A hole transport layer with a cross-linked network composite structure and a perovskite solar cell and a preparation method thereof

Abstract

This invention discloses a hole transport layer with a cross-linked network composite structure, a perovskite solar cell, and its fabrication method. An inverse perovskite solar cell with a hole transport layer having a cross-linked network composite structure is fabricated by spin coating. The hole transport layer of the cross-linked network composite structure includes an inorganic metal oxide layer adjacent to a conductive glass layer, a cross-linked network modification layer adjacent to a perovskite light-emitting layer, and a self-assembled monolayer located between the two. The cross-linked network modification layer is a cross-linked network formed by free radical cross-linking monomers under the initiation of an initiator. The free radical monomers have two polymerizable carbon-carbon double bonds, which can initiate the formation of a cross-linked network, thus improving interfacial contact and stability. The ester carbonyl groups retained after polymerization provide sites for interaction with unsaturated lead ions at the perovskite buried interface, enabling the modification layer to possess both network stabilization and coordination passivation functions, supporting improvements in the device's photoelectric conversion efficiency and light-illuminated stability.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic technology and relates to the improvement and optimization of perovskite solar cells. Specifically, it relates to a hole transport layer with a cross-linked network composite structure achieved by adding free radical cross-linking molecules and a perovskite solar cell, as well as the preparation method thereof. Background Technology

[0002] Perovskite solar cells offer advantages such as high photoelectric conversion efficiency and flexible fabrication processes. Among them, the inverted structure has attracted widespread attention due to its low-temperature processing and stacking compatibility. NiO x Inorganic metal oxides are commonly used hole transport materials, but their surface defects and interfacial chemical reactions may affect the film quality, charge extraction, and device stability of perovskites.

[0003] Spin-coating a self-assembled monolayer (SAM) between a hole transport layer constructed from inorganic metal oxides and a perovskite layer allows for surface defect passivation and interfacial energy level modulation through the interaction of anchoring groups on the substrate surface. However, SAM formation is influenced by factors such as substrate surface condition, molecular aggregation, and deposition conditions, potentially leading to insufficient coverage and uneven local distribution, which in turn affects the uniform formation of the subsequent perovskite film and interfacial contact. Furthermore, under long-term light exposure, thermal stress, and subsequent solution processing, some self-assembled molecules may rearrange or desorb, weakening the stability of the interfacial contact; their passivation effect on the unsaturated lead sites at the perovskite buried interface is also limited by the type and spatial distribution of molecular functional groups.

[0004] To address the aforementioned issues, some studies have proposed co-assembly molecular strategies and molecular engineering strategies. The co-assembly molecular strategy improves the coverage, molecular arrangement, and interfacial properties of SAM by co-depositing molecules with different functions. However, differences in the adsorption capacity, solubility, and intermolecular interactions of different components can lead to competitive adsorption or uneven local component distribution during co-deposition, making the modification effect highly sensitive to component ratios and film formation conditions. Furthermore, SAM assembly and the introduction of functional components occur in the same deposition process, making it difficult to separately adjust their formation conditions and interfacial distribution. The molecular engineering strategy enhances intermolecular connectivity and interfacial stability by modifying the structure of the conjugated core, linker chains, or anchoring groups of self-assembled molecules, or by introducing crosslinkable groups. While this can improve the performance of specific systems to some extent, the formation of crosslinked structures does not necessarily guarantee sufficient exposure of effective passivation sites at the perovskite side interface; a balance must still be struck between structural stability and passivation of buried defects.

[0005] Therefore, there is an urgent need to provide an interface modification scheme that is suitable for existing SAM materials and has both network construction capability and coordination passivation function. While improving the uniformity and stability of interface contact, it provides passivation for the coordination unsaturated lead sites of the perovskite buried interface, thereby reducing interface-related losses and taking into account the photoelectric conversion efficiency and operational stability of perovskite solar cells. Summary of the Invention

[0006] To address the issues of uneven interfacial contact in self-assembled monolayers and the difficulty in simultaneously achieving interfacial stability and passivation of buried defects, this invention proposes a hole transport layer with a cross-linked network composite structure and a perovskite solar cell, along with its fabrication method. By first constructing a self-assembled monolayer on the surface of an inorganic metal oxide, and then introducing cross-linked monomers for in-situ polymerization, the self-assembly process and network modification are implemented step-by-step. The cross-linked network is constructed using the bifunctional structure of the cross-linked monomers, and the ester carbonyl groups retained after polymerization provide sites for interaction with coordinating unsaturated lead ions at the perovskite buried interface. This improves interfacial contact and simultaneously achieves defect passivation without requiring additional cross-linking functionalization of the self-assembled monolayers, thereby enhancing the device's photoelectric conversion efficiency and light stability.

[0007] In a first aspect, the present invention provides a hole transport layer with a cross-linked network composite structure, the hole transport layer comprising an inorganic metal oxide layer, a self-assembled monolayer, and a cross-linked network modification layer. The cross-linked network modification layer is a cross-linked network formed by free radical cross-linking monomers under the initiation of an initiator. The free radical cross-linking monomers have ester carbonyl groups and carbon-carbon double bonds.

[0008] The free radical monomer has two polymerizable carbon-carbon double bonds, which can initiate the formation of a cross-linked network, which is beneficial to improve the interfacial contact and its stability. The ester carbonyl group retained after polymerization can provide a site for interaction with the unsaturated lead ions coordinated at the perovskite buried interface, so that the modified layer has both network stabilization and coordination passivation functions.

[0009] Preferably, the free radical crosslinking monomer is any one of ethylene glycol dimethacrylate (EGDMA), diethylene glycol dimethacrylate (DGDMA), and trimethylolpropane triacrylate (TMTA). The molecular structure of EGDMA is shown in formula (I):

[0010]

[0011] Preferably, the initiator is azobisisobutyronitrile (AIBN), with the molecular structure shown in formula (II):

[0012]

[0013] Preferably, the mass-to-volume ratio of the initiator to the free radical crosslinking monomer is 1:20~30 mg / mL.

[0014] Preferably, the inorganic metal oxide layer is made of NiO. x Any one of CuO2, CuSCN, and V2O5.

[0015] Preferably, the material of the self-assembled monolayer is any one of Ph-4PACZ, Me-4PACZ, 4PADCB, and 4PABCZ.

[0016] Preferably, the inorganic metal oxide layer has a thickness of 10-15 nm, the self-assembled monolayer has a thickness of 3-5 nm, and the cross-linked network modification layer has a thickness of 5-8 nm.

[0017] Secondly, the present invention provides a method for preparing a cross-linked network composite hole transport layer, wherein a self-assembled monomolecular material is dissolved in an organic solvent to prepare a self-assembled monomolecular solution, which is then spin-coated onto the surface of an inorganic metal oxide layer to form a self-assembled monomolecular layer; then, a cross-linking monomer is mixed with an organic solvent and an initiator is added to prepare a cross-linking modification solution, which is then spin-coated onto the surface of the self-assembled monomolecular layer, where the free radical cross-linking monomer forms a cross-linked network under the initiation of the initiator, thereby performing interface modification.

[0018] Preferably, the organic solvent is an ethanol solution.

[0019] Preferably, the volume ratio of the crosslinking monomer to the organic solvent is 1:20, and the concentration of the crosslinking modified solution is 1~1.5 mg / mL.

[0020] Preferably, the concentration of the self-assembled monomolecular solution is 0.5~1 mg / mL.

[0021] Preferably, a self-assembled monomolecular solution is spin-coated onto the surface of the inorganic metal oxide layer at 3000 rpm for 30 s, and a crosslinking modification solution is spin-coated onto the surface of the self-assembled monomolecular layer at 3000 rpm for 30 s.

[0022] Preferably, the solvent is filtered using a 0.22 μm pore size needle filter before the preparation of the mixed solution.

[0023] Thirdly, the present invention provides a perovskite solar cell with a hole transport layer having a cross-linked network composite structure. The perovskite solar cell comprises, from bottom to top, a conductive glass layer, an inorganic metal oxide layer, a self-assembled monolayer, a cross-linked network modification layer, a perovskite light-emitting layer, an electron transport layer, a hole blocking layer, and a metal electrode layer.

[0024] Preferably, the conductive glass layer is ITO or FTO, and the perovskite layer is made of Cs. 0.05 FA 0.95PbI3, the electron transport layer is made of PCBM or C. 60 The hole blocking layer is made of BCP, and the electrode is made of Ag metal.

[0025] The present invention has the following beneficial effects:

[0026] 1. A sequential preparation method is adopted, which involves first constructing a self-assembled monolayer and then introducing EGDMA for in-situ polymerization. This allows the self-assembly process and network modification to be carried out separately, facilitating independent adjustment of the corresponding preparation conditions. This method eliminates the need for additional cross-linking functionalization of SAM, enabling the formation of network modification on the surface of existing self-assembled monolayers, thus providing a way to improve its interfacial contact with perovskites.

[0027] 2. The cross-linked network modification layer provides supplementary modification to the formed SAM surface, helping to improve the localized uneven contact between SAM and perovskite and maintain the stability of the buried interface contact. Simultaneously, the coordination sites in the modification layer can interact with the coordination-unsaturated Pb at the perovskite buried interface. 2+ Interactions passivate related defects, reducing their adverse effects on interface charge extraction. By combining the stabilizing effect of the network structure with interface chemical passivation, the quality of buried contacts is improved, while also reducing defect-related carrier trapping and nonradiative recombination losses, thus supporting the improvement of device photoelectric conversion efficiency and illumination stability.

[0028] 3. Self-assembled monolayers are responsible for constructing selective contacts of holes on the surface of the inorganic metal oxide layer, while the EGDMA polymer network is used for subsequent buried interface modification. The two complement each other functionally. Compared to the comparative example using only self-assembled monolayers, the perovskite buried interface in this embodiment exhibits a denser and more uniform morphology. While maintaining a relatively stable short-circuit current density, the device shows improved fill factor and photoelectric conversion efficiency, and demonstrates higher efficiency retention under the same photo-aging conditions, achieving a balance between device output performance and photo-stability. Attached Figure Description

[0029] Figure 1 This is a structural diagram of the perovskite solar cell with a cross-linked network composite hole transport layer prepared in Example 1;

[0030] Figure 2 These are the JV curves of the solar cells prepared in Example 1 and Comparative Example 1;

[0031] Figure 3 These are SEM images of the buried interface of solar cells prepared in Example 1 and Comparative Example 1;

[0032] Figure 4 These are the stability test results of the solar cells prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0033] The present invention will be further explained below with reference to the accompanying drawings; it should be understood that the scope of protection of the present invention is not limited thereto.

[0034] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. The reagents, materials, and instruments used are commercially available unless otherwise specified.

[0035] Example 1

[0036] This embodiment provides a perovskite solar cell with a hole transport layer having a cross-linked network composite structure, such as... Figure 1 As shown, from bottom to top, the structure comprises a conductive glass layer, an inorganic metal oxide layer, a self-assembled monolayer, a self-crosslinking network modification layer, a perovskite light-emitting layer, an electron transport layer, a hole-blocking layer, and a metal electrode layer. The specific fabrication steps are as follows:

[0037] Step 1: The conductive glass substrate is ultrasonically cleaned sequentially in glass cleaning solution, deionized water, acetone solution, and anhydrous ethanol for 20 minutes each, and then rapidly dried in an oven. It is then treated in oxygen plasma for 15 minutes before use.

[0038] Step 2, NiO x Dissolve in deionized water to prepare an inorganic metal oxide solution with a concentration of 15 mg / mL. Spin-coat the solution onto a conductive glass substrate treated with oxygen plasma at 3000 rpm for 30 s. Then anneal in air at 150 °C for 15 min and cool to room temperature to form an inorganic metal oxide layer.

[0039] Step 3: Dissolve the self-assembled monomolecular material Ph-4PACZ in ethanol to prepare a self-assembled monomolecular solution with a concentration of 0.5 mg / mL. Spin-coat the solution onto the surface of the inorganic metal oxide layer at 3000 rpm for 30 seconds, and anneal at 100°C for 10 minutes to form a self-assembled monomolecular layer.

[0040] Step 4: Mix the crosslinking monomer EGDMA with an ethanol solution at a volume ratio of 1:20, then add the initiator AIBN to prepare a crosslinking modification solution with a concentration of 1.25 mg / mL. Spin-coat the solution onto the surface of the self-assembled monolayer at 3000 rpm for 30 seconds, anneal at 100°C for 10 minutes, and then cool to form a crosslinked network modification layer.

[0041] Step 5: Dissolve FAI in isopropanol to prepare a solution with a concentration of 1 mg / mL, spin-coat it on the surface of the hole transport layer at 3000 rpm for 30 seconds, and then anneal it at 100℃ for 10 minutes.

[0042] Step 6: Weigh the perovskite component Cs according to the stoichiometric ratio. 0.05 FA 0.95 PbI3 was added with appropriate amounts of PbCl2 and MACl as additives to prepare a perovskite precursor. Then, it was dissolved in a mixed solvent of DMF and DMSO with a volume ratio of 4:1 to prepare a precursor solution with a concentration of 1.6M.

[0043] On the hole transport layer, 60 μL of precursor solution was statically added dropwise, followed by spin coating at 1000 rpm for 10 s, and then at 5000 rpm for 35 s. 25 s after the start of the second spin coating stage, 200 μL of anisole was added dropwise as an antisolvent. Immediately after both spin coating steps, the mixture was transferred to a hot plate and annealed at 100 °C for 20 min to form a perovskite luminescent layer.

[0044] Step 7: Dissolve PDADI in isopropanol and chlorobenzene at a volume ratio of 1:2 to prepare a solution with a concentration of 1 mg / mL. Spin-coat the solution onto the perovskite luminescent layer at 5000 rpm for 30 seconds, and then anneal at 100°C for 10 minutes for passivation and subsequent deposition treatment.

[0045] Step 8: Sequentially deposit a 40 nm thick layer of C on the passivated perovskite light-emitting layer surface at a rate of 0.01 nm / s. 60 An 8 nm thick BCP hole-blocking layer was deposited at a rate of 0.01 nm / s, and a 100 nm thick Ag electrode was deposited at a rate of 0.05 nm / s. The vacuum level of the deposition process was less than 1 × 10⁻⁶. -4 bar, to obtain the perovskite solar cell.

[0046] Example 2

[0047] This embodiment provides a method for preparing a perovskite solar cell with a cross-linked network composite hole transport layer. Based on Example 1, CuO2 is used to prepare an inorganic metal oxide solution, and Me-4PACZ is used to prepare a self-assembled monomolecule solution.

[0048] Example 3

[0049] This embodiment provides a method for preparing a perovskite solar cell with a cross-linked network composite hole transport layer. Based on Example 1, an inorganic metal oxide solution is prepared using V2O5, and a cross-linking modification solution with a concentration of 1 mg / mL is prepared using diethylene glycol dimethacrylate (DGDMA) and azobisisobutyronitrile (AIBN).

[0050] Example 4

[0051] This embodiment provides a method for preparing a perovskite solar cell with a cross-linked network composite hole transport layer. Based on Example 3, a self-assembled monomolecular solution is prepared using 4PADCB.

[0052] Example 5

[0053] This embodiment provides a method for preparing a perovskite solar cell with a cross-linked network composite hole transport layer. Based on Example 2, a cross-linking modification solution with a concentration of 1.5 mg / mL is prepared using trimethylolpropane triacrylate (TMTA) and azobisisobutyronitrile (AIBN).

[0054] Comparative Example 1

[0055] Based on Example 1, this comparative example prepares a perovskite solar cell with interface modification through self-assembled monomolecules as a comparison. From bottom to top, it includes a conductive glass layer, an inorganic metal oxide layer, a self-assembled monomolecule layer, a perovskite light-emitting layer, an electron transport layer, a hole blocking layer, and a metal electrode layer.

[0056] The JV curves of the perovskite solar cells prepared in Example 1 and Comparative Example 1 were tested respectively, and the results are as follows: Figure 2 As shown, the open-circuit voltage (V) of the perovskite solar cell prepared in Comparative Example 1 is... oc The voltage is 1.168 V, and the short-circuit current (J) is 1.168 V. sc The value is 24.07 mA·cm. -2 The fill factor (FF) is 75.27%, and the final power conversion efficiency (PCE) is 21.17%. The perovskite solar cell prepared in Example 1 has an open-circuit voltage (V0). oc The voltage is 1.18 V, and the short-circuit current (J) is 1.18 V. sc The value is 24.33 mA·cm. -2 The fill factor (FF) was 82.67%, and the final power conversion efficiency (PCE) was 23.75%. Compared to Comparative Example 1, the short-circuit current of Example 1 did not change significantly, indicating that although the introduction of the cross-linked network modification layer slightly increased the thickness of the hole transport layer, it did not cause additional optical absorption. Simultaneously, due to the dual chemical modification of the single-molecule assembled material and the cross-linked network, defects at the perovskite under-interface were effectively passivated, non-radiative recombination was reduced, and the open-circuit voltage and power conversion efficiency of the device were also improved. SEM images of the buried interface of the perovskite solar cells prepared in Example 1 and Comparative Example 1 are shown below. Figure 3 As shown, in Example 1 with added crosslinking network modification, the morphology of the perovskite buried interface was significantly improved compared to Comparative Example 1, and the interface was more dense and uniform.

[0057] Stability tests were conducted on unencapsulated solar cells under simulated sunlight in a nitrogen atmosphere at 25°C. The results are as follows: Figure 4 As shown, after 800 hours of light aging, the photoelectric conversion efficiency of Comparative Example 1 was only 72.57% of the original efficiency; while that of Example 1 remained at 96.55% after 800 hours of light aging. These results indicate that, under the same testing conditions, introducing a cross-linked network modification layer helps to slow down the decay of the device's photoelectric conversion efficiency and improve the device's light stability.

Claims

1. A hole transport layer with a cross-linked network composite structure, characterized in that: The hole transport layer comprises an inorganic metal oxide layer, a self-assembled monolayer, and a cross-linked network modification layer; the cross-linked network modification layer is a cross-linked network formed by free radical cross-linking monomers under the initiation of an initiator; the free radical cross-linking monomers have polymerizable carbon-carbon double bonds and ester carbonyl groups.

2. The hole transport layer of the cross-linked network composite structure as described in claim 1, characterized in that: The free radical crosslinking monomer is any one of ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and trimethylolpropane triacrylate; the initiator is azobisisobutyronitrile.

3. The hole transport layer of the cross-linked network composite structure as described in claim 1, characterized in that: The material of the inorganic metal oxide layer is NiO. x Any one of CuO2, CuSCN, and V2O5.

4. The hole transport layer of the cross-linked network composite structure as described in claim 1, characterized in that: The material of the self-assembled monolayer is any one of Ph-4PACZ, Me-4PACZ, 4PADCB, and 4PABCZ.

5. The hole transport layer of the cross-linked network composite structure as described in claim 1, characterized in that: The inorganic metal oxide layer has a thickness of 10-15 nm, the self-assembled monolayer has a thickness of 3-5 nm, and the cross-linked network modification layer has a thickness of 5-8 nm.

6. A method for preparing a cross-linked network composite hole transport layer, characterized in that: A self-assembled monomolecular material is dissolved in an organic solvent to prepare a self-assembled monomolecular solution, which is then spin-coated onto the surface of an inorganic metal oxide layer to form a self-assembled monomolecular layer. Next, a crosslinking monomer is mixed with an organic solvent and an initiator is added to prepare a crosslinking modification solution, which is then spin-coated onto the surface of the self-assembled monomolecular layer. The free radical crosslinking monomers form a crosslinked network under the initiation of the initiator, and interface modification is performed to obtain a hole transport layer with a crosslinked network composite structure as described in any one of claims 1 to 5.

7. The method for preparing a cross-linked network composite hole transport layer as described in claim 6, characterized in that: The organic solvent is an ethanol solution; the volume ratio of the crosslinking monomer to the organic solvent is 1:20, and the concentration of the crosslinking modified solution is 1~1.5 mg / mL.

8. The method for preparing a cross-linked network composite hole transport layer as described in claim 6, characterized in that: The solvent was filtered using a 0.22 μm pore size needle filter before the mixed solution was prepared.

9. The method for preparing a cross-linked network composite hole transport layer as described in claim 6, characterized in that: A self-assembled monomolecular solution was spin-coated at 3000 rpm for 30 s on the surface of the inorganic metal oxide layer, and a crosslinking modification solution was spin-coated at 3000 rpm for 30 s on the surface of the self-assembled monomolecular layer.

10. A perovskite solar cell with a hole transport layer having a cross-linked network composite structure, the perovskite solar cell comprising, from bottom to top, a conductive glass layer, a hole transport layer with a cross-linked network composite structure as described in any one of claims 1 to 5, a perovskite light-emitting layer, an electron transport layer, a hole blocking layer, and a metal electrode layer.

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