Self-assembled monomolecular layer hole transport network and construction method thereof

Abstract

According to the self-assembled monomolecular layer hole transport network and the construction method thereof, a cross-linking unit is introduced into a self-assembled hole transport molecule, and an anchoring unit is anchored to a self-assembled monomolecular layer of a substrate, so that a chemical reaction with a cross-linking agent can be realized in situ, and a hand-in-hand stable self-assembled monomolecular layer hole transport network is constructed; the problems that a self-assembly monomolecular hole transport layer is unstable under severe aging conditions such as light, heat and humidity, the ordered self-assembly microstructure of the hole transport layer is easy to damage and the like can be effectively solved, and the stability of a photovoltaic cell is further improved.

Description

Technical Field

[0001] The invention belongs to the field of photovoltaic technology, and specifically relates to the construction of a self-assembled monolayer hole transport network. The constructed hole transport network can be applied to the fields of perovskite solar cells, organic solar cells, and stacked solar cells. Background Art

[0002] In recent years, self-assembled hole transport molecules have received extensive attention and research in the field of solar cells due to their advantages such as high hole selectivity and hole transfer rate. Self-assembled single molecules are adsorbed on the substrate surface through anchoring groups, and then form an orderly arranged ultra-thin hole transport layer on the substrate to achieve efficient hole transport. However, compared with traditional polymer and metal oxide hole transport materials, the ultra-thin self-assembled single molecule hole transport layer is unstable under harsh aging conditions such as light, heat and humidity, and the orderly self-assembled microstructure of the hole transport layer is easily destroyed, which in turn causes the solar cell efficiency to decay, resulting in poor stability of photovoltaic devices. Summary of the invention

[0003] In view of the shortcomings of the background technology, the present invention provides a self-assembled monolayer hole transport network and a method for constructing the same. The present invention introduces a cross-linking unit into the self-assembled hole transport molecule to achieve in-situ "hand-in-hand" cross-linking of the self-assembled hole transport molecule and the cross-linking agent, thereby forming a self-assembled monolayer hole transport network, which can effectively solve the problem of instability of the self-assembled hole transport molecule layer, so as to develop a stable solar cell.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] A self-assembled monolayer hole transport network is constructed by in-situ cross-linking a self-assembled monolayer material capable of in-situ cross-linking with a cross-linking agent; the structure of the hole transport network is:

[0006]

[0007] Among them, A is a hole transport functional unit, B is a connecting unit, C is an anchoring unit, and D is a cross-linking unit. The structure composed of A, B, C and D is a self-assembled monomolecular material that can be cross-linked in situ; CL is a cross-linking agent;

[0008] The self-assembled monolayer anchored to the substrate by the anchoring unit can realize chemical reaction with the cross-linker CL in situ to construct a "hand-in-hand" stable hole transport network to improve the performance of photovoltaic cells.

[0009] Furthermore, the hole transport functional unit A is a P-type conjugated organic hole transport unit, and specifically one of the following structures can be selected:

[0010]

[0011] Among them, (A-1*)-(A-10*) are derivatives corresponding to (A-1)-(A-10), and R in A-6 and A-6* can be selected from O, S, Se, etc.

[0012] Furthermore, in the (A-1*)-(A-10*) derivatives of the hole transport functional unit, the insertion sites are marked in the structure, and one or more units such as amino, cyano, nitro, thiol, halogen (F, Cl, Br), methyl, methoxy, trifluoromethyl, ethyl or ethoxy can be introduced at a single site or a structural symmetric position.

[0013] Furthermore, the linking unit B is a flexible alkyl chain or a conjugated organic unit, and specifically, one of the following structures (B-1) to (B-6) or a combination structure formed by (B-1) and one or more of (B-2) to (B-6) can be selected:

[0014]

[0015] Among them, n=1~10.

[0016] Furthermore, the anchor unit C is a unit that can undergo a condensation reaction with a hydroxyl group, and specifically can be selected from one of the following structures:

[0017]

[0018] Furthermore, the cross-linking unit D is a functional unit that can be cross-linked or added with an unsaturated hydrocarbon, and specifically can be selected from one of the following structures:

[0019]

[0020] In (D-1) and (D-5), n=1 to 10.

[0021] Furthermore, the cross-linking unit D is connected to the hole transport functional unit A via a single site or a structurally symmetrical site in the insertion sites marked in (A-1*)-(A-10*).

[0022] Furthermore, the in-situ cross-linkable self-assembled monomolecular material is one of the following structures:

[0023]

[0024]

[0025] Furthermore, the crosslinking agent CL is a unit containing unsaturated hydrocarbons, and specifically can be selected from one of the following structures:

[0026]

[0027] Among them, n=1~10.

[0028] A method for constructing a self-assembled monolayer hole transport network, comprising:

[0029] Anchoring the in-situ cross-linkable self-assembled monomolecular material on the substrate by immersion or spin coating;

[0030] A cross-linking agent is added to realize an in-situ chemical reaction between the self-assembled monomolecular material that can be in-situ cross-linked and the cross-linking agent in-situ by heat or light, so as to construct a self-assembled monolayer hole transport network.

[0031] A method for constructing a self-assembled monolayer hole transport network is achieved by two-step spin coating and thermal crosslinking, specifically comprising the following steps:

[0032] (1) adding a self-assembled monomolecular material capable of in situ cross-linking into an organic solvent to prepare a self-assembled monomolecular solution with a concentration of 0.1 to 3 mg / mL;

[0033] Dissolving 0.5 to 5 mol% of a cross-linking agent in an organic solvent to obtain a cross-linking agent solution;

[0034] (2) spin coating the self-assembled monomolecular solution on the substrate at a speed of 3000 to 5000 rpm for 10 to 50 seconds, and annealing at 80 to 150° C. for 5 to 30 minutes;

[0035] (3) adding the crosslinking agent solution dropwise onto the substrate treated in step (2), spin coating at a speed of 3000 to 5000 rpm for 10 to 50 seconds, and then annealing at 80 to 150° C. for 10 to 60 minutes to achieve a reaction between the self-assembled monomolecular material capable of in-situ crosslinking and the crosslinking agent;

[0036] (4) adding an organic solvent to the substrate treated in step (3), and spin coating the substrate at a speed of 2000 to 5000 rpm for 20 to 60 seconds to clean unreacted cross-linking agent, and then annealing the substrate at 80 to 150° C. for 5 to 30 minutes to construct a self-assembled monolayer hole transport network.

[0037] A method for constructing a self-assembled monolayer hole transport network is implemented by thermal crosslinking using an immersion method, and specifically comprises the following steps:

[0038] (1) adding a self-assembled monomolecular material capable of in situ cross-linking into an organic solvent to prepare a self-assembled monomolecular solution with a concentration of 0.5 to 5 mg / mL;

[0039] Dissolving 0.5 to 5 mol% of a cross-linking agent in an organic solvent to obtain a cross-linking agent solution;

[0040] (2) immersing the substrate in a self-assembled monomolecular solution and placing it in an air environment for 5 to 10 hours; removing the substrate and rinsing it with an organic solvent to remove residual self-assembled monomolecules that are not firmly bound;

[0041] (3) immersing the substrate treated in step (2) in a crosslinking agent solution, adjusting the pH of the solution to 7 to 9, and heating the solution at 80 to 150° C. for 5 to 60 minutes to promote the crosslinking reaction;

[0042] (4) After the reaction is completed, the substrate is removed and rinsed with an organic solvent, and then annealed at 80 to 150° C. for 5 to 30 minutes to construct a self-assembled monolayer hole transport network.

[0043] The present invention also provides the application of the self-assembled monolayer hole transport network in photovoltaic cells, especially perovskite solar cells.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention provides a self-assembled monolayer hole transport network. The self-assembled monolayer anchored to the substrate by an anchoring unit can realize a chemical reaction with a cross-linking agent in situ to construct a "hand-in-hand" stable hole transport network. The self-assembled monolayer hole transport layer is unstable under harsh aging conditions such as light, heat and humidity, and the orderly self-assembled microscopic morphology of the hole transport layer is easily destroyed, thereby improving the stability of the photovoltaic cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0047] Figure 1 The invention provides a self-assembled monomolecular material and a cross-linking agent material structure capable of in-situ cross-linking.

[0048] Figure 2 It is a schematic diagram of the interlayer structure of the self-assembled monolayer hole transport network of the present invention.

[0049] Figure 3 The following are the changes of the solution in Example 1 over time under heating conditions.

[0050] Figure 4The hole transport layer film prepared in the comparative example and example 4 is applied to the long-term stability of solar cells. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] In the present invention, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0053] In the present invention, the molecular structure examples of the self-assembled monomolecular materials and cross-linking agent materials that can be cross-linked in situ are only part of the molecular structure examples of the present invention, rather than all the molecular structure examples. Based on the molecular structure examples in the present invention, all other molecular structure examples obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0054] In the present invention, the insertion site is marked on the hole transport functional unit A of the in-situ cross-linkable self-assembled monomolecular material, but the derivative group is not limited to the structural symmetric position. The derivative group can be introduced at any site on the hole transport functional unit.

[0055] In the present invention, the insertion site is marked on the hole transport functional unit A of the in-situ cross-linkable self-assembled monomolecular material, but the cross-linking unit is not limited to being introduced at a symmetrical position of the structure, and the cross-linking unit can be introduced at any site on the hole transport functional unit.

[0056] The "combination" and "combination structure" used in the present invention include all suitable combinations of any two, any three or more items in the listed groups.

[0057] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments.

[0058] Comparative Example

[0059] An application of a hole transport layer prepared from a self-assembled monomolecular material in a perovskite solar cell specifically comprises the following steps:

[0060] The glass / ITO substrates were ultrasonically cleaned with detergent, deionized water, acetone, and isopropanol for 20 min in sequence. Then, the glass / ITO substrates were dried in a nitrogen stream, treated with oxygen plasma for 10 min, and finally transferred to a nitrogen-filled glove box before use.

[0061] The in-situ cross-linkable self-assembled monomolecular material (A-5-1) was dissolved in ethanol at a concentration of 0.2 mg / mL. The in-situ cross-linkable self-assembled monomolecular material (A-5-1) solution was spin-coated on an ITO substrate at a speed of 4000 rpm for 30 seconds and annealed at 100° C. for 5 minutes to construct a self-assembled hole transport layer.

[0062] According to the perovskite composition (MA 0.02 Cs 0.05 FA 0.93 )Pb(I 0.97 Br 0.01 Cl 0.02 )3. Prepare a 1.4M perovskite solution (the solvent is a mixed solvent of DMF and DMSO, and the volume ratio of DMF to DMSO is 85:15). The perovskite solution is coated on the self-assembled monomolecular hole transport layer film by spin coating, with a rotation speed of 2000 rpm for 40 seconds and 6000 rpm for 10 seconds to form a perovskite film. In the last 10 seconds of the rotation, 300uL of anisole anti-solvent is added, and then annealed at 100°C for 40 minutes.

[0063] After cooling, a 20 mg / ml PCBM chlorobenzene solution was spin-coated on the substrate at 1500 rpm for 35 seconds, and then annealed at 100°C for 10 minutes. BCP IPA solution (0.5 mg / ml) was spin-coated on the substrate at 4000 rpm for 30 seconds. Finally, a silver electrode was deposited on the top using a resistance evaporation vacuum coater to complete the battery preparation.

[0064] Example 1

[0065] A method for verifying the cross-linking of the self-assembled monomolecular material capable of in-situ cross-linking and a cross-linking agent according to the present invention, specifically comprising the following steps:

[0066] 0.3 mg of in situ cross-linkable self-assembled monomolecular material (A-5-1) and 0.4 mg of cross-linker material (CL-20) were dissolved in 1 mL of DMF, stirred until clear, the solution pH was adjusted to 8 with TEA, and then heated at 80°C for 30 min to achieve in situ cross-linking.

[0067] Figure 3 This is the change of the solution of Example 1 over time under heating conditions. It can be observed that the solution becomes turbid and precipitates are produced, verifying that a cross-linking reaction occurs.

[0068] Example 2

[0069] A two-step spin coating method for preparing the self-assembled monolayer hole transport network of the present invention by thermal crosslinking specifically comprises the following steps:

[0070] The glass / ITO substrate was ultrasonically cleaned with detergent, deionized water, acetone and isopropanol for 20 minutes in sequence. Then, the glass / ITO substrate was dried in an oven at 100°C and then treated with oxygen plasma for 10 minutes to activate the ITO surface. The in-situ cross-linkable self-assembled monomolecular material (A-5-1) was dissolved in ethanol at a concentration of 0.3 mg / mL. The cross-linker material (CL-20) and TEA were dissolved in another ethanol solution (PH=8) according to 2 mol% of the in-situ cross-linkable self-assembled monomolecular material. The in-situ cross-linkable self-assembled monolayer hole transport network was prepared by a two-step process. The self-assembled monomolecular material (A-5-1) solution was spin-coated on the ITO substrate at a speed of 4000 rpm for 30 seconds and annealed at 100°C for 5 minutes. Then the cross-linker material solution was dripped on the ITO substrate anchored with the in-situ cross-linkable self-assembled monomolecular material and spin-coated at 4000 rpm for 30 seconds. Then, the self-assembled monolayer was annealed at 150°C for 10 minutes to achieve the reaction between the in-situ cross-linkable self-assembled monolayer material and the cross-linking agent. Finally, ethanol was spin-coated at 4000 rpm for 30 seconds to clean the unreacted cross-linking agent, etc., and then annealed at 100°C for 5 minutes to construct a self-assembled monolayer hole transport network.

[0071] Example 3

[0072] A method for preparing the self-assembled monolayer hole transport network of the present invention by thermal crosslinking by immersion method specifically comprises the following steps:

[0073] The glass / ITO substrate was ultrasonically cleaned with detergent, deionized water, acetone and isopropanol for 20 minutes in sequence. Then, the glass / ITO substrate was dried in an oven at 100°C and then treated with oxygen plasma for 10 minutes to activate the ITO surface. The in-situ cross-linkable self-assembled monolayer material (A-5-1) was dissolved in a toluene solution at a concentration of 2 mg / mL. Then, the ITO substrate was immersed in the toluene solution and placed in ambient air for 10 hours. The ITO substrate was removed and rinsed with toluene to remove the residual self-assembled monolayers that were not firmly bound to the ITO surface. The substrate was then immersed in a toluene solution containing a cross-linker material (CL-20) and TEA (PH = 8) and heated at 150°C to promote the cross-linking reaction. After the reaction was completed, the substrate was removed, washed with toluene solvent and annealed at 100°C for 5 minutes to construct a self-assembled monolayer hole transport network.

[0074] Example 4

[0075] An application of a hole transport network prepared by an in-situ cross-linkable self-assembled monomolecular material in a perovskite solar cell specifically comprises the following steps:

[0076] The glass / ITO substrates were ultrasonically cleaned with detergent, deionized water, acetone, and isopropanol for 20 min in sequence. Then, the glass / ITO substrates were dried in a nitrogen stream, treated with oxygen plasma for 10 min, and finally transferred to a nitrogen-filled glove box before use.

[0077] The in situ cross-linkable self-assembled monomolecular material (A-5-1) was dissolved in ethanol at a concentration of 0.2 mg / mL. The cross-linker material (CL-20) was dissolved in another ethanol solution at 0.5 mol% of the in situ cross-linkable self-assembled monomolecular material and the solution pH was adjusted to 8 with TEA. The self-assembled monolayer hole transport network was prepared by a two-step process. The in situ cross-linkable self-assembled monomolecular material (A-5-1) solution was spin-coated on an ITO substrate at a speed of 4000 rpm for 30 seconds and annealed at 100°C for 5 minutes. Then the cross-linker (CL-20) solution was dripped onto the ITO substrate anchored with the in situ cross-linkable self-assembled monomolecule, spin-coated at 3000 rpm for 30 seconds, and then annealed at 150°C for 10 minutes to achieve the in situ cross-linking reaction between the self-assembled monomolecule and the cross-linker. Finally, ethanol was spin-coated at 4000 rpm for 30 seconds to clean the unreacted cross-linking agent, etc., and then annealed at 100°C for 5 minutes to construct a self-assembled monolayer hole transport network.

[0078] According to the perovskite composition (MA 0.02 Cs 0.05 FA 0.93 )Pb(I 0.97 Br 0.01 Cl 0.02 )3. Prepare a 1.4M perovskite solution (the solvent is a mixed solvent of DMF and DMSO, and the volume ratio of DMF to DMSO is 85:15). The perovskite solution is coated on the self-assembled monolayer hole transport network film by spin coating, with a rotation speed of 2000 rpm for 40 seconds and 6000 rpm for 10 seconds to form a perovskite film. During the last 10 seconds of the rotation, 300uL of anisole anti-solvent is added, and then annealed at 100°C for 40 minutes.

[0079] After cooling, a 20 mg / ml PCBM chlorobenzene solution was spin-coated on the substrate at 1500 rpm for 35 seconds, and then annealed at 100°C for 10 minutes. BCP IPA solution (0.5 mg / ml) was spin-coated on the substrate at 4000 rpm for 30 seconds. Finally, a silver electrode was deposited on the top using a resistance evaporation vacuum coater to complete the battery preparation.

[0080] Figure 4To test the long-term stability of the hole transport layer films prepared in the comparative example and Example 4 for application in solar cells, the two were placed in a nitrogen environment and operated continuously for 1000 hours under a standard simulated sunlight and 65°C. The efficiency of the perovskite solar cell prepared by the self-assembled monolayer hole transport network constructed by (A-5-1) based on Example 4 only decayed by 1% after 1000 hours of continuous operation, while the efficiency of the cell based on the uncrosslinked (A-5-1) decayed by 15%. This strongly proves that the strategy of constructing efficient and stable photovoltaic cells with the self-assembled monolayer hole transport network proposed in the present invention is feasible.

[0081] The above description is only an example of the present invention and is not intended to limit the scope of protection of the present invention. Any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A self-assembled monolayer hole transport network, characterized in that: The structure of the hole transport network is: Among them, A is a hole transport functional unit, B is a connecting unit, C is an anchoring unit, D is a cross-linking unit; CL is a cross-linking agent; The cross-linking unit is a functional unit that can be cross-linked or added with unsaturated hydrocarbons, the cross-linking agent is a unit containing unsaturated hydrocarbons, the hole transport functional unit is a P-type conjugated organic hole transport unit, the connecting unit is a flexible alkyl chain or a conjugated organic unit, and the anchoring unit is a unit that can undergo a condensation reaction with a hydroxyl group.

2. The self-assembled monolayer hole transport network according to claim 1, characterized in that: The crosslinking unit D is one of the following structures: Among them, n=1~10.

3. The self-assembled monolayer hole transport network according to claim 1, characterized in that: The cross-linking agent CL is one of the following structures: Among them, n=1~10.

4. The self-assembled monolayer hole transport network according to claim 1, characterized in that: The hole transport functional unit is one of the following structures: wherein R in A-6 and A-6* is selected from O, S or Se; The cross-linking unit is connected to the hole transport functional unit through a single site or a structurally symmetrical site among the insertion sites marked in (A-1*) to (A-10*).

5. The self-assembled monolayer hole transport network according to claim 1, characterized in that: In the (A-1*)-(A-10*) derivatives of the hole transport functional unit, one or more of amino, cyano, nitro, thiol, halogen, methyl, methoxy, trifluoromethyl, ethyl or ethoxy groups are introduced at a single site or a structurally symmetrical position.

6. The self-assembled monolayer hole transport network according to claim 1, characterized in that: The linking unit B is one of the following structures (B-1) to (B-6), or a combination of (B-1) and one or more of (B-2) to (B-6): Wherein, n = 1 to 10; The anchoring unit C is one of the following structures:

7. The self-assembled monolayer hole transport network according to claim 1, characterized in that: The self-assembled monomolecular material capable of in-situ cross-linking is one of the following structures:

8. A method for constructing a self-assembled monolayer hole transport network, characterized in that: include: Anchoring the in-situ cross-linkable self-assembled monomolecular material to the substrate by immersion or spin coating; A cross-linking agent is added to realize an in-situ chemical reaction between the in-situ cross-linkable self-assembled monomolecular material and the cross-linking agent by heat or light to construct a self-assembled monolayer hole transport network.

9. The method for constructing a self-assembled monolayer hole transport network according to claim 8, characterized in that: Thermal crosslinking is achieved using a two-step spin coating method, including the following steps: (1) adding a self-assembled monomolecular material capable of in situ cross-linking into an organic solvent to prepare a self-assembled monomolecular solution with a concentration of 0.1 to 3 mg / mL; Dissolving 0.5 to 5 mol% of a cross-linking agent in an organic solvent to obtain a cross-linking agent solution; (2) spin coating the self-assembled monomolecular solution on the substrate at a speed of 3000 to 5000 rpm for 10 to 50 seconds, and annealing at 80 to 150° C. for 5 to 30 minutes; (3) adding the crosslinking agent solution dropwise onto the substrate treated in step (2), spin coating at a speed of 3000 to 5000 rpm for 10 to 50 seconds, and then annealing at 80 to 150° C. for 10 to 60 minutes to achieve a reaction between the self-assembled monomolecular material capable of in-situ crosslinking and the crosslinking agent; (4) adding an organic solvent to the substrate treated in step (3), and spin coating the substrate at a speed of 2000 to 5000 rpm for 20 to 60 seconds to clean the unreacted cross-linking agent, and then annealing the substrate at 80 to 150° C. for 5 to 30 minutes to construct a self-assembled monolayer hole transport network.

10. The method for constructing a self-assembled monolayer hole transport network according to claim 8, characterized in that: The thermal cross-linking is achieved by immersion method, including the following steps: (1) adding a self-assembled monomolecular material capable of in situ cross-linking into an organic solvent to prepare a self-assembled monomolecular solution with a concentration of 0.5 to 5 mg / mL; Dissolving 0.5 to 5 mol% of a crosslinking agent in an organic solvent to obtain a crosslinking agent solution; (2) immersing the substrate in a self-assembled monomolecule solution and placing it in an air environment for 5 to 10 hours; removing the substrate and rinsing it with an organic solvent to remove residual self-assembled monomolecules that are not firmly bound; (3) immersing the substrate treated in step (2) in a crosslinking agent solution, adjusting the pH of the solution to 7 to 9, and heating the solution at 80 to 150° C. for 5 to 60 minutes to promote the crosslinking reaction; (4) After the reaction is completed, the substrate is removed and rinsed with an organic solvent, and then annealed at 80 to 150° C. for 5 to 30 minutes to construct a self-assembled monolayer hole transport network.

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