Preparation method of methylamine-free tin-based perovskite single crystal and photodetector

Abstract

The present invention discloses a method for preparing a methylamine-free tin-based perovskite single crystal and a photodetector. The present invention develops a tin-based perovskite single crystal suitable for preparing a low-noise photodetector. In the later stage of the growth and preparation of the tin-based perovskite single crystal solution, a zinc subgroup metal cation (Zn 2+ 、Cd 2+ or Hg 2+ ) is introduced into the methylamine-free tin-based perovskite single crystal growth solution, and a trace amount of soft acid zinc subgroup metal cations is strongly bonded with soft base halogen anions, and without introducing additional internal defects, the point vacancies formed on the shallow surface of the tin-based perovskite single crystal in the late growth stage can be in situ passivated, thereby inhibiting the Sn on the crystal surface. 2+ The oxidation of methylamine-free tin-based perovskite can greatly reduce the dark current of the photodetector, thereby effectively reducing the noise problem in the existing methylamine-free tin-based perovskite detector and improving the signal-to-noise ratio, thereby preparing a high-performance methylamine-free tin-based perovskite single crystal photodetector.

Description

Technical Field

[0001] The present invention belongs to the field of photoelectric devices, and in particular relates to a preparation method of a methylamine-free tin-based perovskite single crystal and a photoelectric detector. Background Art

[0002] Three-dimensional organic-inorganic lead halide perovskites, due to their direct band gap, have the characteristics of high extinction coefficient and wide absorption range. In addition, their advantages of carrier transport length and low intrinsic carrier concentration have also attracted widespread research interest. In addition, studies have shown that perovskite single crystal materials have lower trap density and higher mobility than perovskite thin film materials, making them ideal materials for the preparation of high-performance photodetectors. Three-dimensional perovskite single crystals, of which the most typical is methylamine (MA) three-dimensional perovskite single crystal MAPbX3, but the structure is prone to MA loss due to heating, which hinders the further development and application of methylamine three-dimensional perovskites. The easily oxidized tin-based three-dimensional perovskite single crystal MASnX3 faces even more serious problems.

[0003] In light of this, the use of mixed cations to replace methylamine has emerged. Their basic formula is also ABX3, but A is a mixture of cations such as formamidine (FA) or cesium (Cs). This represents a promising new structure that can significantly improve stability. However, the overall performance of methylamine-free three-dimensional perovskite single crystals is still slightly inferior to that of methylamine-based three-dimensional perovskite single crystals. The main reason is that such perovskite single crystals have a high defect state density. Recently, studies have shown that the introduction of guanidine (GA) can significantly reduce the defect density of halide anions. However, the disordered crystallization of A-site ions in ternary mixed-cation perovskite single crystals easily leads to the formation of other types of defects. More importantly, the large number of defects in the mixed cations also exacerbates Sn oxidation, especially in the shallow surface of the crystal, which is considered to be the main source of defects. To further improve the quality of methylamine-free tin-based perovskite single crystals and use them in the preparation of low-noise photodetectors, an effective approach is to inhibit the oxidation of the shallow surface of the crystal and hinder the formation of defects during crystal growth. Adding dopants is a well-known method, and many doping attempts have been reported for existing perovskite single crystals. However, the introduction of dopants usually easily forms additional defect states inside the crystal, which is detrimental to the detection performance of the detector. Summary of the Invention

[0004] The purpose of the present invention is to solve the above problems and provide a method for preparing a methylamine-free tin-based perovskite single crystal and a photodetector, based on a modified growth process to inhibit the formation of defects on the shallow surface of the methylamine-free tin-based perovskite single crystal, thereby preparing a method for preparing a low-noise tin-based perovskite single crystal photodetector.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention provides a method for preparing a methylamine-free tin-based perovskite single crystal, wherein a trace amount of zinc subgroup equivalent cations (Zn 2+ 、Cd 2+ or Hg 2+ ), through the strong bonding between the soft acid zinc subgroup cations and the soft base halogen anions, the point vacancies on the shallow surface of the methylamine-free tin-based perovskite single crystal are in situ passivated, thereby hindering the S n 2+ The method of reducing the noise of the photodetector prepared by the perovskite single crystal by oxidizing the ions and reducing the defect density on the surface of the single crystal. The A position of the methylamine-free tin-based perovskite single crystal structure ABX3 is a guanidine cation, Cs + 、a ternary cation mixture of formamidinium cation, in which guanidine cation GA + The chemical formula is C(NH2)3 + , formamidinium cation FA + The chemical formula is CH(NH2)2 + , B position is Sn 2+ Cation, X position is Br - or I - Anion or a mixture of the two, the specific structural formula is Cs x GA y FA 1-x-y Sn(Br z I 1-z )3, 0.05≤x≤0.2; 0.01≤y≤0.1, 0≤z<1. The specific method includes the following steps:

[0007] (1) AX and SnX2 are mixed in a stoichiometric ratio, and then a polar organic solvent is added. After stirring and dissolving, a methylamine-free tin-based ASnX3 perovskite single crystal growth solution with a molar concentration of 0.8 mol / L to 1.2 mol / L is obtained. Finally, stirring is continued for 12 to 24 hours until the solution is completely clear.

[0008] (2) The ASnX3 methylamine-free tin-based perovskite single crystal growth solution finally obtained in step (1) is slowly heated from 40°C to 80°C to 90°C to 130°C at 1°C / h until a 1mm to 1cm perovskite single crystal is generated. A low concentration zinc subgroup metal halide solution dissolved in a solvent of the same polarity is added one hour before the end of the reaction. After continuing to keep warm for 1 hour, the single crystal is taken out from the solution, and after surface cleaning with ether and vacuum drying, the final shallow surface doped methylamine-free tin-based perovskite single crystal is obtained.

[0009] In the step (1), the polar organic solvent is any one of γ-butyrolactone, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, or a mixture of two thereof.

[0010] In the step (2), in the ASnX3 methylamine-free tin-based perovskite single crystal growth solution, the zinc subgroup metal halide is ZnX2, CdX2 or HgX2, and x=Br - or I - , the molar concentration of zinc subgroup metal ions is Sn 2+ 0.01%-1.0% of the ion molar concentration.

[0011] The present invention also provides a photoelectric detector comprising a methylamine-free tin-based perovskite single crystal obtained by the above-mentioned preparation method and metal electrodes located on the upper and lower crystal surfaces of the methylamine-free tin-based perovskite single crystal.

[0012] Mechanism of the present invention:

[0013] Tin-based perovskite single crystals are prone to produce point vacancies on the shallow surface. The formation of point vacancies reduces the Sn-O bond formation energy and aggravates the Sn 2+ The combination of ions and oxygen molecules greatly increases the defect density on the surface of the tin-based perovskite single crystal, resulting in an excessively high dark current of the corresponding photodetector and an inability to reduce noise. The traditional method of metal ion doping is to add metal ions to the precursor solution of the single crystal growth at the beginning. The impurity atoms introduced by this scheme easily lead to micro-stresses that cause structural disorder inside the crystal, resulting in internal defects that cannot be eliminated. In the late stage of the growth of the methylamine-free tin-based perovskite single crystal, a trace amount of zinc subgroup equivalent cations (Zn 2+ 、Cd 2+ or Hg 2+ ) occupying the B site allows for strong bonding with soft alkali halide anions. This, without introducing additional internal defects, in situ passivates shallow surface vacancies formed in the late stages of growth of tin-based perovskite single crystals. This increases the Sn-O bond formation energy and effectively inhibits surface oxidation of the tin-based crystals. This, in turn, significantly reduces the dark current in existing methylamine-free tin-based perovskite detectors and improves the signal-to-noise ratio. The methylamine-free A-site ternary cation mix imparts excellent stability to the perovskite single crystal, ultimately resulting in high-performance, stable methylamine-free tin-based perovskite single crystal photodetectors.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The present invention proposes to add a trace amount of zinc subgroup equivalent cations in the late stage of tin-based single crystal growth to reduce the shallow surface defect density of methylamine-free tin-based perovskite crystals. This method has a simple operation process and low cost, and does not affect the growth of the internal body of the perovskite single crystal and does not cause structural disorder to the crystal structure. Without introducing additional internal defects, the zinc subgroup cations (Zn) occupying the B position are used to reduce the surface defect density of the methylamine-free tin-based perovskite crystals. 2+ 、Cd 2+ or Hg 2+) strongly bonds with the soft alkali halide anions, thereby in-situ passivating the large number of point vacancies formed on the shallow surface of the perovskite single crystal during growth, effectively suppressing the degree of oxidation on the crystal surface, and thus avoiding Sn 2+ Shallow surface defects caused by ion oxidation. Reducing the defect density can significantly reduce the dark current of the perovskite detector, and can obtain low-noise, highly stable methylamine-free tin-based perovskite single crystal photodetectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a flow chart of preparing a tin-based perovskite single crystal with low defect density by shallow surface doping with zinc subgroup metal ions in an embodiment of the present invention. DETAILED DESCRIPTION

[0017] The present invention will be described in further detail below with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.

[0018] Example 1

[0019] Shallow surface doping of CdI2 with methylamine-free tin-based three-dimensional perovskite single crystals (Cs 0.1 GA 0.05 FA 0.85 )Sn(Br 0.1 I 0.9 )3 Infrared photodetector preparation:

[0020] (1) Weigh CsI, FAI, GAI, SnI2 and SnBr2 powders in stoichiometric ratio (1 mmol, 8.5 mmol, 0.5 mmol, 8.5 mmol, 1.5 mmol, respectively) and add them into a reagent bottle. Then add γ-butyrolactone and stir at room temperature to dissolve to obtain clear (Cs 0.1 GA 0.05 FA 0.85 )Sn(Br 0.1 I 0.9 )3 Perovskite single crystal growth solution (10 mL), solution concentration is 1.0 mol / L, stirred for 12 hours until the solution is completely clear.

[0021] (2) The mixed cation perovskite single crystal growth solution obtained in step (1) was slowly placed in an 80°C oil bath, and the temperature was slowly raised to 120°C at a heating rate of 1°C / h. After 40 hours, 500 μL of a γ-butyrolactone solution of CdI2 with a concentration of 0.04 mol / L was slowly added to the perovskite single crystal growth solution. After keeping the temperature for 1 hour, a black dodecahedral perovskite single crystal with a length and width of about 5 mm was obtained. The surface was cleaned with ether and then vacuum dried to obtain a shallow surface-doped methylamine-free three-dimensional perovskite single crystal.

[0022] (3) Select CdI2 shallow surface doping perovskite (Cs 0.1 GA 0.05 FA 0.85 )Sn(Br 0.1 I 0.9 )3 The upper and lower (110) crystal planes of the single crystal were prepared by using a vacuum thermal evaporation device. A 100nm thick gold electrode was deposited on the surface of the upper (110) crystal plane of the single crystal through a square electrode mask as an anode. A 80nm thick indium tin oxide was deposited on the surface of the lower (110) crystal plane of the single crystal through a magnetron sputtering device as a cathode to obtain an infrared photodetector, which was then tested for detector performance.

[0023] Comparative Example 1

[0024] Surface undoped methylamine-free tin-based three-dimensional perovskite single crystal (Cs 0.1 GA 0.05 FA 0.85 )Sn(Br 0.1 I 0.9 )3 Infrared photodetector preparation:

[0025] (1) Weigh CsI, FAI, GAI, SnI2 and SnBr2 powders in stoichiometric ratio (1 mmol, 8.5 mmol, 0.5 mmol, 8.5 mmol, 1.5 mmol, respectively) and add them into a reagent bottle. Then add γ-butyrolactone and stir at room temperature to dissolve to obtain clear (Cs 0.1 GA 0.05 FA 0.85 )Sn(Br 0.1 I 0.9 )3 Perovskite single crystal growth solution (10 mL), solution concentration is 1.0 mol / L, stirred for 12 hours until the solution is completely clear.

[0026] (2) The mixed cation perovskite single crystal growth solution obtained at the end of step (1) was slowly placed in an 80°C oil bath, and the temperature was slowly raised to 120°C at a heating rate of 1°C / h. After 40 hours, a black dodecahedral perovskite single crystal with a length and width of about 5 mm was directly obtained from the solution. The surface was cleaned with ether and then vacuum dried to obtain a surface-undoped methylamine-free tin-based three-dimensional perovskite single crystal.

[0027] (3) Select the unoptimized (Cs 0.1 GA 0.05 FA 0.85 )Sn(Br 0.1 I 0.9)3 The upper and lower (110) crystal planes of the perovskite single crystal are deposited with a 100nm thick gold electrode as an anode on the upper (110) crystal plane of the single crystal through a square electrode mask using a vacuum thermal evaporation device, and a 80nm thick indium tin oxide layer is deposited on the lower (110) crystal plane of the single crystal as a cathode using a magnetron sputtering device to obtain an infrared photodetector, which is then tested for detector performance.

[0028] Based on the shallow surface doping of CdI2 (Cs 0.1 GA 0.05 FA 0.85 )Sn(Br 0.1 I 0.9 )3 The noise of perovskite single crystal is about 1.1×10 -14 A Hz -1 / 2 , which is significantly lower than the noise of unoptimized perovskite single crystals (2.2×10 -13 A Hz -1 / 2 , after shallow surface doping with CdI2, (Cs 0.1 GA 0.05 FA 0.85 )Sn(Br 0.1 I 0.9 )3 Perovskite single crystal at 2V cm -1 The dark current under electric field is from 50nAcm -2 down to 3 nA cm -2 The sensitivity of the infrared photodetector is increased by about 40 times, and the specific detection rate at 900nm is increased by about 20 times to 1.53×10 12 Jones.

[0029] Example 2

[0030] Shallow surface doping of ZnBr2 with methylamine-free tin-based three-dimensional perovskite single crystals (Cs 0.2 GA 0.1 FA 0.7 )Sn(Br 0.9 I 0.1 )3 X-ray detector preparation:

[0031] (1) Weigh CsBr, FABr, GABr, SnBr2 and SnI2 powders in stoichiometric ratio (2.1 mmol, 7.35 mmol, 1.05 mmol, 8.925 mmol, 1.575 mmol, respectively) and add them to a reagent bottle. After adding γ-butyrolactone, stir and dissolve at room temperature to obtain a clear (Cs 0.2 GA 0.1 FA 0.7 )Sn(Br 0.9 I 0.1)3 Perovskite single crystal growth solution (10 mL), solution concentration is 1.05 mol / L, stirred for 18 hours until the solution is completely clear.

[0032] (2) The mixed cation perovskite single crystal growth solution obtained in step (1) was slowly placed in an oil bath at 45°C, and the temperature was slowly raised to 90°C at a heating rate of 1°C / h. After 45 hours, 200 microliters of a 0.05 mol / L ZnBr2 γ-butyrolactone solution was added to the perovskite single crystal growth solution. After keeping the temperature for 1 hour, an orange square perovskite single crystal with a length and width of 8 mm was obtained. The surface was cleaned with ether and then vacuum dried to obtain a shallow surface-doped methylamine-free tin-based three-dimensional perovskite single crystal.

[0033] (3) Select ZnBr2 shallow surface doping perovskite (Cs 0.2 GA 0.1 FA 0.7 )Sn(Br 0.9 I 0.1 )3 The upper and lower (011) crystal planes of the single crystal were prepared by using a vacuum thermal evaporation device. A 100nm thick gold electrode was deposited on the surface of the upper (011) crystal plane of the single crystal through a square electrode mask as an anode. A 200nm thick gallium electrode was deposited on the surface of the lower (011) crystal plane of the single crystal through a magnetron sputtering device as a cathode to obtain an X-ray detector, and then the detector performance test was carried out.

[0034] Comparative Example 2

[0035] Surface undoped methylamine-free tin-based three-dimensional perovskite single crystal (Cs 0.2 GA 0.1 FA 0.7 )Sn(Br 0.9 I 0.1 )3 X-ray detector preparation:

[0036] (1) Weigh CsBr, FABr, GABr, SnBr2 and SnI2 powders in stoichiometric ratio (2.1 mmol, 7.35 mmol, 1.05 mmol, 8.925 mmol, 1.575 mmol, respectively) and add them to a reagent bottle. After adding γ-butyrolactone, stir and dissolve at room temperature to obtain a clear (Cs 0.2 GA 0.1 FA 0.7 )Sn(Br 0.9 I 0.1 )3 Perovskite single crystal growth solution (10 mL), solution concentration is 1.05 mol / L, stirred for 18 hours until the solution is completely clear.

[0037] (2) The mixed cation perovskite single crystal growth solution obtained at the end of step (1) was slowly placed in an oil bath at 45°C, and the temperature was slowly raised to 90°C at a heating rate of 1°C / h. After 45 hours, an orange square perovskite single crystal with a length and width of 8 mm was obtained. The surface was cleaned with ether and then vacuum dried to obtain a surface-undoped methylamine-free tin-based three-dimensional perovskite single crystal.

[0038] (3) Select perovskite (Cs 0.2 GA 0.1 FA 0.7 )Sn(Br 0.9 I 0.1 )3 The upper and lower (011) crystal planes of the single crystal were prepared by using a vacuum thermal evaporation device. A 100nm thick gold electrode was deposited on the surface of the upper (011) crystal plane of the single crystal through a square electrode mask as an anode. A 200nm thick gallium electrode was deposited on the surface of the lower (011) crystal plane of the single crystal through a magnetron sputtering device as a cathode to obtain an X-ray detector, and then the detector performance test was carried out.

[0039] Based on the ZnBr2 shallow surface doping (Cs 0.2 GA 0.1 FA 0.7 )Sn(Br 0.9 I 0.1 )3 The noise of perovskite single crystal is about 1.1×10 -14 A Hz -1 / 2 , which is significantly lower than the noise of unoptimized perovskite single crystals (3.6×10 -13 A Hz -1 / 2 , after shallow surface doping with ZnBr2, (Cs 0.2 GA 0.1 FA 0.7 )Sn(Br 0.9 I 0.1 )3 Perovskite single crystal at 10V cm -1 The dark current under electric field is from 200nA cm -2 down to 15 nA cm -2 The sensitivity of the X-ray detector increased by about 60 times, and the lowest detection limit decreased by about 30 times, which can be used at 28.5nGy air s -1 Capture clear X-ray images at extremely low dose rates.

[0040] The foregoing merely represents preferred embodiments of the present invention, and while the description is relatively specific and detailed, it should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make various modifications, improvements, and substitutions without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing a methylamine-free tin-based perovskite single crystal, characterized in that: The following steps are involved: S1, AX and BX2 are mixed in a stoichiometric ratio, and then a polar organic solvent is added and stirred to dissolve to obtain a ABX3 methylamine-free tin-based perovskite single crystal growth solution with a molar concentration of 0.8 mol / L~1.2 mol / L, and finally stirring is continued for 12~24 hours until the solution is completely clear; A position is guanidine cation, Cs + 、a ternary cation mixture of formamidinium cation, in which guanidine cation GA + The chemical formula is C(NH2)3 + , formamidinium cation FA + The chemical formula is CH(NH2)2 + , B position is Sn 2+ Cation, X position is Br − or I − Anion or a mixture of the two, the specific structural formula is Cs x GA y FA 1-x-y Sn(Br z I 1-z )3, 0.05≤x≤0.2; 0.01≤y≤0.1, 0≤z<1; S2. The methylamine-free tin-based perovskite single crystal growth solution obtained in step S1 is slowly heated from 40°C to 80°C at 1°C / h to 90°C to 130°C until a 1mm to 1cm perovskite single crystal is generated. A low-concentration zinc subgroup metal halide solution dissolved in a solvent of the same polarity is added 1 hour before the end of the reaction. After further heat preservation for 1 hour, the single crystal is taken out from the solution, and after simple cleaning and vacuum drying, the final shallow surface doped methylamine-free tin-based perovskite single crystal is obtained; the molar concentration of the zinc subgroup metal ion is Sn 2+ 0.01%-1.0% of the ion molar concentration.

2. The method for preparing a methylamine-free tin-based perovskite single crystal according to claim 1, wherein: In step S1, the polar organic solvent is one or a mixture of two of γ-butyrolactone, N-methylpyrrolidone, dimethyl sulfoxide, and N,N-dimethylformamide.

3. The method for preparing a methylamine-free tin-based perovskite single crystal according to claim 1, wherein: In step S2, the zinc subgroup metal halide is ZnX2, CdX2 or HgX2, X=Br − or I − .

4. A photoelectric detector, characterized in that: The invention comprises a methylamine-free tin-based perovskite single crystal obtained by the preparation method according to any one of claims 1 to 3 and metal electrodes located on the upper and lower crystal surfaces of the methylamine-free tin-based perovskite single crystal.

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