Colloidal quantum dot photoconductive infrared detector based on trapping mode and its preparation method and application

Abstract

The present invention relates to a colloidal quantum dot photoconductive infrared detector based on a capture mode, its preparation method, and application, and belongs to the technical field of photoelectric detectors. The detector comprises a first colloidal quantum dot layer and an adjacent second colloidal quantum dot layer, as well as a substrate and an electrode, wherein the first colloidal quantum dot layer is arranged closer to the electrode than the second colloidal quantum dot layer; the first colloidal quantum dot layer has a greater carrier mobility than the second colloidal quantum dot layer; the second colloidal quantum dot layer is a p-type semiconductor material layer, in which holes in the p-type semiconductor material layer capture electrons in the first colloidal quantum dot layer and are used to reduce electron-hole recombination noise. The detector designed by the present invention has both excellent photoresponsivity and good specific detectivity.

Description

Technical Field

[0001] The present invention relates to an infrared photosensor component, belonging to the technical field of photoelectric detectors, and specifically to a colloidal quantum dot photoconductive infrared detector based on a capture mode, and a preparation method and application thereof. Background Art

[0002] Infrared detectors are photoelectric sensors that respond to external infrared radiation. Photon detectors sensitive to this wavelength are primarily based on materials such as single-crystal InSb and HgCdTe. However, the cost of single-crystal epitaxial growth remains high, and the process is extremely complex when coupled with silicon-based readout circuits, further increasing costs and limiting detector applications. Consequently, research has been conducted on alternatives such as quantum dot infrared detectors, quantum well infrared detectors, and type II superlattices of III-V semiconductors in search of solutions. As a new generation of optoelectronic semiconductor materials, colloidal quantum dots have made significant progress in the development of optoelectronic devices due to their wide spectral controllability, low-cost synthesis and preparation by hot injection, and liquid-phase processing that allows for direct coating onto silicon electronic devices. However, further reducing the power consumption of infrared colloidal quantum dot detectors and improving their detection performance are key challenges.

[0003] Infrared colloidal quantum dot detectors come in various types, including photoconductive, photovoltaic, and phototransistor types. The prominent advantage of photoconductive detectors is their simple structure, requiring only two electrodes for operation. Their principle is that when infrared radiation strikes the surface of a material, electron-hole pairs are generated in the semiconductor material. Some electrons and holes can transition from their previously non-conductive bound state to a conductive free state, increasing the semiconductor's conductivity. However, photoconductive detectors have higher theoretical noise than photovoltaic detectors. This is because photoconductive detectors have increased generation-recombination noise caused by the combination of electrons and holes, and require an external bias for operation, resulting in higher shot noise.

[0004] Specifically, an important indicator for measuring the performance of a photodetector is the noise equivalent power (NEP). The smaller the noise equivalent power, the higher the sensitivity of the detector. Its calculation formula is shown in equations (1) and (2):

[0005]

[0006] where i n is the noise current, R res is the response rate.

[0007]

[0008] Among them I ph is the photocurrent, and P is the input optical power.

[0009] Therefore, it is particularly important to reduce the composite noise of the detector and use it to improve the photoresponsivity, specific detectivity and external quantum efficiency. Summary of the Invention

[0010] To solve the above technical problems, the present invention discloses a colloidal quantum dot photoconductive infrared detector based on a trapping mode, and its preparation method and application. The photoconductive infrared detector has both excellent photoresponsivity and good specific detectivity.

[0011] The present invention provides a colloidal quantum dot photoconductive infrared detector based on a trapping mode, the detector comprising a first colloidal quantum dot layer and an adjacent second colloidal quantum dot layer, a substrate, and an electrode, wherein the first colloidal quantum dot layer is closer to the electrode than the second colloidal quantum dot layer;

[0012] The carrier mobility of the first colloidal quantum dot layer is greater than that of the second colloidal quantum dot layer; the second colloidal quantum dot layer is a p-type semiconductor material layer, and the first colloidal quantum dot layer is an intrinsic or weak p-type or n-type semiconductor material layer; the holes (majority carriers) in the second colloidal quantum dot layer capture the electrons (minority carriers) in the first colloidal quantum dot layer and are used to reduce the electron-hole recombination noise.

[0013] Furthermore, the structure of the detector includes, from top to bottom, an external packaging coating, a second colloidal quantum dot layer, a first colloidal quantum dot layer, an electrode and a substrate, wherein the electrode is an interdigitated metal electrode or an interdigitated alloy electrode provided on the substrate.

[0014] Furthermore, the intrinsic semiconductor material is a mercury sulfide semiconductor material enriched with mercury ions, the weak p-type semiconductor material is a mercury sulfide semiconductor material, and the n-type semiconductor material is a mercury sulfide semiconductor material treated with bismuth selenide.

[0015] Furthermore, the sulfur-based mercury is at least one of mercury sulfide, mercury selenide or mercury telluride.

[0016] Furthermore, the second colloidal quantum dot layer is made of a chalcogenide silver semiconductor material.

[0017] Furthermore, the sulfide silver is one or more of silver sulfide, silver selenide or silver telluride.

[0018] Furthermore, the sulfide mercury is mercury telluride, and the sulfide silver is silver telluride.

[0019] Furthermore, the structure of the detector includes, from top to bottom, a polymethyl methacrylate encapsulation coating, a silver telluride colloidal quantum dot layer, a mercury telluride colloidal quantum dot layer, a gold electrode, and a sapphire substrate, wherein the carrier mobility of the mercury telluride colloidal quantum dot layer is 1 cm 2 / Vs, the carrier mobility of silver telluride colloidal quantum dot layer is 10 -3 ~10 -4 cm 2 / Vs.

[0020] A second object of the present invention is to provide a method for preparing the above-mentioned colloidal quantum dot photoconductive infrared detector based on the capture mode, which comprises the following steps:

[0021] 1) Designing electrodes on the substrate;

[0022] 2) Producing a first colloidal quantum dot layer on the electrode: spin-coating the first colloidal quantum dot ink onto the electrode surface; wherein, Example 1 of the present invention discloses in detail the preparation process of mercury telluride colloidal quantum dot ink. The preparation of other intrinsic or weak p-type or n-type colloidal quantum dot inks may be different from that of mercury telluride, and everything is subject to the specificity of the quantum dots themselves.

[0023] During the spin coating process, the present invention adopts a single-layer coating method. After each layer of coating is completed, it stops for a period of time to allow the quantum dot solution to fully infiltrate, and then a cleaning agent is used to rinse off the excess ligands in the quantum dot solution, and the above coating is repeated until it is completed.

[0024] 3) Fabricating a second colloidal quantum dot layer on the surface of the first colloidal quantum dot layer:

[0025] 4) Surface encapsulation coating.

[0026] Another technical purpose of the present invention is to disclose the application of the above-mentioned colloidal quantum dot photoconductive infrared detector in the field of 1.1-2.5 μm short wave detection and / or 3-5 μm medium wave detection.

[0027] The technical solution provided by the embodiment of the present invention has the following advantages compared with the existing technology:

[0028] 1. The photoresponsivity of the colloidal quantum dot photoconductive infrared detector based on the capture mode designed by the present invention was measured at 600°C using a calibrated blackbody light source. The detector sample was placed in a liquid nitrogen thermostat at a distance of 20 cm from the light source. -1 Integrating the blackbody spectrum, the luminous flux of the blackbody is 718.906W / m 2 / sr. The thermal power consumption is 6.4×10 -4 At 100 W, the photoresponsivity of the CQD-based infrared detector using the trapping mode reached 24.95 A / W, compared to 10.6 A / W for the mercury telluride CQD-based infrared detector in the control group. Under the same conditions, the CQD-based infrared detector designed by the present invention achieved a 140% improvement in photoresponsivity.

[0029] 2. The specific detectivity of the colloidal quantum dot photoconductive infrared detector based on the capture mode designed by the present invention was measured at 600°C using a calibrated blackbody light source. The detector sample was placed in a liquid nitrogen thermostat at a distance of 20 cm from the light source. -1 Integrating the blackbody spectrum, the luminous flux of the blackbody is 718.906W / m 2 / sr. At 270K, the specific detection rate of the colloidal quantum dot photoconductive infrared detector designed in the capture mode of the present invention can reach up to 6.5×10 11 cm·Hz 1 / 2 W -1 The highest specific detection rate of the mercury telluride colloidal quantum dot infrared detector in the control group can only reach 1.5×10 11 cm·Hz 1 / 2 W -1 In comparison, the specific detection rate of the colloidal quantum dot photoconductive infrared detector in the capture mode designed by the present invention is increased by nearly 330%, effectively improving the specific detection rate of the colloidal quantum dot photoconductive infrared detector.

[0030] 3. The detector designed by the present invention has good application in the fields of shortwave detection of 1.1 to 2.5 μm and / or mediumwave detection of 3 to 5 μm. Specifically, in the shortwave infrared field, the colloidal quantum dot photoconductive infrared detector designed by the present invention in the capture mode can use the reflected light in the environment to form an image, and can be applied to face recognition and target recognition in the security field, space remote sensing detection and other fields. And because shortwave infrared imaging can be performed through the windshield, it can be applied to the night vision system of transportation vehicles to enhance the night vision detection capability. In the medium-wave infrared field, the colloidal quantum dot photoconductive infrared detector designed by the present invention in the capture mode can detect the infrared spectrum radiated by the target object itself, so the external environment has little effect on its detection performance, and it is suitable for target detection in bad weather such as rainy and foggy days. It can be applied to environmental monitoring with obstructions, airport security inspection and other aspects in the field of people's livelihood. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0033] Figure 1This is a schematic diagram of the detector structure disclosed in the present invention;

[0034] Figure 2 This is a schematic diagram of the detector structure disclosed in Example 1 of the present invention;

[0035] Figure 3 for Figure 2 Absorption spectrum of mercury telluride thin film;

[0036] Figure 4 for Figure 2 Spectral response diagram of mercury telluride thin film;

[0037] Figure 5 A schematic diagram of the field effect transistor connection relationship designed for the present invention;

[0038] Figure 6 for Figure 2 Mercury telluride thin film Figure 5 Field effect tube test result diagram;

[0039] Figure 7 for Figure 2 Silver telluride thin film Figure 5 Field effect tube test result diagram;

[0040] Figure 8 for Figure 2 Photoresponsivity test chart of the detector in the middle;

[0041] Figure 9 for Figure 2 Detection rate test chart of the detector. DETAILED DESCRIPTION

[0042] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein can be combined with each other.

[0043] The present invention discloses a colloidal quantum dot photoconductive infrared detector based on a capture mode. The detector includes a first colloidal quantum dot layer and an adjacent second colloidal quantum dot layer, as well as a substrate and an electrode. The first colloidal quantum dot layer is closer to the electrode than the second colloidal quantum dot layer. The first colloidal quantum dot layer has a greater carrier mobility than the second colloidal quantum dot layer. The second colloidal quantum dot layer is a p-type semiconductor material layer, and the first colloidal quantum dot layer 1 is an intrinsic, weak p-type, or n-type semiconductor material. Holes in the p-type semiconductor material layer capture electrons in the intrinsic, weak p-type, or n-type semiconductor material and are used to reduce electron-hole recombination noise. The detector structure disclosed in the present invention includes, from top to bottom, an external encapsulation coating, a second colloidal quantum dot layer, a first colloidal quantum dot layer, an electrode, and a substrate.

[0044] Combine Figure 1 The structure of the detector is preferably as follows: Figure 1 As shown, from top to bottom it includes an external packaging coating 5, a second colloidal quantum dot layer 2, a first colloidal quantum dot layer 1, an electrode 3 and a substrate 4, wherein the electrode 3 is an interdigitated metal electrode or an interdigitated alloy electrode arranged on the substrate, wherein the metal electrode and the alloy electrode are a possible electrode in the art, the substrate is a possible and commonly used substrate in the art, and the external packaging coating is a coating commonly used in the art and does not affect the use effect of the detector. The present invention preferably uses gold electrodes, sapphire substrates and methyl methacrylate packaging coatings.

[0045] The second colloidal quantum dot layer 2 of the present invention is preferably a p-type semiconductor material layer having a carrier mobility lower than that of the first colloidal quantum dot layer 1. The first colloidal quantum dot layer 1 is an intrinsic or weak p-type or n-type photosensitive layer with a relatively high carrier mobility. When the two are superimposed together, since there are holes in the p-type semiconductor material layer, they will capture electrons in the photosensitive layer. Since the carrier mobility in the p-type semiconductor material layer is very low, it can effectively prevent the captured electrons from escaping further outward, which reduces the electron concentration in the photosensitive layer and slows down the recombination rate between the electrons and the internal holes. This not only extends the hole lifetime in the photosensitive layer, but also reduces the recombination noise between holes and electrons, thereby helping to improve the light response rate of the detector.

[0046] The intrinsic semiconductor material of the present invention may be mercury telluride, mercury selenide or mercury sulfide material with mercury ions enriched on the surface.

[0047] The n-type semiconductor material of the present invention may be mercury selenide, mercury sulfide or mercury telluride material treated with bismuth selenide.

[0048] The weak p-type semiconductor material of the present invention can be a mercury sulfide semiconductor material, such as at least one of mercury sulfide, mercury selenide, or mercury telluride. Mercury telluride is preferred in the present invention, but mercury selenide, mercury sulfide, intrinsic semiconductor materials, and n-type semiconductor materials are also within the scope of protection of this application.

[0049] The material of the p-type semiconductor material layer of the present invention can be a chalcogenide silver semiconductor material, such as one or more of silver sulfide, silver selenide or silver telluride. Silver telluride is preferred in the present invention.

[0050] In summary, the present invention is preferably as follows Figure 2 The detector structure includes, from top to bottom, a polymethyl methacrylate encapsulation coating, a silver telluride colloidal quantum dot layer, a mercury telluride colloidal quantum dot layer, a gold electrode and a sapphire substrate.

[0051] The present invention also discloses a method for preparing a detector having the above structure, which comprises the following steps:

[0052] 1) Designing electrodes on a substrate: The present invention chooses to design interdigitated gold electrodes with a length × width = 1 mm × 1 mm on a sapphire substrate;

[0053] 2) Producing a first colloidal quantum dot layer on the electrode: This includes the following specific steps:

[0054] 2.1) Preparation of tellurium precursor solution: Tellurium powder and trioctylphosphine were stirred to form a light yellow solution;

[0055] 2.2) Synthesis of Mercury Telluride Colloidal Quantum Dots: In a nitrogen atmosphere, a certain amount of mercuric chloride was weighed and dissolved in oleylamine. The mixture was heated at 100°C for 1 hour and then equilibrated at 80°C for 30 minutes. The molar ratio of tellurium powder to mercuric chloride was approximately 1:1.

[0056] The tellurium precursor solution prepared in step 2.1) was injected into the thermal equilibrium solution and reacted at 80°C. A quenching solution was then added to terminate the reaction. The solution was then removed from the nitrogen environment and purged. The quenching solution was prepared from tetrachloroethylene, trioctylphosphine, and dodecylmercaptan.

[0057] 2.3) Cleaning of the Mercury Telluride Colloidal Quantum Dots: The mercury telluride colloidal quantum dot solution obtained after quenching in step 2.2) above was added to didodecyldimethylammonium bromide, followed by isopropyl alcohol. The solution was centrifuged and centrifuged. After centrifugation, the supernatant was discarded and the precipitate was dissolved with n-hexane to obtain a cleaned mercury telluride colloidal quantum dot solution.

[0058] 2.4) Preparation of a high-carrier-mobility mercury telluride colloidal quantum dot ink: Butyl chloride, mercuric chloride, 2-mercaptoethanol, and n-butylamine in a molar ratio of 1:1 are dissolved in N,N-dimethylformamide to form a hybrid ligand solution; the mercury telluride colloidal quantum dot solution is then added to the hybrid ligand solution and mixed to transfer the mercury telluride quantum dots from the n-hexane phase to the N,N-dimethylformamide phase. To promote exchange between the solution and the phase ligands, the mixture is vortexed. After the mixture is vortexed, toluene is added as an antisolvent to precipitate the mercury telluride quantum dots. Centrifugation is continued. After the centrifugation is completed, the supernatant is discarded and the precipitated solid is dissolved in N,N-dimethylformamide. Thus, mercury telluride forms a stable colloidal quantum dot ink with high carrier mobility in N,N-dimethylformamide.

[0059] 2.5) Generating a mercury telluride quantum dot film on the electrode surface: The mercury telluride colloidal quantum dot ink prepared in step 2.4) above is spin-coated on the electrode and substrate in step 1) on the substrate under a nitrogen environment. Specifically, the rotation speed is controlled to 3000 r / s, and the spin coating process is performed for 30 seconds. The spin coating process is stopped for 10 seconds to allow the colloidal quantum dots to be fully infiltrated. Then, isopropyl alcohol is used for 30 seconds to remove excess ligands in the colloidal quantum dots. The above steps are repeated until the generated mercury telluride quantum dot film has a thickness of approximately 200 nm, that is, the mercury telluride quantum dot film is the first colloidal quantum dot layer with relatively high carrier mobility.

[0060] 3) Fabricating a second colloidal quantum dot layer on the surface of the first colloidal quantum dot layer:

[0061] It includes the following specific steps:

[0062] 3.1) Synthesis of silver telluride colloidal quantum dots: Silver nitrate was dissolved in oleylamine and oleic acid, and the mixture was stirred at 70°C in a glove box for 30 minutes to obtain a uniform solution. Trioctylphosphine was then added and the mixture was rapidly heated to 160°C for 35-45 minutes. The solution turned from clear to yellow. The tellurium precursor solution from step 2.1) was then added, and the yellow solution immediately turned black. The reaction was continued for 10 minutes. After the reaction was completed, the reaction solution could be further cleaned and subsequently processed, or the reaction solution could be refrigerated at -8°C. The molar ratio of silver nitrate to tellurium powder was 2:1.

[0063] 3.2) Cleaning the silver telluride colloidal quantum dots: Take the above reaction solution at room temperature, add methanol, and place it in a vortex instrument to mix, continue ultrasonic treatment for about 20 seconds, and then centrifuge. After the centrifugation is completed, the supernatant is discarded, and the solid precipitate is dissolved in a mixture of dodecanethiol and chlorobenzene. After mixing, methanol is added to mix, and ultrasonic treatment is continued for about 20 seconds, and then centrifuge. After the centrifugation is completed, the supernatant is discarded, and the solid precipitate is dissolved in chlorobenzene, and methanol is added to mix, and ultrasonic treatment is continued for about 20 seconds, and then centrifuge for 5 minutes. After the centrifugation is completed, the supernatant is discarded, and the solid precipitate is dissolved in a n-hexane + octane solution with a volume ratio of 9:1 to form a cleaned silver telluride colloidal quantum dot solution;

[0064] 3.3) Fabricating a low carrier mobility p-type doped layer on the surface of the first colloidal quantum dot layer: Take the cleaned silver telluride colloidal quantum dot solution prepared in step 3.2) above and spin-coat it on the surface of the first colloidal quantum dot layer in step 2.5) under a nitrogen environment. Specifically, control the rotation speed to 3000 r / s and spin-coat for 15 seconds to complete the spin-coating of a layer of silver telluride. Then, spin-coat with mercuric chloride and methanol for 10 seconds. Repeat the above steps until a silver telluride colloidal quantum dot layer is formed.

[0065] 4) Surface encapsulation coating: A polymethyl methacrylate solution is used to seal the surface of the silver telluride colloidal quantum dot layer in step 3.3) to reduce the impact of external conditions such as air and moisture on the detector.

[0066] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all the embodiments.

[0067] Example 1

[0068] This embodiment discloses a Figure 2 The specific preparation method of the detector shown includes the following steps:

[0069] 1) Designing electrodes on a substrate: The present invention chooses to design interdigitated gold electrodes with a length × width = 1 mm × 1 mm on a sapphire substrate;

[0070] 2) Producing a first colloidal quantum dot layer on the electrode: This includes the following specific steps:

[0071] 2.1) Preparation of tellurium precursor solution: 3 mmol of tellurium powder was stirred with 3 mL of trioctylphosphine to form a light yellow solution.

[0072] 2.2) Synthesis of Mercury Telluride Colloidal Quantum Dots: In a nitrogen atmosphere, 81.6 mg of mercuric chloride was dissolved in 12 mL of oleylamine, heated at 100°C for 1 hour, and then equilibrated at 80°C for half an hour.

[0073] 0.3 mL of the tellurium precursor solution prepared in step 2.1) was injected into the thermal equilibrium solution. The reaction was allowed to proceed at 80°C for 4 minutes. The quenching solution was then added to terminate the reaction. The solution was then removed from the nitrogen atmosphere for purging. The quenching solution was prepared by combining 24 mL of tetrachloroethylene, 0.9 mL of trioctylphosphine, and 3 mL of dodecyl mercaptan.

[0074] 2.3) Cleaning of the Mercury Telluride Colloidal Quantum Dots: The mercury telluride colloidal quantum dot solution obtained after quenching in step 2.2) above was added to 0.7 mL of didodecyldimethylammonium bromide, followed by 25 mL of isopropanol. The solution was centrifuged at 7500 rpm for 6 minutes. After centrifugation, the supernatant was discarded and the precipitate was dissolved with n-hexane to obtain a cleaned mercury telluride colloidal quantum dot solution.

[0075] 2.4) Preparation of mercury telluride colloidal quantum dot ink with high carrier mobility: First, 0.5 mmol butylammonium chloride, 0.5 mmol mercuric chloride, 140 μL 2-mercaptoethanol and 400 μL n-butylamine were dissolved in 5 mL N,N-dimethylformamide to form a hybrid ligand solution; then 400 μL of the above-mentioned mercury telluride colloidal quantum dot solution (about 80 mg / mL) was added to the hybrid ligand solution, and the mixture was slightly shaken to cause the mercury telluride quantum dots to transfer from the n-hexane to the N,N-dimethylformamide phase. To promote the exchange between the solution and the phase ligand, the mixture was vortexed for 1 minute. After the end, toluene was added as an antisolvent to precipitate the mercury telluride quantum dots. The speed was continued to be controlled at 4000 rpm and centrifuged for 30 seconds. After the centrifugation, the supernatant was discarded and 40 μL N,N- Dimethylformamide dissolves the precipitated solid, that is, mercury telluride generates a stable colloidal quantum dot ink with high carrier mobility in N,N-dimethylformamide.

[0076] 2.5) Generating a mercury telluride quantum dot film on the electrode surface: Take the mercury telluride colloidal quantum dot ink prepared in step 2.4) above and spin-coat it on the electrode and substrate in step 1) on the substrate under a nitrogen environment. Specifically, control the rotation speed to 3000 r / s, spin-coat for 30 seconds, stop for 10 seconds to allow the colloidal quantum dots to fully infiltrate, and then use isopropyl alcohol to spin for 30 seconds to remove excess ligands in the colloidal quantum dots. Repeat the above steps until the generated mercury telluride quantum dot film has a thickness of about 200 nm, that is, the mercury telluride quantum dot film is the first colloidal quantum dot layer with relatively high carrier mobility. Among them, Figure 3 and Figure 4 The absorption spectrum and spectral response diagram of mercury telluride are given respectively. Figure 3 、 Figure 4 It can be seen that mercury telluride colloidal quantum dots from 4000cm -1 It begins to have a spectral response, which is consistent with the absorption peak position.

[0077] 3) Fabricating a second colloidal quantum dot layer on the surface of the first colloidal quantum dot layer:

[0078] It includes the following specific steps:

[0079] 3.1) Synthesis of Silver Telluride Colloidal Quantum Dots: 34 mg of silver nitrate was dissolved in 5 mL of oleylamine and 5 mL of oleic acid. The mixture was stirred at 70°C in a glove box for 30 min to obtain a uniform solution. 0.5 mL of trioctylphosphine was then added and the mixture was rapidly heated to 160°C for 35-45 min. The solution turned from clear to yellow. The tellurium precursor solution from step 2.1) was then added, and the yellow solution immediately turned black. The reaction was allowed to proceed for 10 minutes. After the reaction, the reaction solution could be further cleaned and subsequently processed, or the reaction solution could be refrigerated at -8°C.

[0080] 3.2) Cleaning the silver telluride colloidal quantum dots: Take 200 μL of the above reaction solution at room temperature, add 2 mL of methanol and place it in a vortex instrument to mix, continue ultrasonic treatment for about 20 seconds, then control the centrifugal speed to 5000 rpm, centrifuge for 5 minutes, and after the centrifugation is completed, pour out the supernatant, take the solid precipitate and dissolve it in a mixture of 50 μL of dodecanethiol and 150 μL of chlorobenzene, mix, add 2 mL of methanol and mix, continue ultrasonic treatment for about 20 seconds, then control the centrifugal speed to 5000 rpm, centrifuge for 5 minutes, after the centrifugation is completed, pour out the supernatant, take the solid precipitate and dissolve it in 200 μL of chlorobenzene, add 2 mL of methanol and mix, continue ultrasonic treatment for about 20 seconds, then control the centrifugal speed to 5000 rpm, centrifuge for 5 minutes, after the centrifugation is completed, pour out the supernatant, take the solid precipitate and dissolve it in 400 μL of n-hexane + octane solution with a volume ratio of 9:1 to form a solution with a concentration of 12.5 mg / mL;

[0081] 3.3) Fabricating a low carrier mobility p-type doped layer on the surface of the first colloidal quantum dot layer: Take the cleaned silver telluride colloidal quantum dot solution prepared in step 3.2) above and spin-coat it on the surface of the first colloidal quantum dot layer in step 2.5) under a nitrogen environment. Specifically, control the rotation speed to 3000 r / s and spin-coat for 15 seconds to complete the spin-coating of a layer of silver telluride. Then, spin-coat with mercuric chloride and methanol for 10 seconds. Repeat the above steps until a silver telluride colloidal quantum dot layer is formed.

[0082] 4) Surface encapsulation coating: A polymethyl methacrylate solution is used to seal the surface of the silver telluride colloidal quantum dot layer in step 3.3) to reduce the impact of external conditions such as air and moisture on the detector.

[0083] In summary, this embodiment has produced a Figure 2 Schematic diagram of the detector structure.

[0084] In order to further explore whether the mercury telluride film is p-type or n-type and calculate the mobility of the first colloidal quantum dot layer prepared in this embodiment, the present invention chooses to Figure 5 、 Figure 6 The schematic diagram shows the construction of a field effect tube to measure mercury telluride thin film. Figure 5 It can be seen that the detector prepared by the present invention is a slightly p-type eigenstate, combined with Figure 6 , and further select the calculation formula (3) of the field effect tube listed below to calculate the mobility of the colloidal quantum dot film:

[0085]

[0086] Among them, in the above mathematical relationship (3), C iThe capacitance of 300nm SiO2 is 1.15×10 -4 F / m 2 , gap L = 10 μm, total channel width W = 5 μm, drain voltage V D =1V, The slope of the source-drain current versus gate voltage is 5.75×10 -5 A / V.

[0087] The mobility of mercury telluride semiconductor material is calculated to be 1cm 2 / Vs.

[0088] The present invention also selects to construct a field effect tube to measure the silver telluride film, and the results are as follows Figure 7 As shown by Figure 7 It can be seen that silver telluride semiconductor material is a strong P-type, and its carrier mobility calculated by the above formula is 10 -3 ~10 -4 cm 2 / Vs.

[0089] It can be seen from this that the carrier mobility of the mercury telluride semiconductor material prepared by the present invention is more than three to four orders of magnitude higher than that of the silver telluride semiconductor material. Therefore, when the two are superimposed together, due to the presence of holes in the p-type semiconductor material layer, they will capture electrons in the mercury telluride semiconductor material layer. Since the carrier mobility in the p-type semiconductor material layer is very low, it can effectively prevent the captured electrons from further escaping outward. This reduces the electron concentration in the mercury telluride semiconductor material layer and slows down the recombination rate between the electrons and the internal holes. This not only extends the hole lifetime in the mercury telluride semiconductor material layer, but also reduces the recombination noise between holes and electrons, thereby helping to improve the photoresponsivity of the detector.

[0090] In order to further explore the photoresponsivity of the detector prepared in this embodiment, the present invention also prepared a detector of comparative example 1. The difference between the detector of comparative example 1 and the detector of embodiment 1 is that the first colloidal quantum dot layer is directly encapsulated, and the other parts remain the same. Figure 8 The thermal power consumption and response rate curves of the two detectors are given. Figure 8 It can be seen that under the same thermal power consumption, the response rate of the quantum dot film treated with silver telluride is about 140% higher than that of the untreated film.

[0091] The response rate is calculated as I ph is the photocurrent of the detector, is the input optical power, A BB =πr 2 is the area of ​​blackbody radiation, r = 2cm, L = 20cm is the distance between the blackbody and the detector, Ap =0.5mm 2 is the effective detector area, is the luminous flux.

[0092] In addition, the present invention also explores the detection capabilities of the above two detectors for weak light, specifically Figure 9 As shown, combined Figure 9 It can be seen that the detector designed in the present invention has a detection rate increased by about 330% when the temperature is 270K.

[0093] In summary, the photoconductive infrared detector prepared by the present invention has both excellent photoresponsivity and good specific detectivity.

[0094] In addition, the external quantum efficiency calculation formula is: R is the photoresponsivity of the colloidal quantum dot infrared detector, which is 6.4×10 -4 When W, the light response rate of the infrared colloidal quantum dot infrared detector based on the capture mode designed by the present invention is Figure 8 It can be seen that it is 24.9A / W, and λ0=2.3μm is the absorption wavelength of the infrared detector. Therefore, under the same conditions, the external quantum efficiency of the infrared colloidal quantum dot infrared detector based on the capture mode designed by the present invention is increased to about 1500%.

[0095] The detector designed by the present invention has good application in the fields of short-wave detection of 1.1 to 2.5 μm and / or medium-wave detection of 3 to 5 μm. Specifically, in the short-wave infrared field, the colloidal quantum dot photoconductive infrared detector designed by the present invention in the capture mode can use the reflected light in the environment to form an image, and can be applied to face recognition and target recognition in the security field, space remote sensing detection and other fields. And because short-wave infrared imaging can be performed through the windshield, it can be applied to the night vision system of transportation vehicles to enhance the night vision detection capability. In the medium-wave infrared field, the colloidal quantum dot photoconductive infrared detector designed by the present invention in the capture mode can detect the infrared spectrum radiated by the target object itself, so the external environment has little effect on its detection performance, and it is suitable for target detection in bad weather such as rainy and foggy days. It can be applied to environmental monitoring with obstructions, airport security in the field of people's livelihood, and other aspects.

[0096] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0097] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments described herein, but is to be construed in the widest manner consistent with the principles and novel features disclosed herein.

Claims

1. A colloidal quantum dot photoconductive infrared detector based on the capture mode, characterized in that: The detector includes a first colloidal quantum dot layer and an adjacent second colloidal quantum dot layer, and further includes a substrate and an electrode, wherein the first colloidal quantum dot layer is closer to the electrode than the second colloidal quantum dot layer; The carrier mobility of the first colloidal quantum dot layer is greater than that of the second colloidal quantum dot layer, and the second colloidal quantum dot layer is a p-type semiconductor material layer, the first colloidal quantum dot layer is an intrinsic type or weak p-type or n-type semiconductor material layer, and the holes in the second colloidal quantum dot layer capture electrons in the first colloidal quantum dot layer and are used to reduce electron-hole recombination noise; The structure of the detector includes, from top to bottom, an external packaging coating, a second colloidal quantum dot layer, a first colloidal quantum dot layer, electrodes and a substrate. The electrodes are interdigitated metal electrodes or interdigitated alloy electrodes arranged on the substrate.

2. The colloidal quantum dot photoconductive infrared detector based on the capture mode according to claim 1, characterized in that: The intrinsic semiconductor material is a mercury sulfide semiconductor material enriched with mercury ions, the weak p-type semiconductor material is a mercury sulfide semiconductor material, and the n-type semiconductor material is a mercury sulfide semiconductor material treated with bismuth selenide.

3. The colloidal quantum dot photoconductive infrared detector based on the capture mode according to claim 2, characterized in that: The sulfide mercury semiconductor material is at least one of mercury sulfide, mercury selenide or mercury telluride.

4. The colloidal quantum dot photoconductive infrared detector based on the trapping mode according to claim 2 or 3, characterized in that: The material of the second colloidal quantum dot layer is a chalcogenide silver semiconductor material.

5. The colloidal quantum dot photoconductive infrared detector based on the trapping mode according to claim 4, characterized in that: The chalcogenide silver semiconductor material is one or more of silver sulfide, silver selenide or silver telluride.

6. The colloidal quantum dot photoconductive infrared detector based on the trapping mode according to claim 4 or 5, characterized in that: The mercury sulfide semiconductor material is mercury telluride, and the silver sulfide semiconductor material is silver telluride.

7. The colloidal quantum dot photoconductive infrared detector based on the capture mode according to claim 6, characterized in that: The structure of the detector includes a polymethyl methacrylate encapsulation coating, a silver telluride colloidal quantum dot layer, a mercury telluride colloidal quantum dot layer, a gold electrode and a sapphire substrate from top to bottom. The carrier mobility of the mercury telluride colloidal quantum dot layer is 1 cm 2 / Vs, the carrier mobility of silver telluride colloidal quantum dot layer is 10 -3 ~10 -4 cm 2 / Vs.

8. A method for preparing a colloidal quantum dot photoconductive infrared detector based on a trapping mode according to any one of claims 1 to 7, characterized in that: It includes the following steps: 1) Design electrodes on the substrate; 2) Fabricating a first colloidal quantum dot layer on the electrode: spin-coating the first colloidal quantum dot ink onto the electrode surface; 3) Fabricating a second colloidal quantum dot layer on the surface of the first colloidal quantum dot layer: spin-coating the second colloidal quantum dot ink onto the surface of the first colloidal quantum dot layer; 4) Surface encapsulation coating.

9. Use of the colloidal quantum dot photoconductive infrared detector according to any one of claims 1 to 7 in the field of 1.1 to 2.5 μm short wave detection and / or 3 to 5 μm medium wave detection.

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