CN111286779A

CN111286779A - Method for growing large-size perovskite single crystal by using ternary mixed solvent

Info

Publication number: CN111286779A
Application number: CN202010181819.8A
Authority: CN
Inventors: 丁建旭; 程晓华; 李正宵; 张�杰; 姚青; 王开宇; 袁野
Original assignee: Shandong University of Science and Technology
Current assignee: Shandong University of Science and Technology
Priority date: 2020-03-16
Filing date: 2020-03-16
Publication date: 2020-06-16

Abstract

The invention provides a pure inorganic large-size iodine-containing optical band gap tunable CsPbI grown by adopting a ternary mixed solvent_xBr_3‑xA perovskite single crystal. The method utilizes CsPbI_xBr_3‑xThe inverse temperature solubility characteristic in the ternary solvent, and the large-size single crystal grows from the stable solution formed by the ternary solvent. The method comprises the following steps: lead bromide (PbBr)₂) Cesium iodide (CsI) at a molar ratio of 1:1, respectively mixing and dissolving in DMSO, and continuously dropwise adding two solvents of DMF and GBL to obtain a precursor solution dissolved in the ternary mixed solvent. Sealing the solution, gradually heating to 90 deg.C, and growing large-size CsPbI by using inverse solubility principle_xBr_3‑xThe perovskite single crystal is characterized in that x is the doping content of I and is any value selected from 0-3; the absorption spectrum range is 560-700 nm.

Description

Method for growing large-size perovskite single crystal by using ternary mixed solvent

Technical Field

The invention relates to the field of preparation and crystal growth of pure inorganic and mixed halogen perovskite materials, in particular to CsPbI with large size and iodine contained grown from ternary mixed solvent_xBr_3-xA perovskite single crystal.

Background

First, perovskite materials are used as a light absorption layer of a solar cell, and absorption of sunlight by the absorption layer is an important factor determining photoelectric conversion efficiency. The material mainly utilizes the wider light absorption range of the material to absorb light energy to a greater extent, improves the illumination utilization rate, generates larger current density and further improves the photoelectric conversion efficiency when the material is utilized on a photovoltaic device.

Secondly, perovskite materials may be classified into organic-inorganic hybrid perovskites and all-inorganic perovskites according to their physical composition. The organic-inorganic hybrid perovskite has poor water resistance, thermal and chemical stability due to the problems of easy volatilization, easy decomposition and the like of organic groups, and further development of devices is seriously influenced. In contrast, all-inorganic perovskites are currently the focus of research due to their excellent stability, especially CsPbI₃The optical band gap of 1.73eV is provided, and the method is very suitable for improving the utilization rate of the photovoltaic device. According to the research finding, CsPbBr₃Can exist stably under normal temperature and pressure, but CsPbBr₃Since the band gap itself is wide (2.3eV), CsPbBr is required to expand the use of sunlight₃The regulation and control of optical band gap reduction and absorption broadening. Because Br and I are halogen elements and have similar properties, CsPbBr₃Adding element I to prepare CsPbI with different I doping amounts_xBr_3-xCsPbI can be avoided to some extent₃Phase transition of (1) and CsPbBr₃The wide band gap and the like, and the requirement of the photovoltaic device on the material band gap sumAnd (5) the requirement of stability.

Thirdly, due to the characteristics of low cost and easy preparation of the perovskite thin film, the perovskite material is generally used as a light absorption layer of the solar cell in the form of a thin film. However for CsPbI_xBr_3-xContinuing to use conventional thin film forms will not determine whether I has entered the interior of the crystal lattice and accurately obtain the specific stoichiometric ratio of I to Br in the material. Thus, CsPbI_xBr_3-xThe single crystal is the best medium for ensuring the acquisition of I into the crystal lattice, and is the research of CsPbI_xBr_3-xBandgap control and basic conditions for optical properties. However, CsPbI_xBr_3-xThe growth of single crystals is currently still faced with difficulties, such as the need for strong acid environments, high temperature conditions, etc.

Therefore, the invention provides a method for growing large-size mixed halogen CsPbI by using simple low-temperature solution_xBr_3-xA perovskite single crystal. On one hand, the strong corrosion environment of inorganic acid is avoided, and on the other hand, the high temperature condition of growing single crystal from high temperature melt is also avoided; and grown large size CsPbI_xBr_3-xThe single crystal has excellent stability and a narrower optical band gap, can be further used as a light absorption material of a perovskite solar cell, improves the photoelectric conversion efficiency, and has extremely important significance for the development of pure inorganic materials and the application of the pure inorganic materials in photovoltaic devices.

Disclosure of Invention

Based on the problems, the invention provides a simple method for growing large-size mixed halogen perovskite single crystal by a low-temperature solution method, namely CsPbI grows from a ternary mixed solvent_xBr_3-xAnd (3) single crystal. CsPbI obtained using this method_xBr_3-xThe single crystal can effectively expand CsPbBr₃The light absorption range of (1); based on different I doping contents, the adjustable and controllable wide-band visible light absorption range can reach 560-700 nm; the obtained single crystal is a millimeter-grade single crystal with the large size of 4mm, and has important significance for the application of the all-inorganic perovskite material on photovoltaic and photoelectric devices. In addition, unlike the existing methods which are complicated, time-consuming and seriously contaminated, the method of the present inventionSimple, green and environment-friendly; the growth method is controllable, and the growth of large-size crystals is particularly easy to realize.

The invention is realized by the following technical scheme:

the invention provides a method for growing large-size perovskite single crystals from a ternary mixed solvent, which utilizes the property of inverse temperature solubility of the material to achieve the solution saturation concentration in the ternary mixed solvent by utilizing a high-temperature condition so as to precipitate the large-size perovskite single crystals with optical band gaps capable of being regulated and controlled along with the I doping concentration;

wherein the chemical formula of the large-size perovskite single crystal which grows from the ternary mixed solvent and can adjust and control the band gap along with the I doping concentration is CsPbI_xBr_3-xAnd x is the doping content of I and is any value selected from 0-3.

Further, the inverse temperature solubility is different from conventional temperature-reduced crystallization or crystal culture means. But the crystal growth mode is obtained by using the initial low temperature (such as 40 ℃) and then raising the temperature (such as raising the temperature to 100 ℃); moreover, the crystal growth of the present invention is maintained throughout a lower temperature range relative to the prior art.

Further, the ternary mixed solvent is dimethyl sulfoxide (DMSO), N-N-Dimethylformamide (DMF) and lambda-butyrolactone (GBL).

Further, the ratio of the ternary mixed solvent is 1:1:1, and is further 3: 1: 1; further, DMSO: DMF: GBL ═ 5:1: 1.

Further, x is selected from any value of 0 to 3, and further from any value of 0 to 2.

Furthermore, by regulating the doping amount of I, the method can grow the large-size CsPbI with specific x value_xBr_3-xA perovskite single crystal. Such as: CsPbI₂Br、CsPbIBr₂And CsPbI_1.5Br_1.5And the like.

Further, the ternary solvent grown large size CsPbI_xBr_3-xThe size of the perovskite single crystal is millimeter grade, further 1-10 mm, further 5 mm.

Further, the ternary solvent grown large size CsPbI_xBr_3-xThe absorption spectrum range of the perovskite single crystal is 560-700 nm.

Further, the CsPbI_xBr_3-xIn the growth system, the selected raw materials are compounds containing Cs, Pb, Br and I, and are CsI and PbBr₂Or PbI₂And CsBr.

Further, the CsPbI_xBr_3-xThe concentration of the growth system is not more than 0.6mol/L, further 0.4 mol/L.

The method comprises the following steps: mixing CsI with PbBr₂Proportionally mixing and dissolving in DMSO, fully stirring and dissolving at 40 ℃ in a water bath to obtain a precursor solution required by the growth of single crystals, and then proportionally dripping DMF and GBL. Then the temperature is increased to be not higher than 100 ℃ and the saturation concentration is reached, and then the large-size perovskite CsPbI with the band gap being adjustable and controllable along with the I doping concentration can be grown_xBr_3-xAnd (3) single crystal.

Further, the DMF and the GBL are added dropwise according to the proportion, and the volume ratio of the DMF to the GBL is further defined as that no precipitate or suspended substance is generated during the dropwise adding: DMF: GBL ═ 5:1: 1;

furthermore, the order of dripping the other solvents is not distinguished except that DMSO is used for dissolving the raw materials;

further, the crystallization finishing temperature is 40-100 ℃, and further 90 ℃.

The invention provides the large-size perovskite CsPbI with the band gap capable of being regulated and controlled along with the I doping concentration, which is obtained by the growth of the method_xBr_3-xAnd (3) single crystal. The method uses low-cost CsI and PbBr₂Or PbI₂CsBr as solute raw material, ordinary nontoxic DMSO, GBL, DMF and the like as solvents, and the growth is carried out in a low-temperature and acid-free environment through simpler and environment-friendly equipment and process. The perovskite CsPbI grown by the method provided by the invention_xBr_3-xThe single crystal band gap can be regulated and controlled along with the doping concentration of I, the absorption spectrum range is 560-700nm, the adjustable wide light absorption range is achieved, the size of the single crystal is large, the millimeter level is achieved, and the size is about 5 mm.

Compared with the prior art, the growth method has the following advantages:

(1) different from CsPbI in the prior art_xBr_3-xThe invention provides perovskite quantum dots, powder or thin films, and provides a growing CsPbBr₃Large-size perovskite CsPbI with structure band gap capable of being regulated and controlled along with I doping concentration_xBr_3-xCompared with powder, thin film and quantum dot, the perovskite single crystal material is purer and less influenced by environment, and has the advantages of lower defect state density, higher carrier mobility, longer carrier recombination life and the like which are proved by common single crystal materials. In addition, the single crystal can ensure that the doping element I enters the crystal lattice of the perovskite single crystal, and the problems of uncontrollable crystal boundary, existence of the crystal boundary of I and the like in quantum dots, powder or films are solved.

(2) The large-size perovskite CsPbI grown by the invention_xBr_3-xThe single crystal has excellent sunlight absorption capacity, can regulate and control the optical band gap along with the I doping concentration so as to meet the requirements of different devices, is more suitable for being used as a light absorption layer in a photovoltaic device, and improves the photoelectric conversion efficiency.

(3) The single crystal growth method adopts a unique ternary growth system, wherein the ternary solvent is a mixed solvent consisting of dimethyl sulfoxide (DMSO), N-N-Dimethylformamide (DMF) and lambda-butyrolactone (GBL) according to a certain proportion, can provide a higher-concentration and purer solution system for single crystal growth, and can effectively prevent other substances in the solution system from being separated out; and in the growth system, spontaneous crystallization can be realized without an environment higher than 100 ℃ (further at 90 ℃).

(3) The raw materials required by the single crystal growth method are more environment-friendly, the growth temperature is lower, an oil bath condition higher than 100 ℃ is not needed, a strong acid environment is not needed, a high-pressure condition is not needed, the solution is easy to prepare, and the growth condition is easy to realize.

(4) The single crystal growth method is simple and easy to control, has low requirements on equipment and reaction conditions, has a short period, is beneficial to reducing cost and large-scale industrialization, and compared with a method for cooling crystallization in acid (the method cannot grow large-size single crystals), the method is environment-friendly, avoids corrosion of strong acid to the equipment, and realizes growth of the large-size single crystals.

Drawings

Embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 shows CsPbBr of large-size perovskite grown from three mixed solvents in example 1 of the present invention₃Single crystal photo, crystal light orange;

FIG. 2 shows CsPbI obtained in example 2 of the present invention_xBr_3-x(X ═ 1.5) single crystal photographs, the crystals were orange-red;

FIG. 3 is an X-ray diffraction pattern of single crystals grown according to examples 1 and 2 of the present invention. XRD the phase of the sample, Cu K, was analyzed using X-ray diffractometer model D/Max2500PC_αAnd (3) radiation (lambda is 0.154nm), and the measurement range is 10-60. Wherein A is the XRD of the single crystal grown in example 1 and B is the XRD of the single crystal grown in example 2;

FIG. 4 is an EDS analysis of the element content of single crystals grown in examples 1 and 2 of the present invention. EDS was performed on samples using an INCA spectrometer equipped on a Nova Nano SEM450 with an acceleration voltage of 15 kV. Wherein A is the EDS of the single crystal grown in example 1 and B is the EDS of the single crystal grown in example 2;

FIG. 5 is an elemental distribution analysis of a single crystal grown in example 2 of the present invention. Performing sample analysis by using an INCA energy spectrometer assembled on a Nova Nano SEM450, wherein the accelerating voltage is 15 kV;

FIG. 6 is a graph showing UV-visible absorption of a single crystal grown in example 1 of the present invention. The ultraviolet visible absorption spectrum adopts an Shimadzu UV-2550 ultraviolet visible spectrophotometer, a small integrating sphere accessory and barium sulfate powder as a reference, a test sample is powder particles, and the scanning wavelength range is 450-700 nm;

FIG. 7 is a graph of UV-visible absorption of a single crystal grown in example 2 of the present invention. The test mode is the same as above;

Detailed Description

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out according to conventional conditions or according to conditions recommended by the manufacturers.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, any methods and materials similar or equivalent to those described herein can be used in the methods of the present invention. The preferred embodiments and materials described herein are intended to be exemplary only.

It should be understood that the invention provides a method for growing a single crystal by using a ternary mixed solvent, and the single crystal grown by the method can successfully enable a doping element I to enter CsPbBr₃In the crystal lattice, the doping amount of I can be regulated and controlled, the aim of regulating and controlling the optical band gap along with the doping concentration of I is achieved, the requirements of different devices are met, the specific range of the optical band gap is 1.8-2.4 eV, the range can meet the requirement of the material serving as a light absorption layer on high utilization rate of sunlight, and CsPbI with x of any value in 0-3 can be grown by using the method and regulating and controlling the doping amount of I_xBr_3-xSingle crystals, so that they have different optical band gaps.

It should be understood that the present invention is not exhaustive list of all single crystals, and in order to demonstrate the effects of the present invention, examples of the growth of only two ratio single crystals, CsPbBr with cubic crystal phase, of the three single crystals are shown in the following examples₃The structure, and the optical band gap is between 1.7-2.3 eV.

The reagents used in the following comparative examples and examples are all commercially available.

Example 1

Lead bromide (PbBr)₂) Cesium bromide (CsBr) in a molar ratio of 1:1, mixed and dissolved in DMSO to obtain a mixed solution with a concentration of 0.4 mol/L. After the solution is fully and uniformly stirred at the temperature of 40 ℃, continuously dropwise adding two solvents of DMF and GBL, wherein the volume ratio of the three solvents is DMSO: DMF: GBL ═ 5:1:1, a precursor solution dissolved in the ternary mixed solvent was obtained. The solution is sealed and transferred to a crystal growth tank, and the temperature is raised to 90 ℃ to start crystal growth. By spontaneous crystallization, large size is finally obtainedCsPbBr of₃The perovskite single crystal has the size of about 2mm, the ultraviolet absorption edge of 560nm and the optical band gap of 2.3 eV.

FIG. 1 shows CsPbBr obtained in example 1₃A physical photograph of the single crystal;

FIG. 3A shows X-ray diffraction analysis of CsPbBr obtained in example 1₃XRD for structural analysis;

FIG. 4A shows CsPbBr obtained in example 1₃Elemental analysis of the single crystal;

FIG. 6 shows CsPbBr obtained in example 1₃Ultraviolet-visible absorption spectrum of single crystal;

example 2

Lead bromide (PbBr)₂) Cesium iodide (CsI) at a molar ratio of 1:1, respectively, were mixed and dissolved in DMSO so that the concentration of the mixed solution was 0.4 mol/L. After the solution is fully and uniformly stirred at the temperature of 40 ℃, continuously dropwise adding two solvents of DMF and GBL, wherein the volume ratio of the three solvents is DMSO: DMF: GBL ═ 5:1:1, a precursor solution dissolved in the ternary mixed solvent was obtained. The solution is sealed and transferred to a crystal growth tank, and the temperature is raised to 90 ℃ to start crystal growth. According to the principle of inverse solubility, the crystal is spontaneously nucleated and grows, and finally the large-size CsPbI is obtained_xBr_3-xA perovskite single crystal having a single crystal size of about 5mm, wherein Br: i is 1:1, the ultraviolet absorption edge is positioned at 575nm, and the optical band gap is 2.1 eV.

FIG. 2 shows CsPbBr obtained in example 2₃A physical photograph of the single crystal;

FIG. 3B shows X-ray diffraction analysis of CsPbI obtained in example 2_xBr_3-xXRD for structural analysis;

FIG. 4B shows CsPbI obtained in example 2_xBr_3-xAnalyzing element content of the single crystal;

FIG. 5 shows CsPbI obtained in example 2_xBr_3-xThe distribution uniformity of Br and I is analyzed by the single crystal;

FIG. 7 shows CsPbI obtained in example 2_xBr_3-xUltraviolet-visible absorption spectrum of single crystal.

Claims

1. A method for growing large-size perovskite single crystals by using a ternary mixed solvent is characterized by comprising the following steps: the optical band gap of the perovskite single crystal can be regulated and controlled along with the doping concentration of I, and the method is to culture the perovskite single crystal in a ternary mixed solvent growth system by utilizing the inverse temperature solubility;

wherein the chemical formula for growing the large-size perovskite single crystal from the ternary mixed solvent is CsPbI_xBr_3-xAnd X is the doping content of the element I and is any value selected from 0-3.

2. The method of claim 1, wherein: the optical band gap can be regulated and controlled along with the I doping concentration of the large-size perovskite CsPbI_xBr_3-xThe size of the luminescent single crystal is in the millimeter level of 2-6 mm.

3. The method of claim 2, wherein: the optical band gap can be regulated and controlled along with the I doping concentration of the large-size perovskite CsPbI_xBr_3-xThe size of the luminescent single crystal is 4 mm.

4. The method of claim 1, wherein: the optical band gap can be regulated and controlled along with the I doping concentration of the large-size perovskite CsPbI_xBr_3-xThe optical band gap of the luminescent single crystal is 1.7-2.3 eV, and the ultraviolet absorption edge range is 560-700 nm.

5. The method according to any one of claim 1, wherein: the ternary mixed solvent is dimethyl sulfoxide (DMSO), N-N-Dimethylformamide (DMF) and lambda-butyrolactone (GBL).

6. The method of claim 5, wherein: in the ternary mixed solvent, the volume ratio of three solvents is DMSO: DMF: GBL ═ 1-5: 1: 1.

7. the method of claim 6, wherein: the concentration of the ternary mixed solvent growth system is lower than 1 mol/L.

8. The method according to any one of claims 1 to 7, characterized in that: the method comprises the following steps: lead bromide (PbBr)₂) Cesium iodide (CsI) at a molar ratio of 1:1, mixing and dissolving in DMSO under the condition of 40 ℃ water bath to ensure that the concentration of the mixed solution is 0.4 mol/L; after fully and uniformly stirring, continuously dropwise adding two solvents of DMF and GBL to limit that no precipitate or suspended matter is generated in the solution to obtain a precursor solution dissolved in the ternary mixed solvent, sealing the solution, heating to a temperature lower than 100 ℃ to start crystal growth, and finally obtaining the large-size CsPbI by utilizing the inverse temperature growth principle_xBr_3-xA perovskite single crystal.

9. The method of claim 8, wherein: the crystallization temperature is 40-100 ℃.

10. Large-size perovskite CsPbI with optical band gap capable of being regulated and controlled according to I doping concentration and grown according to method of any one of claims 1 to 9_xBr_3-xAnd (3) single crystal.