Laminated cell and preparation method thereof

Abstract

The invention relates to a laminated cell and a preparation method thereof, the laminated cell comprises a narrow-band-gap bottom cell and a wide-band-gap top cell, and the preparation method comprises the following steps: preparing a hole transport layer on a transparent conductive substrate of the narrow-band-gap bottom cell; sequentially arranging a first inorganic salt layer and an organic salt layer on the surface of the hole transport layer to obtain a perovskite layer; evaporating a second inorganic salt layer on the surface of the perovskite layer to enable the second inorganic salt layer to react with residual organic salt on the surface of the perovskite layer, and annealing to obtain a passivation layer; and sequentially preparing an electron transport layer, a buffer layer, a conductive layer and an electrode layer on the passivation layer to obtain the laminated cell. According to the invention, the problem of surface organic salt residue in a dry-wet two-step method is overcome, and non-radiative recombination is reduced, so that the service life of a carrier is prolonged, the overall efficiency of the cell is improved, the sensitivity of a perovskite material to moisture and oxygen is reduced, and the long-term stability is improved; the quality of an interface between the perovskite thin film and the electron transport layer is improved, and charge recombination at the interface is reduced.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and relates to a solar cell, and more particularly to a tandem cell and its preparation method. Background Technology

[0002] As a representative of new energy technologies, solar energy is accounting for an increasing proportion of the global energy structure year by year. Solar photovoltaics can be divided into three stages based on its development history: the first generation of solar energy technology represented by silicon, the second generation of thin-film photovoltaic technology mainly based on compound materials, and the third generation of new, high-efficiency solar cell technology. Among these, the conversion efficiency of silicon photovoltaics has reached 26.81%, essentially reaching its limit. Perovskite crystalline silicon tandem solar cells, on the other hand, have a theoretical efficiency of up to 46%, far exceeding the theoretical limit of crystalline silicon cells. This promises to reduce costs by improving conversion efficiency, thus achieving affordable and affordable solar energy applications.

[0003] Perovskite-silicon tandem solar cells are generally classified into two categories: those with a planar silicon substrate and those with a textured silicon substrate. Planar substrate perovskite cells can be fabricated using a conventional one-step solution method. Textured substrate perovskite cells require wafer polishing, which sacrifices current and reduces overall efficiency. Without textured substrate preparation, solution-based perovskite film fabrication is difficult. A two-step wet-dry method for perovskite film deposition ensures high-quality conformal growth of wide-bandgap perovskite films on industrially produced large-textured silicon substrates, with no current loss and no increase in equipment cost.

[0004] The wet-dry two-step method involves first evaporating inorganic salts and then preparing organic salts through a solution method. During the organic salt conversion process, organic salt residues remain at the top and bottom of the textured pyramid, posing a risk of adverse reactions with the perovskite material, affecting the chemical stability of the perovskite layer, and causing the battery performance to decline over time. It also increases the recombination of electron-hole pairs, affecting the photoelectric conversion and stability of the tandem battery.

[0005] Therefore, it is necessary to overcome the adverse effects of surface organic salt residue in the wet and dry two-step process. Summary of the Invention

[0006] The purpose of this invention is to provide a tandem battery and its preparation method, which can effectively overcome the problem of surface organic salt residue in the dry and wet two-step method, reduce non-radiative recombination, thereby improving the carrier lifetime and the overall efficiency of the battery, reduce the sensitivity of perovskite materials to moisture and oxygen, thereby improving long-term stability; and also improve the interface quality between the perovskite thin film and the electron transport layer, reducing charge recombination at the interface.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a stacked battery, the stacked battery comprising a narrow bandgap bottom cell and a wide bandgap top cell, the preparation method comprising the following steps:

[0009] A hole transport layer is prepared on a transparent conductive substrate of a narrow bandgap bottom cell; a first inorganic salt layer and an organic salt layer are sequentially deposited on the surface of the hole transport layer to obtain a perovskite layer; a second inorganic salt layer is vapor-deposited on the surface of the perovskite layer to react with the organic salt remaining on the surface of the perovskite layer, and then annealed to obtain a passivation layer; an electron transport layer, a buffer layer, a conductive layer, and an electrode layer are sequentially prepared on the passivation layer to obtain the stacked cell.

[0010] Existing techniques for cleaning residual organic salts on the surface in wet-dry two-step processes include organic solvent cleaning. This method is difficult to completely remove organic salts and may adversely affect the quality of the perovskite layer. Furthermore, residual organic salts introduce additional defect states into the perovskite layer, increasing electron-hole recombination and reducing solar cell efficiency. They also form harmful intermediate phases with different electronic properties, affecting charge transport and extraction. Additionally, they cause uneven surface morphology of the perovskite layer, increasing charge transport resistance within the cell. This invention addresses this by depositing a second inorganic salt layer after forming the perovskite layer. The second inorganic salt near the perovskite layer reacts completely with the residual organic salt to form perovskite, and simultaneously binds to defect sites in the perovskite material, reducing non-radiative recombination, thereby improving carrier lifetime and overall cell efficiency. The resulting passivation layer reduces the perovskite layer's sensitivity to moisture and oxygen, improving its long-term stability. The second inorganic salt layer also improves the interface quality between the perovskite layer and the electron transport layer, reducing charge recombination at the interface.

[0011] In some embodiments, the material of the first inorganic salt layer includes a combination of a first cation and a first anion; the first cation includes any one or a combination of at least two of lead (Pb) ions, tin (Sn) ions or cesium (Cs) ions; the first anion includes any one or a combination of at least two of chloride (Cl) ions, bromide (Br) ions or iodide (I) ions.

[0012] In some embodiments, the material of the organic salt layer includes a combination of organic cations and anions; the organic cations include any one or a combination of at least two of methyl ether (FA) ions, methylamine (MA) ions, or dimethylamine (DMA) ions; the anions include any one or a combination of at least two of chloride (Cl) ions, bromide (Br) ions, or iodide (I) ions.

[0013] In some embodiments, the material of the second inorganic salt layer includes a combination of a second cation and a second anion; the second cation includes any one or a combination of at least two of lead (Pb) ions, tin (Sn) ions or cesium (Cs) ions; the second anion includes any one or a combination of at least two of chloride (Cl) ions, bromide (Br) ions or iodide (I) ions.

[0014] In some embodiments, the thickness of the second inorganic salt layer is 1 nm to 9 nm.

[0015] In some embodiments, the annealing temperature is 90°C-120°C and the time is 15 min-25 min.

[0016] In some embodiments, the hole transport layer is made of nickel oxide (NiO). x Any one or a combination of at least two of the following: self-assembled monolayer (SAM) materials or poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine) (PTAA).

[0017] In some embodiments, the electron transport layer is made of fullerene (C 60 ), [6,6]-phenyl-C61-butyrate methyl ester (PCBM), TiO2 or ZnO, or a combination of at least two of them.

[0018] In some embodiments, the buffer layer is made of molybdenum oxide (MoO). x ) and / or tin oxide (SnO2).

[0019] In some embodiments, the conductive layer is made of any one or a combination of at least two of indium tin oxide (ITO), indium zinc oxide (IZO), indium cobalt oxide (ICO), aluminum-doped zinc oxide (AZO), fluorine-doped tin oxide (FTO), or indium tungsten oxide (IWO).

[0020] In some embodiments, the electrode layer is made of any one or a combination of at least two of gold, silver, or copper.

[0021] In some embodiments, an antireflection layer is further provided on the side of the conductive layer away from the buffer layer.

[0022] In some embodiments, the antireflective layer is made of magnesium fluoride (MgF2) and / or lithium fluoride (LiF).

[0023] In some embodiments, the narrow bandgap bottom cell includes any one of silicon cells, narrow bandgap perovskite cells, copper indium gallium selenide cells, or cadmium telluride cells.

[0024] In a second aspect, the present invention provides a stacked battery, which is prepared by the preparation method described in the first aspect.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] This invention sequentially deposits a first inorganic salt layer and an organic salt layer on the surface of the hole transport layer. The resulting perovskite layer has residual organic salt on its surface. This residual organic salt introduces additional defect states into the perovskite layer, increasing electron-hole recombination and reducing the efficiency of the solar cell. It also forms harmful intermediate phases with different electronic properties, affecting charge transport and extraction. Furthermore, it leads to uneven surface morphology of the perovskite layer, increasing charge transport resistance within the cell. During annealing, the second inorganic salt layer deposited by vapor deposition reacts completely with the residual organic salt on the side closest to the perovskite layer to form perovskite. It can also bind to defect sites in the perovskite material, reducing non-radiative recombination and thus improving carrier lifetime and overall cell efficiency. The remaining second inorganic salt also provides a passivation layer, reducing the perovskite layer's sensitivity to moisture and oxygen, and improving its long-term stability. The second inorganic salt layer also improves the interface quality between the perovskite layer and the electron transport layer, reducing charge recombination at the interface. Therefore, the preparation method provided by this invention can obtain a tandem solar cell with high photoelectric conversion efficiency. Attached Figure Description

[0027] Figure 1 A process flow diagram of the preparation method provided for this invention is shown.

[0028] Figure 2 This is a surface SEM image of the perovskite layer obtained by the conventional wet-dry two-step method.

[0029] Figure 3 This is a structural diagram of the stacked battery provided in Embodiment 1 of the present invention.

[0030] Figure 4 This is a surface SEM image of the perovskite layer in the stacked battery provided in Embodiment 1 of the present invention.

[0031] Figure 5 This is a side view showing the stability of the stacked battery provided in Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention.

[0032] The structure includes: 1. Hole transport layer; 2. Perovskite layer; 3. Passivation layer; 4. Electron transport layer; 5. Buffer layer; 6. Conductive layer; 7. Electrode layer; 8. Antireflection layer. Detailed Implementation

[0033] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0034] An embodiment of the present invention provides a method for fabricating a tandem solar cell, the tandem solar cell comprising a narrow bandgap bottom cell and a wide bandgap top cell, and the process flow diagram of the fabrication method is shown below. Figure 1 As shown, it includes the following steps:

[0035] Step 101: Prepare a hole transport layer on the transparent conductive substrate of the narrow bandgap bottom cell.

[0036] Step 102: Sequentially deposit a first inorganic salt layer and an organic salt layer on the surface of the hole transport layer to obtain a perovskite layer.

[0037] Step 103: A second inorganic salt layer is vapor-deposited on the surface of the perovskite layer to react with the residual organic salt on the surface of the perovskite layer, and then annealed to obtain a passivation layer.

[0038] Step 104: Sequentially prepare an electron transport layer, a buffer layer, a conductive layer, and an electrode layer on the passivation layer to obtain the stacked battery.

[0039] The preparation method provided by this invention is for the textured structure of the transparent conductive substrate of a narrow bandgap bottom battery. In the conventional dry-wet two-step method, a first inorganic salt layer and an organic salt layer are sequentially deposited on the surface of the hole transport layer. Figure 2 It is known that after the first inorganic salt layer and organic salt layer transform to form the perovskite layer, there is a problem of residual organic salt on the surface. The residual organic salt introduces additional defect states into the perovskite layer, increases the recombination of electron-hole pairs, and thus reduces the photoelectric conversion efficiency of the solar cell; it also forms a harmful intermediate phase, affecting charge transport and extraction; the residue of organic salt also leads to uneven surface morphology of the perovskite layer, increasing the charge transport resistance inside the cell.

[0040] Based on this, after generating the perovskite layer, the present invention treats the residual organic salt on the surface of the perovskite layer by re-evaporating a second inorganic salt layer. The second inorganic salt used has the effect of surface passivation of perovskite, and can combine with defect sites in perovskite material to reduce non-radiative recombination, thereby improving carrier lifetime and overall battery efficiency. The resulting passivation layer can also provide a layer of protection, reduce the sensitivity of the perovskite layer to moisture and oxygen, thereby improving its long-term stability; it can also improve the interface quality between the perovskite layer and the electron transport layer, and reduce charge recombination at the interface.

[0041] In some embodiments, the passivation layer may be a halogenated phenylethylamine, such as phenylethyl ammonium iodide (PEAI).

[0042] In some embodiments, the material of the first inorganic salt layer includes a combination of a first cation and a first anion.

[0043] The first cation includes any one or a combination of at least two of lead (Pb) ions, tin (Sn) ions or cesium (Cs) ions. Typical but non-limiting combinations include combinations of Pb ions and Sn ions, combinations of Sn ions and Cs ions, combinations of Pb ions and Cs ions, or combinations of Pb ions, Sn ions and Cs ions.

[0044] The first anion includes any one or a combination of at least two of chloride (Cl) ions, bromide (Br) ions, or iodide (I) ions. Typical but non-limiting combinations include combinations of Cl ions and Br ions, combinations of Cl ions and I ions, combinations of Br ions and I ions, or combinations of Cl ions, Br ions, and I ions.

[0045] In some embodiments, the material of the first inorganic salt layer includes any one or a combination of at least two of lead iodide (PbI2), lead bromide (PbBr2), lead chloride (PbCl2), cesium iodide (CsI), cesium bromide (CsBr), or cesium chloride (CsCl).

[0046] In some embodiments, the material of the organic salt layer includes a combination of organic cations and anions.

[0047] The organic cation includes any one or a combination of at least two of the following: methyl ether (FA) ions, methylamine (MA) ions, or dimethylamine (DMA) ions. Typical but non-limiting combinations include combinations of FA ions and MA ions, combinations of MA ions and DMA ions, combinations of FA ions and DMA ions, or combinations of FA ions, MA ions, and DMA ions.

[0048] The anion includes any one or a combination of at least two of chloride (Cl) ions, bromide (Br) ions, or iodide (I) ions. Typical but non-limiting combinations include combinations of Cl ions and Br ions, combinations of Cl ions and I ions, combinations of Br ions and I ions, or combinations of Cl ions, Br ions, and I ions.

[0049] In some embodiments, the material of the organic salt layer includes any one or a combination of at least two of methyl iodide (FAI), methyl bromide (FABr), methyl chloride (FACl), methyl iodide (MAI), methyl bromide (MABr), or methyl chloride (MACl).

[0050] In some embodiments, the material of the second inorganic salt layer includes a combination of a second cation and a second anion.

[0051] The second cation includes any one or a combination of at least two of lead (Pb) ions, tin (Sn) ions or cesium (Cs) ions. Typical but non-limiting combinations include combinations of Cl ions and Br ions, combinations of Cl ions and I ions, combinations of Br ions and I ions, or combinations of Cl ions, Br ions and I ions.

[0052] The second anion includes any one or a combination of at least two of chloride (Cl) ions, bromide (Br) ions, or iodide (I) ions. Typical but non-limiting combinations include combinations of Cl ions and Br ions, combinations of Cl ions and I ions, combinations of Br ions and I ions, or combinations of Cl ions, Br ions, and I ions.

[0053] The appropriate thickness of the second inorganic salt layer can not only reduce the influence of residual organic salts, but also avoid the influence of excessive thickness on light absorption. By controlling the appropriate thickness of the second inorganic salt layer, this invention can ensure the photoelectric conversion efficiency of the tandem battery.

[0054] In some embodiments, the thickness of the second inorganic salt layer is 1nm-9nm, for example, it can be 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 8nm or 9nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 1nm-5nm.

[0055] In some embodiments, the annealing temperature is 90°C-120°C and the time is 15 min-25 min.

[0056] The annealing temperature is 90℃-120℃, for example, it can be 90℃, 95℃, 100℃, 105℃, 110℃, 115℃ or 120℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0057] The annealing time is 15-25 minutes, for example, it can be 15 minutes, 18 minutes, 20 minutes, 22 minutes or 25 minutes, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0058] In some embodiments, the hole transport layer is made of nickel oxide (NiO). x, 1.10≤x≤1.21), any one or combination of at least two of self-assembled monolayer (SAM) or poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine) (PTAA), typical but non-limiting combinations include combinations of nickel oxide and SAM, combinations of SAM and PTAA, combinations of nickel oxide and PTAA, or combinations of nickel oxide, SAM and PTAA.

[0059] In some embodiments, the electron transport layer is made of fullerene (C... 60 ), [6,6]-phenyl-C61-butyrate methyl ester (PCBM), TiO2 or ZnO, or any combination of at least two of these, with typical but non-limiting combinations including C 60 Combinations with PCBM, combinations of PCBM and TiO2, combinations of TiO2 and ZnO, C 60 A combination of PCBM, TiO2 and ZnO.

[0060] In some embodiments, the buffer layer is made of molybdenum oxide (MoO). x ,2≤x≤3) and / or tin oxide (SnO2).

[0061] In some embodiments, the conductive layer is made of any one or a combination of at least two of indium tin oxide (ITO), indium zinc oxide (IZO), indium cobalt oxide (ICO), aluminum-doped zinc oxide (AZO), fluorine-doped tin oxide (FTO), or indium tungsten oxide (IWO). Typical but non-limiting combinations include combinations of ITO and IZO, IZO and ICO, ICO and IWO, ITO, IZO, ICO and IWO, ITO, IZO, ICO and IWO, or combinations of ITO, IZO, ICO, AZO, FTO and IWO.

[0062] In some embodiments, the electrode layer is made of any one or a combination of at least two of gold, silver, or copper. Typical but non-limiting combinations include combinations of gold and silver, gold and copper, silver and copper, or gold, silver, and copper.

[0063] In some embodiments, an anti-reflection layer is also provided on the side of the conductive layer away from the buffer layer.

[0064] In some embodiments, the antireflective layer is made of magnesium fluoride (MgF2) and / or lithium fluoride (LiF).

[0065] In some embodiments, the narrow bandgap bottom cell includes any one of silicon cells, narrow bandgap perovskite cells, copper indium gallium selenide cells, or cadmium telluride cells.

[0066] In some embodiments, the hole transport layer is prepared by any one or a combination of at least two of magnetron sputtering, spin coating, thermal evaporation, or atomic deposition.

[0067] In some embodiments, the method for forming the first inorganic salt layer includes vapor deposition.

[0068] In some embodiments, the method of applying the organic salt layer includes any one or a combination of at least two of spin coating, coating, or spraying.

[0069] In some embodiments, the method for forming the second inorganic salt layer includes vapor deposition.

[0070] In some embodiments, the method of setting the electron transport layer, buffer layer, conductive layer, electrode layer, and antireflection layer each independently includes deposition.

[0071] In some embodiments, the operating temperature for depositing the buffer layer is 90°C-110°C, for example, 90°C, 95°C, 100°C, 105°C or 110°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0072] One embodiment of the present invention provides a stacked battery, which is prepared by the preparation method described in any embodiment.

[0073] In some embodiments, the thickness of the narrow bandgap bottom cell in the stacked battery is 130μm-280μm, for example, it can be 130μm, 150μm, 180μm, 200μm, 240μm, 250μm or 280μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0074] Optionally, the narrow bandgap bottom cell is a commercial M6 silicon heterojunction, in which the thickness of the bottom ITO is 80nm-120nm, for example, it can be 80nm, 90nm, 100nm, 110nm or 120nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0075] In some embodiments, the thickness of the electron transport layer in the tandem battery is 15nm-25nm, for example, it can be 15nm, 18nm, 20nm, 22nm, 24nm or 25nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0076] In some embodiments, the thickness of the conductive layer in the tandem battery is 40nm-140nm, for example, it can be 40nm, 50nm, 60nm, 80nm, 100nm, 120nm or 140nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0077] In some embodiments, the thickness of the antireflection layer in the stacked battery is 100nm-200nm, for example, it can be 100nm, 120nm, 150nm, 160nm, 180nm or 200nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0078] Example 1

[0079] This embodiment provides a method such as Figure 3 The stacked battery shown includes a narrow bandgap bottom cell and a wide bandgap top cell.

[0080] The narrow bandgap bottom cell uses a commercial M6 silicon heterojunction with a thickness of 200μm. The N-side and P-side are texturized, and the bottom ITO thickness is 100nm. After the back ITO is prepared, it is vacuum evaporated and metallized. Then it is cut into small silicon wafers of 25mm×25mm as the bottom cell in this embodiment and treated with ultraviolet ozone for 20 minutes for later use.

[0081] The method for preparing the tandem battery in this embodiment includes the following steps:

[0082] (1) Under the condition of DC sputtering power of 100W, an ITO intermediate layer with a thickness of 20nm and a sheet resistance of 400Ω / sq is prepared on the transparent conductive substrate of the bottom cell.

[0083] (2) Then, in an Ar atmosphere, under the condition of RF sputtering power of 400W, a hole transport layer 1 with a thickness of 10nm was prepared by magnetron sputtering on the surface of the ITO intermediate layer; the material of hole transport layer 1 is NiO. x (x is 1.15).

[0084] (3) First, an inorganic salt layer with a thickness of 450 nm is deposited on the surface of hole transport layer 1 by vapor deposition. The rate ratio of PbI2 to PbBr2 during vapor deposition is: (angtzes per second): (Å / s); then an organic salt layer was set by spin coating to obtain perovskite layer 2; wherein, the spin coating rate was 3000 rpm and the time was 30 s, without annealing, and the mass ratio of FAI, FABr, MAI and MACl in each milliliter of solution was 30:30:10:4 when the organic salt layer was set by spin coating.

[0085] (4) Then, a second inorganic salt layer with a thickness of 3 nm is deposited by vapor deposition so that the second inorganic salt layer reacts with the organic salt remaining on the surface of the perovskite layer 2. The passivation layer 3 is obtained by annealing at 100°C for 20 min.

[0086] The second inorganic salt layer is made of CsI. When CsI is used as the second inorganic layer 3, the surface SEM image of the perovskite layer 2 after the reaction of organic and inorganic salts is shown in the figure. Figure 4 As shown.

[0087] (5) An electron transport layer 4 with a thickness of 20 nm was deposited on the surface of the passivation layer 3 by vacuum evaporation at a deposition rate of 0.01 nm / s; the material of the electron transport layer 4 was C. 60 .

[0088] (6) A SnO2 buffer layer 5 is deposited on the surface of electron transport layer 4 by atomic layer deposition. The tin source used is tetramethyldiaminotin (TDMASn). The cycle consists of 0.1s source extraction, 10s purge, 0.08s source extraction and 10s purge, and is repeated 150 times at a working temperature of 100℃.

[0089] (7) An IZO conductive layer 6 with a thickness of 80 nm and a sheet resistance of 200 Ω / sq was prepared on the surface of the buffer layer 5 using DC magnetron sputtering with a sputtering power of 100 W; then, the Ag gate electrode layer 7 was deposited by evaporation according to a pre-designed mask pattern at a deposition rate of [missing information]. (angstroms / second), thickness is 150nm.

[0090] (8) Then, a MgF2 antireflection layer with a thickness of 100 nm is deposited by vapor deposition.

[0091] Example 2

[0092] This embodiment provides a stacked battery, which is the same as that in Embodiment 1 except that the thickness of the second inorganic salt layer is 1 nm.

[0093] Compared with Example 1, the thickness of the second inorganic salt layer in this embodiment is reduced from 3 nm to 1 nm, while still achieving the effect of completely reacting off the residual organic salt without affecting the normal light absorption. Therefore, the tandem battery provided in this embodiment has an open-circuit voltage of 1890 mV and an open circuit voltage of 20.4 mA / cm² under the test conditions. 2 It has a short-circuit current density, a fill factor of 80.4%, and a photoelectric conversion efficiency of 31.00%.

[0094] Example 3

[0095] This embodiment provides a stacked battery, which is the same as that in Embodiment 1 except that the thickness of the second inorganic salt layer is 5 nm.

[0096] Compared to Example 1, the thickness of the second inorganic salt layer in this embodiment is increased from 3 nm to 5 nm. This not only ensures the complete reaction of residual organic salts but also does not affect the normal light absorption. Therefore, the tandem solar cell provided in this embodiment exhibits an open-circuit voltage of 1900 mV and an open-circuit voltage of 20.6 mA / cm² under test conditions. 2 It has a short-circuit current density, a fill factor of 80.9%, and a photoelectric conversion efficiency of 31.66%.

[0097] Example 4

[0098] This embodiment provides a stacked battery, which is the same as that in Embodiment 1 except that the thickness of the second inorganic salt layer is 9 nm.

[0099] Compared to Example 1, the thickness of the second inorganic salt layer in this embodiment is increased from 3 nm to 9 nm, which can completely react away the residual organic salt. This slightly affects the normal light absorption process. Under the test conditions, the tandem solar cell exhibits an open-circuit voltage of 1890 mV and an open-circuit voltage of 20.1 mA / cm². 2 It has a short-circuit current density, a fill factor of 79.8%, and a photoelectric conversion efficiency of 29.83%.

[0100] Example 5

[0101] This embodiment provides a stacked battery, which is the same as that in Embodiment 1 except that the thickness of the second inorganic salt layer is 14 nm.

[0102] Compared to Example 1, the thickness of the second inorganic salt layer in this embodiment is increased from 3 nm to 14 nm. Although this achieves the effect of completely reacting away the residual organic salt, it affects the normal light absorption. Under the test conditions, the tandem solar cell can still have an open-circuit voltage of 1830 mV and an open circuit voltage of 19.5 mA / cm². 2 It has a short-circuit current density, a fill factor of 76.8%, and a photoelectric conversion efficiency of 27.41%.

[0103] Example 6

[0104] This embodiment provides a stacked battery, which is the same as that in Embodiment 1 except that the material of the second inorganic salt layer is PbI2.

[0105] Compared with Example 1, in this embodiment, the material of the second inorganic salt layer is replaced by PbI2 instead of CsI. Under the test conditions, the tandem battery has an open-circuit voltage of 1880mV and an open circuit voltage of 20.6mA / cm². 2The short-circuit current density, fill factor of 81.0%, and photoelectric conversion efficiency of 31.37% are shown. This indicates that when the second cation in the second inorganic salt layer is Pb ion, it can also achieve good technical effects. However, PbI2 will decompose under light conditions, affecting long-term stability. Therefore, the preferred material for the second inorganic salt layer in this invention is CsI.

[0106] Example 7

[0107] This embodiment provides a stacked battery, which is the same as that in Embodiment 1 except that the material of the second inorganic salt layer is CsBr.

[0108] Compared to Example 1, the material of the second inorganic salt layer in this embodiment is changed from CsI to CsBr. Since the perovskite with Br as the anion has lower crystal quality and defect density than that with I as the anion, non-radiative recombination increases. Therefore, the tandem solar cell provided in this embodiment only exhibits an open-circuit voltage of 1870 mV and an open-circuit voltage of 20.4 mA / cm² under the test conditions. 2 It has a short-circuit current density, a fill factor of 80.4%, and a photoelectric conversion efficiency of 30.67%.

[0109] Example 8

[0110] This embodiment provides a stacked battery, which is the same as that in Embodiment 1 except that the material of the second inorganic salt layer is PbBr2.

[0111] Compared to Example 1, in this embodiment, the material of the second inorganic salt layer is replaced by PbBr instead of CsI. Since the crystal quality and defect density of perovskite with Br anions are inferior to those of perovskite with I anions, non-radiative recombination increases. Therefore, the tandem solar cell provided in this embodiment only exhibits an open-circuit voltage of 1850 mV and an open-circuit voltage of 20.5 mA / cm² under the test conditions. 2 It has a short-circuit current density, a fill factor of 80.8%, and a photoelectric conversion efficiency of 30.64%.

[0112] Comparative Example 1

[0113] This comparative example provides a tandem battery, which is identical to Example 1 except that the second inorganic salt layer is not deposited.

[0114] Compared to Example 1, this comparative example did not involve the deposition of a second inorganic salt layer. This failure to eliminate the increased electron-hole recombination caused by residual organic salts on the perovskite layer surface resulted in a decrease in photoelectric conversion efficiency. Under the test conditions, the tandem cell provided in this comparative example exhibited only an open-circuit voltage of 1810 mV and an open-circuit voltage of 19.5 mA / cm². 2 It has a short-circuit current density, a fill factor of 79.1%, and a photoelectric conversion efficiency of 27.92%.

[0115] Comparative Example 2

[0116] This comparative example provides a stacked battery, including a narrow bandgap bottom cell and a wide bandgap top cell.

[0117] The narrow bandgap bottom battery is the same as in Example 1.

[0118] The fabrication method of the tandem battery in this comparative example includes the following steps:

[0119] (1) Under the condition of DC sputtering power of 100W, an ITO intermediate layer with a thickness of 20nm and a sheet resistance of 400Ω / sq is prepared on the transparent conductive substrate of the bottom cell.

[0120] (2) Then, in an Ar atmosphere, under the condition of RF sputtering power of 400W, a hole transport layer with a thickness of 10nm was prepared by magnetron sputtering on the surface of the ITO intermediate layer; the hole transport layer was made of NiO. x (x is 1.15).

[0121] (3) First, an inorganic salt layer with a thickness of 450 nm is deposited on the surface of the hole transport layer by vapor deposition. The rate ratio of PbI2 to PbBr2 during vapor deposition is: (angtzes per second): (Å / s); then an organic salt layer was set by spin coating to obtain a perovskite layer; wherein, the spin coating rate was 3000 rpm and the time was 30 s, without annealing, and the mass ratio of FAI, FABr, MAI and MACl in each milliliter of solution was 30:30:10:4 when the organic salt layer was set by spin coating.

[0122] (4) Then spin-coat IPA (isopropanol) at 3000 rpm for 30 s and then treat at 100°C for 5 min.

[0123] (5) An electron transport layer with a thickness of 20 nm was deposited using vacuum evaporation at a deposition rate of 0.01 nm / s; the material of the electron transport layer was C. 60 .

[0124] (6) An atomic layer deposition method is used to set a SnO2 buffer layer on the surface of the electron transport layer. The tin source used is tetramethyldiaminotin (TDMASn). The cycle consists of 0.1s source extraction, 10s purge, 0.08s source extraction and 10s purge, and is repeated 150 times at a working temperature of 100℃.

[0125] (7) An IZO conductive layer with a thickness of 80 nm and a sheet resistance of 200 Ω / sq was prepared on the surface of the buffer layer using DC magnetron sputtering with a sputtering power of 100 W; then, an Ag gate electrode layer was deposited according to a pre-designed mask pattern at a deposition rate of [missing information]. (angstroms / second), thickness is 150nm.

[0126] (8) Then, a MgF2 antireflection layer with a thickness of 100 nm is set by vapor deposition.

[0127] This comparative example uses isopropanol to remove residual organic salts from the perovskite layer surface, but this method is ineffective in dissolving the organic salts, thus affecting the photoelectric conversion efficiency of the tandem solar cell. Under the test conditions, the tandem solar cell provided in this comparative example only exhibits an open-circuit voltage of 1830mV and an open-circuit voltage of 19.9mA / cm². 2 It has a short-circuit current density, a fill factor of 79.8%, and a photoelectric conversion efficiency of 29.06%.

[0128] Performance Characterization

[0129] The open-circuit voltage (Voc, mV) and short-circuit current density (Jsc, mA / cm²) of the tandem cells obtained in the above embodiments and comparative examples are... 2 The fill factor (FF, %) and photoelectric conversion efficiency (PCE, %) were tested under the following conditions: a solar energy simulation test device was used, with a 500W xenon lamp solar spectrum simulator as the light source, and a solar irradiance (AM 1.5G: 100mW / cm²) was maintained. 2 The tests were conducted under the following conditions: 12 stacked cells were tested in each group, and the average value was calculated. The results are shown in Table 1.

[0130] Table 1

[0131]

[0132]

[0133] As shown in Table 1, the tandem solar cell provided in Example 1 of this invention achieves a photoelectric conversion efficiency of 32.1%, which is significantly better than the 27.92% in Comparative Example 1 and the 29.06% in Comparative Example 2. In Comparative Example 1, no treatment was performed, and the residual organic salts on the surface increased electron-hole recombination, thereby reducing the efficiency of the tandem solar cell and resulting in a decrease in photoelectric conversion efficiency. In Comparative Example 2, isopropanol was used for cleaning, but it could not effectively dissolve the organic salts, thus also affecting the photoelectric conversion efficiency of the tandem solar cell.

[0134] A suitable thickness of the second inorganic salt layer can not only reduce the influence of residual organic salts but also avoid the impact of excessive thickness on light absorption. If the thickness of the second inorganic salt layer is insufficient, the residual organic salts cannot be completely reacted, affecting the photoelectric conversion efficiency of the tandem solar cell. While a thicker second inorganic salt layer can completely react with the residual organic salts, it will significantly affect light absorption and cause an excess of inorganic salts, leading to a decrease in current and fill power. This invention achieves a photoelectric conversion efficiency of over 27.41% when the thickness of the second inorganic salt layer is controlled to be 1nm-14nm. As a preferred embodiment, a photoelectric conversion efficiency of over 29.83% is achieved when the thickness of the second inorganic salt layer is controlled to be 1nm-9nm. As a further preferred embodiment, a photoelectric conversion efficiency of over 31.66% is achieved when the thickness of the second inorganic salt layer is 1nm-5nm.

[0135] The present invention conducts a 1500-hour stability monitoring test on the tandem batteries provided in Example 1, Comparative Example 1, and Comparative Example 2, and the results are as follows: Figure 5 As shown. By Figure 5 It is known that the tandem battery with the second inorganic salt layer deposited on it can still maintain 98% of its initial efficiency after 1500 hours of operation. In contrast, the performance of the untreated or IPA-cleaned tandem battery shows a significant decline after 1500 hours of operation. This indicates that the present invention, through the setting of the second inorganic salt layer, forms a barrier on the surface of the perovskite layer, effectively isolating water and oxygen, reducing the sensitivity of the perovskite, and thus improving its long-term stability. Furthermore, the material of the second inorganic salt layer has good chemical stability and hydrophobicity, is not easily chemically reacted with other substances, and can isolate and repel water molecules, helping to protect the perovskite material from environmental corrosion and improving the long-term operational stability of the tandem battery.

[0136] In summary, this invention, by depositing a second inorganic salt layer after forming a perovskite layer, allows the second inorganic salt near the perovskite layer to completely react with the residual organic salt to form perovskite. Simultaneously, it can bind to defect sites in the perovskite material, reducing non-radiative recombination and thus improving carrier lifetime and overall battery efficiency. The resulting passivation layer also provides protection, reducing the perovskite layer's sensitivity to moisture and oxygen, and improving its long-term stability. Furthermore, the second inorganic salt layer improves the interface quality between the perovskite layer and the electron transport layer, reducing charge recombination at the interface.

[0137] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a stacked battery, wherein the stacked battery comprises a narrow bandgap bottom cell and a wide bandgap top cell, characterized in that, The preparation method includes the following steps: A hole transport layer is fabricated on a transparent conductive substrate of a narrow bandgap bottom battery; A first inorganic salt layer and an organic salt layer are sequentially deposited on the surface of the hole transport layer to obtain a perovskite layer. A second inorganic salt layer is vapor-deposited on the surface of the perovskite layer to react with the residual organic salt on the surface of the perovskite layer, and then annealed to obtain a passivation layer. An electron transport layer, a buffer layer, a conductive layer, and an electrode layer are sequentially fabricated on the passivation layer to obtain a stacked battery.

2. The preparation method according to claim 1, characterized in that, The material of the first inorganic salt layer includes a combination of a first cation and a first anion; The first cation includes any one or a combination of at least two of Pb ions, Sn ions, or Cs ions; The first anion includes any one or a combination of at least two of Cl ions, Br ions, or I ions.

3. The preparation method according to claim 1, characterized in that, The organic salt layer is made of a combination of organic cations and anions; The organic cation includes any one or a combination of at least two of FA ions, MA ions, or DMA ions; The anion includes any one or a combination of at least two of Cl ions, Br ions, or I ions.

4. The preparation method according to claim 1, characterized in that, The material of the second inorganic salt layer includes a combination of a second cation and a second anion; The second cation includes any one or a combination of at least two of Pb ions, Sn ions, or Cs ions; The second anion includes any one or a combination of at least two of Cl ions, Br ions, or I ions.

5. The preparation method according to any one of claims 1-4, characterized in that, The thickness of the second inorganic salt layer is 1nm-9nm.

6. The preparation method according to claim 1, characterized in that, The annealing temperature is 90℃-120℃, and the time is 15min-25min.

7. The preparation method according to claim 1, characterized in that, The hole transport layer is made of NiO. x Any one or at least two of SAM materials or PTAA; And / or, the material of the electron transport layer includes C 60 Any one or at least two of PCBM, TiO2, or ZnO; And / or, the material of the buffer layer includes molybdenum oxide and / or tin oxide; And / or, the material of the conductive layer includes any one or a combination of at least two of ITO, IZO, ICO, AZO, FTO or IWO; And / or, the electrode layer is made of any one or a combination of at least two of gold, silver or copper.

8. The preparation method according to claim 1, characterized in that, An anti-reflection layer is also provided on the side of the conductive layer away from the buffer layer; And / or, the antireflective layer is made of MgF2 and / or LiF.

9. The preparation method according to claim 1, characterized in that, The narrow bandgap bottom cell includes any one of silicon cells, narrow bandgap perovskite cells, copper indium gallium selenide cells, or cadmium telluride cells.

10. A stacked battery, characterized in that, The stacked battery is prepared using the preparation method described in any one of claims 1-9.

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