Carbon-based organic-inorganic perovskite solar cell based on 4-fluorobenzamidine hydrochloride modification

Abstract

The invention relates to a carbon-based organic-inorganic perovskite solar cell based on modification of 4-fluorobenzamidine hydrochloride. The solar cell sequentially comprises a transparent conductive substrate, an electron transport layer, a 4-fluorobenzamidine hydrochloride modification layer, a perovskite layer and a carbon electrode from bottom to top, and the thickness of the 4-fluorobenzamidine hydrochloride modification layer is 5 to 10 nm. The preparation process is simple, the operation is convenient, the cost is low, and the carrier transport performance, the perovskite stability and the photoelectric conversion efficiency of the obtained carbon electrode perovskite solar cell are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor optoelectronic materials and devices, and particularly relates to a carbon-based organic-inorganic perovskite solar cell modified with 4-fluorobenzamidine hydrochloride. Background Art

[0002] With the continuous consumption of fossil energy, the energy crisis and environmental problems have become increasingly prominent, attracting extensive attention from countries around the world. As a new type of energy, solar energy mainly converts light energy into electrical energy through the way of photoelectric conversion, and has many advantages such as environmental protection, rich resources, and clean and renewable. Due to the advantages of high light absorption coefficient, long carrier lifetime, and simple preparation process of perovskite solar cells (PSCs), they have become the focus of research on the new generation of solar cells.

[0003] In perovskite solar cell devices, carbon materials are considered the most promising electrode materials because they are rich in reserves, cheap, have a good work function match, and stable performance, which helps to improve the performance of PSCs. However, there is still a certain gap in the photoelectric conversion efficiency between carbon-based perovskite solar cells and traditional metal electrodes. The main reason is that there are defects between the perovskite layer and the upper and lower interfaces, which affect the carrier migration. And the current technology mainly focuses on modifying the perovskite layer / carbon electrode layer, and there is little research on modifying the electron transport layer / perovskite layer. For example, in patent CN118890912A, the upper interface of the perovskite layer is modified with dodecyl acetate, and the positive and negative charge defects on the surface of the perovskite layer are passivated by the carboxylic acid group and the amino ion, thereby improving the interfacial contact between the perovskite layer and the carbon electrode. However, due to the pinhole defects and the reason of being dense at the grain boundaries, the antisolvent chlorobenzene needs to be added when spin-coating the perovskite layer at high speed; and because there are still a large number of dangling bonds at the buried interface of the perovskite, non-radiative recombination losses are generated, thereby reducing the photoelectric conversion efficiency of the device. In patent CN118488720A, by adding a Mxene nanomaterial layer between the perovskite layer and the carbon layer of the all-inorganic perovskite solar cell, a more suitable energy level matching is achieved to improve the performance of the device. However, due to the lack of effective modification of the buried interface of the perovskite layer, there are still defects, which will become the recombination centers of carriers, resulting in an increase in non-radiative recombination losses, thereby reducing the photoelectric conversion efficiency of the device. Especially the preparation process of the Mxene nanomaterial layer is complex and time-consuming. Summary of the Invention

[0004] The object of the present invention is to propose a carbon-based organic-inorganic perovskite solar cell modified with 4-fluorobenzamidine hydrochloride in view of the problems of poor contact between the electron transport layer / perovskite layer and strict and complex preparation conditions in the current technology. In this perovskite solar cell, 4-fluorobenzamidine hydrochloride is used to modify the perovskite layer between the two interface layers. By using 4-fluorobenzamidine cations (C7H6FN2 + ) and chloride ions (Cl - ) to passivate the cation and anion defects of the perovskite thin film synergistically, charge recombination can be significantly reduced, defects can be passivated, and the charge transport performance of the perovskite layer can be improved. During the preparation process, 4-fluorobenzamidine hydrochloride can be uniformly dispersed on the surface of the perovskite light-absorbing layer through two steps of spin coating and annealing to form a 4-fluorobenzamidine hydrochloride modification layer. The carrier transport performance, perovskite stability, and photoelectric conversion efficiency of the carbon electrode perovskite solar cell obtained by the present invention are all significantly improved.

[0005] The technical solution of the present invention is as follows:

[0006] A carbon-based organic-inorganic perovskite solar cell modified with 4-fluorobenzamidine hydrochloride, which successively includes a transparent conductive substrate, an electron transport layer, a 4-fluorobenzamidine hydrochloride modification layer, a perovskite layer, and a carbon electrode from bottom to top;

[0007] The thickness of the 4-fluorobenzamidine hydrochloride modification layer is 5-10 nm.

[0008] The substrate is preferably fluorine-doped tin oxide transparent conductive glass (FTO), indium tin oxide transparent conductive glass (ITO), PET / ITO (PET is polyethylene terephthalate), or PEN / ITO (PEN is polyethylene naphthalate);

[0009] The electron transport layer is at least one of tin dioxide (SnO2), titanium dioxide (TiO2), chlorine-doped titanium dioxide, C60 (C 60 ), [6,6]-phenyl C61 butyric acid methyl ester (PCBM), zinc oxide (ZnO), TiO2-SnO2, ZnO-TiO2, ZnO-SnO2; the thickness is 5-180 nm;

[0010] The structural formula of the perovskite layer material is APbX3, where the A site is at least one of formamidinium cations (NH2CH=NH2 + , FA + ) and methylammonium cations (CH3NH 3+ , MA + ); the X site is F - , Cl - , Br - , and I -at least one of; the thickness is 200 to 1000 nm;

[0011] the carbon electrode described; the thickness is 5 to 100 μm.

[0012] The preparation method of the carbon-based organic-inorganic perovskite solar cell modified by 4-fluorobenzamidine hydrochloride, the method comprising the following steps:

[0013] 1) Prepare an electron transport layer on a transparent conductive substrate;

[0014] 2) Spin-coat a 4-fluorobenzamidine hydrochloride solution on the surface of the electron transport layer, and perform annealing treatment to obtain a 4-fluorobenzamidine hydrochloride modified layer;

[0015] The concentration of the 4-fluorobenzamidine hydrochloride solution is 0.5 to 3 mg / mL; the spin-coating speed is 1000 to 6000 rpm, and the spin-coating time is 10 to 60 s; the annealing temperature is 100 to 120 °C, and the treatment time is 5 to 20 min;

[0016] The spin-coating amount is 10 to 200 μL / 4 to 25 cm 2 ;

[0017] 3) Use a spin coater to spin-coat a perovskite precursor solution on the 4-fluorobenzamidine hydrochloride modified layer, perform annealing after treatment by a low-pressure auxiliary device to obtain a perovskite layer;

[0018] The solvent of the perovskite precursor solution is at least one of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), acetonitrile (MeCN), methylammonium acetate, methylammonium formate, methylammonium butyrate, γ-butyrolactone, absolute ethanol;

[0019] The concentration of the perovskite precursor solution is 0.2 to 2 mol / L, and the concentration is based on the content of Pb;

[0020] 4) Doctor-blade coat a carbon paste on the surface of the perovskite layer, and then perform annealing treatment to finally obtain a carbon electrode perovskite solar cell based on the perovskite lower interface modified by 4-fluorobenzamidine hydrochloride.

[0021] In step 2), the preparation method of the 4-fluorobenzamidine hydrochloride solution is to add 4-fluorobenzamidine hydrochloride to ethanol to obtain an ethanol solution of 4-fluorobenzamidine hydrochloride;

[0022] In step 3), the spin coating speed is 1000 - 6000 rpm, and the spin coating time is 10 - 60 s; when the low-pressure auxiliary equipment is used for treatment, the vacuum degree is 1 - 100 Pa, and the treatment time is 1 - 60 s; the annealing temperature is 100 - 120 °C, and the treatment time is 5 - 20 min;

[0023] In step 4), the annealing temperature is 100 - 120 °C, and the treatment time is 15 - 20 min;

[0024] For the carbon paste in step 4), the sheet resistance is < 30 Ω, and the solid content is 40 - 60%.

[0025] The substantial characteristics of the present invention are:

[0026] In the current technology, in order to improve the stability of the perovskite layer, interface modification is usually used to improve the stability of the perovskite. For example, in patent CN118890912A, the upper interface of the perovskite layer is modified with dodecyl acetate, and the positive and negative charge defects on the surface of the perovskite layer are passivated through the carboxylic acid group and amino ions, thereby improving the interface contact situation between the perovskite layer and the carbon electrode; in patent CN118488720A, by adding an Mxene nanomaterial layer between the perovskite layer and the carbon layer of the all-inorganic perovskite solar cell, a more suitable energy level matching is achieved to improve the performance of the device.

[0027] The present invention improves the stability of the perovskite by adding a 4-fluorobenzamidine hydrochloride modification layer between the electron transport layer and the perovskite layer. The principle is that the 4-fluorobenzamidine cation (C7H6FN2 + ) in 4-fluorobenzamidine hydrochloride can combine with lead ions (Pb 2+ ), formamidinium ions (FA + ) in the perovskite layer to form stable chemical bonds, passivate the defects in the lattice, reduce non-radiative recombination, enhance the photoelectric conversion efficiency (PCE). At the same time, since the electronegativity of chloride ions (Cl - ) is greater than that of iodide ions (I - ), so Cl - can partially fill the vacancies of I - . The presence of the passivation layer containing chloride ions (Cl - ) helps surface defect passivation and reduces non-radiative recombination losses. The 4-fluorobenzamidine cation (C7H6FN2 + ) and chloride ions (Cl - ) synergistically passivate the cation and anion defects of the perovskite thin film, which can significantly reduce charge recombination and improve the charge transport performance of the perovskite layer, thereby increasing the open-circuit voltage (Voc) and fill factor (FF) of the device.

[0028] In addition, the 4-fluorobenzamidine cation (C7H6FN2+ ) The hydrophobic benzene ring structure is adsorbed on the perovskite surface to form a hydrophobic layer. This hydrophobic layer can effectively prevent direct contact between water and perovskite, thereby reducing the erosion of perovskite by water and further improving the stability of the device.

[0029] The beneficial effects of the present invention are as follows:

[0030] 1) A carbon-based organic-inorganic perovskite solar cell modified by 4-fluorobenzamidine hydrochloride provided by the present invention has a simple preparation process, convenient operation and low cost. As shown in the attached Figure 2 , under the condition of indoor non-encapsulation and storage for 15 days, the efficiency before modification is 83% of the initial value, while the efficiency after modification is 93.4% of the initial value. The adopted modification process improves the overall stability of the device by 12.5%, and the stability improvement is obvious;

[0031] 2) Compared with the standard sample not modified by 4-fluorobenzamidine hydrochloride, the present invention reduces the interface defects between the electron transport layer and the perovskite layer, reduces the number of non-radiative recombinations of carriers, improves the lifetime, and has higher carrier transport performance. Compared with the comparative example, the open-circuit voltage is increased by 11.76%, the fill factor is increased by 3.49%, and the photoelectric conversion efficiency is increased by 6.74%. Although significant progress has been made in the research on perovskite solar cells in the prior art, the key field of interface modification between the electron transport layer and the perovskite layer still needs further exploration. By supplementing the deficiencies of existing research, the present invention provides a more comprehensive research perspective for this field, especially in improving the stability and efficiency of devices. Among them, the 4-fluorobenzamidine cation (C7H6FN2 + ) and chloride ion (Cl - ) in 4-fluorobenzamidine hydrochloride can synergistically passivate the free cations and anions in the perovskite thin film, passivate the defects in the lattice, significantly reduce the non-radiative recombination of carriers, and improve the photoelectric conversion efficiency; the benzene ring structure in the 4-fluorobenzamidine cation (C7H6FN2 + ) can effectively isolate the water molecules that damage the perovskite layer from contacting it, play a protective role in the perovskite layer, and is beneficial to improving the stability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic structural diagram of the solar cell of Example 1; wherein, 1 is a transparent conductive substrate, 2 is an electron transport layer, 3 is a 4-fluorobenzamidine hydrochloride modification layer, 4 is a perovskite layer, and 5 is a carbon electrode;

[0033] Figure 2 is the stability test curve of the carbon electrode perovskite solar cell device obtained in Example 1 and Example 11 (comparative example);

[0034] Figure 3J-V test curve of the carbon electrode perovskite solar cell device obtained in Example 1 and Example 11 (comparative example). Detailed implementation mode

[0035] The 4-fluorobenzamidine hydrochloride involved in the present invention is a well-known material, and those in the following examples are from Shanghai Aladdin Biochemical Technology Co., Ltd. and Beijing InnoChem Technology Co., Ltd.; but not limited thereto.

[0036] Example 1.

[0037] A carbon electrode perovskite solar cell based on a 4-fluorobenzamidine hydrochloride solution modified perovskite lower interface, and the schematic diagram of the structure of the solar cell is as Figure 1 shown. From bottom to top, it is a transparent conductive substrate 1, an electron transport layer 2, 4-fluorobenzamidine hydrochloride 3, a perovskite layer 4, and a carbon electrode 5. The specific preparation process is as follows:

[0038] Step 1. Clean the FTO substrate:

[0039] The commercial FTO (2.5 cm × 2.5 cm) transparent conductive substrate used in this example has an average light transmittance of 90%. The FTO substrate is ultrasonically cleaned with glass cleaning agent, deionized water, and alcohol for 30 minutes in sequence, and then dried with a nitrogen gun.

[0040] Step 2. Prepare the SnO2 electron transport layer:

[0041] Weigh 625 mg of urea and 137.5 mg of SnCl2·2H2O with a balance and put them into a blue mouth bottle. Then add 625 μL of HCl, 12.5 μL of TGA, and 50 mL of deionized water with a pipette gun in sequence, and mix evenly to obtain the SnO2 growth solution for standby.

[0042] Immerse the cleaned FTO substrate into the staining dish containing the SnO2 growth solution, place it in an oven at 90 °C for 4 hours, and then take it out. Ultrasonically clean it with deionized water for 5 minutes, and then dry its surface with a nitrogen gun; then perform annealing treatment (annealing temperature 170 °C, annealing time 60 minutes), and finally obtain the electron transport layer SnO2; the thickness is 30 nm.

[0043] Step 3. Prepare the 4-fluorobenzamidine hydrochloride modification layer:

[0044] Weigh 1 mg of 4-fluorobenzamidine hydrochloride with an electronic balance, add it to a reagent glass bottle, and then add 1 mL of ethanol to obtain a 4-fluorobenzamidine hydrochloride ethanol solution with a concentration of 1 mg / mL. Place the annealed device in the previous step on a spin coater for adsorption. After dropping 100 μL on the SnO2 electron transport layer, spin it at 4000 rmp for 30 s, and then anneal it at 100 °C for 10 minutes; the thickness is 5 nm.

[0045] Step 4. Preparation of FA 0.3 MA 0.7 PbI₃ perovskite layer:

[0046] Prepare 1.33 mol / L FA 0.3 MA 0.7 PbI₃ perovskite precursor solution, the concentration is calculated based on the content of lead, specifically including solute formamidinium iodide (FAI), methylammonium iodide (MAI), and lead iodide (PbI₂), with molar amounts of 0.36 mmol, 0.84 mmol, and 1.2 mmol respectively. Then, 100 μL of NMP and 800 μL of DMF are added as solvents in sequence to obtain 900 μL of perovskite precursor solution.

[0047] Using a spin coater, spin coat the prepared perovskite precursor solution on the 4-fluorobenzamidine hydrochloride modification layer. First, spin coat at 2500 rpm for 10 s, then at 4500 rpm for 10 s, and then immediately place it in a low-pressure auxiliary system (DL-10A type quartz vacuum gauge and vacuum pump) for low-pressure (vacuum degree of 10 Pa) treatment for 60 s to quickly volatilize the solvent, thereby obtaining a well-crystallized intermediate phase thin film. After the low-pressure treatment, anneal on a heating table at 120 °C for 20 min to obtain a well-crystallized perovskite thin film. Among them, the volume of the spin-coated perovskite precursor is 60 μL; the thickness is 600 nm.

[0048] Step 5. Preparation of carbon electrode:

[0049] Attach two 3M tapes on the surface of the perovskite layer to control the thickness of the carbon electrode, leaving a rectangular gap with a width of 0.3 cm and a length of 2.5 cm in the middle. Take 50 mg of low-temperature carbon paste (sheet resistance < 30 ohms, solid content of 50%, cleaning agent is cyclohexanone, CAS number is 7440-44-0. The same applies to the following examples and will not be repeated) and put it into the gap, and scrape it multiple times in the same direction with a blade until the gap is completely filled. The area of the scraped carbon electrode is 0.3 cm × 2.5 cm, and then anneal on a heating table at 100 °C for 15 min; the thickness is 10 μm.

[0050] In this example, four measurement points are randomly selected for a single carbon electrode perovskite solar cell, and the effective area of each measurement point is 0.075 cm 2 .

[0051] In this example, a solar simulator is used to select a K-2400 light source to simulate AM 1.5G illumination for J-V testing of a carbon electrode perovskite solar cell with a 4-fluorobenzamidine hydrochloride-modified perovskite light-absorbing layer lower interface, as Figure 3As shown by the solid line, the photoelectric conversion efficiency of the solar cell obtained from the J-V curve is 11.69%, and the open-circuit voltage, short-circuit current density, and fill factor are 0.8520 V, 23.37 mA / cm 2 and 58.73% respectively.

[0052] In this embodiment, a solar simulator was used to select a K-2400 light source to simulate AM 1.5G illumination, and a 15-day tracking test was conducted on the stability of the photoelectric conversion efficiency of a carbon electrode perovskite solar cell with a perovskite light-absorbing layer modified with 4-fluorobenzamidine hydrochloride at the lower interface. As Figure 2 shown by the solid line, the photoelectric conversion efficiency after 15 days of storage is 10.91%, which is 93.4% of the initial efficiency.

[0053] Example 2:

[0054] A carbon electrode perovskite solar cell with a perovskite lower interface modified with an ethanol solution of 4-fluorobenzamidine hydrochloride, and other steps are the same as those in Example 1. The differences are as follows:

[0055] In the preparation of the ethanol solution of 4-fluorobenzamidine hydrochloride in Step 3, 2 mg of 4-fluorobenzamidine hydrochloride was added to 1 mL of ethanol, and the concentration was 2 mg / mL.

[0056] Example 3:

[0057] A carbon electrode perovskite solar cell with a perovskite lower interface modified with an ethanol solution of 4-fluorobenzamidine hydrochloride, and other steps are the same as those in Example 1. The differences are as follows:

[0058] In the preparation of the ethanol solution of 4-fluorobenzamidine hydrochloride in Step 3, 3 mg of 4-fluorobenzamidine hydrochloride was added to 1 mL of ethanol, and the concentration was 3 mg / mL.

[0059] Example 4:

[0060] A carbon electrode perovskite solar cell with a perovskite lower interface modified with an ethanol solution of 4-fluorobenzamidine hydrochloride, and other steps are the same as those in Example 1. The differences are as follows:

[0061] In the preparation of the ethanol solution of 4-fluorobenzamidine hydrochloride in Step 3, 0.5 mg of 4-fluorobenzamidine hydrochloride was added to 1 mL of ethanol, and the concentration was 0.5 mg / mL.

[0062] Example 5.

[0063] A carbon electrode perovskite solar cell with a perovskite lower interface modified with an ethanol solution of 4-fluorobenzamidine hydrochloride, and other steps are the same as those in Example 1. The differences are as follows:

[0064] In Step 4, the perovskite layer is prepared. The perovskite layer is FAPbI3 with a concentration of 1.33 mol / L, which is based on the content of lead. Specifically, the solutes are formamidinium iodide, lead iodide, and methylammonium chloride, with molar amounts of 1.2 mmol, 1.2 mmol, and 0.18 mmol respectively. 100 μL of NMP and 800 μL of DMF are successively added as solvents to obtain 900 μL of perovskite precursor solution.

[0065] Example 6.

[0066] For a perovskite solar cell with a carbon electrode modified by an ethanol solution of 4-fluorobenzamidine hydrochloride at the perovskite lower interface, other steps are the same as in Example 1, except that:

[0067] In Step 4, the perovskite layer is prepared. The perovskite layer is MAPbI3 with a concentration of 1.33 mol / L, which is based on the content of lead. Specifically, the solutes are methylammonium iodide, lead iodide, and methylammonium chloride, with molar amounts of 1.2 mmol, 1.2 mmol, and 0.18 mmol respectively. 100 μL of NMP and 800 μL of DMF are successively added as solvents to obtain 900 μL of perovskite precursor solution.

[0068] Example 7.

[0069] For a perovskite solar cell with a carbon electrode modified by an ethanol solution of 4-fluorobenzamidine hydrochloride at the perovskite lower interface, other steps are the same as in Example 1, except that:

[0070] In Step 4, the perovskite layer is prepared. The perovskite layer is FA 0.85 MA 0.15 PbI3 with a concentration of 1.33 mol / L, which is based on the content of lead. Specifically, the solutes are formamidinium iodide, methylammonium iodide, lead iodide, and methylammonium chloride, with molar amounts of 1.02 mmol, 0.18 mmol, 1.2 mmol, and 0.18 mmol respectively. 100 μL of NMP and 800 μL of DMF are successively added as solvents to obtain 900 μL of perovskite precursor solution.

[0071] Example 8.

[0072] For a perovskite solar cell with a carbon electrode modified by an ethanol solution of 4-fluorobenzamidine hydrochloride at the perovskite lower interface, other steps are the same as in Example 1, except that:

[0073] In Step 3, the ethanol solution of 4-fluorobenzamidine hydrochloride is prepared by adding 2 mg of 4-fluorobenzamidine hydrochloride to 1 mL of ethanol, with a concentration of 2 mg / mL;

[0074] In Step 4, the perovskite layer is prepared. The perovskite layer is FA 0.85 MA 0.15PbI3, with a concentration of 1.33 mol / L, calculated based on the lead content. Specifically, it includes solutes formamidinium iodide, methylammonium iodide, lead iodide, and methylammonium chloride, with molar amounts of 1.02 mmol, 0.18 mmol, 1.2 mmol, and 0.18 mmol respectively. 100 μL of NMP and 800 μL of DMF are successively added as solvents to obtain 900 μL of the perovskite precursor solution.

[0075] Example 9.

[0076] For the perovskite solar cell with a carbon electrode modified by an ethanol solution of 4-fluorobenzamidine hydrochloride at the perovskite lower interface, other steps are the same as in Example 1, except that:

[0077] In the preparation of the ethanol solution of 4-fluorobenzamidine hydrochloride in Step 3, 3 mg of 4-fluorobenzamidine hydrochloride is added to 1 mL of ethanol, with a concentration of 3 mg / mL;

[0078] In the preparation of the perovskite layer in Step 4, the perovskite layer is FA 0.85 MA 0.15 PbI3, with a concentration of 1.33 mol / L, calculated based on the lead content. Specifically, it includes solutes formamidinium iodide, methylammonium iodide, lead iodide, and methylammonium chloride, with molar amounts of 1.02 mmol, 0.18 mmol, 1.2 mmol, and 0.18 mmol respectively. 100 μL of NMP and 800 μL of DMF are successively added as solvents to obtain 900 μL of the perovskite precursor solution.

[0079] Example 10.

[0080] For the perovskite solar cell with a carbon electrode modified by an ethanol solution of 4-fluorobenzamidine hydrochloride at the perovskite lower interface, other steps are the same as in Example 1, except that:

[0081] In the preparation of the ethanol solution of 4-fluorobenzamidine hydrochloride in Step 3, 0.5 mg of 4-fluorobenzamidine hydrochloride is added to 1 mL of ethanol, with a concentration of 0.5 mg / mL;

[0082] In the preparation of the perovskite layer in Step 4, the perovskite layer is FA 0.85 MA 0.15 PbI3, with a concentration of 1.33 mol / L, calculated based on the lead content. Specifically, it includes solutes formamidinium iodide, methylammonium iodide, lead iodide, and methylammonium chloride, with molar amounts of 1.02 mmol, 0.18 mmol, 1.2 mmol, and 0.18 mmol respectively. 100 μL of NMP and 800 μL of DMF are successively added as solvents to obtain 900 μL of the perovskite precursor solution.

[0083] Example 11. (Comparative Example)

[0084] For the perovskite solar cell with a carbon electrode at the lower interface of the perovskite modified by an ethanol solution of 4-fluorobenzamidine hydrochloride, other steps are the same as those in Example 1, except that:

[0085] Omit the operation in Step 3, do not prepare the 4-fluorobenzamidine hydrochloride modification layer, and directly scrape the carbon electrode on the surface of the perovskite light-absorbing layer.

[0086] In this example, a solar simulator was used to select a K-2400 light source to simulate AM 1.5G illumination for J-V testing of a perovskite solar cell with an interface between a perovskite layer and a carbon electrode that was not modified with 4-fluorobenzamidine hydrochloride. As Figure 3 shown by the dashed line in the figure, from the J-V curve, the power conversion efficiency of the solar cell was 10.94%, and the open-circuit voltage, short-circuit current density, and fill factor were 0.7623 V, 22.58 mA / cm 2 and 55.02% respectively.

[0087] In this example, a solar simulator was used to select a K-2400 light source to simulate AM 1.5G illumination for a 15-day tracking test on the stability of the power conversion efficiency of a perovskite solar cell with a carbon electrode at the lower interface of a perovskite light-absorbing layer that was not modified with 4-fluorobenzamidine hydrochloride. As Figure 2 shown by the dashed line in the figure, the power conversion efficiency after 15 days of storage was 9.08%, which was 83% of the initial efficiency.

[0088] By comparing the device test parameters in Example 1 and Example 11 (control example), it shows that in an organic-inorganic hybrid perovskite solar cell with a carbon electrode, introducing a 4-fluorobenzamidine hydrochloride modification layer between the perovskite light-absorbing layer and the carbon electrode layer by the drop-coating method can significantly improve the power conversion efficiency of the device.

[0089] The present invention is not limited to the above embodiments and can be changed within the scope of the claims. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

[0090] Matters not described in the present invention are well-known technologies.

Claims

1. A carbon-based organic-inorganic perovskite solar cell modified with 4-fluorobenzamidine hydrochloride, characterized in that, The solar cell comprises, from bottom to top, a transparent conductive substrate, an electron transport layer, a 4-fluorobenzamidine hydrochloride modification layer, a perovskite layer, and a carbon electrode; The thickness of the 4-fluorobenzamidine hydrochloride modification layer is 5 - 10 nm.

2. The carbon-based organic-inorganic perovskite solar cell modified with 4-fluorobenzamidine hydrochloride according to claim 1, characterized in that, The substrate is fluorine-doped tin oxide transparent conductive glass (FTO), indium tin oxide transparent conductive glass (ITO), PET / ITO (PET is polyethylene terephthalate), or PEN / ITO (PEN is polyethylene naphthalate); The electron transport layer described above is at least one of tin dioxide (SnO2), titanium dioxide (TiO2), chlorine-doped titanium dioxide, fullerene (C 60 ), [6,6]-phenyl C61 butyric acid methyl ester (PCBM), zinc oxide (ZnO), TiO2-SnO2, ZnO-TiO2, ZnO-SnO2; and has a thickness of 5 to 180 nm; The structural formula of the perovskite layer material is APbX3. The A site is at least one of formamidinium cations (NH2CH=NH2 + , FA + ) and methylammonium cations (CH3NH 3+ , MA + ); the X site is at least one of F - , Cl - , Br - and I - ; and the thickness is 200 - 1000 nm.

3. The carbon-based organic-inorganic perovskite solar cell modified with 4-fluorobenzamidine hydrochloride as claimed in claim 1, characterized in that, The carbon electrode has a thickness of 5 - 100 μm.

4. The preparation method of the carbon-based organic-inorganic perovskite solar cell modified by 4-fluorobenzamidine hydrochloride as claimed in claim 1, characterized in that, The method comprises the following steps: 1) Prepare an electron transport layer on the transparent conductive substrate; 2) Spin-coat a 4-fluorobenzamidine hydrochloride solution on the surface of the electron transport layer, and then perform annealing treatment to obtain a 4-fluorobenzamidine hydrochloride modification layer; The concentration of the 4-fluorobenzamidine hydrochloride solution is 0.5 - 3 mg / mL; the spin-coating speed is 1000 - 6000 rpm, and the spin-coating time is 10 - 60 s; the annealing temperature is 100 - 120 °C, and the treatment time is 5 - 20 min; The spin coating amount is 10 to 200 μL / 4 to 25 cm 2 ; 3) Spin-coat a perovskite precursor solution on the 4-fluorobenzamidine hydrochloride modification layer by using a spin coater, perform annealing after treatment with a low-pressure auxiliary device to obtain a perovskite layer; The solvent of the perovskite precursor solution is at least one of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), acetonitrile (MeCN), methylammonium acetate, methylammonium formate, butylammonium formate, γ-butyrolactone, and absolute ethanol; The concentration of the perovskite precursor solution is 0.2 - 2 mol / L, calculated based on the content of Pb; 4) Knife-coat a carbon paste on the surface of the perovskite layer, and then perform annealing treatment to finally obtain a carbon electrode perovskite solar cell based on the perovskite lower interface modified by 4-fluorobenzamidine hydrochloride.

5. The preparation method of the carbon-based organic-inorganic perovskite solar cell modified with 4-fluorobenzamidine hydrochloride as claimed in claim 4, characterized in that, In step 2), the solvent of the 4-fluorobenzamidine hydrochloride solution is ethanol.

6. The preparation method of the carbon-based organic-inorganic perovskite solar cell modified with 4-fluorobenzamidine hydrochloride according to claim 4, characterized in that, In step 3), the spin-coating speed is 1000 - 6000 rpm, and the spin-coating time is 10 - 60 s; the vacuum degree during the treatment with the low-pressure auxiliary device is 1 - 100 Pa, and the treatment time is 1 - 60 s; the annealing temperature is 100 - 120 °C, and the treatment time is 5 - 20 min; In step 4), the annealing temperature is 100 - 120 °C, and the treatment time is 15 - 20 min; For the carbon paste in step 4), the sheet resistance is < 30 Ω, and the solid content is 40 - 60%.

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