阅读说明：本技术 一种铬掺杂硫镓银晶体实现多光子吸收的方法 (Method for realizing multi-photon absorption of chromium-doped sulfur gallium silver crystal ) 是由 彭文豪 陈平 李彬彬 施凯旋 于 2021-06-17 设计创作，主要内容包括：本发明涉及一种铬掺杂硫镓银晶体实现多光子吸收的方法,具体通过Cr掺杂在宿主材料AgGaS-(2)的阳离子Ga位,以此形成的半导体化学分子式为AgGa-(1-x)Cr-(x)S-(2),式中0.008<x<0.1。与现有技术相比,本发明引入一条金属性的半占据中间带,中间带主要由Cr的3d态价电子构成。因为这一金属性的中间带出现,实现了多种低能光子吸收,提高了光生电子空穴对的数量,故其光子能量能够很好地覆盖太阳光谱的可见光范围,有效利用了太阳光,极大地提高了可见光的光学吸收效率,进而有效提升太阳能电池的光电转换效率和光解水制氢活性,因此本材料有望改进传统半导体光学效率低下的问题,并有望成为新一代光催化制氢材料。(The invention relates to a method for realizing multi-photon absorption by chromium-doped sulfur gallium silver crystal, in particular to a method for doping Cr in host material AgGaS 2 The semiconductor chemical molecule formed thereby is AgGa 1‑x Cr x S 2 0.008 in the formula<x<0.1. Compared with the prior art, the invention introduces a metallic semi-occupied intermediate band, and the intermediate band is mainly composed of 3d valence electrons of Cr. Because the metallic intermediate band appears, the absorption of various low-energy photons is realized, and the number of photo-generated electron hole pairs is increased, so that the photon energy can well cover the visible light range of the solar spectrum, the sunlight is effectively utilized, and the light of the visible light is greatly increasedThe absorption efficiency is learned, and the photoelectric conversion efficiency and the hydrogen production activity by water photolysis of the solar cell are effectively improved, so that the material is expected to improve the problem of low optical efficiency of the traditional semiconductor and is expected to become a new generation of photocatalytic hydrogen production material.)

1. Cr-doped AgGaS₂The method for realizing multi-photon absorption is characterized in that the host material AgGaS is doped with Cr₂The semiconductor chemical molecule formed thereby is AgGa_1-xCr_xS₂0.008 in the formula<x<0.1。

2. The Cr-doped AgGaS according to claim 1₂A method of achieving multiphoton absorption, wherein x is in the range of 0.008<x≤0.03。

3. The Cr-doped AgGaS according to claim 2₂A method for realizing multiphoton absorption, wherein x is in the range of 0.01. ltoreq. x.ltoreq.0.03.

4. The Cr-doped AgGaS according to claim 1₂The method for realizing multi-photon absorption is characterized in that the Cr is doped in a host material AgGaS₂The process of cationic Ga site of (a) is:

s1: sintering Ag powder, Ga blocks and S powder in a stoichiometric ratio in vacuum at the sintering temperature of 700-900 ℃ to obtain AgGaS₂Powder;

s2: sintering Ag powder, Cr powder and S powder in a stoichiometric ratio in vacuum at the sintering temperature of 700-900 ℃ to obtain AgCrS₂Powder;

s3: vacuum sintering the AgGaS obtained in S1 and S2₂And AgCrS₂Crushing the powder, grinding and mixing the powder, then sintering the powder in vacuum at the sintering temperature of 700-900 ℃, taking out the powder, grinding the powder again to obtain AgGa_1-xCr_xS₂。

5. According to the rightThe Cr-doped AgGaS of claim 4₂The method for realizing multi-photon absorption is characterized in that the vacuum sintering process in S1, S2 and S3 is as follows: packaging the material to be sintered in a quartz glass tube, placing the quartz glass tube in a muffle furnace for sintering at a heating speed of 10 ℃/min, heating to 900 ℃, preserving heat for 48 hours, and taking out after the temperature in the furnace is cooled to room temperature.

6. The Cr-doped AgGaS according to claim 1₂The method for realizing multi-photon absorption is characterized in that in the Cr doping process, the intermediate band is introduced by utilizing the delocalization characteristic of the bonding of a transition metal element Cr.

7. The Cr-doped AgGaS according to claim 1₂A method for realizing multiphoton absorption, characterized in that Cr forms a metallic half-occupied intermediate band in a host material after doping of Cr, and has triplet optical absorption.

8. The Cr-doped AgGaS according to claim 1₂The method for realizing multi-photon absorption is characterized in that after Cr is doped, a metallic intermediate band consists of Cr-3d state, Ag-4d state and S-3p state.

9. The Cr-doped AgGaS according to claim 1₂The method for realizing multi-photon absorption is characterized in that after Cr is doped, a metallic intermediate band is in an isolated structure.

10. The Cr-doped AgGaS according to claim 1₂The method for realizing multiphoton absorption is characterized in that AgGa obtained after Cr doping_1-xCr_xS₂The higher the concentration of the doping element Cr, the stronger the optical absorption of the semiconductor material.

Technical Field

The invention relates to the field of semiconductor photoelectric materials, in particular to Cr-doped AgGaS₂A method for achieving multiphoton absorption.

Background

In recent years, the living standard of people is continuously improved, the society is continuously developed, the demand of various industries on electric energy is also continuously improved, however, the shortage of electric energy is gradually a key factor for hindering the stable development of the electric industry. In spite of rapid development of new energy in recent years, fossil energy still occupies a major position in energy supply in China. Meanwhile, the problem of environmental pollution caused by fossil energy is becoming more serious, the social development at the cost of environmental sacrifice is not a long-term measure, and China must make a balance between development and environment if sustainable development is required. Therefore, the development of clean energy is urgently needed.

In recent years, new energy and renewable energy such as nuclear power, wind power, solar energy, tidal energy and the like are rapidly developed, but the nuclear power and the wind power have very high requirements on environment and safety, and the solar energy has the advantages of universality, harmlessness, convenience in installation and the like, so that the development of the solar energy has wide prospects. At present, solar cells are mainly classified into three main categories: silicon-based solar cells, compound thin-film solar cells, and third-generation solar cells. The silicon-based solar cell is limited in development due to complex manufacturing process and high cost, and the thin film solar cell is lighter than the silicon-based solar cell, but the efficiency of the thin film solar cell is limited by the Shockley-Queisser limit.

The third generation solar cell is a high-efficiency and low-cost solar cell, has a wider photon absorption range than a single band gap due to the existence of an intermediate band, and has a theoretical photoelectric conversion efficiency which breaks through the S-Q limit, so that the third generation solar cell is widely concerned. There are currently several main methods for obtaining the interzone: the first is to design the quantum dot intermediate band, which has the disadvantage that the intermediate band comes from a finite electronic state in the conduction band and therefore lacks sufficient state density; the second is a highly mismatched alloy, but for the growth of highly mismatched alloys expensive epitaxial or pulsed laser melting techniques are required.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a Cr-doped AgGaS₂The method for realizing multi-photon absorption introduces metallic half-occupied intermediate energy band by doping transition metal element Cr, thereby realizing the absorption of a plurality of low-energy photons of the semiconductor material and improving the optical absorption efficiency.

As a starting point of the concept of the present solution, introducing an intermediate band by impurities is the best method to improve the optical absorption efficiency at present.

The purpose of the invention can be realized by the following technical scheme:

the purpose of the application is to protect Cr-doped AgGaS₂Method for realizing multiphoton absorption by doping Cr in host material AgGaS₂The semiconductor chemical molecule formed thereby is AgGa_1-xCr_xS₂0.008 in the formula<x<0.1. When x is more than or equal to 0.1, a mixed phase can be obviously generated, and when x is less than or equal to 0.008, the absorption is weaker because the Cr content is too low.

Further preferably, wherein x is in the range of 0.008< x.ltoreq.0.03.

Further preferably, x is in the range 0.01. ltoreq. x.ltoreq.0.03, this range being the experimentally proven, impurity-free and absorption-optimum interval.

Further, the Cr is doped in a host material AgGaS₂The process of cationic Ga site of (a) is:

s1: sintering Ag powder, Ga blocks and S powder in a stoichiometric ratio in vacuum at the sintering temperature of 700-900 ℃ to obtain AgGaS₂Powder;

s2: sintering Ag powder, Cr powder and S powder in a stoichiometric ratio in vacuum at the sintering temperature of 700-900 ℃ to obtain AgCrS₂Powder;

s3: vacuum sintering the AgGaS obtained in S1 and S2₂And AgCrS₂Crushing the powder, grinding and mixing to obtain an ideal powder material, carrying out vacuum sintering at the sintering temperature of 700-900 ℃, taking out, and grinding again to obtain AgGa_1-xCr_xS₂。

Further, the vacuum sintering process in S1, S2, S3 is: packaging the material to be sintered in a quartz glass tube, placing the quartz glass tube in a muffle furnace for sintering at a heating speed of 10 ℃/min, heating to 900 ℃, preserving heat for 48 hours, and taking out after the temperature in the furnace is cooled to room temperature.

Further, in the Cr doping process, the intermediate zone is introduced by utilizing the delocalization characteristic of the bonding of the transition metal element Cr.

Further, after Cr doping, Cr forms a metallic half-occupied intermediate band in the host material and has triplet optical absorption, see fig. 1.

Further, after Cr doping, the metallic intermediate band consists of Cr-3d, Ag-4d and S-3p states.

Further, after Cr doping, the metallic intermediate band is an isolated structure.

Further, after Cr is doped, the obtained AgGa_1-xCr_xS₂The higher the concentration of the doping element Cr, the stronger the optical absorption of the semiconductor material.

Compared with the prior art, the invention has the following technical advantages:

1) chalcopyrite structured sulphides mostly have a low bandwidth, which plays a very important role in forming an ideal intermediate band material. Aiming at the problems of low optical absorption efficiency and low photolytic water activity of the Si-based semiconductor, the invention dopes AgGaS by the transition metal element Cr₂Chalcopyrite material introduces a metallic semi-occupied intermediate band, which is mainly composed of 3d valence electrons of Cr. Due to the appearance of the metallic intermediate band, the absorption of various low-energy photons is realized, and the number of photo-generated electron hole pairs is increased, so that the photon energy can well cover the visible light range of the solar spectrum, the sunlight is effectively utilized, the optical absorption efficiency of visible light is greatly improved, and the photoelectric conversion efficiency and the hydrogen production activity by water photolysis of the solar cell are further effectively improved. Therefore, the material is expected to improve the problem of low optical efficiency of the traditional semiconductor and is expected to become a new generation of photocatalytic hydrogen production material.

2）AgGa in the technical scheme_1-xCr_xS₂The synthesis method of the material is a two-step method, reduces the generation of impurities and reaction temperature, and is beneficial to industrialized popularization and improvement of the problems of low optical absorption efficiency of the solar cell and hydrogen production activity by photolysis of water in the field of photocatalysis at present.

Drawings

FIG. 1 is a metallic intermediate band triplet optical absorption diagram.

FIG. 2 is AgGa_1-xCr_xS₂(x =0, 0.01, 0.02, 0.03) XRD pattern of the series of samples.

FIG. 3 is AgGaS₂Band structure diagrams for undoped (left) and doped (right) samples.

FIG. 4 is Cr doped AgGaS₂Electron-wavelength-division density of states (PDOS).

FIG. 5 shows AgGa with different doping concentrations_1-xCr_xS₂The solar absorption spectrum of (1).

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

In the conception of the technical scheme, a plurality of transition metal elements are found, so how to find a proper element to be doped into AgGaS₂And to obtain good optical properties is critical, and this conceptual process is appreciated by those skilled in the art. Through a large amount of experimental researches, the applicant finally finds that the transition metal element Cr is doped with AgGaS₂The purpose of improving the optical absorption efficiency can be achieved by realizing multi-photon absorption.

The semiconductor material is AgGaS₂The chalcopyrite compound is a multi-element chalcopyrite compound, is the most main near-infrared nonlinear optical material so far, and has wide application prospect in the fields of photocatalysis, photoelectron, biosensors and the like. In the field of solar cells, AgGaS₂The semiconductor material has a direct band gap closely matched with the solar spectrum, and has an optical band gap value of about 2.51-2.73eV, andthe material is close to the forbidden bandwidth of an ideal intermediate band semiconductor material, and has higher absorption coefficient to visible light and better thermal, electrical and environmental stability. And because of AgGaS₂Has wide band gap, high light transmittance and low birefringence, and therefore, the AgGaS can be enlarged by selecting a suitable method₂The method has important practical significance for the absorption range of the solar spectrum and the high-efficiency solar cell manufactured by the method. In the field of photocatalysis, AgGaS₂The semiconductor material has important application in two aspects of photocatalytic hydrogen production and photocatalytic degradation of organic dye. In the photocatalysis process, electrons in a semiconductor are excited through irradiation of light to generate electron-hole pairs, part of electrons and holes are compounded, the other part of electrons and holes are separated, the separated photoproduction electrons are subjected to reduction reaction on the surface of a catalyst to reduce hydrogen ions into hydrogen, and the separated holes are subjected to oxidation reaction on the surface of the catalyst to oxidize water into oxygen. Chinese invention patent (CN110422873A) discloses doping AgGaS with elemental Sn₂An impurity band is introduced to improve optical absorption.

However, according to the current research situation at home and abroad, no AgGaS doping transition metal Cr element is selected₂To achieve multiphoton absorption. Through a large amount of theoretical research and experimental exploration, the invention discovers that the transition metal element Cr replaces AgGaS₂The Ga cation position of the crystal can obtain a metallic intermediate band in a semi-occupied state, and a plurality of absorption peaks appear in a visible light low energy range along with the increase of the doping concentration, which shows that photon absorption with different energies is realized due to the existence of the intermediate band, and the number of pairs of electrons and holes can be increased. Therefore, the material is expected to improve the problem of low optical efficiency of the traditional semiconductor and is expected to become a new generation of photocatalytic hydrogen production material.

The invention utilizes a vacuum solid state reaction sintering method to prepare a Cr-doped compound, and verifies AgGa through energy band analysis, state density analysis and spectral analysis_1-xCr_xS₂Formation of a dopant compound, multiphoton absorption observed, and no other impurity-forming phase during doping, good optical propertiesThe absorption properties are as desired in the present invention.

Examples 1 to 3

AgGa_1-xCr_xS₂(xMaterial of =0, 0.01, 0.02, 0.03) is prepared by a vacuum solid state sintering reaction method, and the specific flow is as follows:

the method comprises the following steps: firstly, Ag powder (4N), Ga blocks (5N) and S powder (5N) are packaged in a quartz glass tube in a vacuum mode according to stoichiometric ratio, then the quartz glass tube is placed in a muffle furnace to be sintered, the sintering temperature range is 700-900 ℃, the heating speed is 10 ℃/min, after the quartz glass tube is insulated for 48 hours at 900 ℃, an experimental sample can be taken out after the temperature in the furnace is cooled to the room temperature, and the sample is marked and packaged.

Step two: vacuum packaging Ag powder (4N), Cr powder (4N) and S powder (5N) in a quartz glass tube according to the stoichiometric ratio, then placing the quartz glass tube in a muffle furnace for sintering, wherein the sintering temperature range is 700-900 ℃, the heating speed is 10 ℃/min, keeping the temperature at 900 ℃ for 48 hours, taking out an experimental sample after the temperature in the furnace is cooled to room temperature, marking the sample, and bagging.

Step three: the reaction product obtained by vacuum sintering is AgGaS₂And AgCrS₂And (2) crushing the obtained sample, grinding and mixing to obtain an ideal powder material, carrying out vacuum packaging again, heating to 900 ℃, keeping the temperature, sintering again to the highest temperature, keeping the temperature for 48 hours, taking out the experimental sample after the temperature in the furnace is cooled to room temperature, and grinding again in an agate mortar to obtain the final sample.

The X-ray diffraction pattern of the material was measured by a Bruker D8 ADVANCE X-ray diffractometer using Cu Ka1 radiation (0.15405 nm), a scanning voltage of 40 kV and a scanning current of 40 mA. The ultraviolet-visible-near infrared absorption spectrum of the material was measured on a Hitachi U4100 UV-Vis-NIR spectrophotometer.

Prepared AgGa_1-xCr_xS₂Semiconductor material characterization

AgGa_1-xCr_xS₂(x =0, 0.01, 0.02, 0.03) powder sample XRD pattern was consistent with that of standard card (JCPDS #27-0615) (fig. 2), indicating that the sample was producedThere were no other impurity phases and Cr had been successfully doped into the cationic Ga sites. The sample powder was subjected to band analysis and a comparison of the host material band diagram before doping with the sample band diagram after doping (FIG. 3) shows that metallic, semi-occupied intermediate bands are present in the doped sample band diagram and isolated.

As can be seen from the wavelength-division density diagram (PDOS) of the sample powder (fig. 4), the introduced intermediate band is mainly composed of the 3d state of Cr, the 4d state of Ag and the 3p state of S (black-S state, red-p state, blue-d state). It can be seen from the optical absorption chart (fig. 5) of the sample powder that in the visible light range, additional absorption peaks are observed in both low-energy and high-energy regions, and it can be seen from the chart that the absorption coefficient of the sample after Cr doping is obviously improved compared with the sample before doping, and the absorption coefficient is also increased along with the increase of doping concentration, which proves that the sample has the absorption of photons with various energies.

In summary, AgGaS₂The reason for the enhanced optical absorption of the material is that the doping of the transition metal element Cr introduces a metallic semi-occupied intermediate band which is mainly composed of d-state electrons of the transition metal element Cr and no other impurity phase is generated during the doping process. It can be seen from the absorption spectrum that the absorption curve after doping shows additional absorption peaks, thus proving that there is photon absorption of different energies, and the number of electron and hole pairs is increased because of the absorption of multiple photons. Thus, by using in AgGaS₂The Cr element is doped in the material to prepare the solar cell material with high-efficiency photon absorption and the activity of hydrogen production by photolysis of water is improved by multiphoton absorption.

From AgGa_1-xCr_xS₂The band diagram of the powder sample shows (fig. 4) that due to the doping of Cr, a metallic semi-occupied intermediate band appears in the sample band diagram and consists mainly of d-valence electrons of the transition metal Cr, which makes it possible for the doped material to absorb multiple photons. From the optical absorption diagram (FIG. 5, it can be seen that the absorption curve shows distinct absorption peaks in both the low-energy and high-energy ranges, and the doped system is compared with the undoped systemThe absorption curve is obviously increased, and the absorption coefficient is obviously enhanced in the visible light range, which just indicates that the metallic semi-occupied intermediate band causes the absorption of multiphoton, so that the number of electron hole pairs is increased, and the absorption coefficient is greatly improved. And with the increase of the doping concentration, the absorption curve gradually rises, and the absorption coefficient is obviously improved.

The invention provides a new method for realizing AgGaS₂The multiphoton absorption method successfully increases the absorption range of the material in the solar spectrum and improves the utilization efficiency of visible light, so that the material has great application prospects in the fields of solar cells, photocatalytic water photolysis hydrogen production, photoelectric sensors and the like.

Comparative example 1

CN110422873A discloses an AgGaS₂Intermediate base band semiconductor material and preparation method thereof, and intrinsic semiconductor AgGaS doped with VI group element Sn₂The Ga site of the precursor compound AgGaS is sintered in a vacuum solid-phase reaction process₂The Ga site doping element Sn forms an impurity band; compared with the traditional solar cell material, the material widens the absorption spectrum capability.

Compared with the corresponding examples 1 to 3 of the present invention, examples 1 to 3 realized AgGaS₂In the semiconductor multiphoton absorption method, a host material is doped with a transition metal element Cr, a metallic semi-occupied intermediate band is introduced, non-radiative recombination can be effectively inhibited, and phase stability analysis is performed to further ensure that the intermediate band is caused by doping of the transition metal element Cr but not other impurity phases, so that the metallic intermediate band is introduced to realize multiphoton absorption, the number of electron-hole pairs is increased, and the photon absorption capacity is enhanced along with the increase of doping concentration, which plays an important role in improving solar energy absorption efficiency and hydrogen production activity by photolysis of water.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.