Three-dimensional urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction, preparation method thereof and application of heterojunction in photoelectric detector

Abstract

The invention relates to a three-dimensional urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction, a preparation method of the three-dimensional urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction and application of the three-dimensional urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction in a photoelectric detector, the Bi2S3 / Bi2O2S heterojunction is composed of Bi2S3 nanorods and Bi2O2S nanoflowers, and the ZnO / Bi2O2S heterojunction is composed of ZnO nanorods and Bi2O2S nanoflowers. The Bi2O2S nanoflowers are formed by ultrathin Bi2O2S nanosheets, and the Bi2O2S nanoflowers are uniformly grown on the substrate; the Bi2S3 nanorod is grown on the surface of the ultrathin Bi2O2S nanosheet which is used for forming the Bi2O2S nanoflower; the ZnO nanorod is grown on the surface of the ultrathin Bi2O2S nanosheet which forms the Bi2O2S nanoflower; the Bi2S3 / Bi2O2S heterojunction or the ZnO / Bi2O2S heterojunction is of a three-dimensional sea urchin-shaped structure on the whole. The method provided by the invention can effectively promote carrier separation of Bi2O2S and improve the sensitivity and responsivity of the photoelectric detector. Meanwhile, a one-dimensional Bi2S3 nanorod or a ZnO nanorod grows on the surface of Bi2O2S to form a three-dimensional urchin-shaped Bi2S3 / Bi2O2S heterojunction or a ZnO / Bi2O2S heterojunction, light is reflected and absorbed for multiple times on the surface of the material, the absorption and utilization rate of the light is improved, and the detection performance of the photoelectric detector is further improved.

Description

Technical Field

[0001] The present invention belongs to the field of photoelectric detector materials, and specifically relates to a three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction, a preparation method thereof, and an application thereof in a photoelectric detector. Background Art

[0002] In recent years, photoelectric detectors have been widely used in various fields such as environmental monitoring, national defense and military, aerospace, and biomedicine, playing an indispensable role in the development of society. Compared with single-band photoelectric detectors, wide-spectrum detectors can detect a larger spectral range and have the advantages of higher integration and wider application range in practical applications.

[0003] Semiconductor materials have extensive and important applications in the field of photoelectric detection due to their unique energy band structure. Bi2O2S is a two-dimensional layered compound with ultra-high carrier mobility, good room temperature stability, and tunable band gap. It has become a research hotspot in recent years. Compared with the common two-dimensional sheet structure, the three-dimensional Bi2O2S nanoflower structure can cause multiple reflections of light irradiated on the surface of the nanoflower, thereby having a higher absorption utilization rate of light and better photoelectric detection performance. However, in a single Bi2O2S material, photogenerated carriers cannot be separated in time, and carrier recombination is prone to occur, which will reduce the photoelectric conversion efficiency of the device and affect the response speed of the device. At present, the key problem of low detection efficiency caused by photogenerated carrier recombination has not been overcome, so it is difficult to obtain high-performance Bi2O2S photodetectors.

[0004] In order to improve the detection efficiency of Bi2O2S, it is an effective method to construct a heterojunction with other semiconductor materials with different band gaps that have excellent photodetection performance to promote the separation of photogenerated carriers. Both Bi2S3 and ZnO have shown excellent performance in the field of photodetection. The composite construction of Bi2S3 and Bi2O2S type II heterojunction, or the composite construction of ZnO and Bi2O2S type II heterojunction, can effectively promote carrier separation and is an effective way to improve the photodetection performance of Bi2O2S. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes a three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction and a preparation method thereof and an application in a photoelectric detector.

[0006] The invention relates to a three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction. The Bi2S3 / Bi2O2S heterojunction is composed of Bi2S3 nanorods and Bi2O2S nanoflowers, and the ZnO / Bi2O2S heterojunction is composed of ZnO nanorods and Bi2O2S nanoflowers; the Bi2O2S nanoflowers are composed of ultrathin Bi2O2S nanosheets, and the Bi2O2S nanoflowers are uniformly grown on a substrate; the Bi2S3 nanorods grow on the surfaces of the ultrathin Bi2O2S nanosheets constituting the Bi2O2S nanoflowers; the ZnO nanorods grow on the surfaces of the ultrathin Bi2O2S nanosheets constituting the Bi2O2S nanoflowers; and the Bi2S3 / Bi2O2S heterojunction or the ZnO / Bi2O2S heterojunction presents a three-dimensional sea urchin-shaped structure as a whole.

[0007] Furthermore, the substrate is one of FTO and ITO, the Bi2S3 nanorods are one-dimensional rod-like structures, the ZnO nanorods are one-dimensional rod-like structures, and the thickness of the ultra-thin Bi2O2S nanosheets is 10-30 nm.

[0008] A method for preparing a three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction comprises the following steps:

[0009] Step 1, preparing a mixed solution of deionized water and ethylene glycol in a volume ratio of 1:1 as a solvent, dissolving bismuth nitrate pentahydrate and thiourea with equal concentrations in the range of 0.04-0.06 mol / L, and potassium hydroxide in the range of 0.2-0.6 mol / L in the solvent, and stirring them evenly to obtain a precursor solution;

[0010] Step 2: ultrasonically clean the substrate alternately in deionized water and anhydrous ethanol for 10-30 minutes, repeat twice, take it out and blow dry; then put the substrate into a reactor containing the reaction solution at an angle of 45-60° to the horizontal plane, keep it warm at 100-140°C for 2-7 hours, wash the surface with deionized water and anhydrous ethanol after cooling, and air dry it naturally to obtain Bi2O2S nanoflowers;

[0011] Step 3: Prepare Bi2O2S with a Bi2S3 seed layer or a ZnO seed layer, and obtain a Bi2S3 / Bi2O2S heterojunction or a ZnO / Bi2O2S heterojunction by a hydrothermal method.

[0012] Furthermore, in step three, the method for preparing Bi2O2S with a Bi2S3 seed layer is as follows: prepare 0.05 mol / L bismuth nitrate ethylene glycol solution A and 0.1 mol / L sodium sulfide aqueous solution B, soak the Bi2O2S nanoflowers obtained in step two in A for 1-2 min, rinse with deionized water for 30 s, and dry in an oven at 60-80°C; soak in B for 1-2 min, rinse with deionized water for 30 s, and dry in an oven at 60-80°C, which is recorded as one cycle; after repeating 3-12 cycles, dry at 120-180°C for 60 min to obtain Bi2O2S with a Bi2S3 seed layer.

[0013] Furthermore, in step three, the method for preparing a Bi2S3 / Bi2O2S heterojunction by a hydrothermal method is as follows: placing a Bi2O2S substrate with a Bi2S3 seed layer in an ethylene glycol solution of 0.1-0.5 mol / L bismuth nitrate and thiourea, reacting in a water bath at a temperature of 50-90°C for 4-36 hours, and rinsing with deionized water and ethanol alternately after the water bath reaction, and naturally drying the prepared Bi2S3 / Bi2O2S heterojunction sample to obtain a sea urchin-shaped Bi2S3 / Bi2O2S heterojunction.

[0014] Furthermore, in step three, the prepared Bi2S3 / Bi2O2S heterojunction sample is annealed at 200-300°C for 1h.

[0015] Furthermore, in step three, the method for preparing Bi2O2S with a ZnO seed layer is as follows: 20 mL of an ethanol solution containing 0.02-0.04 g of NaOH and 50 mL of an ethanol solution containing 0.1-0.2 g of zinc acetate are mixed, heated in a water bath at 60°C with stirring for 1-3 h, and allowed to stand in the dark for 10-24 h to obtain a ZnO seed solution; the Bi2O2S nanoflowers are immersed in the ZnO seed solution for 30 min, taken out and dried at 60°C for 40 min to obtain Bi2O2S with a ZnO seed layer.

[0016] Furthermore, in step three, the method for preparing the ZnO / Bi2O2S heterojunction by a hydrothermal method is as follows: prepare a Zn(NO3)2·6H2O and hexamethylenetetramine aqueous solution with a concentration of 0.05-0.5 mol / L as a ZnO growth mother solution; put the Bi2O2S with a ZnO seed layer into a reactor filled with the ZnO growth mother solution, take it out after heating it in a water bath, use deionized water and ethanol to drip wash alternately, and air dry it naturally to obtain a sea urchin-shaped ZnO / Bi2O2S heterojunction grown on a substrate.

[0017] Furthermore, in step three, the ZnO is heated in a water bath at 80-95° C. for 10-40 min.

[0018] A three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction is used in a photodetector. The photodetector uses a substrate on which a Bi2O2S sea urchin-shaped heterojunction is grown as a working electrode, connects the working electrode and a counter electrode via a heat-sealing film, and injects an iodine electrolyte, a polysulfide electrolyte or a potassium hydroxide solution between the two electrodes as an electrolyte; the counter electrode is one of a Pt electrode, ITO and FTO.

[0019] Beneficial Effects

[0020] The present invention constructs a type II heterojunction by compounding Bi2S3 with Bi2O2S, or by compounding ZnO with Bi2O2S to construct a type II heterojunction, which can effectively promote the carrier separation of Bi2O2S and improve the sensitivity and responsiveness of the photodetector. At the same time, one-dimensional Bi2S3 nanorods or ZnO nanorods are grown on the surface of Bi2O2S to form a three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S heterojunction or ZnO / Bi2O2S heterojunction, and light is reflected and absorbed multiple times on the surface of the material, thereby improving the absorption utilization rate of light and further improving the detection performance of the photodetector. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a SEM image of the Bi2O2S nanoflower prepared in Example 1 of the present invention;

[0022] Figure 2 This is a SEM image of the sea urchin-shaped Bi2S3 / Bi2O2S heterojunction structure prepared in Example 1 of the present invention;

[0023] Figure 3 This is a low-magnification SEM image of the sea urchin-shaped ZnO / Bi2O2S heterojunction structure prepared in Example 2 of the present invention;

[0024] Figure 4 This is a high-magnification SEM image of the sea urchin-shaped ZnO / Bi2O2S heterojunction structure prepared in Example 2 of the present invention;

[0025] Figure 5 The photocurrent density curve of the sea urchin-shaped ZnO / Bi2O2S heterojunction structure photodetector prepared in Example 3 of the present invention under ultraviolet light irradiation;

[0026] Figure 6 This is a photocurrent density curve of the sea urchin-shaped ZnO / Bi2O2S heterojunction structure photodetector prepared in Example 3 of the present invention under infrared light irradiation. DETAILED DESCRIPTION

[0027] The following combination Figures 1 to 6 This embodiment will be described in detail.

[0028] The purpose of the present invention is to construct a three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S heterojunction composite material or a ZnO / Bi2O2S heterojunction composite material, provide a method for preparing the heterojunction, and apply it in the field of photoelectric detection. By controlling the growth conditions, the growth rate of Bi2S3 along a certain crystal plane can be made faster than that of other crystal planes, and a one-dimensional rod-like structure with a specific aspect ratio can be formed. ZnO is a polar crystal with a hexagonal crystal structure, which has a faster growth rate along the c-axis direction and is easy to form a one-dimensional rod-like or columnar structure.

[0029] The present invention adopts a solution method to grow a one-dimensional Bi2S3 nanorod or ZnO nanorod on a three-dimensional Bi2O2S nanoflower. The prepared Bi2O2S heterojunction photodetector has high sensitivity, rapid response, self-powered characteristics, and can achieve wide spectrum detection. The one-dimensional nanostructure has excellent carrier transmission ability and can effectively increase the specific surface area of ​​the material. After the one-dimensional nanorod grows on the Bi2O2S surface, on the basis of maintaining the Bi2O2S three-dimensional nanoflower morphology structure, a special three-dimensional sea urchin-like heterostructure is formed, which can not only improve the absorption and utilization efficiency of light, but also effectively inhibit the recombination of photogenerated carriers and improve the photoelectric detection performance of Bi2O2S. In addition, both the synthetic Bi2S3 and ZnO can be prepared using a simple solution method, which is low in cost, suitable for large-scale production, and has a high practical value in production.

[0030] The invention relates to a three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction. The Bi2S3 / Bi2O2S heterojunction is composed of Bi2S3 nanorods and Bi2O2S nanoflowers, and the ZnO / Bi2O2S heterojunction is composed of ZnO nanorods and Bi2O2S nanoflowers; the Bi2O2S nanoflowers are composed of ultrathin Bi2O2S nanosheets, and the Bi2O2S nanoflowers are uniformly grown on a substrate; the Bi2S3 nanorods grow on the surfaces of the ultrathin Bi2O2S nanosheets constituting the Bi2O2S nanoflowers; the ZnO nanorods grow on the surfaces of the ultrathin Bi2O2S nanosheets constituting the Bi2O2S nanoflowers; and the Bi2S3 / Bi2O2S heterojunction or the ZnO / Bi2O2S heterojunction presents a three-dimensional sea urchin-shaped structure as a whole.

[0031] The substrate is one of FTO and ITO, the Bi2S3 nanorods are one-dimensional rod-shaped structures, the ZnO nanorods are one-dimensional rod-shaped structures, and the thickness of the ultra-thin Bi2O2S nanosheets is 10-30nm.

[0032] A method for preparing a three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction comprises the following steps:

[0033] Step 1, preparing a mixed solution of deionized water and ethylene glycol in a volume ratio of 1:1 as a solvent, dissolving bismuth nitrate pentahydrate and thiourea with equal concentrations in the range of 0.04-0.06 mol / L, and potassium hydroxide in the range of 0.2-0.6 mol / L in the solvent, and stirring them evenly to obtain a precursor solution;

[0034] Step 2: ultrasonically clean the substrate alternately in deionized water and anhydrous ethanol for 10-30 minutes, repeat twice, take it out and blow dry; then put the substrate into a reactor containing the reaction solution at an angle of 45-60° to the horizontal plane, keep it warm at 100-140°C for 2-7 hours, wash the surface with deionized water and anhydrous ethanol after cooling, and air dry it naturally to obtain Bi2O2S nanoflowers;

[0035] Step 3: Prepare Bi2O2S with a Bi2S3 seed layer or a ZnO seed layer, and obtain a Bi2S3 / Bi2O2S heterojunction or a ZnO / Bi2O2S heterojunction by a hydrothermal method.

[0036] The method for preparing Bi2O2S with a Bi2S3 seed layer is as follows: prepare 0.05 mol / L bismuth nitrate ethylene glycol solution A and 0.1 mol / L sodium sulfide aqueous solution B, soak the Bi2O2S nanoflowers obtained in step 2 in A for 1-2 min, rinse with deionized water for 30 s, and dry in an oven at 60-80°C; soak in B for 1-2 min, rinse with deionized water for 30 s, and dry in an oven at 60-80°C, which is marked as one cycle; after repeating 3-12 cycles, dry at 120-180°C for 60 min to obtain Bi2O2S with a Bi2S3 seed layer.

[0037] The method for preparing Bi2S3 / Bi2O2S heterojunction by hydrothermal method is as follows: placing a Bi2O2S substrate with a Bi2S3 seed layer in an ethylene glycol solution of 0.1-0.5 mol / L bismuth nitrate and thiourea, reacting in a water bath at a temperature of 50-90°C for 4-36 hours, and rinsing with deionized water and ethanol alternately after the water bath reaction. The prepared Bi2S3 / Bi2O2S heterojunction sample is naturally dried to obtain a sea urchin-shaped Bi2S3 / Bi2O2S heterojunction.

[0038] The prepared Bi2S3 / Bi2O2S heterojunction sample was annealed at 200-300°C for 1h to obtain Bi2S3 nanorods with higher crystallinity.

[0039] The method for preparing Bi2O2S with a ZnO seed layer is as follows: 20 mL of an ethanol solution containing 0.02-0.04 g of NaOH and 50 mL of an ethanol solution containing 0.1-0.2 g of zinc acetate are mixed, heated in a water bath at 60° C. with stirring for 1-3 h, and allowed to stand in the dark for 10-24 h to obtain a ZnO seed solution; the Bi2O2S nanoflowers are placed in the ZnO seed solution and soaked for 30 min, and after being taken out, they are dried at 60° C. for 40 min to obtain Bi2O2S with a ZnO seed layer.

[0040] The method for preparing a ZnO / Bi2O2S heterojunction by a hydrothermal method is as follows: prepare a Zn(NO3)2·6H2O and hexamethylenetetramine aqueous solution with a concentration of 0.05-0.5 mol / L as a ZnO growth mother solution; put Bi2O2S with a ZnO seed layer into a reactor filled with the ZnO growth mother solution, heat the reaction in a water bath at 80-95°C for 10-40 minutes, then take it out, use deionized water and ethanol to drip wash alternately, and naturally air dry to obtain a sea urchin-shaped ZnO / Bi2O2S heterojunction grown on a substrate.

[0041] A three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction is used in a photodetector. The photodetector uses a substrate on which a Bi2O2S sea urchin-shaped heterojunction is grown as a working electrode, connects the working electrode and a counter electrode via a heat-sealing film, and injects an iodine electrolyte, a polysulfide electrolyte or a potassium hydroxide solution between the two electrodes as an electrolyte; the counter electrode is one of a Pt electrode, ITO and FTO.

[0042] Example 1

[0043] A method for preparing a three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S heterojunction, the specific steps are as follows:

[0044] Step 1: prepare a mixed solution of deionized water and ethylene glycol in a volume ratio of 1:1 as a solvent, totaling 20 mL, then add 1 mmol bismuth nitrate, 1 mmol thiourea, and 4 mmol potassium hydroxide, and stir for 2.5 hours to obtain a precursor solution.

[0045] Step 2: Place the FTO substrate with the conductive surface facing down and lean it against the polytetrafluoroethylene lining wall at an angle of 60° to the horizontal plane, add the precursor solution, place it in a reactor, put it in an oven at 120°C for 200 minutes, then take it out directly, cool it to room temperature and take it out, wash the surface with deionized water and anhydrous ethanol, and air-dry it naturally to obtain Bi2O2S nanoflowers.

[0046] Step 3: Prepare 0.05 mol / L bismuth nitrate ethylene glycol solution A and 0.1 mol / L sodium sulfide aqueous solution B. Soak the Bi2O2S nanoflowers in A for 1 min, rinse with deionized water for 30 s, and dry in an oven at 75°C; soak in B for 1 min, rinse with deionized water for 30 s, and dry in an oven at 75°C, which is counted as one cycle. Repeat 5 cycles and dry at 130°C for 60 min to obtain Bi2O2S with a Bi2S3 seed layer.

[0047] The Bi2O2S with Bi2S3 seeds was placed in a 0.1 mol / L bismuth nitrate and thiourea ethylene glycol solution, and reacted for 24 hours in a water bath at 60°C. After being taken out, it was drip-washed with deionized water and anhydrous ethanol. After natural air drying, the sample was annealed at 250°C for 1 hour to obtain a sea urchin-like Bi2S3 / Bi2O2S heterojunction structure.

[0048] like Figure 1 As shown in the figure, it can be clearly observed that the Bi2O2S nanoflowers are regularly arranged and evenly cover the FTO surface to form a Bi2O2S nanoflower array. The diameter of a single nanoflower is about 2μm, and the Bi2O2S nanoflower is assembled from ultra-thin Bi2O2S nanosheets.

[0049] After growing one-dimensional Bi2S3 nanorods on Bi2O2S nanoflowers, the urchin-like Bi2S3 / Bi2O2S heterojunction structure is shown in Figure 2 As shown in the figure, it can be seen that the basic morphology of the Bi2O2S nanoflower is not destroyed, and the overall morphology is still a three-dimensional flower-like structure and is evenly distributed on the substrate surface. Note that the one-dimensional Bi2S3 nanorods extend outward along the nanosheets that make up the Bi2O2S nanoflowers. The nanorods are in the form of long sheets with a length of about 400nm. The material as a whole presents a three-dimensional sea urchin-like structure of Bi2S3 nanorods growing on the surface of the Bi2O2S nanoflowers.

[0050] Example 2

[0051] A method for preparing a three-dimensional sea urchin-shaped ZnO / Bi2O2S heterojunction, the specific steps are as follows:

[0052] Step 1: prepare a solution with a concentration of 0.05 mol / L bismuth nitrate pentahydrate, 0.05 mol / L thiourea and 0.2 mol / L potassium hydroxide, wherein the solvent is a mixed solution of deionized water and ethylene glycol in a volume ratio of 1:1 as a reaction precursor solution.

[0053] Step 2: Place the conductive surface of FTO downward on the inner wall of the polytetrafluoroethylene liner at a 45° angle to the horizontal plane, and add the reaction precursor solution. Place the polytetrafluoroethylene liner into the reactor and react at 120°C for 190 minutes. After cooling and taking out, wash the surface with deionized water and anhydrous ethanol, and air dry naturally to obtain Bi2O2S nanoflowers.

[0054] Step 3: Mix 20 mL of ethanol solution containing 0.024 g of NaOH and 50 mL of ethanol solution containing 0.109 g of zinc nitrate, heat in a water bath at 60 ° C with stirring for 2 hours, and stand in the dark for 15 hours to obtain a ZnO seed solution. Soak the Bi2O2S nanoflowers in the ZnO seed solution for 30 minutes, take them out and dry them at 60 ° C for 40 minutes to obtain Bi2O2S with a ZnO seed layer. Prepare aqueous solutions of zinc nitrate and hexamethylenetetramine with a concentration of 0.1 mol / L as the growth mother solution of ZnO. Put the Bi2O2S with a ZnO seed layer into a reactor containing the ZnO growth mother solution, heat it in a water bath at 95 ° C for 25 minutes, then take it out directly, use deionized water and ethanol to drip wash alternately, and air dry naturally to obtain a sea urchin-shaped ZnO / Bi2O2S heterojunction structure grown on the substrate.

[0055] The grown ZnO / Bi2O2S heterojunction structure is as follows Figure 3 , Bi2O2S grows evenly on the surface of the FTO substrate and maintains a good flower-like structure. The Bi2O2S nanosheets that make up the nanoflowers become significantly thicker. From the high-magnification image ( Figure 4 ) It can be seen that the thickening of the nanosheet is caused by the growth of ZnO. A large number of tiny ZnO nanorods are evenly wrapped on the surface of the Bi2O2S nanoflower. The ZnO nanorods are uniform in length and diameter, in the shape of round rods, and grow vertically on the surface of the nanosheet. The ZnO / Bi2O2S heterojunction presents a three-dimensional sea urchin-like structure as a whole.

[0056] Example 3

[0057] A method for preparing a three-dimensional sea urchin-shaped ZnO / Bi2O2S heterojunction and its application in wide spectrum detectors.

[0058] The ZnO / Bi2O2S nanoflower urchin-shaped heterojunction structure prepared in Example 2 was used as the working electrode, and the FTO coated with a thin layer of Pt metal was used as the counter electrode. The two were hot-pressed at 150°C for 15s and connected together through a heat-sealing film. Iodine electrolyte was injected into the device to prepare a Bi2O2S urchin-shaped heterojunction photodetector.

[0059] The prepared Bi2O2S sea urchin-shaped heterojunction photodetector was tested under zero bias conditions. Ultraviolet light (365nm) and infrared light (850nm) were used to illuminate the ZnO / Bi2O2S heterojunction photodetector, with 5s on and 5s off as a cycle. The Keithley 2400 digital source meter was used to measure the following results: Figure 5 , Figure 6 The photocurrent density curve is shown.

[0060] Figure 5 The photocurrent density curve is measured by using ultraviolet light to illuminate the ZnO / Bi2O2S heterojunction photodetector. It can be seen from the figure that when there is no light, the dark current density in the detector is almost zero; when ultraviolet light shines on the detector surface, photocurrent is immediately generated, and the photocurrent density increases rapidly to 73μA / cm 2 After turning off the ultraviolet light, the photocurrent of the ZnO / Bi2O2S photodetector dropped rapidly and returned to its initial state. Under the condition of multiple on / off ultraviolet light, the photocurrent value of the photodetector remained at the original level when illuminated, without obvious attenuation. It can be seen that the above ZnO / Bi2O2S photodetector has fast response characteristics and good stability to ultraviolet light.

[0061] Figure 6 The photocurrent density curve is measured by using infrared light to illuminate the ZnO / Bi2O2S heterojunction photodetector. Under no light conditions, the photodetector maintains a weak dark current state; when infrared light is irradiated to the detector surface, the photocurrent density increases rapidly and finally stabilizes at 12μA / cm 2 About. In addition, after 5 on / off cycles, the response time and photocurrent density of the photodetector to infrared light remain basically unchanged, which shows that the sea urchin-shaped ZnO / Bi2O2S heterojunction photodetector also has excellent photodetection performance for infrared light. It can be seen that the sea urchin-shaped ZnO / Bi2O2S heterojunction photodetector can achieve wide spectrum detection from ultraviolet to infrared bands. In addition, all tests of photodetection performance were carried out under zero bias, indicating that the ZnO / Bi2O2S heterojunction photodetector has self-powered characteristics.

[0062] The above contents of the present invention are only preferred embodiments of the present invention and are not intended to limit the implementation scheme of the present invention. A person skilled in the art can easily make corresponding changes or modifications based on the main concept and spirit of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope required by the claims.

Claims

1. A three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction, characterized in that: The Bi2S3 / Bi2O2S heterojunction is composed of Bi2S3 nanorods and Bi2O2S nanoflowers, and the ZnO / Bi2O2S heterojunction is composed of ZnO nanorods and Bi2O2S nanoflowers; the Bi2O2S nanoflowers are composed of ultrathin Bi2O2S nanosheets, and the Bi2O2S nanoflowers are uniformly grown on a substrate; the Bi2S3 nanorods grow on the surface of the ultrathin Bi2O2S nanosheets that constitute the Bi2O2S nanoflowers; the ZnO nanorods grow on the surface of the ultrathin Bi2O2S nanosheets that constitute the Bi2O2S nanoflowers; the Bi2S3 / Bi2O2S heterojunction or the ZnO / Bi2O2S heterojunction presents a three-dimensional sea urchin-like structure as a whole.

2. The three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction according to claim 1, characterized in that: The substrate is one of FTO and ITO, the Bi2S3 nanorods are one-dimensional rod-shaped structures, the ZnO nanorods are one-dimensional rod-shaped structures, and the thickness of the ultra-thin Bi2O2S nanosheets is 10-30nm.

3. The method for preparing a three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction according to claim 1, characterized in that: The steps include: Step 1, preparing a mixed solution of deionized water and ethylene glycol in a volume ratio of 1:1 as a solvent, dissolving bismuth nitrate pentahydrate and thiourea with equal concentrations in the range of 0.04-0.06 mol / L, and potassium hydroxide in the range of 0.2-0.6 mol / L in the solvent, and stirring them evenly to obtain a precursor solution; Step 2: ultrasonically clean the substrate alternately in deionized water and anhydrous ethanol for 10-30 minutes, repeat twice, take it out and blow dry; then put the substrate into a reactor containing the reaction solution at an angle of 45-60° to the horizontal plane, keep it warm at 100-140°C for 2-7 hours, wash the surface with deionized water and anhydrous ethanol after cooling, and air dry it naturally to obtain Bi2O2S nanoflowers; Step 3: Prepare Bi2O2S with a Bi2S3 seed layer or a ZnO seed layer, and obtain a Bi2S3 / Bi2O2S heterojunction or a ZnO / Bi2O2S heterojunction by a hydrothermal method.

4. The method for preparing a three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction according to claim 3, characterized in that: In step three, the method for preparing Bi2O2S with a Bi2S3 seed layer is as follows: prepare 0.05 mol / L bismuth nitrate ethylene glycol solution A and 0.1 mol / L sodium sulfide aqueous solution B, soak the Bi2O2S nanoflowers obtained in step two in A for 1-2 min, rinse with deionized water for 30 s, and dry in an oven at 60-80°C; soak in B for 1-2 min, rinse with deionized water for 30 s, and dry in an oven at 60-80°C, which is marked as one cycle; after repeating 3-12 cycles, dry at 120-180°C for 60 min to obtain Bi2O2S with a Bi2S3 seed layer.

5. The method for preparing a three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction according to claim 4, characterized in that: In step three, the method for preparing a Bi2S3 / Bi2O2S heterojunction by a hydrothermal method is as follows: placing a Bi2O2S substrate with a Bi2S3 seed layer in an ethylene glycol solution of 0.1-0.5 mol / L bismuth nitrate and thiourea, reacting in a water bath at 50-90°C for 4-36 hours, and rinsing with deionized water and ethanol alternately after the water bath reaction. The prepared Bi2S3 / Bi2O2S heterojunction sample is naturally dried to obtain a sea urchin-shaped Bi2S3 / Bi2O2S heterojunction.

6. The method for preparing a three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction according to claim 5, characterized in that: In step three, the prepared Bi2S3 / Bi2O2S heterojunction sample is annealed at 200-300°C for 1h.

7. The method for preparing a three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction according to claim 3, characterized in that: In step three, the method for preparing Bi2O2S with a ZnO seed layer is as follows: 20 mL of an ethanol solution containing 0.02-0.04 g of NaOH and 50 mL of an ethanol solution containing 0.1-0.2 g of zinc acetate are mixed, heated in a water bath at 60°C with stirring for 1-3 h, and allowed to stand in the dark for 10-24 h to obtain a ZnO seed solution; the Bi2O2S nanoflowers are immersed in the ZnO seed solution for 30 min, taken out and dried at 60°C for 40 min to obtain Bi2O2S with a ZnO seed layer.

8. The method for preparing a three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction according to claim 7, characterized in that: In step three, the method for preparing the ZnO / Bi2O2S heterojunction by a hydrothermal method is as follows: prepare a Zn(NO3)2·6H2O and hexamethylenetetramine aqueous solution with a concentration of 0.05-0.5 mol / L as a ZnO growth mother solution; put the Bi2O2S with a ZnO seed layer into a reactor filled with the ZnO growth mother solution, take it out after heating in a water bath, use deionized water and ethanol to drip wash alternately, and air dry naturally to obtain a sea urchin-shaped ZnO / Bi2O2S heterojunction grown on a substrate.

9. The method for preparing a three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction according to claim 8, characterized in that: In step 3, the ZnO is heated in a water bath at 80-95° C. for 10-40 min.

10. Application of a three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction in a photodetector, characterized in that: The three-dimensional urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction described in claim 1 or the Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction prepared by the preparation method described in any one of claims 3 to 9 is used in a photodetector; the photodetector uses a substrate on which a Bi2O2S urchin-shaped heterojunction is grown as a working electrode, the working electrode and the counter electrode are connected by a heat-sealing film, and one of iodine electrolyte, polysulfide electrolyte or potassium hydroxide solution is injected between the two electrodes as an electrolyte; the counter electrode is one of a Pt electrode, ITO and FTO.

Images