A carbon quantum dots modified solar cell

Abstract

The application relates to the field of solar cells, and particularly provides a carbon quantum dot modified solar cell, which comprises, from top to bottom, a metal electrode, a hole transport layer, a perovskite layer, an electron transport layer and a transparent electrode. A carbon quantum dot modification layer is arranged between the hole transport layer and the perovskite layer, and the metal electrode, the hole transport layer, the carbon quantum dot modification layer, the perovskite layer, the electron transport layer and the transparent electrode are fixedly connected between adjacent components. The carbon quantum dot modification layer is arranged, and carbon quantum dot particles fill the gaps between the perovskite layer crystal grains. On the one hand, the carbon quantum dot modification layer enables the carrier to migrate between the crystal grains, a larger carrier migration path is constructed, and the photoelectric conversion efficiency is improved; on the other hand, the perovskite and the carbon quantum dot particles form a heterostructure, the carrier is more easily transferred from the perovskite to the hole transport layer, the recombination of photo-generated electrons and photo-generated holes in the perovskite is reduced, and the photoelectric conversion efficiency is improved.

Description

Technical Field

[0001] This application relates to the field of solar cells, and more specifically, to a carbon quantum dot-modified solar cell. Background Technology

[0002] Solar cells convert solar energy into electrical energy to power electrical appliances. Traditional solar cells utilize the photovoltaic effect of silicon, but they are expensive and have a low conversion efficiency.

[0003] Existing solar cells utilize the photovoltaic effect of perovskite, which possesses advantages such as high carrier mobility, high absorption coefficient, and low cost. Examples include: an invention patent titled "A Method for Improving the Efficiency and Stability of Perovskite Solar Cells and a Perovskite Solar Cell," authorized publication number "CN 109545970 B"; an invention patent titled "Perovskite Thin Film, Perovskite Solar Cell and its Preparation Method," authorized publication number "CN108922972B"; and a utility model patent titled "Perovskite Solar Cell Structure," authorized publication number "CN 206098167 U," etc. However, due to its soft lattice characteristics, perovskite grows outward from the crystal nucleus, resulting in fractures at grain boundaries and irregular gaps between grains, leading to numerous defects and reduced photoelectric conversion efficiency.

[0004] In summary, due to the soft lattice characteristics of perovskite, existing solar cells have many defects at the perovskite grain boundaries, resulting in low photoelectric conversion efficiency. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by providing a carbon quantum dot-modified solar cell to solve the problem of low photoelectric conversion efficiency in existing solar cells.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This application provides a carbon quantum dot-modified solar cell, which comprises, from top to bottom, a metal electrode, a hole transport layer, a perovskite layer, an electron transport layer, and a transparent electrode. A carbon quantum dot modification layer is disposed between the hole transport layer and the perovskite layer. Adjacent components, including the metal electrode, hole transport layer, carbon quantum dot modification layer, perovskite layer, electron transport layer, and transparent electrode, are fixedly connected. The carbon quantum dot modification layer increases carrier migration paths and promotes carrier migration, thereby improving the photoelectric conversion efficiency of the solar cell.

[0008] Furthermore, the side of the carbon quantum dot-modified layer away from the perovskite layer is planar, while the side of the carbon quantum dot-modified layer closer to the perovskite layer intersects with the perovskite layer. The carbon quantum dot particles penetrate deep into the gaps between perovskite grains, enabling carrier migration between adjacent perovskite grains and improving the photoelectric conversion efficiency of the solar cell.

[0009] Furthermore, the carbon quantum dot modification layer is formed by carbon quantum dot particles with a diameter of less than 3 nm. This allows them to easily enter the interstices of the perovskite grains, increasing the contact area with the perovskite and providing more carrier migration paths, thereby improving the photoelectric conversion efficiency of the solar cell.

[0010] Furthermore, carbon quantum dot particles fill the gaps between grains in the perovskite layer.

[0011] Furthermore, the perovskite layer is made of all-inorganic perovskite, and its thickness is 300nm-700nm.

[0012] Furthermore, the perovskite layer is made of CsPbX. a Y 3-a (X = I, Y = Br, a ≤ 3); preferably, the material of the perovskite layer is CsPbIBr2.

[0013] Furthermore, the hole transport layer is made of PEDOT:PSS or Spiro-MeOTAD (2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene).

[0014] Furthermore, the electron transport layer is made of TiO2 or SnO2, and its thickness is 50nm-100nm.

[0015] Furthermore, the metal electrode is made of gold or silver, and its thickness is 80nm-120nm.

[0016] Furthermore, the transparent electrode is FTO or ITO.

[0017] Compared with the prior art, the beneficial effects of this invention are as follows: This application provides a carbon quantum dot modification layer; simultaneously, carbon quantum dot particles fill the gaps between perovskite layer grains. On one hand, the carbon quantum dot particles filling the gaps between perovskite layer grains connect the gaps between the grains, reducing the carrier concentration at the grain edges and allowing carriers to migrate between adjacent grains; the carbon quantum dot particles covering the perovskite layer construct migration paths for carriers on the surface of the perovskite layer, thereby enabling carrier migration between non-adjacent grains of the perovskite layer; by constructing more carrier migration paths, the photoelectric conversion efficiency is improved. On the other hand, carbon quantum dot particles have strong absorption in both the ultraviolet and visible bands. The band gap of perovskite is 1.7 eV-2.3 eV. At the crystal boundary, perovskite and carbon quantum dot particles form a heterostructure. The band structure of carbon quantum dot particles provides an intermediate energy level for charge carriers to enter the hole transport layer from the perovskite, making it easier for charge carriers to enter the hole transport layer from the perovskite and then reach the metal electrode. This reduces the recombination of photogenerated electrons and photogenerated holes in the perovskite and improves the photoelectric conversion efficiency. Attached Figure Description

[0018] Figure 1 A schematic diagram of a carbon quantum dot-modified solar cell provided by the present invention;

[0019] Figure 2 SEM image of a perovskite layer (material CsPbIBr2) in a carbon quantum dot modified solar cell provided by the present invention;

[0020] Figure 3 A partial structural schematic diagram of another carbon quantum dot-modified solar cell provided by the present invention.

[0021] Icons: 1-Metal electrode; 2-Hole transport layer; 3-Carbon quantum dot modified layer; 4-Perovskite layer; 5-Electron transport layer; 6-Transparent electrode. Detailed Implementation

[0022] To make the implementation process of this invention clearer, a detailed description will be provided below in conjunction with the accompanying drawings.

[0023] This invention provides a carbon quantum dot-modified solar cell, such as... Figure 1As shown, the solar cell comprises, from top to bottom, a metal electrode 1, a hole transport layer 2, a carbon quantum dot modification layer 3, a perovskite layer 4, an electron transport layer 5, and a transparent electrode 6, with adjacent components fixedly connected. The metal electrode 1 is made of gold or silver, preferably with a thickness of 80 nm-120 nm. The hole transport layer 2 is made of PEDOT:PSS or Spiro-MeOTAD (2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene). The electron transport layer 5 is made of TiO2 or SnO2, with a thickness of 50 nm-100 nm. The transparent electrode 6 is made of FTO or ITO. The perovskite layer 4 is made of all-inorganic perovskite, specifically CsPbX. a Y 3-a (X = I, Y = Br, a ≤ 3); preferably, the material of the perovskite layer is CsPbIBr2. The thickness of the perovskite layer 4 is 300 nm-700 nm.

[0024] The carbon quantum dot modification layer 3 is formed from carbon quantum dot particles with a diameter of less than 3 nm. The side of the carbon quantum dot modification layer 3 away from the perovskite layer 4 is planar, while the side of the carbon quantum dot modification layer 3 closer to the perovskite layer 4 intersects with it. For example... Figure 2 As shown, irregular gaps exist between the grains of the perovskite layer 4, and carbon quantum dot particles fill these gaps. The carbon quantum dot particles penetrate deep into the gaps between the perovskite grains, allowing carrier migration between adjacent grains and improving the photoelectric conversion efficiency of the solar cell. Entering the gaps between the perovskite grains increases the contact area with the perovskite, resulting in more carrier migration paths and further improving the photoelectric conversion efficiency of the solar cell. The carbon quantum dot modification layer 3 serves to increase carrier migration paths and promote carrier migration, thereby improving the photoelectric conversion efficiency of the solar cell.

[0025] Specifically, on the one hand, the carbon quantum dot particles filling the gaps between the perovskite layer 4 grains connect the interstices between the grains, thereby reducing the carrier concentration at the grain edges (excessive concentration at the grain edges is the main factor in the formation of gaps), allowing carriers to migrate between adjacent grains; the carbon quantum dot particles covering the perovskite layer 4 construct migration paths for carriers on the surface of the perovskite layer 4, thereby enabling carrier migration between non-adjacent grains of the perovskite layer 4; by constructing more carrier migration paths, the photoelectric conversion efficiency is improved. On the other hand, carbon quantum dot particles exhibit strong absorption in both the ultraviolet and visible bands. The band gap of the perovskite is 1.7 eV-2.3 eV. At the crystal boundary, the perovskite and carbon quantum dot particles form a heterostructure. The conduction band of the carbon quantum dot particles is higher than the conduction band of the hole transport layer 2 but lower than the conduction band of the perovskite layer 4. The valence band of the carbon quantum dot particles is higher than the valence band of the perovskite layer 4 but lower than the conduction band of the hole transport layer 2. This band structure provides an intermediate energy level for charge carriers to enter the hole transport layer 2 from the perovskite layer 4, making it easier for charge carriers to enter the hole transport layer 2 from the perovskite layer 4 and then reach the metal electrode 1. This reduces the recombination of photogenerated electrons and photogenerated holes in the perovskite and improves the photoelectric conversion efficiency.

[0026] In the preparation process, the transparent electrode 6 is first treated. In this example, FTO conductive glass produced by Opivet is used. Specifically, the FTO conductive glass is cut to the required size, preferably 1.5cm-2.5cm in length and width. A 2mm-5mm margin is reserved for etching, and the remaining portion is tightly adhered with zinc tape to prevent etching. Zinc powder is evenly sprinkled on the area to be etched, and then an HCl aqueous solution is dropped onto the zinc powder. A large amount of gas is generated during the etching process. After the reaction is complete, the surface is wiped clean, and the FTO layer is completely etched. If the etching is not complete, the above etching process can be repeated until the FTO layer is completely etched. The tightly adhered zinc tape is then removed, and the etched FTO conductive glass is cleaned using detergent, deionized water, anhydrous ethanol, isopropanol, and acetone, respectively, with ultrasonic cleaning for at least 25 minutes each, to obtain the prepared transparent electrode 6. Taking TiO2 as an example, the electron transport layer 5 is prepared by first preparing a TiO2 solution. Specifically, diethanolamine and tetraisopropyl titanate are added to a beaker sequentially, shaken to mix thoroughly, and then ethanol is added. After ultrasonic treatment for 40 minutes, the TiO2 solution is obtained. The TiO2 solution is then spin-coated onto a transparent electrode 6. The transparent electrode 6 is first subjected to plasma treatment, and 100μL-300μL of TiO2 solution is dropped onto it. Spin-coating is performed at 65,000 rpm for 40 seconds. After spin-coating, the transparent electrode 6 is placed in a muffle furnace and annealed at 450℃-500℃ for 2-2.5 hours. The electron transport layer 5 and the transparent electrode 6 are then prepared. This embodiment takes CsPbIBr2 perovskite as an example. First, a CsPbIBr2 solution is prepared by taking CsI and PbBr2 powders in a 1:1 molar ratio and dissolving them in dimethyl sulfoxide (DMSO) to obtain a precursor solution. The prepared electron transport layer 5 and transparent electrode 6 are treated with plasma, with the treatment surface being the side of electron transport layer 5 away from transparent electrode 6. 100μL-300μL of precursor solution is added dropwise. First, spin-coating is performed at 1000rpm-1200rpm for 8-10s, and then at 3000rpm-4000rpm for 40s-50s. After spin-coating, the film is heated on a hot plate at 30℃-40℃ for 1min-3min, and then heated on a hot plate at 220℃-260℃ for 10min-20min. When the two heat treatments are completed, the perovskite film completes the crystallization process, and a well-crystallized CsPbIBr2 perovskite film is obtained. The preparation of CsPbIBr2 perovskite thin films was carried out in a glove box.Similarly, carbon quantum dot modified layer 3 (carbon quantum dot solution) and hole transport layer 2 are prepared through two spin-coating processes. The spin-coating of carbon quantum dot modified layer 3 is divided into two steps: first, spin-coating at 2000-3000 rpm for 50-60 seconds to ensure that carbon quantum dot particles fully fill the gaps between perovskite grains; then, spin-coating at 7000-9000 rpm for 10-15 seconds to create a layer of carbon quantum dot particles covering the side of perovskite layer 4 away from electron transport layer 5. Plasma treatment is required before each preparation to open chemical bonds, resulting in tighter bonding and mutual fixation between adjacent layers. Metal electrode 1 can be prepared by electron beam evaporation deposition. Note that plasma treatment is also required before evaporation deposition.

[0027] Based on the above embodiments, the contact surface between the perovskite layer 4 and the electron transport layer 5 is curved, such as... Figure 3 As shown, specifically, the perovskite layer 4 bends towards one side, preferably with the radius of curvature at the top of the bend smaller than that at the two sides. This has several advantages: First, the surface of the perovskite layer 4 in contact with light is curved, resulting in a larger contact area and the absorption of more photons, thus generating more electron-hole pairs and improving photoelectric conversion efficiency. Second, the curvature at the top center is the largest, accumulating more electrons and holes, generating a stronger built-in electric field. This makes it easier for electrons and holes to migrate towards both ends—electrons through the electron transport layer 5 to the transparent electrode 6, and holes through the hole transport layer 2 to the metal electrode 1—making recombination less likely and improving photoelectric conversion efficiency. Third, holes at the middle of the curved surface travel a shorter distance to the side of the perovskite layer 4 closest to the carbon quantum dot modification layer 3, making them easier to capture by surface defects and enter the carbon quantum dot modification layer 3, ultimately migrating to the metal electrode 1. This avoids recombination of photogenerated electrons and holes, further improving photoelectric conversion efficiency. Therefore, the solar cell of this application has a high photoelectric conversion efficiency.

[0028] In application, light enters from one side of the transparent electrode 1, passes through the transparent electrode 6 and the electron transport layer 5, and illuminates the perovskite layer 4. Photogenerated electrons and holes are generated in the perovskite layer 4. Some of these photogenerated electrons and holes move to opposite ends. Specifically, photogenerated electrons travel through the electron transport layer 5 to the transparent electrode 6, while photogenerated holes travel through the carbon quantum dot modification layer 3 and the hole transport layer 2 to the metal electrode 1. The metal electrode 1 and the transparent electrode 6 are connected to an external circuit, providing power to the external circuit. The carbon quantum dot modification layer 3 increases the carrier migration path and promotes carrier migration, thereby improving the photoelectric conversion efficiency of the solar cell. Specifically, on the one hand, the carbon quantum dot particles filling the gaps between the perovskite layer 4 connect the intergranular spaces, thereby reducing the carrier concentration at the grain edges and enabling carriers to migrate between adjacent grains; on the other hand, the carbon quantum dot particles covering the perovskite layer 4 construct migration paths for carriers on the surface of the perovskite layer 4, thus enabling carrier migration between non-adjacent grains of the perovskite layer 4; by constructing more carrier migration paths, the photoelectric conversion efficiency is improved. On the other hand, carbon quantum dot particles exhibit strong absorption in both the ultraviolet and visible bands. The band gap of the perovskite is 1.7 eV-2.3 eV. At the crystal boundary, the perovskite and carbon quantum dot particles form a heterostructure. The conduction band of the carbon quantum dot particles is higher than the conduction band of the hole transport layer 2 but lower than the conduction band of the perovskite layer 4. The valence band of the carbon quantum dot particles is higher than the valence band of the perovskite layer 4 but lower than the conduction band of the hole transport layer 2. This band structure provides an intermediate energy level for charge carriers to enter the hole transport layer 2 from the perovskite layer 4, making it easier for charge carriers to enter the hole transport layer 2 from the perovskite layer 4 and then reach the metal electrode 1. This reduces the recombination of photogenerated electrons and photogenerated holes in the perovskite and improves the photoelectric conversion efficiency.

[0029] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A carbon quantum dot-modified solar cell, wherein the solar cell comprises, from top to bottom, a metal electrode, a hole transport layer, a perovskite layer, an electron transport layer, and a transparent electrode, characterized in that, A carbon quantum dot modification layer is disposed between the hole transport layer and the perovskite layer. The metal electrode, the hole transport layer, the carbon quantum dot modification layer, the perovskite layer, the electron transport layer, and the transparent electrode are fixedly connected to each other. The side of the carbon quantum dot modification layer away from the perovskite layer is planar, while the side of the carbon quantum dot modification layer closer to the perovskite layer intersects with the perovskite layer. The carbon quantum dot modification layer is formed of carbon quantum dot particles with a diameter less than 3 nm, which fill the gaps between the grains in the perovskite layer. The perovskite layer is made of CsPbX. a Y 3-a Where X=I, Y=Br, a≤3; the contact surface between the perovskite layer and the electron transport layer is curved and bends toward the perovskite layer; the perovskite layer and the carbon quantum dot modification layer are obtained by the following steps: first spin-coating a perovskite precursor solution, then performing heat treatment, and after heat treatment, spin-coating a carbon quantum dot solution onto the surface of the perovskite layer.

2. The carbon quantum dot-modified solar cell according to claim 1, characterized in that, The thickness of the perovskite layer is 300nm-700nm.

3. The carbon quantum dot-modified solar cell according to any one of claims 1-2, characterized in that, The hole transport layer is made of PEDOT:PSS or Spiro-MeOTAD.

4. The carbon quantum dot-modified solar cell according to claim 2, characterized in that, The electron transport layer is made of TiO2 or SnO2, and its thickness is 50nm-100nm.

5. The carbon quantum dot-modified solar cell according to claim 4, characterized in that, The metal electrode is made of gold or silver, and its thickness is 80nm-120nm.

6. The carbon quantum dot-modified solar cell according to claim 5, characterized in that, The transparent electrode is FTO or ITO.

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