Preparation method of novel perovskite solar cell self-assembly hole transport layer

Abstract

The invention relates to the technical field of perovskite solar cells, and discloses a preparation method of a novel perovskite solar cell self-assembled hole transport layer, which comprises the following steps: injecting a hole transport solution into water for drag coating by adopting a liquid-liquid interface transfer method, then sucking out the solution, and finally preparing the hole transport layer. Different from a traditional mode of spin-coating self-assembly hole transport molecules and cleaning with ethanol, the method selects a liquid-liquid interface transfer method to inject a hole transport solution into water for drag coating, then sucks out the solution, and finally prepares the hole transport layer. According to the method, the arrangement mode of the hole transport molecule solution is changed through the water surface, the coverage rate of hole transport molecules is increased, the method is suitable for preparation of various different hole transport layers, meanwhile, the hole transport layer prepared through liquid-liquid interface transfer has the advantage of being easy to operate, and large-area production of perovskite solar cells is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a method for preparing a novel self-assembled hole transport layer of a perovskite solar cell. Background Art

[0002] In recent years, with the rapid development of social economy, the demand for energy has been growing, but the reserves of traditional non-renewable energy have been sharply reduced, and its use will cause a series of environmental problems. Therefore, it is necessary to find a clean energy to replace traditional energy. Among them, solar energy is the most ideal renewable energy among many clean energy sources. Therefore, the development and utilization of solar energy is of great significance to the sustainable development of human society and solving the problem of energy shortage. Perovskite solar cells have excellent photoelectric properties such as high absorption coefficient, long carrier lifetime, adjustable band gap and high carrier mobility. At the same time, their preparation process is simple and the cost of raw materials is low. They have always been a research hotspot in the field of solar cells. As the key functional layer of perovskite solar cells, the hole transport layer mainly collects and transports holes to achieve effective separation of electrons and holes, and protects the perovskite layer from external water, oxygen and light erosion, which has an important impact on the efficiency and stability of the cell. Among the hole transport materials, self-assembled monolayer materials (SAM) show extremely high conductivity, thickness tolerance and uniformity. These excellent properties significantly improve the light stability and scalability of organic solar cells. The common method of processing SAM solutions is spin coating. However, during the spin coating process, the shear fluid inside the solution will flow, causing turbulent mass transfer, and ultimately leading to molecular stacking dislocation and crystal orientation disorder, which will greatly hinder the effective transport of charges. In addition, the spin coating process has the disadvantage of not being able to prepare on a large scale. Based on this, the further improvement of the photovoltaic performance and stability of perovskite solar cells and their commercial application are limited.

[0003] Therefore, finding a new method for preparing self-assembled hole transport layers, improving the coverage of self-assembled monolayers, and adjusting their crystal orientation to facilitate large-area preparation are of great significance for the performance improvement and industrial development of perovskite solar cells. Summary of the invention

[0004] The purpose of the present invention is to solve the problems of molecular stacking dislocation, crystal orientation disorder and spin coating process in the preparation process of the self-assembled hole transport layer commonly used in the current perovskite solar cell, which is difficult to meet the industrialization needs of the perovskite solar cell. The present invention provides a novel self-assembled hole monolayer and a method for preparing a long-term, efficient and stable perovskite solar cell comprising a hole transport layer prepared by the method.

[0005] Self-assembled monolayer materials have excellent hole extraction capabilities, so organic self-assembled hole monolayers are often used in high-efficiency devices. However, during the spin coating process, the shear fluid inside the solution will flow, causing turbulent mass transfer, which will eventually lead to molecular stacking dislocation and crystal orientation disorder. Therefore, it is urgent to develop a new deposition strategy to completely change the unfavorable fluid dynamics, thereby improving the coverage and crystallinity of the resulting film.

[0006] In order to achieve the above object, one aspect of the present invention provides a novel method for preparing a self-assembled hole transport layer, which uses a liquid-liquid interface transfer method to inject a hole transport solution into water and then apply it, and then suck out the solution to finally prepare a hole transport layer. The method comprises the following steps:

[0007] The ITO conductive glass substrate was placed in an ultrasonic cleaner and cleaned with pH=8 weak alkaline liquid detergent, deionized water, anhydrous ethanol, and acetone for 5 minutes each;

[0008] Weigh a certain amount of [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphonic acid (Me-4PACz) powder, add an appropriate amount of ethanol (CH3CH2OH) solvent to prepare a solution with a concentration of about 0.5-1 mg / mL;

[0009] Place the ITO conductive glass in a polytetrafluoroethylene water tank and add an appropriate amount of deionized water until the water completely covers the ITO conductive glass;

[0010] Slowly inject the Me-4PACz solution into the water surface along one side of the polytetrafluoroethylene water tank wall. The solution quickly spreads on the water surface. Use a thin glass rod to drag the solution until the solution is completely spread on the water surface.

[0011] After standing for 3-5 minutes, remove all the solution and deionized water with a syringe;

[0012] The ITO conductive glass was taken out and cleaned by spin coating with a certain amount of ethanol to obtain a self-assembled hole monolayer.

[0013] Another aspect of the present invention provides a solar cell, the structure of which includes, from bottom to top, a transparent conductive substrate, a self-assembled hole transport layer, a perovskite layer, an electron transport layer, a buffer layer and an electrode layer, and the hole transport layer is prepared using the above-mentioned liquid-liquid interface transfer method.

[0014] Preferably, the perovskite light-absorbing material is ABX3, A = CH3NH3, NH2CHNH2, Cs or a mixture thereof; B = Pb or Sn or a mixture thereof; X = I, Br, Cl, CN, SCN or a mixture thereof.

[0015] Beneficial Effects

[0016] The present invention adopts the self-assembled hole transport layer deposition strategy, uses the water surface to change the arrangement mode of the hole transport molecule solution, improves the coverage rate of the hole transport molecules, and can obtain long-term, efficient and stable perovskite solar cells. At the same time, the hole transport layer prepared by liquid-liquid interface transfer is easy to operate, which is beneficial to the large-scale production of perovskite solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description in conjunction with the accompanying drawings, in which:

[0018] Figure 1 A schematic diagram of a solar cell according to an embodiment of the present invention is shown;

[0019] Figure 2 A schematic diagram of a process for preparing a hole transport layer for a solar cell according to Embodiment 2 of the present invention is shown;

[0020] Figure 3 A schematic diagram of a process for preparing a hole transport layer for a solar cell according to Embodiment 3 of the present invention is shown;

[0021] Figure 4 The current-voltage characteristic curves of the perovskite solar cell No. 1 (target device) and the perovskite solar cell No. 2 (control device) prepared in Examples 2 and 3 of the present invention are shown;

[0022] Figure 5 A maximum output power stability test graph of perovskite solar cell No. 1 (target device) and perovskite solar cell No. 2 (control device) prepared in Examples 2 and 3 of the present invention under a simulated standard solar illumination intensity is shown. DETAILED DESCRIPTION

[0023] The existing perovskite solar cells using self-assembled hole transport layers have high photoelectric conversion efficiency, but the low coverage of the hole transport layer and the difficulty of large-scale production are important factors restricting its commercialization. The present application provides a novel preparation process of perovskite solar cells, which adopts a liquid-liquid interface transfer method, injects a hole transport solution into water and drags it, then sucks out the solution, and finally prepares a hole transport layer.

[0024] The self-assembled hole transport layer deposition strategy used in this application is specifically:

[0025] (1) The ITO conductive glass substrate was placed in an ultrasonic cleaner and cleaned with pH = 8 weak alkaline liquid detergent, deionized water, anhydrous ethanol, and acetone for 5 minutes each;

[0026] (2) Weigh a certain amount of [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphonic acid (Me-4PACz) powder, add an appropriate amount of ethanol (CH3CH2OH) solvent to prepare a solution with a concentration of about 0.5-1 mg / mL;

[0027] (3) Place the ITO conductive glass in a polytetrafluoroethylene water tank and add an appropriate amount of deionized water until the water completely covers the ITO conductive glass;

[0028] (4) Slowly inject the Me-4PACz solution into the water surface along one side of the polytetrafluoroethylene water tank wall. The solution quickly spreads on the water surface. Use a thin glass rod to drag the solution until the solution is completely spread on the water surface.

[0029] (5) After standing for 3-5 minutes, remove all the solution and deionized water with a syringe;

[0030] (6) Take out the ITO conductive glass, and clean it by spin coating with a certain amount of ethanol to obtain a self-assembled hole monolayer.

[0031] The novel self-assembled hole transport layer deposition strategy of the present application can be used to prepare high-quality Me-4PACz films, and used as hole transport layers in perovskite solar cells. Preferably, the thickness of the Me-4PACz hole transport layer is 3 to 100 nm, preferably 10 to 15 nm. Controlling the thickness of the hole transport layer within the range can ensure the effective extraction of charges in the device. Since the hole transport layer prepared by the liquid-liquid interface transfer method has high crystallinity and uniform orientation, the prepared perovskite solar cell has better surface morphology and higher performance parameters. At the same time, because the immersion plating method is used in the preparation process, the preparation process is simpler, the repeatability is higher, and large-area devices can be used. Therefore, by adopting the self-assembled hole transport layer deposition strategy, a long-term, efficient and stable perovskite solar cell can be obtained.

[0032] According to some embodiments of the present application, a Me-4PACz self-assembled hole monolayer can be prepared by a liquid-liquid interface transfer method. This hole transport layer preparation method has a simple process, does not require expensive equipment and complex conditions, is convenient for device assembly, and can also be applied to the preparation of large-area devices, which is conducive to the commercial production of perovskite solar cells.

[0033] Utilizing a self-assembled hole monolayer prepared by a liquid-liquid interface transfer method, the present application provides an implementation scheme of a solar cell, the structure of which comprises, from bottom to top, a transparent conductive substrate, a self-assembled hole transport layer, a perovskite layer, an electron transport layer and an electrode layer, wherein the hole transport layer is prepared using the above-mentioned liquid-liquid interface transfer method.

[0034] Preferably, the perovskite light-absorbing material is ABX3, A = CH3NH3, NH2CHNH2, Cs or a mixture thereof; B = Pb or Sn or a mixture thereof; X = I, Br, Cl, CN, SCN or a mixture thereof.

[0035] Preferably, the transparent conductive substrate is ITO conductive glass or ITO conductive glass.

[0036] Preferably, the hole transport layer is a Me-4PACz layer, and more preferably, the hole transport layer has a thickness of 30 to 50 nm.

[0037] Preferably, the thickness of the perovskite layer is 300-500 nm.

[0038] Preferably, the electron transport layer is a dense C 60 layer, more preferably, the dense C 60 The layer thickness is 40 to 100 nm.

[0039] Preferably, the electrode layer is Au or Ag, and more preferably, the electrode layer has a thickness of 60-100 nm.

[0040] The solar cell containing the hole transport layer prepared by the liquid-liquid interface transfer method can be prepared by the following method:

[0041] preparing a transparent conductive substrate;

[0042] forming a hole transport layer on the transparent conductive substrate;

[0043] forming a perovskite layer on the hole transport layer;

[0044] forming an electron transport layer on the perovskite layer;

[0045] forming a buffer layer on the electron transport layer;

[0046] forming an electrode layer on the buffer layer,

[0047] Wherein, the hole transport layer is a Me-4PACz monolayer prepared by a liquid-liquid interface transfer method, and has a thickness of 30 to 50 nm.

[0048] More specifically, the preparation of the transparent conductive substrate may be a step of cleaning the transparent conductive substrate. For example, the FTO or ITO conductive glass substrate may be cleaned in an ultrasonic cleaner, and more preferably, it may be cleaned in sequence with pH=8-10 weak alkaline liquid detergent, deionized water, anhydrous ethanol, and acetone for 5-20 minutes each. Cleaning the transparent conductive substrate may be performed using other methods that can be used in the art.

[0049] In the step of forming a hole transport layer on the transparent conductive substrate, a liquid-liquid interface transfer method is used to inject the hole transport solution into the water and drag it, then suck out the solution, and finally obtain the hole transport layer. More specifically, for example, the cleaned ITO conductive glass substrate can be placed in a 200mL polytetrafluoroethylene water tank and 20mL of deionized water can be added. 1mg / mL Me-4PACz solution is slowly injected into the water surface along one side of the water tank wall, and then a thin glass rod is taken to drag the solution until the solution is completely spread on the water surface, and then the deionized water and solution are sucked dry with a syringe. Finally, the retained Me-4PACz molecules are spin-coated and cleaned with ethanol to form a dense monolayer with a thickness of 30 to 50nm.

[0050] The perovskite layer, preferably the perovskite material as mentioned above, can be ABX3, wherein A = CH3NH3, NH2CHNH2, Cs or a mixture thereof; B = Pb or Sn or a mixture thereof; X = I, Br, Cl, CN, SCN or a mixture thereof. More specifically, a 1.0-1.5 mol / L perovskite solution is deposited on a substrate by a one-step or two-step spin coating method, and heated at 100-150°C for 0.5-1h to form a 200-1000 nm perovskite active layer;

[0051] The electron transport layer can be formed by vacuum coating. 60 More specifically, by regulating the C 60 The evaporation speed and evaporation time control the thickness of the buffer layer, thereby forming an electron transport layer with a thickness of 10 to 100 nm.

[0052] The buffer layer can be formed by evaporating 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) on the hole transport mixed perovskite layer by vacuum coating. More specifically, the thickness of the buffer layer is controlled by adjusting the evaporation speed and evaporation time of BCP, thereby forming a buffer layer with a thickness of 1 to 10 nm.

[0053] The electrode layer can be formed by evaporating Au or Ag on the hole transport layer by vacuum coating. More specifically, the thickness of the electrode is controlled by adjusting the evaporation speed and evaporation time of Au or Ag, thereby forming an electrode layer with a thickness of 40 to 200 nm.

[0054] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. If no specific technology or conditions are indicated in the embodiments, the technology or conditions described in the literature in this area or the product instructions are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0055] Example 1: Novel self-assembled hole transport layer deposition strategy

[0056] The self-assembled hole transport layer was prepared by liquid-liquid interface transfer method as follows:

[0057] (1) The ITO conductive glass substrate was placed in an ultrasonic cleaner and cleaned with pH = 8 weak alkaline liquid detergent, deionized water, anhydrous ethanol, and acetone for 5 minutes each;

[0058] (2) Weigh a certain amount of [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphonic acid (Me-4PACz) powder and add an appropriate amount of ethanol (CH3CH2OH) solvent to prepare a solution with a concentration of 0.5 mg / mL;

[0059] (3) Place the ITO conductive glass in a polytetrafluoroethylene water tank and add an appropriate amount of deionized water until the water completely covers the ITO conductive glass;

[0060] (4) Slowly inject the Me-4PACz solution into the water surface along one side of the polytetrafluoroethylene water tank wall. The solution quickly spreads on the water surface. Use a thin glass rod to drag the solution until the solution is completely spread on the water surface.

[0061] (5) After standing for 3 minutes, remove all the solution and deionized water with a syringe;

[0062] (6) Take out the ITO conductive glass, and clean it by spin coating with a certain amount of ethanol to obtain a self-assembled hole monolayer.

[0063] Example 2: Preparation of perovskite solar cell No. 1

[0064] According to the following steps, the Figure 1 The perovskite solar cell No. 1 with the hole transport layer preparation process shown in the figure includes a transparent conductive substrate, a self-assembled hole transport layer, a perovskite layer, an electron transport layer and an electrode layer distributed in sequence from bottom to top:

[0065] (1) Cleaning: Place the ITO conductive glass substrate in an ultrasonic cleaner and clean it with pH = 8 weak alkaline liquid detergent, deionized water, anhydrous ethanol, and acetone for 5 minutes each;

[0066] (2) Preparation of hole transport layer: Place the cleaned ITO conductive glass substrate in a 200mL polytetrafluoroethylene water tank and add 20mL of deionized water. Slowly inject 1mg / mL Me-4PACz solution into the water surface along one side of the water tank wall, then use a thin glass rod to drag the solution until the solution is completely spread on the water surface, and then use a syringe to absorb the deionized water and solution. Finally, spin-coat and clean the retained Me-4PACz molecules with ethanol to form a dense monolayer with a thickness of 10nm;

[0067] (3) Preparation of perovskite layer: 50uL of the prepared perovskite solution was dropped onto the hole blocking layer, and the mixture was rotated at 5000rpm / s for 30s. At the 5th second before the end, the anti-solvent chlorobenzene was dropped into the mixture, and the mixture was heated at 100°C for 40 minutes to evaporate the perovskite material solvent and obtain the perovskite active layer.

[0068] (4) Preparation of electron transport layer: The half-cell prepared in steps (1) to (3) above was placed in an evaporator, and a C layer with a thickness of 30 nm was obtained by adjusting the evaporation rate. 60 Electron transport layer;

[0069] (5) Preparation of buffer layer: placing the half-cell prepared in steps (1) to (4) above in an evaporator, and adjusting the evaporation rate to obtain a BCP electrode layer with a thickness of 5 nm;

[0070] (6) Preparation of electrode layer: The half-cell prepared in the above steps (1)-(5) is placed in a vapor deposition machine, and an Au electrode layer with a thickness of 100 nm is obtained by adjusting the evaporation rate, and finally perovskite solar cell No. 1 is prepared.

[0071] Example 3: Preparation of Perovskite Solar Cell No. 2

[0072] According to the following steps, the Figure 2 The structure of the perovskite solar cell No. 2 with the hole transport layer preparation process shown in the figure includes: a transparent conductive substrate, a self-assembled hole transport layer, a perovskite layer, an electron transport layer, a buffer layer and an electrode layer from bottom to top:

[0073] (1) Cleaning: Place the ITO transparent conductive glass substrate in an ultrasonic cleaner and clean it in pH = 10 weak alkaline liquid detergent, deionized water, anhydrous ethanol, and acetone for 10 min each;

[0074] (2) Preparation of hole transport layer: The cleaned ITO conductive glass substrate was heated at 500°C, and the prepared 1 mg / mL Me-4PACz ethanol solution was spin-coated on the substrate, and heated on a heating table at 100°C for 10 min to obtain an 80 nm hole transport layer;

[0075] (3) Preparation of perovskite active layer: 100 μL of perovskite solution was spin-coated on the dense CuCrO2-Cl hole transport layer and heated on a heating table at 100 °C for 60 min to obtain a 500 nm perovskite active layer;

[0076] (4) Preparation of electron transport layer: The half-cell prepared in steps (1) to (3) above was placed in an evaporator, and a C layer with a thickness of 30 nm was obtained by adjusting the evaporation rate. 60 Electron transport layer;

[0077] (5) Preparation of buffer layer: placing the half-cell prepared in steps (1) to (4) above in an evaporator, and adjusting the evaporation rate to obtain a BCP electrode layer with a thickness of 5 nm;

[0078] (6) Preparation of electrode layer: The half-cell prepared in the above steps (1)-(5) is placed in a vapor deposition machine, and an Ag electrode layer with a thickness of 100 nm is obtained by adjusting the evaporation rate to obtain perovskite solar cell No. 2.

[0079] Perovskite solar cell No. 1 was placed under a standard solar simulator for testing, as shown in Table 1 and Figure 2 As shown, the inverted perovskite solar cell containing a hole transport layer prepared by the liquid-liquid interface transfer method has more excellent photoelectric performance. The cell device perovskite solar cell No. 2 in Example 3, which does not use the liquid-liquid interface transfer method to prepare the hole transport layer, has an open circuit voltage of 1.08V and a short circuit current of 24.49mA / cm 2 , the filling factor is 78.16%, the photoelectric conversion efficiency is 20.67%, and the perovskite solar cell No. 1 of the battery device in Example 2 using the liquid-liquid interface transfer method to prepare the hole transport layer has an open circuit voltage of 1.16V and a short circuit current of 26.18mA / cm 2 , the filling factor is 88.09%, and the photoelectric conversion efficiency is 24.32%. The test results show that the use of liquid-liquid interface transfer method to prepare the self-assembled hole transport layer improves the open circuit voltage and photoelectric conversion efficiency of the perovskite solar cell device. Since the liquid-liquid interface transfer method is a self-assembly process in a balanced state, such continuous growth ensures that the obtained film has high crystallinity and uniform orientation, thereby improving the coverage and crystallinity of the film, and thus can improve the photovoltaic performance of the device.

[0080] Table 1 (Perovskite solar cell performance parameters)

[0081] Devices Open circuit voltage(V) <![CDATA[Short-circuit current density (mA / cm 2 )]]> Fill factor (%) Photoelectric conversion efficiency (%) Comparison Device 1.08 24.49 78.16 20.67 Target Device 1.16 26.18 80.09 24.32

[0082] In addition, according to Figure 4 The stability test results show that the efficiency of the inverted perovskite solar cell device that did not use the liquid-liquid interface transfer method to prepare the hole transport layer began to decrease after 200 hours of operation, while the efficiency of the device perovskite solar cell No. 2 that used the liquid-liquid interface transfer method to prepare the hole transport layer remained above 90% after 1000 hours of illumination at one sun intensity, where the test conditions were to encapsulate the device and in a nitrogen atmosphere. The above data results show that due to higher coverage and better crystallinity, the hole transport layer prepared by the liquid-liquid interface transfer method has fewer defect sites, and a long-term stable perovskite solar cell is obtained. Therefore, the method of preparing the hole transport layer by the liquid-liquid interface transfer method can obtain efficient and stable perovskite solar cells, which provides new ideas for subsequent research and its commercial development.

[0083] The above description is a detailed description of the preferred feasible embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modified changes completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A novel method for preparing a self-assembled hole transport layer, characterized in that: The method uses a liquid-liquid interface transfer method to inject a hole transport solution into water and then apply it, and then suck out the solution to finally prepare a hole transport layer. The method specifically includes the following steps: Weigh a certain amount of [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphonic acid (Me-4PACz) powder, add an appropriate amount of ethanol (CH3CH2OH) solvent to prepare a solution with a concentration of about 0.5-5 mg / mL; Place the ITO conductive glass in a polytetrafluoroethylene water tank and add an appropriate amount of deionized water until the water completely covers the ITO conductive glass; The Me-4PACz solution was slowly injected into the water surface along one side of the polytetrafluoroethylene water tank wall. The solution quickly spread on the water surface. A thin glass rod was used to drag the solution until the solution was completely spread on the water surface. After standing for 1-15 minutes, remove all the solution and deionized water with a syringe; The ITO conductive glass was taken out and cleaned by spin coating with a certain amount of ethanol to obtain a self-assembled hole monolayer.

2. A solar cell, characterized in that: The structure of the solar cell includes, from bottom to top, a transparent conductive substrate, a self-assembled hole transport layer, a perovskite layer, an electron transport layer, a buffer layer and an electrode layer. The hole transport layer is prepared using the hole transport layer preparation method as described in claim 1.

3. The solar cell according to claim 2, characterized in that: The perovskite light-absorbing material is ABX3, A=CH3NH3, NH2CHNH2, Cs or a mixture thereof; B=Pb or Sn or a mixture thereof; X=I, Br, Cl, CN, SCN or a mixture thereof.

4. A method for preparing a solar cell according to claim 3, characterized in that: The method comprises the following steps: preparing and processing transparent conductive glass substrates; forming a hole transport layer on the transparent conductive substrate; forming a perovskite layer on the hole transport layer; forming an electron transport layer on the perovskite layer; forming a buffer layer on the electron transport layer; forming an electrode layer on the buffer layer; The hole transport layer is prepared by liquid-liquid interface transfer method, in which a hole transport solution is injected into water and then coated, and then the solution is sucked out to finally prepare the hole transport layer.

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