Perovskite / silicon heterojunction laminated solar cell, and preparation method therefor

Abstract

Provided in the present application are a perovskite / silicon heterojunction laminated solar cell and a preparation method therefor. The preparation method comprises preparing a silicon heterojunction bottom cell; on one side of the silicon heterojunction bottom cell, sequentially preparing a composite layer, a hole transport layer, a perovskite absorption layer, an electron transport layer, and a front transparent conductive layer; protecting the silicon heterojunction bottom cell and the perovskite absorption layer, and heating the front transparent conductive layer, so that the front transparent conductive layer in the prepared laminated solar cell is at least partially crystallized. By heating the front transparent conductive layer on the basis of protecting the silicon heterojunction bottom cell and the perovskite absorption layer, the material of the front transparent conductive layer can be crystallized without affecting a silicon laminated cell substrate, thus the optical performance and electrical performance of the material of the front transparent conductive layer are improved, and the overall efficiency of a laminated cell is increased.

Description

A perovskite / silicon heterojunction stacked solar cell and its preparation method

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the Patent Office of China on June 15, 2023, with application number 202310713067.9, entitled “PEROVSKITE / SILICON HETEROJUNCTION TANK SOLAR CELLS AND METHODS FOR MANUFACTURING THEM”, and the Chinese patent application filed with the Patent Office of China on June 19, 2023, with application number 202310729455.6, entitled “PEROVSKITE / SILICON HETEROJUNCTION TANK SOLAR CELLS AND METHODS FOR MANUFACTURING THEM”. The entire contents of the aforementioned two patent applications are incorporated into this application by reference. Technical Field

[0003] The present application relates to the field of solar energy technology, and in particular to a perovskite / silicon heterojunction stacked solar cell and a preparation method thereof. Background Art

[0004] Organic-inorganic hybrid perovskite solar cells (PSCs) are attracting widespread attention worldwide as a new type of high-efficiency, low-cost solar cell. In just a few years, the photoelectric conversion efficiency of small-area single-junction PSCs has rapidly climbed from 3.8% in 2009 to over 25%, and the photoelectric conversion efficiency of PSCs with heterojunctions of perovskite / silicon has reached over 33%. This rapid efficiency improvement has made them a key focus for photovoltaic research institutions and companies. Compared to traditional thin-film solar cells (such as copper indium gallium selenide and cadmium telluride), PSCs offer advantages such as high conversion efficiency, simple fabrication processes, and low-cost potential, making them the thin-film solar cell technology with the greatest potential for industrialization. By adjusting the composition of the precursor solution, the cutoff wavelength of the solar cell's spectral response can be controlled, making them the ideal top cell absorber layer material.

[0005] Silicon heterojunction solar cell technology has advantages such as simple process (texture cleaning → amorphous silicon deposition → TCO deposition → silver electrode printing), low preparation temperature (<220°C), high conversion efficiency (>25%), and symmetrical structure (double-sided), and is considered to be the third generation of cell technology after PERC cells. The high infrared band absorption, strong low-light effect, and structural advantages of silicon heterojunction cells that can match PIN make them one of the best bottom cell options. The "perovskite / silicon-based heterojunction" stacked cell structure formed by the perovskite cell (top cell) and the silicon-based heterojunction cell (bottom cell) realizes the distributed absorption of the solar spectrum and has achieved a conversion efficiency of more than 33%.

[0006] Because both silicon heterojunction solar cells and perovskite solar cells cannot withstand high temperatures (the fabrication temperature for silicon heterojunction solar cells is less than 220°C, and the fabrication temperature for perovskite solar cells is less than 150°C), the front transparent conductive layer (TCO) can only be prepared at low temperatures, and conventional heating treatment cannot be performed on the prepared TCO material. This also prevents the TCO material from crystallizing, and its electrical and optical properties cannot reach their optimal state, thus limiting the efficiency improvement of the tandem cell.

[0007] Summary of the Invention

[0008] The present application provides a perovskite / silicon heterojunction stacked solar cell and a preparation method thereof, in order to solve or at least partially solve the problems existing in the prior art.

[0009] The technical solution of this application is as follows:

[0010] The present application provides a method for preparing a perovskite / silicon heterojunction tandem solar cell, comprising: preparing a silicon heterojunction bottom cell; sequentially preparing a composite layer, a hole transport layer, a perovskite absorption layer, an electron transport layer, and a front transparent conductive layer on one side of the silicon heterojunction bottom cell; protecting the silicon heterojunction bottom cell and the perovskite absorption layer, and heating the front transparent conductive layer to at least partially crystallize the front transparent conductive layer in the prepared tandem solar cell.

[0011] Preferably, the protecting the silicon heterojunction bottom cell and the perovskite absorption layer and heat-treating the front transparent conductive layer so that the front transparent conductive layer in the prepared stacked solar cell is at least partially crystallized comprises: using a laser to treat the front transparent conductive layer so that the front transparent conductive layer is at least partially crystallized, and the laser does not damage the silicon heterojunction bottom cell and the perovskite absorption layer.

[0012] Preferably, the laser causes the temperature of the front transparent conductive layer to reach 400-800°C; the laser is a violet laser with a wavelength of 355nm; the pulse width of the laser is 0.75-20ns; the X-ray diffraction pattern of the front transparent conductive layer has a characteristic peak at a diffraction angle 2θ of 30.73°±0.02.

[0013] Preferably, when the front transparent conductive layer is processed with laser, the laser is applied by using a galvanometer system.

[0014] Preferably, the protecting the silicon heterojunction bottom cell and the perovskite absorption layer and heating the front transparent conductive layer so that the front transparent conductive layer in the prepared stacked solar cell is at least partially crystallized comprises: controlling the temperature of the prepared stacked solar cell so as to protect the silicon heterojunction bottom cell and the perovskite absorption layer; and providing a heat source to at least partially crystallize the front transparent conductive layer.

[0015] Preferably, the temperature control is achieved by placing the prepared stacked solar cell on a temperature control table, with the side of the stacked solar cell away from the front transparent conductive layer in contact with the temperature control table; the temperature of the temperature control table is set at -20 to -10°C.

[0016] Preferably, the heat source causes the temperature of the front transparent conductive layer to reach 350-400°C; the heat source is provided for 1-10 minutes; the heat source provides heat in a manner selected from one or more of thermal radiation, heat conduction, and thermal convection; the heat source is selected from one or more of an infrared heating lamp, a hot table, and hot air; and the X-ray diffraction pattern of the front transparent conductive layer has a characteristic peak at a diffraction angle 2θ of 30.52°±0.02.

[0017] Preferably, the material of the front transparent conductive layer is selected from one of ITO, IWO, IZO, and ITiO. Preferably, the material of the front transparent conductive layer is ITO. Preferably, the thickness of the front transparent conductive layer is 30-150 nm.

[0018] Preferably, the silicon heterojunction bottom cell includes a back transparent conductive layer, a P-type amorphous silicon layer, a first intrinsic amorphous silicon layer, an N-type crystalline silicon substrate, a second intrinsic amorphous silicon layer, and an N-type amorphous silicon layer stacked in sequence.

[0019] Preferably, the method further comprises: preparing metal electrodes on a side of the silicon heterojunction bottom cell away from the composite layer, and on a side of the front transparent conductive layer or the treated front transparent conductive layer away from the composite layer.

[0020] The present application also provides a perovskite / silicon heterojunction tandem solar cell, comprising: a silicon heterojunction base cell, a recombination layer, a hole transport layer, a perovskite absorber layer, an electron transport layer, and a front transparent conductive layer stacked in sequence, wherein the front transparent conductive layer is at least partially crystallized. Preferably, the tandem solar cell is prepared by the above-described preparation method.

[0021] The present application provides a perovskite / silicon heterojunction tandem solar cell and a preparation method thereof. By heating the front transparent conductive layer on the basis of protecting the silicon heterojunction bottom cell and the perovskite absorption layer, the material of the front transparent conductive layer can be crystallized without affecting the silicon tandem cell substrate, thereby improving the optical and electrical properties of the material of the front transparent conductive layer and improving the overall efficiency of the tandem cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are provided to facilitate a better understanding of the present application and do not constitute an undue limitation on the present application.

[0023] FIG1 is a schematic diagram of a stacked solar cell according to an embodiment of the present invention;

[0024] FIG2 is a schematic diagram showing the effect of laser treatment on the transmittance of an ITO layer according to an embodiment of the present invention;

[0025] FIG3 shows an XRD diffraction pattern of an ITO layer before and after laser treatment according to an embodiment of the present invention;

[0026] FIG4 is a schematic diagram showing the effect of heat treatment on the transmittance of an ITO layer according to an embodiment of the present invention;

[0027] FIG5 shows XRD diffraction patterns of the ITO layer before and after heat treatment in an embodiment of the present invention.

[0028] Figure numerals: 1-1 back transparent conductive layer, 1-2 P-type amorphous silicon layer, 1-3 first intrinsic amorphous silicon layer, 1-4 N-type crystalline silicon substrate; 1-5 first intrinsic amorphous silicon layer, 1-6 N-type amorphous silicon layer, 1-7 composite layer, 2-1 hole transport layer, 2-2 perovskite absorption layer, 2-3 electron transport layer, 2-4 front transparent conductive layer, 3-1 metal electrode. Specific embodiments

[0029] The following description of exemplary embodiments of the present application includes various details in some embodiments to facilitate understanding, which should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present application. Similarly, for the sake of clarity and conciseness, descriptions of well-known functions and structures are omitted in the following description.

[0030] There are two main processes for preparing TCO films for conventional non-laminated solar cells:

[0031] One method involves high-temperature TCO film formation. This involves heating the substrate to above the crystallization temperature of the TCO material, and then directly depositing the film using magnetron sputtering. This allows the TCO film to crystallize directly, resulting in excellent electrical and optical properties. For example, the crystallization temperature of ITO is 200°C. High-temperature ITO film formation requires heating the substrate to 300-350°C, resulting in a crystallized ITO film.

[0032] Another method involves preparing the TCO film at low temperature and then performing heat treatment. Magnetron sputtering is performed directly on the substrate at room temperature, resulting in an amorphous TCO film. Heat treatment is then performed to crystallize the amorphous TCO film, which exhibits excellent electrical and optical properties. For example, the crystallization temperature of ITO material is 200°C. After preparing the ITO film at room temperature, heating the substrate to 250°C results in a crystallized ITO film.

[0033] As mentioned above, since both silicon heterojunction solar cells and perovskite solar cells cannot withstand high temperatures, when preparing the TCO material of the front transparent conductive layer, only low-temperature preparation can be performed, and the prepared TCO material cannot be subjected to conventional heat treatment. Although the low-temperature preparation process of the TCO material of the front transparent conductive layer matches the preparation process of silicon heterojunction solar cells and perovskite solar cells, it also causes the TCO material to be unable to crystallize, and its electrical and optical properties cannot reach the optimal state, thereby limiting the efficiency improvement of the stacked cell. In response to the problem that the TCO material of the front transparent conductive layer cannot be crystallized, the present application provides a method for preparing a perovskite / silicon heterojunction stacked solar cell, comprising the following steps:

[0034] S1: Preparation of silicon heterojunction bottom cell.

[0035] S2: a composite layer, a hole transport layer, a perovskite absorption layer, an electron transport layer and a front transparent conductive layer are sequentially prepared on one side of the silicon heterojunction bottom cell.

[0036] S3. Protect the silicon heterojunction bottom cell and the perovskite absorption layer, and heat-treat the front transparent conductive layer to at least partially crystallize the front transparent conductive layer in the prepared stacked solar cell. In step S1, the silicon heterojunction bottom cell can be various types of silicon heterojunction bottom cells known in the art, and can be prepared by methods known in the art.

[0037] In a specific embodiment, the structure of the silicon heterojunction bottom cell is shown in Figure 1, comprising a back transparent conductive layer 1-1, a P-type amorphous silicon layer 1-2, a first intrinsic amorphous silicon layer 1-3, an N-type crystalline silicon substrate 1-4, a second intrinsic amorphous silicon layer 1-5, and an N-type amorphous silicon layer 1-6 stacked in sequence. The back transparent conductive layer 1-1 is used to collect carriers and transmit them to the metal electrode. The material of the back transparent conductive layer 1-1 can be ITO, IWO, IZO, ITiO, etc. The P-type amorphous silicon layer 1-2 forms the back electric field of the silicon heterojunction solar cell and can be prepared by PECVD. The first intrinsic amorphous silicon layer 1-3 and the second intrinsic amorphous silicon layer 1-5 mainly play the role of passivating the dangling bonds on the surface of the crystalline silicon substrate and can be prepared by PECVD. The N-type crystalline silicon substrate 1-4 serves as the bottom cell light absorption layer, converting photons into photogenerated carriers (electron-hole pairs). The N-type amorphous silicon layers 1-6 constitute the emission level of the heterojunction battery and can be prepared by the PECVD method.

[0038] In step S2, sequentially preparing a composite layer, a hole transport layer, a perovskite absorption layer, an electron transport layer and a front transparent conductive layer means preparing a composite layer on a silicon heterojunction bottom cell, then preparing a hole transport layer on the composite layer, then preparing a perovskite absorption layer on the hole transport layer, then preparing an electron transport layer on the perovskite absorption layer, and finally preparing a front transparent conductive layer on the electron transport layer. The final stacked cell structure can be shown in Figure 1. Among them, the composite layer can realize the passage of photogenerated carriers from the perovskite layer to the silicon heterojunction, and TCO materials such as ITO, IWO, IZO, ITiO, etc. are usually selected. The hole transport layer can choose Spiro-TTB, Spiro-OMeTAD, Spiro-TAD CuSCN, NiO x 、NiMgO x , V2O5 and MoO3. The perovskite absorption layer usually has a band gap of more than 1.6eV and is generally composed of a single component system such as (Cs0.15FA0.85)Pb(I0.7Br0.3)3. The material of the electron transport layer is generally C 60 , PCBM, SnO2, etc. The material of the front transparent conductive layer can be selected from ITO, IWO, IZO, ITiO, etc., preferably ITO. The thickness of the front transparent conductive layer is generally 30-150nm. The composite layer, hole transport layer, perovskite absorption layer, electron transport layer, and front transparent conductive layer can all be prepared using methods known in the art. Those skilled in the art can adjust the materials, thickness, and preparation process of each layer according to actual needs.

[0039] In step S3, while protecting the silicon heterojunction bottom cell and the perovskite absorber layer, the front transparent conductive layer can be simultaneously subjected to a heat treatment to at least partially crystallize the front transparent conductive layer in the prepared tandem solar cell. In a specific embodiment, step S3 can be achieved by treating the front transparent conductive layer with a laser to at least partially crystallize the front transparent conductive layer, without damaging the silicon heterojunction bottom cell and the perovskite absorber layer.

[0040] The temperature at which the laser is applied to the front transparent conductive layer should be such that the TCO material can crystallize. In a specific embodiment, the laser causes the temperature of the front transparent conductive layer to reach 400-800°C, for example, it can be 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, or any range therebetween. Crystallization of TCO materials can be achieved at 400-800°C.

[0041] In one specific embodiment, the laser is a violet laser with a wavelength of 355 nm. Using a violet laser with a wavelength of 355 nm allows most of the laser light to be absorbed by the TCO material of the front transparent conductive layer. Therefore, the thermal effect is primarily generated in the front transparent conductive layer, without damaging the silicon heterojunction bottom cell and the perovskite absorption layer. In one specific embodiment, the laser pulse width is 0.75-20 ns, for example, 0.75 ns, 1 ns, 2 ns, 3 ns, 4 ns, 5 ns, 6 ns, 7 ns, 8 ns, 9 ns, 10 ns, 11 ns, 12 ns, 13 ns, 14 ns, 15 ns, 16 ns, 17 ns, 18 ns, 19 ns, 20 ns, or any range therebetween.

[0042] Those skilled in the art can select various commercially available laser equipment to perform the above-mentioned laser treatment based on the requirements of the laser wavelength, pulse width, etc. In a specific embodiment, when using laser to treat the transparent conductive layer, the laser is applied by using a galvanometer system. Simply put, a galvanometer is a scanning galvanometer used in the laser industry, and its professional term is a high-speed scanning galvanometer Galvo scanning system. The so-called galvanometer can also be called an ammeter. Its design concept completely follows the design method of the ammeter. The lens replaces the needle, and the probe signal is replaced by a computer-controlled -5V to 5V or -10V to +10V DC signal to complete the predetermined action.

[0043] Similar to rotating mirror scanning systems, this typical control system utilizes a pair of reflex mirrors. However, the stepper motors driving these mirrors are replaced by servo motors. The use of position sensors and a negative feedback loop design further enhance system accuracy, reaching new levels of scanning speed and repeatability. This enables fast and precise processing, ensuring crystallization of the TCO material in the front transparent conductive layer while reducing processing time and increasing speed.

[0044] In a specific embodiment, when the front transparent conductive layer is treated with laser, the temperature of the front transparent conductive layer is made to reach 400-800° C. by the laser.

[0045] In one specific embodiment, when laser treatment is used for the front transparent conductive layer, the laser is a violet laser with a wavelength of 355 nm, the laser pulse width is 0.75-20 ns, and the laser is applied using a galvanometer system. In one specific embodiment, when laser treatment is used for the front transparent conductive layer, the laser causes the temperature of the front transparent conductive layer to reach 400-800° C., the laser is a violet laser with a wavelength of 355 nm, the laser pulse width is 0.75-20 ns, and the laser is applied using a galvanometer system.

[0046] It will be understood that the above-mentioned limitations on various laser parameters are merely exemplary. To achieve at least partial crystallization of the front transparent conductive layer while preventing damage to the silicon heterojunction bottom cell and perovskite absorber layer, those skilled in the art can select appropriate laser equipment and adjust various parameters, such as laser power, pulse frequency, pulse width, laser pulse width, processing speed, focal position, and laser mode. In another specific embodiment, step S3 can be achieved by controlling the temperature of the prepared tandem solar cell to protect the silicon heterojunction bottom cell and the perovskite absorber layer, and providing a heat source to at least partially crystallize the front transparent conductive layer.

[0047] Specifically, the purpose of temperature control for the tandem solar cell prepared in step S2 is to maintain the substrate of the tandem solar cell at a low temperature during the heat treatment of the front transparent conductive layer, thereby ensuring that the substrate is not affected during the crystallization of the TCO material of the front transparent conductive layer. Temperature control can be performed using various methods or equipment known in the art. For example, the tandem solar cell can be placed on a temperature-controlled platform, with the side of the tandem solar cell facing away from the front transparent conductive layer in contact with the platform, i.e., the front transparent conductive layer is away from the platform.

[0048] In a specific embodiment, the temperature of the temperature control table is set at -20 to -10°C, for example, -20°C, -19.5°C, -19°C, -18.5°C, -18°C, -17.5°C, -17°C, -16.5°C, -16°C, -15.5°C, -15°C, -14.5°C, -14°C, -13.5°C, -13°C, -12.5°C, -12°C, -11.5°C, -11°C, -10.5°C, -10°C, or any range therebetween. Various types of temperature control tables can be used as long as they can adequately control the temperature of the stacked solar cell. In a specific embodiment, the stacked solar cell is brought into close contact with the temperature control table by vacuum adsorption to achieve better temperature control.

[0049] Furthermore, the heat source can at least partially crystallize the front transparent conductive layer. Furthermore, because a temperature-controlled platform is used to control the temperature of the laminated cell substrate and heat the front transparent conductive layer, a temperature difference exists in the front transparent conductive layer from the side closest to the silicon heterojunction bottom cell to the side further away from the silicon heterojunction bottom cell. This temperature difference helps to orient the crystal growth of the TCO material during crystallization, resulting in a higher-quality film layer.

[0050] In addition, the presence of temperature differences in the front transparent conductive layer helps to orient the crystal growth of the TCO material during crystallization, thereby obtaining a higher quality film layer. The temperature difference during the crystallization process will not cause detachment and mismatch between the various film layers of the stacked cell. The TCO material of the front transparent conductive layer after crystallization has better optical and electrical properties, thereby improving the overall efficiency of the stacked cell. In addition, silicon wafers, perovskite materials and TCO materials all have very small thermal expansion coefficients and have a certain degree of flexibility, so the temperature difference during the crystallization process will not cause detachment and mismatch between the various film layers of the stacked cell. The TCO material of the front transparent conductive layer after crystallization has better optical and electrical properties, thereby improving the overall efficiency of the stacked cell.

[0051] In a specific embodiment, the heat source causes the temperature of the front transparent conductive layer to reach 350-400°C, for example, 350°C, 351°C, 352°C, 353°C, 354°C, 355°C, 356°C, 357°C, 358°C, 359°C, 360°C, 361°C, 362°C, 363°C, 364°C, 365°C, 366°C, 367°C, 368°C, 369°C, 370°C, 371°C, 372°C , 373°C, 374°C, 375°C, 376°C, 377°C, 378°C, 379°C, 380°C, 381°C, 382°C, 383°C, 384°C, 385°C, 386°C, 387°C, 388°C, 389°C, 390°C, 391°C, 392°C, 393°C, 394°C, 395°C, 396°C, 397°C, 398°C, 399°C, 400°C, or any range therebetween, or any range therebetween.

[0052] In a specific embodiment, the heat source is provided for a time of 1-10 min, for example, 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min, 5 min, 5.5 min, 6 min, 6.5 min, 7 min, 7.5 min, 8 min, 8.5 min, 9 min, 9.5 min, 10 min, or any range between these values.

[0053] The heat source of the present application can provide heat in a manner selected from one or more of thermal radiation, thermal conduction, and thermal convection. For example, it can be a single thermal radiation, thermal conduction, or thermal convection, or it can be a thermal radiation composite thermal conduction, thermal radiation combined with thermal convection, thermal conduction combined with thermal convection, or a combination of thermal radiation, thermal conduction, and thermal convection. For the heat source providing the above-mentioned various heating methods, those skilled in the art can select the corresponding heat source. In a specific embodiment, the heat source is selected from one or more of infrared (IR) heating lamps, hot tables, and hot air. For infrared (IR) heating lamps, those skilled in the art can adjust the power of the heating lamp, the distance from the control console, etc. as needed. For hot tables, those skilled in the art can adjust the temperature of the hot table, the distance from the control console, etc. as needed. For hot air, those skilled in the art can adjust the temperature, flow rate, and the distance from the control console, etc. of the heated air as needed.

[0054] In a specific embodiment, the temperature of the temperature-controlled platform is set at -20 to -10°C, the heat source is an infrared heating lamp, the heat source is provided for 1-10 minutes, and the heat source causes the temperature of the front transparent conductive layer to reach 350-400°C. In a specific embodiment, the temperature of the temperature-controlled platform is set at -20 to -10°C, the heat source is a hot plate, the heat source is provided for 1-10 minutes, and the heat source causes the temperature of the front transparent conductive layer to reach 350-400°C. In a specific embodiment, the temperature of the temperature-controlled platform is set at -20 to -10°C, the heat source is hot air, the heat source is provided for 1-10 minutes, and the heat source causes the temperature of the front transparent conductive layer to reach 350-400°C.

[0055] It will be understood that the above-mentioned limitations on the various parameters of the heat source are merely exemplary. In order to achieve at least partial crystallization of the front transparent conductive layer while ensuring that the heat source used does not damage the laminated battery substrate, such as the silicon heterojunction bottom battery and the perovskite absorption layer, those skilled in the art can select an appropriate heating device as the heat source and adjust various parameters such as the temperature of the heat source, the distance from the control console, the power, and the time.

[0056] Furthermore, the preparation method of the present application may also include the step of preparing a metal electrode. The electrode preparation step may be performed between steps S2 and S3, that is, after the metal electrode is prepared, and the front transparent conductive layer is then heat-treated. At this point, as shown in Figure 1, a metal electrode 3-1 is prepared on the side of the silicon heterojunction bottom cell away from the composite layer 1-7, and on the side of the front transparent conductive layer 2-4 away from the composite layer 1-7. The electrode preparation step may also be performed after S4, that is, on the side of the silicon heterojunction bottom cell away from the composite layer 1-7, and on the side of the heated front transparent conductive layer 2-4 away from the composite layer 1-7. The metal electrode 3-1 may be a conventional metal electrode in the art, such as silver, copper, etc. The preparation method of the present application overcomes the problem of crystallization of the front transparent conductive layer in existing tandem cell preparation. By heat-treating the front transparent conductive layer while maintaining the low temperature of the tandem cell substrate, the material of the front transparent conductive layer can be crystallized without affecting the tandem cell substrate, thereby improving the optical and electrical properties of the material of the front transparent conductive layer and thereby enhancing the overall efficiency of the tandem cell.

[0057] The present application also provides a perovskite / silicon heterojunction tandem solar cell. As shown in Figure 1, the tandem solar cell includes a silicon heterojunction bottom cell, a composite layer 1-7, a hole transport layer 2-1, a perovskite absorption layer 2-2, an electron transport layer 2-3 and a front transparent conductive layer 2-4 stacked in sequence, wherein the front transparent conductive layer 2-4 is at least partially crystallized. In a specific embodiment, the silicon heterojunction bottom cell includes a back transparent conductive layer 1-1, a P-type amorphous silicon layer 1-2, a first intrinsic amorphous silicon layer 1-3, an N-type crystalline silicon substrate 1-4, a second intrinsic amorphous silicon layer 1-5, and an N-type amorphous silicon layer 1-6 stacked in sequence. The degree of crystallization of the front transparent conductive layer 2-4 can be characterized by detection methods known in the art. For example, X-ray diffraction can be used for detection.

[0058] In one specific embodiment, the X-ray diffraction pattern of the front transparent conductive layer 2-4 has a characteristic peak at a diffraction angle 2θ of 30.52°±0.02(222). The characteristic peak of the front transparent conductive layer 2-4 can be located at 2θ of 30.50°, 30.51°, 30.52°, 30.53°, 30.54°, or any value therebetween.

[0059] Furthermore, the perovskite / silicon heterojunction stacked solar cell is prepared by any one of the above-mentioned preparation methods.

[0060] Example

[0061] Example 1

[0062] The structure of the prepared tandem solar cell is shown in Figure 1. The perovskite / silicon heterojunction tandem solar cell includes a back transparent conductive layer 1-1, a P-type amorphous silicon layer 1-2, a first intrinsic amorphous silicon layer 1-3, an N-type crystalline silicon substrate 1-4, a second intrinsic amorphous silicon layer 1-5, an N-type amorphous silicon layer 1-6, a composite layer 1-7, a hole transport layer 2-1, a perovskite absorption layer 2-2, an electron transport layer 2-3 and a front transparent conductive layer 2-4, which are stacked in sequence. A metal electrode 3-1 is provided on the side of the back transparent conductive layer 1-1 and the front transparent conductive layer 2-4 away from the composite layer 1-7. The preparation method of the perovskite / silicon heterojunction tandem solar cell includes the following steps:

[0063] (1) N-type crystalline silicon substrates 1-4 are commercial grade M6 N-type silicon wafers with a resistivity of 1-10 Ω.cm and a thickness of 150-200 μm. The wafers undergo polishing, texturing, and cleaning procedures.

[0064] PECVD is used to deposit the first intrinsic amorphous silicon layer 1-3 and the second intrinsic amorphous silicon layer 1-5 (thickness 5-10nm) on both sides of the silicon wafer to form the front and back passivation layer films. PECVD is used to deposit phosphorus doping (doping concentration 10 19-20 cm -3 ) constitutes the front field structure, namely the N-type amorphous silicon layer 1-6, whose conduction band is about -3.7eV. Boron doping (doping concentration 10 19-20 cm -3 A P-type amorphous silicon layer (5-15 nm thick) forms the rear emitter structure, namely P-type amorphous silicon layer 1-2. A rear transparent conductive material layer 1-1 (70-120 nm thick) made of ITO is deposited using magnetron sputtering. Layers 1-1 through 1-6 form the bottom cell structure of a perovskite / silicon heterojunction tandem solar cell.

[0065] (2) A layer of gradient ITO material was prepared as the composite layer 1-7 using magnetron sputtering method with a thickness of 20 nm.

[0066] (3) Preparation of 50nm NiO using magnetron sputtering x layer, serving as the hole transport layer 2-1.

[0067] (4) Preparation of perovskite precursor layer by thermal evaporation process: A mixed layer of lead iodide and cesium bromide with a thickness of 350-450 nm was evaporated by co-evaporation method, wherein the rate of cesium bromide (CsBr) was The rate of lead iodide (PbI2) is Forming the main structure of the perovskite absorption layer film; preparing a mixed solution of FAI and FABr with a molar concentration ratio of 1.5:2.5 mol / ml to 3.5:0.5 mol / ml, and using ethanol or isopropanol as the solvent; taking 70-100 μL of the mixed solution of FAI and FABr to react with the lead iodide and cesium bromide layers, and annealing at 140-190°C for 20-50 minutes to form a perovskite absorption layer 2-2.

[0068] (5) First, a layer of C60 is prepared by evaporation, and then ALD is used at 80-120°C for 130-190 cycles to prepare 10-20nm SnO2 as the electron transport layer 2-3.

[0069] (6) A 70-120 nm ITO film is prepared by magnetron sputtering to form the front transparent conductive layer 2-4.

[0070] (7) Fine grid lines and main grid lines, i.e., metal electrodes 31, are prepared on the upper and lower surfaces by screen printing to form a complete perovskite / silicon heterojunction stacked solar cell.

[0071] (8) In one implementation, step (8) can be performed by selecting a picosecond laser with a wavelength of 355nm, using a galvanometer system, setting its power to 4W, pulse frequency to 1500KHz, pulse width to 750 picoseconds, processing speed to 6000mm / s, and focus position to 45mm from the processing surface (i.e., the surface of the front transparent conductive layer). Using this laser system to process the perovskite / silicon heterojunction stacked solar cell can achieve crystallization of the front transparent conductive layer, wherein the spot overlap rate is about 65% and the process time is 65s. In another implementation, step (8) can be performed by placing the prepared perovskite / heterojunction stacked cell on a temperature control table, with the back electrode located at the bottom and in close contact with the temperature control table through vacuum adsorption, and the front transparent conductive layer 2-4 located at the top. The temperature of the temperature control table is set to -20°C. Hot air is provided above the temperature control table through a gas tank with heating and insulation functions. The hot air temperature is 350℃, the flow rate is 5L / min, and it is blown onto the temperature control table through the air hole size of the cloth. The blowing time is 10 minutes.

[0072] Example 2

[0073] The only difference between Example 2 and Example 1 is step (8). Step (8) of Example 2 is as follows: the prepared perovskite / heterojunction stacked cell is placed on a temperature control table, with the back electrode located at the bottom and in close contact with the temperature control table via vacuum adsorption, and the front transparent conductive layer located at the top. The temperature control table is set to -20°C. An IR heating lamp with a power of 2 kW is provided above the temperature control table, and the IR heating lamp is 30 cm away from the temperature control table. The heating time is 5 minutes.

[0074] Example 3

[0075] The only difference between Example 3 and Example 1 is step (8). Step (8) of Example 3 is as follows: the prepared perovskite / heterojunction stacked cell is placed on a temperature-controlled platform, with the back electrode located at the bottom and in close contact with the temperature-controlled platform via vacuum adsorption, and the front transparent conductive layer located at the top. The temperature of the temperature-controlled platform is set to -20°C. A hot plate is provided above the temperature-controlled platform, with the temperature set to 350°C and the distance from the temperature-controlled platform to 1 mm. The heating time is 2 minutes.

[0076] Comparative Example 1

[0077] The only difference between Comparative Example 1 and Examples 1, 2, and 3 is that Comparative Example 1 includes only steps (1) to (7), i.e., does not include step (8). Performance testing was conducted on the laser treatment scheme of Example 1 and the perovskite / silicon heterojunction tandem solar cell prepared in Comparative Example 1. The results are shown in Table 1.

[0078] Table 1

[0079] It can be seen from the results in Table 1 that the method of Example 1 greatly improves the efficiency of the stacked battery after adding the laser treatment step. In order to further verify the results of Table 1 above, the present application also characterized the effect of laser treatment on ITO from the aspects of optics, electricity and structure. Using ITO as the front transparent conductive layer, a 100nm thick ITO single film was prepared on a glass substrate. Specifically, a 100nm thick ITO single film was prepared on a glass substrate. The ITO single film was laser treated using the laser conditions in Example 1, and the changes in film performance before and after laser treatment were compared.

[0080] The optical performance is determined by transmittance. Figure 2 shows the transmittance of an ITO film before and after laser treatment. This shows that laser treatment improves the transmittance of the ITO film, thereby increasing incident light and boosting the battery's short-circuit current density. Table 2 shows the Hall effect test results of the ITO film before and after laser treatment. This shows that laser treatment improves the electrical performance of ITO, thereby reducing the battery's internal series resistance, improving charge transfer, and increasing battery efficiency.

[0081] Table 2

[0082] The X-ray diffraction (XRD) test results of the ITO single film before and after laser treatment are shown in Figure 3. As can be seen from Figure 3, the ITO film layer after laser treatment has a characteristic peak in the X-ray diffraction pattern at a diffraction angle 2θ of 30.73°. This shows that the laser treatment method can make the ITO film layer partially crystallize, thereby improving the electrical and optical properties of the ITO film layer. The performance of the perovskite / silicon heterojunction stacked solar cells prepared using the temperature control and heat source treatment scheme of Example 1 and Examples 2, 3 and Comparative Example 1 was tested, and the results are shown in Table 3.

[0083] Table 3

[0084] The results in Table 3 show that the methods of Examples 1-3 significantly improve the efficiency of the stacked battery after adding the heat treatment step. To further verify the results in Table 3, the present application also characterized the effects of heat treatment on ITO from various optical, electrical, and structural perspectives. Using ITO as the front transparent conductive layer, a 100nm thick ITO single film was prepared on a glass substrate. Specifically, a 100nm thick ITO single film was prepared on a glass substrate. The ITO single film was heat treated using conventional conditions, i.e., heating at 250°C for 30 minutes. The optical performance was determined based on transmittance. The transmittance of the ITO single film before and after heat treatment is shown in Figure 4. As shown in Figure 4, heat treatment can improve the transmittance of the ITO single film, thereby increasing the incident light and improving the short-circuit current density of the battery. The Hall effect test results of the ITO single film before and after heat treatment are shown in Table 4. As shown in Table 4, heat treatment can improve the electrical properties of ITO, thereby reducing the internal series resistance of the battery, improving charge transfer, and increasing battery efficiency.

[0085] Table 4

[0086] The X-ray diffraction (XRD) test results of the ITO single film before and after the heat treatment are shown in Figure 5. As can be seen from Figure 5, the heat treatment method can make the ITO film layer partially crystallize, thereby improving the electrical and optical properties of the ITO film layer.

[0087] Although the embodiments of the present application are described above, the present application is not limited to the above-mentioned specific embodiments and application fields. The above-mentioned specific embodiments are merely illustrative and instructive, and not restrictive. A person of ordinary skill in the art, under the guidance of this specification and without departing from the scope of protection of the claims of this application, can also make many forms, all of which fall within the scope of protection of this application.

Claims

1. A method for preparing a perovskite / silicon heterojunction tandem solar cell, characterized in that: include: Preparation of silicon heterojunction bottom cells; On one side of the silicon heterojunction bottom cell, a composite layer, a hole transport layer, a perovskite absorption layer, an electron transport layer and a front transparent conductive layer are sequentially prepared; The silicon heterojunction bottom cell and the perovskite absorption layer are protected, and the front transparent conductive layer is heat-treated, so that the front transparent conductive layer in the prepared stacked solar cell is at least partially crystallized.

2. The method according to claim 1, characterized in that The protecting the silicon heterojunction bottom cell and the perovskite absorption layer and heating the front transparent conductive layer to make the front transparent conductive layer in the prepared stacked solar cell at least partially crystallized comprises: The front transparent conductive layer is processed by laser to at least partially crystallize the front transparent conductive layer, and the laser does not damage the silicon heterojunction bottom cell and the perovskite absorption layer.

3. The method according to claim 2, characterized in that The laser causes the temperature of the front transparent conductive layer to reach 400-800° C.; The laser is a violet laser with a wavelength of 355nm; The pulse width of the laser is 0.75-20ns; The X-ray diffraction spectrum of the front transparent conductive layer has a characteristic peak at a diffraction angle 2θ of 30.73°±0.

02.

4. The method according to claim 2 or 3, characterized in that: When the front transparent conductive layer is processed with laser, the laser is applied by using a galvanometer system.

5. The method according to claim 1, characterized in that The protecting the silicon heterojunction bottom cell and the perovskite absorption layer and heating the front transparent conductive layer to make the front transparent conductive layer in the prepared stacked solar cell at least partially crystallized comprises: Controlling the temperature of the prepared stacked solar cell, thereby protecting the silicon heterojunction bottom cell and the perovskite absorption layer; A heat source is provided to at least partially crystallize the front transparent conductive layer.

6. The method according to claim 5, characterized in that The temperature control is achieved by placing the prepared stacked solar cell on a temperature control platform, wherein a side of the stacked solar cell away from the front transparent conductive layer is in contact with the temperature control platform; the temperature of the temperature control platform is set at -20 to -10°C.

7. The method according to claim 5 or 6, characterized in that: The heat source makes the temperature of the front transparent conductive layer reach 350-400° C.; The heat source is provided for 1-10 minutes; The heat source provides heat in a manner selected from one or more of thermal radiation, thermal conduction, and thermal convection; The heat source is selected from one or more of an infrared heating lamp, a heat table, and hot air; The X-ray diffraction spectrum of the front transparent conductive layer has a characteristic peak at a diffraction angle 2θ of 30.52°±0.

02.

8. The method according to any one of claims 1 to 7, characterized in that: The material of the front transparent conductive layer is selected from one of ITO, IWO, IZO and ITiO.

9. The method according to claim 8, characterized in that The material of the front transparent conductive layer is ITO.

10. The method according to any one of claims 1 to 9, characterized in that: The thickness of the front transparent conductive layer is 30-150 nm.

11. The method according to any one of claims 1 to 10, characterized in that: The silicon heterojunction bottom cell comprises a back transparent conductive layer, a P-type amorphous silicon layer, a first intrinsic amorphous silicon layer, an N-type crystalline silicon substrate, a second intrinsic amorphous silicon layer, and an N-type amorphous silicon layer which are stacked in sequence.

12. The method according to any one of claims 1 to 11, characterized in that: The method further comprises: A metal electrode is prepared on a side of the silicon heterojunction bottom cell away from the composite layer, and on a side of the front transparent conductive layer or the heated front transparent conductive layer away from the composite layer.

13. A perovskite / silicon heterojunction tandem solar cell, characterized in that: include: A silicon heterojunction bottom cell, a composite layer, a hole transport layer, a perovskite absorption layer, an electron transport layer and a front transparent conductive layer are stacked in sequence, and the front transparent conductive layer is at least partially crystallized.

14. The tandem solar cell according to claim 13, characterized in that: The stacked solar cell is prepared by the preparation method described in any one of claims 1 to 12.

Images