Preparation and application of low-temperature high-conductivity and work function adjustable carbon paste

Abstract

This invention discloses a method for preparing a low-temperature, high-conductivity, and adjustable-work-function carbon slurry, comprising: (1) grinding appropriate amounts of graphite powder and Ketjen black to make the particles uniform and the mixture homogeneous; (2) drying the homogeneous mixture of graphite powder and Ketjen black to obtain a dry mixture of graphite powder and Ketjen black; and (3) adding appropriate amounts of organic carrier and inorganic binder metal oxide (Mn3O4) to the dried and homogeneous mixture of graphite powder and Ketjen black, and ball milling to obtain the carbon slurry material. This invention, through optimized processes, can prepare a low-temperature carbon slurry with high conductivity, adjustable work function, and strong wear resistance, and the preparation process is simple and reliable. This invention also provides a carbon slurry prepared using the above method that achieves a photoelectric conversion efficiency of 16.24% on carbon-based planar perovskite solar cells, and also exhibits good performance as a working electrode in photodetectors and gas sensors.

Description

Technical Field

[0001] This invention relates to a method for preparing a carbon paste with high conductivity and adjustable work function at medium and low temperatures, specifically a method for doping the carbon paste with a semiconductor metal oxide inorganic binder to improve the energy level matching between the carbon electrode and the functional layer. Background Technology

[0002] In recent years, semiconductor devices such as perovskite solar cells, photodetectors, and gas sensors have developed rapidly. Taking perovskite solar cells as an example, they have achieved a photoelectric conversion efficiency of 25.7%. However, traditional perovskite solar cells often use expensive precious metals such as gold, silver, and copper as the conductive electrode material for the back electrode. The high cost of these precious metals increases the cost of the device, and metal penetration into the perovskite layer is one of the factors contributing to device instability. Furthermore, the fabrication of precious metal electrodes mainly relies on magnetron sputtering, which also significantly increases the manufacturing cost. Compared with traditional solar cells, using carbon as the back electrode has advantages such as simple fabrication process, low cost, and good stability. Therefore, replacing precious metal electrodes with carbon electrodes, which have a simpler fabrication process and lower cost, is a future trend for the commercialization of perovskite solar cells.

[0003] In the current preparation of carbon pastes for low-temperature carbon-based perovskite solar cells, researchers often focus on the conductivity of the carbon electrode after solidification and its interfacial contact with the perovskite layer. However, the energy level matching between the carbon electrode and the perovskite layer is also a key factor limiting the photoelectric conversion efficiency of perovskite solar cells. Therefore, this invention develops a low-temperature, high-conductivity, and work-function-adjustable conductive carbon paste as an electrode material while ensuring the conductivity and interfacial contact of the carbon electrode. By doping with inorganic semiconductor metal oxides with binding function, the conductive carbon paste acquires adjustable work function performance, which can improve the energy level matching of the perovskite / carbon interface, increase the open-circuit voltage and fill factor, and thus improve the operating efficiency of perovskite solar cell devices. Simultaneously, the prepared carbon paste has also achieved good performance in photodetectors and gas sensors. Summary of the Invention

[0004] The purpose of this invention is to provide a simple, convenient and efficient method for improving the energy level matching between a carbon electrode and a perovskite layer. Specifically, it is a method of adding a semiconductor inorganic metal oxide that acts as a binder to a carbon slurry to improve the energy level matching between the carbon electrode and the functional layer.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for preparing a conductive carbon paste is provided, comprising the following steps:

[0006] (1) Mix graphite powder and Ketjen black in a mass ratio of 3:1, grind them, and obtain a uniform mixture of graphite powder and Ketjen black with uniform particles.

[0007] (2) The graphite powder and Kojen black mixture obtained in step (1) is dried in an oven to obtain a dry powder of graphite powder and Kojen black mixture.

[0008] (3) Add the mixture of organic carrier and inorganic binder metal oxide to the dried homogeneous mixture in step (2) at a mass ratio of 1:1-1:5, wherein the total mass ratio of the mixture of organic carrier and inorganic binder metal oxide to the total mass ratio of the mixture obtained in step (2) is 1:4-3:4.

[0009] (4) By ball milling the mixture obtained in (3), a low-temperature, high-conductivity carbon slurry with an adjustable work function can be obtained.

[0010] Preferably, the organic carrier in step (3) is a chlorobenzene solution of ethyl cellulose or a mixed solution of isopropanol, n-butanol and α-terpineol.

[0011] Preferably, the inorganic adhesive metal oxide in step (3) is Mn3O4.

[0012] Preferably, the grinding time in step (1) is in the range of 1-2 hours, and the powder after grinding is flat and smooth after compaction, without obvious particle feel.

[0013] Preferably, the oven temperature in step (2) is in the range of 65-75℃, and the drying time is 30min-1h.

[0014] Preferably, the ball milling time in step (4) is 12-16 hours, and the ball milling speed is preferably controlled within the range of 600-750 r / h.

[0015] According to another aspect of the present invention, a low-temperature, high-conductivity, and work-function-adjustable carbon slurry is provided, which is prepared according to the preparation method described above.

[0016] According to another aspect of the invention, an application of the conductive paste described herein is provided for the fabrication of planar solar cells.

[0017] According to another aspect of the invention, a planar solar cell is provided, wherein the back electrode layer is made of a low-temperature, high-conductivity, and work-function-adjustable carbon paste as described above.

[0018] Overall, the above-described technical solutions conceived by this invention can achieve the following beneficial effects compared with the prior art.

[0019] (1) The conductive carbon paste of the present invention has excellent conductivity and photoelectric conversion efficiency, showing broad application prospects.

[0020] (2) The conductive carbon slurry manufacturing process of the present invention avoids the traditional complicated ultrasonic and rotary evaporation processes, and only adopts ball milling process, which is simple, convenient and easy to operate.

[0021] (3) The conductive carbon paste of the present invention has high conductivity due to the addition of inorganic binders and metal oxides during the preparation process. Its work function can be adjusted within a certain range, which increases the hole transport capability and electron blocking capability of the carbon electrode. Compared with traditional carbon paste, the present invention improves the energy level matching of the perovskite / carbon interface to a certain extent.

[0022] (4) The conductive carbon paste of the present invention uses a mixture of organic carrier and inorganic binder metal oxide as a novel mixed additive during the manufacturing process. Therefore, when the carbon paste is used to prepare the back electrode of planar solar cell, it can be sintered at a low temperature of 65-75℃. Compared with traditional carbon paste materials, the energy consumption of the back electrode prepared by the present invention is greatly reduced. Attached Figure Description

[0023] Figure 1 The graphs show the conductivity test results of the carbon slurry in Examples 1-4.

[0024] Figure 2 The images show the ultraviolet photoelectron spectroscopy (UVP) spectra of the carbon slurry in Examples 1 and 3.

[0025] Figure 3 The JV curves are for batteries assembled in Examples 5-8. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments.

[0027] Example 1

[0028] (1) Weigh Kojen black and graphite by mass ratio of 1:3. After grinding and drying, transfer them to a ball mill and ball mill at 150 rph for 30 min to ensure that Kojen black and graphite are mixed evenly.

[0029] (2) Weigh the carbon material (total mass of Ketjen black and graphite): the mass ratio of ethyl cellulose solution is 2:1, and add it to the ball mill.

[0030] (3) Preferably, the ground carbon slurry is prepared by ball milling at 650 rph for 16 h.

[0031] Example 2

[0032] (1) Weigh Kojen black and graphite by mass ratio of 1:3. After grinding and drying, transfer them to a ball mill and ball mill at 150 rph for 30 min to ensure that Kojen black and graphite are mixed evenly.

[0033] (2) Weigh the carbon material (total mass of Ketjen black and graphite): the mass ratio of ethyl cellulose solution is 2:1, and add it to the ball mill.

[0034] (3) Weigh Mn3O4 to 10% of the mass of the carbon material and add it to a ball mill. Preferably, the ball mill is run at 650 rph for 16 h to prepare the carbon slurry.

[0035] Example 3

[0036] (1) Weigh Kojen black and graphite by mass ratio of 1:3. After grinding and drying, transfer them to a ball mill and ball mill at 150 rph for 30 min to ensure that Kojen black and graphite are mixed evenly.

[0037] (2) Weigh the carbon material (total mass of Ketjen black and graphite): the mass ratio of ethyl cellulose solution is 2:1, and add it to the ball mill.

[0038] (3) Weigh Mn3O4 to 30% of the mass of the carbon material and add it to a ball mill. Preferably, the ball mill is run at 650 rph for 16 h to prepare the carbon slurry.

[0039] Example 4

[0040] (1) Weigh Kojen black and graphite by mass ratio of 1:3. After grinding and drying, transfer them to a ball mill and ball mill at 150 rph for 30 min to ensure that Kojen black and graphite are mixed evenly.

[0041] (2) Weigh the carbon material (total mass of Ketjen black and graphite): the mass ratio of ethyl cellulose solution is 2:1, and add it to the ball mill.

[0042] (3) Weigh Mn3O4 to 50% of the mass of the carbon material and add it to a ball mill. Preferably, the ball mill is run at 650 rph for 16 h to prepare the carbon slurry.

[0043] Figure 1 The figures show the resistance test results of the carbon pastes prepared in Examples 1-4. The carbon pastes were tested using a four-probe resistance meter. As can be seen from the figures, the resistivity gradually increases with the increase of Mn3O4 doping content. When the Mn3O4 content is 50%, the resistance increases sharply.

[0044] Figure 2The image shows the ultraviolet photoelectron spectroscopy (UVP) spectra of the carbon slurries prepared in Examples 1 and 3. As can be seen from the image, the work function has increased by 0.08 eV.

[0045] Example 5:

[0046] Fabrication of planar perovskite solar cells

[0047] (1) Conductive substrate treatment

[0048] Fluorine-doped tin dioxide (FTO) glass with a conductive substrate was ultrasonically cleaned for 30 minutes in sequence with detergent, water, acetone, isopropanol, and ethanol, and then dried for later use.

[0049] (2) Fabrication of electron transport layer

[0050] The SnO2 hydrogel solution was diluted at a ratio of 1:3 and spin-coated onto the FTO washed in (1) at a speed of 5000 rpm. After annealing at 65°C for half an hour, excess water was removed to form a dense SnO2 film.

[0051] (3) Preparation of perovskite layer

[0052] A 1.5 mol / L perovskite precursor solution was spin-coated onto the electron transport layer prepared in (2) at a speed of 4000 rpm, and annealed at 100℃ for 10 min to form a black, mirror-smooth perovskite film.

[0053] The carbon slurry prepared in Example 1 was scraped onto the perovskite layer prepared in (3), and annealed at 100°C for 10 min to obtain a carbon electrode.

[0054] The above steps yield a planar carbon-based perovskite solar cell.

[0055] Example 6:

[0056] Fabrication of planar perovskite solar cells

[0057] (1) Conductive substrate treatment

[0058] Fluorine-doped tin dioxide (FTO) glass with a conductive substrate was ultrasonically cleaned for 30 minutes in sequence with detergent, water, acetone, isopropanol, and ethanol, and then dried for later use.

[0059] (2) Fabrication of electron transport layer

[0060] The SnO2 hydrogel solution was diluted at a ratio of 1:3 and spin-coated onto the FTO washed in (1) at a speed of 5000 rpm. After annealing at 65°C for half an hour, excess water was removed to form a dense SnO2 film.

[0061] (3) Preparation of perovskite layer

[0062] A 1.5 mol / L perovskite precursor solution was spin-coated onto the electron transport layer prepared in (2) at a speed of 4000 rpm, and annealed at 100℃ for 10 min to form a black, mirror-smooth perovskite film.

[0063] The carbon slurry prepared in Example 2 was scraped onto the perovskite layer prepared in (3), and annealed at 100°C for 10 min to obtain a carbon electrode.

[0064] The above steps yield a planar carbon-based perovskite solar cell.

[0065] Example 7:

[0066] Fabrication of planar perovskite solar cells

[0067] (1) Conductive substrate treatment

[0068] Fluorine-doped tin dioxide (FTO) glass with a conductive substrate was ultrasonically cleaned for 30 minutes in sequence with detergent, water, acetone, isopropanol, and ethanol, and then dried for later use.

[0069] (2) Fabrication of electron transport layer

[0070] The SnO2 hydrogel solution was diluted at a ratio of 1:3 and spin-coated onto the FTO washed in (1) at a speed of 5000 rpm. After annealing at 65°C for half an hour, excess water was removed to form a dense SnO2 film.

[0071] (3) Preparation of perovskite layer

[0072] A 1.5 mol / L perovskite precursor solution was spin-coated onto the electron transport layer prepared in (2) at a speed of 4000 rpm, and annealed at 100℃ for 10 min to form a black, mirror-smooth perovskite film.

[0073] The carbon slurry prepared in Example 3 was scraped onto the perovskite layer prepared in (3), and annealed at 100°C for 10 min to obtain a carbon electrode.

[0074] The above steps yield a planar carbon-based perovskite solar cell.

[0075] Example 8:

[0076] Fabrication of planar perovskite solar cells

[0077] (1) Conductive substrate treatment

[0078] Fluorine-doped tin dioxide (FTO) glass with a conductive substrate was ultrasonically cleaned for 30 minutes in sequence with detergent, water, acetone, isopropanol, and ethanol, and then dried for later use.

[0079] (2) Fabrication of electron transport layer

[0080] The SnO2 hydrogel solution was diluted at a ratio of 1:3 and spin-coated onto the FTO washed in (1) at a speed of 5000 rpm. After annealing at 65°C for half an hour, excess water was removed to form a dense SnO2 film.

[0081] (3) Preparation of perovskite layer

[0082] A 1.5 mol / L perovskite precursor solution was spin-coated onto the electron transport layer prepared in (2) at a speed of 4000 rpm, and annealed at 100℃ for 10 min to form a black, mirror-smooth perovskite film.

[0083] The carbon slurry prepared in Example 4 was scraped onto the perovskite layer prepared in (3), and annealed at 100°C for 10 min to obtain a carbon electrode.

[0084] The above steps yield a planar carbon-based perovskite solar cell.

[0085] This conductive carbon paste can be coated onto planar perovskite solar cells as the back electrode, effectively improving the energy level matching between the carbon electrode and the perovskite layer, enabling better carrier extraction and transport, thereby enhancing cell performance. Its performance is shown in the figure below. Figure 3 As shown.

[0086] The assembled batteries were placed under AM1.5 illumination, and their short-circuit current (Jsc), open-circuit voltage (Voc), fill factor (FF), and photoelectric conversion efficiency (η) were tested, as shown in Table 1.

[0087] Table 1

[0088] The prepared carbon slurry has also been successfully used as a working electrode in photodetectors and biosensors.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any modifications, equivalent substitutions, or improvements made by those skilled in the art to the above embodiments without departing from the scope of the present invention and based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a planar perovskite solar cell, characterized in that, Includes the following steps: (a) Conductive substrate treatment, Fluorine-doped tin dioxide (FTO) glass with a conductive substrate is ultrasonically cleaned in sequence with detergent, water, acetone, isopropanol and ethanol for 30 minutes, and then dried for use. (II) Fabrication of the electron transport layer The SnO2 hydrogel solution was diluted at a ratio of 1:3 and spin-coated onto the FTO washed in step (I) at a speed of 5000 rpm. The solution was then annealed at 65°C for half an hour to remove excess water and form a dense SnO2 film. (III) Preparation of the perovskite layer A 1.5 mol / L perovskite precursor solution was spin-coated onto the electron transport layer prepared in step (II) at a speed of 4000 rpm, and annealed at 100℃ for 10 min to form a black, mirror-smooth perovskite film. The carbon slurry was coated onto the perovskite layer prepared in step (III), and annealed at 100°C for 10 minutes to obtain the carbon electrode. The final result is a planar carbon-based perovskite solar cell; The method for preparing the carbon slurry includes: (1) Graphite powder and Ketjen black were ground at a mass ratio of 3:1 to obtain a uniform mixture of graphite powder and Ketjen black with uniform particle size. (2) The mixture obtained in step (1) is dried in an oven to obtain a dry powder mixture of graphite powder and Ketjen black. (3) Add the mixture of organic carrier and inorganic binder metal oxide Mn3O4 in a mass ratio of 1:1-1:5 to the dried homogeneous mixture in step (2), wherein the total mass ratio of the mixture of organic carrier and inorganic binder metal oxide Mn3O4 to the total mass ratio of the mixture in step (1) is 1:4-3:4; (4) The mixture in (3) can be ball-milled to obtain a low-temperature high conductivity work function adjustable carbon slurry.

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