CN110993798B

CN110993798B - Perovskite type solar cell based on synergistic post-treatment of multiple ammonium salts and preparation thereof

Info

Publication number: CN110993798B
Application number: CN201911324787.6A
Authority: CN
Inventors: 朱瑞; 富云齐; 杨晓宇; 赵丽宸; 龚旗煌
Original assignee: Peking University
Current assignee: Peking University
Priority date: 2019-12-20
Filing date: 2019-12-20
Publication date: 2021-11-19
Anticipated expiration: 2039-12-20
Also published as: CN110993798A

Abstract

The invention discloses a perovskite type solar cell based on synergistic post-treatment of multiple ammonium salts and a preparation method thereof, wherein a perovskite layer serving as a light absorption active layer is treated by a mixed solution of multiple ammonium salts after film formation, and non-radiative recombination in a thin film is inhibited in a passivation mode through the synergistic diffusion effect of various added ammonium salts; meanwhile, the distribution of different kinds of ammonium salts after permeation in the film also presents different gradient distribution, the gradient optimization of the film energy band structure is realized, the defect passivation of different gradients is realized, the non-radiative recombination of photon-generated carriers is reduced, and the open-circuit voltage and the filling factor of the device are finally improved. The perovskite solar cell which is subjected to post-treatment by the mixed solution of various ammonium salts has high photoelectric conversion efficiency and good stability.

Description

Perovskite type solar cell based on synergistic post-treatment of multiple ammonium salts and preparation thereof

Technical Field

The invention belongs to the technical field of photoelectric functional materials and devices, and particularly relates to a perovskite type solar cell based on synergistic post-treatment of various ammonium salts and a preparation method thereof.

Background

With the rapid development of modern society, the demand of human beings on energy is increasing continuously; although traditional fossil energy accounts for a large proportion of energy supply, the traditional fossil energy easily causes serious environmental pollution, is non-renewable consumable, and seriously restricts the sustainable development of the economic society, so that the search for clean and efficient renewable energy is urgent. The solar cell is used as a new energy supply device in renewable energy sources, and directly converts light energy into electric energy through photochemical reaction or photovoltaic effect, and the appearance of the solar cell provides a solution with great potential for solving and replacing the use of fossil energy. The development of solar cells widely used in society to date is silicon-based solar cells, but the process is complex, the cost is high, the energy yield and the popularization degree are far behind those of fossil energy, and therefore, the development of new solar cells with low cost and high efficiency is a direction in which people are urgently concerned. Since the metal halide perovskite material is applied to photovoltaic power generation in 2009, the preparation of device technology is rapidly developed, the photoelectric conversion efficiency of the metal halide perovskite material is increased from 3.8% to 25.2% in a short ten-year period, which is very close to the world maximum efficiency of the monocrystalline silicon solar cell, so that the perovskite-based solar cell has gained wide attention from energy sources and is a research hotspot in the novel photovoltaic technical field.

Perovskite materials are generally present in thin film form in solar cells and act as photoactive layers, the film-forming crystalline quality of which largely determines the final properties of the device. However, due to the properties of the perovskite material and the immaturity of the process, the current common solvent annealing method can cause the perovskite light absorption layer to generate a large amount of grain boundaries and intrinsic defects during crystallization film formation, thereby causing the non-radiative recombination of carriers in the perovskite light absorption layer and at the interface between the perovskite layer and the charge transport layer to be serious, and finally causing the open-circuit voltage of the solar cell (c) (a)V _OC) And a Fill Factor (FF) is decreased, restricting the improvement of the photoelectric conversion efficiency. At present, the best scheme for regulating and controlling the phase and interface non-radiative recombination loss of a perovskite light absorption layer is to realize the passivation and secondary growth of a perovskite layer by carrying out secondary treatment on ammonium halide on the surface of the perovskite layer so as to regulate and control and reduce the defects of the perovskite layer phase and interface. However, depending on the molecular properties of ammonium halide salts, the final passivated perovskite thin film may not reach the best film quality, so that various defects existing in the perovskite thin film cannot be completely solved by a single ammonium halide salt; therefore, various defects in the film are simultaneously solved to further reduce non-radiative recombination, so that the efficiency of the film is close to the S-Q theoretical limit of the solar cell, and the film is a key direction for the next development in the field of perovskite type solar cells.

Disclosure of Invention

The invention aims to provide a perovskite type solar cell for post-treating various ammonium salts on a photoactive layer and a preparation method thereof.

The invention provides a perovskite type solar cell, which comprises a transparent substrate, and a transparent electrode, a first charge transmission layer, a perovskite light absorption layer, a second charge transmission layer and a top electrode which are sequentially stacked on the transparent substrate.

The ammonium salts used in the post-treatment modified perovskite light absorbing layer are a combination of two, three or more ammonium salts differing in their ability to diffuse in the perovskite, such ammonium salts including, but not limited to, the following classes of ammonium salts: such as 1, 4-butanediamine hydroiodide (BDADI), octylammonium chloride (OACl), butylammonium iodide (BAI), tert-butylammonium chloride (t-BACl), 3-pyridylmethylamine bromide, isobutylammonium bromide (i-BABr), octylammonium bromide (OABr), 2' - (ethylenedioxy) diethylamine hydrobromide (EDBEBr)₂) And aliphatic chain-containing ammonium salts such as phenethyl ammonium chloride (PEACl), phenethyl ammonium iodide (PEAI), 1, 4-phenylenediamine hydroiodide (PhDADI), benzylammonium iodide (PMAI), phenyl ammonium bromide (PhABr), 1, 4-xylylenediamine iodine and the like aromatic ring-containing ammonium salts such as guanidino hydrobromide (GABr), guanidino thiocyanate (GuSCN) and the like. Various ammonium salts are dissolved in a solvent to carry out post-treatment modification on the perovskite light absorption layer, and the commonly used solvent is a weak-polarity organic solvent such as isopropanol. Different kinds of ammonium salt can permeate into a perovskite layer along a grain boundary under the action of a solvent and an annealing temperature, and the perovskite layer is prepared by the method due to the difference of molecular structures and electric charge properties of the different kinds of ammonium saltThe diffusion rates in the membrane are different. In the case of surface treatment of the perovskite thin film, various ammonium salts will form gradient distribution in the perovskite thin film. Different ammonium salts form different non-uniform gradient distributions in the perovskite layer, wherein the distribution of the various ammonium salts is controlled by the type of ammonium salt and the mode of post-treatment.

In the perovskite type solar cell, the transparent substrate can be made of transparent materials such as glass and flexible plastics. The transparent electrode material may be selected from fluorine-doped tin oxide (FTO), Indium Tin Oxide (ITO), aluminum-doped zinc oxide (AZO), silver nanowires, graphene, tungsten diselenide, carbon nanotubes, or the like. One of ITO conductive glass, FTO conductive glass, AZO conductive glass, silver nanowire-modified conductive glass, graphene-modified conductive glass, and carbon nanotube layer-modified conductive glass is often used as a transparent substrate and a transparent electrode.

According to the perovskite type solar cell, the charge transport layer comprises an electron transport layer and a hole transport layer, the first charge transport layer can be selected to be the electron transport layer or the hole transport layer according to specific conditions, and the corresponding second charge transport layer is selected to be the hole transport layer or the electron transport layer. Wherein the electron transport layer may be selected from tin oxide (SnO)₂) Titanium oxide (TiO)₂) Zinc oxide (ZnO), nickel oxide, magnesium oxide, copper oxide, cuprous oxide, tungsten oxide, PC₆₁BM、C₆₀、C₇₀And the like. For the mesoporous perovskite solar cell, the metal oxide mesoporous layer can be made of TiO₂And sintering the slurry to obtain the high-performance ceramic material. Organic and inorganic materials can be used for the hole transport layer, and include, but are not limited to: organic P-type semiconductor materials such as Spiro-OMeTAD, PEDOT, PSS, TPD, PTAA, P3HT, PCPDTBT and the like; inorganic materials include, but are not limited to: ni_xO、V₂O₅、CuI、MoO₃、CuO、Cu₂And an inorganic P-type semiconductor material such as O.

The perovskite light absorption layer of the perovskite solar cell can adopt the chemical general formula ABX₃The material of (1). Wherein A is an organic ammonium salt cation such as CH₃NH₃ ⁺(MA⁺)、NH₂=CHNH₂ ⁺(FA⁺)、C₄H₉NH₃ ⁺Iso or metal cation Cs⁺、Rb⁺One or more of the components are mixed; b is Pb²⁺、Sn²⁺、Ge²⁺、Sb³⁺、Bi³⁺、Ag⁺、Au³⁺、Ti⁴⁺At least one of; x is Cl^-、Br^-、I^-Or one or more halogen-like substances.

In the perovskite type solar cell, the top electrode can be made of metals such as Au, Ag, Cu, Al and the like by a vacuum thermal evaporation method. In order to make reasonable use of the battery area and to facilitate the testing, different shapes of templates are often used to control the shape of the top electrode.

The preparation of the mixed ammonium salt post-treatment perovskite type solar cell realized by the technical means comprises the following steps:

1) providing a transparent substrate and a transparent electrode;

2) preparing a first charge transport layer on the transparent electrode;

3) preparing a perovskite light absorption layer on the first charge transmission layer, and performing post-treatment by using a mixed solution of multiple ammonium salts;

4) preparing a second charge transport layer on the perovskite light absorption layer;

5) a top electrode is prepared on the second charge transport layer.

In the step 1), the transparent electrode is cleaned, dried and subjected to ultraviolet and/or ozone treatment.

In the step 3), the method for performing post-treatment on the perovskite light absorption layer is specifically divided into spin coating and soaking: the spin coating method is to spin coat a certain amount of mixed solution of various ammonium salts on the prepared perovskite light absorption layer in an oxygen-free atmosphere. In the process, ammonium salt molecules in the solution can permeate into a perovskite layer along a grain boundary, and different types of ammonium salts have passivation effects on perovskite defects and the grain boundary at different depths of the perovskite layer due to the difference of the permeability of the different types of ammonium salts in the perovskite layer; and then, transferring the film to a hot table to carry out annealing treatment at 50-100 ℃ for 5-10 minutes to obtain the perovskite light absorption layer with gradient passivation distribution. The soaking method is that the prepared perovskite light absorption layer is soaked in a mixed solution of a plurality of ammonium salts for 1-6 s in an oxygen-free atmosphere, so that a salt passivation substance permeates into a perovskite layer and forms gradient distribution; and then transferring to a heating table for annealing treatment at 50-100 ℃ for 5-10 minutes to obtain the perovskite light absorption layer with gradient passivation distribution.

In the method for post-treating the perovskite light absorption layer, the solvent used for dissolving the various ammonium salt compounds is a low-polarity organic solvent such as alcohols, ketones, hydrocarbons and the like, and can be selected from the following specific solvents: isopropanol, acetone, n-hexane, and the like. The concentration of each ammonium salt in the mixed ammonium salt solution is preferably 2-5 mg/mL. Different kinds of ammonium salts are dissolved in the same solvent before the perovskite thin film is processed, wherein the concentration ratio of the ammonium salts can be flexibly adjusted. The oxygen-free atmosphere is generally chosen to be N₂And Ar or the like. Preferably, N is used₂And (3) carrying out post-treatment modification on the perovskite thin film by using isopropanol solution of mixed ammonium salt with the concentration of 2.5 mg/mL under a protective atmosphere.

The step 5) can adopt a vacuum thermal evaporation method to prepare the metal top electrode. In order to make reasonable use of the battery area and to facilitate the testing, different shapes of templates are often used to control the shape of the top electrode.

Compared with the existing method for modifying the light absorption layer of the perovskite type solar cell, the method adopts a mode of cooperating a plurality of ammonium salt solutions with post-treatment, realizes defect passivation of different gradients in the film, reduces non-radiative recombination of photon-generated carriers, and finally improves the open-circuit voltage and the filling factor of the device. The process passivates an interface and a bulk phase to inhibit non-radiative recombination, further regulates and controls the electronic structure distribution in the perovskite layer, realizes gradient optimization of an energy band structure, and is beneficial to improving the utilization rate of photons. In addition, the regulation and control of post-treatment ammonium salt can be more accurate and convenient to control by flexibly regulating the concentration, proportion, spin coating speed, treatment time and the like of salts.

In the existing perovskite type solar cell process, post-treatment of multiple (two, three or more than three) mixed ammonium salts on a perovskite light absorption layer is not precedent, and a method for passivating corresponding film defects and accurately regulating and controlling an energy band structure by forming ammonium salt gradient distribution is also innovative. In an experiment, the method has excellent performance, the photoelectric conversion efficiency close to 20% is successfully realized, and in addition, the method is simple to operate, short in time consumption and has the potential of large-scale popularization.

Drawings

FIG. 1 is a view of a perovskite-type solar cell device prepared in example 1J-VCurve line.

Fig. 2 is a schematic diagram of the structure of various ammonium salt post-treated perovskite type solar cells of example 1, with the right side showing the gradient distribution of ammonium salts in the perovskite layer.

FIG. 3 is a surface topography of the treated perovskite of the ammonium salt solution of example 4 observed using a Scanning Electron Microscope (SEM).

Detailed Description

The following are some specific examples of the application of the present invention in a laboratory, including but not limited to the following examples.

Example 1

Firstly, ultrasonic cleaning of an FTO glass substrate (15 omega/□) by using deionized water, acetone, an optical glass cleaner, deionized water and isopropanol in sequence, drying for 4 hours in an oven at 60 ℃, and then utilizing 5 mg/mL TiO₂Colloid of TiO₂Colloidal quantum dots were spin coated onto FTO substrates at 4000 rpm with deionized water as the solvent. The substrate was then heat annealed at 150 ℃ for 30 minutes. After cooling, the TiO is₂Thin film substrate transfer to fill with N₂To produce a perovskite layer.

Second, TiO is added₂Thin film substrate transfer to fill with N₂To produce a perovskite layer. Equal amount of PbI₂And CH₃NH₃I were dissolved in a mixed solvent of DMF: DMSO =4:1 (volume ratio) to prepare a precursor solution. Then on TiO₂The precursor solution is spin-coated on a substrate, 300 mu L of chlorobenzene is dropwise added as an anti-solvent in the spin-coating process, and the substrate is moved to a hot bench for heating and annealing at 100 ℃ for 30 minutes to form a film after the spin-coating is finished.

And thirdly, after the film is cooled, spin-coating a post-treatment solution on the perovskite layer. The post-treatment solution was made by equal volume mixing of 2.5 mg/mL isopropyl alcohol solution of benzylammonium iodide (PMAI) with 5 mg/mL isopropyl alcohol solution of 3-picolyl bromide (3-PYABr). And then the obtained product is transferred to a hot bench to be annealed at 100 ℃ for 5 minutes, so that a perovskite light absorption layer modified by benzyl ammonium iodide and 3-pyridine methylamine bromide is obtained.

And fourthly, after the substrate is cooled, spin-coating a hole transport layer. 80 mg of Spiro-OMeTAD, 17.5. mu.l of lithium salt (520 mg/mL of acetonitrile) and 28.8. mu.l of 4-tBP were added to 1 mL of chlorobenzene to obtain a hole-transporting material. This solution was spin coated on the substrate at 2000 rpm for 25 s. And after film formation, a gold top electrode with the thickness of 80 nm is evaporated on the top of the device. The photoelectric conversion efficiency of such cells can approach 20% (see fig. 1). The basic structure of the device is schematically shown in fig. 2.

Example 2

The first two steps are identical to example 1, and in the third step the composition of the post-treatment solution is such that 2.5 mg of 2,2' - (ethylenedioxy) bis-ethylamine hydrobromide (EDBEBr) are dissolved per ml of isopropanol₂) 2.5 mg of phenylammonium bromide (PhABr) and 5 mg of guanidine thiocyanate (GuSCN). And then moving to a hot table for annealing at 100 ℃ for 5 minutes to obtain three perovskite light absorption layers with gradient distribution of ammonium salt. The rest of the procedure was the same as in example 1. The photoelectric conversion efficiency of the perovskite solar cell can reach 20%.

Example 3

The first step was the same as example 1, and in the second step, the chemical composition of the precursor solution for preparing a perovskite layer was (FA)_0.95PbI_2.95)_0.85(MAPbBr₃)_0.15. In TiO₂The precursor solution is spin-coated on a substrate, 300 mu L of chlorobenzene is dropwise added as an anti-solvent in the spin-coating process, and the substrate is moved to a hot bench for heating and annealing at 100 ℃ for 30 minutes to form a film after the spin-coating is finished.

In the third step, the composition of the post-treatment solution was 5 mg guanidinium hydrobromide (GABr) and 5 mg phenethylammonium iodide (PEAI) per ml isopropanol. And then moving to a hot table for annealing at 100 ℃ for 5 minutes to obtain the perovskite light absorption layer with three substances in gradient distribution. The rest of the procedure was the same as in example 1. The photoelectric conversion efficiency of the perovskite solar cell can reach 20 percent. The SEM cross-sectional view of the surface topography is shown in FIG. 3.

Example 4

The second step adopts a two-step method to prepare a perovskite light absorption layer: 1.5 mol/L PbI was prepared in advance₂The solvent of the precursor solution was DMF: DMSO =9:1 (volume ratio). And 90 mg FAI, 6.3 mg MAI and 9 mg MACl were dissolved in 1 mL IPA to prepare an organic component precursor solution. After the substrate was moved into the glove box, PbI was added₂The precursor solution was spin coated at 1500 rpm for 30s to prepare a lead iodide layer, and transferred to a hot stage for annealing at 70 ℃ for 1 min. The organic component precursor solution was spin-coated at 2000 rmp for 30 seconds to form perovskite, and then transferred to the outside of a glove box and annealed at 150 ℃ for 15 minutes in an air atmosphere (humidity: 30-40%) to form a film. The rest of the procedure was the same as in example 1.

Example 5

The first step was the same as in example 1 and the second step was the same as in example 4. In the third step, the post-treatment solution consisted of 10 mg benzyl ammonium iodide (PMAI), 5 mg isobutyl ammonium bromide (i-BABr) and 2.5 mg octyl ammonium bromide (OABr) per ml. And then moving to a hot table for annealing at 100 ℃ for 5 minutes to obtain the perovskite light absorption layer with three substances in gradient distribution. The photoelectric conversion efficiency of the perovskite solar cell can reach 20 percent.

Claims

1. A perovskite type solar cell comprises a transparent substrate, and a transparent electrode, a first charge transmission layer, a perovskite light absorption layer, a second charge transmission layer and a top electrode which are sequentially stacked on the substrate.

2. The perovskite type solar cell according to claim 1, wherein the ammonium salt is two or more selected from the group consisting of an aliphatic chain-containing ammonium salt, an aromatic ring-containing ammonium salt and a guanidino group-containing ammonium salt.

3. The perovskite solar cell of claim 2, wherein the ammonium salt is selected from the group consisting of: 1, 4-butanediamine hydroiodide, octylammonium chloride, butylammonium iodide, tert-butylammonium chloride, 3-pyridylmethylamine bromide, isobutylammonium bromide, octylammonium bromide, 2' - (ethylenedioxy) diethylamine hydrobromide, phenethylammonium chloride, phenethylammonium iodide, 1, 4-phenylenediamine hydroiodide, benzylammonium iodide, phenylammonium bromide, 1, 4-xylylenediamine iodide, guanidinium hydrobromide, guanidinium thiocyanate.

4. The perovskite type solar cell according to claim 1, wherein the solvent for the mixed solution of the ammonium salt is a weakly polar organic solvent.

5. The perovskite solar cell of claim 1, wherein the perovskite light absorbing layer material has the general chemical formula ABX₃Wherein A is one or a mixture of several of organic ammonium salt cations and metal cations; b is Pb² ⁺、Sn²⁺、Ge²⁺、Sb³⁺、Bi³⁺、Ag⁺、Au³⁺、Ti⁴⁺At least one of; x is Cl^-、Br^-、I^-Or one or more halogen-like substances.

6. The perovskite solar cell of claim 1, wherein different ammonium salts form different non-uniform gradient distributions in the perovskite light absorbing layer.

7. A method of manufacturing a perovskite solar cell as claimed in any one of claims 1 to 6, comprising the steps of:

1) providing a transparent substrate and a transparent electrode;

2) sequentially preparing a first charge transport layer on the transparent electrode;

5) a top electrode is prepared on the second charge transport layer.

8. The production method according to claim 7, wherein in step 3), the method of post-treating the perovskite light absorbing layer is a spin coating method or a dipping method, wherein: the spin coating method is to spin coat a mixed solution of a plurality of ammonium salts on the perovskite light absorption layer in an oxygen-free atmosphere, and then to carry out annealing treatment at 50-100 ℃; the soaking method is that the perovskite light absorption layer is soaked in mixed solution of various ammonium salts for 1-6 seconds in an oxygen-free atmosphere, and then annealing treatment is carried out at 50-100 ℃.

9. The method according to claim 7, wherein in the step 3), the plurality of ammonium salts are dissolved in a weak polar solvent of alcohols, ketones or hydrocarbons to prepare a mixed solution of the plurality of ammonium salts, wherein the concentration of each ammonium salt is 2 to 5 mg/mL.