High-sensitivity wide-spectrum true color quantum dot image sensor and preparation method thereof

Abstract

The invention discloses a high-sensitivity wide-spectrum true color quantum dot image sensor and a preparation method thereof, and belongs to the technical field of image sensors and preparation thereof. A metal lower electrode layer; a wide-spectrum quantum dot material electron transport layer, wherein the quantum dot material is a P-type quantum dot film; a wide-spectrum quantum dot material hole transport layer with a micro-nano light trapping structure, wherein the quantum dot material is an N-type quantum dot film; a transparent upper electrode layer; a support layer; and a light polarizing layer. By adopting the PbS quantum dot or HgTe quantum dot material, the wide spectral response can be realized, and the CMOS (complementary metal oxide semiconductor) process is good in compatibility; the light polarization layer is excellent in light splitting effect and high in light utilization rate; meanwhile, the pixels are composed of red, green, blue and infrared sub-pixels, the color information of the substance is obtained through the red, green and blue sub-pixels, the material information of the substance is obtained through the infrared sub-pixels, and therefore the high-sensitivity wide-spectrum true-color quantum dot image sensor is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of image sensors and preparation thereof, and in particular relates to a high-sensitivity, wide-spectrum true-color quantum dot image sensor and a preparation method thereof. Background Art

[0002] Imaging technology is the core means of modern information collection, and it is of great significance to my country's national defense construction and economic and social development. With the rapid development of informationization and intelligence of modern military equipment, it is necessary to obtain wide-spectrum (400-2500nm) information of targets in complex environments. Due to the band gap limitation, the response wavelength of silicon materials can only reach 1100nm in the near infrared. Traditional infrared bulk materials such as InGaAs, HgCdTe, and InSb are incompatible with CMOS technology, so they need to be mixed and integrated with indium columns and readout circuits by flip-chip welding, which increases the manufacturing cost of imaging chips and reduces production efficiency and yield. At the same time, the size of indium columns also limits the further reduction of the size of detector pixels. In addition, traditional high-sensitivity photodetectors use microlenses for light convergence, reduce light loss, and improve sensor sensitivity. At the same time, filters are used to split the light to produce true color imaging, which leads to large size and power consumption of such image sensors, making it difficult to meet the needs of weapons and equipment such as micro-unmanned platforms and single-soldier portable imaging systems.

[0003] Therefore, there is an urgent need to provide a quantum dot image sensor with high sensitivity, wide spectrum, true color, small size and low power consumption, and the preparation method is simple and easy. Summary of the invention

[0004] In view of the above technical problems, the present invention proposes a high-sensitivity, wide-spectrum, true-color quantum dot image sensor and a preparation method thereof.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention:

[0007] A high-sensitivity wide-spectrum true-color quantum dot image sensor, comprising, from bottom to top:

[0008] Readout circuit layer;

[0009] A metal lower electrode layer;

[0010] A broad spectrum quantum dot material electron transport layer (thickness 30-60 nm), wherein the quantum dot material is a P-type quantum dot film;

[0011] A hole transport layer of a wide-spectrum quantum dot material with a micro-nano light-trapping structure (with a thickness of 400 - 1000 nm), where the quantum dot material is an N-type quantum dot thin film; the micro-nano light-trapping structure is prepared by nanoimprinting from the upper surface of the hole transport layer of the wide-spectrum quantum dot material, and its upper surface needs to have a large contact area. The shape of the micro-nano light-trapping structure is columnar, frustum-shaped or inverted pencil-shaped, and the height is 40% - 100% of the hole transport layer;

[0012] A transparent upper electrode layer;

[0013] A support layer (with a thickness of 0.5 - 1.5 μm); and a light polarization layer.

[0014] Preferably, within each pixel unit of the metal lower electrode layer, four sub-pixel units in a "field" shape are arranged; that is, the metal lower electrode is the four lower electrodes corresponding to the red, green, blue, and infrared four sub-pixel units within each pixel unit;

[0015] The distance between two adjacent sub-pixel units is 0.5 μm - 2 μm.

[0016] Preferably, the wide-spectrum quantum dot material used in the wide-spectrum quantum dot material electron transport layer and the wide-spectrum quantum dot material hole transport layer is a wide-spectrum PbS quantum dot material or a HgTe quantum dot material.

[0017] Preferably, the preparation process of the wide-spectrum quantum dot material electron transport layer or the wide-spectrum quantum dot material hole transport layer is as follows:

[0018] Deposit a wide-spectrum PbS or HgTe quantum dot dispersion liquid on the metal lower electrode layer, and then perform ligand exchange of the quantum dot thin film using an exchange solution to obtain the wide-spectrum quantum dot material electron transport layer;

[0019] Deposit a wide-spectrum PbS or HgTe quantum dot dispersion liquid on the wide-spectrum quantum dot material electron transport layer, and then perform ligand exchange of the quantum dot thin film using an exchange solution to obtain the wide-spectrum quantum dot material hole transport layer.

[0020] Preferably,

[0021] When preparing the wide-spectrum quantum dot material electron transport layer, the exchange solution used is an acetonitrile solution of ethanedithiol;

[0022] When preparing the wide-spectrum quantum dot material hole transport layer, the exchange solution used is a methanol solution of tetrabutylammonium iodide (TBAI).

[0023] Preferably, the transmittance of the transparent upper electrode layer in the wide-spectrum range is greater than 80%;

[0024] Square resistance less than 30Ω·sq -1 ;

[0025] Preferably, it is a silver nanowire film or a graphene film.

[0026] Preferably, the support layer is a silicon oxide layer or an aluminum oxide film layer. The transparent upper electrode layer is deposited by rate evaporation.

[0027] Preferably, the light polarizing layer is a silicon nitride film layer, a barium titanate film layer, or a borosilicate glass film layer;

[0028] and having a micro-nano structure that penetrates the light polarization layer;

[0029] The preparation process of the light polarization layer is as follows: firstly, a silicon nitride film layer, a barium titanate film layer or a borosilicate glass film layer is deposited on the top of the support layer, and then a micro-nano structure capable of polarizing light is prepared by photolithography and etching.

[0030] Beneficial effects: The micro-nano structure of the light polarization layer defined in the present invention can disperse light into red, green, blue and infrared light, and refract the dispersed light to the areas corresponding to the red, green, blue and infrared sub-pixels.

[0031] Preferably, viewed from a direction perpendicular to the light polarization layer, the shape of the micro-nano structure is square and / or "X"-shaped.

[0032] The second technical solution of the present invention:

[0033] A method for preparing a high-sensitivity, wide-spectrum, true-color quantum dot image sensor, characterized in that it comprises the following steps:

[0034] According to the layer structure of the above-mentioned high-sensitivity wide-spectrum true-color quantum dot image sensor, the wide-spectrum quantum dot material electron transport layer, the wide-spectrum quantum dot material hole transport layer, the support layer and the light polarization layer are all prepared by deposition from bottom to top in sequence using a deposition method.

[0035] Preferably, the preparation method specifically comprises the following steps:

[0036] Depositing a wide-spectrum PbS or HgTe quantum dot dispersion on the surface of a quantum dot-specific readout circuit having a four-quadrant sub-pixel electrode on the surface, and using a solution exchange treatment to make it a wide-spectrum quantum dot material electron transport layer;

[0037] A broad-spectrum PbS or HgTe quantum dot dispersion is deposited on the broad-spectrum quantum dot material electron transport layer, and a solution exchange treatment is used to make it a broad-spectrum quantum dot material hole transport layer, and a columnar micro-nano light trapping structure is prepared on the surface of the broad-spectrum quantum dot material hole transport layer by a nanoimprinting method in order to achieve a high sensitivity effect;

[0038] A mesh-shaped metal nanowire film or a graphene film is constructed on the surface of the wide-spectrum quantum dot material hole transport layer as a transparent upper electrode layer;

[0039] Depositing a support layer (for refracting light from the polarization layer and for supporting the polarization layer) on the transparent upper electrode layer (metal nanowires);

[0040] A light-reflecting material (a silicon nitride film layer, a barium titanate film layer, or a borosilicate glass film layer) is deposited on the surface of the support layer and a light polarization layer is obtained by photolithography and etching; wherein the light polarization layer can disperse light into red light, green light, blue light, and infrared light and transmit the light to the sub-pixel units corresponding to the red, green, blue, and infrared corresponding to the wide-spectrum sensitive material, thereby completing the preparation of a high-sensitivity wide-spectrum true-color quantum dot image sensor.

[0041] Beneficial effects: The image sensor prepared by the preparation method defined in the present invention has a small size, low power consumption, high integration, can achieve true color effects, and can be widely used in security monitoring, small unmanned aerial vehicles and other military and civil fields.

[0042] Compared with the prior art, the present invention has the following advantages and technical effects:

[0043] In order to break through the limitation of the response band of traditional materials, the present invention adopts PbS quantum dots or HgTe quantum dots as wide-spectrum sensitive materials. While achieving wide-spectrum response, compared with traditional materials, it also has the advantages of simple process, good CMOS process compatibility, and no isolation between adjacent pixels and no crosstalk. Therefore, PbS quantum dots or HgTe quantum dots are used as the transmission layer of wide-spectrum materials, which can respond to four monochromatic lights: red, green, blue, and infrared. In addition, the micro-nano light-trapping structure is prepared on the surface of the hole transmission layer of the wide-spectrum quantum dot material to further improve light absorption and promote the sensitivity of the image sensor.

[0044] In addition, a light polarization layer is used to disperse the wide spectrum light into four monochromatic lights: red, green, blue, and infrared, and refract them to the corresponding sub-pixel units of red, green, blue, and infrared. The light polarization layer has excellent light splitting effect, high light utilization rate, and small size, avoiding the shortcomings of filters. At the same time, the pixel is composed of four sub-pixels: red, green, blue, and infrared. The color information of the substance is obtained by using the red, green, and blue sub-pixels, and the material information of the substance is obtained by using the infrared sub-pixels, thereby obtaining a highly sensitive wide spectrum true color quantum dot image sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0046] Figure 1 This is a structural diagram of a high-sensitivity, wide-spectrum, true-color quantum dot image sensor prepared in Example 1 of the present invention;

[0047] Among them, 1-readout circuit layer, 2-metal lower electrode layer, 3-broad spectrum quantum dot material electron transport layer, 4-broad spectrum quantum dot material hole transport layer, 5-transparent upper electrode layer, 6-support layer, 7-light polarization layer;

[0048] Figure 2 A top view of a disassembled single layer of the high-sensitivity, wide-spectrum, true-color quantum dot image sensor prepared in Example 1 of the present invention;

[0049] Among them, (a) is a light polarization layer, (b) is a support layer, (c) is a transparent upper electrode layer, (d) is a hole transport layer of a wide spectrum quantum dot material, (e) is an electron transport layer of a wide spectrum quantum dot material, and (f) is a metal lower electrode layer + a readout circuit layer;

[0050] Figure 3 This is a schematic diagram of the wide spectrum sub-pixel distribution of a pixel unit in the high-sensitivity wide spectrum true color quantum dot image sensor prepared in Example 1 of the present invention;

[0051] Figure 4 This is a SEM image of the electron transport layer of the wide spectrum quantum dot material in the high-sensitivity wide spectrum true color quantum dot image sensor prepared in Example 1 of the present invention;

[0052] Figure 5 This is a SEM image of the hole transport layer of the wide spectrum quantum dot material in the high-sensitivity wide spectrum true color quantum dot image sensor prepared in Example 1 of the present invention;

[0053] Figure 6 This is a SEM image of a silver nanowire film on the surface of a micro-nano light trapping structure in a highly sensitive, wide-spectrum, true-color quantum dot image sensor prepared in Example 1 of the present invention;

[0054] Figure 7 This is a diagram of the external quantum efficiency of the quantum dot device (lower electrode + quantum dot electron-hole transport layer + silver nanowire upper electrode) prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0055] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0056] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0057] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0058] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0059] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0060] The "room temperature" in the present invention refers to 20-30°C unless otherwise specified.

[0061] The raw materials used in the present invention are all purchased from the market.

[0062] The technical solution of the present invention is further illustrated by the following embodiments.

[0063] Example 1

[0064] A method for preparing a high-sensitivity, wide-spectrum, true-color quantum dot image sensor comprises the following steps:

[0065] (1) Selection of readout circuit: In view of the non-uniformity of quantum dot film signals and the device characteristics that adjacent horizontal pixels of quantum dot image sensors do not need to be isolated, a 3T op amp is used, and the integration capacitor and filter capacitor are time-division multiplexed; in view of the high impedance and low capacitance characteristics of the quantum dot device model, a CTIA structure with constant detector bias control is used; in order to improve the imaging dynamic range of color pixels and infrared pixels of quantum dots under different illumination environments, the pre-integration circuit uses a "large-small" integration capacitor combination to achieve self-selection of the integration capacitor; in order to achieve low-noise and high-speed readout of large-scale arrays, a scalable column-level ADC and a high-speed LVDS output interface combining SAR and SS are used;

[0066] (2) Preparation of metal lower electrode: Figure 3 As shown, the pixel unit of the readout circuit is divided into four sub-pixel units: red, green, blue, and infrared. The lower electrode of each sub-pixel unit is 6*6μm, the spacing between two adjacent sub-pixel units is 1μm, and the thickness of the lower electrode is 30nm;

[0067] (3) Preparation of materials for broad spectrum quantum dots:

[0068] In order to broaden the response of the image sensor in a wide spectral range, the controllable batch preparation of quantum dots becomes the premise of the experiment. 0.45g of lead oxide, 3mL of 1-octadecene and 1.5mL of oleic acid are added to a three-necked flask and stirred under the action of magnetic force. High-purity nitrogen is filled for 5 minutes to exclude the air in the three-necked flask, and the temperature is adjusted to 110℃, and the temperature is kept at this temperature for 1 hour; after the air is excluded, nitrogen is continued to be passed and the constant temperature magnetic stirrer is turned on to heat and stir the liquid, and the intelligent temperature controller is turned on to adjust the temperature to 190℃. After heating for 1 hour, the precursor of Pb is obtained, and then 10mL of 1-octadecene and 210uL of hexamethyldisilathane mixed solution are injected into the precursor of Pb. After keeping warm for 5 minutes, a wide-spectrum PbS quantum dot material with a wavelength that can respond to 380nm-2500nm is obtained;

[0069] (4) Preparation of electron transport layer of wide spectrum quantum dot material

[0070] The broad spectrum PbS quantum dot material was dispersed in an n-octane solution to obtain a 30 mg / mL broad spectrum PbS quantum dot dispersion, which was first rotated at a low speed of 500 rpm / s for 6 s, and then at a high speed of 2500 rpm / s for 30 s to spin-coat the quantum dot solution on the surface of the readout circuit deposited with the lower electrode to obtain a quantum dot film, and the quantum dot film was ligand exchanged with 200 μL of ethanedithiol stock solution and 9.8 mL of acetonitrile (prepared with a concentration of 2% EDT ligand exchange solution; this was repeated 4 times to obtain a broad spectrum PbS quantum dot material electron transport layer with a film thickness of 40 nm;

[0071] (5) Preparation of hole transport layer of wide spectrum quantum dot material

[0072] The broad-spectrum PbS quantum dot material is dispersed in an n-octane solution to obtain a 30 mg / mL broad-spectrum PbS quantum dot dispersion, and the quantum dot solution is continuously spin-coated on the surface of the broad-spectrum quantum dot material electron transport layer by first rotating at a low speed of 500 rpm for 6 seconds and then at a high speed of 2500 rpm for 30 seconds to obtain a quantum dot film; and an 8 mg / mL TBAI methanol solution (prepared by dissolving 200 mg of tetrabutylammonium iodide crystals in 25 mL of anhydrous methanol) is used to exchange the ligands of the quantum dot film; this is repeated 4 times to obtain a broad-spectrum PbS quantum dot material hole transport layer with a film thickness of 600 nm;

[0073] In the nanoimprint process, mold preparation and imprinting operation are key links; first, through micro-nano processing technologies such as electron beam lithography and dry etching, a precise nanocolumn array structure is produced on the silicon surface to provide a basis for imprinting. In the nanoimprint process, the mold must first be accurately aligned with the surface of the quantum dot film. This step is completed through micromanipulation and alignment system to ensure that the mold pattern can be accurately transferred to the film surface; next, the imprinting process is carried out at a temperature of 110°C and a pressure of 60Pa for 10 minutes; after imprinting, the mold and the film must be separated carefully, usually after cooling, to stabilize the nanocolumn structure; finally, a neatly arranged nanocolumn array will be formed on the surface of the quantum dot film, providing a basis for the subsequent production of optoelectronic devices;

[0074] (6) Preparation of wide-spectrum transparent upper electrode

[0075] Silver nanowires were dispersed in anhydrous ethanol to obtain a 6 mg / mL silver nanowire suspension, which was first rotated at a low speed of 500 rpm for 6 seconds and then at a high speed of 1500 rpm for 30 seconds to form a film on the surface of the micro-nano light-trapping structure of the hole transport layer of the wide-spectrum quantum dot material to complete the preparation of the mesh wide-spectrum transparent upper electrode. The thickness of the upper electrode was about 50 nm, and the average transmittance in the wide spectral range was 87%; the square resistance was 23Ω·sq -1 ;

[0076] (7) Preparation of support layer

[0077] Due to the tiny mesh gaps at the nanoscale, the silver nanowire film The high evaporation rate can deposit a silicon dioxide layer with a thickness of 800nm ​​on the surface of the silver nanowire film as a supporting layer, which can transmit light;

[0078] (8) Preparation of polarizing layer

[0079] In order to disperse the red, green, blue (R, G, B) wavelengths and infrared bands in the spectrum and refract them to specific areas, silicon nitride (Si3N4) is used as the material. Due to its high refractive index and low absorption rate, it has good transmission performance in the visible to near-infrared band; and a super lens structure is also provided, specifically, nanoscale structures (such as nanopillars or nanorings) are introduced (etched) on the surface of silicon nitride. The phases of light of different wavelengths are regulated by the geometric shape and arrangement of these structures to achieve light dispersion. Light of different wavelengths will produce different phase delays when passing through these nanostructures. After precise design, these wavelengths of light can be dispersed in different directions, so that red, green, blue and infrared light are refracted to specific areas respectively; the ultimate design goal is to concentrate the light beams of each wavelength to a specific area through precise phase control, realize multi-color imaging and spectrometry, and also realize light focusing at a specific position for imaging or other optical operations.

[0080] The specific steps for preparing a silicon nitride-based superlens are:

[0081] First, a 900nm thick silicon nitride film was deposited by chemical vapor deposition (CVD) using 8sccm of silane (SiH4) and 38sccm of ammonia (NH3) in an environment of 775°C and 1Torr, with a deposition rate of 10nm / min.

[0082] Next, the nanostructures were etched on the silicon nitride film using electron beam lithography (EBL). The electron beam acceleration voltage was set to 100 kV, the current was 2.8 nA, a 150 nm thick photoresist was used, and the exposure dose was 300 μC / cm 2 The designed nanostructures are typically nanocrosses and nanoprisms with a diameter of 400 nm and a height of 900 nm, and a period of 500 nm.

[0083] Then, the silicon nitride was etched by reactive ion etching (RIE) technology, with the etching gas being 10 sccm of fluorine (CF4) and 7 sccm of oxygen (O2), the power being set at 150 W, the pressure being 40 mTorr, the etching rate being 72 nm / min, and the etching time being 7 minutes.

[0084] Finally, the photoresist residues are cleaned with acetone and isopropyl alcohol, and the surface is cleaned using O2 plasma. The entire process is carried out in a Class 100 cleanliness environment with a humidity of less than 40%.

[0085] Figure 1 This is a structural diagram of the high-sensitivity, wide-spectrum, true-color quantum dot image sensor prepared in this embodiment;

[0086] Among them, 1-readout circuit layer, 2-metal lower electrode layer, 3-broad spectrum quantum dot material electron transport layer, 4-broad spectrum quantum dot material hole transport layer, 5-transparent upper electrode layer, 6-support layer, 7-light polarization layer;

[0087] Figure 2 A top view of a disassembled single layer of the high-sensitivity, wide-spectrum, true-color quantum dot image sensor prepared in this embodiment;

[0088] Among them, (a) is a light polarization layer, (b) is a support layer, (c) is a transparent upper electrode layer, (d) is a hole transport layer of a wide spectrum quantum dot material, (e) is an electron transport layer of a wide spectrum quantum dot material, and (f) is a metal lower electrode layer + a readout circuit layer;

[0089] Figure 4 This is a SEM image of the electron transport layer of the wide spectrum quantum dot material in the high-sensitivity wide spectrum true color quantum dot image sensor prepared in this embodiment. It can be seen from the figure that the electron transport layer is 40nm thick and relatively flat;

[0090] Figure 5 This is a SEM image of the hole transport layer of the wide spectrum quantum dot material in the high-sensitivity wide spectrum true color quantum dot image sensor prepared in this embodiment; it can be seen from the figure that the columnar array with a diameter of 500nm and a height of 600nm prepared on the surface of the hole transport layer;

[0091] Figure 6 This is a SEM image of the silver nanowire film on the surface of the micro-nano light trapping structure in the high-sensitivity wide-spectrum true-color quantum dot image sensor prepared in this embodiment. It can be seen from the figure that the mesh-like silver nanowire film is "built" on the surface of the columnar hole transport layer;

[0092] Figure 7 This is a diagram of the external quantum efficiency of the quantum dot device (lower electrode + quantum dot electron-hole transport layer + silver nanowire upper electrode) prepared in Example 1 of the present invention, further showing the wide spectrum and high sensitivity characteristics of the sensor.

[0093] Example 2

[0094] The difference from Example 1 is that:

[0095] Preparation of electron transport layer of wide spectrum quantum dot material and hole transport layer of wide spectrum quantum dot material:

[0096] The wide spectrum quantum dot material uses HgTe quantum dot material that can respond from visible to short-wave infrared: The synthesis of HgTe quantum dots is as follows: 317 mg of HgCl2 powder and 40 mL of oleylamine (need to be placed in a vacuum box for 10 hours at a temperature of 50°C) are placed in a three-necked flask, stirred at 110°C for 30 minutes and vacuumed to degas the solution (quickly remove the gas in the solution). Subsequently, the heating temperature is adjusted to the required synthesis temperature (80°C) and the heating is continued for 5 minutes. Next, the required synthesis temperature is maintained unchanged, argon is introduced, and the entire synthesis device is carried out in an argon-filled environment. 0.63 mL of the previously prepared Te precursor (TOPTe) and 6.3 mL of oleylamine are mixed and quickly added to the HgCl2 / oleylamine mixed solution, and the solution gradually turns black. Keep for 3 minutes, and quickly add 18 mL of toluene and 2 mL of n-dodecyl mercaptan. Stop heating, immediately cool with an ice water bath, and cool the solution to below 40°C, at which time the reaction is basically over. The reaction product was extracted and the polar solvent methanol was added to make the solution turbid. Then, the black HgTe quantum dots were separated by centrifugation at 6500rmp for 5 minutes. The clearest liquid at the top of the centrifuge tube was aspirated with a rubber-tipped dropper, and the deposited quantum dots were dissolved with n-hexane. Centrifugation and washing were performed three times in total. This process can remove impurities in the product. Then, the quantum dots after centrifugation were dispersed in toluene. The process of centrifugal precipitation is also called the purification process. This process can remove reagents that are not involved in the reaction and the generated impurities. Use a filter with a diameter of 0.22μm for filtration. The final concentration of the HgTe quantum dot solution is 40mg / mL, that is, the HgTe quantum dot solution is prepared.

[0097] Ligand exchange is used to prepare the electron transport layer of the wide spectrum quantum dot material and the hole transport layer of the wide spectrum quantum dot material;

[0098] Preparation of transparent upper electrode layer:

[0099] Unlike Example 1, in addition to the mesh silver nanowire film that can be used as a transparent upper electrode, graphene can also be used as a transparent upper electrode due to its high conductivity and high permeability. The graphene film is prepared by chemical vapor deposition (CVD): a copper foil (thickness of about 25-50 μm) is used as a substrate and placed in a CVD reaction chamber. First, pretreatment is performed at a high temperature of 1000°C to make the surface of the copper foil smooth and free of impurities. Then, hydrogen (H2) and methane (CH4) are introduced as reaction gases, wherein the hydrogen flow rate is 15 sccm, the methane flow rate is 40 sccm, and the pressure is maintained at 15 Torr. The reaction time is 45 minutes. At high temperature, methane decomposes and forms a single layer or multilayer graphene film on the surface of the copper foil. After the reaction is completed, the methane gas supply is turned off and hydrogen is retained to reduce the defects of the graphene film. By controlling the cooling rate, cracks in the graphene film on the surface of the copper foil are avoided. After cooling to room temperature, the copper foil is taken out of the CVD reaction chamber together with the graphene film. In order to facilitate the transfer of graphene film from copper foil, a layer of polymethyl methacrylate (PMMA) was first coated on the surface of the graphene film as a support layer. The spin coating method was adopted, with an initial rotation speed of 500rpm / s for 10 seconds, followed by spin coating at a speed of 2000rpm / s for 60 seconds to form a uniform PMMA layer with a thickness of 100nm. Then it was dried at 80℃ for 30 minutes to enhance the adhesion between PMMA and graphene. The graphene-copper foil sample coated with PMMA was immersed in a 0.5M iron chloride (FeCl3) solution for etching, and the etching time was about 50 minutes until the copper foil was completely dissolved. The dissolved graphene-PMMA film floated on the surface of the solution. It was washed with deionized water several times to remove the residual etching solution and impurities. Then the floating graphene-PMMA film was supported by deionized water and transferred to the upper part of the electron transport layer of the wide spectrum quantum dot material prepared with microstructures. Make sure that the film is flat and wrinkle-free during transfer. The transferred samples were dried at 60°C for 30 minutes to enhance the adhesion of graphene quantum dots. The transferred samples were immersed in acetone solution for 30-60 minutes to remove the PMMA support layer.

[0100] Preparation of support layer:

[0101] In order to further enhance the stability of the graphene film, a 1000nm thick silicon dioxide layer was deposited on the surface of the silver nanowire film as a supporting layer using plasma enhanced chemical vapor deposition (PECVD) technology, with a deposition rate of 25nm / min, 10sccm of silicon tetrafluoride (SiF4) and 20sccm of oxygen (O2) as the process gas, and the deposition was carried out at a temperature of 200°C. By adjusting the deposition conditions, the uniformity and optical transparency of the silicon dioxide layer were ensured, thereby improving the light transmittance and mechanical stability.

[0102] Preparation of polarizing layer:

[0103] In order to further improve the spectral dispersion effect and imaging performance, barium titanate (BaTiO3) with a higher refractive index is selected as the superlens material. Barium titanate has excellent optical properties in the visible and near-infrared bands. First, a 700nm thick barium titanate film is deposited on the silicon nitride layer by radio frequency magnetron sputtering. The sputtering gases are argon (Ar) and oxygen (O2), the sputtering power is set to 400W, the deposition temperature is controlled at 700℃, and the deposition rate is 15nm / min. Then, the designed nanostructure is etched on the barium titanate film by high-resolution electron beam lithography (EBL) technology. The electron beam acceleration voltage is set to 120kV, the current is 2nA, a 200nm thick HSQ photoresist is used, and the exposure dose is 400μC / cm 2 The size of the nanostructure is a nanocolumn or nanoring with a diameter of 150nm and a height of 700nm, with a period of 500nm. Finally, argon ion beam etching technology is used for precise etching, with a gas flow of 15sccm, a power of 200W, an etching rate of 40nm / min, and an etching time of 8 minutes to finally complete the preparation of the light polarization layer. The entire preparation process is carried out in a Class 100 clean environment with a humidity of less than 35% to ensure the stability and reliability of the device performance.

[0104] Example 3

[0105] The difference from Example 1 is that:

[0106] The preparation method for improving the high temperature stability of the wide spectrum transparent upper electrode is:

[0107] In order to improve the stability of the wide-spectrum transparent upper electrode under high temperature environment, silver nanowires were dispersed in a mixed solution of ethanol, deionized water and polyethylene glycol (PEG) at a ratio of ethanol: water: PEG = 3: 1: 0.5 to obtain a 10 mg / mL silver nanowire suspension. The step-by-step speed increase spin coating method was adopted, with an initial speed of 400 rpm / s for 6 seconds; the middle stage was 1200 rpm / s for 30 seconds; the final stage was 2000 rpm / s for 60 seconds to ensure that the silver nanowires formed a uniform and high-temperature stable mesh wide-spectrum transparent upper electrode on the surface of the micro-nano light-trapping structure of the hole transport layer of the wide-spectrum quantum dot material.

[0108] Improved high temperature stability of the support layer:

[0109] In order to further enhance the stability of the silver nanowire film in a high temperature environment, a 1200nm thick aluminum oxide (Al2O3) layer was deposited on the surface of the silver nanowire film using physical vapor deposition (PVD) technology as a support layer. The deposition process uses a DC magnetron sputtering device, with a process gas of 10sccm of oxygen (O2) and 20sccm of argon (Ar), and is deposited at a temperature of 250°C with a deposition rate of 12nm / min. The aluminum oxide layer not only provides mechanical support, but also improves the thermal stability of the film while maintaining good optical transparency.

[0110] Improvements in the light polarization layer:

[0111] For high-temperature application environments, borosilicate glass is selected as the superlens material. Borosilicate glass has excellent thermal expansion coefficient and high-temperature stability. First, a borosilicate glass film with a thickness of 500-800nm ​​is prepared on an alumina support layer by a sol-gel method. Then, a nanostructure is introduced on the film using UV lithography technology. A UV light source with a wavelength of 365nm and a negative photoresist with a thickness of 1-2μm (eg, SU-8) are used, and the exposure dose is 210mJ / cm 2 , the structure size is 300nm diameter, 900nm height nano cross and nano prism, the period is 500nm. Finally, the borosilicate glass is etched using chemical wet etching technology, the etching solution is a mixture of hydrogen fluoride (HF) and ammonium hydrofluoride (NH4F), and the etching time is 5-15 minutes. The entire preparation process is carried out in a Class 10 clean environment with a humidity of less than 30% to ensure optical performance and structural stability under high temperature conditions.

[0112] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A highly sensitive, wide-spectrum, true-color quantum dot image sensor, characterized in that: Comprises, from bottom to top, successively: A readout circuit layer; A metal bottom electrode layer; A wide-spectrum quantum dot material electron transport layer, where the quantum dot material is a P-type quantum dot thin film; A wide-spectrum quantum dot material hole transport layer with a micro-nano light-trapping structure, where the quantum dot material is an N-type quantum dot thin film; A transparent top electrode layer; A support layer; and a light polarization layer.

2. The high-sensitivity, wide-spectrum, true-color quantum dot image sensor according to claim 1, characterized in that: In each pixel unit of the metal bottom electrode layer, four sub-pixel units arranged in a "field" shape are provided; The distance between two adjacent sub-pixel units is 0.5 μm - 2 μm.

3. The high-sensitivity, wide-spectrum, true-color quantum dot image sensor according to claim 1, characterized in that: The wide-spectrum quantum dot material used in the wide-spectrum quantum dot material electron transport layer and the wide-spectrum quantum dot material hole transport layer is a wide-spectrum PbS quantum dot material or a HgTe quantum dot material.

4. The high-sensitivity, wide-spectrum, true-color quantum dot image sensor according to claim 3, characterized in that: The preparation process of the wide-spectrum quantum dot material electron transport layer or the wide-spectrum quantum dot material hole transport layer is as follows: Deposit a wide-spectrum PbS or HgTe quantum dot dispersion liquid on the metal bottom electrode layer, and then perform ligand exchange of the quantum dot thin film using an exchange solution to obtain the wide-spectrum quantum dot material electron transport layer; Deposit a wide-spectrum PbS or HgTe quantum dot dispersion liquid on the wide-spectrum quantum dot material electron transport layer, and then perform ligand exchange of the quantum dot thin film using an exchange solution to obtain the wide-spectrum quantum dot material hole transport layer.

5. The high-sensitivity wide-spectrum true-color quantum dot image sensor according to claim 4, wherein When preparing the wide-spectrum quantum dot material electron transport layer, the exchange solution used is an acetonitrile solution of ethanedithiol; When preparing the wide-spectrum quantum dot material hole transport layer, the exchange solution used is a methanol solution of tetrabutylammonium iodide.

6. The high-sensitivity, wide-spectrum, true-color quantum dot image sensor according to claim 1, characterized in that: The transparent upper electrode layer has a transmittance greater than 80% in a wide spectral range and a square resistance less than 30Ω·sq -1 .

7. The high-sensitivity, wide-spectrum, true-color quantum dot image sensor according to claim 1, characterized in that: The support layer is a silicon oxide layer or an aluminum oxide thin film layer.

8. The high-sensitivity, wide-spectrum, true-color quantum dot image sensor according to claim 1, characterized in that: The light polarization layer is a silicon nitride thin film layer, a barium titanate thin film layer, or a borosilicate glass thin film layer, and has a micro-nano structure penetrating the light polarization layer.

9. The high-sensitivity, wide-spectrum, true-color quantum dot image sensor according to claim 8, characterized in that: Viewed from a direction perpendicular to the light polarization layer, the shape of the micro-nano structure is square and / or "×" shape, which can split the spectrum into red, green, blue, and infrared light rays and refract them into four sub-pixel units of red, green, blue, and infrared.

10. A method for preparing a high-sensitivity, wide-spectrum, true-color quantum dot image sensor, characterized in that: Comprises the following steps: According to the layer structure of the high-sensitivity wide-spectrum true-color quantum dot image sensor according to any one of claims 1-9, the wide-spectrum quantum dot material electron transport layer, the wide-spectrum quantum dot material hole transport layer, the support layer, and the light polarization layer are all deposited and prepared successively from bottom to top using a deposition method.

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