Mercury-sulfide colloidal quantum dot short-mid-infrared detector and its preparation method and application

Abstract

The present invention discloses a thiomercury colloidal quantum dot short and medium infrared detector, which comprises: a substrate, a bottom electrode, a blended quantum dot layer, a thiomercury quantum dot layer, a thin film layer and a top electrode in sequence; wherein the blended quantum dot layer and the thiomercury quantum dot layer are used to form an n‑on‑p type PN junction; the bottom electrode and the top electrode are used to connect positive and negative charges to conduct current; the thin film layer is used to buffer and protect the thiomercury quantum dot layer. The disclosed embodiment forms a thiomercury quantum dot device based on an n‑on‑p type PN junction with top light transmission by forming a blended quantum dot layer and a thiomercury quantum dot layer, which has the advantages of good photoelectric detection performance and low application cost in short and medium wave infrared.

Description

Technical Field

[0001] The invention belongs to the technical field of photoelectric detection, and particularly relates to a mercury-sulfide colloidal quantum dot short-mid-infrared detector and a preparation method and application thereof. Background Art

[0002] The human eye can perceive light in the range of only 300 to 800 nm, while infrared detectors can generate photoelectric responses to external infrared radiation, achieve detection and imaging beyond visual sensitivity (λ>800 nm), and visualize objects even in the absence of visible light. Therefore, infrared photodetectors are widely used in many fields such as industrial inspection, meteorological remote sensing, medical imaging, and aerospace exploration. Traditional infrared detection materials are mainly based on single crystal bulk semiconductors such as indium antimonide (InSb), indium gallium arsenide (InGaAs), and mercury cadmium telluride (HgCdTe). The cost of molecular beam epitaxial growth materials remains high, and complex processes such as flip-chip bonding also make the device cost high, limiting the application of detectors. In recent years, new semiconductor materials based on low-dimensional materials have developed rapidly, bringing new opportunities for infrared photodetectors. In particular, mercury-sulfide colloidal quantum dots have made significant progress in the development of low-cost, high-performance infrared detectors due to their wide infrared tunable spectral range, simple synthesis and preparation, and easy coupling and integration with silicon-based readout circuits.

[0003] Compared to photoconductive devices, PN junction detectors have low dark current and noise. Figure 1 Most of the existing high-performance PN junction sulfur mercury colloidal quantum dot detectors use a bottom-illuminated p-on-n structure, which has the following problems:

[0004] (1) The p-type layer in the device structure is mostly formed by spin-coating an Ag2Te quantum dot layer on the surface of HgTe quantum dots, and then inducing cation exchange with mercuric chloride to form silver-doped mercury telluride quantum dots. The silver ions in this p-type doping method tend to diffuse inward in the HgTe quantum dot film, and this diffusion is uncontrollable for forming a stable PN junction.

[0005] (2) The top electrode is mostly an opaque metal electrode, and the bottom is an infrared transparent substrate. This bottom light-transmitting mode limits its direct application in silicon-based readout circuits. In addition, there are also methods that use semi-transparent ultra-thin gold combined with ITO as the top electrode to achieve top light transmission, but this also sacrifices about 30-40% of the incident light, reducing the light response and affecting the device detector performance.

[0006] (3) Although direct deposition of transparent electrode ITO can achieve top light transmission, the high-energy particles in the magnetron sputtering deposition process have a great destructive effect on the colloidal quantum dot layer. Direct sputtering of ITO without any buffer layer protection will cause interface defects, increase the dark current of the device, and reduce the performance of the detector.

[0007] Therefore, developing a PN junction type mercury-sulfide colloidal quantum dot detector that can overcome the many problems of the above-mentioned p-on-n structure will have great development prospects. Summary of the invention

[0008] The technical problem to be solved by the present invention is that in order to solve the various deficiencies of the existing p-on-n structure short mid-infrared detector, the present invention provides a mercury-sulfide colloidal quantum dot short mid-infrared detector and a preparation method and application thereof.

[0009] In order to solve the above technical problems, the embodiment of the present invention provides a mercury-sulfide colloidal quantum dot short mid-infrared detector, which comprises: a substrate, a bottom electrode, a blended quantum dot layer, a mercury-sulfide quantum dot layer, a thin film layer and a top electrode in sequence;

[0010] Wherein, the blended quantum dot layer and the mercury-sulfide quantum dot layer are used to form an n-on-p type PN junction;

[0011] The bottom electrode and the top electrode are used to connect positive and negative charges to conduct current;

[0012] The thin film layer is used to buffer and protect the thiol-mercury quantum dot layer.

[0013] Preferably, the blended quantum dot layer comprises: HgTe quantum dots and Ag2Te quantum dots, and the synergistic effect of the HgTe quantum dots and the Ag2Te quantum dots forms strong p-type doping.

[0014] Preferably, the mercury-sulfide quantum dot layer includes any one of HgSe quantum dots, HgS quantum dots, and HgTe quantum dots having an absorption cutoff wavelength of 1500 nm to 4000 nm.

[0015] Preferably, the thin film layer includes: any one of Bi2S3 and Bi2Se3.

[0016] Preferably, the bottom electrode comprises: any one or more of Au, tin-doped indium oxide (ITO).

[0017] Preferably, the top electrode is an ITO transparent electrode.

[0018] Preferably, the thickness of the mercury-sulfur quantum dot layer is greater than the thickness of the blended quantum dot layer.

[0019] In addition, the present invention also provides a method for preparing a sulfide-mercury colloidal quantum dot short mid-infrared detector, which is used to prepare the above-mentioned sulfide-mercury colloidal quantum dot short mid-infrared detector, and the method comprises:

[0020] 1) Fabricating a bottom electrode: depositing a bottom electrode on a substrate;

[0021] 2) Preparation of blended quantum dot layer:

[0022] 2.1) Preparing a HgTe quantum dot solution: adding a tellurium precursor to a mercuric chloride oleylamine solution containing a long-chain ligand to synthesize a HgTe quantum dot solution with an absorption cutoff wavelength of 1300nm to 1700nm; wherein the tellurium precursor is telluride of trioctylphosphine (TOPTe);

[0023] 2.2) Preparation of Ag2Te quantum dot solution: Injecting tellurium precursor into an octadecene solution of silver salt and dodecanethiol ligand to synthesize Ag2Te quantum dot solution;

[0024] 2.3) Preparing a blended quantum dot layer: mixing two quantum dot solutions of Ag2Te and HgTe uniformly and then spin coating them on the bottom electrode; soaking the bottom electrode in a methanol solution of HgCl2, and then exchanging solid ligands with an ethanol solution of 1,2-ethanedithiol; washing twice with ethanol after each exchange; repeating 2-6 cycles to obtain the blended quantum dot layer;

[0025] 3) Preparation of sulfur-mercury quantum dot layer:

[0026] 3.1) Preparation of HgTe quantum dot solution: adding tellurium precursor to mercuric chloride oleylamine solution containing long-chain ligands to synthesize HgTe quantum dot solution;

[0027] 3.2) Preparation of HgSe quantum dot solution: Injecting selenourea dissolved in oleylamine into a long-chain ligand solution of mercuric chloride oleylamine to synthesize an n-type HgSe quantum dot solution;

[0028] 3.3) Preparation of HgS quantum dot solution: injecting a sulfur source dissolved in oleylamine into a long-chain ligand solution of mercuric chloride oleylamine to synthesize an n-type HgS quantum dot solution;

[0029] 3.4) Preparing a thiomercuric quantum dot layer: spin coating the HgTe colloidal quantum dot solution, the n-type HgSe quantum dot solution or the n-type HgS quantum dot solution on the blended quantum dot layer; after each coating, soaking the blended quantum dot layer in a methanol solution of HgCl2, and then performing solid ligand exchange with an ethanol solution containing 1,2-ethanedithiol and hydrochloric acid; wherein, washing with ethanol is performed twice after each exchange; repeating 10-14 cycles to obtain the thiomercuric quantum dot layer;

[0030] 4) preparing a thin film layer: depositing any one of Bi2S3 or Bi2Se3 thin films on the sulfide-mercury quantum dot layer;

[0031] 5) Preparation of top electrode: Depositing a transparent ITO electrode on the thin film layer.

[0032] Preferably, the mass ratio of the Ag2Te quantum dots to the HgTe quantum dots is 1:1 to 1:8;

[0033] Preferably, the thickness of the blended quantum dot layer is 50 to 100 nm.

[0034] Preferably, the thickness of the mercury-sulfur quantum dot layer is 200-500 nm.

[0035] Preferably, the film layer has a thickness of 10 to 60 nm.

[0036] Preferably, the top electrode has a thickness of 50 to 120 nm.

[0037] A mercury-sulfide colloidal quantum dot infrared detector is used in the field of 1100-2500nm short-wave detection and / or 3000-5000nm medium-wave detection.

[0038] Implementing the embodiments of the present invention has the following beneficial effects:

[0039] (1) In the embodiment of the present invention, the mixed quantum dot layer and the mercury-sulfide quantum dot layer are constructed to form an n-on-p type PN junction. Compared with the p-on-n type detector, the device has a specific detection rate of 3.2*10 in the short-wave infrared band. 11 Jones has better performance and is well applied in the detection of shortwaves between 1100 and 2500 nm and / or medium waves between 3000 and 5000 nm.

[0040] (2) The blended quantum dot layer in the embodiment of the present invention is formed by mixing Ag2Te and HgTe quantum dots and utilizing the synergistic effect between binary quantum dots to form p-type doping. Under the solid ligand exchange induced by HgCl2, Ag2Te as a p-type dopant is evenly distributed in the HgTe quantum dot film, so that the doping of the p-type layer can be controlled by adjusting the mixing ratio.

[0041] (3) The embodiment of the present invention introduces a thin film layer on the sulfide-mercury quantum dot layer, and uses the Bi2S3 or Bi2Se3 thin film as a buffer layer to block high-energy particles from damaging the sulfide-mercury quantum dot layer, and also as an electron transport layer to reduce interface defects and dark current. In addition, its high infrared transmittance helps the infrared absorption of the quantum dot layer, thereby improving the responsiveness of the device.

[0042] (4) The embodiment of the present invention is advantageous for realizing integration with a focal plane array of a top-incident mode by designing the top electrode as an ITO transparent electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative work.

[0044] Figure 1 It is a schematic diagram of the structure of a p-on-n type mercury-sulfide colloidal quantum dot infrared detector in the prior art;

[0045] Figure 2 A schematic diagram of the structure of a mercury-sulfide colloidal quantum dot short mid-infrared detector provided for the implementation of the present invention;

[0046] Figure 3 Absorption spectrum of Ag2Te and HgTe quantum dots in a mixed quantum dot layer in a mercury-sulfide colloidal quantum dot short-mid-infrared detector provided for the implementation of the present invention;

[0047] Figure 4 A field effect transistor transfer characteristic curve diagram of a blended quantum dot layer and a thiomercuric group quantum dot layer in a thiomercuric group colloidal quantum dot short mid-infrared detector provided for the implementation of the present invention;

[0048] Figure 5 A rectification characteristic curve of a mercury-sulfide colloidal quantum dot short-mid-infrared detector provided for the implementation of the present invention;

[0049] Figure 6 A scanning electron microscope cross-sectional view of a mercury-sulfide colloidal quantum dot short mid-infrared detector provided for the implementation of the present invention;

[0050] Figure 7 A photocurrent response spectrum of a mercury-sulfide colloidal quantum dot short-mid-infrared detector provided for the implementation of the present invention;

[0051] Figure 8 A transmission spectrum diagram of a mercury-sulfide colloidal quantum dot short mid-infrared detector before and after the top electrode is covered on the thin film layer provided for the implementation of the present invention;

[0052] Fig. 9 A specific detectivity diagram of a mercury-sulfide colloidal quantum dot short-mid-infrared detector provided for the implementation of the present invention. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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.

[0054] like Figure 1 As shown, the present embodiment discloses a sulfur-mercury colloidal quantum dot short mid-infrared detector, which includes, from bottom to top, a substrate 10, a bottom electrode 20, a blended quantum dot layer 30, a sulfur-mercury quantum dot layer 40, a thin film layer 50 and a top electrode 60. Among them, the blended quantum dot layer 30 and the sulfur-mercury quantum dot layer 40 are used to form an n-on-p type PN junction. The bottom electrode 20 and the top electrode 60 are used to connect positive and negative charges to conduct current. Specifically, the bottom electrode 20 is used to connect positive charges, and the top electrode 60 is used to connect negative charges. The thin film layer 50 is used to buffer the sulfur-mercury quantum dot layer 40. When infrared light waves are incident, their high-energy particles cannot damage the sulfur-mercury quantum dot layer 40. And the thin film layer 50 is also used for electron transmission, thereby reducing interface defects in the sulfur-mercury colloidal quantum dot short mid-infrared detector and reducing dark current. The substrate 10 is used to support the bottom electrode 20 , the blended quantum dot layer 30 , the sulfide-mercury quantum dot layer 40 , the thin film layer 50 and the top electrode 60 .

[0055] The bottom electrode 20 includes any one or more of Au, tin-doped indium oxide (ITO).

[0056] The blended quantum dot layer 30 includes: HgTe quantum dots and Ag2Te quantum dots, and the synergistic effect of the HgTe quantum dots and the Ag2Te quantum dots forms a strong p-type doping. And the mass ratio of the Ag2Te quantum dots to the HgTe quantum dots is 1:1 to 1:8. The thickness of the blended quantum dot layer 30 is 50 to 100 nm.

[0057] The sulfide-mercury quantum dot layer 40 includes any one of weak p-type sulfide-mercury quantum dots, intrinsic i-type sulfide-mercury quantum dots and n-type sulfide-mercury quantum dots. Among them, HgTe quantum dots with an absorption cutoff wavelength of 1500nm to 2500nm are weak p-type sulfide-mercury quantum dots, HgTe quantum dots with an absorption cutoff wavelength of 2500nm to 4000nm are intrinsic i-type sulfide-mercury quantum dots, and HgSe quantum dots and HgS quantum dots are n-type sulfide-mercury quantum dots. Specifically, the sulfide-mercury quantum dot layer 40 includes any one of HgSe quantum dots, HgS quantum dots and HgTe quantum dots with an absorption cutoff wavelength of 1500nm to 4000nm. The thickness of the sulfide-mercury quantum dot layer 40 is greater than that of the blended quantum dot layer 30.

[0058] The thin film layer 50 includes any one of Bi2S3 and Bi2Se3.

[0059] The top electrode is an ITO transparent electrode.

[0060] The thickness of the mixed quantum dot layer 30, the sulfur-mercury group quantum dot layer 40, the thin film layer 50 and the top electrode 60 in the sulfur-mercury group colloidal quantum dot short mid-infrared detector are specifically as follows:

[0061] The thickness of the blended quantum dot layer 30 is 50-100 nm, with 80 nm being the most preferred thickness.

[0062] The thickness of the mercury-sulfide quantum dot layer 40 is 200-500 nm, with 400 nm being the most preferred thickness.

[0063] The thickness of the thin film layer 50 is 10-60 nm, and if it is a Bi2S3 thin film, the best thickness is 35 nm, and if it is a Bi2Se3 thin film, the best thickness is 25 nm.

[0064] The thickness of the top electrode 60 is 50-120 nm, with 100 nm being the most preferred thickness.

[0065] The present invention also discloses a method for preparing a mercury-sulfur colloidal quantum dot short- and medium-wave infrared detector, which is used to prepare the mercury-sulfur colloidal quantum dot short- and medium-wave infrared detector. The method comprises the following steps:

[0066] 1) Fabricating the bottom electrode 20 : depositing the bottom electrode 20 on the substrate 10 .

[0067] 2) Preparation of blended quantum dot layer 30:

[0068] 2.1) Preparation of HgTe quantum dot solution: A tellurium precursor is added to a mercuric chloride oleylamine solution containing a long-chain ligand by continuous titration to synthesize a HgTe quantum dot solution with an absorption cutoff wavelength of 1300nm to 1700nm; wherein the tellurium precursor is telluride of trioctylphosphine (TOPTe).

[0069] 2.2) Preparation of Ag2Te quantum dot solution: The tellurium precursor was injected into an octadecene solution of silver salt and dodecanethiol ligand by hot injection to synthesize Ag2Te colloidal quantum dot solution.

[0070] 2.3) Preparing a blended quantum dot layer: Evenly mix the two quantum dots of Ag2Te and HgTe and then spin-coat them on the bottom electrode; soak the spin-coated bottom electrode 20 with a methanol solution of HgCl2, and then use an ethanol solution of 1,2-ethanedithiol for solid ligand exchange; wherein, wash twice with ethanol after each exchange; repeat 2-6 cycles to prepare the blended quantum dot layer 30.

[0071] 3) Preparation of sulfur-mercury quantum dot layer 40:

[0072] 3.1) Preparation of HgTe quantum dot solution: Slowly add tellurium precursor into mercuric chloride oleylamine solution containing long-chain ligands. Adjusting the synthesis temperature can change the absorption cutoff wavelength of quantum dots to synthesize HgTe colloidal quantum dots.

[0073] 3.2) Preparation of HgSe quantum dot solution: Selenourea dissolved in oleylamine was injected into the long-chain ligand solution of mercuric chloride oleylamine to synthesize n-type HgSe quantum dots.

[0074] 3.3) Preparation of HgS quantum dot solution: Injecting a sulfur source dissolved in oleylamine into a long-chain ligand solution of mercuric chloride oleylamine to synthesize n-type HgS quantum dots.

[0075] 3.4) Spin coating any one of the HgTe colloidal quantum dots, n-type HgSe quantum dots or n-type HgS quantum dots on the blended quantum dot layer 30; after each coating, immerse the blended quantum dot layer in a methanol solution of HgCl2, and then perform solid ligand exchange with an ethanol solution containing 1,2-ethanedithiol and hydrochloric acid; wherein, wash twice with ethanol after each exchange; repeat 10-14 cycles to prepare the thiomercury quantum dot layer 40.

[0076] 4) Preparing the thin film layer 50 : Depositing a Bi2S3 or Bi2Se3 thin film on the sulfide-mercury quantum dot layer 40 by thermal evaporation deposition, and finally forming the thin film layer 50 .

[0077] 5) Preparing the top electrode 60 : Using magnetron sputtering to deposit thin films, a transparent ITO electrode is deposited on the thin film layer 50 , and finally the top electrode 60 is formed.

[0078] Before making the bottom electrode 20, a substrate is also required. The substrate includes: any one of glass, silicon wafer, quartz wafer, sapphire wafer or flexible substrate. The bottom electrode 20 is a circular electrode with a diameter of 2 mm. The bottom electrode 20 includes: any one or more of Au and ITO. It is preferred to prepare the ITO transparent bottom electrode 20 on a glass substrate.

[0079] In step 2.1), the preparation process of the tellurium precursor is as follows: take tellurium powder (Te) and trioctylphosphine (TOP), heat and stir to form a yellow clear tellurium precursor solution. The molar ratio of Te to HgCl2 is 2:1, and the temperature is 50°C to 70°C. After the HgTe quantum dot solution is synthesized, it is washed once with ethanol and then dispersed in an octane solution for standby use.

[0080] In the step 2.2), the preparation of the Ag2Te quantum dot solution is specifically as follows: in a nitrogen environment, a certain amount of AgNO3 powder is weighed and dissolved in oleic acid and oleylamine at 120°C to form a silver precursor solution, and a tellurium precursor (TOPTe) is injected into the silver precursor solution at 140°C by hot injection to synthesize Ag2Te colloidal quantum dots with an absorption cutoff wavelength of 1450 to 1800nm, and then a quenching solution is added to terminate the reaction and wash. The quenching solution is prepared from tetrachloroethylene and dodecyl mercaptan, and the washing solvent is ethanol. After washing once, it is dispersed in an octane solution for standby use.

[0081] In the step 2.3), the mass ratio of the Ag2Te quantum dots to the HgTe quantum dots is 1:1 to 1:8, preferably the mass ratio of the Ag2Te quantum dots to the HgTe quantum dots is 1:3. The molar solubility of the methanol solution of HgCl2 is 5mM to 40mM (1mM = 1mmol / mL), preferably 20mM. The volume solubility of the ethanol solution of 1,2-ethanedithiol is 0.05‰ to 1‰, preferably 0.2‰. The spin coating speed is 1000 to 4000 revolutions per minute, the spin coating acceleration is 100 to 1000 radians per square second, and the spin coating time is 5 to 30 seconds each time. Preferably, the spin coating speed is 12000 revolutions per minute, the spin coating acceleration is 500 radians per square second, and the spin coating time is 20 seconds each time. The thickness of the blended quantum dot layer 30 is 50 to 100nm, preferably 80nm.

[0082] In the step 3), the preparation process of the tellurium precursor is the same as that in step 2). The synthesis temperature is 60°C to 90°C. The molar solubility of the methanol solution of HgCl2 is 5mM to 40mM (1mM = 1mmol / mL), preferably 20mM. The volume solubility of the ethanol solution of 1,2-ethanedithiol is 0.05‰ to 1‰, preferably 0.2‰. The spin coating speed is 1000 to 4000 revolutions per minute, the spin coating acceleration is 100 to 1000 radians per square second, and the spin coating time is 5 to 30 seconds each time. Preferably, the spin coating speed is 12000 revolutions per minute, the spin coating acceleration is 500 radians per square second, and the spin coating time is 20 seconds each time. The thickness of the thiomercuric quantum dot layer 40 is 200 to 500nm, preferably 400nm. The prepared HgTe quantum dot solution, HgSe quantum dot solution and HgS quantum dot solution all need to be washed once with ethanol and then dispersed in an octane solution for later use.

[0083] In step 4), the specific steps of preparing the thin film layer 50 are as follows: taking a certain amount of Bi2S3 or Bi2Se3 powder with a purity greater than 99.9%, and depositing one of the Bi2S3 or Bi2Se3 thin films on the sulfide-mercury quantum dot layer 40 by thermal evaporation deposition. The Bi2S3 thin film deposition thickness is 20 to 60 nm, preferably 35 nm in the present invention; the Bi2Se3 thin film deposition thickness is 10 to 40 nm, preferably 25 nm in the present invention.

[0084] In the step 5), the thickness of the top electrode 60 is 50-120 nm, with 100 nm being the most preferred thickness.

[0085] Embodiment 1

[0086] In addition, the present invention also provides a specific method for preparing a mercury-sulfide colloidal quantum dot short- and medium-wave infrared detector. The method comprises:

[0087] 1) Providing a substrate 10: The substrate 10 is made of glass, and has dimensions of length×width×thickness=25 mm×25 mm×1 mm.

[0088] 2) Fabrication of the bottom electrode 20 : An ITO film with a thickness of 180 nm is magnetron sputtered on the glass substrate 10 as the bottom electrode 20 .

[0089] 3) Preparation of blended quantum dot layer 30:

[0090] 3.1) Preparation of HgTe colloidal quantum dot solution: TOPTe solution was added to oleylamine solution containing 0.9 mmol HgCl2 by continuous titration, wherein the molar ratio of Te to HgCl2 was about 2:1. HgTe quantum dot solution with an absorption cutoff wavelength of about 1800 nm was synthesized at 65°C. After washing once with ethanol, it was dispersed in octane solution for later use.

[0091] 3.2) Preparation of Ag2Te colloidal quantum dot solution: In a nitrogen environment, weigh a certain amount of AgNO3 powder and dissolve it in oleic acid and oleylamine at 120°C to form a silver precursor solution. Use hot injection method to inject TOPTe solution into the silver precursor solution at 140°C to synthesize Ag2Te colloidal quantum dot solution with an absorption cutoff edge of 1650nm, and then add quenching solution to terminate the reaction and wash. The quenching solution is prepared by tetrachloroethylene and dodecyl mercaptan, and the washing solvent is ethanol. After washing once, disperse it in octane solution for use.

[0092] See also Figure 3 The absorption cutoff edges of the HgTe quantum dots and Ag2Te quantum dots used in the blended quantum dot layer 30 synthesized in this embodiment are approximately 1800 nm and 1650 nm, respectively.

[0093] 3.3) Preparation of a blended quantum dot layer 30: The HgTe quantum dot solution and the Ag2Te quantum dot solution are mixed evenly and then spin-coated on the bottom electrode 20. The spin-coated bottom electrode 20 is first soaked in a methanol solution of HgCl2 for 20 seconds, and then solid ligand exchange is performed with an ethanol solution of 1,2-ethanedithiol. After each exchange, ethanol is used to wash twice, and this step is repeated for a total of 4 cycles on the bottom electrode 20 to generate a Ag2Te and HgTe blended quantum dot layer 30.

[0094] Wherein, Ag2Te quantum dots and HgTe quantum dots are mixed in a mass ratio of 1:3. The molar solubility of HgCl2 in methanol solution is 20mM. The volume solubility of 1,2-ethanedithiol in ethanol solution is 0.2‰. The spin coating speed is 2500 revolutions per minute, the spin coating acceleration is 500 radians per square second, and the spin coating time is 20 seconds each time. The thickness of the Ag2Te and HgTe blended quantum dot layer 30 is 80nm.

[0095] 4) Preparation of sulfur-mercury quantum dot layer 40:

[0096] 4.1) Preparation of HgTe quantum dot solution: 1 mmol / mL TOPTe solution was added to 0.9 mmol HgCl2 dissolved in oleylamine solution by continuous titration. The molar ratio of Te to HgCl2 was about 2:1. The temperature of the mixed solution was controlled at 60°C to 90°C to obtain a synthetic HgTe quantum dot solution with an absorption cutoff wavelength of 1500nm to 4000nm. After washing once with ethanol, it was dispersed in an octane solution for later use.

[0097] 4.2) After each coating of the HgTe colloidal quantum dot solution on the Ag2Te and HgTe blended quantum dot layer 30, it is first soaked in a methanol solution of HgCl2, and then solid ligand exchange is performed with an ethanol solution containing 1,2-ethanedithiol and hydrochloric acid. Wherein, ethanol is used to wash twice after each exchange. The above steps are repeated cyclically for a total of 12 cycles to obtain a sulfmercuric quantum dot layer 40, specifically, a HgTe quantum dot layer. And the sulfmercuric quantum dot layer 40 forms an n-on-p type PN junction with the Ag2Te and HgTe blended quantum dot layer 30.

[0098] The molar solubility of the methanol solution of HgCl2 is 20 mM. The volume fraction ratio of 1,2-ethanedithiol, hydrochloric acid and ethanol is 1:1:30. The spin coating speed is 12000 revolutions per minute, the spin coating acceleration is 500 radians per square second, and the spin coating time is 20 seconds each time. The thickness of the HgTe quantum dot layer is about 400 nm.

[0099] See also Figure 4 , the field effect transistor transfer curve of the mercury-sulfide quantum dot layer 40 is compared with that of the Ag2Te and HgTe blended quantum dot layer 30, specifically, the HgTe quantum dot layer for light absorption is compared with the Ag2Te and HgTe blended quantum dot layer 30. The p-type doping of the Ag2Te and HgTe blended quantum dot layer 30 is more obvious.

[0100] 5) Preparation of bismuth-sulfur thin film layer 50: Take 100 mg of Bi2S3 powder with a purity greater than 99.9%, and use thermal evaporation to deposit a 35 nm Bi2S3 thin film on the HgTe quantum dot layer to obtain the bismuth-sulfur thin film layer 50, specifically, obtain the Bi2S3 thin film layer.

[0101] 6) Preparation of transparent top electrode 60: Using magnetron sputtering to deposit thin films, a 100 nm ITO electrode is deposited on the Bi2S3 thin film layer to obtain a transparent top electrode 60, specifically, a transparent ITO thin film electrode. The deposition thickness of the transparent ITO thin film electrode is 100 nm.

[0102] See also Figure 5-Figure 7 It can be seen that the mercury-sulfide colloidal quantum dot short- and medium-wave infrared detector has good PN junction rectification characteristics, the interfaces of each layer of the device are clearly visible, and there is a light detection response near the infrared light with a wavelength of 1700nm.

[0103] See also Figure 8 The transmission spectrum of the Bi2S3 thin film layer before and after sputtering the transparent ITO thin film electrode shows that the sulfur-mercury colloidal quantum dot short- and medium-wave infrared detector proposed in the present invention has the function of top transmission. Fig. 9The specific detection rate diagram of the mercury-sulfide colloidal quantum dot short- and medium-wave infrared detector proposed in the present invention shows that the detector has good detection performance.

[0104] In summary, the short- and medium-wave infrared detector of the thiomercuric group colloidal quantum dots designed in the present invention forms an n-on-p type PN junction by using the blended quantum dot layer 30 and the thiomercuric group quantum dot layer 40, and then uses the Bi2S3 or Bi2Se3 thin film to form the thin film layer 50. It not only has good detection performance for short and medium infrared waves, but also can achieve top light transmission without destroying the internal structure of the thiomercuric group quantum dot layer 40.

[0105] The sulfur-mercury colloidal quantum dot short- and medium-wave infrared detector designed by the present invention has good application in the field of 1100-2500nm short-wave detection and / or 3000-5000nm medium-wave detection. Specifically, the sulfur-mercury colloidal quantum dot short- and medium-wave infrared detector designed by the present invention can be applied to the night vision system of the car in the short-wave infrared field because it can be imaged through the windshield to enhance the night vision detection capability. It can also penetrate opaque plastics, silicon wafers, etc., so it can be used in non-destructive testing, material identification, etc. In the medium-wave infrared field, it can be applied to medical care, security, and security inspection.

[0106] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of 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 according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A mercury-sulfide colloidal quantum dot short mid-infrared detector, characterized in that: Including in order: Substrate, bottom electrode, blended quantum dot layer, mercury-sulfide quantum dot layer, thin film layer and top electrode; Wherein, the blended quantum dot layer and the mercury-sulfide quantum dot layer are used to form an n-on-p type PN junction; The bottom electrode and the top electrode are used to connect positive and negative charges to conduct current; The thin film layer is used to buffer and protect the thiol-mercury quantum dot layer; Wherein, the preparation method of the blended quantum dot layer comprises: The two quantum dot solutions of Ag2Te and HgTe are mixed evenly and then spin-coated on the bottom electrode; the bottom electrode is immersed in a methanol solution of HgCl2, and then a solid ligand exchange is performed using an ethanol solution of 1,2-ethanedithiol; wherein, after each exchange, ethanol is used for washing twice; and 2-6 cycles are repeated to obtain the blended quantum dot layer.

2. The mercury-sulfide colloidal quantum dot short mid-infrared detector according to claim 1, characterized in that: The blended quantum dot layer includes: HgTe quantum dots and Ag2Te quantum dots, and the synergistic effect of the HgTe quantum dots and the Ag2Te quantum dots forms strong p-type doping; The mercury-sulfide quantum dot layer includes any one of HgSe quantum dots, HgS quantum dots, and HgTe quantum dots with an absorption cutoff wavelength of 1500nm to 4000nm; The thin film layer includes any one of Bi2S3 and Bi2Se3.

3. The mercury-sulfide colloidal quantum dot short mid-infrared detector according to claim 2, characterized in that: The bottom electrode comprises: any one or more of Au, tin-doped indium oxide (ITO); The top electrode is an ITO transparent electrode.

4. The mercury-sulfide colloidal quantum dot short mid-infrared detector according to claim 3, characterized in that: The thickness of the mercury-sulfur quantum dot layer is greater than the thickness of the blended quantum dot layer.

5. A method for preparing the mercury-sulfide colloidal quantum dot short mid-infrared detector according to any one of claims 1 to 4, characterized in that: The method comprises: 1) Fabricating a bottom electrode: depositing a bottom electrode on a substrate; 2) Preparation of blended quantum dot layer: 2.1) Preparing a HgTe quantum dot solution: adding a tellurium precursor to a mercuric chloride oleylamine solution containing a long-chain ligand to synthesize a HgTe quantum dot solution with an absorption cutoff wavelength of 1300nm to 1700nm; wherein the tellurium precursor is telluride of trioctylphosphine (TOPTe); 2.2) Preparation of Ag2Te quantum dot solution: Injecting tellurium precursor into an octadecene solution of silver salt and dodecanethiol ligand to synthesize Ag2Te quantum dot solution; 2.3) Preparing a blended quantum dot layer: mixing two quantum dot solutions of Ag2Te and HgTe uniformly and then spin coating them on the bottom electrode; soaking the bottom electrode in a methanol solution of HgCl2, and then exchanging solid ligands with an ethanol solution of 1,2-ethanedithiol; washing twice with ethanol after each exchange; repeating 2-6 cycles to obtain the blended quantum dot layer; 3) Preparation of sulfur-mercury quantum dot layer: 3.1) Preparation of HgTe quantum dot solution: adding tellurium precursor to mercuric chloride oleylamine solution containing long-chain ligands to synthesize HgTe quantum dot solution; 3.2) Preparation of HgSe quantum dot solution: Injecting selenourea dissolved in oleylamine into a long-chain ligand solution of mercuric chloride oleylamine to synthesize an n-type HgSe quantum dot solution; 3.3) Preparation of HgS quantum dot solution: injecting a sulfur source dissolved in oleylamine into a long-chain ligand solution of mercuric chloride oleylamine to synthesize an n-type HgS quantum dot solution; 3.4) Preparing a thiomercuric quantum dot layer: spin coating the HgTe quantum dot solution, the n-type HgSe quantum dot solution or the n-type HgS quantum dot solution on the blended quantum dot layer; after each coating, soaking the blended quantum dot layer in a methanol solution of HgCl2, and then performing solid ligand exchange with an ethanol solution containing 1,2-ethanedithiol and hydrochloric acid; wherein, washing with ethanol is performed twice after each exchange; repeating 10-14 cycles to obtain the thiomercuric quantum dot layer; 4) preparing a thin film layer: depositing any one of Bi2S3 or Bi2Se3 thin films on the sulfide-mercury quantum dot layer; 5) Preparation of top electrode: Depositing a transparent ITO electrode on the thin film layer.

6. The preparation method according to claim 5, characterized in that: The mass ratio of the Ag2Te quantum dots to the HgTe quantum dots is 1:1 to 1:8; The thickness of the blended quantum dot layer is 50-100 nm.

7. The preparation method according to claim 5, characterized in that: The thickness of the mercury-sulfur quantum dot layer is 200-500 nm.

8. The preparation method according to claim 5, characterized in that: The film layer has a thickness of 10 to 60 nm.

9. The preparation method according to claim 5, characterized in that: The thickness of the top electrode is 50-120 nm.

10. Use of the mercury-sulfide colloidal quantum dot infrared detector according to any one of claims 1 to 4 in the field of 1100 to 2500 nm short-wave detection and / or 3000 to 5000 nm medium-wave detection.

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