Perovskite Solar Cell with Sub-Microscopic Protrusions and Preparation Method Thereof

Abstract

The present invention relates to the technical field of perovskite solar cells, and provides a perovskite solar cell with sub-microscopic protrusions and a preparation method thereof, which includes a conductive glass substrate, an electron transport layer, a perovskite active layer, a hole transport layer, and a metal electrode that are tightly connected in sequence from top to bottom. The lower surface of the perovskite active layer has a plurality of sub-microscopic protrusions with a height of 100 nm to 170 nm, and the interval between the sub-microscopic protrusions is 2.5 μm to 7.5 μm; when incident light shines on the perovskite solar cell and passes through the perovskite active layer, the sub-microscopic protrusions cause the incident light to undergo backscattering, and the backscattered incident light is reflected back to the perovskite active layer by the metal electrode. The present invention can effectively improve the efficiency of the perovskite solar cell.

Description

Technical Field

[0001] The present invention relates to the technical field of perovskite solar cells, and in particular to a perovskite solar cell with sub-microscopic protrusions and a preparation method thereof. Background Art

[0002] Solar energy is rich in reserves and inexhaustible, and is recognized as a clean energy source by countries around the world. Solar cells can convert solar energy into electrical energy. Among them, perovskite solar cells are one of the research hotspots in the field of photovoltaic energy. Its photoelectric conversion efficiency has approached that of crystalline silicon solar cells. In recent years, people have used various methods to prepare high-quality perovskite light-absorbing layers to improve the device efficiency, such as additive engineering, solvent engineering, and designing new charge transport materials. Although these methods have improved the crystallinity and film quality of perovskite, it is difficult to adjust the surface morphology of the perovskite light-absorbing layer. In addition, the theoretical maximum short-circuit current density of perovskite solar cells has not reached the Shockley-Queisser limit because a considerable part of the incident light becomes loss instead of being converted into electrical energy. Specifically, due to its process characteristics, the perovskite light-absorbing layer prepared by the solution method usually exhibits a relatively flat surface, which causes a part of the incident light to directly pass through the perovskite light-absorbing layer and not be utilized by the perovskite light-absorbing layer. And perovskite solar cells are multi-layer structures, and there are interfaces between layers. Poor interface contact is also not conducive to the collection and transport of carriers. The microscopic morphology of the perovskite film determines its absorption, transmission, and reflection of light, thus affecting the density of photo-generated carriers generated. In the prior art, the surface of perovskite is mostly flat, with insufficient light absorption and low density of photo-generated carriers, reducing the device efficiency. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the related art. For this purpose, the present invention provides a perovskite solar cell with sub-microscopic protrusions and a preparation method thereof, realizing the production of a perovskite battery with high light energy utilization rate.

[0004] The present invention provides a perovskite solar cell with sub-microscopic protrusions, including a conductive glass substrate, an electron transport layer, a perovskite active layer, a hole transport layer, and a metal electrode that are tightly connected in sequence from top to bottom. The lower surface of the perovskite active layer has a plurality of sub-microscopic protrusions with a height of 100 nm to 170 nm, and the interval between the sub-microscopic protrusions is 2.5 μm to 7.5 μm;

[0005] When incident light shines on the perovskite solar cell and passes through the perovskite active layer, the sub-microscopic protrusions cause the incident light to undergo backscattering, and the incident light after backscattering is reflected back to the perovskite active layer by the metal electrode.

[0006] The perovskite solar cell with submicroscopic protrusions provided by the present invention has submicroscopic protrusions on the lower surface of the perovskite active layer with a height of 120 nm and a spacing of 3.8 μm between the submicroscopic protrusions.

[0007] The perovskite solar cell with submicroscopic protrusions provided by the present invention has an ITO conductive glass as the conductive glass substrate, a silver electrode as the metal electrode, tin oxide as the electron transport layer, and a first compound doped with lithium bis(trifluoromethanesulfonyl)imide and tert-butylpyridine as the hole transport layer. The structural formula of the first compound is shown as follows:

[0008] 。

[0009] The thickness of the metal electrode of the perovskite solar cell with submicroscopic protrusions provided by the present invention is 50 nm to 150 nm.

[0010] The present invention provides a method for preparing a perovskite solar cell with submicroscopic protrusions, which includes the following steps:

[0011] S1: Cleaning, drying and ultraviolet ozone treatment of the conductive glass substrate;

[0012] S2: Obtaining an electron transport layer solution, spin-coating the electron transport layer solution on the conductive glass substrate, and performing a first annealing treatment on the spin-coated electron transport layer solution to obtain a first substrate to be treated;

[0013] S3: Obtaining a perovskite precursor solution, an antisolvent and a first solution, dissolving the perovskite precursor solution in the first solution, adding a perovskite additive to the perovskite precursor solution to obtain a target precursor solution. The perovskite additive includes a second compound with a molar fraction of 5% to 20%. Spin-coating the precursor solution on the first substrate to be treated and adding the antisolvent, and performing a second annealing treatment on the spin-coated first substrate to be treated to obtain a second substrate to be treated. The structural formula of the second compound is shown as follows:

[0014] ;

[0015] S4: Spin-coating a solution of the first compound on the second substrate to be treated to obtain a third substrate to be treated, selecting an electrode metal, and evaporating the electrode metal on the third substrate to be treated to obtain a perovskite solar cell with submicroscopic protrusions, wherein the solution of the first compound includes lithium bis(trifluoromethanesulfonyl)imide and tert-butylpyridine.

[0016] According to the preparation method of the perovskite solar cell with sub-microscopic protrusions provided by the present invention, in step S2, the electron transport layer solution is a tin oxide colloidal aqueous solution with a mass fraction of 3% to 5%, the duration of the first annealing treatment is 20 minutes to 60 minutes, and the annealing temperature is 90°C to 180°C.

[0017] According to the preparation method of the perovskite solar cell with sub-microscopic protrusions provided by the present invention, in step S3, the perovskite precursor solution includes cesium iodide, lead iodide, lead bromide, and formamidinium iodide, and the molar concentration of lead element in the perovskite precursor solution is 1.0 mol / L to 1.6 mol / L.

[0018] According to the preparation method of the perovskite solar cell with sub-microscopic protrusions provided by the present invention, in step S3, the first solution includes N,N-dimethylformamide and dimethyl sulfoxide, and the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is 2:1 to 5:1. When adding the anti-solvent, the volume ratio of the target precursor solution to the anti-solvent is 0.35:1 to 0.035:1.

[0019] According to the preparation method of the perovskite solar cell with sub-microscopic protrusions provided by the present invention, in step S3, the perovskite additive includes a second compound with a molar fraction of 10%.

[0020] According to the preparation method of the perovskite solar cell with sub-microscopic protrusions provided by the present invention, in step S3, the duration of the second annealing treatment is 5 minutes to 60 minutes, and the annealing temperature is 90°C to 150°C.

[0021] One or more of the above technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0022] For the perovskite solar cell with sub-microscopic protrusions and its preparation method provided by the present invention, the incident light passing through the perovskite active layer undergoes backscattering due to the sub-microscopic protrusions on the lower surface of the perovskite active layer, and thus is reflected back into the perovskite active layer by the metal electrode, improving the utilization efficiency of light energy by the perovskite solar cell. In addition, the sub-microscopic protrusions also increase the contact area between the perovskite active layer and the hole transport layer, which is conducive to the separation and extraction of charges, and improves the efficiency of the perovskite solar cell.

[0023] The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] To more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a schematic structural diagram of a perovskite solar cell with submicroscopic protrusions provided by the present invention.

[0026] Figure 2 It is a comparison diagram of the lower surface morphologies of the perovskite solar cell with submicroscopic protrusions provided by the present invention and a perovskite solar cell without using a perovskite additive including a second compound.

[0027] Figure 3 It is an ultraviolet-visible absorption spectrum diagram of the perovskite solar cell provided by the present invention and a perovskite solar cell without using a perovskite additive including a second compound.

[0028] Figure 4 It is a current density-voltage curve diagram of the perovskite solar cell provided by the present invention and a perovskite solar cell without using a perovskite additive including a second compound.

[0029] Figure 5 It is a schematic diagram of the cross-section of the perovskite active layer of the perovskite solar cell provided by the present invention.

[0030] Figure 6 It is an X-ray diffraction diagram of the perovskite active layer of the perovskite solar cell provided by the present invention at different molar fractions of the second compound.

[0031] Reference numerals:

[0032] 1. Conductive glass substrate; 2. Electron transport layer; 3. Perovskite active layer; 4. Hole transport layer; 5. Metal electrode. Detailed implementation manners

[0033] To make the objectives, technical solutions and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope protected by the present invention. The following embodiments are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0034] In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the embodiments of the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0035] In the description of the embodiments of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0036] In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over", and "on" the second feature can be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath", and "under" the second feature can be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0037] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0038] The following is combined with Figures 1 to 6 Describe the specific embodiments of the present invention:

[0039] Embodiment 1:

[0040] The preparation method of a perovskite solar cell with sub-microscopic protrusions is as follows: First, select a conductive glass substrate 1. In this embodiment, the conductive glass substrate 1 is ITO (Indium tin oxide) conductive glass. Then, use an ultrasonic cleaning device to ultrasonically clean the conductive glass substrate 1, and after ultrasonic cleaning, dry it with nitrogen, thereby completing the cleaning and drying of the conductive glass substrate 1. Then, use an ultraviolet ozone cleaning machine to perform ultraviolet ozone treatment on the conductive glass substrate 1. The ultraviolet ozone cleaning machine removes grease, organic substances, etc. on the surface of the conductive glass substrate 1 through oxidation by ultraviolet light and ozone, making the surface cleaner.

[0041] Next, obtain an electron transport layer solution. The electron transport layer solution is an aqueous solution of tin oxide colloid with a mass fraction of 3% - 5%. In this embodiment, it is preferably an aqueous solution of tin oxide colloid with a mass fraction of 3.75%. Subsequently, place the conductive glass substrate 1 on a spin coater and drop the electron transport layer solution onto the conductive glass substrate. Here, the dropping amount of the electron transport layer solution is 40 μL - 200 μL. In this embodiment, it is preferably 100 μL. Start the spin coater. The spin coater rotates at a high speed and makes the solution spread evenly quickly through centrifugal acceleration, and the excess solution will be thrown off the conductive glass substrate 1 by the spin coater. The spin coater works at a speed of 4000 revolutions per minute for 30 seconds, so that the electron transport layer solution is evenly spin-coated on the conductive glass substrate 1. Perform a first annealing treatment on the spin-coated electron transport layer solution. The annealing temperature of the first annealing treatment is 90°C - 180°C. In this embodiment, it is preferably 150°C. The duration of the first annealing treatment is 20 minutes - 60 minutes. In this embodiment, it is preferably 30 minutes, thereby preparing an electron transport layer 2 on the conductive glass substrate 1 and obtaining a first substrate to be processed.

[0042] Subsequently, obtain a perovskite precursor solution. Here, the perovskite precursor solution includes cesium iodide, lead iodide, lead bromide, lead chloride, and formamidinium iodide, and the molar concentration of lead element in the perovskite precursor solution is 1.0 mol / L - 1.6 mol / L. In this embodiment, it is preferably 1.377 mol / L, where the molar concentration of cesium iodide is 0.405 mol / L, the molar concentration of lead bromide is 0.405 mol / L, the molar concentration of formamidinium iodide is 0.81 mol / L, the molar concentration of lead iodide is 0.945 mol / L, and in addition, there is lead chloride with a molar concentration of 0.027 mol / L. Dissolve the perovskite precursor solution in a first solution. The first solution includes N,N-dimethylformamide and dimethyl sulfoxide, and the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is 2:1 to 5:1. In this embodiment, it is preferably that the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is 4:1.

[0043] In addition, a perovskite additive with a molar fraction of the second compound of 5% to 20% is added to the perovskite precursor solution. The name of the second compound is dimethylamine hydroiodide, and its structural formula is as follows:

[0044] ,

[0045] In this embodiment, the molar fraction of the second compound is preferably 10%. After adding the second compound, the target precursor solution can be obtained. The target precursor solution is spin-coated on the electron transport layer 2 of the first substrate to be processed and an anti-solvent is added. When adding the anti-solvent, the volume ratio of the target precursor solution to the anti-solvent is 0.35:1 to 0.035:1, and the specific ratio needs to be determined according to the type of the anti-solvent. Here, the anti-solvent is a low-polarity solvent, which can be ethyl acetate, chlorobenzene, anisole, diethyl ether, etc. In this embodiment, chlorobenzene is preferably used. And the volume of the target precursor solution spin-coated on the first substrate to be processed in this embodiment is 35 μL, and it is spin-coated at a rotation speed of 6000 revolutions per minute for 30 seconds. The spin-coated first substrate to be processed is subjected to a second annealing treatment. The duration of the second annealing treatment is 5 minutes to 60 minutes, and the annealing temperature is 90 °C to 150 °C. In this embodiment, the annealing time is preferably 30 minutes, and the annealing temperature is preferably 100 °C. After the second annealing treatment is completed, the perovskite active layer 3 is prepared on the first substrate to be processed, thereby obtaining the second substrate to be processed.

[0046] Then, the solution of the first compound is spin-coated on the perovskite active layer 3 of the second substrate to be processed to obtain the third substrate to be processed. The structural formula of the first compound is as follows:

[0047] ,

[0048] The name of the first compound is 2,2',7,7'-tetrakis[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene. In this embodiment, the solution of the first compound is a chlorobenzene solution of the first compound. In addition, the solution of the first compound also contains a small amount of lithium bis(trifluoromethanesulfonyl)imide and a small amount of tert-butylpyridine. In this embodiment, the lithium bis(trifluoromethanesulfonyl)imide is a 17.5 μL chlorobenzene solution of lithium bis(trifluoromethanesulfonyl)imide, and the tert-butylpyridine is a 28.5 μL chlorobenzene solution of tert-butylpyridine. The concentrations of the chlorobenzene solutions of lithium bis(trifluoromethanesulfonyl)imide and tert-butylpyridine are both 520 mg / ml. Finally, an electrode metal is selected. The electrode metal can be gold or silver. In this embodiment, the selected electrode metal is silver. The electrode metal is vacuum-evaporated onto the solution of the first compound after spin-coating on the third substrate to be processed through a vacuum coating system to obtain a hole transport layer 4 and a metal electrode 5. Among them, the thickness of the metal electrode 5 is 50 nm to 150 nm. And the prepared hole transport layer 4 is the first compound doped with lithium bis(trifluoromethanesulfonyl)imide and tert-butylpyridine. In this way, a perovskite solar cell with submicroscopic protrusions is obtained. Incident light enters from the conductive glass substrate 1 and sequentially passes through the electron transport layer 2, the perovskite active layer 3, the hole transport layer 4, and the metal electrode 5. Starting from the incident position of the incident light, the conductive glass substrate 1, the electron transport layer 2, the perovskite active layer 3, the hole transport layer 4, and the metal electrode 5 are tightly connected in sequence from top to bottom. Figure 1 It is a schematic structural diagram of the prepared perovskite solar cell with submicroscopic protrusions.

[0049] The lower surface of the perovskite active layer 3 of the perovskite solar cell with submicroscopic protrusions prepared in this embodiment has a plurality of submicroscopic protrusions with a height of 120 nm, and the interval between two submicroscopic protrusions is 3.8 μm. Here, the lower surface refers to the surface where the perovskite active layer 3 is connected to the hole transport layer 4, which is the same as the lower surface morphology of the perovskite active layer 3 in the perovskite solar cell in this embodiment, as shown in Figure 2 (b) of, and is different from that without using the perovskite additive including the second compound. Figure 2Compared with the perovskite active layer 3 presented in (a), the perovskite additive including the second compound can make the lower surface of the perovskite active layer 3 have obvious sub-microscopic convex structures. Such sub-microscopic convex structures can act as diffraction gratings. After incident light enters the perovskite active layer 3 from the electron transport layer 3 side, most of it will be absorbed, but there is still a part of the incident light that will pass through the perovskite active layer 3. At this time, due to the function of the sub-microscopic convex as a diffraction grating, this part of the incident light will undergo backscattering, thus being reflected by the metal electrode 5 and re-entering the perovskite active layer 3 for utilization. In addition, the sub-microscopic convex also increases the contact area between the perovskite active layer 3 and the hole transport layer 4, thereby optimizing the contact of the interface heterojunction, being conducive to the separation and extraction of charges, and further improving the efficiency of the perovskite solar cell.

[0050] Table 1 shows the performance comparison between the perovskite solar cell without using the perovskite additive including the second compound and the perovskite solar cell provided in this embodiment. Among them, Voc is the open-circuit voltage, which refers to the potential difference across the circuit when the current in the circuit where the battery device is located is zero or the external load impedance is infinite. Jsc is the ratio of the current in the circuit to the unit cross-sectional area when the voltage in the circuit where the battery device is located is zero or the external load is infinite. FF is the ratio of the maximum output power of the battery device to the product of the short-circuit current and the open-circuit voltage. PCE is the ratio of the maximum output power of the battery device to the incident light power. The larger these values are, the better the battery performance.

[0051] Table 1 Performance Comparison between the Perovskite Solar Cell without Using the Perovskite Additive including the Second Compound and the Perovskite Solar Cell Provided in this Embodiment

[0052]

[0053] Figure 3 is the ultraviolet-visible absorption spectrum diagram of the perovskite solar cell without using the perovskite additive including the second compound and the perovskite solar cell provided in this embodiment. a.u. is the absorbance unit. Figure 4 is the current density-voltage curve diagram of the perovskite solar cell without using the perovskite additive including the second compound and the perovskite solar cell provided in this embodiment at different voltages. In Figure 3 and Figure 4 A represents the perovskite solar cell without using the perovskite additive including the second compound, and B represents the perovskite solar cell provided in this embodiment. It can be seen that the performance of the perovskite solar cell provided in this embodiment has obvious progress.

[0054] To describe the morphology of the sub-microscopic protrusions, the cross-section of the sub-microscopic protrusion structure can be regarded as a curve similar to a sine function. Through characterization means such as atomic force microscopy and scanning electron microscopy, the height H of the sub-microscopic protrusion and the distance λ between the tops of two sub-microscopic protrusions can be measured. Here, the height H of the sub-microscopic protrusion and the distance λ between the tops of two sub-microscopic protrusions are the average values of the heights and distances of multiple sub-microscopic protrusions. Figure 5 It is a schematic diagram of the cross-section of the perovskite active layer. By changing the concentration of the second compound in the perovskite additive, the concentration of lead element in the perovskite precursor solution, the volume ratio of N,N-dimethylformamide and dimethyl sulfoxide in the first solution, and the annealing time of the second annealing treatment, the values of H and λ can be changed. Here, based on the preparation method of the perovskite solar cell with sub-microscopic protrusions described above in this embodiment, the concentration of the second compound in the perovskite additive, the concentration of the perovskite precursor solution, the volume ratio of N,N-dimethylformamide and dimethyl sulfoxide in the first solution, and the annealing time of the second annealing treatment are changed in turn. Among them, the mole fraction of the second compound starts from 5% and increases by 5% each time until it reaches 20%, the concentration of lead element in the perovskite precursor solution increases by 0.2 mol / L each time, the volume ratio of N,N-dimethylformamide and dimethyl sulfoxide in the first solution is 2:1, 3:1, 4:1, and 5:1 in turn, and the annealing time of the second annealing treatment is 5 minutes, 20 minutes, 45 minutes, and 60 minutes in turn. Table 2 shows the ranges of λ and H under different preparation conditions.

[0055] Table 2 Schematic table of the ranges of λ and H under different preparation conditions

[0056]

[0057] Here, the higher the mole fraction of the second compound and the concentration of lead element in the perovskite precursor solution, the higher both λ and H; as the volume ratio of N,N-dimethylformamide and dimethyl sulfoxide in the first solution increases, λ increases and H decreases; as the annealing time of the second annealing treatment increases, λ remains unchanged and H decreases.

[0058] It can be seen that the height of the sub-microscopic protrusions is between 70 nm and 230 nm, and the interval between two sub-microscopic protrusions is 2.0 μm to 7.5 μm. Among them, the interval between two sub-microscopic protrusions has a greater impact on the performance of the perovskite solar cell. And changing the mole fraction of the second compound in the perovskite additive has a more obvious regulation effect on λ and H, especially obvious for λ. In the actual preparation process, the mole fraction of the second compound is also relatively easy to regulate and has little impact on other aspects of the performance of the perovskite solar cell. Therefore, a perovskite solar cell with higher performance is mainly prepared by changing the mole fraction of the second compound in the perovskite additive.

[0059] Example 2:

[0060] The preparation method of a perovskite solar cell with sub-microscopic protrusions is as follows: First, select a conductive glass substrate 1. In this example, the conductive glass substrate 1 is ITO conductive glass. Then, use an ultrasonic cleaning device to ultrasonically clean the conductive glass substrate 1, and blow it dry with nitrogen after ultrasonic cleaning, thereby completing the cleaning and drying of the conductive glass substrate 1. Next, use an ultraviolet ozone cleaning machine to perform ultraviolet ozone treatment on the conductive glass substrate 1. The ultraviolet ozone cleaning machine removes grease and organic substances on the surface of the conductive glass substrate 1 through oxidation by ultraviolet light and ozone, making the surface cleaner.

[0061] Next, obtain an electron transport layer solution. The electron transport layer solution is an aqueous solution of tin oxide colloid with a mass fraction of 3% - 5%. In this example, it is preferably an aqueous solution of tin oxide colloid with a mass fraction of 3.75%. Subsequently, place the conductive glass substrate 1 on a spin coater and drop the electron transport layer solution onto the conductive glass substrate. Here, the dropping amount of the electron transport layer solution is 40 μL - 200 μL. In this example, it is preferably 100 μL. Start the spin coater, and the spin coater operates at a speed of 4000 revolutions per minute for 30 seconds, so that the electron transport layer solution is evenly spin-coated on the conductive glass substrate 1. Perform a first annealing treatment on the spin-coated electron transport layer solution. The annealing temperature of the first annealing treatment is 90°C - 180°C. In this example, it is preferably 150°C, and the duration of the first annealing treatment is 20 minutes - 60 minutes. In this example, it is preferably 30 minutes, thereby preparing an electron transport layer 2 on the conductive glass substrate 1 and obtaining a first substrate to be processed.

[0062] Subsequently, obtain a perovskite precursor solution. Here, the perovskite precursor solution includes cesium iodide, lead iodide, lead bromide, lead chloride, and formamidinium iodide, and the molar concentration of lead element in the perovskite precursor solution is 1.0 mol / L - 1.6 mol / L. In this example, it is preferably 1.377 mol / L, where the molar concentration of cesium iodide is 0.405 mol / L, the molar concentration of lead bromide is 0.405 mol / L, the molar concentration of formamidinium iodide is 0.81 mol / L, the molar concentration of lead iodide is 0.945 mol / L, and in addition, there is lead chloride with a molar concentration of 0.027 mol / L. Dissolve the perovskite precursor solution in a first solution. The first solution includes N,N-dimethylformamide and dimethyl sulfoxide, and the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is 2:1 to 5:1. In this example, it is preferably that the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is 4:1.

[0063] In addition, a perovskite additive with a molar fraction of the second compound of 0% to 20% is added to the perovskite precursor solution. The name of the second compound is dimethylamine hydroiodide, and its structural formula is as follows:

[0064] ,

[0065] In this embodiment, the molar fractions of the second compound are 0%, 5%, 10%, 15%, and 20% respectively. The second compounds with these different molar fractions are sequentially added to the perovskite precursor solution respectively, and different target precursor solutions can be obtained. The different target precursor solutions are respectively spin-coated on the electron transport layer 2 of the first substrate to be processed and an anti-solvent is added. When adding the anti-solvent, the volume ratio of the target precursor solution to the anti-solvent is 0.35:1 to 0.035:1, and the specific ratio needs to be determined according to the type of the anti-solvent. Here, the anti-solvent is a low-polarity solvent, which can be ethyl acetate, chlorobenzene, anisole, ether, etc. In this embodiment, chlorobenzene is preferably used. And in this embodiment, the volume of the target precursor solution spin-coated on each first substrate to be processed is 35 μL, and it is spin-coated at a speed of 6000 revolutions per minute for 30 seconds. A second annealing treatment is performed on each spin-coated first substrate to be processed. The duration of the second annealing treatment is 5 minutes to 60 minutes, and the annealing temperature is 90°C to 150°C. In this embodiment, the annealing time is preferably 30 minutes and the annealing temperature is preferably 100°C. After the second annealing treatment is completed, a perovskite active layer 3 is formed on each first substrate to be processed, thereby obtaining a plurality of second substrates to be processed.

[0066] Then, a solution of the first compound is spin-coated on the perovskite active layer 3 of each second substrate to be processed, obtaining a third substrate to be processed. The structural formula of the first compound is as follows:

[0067] ,

[0068] The name of the first compound is 2,2',7,7'-tetra[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene. In this example, the solution of the first compound is a chlorobenzene solution of the first compound. In addition, the solution of the first compound also contains a small amount of lithium bis(trifluoromethanesulfonyl)imide and a small amount of tert-butylpyridine. In this example, the lithium bis(trifluoromethanesulfonyl)imide is a 17.5 μL chlorobenzene solution of lithium bis(trifluoromethanesulfonyl)imide, and the tert-butylpyridine is a 28.5 μL chlorobenzene solution of tert-butylpyridine. The concentrations of the chlorobenzene solutions of lithium bis(trifluoromethanesulfonyl)imide and tert-butylpyridine are both 520 mg / ml. Finally, an electrode metal is selected. The electrode metal can be gold or silver. In this example, the selected electrode metal is silver. The electrode metal is vacuum-evaporated onto the solution of the first compound after spin-coating on each third substrate to be processed through a vacuum coating system, obtaining a hole transport layer 4 and a metal electrode 5. Among them, the thickness of the metal electrode 5 is 50 nm to 150 nm. And the prepared hole transport layer 4 is the first compound doped with lithium bis(trifluoromethanesulfonyl)imide and tert-butylpyridine. In this way, a plurality of perovskite solar cells with submicroscopic protrusions are obtained. Incident light enters from the conductive glass substrate 1, sequentially passes through the electron transport layer 2, the perovskite active layer 3, the hole transport layer 4, and the metal electrode 5. Starting from the incident position of the incident light, the conductive glass substrate 1, the electron transport layer 2, the perovskite active layer 3, the hole transport layer 4, and the metal electrode 5 are tightly connected in sequence from top to bottom.

[0069] Due to the different concentrations of the second compound, the heights and intervals of the submicroscopic protrusions on the lower surface of the perovskite active layer 3 of the obtained perovskite solar cells are also different. Here, the lower surface refers to the surface of the perovskite active layer 3 connected to the hole transport layer 4. The heights and intervals of the submicroscopic protrusions on the lower surface of the perovskite active layer under different mole fractions of the second compound are shown in Table 3:

[0070] Table 3 Schematic table of the heights and intervals of the submicroscopic protrusions on the lower surface of the perovskite active layer under different mole fractions of the second compound

[0071]

[0072] It can be seen that with the increase in the mole fraction of the second compound, both the height and the interval of the submicroscopic protrusions increase. However, since the purpose of the perovskite active layer is to convert light energy into electrical energy, the crystal quality and phase purity of the perovskite active layer also need to be considered. The impurity phase will reduce the light absorption ability of the perovskite active layer. Therefore, the morphology of the submicroscopic protrusions cannot be considered alone. In the present invention, while controlling the morphology of the submicroscopic protrusions, it is necessary to increase the photoactive phase of the perovskite active layer, that is, the black-phase formamidinium lead iodide, and reduce the non-photoactive phases, that is, dimethylamine lead iodide, wide-bandgap yellow non-perovskite phase, and lead iodide. Figure 6X-ray diffraction patterns of perovskite active layers at different mole fractions of different second compounds. Among them, C is the diffraction peak of dimethylammonium lead iodide and the wide-bandgap yellow non-perovskite phase, D is the diffraction peak of lead iodide, and E is the diffraction peak of black-phase formamidinium lead iodide. It can be seen that as Figure 6 shown, when the mole fraction of the second compound is 0, there is more lead iodide in the perovskite active layer, which reduces the light absorption ability of the perovskite as an impurity phase. When the mole fraction of the second compound is 5%, the content of lead iodide begins to decrease. When the mole fraction of the second compound is 10%, the content of lead iodide further decreases, and the content of black-phase formamidinium lead iodide is also relatively high. Continuing to increase the mole fraction of the second compound, when the mole fraction of the second compound is 15 - 20%, dimethylammonium lead iodide and the wide-bandgap yellow non-perovskite phase are generated, which will reduce the light absorption ability of the perovskite active layer, thereby reducing the photoelectric conversion efficiency of the perovskite solar cell. Therefore, when the mole fraction of the second compound is 10%, the photoelectric conversion efficiency of the perovskite solar cell is relatively high.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A perovskite solar cell having submicroscopic protrusions, characterized in that The invention comprises a conductive glass substrate, an electron transport layer, a perovskite active layer, a hole transport layer and a metal electrode which are closely connected in sequence from top to bottom. The lower surface of the perovskite active layer has a plurality of submicroscopic protrusions with a height of 100nm to 170nm, and the intervals between the submicroscopic protrusions are 2.5μm to 7.5μm. The perovskite additive comprising a second compound makes the lower surface of the perovskite active layer have an obvious submicroscopic protrusion structure. Due to different concentrations of the second compound, the height and interval of the submicroscopic protrusions on the lower surface of the perovskite active layer of the obtained perovskite solar cell are also different. The molar fraction of the second compound is 5% to 20%. The structural formula of the second compound is as follows: ； When incident light shines on the perovskite solar cell and passes through the perovskite active layer, the submicroscopic protrusions cause the incident light to be backscattered, and the backscattered incident light is reflected back to the perovskite active layer by the metal electrode.

2. The perovskite solar cell with submicroscopic protrusions according to claim 1, characterized in that: The height of the submicroscopic protrusions on the lower surface of the perovskite active layer is 120 nm, and the interval between the submicroscopic protrusions is 3.8 μm.

3. The perovskite solar cell with submicroscopic protrusions according to claim 1, characterized in that: The conductive glass substrate is ITO conductive glass, the metal electrode is a silver electrode, the electron transport layer is tin oxide, and the hole transport layer is a first compound doped with lithium bis(trifluoromethanesulfonyl)imide and tert-butylpyridine. The structural formula of the first compound is as follows: 。 4. The perovskite solar cell with submicroscopic protrusions according to claim 1, characterized in that: The thickness of the metal electrode is 50nm~150nm.

5. A method for preparing a perovskite solar cell having submicroscopic protrusions, characterized in that: The method for preparing a perovskite solar cell having submicroscopic protrusions as claimed in any one of claims 1 to 4 comprises the following steps: S1: Clean, blow dry and treat the conductive glass substrate with UV ozone; S2: obtaining an electron transport layer solution, spin-coating the electron transport layer solution on a conductive glass substrate, and performing a first annealing treatment on the spin-coated electron transport layer solution to obtain a first substrate to be treated; S3: obtaining a perovskite precursor solution, an anti-solvent and a first solution, dissolving the perovskite precursor solution in the first solution, and adding a perovskite additive to the perovskite precursor solution to obtain a target precursor solution, wherein the perovskite additive includes a second compound with a molar fraction of 5% to 20%, spin-coating the target precursor solution on the first substrate to be processed and adding an anti-solvent, performing a second annealing treatment on the first substrate to be processed after spin coating, and obtaining a second substrate to be processed, wherein the structural formula of the second compound is as follows: ； The perovskite additive including the second compound makes the lower surface of the perovskite active layer have an obvious submicroscopic protrusion structure, and the height and interval of the submicroscopic protrusions on the lower surface of the perovskite active layer of the obtained perovskite solar cell are also different due to different concentrations of the second compound; S4: spin-coating a solution of the first compound on the second substrate to be processed to obtain a third substrate to be processed, selecting an electrode metal, and vapor-depositing the electrode metal on the third substrate to be processed to obtain a perovskite solar cell with submicroscopic protrusions, wherein the solution of the first compound includes lithium bis(trifluoromethanesulfonyl)imide and tert-butylpyridine.

6. The method for preparing a perovskite solar cell having submicroscopic protrusions according to claim 5, characterized in that: In step S2, the electron transport layer solution is a 3% to 5% mass fraction tin oxide colloidal aqueous solution, the first annealing treatment lasts for 20 minutes to 60 minutes, and the annealing temperature is 90°C to 180°C.

7. The method for preparing a perovskite solar cell having submicroscopic protrusions according to claim 5, characterized in that: In step S3, the perovskite precursor solution includes cesium iodide, lead iodide, lead bromide and formamidine iodide, and the molar concentration of the lead element in the perovskite precursor solution is 1.0 mol / L~1.6 mol / L.

8. The method for preparing a perovskite solar cell having submicroscopic protrusions according to claim 5, characterized in that: In step S3, the first solution includes N,N-dimethylformamide and dimethyl sulfoxide, and the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is 2:1 to 5:

1. When the anti-solvent is added, the volume ratio of the target precursor solution to the anti-solvent is 0.35:1 to 0.035:

1.

9. The method for preparing a perovskite solar cell having submicroscopic protrusions according to claim 5, characterized in that: In step S3, the perovskite additive includes a second compound with a molar fraction of 10%.

10. The method for preparing a perovskite solar cell having submicroscopic protrusions according to claim 5, characterized in that: In step S3, the duration of the second annealing treatment is 5 minutes to 60 minutes, and the annealing temperature is 90° C. to 150° C.

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