CN111470528A - Tin-containing semiconductor material and preparation method thereof - Google Patents

Abstract

The invention discloses a tin-containing semiconductor material and a preparation method thereof. The semiconductor material is a crystal with different carrier concentrations grown by adding a metal element or a metal compound during the preparation process of CsSnBr ₃ . The preparation method is as follows: mixing CsBr and SnBr ₂ with a metal element or metal compound, heating and reacting under the protection of an inert gas, and slowly cooling to obtain CsSnBr ₃ semiconductor crystal materials with different carrier concentrations. Compared with the CsSnBr ₃ semiconductor with elemental tin added during the preparation process, its carrier concentration decreased by one order of magnitude, and the defect state density was significantly reduced. The indium-doped CsSnBr ₃ semiconductor has a carrier concentration of 10 ¹⁰ cm ^-3 , which is close to an intrinsic semiconductor; the silver-doped CsSnBr ₃ semiconductor has a p-type carrier concentration of 10 ¹⁹ cm ^-3 , becoming a degenerate semiconductor.

Description

Tin-containing semiconductor material and preparation method thereof

technical field

The invention relates to a novel tin-containing semiconductor material. By changing the preparation conditions and doping elements of the CsSnBr3 _perovskite material, a series of semiconductor materials with different carrier concentrations are obtained, which belongs to the technical field of new materials.

Background technique

In recent years, halide perovskite materials have attracted much attention due to their excellent semiconducting properties and improving photoelectric conversion performance. In the ABX ₃ structure of halide perovskite materials, the A-site elements are generally methylammonium, formamidine cations or cesium ions with large ionic radius, the B-sites are generally divalent cations of lead, tin and germanium, and X is a halogen anion . The B-site cations and six halide anions form a common vertex octahedron, and the A-site cations are located in the gaps between the octahedrons, forming a perovskite structure.

To study the properties of halide perovskite materials, spin coating and vapor deposition are currently commonly used to produce thin films. However, the microcrystalline thin film material thus obtained has many pores, grain boundary inclusions and other defects, which not only hinder the transport of carriers in the perovskite material, but also make the perovskite degrade rapidly in the environment. In contrast, single-crystal bulk perovskite materials can have higher carrier mobility, longer carrier diffusion lengths, and higher stability to ambient moisture and oxygen. Halide perovskites containing organic cations are usually grown from solution, whereas all-inorganic halide perovskites do not decompose upon melting and are more suitable for growing single crystals using the Bridgman method. For example, _CsPbBr3 has obtained large-sized and high-quality single crystals by the Bridgeman method. (Adv.Optical Mater.2017,5,1700157; Nat.Commun.2018,9,1609; J.Phys.Chem.Lett.2018,9,5040) But lead-containing perovskite materials are easy to pollute the environment and endanger human health , thus banned by the RoHS standard and subject to huge restrictions in practical applications, while the use of tin instead of lead as the B-site cation can lead to a new class of perovskite materials.

CsSnBr ₃ exists stably in a cubic phase at room temperature, has good thermal stability, can be passivated by air, and has a band gap suitable for the preparation of photoelectric conversion devices (Angew. Chem. Int. Ed. 2018, 57, 13154). It should be noted that, unlike the lead element, the tin element has two stable valence states of Sn ²⁺ and Sn ⁴⁺ at the same time, which makes the tin-containing perovskite materials easy to contain Sn ^{4+ ,} resulting in Sn vacancy defects and corresponding p-type Doping (J.Am.Chem.Soc. 2012, 134, 8579; J. Phys. Chem. C. 2018, 122, 13926). Doping a semiconductor can improve the conductivity of the material, but it will speed up the recombination of electrons and holes. Therefore, it is an important research direction to adjust the doping state of tin-containing perovskite materials according to different application directions. It has been reported (Adv.Mater.2014, 26, 7122) that adding 20% molar ratio of SnF ₂ during the growth of CsSnI ₃ crystal can reduce the carrier concentration from 10 ¹⁹ cm ^-3 to 10 ¹⁷ cm ^-3 , but Such a high addition ratio has exceeded the normal doping concentration range, and the adjustment effect on the carrier concentration is not significant enough.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a tin-containing semiconductor material and a preparation method thereof, which can control the carrier concentration in the semiconductor by changing the preparation and doping conditions.

In order to solve the above problems, the present invention provides a tin-containing semiconductor material, which is characterized in that it is a crystal with different carrier concentrations grown by adding a metal element or a metal compound for doping during the preparation process of CsSnBr ₃ .

Preferably, the raw materials of the above-mentioned tin-containing semiconductor material include CsBr, SnBr ₂ and metal element or metal compound.

More preferably, the metal element or metal compound is any one or more of tin element or tetravalent tin compound, indium element or indium compound and silver element or silver compound.

Further, the tetravalent tin compound is SnBr ₄ or Cs ₂ SnBr ₆ .

Further, the indium compound is InBr.

Further, the silver compound is AgBr.

Further, the mass of the tin element is not less than the sum of the mass of CsBr and SnBr ₂ .

Further, the mole number of the tetravalent tin compound, other metal element or metal compound is not more than 5% of the mole number of SnBr ₂ .

The present invention also provides a method for preparing the above-mentioned tin-containing semiconductor material, which is characterized in that CsBr and SnBr ₂ are mixed with a metal element or a metal compound, heated and reacted under the protection of an inert gas, and slowly cooled to obtain compounds with different carrier concentrations. CsSnBr ₃ semiconductor crystal material.

Compared with the prior art, the beneficial effects of the present invention are:

1. In the present invention, by doping In element in the CsSnBr ₃ semiconductor material, the carrier concentration is reduced by 6 orders of magnitude, which is close to the level of the intrinsic semiconductor.

2. In the present invention, by adding elemental tin during the preparation of the CsSnBr ₃ semiconductor material, the carrier concentration is reduced by one order of magnitude, and the defect state density is significantly reduced.

3. In the present invention, by doping Ag element in the CsSnBr ₃ semiconductor material, the carrier concentration is increased by 3 orders of magnitude, reaching the level of degenerate semiconductor.

4. The present invention provides a method for regulating the carrier concentration of the tin-containing semiconductor material in the range of 10 ¹⁰ to 10 ¹⁹ cm ^-3 .

5. The doped tin-containing semiconductor material in the present invention does not contain the toxic elements lead or cadmium.

6. The preparation method of the doped tin-containing semiconductor material in the present invention is simple, does not generate waste liquid or by-products, and is suitable for large-scale production.

Description of drawings

Fig. 1 is the CsSnBr ₃ crystal photograph of metal tin treatment;

Fig. 2 is the X-ray diffraction pattern of _CsSnBr crystal and powder treated with metal tin;

Figure 3 shows the structure of the indium-doped CsSnBr ₃ semiconductor device and the space charge limited current (SCLC) test results;

Figure 4 is a photo of InBr-doped CsSnBr ₃ crystal;

Fig. ₅ is the powder X-ray diffraction pattern of CsSnBr doped with AgBr;

FIG. 6 shows the structure of the undoped CsSnBr ₃ semiconductor device and the space charge limited current (SCLC) test results.

Detailed ways

In order to make the present invention more obvious and comprehensible, preferred embodiments are described in detail below with reference to the accompanying drawings.

The raw material CsBr involved in Examples 1-4 and Comparative Example 1 was purified from commercially available reagents according to the method of J.Phys.Chem.Lett.2019,10,3699, and SnBr ₂ was purified according to Angew.Chem.Int.Ed.2018,57 , The method of 13154 was synthesized and purified.

Example 1: Metal Tin Treated _CsSnBr Semiconductor

A tin-containing semiconductor material, the preparation method is: in a nitrogen environment, weigh 10.6g (50.0mmol) of CsBr and 13.9g (50.0mmol) of SnBr ₂ solids, mix them evenly and fully grind them, and put them together with 40g of tin particles. In a glass ampoule containing about 1/3 atmosphere nitrogen and melt-sealed. The neck of this ampoule is vertically downward for Bridgman crystal growth, and the conditions are as follows: heating rate 5℃·min ^-1 , holding temperature 490℃, holding time 3h, seed rod descending rate 2mm·h ^-1 , annealing The temperature was 280°C, the annealing time was 3h, and finally cooled to room temperature with the furnace. The obtained sample is shown in Figure 1, and the crystal surface is bright and free of cracks and no obvious macroscopic inclusions.

此结果说明本实施例产物为CsSnBr₃的单一晶相。In a nitrogen environment, the crystals were cut, ground, and polished into circular slices with a diameter of about 13 mm and a thickness of 0.95 mm. The X-ray diffraction pattern after grinding part of the crystals into powder is shown in Figure 2(b). The indexing result of this diffraction pattern is: cubic crystal system, Pm-3m space group, and unit cell parameters are

This result indicates that the product of this example is a single crystal phase of CsSnBr ₃ .

Four gold electrodes were evaporated on the edge of the CsSnBr ₃ wafer, and the Hall effect was measured by the van der Pauw method. The results show that the sample contains p-type carrier concentration of 6.2×10 ¹⁵ cm ^-3 , and the carrier mobility is 67cm ² ·V ^-1 ·s ^-1 . Compared to Comparative Example 1, this result demonstrates that the metallic tin treatment reduces the density of defect states within the _CsSnBr3 semiconductor by an order of magnitude.

Example 2: In-doped _CsSnBr semiconductor

A tin-containing semiconductor material, the preparation method is as follows: in a nitrogen environment, weigh 10.6g (50.0mmol) of CsBr and 13.9g (50.0mmol) of SnBr ₂ solids, mix them uniformly and fully grind them, and mix them with 0.057g (0.50mmol) The indium pellets are together filled into glass ampoules containing about 1/3 atmosphere of nitrogen and sealed. The ampoule was tumble heated at 460°C for 8 hours to give a dark liquid which was cooled to room temperature to give a black solid.

In a nitrogen atmosphere, a part of the black solid was ground and polished into a square sheet with a size of about 1×1 cm ² and a thickness of 0.82 mm. Gold electrodes were evaporated on the four corners of the sheet, and the Hall effect was measured by the van der Pauw method. The results show that the sample contains p-type carriers with a concentration of 4.1×10 ¹⁰ cm ^-3 and a carrier mobility of 61 cm ² ·V ^-1 ·s ^-1 .

Gold electrodes were evaporated on the upper and lower sides of another crystal sheet with a thickness of 1.02 mm. The device structure and current-voltage characteristic curve are shown in Figure 3. The defect filling limit voltage V _TFL is 16V. Analyzing this result according to the standard space charge confined current model yields a defect state density of 6.7×10 ¹⁰ cm ⁻³ in the sample. All the above results indicate that the defects in the indium-doped CsSnBr ₃ semiconductor have been significantly eliminated.

Example ₃ : InBr-doped CsSnBr semiconductor

A tin-containing semiconductor material, the preparation method is as follows: in a nitrogen environment, weigh 10.6g (50.0mmol) CsBr, 13.9g (50.0mmol) SnBr ₂ and 0.10g (0.50mmol) InBr solid, mix well and fully grind , loaded into a glass tube with a conical bottom, containing about 1/3 atmosphere of nitrogen, and sealed. The growth conditions of Bridgman crystals are as follows: heating rate 5°C·min ^-1 , holding temperature 490°C, holding time 3h, seed rod descending rate 2mm·h ^-1 , annealing temperature 280°C, annealing time 3h, and finally with the furnace Cool to room temperature. The obtained sample is shown in Figure 4, and the crystal surface is bright and free of cracks and no obvious macroscopic inclusions.

In a nitrogen atmosphere, the crystals were cut, ground, and polished into circular flakes with a diameter of approximately 13 mm and a thickness of 2.30 mm. Four gold electrodes were vapor-deposited on the edges of the flakes, and the Hall effect was measured by the van der Pauw method. The results show that the sample contains p-type carriers with a concentration of 3.0×10 ¹⁰ cm ^-3 and a carrier mobility of 74 cm ² · V ^-1 ·s ^-1 . This result indicates that the defects in the InBr-doped _CsSnBr3 semiconductor have been significantly eliminated.

Example 4: AgBr-doped _CsSnBr semiconductor

A tin-containing semiconductor material, the preparation method is as follows: in a nitrogen environment, weigh 4.17g (19.6mmol) CsBr, 5.40g (19.4mmol) SnBr ₂ , 0.17g (0.20mmol) Cs ₂ SnBr ₆ and 0.075g (0.40g) mmol) AgBr solid, mixed well and thoroughly ground, then charged into a glass ampoule containing about 1/3 atmosphere of nitrogen and sealed. The ampoule was tumble heated at 460°C for 12 hours to give a dark liquid which was cooled to room temperature to give a black solid.

此结果说明本实施例产物为CsSnBr₃的单一晶相，AgBr未产生相分离。In a nitrogen environment, a part of the black solid was ground into powder, and its X-ray diffraction pattern was shown in Figure 5. The indexed result of this diffractogram is: cubic crystal system, Pm-3m space group, and the unit cell parameter is

This result indicates that the product of this example is a single crystal phase of CsSnBr ₃ , and no phase separation of AgBr occurs.

A part of the black solid was ground and polished into a square sheet with a size of about 5×4 mm ² and a thickness of 1.02 mm. Gold electrodes were evaporated on the four corners of the sheet, and the Hall effect was measured by the van der Pauw method. The results show that the sample contains p-type carriers with a concentration of 1.5×10 ¹⁹ cm ^-3 and a carrier mobility of 20cm ² ·V ^-1 ·s ^-1 . This result indicates that the carrier concentration in the AgBr-doped CsSnBr ₃ semiconductor increases significantly, becoming a degenerate doped semiconductor.

Comparative Example 1: Undoped _CsSnBr Semiconductor

In a nitrogen atmosphere, weigh 10.6 g (50.0 mmol) of CsBr and 13.9 g (50.0 mmol) of SnBr ₂ as solids, mix them well and grind them well, put them into a glass ampoule containing about 1/3 atmosphere of nitrogen and seal them. The ampoule was heated at 460°C for 8 hours to obtain a clear wine red liquid which was cooled to room temperature to obtain a black solid.

In a nitrogen atmosphere, a part of the black solid was ground and polished into a square sheet with a size of about 1×1 cm ² and a thickness of 1.32 mm. Gold electrodes were evaporated on the four corners of the sheet, and the Hall effect was measured by the van der Pauw method. The results show that the sample contains p-type carriers with a concentration of 8.5×10 ¹⁶ cm ^-3 and a carrier mobility of 23cm ² ·V ^-1 ·s ^-1 . Gold electrodes were evaporated on the upper and lower sides of another crystal sheet with a thickness of 1.13mm. The device structure and current-voltage characteristic curve are shown in Figure 6. Within the applied voltage range of 0-40V, only the ohmic characteristic of the current linearly changing with the voltage appears. Area. The above results all indicate that there are a lot of defects in the undoped CsSnBr ₃ semiconductor material.

Claims (9)

1. A tin-containing semiconductor material is characterized in that the tin-containing semiconductor material is CsSnBr₃In the preparation process, crystals with different carrier concentrations are grown by adding metal simple substances or metal compounds for doping.

2. The tin-containing semiconductor material of claim 1, wherein the starting material comprises CsBr, SnBr₂And a simple metal or a metal compound.

3. The tin-containing semiconductor material of claim 2, wherein the elemental metal or metal compound is any one or more of elemental tin or tetravalent tin compound, elemental indium or indium compound, and elemental silver or silver compound.

4. The tin-containing semiconducting material of claim 3, wherein the tetravalent tin compound is SnBr₄Or Cs₂SnBr₆。

5. The tin-containing semiconductor material of claim 3, wherein the indium compound is InBr.

6. The tin-containing semiconductor material of claim 3, wherein the silver compound is AgBr.

7. The tin-containing semiconductor material of claim 3, wherein the elemental tin has a mass not less than CsBr and SnBr₂The sum of the masses of (a) and (b).

8. The tin-containing semiconductor material of any one of claims 3 to 7, wherein the mole number of the tetravalent tin compound, the other elemental metal or the metal compound is not more than SnBr₂5% of the mole number.

9. A method for preparing a tin-containing semiconductor material as claimed in any one of claims 2 to 8, characterized in that CsBr, SnBr₂Mixing with metal simple substance or metal compound, heating under the protection of inert gas to react, and slowly cooling to obtain CsSnBr with different carrier concentrations₃A semiconductor crystalline material.

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