Perovskite solar cell doped with perylene diimide assembly and preparation method thereof

Abstract

The application discloses a perovskite solar cell doped with a perylene diimide assembly and a preparation method thereof. The perovskite solar cell doped with the perylene diimide assembly is composed of a conductive substrate, an electron transport layer, a perovskite light-absorbing layer doped with the perylene diimide assembly and a counter electrode layer which are sequentially stacked. The p-pile interaction formed by the perylene diimide assembly improves the separation and transfer of carriers, passivates the perovskite defects, and improves the optical performance and thermal stability of the perovskite solar cell. Meanwhile, the extended p conjugation of the perylene diimide assembly ensures high electronic conductivity to realize effective charge transport, and the oxygen atoms on the carbonyl groups can be coordinated with uncoordinated Pb 2+ Chelated to passivate the surface defects of the perovskite crystal, thereby inhibiting the interface recombination and improving the efficiency. The perovskite solar cell manufactured by the application has a cell efficiency as high as 13.87%.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solar cell materials, and particularly relates to a perovskite solar cell doped with a perylene diimide assembly and a preparation method thereof. BACKGROUND

[0002] Organic-inorganic hybrid halide perovskites have attracted much attention due to their high absorption coefficient, wide absorption range, tunable direct band gap, and long charge carrier diffusion length. Solution-processed perovskite solar cells (PSCs) have shown great promise as a competitive low-cost solar cell due to their high efficiency and easy fabrication, combining the advantages of high efficiency and easy fabrication. Lead-based perovskite solar cells (PSCs) have experienced a dramatic growth, with certified power conversion efficiency (PCE) exceeding 25.5%, a major breakthrough that makes the photoelectric performance of PSCs comparable to that of crystalline silicon and cadmium telluride solar cells. These are attributed to the unique combination of excellent electrical and photoelectric properties of perovskites, such as significantly high absorption in the visible spectrum, long charge carrier diffusion length, high carrier mobility, and low exciton binding energy. As a light absorption layer, perovskite can collect photons to generate excitons that are separated and extracted by the electron transport layer (ETL) and hole transport layer (HTL), respectively, to generate an electric current. Therefore, the quality of the perovskite layer plays a crucial role in the performance of PSCs. During the crystallization of perovskite prepared by the solution method, pinholes and cracks around the grain boundaries are easily generated due to heterogeneous nucleation and growth, thereby reducing the quality of the thin film. Therefore, the use of additives can fill pinholes and repair cracks in the grain boundaries of perovskite to reduce the surface traps of the perovskite film, thereby reducing charge recombination, which has become one of the hotspots in the research of perovskite solar cells.

[0003] Perylene diimides are traditional n-type organic semiconductor materials with excellent photoelectric properties, with rigidity and extended p-p stacking in their molecular structure, good stability and high mobility. In the past few years, some research groups have also conducted research and proved that perylene diimides can be successfully added to perovskite solar cells as electron transport layers. Unfortunately, due to its inherent insolubility in organic solvents, perylene diimides can only be carried out in a few special solvents, such as concentrated sulfuric acid or m-cresol, which greatly limits its structural tunability. SUMMARY

[0004] To solve the above technical problems, the application provides a perovskite solar cell doped with a perylene diimide assembly and a preparation method thereof.

[0005] The perovskite solar cell with doped perylene diimide assembly of the present application is composed of a conductive substrate, an electron transport layer, a perovskite light-absorbing layer with doped perylene diimide assembly and a counter electrode layer which are stacked in sequence.

[0006] The preparation steps of the electron transport layer are as follows: the conductive substrate is sequentially cleaned by a detergent, deionized water, isopropanol and anhydrous ethanol, and then a titanium isopropoxide ethanol solution with a concentration of 0.2-0.5M is spin-coated at a speed of 1000-2500rpm for 3-50s, and then heated at 80-150℃ to form a dense titanium dioxide layer; then a mesoporous TiO2 ethanol dispersion solution with a concentration of 2-4mol / L is spin-coated at a speed of 1000-3500rpm for 3-50s, and then sintered at a high temperature of 450-550℃ in a muffle furnace to form a mesoporous titanium dioxide layer.

[0007] The preparation steps of the perovskite light-absorbing layer with doped perylene diimide assembly are as follows: a perovskite precursor solution is spin-coated on the electron transport layer at a speed of 1000-2000rpm for 8-12s, and then spin-coated at a speed of 3000-5000rpm for 5-40s, and during the spin-coating at a speed of 3000-5000rpm, a perylene diimide assembly precursor solution with a concentration of 0.1-0.8g / ml is added dropwise, and finally annealed at 80-100℃ for 5-15min.

[0008] The counter electrode layer is a carbon electrode layer.

[0009] The preparation steps of the counter electrode layer are as follows: a carbon paste is blade-coated on the perovskite light-absorbing layer with doped perylene diimide assembly, and then annealed at 100-150℃ for 20-40min.

[0010] The perovskite precursor solution is prepared by dissolving methyl iodide amine and lead iodide in a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide, wherein the concentration of methyl iodide amine is 0.1-0.2mol / L, the molar ratio of methyl iodide amine to lead iodide is 1:1, and the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is 10:1.

[0011] The preparation method of the perylene diimide assembly precursor solution is as follows: perylene diimide intercalated hydrotalcite is dispersed in methanol, an acidic solution is added to remove the hydrotalcite plate, centrifugal washing is performed using an organic solvent, and finally dispersed in chlorobenzene.

[0012] The acidic solution is propionic acid or hydrochloric acid.

[0013] The organic solvent is selected from one or more of chlorobenzene, toluene, ethyl acetate, chloroform and mesitylene.

[0014] The perylene diimide intercalated hydrotalcite is prepared by ion exchange method or coprecipitation method.

[0015] The perylene diimide molecules are inserted into the interlayer of hydrotalcite, after removing the LDH layer by adding a small amount of acidic solvent, the poor solvent of perylene diimide is quickly added to make the active elongation, and the perylene diimide assembly is formed. The π-π stacking interaction of the perylene diimide assembly improves the separation and transfer of the charge carriers, passivates the perovskite defects, and improves the optical performance and thermal stability of the perovskite solar cell. At the same time, the extended π conjugation of the perylene diimide assembly ensures high electronic conductivity to realize effective charge transport, and the oxygen atom on the carbonyl group can coordinate with the uncoordinated Pb 2+ The surface defects of the perovskite crystal are passivated by chelation, thereby inhibiting the interface recombination and improving the efficiency. The perovskite solar cell manufactured by using the perylene diimide assembly of the present application has a cell efficiency as high as 13.87%. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The spectrograms of the perylene diimide assembly and the perylene diimide monomer obtained in Example 1 of the present application are shown in the figure (A) is the fluorescence spectrum, (B) is the ultraviolet absorption spectrum. The fluorescence spectrum shows that the emission peak of the perylene diimide assembly is at 650 nm, and the emission peak of the perylene diimide monomer is at 530 nm. It can be seen that red shift occurs after assembly, indicating that the conjugation degree of the perylene diimide assembly increases. The ultraviolet absorption spectrum shows that the perylene diimide assembly has a peak at 500 nm, while the perylene diimide monomer has a peak at 525 nm. Compared with the perylene diimide monomer, the perylene diimide assembly has a blue shift, indicating that the perylene diimide monomer forms a perylene diimide assembly.

[0017] Figure 2 The Raman spectra of the perylene diimide assembly and the perylene diimide monomer obtained in Example 1 of the present application are shown in the figure. The Raman spectrum reveals that the relative intensity of 1572 cm -1 to 1301 cm -1 of the perylene diimide assembly sample is higher than that of the perylene diimide monomer, indicating that the perylene diimide assembly has higher π-π conjugation. Higher π-π stacking leads to long-range π electron delocalization, which is beneficial to the migration and separation of charge carriers.

[0018] Figure 3 The XRD spectra of the perylene diimide assembly and the perylene diimide monomer obtained in Example 1 of the present application are shown in the figure. The liquid XRD spectrum shows that the relative intensity of P1 and P0 (AP1 / AP0>1) in the perylene diimide assembly is opposite to that (AP1 / AP0<1) in the perylene diimide monomer. The relative intensity of P1 peak in the perylene diimide assembly increases, indicating that the order of the perylene diimide assembly is higher.

[0019] Figure 4 SEM images of the perylene diimide assembly and perylene diimide monomer obtained in Example 1 of the present application, Figure (A) is the SEM image of the perylene diimide monomer, Figure (B) is the SEM image of the perylene diimide assembly. According to the SEM images of the perylene diimide assembly and perylene diimide monomer, it can be seen that the perylene diimide monomer presents irregular rod shape, while the shape of the perylene diimide assembly changes and presents needle shape, indicating that the perylene diimide monomer is assembled.

[0020] Figure 5 Transient photocurrent curves of the perylene diimide assembly and perylene diimide monomer obtained in Example 1 of the present application. The enhancement of the transient photocurrent of the perylene diimide assembly compared with the perylene diimide monomer is due to the promotion of the separation and migration of the photo-generated carriers, indicating that the perylene diimide assembly has higher carrier separation efficiency.

[0021] Figure 6 C 1s spectra of the perylene diimide assembly obtained in Example 1 of the present application. 1s High-resolution XPS spectra. The C 1s spectra of the perylene diimide assembly obtained in Example 1 of the present application. 1s The core level contains two parts: the peak at 284 eV is due to C-C / C=C, and the peak at 288 eV is due to C=O.

[0022] Figure 7 SEM images of the perovskite absorption layer formed by adding and not adding the perylene diimide assembly during the preparation of the perovskite absorption layer in step c of Example 1 of the present application, Figure (A) is without adding the perylene diimide assembly, Figure (B) is adding the perylene diimide assembly. When the perylene diimide assembly is added to the perovskite, a denser morphology with larger grain size and fewer pinholes can be obtained.

[0023] Figure 8 XRD patterns of the perovskite absorption layer formed by adding and not adding the perylene diimide assembly during the preparation of the perovskite absorption layer in step c of Example 1 of the present application. XRD shows that the diffraction peaks of the two perovskite films are the same, indicating that the perylene diimide assembly is not embedded in the perovskite lattice, but only exists in the grain boundaries or surface of the perovskite film; the stronger diffraction intensity means higher crystallinity or larger grain size.

[0024] Figure 9The steady-state photoluminescence spectra of the perovskite absorber layers formed by adding and not adding perylene diimide assemblies during the preparation of the perovskite absorber layer in step c of Example 1 of the present application. The significant enhancement of the steady-state photoluminescence intensity of the perylene diimide assembly doped perovskite film provides strong evidence that the perylene diimide assembly passivates the defects at the grain boundaries, and is accompanied by a blue shift in the fluorescence emission peak position, indicating that the addition of the perylene diimide assembly effectively reduces the trap states in the perovskite film, and the addition of the perylene diimide assembly facilitates the separation and transfer of carriers.

[0025] Figure 10 The UV absorption spectra of the perovskite absorber layers formed by adding and not adding perylene diimide assemblies during the preparation of the perovskite absorber layer in step c of Example 1 of the present application. This shows that the addition of the perylene diimide assembly has no effect on the absorption of the perovskite film.

[0026] Figure 11 The time-resolved photoluminescence spectra of the perovskite absorber layers formed by adding and not adding perylene diimide assemblies during the preparation of the perovskite absorber layer in step c of Example 1 of the present application. After incorporating the perylene diimide assembly, the average luminescence lifetime is improved, and the longer exciton lifetime of the perylene diimide assembly introduced into the perovskite film is attributed to the improvement in its crystallinity and the reduction in defect states, and the introduction of the perylene diimide assembly enables more efficient carrier transfer and separation in the perovskite.

[0027] Figure 12 The thermal stability diagrams of the perovskite absorber layers formed by adding and not adding perylene diimide assemblies during the preparation of the perovskite absorber layer in step c of Example 1 of the present application, with the perovskite film on the left and the perovskite / perylene diimide assembly film on the right. Compared with the perovskite film, the color of the perovskite film with the added perylene diimide assembly (FTO / TiO2 / perovskite + perylene diimide assembly) slowly changes from black to yellow, while the blank perovskite film has basically turned yellow after 100 h, indicating that the perovskite has decomposed. The color change of the corresponding perovskite film at different times can more directly prove that the perovskite film modified by the perylene diimide assembly has good thermal stability.

[0028] Figure 13 The J-V curve diagram of the PSCs of the perylene diimide assembly obtained in Example 1 of the present application. According to the photovoltaic parameters and current density-voltage (J-V) curves of the best PSCs of the perylene diimide assembly and the control PSCs, it can be seen that the PCE of the PSCs with the perylene diimide assembly is 13.87%, while the PCE of the control PSCs is only 12.48%. DETAILED DESCRIPTION

[0029] Example 1

[0030] 1. Preparation of perylene diimide

[0031] Take 1.376 g of perylene-3,4,9,10-tetracarboxylic dianhydride, 2.5 g of 3-aminopropionic acid and 18 g of imidazole, and add them to a round-bottom flask. Stir and heat at 100°C under a nitrogen atmosphere for 4 h. After the reaction is complete, cool to room temperature and disperse in 100 ml of ethanol. Add 300 ml of dilute hydrochloric acid and stir for 24 h. Vacuum filter the final product using a 0.45 μm membrane and collect the red solid. Wash several times with distilled water until the pH of the wash solution becomes neutral. Dry the obtained solid at 60°C under vacuum to obtain pure perylene diimide powder.

[0032] 2. Preparation of perylene diimide-LDH (ion exchange method)

[0033] Preparation of LDH precursor:

[0034] Take magnesium nitrate hexahydrate (3.8461 g) and aluminum nitrate nonahydrate (1.8760 g) in a molar ratio of 2:1, dissolve in 200 ml of CO2-free water to prepare a mixed salt solution, which is referred to as solution A. Dissolve 2 g of NaOH in 200 ml of CO2-free water to prepare a base solution, which is referred to as solution B. First, add a 200 ml solution of 0.1 mol / L sodium nitrate to a round-bottom flask, and stir vigorously under a nitrogen stream at 60°C. Then, slowly add solutions A and B to the sodium nitrate solution, and maintain the pH at 8-9 during the entire process under a nitrogen atmosphere with vigorous stirring. After the addition is complete, stir and heat the reaction mixture at 60°C for 24 h to obtain NO3-LDH. Finally, wash the NO3-LDH with CO2-free water until the pH is neutral, dry into powder, and reserve for use.

[0035] Ion exchange intercalation:

[0036] Take 1 g of NO3-LDH and add it to 50 mL of a 0.1 mol / L perylene diimide aqueous solution, and react under the conditions of 80°C, nitrogen protection and vigorous stirring for 24 h to obtain the perylene diimide-LDH intercalation product. Finally, wash the perylene diimide-LDH with CO2-free water until the pH is neutral, and store in a methanol solution for use.

[0037] 3. Preparation of perylene diimide assembly precursor solution

[0038] Disperse the perylene diimide-LDH in 3 mL of methanol at a concentration of 20 g / L, add 100 μL of concentrated hydrochloric acid to remove the LDH layers, then wash with chlorobenzene, and finally disperse in chlorobenzene to make it active and elongated to form a perylene diimide assembly.

[0039] 4. Preparation of perovskite solar cell device

[0040] a. Transparent conductive substrate: The substrate was selected from FTO conductive glass, which was sequentially cleaned in detergent, deionized water, isopropanol and anhydrous ethanol by ultrasonic cleaning for 15 min.

[0041] b. Electron transport layer: The cleaned FTO glass sheet was coated with a 0.4M titanium isopropoxide ethanol solution, first at 1000 rpm for 3s, then at 2500 rpm for 30s, and then heated at 125°C for 5min to form a dense titanium dioxide layer. Then continue to spin-coat 4mol / L mesoporous TiO2 ethanol dispersion, first at 1000 rpm for 3s, then at 3500 rpm for 30s, and finally sintered at 500°C for 30min to form a mesoporous titanium dioxide layer.

[0042] c. Perovskite absorption layer: A perovskite precursor solution was prepared by dissolving 0.461g PbI2 and 0.159g MAI in a mixed solution of 0.72mL DMF and 0.072mL DMSO. The perovskite precursor solution was spin-coated on the electron transport layer, first at 1000 rpm for 10s, then at 4000 rpm for 20s, and at 4000 rpm at the 7th s, drop 0.2g / ml perylene diimide assembly chlorobenzene dispersion, and finally heated at 100°C for 10min.

[0043] d. Counter electrode: Carbon paste was scraped as a carbon electrode on the perovskite absorption layer, and then heated at 100°C for 30min.

[0044] The perovskite solar cell doped with perylene diimide assembly prepared above was tested for photovoltaic performance, and the results are shown in Table 1:

[0045] Table 1

[0046]

[0047] Example 2

[0048] 1. Preparation of perylene diimide

[0049] 1.376g of perylene-3,4,9,10-tetracarboxylic dianhydride, 2.5g of 3-aminopropionic acid and 18g of imidazole were weighed into a round-bottom flask and heated with stirring under a nitrogen atmosphere at 100°C for 4h. After the reaction was completed, it was cooled to room temperature and dispersed in 100ml of ethanol. 300ml of dilute hydrochloric acid was added, and stirred for 24h. The final product was vacuum filtered using a 0.45μm membrane, and the red solid was collected. It was washed several times with distilled water until the pH of the washing liquid became neutral. The obtained solid was dried at 60°C under vacuum to obtain pure perylene diimide powder.

[0050] 2. Preparation of perylene diimide-LDH (co-precipitation method intercalation)

[0051] The magnesium nitrate hexahydrate (3.8461 g) and aluminum nitrate nonahydrate (1.8760 g) with a molar ratio of 2:1 were dissolved in 200 ml CO2-free water to prepare a mixed salt solution, which was referred to as solution A. 2 g of NaOH was dissolved in 200 ml CO2-free water to prepare a base solution, which was referred to as solution B. 200 ml of 0.1 mol / L perylene diimide solution was first added to a round-bottom flask, and then solution A and B were slowly added to the perylene diimide solution under the nitrogen atmosphere at 60°C with vigorous stirring. The pH value was maintained at 8-9 during the whole process. After the addition was completed, the reaction mixture was heated and stirred at 60°C for 24 h to obtain the intercalation product perylene diimide-LDH. Finally, the perylene diimide-LDH was washed with CO2-free water until it was neutral, and then stored in a methanol solution for later use.

[0052] 3. Preparation of perylene diimide assembly

[0053] The perylene diimide-LDH was dispersed in 3 mL of methanol at a concentration of 20 g / L. After adding 100 μL of concentrated hydrochloric acid to remove the LDH layer, chlorobenzene was added for washing. Finally, the perylene diimide assembly was formed by dispersing it in chlorobenzene to make it active and elongated.

[0054] 4. Preparation of perovskite solar cell device

[0055] a. Transparent conductive substrate: The substrate was selected from FTO conductive glass, and the FTO glass substrate was ultrasonically cleaned in detergent, deionized water, isopropanol and anhydrous ethanol for 15 min.

[0056] b. Electron transport layer: The cleaned FTO glass sheet was coated with a 0.4 M titanium tetraisopropoxide ethanol solution, first 1000 rpm spin coating for 3 s, then 2500 rpm spin coating for 30 s, and then heating at 125°C for 5 min to form a dense titanium dioxide layer. Then continue to spin coat 4 mol / L mesoporous TiO2 ethanol dispersion, first 1000 rpm spin coating for 3 s, then 3500 rpm spin coating for 30 s, and finally sintering at 500°C for 30 min to form a mesoporous titanium dioxide layer.

[0057] c. Perovskite absorption layer: 0.461 g of PbI2 and 0.159 g of MAI were dissolved in a mixed solution of 0.72 mL of DMF and 0.072 mL of DMSO to prepare a perovskite precursor solution. The perovskite precursor solution was spin-coated on the electron transport layer, first 1000 rpm spin coating for 10 s, then 4000 rpm spin coating for 20 s, and at the 7th s of 4000 rpm spin coating, 0.2 g / ml of perylene diimide assembly chlorobenzene dispersion was added dropwise, and finally heated at 100°C for 10 min.

[0058] d. Counter electrode: Carbon paste was scraped on the perovskite absorber layer as carbon electrode and then heated at 100 °C for 30 min.

Claims

1. A perovskite solar cell doped with perylene diimide assemblies, characterized in that, The battery consists of a conductive substrate, an electron transport layer, a perovskite light-absorbing layer doped with perylene diimide assembly, and a counter electrode layer stacked sequentially. The preparation steps of the perovskite light-absorbing layer of the doped perylene diimide assembly are as follows: spin-coating a perovskite precursor solution onto the electron transport layer at a spin speed of 1000-2000 rpm for 8-12 s, then spin-coating at 3000-5000 rpm for 5-40 s, adding a perylene diimide assembly precursor solution with a concentration of 0.1-0.8 g / ml during the 3000-5000 rpm spin-coating, and finally annealing at 80-100℃ for 5-15 min; The preparation method of the perylene diimide assembly precursor solution is as follows: perylene diimide intercalated hydrotalcite is dispersed in methanol, an acidic solution is added to remove the hydrotalcite layers, the solution is centrifuged and washed with an organic solvent, and finally dispersed in chlorobenzene.

2. The perovskite solar cell with a doped perylene diimide assembly according to claim 1, characterized in that, The electron transport layer is prepared by the following steps: the conductive substrate is ultrasonically cleaned sequentially with detergent, deionized water, isopropanol and anhydrous ethanol, and then a 0.2-0.5M tetraisopropoxide titanium ethanol solution is spin-coated at a speed of 1000-2500 rpm for 3-50 s. After spin-coating, the substrate is heated to 80-150℃ to form a dense titanium dioxide layer. Then, a 2-4 mol / L mesoporous TiO2 ethanol dispersion is spin-coated at a speed of 1000-3500 rpm for 3-50 s. After spin-coating, the substrate is sintered at 450-550℃ in a muffle furnace to form a mesoporous titanium dioxide layer.

3. The perovskite solar cell with a doped perylene diimide assembly according to claim 1, characterized in that, The counter electrode layer is a carbon electrode layer.

4. The perovskite solar cell with a doped perylene diimide assembly according to claim 1, characterized in that, The perovskite precursor solution is prepared by dissolving methyl iodine and lead iodide in a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide.

5. The perovskite solar cell with a doped perylene diimide assembly according to claim 1, characterized in that, The acidic solution is propionic acid or hydrochloric acid.

6. The perovskite solar cell with a doped perylene diimide assembly according to claim 1, characterized in that, The organic solvent is selected from one or more of chlorobenzene, toluene, ethyl acetate, chloroform, and trimethylbenzene.

7. The perovskite solar cell with a doped perylene diimide assembly according to claim 1, characterized in that, The perylene diimide intercalated hydrotalcite is prepared by ion exchange or coprecipitation.

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