Hole transport layer solution with photoactive layer passivation and preparation and application thereof

Abstract

The application relates to a hole transport layer solution with light active layer passivation and a preparation method and application thereof, and the preparation method comprises the following steps: mixing a dopant with a hole transport layer base solution, so that the hole transport layer solution with high performance and light active layer passivation is obtained. Compared with the prior art, the application can realize p-type doping of the hole transport layer in an oxygen-free environment. More importantly, the reaction product generated in the doping process can be used as a passivation agent, spontaneously enters the perovskite layer from the hole transport layer, and passivates defects of the perovskite body and defects of upper and lower interfaces. The method further improves the photoelectric conversion efficiency of the perovskite solar cell, and improves the stability and repeatability of the device.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, and relates to a hole transport layer solution with photoactive layer passivation function, its preparation method and application. Background Technology

[0002] A solar cell is a device that directly converts light energy into electrical energy through photochemical reactions or the photovoltaic effect; it is also known as a photovoltaic cell or solar cell. Due to the rapid improvement in photoelectric performance and the wide range of raw material choices, perovskite solar cells have attracted considerable attention. A perovskite solar cell consists of a transparent conductive substrate, a hole transport layer, a perovskite active layer, an electron transport layer, a back electrode, and various interface modification layers. Furthermore, the main structures of perovskite solar cells include formal mesoporous structures, formal planar structures, and inverse planar structures. A formal mesoporous structure is: transparent conductive substrate / mesoporous electron transport layer / perovskite active layer / hole transport layer / back electrode; a formal planar structure is similar to a formal mesoporous structure, except that the mesoporous electron transport layer is replaced with a planar electron transport layer; the difference between the inverse planar structure and the formal planar structure lies in the relative positions of the electron and hole transport layers. After ten years of research, the certified efficiency of perovskite solar cells based on the formal structure has reached 25.7% (pore area approximately 0.1 cm²). 2 ).

[0003] However, as the aperture area of ​​perovskite solar cells increases, their efficiency decreases significantly, severely hindering their industrialization. To address this issue, past work has primarily focused on improving the uniformity of the functional layer. For example, improvements have been made to doctor blade coating, slot coating, inkjet printing, and the development of novel large-area thin-film fabrication methods such as the soft film method to fabricate high-quality perovskite active layers over large areas. Modification of the charge transport layer to improve its conductivity has also been implemented, thereby increasing its thickness to improve charge transport layer uniformity. In contrast, research on passivation technology for large-area perovskite active layers is limited and fraught with challenges: i) Perovskite is an organic-inorganic hybrid ionic crystal, making it difficult to adopt methods commonly used in silicon solar cells, such as plasma-enhanced chemical vapor deposition; ii) Solution spin coating, commonly used in laboratories, struggles to form uniform passivation layers over large areas; iii) The precision of large-scale equipment such as slot coating is insufficient for fabricating nanoscale passivation layers; and iv) Increasing the passivation layer thickness to improve uniformity can impede charge transport in the device.

[0004] Furthermore, for commercialization, perovskite solar cells must possess long-term operational stability. However, the instability issues arising from dopants in the hole transport layer of high-efficiency perovskite solar cells have not yet been well resolved. Currently, almost all high-efficiency perovskite solar cells use spiro-OMeTAD or PTAA as the hole transport layer. Both of these materials require doping with hygroscopic lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) in an oxygen-rich environment to achieve p-type doping and improve conductivity. This externally dependent oxidation process accelerates the accumulation of Li-TFSI in the hole transport layer and triggers the degradation of the perovskite layer through water absorption. Recent reports indicate that lithium ions from Li-TFSI can enter the perovskite layer and promote its decomposition, significantly reducing device stability and reproducibility. Summary of the Invention

[0005] The purpose of this invention is to provide a hole transport layer solution with photoactive layer passivation function, its preparation method and application, for realizing large-area, stable and efficient perovskite solar cells based on stable doping and uniform passivation.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for preparing a hole transport layer solution with photoactive layer passivation function, comprising:

[0008] Mixing the dopant solution with the hole transport layer base liquid yields a hole transport layer solution with photoactive layer passivation function.

[0009] The hole transport layer base fluid comprises hole transport layer material with a concentration of 10-72.3 mg / ml and 4-tert-butylpyridine with a concentration of 2-32.8 μL / ml.

[0010] Furthermore, the mass percentage of the dopant relative to the hole transport layer material is 1-20 wt%.

[0011] Further, the dopant includes one or more of the following: 1-ethyl-3-methylimidazoline bis(trifluoromethanesulfonyl)imide (EIm-TFSI), 1-butyl-3-methylimidazoline bis(trifluoromethanesulfonyl)imide, 1-allyl-3-methylimidazoline bis(trifluoromethanesulfonyl)imide, 1,2-dimethyl-3-propylimidazoline bis(trifluoromethanesulfonyl)imide, 1-hexyl-3-methylimidazoline bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylpyridine bis(trifluoromethanesulfonyl)imide, diethylmethyl-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide, 1-butyl-2,3-dimethylimidazoline bis(trifluoromethanesulfonyl)imide, and 1-propyl-3-methylimidazoline bis(trifluoromethanesulfonyl)imide;

[0012] The hole transport layer material includes one or more of the following: CuSCN, CuI, CuS, CuGaO2, MoS2, molybdenum oxide, copper phthalocyanine, copper-nickel composite oxide, nickel oxide, WO3, vanadium oxide, polymer of 3-hexylthiophene, polycarbazole-thiophene-benzothiadiazole-thiophene, 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (spiro-OMeTAD), and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA).

[0013] Furthermore, the solvent of the dopant solution is acetonitrile.

[0014] Furthermore, the solvent of the hole transport layer base fluid is chlorobenzene or toluene.

[0015] Furthermore, the mixing process of the dopant solution and the hole transport layer base liquid includes: thorough stirring.

[0016] A hole transport layer solution with photoactive layer passivation function is prepared by the method described above.

[0017] An application of a hole transport layer solution with photoactive layer passivation function includes using the hole transport layer solution to prepare a hole transport layer for a perovskite solar cell.

[0018] Furthermore, the method for preparing the hole transport layer includes: applying the hole transport layer solution onto the perovskite active layer using spin coating, doctor blade coating, slot coating, inkjet printing, or soft overlay deposition.

[0019] Furthermore, the perovskite solar cell comprises a transparent conductive substrate, an electron transport layer, a perovskite active layer, a hole transport layer, and a back electrode stacked sequentially.

[0020] The electron transport layer includes one or more of TiO2, SnO2, ZnO, SrTiO3, and BaSnO3;

[0021] The back electrode comprises one or more of gold, silver, copper, carbon, fluorine-doped tin oxide, and tin-doped indium oxide.

[0022] Compared with the prior art, the present invention has the following characteristics:

[0023] 1) This invention provides a large-area passivation technology for the photoactive layer of a perovskite solar cell, comprising: p-type doping of the hole transport layer by adding a dopant, with the reaction products generated during the doping process serving as a passivating agent; and during the fabrication of the perovskite solar cell, allowing the passivating agent to spontaneously enter the perovskite layer from the hole transport layer, passivating perovskite defects and defects at the upper and lower interfaces. Furthermore, compared to hydrophilic Li-TFSI, this invention can achieve p-type doping of the hole transport layer in an oxygen-free environment. Therefore, this invention can further improve the photoelectric conversion efficiency, stability, and reproducibility of perovskite solar cells.

[0024] 2) Based on the integrated doping and passivation technology provided by this invention, the fabrication process of perovskite solar cells can be simplified, achieving integrated fabrication of the hole transport layer and passivation layer. Pore area: 0.09 cm² 2 The perovskite solar cell can achieve a photoelectric conversion efficiency of over 24%. This is further improved when the aperture area is increased to 1 cm². 2 At that time, a photoelectric conversion efficiency of over 23% can be obtained, with a relative efficiency loss of less than 1.25%;

[0025] 3) Based on the stable and uniform doping method and uniform passivation of the perovskite active layer provided by this invention, perovskite solar cells can operate under AM1.5G sunlight (100mW cm⁻¹). -2 After running at maximum power point (MPP) for 1600 hours, it still retains more than 90% of its initial efficiency. Detailed Implementation

[0026] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0027] Example 1:

[0028] A perovskite solar cell with a large-area passivated photoactive layer is fabricated by the following steps:

[0029] S1: Fabrication of patterned transparent conductive substrate:

[0030] S1-1: A glass substrate with a fluorine-doped tin oxide conductive layer was etched using zinc powder and 6M hydrochloric acid for 15 seconds. It was then ultrasonically cleaned with deionized water, ethanol, acetone, and isopropanol for 15 minutes each. Subsequently, it was dried in dry air with nitrogen and subjected to ultraviolet ozone treatment. The ultraviolet light wavelength was 185 nm, the power was 2250 W, and the irradiation time was 20 minutes, resulting in a clean, patterned transparent conductive substrate with a fluorine-doped tin oxide conductive layer.

[0031] S2: Fabrication of the electron transport layer:

[0032] S2-1: A water dispersion of tin oxide nanoparticles (volume ratio of tin oxide nanoparticles to water is 1:9.5) was spin-coated onto a fluorine-doped tin oxide conductive layer at a speed of 3000 rpm for 30 s.

[0033] S2-2: Transfer to a heating plate and anneal at 150°C for 30 minutes. Then, perform ultraviolet ozone treatment with a wavelength of 185nm, a power of 2250W, and an irradiation time of 20 minutes. The resulting electron transport layer has a thickness of about 20nm and an average particle size of about 2nm for tin oxide nanoparticles.

[0034] S3: Preparation of the perovskite active layer:

[0035] S3-1: Transfer the substrate with the electron transport layer into a glove box filled with nitrogen;

[0036] S3-2: Using a mixture of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) as a solvent (V DMF :V DMSO =9:1), prepare a 1.5M lead iodide solution, and then spin-coat it onto the electron transport layer at a speed of 1500 rpm for 30 s to form a 500 nm lead iodide film.

[0037] S3-3: Prepare a mixed solution of isopropanol containing formamidine iodide (FAI), methylamine iodide (MAI), and methylamine chloride (MACl) (feed ratio of 90mg:13mg:9mg:1mL), and spin-coat it onto a lead iodide film at a speed of 1800rpm for 30s to obtain a 900nm mesophase film.

[0038] S3-4: The substrate with the mesophase film is placed in an air environment (ambient humidity of 30-35%RH) and annealed at 150℃ for 15 min to obtain a perovskite active layer with a thickness of about 850nm.

[0039] S4: Fabrication of the hole transport layer:

[0040] S4-1: Prepare a hole transport layer solution by mixing 72.3 mg of 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (spiro-OMeTAD), 4-tert-butylpyridine (tBP), and 1 mL of chlorobenzene.

[0041] S4-2: Mix EIm-TFSI with acetonitrile at a feed ratio of 231.65μL:1mL and prepare a passivation solution;

[0042] S4-3: In a nitrogen glove box, the hole transport layer solution and passivation solution were mixed according to the mass percentages of EIm-TFSI relative to spiro-OMeTAD of 3.5wt%, 10.5wt%, and 19.5wt%, respectively, with corresponding tBP addition amounts of 5.8μL, 17.6μL, and 32.8μL, respectively. After stirring for 24h, the hole transport layer solution doped with EIm-TFSI was obtained.

[0043] S4-4: In a nitrogen glove box, the EIm-TFSI doped hole transport layer solution was spin-coated onto the surface of the perovskite active layer at a speed of 3000 rpm for 30 s to obtain a hole transport layer with a thickness of about 150 nm.

[0044] S5: Fabrication of perovskite solar cells:

[0045] Using a vacuum evaporation apparatus, By evaporating an 80 nm gold electrode onto the hole transport layer at a certain speed, a perovskite solar cell was obtained, and its performance parameters are shown in Tables 1 and 2.

[0046] Table 1. Pore area (0.09 cm²) at different EIm-TFSI doping concentrations. 2 Perovskite solar cell performance parameters

[0047]

[0048] Table 2 Performance parameters of perovskite solar cells with different pore areas at 10.5 wt% EIm-TFSI doping concentration

[0049]

[0050] Where WF: work function; J SC Short-circuit current density; V OC Open-circuit voltage; FF: fill factor; Eff.: photoelectric conversion efficiency of the perovskite solar cell. These parameters of the perovskite solar cell are obtained through AM1.5G (100mW cm⁻¹)... -2 The current-voltage (JV) curves were obtained by measuring a solar simulator and a Keithley 2400 digital source meter using WacomDenso Co., Japan. The solar simulator was calibrated using a standard silicon reference cell. The voltage range measured by the JV curves was -0.2V to 1.2V. It is evident that the combined effect of doping and passivation is optimal at a doping concentration of 10.5wt%, achieving excellent charge transport and collection, resulting in the highest photoelectric conversion efficiency for the perovskite solar cell. Furthermore, for devices based on integrated doping and passivation technology, when the pore area increases from 0.09 cm², the JV curves show the best performance. 2 Expanded to 1.04cm 2When the relative efficiency loss of the device is less than 1.25%, it indicates that this method is beneficial for achieving uniform passivation of the active layer on a large area, thereby reducing the efficiency gap between large-area and small-area devices.

[0051] Example 2:

[0052] This embodiment is used to investigate the universality of dopant EIm-TFSI in large-area passivation of the photoactive layer of perovskite solar cells. The specific process includes:

[0053] In step S4: During the fabrication of the hole transport layer:

[0054] Experimental group: In a nitrogen glove box, 2.45 μL of EIm-TFSI solution (231.65 μL EIm-TFSI: 1 mL acetonitrile) was mixed with hole transport layer solution (10 mg PTAA + 2 μL tBP + 1 mL toluene) and stirred for 24 h to obtain EIm-TFSI doped hole transport layer solution.

[0055] Control group: In a nitrogen glove box, 2.45 μL of Li-TFSI solution (520 mg Li-TFSI: 1 mL acetonitrile) was mixed with a hole transport layer solution (10 mg PTAA + 4 μL tBP + 1 mL toluene) to obtain a Li-TFSI-doped hole transport layer solution. This solution was spin-coated onto the surface of the perovskite active layer at 3000 rpm for 30 s, followed by oxidation in an air-filled drying oven for 4 days to prepare the hole transport layer. The experimental conditions of this control group were the optimal experimental conditions described in the literature DOI:10.1126 / science.abc4417, and the test methods and conditions in this embodiment were the same as those in that literature.

[0056] The corresponding perovskite solar cells were prepared separately, and the rest of the preparation process was the same as in Example 1. The performance parameters are shown in Table 3.

[0057] Table 3. Pore area (1.04 cm²) under different dopant types 2 Perovskite solar cell performance parameters

[0058]

[0059] Where WF: work function; J SC Short-circuit current density; V OC : Open-circuit voltage; FF: Fill factor; Eff.: Photovoltaic conversion efficiency of perovskite solar cells.

[0060] Therefore, the large-area passivation technology of the photoactive layer described in this invention has universality in other hole transport layers. Furthermore, compared to Li-TFSI and oxygen doping, EIm-TFSI doped devices have V...OC The significant improvement demonstrates the excellent passivation effect of the passivating agent generated by the reaction between the dopant and the hole transport layer on the perovskite layer. This is because Li-TFSI, as a dopant, only acts as a dopant and can only oxidize spiro in air, without producing a passivating agent. In contrast, EIm-TFSI can both dop the hole transport layer and generate a passivating agent (EIM) through a redox reaction with the hole transport layer.

[0061] Example 3:

[0062] This embodiment investigates the designability and optimization potential of dopants in integrated doping and passivation technology. EIm-TFSI, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide were used as dopants to prepare a hole transport layer solution with photoactive layer passivation function. The specific process includes:

[0063] In step S4: During the fabrication of the hole transport layer:

[0064] S4-1: Prepare a hole transport layer solution by mixing 72.3 mg spiro-OMeTAD, 17.6 μL tBP, and 1 mL chlorobenzene.

[0065] S4-2: Mix the dopants shown in Table 4 with acetonitrile at a feed ratio of 231.65 μL: 1 mL and prepare the corresponding passivation solutions.

[0066] S4-3: In a nitrogen glove box, the hole transport layer solution and the passivation solution are mixed according to the mass percentage of the dopant relative to spiro-OMeTAD being 10.5wt%. After stirring for 24 hours, the corresponding doped hole transport layer solution is obtained.

[0067] S4-4: In a nitrogen-filled glove box, a hole transport layer solution doped with EIm-TFSI, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide was spin-coated onto the perovskite active layer at a speed of 3000 rpm for 30 s, resulting in a hole transport layer with a thickness of approximately 150 nm.

[0068] The corresponding perovskite solar cells were prepared separately, and the rest of the preparation process was the same as in Example 1. Their performance parameters are shown in Table 4.

[0069] Table 4. Pore area (0.09 cm²) under different dopants 2 Perovskite solar cell performance parameters

[0070]

[0071] Where WF: work function; J SC Short-circuit current density; V OC : Open-circuit voltage; FF: Fill factor; Eff.: Photovoltaic conversion efficiency of perovskite solar cells.

[0072] Therefore, this method can be used to design a variety of doped materials to achieve hole transport layer doping and perovskite active layer passivation, demonstrating designability and optimization potential.

[0073] Example 4:

[0074] This embodiment is used to investigate the effect of dopant EIm-TFSI on improving the stability of perovskite solar cells. The specific process includes:

[0075] In step S4: During the fabrication of the hole transport layer:

[0076] Experimental group: The mass percentage of EIm-TFSI and spiro-OMeTAD was 10.5 wt%.

[0077] Control group: 17.5 μL of Li-TFSI solution (520 mg Li-TFSI: 1 mL acetonitrile) was mixed with hole transport solution (72.3 mg spiro-OMeTAD + 28.8 μL tBP + 1 mL chlorobenzene) to obtain a Li-TFSI-doped hole transport layer solution. This solution was spin-coated onto the surface of the perovskite active layer at 3000 rpm for 30 s, followed by oxidation in an air-filled drying oven for 4 days to prepare the hole transport layer. The experimental conditions for this control group were the optimal experimental conditions described in the literature DOI: 10.1038 / s41566-021-00829-4. The test methods and conditions in this embodiment are the same as those in that literature.

[0078] The corresponding perovskite solar cells (pore area 1.04 cm²) were fabricated respectively. 2 The remaining preparation process is the same as in Example 1. EIm-TFSI and Li-TFSI doped perovskite solar cells were tested under AM1.5G sunlight (100mW / cm²). -2 After running at maximum power point (MPP) for 1600 hours, the initial efficiencies were maintained at 91% and 66%, respectively; this test was conducted on a solar cell photoresistance testing system (Bunkoukeiki, Japan).

[0079] Therefore, it can be seen that the large-area passivation technology of the photoactive layer in this invention can significantly improve the stability of perovskite solar cells. Compared with Li-TFSI doping, the device operating stability of EIm-TFSI doping is significantly improved, which shows that the doping mode of EIm-TFSI dopant on the hole transport layer is more stable than that of Li-TFSI. Furthermore, the passivation effect of the passivator generated by EIm-TFSI doping on the hole transport layer is also beneficial to the stability of perovskite solar cells.

[0080] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a hole transport layer solution having a passivation effect on a photoactive layer, characterized by, The method comprises: mixing the dopant solution with a hole transport layer base solution to obtain a hole transport layer solution with passivation of a photoactive layer; the hole transport layer base solution comprises a hole transport layer material with a concentration of 10-72.3 mg / ml and 4-tert-butylpyridine with a concentration of 2-32.8 μL / ml; the mass percentage of the dopant relative to the hole transport layer material is 1-20 wt%; the dopant is 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide; and the hole transport layer material is 2,2',7,7'-tetrakis[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene.

2. The method for preparing a hole transport layer solution with photoactive layer passivation function according to claim 1, characterized in that, the solvent of the dopant solution is acetonitrile.

3. The solution preparation method of a hole transport layer with photoactive layer passivation according to claim 1, wherein, the solvent of the hole transport layer base solution is chlorobenzene or toluene.

4. The method for preparing a hole transport layer solution with photoactive layer passivation function according to claim 1, characterized in that, the mixing process of the dopant solution and the hole transport layer base solution comprises sufficient stirring.

5. A hole transport layer solution having photoactive layer passivation, characterized by, prepared by the method of any one of claims 1-4.

6. Use of a hole transport layer solution having a passivation effect on a photoactive layer according to claim 5, characterized in that the hole transport layer solution is used for preparing a hole transport layer of a perovskite solar cell.

7. Use of a hole transport layer solution with photoactive layer passivation according to claim 6, characterized in that, the preparation method of the hole transport layer comprises: using a spin coating method, a doctor blade method, a slot coating method, an inkjet printing method or a soft overlay deposition method to coat the hole transport layer solution on a perovskite active layer to obtain the hole transport layer.

8. Use of a hole transport layer solution having photoactive layer passivation according to claim 6, characterized in that, the perovskite solar cell comprises a transparent conductive substrate, an electron transport layer, a perovskite active layer, a hole transport layer and a back electrode which are sequentially stacked; the electron transport layer comprises one or more of TiO2, SnO2, ZnO, SrTiO3 and BaSnO3; the back electrode comprises one or more of gold, silver, copper, carbon, fluorine-doped tin oxide and tin-doped indium oxide.

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