombination at the interface and reducing the photoelectric performance of the device. In addition, the tin source precursor tetratetra(dimethylamino)tin (TDMASn) reacts chemically with the perovskite layer to generate byproducts such as interfacial nitrides, introducing additional defects.

[0005] (2) Optical parasitic absorption problem: In order to effectively block sputtering damage, SnO prepared by ALD process x The buffer layer typically needs to be 15-20 nm thick, which leads to significant optical parasitic absorption, thus limiting the photoelectric conversion efficiency of the tandem solar cell.

[0006] (3) Poor interfacial adhesion and insufficient mechanical stability: electron transport layer and SnO xDue to significant differences in thermodynamic parameters and the fact that the bonding primarily relies on weak van der Waals forces, the interfacial adhesion is weak. During device operation, thermal shocks caused by diurnal temperature variations or mechanical stresses from electrode printing accumulate at the interface, easily leading to interfacial delamination. Excessive stress can even cause film fracture, disrupting carrier transport paths and providing pathways for external water and oxygen intrusion and internal component volatilization, severely limiting the long-term operational stability of the device.

[0007] (4) Process compatibility and large-area preparation challenges: The above-mentioned interface problems and the dependence of the ALD process on water vapor make it face uniformity and repeatability challenges when preparing perovskite / crystalline silicon tandem cells on a large scale, which is not conducive to industrial application.

[0008] In summary, existing ALD-SnO-based... x The buffer layer technology has significant shortcomings in terms of interface electrical performance, optical loss, mechanical stability and process compatibility, which restricts the further improvement of the efficiency and stability of perovskite / crystalline silicon tandem solar cells. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention aims to solve the problem of ALD-SnO in perovskite / crystalline silicon tandem solar cells. x Technical problems related to interface damage, parasitic absorption, and interfacial adhesion caused by buffer layers.

[0010] To achieve the above objectives, the present invention provides a perovskite-silicon tandem solar cell, comprising a crystalline silicon bottom cell, an intermediate connecting layer, and a perovskite top cell stacked from bottom to top. The perovskite top cell includes a hole transport layer, a perovskite absorber layer, an electron transport layer, a buffer layer, and a transparent top electrode layer stacked from bottom to top. The buffer layer is composed of a Cr thin film and CrO stacked from bottom to top. x Thin film composition.

[0011] This invention develops a novel buffer layer material, utilizing Cr / CrO x The unique physicochemical properties of the composite structure can simultaneously address issues of interface damage, optical loss, and mechanical stability. Specifically, the lower Cr film utilizes its excellent electrical conductivity and oxygen affinity to optimize electrical contact with the electron transport layer and enhance interlayer adhesion; the upper CrO... x The thin film, with its stable oxide properties and suitable band structure, acts as a barrier against subsequent process damage while ensuring high light transmittance. This Cr / CrO film... x The composite design achieves the integration of electrical, optical and mechanical functions that are difficult to achieve with a single material layer, laying the foundation for improving the overall performance of tandem batteries.

[0012] Furthermore, the thickness of the buffer layer is 3-5 nm. Cr / CrO x The thinness of the buffer layer is small, which helps to reduce the parasitic absorption of light in the buffer layer, ensuring that light energy can pass through efficiently and reach the bottom crystalline silicon cell, thereby effectively improving the short-circuit current density and final conversion efficiency of the tandem cell.

[0013] Furthermore, in the buffer layer, the Cr film and the CrO x The thickness ratio of the thin film is 1:2 to 2:1. By controlling the thickness ratio, the electrical and chemical functional ratio within the buffer layer is optimized, ensuring sufficient Cr layer to maintain good lateral conductivity and oxygen affinity, while also ensuring sufficient CrO. x The layer leverages its wide bandgap, high transparency, and hole-blocking capabilities to achieve the best balance of performance.

[0014] Furthermore, the buffer layer has an amorphous structure. The buffer layer possesses a dense, uniform, and grain-bound thin film morphology, which can effectively disperse the physical stress introduced by the subsequent magnetron sputtering process and provide excellent damage resistance.

[0015] Furthermore, the CrO x In the thin film, Cr exists in a mixed valence state of +3 and +4. This mixed valence state endows the buffer layer with bipolar carrier transport properties, enabling it to both transport electrons and block holes, which helps to optimize the carrier balance at the interface and reduce recombination.

[0016] Furthermore, the CrOx thin film has a bandgap of 3.3~3.5 eV and a highest occupied molecular orbital energy level of -7.3~-7.5 eV. The wide bandgap ensures high transparency, while the deep HOMO energy level provides strong hole blocking capability. Together, they ensure high open-circuit voltage and high short-circuit current of the battery from both optical and electrical perspectives.

[0017] Furthermore, the transmittance of the buffer layer is higher than 90% in the wavelength range of 300~1200nm. Ensuring that the absorption loss of the buffer layer to the working spectrum is minimized is a key optical guarantee for realizing high-efficiency tandem solar cells.

[0018] Furthermore, the electron transport layer contains Cr atoms diffused from the buffer layer. The diffused Cr atoms can act as dopant, increasing the conductivity of the electron transport layer and thus improving electron extraction and transport efficiency.

[0019] Furthermore, the interface between the buffer layer and the transparent top electrode layer forms an ion bond. This ion bond enhances interfacial adhesion and mechanical stability, enabling the device to resist thermal and mechanical stresses and extending its operational life.

[0020] The present invention also provides a method for preparing the above-mentioned perovskite-silicon tandem solar cell, comprising the following steps: Provides monocrystalline silicon base cells; An intermediate interconnect layer, a hole transport layer, a perovskite absorber layer, and an electron transport layer are sequentially fabricated on the crystalline silicon bottom cell. On the electron transport layer, a thin film of Cr and CrO is prepared by a thermal evaporation process. x A buffer layer composed of thin films; A transparent top electrode layer is fabricated on the buffer layer.

[0021] This invention prepares a buffer layer through a thermal evaporation process, which avoids the electron transport layer from contacting air or water sources. This process suppresses the generation of interface defect states and byproducts from the source of the process, and is a reliable and critical process guarantee for obtaining high-performance, high-stability devices suitable for large-area production.

[0022] In summary, the present invention has the following beneficial effects: (1) Optimization of electrical performance: The buffer layer has Cr / CrO x Composite structure, in which CrO x The thin film possesses multiple chemical valence states, endowing it with unique bipolar carrier transport properties, which can both assist electron transport and effectively block holes. Its wide bandgap combined with deep highest occupied molecular orbital energy levels results in excellent hole blocking capability. Simultaneously, Cr atoms diffusing from the buffer layer to the electron transport layer enhance the conductivity of the electron transport layer. The synergistic effect of these factors significantly suppresses nonradiative recombination losses at the interface, laying the electrical foundation for obtaining high open-circuit voltage and high fill factor.

[0023] (2) Excellent optical performance: The ultra-thin Cr / CrO used in this invention x The buffer layer exhibits extremely high transmittance over a wide spectral range. This high transparency minimizes the parasitic absorption loss of the buffer layer itself, ensuring that most sunlight, especially long-wavelength photons, can effectively penetrate and reach the crystalline silicon bottom cell for full absorption, thereby significantly improving the short-circuit current density of the tandem cell.

[0024] (3) Excellent mechanical stability: This invention utilizes the oxygen-loving properties of Cr materials in Cr / CrO x The buffer layer forms a strong ionic bond with the transparent top electrode layer above. This structure fundamentally solves the problems of poor interfacial adhesion and easy delamination caused by weak van der Waals forces in traditional devices, greatly enhancing the mechanical stability of the device under thermal and mechanical stress, and providing a key guarantee for long-term reliability.

[0025] (4) Process-friendly preparation: From the perspective of preparation process, this invention abandons the ALD technology that uses water and is prone to causing interfacial chemical damage, and adopts a continuous thermal evaporation process to prepare the buffer layer. This process firstly avoids the electron transport layer from contacting oxygen / water vapor, thus suppressing the generation of by-products and interfacial defects from the source; secondly, the Cr / CrO prepared by thermal evaporation x The film is uniform and dense, effectively resisting high-energy particle bombardment during subsequent magnetron sputtering of the transparent top electrode layer, thus protecting the underlying sensitive functional layer. Furthermore, the low melting point of metallic chromium makes it highly compatible with the conformal coating requirements of large-area surfaces and various light-trapping structures, demonstrating significant potential for industrial applications. Attached Figure Description

[0026] Figure 1 This is a high-resolution transmission electron microscope (HR-STEM) image of the perovskite top solar cell in Embodiment 1 of the present invention.

[0027] Figure 2 The Cr / CrO in Example 1 of this invention x X-ray photoelectron spectroscopy (XPS) of the buffer layer.

[0028] Figure 3 This is a schematic diagram of the elemental depth distribution (Tof-SIMS) of the perovskite top solar cell in Embodiment 1 of the present invention.

[0029] Figure 4 The current-voltage (JV) curves of the perovskite-silicon tandem solar cells prepared in Example 2 and Comparative Example 1 of this invention are shown. Detailed Implementation

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0031] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0032] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art.

[0033] A specific embodiment of the present invention provides a perovskite-silicon tandem solar cell, comprising a crystalline silicon bottom cell, an intermediate connecting layer, and a perovskite top cell stacked from bottom to top. The perovskite top cell includes a hole transport layer, a perovskite absorber layer, an electron transport layer, a buffer layer, and a transparent top electrode layer stacked from bottom to top. The buffer layer is composed of a thin film of metallic chromium (Cr) and chromium oxide (CrO) stacked from bottom to top. x ) Thin film composition.

[0034] This tandem battery incorporates a Cr / CrO2 composition, consisting of metallic chromium and its oxides, between the electron transport layer and the transparent top electrode layer. x The buffer layer effectively solves the problems of traditional ALD-SnO. x The buffer layer addresses efficiency loss and stability issues caused by interfacial chemical damage, severe optical parasitic absorption, and poor interfacial adhesion, achieving high photoelectric conversion efficiency and excellent long-term stability.

[0035] In a specific embodiment, the total thickness of the buffer layer is 3-5 nm, and its transmittance in the wavelength range of 300-1200 nm is higher than 90%, with minimal light absorption loss. CrO x The thin film has a band gap of 3.3~3.5eV and a highest occupied molecular orbital (HOMO) energy level of -7.3~-7.5eV, exhibiting excellent hole blocking ability; moreover, Cr exists in a mixed valence state of +3 and +4, endowing it with bipolar carrier transport characteristics.

[0036] Preferably, the thickness of the Cr film is related to the thickness of the CrO film. x A film thickness ratio of 1:2 to 2:1 ensures sufficient metallic Cr to maintain good electrical contact and oxygen affinity, while also ensuring sufficient CrO. x To take advantage of its wide bandgap characteristics and hole blocking capabilities.

[0037] In some embodiments, the electron transport layer is made of fullerene (C 60 The presence of Cr atoms diffusing from the buffer layer enhances its electrical conductivity. Ionic bonds form at the interface between the transparent top electrode layer and the buffer layer. For example, if indium zinc oxide (IZO) is used as the material for the transparent top electrode layer, Cr-O-In bonds, primarily ionic, form at the interface, significantly improving adhesion and mechanical stability.

[0038] The fabrication method of the above-mentioned perovskite / crystalline silicon tandem solar cell includes the following steps: S1, provides a single-layer silicon base cell.

[0039] S2. An intermediate connecting layer, a hole transport layer, a perovskite absorption layer, and an electron transport layer are sequentially fabricated on a crystalline silicon bottom cell.

[0040] S3. Using thermal evaporation technology, a thin film of metallic Cr is deposited on the electron transport layer, and its surface naturally oxidizes to form CrO. x Thin films were thus prepared, thereby producing Cr thin films and CrO. x A buffer layer composed of thin films. This continuous thermal evaporation process prevents the electron transport layer from coming into contact with oxygen / water vapor.

[0041] S4. A transparent top electrode layer is prepared on the buffer layer by magnetron sputtering.

[0042] S5. Using thermal evaporation technology, a metal electrode is fabricated on the transparent top electrode layer to complete the device fabrication.

[0043] This invention introduces a novel Cr / CrO x The use of buffer layer materials, combined with a low-damage thermal evaporation preparation process, provides a reliable technical solution for the preparation of high-efficiency, stable, and large-area compatible perovskite-silicon tandem solar cells.

[0044] The technical solution and effects of the present invention will be illustrated below with reference to specific embodiments.

[0045] Example 1 The specific steps for fabricating perovskite-silicon tandem solar cells are as follows: (1) Provide a crystalline silicon bottom cell.

[0046] (2) Using magnetron sputtering technology, a 10nm thick ITO thin film is deposited on the light-receiving surface of the crystalline silicon bottom cell to form an intermediate connection layer.

[0047] (3) Spin-coat a carbazole-based self-assembled monolayer (SAMs) ethanol solution (concentration of 1 mg / mL) onto the intermediate linker layer to form a hole transport layer.

[0048] (4) A perovskite precursor solution is spin-coated onto the hole transport layer and then annealed to form a perovskite absorption layer.

[0049] (5) A 20 nm thick C layer was deposited on the perovskite absorber layer using thermal evaporation technology. 60 Thin film, as an electron transport layer.

[0050] (6) A thin film of metallic chromium was deposited on the electron transport layer using thermal evaporation technology. The thickness of the Cr film was controlled to approximately 4 nm by controlling the evaporation process. After the sample was removed from the vacuum chamber, the surface of the metallic chromium was naturally oxidized in the air to form a CrO film with a thickness of approximately 1.5 nm. x Thin film, Cr / CrO x Composite buffer layer.

[0051] (7) Using magnetron sputtering technology, in Cr / CrO xA 40 nm thick IZO film is deposited on the buffer layer as a transparent top electrode.

[0052] (8) Using thermal evaporation technology, a silver (Ag) electrode of about 300 nm thickness is deposited on the transparent top electrode, and finally the complete stacked battery device is packaged.

[0053] The prepared perovskite top solar cell and buffer layer were characterized: the perovskite top solar cell was observed using high-resolution transmission electron microscopy, and the results are as follows: Figure 1 As shown, Cr / CrO x The buffer layer has a uniform and dense amorphous structure. X-ray photoelectron spectroscopy was used to test the buffer layer, and the results are as follows: Figure 2 As shown, the buffer layer has Cr / CrO x Composite structure, CrO x Cr exists in the thin film in a mixed oxidation state of +3 and +4. The elemental distribution analysis results are as follows. Figure 3 As mentioned above, it is evident that Cr element is directed towards C. 60 Diffusion occurs in the electron transport layer.

[0054] Example 2 The difference between this embodiment and Embodiment 1 is that in step (6), a Cr film with a thickness of 3.5 nm is deposited using thermal evaporation technology, and its surface is naturally oxidized to form a CrO film with a thickness of approximately 1.7 nm. x A thin film of Cr / CrO with a total thickness of approximately 3.5 nm was obtained. x Composite buffer layer. Other preparation steps and processes are the same.

[0055] Comparative Example 1 The difference between this comparative example and Example 1 is that in step (6), atomic layer deposition (ALD) technology is used to prepare a 20 nm thick SnO layer on the electron transport layer. x It serves as a buffer layer. Other preparation steps and processes are the same.

[0056] The performance of the tandem cells prepared in Example 2 and Comparative Example 1 was tested: the JV curves are shown below. Figure 4 As shown in Table 1, the performance test results are as follows: Based on Cr / CrO x The perovskite-silicon tandem solar cell with a buffer layer exhibits higher current density, open-circuit voltage, and fill factor, resulting in a significant improvement in photoelectric conversion efficiency.

[0057] Table 1 Performance parameters of perovskite-silicon tandem solar cells in Example 2 and Comparative Example 1

[0058]

[0059] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the scope of protection of this invention.

Claims

1. A perovskite-silicon tandem solar cell, characterized in that, The battery comprises a crystalline silicon bottom cell, an intermediate connecting layer, and a perovskite top cell stacked from bottom to top. The perovskite top cell includes a hole transport layer, a perovskite absorber layer, an electron transport layer, a buffer layer, and a transparent top electrode layer stacked from bottom to top. The buffer layer is composed of a Cr thin film and CrO stacked from bottom to top. x Thin film composition.

2. The perovskite-silicon tandem solar cell according to claim 1, characterized in that, The thickness of the buffer layer is 3~5nm.

3. The perovskite-silicon tandem solar cell according to claim 2, characterized in that, In the buffer layer, the Cr film and the CrO x The thickness ratio of the thin film is 1:2 to 2:

1.

4. The perovskite-silicon tandem solar cell according to any one of claims 1-3, characterized in that, The buffer layer has an amorphous structure.

5. The perovskite-silicon tandem solar cell according to claim 1, characterized in that, The CrO x In the thin film, Cr exists in a mixed valence state of +3 and +4.

6. The perovskite-silicon tandem solar cell according to claim 5, characterized in that, The CrOx thin film has a band gap of 3.3~3.5eV and a highest occupied molecular orbital energy level of -7.3~-7.5eV.

7. The perovskite-silicon tandem solar cell according to claim 1, characterized in that, The buffer layer has a transmittance of over 90% in the wavelength range of 300~1200nm.

8. The perovskite-silicon tandem solar cell according to claim 1, characterized in that, The electron transport layer contains Cr atoms that diffuse from the buffer layer.

9. The perovskite-silicon tandem solar cell according to claim 1, characterized in that, The interface between the buffer layer and the transparent top electrode layer forms an ionic bond.

10. A method for preparing a perovskite-silicon tandem solar cell as described in any one of claims 1-9, characterized in that, Includes the following steps: Provides monocrystalline silicon base cells; An intermediate interconnect layer, a hole transport layer, a perovskite absorber layer, and an electron transport layer are sequentially fabricated on the crystalline silicon bottom cell. On the electron transport layer, a thin film of Cr and CrO is prepared by a thermal evaporation process. x A buffer layer composed of thin films; A transparent top electrode layer is fabricated on the buffer layer.

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