A detector with positive and negative light responses and its fabrication method

Abstract

This invention proposes a detector with positive and negative light responses and its fabrication method, relating to the field of photoelectric detection technology. The detector comprises: a substrate layer, and a perovskite thin film layer, an upconversion layer, and an electrode layer sequentially stacked on the substrate layer; the upconversion layer comprises a core-shell structure NaYGdF4:Yb 3+ Er 3+ @NaYF4 upconversion particles. The photodetector of this invention can simultaneously detect visible and near-infrared light on a single pixel and generate bidirectional photoelectric responses, realizing diversified encoding of optical signals within the same pixel and providing new possibilities for optical information processing.

Description

Technical Field

[0001] This invention relates to the field of photoelectric detection technology, and in particular to a detector with positive and negative light responses and its fabrication method. Background Technology

[0002] As a crucial bridge for converting optical signals to electrical signals, photoelectric detection technology has become a research hotspot in optical information communication terminals due to its potential for extracting multi-degree-of-freedom information from optical signals. With the rapid development of the Internet of Things (IoT) era, traditional photoelectric detectors have faced severe challenges in improving their overall performance, including size reduction, low power consumption, and system integration. Against this backdrop, inspired by the retinal sensing mechanism, dual-band photoelectric detectors have emerged in recent years. These detectors can simultaneously identify two independent frequency optical signals, significantly reducing the number of effective pixels and opening up new avenues for improving system integration.

[0003] Currently, photodetectors based on perovskite and organic heterostructures have achieved visible-near-infrared dual-band detection through electric field direction modulation; however, their initial bias voltage setting limits their rapid response capability in complex environments. (FAPbBr) 2.4 I 0.6 Although the FAPbI3 heterojunction photodetector can achieve dual-mode spectral selection of 532nm and 650nm without bias setting, the identification wavelength is highly dependent on the incident photon direction controlled by the digital micromirror device, which requires the construction of a free-space optical waveguide system at the front end of the device, increasing the complexity of the system. In addition, the wavelength identification method based on the difference of conversion current relies on bandpass filters or condensers to maintain the consistency of light intensity at each wavelength, which to some extent restricts the further improvement of detection accuracy and integration.

[0004] Therefore, developing a novel wavelength resolution method that does not require additional optical components and complex operations has become a key problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In view of this, the present invention proposes a detector with positive and negative light response and its preparation method. By synergistic effect of methylammonium lead iodide (MAPbI3) and upconversion nanoparticles (UCNPs), bipolar light response of green light and infrared light is achieved, providing a novel, simple and effective technical strategy for the development of high-performance photodetectors in complex optical communication scenarios.

[0006] In a first aspect, the present invention provides a detector with positive and negative light responses, comprising: a substrate layer, and a perovskite thin film layer, an upconversion layer and an electrode layer sequentially stacked on the substrate layer;

[0007] The upconversion layer comprises a core-shell structure of NaYGdF4:Yb 3+Er 3+ @NaYF4 upconversion particles.

[0008] In one or more possible embodiments, the thickness of the upconversion layer is 400–500 nm.

[0009] Secondly, the present invention relates to a method for fabricating the above-mentioned detector with positive and negative light responses, comprising the following steps:

[0010] S1. A perovskite thin film layer is prepared on the substrate using a two-step spin coating method;

[0011] S2. Using a static spin-coating method, the core-shell structured NaYGdF4:Yb 3+ Er 3+ @NaYF4 upconversion particles are coated onto the perovskite thin film to prepare an upconversion layer;

[0012] S3. An electrode layer is deposited on the upconversion layer to obtain a photodetector.

[0013] In one or more possible embodiments, step S1, specifically includes:

[0014] A MAPbI3 perovskite precursor solution was prepared and spin-coated onto the substrate under an inert gas atmosphere. The spin-coating conditions were as follows: first, spin-coating was performed at 800–1000 rpm for 10–15 s; second, spin-coating was performed at 3000–3500 rpm for 40–45 s. 15–20 s before the end of the second spin-coating step, chlorobenzene was dropped onto the rotating MAPbI3 substrate. After spin-coating, the substrate was annealed at 100–120 °C for 5–10 min to form a perovskite thin film layer on the substrate.

[0015] Furthermore, the volume of the MAPbI3 perovskite precursor solution is 200–250 μL.

[0016] Furthermore, to regulate the crystallization kinetics of the perovskite precursor solution and optimize the film microstructure and surface uniformity, chlorobenzene needs to be introduced as a highly volatile antisolvent. The chlorobenzene is added vertically.

[0017] By adopting the above technical solution, chlorobenzene can accelerate the evaporation of solvent in the precursor solution, induce uniform nucleation by changing the supersaturation of the solution and inhibit abnormal grain growth, and finally form a perovskite crystalline thin film with high density, thereby obtaining better photoelectric performance.

[0018] In one or more possible embodiments, the MAPbI3 perovskite precursor solution is prepared by mixing and dissolving methylammonium iodide and lead iodide in an organic solvent at a molar ratio of 1:1 to 1.2, and stirring at 60 to 80°C for more than 24 hours to obtain the MAPbI3 perovskite precursor solution.

[0019] Furthermore, the molar ratio of methylammonium iodide to lead iodide is 1:(1.0-1.2); the organic solvent is selected from one of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) or γ-butyrolactone (GBL).

[0020] Furthermore, the thickness of the perovskite thin film layer is 200–400 nm.

[0021] In one or more possible embodiments, step S2, specifically includes:

[0022] A core-shell structured NaYGdF4:Yb was spin-coated onto the perovskite thin film layer at a rotation speed of 2000–3000 rpm. 3+ Er 3+ After dispersing the NaYF4 upconversion particles, the upconversion layer was obtained by annealing at 100–130 °C for 5–10 min.

[0023] Furthermore, the core-shell structure of NaYGdF4:Yb 3+ Er 3+ The mass concentration of the @NaYF4 upconversion particle dispersion is 0.1 mmol / mL.

[0024] In one or more possible embodiments, the core-shell structure NaYGdF4:Yb 3+ Er 3+ The preparation of the @NaYF4 upconversion particle dispersion includes the following steps:

[0025] S21. After preparing a precursor solution containing yttrium, gadolinium, ytterbium, and erbium sources, an ammonium fluoride methanol solution and a sodium hydroxide methanol solution are added, stirred to dissolve, heated under an inert gas atmosphere, and then ethanol is added to precipitate the product. The precipitate is separated by centrifugation, washed, and dissolved in cyclohexane to obtain NaYGdF4:Yb. 3+ Er 3+ Nuclear layer solution;

[0026] S22. Add the yttrium source-containing precursor solution, ammonium fluoride methanol solution, and sodium hydroxide methanol solution to the NaYGdF4:Yb from step S2. 3+ Er 3+In the core-shell solution, after heating under an inert gas atmosphere, the particulate precipitate was centrifuged and collected, washed, and then dispersed in cyclohexane to prepare the core-shell structured NaYGdF4:Yb. 3+ Er 3+ @NaYF4 upconversion particle dispersion.

[0027] In one or more possible embodiments, in step S21, the molar ratio of the yttrium source, gadolinium source, ytterbium source, and erbium source is 78:5:20:2; and the molar ratio of the ammonium fluoride to the sodium hydroxide is 8:3 to 3.5.

[0028] Furthermore, the yttrium source is selected from yttrium acetate (Y(CH3COO)3) or yttrium chloride (YCl3); the gadolinium source is selected from gadolinium acetate hexahydrate (Gd(CH3COO)3·6H2O) or gadolinium chloride (GdCl3); the ytterbium source is selected from ytterbium acetate tetrahydrate (Yb(CH3COO)3·4H2O) or ytterbium chloride (YbCl3); and the erbium source is selected from erbium acetate (Er(CH3COO)3) or erbium chloride (ErCl3).

[0029] Furthermore, the method for preparing the precursor solution containing yttrium, gadolinium, ytterbium, and erbium sources is as follows: Y(CH3COO)3, Gd(CH3COO)3·6H2O, Yb(CH3COO)3·4H2O, and Er(CH3COO)3 are dissolved in 1-octadecene (ODE) and oleic acid (OA) in the above molar ratio to obtain the precursor solution containing yttrium, gadolinium, ytterbium, and erbium sources.

[0030] Furthermore, the volume of the ODE is 15-20 mL, and the volume of the OA is 6-10 mL.

[0031] In one or more possible embodiments, in step S22, the molar ratio of ammonium fluoride to sodium hydroxide is 8:5 to 5.5.

[0032] Furthermore, after the yttrium-containing precursor solution is heated to form a transparent solution, it is cooled to about 80°C and added to the core layer solution in step S21.

[0033] In one or more possible embodiments, in step S3, the thickness of the electrode layer is 80-100 nm, and the spacing between two adjacent electrode layers is 150-180 nm.

[0034] The detector with positive and negative light responses and its fabrication method provided by this invention have the following advantages over the prior art:

[0035] (1) The photodetector prepared by this invention has a wavelength of 500 nm and an intensity of 0.8 mW / cm. 2Under green light excitation and with a bias voltage of 10V, the responsivity is 41.22 mA / W, and the normalized ratio detectivity is 3.31 × 10⁻⁶. 8 Jones, with an external quantum efficiency of 10.22%. At a wavelength of 980 nm and an intensity of 50 mW / cm². 2 Under near-infrared light excitation and a bias voltage of 10V, the photocurrent was found to be lower than the dark current. The responsivity was calculated to be 100.24 μA / W, and the normalized responsivity was 7.91 × 10⁻⁶. 5 Jones, with an external quantum efficiency of 1.273 × 10⁻⁶. -2 %.

[0036] (2) The photodetector prepared by this invention can simultaneously detect visible and near-infrared light on a single pixel and generate bidirectional photoelectric responses. By utilizing the cross-relaxation effect generated by upconversion nanoparticles excited by 980nm near-infrared light, which causes a decrease in photocurrent, and the mechanism by which perovskite materials promote current increase through the positive photoconductivity effect under visible light illumination, unique symbolic encoding of light of different wavelengths is achieved within the same device. Combining these photoelectric response characteristics and light intensity information for analysis, the photodetector of this invention can achieve multi-dimensional optical signal discrimination, demonstrating its application potential in the field of intelligent photoelectric detection. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the structure of the photodetector provided by the present invention; in the figure, 1 is the substrate layer, 2 is the perovskite thin film layer, 3 is the upconversion layer, and 4 is the electrode layer;

[0039] Figure 2 This is a scanning electron microscope image of a perovskite thin film layer provided as an example of the present invention;

[0040] Figure 3 This is a scanning electron microscope image of upconversion particles provided as an example of the present invention;

[0041] Figure 4 This is a scanning electron microscope image of the upconversion layer provided as an example of the present invention;

[0042] Figure 5 The following are voltage-current performance test diagrams of the photodetector under different conditions, which are provided as an example of the present invention. Detailed Implementation

[0043] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0044] like Figure 1 As shown, the present invention provides a detector with positive and negative light response, comprising: a substrate layer 1, and a perovskite thin film layer 2, an upconversion layer 3 and an electrode layer 4 sequentially stacked on the substrate layer 1.

[0045] In this embodiment of the invention, the perovskite thin film layer 2 serves as a light absorption layer with a thickness of 200–400 nm; the upconversion layer 3 has a thickness of 400–500 nm; the electrode layer 4 has a thickness of 80–100 nm; and the spacing between two adjacent electrode layers 4 is 150–180 nm.

[0046] Specifically, the thickness of the perovskite thin film layer 2 can be any value among 200nm, 300nm, and 400nm, or a range between any two of the above; the thickness of the upconversion layer 3 can be any value among 400nm, 450nm, and 500nm, or a range between any two of the above; the thickness of the electrode layer 4 can be any value among 80nm, 90nm, and 100nm, or a range between any two of the above; and the spacing between two adjacent electrode layers 4 can be any value among 150nm, 160nm, 170nm, and 180nm, or a range between any two of the above.

[0047] In this embodiment of the invention, the substrate layer is a glass substrate; the perovskite thin film layer 2 is a MAPbI3 perovskite thin film; and the upconversion layer 3 includes a core-shell structure of NaYGdF4:Yb. 3+ Er 3+ @NaYF4 upconversion particles; the material of the electrode layer includes, but is not limited to, gold (Au) electrodes.

[0048] In this embodiment of the invention, the method for preparing the MAPbI3 perovskite precursor solution includes:

[0049] A MAPbI3 perovskite precursor solution was prepared by mixing and dissolving methylammonium iodide (MAI) and lead iodide (PbI2) in an organic solvent at a molar ratio of 1:(1.0-1.2) and stirring at 60-80°C for more than 24 hours.

[0050] Specifically, the molar ratio of MAI to PbI2 can be set to any value among 1:1, 1:1.1, or 1:1.2, or a range between any two of the above; the heating temperature can be set to any value among 60℃, 70℃, or 80℃, or a range between any two of the above.

[0051] In this embodiment of the invention, the preparation of the perovskite thin film layer 2 includes the following steps:

[0052] Take 200-250 μL of MAPbI3 perovskite precursor solution and spin-coat it onto the substrate 1 under nitrogen protection. The spin-coating conditions are as follows: First, spin-coat at 800-1000 rpm for 10-15 s. Second, spin-coat at 3000-3500 rpm for 40-45 s. 15-20 s before the end of the second spin-coating, vertically drop 100-150 μL of chlorobenzene onto the rotating MAPbI3 substrate. After spin-coating, anneal at 100-120℃ for 5-10 min to form a perovskite thin film layer 2 on the substrate 1.

[0053] Specifically, the volume of the MAPbI3 perovskite precursor solution can be any value from 200 μL, 210 μL, 220 μL, 230 μL, 240 μL, 250 μL, or a range between any two of the above; the rotation speed of the first spin coating step can be any value from 800 rpm, 900 rpm, 1000 rpm, or a range between any two of the above, and the time can be any value from 10 s, 11 s, 12 s, 13 s, 14 s, 15 s, or a range between any two of the above; the rotation speed of the second spin coating step can be 3000 rpm. The annealing temperature can be any value among 3100 rpm, 3200 rpm, 3300 rpm, 3400 rpm, and 3500 rpm, or a range between any two of the above; the annealing time can be any value among 40 s, 41 s, 42 s, 43 s, 44 s, and 45 s, or a range between any two of the above; the annealing temperature can be any value among 100 ℃, 110 ℃, and 120 ℃, or a range between any two of the above; the annealing time can be any value among 5 min, 6 min, 7 min, 8 min, 9 min, and 10 min, or a range between any two of the above.

[0054] Example 1

[0055] This embodiment provides a method for preparing a MAPbI3 perovskite thin film layer 1, including the following steps:

[0056] 0.158 g of methylamine iodide (MAI) and 0.461 g of lead iodide (PbI2) were added to 1 ml of N,N-dimethylformamide (DMF) and stirred continuously at 60 °C for at least 24 h to form a precursor solution. 200 μL of the perovskite precursor solution was spin-coated onto a glass substrate. The first spin-coating was performed at 800 rpm for 15 s, followed by a second spin-coating at 3000 rpm for 40 s. 20 s before the end of the second spin-coating step, 100 μL of chlorobenzene was vertically added to the rotating MAPbI3 substrate. Finally, the substrate was annealed at 100 °C for 5 min to obtain a 300 nm thick MAPbI3 perovskite thin film layer 1. Figure 2 As shown.

[0057] Depend on Figure 2 It can be seen that the MAPbI3 perovskite thin film prepared by this invention has good crystallinity.

[0058] Example 2

[0059] This embodiment provides a method for preparing a MAPbI3 perovskite thin film layer 1, including the following steps:

[0060] 0.158 g of methylamine iodide (MAI) and 0.461 g of lead iodide (PbI2) were added to 1 ml of dimethyl sulfoxide (DMSO) and stirred continuously at 70 °C for at least 24 h to form a precursor solution. 220 μL of the perovskite precursor solution was spin-coated onto a glass substrate. The first spin-coating was performed at 900 rpm for 12 s, followed by a second spin-coating at 3100 rpm for 42 s. 15 s before the end of the second spin-coating step, 100 μL of chlorobenzene was vertically added dropwise onto the rotating MAPbI3 substrate. Finally, the substrate was annealed at 110 °C for 8 min to obtain a 200 nm thick MAPbI3 perovskite thin film.

[0061] Example 3

[0062] This embodiment provides a method for preparing a MAPbI3 perovskite thin film layer 1, including the following steps:

[0063] 0.158 g of methylamine iodide (MAI) and 0.469 g of lead iodide (PbI2) were added to 1 ml of γ-butyrolactone (GBL), and stirred continuously at 80 °C for at least 24 h to form a precursor solution. 240 μL of the perovskite precursor solution was spin-coated onto a glass substrate. The first spin-coating was performed at 1000 rpm for 10 s, followed by a second spin-coating at 3400 rpm for 40 s. 18 s before the end of the second spin-coating step, 100 μL of chlorobenzene was vertically added dropwise onto the rotating MAPbI3 substrate. Finally, the substrate was annealed at 120 °C for 10 min to obtain a MAPbI3 perovskite thin film layer with a thickness of 400 nm.

[0064] Example 4

[0065] This embodiment provides a method for preparing a MAPbI3 perovskite thin film layer 1, including the following steps:

[0066] 0.158 g of methylamine iodide (MAI) and 0.461 g of lead iodide (PbI2) were added to 1 ml of N,N-dimethylformamide (DMF) and stirred continuously at 60 °C for at least 24 h to form a precursor solution. 250 μL of the perovskite precursor solution was spin-coated onto a glass substrate. The first spin-coating was performed at 800 rpm for 14 s, followed by a second spin-coating at 3500 rpm for 45 s. Twenty s before the end of the second spin-coating step, 100 μL of chlorobenzene was vertically added dropwise onto the rotating MAPbI3 substrate. Finally, the substrate was annealed at 100 °C for 5 min to obtain a MAPbI3 perovskite thin film layer with a thickness of 360 nm.

[0067] In this embodiment of the invention, the core-shell structure NaYGdF4:Yb 3+ Er 3+ The preparation of the @NaYF4 upconversion particle dispersion includes the following steps:

[0068] S21. Dissolve yttrium source, gadolinium source, ytterbium source and erbium source in 15-20 mL of 1-octadecene and 6-10 mL of oleic acid at a molar ratio of 78:5:20:2. Heat the mixture at 100-130°C for 10-20 min, then stir and heat to 150-180°C under a nitrogen atmosphere, and then cool to room temperature to obtain a precursor solution containing yttrium source, gadolinium source, ytterbium source and erbium source. Ammonium fluoride and sodium hydroxide were dissolved in 10-20 mL of methanol solution at a molar ratio of 8:(5-5.5). The solutions were heated to 50 °C with stirring and held for 30-45 min, then heated to 100-120 °C under vacuum and held for 30-45 min, followed by heating to 300-320 °C and held for 1-1.5 h. After cooling to room temperature, ethanol was added to precipitate the product. The precipitate was centrifuged at 7000-8000 rpm for 20-30 min, separated, and washed. The precipitate was dispersed in 10-15 mL of cyclohexane to obtain NaYGdF4:Yb. 3+ Er 3+ Nuclear layer solution;

[0069] S22. Dissolve the yttrium source in 6–10 ml of oleic acid and 15–20 ml of 1-octadecene, stir and heat to 150–180°C to form a transparent solution. When the temperature drops to 80°C, add NaYGdF4:Yb 3+ Er 3+After dissolving in the core layer solution and cooling to room temperature, ammonium fluoride and sodium hydroxide were dissolved separately in 10-20 mL of methanol solution at a molar ratio of 8:(5-5.5), and then added to the mixed solution. The mixture was heated under vacuum at 100-130 °C for 20-30 min, followed by heating to 300-320 °C and holding for 1-1.5 h. Finally, it was centrifuged at 7000-8000 r / min for 20-30 min to separate the particulate precipitate. After washing, the particulate precipitate was dispersed in 10-15 mL of cyclohexane to obtain the core-shell structured NaYGdF4:Yb. 3+ Er 3+ @NaYF4 upconversion particle dispersion.

[0070] In step S21, exemplarily: the volume of 1-octadecene can be any value among 15 mL, 16 mL, 18 mL, and 20 mL, or a range between any two of the above; the volume of oleic acid can be any value among 6 mL, 8 mL, and 10 mL, or a range between any two of the above; the molar ratio of ammonium fluoride to sodium hydroxide can be any value among 8:5, 8:5.2, and 8:5.5, or a range between any two of the above. The remaining ranges involved in the steps can also be explained similarly above, and will not be repeated here.

[0071] In step S22, for example, the molar ratio of ammonium fluoride to sodium hydroxide can be any value among 8:5, 8:5.2, 8:5.4, and 8:5.5, or a range between any two of the above. The remaining ranges involved in the steps can also be described similarly above, and will not be repeated here.

[0072] Example 5

[0073] This embodiment provides a core-shell structured NaYGdF4:Yb 3+ Er 3+ The preparation method of @NaYF4 upconversion particle dispersion includes the following steps:

[0074] 0.78 mmol of yttrium acetate, 0.05 mmol of gadolinium acetate hexahydrate, 0.2 mmol of ytterbium acetate tetrahydrate, and 0.02 mmol of erbium acetate were dissolved in 15 mL of 1-octadecene and 6 mL of oleic acid, and the mixture was placed in a 100 mL three-necked flask. Nitrogen gas was slowly introduced into the three-necked flask to remove as much air as possible. The mixture was then heated at 110 °C for 15 min, with nitrogen gas being continuously introduced to remove any moisture that might be present in the flask. Subsequently, the mixture was heated to 160 °C with stirring under a nitrogen atmosphere, and then cooled to room temperature. Next, 4 mmol of ammonium fluoride and 2.5 mmol of sodium hydroxide were added separately to 10 mL of methanol solution and dissolved evenly with magnetic stirring. The resulting solution was added to the previous mixture and dissolved completely. The mixture was then heated to 50 °C with stirring under nitrogen and held for 30 min, and then heated to 100 °C under vacuum and held for 30 min to completely remove methanol. The mixture was then heated to 310°C and maintained at that temperature for 1.2 h. Finally, after naturally cooling to room temperature, ethanol was added to obtain a precipitate. The precipitate was centrifuged at 7500 r / min for 25 min, the supernatant was discarded, and the precipitate was collected. The precipitate was washed twice, successively with ethanol and cyclohexane, and then dispersed in 10 mL of cyclohexane to obtain NaYGdF4:Yb. 3+ Er 3+ Nuclear layer solution.

[0075] Dissolve 1 mmol of yttrium acetate in 6 ml of oleic acid and 15 ml of 1-octadecene in a three-necked flask, stirring continuously and heating to 160°C until a clear solution is formed. Remove residual water and residues. When the temperature drops to 80°C, add NaYGdF4:Yb. 3+ Er 3+ After complete dissolution in the core-shell solution, the mixed solution was cooled to room temperature. 4 mmol of NH4F and 2.5 mmol of NaOH were added to 10 mL of methanol solution, respectively, and dissolved uniformly under magnetic stirring. The resulting solution was then added to the mixed solution, and the mixture was heated to 120 °C under vacuum for 25 min to completely remove methanol. Subsequently, the mixed solution was heated to 320 °C under nitrogen atmosphere for 1 h. Finally, the resulting mixed solution was centrifuged at 7000-8000 r / min for 25 min, the supernatant was discarded, and the particulate precipitate was collected. After washing twice with ethanol and cyclohexane, the core-shell structured NaYGdF4:Yb was obtained. 3+ Er 3+ @NaYF4 upconversion particles, such as Figure 3 As shown;

[0076] NaYGdF4:Yb core-shell structure 3+ Er 3+@NaYF4 upconversion particles were dispersed in 10 mL of cyclohexane to obtain core-shell structured NaYGdF4:Yb 3+ Er 3+ @NaYF4 upconversion particle dispersion.

[0077] Depend on Figure 3 It can be seen that the upconversion particles prepared by the present invention have a size of 30-40 nm, and the upconversion nanoparticles have a relatively stable hexagonal phase crystal phase, and their interplanar spacing conforms to the (100) crystal plane of the hexagonal phase of the upconversion nanoparticles.

[0078] Example 6

[0079] This embodiment provides a core-shell structured NaYGdF4:Yb 3+ Er 3+ The preparation method of @NaYF4 upconversion particle dispersion includes the following steps:

[0080] 0.78 mmol of yttrium chloride, 0.05 mmol of gadolinium chloride, 0.2 mmol of ytterbium chloride, and 0.02 mmol of erbium chloride were dissolved in 15 mL of 1-octadecene and 6 mL of oleic acid, and the mixture was placed in a 100 mL three-necked flask. Nitrogen gas was slowly introduced into the three-necked flask to remove as much air as possible. The mixture was then heated at 110 °C for 15 min, and nitrogen gas was continued to be introduced to remove any moisture that might be present in the flask. Subsequently, the mixture was heated to 160 °C with stirring under a nitrogen atmosphere, and then cooled to room temperature. Next, 4 mmol of ammonium fluoride and 2.5 mmol of sodium hydroxide were added separately to 10 mL of methanol solution and dissolved evenly with magnetic stirring. The resulting solution was added to the previous mixture and dissolved completely. The mixture was then heated to 50 °C with stirring under nitrogen atmosphere and held for 30 min, and then heated to 100 °C under vacuum and held for 30 min to completely remove methanol. The mixture was then heated to 310°C and maintained at that temperature for 1.2 h. Finally, after naturally cooling to room temperature, ethanol was added to obtain a precipitate. The precipitate was centrifuged at 7500 r / min for 25 min, the supernatant was discarded, and the precipitate was collected. The precipitate was washed twice, successively with ethanol and cyclohexane, and then dispersed in 10 mL of cyclohexane to obtain NaYGdF4:Yb. 3+ Er 3+ Nuclear layer solution.

[0081] Dissolve 1 mmol of yttrium chloride in 6 ml of oleic acid and 15 ml of 1-octadecene in a three-necked flask, stirring continuously and heating to 160°C until a clear solution is formed. Remove residual water and residues. When the temperature drops to 80°C, add NaYGdF4:Yb. 3+ Er 3+After complete dissolution in the core-shell solution, the mixed solution was cooled to room temperature. 4 mmol of NH4F and 2.5 mmol of NaOH were added to 10 mL of methanol solution, respectively, and dissolved uniformly under magnetic stirring. The resulting solution was then added to the mixed solution, and the mixture was heated to 120 °C under vacuum for 25 min to completely remove methanol. Subsequently, the mixed solution was heated to 320 °C under nitrogen atmosphere for 1 h. Finally, the resulting mixed solution was centrifuged at 7000-8000 r / min for 25 min, the supernatant was discarded, and the particulate precipitate was collected. After washing twice with ethanol and cyclohexane, the core-shell structured NaYGdF4:Yb was obtained. 3+ Er 3+ @NaYF4 upconversion particles;

[0082] NaYGdF4:Yb core-shell structure 3+ Er 3+ @NaYF4 upconversion particles were dispersed in 10 mL of cyclohexane to obtain core-shell structured NaYGdF4:Yb 3+ Er 3+ @NaYF4 upconversion particle dispersion.

[0083] Example 7

[0084] This embodiment provides a core-shell structured NaYGdF4:Yb 3+ Er 3+ The preparation method of @NaYF4 upconversion particle dispersion includes the following steps:

[0085] 0.78 mmol of yttrium chloride, 0.05 mmol of gadolinium chloride, 0.2 mmol of ytterbium chloride, and 0.02 mmol of erbium chloride were dissolved in 15 mL of 1-octadecene and 6 mL of oleic acid, and the mixture was placed in a 100 mL three-necked flask. Nitrogen gas was slowly introduced into the three-necked flask to remove as much air as possible. The mixture was then heated at 110 °C for 15 min, with nitrogen gas being continuously introduced to remove any moisture that might be present in the flask. Subsequently, the mixture was heated to 160 °C with stirring under a nitrogen atmosphere, and then cooled to room temperature. Next, 4 mmol of ammonium fluoride and 2.7 mmol of sodium hydroxide were added separately to 10 mL of methanol solution and dissolved evenly with magnetic stirring. The resulting solution was added to the previous mixture and dissolved completely. The mixture was then heated to 50 °C with stirring under nitrogen and held for 30 min, and then heated to 100 °C under vacuum and held for 30 min to completely remove methanol. The mixture was then heated to 310°C and maintained at that temperature for 1.2 h. Finally, after naturally cooling to room temperature, ethanol was added to obtain a precipitate. The precipitate was centrifuged at 7500 r / min for 25 min, the supernatant was discarded, and the precipitate was collected. The precipitate was washed twice, successively with ethanol and cyclohexane, and then dispersed in 10 mL of cyclohexane to obtain NaYGdF4:Yb. 3+ Er 3+ Nuclear layer solution.

[0086] Dissolve 1 mmol of yttrium chloride in 6 ml of oleic acid and 15 ml of 1-octadecene in a three-necked flask, stirring continuously and heating to 160°C until a clear solution is formed. Remove residual water and residues. When the temperature drops to 80°C, add NaYGdF4:Yb. 3+ Er 3+ After complete dissolution in the core-shell solution, the mixed solution was cooled to room temperature. 4 mmol of NH4F and 2.7 mmol of NaOH were added to 10 mL of methanol solution, respectively, and dissolved uniformly under magnetic stirring. The resulting solution was then added to the mixed solution, and the mixture was heated to 120 °C under vacuum for 25 min to completely remove methanol. Subsequently, the mixed solution was heated to 320 °C under nitrogen atmosphere for 1 h. Finally, the resulting mixed solution was centrifuged at 7000-8000 r / min for 25 min, the supernatant was discarded, and the particulate precipitate was collected. After washing twice with ethanol and cyclohexane, the core-shell structured NaYGdF4:Yb was obtained. 3+ Er 3+ @NaYF4 upconversion particles;

[0087] NaYGdF4:Yb core-shell structure 3+ Er 3+ @NaYF4 upconversion particles were dispersed in 10 mL of cyclohexane to obtain core-shell structured NaYGdF4:Yb3+ Er 3+ @NaYF4 upconversion particle dispersion.

[0088] Example 8

[0089] This embodiment provides a core-shell structured NaYGdF4:Yb 3+ Er 3+ The preparation method of @NaYF4 upconversion particle dispersion includes the following steps:

[0090] 0.78 mmol of yttrium acetate, 0.05 mmol of gadolinium acetate hexahydrate, 0.2 mmol of ytterbium acetate tetrahydrate, and 0.02 mmol of erbium acetate were dissolved in 15 mL of 1-octadecene and 6 mL of oleic acid, and the mixture was placed in a 100 mL three-necked flask. Nitrogen gas was slowly introduced into the three-necked flask to remove as much air as possible. The mixture was then heated at 110 °C for 15 min, with nitrogen gas being continuously introduced to remove any moisture that might be present in the flask. Subsequently, the mixture was heated to 160 °C with stirring under a nitrogen atmosphere, and then cooled to room temperature. Next, 4 mmol of ammonium fluoride and 2.5 mmol of sodium hydroxide were added separately to 10 mL of methanol solution and dissolved evenly with magnetic stirring. The resulting solution was added to the previous mixture and dissolved completely. The mixture was then heated to 50 °C with stirring under nitrogen and held for 30 min, and then heated to 100 °C under vacuum and held for 30 min to completely remove methanol. The mixture was then heated to 310°C and maintained at that temperature for 1.2 h. Finally, after naturally cooling to room temperature, ethanol was added to obtain a precipitate. The precipitate was centrifuged at 7500 r / min for 25 min, the supernatant was discarded, and the precipitate was collected. The precipitate was washed twice, successively with ethanol and cyclohexane, and then dispersed in 10 mL of cyclohexane to obtain NaYGdF4:Yb. 3+ Er 3+ Nuclear layer solution.

[0091] Dissolve 1 mmol of yttrium acetate in 6 ml of oleic acid and 15 ml of 1-octadecene in a three-necked flask, stirring continuously and heating to 160°C until a clear solution is formed. Remove residual water and residues. When the temperature drops to 80°C, add NaYGdF4:Yb. 3+ Er 3+After complete dissolution in the core-shell solution, the mixed solution was cooled to room temperature. 4 mmol of NH4F and 2.5 mmol of NaOH were added to 10 mL of methanol solution, respectively, and dissolved uniformly under magnetic stirring. The resulting solution was then added to the mixed solution, and the mixture was heated to 120 °C under vacuum for 25 min to completely remove methanol. Subsequently, the mixed solution was heated to 320 °C under nitrogen atmosphere for 1 h. Finally, the resulting mixed solution was centrifuged at 7000-8000 r / min for 25 min, the supernatant was discarded, and the particulate precipitate was collected. After washing twice with ethanol and cyclohexane, the core-shell structured NaYGdF4:Yb was obtained. 3+ Er 3+ @NaYF4 upconversion particles;

[0092] NaYGdF4:Yb core-shell structure 3+ Er 3+ @NaYF4 upconversion particles were dispersed in 10 mL of cyclohexane to obtain core-shell structured NaYGdF4:Yb 3+ Er 3+ @NaYF4 upconversion particle dispersion.

[0093] Example 9

[0094] This embodiment provides a core-shell structured NaYGdF4:Yb 3+ Er 3+ The preparation method of @NaYF4 upconversion particle dispersion includes the following steps:

[0095] 0.78 mmol of yttrium acetate, 0.05 mmol of gadolinium acetate hexahydrate, 0.2 mmol of ytterbium acetate tetrahydrate, and 0.02 mmol of erbium acetate were dissolved in 15 mL of 1-octadecene and 6 mL of oleic acid, and the mixture was placed in a 100 mL three-necked flask. Nitrogen gas was slowly introduced into the three-necked flask to remove as much air as possible. The mixture was then heated at 110 °C for 15 min, with nitrogen gas being continuously introduced to remove any moisture that might be present in the flask. Subsequently, the mixture was heated to 160 °C with stirring under a nitrogen atmosphere, and then cooled to room temperature. Next, 4 mmol of ammonium fluoride and 2.5 mmol of sodium hydroxide were added separately to 10 mL of methanol solution and dissolved evenly with magnetic stirring. The resulting solution was added to the previous mixture and dissolved completely. The mixture was then heated to 50 °C with stirring under nitrogen and held for 30 min, and then heated to 100 °C under vacuum and held for 30 min to completely remove methanol. The mixture was then heated to 310°C and maintained at that temperature for 1.2 h. Finally, after naturally cooling to room temperature, ethanol was added to obtain a precipitate. The precipitate was centrifuged at 7500 r / min for 25 min, the supernatant was discarded, and the precipitate was collected. The precipitate was washed twice, successively with ethanol and cyclohexane, and then dispersed in 10 mL of cyclohexane to obtain NaYGdF4:Yb. 3+ Er 3+ Nuclear layer solution.

[0096] Dissolve 1 mmol of yttrium acetate in 6 ml of oleic acid and 15 ml of 1-octadecene in a three-necked flask, stirring continuously and heating to 160°C until a clear solution is formed. Remove residual water and residues. When the temperature drops to 80°C, add NaYGdF4:Yb. 3+ Er 3+ After complete dissolution in the core-shell solution, the mixed solution was cooled to room temperature. 4 mmol of NH4F and 2.5 mmol of NaOH were added to 10 mL of methanol solution, respectively, and dissolved uniformly under magnetic stirring. The resulting solution was then added to the mixed solution, and the mixture was heated to 120 °C under vacuum for 25 min to completely remove methanol. Subsequently, the mixed solution was heated to 320 °C under nitrogen atmosphere for 1 h. Finally, the resulting mixed solution was centrifuged at 7000-8000 r / min for 25 min, the supernatant was discarded, and the particulate precipitate was collected. After washing twice with ethanol and cyclohexane, the core-shell structured NaYGdF4:Yb was obtained. 3+ Er 3+ @NaYF4 upconversion particles;

[0097] NaYGdF4:Yb core-shell structure 3+ Er 3+ @NaYF4 upconversion particles were dispersed in 10 mL of cyclohexane to obtain core-shell structured NaYGdF4:Yb3+ Er 3+ @NaYF4 upconversion particle dispersion.

[0098] In this embodiment of the invention, the preparation of the upconversion layer 3 includes the following steps: spin-coating a core-shell structure of NaYGdF4:Yb onto the perovskite thin film layer 2 at a rotation speed of 2000-3000 rpm. 3+ Er 3+ After dispersing the NaYF4 upconversion particles, the mixture was annealed at 100–130 °C for 5–10 min to obtain the upconversion layer 3.

[0099] Specifically, the spin coating speed can be any value among 2000 rpm, 2500 rpm, and 3000 rpm, or a range between any two of the above; the annealing temperature can be any value among 100℃, 110℃, 120℃, and 130℃, or a range between any two of the above; and the annealing time can be any value among 5 min, 8 min, and 10 min, or a range between any two of the above.

[0100] Based on the MAPbI3 perovskite thin film layer 2 prepared in Example 1 and the core-shell structure NaYGdF4:Yb prepared in Example 5 3+ Er 3+ The upconversion layer 3 was prepared by dispersing NaYF4 upconversion particles, and the following examples are provided.

[0101] Example 11

[0102] The preparation method of the upconversion layer 3 in this embodiment includes the following steps:

[0103] A core-shell structured NaYGdF4:Yb film was spin-coated onto a MAPbI3 perovskite thin film layer 2 at a spin speed of 2000 rpm. 3+ Er 3+ After dispersing the NaYF4 upconversion particles, annealing at 100℃ for 5 min yielded upconversion layer 3 with a thickness of 460 nm. Figure 4 As shown.

[0104] Depend on Figure 4 It can be seen that the upconversion nanoparticles prepared by this invention have good dispersibility after being spin-coated onto the surface of the perovskite layer.

[0105] Example 12

[0106] The preparation method of the upconversion layer 3 in this embodiment includes the following steps:

[0107] A core-shell structured NaYGdF4:Yb film was spin-coated onto a MAPbI3 perovskite thin film layer 2 at a spin speed of 2400 rpm.3+ Er 3+ After dispersing the NaYF4 upconversion particles, annealing at 110℃ for 6 min yielded an upconversion layer 3 with a thickness of 440 nm.

[0108] Example 13

[0109] The preparation method of the upconversion layer 3 in this embodiment includes the following steps:

[0110] A core-shell structured NaYGdF4:Yb film was spin-coated onto a MAPbI3 perovskite thin film layer 2 at a spin speed of 2600 rpm. 3+ Er 3+ After dispersing the NaYF4 upconversion particles, annealing at 120℃ for 8 min yielded an upconversion layer 3 with a thickness of 400 nm.

[0111] Example 14

[0112] The preparation method of the upconversion layer 3 in this embodiment includes the following steps:

[0113] A core-shell structured NaYGdF4:Yb film was spin-coated at a speed of 3000 rpm onto a MAPbI3 perovskite thin film layer 2. 3+ Er 3+ After dispersing the NaYF4 upconversion particles, annealing at 100℃ for 10 min yielded an upconversion layer 3 with a thickness of 500 nm.

[0114] In this embodiment of the invention, the preparation of the electrode layer 4 includes the following steps: depositing an electrode layer 4 with a thickness of 80nm to 100nm and a spacing of 150 to 180μm on the upconversion layer 3 by a thermal evaporation process to obtain a photodetector.

[0115] Furthermore, the thermal evaporation deposition process conditions include: using a mechanical pump and a molecular pump to maintain a vacuum of 3 × 10⁻⁶ within the sample chamber. -4 -5×10 -4 The current is applied to the tungsten boat containing solid gold particles and the temperature is increased to about 2800°C. After the gold atoms or molecules gain sufficient kinetic energy, they detach from the solid / liquid surface and form a vapor phase, which is then deposited onto the sample to form a gold electrode.

[0116] Specifically, the thickness of the electrode layer 4 can be any value among 80nm, 90nm, and 100nm or any value between any two of the above, and the spacing can be any value among 150μm, 160μm, 170μm, and 180μm or any value between any two of the above.

[0117] The electrode layer 4 is prepared based on the upconversion layer 3 prepared in Example 11, and the following examples are provided.

[0118] Example 15

[0119] This embodiment provides a method for preparing an electrode layer 4, including the following steps:

[0120] A photodetector was fabricated by depositing a gold electrode layer 4 with a thickness of 90 nm and a spacing of 150 μm on the upconversion layer 3 using a thermal evaporation process.

[0121] Example 16

[0122] This embodiment provides a method for preparing an electrode layer 4, including the following steps:

[0123] A photodetector was fabricated by depositing a gold electrode layer 4 with a thickness of 80 nm and a spacing of 160 μm on the upconversion layer 3 using a thermal evaporation process.

[0124] Example 17

[0125] This embodiment provides a method for preparing an electrode layer 4, including the following steps:

[0126] A photodetector was fabricated by depositing a 100 nm thick gold electrode layer 4 with a spacing of 170 μm on the upconversion layer 3 using a thermal evaporation process.

[0127] Example 18

[0128] This embodiment provides a method for preparing an electrode layer 4, including the following steps:

[0129] A photodetector was fabricated by depositing a gold electrode layer 4 with a thickness of 90 nm and a spacing of 180 μm on the upconversion layer 3 using a thermal evaporation process.

[0130] The photodetector prepared in Example 15 was subjected to voltage-current testing using a Keithley 4200 digital source meter, with a voltage testing range of -10V to 10V. Testing was conducted in darkness at a wavelength of 500nm and an intensity of 0.8mW / cm². 2 Under green light at 980nm and an intensity of 50mW / cm² 2 The current diagram under near-infrared light excitation. The test results are as follows: Figure 5 As shown.

[0131] Depend on Figure 5 It can be seen that under green light illumination, the photocurrent is higher than the dark current, exhibiting positive photoconductivity; under infrared light illumination, the photocurrent is lower than the dark current, exhibiting reverse photoconductivity. This demonstrates that the photodetector prepared by this invention can exhibit bipolar response under fixed bias conditions and different wavelengths of light excitation, showing excellent photoelectric performance characteristics.

[0132] The photoelectric performance of the fabricated photodetector was tested by measuring the photocurrent and dark current of the device under a bias voltage of 10V. Typically, the performance of a photodetector is evaluated using photoresponsivity, photonormalized resonant ratio, and external quantum efficiency. The formulas are described below:

[0133]

[0134]

[0135] In the formula, I photo and I dark Let be the photocurrent and dark current of the detector, respectively; P be the light power density of the light source; S be the effective response area; h be Planck's constant; e be the charge; and c be the speed of light.

[0136] The test results were: at a wavelength of 500 nm and an intensity of 0.8 mW / cm². 2 Under green light excitation and with a bias voltage of 10V, the responsivity is 41.22 mA / W, and the normalized ratio detectivity is 3.31 × 10⁻⁶. 8 Jones, with an external quantum efficiency of 10.22%. At a wavelength of 980 nm and an intensity of 50 mW / cm². 2 Under near-infrared light excitation and a bias voltage of 10V, the photocurrent was found to be lower than the dark current. The responsivity was calculated to be 100.24 μA / W, and the normalized responsivity was 7.91 × 10⁻⁶. 5 Jones, with an external quantum efficiency of 1.273 × 10⁻⁶. -2 %.

[0137] Comparative Example 1

[0138] The difference from Example 15 is that gadolinium acetate hexahydrate was not added when preparing the upconversion particles, the steps were adapted, and the other conditions remained unchanged.

[0139] The photodetector prepared in Comparative Example 1 was subjected to the above photoelectric performance tests. The test results were as follows: at a wavelength of 500 nm and an intensity of 0.8 mW / cm², the photodetector was tested. 2 Under green light excitation and with a bias voltage of 10V, the responsivity is 28.45 mA / W, and the normalized ratio detectivity is 2.67 × 10⁻⁶. 8 Jones, with an external quantum efficiency of 7.06%. At a wavelength of 980 nm and an intensity of 50 mW / cm². 2 Under near-infrared light excitation and a bias voltage of 10V, the photocurrent was found to be lower than the dark current. The calculated responsivity was 46.41 μA / W, and the normalized responsivity was 5.48 × 10⁻⁶. 5Jones, with an external quantum efficiency of 5.89 × 10⁻⁶. -3 %.

[0140] Comparison reveals that upconversion particles containing Gd improve the photoelectric performance of photodetectors. This is because Gd... 3+ Ion doping into the NaYF4 matrix did not replace the Y in the matrix. 3+ ions, and Gd 3+ The effective radius of the ion is greater than that of Y. 3+ The effective radius of the ions, this substitution leads to lattice expansion of the upconversion nanoparticles, which in turn increases the interplanar spacing of NaYGdF4. This change not only helps the formation of the hexagonal phase of the upconversion nanoparticles, but also enhances the upconversion effect, thereby improving the optoelectronic performance of the device.

[0141] Comparative Example 2

[0142] The difference from Example 15 is that 0.1 mmol / ml of NaYGdF4:Yb was used directly. 3+ Er 3+ The upconversion layer 3 was prepared from the core layer solution with adaptive adjustments to the steps, while keeping the other conditions unchanged.

[0143] The photodetector prepared in Comparative Example 2 was subjected to the above photoelectric performance tests. The test results were as follows: at a wavelength of 500 nm and an intensity of 0.8 mW / cm², the photodetector was tested. 2 Under green light excitation and with a bias voltage of 10V, the responsivity is 29.25 mA / W, and the normalized ratio detectivity is 2.74 × 10⁻⁶. 8 Jones, with an external quantum efficiency of 7.25%. At a wavelength of 980 nm and an intensity of 50 mW / cm². 2 Under near-infrared light excitation and a bias voltage of 10V, the photocurrent was found to be lower than the dark current. The responsivity was calculated to be 57.4 μA / W, and the normalized ratio detectivity was 5.98 × 10⁻⁶. 5 Jones, with an external quantum efficiency of 7.29 × 10⁻⁶. -3 %.

[0144] Comparison reveals that core-shell upconversion particles enhance the optoelectronic performance of devices. This is because epitaxial growth of an inert shell suppresses surface defects and stabilizes the hexagonal phase structure. Furthermore, the shell isolates the core particles from external contact, reducing energy loss in the core nanoparticles and thus enhancing the upconversion effect.

[0145] Comparative Example 3

[0146] The difference from Example 15 is that, in preparing the upconversion layer 3, a core-shell structure of NaYGdF4:Yb was used.3+ Er 3+ @NaYF4 upconversion particle dispersion was spin-coated, with all other conditions remaining unchanged.

[0147] The photodetector prepared in Comparative Example 3 was subjected to the above photoelectric performance tests. The test results were as follows: at a wavelength of 500 nm and an intensity of 0.8 mW / cm², the photodetector was tested. 2 Under green light excitation and with a bias voltage of 10V, the responsivity is 225.66 mA / W, and the normalized ratio detectivity is 2.61 × 10⁻⁶. 8 Jones, with an external quantum efficiency of 6.36%. At a wavelength of 980 nm and an intensity of 50 mW / cm². 2 Under near-infrared light excitation and with a bias voltage of 10V, the photocurrent was found to be lower than the dark current. The calculated responsivity was 36.91 μA / W, and the normalized responsivity was 4.78 × 10⁻⁶. 5 Jones, with an external quantum efficiency of 46.8 × 10⁻⁶. -3 %.

[0148] Comparison reveals that different concentrations of upconversion nanoparticles affect the upconversion effect. The detector prepared using the upconversion nanoparticle dispersion with a concentration of 0.1 mmol / L as described in this invention exhibits a stronger upconversion effect, thus providing a stronger inhibition of charge carriers under 980 nm illumination.

[0149] Comparative Example 4

[0150] The difference from Example 15 is that the thickness of the upconversion layer is 520 nm, while the other conditions remain unchanged.

[0151] The photodetector prepared in Comparative Example 4 was subjected to the above photoelectric performance tests. The test results were as follows: at a wavelength of 500 nm and an intensity of 0.8 mW / cm², the photodetector was tested. 2 Under green light excitation and with a bias voltage of 10V, the responsivity is 20.26 mA / W, and the normalized ratio detectivity is 2.01 × 10⁻⁶. 8 Jones, with an external quantum efficiency of 5.31%. At a wavelength of 980 nm and an intensity of 50 mW / cm². 2 Under near-infrared light excitation and a bias voltage of 10V, the photocurrent was found to be lower than the dark current. The calculated responsivity was 30.82 μA / W, and the normalized responsivity was 4.05 × 10⁻⁶. 5 Jones, with an external quantum efficiency of 41.2 × 10⁻⁶. -3 %.

[0152] Comparative Example 5

[0153] The difference from Example 15 is that the thickness of the upconversion layer is 350 nm, while the other conditions remain unchanged.

[0154] The photodetector prepared in Comparative Example 5 was subjected to the above photoelectric performance tests. The test results were as follows: at a wavelength of 500 nm and an intensity of 0.8 mW / cm², the photodetector was tested. 2 Under green light excitation and with a bias voltage of 10V, the responsivity is 34.62 mA / W, and the normalized ratio detectivity is 2.62 × 10⁻⁶. 8 Jones, with an external quantum efficiency of 7.42%. At a wavelength of 980 nm and an intensity of 50 mW / cm². 2 Under near-infrared light excitation and a bias voltage of 10V, the photocurrent was found to be lower than the dark current. The responsivity was calculated to be 45.02 μA / W, and the normalized ratio detectivity was 5.24 × 10⁻⁶. 5 Jones, with an external quantum efficiency of 56.1 × 10⁻⁶. -3 %.

[0155] Comparison reveals that the thickness of the upconversion particle film affects the photoelectric performance of the device. A higher thickness results in a stronger barrier effect of the upconversion layer on charge carriers, making it more difficult for them to cross the upconversion layer and reach the top electrode, thus enhancing the device's negative response. Conversely, a thinner film leads to less light absorption and a lower negative response.

[0156] In summary, the photodetector prepared by the method of this invention has excellent responsivity and external quantum efficiency, indicating that its photoelectric performance is superior.

[0157] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A detector having positive and negative photoresponse, characterized in that, The application relates to a photodetector, comprising: a substrate layer (1), and a perovskite thin film layer (2), an up-conversion layer (3) and an electrode layer (4) which are sequentially arranged on the substrate layer (1); The upconversion layer comprises NaYGdF4:Yb 3+ ,Er 3+ @NaYF4 upconversion particles; NaYGdF4:Yb 3+ ,Er 3+ @NaYF4 upconversion particle dispersion liquid preparation, comprising the following steps: S21, after preparing a precursor solution containing yttrium source, gadolinium source, ytterbium source and erbium source, adding ammonium fluoride methanol solution and sodium hydroxide methanol solution, stirring and dissolving, heating under inert gas, adding ethanol to precipitate the product, centrifugal separation and washing the precipitate, dissolving in cyclohexane to prepare NaYGdF4:Yb 3+ ,Er 3+ core layer solution; S22, adding a yttrium-containing precursor solution, a methanol solution of ammonium fluoride, and a methanol solution of sodium hydroxide to the NaYGdF4:Yb 3+ ,Er 3+ core layer solution, centrifuging and collecting the particle precipitate after heating under an inert gas, and dispersing the precipitate in cyclohexane after washing to obtain NaYGdF4:Yb 3+ ,Er 3+ @NaYF4 up-conversion particle dispersion liquid; The molar ratio of the yttrium source, the gadolinium source, the ytterbium source and the erbium source is 78:5:20:

2.

2. The detector having positive and negative optical responses as claimed in claim 1, wherein, The thickness of the up-conversion layer (3) is 400-500 nm.

3. The detector having positive and negative optical responses as claimed in claim 1, wherein, In step S21, the molar ratio of the ammonium fluoride to the sodium hydroxide is 8:5-5.

5.

4. The detector having positive and negative optical responses as claimed in claim 1, wherein, In step S22, the molar ratio of the ammonium fluoride to the sodium hydroxide is 8:5-5.

5.

5. A method of manufacturing a detector having positive and negative optical response as claimed in any one of claims 1-4, characterized in that, The application further discloses a preparation method of the photodetector. S1, preparing a perovskite thin film layer (2) on a substrate layer (1) by using a two-step spin coating method; S2, coating the core-shell structured NaYGdF4:Yb 3+ ,Er 3+ @NaYF4 up-conversion particles onto the perovskite thin film layer (2) to prepare an up-conversion layer (3); S3, evaporating an electrode layer (4) on the up-conversion layer (3) to obtain the photodetector.

6. The method of claim 5, wherein the photoresponse is positive or negative. In step S1, the preparation of the perovskite thin film layer (2) specifically comprises the following steps: Preparation of a MAPbI3 perovskite precursor solution, spin coating the MAPbI3 perovskite precursor solution on the substrate layer (1) under the protection of inert gas, the spin coating conditions are as follows: first spin coating at a rotating speed of 800-1000 rpm for 10-15 s, and then spin coating at a rotating speed of 3000-3500 rpm for 40-45 s, at 15-20 s before the end of the second step of spin coating, chlorobenzene is added on the rotating MAPbI3 substrate, and after spin coating, annealing is carried out at 100-120 DEG C for 5-10 min, so as to form a perovskite thin film layer (2) on the substrate layer (1).

7. The method of claim 6, wherein the photoresponse is positive or negative. The preparation method of the MAPbI3 perovskite precursor solution is as follows: methylammonium iodide and lead iodide are mixed and dissolved in an organic solvent at a molar ratio of 1:1-1.2, and stirring is carried out at 60-80 DEG C for more than 24 h to obtain the MAPbI3 perovskite precursor solution.

8. The method for fabricating a detector with positive and negative light responses as described in claim 5, characterized in that, In step S2, the preparation of the up-conversion layer (3) specifically comprises the following steps: A core-shell structure NaYGdF4:Yb, Er is spin-coated on the perovskite thin film layer (2) at a rotation speed of 2000-3000 rpm 3+ ,Er 3 + After the NaYF4 up-conversion particle dispersion solution, the up-conversion layer (3) is obtained by annealing at 100-130°C for 5-10 min.

9. The method for fabricating a detector with positive and negative light responses as described in claim 5, characterized in that, In step S3, the thickness of the electrode layer is 80-100 nm, and the interval between two adjacent electrode layers is 150-180 nm.

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