Hole transport layer for perovskite-crystalline silicon tandem solar cell and preparation method thereof
By doping short-chain phosphoryl small molecules into self-assembled molecules, the problems of hole transport layer compactness and energy level matching in perovskite-crystalline silicon tandem solar cells were solved, thereby improving the performance and stability of perovskite-crystalline silicon tandem solar cells.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- UNIV OF ELECTRONICS SCI & TECH OF CHINA
- Filing Date
- 2026-03-12
- Publication Date
- 2026-06-16
Smart Images
Figure CN122227770A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of perovskite solar cell manufacturing, and relates to perovskite-crystalline silicon tandem solar cells. Specifically, it provides a method for preparing a hole transport layer for perovskite-crystalline silicon tandem solar cells. Background Technology
[0002] Perovskite solar cells, with their superior photoelectric conversion efficiency and low-cost solution processing characteristics, have become a core research direction for the next generation of photovoltaic technology. After more than ten years of technological iteration, the certified efficiency of single-junction perovskite solar cells has exceeded 27%, and the certified efficiency of perovskite-crystalline silicon tandem cells has reached 34.8%, demonstrating great potential to replace traditional crystalline silicon cells. However, the lack of long-term stability of the devices has become the core bottleneck restricting their industrialization.
[0003] In the inverse structure, the hole transport layer is typically made of self-assembled molecules. These functionalized molecules form an ordered monolayer on the substrate surface, enabling precise control of the interfacial physicochemical properties and thus optimizing device performance. However, single self-assembled molecule systems have several significant technical drawbacks: they contain both hydrophilic phosphate groups and hydrophobic carbazole groups, making them prone to aggregation in common solvents such as ethanol; their flexible alkyl chain structure leads to random orientation of molecules on the substrate surface, reducing the orderliness and coverage of the molecular layer and creating localized exposed areas; the limited anchoring points between a single molecule and the substrate result in poor wettability of the perovskite precursor solution at the modified interface, insufficient interaction between the precursor and the substrate, leading to random nucleation and disordered growth of perovskite crystals; these problems create numerous voids and pores at the interface, increasing charge transport resistance and providing channels for ion migration and water penetration, accelerating device performance degradation and severely limiting long-term stability.
[0004] In summary, due to the inherent configuration of single self-assembled molecules and the relatively weak intermolecular forces, existing technologies struggle to construct a highly dense, fully covered hole transport layer on the electrode surface. This hinders the effective passivation of interface defects and optimization of energy level matching, ultimately limiting further improvements in device performance. Therefore, developing a novel interface modification strategy that enhances molecular layer density, strengthens interface anchoring, and optimizes energy level matching is crucial for unlocking the performance potential of perovskite-crystalline silicon tandem solar cells. Summary of the Invention
[0005] The purpose of this invention is to provide a hole transport layer for perovskite-silicon tandem solar cells and its preparation method, thereby solving problems such as poor coverage of self-assembled molecules, weak interface anchoring, low perovskite crystal quality, and poor energy level matching in inverted perovskite solar cells. This invention dops the self-assembled molecules with phosphoryl groups of different chain lengths to improve the density and coverage of the self-assembled molecular layer, eliminating exposed areas at the interface; strengthens the anchoring effect between the self-assembled molecules and the substrate, improving the wettability of the perovskite precursor; optimizes the crystal quality of the perovskite thin film, reducing interface defects and non-radiative recombination; regulates the energy levels of the hole transport layer, lowering the energy barrier with the perovskite absorber layer, and improving charge extraction efficiency; ultimately achieving a synergistic improvement in the photoelectric conversion efficiency and long-term stability of perovskite-silicon tandem solar cells.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0007] A hole transport layer for perovskite-crystalline silicon tandem solar cells, characterized in that the hole transport layer material is composed of a self-assembled molecule doped with a phosphoryl group; the self-assembled molecule is [4-(7H-dibenzocarbazole-7-yl)butyl]phosphate, and the phosphoryl group is one or more of phosphorylated acetic acid, 3-phosphonopropionic acid, or 4-phosphobutyric acid.
[0008] Furthermore, the mass ratio of the self-assembled molecule to the phosphoryl group small molecule is 1:0.05 to 1:0.3, preferably 9:1.
[0009] Furthermore, the method for preparing the hole transport layer for the perovskite-crystalline silicon tandem solar cell includes the following steps:
[0010] Step 1, Preparation of self-assembled molecular solution: Dissolve [4-(7H-dibenzocarbazole-7-yl)butyl]phosphoric acid in ethanol solvent to obtain self-assembled molecular solution A;
[0011] Step 2, Preparation of phosphoryl small molecule solution: Add phosphorylacetic acid, 3-phosphonopropionic acid or 4-phosphobutyric acid powder to ethanol solvent to obtain phosphoryl small molecule solution B with the same concentration as self-assembled molecule solution A;
[0012] Step 3: Preparation of doped self-assembled molecule solution: Mix self-assembled molecule solution A and phosphoryl small molecule solution B in a certain proportion and mix evenly to obtain doped self-assembled molecule solution;
[0013] Step 4, Spin Coating and Annealing: The solution of doped self-assembled molecules is dropped onto the substrate surface and deposited by spin coating. After completion, it is placed on a hot stage for annealing to form a hole transport layer.
[0014] Furthermore, the concentrations of the self-assembled molecule solution A and the phosphoryl small molecule solution B are 0.2 mg / mL to 2 mg / mL.
[0015] Furthermore, the spin coating speed is 2500 rpm to 5000 rpm, and the spin coating time is 20 s to 40 s.
[0016] Furthermore, the annealing temperature is 90℃~120℃, and the annealing time is 8 min~15 min.
[0017] Furthermore, the hole transport layer is applied in a perovskite-crystalline silicon tandem solar cell, which includes: a negative electrode, a crystalline silicon base cell, a hole transport layer, a perovskite absorber layer, an electron transport layer, a transparent conductive oxide layer, a positive electrode, and an antireflection layer stacked sequentially.
[0018] Based on the above technical solution, the beneficial effects of the present invention are as follows:
[0019] This invention improves the anchoring density of self-assembled molecules per unit area and enhances the coverage of the hole transport layer by doping self-assembled molecules with small molecules of different chain lengths, thereby significantly improving battery performance. Specifically, due to their flexible alkyl chains, the self-assembled molecules are randomly oriented on the substrate. When short-chain phosphoryl small molecules (such as phosphorylated acetic acid) are introduced as dopants, their small molecular size allows them to effectively penetrate into the voids within the self-assembled molecule layer, thus increasing the overall packing density. Furthermore, the relatively rigid conformation imparted by their shorter chain length helps to restrict the movement of flexible linking groups in adjacent self-assembled molecules. This restriction significantly promotes the preferential vertical orientation of the self-assembled molecules relative to the substrate. Moreover, the improved molecular arrangement promotes stronger π-π stacking interactions between adjacent carbazole units, thereby improving the conductivity and charge transport efficiency of the film.
[0020] Meanwhile, by doping the hole transport layer with short-chain phosphoryl small molecules (such as phosphorylated acetic acid), the energy level matching between the hole transport layer and the perovskite absorber layer was successfully optimized while improving the coverage of self-assembled molecules. By reducing the energy level barrier at the interface, passivating defects at the buried interface, suppressing non-radiative recombination, and accelerating carrier extraction, the carrier transport efficiency between the hole transport layer and the perovskite absorber layer was greatly improved, significantly enhancing the overall performance of the solar cell.
[0021] In summary, this invention improves the coverage of the self-assembled molecular layer by doping the hole transport layer with short-chain phosphoryl small molecules, reduces the formation of defect sites at the buried interface, promotes the crystallization process of the perovskite film, effectively improves the crystal quality of the perovskite film, reduces the formation of excess PbI2 at the buried interface, fills iodine vacancy defects at the buried interface, thereby reducing the formation of carrier recombination centers, optimizes the energy level matching between the hole transport layer and the perovskite absorber layer, and thus improves the overall photoelectric conversion efficiency of the perovskite solar cell, laying a solid foundation for its commercial application and further technological development. Attached Figure Description
[0022] Figure 1 This is a schematic diagram of the perovskite-crystalline silicon solar cell structure for both the example and comparative examples.
[0023] Figure 2 The figures show the cyclic voltammetry curves of the examples and comparative examples at different scan rates.
[0024] Figure 3 The graph shows the molecular adsorption density fitting curves of the examples and comparative examples calculated based on cyclic voltammetry.
[0025] Figure 4 These are scanning electron microscope (SEM) images of the buried interface of the perovskite thin films in the examples and comparative examples; wherein, Figure 4 (a) shows the perovskite film obtained in the comparative example. Figure 4 (b) shows the perovskite film obtained in Example 1; Figure 4 (c) is the perovskite thin film obtained in Example 2; Figure 4 (b) is the perovskite film obtained in Example 3.
[0026] Figure 5 The X-ray diffraction (XRD) patterns of the perovskite thin films obtained in the examples and comparative examples are shown.
[0027] Figure 6 The images show the photoluminescence (PL) spectra of the perovskite thin films obtained in the examples and comparative examples.
[0028] Figure 7 The JV curves of the perovskite-crystalline silicon tandem perovskite solar cells obtained in the examples and comparative examples are shown. Detailed Implementation
[0029] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. In addition, unless otherwise expressly stated, the technical terms used in this invention have the same meaning as commonly understood by those skilled in the art. The raw materials, reagents, instruments, and equipment used, unless otherwise specified, can be purchased through market channels or prepared by existing publicly available methods.
[0030] Example 1
[0031] This embodiment provides a hole transport layer for perovskite-crystalline silicon tandem solar cells. The hole transport layer material is composed of a self-assembled molecule doped with a phosphoryl group. The self-assembled molecule is [4-(7H-dibenzocarbazole-7-yl)butyl]phosphate, and the phosphoryl group is phosphorylated acetic acid. The mass ratio of the two is 9:1.
[0032] The hole transport layer is used in perovskite-crystalline silicon tandem solar cells, such as... Figure 1 As shown, the perovskite-crystalline silicon tandem solar cell comprises: a negative electrode, a crystalline silicon base cell, a hole transport layer, a perovskite absorber layer, an electron transport layer, a transparent conductive oxide layer, a positive electrode, and an antireflection layer, stacked sequentially; it is prepared by the following steps:
[0033] (1) Preparation of perovskite precursor solution;
[0034] Weigh out 22.1 mg of CsI, 28.6 mg of MABr, 233.9 mg of FAI, 560.4 mg of PbI2, and 177.8 mg of PbBr2, and dissolve them in 1 mL of a mixed solution of DMF (N,N-dimethylformamide) and DMSO (dimethyl sulfoxide) (volume ratio 4:1). Stir overnight at room temperature, and then filter the solution using a 0.22 μm polytetrafluoroethylene needle filter to obtain the final perovskite precursor solution for film formation.
[0035] (2) Fabrication of silicon-based solar cells;
[0036] A 21 cm × 10.5 cm silicon base cell was cut into 2 cm × 2 cm small cells. A patterned 1.2 cm × 1.2 cm composite layer was formed at the center of each small cell. The cutting precision deviation was controlled so that the size difference of each patterned composite layer was kept within 1 mm. The cut base cell pieces were annealed at 200 °C for 15 min to obtain a "silicon base cell / composite layer" structure, wherein the thickness of the silicon base cell was 130 µm and the thickness of the composite layer was 10 nm.
[0037] (3) Preparation of the hole transport layer;
[0038] In this embodiment, self-assembled molecules are deposited on a substrate using spin coating. The detailed preparation steps are as follows:
[0039] Weigh 1 mg of [4-(7H-dibenzocarbazole-7-yl)butyl]phosphate powder and add it to 1 mL of ethanol solution. Dissolve the powder by shaking and stirring for 12 h to obtain solution A. Weigh 1 mg of phosphorylacetic acid additive and add it to 1 mL of ethanol solution. Dissolve the phosphorylacetic acid additive by shaking and stirring for 12 h to obtain solution B. Mix solution A and solution B in a ratio of 9:1 to obtain solution C.
[0040] The cut crystalline silicon bottom cell was treated in an ultraviolet-ozone plasma cleaner for 30 min. 65 μL of hole transport layer solution C was dropped onto the treated crystalline silicon bottom cell. After standing for 15 s, it was spin-coated at 3000 rpm for 30 s. Subsequently, it was annealed on a hot stage at 100℃ for 10 min to obtain the "crystalline silicon bottom cell / hole transport layer" structure.
[0041] (4) Preparation of perovskite absorber layer;
[0042] Take 70 μL of the prepared perovskite precursor solution and drop it onto the hole transport layer. Then, form a film using a two-step spin-coating method:
[0043] First stage: Spin coat at 2000 rpm for 45 seconds to allow the solution to spread rapidly;
[0044] Second stage: Spin coat at 6000 rpm for 10 s, and in the first second after the start of the second stage, use a pipette to quickly add 0.2 mL of anisole as an antisolvent;
[0045] After spin coating, the film was immediately transferred to a hot stage at 100°C and annealed for 20 min to form a dense and smooth black perovskite film, thus obtaining a device with a "crystalline silicon bottom cell / hole transport layer / perovskite layer" structure.
[0046] (5) Fabrication of electron transport layer
[0047] The "crystalline silicon substrate / hole transport layer / perovskite layer" structure was placed in a vacuum deposition mask, and the mask was placed in a vacuum deposition apparatus and evacuated to 7×10⁻⁶. -4 Below Pa, LiF and C vapor deposition 60 Layers with a velocity of about 0.1 Å / s and thicknesses of 1 nm and 10 nm were used to obtain a device with a structure of "crystalline silicon bottom cell / hole transport layer / perovskite layer / electron transport layer".
[0048] (6) Preparation of transparent conductive oxide layer;
[0049] The "crystalline silicon substrate / hole transport layer / perovskite layer / electron transport layer" structure was placed in an atomic layer deposition chamber. A vacuum was applied, and the chamber temperature was kept below 200°C. The water source and tin source pressures were set to 44 Pa and 26 Pa, respectively. The cycle count was 200, and a 15 nm layer of tin oxide was deposited. The wafer was then placed in a mask for IZO sputtering, and the mask was placed in a magnetron sputtering instrument until the chamber pressure reached 1 × 10⁻⁶. -4 Sputtering begins below Pa, with argon flow rate controlled at 8 sccm and oxygen flow rate at 6 sccm. The sputtering mode is DC magnetron sputtering, followed by sputtering at 200 W for 210 s to obtain a device with a structure of "crystalline silicon bottom cell / hole transport layer / perovskite layer / electron transport layer / transparent conductive oxide layer".
[0050] (7) Preparation of the positive electrode and the back electrode;
[0051] The structure of "crystalline silicon substrate / hole transport layer / perovskite layer / electron transport layer / transparent conductive oxide layer" is placed in a mask for evaporating the positive and negative electrodes. The mask is then placed in a vacuum deposition apparatus and evacuated to a vacuum level of 1×10⁻⁶. -4 Below Pa, a 600 nm thick positive electrode and a 200 nm thick back electrode are deposited by vapor deposition to obtain a device with a structure of "negative electrode / crystalline silicon bottom cell / hole transport layer / perovskite layer / electron transport layer / transparent conductive oxide layer / positive electrode".
[0052] (8) Preparation of antireflection layer;
[0053] The structure of "negative electrode / crystalline silicon substrate / hole transport layer / perovskite layer / electron transport layer / transparent conductive oxide layer / positive electrode" was placed on a mask with a central 1.1 cm × 1.1 cm cutout. The mask was then placed in a vacuum deposition apparatus and evacuated to a depth of 1 × 10⁻⁶ cm. -4 Below Pa, LiF is evaporated to form an antireflection layer with a thickness of 100 nm, thus obtaining a perovskite-crystalline silicon tandem solar cell.
[0054] Example 2
[0055] This embodiment provides a hole transport layer for perovskite-crystalline silicon tandem solar cells, which differs from Embodiment 1 in that the phosphoryl small molecule is 3-phosphonopropionic acid.
[0056] Example 3
[0057] This embodiment provides a hole transport layer for perovskite-crystalline silicon tandem solar cells, which differs from Embodiment 1 in that the phosphoryl small molecule is 4-phosphobutyric acid.
[0058] Meanwhile, in order to intuitively demonstrate the beneficial effects of the present invention, the present invention also provides a comparative example: a perovskite-crystalline silicon tandem solar cell is provided, the difference from Example 1 is that the hole transport layer material adopts the self-assembled molecule [4-(7H-dibenzocarbazole-7-yl)butyl]phosphoric acid.
[0059] The above embodiments and comparative examples are analyzed and tested below.
[0060] Cyclic voltammetry (CV) tests were performed on the hole transport layer films obtained in the examples and comparative examples to evaluate the surface coverage of self-assembled molecules on ITO conductive glass substrates; such as Figure 2 As shown, the peak redox currents of Examples 1, 2, and 3 at different scan rates are all higher than those of the comparative example, indicating that the conductivity of the hole transport layer is significantly improved after introducing phosphoryl group small molecules into the hole transport layer. The molecular weight anchored on the ITO conductive glass substrate per unit area is obtained by fitting the peak current at different scan rates. Figure 3 As shown, the molecular density of Example 1 is significantly increased compared to the comparative example. This significant increase indicates that the incorporation of short-chain phosphoryl small molecules effectively alters the orientation of self-assembled molecules, thereby enhancing their adsorption behavior and resulting in a more compact and dense monolayer structure.
[0061] Scanning electron microscopy was performed on the wide-bandgap perovskite films obtained in the examples and comparative examples, and the results are as follows: Figure 4 As shown, where, Figure 4 (a) shows the perovskite subsurface interface obtained by corresponding proportions. Figure 4 (b) corresponds to the perovskite buried interface obtained in Example 1. Figure 4 (c) corresponds to the perovskite buried interface film in Example 2. Figure 4 (d) corresponds to the perovskite buried interface obtained in Example 3. From the SEM images, it is clearly visible that the buried interface of the perovskite films obtained in the comparative examples exhibits significant porosity at the nanometer or even micrometer scale. This is due to the uneven coverage of self-assembled molecules caused by structural constraints. The morphology of the perovskite buried interface in Examples 1, 2, and 3 is significantly improved, with Example 1 showing the most significant improvement. Porosity is essentially eliminated, grain boundaries are negligible, and the buried interface is more uniform and dense. Simultaneously, the average grain size of the perovskite film also increases significantly. This is beneficial for reducing interface trap density and charge recombination, thereby improving FF and V. OC .
[0062] XRD analysis was performed on the perovskite films obtained in the examples and comparative examples, and the results are as follows: Figure 5As shown, compared to the comparative example, the characteristic peak intensity of perovskite in Example 1 was enhanced after the introduction of phosphorylated acetic acid into the hole transport layer, indicating that the optimization of the hole transport layer is beneficial to improving the crystallinity of perovskite. At the same time, compared with the comparative example, the intensity of the PbI2 characteristic peak at 12.7° in Examples 1, 2 and 3 was significantly reduced, which is beneficial to the photothermal stability of the perovskite film. The XRD results show that the introduction of phosphorylated small molecules in the hole transport layer helps to enhance the crystallinity quality of the perovskite film and the stability of the device.
[0063] Photoluminescence (PL) spectroscopy analysis was performed on the buried perovskite films obtained in the examples and comparative examples to study the carrier dynamics at the perovskite heterojunction, such as... Figure 6 As shown, the results indicate that, compared with the comparative perovskite films, the PL peak of the buried interface perovskite films in Examples 1, 2, and 3 was effectively enhanced, with the most significant enhancement observed in Example 1, indicating that defect-induced nonradiative recombination was suppressed.
[0064] The JV performance of the perovskite-crystalline silicon tandem solar cell devices prepared based on the examples and comparative examples is shown in Table 1 and... Figure 7 As shown in the table, the V of the embodiment device can be seen. OC Both V and FF show very significant improvements. Compared with the comparative example, the V of the device in Example 1 is significantly improved. OC The voltage was increased by approximately 40 mV, achieving a high opening voltage of 2,000 V. At the same time, the overall performance also improved from 31.97% to 33.29%. As can be seen from the table, the overall performance of Examples 2 and 3 was also significantly improved compared to the comparative example. However, it is obvious that the overall performance of the device decreased as the chain length increased. This may be because the carbon chain backbone is flexible. As the chain length increases, the randomness of the self-assembled molecules also begins to increase, causing the self-assembled molecular layer to gradually shift from an ordered arrangement to a random orientation, and the coverage of the self-assembled molecules also begins to decrease.
[0065] Table 1 Performance Comparison of Perovskite Solar Cells
[0066]
[0067] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.
Claims
1. A hole transport layer for a perovskite-crystalline silicon tandem solar cell, characterized in that, The hole transport layer material is composed of a self-assembled molecule doped with a phosphoryl group; the self-assembled molecule is [4-(7H-dibenzocarbazole-7-yl)butyl]phosphate, and the phosphoryl group is one or more of phosphorylated acetic acid, 3-phosphonopropionic acid or 4-phosphobutyric acid.
2. The hole transport layer for perovskite-crystalline silicon tandem solar cells according to claim 1, characterized in that, The mass ratio of self-assembled molecules to phosphoryl small molecules is 1:0.05 to 1:0.
3.
3. The hole transport layer for perovskite-crystalline silicon tandem solar cells according to claim 1, characterized in that, The hole transport layer is used in a perovskite-crystalline silicon tandem solar cell, which includes: a negative electrode, a crystalline silicon base cell, a hole transport layer, a perovskite absorber layer, an electron transport layer, a transparent conductive oxide layer, a positive electrode, and an antireflection layer stacked sequentially.
4. The method for preparing the hole transport layer for perovskite-crystalline silicon tandem solar cells according to claim 1, characterized in that, Includes the following steps: Step 1, Preparation of self-assembled molecular solution: Dissolve [4-(7H-dibenzocarbazole-7-yl)butyl]phosphoric acid in ethanol solvent to obtain self-assembled molecular solution A; Step 2, Preparation of phosphoryl small molecule solution: Add phosphorylacetic acid, 3-phosphonopropionic acid or 4-phosphobutyric acid powder to ethanol solvent to obtain phosphoryl small molecule solution B with the same concentration as self-assembled molecule solution A; Step 3: Preparation of doped self-assembled molecule solution: Mix self-assembled molecule solution A and phosphoryl small molecule solution B in a certain proportion and mix evenly to obtain doped self-assembled molecule solution; Step 4, Spin Coating and Annealing: The solution of doped self-assembled molecules is dropped onto the substrate surface and deposited by spin coating. After completion, it is placed on a hot stage for annealing to form a hole transport layer.
5. The method for preparing the hole transport layer for perovskite-crystalline silicon tandem solar cells according to claim 4, characterized in that, The concentrations of the self-assembled molecule solution A and the phosphoryl small molecule solution B are 0.2 mg / mL to 2 mg / mL.
6. The method for preparing the hole transport layer for perovskite-crystalline silicon tandem solar cells according to claim 4, characterized in that, The spin coating speed is 2500 rpm to 5000 rpm, and the spin coating time is 20 s to 40 s.
7. The method for preparing the hole transport layer for perovskite-crystalline silicon tandem solar cells according to claim 4, characterized in that, The annealing temperature is 90℃~120℃, and the annealing time is 8 min~15 min.