Solar cells modified with functional ligand-perovskite quantum dot composites

Abstract

This invention discloses a solar cell modified with a functional ligand-perovskite quantum dot composite material, comprising a layered conductive substrate, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer, and a metal electrode. The functional ligand-perovskite quantum dot composite material includes a short-chain aromatic carboxylic acid ligand-perovskite quantum dot composite material for modifying the interface between the perovskite light-absorbing layer and the hole transport layer, and a free radical polymer ligand-perovskite quantum dot composite material added to the hole transport layer to modify it. The solar cell modified with the functional ligand-perovskite quantum dot of this invention exhibits high stability, low surface roughness, few surface defects, and excellent electrochemical performance.

Description

Technical Field

[0001] This invention relates to the field of perovskite solar cell technology, specifically to a solar cell modified with a functional ligand-perovskite quantum dot composite material. Background Technology

[0002] In photovoltaic applications, perovskite quantum dots have demonstrated many unique advantages. These include the ability to adjust the bandgap by changing the size of the dot, and the ability to achieve multiexciton effects or carrier multiplication processes under the excitation of a single high-energy photon, thereby effectively increasing the photocurrent of the cell. Furthermore, perovskite quantum dots can achieve a fluorescence quantum yield close to 100%, and their low internal nonradiative recombination reduces voltage loss and increases the open-circuit voltage of the cell. Therefore, perovskite quantum dots are widely used in photovoltaics.

[0003] Currently, solar cells using perovskite quantum dots as the light-absorbing layer have achieved an efficiency of 17.4%. However, the thickness of the nanocrystalline light-absorbing layer makes it difficult to simultaneously achieve excellent light absorption and carrier transport performance, resulting in slow development of perovskite quantum dot photovoltaic devices. Their efficiency is still significantly lower than that of perovskite solar cells based on polycrystalline perovskite thin films. Although the efficiency of perovskite solar cells has reached as high as 25%, several problems remain to be solved. During the preparation of polycrystalline perovskite thin films, there may be residual reaction residues or excessive lead iodide (PbI2) generated by heating. A moderate excess of PbI2 is beneficial for perovskite crystal growth, reducing halogen vacancies in the perovskite film, passivating defects at perovskite grain boundaries, and facilitating the orientation and growth of α-phase perovskite crystals. However, excessive PbI2 is one of the factors that exacerbates the hysteresis effect of the cell. Furthermore, excessive PbI2 at the charge transport interface can induce perovskite decomposition during long-term cell operation. Therefore, a post-processing method for perovskite thin films is needed to eliminate residual PbI2. Furthermore, to improve the conductivity and hole mobility of hole transport materials such as Spiro-OMeTAD, it is typically necessary to dope them with lithium bis(trifluoromethanesulfonylimide) (Li-TFSI) and 4-tert-butylpyridine (tBP). However, Li-TFSI is highly hygroscopic, making Spiro-OMeTAD and the underlying perovskite susceptible to water corrosion in high humidity environments, ultimately affecting the humidity stability of the entire device.

[0004] In perovskite polycrystalline thin-film solar cells, perovskite quantum dots are often used as an interface layer between the perovskite and hole transport layer to passivate surface defects in the perovskite polycrystalline film or as an additive to regulate the nucleation and crystallization of perovskite. Currently, oleylamine is commonly used as a ligand to stabilize quantum dots. Oleylamine has been shown to have a certain passivation effect on perovskite, but the long-chain oleylamine has insulating properties that can affect charge transport between the perovskite and hole transport layer. However, while reducing the amount of oleylamine through cleaning and purification can improve the conductivity of quantum dots, it also significantly reduces their stability. Summary of the Invention

[0005] The purpose of this invention is to provide a solar cell modified with a functional ligand-perovskite quantum dot composite material, which has the characteristics of high stability, low surface roughness, few surface defects and excellent electrochemical performance.

[0006] This invention can be achieved through the following technical solutions: This invention discloses a solar cell modified with a functional ligand-perovskite quantum dot composite material, comprising a layered conductive substrate, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer, and a metal electrode. An interface modification layer is also provided between the perovskite light-absorbing layer and the hole transport layer. The hole transport layer is made of a free radical polymer ligand-perovskite quantum dot composite material, and the interface modification material is a short-chain aromatic carboxylic acid ligand-perovskite quantum dot composite material.

[0007] In this invention, the application of functional ligand-perovskite quantum dot composite materials to perovskite solar cells can regulate the key interface energy levels of perovskite solar cells, reduce interface charge recombination, and improve charge transport efficiency, thereby effectively improving the device performance and stability of perovskite solar cells. The functional ligand-perovskite quantum dot composite materials also enhance the photoelectric conversion efficiency, open-circuit voltage, short-circuit current density, and fill factor of perovskite solar cells.

[0008] In this invention, modifying the carrier transport layer with a free radical polymer-perovskite quantum dot composite material can improve the morphology, electrical properties, and stability of the carrier transport layer. By using a short-chain aromatic carboxylic acid ligand-perovskite quantum dot composite material, the interfacial energy level between the carrier transport layer and the perovskite light-absorbing layer in the perovskite solar cell can be effectively controlled, thereby achieving efficient charge transfer. At the same time, excess lead iodide and passivation defects on the perovskite surface are removed, thus significantly improving the photoelectric conversion efficiency and stability of the perovskite solar cell.

[0009] Furthermore, the general formulas of free radical polymer monomers are classified into the following four types:

[0010] Wherein, X is one of alkyl, alkoxy, nitrogen, ester, or amide groups with a chain length of 1–2; R 1 R 2 R 3 and R 4 Not both are hydrogen; Y is one of oxygen, nitrogen, or alkyl; R 5 It is one of alkyl, isopropyl, or tert-butyl with a chain length of 1–4; depending on the polymerization method, the degree of polymerization n of the free radical polymer ranges from 20 to 10000. The free radical polymer is a homopolymer of one of the above monomers 1–4, or a homopolymer of several of the above monomers 1–4, or a copolymer of any one or several of the above monomers 1–4 with methyl methacrylate, styrene, or acrylamide.

[0011] In this invention, the hole transport layer is modified with a free radical polymer-perovskite quantum dot composite material to reduce its surface roughness and inhibit Li salt aggregation; the conductivity and hole mobility of the hole transport layer are improved; and the humidity stability of the hole transport layer is enhanced by the modification of the hole transport layer with the free radical polymer-perovskite quantum dot composite material.

[0012] Furthermore, the short-chain aromatic carboxylic acid ligands are cyclic acids and / or benzoic acid.

[0013] In this invention, a short-chain aromatic carboxylic acid-perovskite quantum dot composite material is used to modify the interface between the hole transport layer and the perovskite light-absorbing layer. Excess lead iodide on the surface of the perovskite light-absorbing layer is removed, reducing surface roughness and surface defects. Modifying the interface between the hole transport layer and the perovskite light-absorbing layer with the short-chain aromatic carboxylic acid-perovskite quantum dot composite material results in a better energy level match at the interface, significantly improving charge transport efficiency. Furthermore, modifying the interface between the hole transport layer and the perovskite light-absorbing layer with the short-chain aromatic carboxylic acid-perovskite quantum dot composite material significantly improves the humidity stability and light stability of the perovskite light-absorbing layer.

[0014] Furthermore, the quantum dots of the perovskite light-absorbing layer are one or more of cesium lead bromine quantum dots, cesium lead iodine quantum dots, methylamine lead iodine and / or methylamine lead bromine.

[0015] Furthermore, the semiconductor material of the hole transport layer is one or more of 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene, thiophenes, fluorenes, triphenylamine derivatives, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], poly(3-hexylthiophene) and / or poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid).

[0016] Furthermore, the conductive substrate includes one of indium tin oxide conductive glass (ITO glass) and fluorine-doped tin oxide glass (FTO glass).

[0017] Furthermore, the electron transport layer is made of one or more of tin oxide, titanium oxide, zinc oxide, poly(3-hexylthiophene) and / or poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid).

[0018] Furthermore, the perovskite light-absorbing layer includes, but is not limited to, MAPbI3, FAPbI3, and (FAPbI3). 0.95 (MAPbBr3) 0.05 One or more of them.

[0019] Furthermore, the method for preparing an interface modification layer by adding a hole transport layer to a free radical polymer-perovskite quantum dot composite material includes the following steps: Step 1: Prepare perovskite quantum dot solution using the hot-injection method: Step 2: Dissolve the free radical polymer in ethyl acetate to obtain a free radical polymer solution; Step 3: Mix the free radical polymer solution and the perovskite quantum dot solution at a volume ratio of 1:2; Step 4. Centrifuge the mixed solution at 5000 rpm for 5 min, then discard the supernatant and redisperse the precipitate in a polar solvent to obtain the free radical polymer-perovskite quantum dot composite material; Step 5: Add the free radical polymer-perovskite quantum dot composite material to the hole transport layer solution and stir until homogeneous.

[0020] Furthermore, the method for preparing the interface modification layer of short-chain aromatic carboxylic acid ligand-perovskite quantum dot composite material includes the following steps: Step 1: Prepare perovskite quantum dot solution using the hot-injection method: Step 2: Add the short-chain aromatic carboxylic acid directly to the perovskite quantum dot solution and stir for 1 h; Step 3: Use a polytetrafluoroethylene filter to remove impurities from the solution; Step 4: Spin-coat the short-chain aromatic carboxylic acid-perovskite quantum dot composite material onto the surface of the perovskite light-absorbing layer at high speed, and anneal at 50 °C for 10 min.

[0021] Furthermore, the perovskite quantum dot solution includes the following steps: (1) Mix 0.814 g of cesium carbonate, 40 mL of octadecene and 2.5 mL of oleic acid in a 100 mL three-necked flask and dry the reaction mixture under vacuum at 120 °C for 1 h; then raise the temperature to 150 °C and heat it while purging nitrogen until the cesium carbonate and oleic acid react completely. (2) 0.88 mmol of lead halide (including lead bromide and lead iodide) (322.96 mg PbBr2, 405.68 mg PbI2) was mixed with 20 mL of octadecene and placed in a 50 mL three-necked flask; it was dried under vacuum at 120 °C for 1 h; nitrogen gas was introduced, and 2 mL of oleic acid and 2 mL of oleylamine were injected into the three-necked flask respectively; after the injection was completed, the reaction mixture was further dried under vacuum at 120 °C for 30 min; then nitrogen gas was introduced and the temperature was raised to 160 °C; after the temperature stabilized, it was heated for 10 min; then 3.2 mL of cesium oleate precursor solution was taken and the solution was preheated to 100 °C; the preheated cesium oleate was quickly injected into the reaction mixture, and after 5 s, the solution was quickly transferred to an ice-water mixture to cool to room temperature; (3) Add ethyl acetate (the volume ratio of ethyl acetate to the original solution is 3:1) to the reaction stock solution cooled to room temperature, and then centrifuge the mixed solution at 12000 rpm for 5 min; then discard the supernatant to remove octadecene and free oleic acid oleylamine, and redisperse the bottom precipitate in n-hexane; centrifuge the redispersed colloidal solution at 5000 rpm for 3 min; discard the bottom precipitate, and place the supernatant in a refrigerator in a nitrogen glove box and let it stand overnight at 4 ℃; then centrifuge the solution at 5000 rpm for 3 min, discard the bottom precipitate, and keep the supernatant to obtain the perovskite quantum dot solution.

[0022] This invention discloses a solar cell modified with a functional ligand-perovskite quantum dot composite material, which has the following beneficial effects: The functional ligand-perovskite quantum dot composite material provided by this invention exhibits excellent photoelectric performance and stability. The hole transport material modified with the free radical polymer-perovskite quantum dot composite material demonstrates high film-forming and hydrophobic properties, inhibits Li salt aggregation, and can modulate the HOMO energy level of the hole transport layer, thereby improving hole extraction and transport efficiency. The hole transport material modified with the free radical polymer-perovskite quantum dot composite material shows significantly improved humidity stability. Modifying the interface between the hole transport layer and the perovskite light-absorbing layer with the short-chain aromatic carboxylic acid-perovskite quantum dot composite material removes excess lead iodide from the surface of the perovskite light-absorbing layer, reducing surface roughness and defects. This modification further improves the interface energy level matching between the perovskite and hole transport layers, making hole extraction easier. When applied to perovskite solar cells, the functional ligand-perovskite quantum dot composite material reduces charge recombination and improves four parameters: VOC, JSC, FF, and PCE, while also significantly improving humidity stability. Attached Figure Description

[0023] Figure 1(A) is a scanning electron microscope (SEM) image of the surface of the Spiro-OMeTAD hole transport layer prepared in Example 1 of the present invention.

[0024] Figure 1(B) is a scanning electron microscope (SEM) image of the surface of the Spiro-OMeTAD hole transport layer prepared in Comparative Example 1 of the present invention.

[0025] Figure 2(A) is a surface scanning electron microscope (SEM) image of the Spiro-OMeTAD hole transport layer prepared in Example 2 of the present invention after being stored at 30%~50% humidity for 30 days.

[0026] Figure 2(B) is a surface scanning electron microscope (SEM) image of the Spiro-OMeTAD hole transport layer prepared in Comparative Example 2 of the present invention after being stored at 30%~50% humidity for 30 days.

[0027] Figure 3 The dark-state IV curves of the Spiro-OMeTAD hole transport layer prepared in Example 4 and Comparative Example 4 of this invention are shown.

[0028] Figure 4(A) is a scanning electron microscope (SEM) image of the surface of the perovskite light-absorbing layer prepared in Example 5 of the present invention.

[0029] Figure 4(B) is a scanning electron microscope (SEM) image of the surface of the perovskite light-absorbing layer prepared in Comparative Example 5 of the present invention.

[0030] Figure 5(A) is a scanning electron microscope (SEM) image of the perovskite light-absorbing layer prepared in Example 7 of the present invention after photoaging in air for 100 h.

[0031] Figure 5(B) is a scanning electron microscope (SEM) image of the perovskite light-absorbing layer prepared in Comparative Example 7 of the present invention after photoaging in air for 100 h.

[0032] Figure 6 The perovskite solar cells prepared in Example 8 and Comparative Example 8 of this invention JV curve. Detailed Implementation

[0033] To enable those skilled in the art to better understand the technical solution of the present invention, the product of the present invention will be further described in detail below with reference to embodiments and accompanying drawings.

[0034] This invention discloses a solar cell modified with a functional ligand-perovskite quantum dot composite material, comprising a layered conductive substrate, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer, and a metal electrode. An interface modification layer is also provided between the perovskite light-absorbing layer and the hole transport layer. The hole transport layer is made of a free radical polymer ligand-perovskite quantum dot composite material, and the interface modification material is a short-chain aromatic carboxylic acid ligand-perovskite quantum dot composite material.

[0035] Furthermore, the general formulas of free radical polymer monomers are classified into the following four types:

[0036] Wherein, X is one of alkyl, alkoxy, nitrogen, ester, or amide groups with a chain length of 1–2; R 1 R 2 R 3 and R 4 Not both are hydrogen; Y is one of oxygen, nitrogen, or alkyl; R 5 It is one of alkyl, isopropyl, or tert-butyl with a chain length of 1–4; depending on the polymerization method, the degree of polymerization n of the free radical polymer ranges from 20 to 10000. The free radical polymer is a homopolymer of one of the above monomers 1–4, or a homopolymer of several of the above monomers 1–4, or a copolymer of any one or several of the above monomers 1–4 with methyl methacrylate, styrene, or acrylamide.

[0037] Furthermore, the short-chain aromatic carboxylic acid ligands are cyclic acids and / or benzoic acid.

[0038] Furthermore, the perovskite quantum dots are one or more of cesium lead bromine quantum dots, cesium lead iodine quantum dots, methylamine lead iodine and / or methylamine lead bromine.

[0039] Furthermore, the semiconductor material of the hole transport layer is one or more of 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene, thiophenes, fluorenes, triphenylamine derivatives, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], poly(3-hexylthiophene) and / or poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid).

[0040] Furthermore, the conductive substrate includes one of indium tin oxide conductive glass (ITO glass) and fluorine-doped tin oxide glass (FTO glass).

[0041] Furthermore, the electron transport layer is made of one or more of tin oxide, titanium oxide, zinc oxide, poly(3-hexylthiophene) and / or poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid).

[0042] Furthermore, the perovskite light-absorbing layer includes, but is not limited to, MAPbI3, FAPbI3, and (FAPbI3). 0.95 (MAPbBr3) 0.05 One or more of them.

[0043] Furthermore, the method for preparing an interface modification layer by adding a hole transport layer to a free radical polymer-perovskite quantum dot composite material includes the following steps: Step 1: Prepare perovskite quantum dot solution using the hot-injection method: Step 2: Dissolve the free radical polymer in ethyl acetate to obtain a free radical polymer solution; Step 3: Mix the free radical polymer solution and the perovskite quantum dot solution at a volume ratio of 1:2; Step 4. Centrifuge the mixed solution at 5000 rpm for 5 min, then discard the supernatant and redisperse the precipitate in a polar solvent to obtain the free radical polymer-perovskite quantum dot composite material; Step 5: Add the free radical polymer-perovskite quantum dot composite material to the hole transport layer solution and stir until homogeneous.

[0044] Furthermore, the method for preparing the interface modification layer of short-chain aromatic carboxylic acid ligand-perovskite quantum dot composite material includes the following steps: Step 1: Prepare perovskite quantum dot solution using the hot-injection method: Step 2: Add the short-chain aromatic carboxylic acid directly to the perovskite quantum dot solution and stir for 1 h; Step 3: Use a polytetrafluoroethylene filter to remove impurities from the solution; Step 4: Spin-coat the short-chain aromatic carboxylic acid-perovskite quantum dot composite material onto the surface of the perovskite light-absorbing layer at high speed, and anneal at 50 °C for 10 min.

[0045] Furthermore, the perovskite quantum dot solution includes the following steps: (1) Mix 0.814 g of cesium carbonate, 40 mL of octadecene and 2.5 mL of oleic acid in a 100 mL three-necked flask and dry the reaction mixture under vacuum at 120 °C for 1 h; then raise the temperature to 150 °C and heat it while purging nitrogen until the cesium carbonate and oleic acid react completely. (2) 0.88 mmol of lead halide (including lead bromide and lead iodide) (322.96 mg PbBr2, 405.68 mg PbI2) was mixed with 20 mL of octadecene and placed in a 50 mL three-necked flask; it was dried under vacuum at 120 °C for 1 h; nitrogen gas was introduced, and 2 mL of oleic acid and 2 mL of oleylamine were injected into the three-necked flask respectively; after the injection was completed, the reaction mixture was further dried under vacuum at 120 °C for 30 min; then nitrogen gas was introduced and the temperature was raised to 160 °C; after the temperature stabilized, it was heated for 10 min; then 3.2 mL of cesium oleate precursor solution was taken and the solution was preheated to 100 °C; the preheated cesium oleate was quickly injected into the reaction mixture, and after 5 s, the solution was quickly transferred to an ice-water mixture to cool to room temperature; (3) Add ethyl acetate (the volume ratio of ethyl acetate to the original solution is 3:1) to the reaction stock solution cooled to room temperature, and then centrifuge the mixed solution at 12000 rpm for 5 min; then discard the supernatant to remove octadecene and free oleic acid oleylamine, and redisperse the bottom precipitate in n-hexane; centrifuge the redispersed colloidal solution at 5000 rpm for 3 min; discard the bottom precipitate, and place the supernatant in a refrigerator in a nitrogen glove box and let it stand overnight at 4 ℃; then centrifuge the solution at 5000 rpm for 3 min, discard the bottom precipitate, and keep the supernatant to obtain the perovskite quantum dot solution.

[0046] The following are some more specific embodiments and comparative examples provided by the present invention, using free radical polymer poly(2,2,6,6-tetramethylpiperidinoxymethacrylate)-perovskite quantum dot composite material (PTMA-QD) and short-chain aromatic carboxylic acid (cyclic acid)-perovskite quantum dot composite material (CA-QD) as examples. Example 1

[0047] Step 1: Cleaning and pretreatment of the conductive substrate: The ITO glass was successively immersed in detergent, deionized water, acetone, and ethanol for ultrasonic cleaning for 15 min each. The ITO glass was then removed and dried with dry air. Before fabricating the battery, the ITO glass was pretreated on the ITO surface in a plasma cleaner for 5 min. Step 2: Preparation of the perovskite light-absorbing layer: 8.4 mg MABr, 27.53 mg PbBr2, 35.18 mg MACl, 245.06 mg FAI, and 689.77 mg PbI2 were dissolved in 1 mL of a mixed solvent of DMF and DMSO (DMF to DMSO volume ratio 4:1). After thorough mixing, the solution was filtered using a 0.22 μm organic filter. The perovskite solution was spin-coated onto the conductive substrate prepared in Step 1 in two consecutive steps. In the first step, the spin-coating speed was 1000 rpm and the acceleration was 500 r / s for 10 s. In the second step, the spin-coating parameters were 5000 rpm and 1000 r / s for 30 s. At the 5th s before the end of the second step, 120 μL of the antisolvent ethyl acetate was added dropwise. After spin-coating, the perovskite precursor was annealed on a hot plate at 100 ℃ for 30 min.

[0048] Step 3: Preparation of the hole transport layer: First, dissolve 520 mg of Li-TFSI in 1 mL of acetonitrile and mix thoroughly. Dissolve 72.3 mg of Spiro-OMeTAD in 1 mL of chlorobenzene, then add 17.5 μL of Li-TFSI solution and 28.8 μL of tBP to the Spiro solution and mix thoroughly. Add 80 μL of free radical polymer-perovskite quantum dot composite material (PTMA-QD) to the prepared Spiro-OMeTAD solution and mix thoroughly. Finally, spin-coat the mixture onto the perovskite light-absorbing layer from Step 2 at 3000 rpm to obtain the Spiro-OMeTAD / PTMA-QD film. Comparative Example 1

[0049] The perovskite light-absorbing layer and hole transport layer were prepared according to the method of Example 1, except that the free radical polymer-perovskite quantum dot composite material was not added when preparing the hole transport layer in step 3 of Example 1, while the other steps remained unchanged, to obtain a Spiro-OMeTAD film without modification by the free radical polymer-perovskite quantum dot composite material.

[0050] Figures 1(A) and 1(B) are SEM images of the Spiro-OMeTAD hole transport layer surfaces prepared in Example 1 and Comparative Example 1 of the present invention. In Example 1, a Spiro-OMeTAD hole transport layer modified with the radical polymer-perovskite quantum dot composite material PTMA-QD was prepared on a perovskite substrate. The surface morphology of the Spiro-OMeTAD hole transport layer modified with the radical polymer-perovskite quantum dot composite material PTMA-QD was tested using SEM, as shown in Figure 1(A). In Comparative Example 1, a Spiro-OMeTAD hole transport layer without modification with the radical polymer-perovskite quantum dot composite material PTMA-QD was prepared on a perovskite substrate. The surface morphology of the Spiro-OMeTAD hole transport layer without modification with the radical polymer-perovskite quantum dot composite material PTMA-QD was tested using SEM, as shown in Figure 1(B). By comparing Figure 1(A) and Figure 1(B), it can be found that the surface of the Spiro-OMeTAD hole transport layer without the use of free radical polymer-perovskite quantum dot composite material PTMA-QD has many bright spots, while the surface of the Spiro-OMeTAD hole transport layer with the use of free radical polymer-perovskite quantum dot composite material PTMA-QD does not have obvious bright spots.

[0051] Based on the comparison of Example 1 and Comparative Example 1, it can be seen that the hole transport layer modified with PTMA-QD, a free radical polymer-perovskite quantum dot composite material, can improve the film-forming properties of the Spiro-OMeTAD hole transport layer. Example 2

[0052] Spiro-OMeTAD hole transport layer modified with free radical polymer-perovskite quantum dot composite material PTMA-QD was prepared on a perovskite substrate according to the method of Example 1. Comparative Example 2

[0053] The perovskite light-absorbing layer and hole transport layer were prepared according to the method of Example 1, except that the free radical polymer-perovskite quantum dot composite material PTMA-QD was not added when preparing the hole transport layer in step 3 of Example 1, while the other steps remained unchanged, to obtain a Spiro-OMeTAD film without the modification of free radical polymer-perovskite quantum dot composite material PTMA-QD.

[0054] Figures 2(A) and 2(B) are SEM images of the Spiro-OMeTAD hole transport layers prepared in Example 2 and Comparative Example 2 of the present invention after being stored at 30%~50% humidity for 30 days. In Example 2, a Spiro-OMeTAD hole transport layer modified with the free radical polymer-perovskite quantum dot composite material PTMA-QD was prepared on a perovskite substrate and aged in air for 30 days. Figure 2(A) is a SEM image of the Spiro-OMeTAD hole transport layer modified with the free radical polymer-perovskite quantum dot composite material PTMA-QD after aging. In Comparative Example 2, a Spiro-OMeTAD hole transport layer without modification with the free radical polymer-perovskite quantum dot composite material PTMA-QD was prepared on a perovskite substrate and aged in air for 30 days. Figure 2(B) is a SEM image of the Spiro-OMeTAD hole transport layer without modification with the free radical polymer-perovskite quantum dot composite material PTMA-QD after aging. By comparing Figure 1(A) and Figure 1(B), it can be found that the surface of the Spiro-OMeTAD hole transport layer without modification by the free radical polymer-perovskite quantum dot composite material PTMA-QD liquefies after aging, but the Spiro-OMeTAD hole transport layer modified by the free radical polymer-perovskite quantum dot composite material PTMA-QD does not show significant changes after aging.

[0055] Based on the comparison of Example 2 and Comparative Example 2, it can be seen that the hole transport layer modified with PTMA-QD, a free radical polymer-perovskite quantum dot composite material, can significantly improve the stability of the Spiro-OMeTAD hole transport layer. Example 3

[0056] Step 1: Cleaning and pretreatment of the conductive substrate: The ITO glass was successively immersed in detergent, deionized water, acetone, and ethanol for ultrasonic cleaning for 15 min each. The ITO glass was then removed and dried with dry air. Before fabricating the battery, the ITO glass was pretreated on the ITO surface in a plasma cleaner for 5 min. Step 2: Preparation of the hole transport layer: First, dissolve 520 mg of Li-TFSI in 1 mL of acetonitrile and mix thoroughly. Dissolve 72.3 mg of Spiro-OMeTAD in 1 mL of chlorobenzene, then add 17.5 μL of Li-TFSI solution and 28.8 μL of tBP to the Spiro solution and mix thoroughly. Add 80 μL of free radical polymer-perovskite quantum dot composite material (PTMA-QD) to the prepared Spiro-OMeTAD solution and mix thoroughly. Finally, spin-coat the mixture onto the conductive substrate from Step 1 at 3000 rpm to obtain the Spiro-OMeTAD / PTMA-QD film.

[0057] Step 3: Gold Electrode Evaporation: Place the sample with the prepared hole transport layer onto a mask and transfer it to an evaporator. The evaporation process is carried out at a temperature of less than 3 × 10⁻⁶. −4 Au was deposited at a vacuum level with an evaporation rate of 0.1–0.5 Å / s to a thickness of 80 nm. Comparative Example 3

[0058] The hole transport layer and gold electrode were prepared according to the method of Example 3, except that the radical polymer-perovskite quantum dot composite material PTMA-QD was not added when preparing the hole transport layer in step 2 of Example 3, while the other steps remained unchanged, to obtain a Spiro-OMeTAD film without modification by the radical polymer-perovskite quantum dot composite material PTMA-QD.

[0059] Figure 3 The figures show the dark-state IV curves of the Spiro-OMeTAD hole transport layer films prepared in Example 3 and Comparative Example 3 of this invention. Example 3 corresponds to the Spiro-OMeTAD hole transport layer modified with the free radical polymer-perovskite quantum dot composite material PTMA-QD. Comparative Example 3 corresponds to the Spiro-OMeTAD hole transport layer without the free radical polymer-perovskite quantum dot composite material PTMA-QD modification. Comparison calculations in the figures show that the conductivity of the Spiro-OMeTAD hole transport layer modified with the free radical polymer-perovskite quantum dot composite material PTMA-QD is significantly higher than that of the Spiro-OMeTAD hole transport layer without the free radical polymer-perovskite quantum dot composite material PTMA-QD modification.

[0060] A comprehensive comparison of Example 3 and Comparative Example 3 shows that the introduction of the free radical polymer-perovskite quantum dot composite material PTMA-QD can significantly improve the conductivity of Spiro-OMeTAD. Example 4

[0061] A Spiro-OMeTAD hole transport layer modified with the radical polymer-perovskite quantum dot composite material PTMA-QD was prepared according to Example 3, and its hole mobility was tested. The hole mobility of the Spiro-OMeTAD hole transport layer modified with the radical polymer-perovskite quantum dot composite material PTMA-QD was 1.92 × 10⁻⁶. −4 cm 2 V −1 s −1 . Comparative Example 4

[0062] A Spiro-OMeTAD hole transport layer without modification using the radical polymer-perovskite quantum dot composite material PTMA / QD was prepared according to Example 3. The only difference was that the radical polymer-perovskite quantum dot composite material PTMA-QD was not added during step 2 of Example 3 when preparing the hole transport layer; all other steps remained the same. The resulting Spiro-OMeTAD hole transport layer without PTMA-QD modification was then tested for its hole mobility. The hole mobility of the Spiro-OMeTAD hole transport layer without PTMA-QD modification was 4.11 × 10⁻⁶. −5 cm 2 V −1 s −1 .

[0063] Based on the comparison of Example 4 and Comparative Example 4, it can be seen that the introduction of the free radical polymer-perovskite quantum dot composite material PTMA-QD enhances the electrical properties of the Spiro-OMeTAD hole transport layer, resulting in a significant improvement in both the conductivity and hole mobility of the Spiro-OMeTAD hole transport layer. Example 5

[0064] Step 1: Cleaning and pretreatment of the conductive substrate: The ITO glass was successively immersed in detergent, deionized water, acetone, and ethanol for ultrasonic cleaning for 15 min each. The ITO glass was then removed and dried with dry air. Before fabricating the battery, the ITO glass was pretreated on the ITO surface in a plasma cleaner for 5 min. Step 2: Preparation of the perovskite light-absorbing layer: 8.4 mg MABr, 27.53 mg PbBr2, 35.18 mg MACl, 245.06 mg FAI, and 689.77 mg PbI2 were dissolved in 1 mL of a mixed solvent of DMF and DMSO (DMF to DMSO volume ratio 4:1). After thorough mixing, the solution was filtered using a 0.22 μm organic filter. The perovskite solution was spin-coated onto the conductive substrate prepared in Step 1 in two consecutive steps. In the first step, the spin-coating speed was 1000 rpm and the acceleration was 500 r / s for 10 s. In the second step, the spin-coating parameters were 5000 rpm and 1000 r / s for 30 s. At the 5th s before the end of the second step, 120 μL of the antisolvent ethyl acetate was added dropwise. After spin-coating, the perovskite precursor was annealed on a hot plate at 100 ℃ for 30 min. 60 μL of a short-chain aromatic carboxylic acid-perovskite quantum dot composite solution (CA-QD) was dropped onto a perovskite film. After standing for about 5 seconds, spin-coating was performed at 3000 rpm, 2000 r / s, and 40 s. After spin-coating, the film was annealed at 50 °C for 10 min. Comparative Example 5

[0065] The perovskite light-absorbing layer was prepared according to the method of Example 5, except that the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD was not added when preparing the perovskite light-absorbing layer in step 2 of Example 5, while the other steps remained unchanged, resulting in a perovskite film without modification by the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD.

[0066] Figures 4(A) and 4(B) are SEM images of the perovskite light-absorbing layers prepared in Example 5 and Comparative Example 5 of the present invention. In Example 5, a perovskite film modified with the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD was prepared on a conductive substrate. The surface morphology of the perovskite film modified with CA-QD was tested using SEM, as shown in Figure 4(A). In Comparative Example 5, a perovskite film without modification with CA-QD was prepared on a conductive substrate. The surface morphology of the perovskite film without modification with CA-QD was tested using SEM, as shown in Figure 4(B). By comparing Figure 4(A) and Figure 4(B), it can be found that the surface of the perovskite film without modification with the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD has a lot of residual lead iodide, while the surface of the perovskite film modified with the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD has no residual lead iodide and has a dense quantum dot coverage.

[0067] Based on the comparison of Example 5 and Comparative Example 5, it can be seen that the residual lead iodide on the perovskite surface can be effectively removed and defects reduced after modification with the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD. Example 6

[0068] Perovskite films modified with short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD were prepared on a conductive substrate according to the method of Example 5, and the positions of their valence band and conduction band were tested. The valence band of the perovskite film modified with short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD was located at -5.44 eV, and the conduction band was located at -3.89 eV. Comparative Example 6

[0069] The perovskite light-absorbing layer was prepared according to the method of Example 5, except that the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD was not added during step 2 of Example 5. All other steps remained the same, resulting in a perovskite film without modification by the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD. The positions of its valence band, conduction band, and Fermi level were then tested. The valence band of the perovskite film without modification by the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD was located at -5.64 eV, and the conduction band was located at -4.09 eV.

[0070] Comparative Example 6 and Comparative Example 6 show that after surface modification with the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD, the energy level is more matched with the hole transport layer Spiro-OMeTAD, which is more conducive to charge extraction. Example 7

[0071] Perovskite films modified with short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD were prepared on a conductive substrate according to the method of Example 5. Comparative Example 7

[0072] The perovskite light-absorbing layer was prepared according to the method of Example 5, except that the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD was not added when preparing the perovskite light-absorbing layer in step 2 of Example 5, while the other steps remained unchanged, resulting in a perovskite film without modification by the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD.

[0073] Figures 5(A) and 5(B) are SEM images of the perovskite light-absorbing layers prepared in Example 7 and Comparative Example 7 of the present invention after photoaging in air for 100 h. Example 7 prepared a perovskite film modified with the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD on a conductive substrate and aged it for 100 h. Figure 5(A) is a SEM image of the perovskite film modified with the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD after aging. Comparative Example 7 prepared a perovskite film without modification with the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD on a conductive substrate and aged it for 100 h. Figure 5(B) is a SEM image of the perovskite film without modification with the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD after aging. By comparing Figure 5(A) and Figure 5(B), it can be found that the perovskite film without modification by the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD showed many voids and cracks on its surface after photoaging, while the perovskite film modified by the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD showed a significant reduction in voids and cracks after aging.

[0074] Comparative Example 7 and Comparative Example 7 show that the light stability of the perovskite film is significantly improved after surface modification with the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD. Example 8

[0075] Step 1: Immerse the ITO glass successively in detergent, deionized water, acetone, and ethanol for ultrasonic cleaning for 15 minutes each. Then remove the ITO glass and dry it with dry air. Before fabricating the battery, place the ITO glass in a plasma cleaner for surface pretreatment for 5 minutes. Step 2: Preparation of the electron transport layer: SnO2 dispersion and deionized water were mixed at a volume ratio of 1:5.5 and stirred until homogeneous to obtain an aqueous SnO2 solution. Before use, the solution was filtered using a 0.22 μm aqueous filter. 60 μL of the solution was dropped onto the pretreated ITO glass, ensuring complete coverage. Spin-coating was then performed using spin-coating parameters of 3000 rpm, 1000 r / s, and 30 s. After spin-coating, the SnO2 film was annealed at 180 ℃ for 30 min. After complete cooling, the SnO2 film underwent surface pretreatment using plasma cleaning for 5 min.

[0076] Step 3: Preparation of the perovskite light-absorbing layer: 8.4 mg MABr, 27.53 mg PbBr2, 35.18 mg MACl, 245.06 mg FAI, and 689.77 mg PbI2 were dissolved in 1 mL of a mixed solvent of DMF and DMSO (DMF to DMSO volume ratio 4:1). After thorough mixing, the solution was filtered using a 0.22 μm organic filter. The perovskite solution was spin-coated onto the electron transport layer prepared in Step 2 in two consecutive steps. In the first step, the spin-coating speed was 1000 rpm and the acceleration was 500 r / s for 10 s. In the second step, the spin-coating parameters were 5000 rpm and 1000 r / s for 30 s. At the 5th s before the end of the second step, 120 μL of the antisolvent ethyl acetate was added dropwise. After spin-coating, the perovskite precursor was annealed on a hot plate at 100 ℃ for 30 min. 60 μL of a short-chain aromatic carboxylic acid-perovskite quantum dot composite solution (CA-QD) was dropped onto a perovskite film. After standing for about 5 seconds, spin-coating was performed at 3000 rpm, 2000 r / s, and 40 s. After spin-coating, the film was annealed at 50 °C for 10 min.

[0077] Step 4: Preparation of the hole transport layer: First, dissolve 520 mg of Li-TFSI in 1 mL of acetonitrile and mix thoroughly. Dissolve 72.3 mg of Spiro-OMeTAD in 1 mL of chlorobenzene, then add 17.5 μL of Li-TFSI solution and 28.8 μL of tBP to the Spiro solution and mix thoroughly. Add 80 μL of free radical polymer-perovskite quantum dot composite material (PTMA-QD) to the prepared Spiro-OMeTAD solution and mix thoroughly. Finally, spin-coat the mixture onto the perovskite light-absorbing layer from Step 3 at 3000 rpm to obtain the Spiro-OMeTAD / PTMA-QD film.

[0078] Step 5: Prepare the metal electrode layer: Deposit approximately 80 nm of metal Au onto the hole transport layer prepared in Step 4 using a vapor deposition method to obtain a perovskite solar cell modified with a functional ligand-perovskite quantum dot composite material. Comparative Example 8

[0079] Perovskite solar cells were prepared according to the method of Example 8, except that the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD was not added when preparing the perovskite light-absorbing layer in step 3 of Example 8, and the free radical polymer-perovskite quantum dot composite material PTMA-QD was not added when preparing the hole transport layer in step 4. The other steps remained unchanged, resulting in a perovskite solar cell prepared without the use of functional ligand-perovskite quantum dot composite material.

[0080] Figure 6 The perovskite solar cells prepared in Example 8 and Comparative Example 8 of this invention operate at 100 mW / cm². −2 Measured under simulated solar light conditions JV The curves show that the perovskite solar cell modified with a functional ligand-perovskite quantum dot composite material, corresponding to Example 8, has a photoelectric conversion efficiency of 22.15%, an open-circuit voltage of 1.147 V, and a short-circuit current density of 24.41 mA / cm². 2 The fill factor was 0.791. In contrast, the perovskite solar cell modified with the unfunctionalized ligand-perovskite quantum dot composite material (Comparative Example 8) exhibited a photoelectric conversion efficiency of 20.06%, an open-circuit voltage of 1.110 V, and a short-circuit current density of 24.16 mA / cm². 2 The fill factor is 0.748.

[0081] Comparative Example 8 and Comparative Example 8 show that modifying perovskite solar cells with functional ligand-perovskite quantum dot composite materials can improve the photoelectric conversion efficiency, open-circuit voltage, short-circuit current density and fill factor of perovskite solar cells. Example 9

[0082] According to Example 8, a perovskite solar cell modified with a functional ligand-perovskite quantum dot composite material was obtained. Comparative Example 9

[0083] Perovskite solar cells were prepared according to the method of Example 8, except that the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD was not added when preparing the perovskite light-absorbing layer in step 3 of Example 8, and the free radical polymer-perovskite quantum dot composite material PTMA-QD was not added when preparing the hole transport layer in step 4. The other steps remained unchanged, resulting in a perovskite solar cell prepared without the use of functional ligand-perovskite quantum dot composite material.

[0084] The perovskite solar cells prepared in Example 9 and Comparative Example 9 were aged in air at a relative humidity of 50%–60% and a temperature of 25 °C. After 1400 h of aging, the perovskite solar cell modified with the functional ligand-perovskite quantum dot composite material corresponding to Example 9 still retained 78% of its initial photoelectric conversion efficiency. However, the perovskite solar cell not modified with the functional ligand-perovskite quantum dot composite material corresponding to Comparative Example 9 only retained 32% of its initial photoelectric conversion efficiency after 1400 h of aging.

[0085] By comparing Example 9 and Comparative Example 9, it can be seen that modifying perovskite solar cells with functional ligand-perovskite quantum dot composite materials can improve the device humidity stability of perovskite solar cells.

[0086] Specifically, the open-circuit voltage of a perovskite solar cell is: the output voltage of a perovskite solar cell under standard sunlight conditions when it is open-circuited; the short-circuit current density is: the output current density of a perovskite solar cell under standard sunlight conditions when the voltage across its terminals is zero; the fill factor is: defined as the ratio of the maximum output power of a perovskite solar cell to its limiting output power (the product of the open-circuit voltage and the short-circuit current density); and the photoelectric conversion efficiency is: the ratio of the maximum output power of a perovskite solar cell to the total input optical power.

[0087] It should be noted that in this invention, Examples 4-5 illustrate the modification of the Spiro-OMeTAD hole transport layer with the free radical polymer-perovskite quantum dot composite material PTMA-QD, Examples 5-7 illustrate the modification of perovskite films with the short-chain aromatic carboxylic acid-perovskite quantum dot composite material CA-QD, and Examples 8-9 illustrate the modification of perovskite solar cells with the functional ligand-perovskite quantum dot composite material. Some experimental data in this invention have been simplified, and the final conclusions are given. Those skilled in the art will understand that the modification of perovskite solar cells with the functional ligand-perovskite quantum dot composite material is universal.

[0088] The above embodiments are merely specific examples of the present invention, and their descriptions are quite specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these obvious substitutions all fall within the protection scope of the present invention.

Claims

1. A solar cell modified with a functional ligand-perovskite quantum dot composite material, comprising a layered conductive substrate, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer, and a metal electrode, characterized in that: The hole transport layer is made of a free radical polymer ligand-perovskite quantum dot composite material, and an interface modification layer is provided between the perovskite light-absorbing layer and the hole transport layer. The interface modification material is a short-chain aromatic carboxylic acid ligand-perovskite quantum dot composite material. The free radical polymer is poly(2,2,6,6-tetramethylpiperidinoxymethacrylate) (PTMA). The short-chain aromatic carboxylic acid ligand is a cyclic acid; The semiconductor material of the hole transport layer is one or more of 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], poly(3-hexylthiophene) and / or poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid); The method for preparing a hole transport layer with added free radical polymer-perovskite quantum dot composite material includes the following steps: Step 1: Prepare perovskite quantum dot solution using the hot-injection method: Step 2: Dissolve the free radical polymer in ethyl acetate to obtain a free radical polymer solution; Step 3: Mix the free radical polymer solution and the perovskite quantum dot solution at a volume ratio of 1:2; Step 4. Centrifuge the mixed solution at 5000 rpm for 5 min, then discard the supernatant and redisperse the precipitate in a polar solvent to obtain the free radical polymer-perovskite quantum dot composite material; Step 5: Add the free radical polymer-perovskite quantum dot composite material to the hole transport layer solution and stir until homogeneous; The method for preparing the interface modification layer of short-chain aromatic carboxylic acid ligand-perovskite quantum dot composite material includes the following steps: Step 1: Prepare perovskite quantum dot solution using the hot-injection method: Step 2: Add the short-chain aromatic carboxylic acid directly to the perovskite quantum dot solution and stir for 1 h; Step 3: Use a polytetrafluoroethylene filter to remove impurities from the solution; Step 4: Spin-coat the short-chain aromatic carboxylic acid-perovskite quantum dot composite material onto the surface of the perovskite light-absorbing layer at high speed, and anneal at 50 °C for 10 min. The perovskite quantum dot solution includes the following steps: (1) Mix 0.814 g of cesium carbonate, 40 mL of octadecene and 2.5 mL of oleic acid in a 100 mL three-necked flask and dry the reaction mixture under vacuum at 120 °C for 1 h; then raise the temperature to 150 °C and heat it while purging nitrogen until the cesium carbonate and oleic acid react completely. (2) 0.88 mmol of lead halide, including 322.96 mg PbBr2 and 405.68 mg PbI2, was mixed with 20 mL of octadecene and placed in a 50 mL three-necked flask. The mixture was dried under vacuum at 120 °C for 1 h. Nitrogen gas was introduced, and 2 mL of oleic acid and 2 mL of oleylamine were injected into the three-necked flask. After the injection was completed, the reaction mixture was further dried under vacuum at 120 °C for 30 min. Nitrogen gas was then introduced, and the temperature was raised to 160 °C. After the temperature stabilized, the mixture was heated for 10 min. Then, 3.2 mL of cesium oleate precursor solution was taken and the solution was preheated to 100 °C. The preheated cesium oleate was quickly injected into the reaction mixture, and after 5 s, the solution was quickly transferred to an ice-water mixture to cool to room temperature. (3) Add ethyl acetate to the reaction stock solution cooled to room temperature. The volume ratio of ethyl acetate to the stock solution is 3:

1. Then centrifuge the mixed solution at 12000 rpm for 5 min. Then discard the supernatant to remove octadecene and free oleic acid oleylamine. Redisperse the bottom precipitate in n-hexane. Centrifuge the redispersed colloidal solution at 5000 rpm for 3 min. Discard the bottom precipitate and place the supernatant in a nitrogen glove box refrigerator and let it stand overnight at 4 ℃. Then centrifuge the solution at 5000 rpm for 3 min, discard the bottom precipitate, and keep the supernatant to obtain the perovskite quantum dot solution.

2. The solar cell modified with the functional ligand-perovskite quantum dot composite material according to claim 1, characterized in that: The quantum dots of the perovskite light-absorbing layer are one or more of cesium lead bromine quantum dots, cesium lead iodine quantum dots, methylamine lead iodine and / or methylamine lead bromine.

Images