Extended wavelength lead-based quantum dot short-wave infrared detector and preparation method thereof

Abstract

The invention relates to an extended wavelength lead-based quantum dot short-wave infrared detector and a preparation method thereof, the infrared detector sequentially comprises a substrate, a bottom electrode, an electron transport layer, an extended wavelength lead-based quantum dot layer, a hole transport layer and a top electrode, and the preparation method comprises the following steps: (1) providing the substrate; (2) preparing a bottom electrode on the substrate; (3) preparing an electron transport layer on the bottom electrode; (4) preparing an extended wavelength lead-based quantum dot layer on the electron transport layer; (5) preparing a hole transport layer on the extended wavelength lead-based quantum dot layer; and (6) preparing a top electrode on the hole transport layer. According to the invention, SnO2 is deposited by ALD, so that the energy level barrier of the electron transport layer and the extended wavelength quantum dot layer is solved; when the extended wavelength lead-based quantum dot layer is prepared, the monomer ligand is adopted for surface passivation, the quantum dot surface defect state density is reduced, the quantum dot colloid dispersity is enhanced, the film compactness is improved, and the quantum dot has the characteristics of low dark current, high responsivity and the like when being applied to a short-wave infrared detector.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoelectric detectors, and in particular relates to an extended wavelength lead-based quantum dot short-wave infrared detector and a preparation method thereof. Background Art

[0002] Shortwave infrared (SWIR) is an important atmospheric window, possessing significant scientific value and economic benefits in aerospace, military reconnaissance, security monitoring, spectral detection, and smart cities. Based on the response characteristics of existing detectors, SWIR is generally divided into conventional wavelengths (0.9-1.7 μm) and extended wavelengths (1.7-2.5 μm). In recent years, with the rapid development of SWIR detection and imaging technology, demand for applications in the extended SWIR band has been growing. Compared to conventional wavelengths, this band offers deeper material penetration, richer spectral information, and stronger material recognition capabilities.

[0003] Short-wave infrared detectors based on III-V InGaAs materials offer high sensitivity, good uniformity, and excellent stability, making them an ideal material choice for developing short-wave infrared detectors. However, the spectral response range of lattice-matched In0.53Ga0.47As materials is generally limited to the conventional short-wave infrared, limiting their spectral response range. While further increasing the indium content can extend the spectral absorption range to the entire extended-wavelength short-wave infrared, the lattice mismatch between the high-indium content InGaAs material and the InP substrate severely degrades the detector's photoelectric performance. Detectors made from materials such as mercury cadmium telluride (HgCdTe) or indium antimonide (InSb) can detect light in the extended short-wave infrared. However, to improve their signal-to-noise ratio to a usable level, these cameras must be mechanically cooled to extremely low temperatures. Furthermore, all of these infrared detection materials require single-crystal epitaxial growth, which not only imposes a high manufacturing barrier but also requires complex bonding processes for chip integration, limiting the fabrication of large-array infrared imaging chips. Therefore, it is crucial to develop new extended-wavelength short-wave infrared detection technologies that are easy to integrate into large arrays, have wide spectral response, and are low-cost.

[0004] Lead-based (PbS, PbSe) colloidal quantum dots (CQDs) can be used as the development material for the next generation of extended-wavelength short-wave infrared detectors because of their tunable band gap, response spectrum that covers the entire short-wave infrared, solution preparation, low cost, and easy integration with silicon-based readout circuits. However, most existing lead-based colloidal quantum dot detectors use conventional wavelength quantum dots, which makes it difficult to achieve extended short-wave infrared detection. By increasing the size of colloidal quantum dots, the response spectrum can be extended to 1.7-2.5μm, but extended-wavelength colloidal quantum dots have problems such as low passivation efficiency, poor solution processability, easy agglomeration, and energy level mismatch, which greatly limit their application in high-performance detectors.

[0005] Therefore, developing an extended wavelength lead-based quantum dot short-wave infrared detector that solves many of the above problems will be of great development significance. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides an extended wavelength lead-based quantum dot short-wave infrared detector and a preparation method thereof.

[0007] In the first aspect, the present application provides an extended wavelength lead-based quantum dot short-wave infrared detector, which includes, from bottom to top, a substrate, a bottom electrode, an electron transport layer, an extended wavelength lead-based quantum dot layer, a hole transport layer and a top electrode, wherein the electron transport layer, the extended wavelength lead-based quantum dot layer and the hole transport layer form a p-on-n type junction.

[0008] Preferably, the substrate is one of quartz and sapphire to meet the requirement of having high transmittance in the extended wavelength range; the bottom electrode is tin-doped indium oxide (ITO); and the electron transport layer is SnO2.

[0009] Preferably, the bottom electrode has a thickness of 100 to 200 nm, the electron transport layer has a thickness of 30 to 100 nm, the extended wavelength lead-based quantum dot layer has a thickness of 200 to 500 nm, the hole transport layer has a thickness of 10 to 60 nm, and the top electrode has a thickness of 50 to 120 nm.

[0010] Further preferably, the bottom electrode has a thickness of 150 nm, the electron transport layer has a thickness of 50 nm, the extended wavelength lead-based quantum dot layer has a thickness of 350 nm, the hole transport layer has a thickness of 40 nm, and the top electrode has a thickness of 100 nm.

[0011] Preferably, the extended wavelength lead-based quantum dots in the extended wavelength lead-based quantum dot layer are one of PbSe and PbS, and the response wavelength range is 1.7 to 2.5 μm.

[0012] In a second aspect, the present application provides a method for preparing an extended-wavelength lead-based quantum dot short-wave infrared detector, comprising the following steps: (1) providing a substrate; (2) preparing a bottom electrode on the substrate; (3) preparing an electron transport layer on a side of the bottom electrode away from the substrate; (4) preparing an extended-wavelength lead-based quantum dot layer on a side of the electron transport layer away from the bottom electrode; (5) preparing a hole transport layer on the extended-wavelength lead-based quantum dot layer; (6) preparing a top electrode on a side of the hole transport layer away from the bottom electrode;

[0013] In the step (iv), preparing the extended wavelength lead-based quantum dot layer on the side of the electron transport layer away from the bottom electrode specifically includes: preparing an extended wavelength lead-based quantum dot solution, using a monomer ligand to perform ligand exchange on the extended wavelength lead-based quantum dots to obtain an extended wavelength quantum dot ink, and spin-coating the extended wavelength quantum dot ink on the side of the electron transport layer away from the bottom electrode to prepare the extended wavelength lead-based quantum dot layer.

[0014] Preferably, in the step (ii), a bottom electrode is deposited on the substrate by magnetron sputtering, and in the step (iii), an electron transport layer is prepared on the side of the bottom electrode away from the substrate by atomic force deposition. In the step (v), a hole transport layer is prepared on the extended wavelength lead-based quantum dot layer, specifically comprising: spin coating the extended wavelength lead-based quantum dot solution on the side of the extended wavelength lead-based quantum dot layer away from the electron transport layer, the spin coating speed is 1000 to 4000 revolutions per minute, the spin coating acceleration is 1000 to 2000 radians per square second, and the spin coating time is 10 to 60 seconds. A solid-phase ligand exchange is performed using an acetonitrile solution of 1,2-ethanedithiol, wherein the ligand exchange time is 10 to 40 seconds and the volume concentration of the acetonitrile solution of 1,2-ethanedithiol is 0.01% to 0.1%. The residual ligand is then removed by washing with an acetonitrile solution. The above process is repeated 1 to 4 times to prepare a hole transport layer. Step (six) prepares a top electrode on the side of the hole transport layer away from the bottom electrode, specifically by depositing an Au electrode on the hole transport layer prepared in step (fifth) by thermal evaporation deposition of a thin film, thereby forming a top electrode.

[0015] Further preferably, in the step (v), the spin coating speed is 2500 rpm, the spin coating acceleration is 1000 rad / s2, the spin coating time is 20 seconds, the volume concentration of the acetonitrile solution of 1,2-ethanedithiol is 0.02%, and the ligand exchange time is 20 seconds.

[0016] Preferably, the method for preparing the extended wavelength lead-based quantum dot solution in step (iv) comprises the following steps:

[0017] S1: dissolving lead chloride powder in oleylamine, degassing at room temperature, and heating under a nitrogen atmosphere to obtain an oleylamine lead precursor solution;

[0018] S2: Rapidly injecting a high concentration of CdSe or ZnS quantum dot solution into the oleylamine lead precursor solution described in S1, so that the oleylamine lead precursor reacts with the CdSe or ZnS quantum dots to generate PbSe or PbS quantum dot cores;

[0019] S3: Continue to inject a low concentration of CdSe or ZnS quantum dot solution into the PbSe or PbS quantum dot core solution described in S2, so that the PbSe or PbS quantum dots grow until the response wavelength range reaches 1.7 to 2.5 μm;

[0020] S4: The quantum dot solution obtained in S3 is cooled to room temperature in a water bath, and then n-hexane and oleic acid are injected to stop the reaction. After stirring for a period of time, a certain amount of anti-solvent is added to obtain extended wavelength lead-based quantum dot powder;

[0021] S5: dissolving the extended wavelength lead-based quantum dot powder obtained in S4 in a non-polar solvent to obtain an extended wavelength lead-based quantum dot solution.

[0022] Preferably, the concentration ratio of the CdSe or ZnS quantum dots in step S2 to the CdSe or ZnS quantum dots in step S3 is 2 to 5:1.

[0023] Preferably, the size of the CdSe or ZnS quantum dots in step S2 is larger than the size of the CdSe or ZnS quantum dots in step S3.

[0024] Preferably, the volume of the antisolvent added in step S4 is 1 to 2 times the volume of the extended wavelength lead-based quantum dot solution (CdSe or ZnS quantum dot solution), and the antisolvent is a mixture of one or more of ethanol, acetone, ethyl acetate, and acetonitrile.

[0025] Preferably, the non-polar solvent in step S5 is one of n-octane or n-hexane, and the concentration of the obtained extended wavelength lead-based quantum dot solution is 10-100 mg / mL.

[0026] Preferably, the monomer ligand in step (iv) is prepared by the following method: (1) dissolving metal halogen powder in N,N-dimethylformamide to obtain metal halogen ligand; (2) dissolving Group V-VI sulfide powder in n-butylamine to obtain Group V-VI sulfide ligand; (3) mixing the metal halogen ligand and the Group V-VI sulfide ligand and shaking them to obtain the monomer ligand.

[0027] Preferably, in the step (iv), the extended wavelength lead-based quantum dots are ligand-exchanged with monomeric ligands to obtain extended wavelength quantum dot ink, and the extended wavelength quantum dot ink is spin-coated on the side of the electron transport layer away from the bottom electrode to prepare an extended wavelength lead-based quantum dot layer, specifically comprising: mixing the extended wavelength lead-based quantum dot solution with the monomeric ligand for ligand exchange, adding toluene, centrifuging to obtain an extended wavelength lead-based quantum dot solid, degassing and drying it, and dispersing it in a solvent (the solvent composition and ratio are DMF:DMSO:BTA:AMPY=500:300:170:30), with a dissolution concentration of 100-500 mg / mL to obtain an extended wavelength quantum dot ink, and spin-coating the extended wavelength quantum dot ink on one side of the electron transport layer to prepare a lead-based quantum dot layer, wherein the spin coating speed is 1000-4000 revolutions per minute, the spin coating acceleration is 1000-2000 radians per square second, and the spin coating time is 10-60 seconds, the lead-based quantum dot layer.

[0028] More preferably, the solvent composition and ratio in step (iv) are

[0029] DMF:DMSO:BTA:AMPY=500:300:170:30, the dissolved concentration is 350 mg / mL, the spin coating speed is 2500 revolutions per minute, the spin coating acceleration is 1000 radians per square second, and the spin coating time is 40 seconds.

[0030] The method for preparing an extended wavelength lead-based quantum dot short-wave infrared detector provided in the embodiments of the present application, and the infrared detector prepared have the following beneficial effects:

[0031] (1) The extended wavelength lead-based quantum dots of the present invention (wavelength response range 1.7-2.5 μm) can extend the response range to the entire short-wave infrared compared to conventional wavelength quantum dots, thus having a wider detection range and more application scenarios;

[0032] (2) The extended wavelength short-wave infrared quantum dot layer of the present invention uses monomeric ligands for ligand exchange. Compared with the traditional liquid-phase ligand exchange method, it solves the problems of low passivation efficiency, poor solution processability, and easy agglomeration of large-sized quantum dots, enhances the surface passivation effect, improves the colloid stability of the ink, and produces a denser film.

[0033] (3) The present invention constructs an electron transport layer, an extended wavelength lead-based quantum dot layer, and a hole transport layer to form a p-on-n photovoltaic detector, which has excellent performance in the entire extended wavelength short-wave infrared band (1.7-2.5 μm). The unique PbSe quantum dot detector with a cutoff of 2.5 μm has a peak responsivity of 0.445 A / W and a specific detectivity of up to 3*10 11 Jones.

[0034] (4) The present invention prepares an extended wavelength lead-based quantum dot layer through monomer ligand passivation, which reduces the defect state density and improves the carrier mobility, so that the infrared detector prepared by using the same has a lower dark current density and a higher light response. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] 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, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 This is a flow chart of an embodiment of a method for preparing an extended-wavelength lead-based quantum dot short-wave infrared detector disclosed in this application;

[0037] Figure 2 This is a flow chart of another embodiment of a method for preparing an extended-wavelength lead-based quantum dot short-wave infrared detector disclosed in this application;

[0038] Figure 3 The absorption curve (3a) and TEM image (3b) of the 2360nm PbSe quantum dot solution prepared in the examples of this application;

[0039] Figure 4 The absorption curve (4a) and TEM image (4b) of the 2100nm PbS quantum dot solution prepared in the examples of this application;

[0040] Figure 5 The actual comparison images (5a and 5b) and SEM comparison images (5c and 5d) of the 2360nm PbSe quantum dot film prepared in the embodiment of the present application and the 2360nm PbSe quantum dot film prepared in the control example;

[0041] Figure 6 This is a schematic diagram of the structure of an extended wavelength lead-based quantum dot short-wave infrared detector provided by this application;

[0042] Wherein: 1. substrate, 2. bottom electrode, 3. electron transport layer, 4. extended wavelength lead-based quantum dot layer, 5. hole transport layer, 6. top electrode;

[0043] Figure 7 This is a performance comparison chart of 2360nm PbSe quantum dot short-wave infrared detectors prepared in the embodiment of the present invention and the comparative example. DETAILED DESCRIPTION

[0044] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0045] See Figure 1 , Figure 1The present invention provides a schematic flow diagram of an embodiment of a method for preparing an extended-wavelength lead-based quantum dot short-wave infrared detector disclosed herein. The extended-wavelength lead-based quantum dot short-wave infrared detector comprises an electron transport layer, an extended-wavelength lead-based quantum dot layer, and a hole transport layer, wherein the electron transport layer, the extended-wavelength lead-based quantum dot layer, and the hole transport layer form a p-on-n junction; that is, the electron transport layer is located below the extended-wavelength lead-based quantum dot layer, while the hole transport layer is located above the extended-wavelength lead-based quantum dot layer.

[0046] like Figure 1 As shown, the preparation method of the extended wavelength lead-based quantum dot short-wave infrared detector of the present application includes:

[0047] Step S11: preparing a wavelength-extended lead-based quantum dot solution.

[0048] Please combine Figure 2 , Figure 2 This is a flow chart of another embodiment of a method for preparing an extended wavelength lead-based quantum dot short-wave infrared detector disclosed in this application. Figure 1 The embodiment shown, Figure 2 The embodiment shown further includes, before step S11:

[0049] Step S21: providing a substrate.

[0050] In one embodiment, the substrate is a quartz plate with dimensions of length×width×thickness=20 mm×20 mm×1 mm.

[0051] Step S22: preparing a bottom electrode on the substrate.

[0052] The bottom electrode is tin-doped indium oxide (ITO), and is a rectangular electrode with a length×width=20 mm×10 mm. Specifically, the ITO electrode is magnetron sputtered on a quartz substrate, and has a thickness of 150 nm.

[0053] Step S23: preparing an electron transport layer on the side of the bottom electrode away from the substrate.

[0054] The electron transport layer is SnO2. Specifically, a SnO2 film with a thickness of 50 nm is deposited on the side of the bottom electrode away from the substrate by atomic force deposition.

[0055] After preparing the electron transport layer, it is necessary to prepare the extended wavelength lead-based quantum dot solution. For details, please refer to Figure 1 Step S11 in .

[0056] Step S11: preparing a wavelength-extended lead-based quantum dot solution.

[0057] In one embodiment, the prepared extended wavelength lead-based quantum dot material is PbSe quantum dots, specifically comprising:

[0058] 4.17 g of lead chloride powder was dissolved in 50 mL of oleylamine solution, vacuum-evacuated at room temperature and vigorously stirred for 30 minutes to remove gas, and then heated to 140°C under nitrogen protection and maintained at this temperature for 30 minutes to form an oleylamine lead precursor solution;

[0059] The oleylamine lead precursor solution was further heated to 190°C, and 10 mL of 550 nm CdSe quantum dot solution (CdSe quantum dot concentration was 0.4 mol / L) was rapidly injected and maintained at this temperature for 40 s to form PbSe quantum dot cores.

[0060] The nucleated solution was cooled to 160°C and maintained for 4 minutes. A 444 nm CdSe quantum dot solution (CdSe quantum dot concentration of 0.133 mol / L) was injected using a 50 mL syringe at a controlled rate of 1.33 mm / min for 25 minutes to promote size growth. The injection rate was then increased to 1.86 mm / min and the reaction was maintained until PbSe quantum dots of the desired wavelength were obtained.

[0061] The obtained PbSe quantum dot stock solution was cooled in a water bath, 60 mL of n-hexane was injected into it at 70 °C, and 25 mL of OA was injected at 40 °C. Finally, the solution was stirred for 10 minutes;

[0062] The original solution was centrifuged to remove unreacted lead chloride, and the supernatant was purified with acetone and centrifuged to obtain extended wavelength PbSe quantum dot powder. The powder was redispersed in n-octane to obtain an extended wavelength PbSe quantum dot solution, wherein the ratio of acetone to the original solution was 2:1, and the obtained extended wavelength PbSe quantum dot solution was 50 mg / mL.

[0063] The absorption peak of the extended wavelength PbSe quantum dots prepared in this example is located at 2360nm, and its absorption curve is as follows: Figure 3 As shown in (a), the TEM image is as follows Figure 3 As shown in (b), the diameter of the quantum dots is about 11 nm.

[0064] In another embodiment, the prepared extended wavelength lead-based quantum dot material is PbS quantum dots, specifically comprising:

[0065] 4.17 g of lead chloride powder was dissolved in 50 mL of oleylamine solution, vacuum-evacuated at room temperature and vigorously stirred for 30 minutes to remove gas, and then heated to 140°C under nitrogen protection and maintained at this temperature for 30 minutes to form an oleylamine lead precursor solution;

[0066] The oleylamine lead precursor solution was further heated to 190°C, and 10 mL of 286 nm ZnS quantum dot solution (ZnS quantum dot concentration was 0.6 mol / L) was rapidly injected and maintained at this temperature for 4 minutes to form PbS quantum dot cores.

[0067] The nucleated solution was cooled to 160°C and maintained for 4 minutes. A 256 nm ZnS quantum dot solution (ZnSe quantum dot concentration was 0.2 mol / L) was injected using a 50 mL syringe at a controlled rate of 1.33 mm / min for 40 minutes to promote size growth. The injection rate was then increased to 1.86 mm / min and the reaction was maintained until PbS quantum dots of the desired wavelength were obtained.

[0068] The obtained PbS quantum dot stock solution was cooled in a water bath, 60 mL of n-hexane was injected into it at 70 °C, and 25 mL of OA was injected at 40 °C. Finally, the solution was stirred for 10 minutes;

[0069] The original solution was centrifuged to remove unreacted lead chloride, and the supernatant was purified with acetone and centrifuged. Ultimately, the resulting extended-wavelength PbS quantum dot powder was redispersed in n-octane to create an extended-wavelength PbS quantum dot solution. The ratio of acetone to the original solution was 2:1, resulting in a 50 mg / mL extended-wavelength PbS quantum dot solution.

[0070] The absorption peak of the extended wavelength PbS quantum dots prepared in this example is located at 2100 nm, and its absorption curve is as follows: Figure 4 As shown in (a), the TEM image is as follows Figure 4 As shown in (b), the diameter of the quantum dots is about 10.5 nm.

[0071] After preparing the extended wavelength lead-based quantum dot solution, prepare the extended wavelength lead-based quantum dot layer on the electron transport layer side. For details, please refer to Figure 1 S12 in.

[0072] Step S12: In one embodiment, a 2360 nm PbSe quantum dot layer is prepared, specifically comprising:

[0073] Dissolve 614 mg of lead iodide and 106 mg of lead bromide powder in 3 mL of N,N-dimethylformamide to obtain a metal halide ligand solution;

[0074] Dissolve 185.6 mg of arsenic selenide powder in 15 mL of n-butylamine, stir at 40°C for 12 hours, and filter to obtain the V-VI group arsenic selenide ligand;

[0075] 3 mL of metal halide ligand was mixed with 1 mL of arsenic selenide ligand and shaken to obtain monomeric ligand. The shaking time was 30 seconds.

[0076] 5 mL of PbSe quantum dots were mixed with monomeric ligands for ligand exchange. After washing twice with n-octane, toluene was added to the PbSe quantum dots, with a volume ratio of toluene to PbSe quantum dots of 2:1. The mixture was centrifuged at 9000 rpm for 3 minutes to obtain a PbSe quantum dot solid. The obtained PbSe quantum dot solid was degassed and dried for 15 minutes, and then dispersed in a mixed solvent of N,N-dimethylformamide, dimethyl sulfoxide, and n-butylamine to obtain a PbSe quantum dot ink, wherein the volume ratio of N,N-dimethylformamide, dimethyl sulfoxide, and n-butylamine was 5:3:2, and the dissolved concentration was 350 mg / mL. The PbSe quantum dot ink was spin-coated on one side of the electron transport layer to prepare an extended wavelength PbSe quantum dot layer. The spin coating speed was 2500 rpm, the spin coating acceleration was 1000 rad / s2, the spin coating time was 40 seconds, and the thickness of the PbSe quantum dot layer was 350 nm.

[0077] In a comparative example, ligand exchange was performed using only metal halide ligands to prepare a 2360nm PbSe quantum dot film. The actual comparison between the film and the PbSe quantum dot film prepared in an embodiment is shown in the figure below. Figure 5 As shown in (a), the film prepared in the control example is obviously gray, which is due to the instability of the quantum dot ink resulting in poor film density. Figure 5 (b) The SEM image further confirms that the film prepared in Example 1 is denser.

[0078] After preparing the extended wavelength lead-based quantum dot layer, prepare the hole transport layer on the extended wavelength lead-based quantum dot layer. For details, please refer to Figure 1 Step S13 in .

[0079] Step S13 specifically includes: spin coating 40 mg / mL of 880nm PbS quantum dot solution on one side of the extended wavelength PbSe quantum dot layer described in S12, with a spin coating speed of 2500 revolutions per minute, a spin coating acceleration of 1000 radians per square second, and a spin coating time of 20 seconds, using 1,2-ethanedithiol acetonitrile solution for solid-phase ligand exchange, the volume concentration of 1,2-ethanedithiol acetonitrile solution is 0.02%, and the ligand exchange time is 20 seconds, and then the exchanged film is washed twice with acetonitrile solution to remove residual ligands, and the above process is repeated 2 rounds to prepare a hole transport layer, and the hole transport layer has a thickness of 40nm.

[0080] Please continue to see Figure 2 After the hole transport layer is prepared through the above step S13, step S24 is further performed: a top electrode is prepared on the side of the hole transport layer away from the bottom electrode.

[0081] In one embodiment, a thin film is deposited by thermal evaporation to deposit an Au electrode on the hole transport layer prepared in S13, thereby forming a top electrode. The thickness of the top electrode is 100 nm.

[0082] See Figure 6 , Figure 6 The invention provides a schematic structural diagram of an extended wavelength lead-based quantum dot short-wave infrared detector. Specifically, the invention discloses an extended wavelength lead-based quantum dot short-wave infrared detector comprising, from bottom to top, a substrate 1, a bottom electrode 2, an electron transport layer 3, an extended wavelength lead-based quantum dot layer 4, a hole transport layer 5 and a top electrode 6. The substrate 1 is used to support the bottom electrode 2, the electron transport layer 3, the extended wavelength lead-based quantum dot layer 4, the hole transport layer 5 and the top electrode 6. The electron transport layer 3, the extended wavelength lead-based quantum dot layer 4, the hole transport layer 5 and the top electrode 6 are Layer 4 and hole transport layer 5 form a p-on-n type junction, the bottom electrode 2 is tin-doped indium oxide (ITO), the electron transport layer 3 is a SnO2 thin film, the electron transport layer 3 has a thickness of 50nm, the extended wavelength lead-based quantum dot layer 4 is one of PbSe or PbS quantum dots with an absorption cutoff wavelength of 1700nm to 2500nm, the extended wavelength lead-based quantum dot layer 4 has a thickness of 350nm, the hole transport layer 5 has a thickness of 40nm, and the top electrode 6 is an Au electrode with a thickness of 100nm.

[0083] The bottom electrode 2 and the top electrode 6 are used to connect positive and negative charges to conduct current and extend the wavelength. The lead-based quantum dot layer 4 is a type of PbSe or PbS quantum dot film. The PbSe or PbS quantum dot film is obtained by exchanging monomer ligands generated by the reaction of metal halide ligands and V-VI group sulfide ligands. Compared with the traditional liquid phase ligand exchange method, the use of monomer ligands for ligand exchange solves the problems of low passivation efficiency of large-size quantum dots, poor solution processability, and easy agglomeration, enhances the surface passivation effect, improves the stability of the ink colloid, and makes the prepared film denser. It reduces the defect state density and improves the carrier mobility, so that the infrared detector prepared therefrom has a lower dark current density and a higher light response.

[0084] Figure 7 The performance comparison of the 2360nm PbSe quantum dot short-wave infrared detector prepared in one embodiment of the present invention and a comparative example is shown. Figure 7 a in the figure is the current-voltage characteristic curve of the 2360nm PbSe quantum dot infrared detector. The control device exhibits a high dark current density and poor rectification characteristics, resulting in a negligible photocurrent response. In contrast, the rectification ratio of the photodiode according to an embodiment of the present invention is as high as 5000. At the same time, the dark current density is reduced by one to two orders of magnitude compared to the dark current density of the control device. Figure 7b in the figure represents the exciton peak EQE and photoresponsivity measured for the device according to an embodiment of the present invention, which are 23.4% and 0.445 A / W, respectively; Figure 7 c is the noise current spectrum of the device according to an embodiment of the present invention. At 500 Hz and zero bias, the noise current is 4.16×10 -13 A / Hz 1 / 2 ; Figure 7 The d in the figure is the wide spectrum ratio detectivity, and D* is calculated to be 3.0×10 at 500 Hz. 11 Jones, higher than the D* of commercial uncooled InGaAs photodetectors at similar wavelengths.

[0085] In summary, the extended wavelength lead-based quantum dots in the embodiment of the present invention have a response range that can be extended to the entire short-wave infrared compared to conventional wavelength quantum dots, and have a wider detection range and more application scenarios; the extended wavelength short-wave infrared quantum dot layer in the embodiment of the present invention uses monomeric ligands for ligand exchange, which solves the problems of low passivation efficiency, poor solution processability, and easy agglomeration of large-sized quantum dots compared to the traditional liquid-phase ligand exchange method, enhances the surface passivation effect, improves the stability of the ink colloid, and makes the prepared film denser; (3) The embodiment of the present invention constructs the electron transport layer, the extended wavelength lead-based quantum dot layer and the hole transport layer to form a p-on-n photovoltaic detector, which has excellent performance in the entire extended wavelength short-wave infrared band (1.7 to 2.5 μm), and the peak responsivity of the PbSe quantum dot detector with a cutoff of 2.5 μm is unique, which is 0.445 A / W, 3.0*10 higher than the detection rate. 11 Jones; The embodiment of the present invention prepares an extended wavelength lead-based quantum dot layer through monomer ligand passivation, which reduces the defect state density while improving the carrier mobility, so that the infrared detector prepared therefrom has a lower dark current density and a higher light response.

[0086] The above disclosure is only a preferred embodiment of the present invention, and certainly cannot be used to limit the scope of the rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. An extended wavelength lead-based quantum dot shortwave infrared detector, characterized by: From bottom to top, it includes: a substrate, a bottom electrode, an electron transport layer, an extended wavelength lead-based quantum dot layer, a hole transport layer and a top electrode. The electron transport layer, the extended wavelength lead-based quantum dot layer and the hole transport layer form a p-on-n type junction.

2. The extended wavelength lead-based quantum dot short-wave infrared detector according to claim 1, characterized in that: The substrate is one of quartz and sapphire, the bottom electrode is tin-doped indium oxide (ITO), the electron transport layer is SnO2, the bottom electrode thickness is 100-200nm, the electron transport layer thickness is 30-100nm, the extended wavelength lead-based quantum dot layer thickness is 200-500nm, the hole transport layer thickness is 10-60nm, and the top electrode thickness is 50-120nm.

3. The extended wavelength lead-based quantum dot short-wave infrared detector according to claim 2, characterized in that: The bottom electrode has a thickness of 150 nm, the electron transport layer has a thickness of 50 nm, the extended wavelength lead-based quantum dot layer has a thickness of 350 nm, the hole transport layer has a thickness of 40 nm, and the top electrode has a thickness of 100 nm.

4. The extended wavelength lead-based quantum dot short-wave infrared detector according to claim 1, characterized in that: The extended wavelength lead-based quantum dots in the extended wavelength lead-based quantum dot layer are one of PbSe and PbS, and the response wavelength range is 1.7 to 2.5 μm.

5. A method for preparing the extended wavelength lead-based quantum dot short-wave infrared detector according to claim 1, characterized in that: The method comprises the following steps: (1) providing a substrate; (2) preparing a bottom electrode on the substrate; (3) preparing an electron transport layer on a side of the bottom electrode away from the substrate; (4) preparing an extended wavelength lead-based quantum dot layer on a side of the electron transport layer away from the bottom electrode; (5) preparing a hole transport layer on the extended wavelength lead-based quantum dot layer; and (6) preparing a top electrode on a side of the hole transport layer away from the bottom electrode. In the step (iv), preparing the extended wavelength lead-based quantum dot layer on the side of the electron transport layer away from the bottom electrode specifically includes: preparing an extended wavelength lead-based quantum dot solution, using a monomer ligand to perform ligand exchange on the extended wavelength lead-based quantum dots to obtain an extended wavelength quantum dot ink, and spin-coating the extended wavelength quantum dot ink on the side of the electron transport layer away from the bottom electrode to prepare the extended wavelength lead-based quantum dot layer.

6. The method for preparing an extended wavelength lead-based quantum dot short-wave infrared detector according to claim 5, characterized in that: The step (ii) is to form a bottom electrode on a substrate by magnetron sputtering, the step (iii) is to form an electron transport layer on a side of the bottom electrode away from the substrate by atomic force deposition, and the step (v) is to form a hole transport layer on the extended wavelength lead-based quantum dot layer, specifically comprising: spin coating an extended wavelength lead-based quantum dot solution on a side of the extended wavelength lead-based quantum dot layer away from the electron transport layer, the spin coating speed is 1000 to 4000 revolutions per minute, the spin coating acceleration is 1000 to 2000 radians per square second, the spin coating time is 10 to 60 seconds, and the use A solid-phase ligand exchange is performed using an acetonitrile solution of 1,2-ethanedithiol, wherein the ligand exchange time is 10 to 40 seconds and the volume concentration of the acetonitrile solution of 1,2-ethanedithiol is 0.01% to 0.1%. The residual ligand is then removed by washing with an acetonitrile solution. The above process is repeated 1 to 4 times to prepare a hole transport layer. In step (six), a top electrode is prepared on a side of the hole transport layer away from the bottom electrode, specifically by depositing an Au electrode on the hole transport layer prepared in step (fifth) by thermal evaporation deposition of a thin film, thereby forming a top electrode.

7. The method for preparing an extended wavelength lead-based quantum dot short-wave infrared detector according to claim 6, characterized in that: In the step (5), the spin coating speed is 2500 revolutions per minute, the spin coating acceleration is 1000 radians per square second, the spin coating time is 20 seconds, the volume concentration of the acetonitrile solution of 1,2-ethanedithiol is 0.02%, and the ligand exchange time is 20 seconds.

8. The method for preparing an extended wavelength lead-based quantum dot short-wave infrared detector according to claim 5, characterized in that: The method for preparing the extended wavelength lead-based quantum dot solution in step (4) comprises the following steps: S1: dissolving lead chloride powder in oleylamine, degassing at room temperature, and heating under a nitrogen atmosphere to obtain an oleylamine lead precursor solution; S2: Rapidly injecting a high concentration of CdSe or ZnS quantum dot solution into the oleylamine lead precursor solution described in S1, so that the oleylamine lead precursor reacts with the CdSe or ZnS quantum dots to form PbSe or PbS quantum dot cores, wherein the concentration ratio of the CdSe or ZnS quantum dots to the CdSe or ZnS quantum dots in S3 is 2 to 5:1; S3: Continue to inject a low concentration of CdSe or ZnS quantum dot solution into the PbSe or PbS quantum dot core solution described in S2, so that the PbSe or PbS quantum dots grow to a response wavelength range of 1.7 to 2.5 μm, and the size of the CdSe or ZnS quantum dots in S2 is larger than the size of the CdSe or ZnS quantum dots in S3; S4: Cooling the quantum dot solution obtained in S3 to room temperature in a water bath, then injecting n-hexane and oleic acid to stop the reaction, stirring for a period of time, and adding a certain amount of anti-solvent to obtain extended wavelength lead-based quantum dot powder, wherein the volume of the added anti-solvent is 1 to 2 times the volume of the extended wavelength lead-based quantum dot solution (CdSe or ZnS quantum dot solution), and the anti-solvent is a mixture of one or more of ethanol, acetone, ethyl acetate, and acetonitrile; S5: dissolving the extended wavelength lead-based quantum dot powder obtained in S4 in a non-polar solvent to obtain an extended wavelength lead-based quantum dot solution, wherein the non-polar solvent is one of n-octane or n-hexane, and the concentration of the obtained extended wavelength lead-based quantum dot solution is 10 to 100 mg / mL.

9. The method for preparing an extended wavelength lead-based quantum dot short-wave infrared detector according to claim 5, characterized in that: The monomer ligand in step (4) is prepared by the following method: (1) dissolving metal halogen powder in N,N-dimethylformamide to obtain metal halogen ligand; (2) dissolving V-VI group sulfide powder in n-butylamine to obtain V-VI group sulfide ligand; (3) mixing the metal halogen ligand and the V-VI group sulfide ligand and shaking them to obtain the monomer ligand; In the step (iv), the extended wavelength lead-based quantum dots are ligand-exchanged with monomer ligands to obtain extended wavelength quantum dot ink, and the extended wavelength quantum dot ink is spin-coated on the side of the electron transport layer away from the bottom electrode to prepare the extended wavelength lead-based quantum dot layer, specifically comprising: mixing the extended wavelength lead-based quantum dot solution with the monomer ligand for ligand exchange, adding toluene, centrifuging to obtain an extended wavelength lead-based quantum dot solid, degassing and drying it, and dispersing it in a solvent (the solvent composition and ratio are DMF:DMSO:BTA:AMPY=500:300:170:30), with a dissolution concentration of 100-500 mg / mL to obtain an extended wavelength quantum dot ink, and spin-coating the extended wavelength quantum dot ink on one side of the electron transport layer to prepare the lead-based quantum dot layer, wherein the spin coating speed is 1000-4000 revolutions per minute, the spin coating acceleration is 1000-2000 radians per square second, and the spin coating time is 10-60 seconds, to obtain the lead-based quantum dot layer.

10. The method for preparing an extended wavelength lead-based quantum dot short-wave infrared detector according to claim 9, characterized in that: The solvent composition and ratio in the step (iv) are DMF:DMSO:BTA:AMPY=500:300:170:30, the dissolved concentration is 350 mg / mL, the spin coating speed is 2500 rpm, the spin coating acceleration is 1000 rad / s2, and the spin coating time is 40 seconds.

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