Additive capable of improving thermal stability of perovskite battery and use method of additive

Abstract

The invention relates to an additive capable of improving the thermal stability of a perovskite battery. The additive comprises BMDP and DMIMBF6 in a molar ratio of 2: 1, and acetonitrile for completely dissolving BMDP and DMIMBF6. The invention further relates to a using method of the additive. The using method comprises the steps of preparing a perovskite precursor solution, preparing the additive, preparing a coating solution and coating. The additive can effectively slow down the crystallization rate, facilitates crystallization control, inhibits the condensation reaction of methylamine hydrochloride and formamidine hydriodate, and also promotes the uniform distribution of elements in the film, so that the high-quality perovskite film with oriented growth and large crystal grains is prepared, and the perovskite film has good thermal stability. The method is especially suitable for manufacturing large-area perovskite solar cells.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to an additive capable of improving the thermal stability of a perovskite cell and a method for using the additive. Background Art

[0002] The working principle of perovskite solar cells is: when sunlight shines on the perovskite light-absorbing layer, it will stimulate electron-hole pairs. Electrons flow from the light-absorbing layer through the electron transport layer to the electrode, forming a current, thereby generating electrical energy. Holes flow through the hole transport layer to the other electrode, forming a current loop.

[0003] Organic-inorganic hybrid perovskite solar cells are a new type of solar cell that combines organic and inorganic components. The core material of this type of cell is a perovskite semiconductor, which usually has a structure of ABX3, where A is an organic cation (such as MA + or FA + ), B is an inorganic cation (such as Pb 2+ ), X is a halogen anion (such as I - or Br - ). This combination gives perovskite materials unique optoelectronic properties, making them excellent in solar cell applications.

[0004] However, as people expand this technology from the laboratory to industrial-scale production, a series of challenges have gradually emerged, mainly focusing on the preparation of large-area high-quality perovskite films and ensuring the stability of the films. The self-degradation and recombination losses caused by high temperature heat greatly affect the optoelectronic performance and service life of perovskite solar cell devices, especially in real outdoor applications. The temperature of the external environment plus the accumulated heat when the cell is working make the black perovskite film layer work continuously in a high temperature environment for a long time, which is not only a great challenge to the thermal stability of the perovskite light-absorbing layer, but also seriously affects the carrier transport between the light-absorbing layer and the transport layer, increasing the negative impact of the interface.

[0005] In order to solve this problem, Chinese patent CN116916724A discloses an ionic liquid thermal management method for perovskite solar cells, the principle of which can be briefly described as the ionic liquid BMDP (1-butyl-3-methylimidazolium dibutyl phosphate) forms a chelate with the perovskite component, the hydrophobic complex fills along the grain boundary and diffuses on the surface, thereby resulting in the encapsulation of the perovskite grains, trap passivation, inhibition of ion migration, etc., which overall manifests as accelerated thermal conductivity of the device, avoiding continuous accumulation of heat, and achieving a reduction in the operating temperature of the device, with the average temperature being reduced by about 10°C. However, the encapsulation of the grains results in a large number of grain boundaries in the perovskite film, which is not conducive to the transmission and collection of photoinduced charges.

[0006] Therefore the present invention provides a new additive formula to solve the above problems. Summary of the invention

[0007] The main purpose of the present invention is to provide an additive that can improve the thermal stability of perovskite cells, which can effectively slow down the crystallization rate, facilitate crystallization control, inhibit the condensation reaction of methylamine hydrochloride and formamidine hydroiodide, and promote the uniform distribution of various elements in the film, thereby preparing a high-quality perovskite film with directional growth and large grains.

[0008] The present invention achieves the above-mentioned purpose through the following technical scheme: an additive that can improve the thermal stability of perovskite batteries, including BMDP and DMIMBF6 with a molar ratio of 2:1 and acetonitrile that completely dissolves BMDP and DMIMBF6.

[0009] Another main purpose of the present invention is to provide a method for using the above additives, which can improve the thermal stability of large-area perovskite cells and ensure that the surface of the perovskite film is smoother.

[0010] A method for using an additive, comprising the steps of:

[0011] S1. Prepare the perovskite precursor solution: according to Cs m FA 1-m Pb(I n Br 1-n )3, wherein m is 0-0.2, n is 0.9-1, the perovskite precursor raw material is dispersed in a DMF and NMP mixed solvent with a volume ratio of 6:1, and stirred until no precipitation occurs to obtain a perovskite precursor solution;

[0012] S2. preparing the additive: dispersing BMDP and DMIMBF6 in acetonitrile according to the formula of the additive, stirring evenly, to obtain the additive;

[0013] S3, preparing a coating solution: mixing the perovskite precursor solution and the additive, stirring them sufficiently, and then filtering them with a PTFE filter head to obtain a coating solution;

[0014] S4, coating: using a slit coater to coat the coating liquid onto a substrate to form a perovskite wet film, and the perovskite wet film is subjected to a flash evaporation process and then annealed at 140-200° C. for 30-60 minutes to obtain a perovskite thin film.

[0015] Specifically, the value of m is 0.17 and the value of n is 1.

[0016] Specifically, the volume ratio of the perovskite precursor solution to acetonitrile is 7:3, the molar concentration of the lead element in the coating solution is 0.8-1.2 mol / L, the molar amount of the BMDP is 0.2% of the lead element, and the molar amount of the DMIMBF6 is 0.1% of the lead element.

[0017] Specifically, the PTFE filter head adopts PTFE with a pore size of 0.22um.

[0018] Specifically, the coating speed of the slit coater is 25 mm / s, and the distance between the substrate and the lip is 120 um.

[0019] The beneficial effects of the technical solution of the present invention are:

[0020] This additive can effectively slow down the crystallization rate, facilitate crystallization control, inhibit the condensation reaction of methylamine hydrochloride and formamidine hydroiodide, and promote the uniform distribution of various elements in the film, thereby preparing a high-quality perovskite film with directional growth and large grains, so that the perovskite film has good thermal stability and is particularly suitable for the manufacture of large-area perovskite solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The size comparison of perovskite grains using DMIMBF6 (left) and not using DMIMBF6 (right) under electron microscope scanning;

[0022] Figure 2 Comparison of the appearance of photovoltaic modules using DMIMBF6 (left) and not using DMIMBF6 (right) after being placed outdoors in summer for one month. DETAILED DESCRIPTION

[0023] The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0024] Example:

[0025] An additive capable of improving the thermal stability of a perovskite battery comprises BMDP and DMIMBF6 in a molar ratio of 2:1 and acetonitrile in which BMDP and DMIMBF6 are completely dissolved.

[0026] The process of preparing perovskite film using this additive is as follows:

[0027] S1. Prepare perovskite precursor solution: weigh 14.176g of PbI2 (lead iodide), 4.282g of FAI (formamidine hydroiodide), 1.325g of CsI (cesium iodide), 0.3038g of MACl (methylamine hydrochloride), and 0.2086g of PbCl2 (lead chloride) in sequence, disperse them in 18mL of DMF (N,N-dimethylformamide) and 3mL of NMP (N-methylpyrrolidone) solvent, and stir evenly until there is no precipitation.

[0028] After accounting for the lead element loss in filtration, the perovskite precursor solution contains 0.03 mol Pb, 0.0051 mol Cs, 0.249 mol FA, and 0.09 mol I, satisfying Cs 0.17 FA 0.85 In practical applications, the ratio of perovskite raw materials only needs to meet the requirements of Cs m FA 1-m Pb(I n Br 1-n )3, where m is 0-0.2, n is 0.9-1, and the specific ratio can be fine-tuned.

[0029] The perovskite precursor solution contains the film-forming solid components of perovskite. In order to mix them better, these solid components need to be dispersed into the solution first, so that the solute is uniform in the solution, and then they can react more fully with acetonitrile.

[0030] S2. Preparation of additives: Disperse 2.091 g BMDP (0.006 mol) and 1.105 g DMIMBF6 (0.003 mol) in 9 mL acetonitrile and stir well to obtain additives.

[0031] Because the solubility of CsI and FAI is different, if acetonitrile is mixed with the precursor solution solvent in advance, turbid precipitation is very likely to occur, affecting the ratio of the perovskite precursor solution, so acetonitrile and the perovskite precursor solution need to be prepared separately. Acetonitrile does not react with BMDP and DMIMBF6, so they are mixed into a uniform liquid in advance.

[0032] S3, preparing a coating solution: 21 mL of the perovskite precursor solution and 9 mL of the additive are mixed, stirred thoroughly, and then filtered through a PTFE (polytetrafluoroethylene) filter head to obtain a coating solution. The PTFE filter head uses 0.22 um pore size PTFE.

[0033] Because the solute dissolution and the miscibility of the solution hardly cause the volume of the solution to change, the total amount of the coating solution is 30 mL, and the molar concentration of the lead element in the coating solution of this embodiment is about 1 mol / L. Because the solvent will always evaporate during annealing, the amount of the solvent used only needs to ensure that the coating solution has uniform quality and no precipitation, so the molar concentration of the lead element in the coating solution can have a floating space of 20%, that is, the molar concentration can vary between 0.8-1.2 mol / L.

[0034] Because the substances in the perovskite precursor solution have purity problems, impurities will be formed, and some precipitated substances will inevitably be produced after mixing with acetonitrile. The presence of these two will destroy the uniformity of the coating solution and then affect the quality of the perovskite film. Therefore, a filtration is required here to retain impurities with relatively large molecular weight in the PTFE filter head.

[0035] DMIMBF6 (1-decyl-3-methylimidazolium hexafluorophosphate) is a stable ionic liquid with the following molecular structure:

[0036]

[0037] From its structure, it can be seen that DMIMBF6 is not easy to decompose and oxidize, is stable at room temperature, is not volatile, and has high ionic conductivity and thermal stability. It has a long carbon chain structure and strong electronegativity. The long carbon chain can improve hydrophobicity and thermal conductivity. At the same time, the high boiling point and non-volatile properties can effectively slow down the crystallization rate, which is conducive to crystallization control and is suitable for the coating process of large-area perovskite films. The strong electronegativity of the anion can provide multiple hydrogen bonding sites. This strong interaction enables the combined ionic liquid strategy to achieve better results. It can not only effectively inhibit the condensation reaction of methylamine hydrochloride and formamidine hydroiodide, but also promote the uniform distribution of various elements in the film, thereby preparing high-quality perovskite films with oriented growth and large grains.

[0038] S4, coating: using a slit coater to coat the coating liquid onto a substrate to form a perovskite wet film, and the perovskite wet film is subjected to a flash evaporation process and then annealed at 140-200° C. for 30-60 minutes to obtain a perovskite thin film.

[0039] In this embodiment, the coating speed of the slit coater is 25 mm / s, and the distance between the substrate and the lip is 120 um. Flash evaporation will cause the solvent to evaporate quickly and the perovskite to crystallize into a film, and then annealing will allow the perovskite to grow into a thin film structure.

[0040] The perovskite solar cell prepared by the above method (using DMIMBF6) was compared with the perovskite solar cell prepared by the method described in CN116916724A (control example):

[0041] from Figure 1 It can be seen that the perovskite film layer prepared by the embodiment has a significantly smoother surface than the control example, which proves that the additive is conducive to crystallization control and the quality of the perovskite battery is high.

[0042] Because the temperature difference between day and night is large in summer, and solar cells have to work outdoors in sunny places, the perovskite film must be able to withstand drastic temperature changes. Figure 2 It can be seen that the appearance damage of the control example after working outdoors for one month in summer is much more obvious than that of the example. This proves that the additive of the present invention makes the perovskite film have good thermal stability, and is particularly suitable for the manufacture of large-area perovskite solar cells.

[0043] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. An additive capable of improving the thermal stability of a perovskite battery, characterized in that: The mixture includes BMDP and DMIMBF6 in a molar ratio of 2:1 and acetonitrile in which BMDP and DMIMBF6 are completely dissolved.

2. A method for using the additive according to claim 1, characterized in that The steps include: S1. Prepare the perovskite precursor solution: according to Cs m FA 1-m Pb(I n Br 1-n )3, wherein m is 0-0.2, n is 0.9-1, the perovskite precursor raw material is dispersed in a DMF and NMP mixed solvent with a volume ratio of 6:1, and stirred until no precipitation occurs to obtain a perovskite precursor solution; S2. preparing the additive: dispersing BMDP and DMIMBF6 in acetonitrile according to the formula of the additive, stirring evenly, to obtain the additive; S3, preparing a coating solution: mixing the perovskite precursor solution and the additive, stirring them sufficiently, and then filtering them with a PTFE filter head to obtain a coating solution; S4, coating: using a slit coater to coat the coating liquid onto a substrate to form a perovskite wet film, and the perovskite wet film is subjected to a flash evaporation process and then annealed at 140-200° C. for 30-60 minutes to obtain a perovskite thin film.

3. The method for using the additive according to claim 2, characterized in that: The value of m is 0.17 and the value of n is 1.

4. The method for using the additive according to claim 2, characterized in that: The volume ratio of the perovskite precursor solution to acetonitrile is 7:3, the molar concentration of the lead element in the coating solution is 0.8-1.2 mol / L, the molar dosage of the BMDP is 0.2% of the lead element, and the molar dosage of the DMIMBF6 is 0.1% of the lead element.

5. The method for using the additive according to claim 2, characterized in that: The PTFE filter head adopts 0.22um pore size PTFE.

6. The method for using the additive according to claim 2, characterized in that: The coating speed of the slit coater is 25 mm / s, and the distance between the substrate and the lip is 120 um.

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