An orthorhombic Mn2GeS4 nanomaterial, its preparation method and application

Abstract

The application belongs to the field of multi-component novel photoelectric conversion materials, and particularly relates to an orthorhombic phase Mn2GeS4 nanomaterial and a preparation method and application thereof. The crystal form of the Mn2GeS4 nanomaterial is orthorhombic phase, and the micro-morphology is nanoscale spherical and / or polyhedral structure. The preparation method comprises the following steps: (1) dissolving germanium source in mercaptoacetic acid and / or oleylamine medium to obtain a germanium solution; (2) adding a manganese source, the germanium solution prepared in step (1) and a sulfur source into a high-boiling-point reaction medium to perform a solvothermal reaction, and then separating the solid product in the reaction medium to obtain the Mn2GeS4 nanomaterial. The synthesis method of the Mn2GeS4 nanomaterial has mild reaction conditions and simple process, and realizes controllable synthesis of the orthorhombic phase Mn2GeS4 nanomaterial with controllable size, uniform morphology, high crystallinity and monodispersity. The nanomaterial can be potentially applied to the field of photoelectric conversion applications.

Description

Technical Field

[0001] This invention belongs to the field of novel multi-component photoelectric conversion materials, specifically relating to an orthorhombic Mn2GeS4 nanomaterial, the preparation method of the nanomaterial, and its application in the field of photoelectric conversion. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Multi-dichalcogenides II2-IV-VI4 (II= Mn, Fe, Co; IV= Si, Ge, Sn; VI= S, Se, Te) have become ideal materials to replace cadmium-based or lead-based sulfides due to their tunable atomic ratios, rich crystal structures, high light absorption coefficients and high carrier mobility. They have been extensively studied in energy storage and conversion, environmental remediation and biomedical applications.

[0004] In recent years, Mn₂GeS₄ has been widely used in thermoelectric conversion, and its synthesis methods, structure, and properties have attracted close attention from researchers. One study reported that Mn₂GeS₄ could be obtained by heating pure elements in a sealed ampoule at ~850°C for 3 days via chemical vapor transport, followed by cooling. However, this method is energy-intensive and time-consuming in synthesizing Mn₂GeS₄, and the product size is uncontrollable and the morphology is inhomogeneous, thus affecting or limiting the application of Mn₂GeS₄ in micro / nano devices. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides an orthorhombic Mn2GeS4 nanomaterial, its preparation method, and its applications. The preparation process of this nanomaterial is simple, the reaction conditions are mild, and it achieves the controllable preparation of orthorhombic Mn2GeS4 nanomaterials with controllable size, uniform morphology, and monodispersity.

[0006] Based on the achieved technical effects, the present invention provides the following technical solution: In a first aspect, an orthorhombic Mn2GeS4 nanomaterial is provided, wherein the nanomaterial has an orthorhombic crystal system and its XRD diffraction is within the range of 2... θ Characteristic peaks are observed at 18.3±0.2°, 20.3±0.2°, 23.9±0.2°, 25.6±0.2°, 28.4±0.2°, 29.1±0.2°, 31.6±0.2°, 32.8±0.2°, 41.0±0.2°, 44.8±0.2°, 48.8±0.2°, 49.2±0.2°, and 53.7±0.2°.

[0007] The microstructure of the aforementioned orthorhombic Mn2GeS4 nanomaterials is spherical or polyhedral, with a particle size of 2–20 nm. In some embodiments, the nanomaterials are spherical nanoparticles or quantum dots with an average diameter of approximately 5–10 nm, exhibiting uniform and controllable size, good crystallinity, and monodispersity. Furthermore, the quantum dots can self-assemble into spherical products with a particle size of 100–400 nm.

[0008] Secondly, a method for preparing the orthorhombic Mn2GeS4 nanomaterials described in the first aspect is provided, the method comprising the following steps: (1) Add the germanium source to mercaptoacetic acid and / or oleylamine medium to completely dissolve the germanium source and obtain a germanium solution; (2) Add the manganese source, the germanium solution prepared in step (1), and the sulfur source to a high-boiling-point reaction medium and carry out a solvothermal reaction under an inert atmosphere. After the reaction is completed, separate the solid product to obtain the product.

[0009] In step (1) above, the germanium source includes, but is not limited to, germanium dioxide, germanium tetraiodide and / or germanium tetrachloride.

[0010] When the germanium source is germanium dioxide, the dosage ratio of germanium dioxide, mercaptoacetic acid and oleylamine is 0.1 mmol: 100~200 μL: 0.5~1.5 mL. Germanium dioxide can be dissolved with the aid of ultrasound, heating, magnetic stirring and other methods.

[0011] In step (2) above, there is also the following preferred technical solution: The manganese source is an organic or inorganic salt containing manganese, such as manganese acetylacetone, manganese oxide, manganese chloride, or manganese acetate.

[0012] The sulfur source is preferably an organic sulfide, including but not limited to mercaptoacetic acid, mercaptopropionic acid, n-dodecyl mercaptoethanol, diphenyl disulfide and / or dibenzyl disulfide.

[0013] The molar ratio of Mn:Ge:S in the above manganese, germanium and sulfur sources is 2:(1-1.5):(4-30).

[0014] The high-boiling-point reaction medium is selected from any one or a combination of organic amines, oleic acid, octadecene, and trioctylphosphine oxide; wherein the organic amine is selected from one or more of oleylamine, octadecylamine, or hexadecylamine.

[0015] In some embodiments, the high-boiling-point medium is oleylamine, and the dosage ratio of the germanium source to oleylamine is 0.1 mmol: 6~10 mL.

[0016] In some other embodiments, the high-boiling-point medium is a combination of oleylamine and trioctylphosphine oxide, and the dosage ratio of the germanium source to oleylamine and trioctylphosphine oxide is 0.1 mmol: 6~10 mL: 1~3 mmol.

[0017] In some other embodiments, the high-boiling-point medium is a combination of oleylamine and octadecene, and the dosage ratio of the germanium source to oleylamine and octadecene is 0.1 mmol: 5~9 mL: 1~4 mL.

[0018] In some other embodiments, the high-boiling-point medium is a combination of oleylamine and oleic acid, and the dosage ratio of the germanium source to oleylamine and oleic acid is 0.1 mmol: 5.5~9.5 mL: 0.1~1.0 mL.

[0019] The solvothermal reaction adopts a two-stage heating program: the manganese source, the germanium solution prepared in step (1) and the sulfur source are added to a high-boiling-point reaction medium to obtain a mixture. The mixture is placed under an inert atmosphere and magnetic stirring conditions. In the first stage, the temperature is increased to 100-210℃ at 8-12℃ / min and kept at a constant temperature for 15-120min to fully dissolve the manganese source, germanium source and sulfur source. In the second stage, the temperature is increased rapidly to 260-320℃ at 18-22℃ / min and kept at a constant temperature for 5-120min.

[0020] After the hydrothermal reaction is complete, the reaction system is cooled to room temperature, and the solid product in the reaction solution is separated by centrifugation or filtration; this is the target product. According to common practice in the art, the solid product can be washed with an organic reagent, such as anhydrous ethanol or cyclohexane.

[0021] According to the research of the present invention, the nanomaterials provided in the first aspect above exhibit strong absorption in the visible light range, absorb photons to generate excitons, and have high photoelectric conversion efficiency. Therefore, in a third aspect of the present invention, the application of the orthorhombic Mn2GeS4 nanomaterials described in the first aspect is provided in the field of photoelectric conversion.

[0022] In the above applications, the field of photoelectric conversion is further selected from any one or more of photoelectric detection, photovoltaic power generation, optoelectronic integration, optical signal processing and optical communication, wherein the above orthogonal Mn2GeS4 nanomaterial is used as a photoelectric conversion active layer, photosensitive layer, light-absorbing layer or photogenerated carrier generation layer.

[0023] In one embodiment, the orthorhombic Mn2GeS4 nanomaterial is used to fabricate a photodetector; the photodetector is selected from any one of photoconductive detectors, photovoltaic detectors, photodiodes, phototransistors, photoresistors, position-sensitive detectors, and imaging sensors. In one example verified by this invention, the orthorhombic Mn2GeS4 nanomaterial is used to fabricate a photodetector. Specifically, the nanomaterial is dispersed in an organic solvent (such as cyclohexane) to prepare a dispersion, coated onto a device substrate (such as a glass substrate) to form a film, and Au is used as an electrode to construct the photodetector. Verification shows that this photodetector exhibits good responsiveness and stability under white light irradiation and an applied 0.5V bias voltage.

[0024] In another embodiment, the orthorhombic Mn2GeS4 nanomaterial is used to prepare a photovoltaic device; the photovoltaic device is selected from any one of solar cells, photoelectrochemical cells, quantum dot sensitized solar cells, tandem solar cells, flexible solar cells, and semi-transparent photovoltaic devices.

[0025] In another embodiment, the orthogonal Mn2GeS4 nanomaterial is used to fabricate optoelectronic integrated devices; the optoelectronic integrated devices are selected from any one of photonic chips, on-chip optical interconnect devices, on-chip photodetectors, optical waveguide coupling devices, optical switching devices, and photonic computing devices.

[0026] Compared with the prior art, the beneficial effects of the present invention are: 1. In existing research, Mn2GeS4 nanomaterials are mostly synthesized using high-temperature solid-state methods, which involve high reaction temperatures and long reaction times. This invention optimizes the preparation method of Mn2GeS4 nanomaterials by first using a milder preparation process to obtain a pure-phase orthorhombic nanomaterial, effectively reducing the energy consumption of the preparation process.

[0027] 2. The orthorhombic Mn2GeS4 nanomaterial obtained in this invention belongs to the pure-phase orthorhombic crystal system. Its orthorhombic crystal system characteristics (a≠b≠c, the three axes are mutually perpendicular) have many advantages in optoelectronic applications: (1) The low symmetry of the orthorhombic crystal system results in different dielectric functions and absorption coefficients in the three crystal directions. After the absorption edges of each crystal direction are superimposed, the overall absorption covers a wider visible light range, achieving a broad spectral response, which is consistent with the present invention. Figure 3 The results echoed each other.

[0028] (2) The band dispersion of orthorhombic crystal systems is directional, and higher carrier mobility can be obtained along a specific crystal orientation. As a photoelectric conversion material, it helps to improve photoelectric response speed and sensitivity.

[0029] (3) This orthorhombic Mn2GeS4 nanomaterial belongs to the thio-olivine structure, S2- Approximately hexagonal close-packed, Mn 2+ Occupying 1 / 2 of the octahedral position, Ge 4+ Occupying 1 / 8 of the tetrahedral sites, it forms a three-dimensional covalent framework. This structure exhibits good chemical stability, resistance to oxidation and solvent corrosion, and high thermal stability, which is beneficial for the long-term operational stability of optoelectronic devices. Attached Figure Description

[0030] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0031] Figure 1 X-ray diffraction (XRD) pattern of the target product obtained in Example 1.

[0032] Figure 2 This is a transmission electron microscope (TEM) image of the target product obtained in Example 1.

[0033] Figure 3 This is the UV-Vis-NIR absorption spectrum of the target product obtained in Example 1.

[0034] Figure 4 The image shows the It curve of the photodetector constructed from the target product obtained in Example 1 under white light irradiation.

[0035] Figure 5 This is the X-ray diffraction pattern (XRD) of the target product obtained in Example 2.

[0036] Figure 6 This is a transmission electron microscope (TEM) image of the target product obtained in Example 3.

[0037] Figure 7 This is the X-ray diffraction pattern (XRD) of the target product obtained in Example 4.

[0038] Figure 8 This is a transmission electron microscope (TEM) image of the target product obtained in Example 5.

[0039] Figure 9 This is a scanning electron microscope (SEM) image of the target product obtained in Example 6. Detailed Implementation

[0040] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0041] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0042] In the context of this invention, the word "comprising" is considered to mean "particularly including". It should not be interpreted as "consisting of only".

[0043] In the description of this invention, it should be understood that the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. The symbol " / " in this document indicates that the related objects are in an "or" relationship; for example, A / B means A or B.

[0044] In the description of embodiments of the present invention, the words "exemplary" or "for example" are used to indicate that they are examples, illustrations, or descriptions. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of the present invention should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the words "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0045] In the description of the embodiments of the present invention, unless otherwise stated, "a plurality of" means two or more.

[0046] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0047] Example 1 In this embodiment, an orthorhombic Mn2GeS4 nanomaterial and its preparation method are provided, including the following steps: (1) In a 5 mL test tube, add 0.1 mmol germanium dioxide, 100 μL mercaptoacetic acid and 0.5 mL oleylamine respectively, and sonicate to completely dissolve germanium dioxide to obtain germanium source.

[0048] (2) Add the germanium source prepared in (1) above, 0.2 mmol of manganese acetylacetone and 8 mL of oleylamine to a 100 mL three-necked flask. Purge with nitrogen and heat the mixture to 110 °C at 10 °C / min under magnetic stirring for 60 min to remove moisture and low-boiling-point impurities from the reaction system.

[0049] (3) Continue to heat the mixture rapidly at 20℃ / min to 300℃ and react for 30 min. After the reaction is completed, cool to room temperature and then wash the solid product three times with anhydrous ethanol and cyclohexane respectively. The solid product obtained by centrifugation is the target product.

[0050] Example 2 In this embodiment, an orthorhombic Mn2GeS4 nanomaterial and its preparation method are provided, including the following steps: (1) In a 5 mL test tube, add 0.1 mmol germanium dioxide, 150 μL mercaptoacetic acid and 0.75 mL oleylamine respectively, and sonicate to completely dissolve germanium dioxide to obtain germanium source.

[0051] (2) Add the germanium source prepared in (1) above, 0.2 mmol of manganese acetylacetone, 7.0 mL of oleylamine and 1.0 mL of octadecene to a 100 mL three-necked flask. Purge with nitrogen and heat the mixture to 160 °C at 10 °C / min under magnetic stirring for 30 min to remove moisture and low-boiling-point impurities from the reaction system.

[0052] (3) Continue to heat the mixture rapidly at 20℃ / min to 280℃ and react for 60 min. After the reaction is completed, cool to room temperature and then wash the solid product three times with anhydrous ethanol and cyclohexane respectively. The solid product obtained by centrifugation is the target product.

[0053] Example 3 In this embodiment, an orthorhombic Mn2GeS4 nanomaterial and its preparation method are provided, including the following steps: (1) In a 5 mL test tube, add 0.1 mmol germanium dioxide, 200 μL mercaptoacetic acid and 1.0 mL oleylamine respectively, and sonicate to completely dissolve germanium dioxide to obtain germanium source.

[0054] (2) Add the germanium source prepared in (1) above, 0.2 mmol of manganese acetylacetone and 8 mL of oleylamine to a 100 mL three-necked flask. Purge with nitrogen and heat the mixture to 180 °C at 10 °C / min under magnetic stirring for 20 min to remove moisture and low-boiling-point impurities from the reaction system.

[0055] (3) Continue to heat the mixture rapidly at 20℃ / min to 320℃ and react for 5 min. After the reaction is completed, cool to room temperature and then wash the solid product three times with anhydrous ethanol and cyclohexane respectively. The solid product obtained by centrifugation is the target product.

[0056] Example 4 In this embodiment, an orthorhombic Mn2GeS4 nanomaterial and its preparation method are provided, including the following steps: (1) In a 5 mL test tube, add 0.1 mmol germanium dioxide, 100 μL mercaptopropionic acid and 0.5 mL oleylamine respectively, and sonicate to completely dissolve germanium dioxide to obtain germanium source.

[0057] (2) Add the germanium source prepared in (1) above, 0.2 mmol of manganese chloride and 8 mL of oleylamine to a 100 mL three-necked flask. Purge with nitrogen and heat the mixture to 110 °C at 10 °C / min under magnetic stirring for 60 min to remove moisture and low-boiling-point impurities from the reaction system.

[0058] (3) Continue to heat the mixture rapidly at 20℃ / min to 300℃ and react for 60 min. After the reaction is completed, cool to room temperature and then wash the solid product three times with anhydrous ethanol and cyclohexane respectively. The solid product obtained by centrifugation is the target product.

[0059] Example 5 In this embodiment, an orthorhombic Mn2GeS4 nanomaterial and its preparation method are provided, including the following steps: (1) In a 5 mL test tube, add 0.1 mmol germanium dioxide, 100 μL mercaptoacetic acid and 0.5 mL oleylamine respectively, and sonicate to completely dissolve germanium dioxide to obtain germanium source.

[0060] (2) Add the germanium source prepared in (1) above, 0.2 mmol of manganese acetylacetone, 7.5 mL of oleylamine and 0.5 mL of oleic acid to a 100 mL three-necked flask. Purge with nitrogen and heat the mixture to 110 °C at 10 °C / min under magnetic stirring for 60 min to remove moisture and low-boiling-point impurities from the reaction system.

[0061] (3) Continue to heat the mixture rapidly at 20℃ / min to 260℃ and react for 120 min. After the reaction is completed, cool to room temperature and then wash the solid product three times with anhydrous ethanol and cyclohexane respectively. The solid product obtained by centrifugation is the target product.

[0062] Example 6 In this embodiment, an orthorhombic Mn2GeS4 nanomaterial and its preparation method are provided, including the following steps: (1) In a 5 mL test tube, add 0.1 mmol germanium dioxide, 100 μL mercaptoacetic acid and 0.5 mL oleylamine respectively, and sonicate to completely dissolve germanium dioxide to obtain germanium source.

[0063] (2) Add the germanium source prepared in (1) above, 0.2 mmol manganese acetylacetone, 8 mL of oleylamine and 2 mmol of trioctylphosphine oxide to a 100 mL three-necked flask. Purge with nitrogen and heat the mixture to 160 °C at 10 °C / min under magnetic stirring for 60 min to remove moisture and low-boiling-point impurities from the reaction system.

[0064] (3) Continue to heat the mixture rapidly at 20℃ / min to 300℃ and react for 60 min. After the reaction is completed, cool to room temperature and then wash the solid product three times with anhydrous ethanol and cyclohexane respectively. The solid product obtained by centrifugation is the target product.

[0065] Composition, structure characterization and performance testing Figure 1 The image shows the X-ray diffraction pattern of the target product obtained in Example 1. As can be seen from the figure, all diffraction peaks accurately represent the corresponding crystal planes in Mn₂GeS₄ (JCPDS Card No. 18-0786), and no other impurity peaks appear, indicating that the target product prepared by the method of this example is an orthorhombic Mn₂GeS₄ crystal. Similarly, Figure 5 , Figure 7 The results also showed that the target products prepared in Examples 2 and 4 had the same properties as... Figure 1 Similar results.

[0066] Figure 2 The transmission electron microscope (TEM) image of the target product obtained in Example 1 shows that the Mn2GeS4 prepared by this method is a spherical nanomaterial with an average diameter of approximately 10.0 nm, and the size of the obtained Mn2GeS4 is uniform and controllable. Similarly, Figure 6 , Figure 8 The results also showed that the target products prepared in Examples 3 and 5 were monodisperse and had uniform and controllable size.

[0067] Figure 3 The UV-Vis-NIR light absorption spectrum of the product obtained in Example 1 shows that the orthorhombic Mn2GeS4 nanomaterials have strong absorption in the visible light range, indicating that the Mn2GeS4 nanomaterials prepared by this method can be used as broadband photoelectric conversion materials.

[0068] Figure 4 The It curve is shown for the photodetector constructed using the product obtained in Example 1. The target product obtained in Example 1 was ultrasonically dispersed in cyclohexane to prepare a viscous solution, which was then spin-coated onto glass and used Au as an electrode to construct a Mn₂GeS₄ photodetector. Figure 4 The photodetector exhibits good responsiveness and stability under the conditions of white light irradiation and an applied bias voltage of 0.5V.

[0069] Figure 8 The image shown is a transmission electron microscope (TEM) image of the target product obtained in Example 5, which shows that the Mn2GeS4 quantum dots prepared by this method have a diameter of approximately 5 nm, and the size is uniform and controllable, with good crystallinity.

[0070] Figure 9 The image shown is a scanning electron microscope (SEM) image of the target product obtained in Example 6, indicating that the Mn2GeS4 prepared by this method is formed by the self-assembly of nanoparticles into nanospheres with a diameter of 100-400 nm.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An orthorhombic Mn2GeS4 nanomaterial, characterized in that, The nanomaterial has an orthorhombic crystal system, and its XRD diffraction is at 2... θ Characteristic peaks are observed at 18.3±0.2°, 20.3±0.2°, 23.9±0.2°, 25.6±0.2°, 28.4±0.2°, 29.1±0.2°, 31.6±0.2°, 32.8±0.2°, 41.0±0.2°, 44.8±0.2°, 48.8±0.2°, 49.2±0.2°, and 53.7±0.2°.

2. The orthorhombic Mn2GeS4 nanomaterial as described in claim 1, characterized in that, The orthorhombic Mn2GeS4 nanomaterial has a spherical or polyhedral structure with a particle size of 2~20 nm. Furthermore, the nanomaterial is a spherical nanoparticle or quantum dot with an average diameter of about 5 to 10 nm; in addition, the quantum dot can self-assemble into a spherical product with a particle size of 100 to 400 nm.

3. The method for preparing the orthorhombic Mn2GeS4 nanomaterial according to claim 1 or 2, characterized in that, The preparation method includes the following steps: (1) Add the germanium source to mercaptoacetic acid and / or oleylamine medium to completely dissolve the germanium source and obtain a germanium solution; (2) Add the manganese source, the germanium solution prepared in step (1), and the sulfur source to a high-boiling-point reaction medium and carry out a solvothermal reaction under an inert atmosphere. After the reaction is completed, separate the solid product to obtain the product.

4. The preparation method according to claim 3, characterized in that, In step (1), the germanium source includes, but is not limited to, germanium dioxide, germanium tetraiodide, and / or germanium tetrachloride; When the germanium source is germanium dioxide, the dosage ratio of germanium dioxide, mercaptoacetic acid and oleylamine is 0.1 mmol: 100~200 μL: 0.5~1.5 mL. Germanium dioxide is dissolved with the aid of ultrasound, heating or magnetic stirring.

5. The preparation method according to claim 3, characterized in that, In step (2), the manganese source is an organic or inorganic salt containing manganese, and is further selected from manganese acetylacetone, manganese oxide, manganese chloride or manganese acetate; The sulfur source is preferably an organic sulfide, including but not limited to mercaptoacetic acid, mercaptopropionic acid, n-dodecyl mercaptoethanol, diphenyl disulfide and / or dibenzyl disulfide; The molar ratio of Mn:Ge:S in the manganese source, germanium source and sulfur source is 2:(1-1.5):(4-30).

6. The preparation method according to claim 3, characterized in that, The high-boiling-point reaction medium is selected from any one or a combination of organic amines, oleic acid, octadecene, and trioctylphosphine oxide; wherein the organic amine is selected from one or more of oleylamine, octadecylamine, or hexadecylamine.

7. The preparation method according to claim 3, characterized in that, The high-boiling-point medium is oleylamine, and the dosage ratio of germanium source to oleylamine is 0.1 mmol: 6~10 mL; Alternatively, the high-boiling-point medium is a combination of oleylamine and trioctylphosphine oxide, and the dosage ratio of the germanium source to oleylamine and trioctylphosphine oxide is 0.1 mmol: 6~10 mL: 1~3 mmol. Alternatively, the high-boiling-point medium is a combination of oleylamine and octadecene, and the dosage ratio of the germanium source to oleylamine and octadecene is 0.1 mmol: 5~9 mL: 1~4 mL; Alternatively, the high-boiling-point medium is a combination of oleylamine and oleic acid, and the dosage ratio of the germanium source to oleylamine and oleic acid is 0.1 mmol: 5.5~9.5 mL: 0.1~1.0 mL.

8. The preparation method according to claim 3, characterized in that, The solvothermal reaction adopts a two-stage heating program: the manganese source, the germanium solution prepared in step (1) and the sulfur source are added to a high-boiling-point reaction medium to obtain a mixture. The mixture is placed under an inert atmosphere and magnetic stirring conditions. In the first stage, the temperature is increased to 100-210℃ at 8-12℃ / min and kept at a constant temperature for 15-120min to fully dissolve the manganese source, germanium source and sulfur source. In the second stage, the temperature is increased rapidly to 260-320℃ at 18-22℃ / min and kept at a constant temperature for 5-120min.

9. The application of the orthorhombic Mn2GeS4 nanomaterial as described in claim 1 or 2 in the field of photoelectric conversion. Its characteristic is that... The field of photoelectric conversion is further selected from any one or more of photoelectric detection, photovoltaic power generation, optoelectronic integration, optical signal processing and optical communication; wherein the above-mentioned orthogonal Mn2GeS4 nanomaterial is used as a photoelectric conversion active layer, photosensitive layer, light-absorbing layer or photogenerated carrier generation layer.

10. The application as described in claim 9, characterized in that, The orthorhombic Mn2GeS4 nanomaterial is used to fabricate a photodetector; the photodetector is selected from any one of photoconductive detectors, photovoltaic detectors, photodiodes, phototransistors, photoresistors, position-sensitive detectors, and imaging sensors; Furthermore, the orthorhombic Mn2GeS4 nanomaterial is used to prepare a photodetector: the nanomaterial is dispersed in an organic solvent to prepare a dispersion, coated on a device substrate to form a film, and Au is used as an electrode to construct the photodetector; Alternatively, the orthorhombic Mn2GeS4 nanomaterials may be used to fabricate photovoltaic devices; the photovoltaic devices may be selected from any one of solar cells, photoelectrochemical cells, quantum dot-sensitized solar cells, tandem solar cells, flexible solar cells, and semi-transparent photovoltaic devices. Alternatively, the orthogonal Mn2GeS4 nanomaterials are used to fabricate optoelectronic integrated devices; the optoelectronic integrated devices are selected from any one of photonic chips, on-chip optical interconnect devices, on-chip photodetectors, optical waveguide coupling devices, optical switching devices, and photonic computing devices.

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