Preparation method of long-wave and very long-wave infrared quantum dots and application thereof in photoconductive detector

Abstract

The application relates to a preparation method of long-wave and very long-wave infrared quantum dots and application of the quantum dots in photoconductive detectors. The application belongs to the field of infrared colloidal quantum dots. The application aims to solve the technical problems of poor stability of existing large-size quantum dot colloids, low response wavelength and low specific detectivity. The application prepares quantum dots with photoelectric response to long-wave and very long-wave by adjusting the Hg:Te ratio of HgTe quantum dots, simultaneously adopting a method of fast nucleation of a trisubstituted tellurium-containing precursor and continuous growth of a disubstituted tellurium-containing precursor. In addition, precise doping control is realized through surface modification, so that a long enough carrier drift length is obtained, the quantum dot mobility is increased by 100 times, and high responsivity and specific detectivity of the device are facilitated.

Description

Technical Field

[0001] This invention belongs to the field of infrared colloidal quantum dots, specifically relating to a method for preparing long-wavelength and very long-wavelength infrared quantum dots and their application in photoconductive detectors. Background Technology

[0002] Traditional commercial long-wavelength or very long-wavelength detectors primarily employ molecular beam epitaxy (MBE), using materials such as cadmium telluride (MCT), quantum wells, and type II superlattices. Indium pillars are first grown epitaxially and then coupled to silicon-based readout circuits via flip-chip bonding. This processing method is time-consuming, has slow production rates, and high material processing costs. Furthermore, flip-chip bonding results in low bonding success rates. The difficulty in controlling the bandgap of bulk materials, coupled with high technical requirements and high costs, limits its application and has prevented large-scale civilian production.

[0003] Colloidal quantum dots (CQDs) possess advantages such as scalable synthesis, mechanical flexibility, broad spectral tunability, low cost, and simple preparation. Mercury telluride colloidal quantum dots (HgTe CQDs) have been successfully applied in short-wave and mid-wave infrared light detection, achieving performance close to that of traditional commercial detectors. However, quantum dots capable of absorbing long or very long wavelengths have large diameters, even approaching the Bohr radius, and their colloidal stability is typically poor. This necessitates the development of suitable ligands to maintain colloidal stability. Furthermore, the increase in quantum dot size leads to a decrease in band gap, resulting in an increase in thermally excited carrier concentration and the formation of naturally n-type doped quantum dots. The electrical properties of these materials become highly dependent on intrinsic thermal excitation, causing a rapid decline in the sensitivity and performance of long-wave infrared devices.

[0004] Currently, the synthesis of long-wavelength (large-size) quantum dots requires an excess of Hg precursor. Quantum dots of 12-15 nm typically correspond to wavelengths of 8-12 μm, and the commonly used Hg:Te ratio is 2:1. In the synthesis of large-size quantum dots, a one-step method using the highly reactive TMSTe (bis(trimethylsilyl)telluride) can be employed. The absorption spectrum consists of two parts: high-energy interband transitions and low-energy intraband transitions, generally occurring in the range of 1500 cm⁻¹. -1 ~500cm -1 Induced intraband transitions lead to the formation of naturally heavy n-type doped quantum dots. Currently, the response spectrum of HgTe quantum dots with intraband transitions extends down to 12 μm, with the highest specific detectivity reaching 10. 7 Jones. Furthermore, large-size quantum dots can also be synthesized using a two-step growth process with a low-reactivity TOPTe (a mixture of tri-n-octylphosphine (TOP) and tellurium (Te)) precursor. The absorption spectra of quantum dots synthesized by this method show only interband transitions, but their specific detectivity at 12 μm is only 10. 6Jones showed that the Fermi level of quantum dots synthesized by this method is not in the middle band gap, forming n-type doped quantum dots.

[0005] In summary, the reported response wavelength of quantum dots for long wavelengths is currently reported to be 12 μm. However, whether quantum dot photodetectors can reach the very long wavelength region remains unproven. Furthermore, due to the inherent heavy n-type doping of quantum dots, current development of long-wavelength quantum dot detectors is primarily focused on photoconductive types, with a maximum detectivity of 10-1. 7 Jones. Doping and carrier lifetime in quantum dots limit the performance of large-size quantum dots. Therefore, optimizing the performance of large-size quantum dots is a challenging problem that needs to be solved. Summary of the Invention

[0006] The purpose of this invention is to solve the technical problems of poor stability, low response wavelength and specific detectivity of existing large-size quantum dot colloids, and to provide a method for preparing long-wavelength and very long-wavelength infrared quantum dots and their application in photoconductive detectors.

[0007] One of the objectives of this invention is to provide a high specific detectivity long-wave infrared quantum dot, wherein the infrared quantum dot is prepared by a two-step method using mercury salt and a trisubstituted tellurium precursor shown in Formula 1 and a disubstituted tellurium precursor shown in Formula 2.

[0008]

[0009] In the formula, R 1 R 2 R 3 Each is independently selected from one of the following: substituted or unsubstituted C1-12 alkyl chains, substituted or unsubstituted C3-12 cycloalkyl chains, substituted or unsubstituted C2-12 olefin chains, or substituted or unsubstituted aryl groups. The total molar ratio of the trisubstituted tellurium precursor shown in Formula 1 and the disubstituted tellurium precursor shown in Formula 2 to the mercury salt is 1:(3-5), and the molar ratio of the trisubstituted tellurium precursor shown in Formula 1 to the disubstituted tellurium precursor shown in Formula 2 is (2-4):1.

[0010] Preferably, R in Equations 1 and 2 1 It is selected from one of the C1-12 alkyl chains, whether substituted or unsubstituted.

[0011] More preferably, R in Formula 1 2 R 3 Each is independently selected from one of the substituted or unsubstituted aryl groups.

[0012] Most preferably, R in Equations 1 and 2 1 Selected from one of the substituted or unsubstituted C1-12 alkyl chains, R in Formula 1 2 R 3Each is independently selected from one of the substituted or unsubstituted aryl groups, R in Formula 2 2 It is selected from one of the C1-12 alkyl chains, whether substituted or unsubstituted.

[0013] Preferably, the total molar ratio of the trisubstituted tellurium precursor shown in Formula 1 and the disubstituted tellurium precursor shown in Formula 2 to the mercury salt is 1:4.

[0014] Preferably, the molar ratio of the trisubstituted tellurium precursor shown in Formula 1 to the disubstituted tellurium precursor shown in Formula 2 is 3:1.

[0015] The second objective of this invention is to provide a very long-wave infrared quantum dot, which is prepared by a two-step method using mercury salt and a trisubstituted tellurium precursor shown in Formula 1 and a disubstituted tellurium precursor shown in Formula 2.

[0016]

[0017] In the formula, R 1 R 2 R 3 Each is independently selected from one of the following: substituted or unsubstituted C1-12 alkyl chains, substituted or unsubstituted C3-12 cycloalkyl chains, or substituted or unsubstituted C2-12 olefin chains. The total molar ratio of the trisubstituted tellurium precursor shown in Formula 1 and the disubstituted tellurium precursor shown in Formula 2 to the mercury salt is 1:(3-5), and the molar ratio of the trisubstituted tellurium precursor shown in Formula 1 to the disubstituted tellurium precursor shown in Formula 2 is 1:(2-4).

[0018] Preferably, R in Equations 1 and 2 1 It is selected from one of the C1-12 alkyl chains, whether substituted or unsubstituted.

[0019] More preferably, R in Formula 1 2 R 3 Each is independently selected from one of the substituted or unsubstituted aryl groups.

[0020] Most preferably, R in Equations 1 and 2 1 Selected from one of the substituted or unsubstituted C1-12 alkyl chains, R in Formula 1 2 R 3 Each is independently selected from one of the substituted or unsubstituted aryl groups, R in Formula 2 2 It is selected from one of the C1-12 alkyl chains, whether substituted or unsubstituted.

[0021] Preferably, the total molar ratio of the trisubstituted tellurium precursor shown in Formula 1 and the disubstituted tellurium precursor shown in Formula 2 to the mercury salt is 1:4.

[0022] Preferably, the molar ratio of the trisubstituted tellurium precursor shown in Formula 1 to the disubstituted tellurium precursor shown in Formula 2 is 1:3.

[0023] The third objective of this invention is to provide a method for preparing high-detectability long-wavelength infrared quantum dots or very long-wavelength infrared quantum dots, the method comprising the following steps:

[0024] S1: Dissolve the tellurium precursors shown in Formula 1 and Formula 2 in oleylamine (OAm) respectively to obtain trisubstituted tellurium precursor solution and disubstituted tellurium precursor solution respectively.

[0025] S2: Under heating conditions, the trisubstituted tellurium precursor solution is first injected into the mercury salt / oleylamine solution for nucleation for 30-90s, and then the disubstituted tellurium precursor solution is injected at a constant rate. After terminating the reaction, the solution is washed and then liquid-phase ligand exchange is performed to obtain high specific detectivity long-wave infrared quantum dots or very long-wave infrared quantum dots.

[0026] Preferably, the heating temperature in S2 is 110-130℃.

[0027] Preferably, the constant injection rate in S2 is 0.4-0.6 mL / min.

[0028] Preferably, the liquid-phase ligand exchange in S2 is carried out in DMF (dimethylformamide) using 2-me (2-mercaptoethanol) and DDAB (bis(octadecyl)ammonium bromide).

[0029] The fourth objective of this invention is to provide a method for preparing intrinsic long-wavelength / very long-wavelength infrared quantum dot thin films, wherein the method includes:

[0030] High-detectivity long-wave infrared quantum dots or very long-wave infrared quantum dot solutions were spin-coated or drop-coated onto a substrate in stages to a specified film thickness. Solid-state ligand exchange was performed after each spin-coating or drop-coating. After reaching the specified film thickness, the entire substrate was immersed in a solution with a concentration of 2×10⁻⁶. -3 -2×10 -5 Intrinsic long-wave / very long-wave infrared quantum dot films were obtained in an iodine / ethanol solution of M.

[0031] Preferably, soaking time is 0.5-1.5 minutes.

[0032] The fifth objective of this invention is to provide an intrinsic long-wavelength / very long-wavelength infrared quantum dot thin film prepared by the above method.

[0033] The sixth objective of this invention is to provide an application of the intrinsic long-wavelength / very long-wavelength infrared quantum dot thin film prepared by the above method in a photoconductive detector.

[0034] The significant advantages of this invention compared to existing technologies are:

[0035] (1) This invention prepares quantum dots with photoelectric response to long wavelengths (10 μm) and very long wavelengths (18 μm) by controlling the Hg:Te ratio of HgTe quantum dots and simultaneously employing rapid nucleation of trisubstituted tellurium-containing precursors and continuous growth of disubstituted tellurium-containing precursors. Furthermore, precise doping control is achieved through surface modification, resulting in a sufficiently long carrier drift length and increasing the quantum dot mobility by 100 times, which is beneficial for obtaining high responsivity and specific detectivity of the device.

[0036] (2) This invention utilizes the oxidation effect of iodine / alcohol solution to modulate strong n-type quantum dots with intraband transitions into intrinsic quantum dots, while simultaneously passivating the surface to make the film less susceptible to atmospheric influences. For the first time in the quantum dot field, a spectral response of an 18μm very long wave detector was obtained, with specific detectivity of 2.3 × 10⁻⁶ for the 10μm long wave detector and the 18μm very long wave detector, respectively. 9 Jones and 6×10 8 Jones. Attached Figure Description

[0037] Figure 1 Transmission electron microscope image and size distribution diagram of the long-wavelength HgTe CQD obtained in Example 1;

[0038] Figure 2 Transmission electron microscope image and size distribution diagram of the very long wavelength HgTe CQD obtained in Example 2;

[0039] Figure 3 The images show the absorption spectra of iodine / ethanol solutions of different concentrations and the long-wave infrared quantum dot films before and after treatment; where a is a photograph of the solution and b is the absorption spectrum.

[0040] Figure 4 The absorption spectra of HgTe CQD before and after iodination at a long wavelength of 10 μm are shown.

[0041] Figure 5 The absorption spectra of HgTe CQD before and after iodination at a very long wavelength of 18 μm are shown.

[0042] Figure 6 FET curves before and after very long wavelength (VLWIR) HgTe CQD iodination;

[0043] Figure 7 The IV curve is for a long-wavelength (LWIR) photoconductive thin film.

[0044] Figure 8 IV curves for very long wavelength (VLWIR) photoconductive thin films;

[0045] Figure 9 The response spectrum of a long-wavelength (LWIR) photoconductive thin film at 80 kJ;

[0046] Figure 10 The response spectrum of a very long wavelength (VLWIR) photoconductive thin film at 80 kK. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below.

[0048] A specific embodiment of the present invention provides a long-wavelength / very long-wavelength infrared quantum dot, wherein the infrared quantum dot is composed of mercury salt and...

[0049] The trisubstituted tellurium precursor shown in Formula 1 and the disubstituted tellurium precursor shown in Formula 2 were prepared in two steps.

[0050]

[0051] In the formula, R 1 R 2 R 3 Each is independently selected from one of substituted or unsubstituted C1-12 alkyl chains, substituted or unsubstituted C3-12 cycloalkyl chains, substituted or unsubstituted C2-12 olefin chains, or substituted or unsubstituted aryl groups; preferably, R in Formula 1 and Formula 2 1 Selected from one of the C1-12 alkyl chains, whether substituted or unsubstituted. More preferably, R in Formula 1 2 R 3 Each is independently selected from one of substituted or unsubstituted aryl groups. Most preferably, R in Formulas 1 and 2 1 Selected from one of the substituted or unsubstituted C1-12 alkyl chains, R in Formula 1 2 R 3 Each is independently selected from one of the substituted or unsubstituted aryl groups, R in Formula 2 2 It is selected from one of the C1-12 alkyl chains, whether substituted or unsubstituted.

[0052] The total molar ratio of the trisubstituted tellurium precursor shown in Formula 1 and the disubstituted tellurium precursor shown in Formula 2 to the mercury salt is 1:(3-5). Preferably, the total molar ratio of the trisubstituted tellurium precursor shown in Formula 1 and the disubstituted tellurium precursor shown in Formula 2 to the mercury salt is 1:4.

[0053] When the molar ratio of the trisubstituted tellurium precursor shown in Formula 1 to the disubstituted tellurium precursor shown in Formula 2 is (2-4):1, preferably, when the molar ratio of the trisubstituted tellurium precursor shown in Formula 1 to the disubstituted tellurium precursor shown in Formula 2 is 3:1, it is a long-wave infrared quantum dot.

[0054] When the molar ratio of the trisubstituted tellurium precursor shown in Formula 1 to the disubstituted tellurium precursor shown in Formula 2 is 1:(2-4), preferably, when the molar ratio of the trisubstituted tellurium precursor shown in Formula 1 to the disubstituted tellurium precursor shown in Formula 2 is 1:3, it is a very long-wave infrared quantum dot.

[0055] A second specific embodiment of the present invention provides a method for synthesizing a tri / disubstituted tellurium precursor, the reaction equation and specific steps of which are as follows:

[0056]

[0057] Among them, R 1 R 2 R 3 The definition of R in tellurium precursor is shown in Equations 1 and 2. 1 R 2 R 3 As shown.

[0058] In a nitrogen atmosphere, tellurium powder, amine, and isocyanate are added to toluene in a molar ratio of 1:(1-2):1, and the mixture is heated to 90-110°C in an oil bath with constant stirring. During this process, all the tellurium powder is consumed, and the reaction mixture becomes colorless or yellow. The resulting mixture is filtered, and volatiles are removed under vacuum. Recrystallization is performed by adding pentane to a saturated toluene solution to obtain a recrystallized solid tellurium-containing precursor, which is separated by filtration using a glass frit funnel and dried under vacuum. The finally separated tellurium-containing precursor powder can be stored long-term in a glove box under a nitrogen atmosphere.

[0059] A third specific embodiment of the present invention provides a method for preparing long-wavelength infrared quantum dots, the reaction equation and specific steps of which are as follows:

[0060]

[0061] (1) Weigh mercuric chloride (HgCl2) in a nitrogen atmosphere, dissolve it in oleylamine (OAm) at a concentration of 0.04-0.1M, and heat at 90-110℃ for 0.5-1.5h to obtain HgCl2 / OAm solution.

[0062] (2) Dissolve the trisubstituted tellurium precursor shown in Formula 1 in degassed OAm at a concentration of 0.05-0.1M and heat at 150-200℃ for 1-3h to finally generate a trisubstituted tellurium precursor solution.

[0063] (3) Dissolve the disubstituted tellurium precursor shown in Formula 2 at a concentration of 15-25 mM in degassed OAm, and heat at 150-200℃ for 1-3 h to finally generate a disubstituted tellurium precursor solution.

[0064] (4) Inject the trisubstituted tellurium precursor solution into the HgCl2 / OAm solution and nucleate at 110-130℃ for 30-90s. Then inject the disubstituted tellurium precursor solution at a constant rate of 0.4-0.6mL / min for 2-3min. Then inject anhydrous tetrachloroethylene (TCE) to rapidly cool the reaction. Then, immediately remove it from the glove box and cool it to room temperature with cool water. The total molar ratio of the trisubstituted tellurium precursor and the disubstituted tellurium precursor to mercuric chloride (HgCl2) is 1:(3-5), and the molar ratio of the trisubstituted tellurium precursor to the disubstituted tellurium precursor is (2-4):1.

[0065] (5) Place the synthesized quantum dots into a centrifuge tube and add IPA (isopropanol) for washing. After stirring until turbid, place the tube into a centrifuge and centrifuge to separate the precipitate. The centrifuge speed is 7500 r / min and the time is 6 min. Discard the supernatant. Dry the precipitated quantum dots with a nitrogen gun and redissolve them with 6 mL of n-hexane. Then add 2-me (2-mercaptoethanol) and DDAB (bis(octadecylammonium bromide)) and sonicate for 0.5-1.5 min to accelerate dissolution. Then add DMF (dimethylformamide) and sonicate for 0.5-1.5 min to accelerate the transfer of quantum dots from n-hexane to DMF. After the solution shows a layering phenomenon, remove the upper n-hexane layer. The quantum dots are stably distributed in DMF.

[0066] The fourth specific embodiment of the present invention provides a method for preparing very long-wave infrared quantum dots, the reaction equation and specific steps of which are as follows:

[0067]

[0068] (1) Weigh mercuric chloride (HgCl2) in a nitrogen atmosphere, dissolve it in oleylamine (OAm) at a concentration of 0.04-0.1M, and heat at 90-110℃ for 0.5-1.5h to obtain HgCl2 / OAm solution.

[0069] (2) Dissolve the trisubstituted tellurium precursor shown in Formula 1 in degassed OAm at a concentration of 0.04-0.06M and heat at 150-200℃ for 1-3h to finally generate a trisubstituted tellurium precursor solution.

[0070] (3) Dissolve the disubstituted tellurium precursor shown in Formula 2 at a concentration of 25-35 mM in degassed OAm, and heat at 150-200℃ for 1-3 h to finally generate a disubstituted tellurium precursor solution.

[0071] (4) Inject the trisubstituted tellurium precursor solution into the HgCl2 / OAm solution and nucleate at 110-130℃ for 30-90s. Then inject the disubstituted tellurium precursor solution at a constant rate of 0.4-0.6mL / min for 4-6min. Then inject anhydrous tetrachloroethylene (TCE) to rapidly cool the reaction. Then, immediately remove it from the glove box and cool it to room temperature with cool water. The total molar ratio of the trisubstituted tellurium precursor and the disubstituted tellurium precursor to mercuric chloride (HgCl2) is 1:(3-5), and the molar ratio of the trisubstituted tellurium precursor to the disubstituted tellurium precursor is 1:(2-4).

[0072] (5) Place the synthesized quantum dots into a centrifuge tube and add IPA (isopropanol) for washing. After stirring until turbid, place the tube into a centrifuge and centrifuge to separate the precipitate. The centrifuge speed is 7500 r / min and the time is 6 min. Discard the supernatant. Dry the precipitated quantum dots with a nitrogen gun and redissolve them with 6 mL of n-hexane. Then add 2-me (2-mercaptoethanol) and DDAB (bis(octadecylammonium bromide)) and sonicate for 0.5-1.5 min to accelerate dissolution. Then add DMF (dimethylformamide) and sonicate for 0.5-1.5 min to accelerate the transfer of quantum dots from n-hexane to DMF. After the solution shows a layering phenomenon, remove the upper n-hexane layer. The quantum dots are stably distributed in DMF.

[0073] A fifth specific embodiment of the present invention provides a method for preparing intrinsic long-wavelength / very long-wavelength infrared quantum dot thin films, the method comprising the following steps:

[0074] (1) Gold interdigitated electrodes are deposited on an aluminum oxide (AL2O3) substrate to serve as the substrate for PC-type devices.

[0075] (2) Spin-coat the long-wave / very long-wave infrared quantum dot solution onto the substrate in step (1) in multiple stages. After each spin-coating, immerse the film in an EdT / HCl / IPA (ethylene dithiol / hydrochloric acid / isopropanol) solution (volume ratio 1:1:20) for 10 seconds, then rinse with IPA and dry with a nitrogen gun. Continue until a quantum dot film of the specified thickness is obtained.

[0076] (3) The quantum dot film obtained in step (2) is subjected to a 2×10⁻⁶ saturation process. -3 -2×10 -5 Immersing in M-iodine / ethanol solution for 0.5-0.5 min yields intrinsic long-wave / very long-wave infrared quantum dot films.

[0077] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0078] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0079] Tellurium precursor preparation:

[0080] Preparation Example 1: The specific steps of the synthesis method of the trisubstituted N,N-diphenyl-N'-butyltellurium precursor are as follows:

[0081]

[0082] Among them, R 1 =C4H9, R 2 =C6H6, R 3 =C6H6.

[0083] In a nitrogen atmosphere, 5 mmol of tellurium powder, 10 mmol of diphenylamine, and 5 mmol of butylisocyanate were added to 10 mL of toluene, and the mixture was heated to 100 °C in an oil bath with constant stirring. During this process, all the tellurium powder was consumed. The resulting mixture was filtered, and volatiles were removed under vacuum. Recrystallization was performed by adding pentane to a saturated toluene solution to obtain a recrystallized solid tellurium-containing precursor, which was separated by filtration using a glass frit funnel and dried under vacuum. The finally separated tellurium-containing precursor powder can be stored long-term in a glove box under a nitrogen atmosphere.

[0084] Preparation Example 2: The specific steps of the synthesis method of the disubstituted N,N-dibutyltellurium precursor are as follows:

[0085]

[0086] Among them, R 1 =C4H9, R 2 =C4H9.

[0087] In a nitrogen atmosphere, 5 mmol of tellurium powder, 5 mmol of butylamine, and 5 mmol of butylisocyanate were added to 10 mL of toluene and heated to 100 °C in an oil bath with constant stirring. During this process, all the tellurium powder was consumed. The resulting mixture was filtered, and volatiles were removed under vacuum. Recrystallization was performed by adding pentane to a saturated toluene solution to obtain a recrystallized solid tellurium-containing precursor, which was separated by filtration using a glass frit funnel and dried under vacuum. The finally separated tellurium-containing precursor powder can be stored long-term in a glove box under a nitrogen atmosphere.

[0088] Infrared quantum dot preparation

[0089] Example 1: The specific steps of the preparation method of 10μm long-wavelength infrared quantum dots are as follows:

[0090] (1) In a nitrogen atmosphere, 108 mg of mercuric chloride (0.4 mmol) was dissolved in 8 mL of OAM and heated at 100 °C for 1 h until it became a transparent solution, yielding an HgCl2 / OAm solution. 0.075 mmol of the trisubstituted tellurium precursor prepared in Preparation Example 1 was dissolved in 900 μL of degassed OAM and heated at 180 °C for 2 h, ultimately producing a trisubstituted tellurium precursor solution. 0.025 mmol of the disubstituted tellurium precursor prepared in Preparation Example 2 was dissolved in 1.25 mL of degassed OAM and heated at 180 °C for 2 h, ultimately producing a disubstituted tellurium precursor solution.

[0091] (2) The trisubstituted tellurium precursor solution was injected into the HgCl2 / OAm solution and nucleated at 120°C for 60s. Then, the disubstituted tellurium precursor solution was injected at a constant rate of 0.5mL / min for 2.5min. Then, 20mL of anhydrous tetrachloroethylene (TCE) was injected to rapidly cool the reaction. Then, it was immediately removed from the glove box and cooled to room temperature with cool water.

[0092] (3) Place the synthesized quantum dots into a centrifuge tube and add IPA (isopropanol) for washing. After stirring until turbid, place the tube into a centrifuge and centrifuge to separate the precipitate. The centrifuge speed is 7500 r / min and the time is 6 min. Discard the supernatant. Dry the precipitated quantum dots with a nitrogen gun. Redissolve them in 6 mL of n-hexane. Then add 50 μL of 2-me (2-mercaptoethanol) and 15 mg of DDAB (bis(octadecylammonium bromide)) and sonicate for 1 min to accelerate dissolution. Then add 2.5 mL of DMF (dimethylformamide) and sonicate for 1 min to accelerate the transfer of quantum dots from n-hexane to DMF. After the solution shows a layering phenomenon, remove the upper n-hexane layer. The quantum dots are stably distributed in DMF.

[0093] The transmission electron microscope (TEM) image and size distribution map of the obtained long-wavelength HgTe CQD are as follows: Figure 1 As shown, HgTe CQD exhibits good dispersion and a size of 13.9 nm.

[0094] Example 2: The specific steps of the preparation method of 18μm very long wavelength infrared quantum dots are as follows:

[0095] (1) In a nitrogen atmosphere, 108 mg of mercuric chloride (0.4 mmol) was dissolved in 8 mL of OAM and heated at 100 °C for 1 h until it became a transparent solution, yielding an HgCl2 / OAm solution. 0.025 mmol of the trisubstituted tellurium precursor prepared in Preparation Example 1 was dissolved in 500 μL of degassed OAM and heated at 180 °C for 2 h, ultimately producing a trisubstituted tellurium precursor solution. 0.075 mmol of the disubstituted tellurium precursor prepared in Preparation Example 2 was dissolved in 2.5 mL of degassed OAM and heated at 180 °C for 2 h, ultimately producing a disubstituted tellurium precursor solution.

[0096] (2) The trisubstituted tellurium precursor solution was injected into the HgCl2 / OAm solution and nucleated at 120°C for 60s. Then, the disubstituted tellurium precursor solution was injected at a constant rate of 0.5mL / min for 2.5min. Then, 20mL of anhydrous tetrachloroethylene (TCE) was injected to rapidly cool the reaction. Then, it was immediately removed from the glove box and cooled to room temperature with cool water.

[0097] (3) Place the synthesized quantum dots into a centrifuge tube and add IPA (isopropanol) for washing. After stirring until turbid, place the tube into a centrifuge and centrifuge to separate the precipitate. The centrifuge speed is 7500 r / min and the time is 6 min. Discard the supernatant. Dry the precipitated quantum dots with a nitrogen gun. Redissolve them in 6 mL of n-hexane. Then add 50 μL of 2-me (2-mercaptoethanol) and 15 mg of DDAB (bis(octadecylammonium bromide)) and sonicate for 1 min to accelerate dissolution. Then add 2.5 mL of DMF (dimethylformamide) and sonicate for 1 min to accelerate the transfer of quantum dots from n-hexane to DMF. After the solution shows a layering phenomenon, remove the upper n-hexane layer. The quantum dots are stably distributed in DMF.

[0098] The transmission electron microscope (TEM) image and size distribution map of the very long wavelength HgTe CQD are shown below. Figure 1 As shown, HgTe CQD exhibits good dispersion and a size of 15.6 nm.

[0099] Application example: A method for fabricating a photoconductive detector, the method comprising the following steps:

[0100] (1) Gold interdigitated electrodes are deposited on an aluminum oxide (AL2O3) substrate to serve as the substrate for PC-type devices.

[0101] (2) The long-wave infrared quantum dot solution prepared in Example 1 and the very long-wave infrared quantum dot solution prepared in Example 2 were spin-coated onto the substrate in step (1) in several stages. After each spin-coating, the film was immersed in an EdT / HCl / IPA (ethylene dithiol / hydrochloric acid / isopropanol) solution (volume ratio of 1:1:20) for 10 seconds, then rinsed with IPA and dried with a nitrogen gun. This process was repeated until a quantum dot film with a thickness of 500 nm was obtained.

[0102] (3) The quantum dot films obtained in step (2) are respectively subjected to 2×10 -3 1×10 -3 2×10 -4 1×10 -4 2×10 -5 Intrinsic long-wave infrared quantum dot films and intrinsic very long-wave infrared quantum dot films were obtained by immersing the films in M-iodine / ethanol solution for 1 min.

[0103] Figure 3 The images show the absorption spectra of long-wave infrared quantum dot films before and after treatment with iodine / ethanol solutions of different concentrations. It can be seen that the absorption spectrum of the synthesized quantum dots without any modification is strongly N-type, consisting of two parts: high-energy interband transitions and low-energy intraband transitions, typically occurring in the wavenumber range of 1500 cm⁻¹. -1 ~500cm -1 Inducing in-band transitions leads to the formation of naturally occurring heavy n-type doped quantum dots. Iodine / ethanol solutions can be used to bleach these in-band transitions (within-band absorption peaks around 500 cm⁻¹). -1 ~1500cm -1 As the concentration of iodine solution increases, the intra-band transition absorption peak gradually decreases, while the inter-band transition absorption peak becomes more pronounced and gradually red-shifts. When the iodine concentration increases to 2 × 10⁻⁶, the absorption peaks of intra-band transitions gradually decrease, while those of inter-band transitions become more pronounced and gradually red-shifted. -4 M, the intraband transition (electron doping) disappears.

[0104] Figure 4-5 The absorption spectra of 10 μm long-wave infrared quantum dots and 18 μm very long-wave infrared quantum dots (HgTe CQD) before and after iodination are shown. The absorption spectra reveal that 2 × 10⁻⁶ -4 After treatment with M-iodine solution, intraband transitions in both long-wavelength and very long-wavelength absorption spectra disappeared, while interband transitions exhibited a redshift. FET detection showed that the quantum dot transitioned from N-type doping to its intrinsic state.

[0105] Figure 6 The FET (field-effect transistor transfer) curves before and after iodination with Very Long Wavelength (VLWIR) HgTe CQD are shown. Figure 6The diagram illustrates that before and after iodine treatment, the quantum dots in the FET exhibit n-type doping (left dashed line), while after iodine treatment, they exhibit intrinsic doping (right dashed line). The carrier mobilities at different bias voltages are shown by the solid lines in the figure above. The mobilities do not change significantly before and after iodine treatment; at 80 kJ, the quantum dot mobility is approximately 10 cm⁻¹. 2 / vs.

[0106] Figure 7-8 The figure shows the IV curves for long-wavelength (LWIR) and very-long-wavelength (VLWIR) photoconductive thin films. The figure shows the dark current (background) under no light (without blackbody illumination) and the blackbody@600℃ current under blackbody illumination. Subtracting the background curve from the blackbody@600℃ curve yields the photocurrent under different bias voltages. The calculated responsivity of the long-wavelength and very-long-wavelength devices are 0.13 A / W and 0.3 A / W, respectively, and the specific detectivity is 2.3 × 10⁻⁶. 9 Jones and 6.6×10 8 Jones.

[0107] Figure 9-10 The response spectra of long-wavelength (LWIR) and very long-wavelength (VLWIR) detectors at 80 kHz are shown. It can be seen that the response spectra of the LWIR and VLWIR detectors at 80 kHz include a relative response spectrum and a response spectrum normalized to the DTGS background, respectively. The cutoff wavelength of the spectral response is defined as the cutoff absorption edge of the falling edge, which is 10 μm and 18 μm, respectively.

[0108] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A high specific detectivity long-wavelength infrared quantum dot, characterized in that, It is prepared by a two-step method using mercury salt, trisubstituted tellurium precursor shown in Formula 1, and disubstituted tellurium precursor shown in Formula 2. In the formula, R 1 R 2 R 3 Each is independently selected from one of the following: substituted or unsubstituted C1-12 alkyl chains, substituted or unsubstituted C3-12 cycloalkyl chains, substituted or unsubstituted C2-12 olefin chains, or substituted or unsubstituted aryl groups. The total molar ratio of the trisubstituted tellurium precursor shown in Formula 1 and the disubstituted tellurium precursor shown in Formula 2 to the mercury salt is 1:(3-5), and the molar ratio of the trisubstituted tellurium precursor shown in Formula 1 to the disubstituted tellurium precursor shown in Formula 2 is (2-4):

1.

2. The long-wave infrared quantum dot of claim 1, wherein, In Equations 1 and 2, R 1 Selected from one of the substituted or unsubstituted C1-12 alkyl chains, the total molar ratio of the trisubstituted tellurium precursor shown in Formula 1 and the disubstituted tellurium precursor shown in Formula 2 to the mercury salt is 1:4, and the molar ratio of the trisubstituted tellurium precursor shown in Formula 1 to the disubstituted tellurium precursor shown in Formula 2 is 3:

1.

3. A very long wave infrared quantum dot, characterized in that, It is prepared by a two-step method using mercury salt, trisubstituted tellurium precursor shown in Formula 1, and disubstituted tellurium precursor shown in Formula 2. In the formula, R 1 R 2 R 3 Each is independently selected from one of the following: substituted or unsubstituted C1-12 alkyl chains, substituted or unsubstituted C3-12 cycloalkyl chains, or substituted or unsubstituted C2-12 olefin chains. The total molar ratio of the trisubstituted tellurium precursor shown in Formula 1 and the disubstituted tellurium precursor shown in Formula 2 to the mercury salt is 1:(3-5), and the molar ratio of the trisubstituted tellurium precursor shown in Formula 1 to the disubstituted tellurium precursor shown in Formula 2 is 1:(2-4).

4. The very long wave infrared quantum dot of claim 3, wherein, In Equations 1 and 2, R 1 Selected from one of the substituted or unsubstituted C1-12 alkyl chains, the total molar ratio of the trisubstituted tellurium precursor shown in Formula 1 and the disubstituted tellurium precursor shown in Formula 2 to the mercury salt is 1:4, and the molar ratio of the trisubstituted tellurium precursor shown in Formula 1 to the disubstituted tellurium precursor shown in Formula 2 is 1:

3.

5. The long-wave or very long-wave infrared quantum dot according to claim 3 or 4, characterized in that, R in formula 1 2 3 each independently is selected from one of substituted or unsubstituted aryl.​ 6. The method of claim 1 or 3 for the preparation of long- or very long- wave infrared quantum dots, characterized in that, The method described: S1: Dissolve the tellurium precursors shown in Formula 1 and Formula 2 in OAm respectively to obtain trisubstituted tellurium precursor solution and disubstituted tellurium precursor solution respectively. S2: Under heating conditions, the trisubstituted tellurium precursor solution is first injected into the mercury salt / oleylamine solution for nucleation for 30-90s, and then the disubstituted tellurium precursor solution is injected at a constant rate. After terminating the reaction, the solution is washed and then liquid-phase ligand exchange is performed to obtain high specific detectivity long-wave infrared quantum dots or very long-wave infrared quantum dots.

7. The method of claim 6, wherein, The heating temperature in S2 is 110-130℃, the constant injection rate is 0.4-0.6 mL / min, and the liquid phase ligand exchange is carried out in DMF using 2-me and DDAB.

8. A method for preparing an intrinsic long / very long wave infrared quantum dot thin film, characterized in that, The method described: The long-wavelength or very long-wavelength infrared quantum dot solution of claim 1 or 3 is spin-coated or drop-coated onto the substrate in stages to a specified film thickness. Solid-state ligand exchange is performed after each spin-coating or drop-coating. After reaching the specified film thickness, the entire substrate is immersed in a solution with a concentration of 2×10⁻⁶. -3 -2×10 -5 Intrinsic long-wave / very long-wave infrared quantum dot films were obtained in an iodine / ethanol solution of M.

9. The intrinsic long-wavelength / very long-wavelength infrared quantum dot thin film prepared by the method of claim 8.

10. The application of the intrinsic long-wavelength / very long-wavelength infrared quantum dot thin film as described in claim 9 in a photoconductive detector.

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