A preparation method of a perovskite solar cell based on a mixed ionic liquid additive

Abstract

The application relates to a preparation method of a perovskite solar cell based on a mixed ionic liquid additive, and relates to the technical field of solar cells. The cell structure comprises, from bottom to top, a transparent conductive substrate, a double hole transport layer, a perovskite light absorption layer, an interface modification layer, an electron transport layer, a buffer layer and a metal electrode. The application provides a novel mixed ionic liquid additive for the above-mentioned cell, which comprises imidazole acetate and 1-butyl-3-methyl imidazole tetrafluoroborate. By introducing the additive into a perovskite precursor solution, the interaction between cations and the perovskite Pb-I framework is enhanced through the pi-pi interaction between imidazole cations and 1-butyl-3-methyl imidazole cations, and the formation of an adverse intermediate phase in the perovskite crystallization process is effectively inhibited. Therefore, a single crystallization route from an NMP+PbI2 intermediate phase to alpha-perovskite is realized. The method reduces perovskite body phase defects and improves the crystallization quality of alpha-perovskite, and further significantly improves the photoelectric conversion efficiency of the solar cell.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar cells, and particularly relates to a mixed ionic liquid additive, a preparation method of the mixed ionic liquid additive for synergistically passivating a wide-bandgap perovskite solar cell. BACKGROUND

[0002] In the past decade, the field of perovskite solar cells (PSCs) has made remarkable progress, with power conversion efficiency (PCE) being pushed to a new level. Wide-bandgap perovskite materials can be used as top cells in tandem cells to improve the utilization of solar spectrum and further improve the photoelectric conversion efficiency. However, due to the characteristics of perovskite materials, a large number of defects will inevitably be formed at the grain boundaries and surfaces during the film formation process of multi-component perovskite. In addition, the preparation methods of most high-efficiency PSCs reported at present are limited to laboratory-scale spin coating method. In order to promote the transformation of PSCs to commercial applications, it has become an important task to develop scalable deposition technology.

[0003] Blade coating has been proved to be a low-cost and scalable manufacturing technology, and some progress has been made in the manufacture of PSCs devices. However, the inherent fluid dynamics complexity in the blade coating preparation process poses a major challenge to effectively control the nucleation and crystallization of perovskite, resulting in device efficiency usually lower than that prepared by spin coating method. Therefore, further research is needed to develop effective strategies to control the crystallization kinetics of wide-bandgap perovskite during the coating process.

[0004] In order to overcome the above problems, a large number of passivation strategies have been reported. The introduction of non-volatile additives with suitable functional groups not only helps to accurately regulate the perovskite nucleation and crystallization process, but also effectively alleviates the perovskite defects. Many materials, such as polymers, organic salts, and ionic liquids, are often used as additives to improve the efficiency and stability of perovskite devices. Ionic liquids have low vapor pressure and excellent thermal stability, and can effectively regulate the crystallization process from perovskite precursor solution to film formation. However, there is limited research on the use of ionic liquids to control the crystallization kinetics of perovskite during the coating deposition process.

[0005] In summary, the problems existing in the preparation of organic-inorganic hybrid wide-bandgap perovskite solar cells based on blade coating method can be summarized as follows: 1) It is difficult to effectively control the nucleation and crystallization of perovskite during the coating process. 2) The defect density of perovskite thin film prepared by blade coating method is still high. 3) There is limited research on ionic liquid materials for passivating the crystallization process of perovskite prepared by blade coating method. SUMMARY

[0006] The present application aims to overcome the above-mentioned deficiencies in the prior art and provide a preparation method of perovskite solar cell based on mixed ionic liquid additive.

[0007] To achieve the above-mentioned object, the present application provides the following technical solutions.

[0008] The present application provides a preparation method of a perovskite solar cell with a mixed ionic liquid additive, the cell has a P-I-N structure and comprises, from bottom to top, a transparent conductive substrate, a hole transport layer, a perovskite light absorption layer, an interface modification layer, an electron transport layer, a buffer layer and a metal electrode; the perovskite solar cell has a band gap of 1.6-1.72 eV.

[0009] The perovskite light absorption layer satisfies the following conditions simultaneously:

[0010] The perovskite light absorption layer is an organic-inorganic hybrid multi-element halogen mixed perovskite.

[0011] The perovskite light absorption layer has a thickness of 500 nm-1 μm.

[0012] The additive material is imidazole acetate and 1-butyl-3-methylimidazole tetrafluoroborate, and the chemical formula is shown in formula 1 and formula 2.

[0013]

[0014]

[0015] The additive passivates the perovskite light absorption layer by being introduced into a perovskite precursor solution.

[0016] In some embodiments, the transparent conductive substrate is selected from one of FTO conductive glass and ITO conductive glass.

[0017] In some embodiments, the material of the hole transport layer is selected from one or more of a self-assembled monolayer, P3CT-N, NiO x an organic or inorganic hole transport material;

[0018] The self-assembled monolayer comprises one or more of (2-(9H-carbazol-9-yl)ethyl)phosphonic acid, (2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl)phosphonic acid, (4-(3,6-dimethyl-9H-carbazol-9-yl)butyl)phosphonic acid and (2-(7H-dibenzo-carbazol-7-yl)ethyl)phosphonic acid self-assembled monolayer.

[0019] In some embodiments, the interface modification layer comprises one or more of PEAI, MAI, bis(2-hydroxyethyl)dimethylammonium chloride and choline chloride.

[0020] In some embodiments, the material of the electron transport layer (5) is selected from one of PCBM, C 60 60B.

[0021] In some embodiments, the material of the buffer layer is selected from one of BCP, SnO2.

[0022] In some embodiments, the metal electrode satisfies the following conditions simultaneously:

[0023] The metal electrode is a metal electrode prepared by a thermal evaporation process;

[0024] The thickness of the metal electrode is 50-120 nm.

[0025] In some embodiments, the metal electrode is preferably Ag, Cu, Au as the metal electrode.

[0026] In some embodiments, the preparation method of the perovskite light absorption layer is a one-step doctor blade coating method, an ionic liquid additive including imidazole acetate and 1-butyl-3-methylimidazolium tetrafluoroborate is introduced into a perovskite precursor solution to passivate a perovskite phase, a perovskite absorption layer wet film is prepared by using a one-step doctor blade coating method, and annealing is performed. The perovskite light absorption layer is obtained.

[0027] In some embodiments, the preparation method of the additive includes:

[0028] The imidazole acetate and 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid are mixed with the perovskite precursor solution;

[0029] The solvent in the perovskite precursor solution is one or more of dimethylformamide, methylpyrrolidone, and dimethyl sulfoxide;

[0030] The solute in the perovskite precursor solution is one or more of CsI, MAI, FAI, PbI2, and PbBr2.

[0031] In some embodiments, the doctor blade coating operation is performed under a nitrogen purge with a pressure of 0.15-0.2 MPa.

[0032] In some embodiments, the annealing operation is performed at an annealing temperature of 100-150°C for an annealing time of 20-30 min.

[0033] Further, the application provides an application of a perovskite light absorption layer prepared by the above method. The perovskite light absorption layer is suitable for a perovskite-based stacked solar cell, and at least includes the following structural devices:

[0034] 1) inorganic perovskite / perovskite stacked solar cell;

[0035] 2) inorganic perovskite / crystalline silicon stacked solar cell;

[0036] 3) Inorganic perovskite / copper indium gallium selenide stacked solar cell.

[0037] Advantages and positive effects of the present application:

[0038] 1. The preparation method of the perovskite solar cell based on mixed ionic liquid additive disclosed by the present application, by adding imidazole acetate and 1-butyl-3-methyl imidazole tetrafluoroborate two kinds of ionic liquid into the perovskite precursor solution, the nucleation and growth of perovskite crystal are controlled, so as to improve the quality of perovskite thin film.

[0039] 2. The method disclosed by the present application enhances the interaction between cations and perovskite Pb-I framework by utilizing the π-π interaction between imidazole cations and 1-butyl-3-methyl imidazole cations, reduces the disorder degree of Pb-I structure, and effectively inhibits the formation of adverse intermediate phase in the perovskite crystallization process. This method effectively eliminates the occurrence of stacking defects in the conversion process of δ-perovskite intermediate to α-perovskite, so as to ensure that α-perovskite has lower defect density and excellent photoelectric properties. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 The structure schematic diagram of the perovskite solar cell described in Example 1; in the figure: 1 is a transparent conductive substrate, 2 is a hole transport layer, 3 is a perovskite light absorption layer, 4 is an interface modification layer, 5 is an electron transport layer, 6 is a buffer layer, and 7 is a metal electrode;

[0041] Figure 2 The J-V curve of the perovskite solar cell described in Example 1;

[0042] Figure 3 The J-V curve of the perovskite solar cell described in Example 2;

[0043] Figure 4 The J-V curve of the perovskite solar cell described in Comparative Example 1;

[0044] Figure 5 The SEM diagram of the perovskite light absorption layer described in Comparative Example 1, Examples 1 and 2;

[0045] Figure 6 The XRD diagram of the perovskite light absorption layer corresponding to Examples 1 and 2 and Comparative Example 1; DETAILED DESCRIPTION

[0046] The technical solutions of the present application are described in further detail below in combination with the drawings and specific examples. The following examples are provided to better further understand the present application and are not limited to the best mode of the present application, and do not limit the content and scope of protection of the present application. If the specific experimental steps or conditions are not specified in the examples, the operation or conditions can be carried out according to the conventional experimental steps described in the literature in the art. If the reagents or instruments used are not specified by the manufacturer, they are all conventional reagent products that can be obtained by purchase on the market.

[0047] The present application provides a perovskite solar cell based on a mixed ionic liquid additive, which is a P-I-N structure, and comprises, from bottom to top, a transparent conductive substrate (1), a hole transport layer (2), a perovskite light absorption layer (3), an interface modification layer (4), an electron transport layer (5), a buffer layer (6), and a metal electrode (7); wherein the thickness of the perovskite light absorption layer (3) is 500 nm-1 μm, and the perovskite light absorption layer (3) is an organic-inorganic hybrid multi-element halogen mixed perovskite.

[0048] The additive is imidazole acetate and 1-butyl-3-methylimidazole tetrafluoroborate, which passivates the perovskite phase by being introduced into the perovskite precursor solution. The chemical formula of imidazole acetate and 1-butyl-3-methylimidazole tetrafluoroborate is shown as formula 1 and formula 2:

[0049]

[0050] Example 1

[0051] The P-I-N type perovskite solar cell provided in this example has a band gap of about 1.68 eV, and the structure is as shown in Figure 1 from bottom to top, comprising: a transparent conductive substrate, NiO x (HTL), P3CT-N (HTL), a perovskite light absorption layer, BDAC (interface modification layer), PCBM (ETL), BCP (buffer layer), and a silver electrode.

[0052] The P-I-N type perovskite solar cell of this example is prepared by a one-step doctor blade method, comprising the following steps:

[0053] Step 1, transparent conductive substrate pretreatment: the ITO conductive glass is sequentially ultrasonically cleaned with a detergent, deionized water, acetone and isopropanol, dried with nitrogen, and treated with ultraviolet ozone for 15-20 min.

[0054] Step 2, preparation of the hole transport layer: (1) spin-coating NiO x(1) The solution is used as a hole transport layer; (2) Anneal at 130℃ for 10 min; (3) Transfer to N2 glove box and spin-coat P3CT-N on NiOx surface as a double hole transport layer; (4) Anneal at 100℃ for 10 min.

[0055] Step 3, Preparation of perovskite light-absorbing layer: (1) Preparation of 1.6M Cs x FA 1-x Pb(I y Br 1-y (2) Dissolve imidazole acetate in the perovskite precursor solution; (3) Prepare a perovskite wet film by one-step coating method using the perovskite precursor solution obtained in step (2); (4) Anneal the obtained wet film at 130°C for 30 min and cool it to room temperature to obtain the perovskite light absorption layer.

[0056] Step 5, Prepare the interface modification layer: Spin-coat the perovskite surface with BDAC solution as the interface modification layer.

[0057] Step 6, Prepare the electron transport layer: Prepare a PCBM layer on the surface of the interface modification layer as the electron transport layer.

[0058] Step 7, Prepare a buffer layer: Prepare a BCP layer as a buffer layer on the surface of the electron transport layer.

[0059] Step 8, Prepare the metal electrode: Prepare a silver metal electrode on the surface of the buffer layer.

[0060] Step 9, Photovoltaic performance testing: The effective area of ​​the perovskite solar cell device prepared by the above method is 0.0755 cm². 2 At 100mW / cm 2 Measurements were taken under illumination (AM 1.5G), with a scanning range from 1.3V to 0V and a scanning step size of 0.02V.

[0061] The JV characteristic curves of the obtained perovskite solar cells are as follows: Figure 2 As shown, by Figure 2 It is known that the open-circuit voltage of the perovskite solar cell is 1.17V, the fill factor is 79.71%, and the short-circuit current density is 19.68mA / cm². 2 The photoelectric conversion efficiency is 18.40%.

[0062] Example 2

[0063] The PIN-type perovskite solar cell provided in this embodiment has a band gap of approximately 1.68 eV, and its structure is as follows: Figure 1 As shown, from bottom to top, it includes: a transparent conductive substrate, NiO x(HTL), P3CT-N (HTL), perovskite light absorption layer, BDAC (interface modification layer), PCBM (ETL), BCP (buffer layer), silver electrode.

[0064] The P-I-N perovskite solar cell of the present embodiment is prepared by one-step doctor blade method, comprising the following steps:

[0065] Step 1, transparent conductive substrate pretreatment: the ITO conductive glass is ultrasonically cleaned with detergent, deionized water, acetone and isopropanol in turn, dried with nitrogen, and treated with ultraviolet ozone for 15-20 min.

[0066] Step 2, preparation of hole transport layer: (1) spin-coating NiO x solution as hole transport layer on the surface of ITO; (2) annealing at 130℃ for 10 min; (3) transferring to N2 glove box and spin-coating P3CT-N as double hole transport layer on the surface of NiOx; (4) annealing at 100℃ for 10 min.

[0067] Step 3, preparation of perovskite light absorption layer: (1) preparing 1.6M Cs x FA 1-x Pb(I y Br 1-y )3 perovskite precursor solution; (2) dissolving imidazole acetate and 1-butyl-3-methylimidazolium tetrafluoroborate in the perovskite precursor solution; (3) preparing perovskite wet film by one-step doctor blade method from the perovskite precursor solution obtained in step (2); (4) annealing the obtained wet film at 130℃ for 30 min rapidly, and cooling to room temperature, to obtain perovskite light absorption layer.

[0068] Step 5, preparation of interface modification layer: spin-coating BDAC solution as interface modification layer on the surface of perovskite.

[0069] Step 6, preparation of electron transport layer: preparing PCBM layer as electron transport layer on the surface of interface modification layer.

[0070] Step 7, preparation of buffer layer: preparing BCP layer as buffer layer on the surface of electron transport layer.

[0071] Step 8, preparation of metal electrode: preparing metal silver electrode on the surface of buffer layer.

[0072] Step 9, photovoltaic performance test: the effective area of the perovskite solar cell device prepared by the above method is 0.0755cm 2 , and the photovoltaic performance is measured under 100mW / cm 2 light intensity (AM 1.5G), with scanning interval from 1.3V to 0V and scanning step of 0.02V.

[0073] The J-V characteristic curve of the obtained perovskite solar cell is shown in Figure 3 As shown in Figure 3 , the open circuit voltage of the perovskite solar cell is 1.21V, the fill factor is 84.89%, the short circuit current density is 19.44mA / cm 2 , and the photoelectric conversion efficiency is 20.12%.

[0074] Comparative Example 1

[0075] The provided P-I-N type perovskite solar cell has a band gap of about 1.68eV, and the structure is shown in Figure 1 from bottom to top, including: a transparent conductive substrate, NiO x (HTL), P3CT-N(HTL), a perovskite light absorption layer, BDAC(an interface modification layer), PCBM(ETL), BCP(a buffer layer), and a silver electrode.

[0076] The P-I-N type perovskite solar cell of the present embodiment is prepared by one-step doctor blade method, including the following steps:

[0077] Step 1, transparent conductive substrate pretreatment: the ITO conductive glass is sequentially ultrasonically cleaned with detergent, deionized water, acetone and isopropanol, dried with nitrogen, and treated with ultraviolet ozone for 15-20min.

[0078] Step 2, preparation of hole transport layer: (1) spin-coating NiO x solution on the surface of ITO as a hole transport layer; (2) annealing at 130℃ for 10min; (3) transferring to a N2 glove box to spin-coat P3CT-N on the surface of NiOx as a double hole transport layer; (4) annealing at 100℃ for 10min.

[0079] Step 3, preparation of perovskite light absorption layer: (1) preparation of 1.6M Cs x FA 1-x Pb(I y Br 1-y )3 perovskite precursor solution; (2) preparation of a perovskite wet film by one-step doctor blade method using the perovskite precursor solution obtained in step (1); (3) rapid annealing of the obtained wet film at 130℃ for 30min, and cooling to room temperature to obtain a perovskite light absorption layer.

[0080] Step 5, preparation of interface modification layer: spin-coating BDAC solution on the surface of the perovskite as an interface modification layer.

[0081] Step 6, preparation of electron transport layer: preparation of a PCBM layer on the surface of the interface modification layer as an electron transport layer.

[0082] Step 7, preparation of buffer layer: preparation of a BCP layer on the surface of the electron transport layer as a buffer layer.

[0083] Step 8, Prepare the metal electrode: Prepare a silver metal electrode on the surface of the buffer layer.

[0084] Step 9, Photovoltaic performance testing: The effective area of ​​the perovskite solar cell device prepared by the above method is 0.0755 cm². 2 At 100mW / cm 2 Measurements were taken under illumination (AM 1.5G), with a scanning range from 1.3V to 0V and a scanning step size of 0.02V.

[0085] The JV characteristic curves of the obtained perovskite solar cells are as follows: Figure 4 As shown, by Figure 4 It can be seen that the open-circuit voltage of the perovskite solar cell is 1.11V, the fill factor is 73.81%, and the short-circuit current density is 19.52mA / cm². 2 The photoelectric conversion efficiency is 16.03%.

[0086] The obtained SEM images of the perovskite solar thin films described in Comparative Example 1, Examples 1 and 2 are as follows: Figure 5 As shown, the synergistic passivation of the two ionic liquid additives significantly improved the surface morphology of the perovskite film.

[0087] The XRD patterns of the perovskite thin films obtained in Example 1 and Comparative Example 1 are as follows: Figure 6 As shown, the synergistic passivation of the two ionic liquid additives significantly improved the crystallinity of the perovskite film.

[0088] In summary, this invention enhances the interaction between the cation and the perovskite Pb-I framework by utilizing the π-π interaction between the imidazole cation and the 1-butyl-3-methylimidazolium cation, thereby reducing the disorder of the Pb-I structure and effectively suppressing the formation of undesirable intermediate phases during perovskite crystallization. This method effectively eliminates the occurrence of stacking defects during the transformation of δ-perovskite intermediates to α-perovskite, thus ensuring that α-perovskite possesses a low defect density and excellent photoelectric properties. The method is simple to operate, easy to implement, and has good application prospects.

[0089] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A perovskite solar cell based on a mixed ionic liquid additive, the cell having a PIN structure, comprising, from bottom to top, a transparent conductive substrate (1), a hole transport layer (2), a perovskite light absorption layer (3), an interface modification layer (4), an electron transport layer (5), a buffer layer (6), and a metal electrode (7). The perovskite light-absorbing layer (3) therein simultaneously satisfies the following conditions: The perovskite light-absorbing layer (3) is an organic-inorganic hybrid multi-halogen mixed perovskite; The thickness of the perovskite light-absorbing layer (3) is 500 nm-1 μm; The additives are imidazole acetate and 1-butyl-3-methylimidazolium tetrafluoroborate. By introducing them into the perovskite precursor solution, the perovskite bulk phase is passivated. The π-π interaction between the imidazole cation and the 1-butyl-3-methylimidazolium cation enhances the interaction between the cation and the perovskite Pb-I framework, reduces the disorder of the Pb-I structure, and inhibits the formation of unfavorable intermediate phases during the perovskite crystallization process.

2. The perovskite solar cell as described in claim 1, characterized in that, The transparent conductive substrate (1) is selected from FTO conductive glass and ITO conductive glass.

3. The perovskite solar cell as described in claim 1, characterized in that, The hole transport layer (2) is made of a material selected from self-assembled monolayers, P3CT-N, and NiO. x One or more of them; The self-assembled monolayer includes one or more of the following: (2-(9H-carbazole-9-yl)ethyl)phosphonic acid, (2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl)phosphonic acid, (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid, and (2-(7H-dibenzocarbazole-7-yl)ethyl)phosphonic acid self-assembled monolayer.

4. The perovskite solar cell as described in claim 1, characterized in that, The electron transport layer (5) is made of methyl [6,6]phenyl C61-butyrate PC. 61 BM, Fullerene C 60 One of them.

5. The perovskite solar cell as described in claim 1, characterized in that, The interface modification layer (4) includes one or more of PEAI, MAI, bis(2-hydroxyethyl)dimethylammonium chloride (BDAC), and choline chloride.

6. The perovskite solar cell as described in claim 1, characterized in that, The material of the buffer layer (6) is selected from either BCP or SnO2.

7. The perovskite solar cell as described in claim 1, characterized in that, The metal electrode (7) simultaneously satisfies the following conditions: The metal electrode (7) is a metal electrode prepared by a thermal evaporation process; The thickness of the metal electrode (7) is 50~120 nm.

8. A method for preparing a perovskite solar cell according to any one of claims 1-7, characterized in that, The perovskite light-absorbing layer is prepared by a one-step coating method, which involves mixing ionic liquid additives, including imidazole acetate and 1-butyl-3-methylimidazole tetrafluoroborate, and introducing them into the perovskite precursor solution to passivate the perovskite bulk phase. The perovskite light-absorbing layer wet film is prepared by the one-step coating method and then annealed to obtain the perovskite light-absorbing layer. The preparation methods of the additives include: Imidazole acetate and 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquids were mixed with a perovskite precursor solution; The solvent in the perovskite precursor solution is one or more of dimethylformamide, methylpyrrolidone, and dimethyl sulfoxide. The solute in the perovskite precursor solution is one or more of CsI, MAI, FAI, PbI2, and PbBr2.

9. The method for preparing a perovskite solar cell as described in claim 8, characterized in that, During the scraping operation, the purging nitrogen pressure is set to 0.15~0.2 MPa; The annealing operation is performed at a temperature of 100~150 ℃ for a time of 20~30 min.

10. The application of the perovskite light-absorbing layer prepared by the method of claim 8 or 9, characterized in that, Suitable for perovskite-based tandem solar cells, including the following structural devices: Inorganic perovskite / perovskite tandem solar cells.

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