CN112054126B - Cesium-tin-iodine film, and preparation method and application thereof - Google Patents

Abstract

The invention discloses a cesium tin iodine film, a preparation method and application thereof, and Cs₂SnI₆The preparation method of the film comprises the following steps: (1) adding cesium iodide and tin iodide into DMSO or a mixed solvent of DMSO and DMF, stirring and dissolving at 20-70 ℃ to prepare Cs₂SnI₆Precursor solution; (2) the precursor solution prepared in the step (1) is added into N₂Standing and aging for 3-10 days in the atmosphere, and performing spin coating deposition on the substrate to obtain a precursor film; (3) placing the precursor film obtained in the step (2) on a hot bench with the temperature of 30-70 ℃ for standing for 1.0-40 min; then putting the mixture on a spin coater, dripping 40-100 mu L of supplement solution, and spin-drying the solution after dripping; (4) annealing the film obtained in the step (3) to obtain Cs₂SnI₆A film.

Description

Cesium-tin-iodine film, and preparation method and application thereof

Technical Field

The invention belongs to the field of perovskite photodetectors, and particularly relates to a cesium tin iodine thin film, and a preparation method and application thereof.

Background

Organic-inorganic hybrid lead-perovskite halide (OIHPs) is a novel photoelectric material appearing in recent years, wherein organic-inorganic hybrid perovskite thin film Photodetectors (PDs) benefit from the characteristics of low preparation and material cost, simple preparation process, easy flexible integration and the like, and the development is rapid. Currently, most of the PDs studied at present mainly adopt toxic lead element, which is easy to cause environmental pollution. Tin element is often adopted to replace lead in the non-lead perovskite thin film photoelectric detector, but the tin in the pure tin perovskite of the photoelectric detector with better performance is + 2-valent, and the tin is easily oxidized into + 4-valent tin in the air, so that the performance of the perovskite thin film photoelectric device is easily seriously reduced. The development of novel and stable tin-based perovskite thin films and photoelectric detectors has important scientific significance and application value.

Whereas + 2-valent tin, + 4-valent tin forms a double perovskite phase when forming a perovskite, with cesium tin iodide (Cs)₂SnI₆) Exist in the form of (1). The reported value of the band gap of the bulk material is more between 1.45 and 1.6eV, and the bulk material is a photoelectric material with high potential. However, the current research reports Cs₂SnI₆In the preparation, a vacuum evaporation method is mainly adopted, namely cesium iodide and tin iodide are evaporated on a substrate, and then cesium tin iodide Cs is generated through an annealing reaction₂SnI₆The perovskite phase of (a). The vacuum evaporation method has the advantages of high requirements on equipment conditions, high energy consumption and high cost, and is not beneficial to large-scale industrial application. Also, the first synthesis of Cs-Sn-I by solution method has been reported in part₂SnI₆The powder is dissolved in a certain solvent, and a thin film is prepared by spin coating. The process adopts a liquid phase process, reduces the cost, but has the disadvantages of complicated preparation process, low yield and poor product solubility. When the conventional organic-inorganic hybrid perovskite thin film is prepared, precursors of the conventional organic-inorganic hybrid perovskite thin film are directly mixed and dissolved, the precursor thin film is prepared in a spin coating mode, and then a perovskite phase is generated through annealing, so that the process is simple and easy to control, the quality is high, and the film is suitable for being used as an efficient thin film photoelectric device. However, Cs₂SnI₆Similar processes have been rarely reported for thin films.

Disclosure of Invention

The invention aims at the existing Cs₂SnI₆The limitation of the film preparation process provides a simple solution method for preparing Cs₂SnI₆Thin film, and the use of the thin film as an absorption sensitive layer of a perovskite photodetector. By Cs₂SnI₆The precursor mixed solution is used as spin coating liquid to prepare a precursor film, and the Cs is generated through certain tin iodide supplement and annealing₂SnI₆The film has good crystalline phase and higher phase purity, is compact and bright and is suitable forAnd the material is used as a photoelectric detector or a solar cell.

Based on the purpose, the invention adopts the following technical scheme:

solution method for preparing Cs₂SnI₆A method of making a film comprising the steps of:

(1) adding cesium iodide and tin iodide into DMSO or a mixed solvent of DMSO and DMF, stirring and dissolving at 20-70 ℃ to prepare Cs₂SnI₆Precursor solution;

(2) the precursor solution prepared in the step (1) is added into N₂Standing and aging for 3-10 days in the atmosphere, and performing spin coating deposition on the substrate to obtain a precursor film; the aging is to increase DMSO and metal cation Cs in the solution⁺And Sn⁴⁺The complexing ability of the composite is beneficial to improving the quality of the film.

(3) Placing the precursor film obtained in the step (2) on a hot bench with the temperature of 30-70 ℃ and heating for 1.0-40 min; then putting the mixture on a spin coater, and dripping 40-100 mu L of supplement solution, wherein the solution is dried by spin coating at 1500-3000 r/min;

(4) annealing the film obtained in the step (3) at the temperature of 150-200 ℃ for 10-300 s to obtain Cs₂SnI₆A film.

Further, the molar ratio of cesium iodide to tin iodide in the step (1) is (1-2): (1-2), and when a mixed solvent of DMSO and DFM is used, the volume ratio of DMSO to DFM is 1-6:1, and Cs in the precursor solution₂SnI₆The concentration is 0.2mol/L-1.0 mol/L.

Further, the spin coating deposition in the step (2) adopts a two-step spin coating method, wherein the first-stage rotating speed is 1000-; at 20-60 seconds after the start of the second stage of rotation, 100-500. mu.L of an anti-solvent, which is isopropanol, chlorobenzene, toluene, ethanol or ethyl acetate, is quickly dropped.

Further, in the step (3), the component of the supplementary solution is an isopropanol solution of tin iodide, and the concentration is 1mg/ml-10 mg/ml.

Prepared by the preparation methodCs of (A)₂SnI₆A film.

The above Cs₂SnI₆Use of a thin film in a photodetector, said Cs₂SnI₆The film is used as a light absorption layer of a photoelectric detector, and specifically, the photoelectric detector sequentially comprises FTO and TiO from top to bottom₂Porous layer, Cs₂SnI₆Thin film layer, spiro-OMeTAD layer, gold electrode, Cs₂SnI₆The thickness of the thin film layer is 150-300 nm.

By Cs₂SnI₆The preparation process of the photoelectric detector with the film as the light absorbing layer is as follows. First of all, Cs prepared as described above₂SnI₆The hole-collecting layer (spirobifluorene) was spin-coated on the thin film at 3000-4000 rpm, then 10^-4And (5) evaporating a 100nm gold electrode under Pa vacuum to finish the preparation of the device. Wherein the Cs2SnI6 film is a light absorption layer, and the Cs is obtained by the preparation process₂SnI₆The thickness of the film is 150 nm-300 nm.

The invention has the beneficial effects that:

the invention adopts a solution film forming method to prepare the Cs suitable for being used as the light absorption layer of the perovskite photoelectric detector through a multi-step spin coating process₂SnI₆A film. The film has good crystallization property and crystal phase purity, wide absorption spectrum range and high absorption intensity, and is a potential photoelectric detector material.

The invention aims at the problems that the stability of the currently reported cesium tin (stannous) iodine film in the air is poor and Cs is₂SnI₆The current situation that the preparation scheme of the thin film solution method is lacked is to develop a simple and effective multi-step solution method film forming and post-treatment process to obtain Cs₂SnI₆The film is mainly characterized in that the band gap of the film prepared by the method is about 1.5eV, the film is suitable for being used as a light absorption layer of a photoelectric detector, and 4 is used as the light absorption layer⁺The tin oxide exists stably in the air, and the thin film does not have the problem of easy oxidation. The film obtained by the method has smooth and compact surface, no pin hole, high purity of double perovskite phase and no cesium iodide impurity phase basically. The absorption spectrum response range is wide, and the absorption intensity in the light response range is generally large; of filmsThe steady-state photoluminescence spectrum and the absorption spectrum have good correspondence. When the titanium dioxide porous membrane is adopted as the substrate and the electron collecting layer, the Cs prepared by the method₂SnI₆When the film is used as a light absorption layer and spirobifluorene (spiro-OMeTAD) is used as a hole collection layer, the initial on-off ratio of the prepared film photoelectric detector is 30.

Drawings

FIG. 1 shows Cs prepared in example 1₂SnI₆A Scanning Electron Microscope (SEM) image of the film;

FIG. 2 shows Cs prepared in example 1₂SnI₆X-ray diffraction pattern (XRD) of the film;

FIG. 3 shows Cs prepared in example 1₂SnI₆A light absorption spectrum (Abs) and a photoluminescence spectrum (PL) of the thin film;

FIG. 4 shows Cs prepared in example 1₂SnI₆The film is a structural schematic diagram and a current-voltage performance curve of a photoelectric detector of a light absorption layer;

FIG. 5 shows Cs prepared in example 1₂SnI₆The film is a photo-voltage pattern on the surface of the photodetector of the light absorbing layer.

Detailed Description

In order to make the technical purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention are further described below with reference to the accompanying drawings and specific embodiments.

Example 1

Solution method for preparing cesium tin iodine (Cs)₂SnI₆) A method of making a film comprising the steps of:

(1) 117mg of cesium iodide and 282mg of tin iodide were weighed, and 0.5ml of a mixed solvent of DMSO and DMF (wherein the volume ratio of DMSO to DMF was 3: 1) was added thereto, and the mixture was dissolved by stirring at 60 ℃ and 1000 rpm to prepare 0.45mol/L of Cs₂SnI₆The precursor solution of (1);

(2) placing the solution prepared in the step (1) for 7 days in a nitrogen atmosphere for aging;

(3) 60 μ L of the aged solution was dropped onto a clean FTO glass substrate (1.6) by using a pipettemm 1.8 mm), Cs was prepared by spin-coating₂SnI₆Film, specifically, the first stage rotation speed is 1000 rpm, and the time is 10 seconds; the rotating speed of the second stage is 2500 rpm, and the time is 60 seconds; at 30 seconds after the start of the second stage rotation, 200. mu.L of isopropyl alcohol was quickly dropped. Then the substrate is placed on a hot bench with the temperature of 50 ℃ to be heated for 20 minutes;

(4) after the substrate is naturally cooled to room temperature, 50 microliter of 5mg/ml tin iodide isopropanol solution is dripped on the substrate, and then the substrate is spin-coated at the rotating speed of 2000 r/min to be dry;

(5) the film obtained above was annealed at 180 ℃ for 240 seconds to obtain black Cs₂SnI₆A film;

cs prepared in this example₂SnI₆The film is applied to a light absorption layer of a photoelectric detector: first, a titania porous layer precursor solution and a spirobifluorene solution are prepared. Preparing a titanium dioxide precursor solution: taking out 1g of titanium dioxide colloid (Dyesol, 18NR-T, 20 nm) to be dissolved in 10ml of ethanol, and then carrying out ultrasonic treatment at room temperature for 15 minutes, and stirring at room temperature for 20-30 hours to obtain a titanium dioxide precursor solution; preparation of spirobifluorene solution: 94.5mg of spiro, 45.7mg of Li-TFSI and 39.2. mu.L of TBP were taken out and dissolved in 1.307ml of chlorobenzene solvent to obtain a spirobifluorene solution, and a titanium dioxide porous membrane was prepared on a clean FTO (1.6 mm. times.1.8 mm) conductive substrate by a spin coating method at a rotation speed of 3000 rpm for 30 s. Then the substrate is placed on a hot bench with the temperature of 280 ℃ to be heated for 10 minutes, then the substrate is placed into a muffle furnace to be sintered for 1 hour at the temperature of 450 ℃ to obtain a titanium dioxide porous layer with the thickness of 30nm, and then the method of the embodiment is used for preparing Cs with the thickness of 300nm on the titanium dioxide porous film₂SnI₆The film is prepared into a cavity collecting layer (spirobifluorene) by a spin coating method, the rotating speed is 2500 rpm, the time is 30s, and the cavity collecting layer (spirobifluorene) with the thickness of 200nm is obtained, and the thickness is 10 DEG^-4And (5) evaporating a 100nm gold electrode under Pa vacuum to finish the preparation of the device.

The XRD results of the film are shown in fig. 2. Wherein the first three strong peaks correspond to Cs₂SnI₆The (222) (004) and (044) crystal faces of the film, no other impurity phase exists,indicating that the solution method produces Cs₂SnI₆The film has good crystallinity and high purity. The surface topography of the film observed by a scanning electron microscope is shown in FIG. 1. It can be seen that the deposited film consists of large particles with a diameter of about 1 μm, and the film is dense and uniform without significant pores. As shown in FIG. 3, the absorption spectrum of the film measured by an ultraviolet-visible near-infrared spectrophotometer is very strong in absorption in the range of 350nm to 800nm, and the high-intensity absorption range (400 nm to 700 nm) is wide. After 750 nm, there was a significant decrease in the absorption intensity, calculated to yield Cs prepared by this method₂SnI₆The optical band gap of the film is 1.55 eV. The corresponding photoluminescence spectrum (PL spectrum) shows that the fluorescence peak of the film is at 767nm and is consistent with the corresponding absorption edge, and the stronger fluorescence intensity shows that the non-radiative recombination defect density in the film is lower, and the film has good electrical properties. The Cs prepared in this example was used with titanium dioxide as the electron transport layer and spirobifluorene as the hole-collecting layer₂SnI₆The current-time curve and the surface photovoltage of the photodetector with the thin film as the absorption layer are shown in fig. 4 and 5. Fig. 4 shows a waveform of the instantaneous light response under periodic illumination, which has a regular light response curve and is calculated to have a switching ratio of 30. FIG. 5 shows that the surface photovoltage spectrum is in the range of 360nm-920nm, and the film has photovoltage, which means that under the radiation of the wave band, the interface accumulates positive charge and has higher charge mobility. Is a material very suitable for being used as a photoelectric detector.

Example 2

Solution method for preparing cesium tin iodine (Cs)₂SnI₆) A method of making a film comprising the steps of:

(1) 468mg of cesium iodide and 564mg of tin iodide were weighed, 1.0ml of a mixed solution of DMSO and DMF (wherein the volume ratio of DMSO to DMF is 1: 0) was added thereto, and the mixture was dissolved by stirring at 60 ℃ and 1000 rpm to prepare 0.9mol/L Cs₂SnI₆The precursor solution of (1);

(2) placing the solution prepared in the step (1) at room temperature for 30 days;

(3) using a liquid-transfering gun to age the solution60 μ L of the solution was dropped onto a clean FTO glass substrate (1.6 mm. times.1.8 mm) and Cs was prepared by spin-coating₂SnI₆Film, specifically, the first stage rotation speed is 1000 rpm, and the time is 10 seconds; the rotating speed of the second stage is 2500 rpm/s, and the time is 60 seconds; at 30 seconds after the start of the second stage rotation, 200. mu.L of isopropyl alcohol was quickly dropped. Then the substrate is placed on a hot bench with the temperature of 30 ℃ to be heated for 40 minutes;

(4) after the substrate is naturally cooled to room temperature, 100 microliters of 10mg/ml tin iodide isopropanol solution is dripped on the substrate, and then the substrate is spin-coated dry at the rotating speed of 2000 revolutions per second;

(5) annealing the obtained film at 200 ℃ for 10 seconds to obtain black Cs₂SnI₆A film.

Example 3

Solution method for preparing cesium tin iodine (Cs)₂SnI₆) A method of making a film comprising the steps of:

(1) 117mg of cesium iodide and 564mg of tin iodide were weighed, 1.0ml of a mixed solution of DMSO and DMF (wherein the volume ratio of DMSO to DMF was 6: 1) was added thereto, and the mixture was dissolved by stirring at 60 ℃ and 1000 rpm to prepare 0.225mol/L of Cs₂SnI₆The precursor solution of (1);

(2) placing the solution prepared in the step (1) at room temperature for 4 days;

(3) dripping 60 μ L of the aged solution onto a clean FTO glass substrate (1.6 mm × 1.8 mm) by using a pipette gun, and preparing Cs by spin coating₂SnI₆Film, specifically, the first stage rotation speed is 1000 rpm, and the time is 10 seconds; the rotating speed of the second stage is 2500 rpm/s, and the time is 60 seconds; at 30 seconds after the start of the second stage rotation, 500. mu.L of isopropyl alcohol was quickly dropped. Then the substrate was heated on a hot stage at a temperature of 70 ℃ for 1 minute;

(4) after the substrate is naturally cooled to room temperature, 40 microliter of 1mg/ml tin iodide isopropanol solution is dripped on the substrate, and then the substrate is spin-coated at the rotating speed of 2000 r/s;

(5) the film obtained above was annealed at 150 ℃ for 300 seconds to obtain black Cs₂SnI₆A film.

Finally, it should be noted that: the above embodiments are merely illustrative and not restrictive of the technical solutions of the present invention, and any equivalent substitutions and modifications or partial substitutions made without departing from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims (5)

1. Solution method for preparing Cs₂SnI₆A method of making a film, comprising the steps of:

(1) adding cesium iodide and tin iodide into DMSO or a mixed solvent of DMSO and DMF, stirring and dissolving at 20-70 ℃ to prepare Cs₂SnI₆Precursor solution;

(2) the precursor solution prepared in the step (1) is added into N₂Standing and aging for 3-10 days in the atmosphere, and performing spin coating deposition on the substrate to obtain a precursor film;

(3) placing the precursor film obtained in the step (2) on a hot bench with the temperature of 30-70 ℃ and heating for 1.0-40 min; then placing the solution on a spin coater, dripping 40-100 mu L of supplement solution, and spin-coating the solution on the solution to dry, wherein the supplement solution is isopropanol solution of tin iodide, and the concentration of the supplement solution is 1-10 mg/mL;

(4) annealing the film obtained in the step (3) at the temperature of 150-200 ℃ for 10-300 s to obtain Cs₂SnI₆A film.

2. The solution process of claim 1 for the preparation of Cs₂SnI₆The method for preparing the thin film is characterized in that the molar ratio of cesium iodide to tin iodide in the step (1) is (1-2): 1-2, when a mixed solvent of DMSO and DFM is adopted, the volume ratio of DMSO to DFM is 1-6:1, and Cs in a precursor solution₂SnI₆The concentration is 0.2mol/L-1.0 mol/L.

3. The solution process of claim 1 for the preparation of Cs₂SnI₆The method of the film is characterized in that the spin coating deposition in the step (2) adopts a two-step spin coating method, the rotating speed of the first stage is 1000-1500 rpm for 5-10 seconds, and the second stage rotation speed is 1500-4000 rpm for 30-90 seconds; at 20-60 seconds after the start of the second stage rotation, 500. mu.L of 100-one anti-solvent, which is isopropanol, chlorobenzene, toluene, ethanol or ethyl acetate, is dropped.

4. Cs produced by the production method according to any one of claims 1 to 3₂SnI₆A film.

5. The Cs of claim 4₂SnI₆Use of a thin film in a photodetector, characterized in that said Cs₂SnI₆The film is used as a light absorbing layer of a photodetector.

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