Method for preparing perovskite solar cell hole transport layer through direct current sputtering of metal nickel target

Abstract

The invention discloses a method for preparing a hole transport layer of a perovskite solar cell by direct-current sputtering of a metallic nickel target, which comprises the following steps of: performing direct-current sputtering twice by using the metallic nickel target in atmospheres with different oxygen contents to form a bottom-layer nickel oxide film and a top-layer nickel oxide film; and carrying out annealing treatment, supercritical fluid treatment and alkali metal halide salt surface passivation to prepare the nickel oxide hole transport layer for the perovskite solar cell. According to the method, the large-area hole transport layer can be prepared, and the photoelectric conversion efficiency of the perovskite solar cell can be improved.

Description

Technical Field

[0001] The invention relates to the field of thin-film perovskite solar cell materials and devices, and in particular to a method for preparing a hole transport layer of a perovskite solar cell by using a direct current sputtering metal nickel target. Background Art

[0002] The concept of "dual carbon" has been highly valued by the country in recent years as an important strategic goal of low-carbon environmental protection and sustainable development. In the current ecological context of increasing climate warming, researchers are committed to finding a renewable energy source to replace fossil fuels, including solar energy, wind energy, nuclear energy, etc. Among them, solar energy, as a new energy source with huge reserves, easy access and convenient use, is considered to be the main direction of future new energy development. Solar cells, as a medium that can effectively convert solar energy in nature into daily electricity, play an indispensable role in this type of energy revolution.

[0003] As a new type of solar cell, perovskite solar cells have very promising application prospects due to their high photoelectric conversion efficiency and low preparation cost. The functional layers of perovskite solar cell devices mainly include transparent conductive glass layer, electron transport layer, perovskite light absorption layer, hole transport layer and back electrode. At present, the photoelectric conversion efficiency of single-cell laboratory small-area perovskite solar cells has rapidly broken through to more than 26%, close to commercial crystalline silicon solar cells. The mainstream preparation method of high-efficiency devices is solution spin coating, which greatly limits the commercial development of such photovoltaic devices.

[0004] As an important functional layer for hole extraction and transport, the hole transport layer has a great influence on the performance of photovoltaic devices. The commonly used Spiro-OMeTAD hole transport material is mainly used in formal perovskite devices, but its stability is poor and it is easy to absorb moisture. Trans perovskite devices have attracted much attention in recent years due to their low hysteresis and high stability. However, commonly used hole transport materials with trans structures, such as nickel oxide nanocrystals, self-assembled monolayers (SAMs), polytriarylamines (PTAA), etc., all require solution spin coating to be uniformly prepared, which is not suitable for the preparation of large-area photovoltaic devices. Summary of the invention

[0005] Based on the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a method for preparing a hole transport layer of a perovskite solar cell by DC sputtering of a metal nickel target, which can obtain a uniform and dense thin film as a nickel oxide hole transport layer through physical vapor deposition, and is suitable for the preparation of large-scale hole transport layers and photovoltaic devices.

[0006] In order to achieve the purpose, the present invention adopts the following preparation method:

[0007] In one aspect of the present invention, the present invention provides a method for preparing a nickel oxide hole transport layer by DC sputtering a metal nickel target, comprising the following steps:

[0008] (1) A metal nickel target is used for direct current sputtering in a first atmosphere to form an underlying nickel oxide film, wherein the first atmosphere contains oxygen and argon, wherein the volume ratio of oxygen to argon is 1-20:0-1.

[0009] (2) Direct current sputtering is performed using a metal nickel target in a second atmosphere to form a top nickel oxide film, wherein the second atmosphere contains oxygen and argon, wherein the volume ratio of oxygen to argon is 1:2-4.

[0010] (3) Annealing the prepared double-layer nickel oxide film.

[0011] (4) Using a supercritical fluid device to perform supercritical fluid treatment on the double-layer nickel oxide film after annealing.

[0012] (5) Using alkali metal halide salt to passivate the surface of the double-layer nickel oxide film after supercritical fluid treatment, that is, obtaining a nickel oxide hole transport layer for perovskite solar cells.

[0013] Preferably, in step (1) and step (2), the sputtering is magnetron sputtering, the purity of the metal nickel target used is not less than 95% (by weight), the sputtering power is 20W-120W, and the gas pressure is 0.1Pa-10Pa. The thickness of the bottom nickel oxide film and / or the top nickel oxide film is 5-30nm.

[0014] Preferably, in step (3), the annealing treatment is carried out in an air environment, the annealing temperature is 200-500° C., and the annealing time is 1-60 min.

[0015] Preferably, in step (4), the supercritical fluid used is one of O2, CO2, H2O or any mixture thereof, and the pressure of the supercritical fluid is 5-8 MPa and the temperature is -120-120°C.

[0016] Preferably, in step (5): the alkali metal halide is AX, wherein A includes one or more of Li, Na, K, Rb, and Cs, and X includes one or more of F, Cl, Br, and I; and the passivation treatment is to dissolve the alkali metal halide in any one of isopropanol, ethanol, and water to prepare an alkali metal halide solution with a concentration of 1-6 mg / mL, and then spin-coat the solution on the surface of the double-layer nickel oxide film and anneal.

[0017] In another aspect of the present invention, a perovskite solar cell is provided, which comprises the nickel oxide hole transport layer prepared according to the above method.

[0018] Furthermore, the perovskite solar cell includes a transparent substrate; a transparent conductive layer is formed on the transparent substrate; a nickel oxide hole transport layer is formed on the transparent conductive layer; a perovskite layer is formed on the nickel oxide hole transport layer; an electron transport layer is formed on the perovskite layer; and a back electrode is formed on the electron transport layer.

[0019] Preferably, the transparent conductive layer is selected from one or more of indium tin oxide (ITO), fluorine-doped tin dioxide (FTO) and indium-doped zinc oxide (AZO).

[0020] Preferably, the component of the perovskite layer is MA x FA 1-x PbI3. MAI, FAI, and PbI2 were dissolved in a mixed solvent of DMF:DMSO (0-5):(0-5) in a mass ratio of (0-250):(0-200):(500-800), and stirred at 65°C±5°C for 10-12h to obtain a perovskite precursor solution. The perovskite precursor solution was then spin-coated on the nickel oxide hole transport layer at a spin-coating speed of 3000-4000 rpm for 30-40 seconds. Ethyl acetate was used as an anti-solvent during the spin-coating process, and the layer was finally placed on a heating table at 120±5°C and dried for 15±2min to obtain MA. x FA 1-x PbI3 perovskite layer.

[0021] Preferably, the electron transport layer is selected from one or more of [6,6]-phenyl-C61-butylene isomethyl ester (PCBM), C60, and BCP (2,9-dimethyl-4,7-biphenyl-1,10-phenanthroline). More preferably, at 3×10 -4 Pa, vacuum evaporated C60 with a thickness of 30-80 nm at a deposition rate of 0.5-1 A° / s as an electron transport layer, and then continued to evaporate BCP with a thickness of 1-10 nm at a deposition rate of 0.5-1 A° / s as a secondary electron layer.

[0022] Preferably, the back electrode is selected from one or more of ITO, AZO, IWO, Au, Ag, Cu, Al, Ni, Cr, and Pt; further preferably, 80-120 nm thick Ag is evaporated at a deposition rate of 1 to 2 A° / s as the back electrode.

[0023] Preferably, the transparent substrate is glass.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1) Existing high-performance NiO XHole transport layers are mostly prepared based on solution spin coating, which cannot achieve uniform large-area thin film deposition, limiting the commercial development of perovskite solar cells. However, the present invention uses a direct current sputtering nickel target to deposit NiO X The hole transport layer can shield the influence of water and oxygen in the environment on the film while ensuring uniform deposition of the film over a large area.

[0026] 2) Most common magnetron sputtering nickel oxide films use ceramic nickel oxide targets as sputtering sources and adopt radio frequency sputtering to deposit films, which greatly increases the preparation cost of the film and has low deposition efficiency. The present invention adopts direct current sputtering metal nickel targets, which can effectively increase the sputtering rate and reduce the device preparation cost.

[0027] 3) The method of the present invention can be used to easily prepare a hole transport layer with high repeatability and good quality, greatly reduce the surface defects of the nickel oxide film, and significantly improve the photoelectric performance of the nickel oxide film, thereby obtaining a high-performance perovskite solar cell device. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic structural diagram of a perovskite cell based on direct current sputtering nickel oxide as a hole transport layer in Example 1 of the present invention;

[0029] Figure 2 The supercritical fluid treatment of NiO in Examples 1, 2 and 4 of the present invention X Schematic diagram of the film device;

[0030] Figure 3 This is a dark current test diagram of the perovskite solar cell prepared in Examples 1 and 3 of the present invention;

[0031] Figure 4 It is a JV curve diagram of the perovskite solar cell prepared in Examples 1-4 of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] This embodiment provides a NiO prepared by direct current sputtering of a metal nickel target. X The method of hole transport layer and constructing perovskite solar cell based on the hole transport layer comprises the following steps:

[0035] (1) In order to prevent the test fixture from piercing the film and causing a short circuit in the battery, part of the surface of the FTO conductive substrate is etched. The specific method is as follows:

[0036] Take a set of FTO conductive glass sheets with a size of 1.5×2cm, first spread zinc powder on the surface of the 5×15mm area on one side, then add 2M HCl solution, use the reaction between HCl and zinc powder to remove the FTO layer, expose the glass substrate, and seal the non-etched area with 3M waterproof glue during the etching process. After etching, remove the tape, and ultrasonically clean it with deionized water, acetone, and ethanol for 20 minutes in turn. After cleaning, blow dry with N2, and dry it on a 120℃ heating table for 10 minutes to obtain a clean and dust-free FTO substrate.

[0037] (2) Deposition of dense NiO on the surface of FTO substrate x Hole transport layer, the specific method is:

[0038] The clean FTO substrate obtained in step (1) was placed in an ozone cleaning machine for 15 minutes, and the cleaned FTO substrate was placed in a magnetron sputtering device for the bottom NiO x Deposition of thin film. A DC sputtering power supply with a power of 20W, a chamber pressure of 0.3Pa, an oxygen flow rate of 20sccm (standard cubic centimeters per minute), and an argon flow rate of 0sccm were used in the sputtering, so the volume ratio of oxygen to argon was 20:0. The coating time was 3min, and the film thickness was 15nm.

[0039] Continue to carry out the top layer NiO without breaking the vacuum x Deposition of thin film. A DC sputtering power supply with a power of 20W, a chamber pressure of 0.3Pa, an oxygen flow rate of 10sccm (standard cubic centimeters per minute), and an argon flow rate of 20sccm were used in the sputtering, so the volume ratio of oxygen to argon was 1:2. The coating time was 1min, and the film thickness was 5nm. After the sputtering was completed, the substrate was taken out of the magnetron sputtering device and annealed in air at 300℃ for 30min.

[0040] (3) The annealed substrate was placed in a supercritical fluid device, CO2 was introduced into the device at a flow rate of 20 sccm, the device pressure was set to 7.5 MPa, the temperature was set to 35°C, and the film was treated for 10 minutes.

[0041] (4) Weigh 2 mg of RbF powder and dissolve it in 1 mL of anhydrous ethanol. The passivation solution obtained is stirred at a speed of 4000 rpm for 1 h at room temperature. x The surface was spin coated for 30 s and then annealed on a heating stage at 100 °C for 5 min.

[0042] (5) In the above NiO xPreparation of MA on the surface of hole transport layer 0.85 FA 0.15 PbI3 thin film as light absorption layer:

[0043] 182.3 mg of MAI (methylamine iodide), 34.8 mg of FAI (formamidine iodide) and 622.3 mg of PbI2 (lead iodide) were added to 1 mL of a mixed solution of DMF and DMSO in a volume ratio of 4:1 to prepare 1.35 mol / L MA 0.85 FA 0.15 The PbI3 precursor solution was stirred at 70 °C for 2 h until completely dissolved, and filtered with a 0.22 μm PTFE filter to obtain a clear and transparent orange-yellow solution as MA 0.85 FA 0.15 PbI3 perovskite precursor solution. Take 2 drops of the obtained precursor solution and add them to the substrate obtained in step (4). Adjust the parameters of the coating machine to 1000 rpm for 10 seconds and 4000 rpm for 30 seconds. Use ethyl acetate as the anti-solvent during the spin coating process. After spin coating, remove the substrate and anneal it on a heating table at 120°C for 15 minutes to obtain MA. 0.85 FA 0.15 PbI3 light absorbing layer.

[0044] (6) Preparation of C60 electron transport layer and BCP secondary electron transport layer:

[0045] After the perovskite light absorption layer was formed, the sample was placed in a vacuum coating machine, and C60 and BCP powders were placed in an alumina crucible at 3×10 -4 Under a pressure of 1.5 Pa, C60 and BCP were sequentially evaporated at a speed of 0.5 A° / s to obtain an electron transport layer.

[0046] (7) Electrode preparation:

[0047] After the electron transport layer is formed, the sample is placed in a vacuum coating machine, and pure Ag particles are deposited in a tungsten boat at 3×10 -4 Under a pressure of 1.3 Pa, the Ag back electrode is evaporated at a rate of 1A° / s to complete the preparation of the perovskite solar cell.

[0048] Example 2

[0049] Same as Example 1, except that NiO is not used twice in step (2). xThe film was sequentially sputtered and deposited, and only one sputtering deposition was used. A DC sputtering power supply was used during sputtering, with a power of 20W, a chamber pressure of 0.3Pa, an oxygen flow rate of 20sccm (standard cubic centimeters per minute), and an argon flow rate of 0sccm, so the volume ratio of oxygen to argon was 20:0. The coating time was 5min, and the film thickness was 20nm. After the sputtering was completed, the substrate was taken out of the magnetron sputtering device and annealed in air at 300℃ for 30min.

[0050] Example 3

[0051] Same as Example 1, except that step (3) is removed.

[0052] Example 4

[0053] Same as Example 1, except that step (4) is removed.

[0054] The schematic diagram of the structure of the perovskite solar cell based on the DC sputtering metal nickel hole transport layer prepared in Example 1 is as follows Figure 1 As shown, this type of perovskite solar cell consists of FTO, bottom NiO, and x , top layer NiO x 、MA x FA 1-x PbI3, C60, BCP and Ag.

[0055] Figure 2 For the supercritical fluid treatment of NiO in Examples 1, 2, and 4 x Schematic diagram of the film surface. NiO after magnetron sputtering x The film substrate is placed in a sealed container resistant to high temperature and pressure, one or more gases of H2O / CO2 / O2 are continuously injected into the sealed container, and the sealed container is heated to make these gases become supercritical fluids, and the film is subjected to supercritical fluid treatment.

[0056] Figure 3 The dark current test was performed on the perovskite solar cells prepared in Examples 1 and 4. The perovskite device passivated by RbF surface in Example 1 showed a lower circuit density, proving that RbF can effectively reduce NiO x The defect density on the film surface improves the photoelectric conversion performance of the device.

[0057] Figure 4 The JV curves of the solar cell devices prepared in different embodiments under standard test conditions (AM1.5G illumination) are as follows: energy conversion efficiency 19.29%, open circuit voltage 1.06V, short circuit current 22.71mA / cm 2, the filling factor is 80.10%. The performance parameters of the perovskite battery device prepared in Example 2 are as follows: energy conversion efficiency is 16.10%, open circuit voltage is 1.00V, short circuit current is 22.51mA / cm 2 , the filling factor is 71.40%. The performance parameters of the perovskite battery device prepared in Example 3 are as follows: energy conversion efficiency is 18.35%, open circuit voltage is 1.06V, short circuit current is 22.53mA / cm 2 , the filling factor is 76.61%. The performance parameters of the perovskite battery device prepared in Example 4 are as follows: energy conversion efficiency 17.53%, open circuit voltage 1.05V, short circuit current 21.32mA / cm 2 , the filling factor is 77.93%. From the above data, it can be seen that based on the double-layer NiO x The perovskite solar cell constructed with a hole transport layer has reduced adverse interface reactions, which increases the open circuit voltage. x After the hole transport layer, the residual metal Ni in the film is fully oxidized to NiOx, which improves the PCE of the device. x After the hole transport layer, the carrier extraction capability of the device is enhanced and the defect density is reduced, which improves the short-circuit current.

[0058] The above is only an exemplary embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. The structures, devices and operating methods not specifically described and explained in the present invention shall be implemented according to the conventional means in the art unless otherwise specified and limited.

Claims

1. A method for preparing a hole transport layer for a perovskite solar cell by DC sputtering a metal nickel target, characterized in that: The steps include: (1) forming an underlying nickel oxide film by direct current sputtering using a metal nickel target in a first atmosphere, wherein the first atmosphere comprises oxygen and argon, wherein the volume ratio of oxygen to argon is 1-20:0-1; (2) forming a top nickel oxide film by direct current sputtering using a metal nickel target in a second atmosphere, wherein the second atmosphere comprises oxygen and argon, wherein the volume ratio of oxygen to argon is 1:2-4; (3) annealing the prepared double-layer nickel oxide film; (4) subjecting the annealed double-layer nickel oxide film to supercritical fluid treatment; (5) Using alkali metal halide salt to passivate the surface of the double-layer nickel oxide film after supercritical fluid treatment, that is, obtaining a nickel oxide hole transport layer for perovskite solar cells.

2. The method according to claim 1, characterized in that The sputtering described in step (1) and step (2) is magnetron sputtering, the purity of the metal nickel target used is not less than 95%, the sputtering power is 20W-120W, and the gas pressure is 0.1Pa-10Pa.

3. The method according to claim 1 or 2, characterized in that: The thickness of the bottom nickel oxide film and / or the top nickel oxide film is 5-30 nm.

4. The method according to claim 1 or 2, characterized in that: In step (3), the annealing treatment is carried out in an air environment, the annealing temperature is 200-500° C., and the annealing time is 1-60 min.

5. The method according to claim 1 or 2, characterized in that: In step (4), the supercritical fluid used is one of O2, CO2, H2O or any mixture thereof, and the pressure of the supercritical fluid is 5-8MPa and the temperature is -120-120°C.

6. The method according to claim 1 or 2, characterized in that: In step (5), the alkali metal halide is AX, wherein A includes one or more of Li, Na, K, Rb, and Cs, and X includes one or more of F, Cl, Br, and I; the passivation treatment is to dissolve the alkali metal halide in any one of isopropanol, ethanol, and water to prepare an alkali metal halide solution with a concentration of 1-6 mg / mL, and then spin-coat the solution on the surface of the double-layer nickel oxide film and anneal.

7. A nickel oxide hole transport layer prepared by the method according to any one of claims 1 to 6.

8. A perovskite solar cell, characterized in that: Comprising the nickel oxide hole transport layer as claimed in claim 7.

9. The perovskite solar cell according to claim 8, characterized in that: It includes a transparent substrate; a transparent conductive layer is formed on the transparent substrate; a nickel oxide hole transport layer is formed on the transparent conductive layer; a perovskite layer is formed on the nickel oxide hole transport layer; an electron transport layer is formed on the perovskite layer; and a back electrode is formed on the electron transport layer.

10. The perovskite solar cell according to claim 9, characterized in that: The transparent conductive layer is selected from one or more of indium tin oxide, fluorine-doped tin dioxide and indium-doped zinc oxide; the component of the perovskite layer is MA x FA 1- x PbI3; the electron transport layer is selected from one or more of [6,6]-phenyl-C61-butylene isomethyl ester, C60, 2,9-dimethyl-4,7-biphenyl-1,10-phenanthroline; the back electrode is selected from one or more of ITO, AZO, IWO, Au, Ag, Cu, Al, Ni, Cr, Pt; the transparent substrate is glass.

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