CN106571427A - Novel photoelectric conversion composite material sol and preparation method thereof - Google Patents

Abstract

The invention relates to a novel photoelectric conversion composite material sol and a preparation method thereof. For the first time, a perovskite-type photoelectric conversion composite material sol is prepared by mixing cyclophosphazene halide and methylamine. The novel photoelectric conversion composite material sol of the invention is composed of lead halide, cyclophosphazene halide, methylamine hydrohalide, dehydration catalyst and organic solvent. The present invention prepares novel perovskite photoelectric conversion materials with cyclic phosphazene halides, the range of preparation process conditions is relatively wide, and the synthesized photoelectric conversion materials have better environmental stability, which can expand the light absorption wavelength range of sunlight and improve photoelectricity. The conversion efficiency is 1.8%‑2.2%.

Description

A new photoelectric conversion composite material sol and its preparation method

technical field

The invention relates to a novel photoelectric conversion composite material sol and a preparation method thereof, especially to prepare a perovskite-type photoelectric conversion composite material sol by mixing cyclophosphazene halide and methylamine, so as to adjust the band gap and Improving photoelectric conversion efficiency belongs to the field of new energy and new materials.

technical background

Solar cells based on organic metal halide perovskite structured light-absorbing materials are called perovskite solar cells. At present, their photoelectric conversion efficiency has exceeded 20%, and it is expected to reach 50% in the future. Perovskite solar cells are usually composed of five parts: transparent conductive glass, dense layer, perovskite light absorbing layer, hole transport layer, and metal back electrode. The thickness of the perovskite light-absorbing layer is generally 200-600nm, and its main function is to absorb sunlight and generate electron-hole pairs, and can efficiently transport electron-hole pairs.

The typical molecular formula of perovskite light-absorbing materials is AMX ₃ , where A represents monovalent ammonium ions or metal ions, M represents metal cations, and X represents halogen anions. At present, the research on metal cations and halogen anions is relatively thorough at home and abroad, but there are few studies on the composition, structure and mechanism of action of monovalent ammonium ions.

At present, there are many studies on the perovskite-type light-absorbing material methylamine lead iodide (CH ₃ NH ₃ PbI ₃ ), which is an inorganic-organic double salt or coordination compound formed by the reaction of methyl iodide and lead iodide. , it is also a semiconductor light-absorbing material with a band gap of about 1.5eV, which can fully absorb visible light with a wavelength of 400-800nm, and has the characteristics of good light absorption performance, simple preparation and high photoelectric conversion efficiency. Its main shortcomings are: (1) poor temperature resistance, requiring the heat treatment temperature of the light-absorbing layer to be less than 150°C, at which temperature the additives in the preparation of the light-absorbing layer cannot be completely decomposed; (2) poor environmental stability, easy to It is decomposed by moisture, ultraviolet light or catalyst in the atmosphere; (3) the wavelength range of absorbed light is limited to the visible light region, and hardly absorbs ultraviolet light and infrared light; (4) the film-forming performance is not good, and loose and coarse crystals are easily formed. Difficult to apply evenly over a large area.

To improve the performance of perovskite-type light-absorbing materials, we can start with the composition design of perovskite-type light-absorbing materials. For example, the Qingdao Institute of Biology of the Chinese Academy of Sciences used C1-C4 primary amines, formamidine or their mixtures to prepare perovskite structured light-absorbing materials to obtain good photoelectric conversion efficiency; Xiamen University invention patent CN106058060 (2016-10-25) disclosed the use Amine and formamidine are mixed to prepare perovskite structured light-absorbing material films; Wuhan University of Technology invention patent CN105742502 (2016-07-06) discloses the use of iodophenethylamine, stannous iodide and lead iodide to prepare band gap adjustable Perovskite structured light absorbing material; Huazhong University of Science and Technology invention patent CN103762344 (2014-04-30) discloses the preparation of perovskite structured light absorbing material by mixing aminobutyric acid amphoteric molecules and methylamine; US patent US20150249170 (2015-09-03 ) discloses the use of long-chain organic amines to prepare perovskite structured light-absorbing materials, but does not disclose the details of long-chain organic amines; US Patent US20150200377 (2015-07-16) discloses the use of a series of primary, secondary, tertiary, and quaternary ammonium compounds Preparation of perovskite structured light-absorbing materials, but did not provide examples of amine compounds; Chinese patent CN103554171 (2014-02-05) discloses the use of 1-aminopyridine Schiffer base and lead chloride as a potential dielectric material; Chinese patent CN102337593 (2012-02-01) discloses a preparation method of a 1-ethyl-3-methylimidazolium iodine tribromide perovskite structured light-absorbing material.

To improve the performance of perovskite light-absorbing films, we can also start with the structure of perovskite light-absorbing materials. For example, the invention patent WO2016126211 (2016-08-11) of Nanyang Technological University in Singapore discloses that perovskite light-absorbing materials and nano-clay particles form a sol in an organic solvent, and nanoparticles are used as crystal seeds to improve the performance of perovskite light-absorbing materials. Microstructure and film-forming properties; Tianjin Vocational University patent CN105789339 (2016-07-20) discloses that perovskite light-absorbing materials and nano-silicon dioxide particles form a sol in an organic solvent, and the nanoparticles are used as light-absorbing material seeds and skeleton materials, one step to obtain a smooth and uniform light-absorbing layer; Nankai University invention patent CN104218109 (2014-12-17) discloses mixing polyvinylpyrrolidone with perovskite light-absorbing materials to improve the microstructure of perovskite light-absorbing materials And film-forming performance, greatly improving the photoelectric conversion efficiency.

Although the photoelectric conversion efficiency data of perovskite solar cells are still being refreshed, the performance of perovskite photoelectric conversion materials or light absorption materials formed by inorganic-organic hybridization is unstable, and cannot meet the test requirements for resistance to heat and humidity and ultraviolet light. Some departments have studied the use of cesium, lithium or ammonium cations instead of methylamine to prepare all-inorganic perovskite light-absorbing materials. Although the environmental stability of perovskite-type light-absorbing materials can be improved, the photoelectric conversion efficiency is greatly reduced.

Cyclophosphazene is a kind of cyclic compound with nitrogen and phosphorus double bonds alternately arranged as the main chain. Its properties are between inorganic compounds, organic compounds and polymer compounds, and it can be polymerized to form inorganic polymer compounds. The most common is the cyclic phosphazene halide, the molecular formula is (NPX ₂ ) _n , where n=3-7, X=Cl, Br, I, F or a mixture thereof. It can also be used as inorganic cations of perovskite photoelectric conversion materials or light absorbing materials, and form new photoelectric conversion materials with lead halide, which is expected to improve the environmental stability and photoelectric conversion efficiency of perovskite photoelectric conversion materials at the same time. Relevant research and exploration have not yet been carried out.

The first phosphazene halide produced is hexachlorocyclotriphosphazene (NPCl ₂ ) ₃ , which is produced by heating reflux reaction of phosphorus pentachloride and ammonium chloride in tetrachloroethane (or chlorobenzene) solvent for a certain period of time. have to. Hexachlorocyclotriphosphazene is a six-membered ring with alternating nitrogen and phosphorus. It is almost a planar ring. The chlorine on phosphorus is not on the plane formed by nitrogen and phosphorus. Many of its properties are similar to benzene.

Before the synthesis of cyclodiphosphazene was reported in the literature, hexachlorocyclotriphosphazene was considered to be the smallest ring in phosphazene. Other cyclochlorophosphazene halides that have been prepared so far include N ₄ P ₄ Cl ₈ , N ₅ P ₅ Cl ₁₀ , N ₆ P ₆ Cl ₁₂ , N ₇ P ₇ Cl ₁₄ and N ₈ P ₈ Cl ₁₆ . Generally, among (NPCl ₂ ) _n phosphazene halides, when n=3-7, it is a solid cyclic phosphazene halide; when n=8-15, it is an oily linear phosphazene halide. Hexabromocyclotriphosphazene can be prepared by the reaction of phosphorus pentabromide and ammonium bromide, and the synthesis of octabromocyclotetraphosphazene has also been reported. Phosphate eye chloride reacts with sodium iodide to generate sodium chloride, and it is speculated that iodocyclophosphazene may be generated. At present, perfluoro-substituted cyclophosphazenes with n=3-7 have been prepared, and various mixed-substituted cyclophosphazenes with different halogens have also been prepared.

There is a lone electron pair on the nitrogen atom in the cyclic phosphazene halide, which may interact with the metal atom, and the group on the phosphorus atom can also interact with the metal compound to form a phosphazene metal compound. Cyclic phosphazene halides can interact with main group elements and certain transition metal compounds, e.g., [N ₃ P ₃ Cl ₅ ] ⁺ [ AlCl ₄ ] ^- purely interionic; while [N ₃ P ₃ Br ₆ ] _{[ AlBr 3 ] The two compounds} are _interacted by _{covalent bonds ;} N participates in the coordinated structure. Cyclic phosphazene halides can also form cations with H ⁺ , while metal compounds are the corresponding anions.

Contents of the invention

The purpose of the present invention is to provide a new photoelectric conversion composite material sol, improve its performance from two aspects of the composition and microstructure of the perovskite photoelectric conversion material, so as to meet the needs of large-area perovskite solar cell light absorption layer preparation.

The present invention uses cyclophosphazene halide and methylamine for the first time to prepare perovskite-type photoelectric conversion composite material sol to adjust the band gap and film-forming performance of perovskite light-absorbing materials. The sol is composed of lead halide (PbX ₂ ), cyclophosphazene Halide (NPX ₂ ) _n , methylamine hydrohalide (CH ₃ NH ₃ X), dehydration catalyst and organic solvent, the molar ratio of each component in the sol is as follows:

PbX ₂ 1

(NPX ₂ ) _n 0.1-0.5

CH ₃ NH ₃ X 0.5-0.8

Dehydration catalyst 0.01-0.05

Nano oxide 0.01-0.05

Organic solvents 20-60.

In the present invention, PbX ₂ is the raw material for forming the perovskite-type photoelectric conversion composite material (NPX ₂ ) _n PbX ₂ and CH ₃ NH ₃ PbX ₃ , and is a commercially available chemical reagent.

The cyclic phosphazene halide in the present invention is a cyclic phosphazene halide with the molecular formula (NPX ₂ ) _n , wherein, n=3-7, X=Cl, Br, I, F or a mixture thereof. Lead halide can react with a halogen atom in the cyclophosphazene halide molecule to form a three-dimensional perovskite photoelectric conversion material N _n P _n X _2n-1 PbX ₃ , and lead halide can also react with the two atoms in the cyclophosphazene halide molecule. The perovskite photoelectric conversion material N _n P _n X _2n-2 PbX ₄ with a two-dimensional layered structure reacts with a halogen atom, and may also react with multiple halogen atoms in the cyclic phosphazene halide molecule to form a complex structure, making the formation of The photoelectric conversion material has a wider light absorption range of sunlight wavelength. Due to the stability of cyclophosphazene, the perovskite photoelectric conversion material formed by it will have better resistance to heat and humidity and UV decomposition.

The methylamine hydrohalide salt in the sol of the present invention is produced by the reaction of methylamine and hydrohalic acid.

The dehydration catalyst in the present invention is one of magnesium methylate, magnesium ethylate, triethylaluminum or aluminum alkoxide, which is a commercially available chemical reagent. It is used to maintain the sol in weak alkalinity, promote the formation of complex compounds between cyclic phosphazene halide and lead halide, and produce nano oxide particles at the same time.

The nano-oxide in the sol of the present invention is a nano-oxide particle generated by hydrolysis of a dehydration catalyst, which can be used as a crystal nucleus when forming a film of a perovskite photoelectric conversion material, changing the microstructure of the photoelectric conversion material and preventing the formation of coarse crystals.

The organic solvent in the present invention is acetonitrile, dimethylformamide, γ-butyrolactone or a mixture of dimethyl sulfoxide and C1-C4 fatty alcohol. Polar solvents are used to dissolve PbX ₂ , (NPX ₂ ) _n PbX ₂ and CH ₃ NH ₃ PbX ₃ , and C1-C4 fatty alcohols are used as dilution solvents, which are commercially available chemical reagents.

There are lead halide molecules, methylamine hydrohalide molecules and cyclic phosphazene halide molecules in the sol of the present invention, as well as a small amount of (NPX ₂ ) _n PbX ₂ and CH ₃ NH ₃ PbX ₃ micelles with inorganic nanoparticles as crystal nuclei Or crystal seeds, when the solvent volatilizes, under the joint drive of coordination, hydrogen bonding, and van der Waals forces, lead halide molecules, methylamine hydrohalide molecules and cyclophosphazene halide molecules self-assemble on the seeds to form calcium Titanium-type photoelectric conversion composite thin film.

The reaction mechanism of lead halide molecule and cyclic phosphazene halide molecule in the present invention is still unclear, adopts methylamine to maintain solution to carry out catalytic complexation reaction under alkaline conditions earlier among the present invention, then adds hydrohalic acid to neutralize methylamine, The complexation reaction is catalyzed under neutral conditions, and finally a dehydrating agent is added to further catalyze the complexation reaction. Excessive methylamine hydrohalide can react with cyclic phosphazene halide, so the range of process conditions in the preparation process is relatively wide, and the product performance is stable and relatively easy to control.

Another object of the present invention is to provide a method for preparing a novel photoelectric conversion composite material sol, the technical solution comprising the following steps:

(1) Add polar organic solvent, methylamine and PbX ₂ into the glass reactor respectively, stir at 60-80°C until completely dissolved, then add cyclophosphazene halide, and control the molar ratio of raw materials: PbX ₂ : Methylamine: cyclic phosphazene halide = 1:0.8-0.9: 0.1-0.5, stirred for 12-24 h to obtain (NPX ₂ ) _n PbX ₂ solution;

(2) Add hydrohalic acid solution to the above reaction solution, control the molar ratio of raw materials: methylamine: HX = 1:1, continue to stir and react for 12-24 h, cool to room temperature, and obtain (NPX ₂ ) _n PbX ₂ and CH ₃ NH ₃ PbX ₃ mixed solution;

(3) Add a dehydration catalyst to the above reaction solution, and control the molar ratio of raw materials: PbX ₂ : dehydration catalyst = 1:0.02-0.05, and the dehydration catalyst reacts with the water in the solution for 1-4 hours to form a sol of nano-oxide particles. The diameter is 5-10nm;

(4) Add C1-C4 fatty alcohol to the above reaction solution until PbX ₂ is saturated and precipitated, making the sol turbid, and then reflux at 80-100°C for 12-24 h to generate (NPX ₂ ) _n PbX ₂ and CH ₃ The sol of NH ₃ PbX ₃ seed crystals, the mass percent concentration of solids in the sol is 10%-20%;

(5) Precisely filter the composite material sol with a biscuit ceramic funnel, drop the sol on a 200mm×300mm fluorine-doped tin dioxide conductive glass substrate with a dense layer with a dropper, and spread it evenly with a stainless steel wire bar coater, Let the solvent evaporate and dry in the air, and finally dry with hot air at 110-150°C for 30 minutes to form a black perovskite light-absorbing layer with a smooth surface, and assemble a perovskite solar cell for testing, using (NPX ₂ ) _n PbX ₂ and CH ₃ NH The photoelectric conversion efficiency of ₃ PbX ₃ composite material is 1.8%-2.2% higher than that of pure CH ₃ NH ₃ PbX ₃ material.

The light absorption performance of the photoelectric conversion material film in the present invention is determined by the absorption rate of the sample in the wavelength range of 250-1100nm with a Lambda 920 spectrophotometer; the perovskite solar cell assembly for the test refers to the Chinese invention patent application 2019109316795 (2016-10 The method adopted in -25) is carried out; the solar cell efficiency is tested with simulated sunlight using a custom-made small solar cell module tester.

The beneficial effects of the present invention are reflected in:

(1) The present invention improves the performance of perovskite-type photoelectric conversion composition and microstructure to meet the needs of large-area perovskite solar cell light absorption layer preparation;

(2) The present invention uses cyclophosphazene halides to prepare new perovskite photoelectric conversion materials. The range of preparation process conditions is relatively wide. The synthesized photoelectric conversion materials have better environmental stability and can reduce the cost of large-area perovskite solar cells. size effect;

(3) The present invention mixes cyclic phosphazene halides and methylamine to prepare perovskite-type photoelectric conversion materials, which can expand the light absorption wavelength range of sunlight and increase the photoelectric conversion efficiency by 1.8%-2.2%.

detailed description

Example 1

Add 246g (6mol) of acetonitrile, 8.29g (0.08mol) of methanol solution of methylamine with a concentration of 30% by mass percentage and 46.1g (0.1mol) of lead iodide respectively in a stirred 500mL glass reactor, at 60-80 Stir at ℃ for 2 hours until completely dissolved, then add 6.95 g (0.02 mol) of hexachlorocyclotriphosphazene, continue stirring for 24 hours to obtain N ₃ P ₃ Cl ₅ PbI ₂ Cl solution; then add 50% concentration of 46.1 g (0.08 mol) of hydroiodic acid, continued stirring for 12 h, cooled to room temperature, and obtained a mixed light-absorbing solution of N ₃ P ₃ Cl ₅ PbI ₂ Cl and CH ₃ NH ₃ PbI ₃ .

Add 29.2 g (0.05 mol) of magnesium methoxide solution with a mass percent concentration of 20% to the above reaction solution, and react the magnesium methoxide with water for 4 hours to form a magnesium oxide nanoparticle sol with a particle size of 10 nm. Continue to add absolute ethanol until PbI ₂ is saturated and precipitated, making the sol slightly turbid, and then reflux at 75-80°C for 24 h to generate a sol containing N ₃ P ₃ Cl ₅ PbI ₂ Cl and CH ₃ NH ₃ PbI ₃ seeds . Use a G5 bisque ceramic funnel to precisely filter the sol of the light-absorbing material, use a dropper to drop the sol on a 200mm×300mm fluorine-doped tin dioxide conductive glass substrate with a dense layer, and apply it evenly with a stainless steel wire bar coater, so that The solvent is evaporated and dried, and finally dried with hot air at 110-150°C for ₃₀ minutes to form a black _perovskite light absorption layer with a smooth surface, which is used as a _perovskite solar cell for assembly and testing. Efficiency increased by 1.8%.

Example 2

Add 365.5g (5mol) of dimethylformamide, 5.18g (0.05mol) of methanol solution of methylamine with a concentration of 30% by mass and 46.1g (0.1mol) of lead iodide in a stirred 500mL glass reactor. , stirred at 60-80°C for 2 hours until completely dissolved, then added 17.4 g (0.05 mol) of hexachlorocyclotriphosphazene, and continued stirring for 24 hours to obtain N ₃ P ₃ Cl ₅ PbI ₂ Cl solution; Divide 28.8 g (0.05 mol) of hydroiodic acid with a concentration of 50%, continue to stir the reaction for 16 h, and cool to room temperature to obtain a mixed light-absorbing solution of N ₃ P ₃ Cl ₅ PbI ₂ Cl and CH ₃ NH ₃ PbI ₃ .

Add 29.2 g (0.05 mol) of magnesium methoxide solution with a mass percent concentration of 20% to the above reaction solution, and react the magnesium methoxide with water for 4 hours to form a magnesium oxide nanoparticle sol with a particle size of 10 nm. Continue to add absolute ethanol until PbI ₂ is saturated and precipitated, making the sol slightly turbid, and then reflux at 75-80°C for 24 h to generate a sol containing N ₃ P ₃ Cl ₅ PbI ₂ Cl and CH ₃ NH ₃ PbI ₃ seeds . Use a G5 bisque ceramic funnel to precisely filter the sol of the light-absorbing material, use a dropper to drop the sol on a 200mm×300mm fluorine-doped tin dioxide conductive glass substrate with a dense layer, and apply it evenly with a stainless steel wire bar coater, so that The solvent is evaporated and dried, and finally dried with hot air at 110-150°C for ₃₀ minutes to form a black _perovskite light absorption layer with a smooth surface, which is used as a _perovskite solar cell for assembly and testing. Efficiency increased by 2.2%.

Claims (4)

1. A novel photoelectric conversion composite material sol is characterized in that a perovskite-type photoelectric conversion composite material sol is prepared by mixing cyclophosphazene halide and methylamine, and is composed of lead halide, cyclophosphazene halide, methylamine hydrohalic acid Salt, dehydration catalyst and organic solvent composition, each component molar ratio in the sol is as follows: Lead halide 1 Cyclophosphazene halide 0.1-0.5 Methylamine hydrohalide 0.5-0.8 Dehydration catalyst 0.01-0.05 Nano oxide 0.01-0.05 Organic solvents 20-60. 2. novel photoelectric conversion composite material sol as claimed in claim 1, is characterized in that cyclophosphazene halide is the cyclophosphazene halide of molecular formula (NPX ₂ ) _n , wherein, n=3-7, X=Cl, Br, I, F or mixtures thereof. 3. The new photoelectric conversion composite material sol according to claim 1, characterized in that the perovskite photoelectric conversion material formed by the reaction of lead halide and cyclophosphazene halide in the sol is a three-dimensional structure of N _n P _n X _2n-1 PbX ₃ or N _n P _n X _2n-2 PbX ₄ with a two-dimensional structure, wherein n=3-7. 4. A preparation method of the novel photoelectric conversion composite material sol according to claim 1, characterized in that the preparation technical solution comprises the following steps: (1) Add polar organic solvent, methylamine and PbX ₂ into the glass reactor respectively, stir at 60-80°C until completely dissolved, then add cyclophosphazene halide, and control the molar ratio of raw materials: PbX ₂ : Methylamine: cyclic phosphazene halide = 1:0.5-0.9: 0.1-0.5, stirred for 12-24 h to obtain (NPX ₂ ) _n PbX ₂ solution; (2) Add hydrohalic acid solution to the above reaction solution, control the molar ratio of raw materials: methylamine: HX = 1:1, continue to stir and react for 12-24 h, cool to room temperature, and obtain (NPX ₂ ) _n PbX ₂ and CH ₃ NH ₃ PbX ₃ mixed solution; (3) Add a dehydration catalyst to the above reaction solution, and control the molar ratio of the raw materials: PbX ₂ : dehydration catalyst = 1:0.02-0.05, and the dehydration catalyst reacts with the water in the solution for 1-4 hours to form a sol of nano-oxide particles. The diameter is 5-10nm; (4) Add C1-C4 fatty alcohol to the above reaction solution until PbX ₂ is saturated and precipitated, making the sol turbid, and then reflux at 80-100°C for 12-24 h to generate (NPX ₂ ) _n PbX ₂ and CH ₃ The sol of NH ₃ PbX ₃ seed crystals, the mass percent concentration of solids in the sol is 10%-20%; (5) Precisely filter the composite material sol with a biscuit ceramic funnel, drop the sol on a 200mm×300mm fluorine-doped tin dioxide conductive glass substrate with a dense layer with a dropper, and spread it evenly with a stainless steel wire bar coater, Let the solvent evaporate and dry in the air, and finally dry with hot air at 110-150°C for 30 minutes to form a black perovskite light-absorbing layer with a smooth surface, and assemble a perovskite solar cell for testing, using (NPX ₂ ) _n PbX ₂ and CH ₃ NH The photoelectric conversion efficiency of ₃ PbX ₃ composite material is 1.8%-2.2% higher than that of pure CH ₃ NH ₃ PbX ₃ material.