A solar cell and preparation method thereof, and photovoltaic module

Abstract

The present application provides a solar cell and a preparation method thereof, and a photovoltaic module, wherein the solar cell comprises a bottom cell, a composite layer and a top cell, the composite layer is located between the bottom cell and the top cell, the light-receiving surface of the bottom cell has an N-type doped layer, the backlight surface of the top cell has a hole transport layer, the composite layer comprises a first composite sublayer and a second composite sublayer arranged in a stacked manner, the first composite sublayer has a side facing away from the second composite sublayer facing the N-type doped layer, and the second composite sublayer has a side facing away from the first composite sublayer facing the hole transport layer; the carrier concentration of the first composite sublayer is greater than the carrier concentration of the second composite sublayer; the resistivity of the first composite sublayer and / or the resistivity of the second composite sublayer is 6.5×10 ‑4 Ω·cm~1.6×10 ‑2 Ω·cm, which improves the open circuit voltage and fill factor of the solar cell, thereby improving the photoelectric conversion efficiency of the solar cell.

Description

Technical Field

[0001] The present application relates to the field of solar cells, and in particular to a solar cell and a preparation method thereof, and a photovoltaic module. Background Art

[0002] Tandem solar cells can further improve the utilization of the solar spectrum, thereby improving the photoelectric conversion efficiency of solar cells.

[0003] In a tandem solar cell, the composite layer plays an important role in the photoelectric conversion efficiency of the solar cell device. How to improve the performance of the composite layer to improve the photoelectric conversion efficiency of the tandem solar cell has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] In order to solve the above technical problems, the present application discloses a solar cell and a preparation method thereof, and a photovoltaic module to improve the performance of the composite layer, thereby improving the photoelectric conversion efficiency of the stacked solar cell.

[0005] In a first aspect, the present application provides a solar cell, comprising a bottom cell, a composite layer and a top cell, wherein the composite layer is located between the bottom cell and the top cell, the light-receiving surface of the bottom cell has an N-type doped layer, and the backlight surface of the top cell has a hole transport layer, wherein:

[0006] The composite layer comprises a first composite sublayer and a second composite sublayer which are stacked, wherein a side of the first composite sublayer facing away from the second composite sublayer faces the N-type doped layer, and a side of the second composite sublayer facing away from the first composite sublayer faces the hole transport layer;

[0007] The carrier concentration of the first composite sublayer is greater than the carrier concentration of the second composite sublayer;

[0008] The resistivity of the first composite sublayer and / or the resistivity of the second composite sublayer is 6.5×10 -4 Ω·cm~1.6×10 -2 Ω·cm.

[0009] In some embodiments of the present application, the carrier concentration of the first composite sublayer is C 1 , the carrier concentration of the second composite sublayer is C 2 , 7.0×10 20 Pieces / cm 3 ≤C 1 ≤1.0×10 21 Pieces / cm 3 , 1.0×10 19 Pieces / cm 3 ≤C 2 ≤2.5×10 20Pieces / cm 3 .

[0010] In some embodiments of the present application, the carrier mobility of the first composite sublayer is CM 1 , the carrier mobility of the second composite sublayer is CM 2 , C.M. 1 <CM 2 .

[0011] In some embodiments of the present application, 1 cm 2 / V·s≤CM 1 ≤13 cm 2 / V·s,30 cm 2 / V·s≤CM 2 ≤40 cm 2 / V·s.

[0012] In some embodiments of the present application, the resistivity of the first composite sublayer is R 1 , 6.5×10 -4 Ω·cm≤R 1 ≤6.5×10 -3 Ω·cm, the resistivity of the second composite sublayer is R 2 , 8.0×10 -4 Ω·cm≤R 2 ≤1.6×10 -2 Ω·cm.

[0013] In some embodiments of the present application, the work function of the first composite sublayer is 3.4 eV~3.8 eV, and the work function of the second composite sublayer is 4.3 eV~5.0 eV.

[0014] In some embodiments of the present application, the thickness of the first composite sublayer is H 1 , the thickness of the second composite sublayer is H 2 , 0nm≤H 2 -H 1 ≤14nm.

[0015] In some embodiments of the present application, 1 nm ≤ H 1 ≤5nm, 3nm≤H 2 ≤15nm.

[0016] In some embodiments of the present application, the material of the first composite sublayer and / or the second composite sublayer includes at least one of indium zinc oxide, indium tin oxide, zinc aluminum oxide, tungsten-doped indium oxide, and cerium-doped indium oxide.

[0017] In some embodiments of the present application, the bottom battery includes a silicon substrate, the light-receiving surface of the silicon substrate is sequentially stacked with a first intrinsic amorphous silicon layer and the N-type doped layer, and the backlight surface of the silicon substrate is sequentially stacked with a second intrinsic amorphous silicon layer, a P-type doped layer and a second transparent electrode layer.

[0018] In some embodiments of the present application, a hole modification layer, a perovskite layer, a passivation layer, an electron transport layer, a buffer layer, a first transparent electrode layer and an anti-reflection layer are sequentially stacked on the hole transport layer.

[0019] In a second aspect, the present application provides a method for preparing a solar cell as described in the first aspect, comprising the following steps:

[0020] Providing a bottom battery, and sequentially preparing a first composite sublayer and a second composite sublayer on a surface of an N-type doped layer of the bottom battery by a magnetron sputtering method to form a composite layer, wherein an oxygen flow rate introduced in preparing the second composite sublayer is greater than an oxygen flow rate introduced in preparing the first composite sublayer;

[0021] Other functional layers are sequentially prepared on the surface of the composite layer, and the other functional layers at least include a hole transport layer, a hole modification layer and a perovskite layer.

[0022] In some embodiments of the present application, the oxygen flow rate for preparing the first composite sublayer is F 1 , 0Sccm≤F 1 ≤6 Sccm, the oxygen flow rate for preparing the second composite sublayer is F 2 , 20 Sccm≤F 2 -F 1 ≤50Sccm.

[0023] In some embodiments of the present application, the sputtering pressure of the magnetron sputtering method is 0.3 Pa~1.0 Pa, the temperature is 23°C~200°C, the flow rate of the argon gas is 500 Sccm~1200 Sccm, and the target sputtering power is 100W~2000W;

[0024] And / or, the coating transmission rate of the first composite sublayer is 4.1 mm / s to 495.0 mm / s, and the coating transmission rate of the second composite sublayer is 1.4 mm / s to 165.0 mm / s.

[0025] In some embodiments of the present application, the preparation method further comprises:

[0026] An electron transport layer, a buffer layer, a first transparent electrode layer and an anti-reflection layer are sequentially prepared on the surface of the passivation layer.

[0027] In a third aspect, the present application provides a photovoltaic module, wherein the photovoltaic module includes the solar cell as described in the first aspect, or the photovoltaic module includes the solar cell prepared by the preparation method as described in the second aspect.

[0028] Compared with the prior art, this application has at least the following beneficial effects:

[0029] The present application provides a solar cell and a preparation method thereof, and a photovoltaic module, wherein the composite layer of the solar cell includes a first composite sublayer and a second composite sublayer arranged in a stacked manner, and the resistivity of the first composite sublayer and / or the resistivity of the second composite sublayer is 6.5×10 -4 Ω·cm~1.6×10 -2 Ω·cm, and the carrier concentration of the first composite sublayer is greater than the carrier concentration of the second composite sublayer. By regulating the resistivity of the first composite sublayer and / or the resistivity of the second composite sublayer within the scope of the present application, the first composite sublayer and the second composite sublayer have appropriate resistivities, which, on the one hand, suppress the lateral charge transfer at the contact interface between the first composite sublayer and the bottom battery, and on the other hand, suppress the lateral charge transfer at the contact interface between the second composite sublayer and the top battery. Moreover, on the basis of meeting the above-mentioned resistivity range, by regulating the carrier concentration of the first composite sublayer to be greater than the carrier concentration of the second composite sublayer, on the one hand, the Fermi level of the first composite sublayer is shifted upward, the energy level matching of the first composite sublayer and the N-type doped layer is achieved, the contact barrier between the interface of the first composite sublayer and the N-type doped layer is reduced, and the transport of electrons from the bottom battery to the composite layer is promoted. On the other hand, the Fermi level of the second composite sublayer is shifted downward, the energy level matching of the second composite sublayer and the hole transport layer is achieved, the interface contact barrier between the second composite sublayer and the hole transport layer is reduced, and the transport of holes from the top battery to the composite layer is promoted. In summary, the composite layer of the present application has a double-layer structure, which simultaneously realizes the contact energy level matching between the composite layer and the N-type doped layer of the bottom battery and the hole transport layer of the top battery, and also inhibits the lateral transmission of charges on the surface of the composite layer, promotes the transport of charges at the interface, reduces the open circuit voltage loss, and improves the open circuit voltage and fill factor of the solar cell, thereby improving the photoelectric conversion efficiency of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 This is a schematic diagram of the structure of a solar cell in one embodiment of the present application.

[0032] Explanation of the accompanying drawings: bottom cell-1, composite layer-2, top cell-3, positive electrode-4, back electrode-5, N-type doped layer-11, first intrinsic amorphous silicon layer-12, silicon substrate-13, second intrinsic amorphous silicon layer-14, P-type doped layer-15, second transparent electrode layer-16, first composite sublayer-21, second composite sublayer-22, hole transport layer-31, hole modification layer-32, perovskite layer-33, passivation layer-34, electron transport layer-35, buffer layer-36, first transparent electrode layer-37, anti-reflection layer-38. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0034] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0035] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0036] In addition, the terms "installed", "set", "provided with", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0037] In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, "plurality" means two or more.

[0038] The technical solution of the present application will be further described below in conjunction with embodiments and drawings.

[0039] At present, one side of the composite layer contacts the N-type doped layer of the bottom battery, and the other side contacts the hole transport layer of the top battery, so it is necessary to make good contact with both interfaces at the same time. It is difficult for a single-film composite layer to match the energy levels of the N-type doped layer and the hole transport layer at the same time, resulting in a high contact barrier at the contact interface, hindering the transport of electrons from the bottom battery and holes from the top battery, causing charge accumulation and loss of open-circuit voltage. In addition, in order to take into account the contact performance of the upper and lower interfaces, the composite layer of a single film layer needs to have a lower surface resistance, and the lower surface resistance allows the charge to be transported laterally on the surface of the composite layer, which leads to the shunting of solar cell devices and causes the open-circuit voltage of the solar cell to decrease.

[0040] In view of this, in a first aspect, the present application provides a solar cell, Figure 1 This is a schematic diagram of the structure of a solar cell according to an embodiment of the present application, referring to Figure 1 The solar cell comprises a bottom cell 1, a composite layer 2 and a top cell 3, wherein the composite layer 2 is located between the bottom cell 1 and the top cell 3, the light-receiving surface of the bottom cell 1 comprises an N-type doped layer 11, and the backlight surface of the top cell 3 comprises a hole transport layer 31; the composite layer 2 comprises a first composite sublayer 21 and a second composite sublayer 22 arranged in a stacked manner, wherein a side of the first composite sublayer 21 facing away from the second composite sublayer 22 faces the N-type doped layer 11, and a side of the second composite sublayer 22 facing away from the first composite sublayer 21 faces the hole transport layer 31; the carrier concentration of the first composite sublayer 21 is greater than the carrier concentration of the second composite sublayer 22; the resistivity of the first composite sublayer 21 and / or the resistivity of the second composite sublayer 22 is 6.5×10 -4 Ω·cm~1.6×10 -2 Ω·cm.

[0041] In the present application, by regulating the resistivity of the first composite sublayer and / or the resistivity of the second composite sublayer within the scope of the present application, the first composite sublayer and the second composite sublayer have appropriate resistivities, which, on the one hand, suppresses the lateral charge transfer at the contact interface between the first composite sublayer and the bottom battery, and on the other hand, suppresses the lateral charge transfer at the contact interface between the second composite sublayer and the top battery. Moreover, on the basis of complying with the above-mentioned resistivity range, by regulating the carrier concentration of the first composite sublayer to be greater than the carrier concentration of the second composite sublayer, on the one hand, the Fermi level of the first composite sublayer is shifted upward, the energy level matching of the first composite sublayer and the N-type doped layer is achieved, the contact barrier between the interface of the first composite sublayer and the N-type doped layer is reduced, and the transport of electrons from the bottom battery to the composite layer is promoted. On the other hand, the Fermi level of the second composite sublayer is shifted downward, the energy level matching of the second composite sublayer and the hole transport layer is achieved, the interface contact barrier between the second composite sublayer and the hole transport layer is reduced, and the transport of holes from the top battery to the composite layer is promoted. In summary, the composite layer of the present application has a double-layer structure, which simultaneously realizes the contact energy level matching between the composite layer and the N-type doped layer of the bottom battery and the hole transport layer of the top battery, and also inhibits the lateral transmission of charges on the surface of the composite layer, promotes the transport of charges at the interface, reduces the open circuit voltage loss, and improves the open circuit voltage and fill factor of the solar cell, thereby improving the photoelectric conversion efficiency of the solar cell.

[0042] In an optional embodiment, the carrier concentration of the first composite sublayer is C 1 , the carrier concentration of the second composite sublayer is C 2 , 7.0×10 20 Pieces / cm 3 ≤C 1 ≤1.0×10 21 Pieces / cm 3 , 1.0×10 19 Pieces / cm 3 ≤C 2 ≤2.5×10 20 Pieces / cm 3 By adjusting the carrier concentration C of the first composite sublayer 1 and the carrier concentration C of the second composite sublayer 2 Within the above range, the transport of electrons from the bottom cell to the composite layer is promoted, and the transport of holes from the top cell to the composite layer is promoted, thereby reducing the open circuit voltage loss and promoting the longitudinal transport of charges; and the lower carrier concentration of the second composite sublayer can increase the resistivity of the second composite sublayer to a certain extent, and inhibit the lateral transport of charges at the contact interface between the second composite sublayer and the top cell. Under the combined effect of the above factors, it is beneficial to improve the open circuit voltage and fill factor, thereby facilitating the improvement of the photoelectric conversion efficiency of the solar cell.

[0043] In an optional embodiment, the carrier mobility of the first composite sublayer is CM 1 , the carrier mobility of the second composite sublayer is CM 2 , C.M. 1 <CM 2 By regulating the carrier mobility CM of the first composite sublayer 1 is smaller than the carrier mobility CM of the second composite sublayer 2 , which can improve the resistivity of the first composite sublayer to a certain extent, thereby inhibiting the lateral charge transfer at the contact interface between the first composite sublayer and the bottom battery, which is beneficial to the improvement of the open circuit voltage and fill factor, and thus is beneficial to the improvement of the photoelectric conversion efficiency of the solar cell.

[0044] In an alternative embodiment, 1 cm 2 / V·s≤CM 1 ≤13 cm 2 / V·s,30 cm 2 / V·s≤CM 2 ≤40 cm 2 / V·s. By adjusting the carrier mobility CM of the first composite sublayer 1 and the carrier mobility CM of the second composite sublayer 2 Within the above range, the carrier mobility CM of the first composite sublayer is 1 is smaller than the carrier mobility CM of the second composite sublayer 2 , which can improve the resistivity of the first composite sublayer to a certain extent, thereby inhibiting the lateral charge transfer at the contact interface between the first composite sublayer and the bottom battery, which is beneficial to the improvement of the open circuit voltage and fill factor, and thus is beneficial to the improvement of the photoelectric conversion efficiency of the solar cell.

[0045] In an optional embodiment, the resistivity of the first composite sublayer is R 1 , 6.5×10 -4 Ω·cm≤R 1 ≤6.5×10 -3 Ω·cm, the resistivity of the second composite sublayer is R 2 , 8.0×10 -4 Ω·cm≤R 2 ≤1.6×10 -2Ω·cm. The first composite sublayer and the second composite sublayer have suitable resistivity, which inhibits the lateral charge transfer between the first composite sublayer and the bottom battery contact interface on the one hand, and inhibits the lateral charge transfer between the second composite sublayer and the top battery contact interface on the other hand, which is beneficial to the improvement of the open circuit voltage and the fill factor, thereby facilitating the improvement of the photoelectric conversion efficiency of the solar cell. Moreover, by synergistically regulating the carrier concentration and the carrier mobility of the first composite sublayer within the scope of the present application, it is beneficial to obtain the first composite sublayer having the above-mentioned resistivity range; by synergistically regulating the carrier concentration and the carrier mobility of the second composite sublayer within the scope of the present application, it is beneficial to obtain the second composite sublayer having the above-mentioned resistivity range.

[0046] In an optional embodiment, the work function of the first composite sublayer is 3.4eV~3.8eV, and the work function of the second composite sublayer is 4.3eV~5.0eV. In the present application, the work function refers to the energy required for an electron to rise from the Fermi level to the static state outside the surface (i.e., the vacuum level). By regulating the work function of the first composite sublayer and the second composite sublayer within the above range, it is beneficial to reduce the contact potential between the composite layer and the bottom battery N-type doped layer and the composite layer and the top battery hole transport layer, so that the electrons in the bottom battery N-type doped layer can be smoothly transported to the top battery hole transport layer, while reducing the contact resistance of the interface.

[0047] In an optional embodiment, the thickness of the first composite sublayer is H 1 , the thickness of the second composite sublayer is H 2 , 0nm≤H 2 -H 1 ≤14nm. The inventors have found that if the thickness difference between the first composite sublayer and the second composite sublayer is too large, the performance of the first composite sublayer will be affected, resulting in a change in the carrier concentration of the first composite sublayer, which in turn leads to poor contact with the N-type doped layer. Therefore, H 2 -H 1 The present application adjusts the thickness difference between the first composite sublayer and the second composite sublayer, i.e., H 2 -H 1 Within the above range, it is beneficial to utilize the high carrier mobility of the second composite sublayer to achieve rapid transport of electrons and avoid interface charge accumulation.

[0048] In an optional embodiment, 1nm≤H 1 ≤5nm, 3nm≤H 2 ≤15nm. By adjusting the thickness H of the first composite sublayer 1 and the thickness H of the second composite sublayer 2Within the above range, it is not only beneficial to achieve good energy level matching between the composite layer and the N-type layer and the hole transport layer, but also to achieve rapid transport of electrons and avoid charge accumulation at the interface.

[0049] In some embodiments of the present application, the material of the first composite sublayer and / or the second composite sublayer includes at least one of indium zinc oxide (IZO), indium tin oxide (ITO), aluminum zinc oxide (AZO), tungsten-doped indium oxide (IWO) and cerium-doped indium oxide (ICO).

[0050] In an optional embodiment, reference Figure 1 The bottom cell 1 includes a silicon substrate 13, a light-receiving surface of the silicon substrate 13 is sequentially stacked with a first intrinsic amorphous silicon layer 12 and an N-type doped layer 11, and a backlight surface of the silicon substrate 13 is sequentially stacked with a second intrinsic amorphous silicon layer 14, a P-type doped layer 15 and a second transparent electrode layer 16.

[0051] In an optional embodiment, reference Figure 1 A hole modification layer 32 , a perovskite layer 33 , a passivation layer 34 , an electron transport layer 35 , a buffer layer 36 , a first transparent electrode layer 37 and an anti-reflection layer 38 are sequentially stacked on the hole transport layer 31 .

[0052] The present application has no particular restrictions on the electrodes of the solar cell, as long as the purpose of the present application can be achieved. Figure 1 A positive electrode 4 can be set on the light-receiving surface of the solar cell, and a back electrode 5 can be set on the backlight surface of the solar cell.

[0053] In the related art, the composite layer can be prepared by the solution method, but the solution method requires multiple processes such as solution preparation, spin coating, annealing, etc., which is cumbersome and time-consuming. In addition, the light-receiving surface of the bottom cell usually has a pyramid-shaped velvet structure. The solution method will cause the valley bottom of the pyramid to be thick and the top of the pyramid to be thin in the velvet structure, resulting in uneven coverage of the composite layer, which is not conducive to mass production of large-area and uniformly covered composite layer films. In addition, deionized water is used in the solution. The presence of water will cause defects in the amorphous silicon of the bottom cell and produce insulating SiO 2 On the other hand, the composite layer prepared by the solution method has a low resistivity, which makes it easy for the charge to be transmitted laterally on the surface of the composite layer, resulting in lateral shunt, which hinders the longitudinal transmission of the charge and affects the photoelectric conversion efficiency of the solar cell.

[0054] In view of this, in a second aspect, the present application provides a method for preparing a solar cell as described in the first aspect, comprising the following steps:

[0055] Step A, providing a bottom battery, and sequentially preparing a first composite sublayer and a second composite sublayer on the surface of the N-type doped layer of the bottom battery by magnetron sputtering to form a composite layer, wherein the oxygen flow rate introduced in preparing the second composite sublayer is greater than the oxygen flow rate introduced in preparing the first composite sublayer;

[0056] Step B: preparing other functional layers in sequence on the surface of the composite layer, wherein the other functional layers at least include a hole transport layer, a hole modification layer and a perovskite layer.

[0057] In step A, a first composite sublayer may be prepared on the surface of the N-type doped layer of the bottom cell by magnetron sputtering, and then a second composite sublayer may be prepared on the surface of the first composite sublayer, thereby forming a composite layer.

[0058] The present application has no particular restrictions on the target materials of the first composite sublayer and the second composite sublayer, as long as the purpose of the present application can be achieved. Exemplarily, the target materials of the first composite sublayer and the second composite sublayer include transparent conductive oxide (TCO) materials, and the TCO materials include but are not limited to indium zinc oxide (IZO), indium tin oxide (ITO), aluminum zinc oxide (AZO), tungsten-doped indium oxide (IWO) or cerium-doped indium oxide (ICO).

[0059] In step B, other functional layers may be prepared on the surface of the composite layer by magnetron sputtering. For example, a hole transport layer, a hole modification layer, a perovskite layer and a passivation layer may be prepared in sequence on the surface of the second composite sublayer. Among them, the material of the hole transport layer includes nickel oxide, and the thickness of the hole transport layer is 10nm~25nm; the present application has no special restrictions on the material of the hole modification layer, for example, it can be selected from [2-(9H-carbazole-9-yl)ethyl]phosphonic acid (2PACz), [2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid (MeO-2PACz), [4-(3,6-dimethoxy-9H-carbazole-9-yl)butyl]phosphonic acid (MeO-4PACz), poly [bis (4-phenyl) (2, 4,6-trimethylphenyl) amine] (PTAA) and other materials, and a hole modification layer with a thickness of 0.5nm~1.5nm can be prepared on the surface of the hole transport layer by spin coating or slit coating; when preparing the perovskite layer, a skeleton layer can be prepared first, and then an organic salt solution can be spin coated on the surface of the skeleton layer, and the perovskite layer can be obtained after thermal annealing. The skeleton layer can be prepared by removing PbI 2and CsX (X represents a halogen element) by evaporation. The present application has no particular restriction on the type of organic salt. For example, at least two of formamidine hydroiodide (FAI), formamidine hydrobromide (FABr), formamidine hydrochloride (FACl), methylammonium iodide (MAI), methylammonium bromide (MABr) and methylammonium chloride (MACl) can be combined and dissolved in a solvent to obtain an organic salt solution. The present application has no particular restriction on the coating method. For example, spin coating, spray coating, slit coating, blade coating and the like can be used. The thickness of the perovskite layer is 400nm~500nm; a LiF film layer with a thickness of 1nm~2nm is prepared on the surface of the perovskite layer by metal evaporation as a passivation layer.

[0060] In an optional embodiment, the oxygen flow rate for preparing the first composite sublayer is F 1 ,0 Sccm≤F 1 ≤6 Sccm, the oxygen flow rate for preparing the second composite sublayer is F 2 , 20 Sccm≤F 2 -F 1 ≤50 Sccm. By controlling F 2 With F 1 The difference between them is within the above range, which can regulate the carrier concentration of the first composite sublayer and the second composite sublayer, thereby regulating the Fermi level of the first composite sublayer and the second composite sublayer, and achieving adjustable work function of the first composite sublayer and the second composite sublayer, which is conducive to obtaining the composite layer of the present application.

[0061] In an optional embodiment, when the first composite sublayer and the second composite sublayer are prepared by magnetron sputtering, the sputtering pressure of the magnetron sputtering method is 0.3 Pa~1.0 Pa, the temperature is 23°C~200°C, the flow rate of argon gas is 500Sccm~1200Sccm, and the target sputtering power is 100W~2000W; and / or, the coating transmission rate of the first composite sublayer is 4.1mm / s~495.0mm / s, preferably 45.0mm / s~225.0mm / s; the coating transmission rate of the second composite sublayer is 1.4mm / s~165.0mm / s, preferably 15.0mm / s~75.0mm / s.

[0062] In an optional embodiment, the preparation method further comprises:

[0063] An electron transport layer, a buffer layer, a first transparent electrode layer and an anti-reflection layer are sequentially prepared on the surface of the passivation layer.

[0064] The present application has no particular restrictions on the preparation methods of the electron transport layer, the buffer layer, the first transparent electrode layer, the anti-reflection layer and the electrode. 60The electron transport layer is obtained by thermal evaporation deposition using a metal evaporation device, with a thickness of 10 nm to 20 nm; the buffer layer material SnO 2 The buffer layer can be obtained by atomic layer deposition (ALD) with a thickness of 10 nm to 17 nm. The transparent electrode layer material indium zinc oxide (IZO) can be obtained by magnetron sputtering to obtain the first transparent electrode layer with a thickness of 30 nm to 110 nm. The anti-reflection layer material LiF or MgF 2 The anti-reflection layer is obtained by thermal evaporation deposition through metal evaporation equipment, and the thickness is 80 nm~130 nm; the electrode material Ag can be obtained by thermal evaporation deposition through metal evaporation equipment to obtain a positive electrode and a back electrode, and the electrode thickness is 300 nm~500 nm.

[0065] The bottom cell of the present application can be a silicon substrate cell available on the market or produced on a production line. In an optional embodiment, the bottom cell is produced by the following steps:

[0066] 1) Prepare a first intrinsic amorphous silicon layer and a second intrinsic amorphous silicon layer on the light-receiving side and the backlight side of the N-type silicon wafer (i.e., silicon substrate), respectively. The thickness of the first intrinsic amorphous silicon layer is 5nm~12nm, and the thickness of the second intrinsic amorphous silicon layer is 5nm~12nm;

[0067] 2) Preparing an N-type doped layer on the surface of the first intrinsic amorphous silicon layer, and preparing a P-type doped layer on the surface of the second intrinsic amorphous silicon layer. The thickness of the N-type doped layer is 5 nm to 25 nm, and the thickness of the P-type doped layer is 10 nm to 30 nm;

[0068] 3) A DC or RF magnetron sputtering process is used to prepare a second transparent electrode layer of ITO material on the surface of the P-type doped layer, and the thickness of the second transparent electrode layer is 90nm~120nm.

[0069] In an optional embodiment, the light-receiving surface of the silicon substrate has a velvet structure. In order to better absorb solar energy, the light-receiving surface of the silicon substrate has a velvet structure, for example, the velvet structure can be a pyramid-shaped velvet structure. Through the velvet structure, a higher surface area can be provided for the solar cell while reducing the reflection and diffusion of light. The present application has no particular restrictions on the preparation method of the velvet structure, as long as the purpose of the present application can be achieved.

[0070] It is understandable that after obtaining the bottom cell, the composite layer of the present application can be prepared on the surface of the N-type doped layer of the bottom cell. The top cell of the present application can be a single-junction perovskite solar cell.

[0071] The preparation method of the solar cell provided in the present application has the advantages of simple preparation process and convenient operation compared with the existing solution method; and the present application forms the first composite sublayer and the second composite sublayer in sequence based on the magnetron sputtering method, and the magnetron sputtering target material will form a uniformly distributed target material atom region, so that the velvet surface can uniformly adhere to the target material atoms in all directions; and the target material atoms have higher energy and higher bonding force with the pyramid surface, which will not cause the atoms to fall off and fall into the valley bottom of the pyramid, so that the valley bottom will not be thick and the top of the pyramid will not be thin, thereby achieving uniform coverage of the pyramid by the magnetron sputtering film, which is conducive to industrial production and suitable for large-scale manufacturing of laminated solar cells.

[0072] In a third aspect, the present application provides a photovoltaic module, wherein the photovoltaic module includes the solar cell as described in the first aspect, or the photovoltaic module includes the solar cell prepared by the preparation method as described in the second aspect.

[0073] The present application also provides a photovoltaic module, which is used to convert received light energy into electrical energy and transmit it to an external load. The photovoltaic module includes: at least one battery string, which is formed by connecting a plurality of the above-mentioned solar cells; a packaging film, which is used to cover the surface of the battery string; and a cover plate, which is used to cover the surface of the packaging film away from the battery string.

[0074] Example

[0075] The solar cell and its preparation method, and photovoltaic module of the present application are further described below in conjunction with more specific embodiments.

[0076] Example 1

[0077] <Preparation of composite layer>

[0078] <Preparation of the First Composite Sublayer>

[0079] A bottom battery is provided, wherein the thickness of the N-type doped layer is 6 nm, the thickness of the first intrinsic amorphous silicon layer is 8 nm, the thickness of the N-type silicon wafer is 120 μm, the thickness of the second intrinsic amorphous silicon layer is 8 nm, the thickness of the P-type doped layer is 10 nm, and the thickness of the second transparent electrode layer is 100 nm;

[0080] IZO target material was selected, and the first composite sublayer was prepared on the surface of the N-type doped layer on the light-receiving side of the bottom cell by magnetron sputtering. The sputtering pressure, temperature, flow rate of argon gas, target RF sputtering power, coating transmission rate, and oxygen flow rate F 1 , the thickness of the first composite sublayer H 1 As shown in Table 1;

[0081] <Preparation of the Second Composite Sublayer>

[0082] IZO target material was selected, and the second composite sublayer was prepared on the surface of the first composite sublayer by magnetron sputtering. The sputtering pressure, temperature, flow rate of argon gas, target RF sputtering power, coating transmission rate, and oxygen flow rate F were 2 , the thickness of the second composite sublayer H 2 As shown in Table 2.

[0083] <Preparation of hole transport layer>

[0084] Nickel oxide (NiO x ) target material, and a hole transport layer with a thickness of 20 nm was prepared on the surface of the second composite sublayer by radio frequency magnetron sputtering.

[0085] <Preparation of Hole Modification Layer>

[0086] The SAM material 2-PACz was prepared on the surface of the hole transport layer by solution spin coating to form a hole modification layer with a thickness of 1 nm.

[0087] <Preparation of Perovskite Layer>

[0088] The organic salt cation solution is spin-coated onto the surface of the skeleton layer, and after the organic salt cation and the skeleton layer are fully reacted, a perovskite layer with a thickness of 450 nm is obtained.

[0089] <Preparation of Passivation Layer>

[0090] A 1 nm thick LiF film is prepared on the surface of the perovskite layer by metal evaporation as a passivation layer.

[0091] <Preparation of other functional layers>

[0092] An electron transport layer, a buffer layer and a first transparent electrode layer are sequentially prepared on the surface of the passivation layer.

[0093] The preparation process of the electron transport layer is as follows: a 20 nm thick C 60 As an electron transport layer;

[0094] The preparation process of the buffer layer is as follows: a 10 nm thick tin dioxide layer is prepared on the electron transport layer by atomic layer deposition as a buffer layer;

[0095] The preparation process of the first transparent electrode layer is as follows: a 100 nm thick IZO layer is prepared on the buffer layer using a magnetron sputtering device as the first transparent electrode layer.

[0096] <Preparation of Solar Cells>

[0097] A 350 nm thick silver layer was prepared on the first transparent electrode layer by thermal evaporation as the positive electrode, and a 300 nm thick silver layer was prepared on the second transparent electrode layer of the bottom cell by thermal evaporation as the back electrode. 2 The anti-reflection layer with a thickness of 100 nm is obtained by thermal evaporation deposition using a metal evaporation device to obtain a solar cell. The cell structure is as follows: Figure 1 shown.

[0098] Embodiment 2 to Embodiment 8

[0099] In addition to adjusting the oxygen flow rate F when preparing the first composite sublayer according to Table 1 and Table 2 in <Preparation of Composite Layer>, 1 , oxygen flow rate F when preparing the second composite sublayer 2 , the thickness of the first composite sublayer H 1 , the thickness of the second composite sublayer H 2 Other than that, the rest is the same as Example 1.

[0100] Comparative Example 1

[0101] Except that the composite layer is a single-layer structure, the rest is the same as Example 1. The preparation process of the composite layer of the single-layer structure is as follows:

[0102] IZO target material was used to prepare the composite layer on the surface of the N-type doped layer on the light-receiving side of the bottom cell by magnetron sputtering. The sputtering pressure, temperature, flow rate of argon gas, target RF sputtering power, coating transmission rate, and oxygen flow rate F 1 , the thickness of the first composite sublayer H 1 As shown in Table 1.

[0103] Comparative Example 2

[0104] In addition to adjusting the oxygen flow rate F when preparing the first composite sublayer according to Table 1 and Table 2 in <Preparation of Composite Layer>, 1 , oxygen flow rate F when preparing the second composite sublayer 2 Other than that, the rest is the same as Example 1.

[0105] Table 1: Preparation parameters of the first composite sublayer of each embodiment and comparative example

[0106]

[0107] Table 2: Preparation parameters of the second composite sublayer of each embodiment and comparative example

[0108]

[0109] In Table 2, “ / ” indicates that there is no relevant preparation parameter.

[0110] Table 3: Difference in oxygen flow and thickness between the second composite sublayer and the first composite sublayer

[0111]

[0112] In Table 3, “ / ” indicates that there is no relevant preparation parameter.

[0113] Table 4: Relevant performance data of the composite layer of each embodiment and comparative example

[0114]

[0115] In Table 4, “ / ” indicates that there is no relevant performance data.

[0116] Performance Test:

[0117] Open circuit voltage, short circuit current, fill factor test:

[0118] The current (I)-voltage (V) of the solar cells of various embodiments and comparative examples were measured using a Wavelabs solar simulator to obtain the open circuit voltage (Voc), short circuit current (Jsc) and fill factor (FF) of the solar cells.

[0119] Photoelectric conversion efficiency test:

[0120] The current (I)-voltage (V) of the solar cells of each embodiment and comparative example was measured using a Wavelabs solar simulator to obtain the photoelectric conversion efficiency (PCE) of the solar cells.

[0121] Table 5: Solar cell performance data of various embodiments and comparative examples

[0122]

[0123] It can be seen from Examples 1 to 8 and Comparative Examples 1 to 2 that the open circuit voltage and fill factor of the solar cell in Comparative Example 1 are low, resulting in low photoelectric conversion efficiency. This may be because the composite layer of the single film layer in Comparative Example 1 is difficult to match the energy levels of the N-type doped layer and the hole transport layer at the same time, resulting in a high contact barrier at the contact interface, which hinders the transport of electrons in the bottom cell and holes in the top cell, resulting in charge accumulation and loss of open circuit voltage and fill factor. The photoelectric conversion efficiency of the solar cell in Comparative Example 2 is also low, which may be due to the fact that the oxygen flow rate introduced into the second composite sublayer is F 2 On the contrary, the oxygen flow rate F 1The carrier concentration of the first composite sublayer is much smaller than that of the second composite sublayer. On the one hand, it is difficult for the first composite sublayer to achieve energy level matching with the N-type doped layer, which increases the interface contact barrier between the first composite sublayer and the N-type doped layer, hindering the transport of electrons from the bottom battery to the composite layer. On the other hand, it is difficult for the second composite sublayer to achieve energy level matching with the hole transport layer, which increases the interface contact barrier between the second composite sublayer and the hole transport layer, hindering the transport of holes from the top battery to the composite layer. The photoelectric conversion efficiency of the solar cell of the present application is significantly improved compared with Comparative Examples 1 and 2, and the maximum improvement is close to 1.5 percentage points, indicating that the solar cell with the double-layer structure composite layer of the present application has excellent photoelectric conversion performance.

[0124] Parameters such as the thickness of the first composite sublayer, the thickness of the second composite sublayer, and the flow rate of oxygen generally also have an impact on the performance of the composite layer. It can be seen from Examples 2 to 8 that by adjusting the above preparation parameters within the scope of this application, it is beneficial to reduce the open circuit voltage loss, improve the open circuit voltage and fill factor of the solar cell, and thus improve the photoelectric conversion efficiency of the solar cell.

[0125] The above is a detailed introduction to a solar cell and its preparation method, and a photovoltaic module disclosed in the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solutions and core inventions of the embodiments of the present application. At the same time, for general technicians in this field, according to the ideas of the present application, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A solar cell, characterized in that: It comprises a bottom battery, a composite layer and a top battery, wherein the composite layer is located between the bottom battery and the top battery, the light-receiving surface of the bottom battery has an N-type doping layer, and the backlight surface of the top battery has a hole transport layer, wherein: The composite layer comprises a first composite sublayer and a second composite sublayer which are stacked, wherein a side of the first composite sublayer facing away from the second composite sublayer faces the N-type doped layer, and a side of the second composite sublayer facing away from the first composite sublayer faces the hole transport layer; The carrier concentration of the first composite sublayer is greater than the carrier concentration of the second composite sublayer; The resistivity of the first composite sublayer and / or the resistivity of the second composite sublayer is 6.5×10 -4 Ω·cm~1.6×10 -2 Ω·cm.

2. The solar cell according to claim 1, characterized in that: The carrier concentration of the first composite sublayer is C1, and the carrier concentration of the second composite sublayer is C2, 7.0×10 20 Pieces / cm 3 ≤C1≤1.0×10 21 Pieces / cm 3 , 1.0×10 19 Pieces / cm 3 ≤C2≤2.5×10 20 Pieces / cm 3 .

3. The solar cell according to claim 1, characterized in that: The carrier mobility of the first composite sublayer is CM1, the carrier mobility of the second composite sublayer is CM2, and CM1<CM2.

4. The solar cell according to claim 3, characterized in that: 1 cm 2 / V·s≤CM1≤13 cm 2 / V·s,30cm 2 / V·s≤CM2≤40 cm 2 / V·s。 5. The solar cell according to claim 1, characterized in that: The resistivity of the first composite sublayer is R1,6.5×10 -4 Ω·cm≤R1≤6.5×10 -3 Ω·cm, the resistivity of the second composite sublayer is R2, 8.0×10 -4 Ω·cm≤R2≤1.6×10 -2 Ω·cm.

6. The solar cell according to claim 1, characterized in that: The work function of the first composite sublayer is 3.4 eV to 3.8 eV, and the work function of the second composite sublayer is 4.3 eV to 5.0 eV.

7. The solar cell according to claim 1, characterized in that: The thickness of the first composite sublayer is H1, the thickness of the second composite sublayer is H2, and 0 nm ≤ H2 - H1 ≤ 14 nm.

8. The solar cell according to claim 7, characterized in that: 1nm≤H1≤5nm, 3nm≤H2≤15nm.

9. The solar cell according to claim 1, characterized in that: The material of the first composite sublayer and / or the second composite sublayer includes at least one of indium zinc oxide, indium tin oxide, zinc aluminum oxide, tungsten-doped indium oxide and cerium-doped indium oxide.

10. The solar cell according to any one of claims 1 to 9, characterized in that: The bottom cell comprises a silicon substrate, the light-receiving surface of the silicon substrate is sequentially stacked with a first intrinsic amorphous silicon layer and the N-type doped layer, and the backlight surface of the silicon substrate is sequentially stacked with a second intrinsic amorphous silicon layer, a P-type doped layer and a second transparent electrode layer.

11. The solar cell according to claim 10, characterized in that: A hole modification layer, a perovskite layer, a passivation layer, an electron transport layer, a buffer layer, a first transparent electrode layer and an anti-reflection layer are sequentially stacked on the hole transport layer.

12. A method for preparing a solar cell according to any one of claims 1 to 11, characterized in that: The following steps are involved: Providing a bottom battery, and sequentially preparing a first composite sublayer and a second composite sublayer on a surface of an N-type doped layer of the bottom battery by a magnetron sputtering method to form a composite layer, wherein an oxygen flow rate introduced in preparing the second composite sublayer is greater than an oxygen flow rate introduced in preparing the first composite sublayer; Other functional layers are sequentially prepared on the surface of the composite layer, and the other functional layers at least include a hole transport layer, a hole modification layer and a perovskite layer.

13. The preparation method according to claim 12, characterized in that: The oxygen flow rate for preparing the first composite sublayer is F1, 0 Sccm≤F1≤6 Sccm, and the oxygen flow rate for preparing the second composite sublayer is F2, 20 Sccm≤F2-F1≤50 Sccm.

14. The preparation method according to claim 12, characterized in that: The sputtering pressure of the magnetron sputtering method is 0.3Pa~1.0Pa, the temperature is 23℃~200℃, the flow rate of the argon gas is 500 Sccm~1200 Sccm, and the target sputtering power is 100W~2000W; And / or, the coating transmission rate of the first composite sublayer is 4.1 mm / s to 495.0 mm / s, and the coating transmission rate of the second composite sublayer is 1.4 mm / s to 165.0 mm / s.

15. The preparation method according to any one of claims 12 to 14, characterized in that: The preparation method further comprises: An electron transport layer, a buffer layer, a first transparent electrode layer and an anti-reflection layer are sequentially prepared on the surface of the passivation layer.

16. A photovoltaic module, characterized in that: The photovoltaic module comprises the solar cell according to any one of claims 1 to 11, or the photovoltaic module comprises the solar cell prepared by the preparation method according to any one of claims 12 to 15.

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