Three-dimensional urchin-like bi2s3 / bi2o2s or zn o / bi2o2s heterojunction, preparation method thereof and application thereof in photoelectric detector

Abstract

The present application relates to a kind of three-dimensional sea urchin-like Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction and its preparation method and application in photoelectric detector, the Bi2S3 / Bi2O2S heterojunction is made of Bi2S3 Nanorod and Bi2O2S nanoflower, the ZnO / Bi2O2S heterojunction is made of ZnO Nanorod and Bi2O2S nanoflower;The Bi2O2S nanoflower is made of ultrathin Bi2O2S nanosheet, Bi2O2S nanoflower is uniformly grown on substrate;Bi2S3 Nanorod is grown on the surface of ultrathin Bi2O2S nanosheet constituting Bi2O2S nanoflower;ZnO Nanorod is grown on the surface of ultrathin Bi2O2S nanosheet constituting Bi2O2S nanoflower;The Bi2S3 / Bi2O2S heterojunction or ZnO / Bi2O2S heterojunction as a whole presents three-dimensional sea urchin-like structure.The method of the present application can effectively promote the carrier separation of Bi2O2S, improve the sensitivity, responsivity of photoelectric detector.Simultaneously, one-dimensional Bi2S3 Nanorod or ZnO Nanorod is grown on the surface of Bi2O2S, forms three-dimensional sea urchin-like Bi2S3 / Bi2O2S heterojunction, or ZnO / Bi2O2S heterojunction, light is reflected and absorbed on the surface of material multiple times, improves the light absorption utilization rate, further improves the detection performance of photoelectric detector.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of photoelectric detector materials, and particularly relates to a three-dimensional urchin-like Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction, a preparation method thereof and application thereof in a photoelectric detector. BACKGROUND

[0002] In recent years, photoelectric detectors are widely applied to various fields such as environmental monitoring, national defense and military, aerospace and biological medicine, and play an indispensable role in the development of the society. Compared with photoelectric detectors for a single waveband, wide-spectrum photoelectric detectors have a larger spectral range, and have the advantages of higher integration and wider application range in actual application.

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

[0004] To improve the detection efficiency of Bi2O2S, it is an effective method to construct a heterojunction with other semiconductor materials with excellent photoelectric detection performance to promote the separation of photo-generated carriers. Bi2S3 and ZnO both exhibit excellent performance in the field of photoelectric detection. Bi2S3 and Bi2O2S are compounded to construct a type II heterojunction, or ZnO and Bi2O2S are compounded to construct a type II heterojunction, which can effectively promote the separation of carriers and is an effective way to improve the photoelectric detection performance of Bi2O2S. SUMMARY

[0005] The application is proposed to solve the above problems, and provides a three-dimensional urchin-like Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction, a preparation method thereof and application thereof in a photoelectric detector.

[0006] The application relates to a three-dimensional urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction, wherein 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 nanoflower is composed of ultrathin Bi2O2S nanosheets, and the Bi2O2S nanoflower is uniformly grown on a substrate; the Bi2S3 nanorod is grown on the surface of the ultrathin Bi2O2S nanosheet constituting the Bi2O2S nanoflower; the ZnO nanorod is grown on the surface of the ultrathin Bi2O2S nanosheet constituting the Bi2O2S nanoflower; and the Bi2S3 / Bi2O2S heterojunction or the ZnO / Bi2O2S heterojunction as a whole presents a three-dimensional urchin-shaped structure.

[0007] Further, the substrate is one of FTO or ITO, the Bi2S3 nanorod is a one-dimensional rod-shaped structure, the ZnO nanorod is a one-dimensional rod-shaped structure, and the thickness of the ultrathin Bi2O2S nanosheet is 10-30 nm.

[0008] A preparation method of a three-dimensional urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction comprises the following steps.

[0009] Step one, a mixed solution of deionized water and ethylene glycol with a volume ratio of 1:1 is prepared as a solvent, bismuth nitrate pentahydrate and thiourea with a concentration range of 0.04-0.06 mol / L are dissolved in the solvent at an equal concentration, and potassium hydroxide with a concentration range of 0.2-0.6 mol / L is dissolved in the solvent, and the mixture is stirred uniformly to serve as a precursor solution;

[0010] Step two, the substrate is alternately ultrasonically cleaned in deionized water and anhydrous ethanol for 10-30 min, and the operation is repeated twice, and the substrate is taken out and blown dry; then the substrate is placed in a reaction kettle containing a reaction solution at an angle of 45-60 degrees with the horizontal plane, and is kept at 100-140 DEG C for 2-7 h, and after cooling, the surface is drop-washed with deionized water and anhydrous ethanol, and is naturally air-dried to obtain Bi2O2S nanoflowers;

[0011] Step three, Bi2O2S with a Bi2S3 seed layer or a ZnO seed layer is prepared, and a Bi2S3 / Bi2O2S heterojunction or a ZnO / Bi2O2S heterojunction is prepared by a hydrothermal method.

[0012] Further, in step three, the method for preparing Bi2O2S with 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 nanoflower prepared 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; repeat 3-12 cycles, and dry at 120-180°C for 60 min to obtain Bi2O2S with Bi2S3 seed layer.

[0013] Further, in step three, the method for preparing Bi2O2S with 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 nanoflower prepared 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; repeat 3-12 cycles, and dry at 120-180°C for 60 min to obtain Bi2O2S with Bi2S3 seed layer.

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

[0015] Further, in step three, the method for preparing Bi2O2S with 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 nanoflower prepared 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; repeat 3-12 cycles, and dry at 120-180°C for 60 min to obtain Bi2O2S with Bi2S3 seed layer.

[0016] Further, in step three, the method for preparing Bi2O2S with 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 nanoflower prepared 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; repeat 3-12 cycles, and dry at 120-180°C for 60 min to obtain Bi2O2S with Bi2S3 seed layer.

[0017] Further, in step three, the ZnO water bath heating conditions are 80-95°C for 10-40 min.

[0018] The application of a three-dimensional urchin-like Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction in a photoelectric detector, the photoelectric detector taking a substrate with a Bi2O2S urchin-like heterojunction as a working electrode, connecting the working electrode and a counter electrode through a heat-sealed film, injecting one of an iodine electrolyte, a polysulfide electrolyte or a potassium hydroxide solution as an electrolyte between the two electrodes; and the counter electrode being one of a Pt electrode, ITO and FTO.

[0019] Advantages

[0020] The application of the application is to compound Bi2S3 with Bi2O2S to construct a type II heterojunction, or to compound ZnO with Bi2O2S to construct a type II heterojunction, which can effectively promote the carrier separation of Bi2O2S and improve the sensitivity and responsivity of the photoelectric detector. Meanwhile, one-dimensional Bi2S3 nanorods or ZnO nanorods are grown on the surface of Bi2O2S to form a three-dimensional urchin-like Bi2S3 / Bi2O2S heterojunction or a ZnO / Bi2O2S heterojunction, and the light is reflected and absorbed on the surface of the material for multiple times, thereby improving the light absorption utilization rate and further improving the detection performance of the photoelectric detector. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 SEM image of the Bi2O2S nanoflower prepared in Example 1 of the application;

[0022] Figure 2 SEM image of the urchin-like Bi2S3 / Bi2O2S heterojunction structure prepared in Example 1 of the application;

[0023] Figure 3 SEM low-magnification image of the urchin-like ZnO / Bi2O2S heterojunction structure prepared in Example 2 of the application;

[0024] Figure 4 SEM high-magnification image of the urchin-like ZnO / Bi2O2S heterojunction structure prepared in Example 2 of the application;

[0025] Figure 5 Photocurrent density curve of the urchin-like ZnO / Bi2O2S heterojunction structure photoelectric detector prepared in Example 3 of the application under ultraviolet light irradiation;

[0026] Figure 6 Photocurrent density curve of the urchin-like ZnO / Bi2O2S heterojunction structure photoelectric detector prepared in Example 3 of the application under infrared light irradiation. DETAILED DESCRIPTION

[0027] The following combines Figures 1 to 6 The present embodiment will be specifically described.

[0028] The application aims to construct a three-dimensional urchin-like Bi2S3 / Bi2O2S heterojunction composite material or a ZnO / Bi2O2S heterojunction composite material, provide a preparation method of the heterojunction, and apply it in the field of photoelectric detection. By controlling the growth conditions, the growth speed of Bi2S3 along a certain crystal plane can be faster than that of other crystal planes, so that a one-dimensional rod-like structure with a specific length-width ratio can be formed. ZnO is a polar crystal with a hexagonal crystal structure, and 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 application grows one-dimensional Bi2S3 nanorods or ZnO nanorods on the three-dimensional Bi2O2S nanoflower by using a solution method. The prepared Bi2O2S heterojunction photoelectric detector has high sensitivity, fast response, self-powered characteristics, and can realize wide spectrum detection. The one-dimensional nanostructure has excellent carrier transport capacity, and can effectively increase the specific surface area of the material. After the one-dimensional nanorods grow on the surface of Bi2O2S, a special three-dimensional urchin-like heterostructure is formed on the basis of the three-dimensional nanoflower morphology structure of Bi2O2S, which can not only improve the light absorption and utilization efficiency, but also effectively suppress the recombination of photo-generated carriers, and improve the photoelectric detection performance of Bi2O2S. In addition, Bi2S3 and ZnO can be synthesized by using a simple solution method, which has low cost and is suitable for large-scale production, and has high practical value in production.

[0030] The application relates to a three-dimensional urchin-like Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction, wherein 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 nanoflower is composed of ultrathin Bi2O2S nanosheets, and the Bi2O2S nanoflower is uniformly grown on a substrate; the Bi2S3 nanorod is grown on the surface of the ultrathin Bi2O2S nanosheet constituting the Bi2O2S nanoflower; the ZnO nanorod is grown on the surface of the ultrathin Bi2O2S nanosheet constituting the Bi2O2S nanoflower; and the Bi2S3 / Bi2O2S heterojunction or the ZnO / Bi2O2S heterojunction has a three-dimensional urchin-like structure as a whole.

[0031] The substrate is one of FTO or ITO, the Bi2S3 nanorod is a one-dimensional rod-like structure, the ZnO nanorod is a one-dimensional rod-like structure, and the thickness of the ultrathin Bi2O2S nanosheet is 10-30 nm.

[0032] A preparation method of a three-dimensional urchin-like Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction comprises the following steps:

[0033] Step one, prepare a mixed solution of deionized water and ethylene glycol with a volume ratio of 1:1 as a solvent, dissolve bismuth nitrate pentahydrate and thiourea with a concentration range of 0.04-0.06 mol / L and potassium hydroxide with a concentration range of 0.2-0.6 mol / L in the solvent, and stir uniformly as a precursor solution;

[0034] Step two, clean the substrate in deionized water and anhydrous ethanol alternately for 10-30 min, repeat twice, and blow dry after taking out; then place the substrate in a reaction kettle containing a reaction solution at an angle of 45-60° with the horizontal, and incubate at 100-140℃ for 2-7 h, then drop wash the surface with deionized water and anhydrous ethanol, and air dry to obtain Bi2O2S nanoflowers;

[0035] Step three, prepare Bi2O2S with a Bi2S3 seed layer or a ZnO seed layer, and prepare Bi2S3 / Bi2O2S heterojunction or ZnO / Bi2O2S heterojunction by a hydrothermal method.

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

[0037] The method for preparing Bi2S3 / Bi2O2S heterojunction by a hydrothermal method is as follows: place the Bi2O2S substrate with a Bi2S3 seed layer in a 0.1-0.5 mol / L bismuth nitrate and thiourea ethylene glycol solution, and perform water bath reaction at a temperature of 50-90℃ for 4-36 h, then rinse alternately with deionized water and ethanol, and naturally dry the prepared Bi2S3 / Bi2O2S heterojunction sample to obtain urchin-like Bi2S3 / Bi2O2S heterojunction.

[0038] Anneal the prepared Bi2S3 / Bi2O2S heterojunction sample at 200-300℃ for 1 h 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 and stirred in a 60°C water bath for 1-3 h, and then left to stand in the dark for 10-24 h to obtain a ZnO seed solution; Bi2O2S nanoflowers are soaked in the ZnO seed solution for 30 min, and then taken out and 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: a Zn(NO3)2·6H2O and hexamethylenetetramine aqueous solution with a concentration of 0.05-0.5 mol / L is prepared as a growth mother liquor of ZnO; Bi2O2S with a ZnO seed layer is placed in a reactor containing the ZnO growth mother liquor, heated and reacted in a water bath at 80-95°C for 10-40 min, then taken out, and then washed with deionized water and ethanol alternately, and naturally air-dried to obtain urchin-like ZnO / Bi2O2S heterojunctions grown on a substrate.

[0041] A three-dimensional urchin-like Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction is applied to a photoelectric detector, the photoelectric detector uses a substrate with grown Bi2O2S urchin-like heterojunctions as a working electrode, connects the working electrode and a counter electrode through a heat-sealed film, injects one of iodine electrolyte, polysulfide electrolyte or potassium hydroxide solution into 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 urchin-like Bi2S3 / Bi2O2S heterojunction, the specific steps are as follows:

[0044] Step one, a mixed solution of deionized water and ethylene glycol with a volume ratio of 1:1 is prepared as a solvent, and then 1 mmol of bismuth nitrate, 1 mmol of thiourea and 4 mmol of potassium hydroxide are added, and the mixture is stirred for 2.5 h to obtain a precursor solution.

[0045] Step two, the conductive surface of the FTO substrate is inclined at an angle of 60° with respect to the horizontal plane and leans against the inner wall of the polytetrafluoroethylene lining, the precursor solution is added, the device is placed in a reaction kettle, and then the kettle is placed in an oven at 120°C for 200 min, and then taken out directly, cooled to room temperature, and then taken out, and the surface is washed with deionized water and anhydrous ethanol alternately, and then naturally air-dried to obtain Bi2O2S nanoflowers.

[0046] Step three, prepare 0.05 mol / L bismuth nitrate ethylene glycol solution A and 0.1 mol / L aqueous solution of sodium sulfide B. Bi2O2S nanoflower in A soaking 1 min, deionized water rinse 30 s, oven drying at 75℃; B soaking 1 min, deionized water rinse 30 s, oven drying at 75℃, recorded as a cycle. Repeat 5 cycles after drying at 130℃ for 60 min, get with Bi2S3 seed layer of Bi2O2S.

[0047] Bi2O2S with Bi2S3 seed is put into 0.1 mol / L bismuth nitrate and thiourea ethylene glycol solution, water bath at 60℃, reaction 24 h, after taking out with deionized water and anhydrous ethanol drop washing. Natural air drying, the sample is annealed at 250℃ for 1 h, get urchin-like Bi2S3 / Bi2O2S heterojunction structure.

[0048] As shown in Figure 1 , from the figure can be clearly observed that Bi2O2S nanoflower regular arrangement, uniform coverage FTO surface, formed Bi2O2S nanoflower array. Single nanoflower diameter is about 2 μm, Bi2O2S nanoflower is assembled by ultra-thin Bi2O2S nanosheet.

[0049] After growing one-dimensional Bi2S3 nanorod on Bi2O2S nanoflower, urchin-like Bi2S3 / Bi2O2S heterojunction structure as shown in Figure 2 , from the figure can be seen that the basic morphology of Bi2O2S nanoflower is not damaged, the overall morphology is still three-dimensional flower-like structure and uniform distribution on the substrate surface. Note that one-dimensional Bi2S3 nanorod grows outward along the nanosheet composed of Bi2O2S nanoflower, nanorod presents long sheet, length is about 400 nm. The material as a whole presents three-dimensional urchin-like structure of Bi2S3 nanorod grown on the surface of Bi2O2S nanoflower.

[0050] Example 2

[0051] A three-dimensional urchin-like ZnO / Bi2O2S heterojunction preparation method, the specific steps are as follows:

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

[0053] Step two, the FTO conductive surface is 45° inclined to the horizontal surface on the inner wall of the polytetrafluoroethylene lining, and the reaction precursor solution is added. The polytetrafluoroethylene lining is loaded into the reaction kettle, and the reaction is carried out at 120℃ for 190min. After cooling and taking out, the surface is drop-washed with deionized water and anhydrous ethanol, and naturally air-dried to obtain Bi2O2S nanoflower.

[0054] Step three, 20mL of ethanol solution containing 0.024g of NaOH and 50mL of ethanol solution containing 0.109g of zinc nitrate are mixed, heated and stirred in a 60℃ water bath for 2h, and placed in the dark for 15h to obtain a ZnO crystal seed solution. The Bi2O2S nanoflower is soaked in the ZnO crystal seed solution for 30min, and then taken out and dried at 60℃ for 40min to obtain Bi2O2S with a ZnO crystal seed layer. Prepare an aqueous solution of zinc nitrate and hexamethylenetetramine with a concentration of 0.1mol / L as the growth mother liquor of ZnO. The Bi2O2S with ZnO crystal seed layer is placed in the reactor containing the ZnO growth mother liquor, and after heating in a 95℃ water bath for 25min, it is directly taken out, drop-washed with deionized water and ethanol alternately, and naturally air-dried to obtain urchin-like ZnO / Bi2O2S heterojunction structure grown on the substrate.

[0055] The grown ZnO / Bi2O2S heterojunction structure is as shown in Figure 3 , Bi2O2S is uniformly grown on the surface of the FTO substrate and maintains a good flower-like structure, and the Bi2O2S nanosheet constituting the nanoflower is obviously thickened. As can be seen from the high-magnification view Figure 4 , the thickening of the nanosheet is caused by the growth of ZnO. A large number of fine ZnO nanorods are uniformly wrapped on the surface of the Bi2O2S nanoflower, the ZnO nanorods are uniform in length and diameter, and present a round rod shape, vertically grown on the surface of the nanosheet. The ZnO / Bi2O2S heterojunction presents a three-dimensional urchin-like structure as a whole.

[0056] Example 3

[0057] Application of a preparation method of a three-dimensional urchin-like ZnO / Bi2O2S heterojunction in a wide-spectrum photodetector.

[0058] The urchin-like ZnO / Bi2O2S heterojunction structure prepared in Example 2 is used as a working electrode, and the FTO coated with a Pt metal thin layer is used as a counter electrode. The two are connected together by heat sealing film through hot pressing at 150℃ for 15s, and an iodine electrolyte is injected into the device to prepare a Bi2O2S urchin-like heterojunction photodetector.

[0059] The prepared Bi2O2S urchin-like heterojunction photodetector was tested under zero bias condition. The ZnO / Bi2O2S heterojunction photodetector was irradiated by ultraviolet light (365 nm) and infrared light (850 nm) respectively, and 5s light on and 5s light off were taken as a cycle. The photocurrent density curves were measured by using Keithley 2400 digital source meter as shown in the following figures. Figure 5 、 Figure 6

[0060] Figure 5 The photocurrent density curve of the ZnO / Bi2O2S heterojunction photodetector irradiated by ultraviolet light was measured. As shown in the figure, the dark current density of the photodetector was almost zero under no light irradiation. When the ultraviolet light irradiated the surface of the photodetector, the photocurrent was immediately generated, and the photocurrent density rapidly increased to 73 μA / cm 2 and remained stable. After the ultraviolet light was turned off, the photocurrent of the ZnO / Bi2O2S photodetector rapidly decreased and returned to the initial state. Under the condition of multiple on / off of the ultraviolet light, the photocurrent value of the photodetector under light irradiation remained the original level, and no obvious decay occurred. It can be seen that the above-mentioned ZnO / Bi2O2S photodetector has fast response characteristics and good stability to ultraviolet light.

[0061] Figure 6 The photocurrent density curve of the ZnO / Bi2O2S heterojunction photodetector irradiated by infrared light was measured. Under no light irradiation, the photodetector maintained a weak dark current state. When the infrared light irradiated the surface of the photodetector, the photocurrent density rapidly increased and finally stabilized at about 12 μA / cm 2 . In addition, after experiencing 5 on / off cycles, the response time and photocurrent density of the photodetector to infrared light remained basically unchanged, which indicated that the urchin-like ZnO / Bi2O2S heterojunction photodetector also had excellent photoelectric detection performance to infrared light. It can be seen that the urchin-like ZnO / Bi2O2S heterojunction photodetector can realize wide spectrum detection from ultraviolet to infrared band. In addition, all the photoelectric detection performance tests were carried out under zero bias, which indicated that the ZnO / Bi2O2S heterojunction photodetector had self-powered characteristics.

[0062] The above content of the present application is only the preferred embodiment of the present application, not for limiting the implementation of the present application, and the person skilled in the art can easily make corresponding modification or change according to the main idea and spirit of the present application. Therefore, the protection scope of the present application should be subject to 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 equal concentrations of bismuth nitrate pentahydrate and thiourea in the solvent at a concentration range of 0.04-0.06 mol / L, and potassium hydroxide in the solvent at a concentration range of 0.2-0.6 mol / L, and stirring the mixture to obtain a precursor solution; Step 2: The substrate is ultrasonically cleaned alternately in deionized water and anhydrous ethanol for 10-30 minutes, repeated twice, and then taken out and blown dry; then the substrate is placed in a reactor containing the reaction solution at an angle of 45-60 degrees to the horizontal plane, and the temperature is kept at 100-140°C for 2-7 hours. After cooling, the surface is dripped with deionized water and anhydrous ethanol, and naturally air-dried to obtain Bi2O2S nanoflowers; Step 3: Prepare Bi2O2S with a Bi2S3 seed layer or a ZnO seed layer, and prepare 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 minutes, rinse with deionized water for 30 seconds, and dry in an oven at 60-80°C; soak in B for 1-2 minutes, rinse with deionized water for 30 seconds, 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 minutes 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 hydrothermal method for preparing a Bi2S3 / Bi2O2S heterojunction is as follows: a Bi2O2S substrate with a Bi2S3 seed layer is placed in a 0.1-0.5 mol / L bismuth nitrate and thiourea ethylene glycol solution, and reacted in a water bath at a temperature of 50-90°C for 4-36 hours. After the water bath reaction, the Bi2S3 / Bi2O2S heterojunction sample is rinsed alternately with deionized water and ethanol, and 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 hours, and allowed to stand in the dark for 10-24 hours to obtain a ZnO seed solution; the Bi2O2S nanoflowers are placed in the ZnO seed solution and soaked for 30 minutes, taken out and dried at 60°C for 40 minutes 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: preparing 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; placing Bi2O2S with a ZnO seed layer into a reactor filled with the ZnO growth mother solution, heating it in a water bath and then taking it out, using deionized water and ethanol to drip wash alternately, and naturally air-drying 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 minutes.

10. Application of a three-dimensional sea urchin-shaped Bi2S3 / Bi2O2S or ZnO / Bi2O2S heterojunction in a photodetector, characterized in that: The three-dimensional sea 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 according to any one of claims 3 to 9 is used in a photodetector; the photodetector uses a substrate on which the Bi2O2S sea 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.

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