Perovskite battery and preparation method thereof

Abstract

The invention provides a perovskite battery and a preparation method thereof. The perovskite cell comprises an anti-reflection layer, a photoelectric conversion efficiency enhancement layer, an electron transport layer, a perovskite layer, a hole transport layer and a top electrode which are sequentially stacked on a conductive substrate. The anti-reflection layer is made of a two-dimensional material lithium-doped graphene layer, and the photoelectric conversion efficiency enhancement layer is a perovskite quantum dot LaFeO functional film layer. The lithium-doped graphene has good electron separation capability and light transmission, and has extremely low reflectivity to infrared and visible light; the perovskite quantum dot LaFeO is excellent in light absorption, and due to the high oxidation state of iron in the structure and the perovskite structure, the perovskite quantum dot LaFeO has very strong electron and hole separation capability. The lithium-doped graphene and the perovskite quantum dot LaFeO have relatively good compatibility in structure, and can effectively improve the transition capability of electrons and improve the photoelectric conversion efficiency of the perovskite battery when being cooperatively applied to the perovskite battery.

Description

Technical Field

[0001] This application relates to the fields of the design and manufacturing process of perovskite solar cells, and particularly relates to a perovskite solar cell and a preparation method thereof. Background Art

[0002] A solar cell is a thin optoelectronic semiconductor sheet that directly generates electricity using sunlight. It directly converts light energy into electrical energy through the photovoltaic effect or the photochemical effect, and has the advantages of high reliability, long life, high conversion efficiency, etc. As the third-generation new concept solar cell, the perovskite solar cell has the advantages of relatively high photoelectric conversion efficiency, low cost, and flexible processing. In recent years, it has developed rapidly, gradually catching up with silicon cells and approaching the commercial application level.

[0003] Since 2009, great progress has been made in solar cells formed by using organometallic halide CH3NH3PbX3 (X = Cl, I, Br) as a dye on the basis of dye-sensitized solar cell technology. Because the organometallic halide has a perovskite-type crystal lattice structure, this type of solar cell using organometallic halide material as the absorption layer is called a perovskite solar cell (Perovskite-based Solar Cell). The band gap of this organometallic halide with a perovskite crystal system is 4.0 - 4.1 eV, which can efficiently absorb broad-spectrum light from visible light to 800 nm, and this material has a high carrier mobility. Currently, the photoelectric conversion efficiency of perovskite solar cells has exceeded 15%, and is expected to reach more than 25%.

[0004] Currently, how to improve the conversion efficiency of perovskite solar cells (PSCs) is a current research hotspot. The existing methods for improving the conversion efficiency of perovskite solar cells can be roughly divided into the following categories: 1. Composition regulation: For example, mixed cations / halogens: such as using FA / MA / Cs mixed cations (formamidine / methylamine / cesium) or I / Br mixed halogens to optimize the band gap and phase stability (such as FA0. 83 MA0. 17 Pb(I0. 83 Br0. 17 )3); low-dimensional perovskite: introducing 2D / 3D heterostructures (such as PEA2PbI4) to improve environmental stability and reduce non-radiative recombination; and additive engineering for passivating defects and improvement.

[0005] 2. Interface engineering: including optimization of the electron transport layer (ETL) (for example, using materials such as SnO2, TiO2, or ZnO to reduce the interface barrier (such as SnO2 can be prepared at low temperature to reduce the hysteresis effect)), surface modification (such as PCBM or C 60SAMs) passivate ETL defects, hole transport layer (HTL) optimization (e.g., replacing Spiro-OMeTAD: using PTAA, CuSCN or inorganic materials such as NiO X ) to improve hole extraction efficiency) and doping to improve conductivity (such as Li-TFSI + tBP doping of Spiro).

[0006] 3. Process improvement: For example, using vapor-assisted deposition to prepare the corresponding functional layers and controlling the annealing parameters, etc.

[0007] 4. Optimization of light absorption management: mainly including introducing nanostructures (such as mesoporous TiO2 or textured substrates) to enhance light absorption, and using metal electrodes (Au / Ag) or dielectric mirrors to reflect the unabsorbed light. Summary of the Invention

[0008] In order to improve the photoelectric conversion efficiency of perovskite solar cells, this application starts from the perspective of optimizing light absorption management, and uses special materials to add an antireflection layer and a photoelectric conversion efficiency enhancement layer on the basis of the original perovskite solar cell to provide a perovskite solar cell with high conversion efficiency and its preparation method.

[0009] On the one hand, the technical solution provided by this application is implemented as a perovskite solar cell. The perovskite solar cell has a "sandwich" structure of a hole transport layer, a perovskite layer, and an electron transport layer. The electron transport layer of the perovskite solar cell is closer to the conductive substrate, and an antireflection layer and a photoelectric conversion efficiency enhancement layer are sequentially stacked on the conductive substrate, and the photoelectric conversion efficiency enhancement layer is in contact with the electron transport layer. The antireflection layer is a lithium-doped graphene layer of two-dimensional material, and the photoelectric conversion efficiency enhancement layer is a perovskite quantum dot LaFeO3 functional film layer.

[0010] Further, a top electrode is also provided on the hole transport layer, and the conductive substrate is used as the bottom electrode. Preferably, the conductive substrate is a flexible conductive substrate.

[0011] Lithium-doped graphene has good electrical conductivity and light transmittance. By doping lithium to adjust the electronic structure of graphene, it can not only reduce the reflection loss of light, but also enhance the carrier transport ability. Lithium-doped graphene (antireflection layer) can provide a good light transport channel and electron transport channel for LaFeO3 quantum dots (functional film) and the perovskite layer, thereby effectively promoting the separation and transport of carriers in the photoelectric conversion process of perovskite solar cells. And the perovskite quantum dot LaFeO3 has a high light absorption coefficient, and its high oxidation state of iron and perovskite structure in the structure enable it to have a strong electron-hole separation ability in the photoelectric conversion process of the perovskite layer, which can effectively improve the photoelectric performance of perovskite solar cells.

[0012] Correspondingly, another aspect of the present application further provides a method for preparing a perovskite solar cell. The preparation method includes: preparing an antireflection layer on a pre-prepared conductive substrate using a pre-prepared two-dimensional material lithium-doped graphene solution; using a pre-prepared LaFeO3 perovskite quantum dot solution to form a photoelectric conversion efficiency enhancement film layer on the antireflection layer; sequentially preparing a stacked electron transport layer, a perovskite layer, a hole transport layer, and a top electrode on the photoelectric conversion efficiency enhancement film layer.

[0013] Further, the preparation of the two-dimensional material lithium-doped graphene solution includes: preparing a graphene precursor solution with a concentration of 0.05M - 0.1M, using ethanol or water as the solvent; adding a corresponding lithium salt to the graphene precursor solution and stirring to obtain a two-dimensional material lithium-doped graphene solution with a lithium salt concentration range of 0.01M - 0.05M. The preparation of the LaFeO3 perovskite quantum dot solution includes: uniformly dissolving the LaFeO3 perovskite quantum dot material in N,N-dimethylformamide (DMF) to obtain a LaFeO3 perovskite quantum dot solution with a concentration of 0.1M.

[0014] Further, the formation of the antireflection layer includes: using a spin coating technique to uniformly coat the two-dimensional material lithium-doped graphene solution on a pre-prepared conductive substrate to form an antireflection layer, and annealing in a first temperature range to cure the antireflection layer. The formation of the photoelectric conversion efficiency enhancement layer includes: depositing the LaFeO3 quantum dot solution on the antireflection layer using a spin coating process, and then annealing in a second temperature range to ensure the crystallinity and stability of the quantum dot film and simultaneously activate the quantum dots. In some embodiments, the first temperature range is 80°C - 100°C, and the second temperature range is 50°C - 60°C.

[0015] The technical solution provided by the present application effectively improves the photoelectric conversion efficiency of perovskite solar cells by adding a two-dimensional material lithium-doped graphene layer as a reflection layer to the traditional perovskite solar cell and cooperating with the addition of a perovskite quantum dot LaFeO3 functional film layer. Utilizing the high oxidation state of iron in the perovskite quantum dot LaFeO3 material improves the separation ability of electrons and holes, and then the lithium-doped graphene layer provides a smooth electron transport channel to quickly separate electrons and holes, reducing the recombination of holes and electrons, and greatly improving the photoelectric conversion efficiency of perovskite solar cells. Description of the Drawings

[0016] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 The structural schematic diagram of the perovskite battery provided for this application in one embodiment.

[0018] Figure 2 The flow chart of the preparation method of the perovskite battery provided for this application in one embodiment. Detailed implementation manners

[0019] To make the objectives, technical solutions and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are some but not all of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the scope of protection of this application.

[0020] As Figure 1 shown, the perovskite battery 10 provided for this application includes, from bottom to top, a conductive substrate 1, an antireflection layer 2, a photo - electric conversion efficiency enhancement layer 3, an electron transport layer 4, a perovskite layer 5, a hole transport layer 6, and a top electrode 7. Compared with the existing perovskite batteries, the above - mentioned perovskite battery 10 provided for this application adds an antireflection layer 2 and a photo - electric conversion efficiency enhancement layer 3. The antireflection layer 2 is a two - dimensional material - doped lithium graphene layer, and the photo - electric conversion efficiency enhancement layer 3 is a perovskite quantum dot LaFeO3 functional film layer. The conductive substrate 1 also serves as the bottom electrode of the perovskite battery 10. Preferably, the conductive substrate is a flexible conductive substrate.

[0021] The two - dimensional material - doped lithium graphene adjusts the surface chemical properties of graphene and optimizes its electronic structure by doping lithium atoms, making it exhibit a lower reflectivity in the infrared and visible spectra. The perovskite battery 10 provided uses the two - dimensional material - doped lithium graphene to make the antireflection layer 2, which can not only reduce the reflection loss of incident light and improve the light absorption rate, but also provide a good transmission channel for electrons to transfer to the bottom electrode. In the perovskite quantum dot LaFeO3 material, the high oxidation state of iron improves the separation ability of electrons and holes in the perovskite battery, and the perovskite structure is also conducive to the transmission of electrons. The synergistic effect of the perovskite quantum dot LaFeO3 and the doped lithium graphene can not only enhance the photo - electric conversion efficiency of the perovskite battery, but also ensure the stability and durability of the perovskite battery. Other perovskite quantum dot materials perform poorly in terms of photo - electric conversion efficiency or stability and cannot be well - matched with the doped lithium graphene in terms of charge - transfer ability.

[0022] Corresponding to the above perovskite battery, another aspect of this application also provides a preparation method of a perovskite battery. As Figure 2 shown in the embodiment, the above - mentioned preparation method includes the following steps: S1. Prepare a conductive substrate; the conductive substrate serves as the basic support of the photovoltaic cell, and it is necessary to ensure structural stability and have good light transmittance. The conductive substrate can be not only conductive glass but also flexible materials such as PET.

[0023] S2. Prepare the solutions required for depositing the electron transport layer, perovskite layer, and hole transport layer. In some embodiments, the hole transport layer (HTL) material is Spiro-OMeTAD or PEDOT:PSS solution to ensure the effective transport of holes from the perovskite layer to the top electrode; optionally, the concentration of the hole transport layer solution is 0.1M - 0.2M, and the solvent is chlorobenzene or n-butanol. The perovskite layer material is MAPbI3 or mixed-halide perovskite (as the light absorption layer), and is prepared into a perovskite precursor solution by a solution method. Optionally, the concentration of the perovskite precursor solution is 0.3M, and the solvent is a mixed solution of N,N-dimethylformamide (DMF) and dichlorobenzene (DCB). The electron transport layer (ETL) material can be selected as TiO2, SnO2, or ZnO to promote the effective conduction of electrons from the light absorption layer to the bottom electrode and avoid the recombination of electrons and holes, and is also prepared in solution form; optionally, the concentration of the electron transport layer solution is 0.1M - 0.2M, and ethanol or acetone is used as the solvent.

[0024] S3. Prepare the lithium-doped graphene solution and the perovskite quantum dot LaFeO3 solution. The preparation of the two-dimensional material lithium-doped graphene solution can specifically include: preparing a graphene precursor solution with a concentration of 0.05M - 0.1M, using ethanol or water as the solvent; adding the corresponding lithium salts (such as LiCl, LiF, etc.) to the graphene precursor solution and stirring to obtain a two-dimensional material lithium-doped graphene solution with a lithium salt concentration range of 0.01M - 0.05M.

[0025] The preparation of the LaFeO3 perovskite quantum dot solution can be carried out in the following way: uniformly dissolve the LaFeO3 perovskite quantum dot material in N,N-dimethylformamide (DMF) to obtain a LaFeO3 perovskite quantum dot solution with a concentration of 0.1M.

[0026] S4. Use the prepared lithium-doped graphene solution to deposit an antireflection layer on the conductive substrate.

[0027] For depositing the antireflection layer, the conventional spin coating-annealing technique can be used to uniformly coat the lithium-doped graphene solution on the flexible substrate. Preferably, the spin coating speed is set at 2000 rpm - 3000 rpm to ensure the uniformity of the film thickness (usually the thickness is maintained at 10 nm - 30 nm), and then anneal at 80°C - 100°C for a predetermined time to cure the film, enhance the adhesion and stability of the film.

[0028] S5. Deposit a photo - electric conversion efficiency enhancement layer on the anti - reflection layer using the prepared perovskite quantum dot LaFeO₃ solution. The LaFeO₃ quantum dot solution is also deposited on the anti - reflection layer using a spin - coating - annealing process to form a photo - electric conversion efficiency enhancement layer. Preferably, the spin - coating speed is set at 1500 rpm, and the annealing temperature is set between 50 °C and 60 °C to ensure the crystallinity and stability of the quantum dot film (usually with a thickness of 20 nm - 50 nm), and at the same time activate the quantum dots.

[0029] S6. Deposit a "sandwich" structure composed of an electron transport layer, a perovskite layer, and a hole transport layer on the photo - electric conversion efficiency enhancement layer using the relevant solutions prepared in step S2 respectively.

[0030] Specifically, for the electron transport layer (ETL), the electron transport material used can be selected from TiO₂, SnO₂ or ZnO solutions to promote the effective conduction of electrons from the light - absorbing layer (perovskite layer) to the bottom electrode and avoid the recombination of electrons and holes. Preferably, the concentration of the electron transport material solution is set at 0.1 M - 0.2 M, and the solvent is ethanol or acetone. When depositing the electron transport layer, the spin - coating speed can be set at 3000 rpm to obtain an electron transport layer with good uniformity and appropriate thickness, and the corresponding annealing temperature is set at 150 °C - 200 °C to promote the crystallization of the electron transport layer, improve its conductivity and stability.

[0031] For the light - absorbing layer (perovskite layer), a solution of MAPbI₃ or mixed - halogen perovskite can be selected as the perovskite precursor solution. Optionally, the concentration of the precursor solution is 0.3 M to ensure that the deposited perovskite layer is uniform and dense, and the solvent is a mixed solution of N,N - dimethylformamide (DMF) and dichlorobenzene (DCB). Correspondingly, when depositing the perovskite layer, the spin - coating speed can be set at 3000 rpm - 4000 rpm to obtain a film layer with good uniformity and appropriate thickness, and the annealing temperature is set at 100 °C - 120 °C. The annealing process of depositing the perovskite layer helps the formation of perovskite crystals, improving the crystallinity and optoelectronic properties of the film layer.

[0032] For the preparation of the hole transport layer (HTL): The hole transport layer is used to ensure the effective transport of holes from the light - absorbing layer to the top electrode. Usually, the hole transport material is selected as Spiro - OMeTAD or PEDOT:PSS solution, the solution concentration is 0.1 M - 0.2 M, and the solvent is chlorobenzene or n - butanol. Correspondingly, when depositing the hole transport layer, the spin - coating speed can be set at 2000 rpm, and the annealing temperature is set at 60 °C - 80 °C to promote the formation of the material's thin film and improve its conductivity.

[0033] The thickness of each film layer in the above "sandwich" structure is usually between dozens and hundreds of nanometers, which can be selected by those skilled in the art according to actual needs. No further elaboration will be provided here.

[0034] S7. Fabricate a top electrode on the hole transport layer. The top electrode cooperates with the bottom electrode (conductive substrate) to export the electric quantity of the battery outward, and it can be made of materials such as silver, copper, or other metals or alloys with good electrical conductivity.

[0035] The technical solution provided by this application can effectively reduce the light reflectivity and increase the light transmittance by introducing a lithium-doped graphene antireflection layer on the basis of the traditional perovskite battery structure, thereby improving the light absorption ability of the perovskite battery. On the basis of reducing the light reflection loss, cooperating with the insertion of LaFeO3 perovskite quantum dots can greatly improve the photoelectric conversion efficiency. The synergistic effect of this double coating structure can effectively improve the light absorption ability of the perovskite battery, optimize the extraction of electrons and holes, reduce non-radiative recombination, and significantly improve the photoelectric conversion efficiency of the perovskite battery (the photoelectric conversion efficiency of the traditional perovskite battery is about 19.8%, and the photoelectric conversion efficiency can reach more than 23.2% after introducing the lithium-doped graphene layer + LaFeO3 perovskite quantum dot layer).

[0036] The above are only the embodiments of this application and are not used to limit this application. For those skilled in the art, various changes and modifications can be made to the technical solutions provided by this application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims

1. A perovskite solar cell having a "sandwich" structure with a hole transport layer, a perovskite layer, and an electron transport layer; characterized in that, The electron transport layer of the perovskite solar cell is closer to the conductive substrate. An antireflection layer and a photoelectric conversion efficiency enhancement layer are sequentially stacked on the conductive substrate, and the photoelectric conversion efficiency enhancement layer is in contact with the electron transport layer; the antireflection layer is a two-dimensional material doped with lithium graphene layer, and the photoelectric conversion efficiency enhancement layer is a perovskite quantum dot LaFeO3 functional film layer.

2. The perovskite cell according to claim 1, characterized in that, The conductive substrate is a flexible conductive substrate.

3. The perovskite cell according to claim 1 or 2, characterized in that, A top electrode is further provided on the hole transport layer.

4. A method for preparing a perovskite solar cell, characterized in that, The preparation method includes: preparing an antireflection layer on a pre-prepared conductive substrate using a pre-prepared two-dimensional material doped with lithium graphene solution; using a pre-prepared LaFeO3 perovskite quantum dot solution to form a photoelectric conversion efficiency enhancement film layer on the antireflection layer; sequentially preparing and stacking an electron transport layer, a perovskite layer, a hole transport layer, and a top electrode on the photoelectric conversion efficiency enhancement film layer.

5. The preparation method according to claim 4, wherein The preparation of the two-dimensional material doped with lithium graphene solution includes: configuring a graphene precursor solution with a concentration of 0.05M - 0.1M, using ethanol or water as the solvent; adding a corresponding lithium salt to the graphene precursor solution and stirring to obtain a two-dimensional material doped with lithium graphene solution with a lithium salt concentration range of 0.01M - 0.05M.

6. The preparation method according to claim 4, characterized in that, The preparation of the LaFeO3 perovskite quantum dot solution includes: uniformly dissolving the LaFeO3 perovskite quantum dot material in N,N-dimethylformamide (DMF) to obtain a LaFeO3 perovskite quantum dot solution with a concentration of 0.1M.

7. The preparation method according to any one of claims 4-6, characterized in that, The formation of the antireflection layer includes: using a spin coating technique to uniformly coat the two-dimensional material doped with lithium graphene solution on a pre-prepared conductive substrate to form an antireflection layer, and annealing in a first temperature range to cure the antireflection layer.

8. The preparation method according to any one of claims 4 to 6, characterized in that, The formation of the photoelectric conversion efficiency enhancement layer includes: depositing the LaFeO3 quantum dot solution on the antireflection layer using a spin coating process, and then annealing in a second temperature range to ensure the crystallinity and stability of the quantum dot film and activate the quantum dots at the same time.

9. The preparation method according to claim 7, characterized in that The first temperature range is 80°C - 100°C.

10. The preparation method according to claim 8, characterized in that, The second temperature range is 50°C - 60°C.

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