Infrared Detector, Infrared Imager and Preparation Method of Infrared Detector

Abstract

An embodiment of the present invention discloses an infrared detector, an infrared imager, and a preparation method of the infrared detector. The infrared detector includes at least one pixel, and the pixel includes: a substrate layer, at least one stacked structure, and a top electrode layer sequentially arranged from bottom to top; the stacked structure includes an electrode layer and a quantum dot infrared absorption layer sequentially arranged from bottom to top; wherein, the quantum dot infrared absorption layer contains a preset number of colloidal quantum dots for detecting infrared radiation; wherein, the wavelengths of the infrared radiation detected by the quantum dot infrared absorption layers in different stacked structures are different. The preparation process of this infrared detector is simple and the cost is low. In addition, since the wavelengths of the infrared radiation detected by the quantum dot infrared absorption layers in different stacked structures are different, integrating infrared detection materials with different detection wavelengths on the same substrate structure can better expand the detection range of the infrared detector and improve the system performance.

Description

Technical Field

[0001] The present invention relates to the field of infrared detection technology, and in particular, to an infrared detector, an infrared imager, and a method for manufacturing an infrared detector. Background Art

[0002] In the early stage, infrared detection and imaging technology was mainly applied in the military field. With the continuous progress of industrial technology, the application scope of infrared detection and imaging technology has gradually expanded to the civilian field, and the development speed has accelerated. Infrared detectors can be divided into two types: cooled photon detectors and uncooled thermal detectors. At present, the research work on infrared detectors in China has developed from single elements and linear arrays to infrared focal planes, and the product coverage has been continuously expanded, gradually forming a relatively complete research and production system for infrared detectors.

[0003] Common uncooled infrared detectors are mostly of the types such as thermopiles / thermocouples, pyroelectric, optomechanical, and microbolometers. Common high-end cooled infrared detectors are mostly prepared using narrow-bandgap mercury cadmium telluride materials, or solid semiconductor quantum wells, quantum dots, etc., and utilize the photoelectric effect related to the direct absorption of photons and electron transitions to detect infrared radiation. These devices have good performance, but their chip materials need to be realized by complex epitaxial technologies, resulting in high costs. For example, the infrared absorption materials of quantum well infrared detectors or epitaxial quantum dot infrared detection devices need to be prepared and synthesized by complex technologies such as molecular beam epitaxy or chemical vapor deposition, and the preparation process is complex; moreover, molecular beam epitaxy also requires an ultra-high vacuum environment, leading to very high preparation costs for this kind of infrared absorption material; in addition, due to the limitations of epitaxial equipment, the preparation size of this kind of infrared absorption material is relatively limited, and at the same time, the adjustability of the wavelengths that can be detected is poor. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention provides an infrared detector, an infrared imager, and a method for manufacturing an infrared detector.

[0005] To solve the above technical problems, the present invention provides the following technical solutions:

[0006] In a first aspect, an embodiment of the present invention provides an infrared detector, including at least one pixel, where the pixel includes: a substrate layer, at least one stacked structure, and a top electrode layer arranged in sequence from bottom to top;

[0007] The stacked structure includes an electrode layer and a quantum dot infrared absorption layer arranged in sequence from bottom to top;

[0008] Wherein, the quantum dot infrared absorption layer contains a preset number of colloidal quantum dots for detecting infrared radiation; wherein, the wavelengths of the infrared radiation detected by the quantum dot infrared absorption layers in different stacked structures are different.

[0009] Further, for each stacked structure, the size of the quantum dot infrared absorption layer is smaller than that of the electrode layer. For two adjacent stacked structures, the size of the electrode layer of the upper stacked structure is the same as that of the quantum dot infrared absorption layer of the lower stacked structure, and the size of the electrode layer of the upper stacked structure is smaller than that of the electrode layer of the lower stacked structure.

[0010] Further, when the infrared detector includes a plurality of pixels, the plurality of pixels are arranged in an array.

[0011] Further, an infrared radiation absorption enhancement layer is provided between the substrate layer and the stacked structure. The infrared radiation absorption enhancement layer includes a preset specific optical structure or a preset optical film to enhance the absorption of infrared radiation.

[0012] Further, the distance between two adjacent pixels is 10-50 μm.

[0013] Further, the thickness of the electrode layer in each stacked structure is 50-500 nm.

[0014] In a second aspect, an embodiment of the present invention provides an infrared imager, including: the infrared detector as described in the first aspect.

[0015] In a third aspect, an embodiment of the present invention provides a method for manufacturing an infrared detector, including:

[0016] Manufacturing a substrate layer;

[0017] Manufacturing at least one stacked structure from bottom to top above the substrate layer, and manufacturing a top electrode layer on the surface of the uppermost stacked structure; wherein, each stacked structure includes an electrode layer and a quantum dot infrared absorption layer arranged in sequence from bottom to top;

[0018] Wherein, the quantum dot infrared absorption layer contains a preset number of colloidal quantum dots for detecting infrared radiation; wherein, the wavelengths of the infrared radiation detected by the quantum dot infrared absorption layers in different stacked structures are different;

[0019] Wherein, the quantum dot infrared absorption layer is prepared by configuring a pre-driving liquid and obtaining it through ligand exchange.

[0020] Further, the step of manufacturing the stacked structure includes:

[0021] Manufacturing the electrode layer by deposition or sputtering;

[0022] Manufacturing a quantum dot infrared absorption layer on the electrode layer, specifically including: configuring a pre-driving liquid and obtaining a doping with a preset concentration through ligand exchange;

[0023] Among them, for different stacked structures, by changing the size and material of the quantum dots, a quantum dot infrared absorption layer capable of absorbing infrared radiation of different wavelengths is obtained.

[0024] Furthermore, the preparation method further includes:

[0025] After the substrate layer is prepared, an infrared radiation absorption enhancement layer is prepared on the substrate layer, and the infrared radiation absorption enhancement layer includes: a preset specific optical structure or a preset optical film;

[0026] Among them, when the infrared radiation absorption enhancement layer includes a preset optical structure, the preset optical structure is prepared on the substrate layer; when the infrared radiation absorption enhancement layer includes a preset optical film, the preset optical film is coated on the substrate layer.

[0027] As can be seen from the above technical solutions, the infrared detector provided by the embodiments of the present invention sets at least one stacked structure including an electrode layer and a quantum dot infrared absorption layer, and disposes the colloidal quantum dots for detecting infrared radiation in the infrared absorption layer in the stacked structure. When a voltage is applied to the two electrode layers of the quantum dot infrared absorption layer, the photoelectrons formed by the quantum dot infrared absorption layer due to the absorption of infrared radiation can be guided out to form a photocurrent, so as to judge the infrared radiation intensity at the corresponding pixel according to the strength of the photocurrent. Thus, it can be seen that the embodiments of the present invention use the easier-to-prepare colloidal quantum dots to achieve direct detection of infrared radiation, so it is convenient to manufacture and has low cost. Compared with the solid semiconductor quantum well and quantum dot infrared detectors that need complex epitaxial techniques to be prepared in the prior art, the embodiments of the present invention can greatly reduce the preparation cost and preparation complexity. In addition, since the quantum dot infrared absorption layers in different stacked structures detect infrared radiation of different wavelengths, integrating infrared detection materials with different detection wavelengths on the same substrate structure can better expand the detection range of the infrared detector and improve the system performance. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to these drawings.

[0029] Figure 1 It is a front view of an infrared detector provided by an embodiment of the present invention;

[0030] Figure 2 It is a perspective view of an infrared detector provided by an embodiment of the present invention;

[0031] Figure 3Top view of a pixel of an infrared detector provided by an embodiment of the present invention;

[0032] Figure 4 Arrangement diagram of multiple pixels of another infrared detector provided by an embodiment of the present invention;

[0033] Figure 5 Front view of an infrared detector provided by an embodiment of the present invention including a stacked structure;

[0034] Figure 6 Front view of an infrared detector provided by an embodiment of the present invention including three stacked structures;

[0035] Figure 7 Flow chart of a method for manufacturing an infrared detector provided by an embodiment of the present invention.

[0036] Reference numerals:

[0037] 1: Substrate layer; 2: First electrode layer; 3: First quantum dot infrared absorption layer; 4: Second electrode layer; 5: Second quantum dot infrared absorption layer; a: Stacked structure; b: Top electrode layer. Detailed implementation manners

[0038] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] As described in the background art, the existing solid-state semiconductor quantum well and quantum dot infrared detectors are fabricated on a semiconductor substrate by means of MBE (molecular beam epitaxy) or MOCVD (metalorganic chemical vapor deposition). Among them, high-quality ones must use MBE. Both are epitaxial technologies, and epitaxial technologies require expensive epitaxial equipment, resulting in high manufacturing costs. At the same time, due to the limitations of the epitaxial equipment, the size of the fabricated detectors is quite limited, and the adjustability of the detectable wavelength is also poor. To address this problem, this embodiment provides an infrared detector and a method for manufacturing the same. This embodiment no longer requires expensive epitaxial equipment for fabrication, and only needs to prepare colloidal quantum dots by chemical solution formulation, thereby greatly reducing the manufacturing cost. At the same time, the manufacturing size can be flexibly set according to needs.

[0040] Figure 1 A front view of an infrared detector provided by an embodiment of the present invention is shown, Figure 5The front view of a stacked structure of an infrared detector provided by an embodiment of the present invention is shown. Figure 6 The front view of an infrared detector provided by an embodiment of the present invention with three stacked structures is shown. Among them Figure 1 It is a schematic diagram taking a structure with two stacked structures as an example, as Figure 1 shown, 1 represents the substrate layer, 2 represents the first electrode layer, 3 represents the first quantum dot infrared absorption layer, 4 represents the second electrode layer, and 5 represents the second quantum dot infrared absorption layer.

[0041] As Figure 1 shown, the infrared detector provided by the first embodiment includes at least one pixel, and the pixel includes: a substrate layer 1, at least one stacked structure a, and a top electrode layer b arranged in sequence from bottom to top; each stacked structure includes an electrode layer and a quantum dot infrared absorption layer arranged in sequence from bottom to top (for example, the stacked structure composed of the first electrode layer 2 and the first quantum dot infrared absorption layer 3, and another example is the stacked structure composed of the second electrode layer 4 and the second quantum dot infrared absorption layer 5), wherein, the quantum dot infrared absorption layer contains a preset number of colloidal quantum dots for detecting infrared radiation; wherein, the wavelengths of the infrared radiation detected by the quantum dot infrared absorption layers in different stacked structures are different; the substrate layer 1 and the electrode layers in each stacked structure are transparent to the infrared radiation absorbed by each quantum dot infrared absorption layer.

[0042] In this embodiment, the substrate layer 1 serves as the carrier of the entire device and is simultaneously transparent to the infrared radiation within the absorption band of each quantum dot infrared absorption layer thereon. The substrate layer 1 can be made of any material that is transparent to the infrared radiation in the desired detection band, such as quartz glass, transparent conductive glass, flexible transparent materials, etc., and the shape of the substrate layer 1 can be set to any shape such as square, circular, triangular, etc., and no specific limitation is made here.

[0043] In this embodiment, both the first quantum dot infrared absorption layer 3 and the second quantum dot infrared absorption layer 5 are quantum dot infrared absorption layers, and contain a certain number of colloidal quantum dots inside for detecting the set infrared radiation. Among them, the colloidal quantum dots can be PbS quantum dots, PbSe quantum dots, etc.

[0044] In this embodiment, it should be noted that the preparation of the infrared absorption layer containing colloidal quantum dots in this embodiment is relatively simple and only requires chemical preparation, without the need for expensive MBE or MOCVD equipment.

[0045] Taking PbS colloidal quantum dots as an example, the preparation and doping process of the infrared absorption layer containing colloidal quantum dots will be described below: Specifically, PbS quantum dots can be prepared by chemical synthesis. For example, 5 grams of high-purity lead monoxide (PbO), 500 milliliters of 90% pure 1-octadecene (ODE), and 38 milliliters of 90% pure oleic acid (OA) can be placed in a three-neck round-bottom flask and degassed in a vacuum environment at 90 degrees Celsius. Then, under argon, the reaction temperature is raised to 95 - 100 degrees Celsius, and 600 microliters of hexamethyldisilathiane ((TMS)2S) diluted in 30 milliliters of 1-octadecene is quickly injected. After several minutes, a solution of 750 microliters of hexamethyldisilathiane in 90 milliliters of 1-octadecene is dropped in at a rate of 7.5 milliliters per minute. Thereafter, the reaction is tested in aliquots until quantum dots of the desired size are obtained, after which the reaction can be stopped and gradually cooled. Subsequently, the quantum dots need to be precipitated and purified several times with anhydrous acetone and ethanol, and then dispersed in anhydrous toluene. Finally, the concentration is adjusted to 300 milligrams per milliliter, and nitrogen is passed into the solution to minimize the oxidation of the quantum dots.

[0046] The prepared quantum dots above also need to be doped. First, the quantum dot solution is spin-coated on a soda-lime glass substrate at a speed of 2000 - 3000 revolutions per minute to form a thin film. Then the thin film is treated with a 3-mercaptopropionic acid solution containing zinc iodide for several seconds, and the spin coater is started again for drying treatment, while methanol is dropped in to remove the excess ligands. The above process is repeated until a thin film of the desired thickness is obtained.

[0047] It should be noted that the above method is only a specific embodiment of preparing doped colloidal quantum dots. The claimed device working principle and device structure of the present invention are applicable to other types and other ways of preparing colloidal quantum dots as well.

[0048] In this embodiment, it should be noted that for two adjacent stacked structures, the electrode layer in the upper stacked structure and the electrode layer in the lower stacked structure together form a bias voltage, which can guide out the photoelectrons formed by the quantum dot infrared absorption layer in the lower stacked structure due to the absorption of infrared photons to form a photocurrent. Thus, based on the strength of the photocurrent, the infrared radiation intensity at the corresponding pixel can be judged. For example, still referring to Figure 1 the infrared detector shown in the figure containing two stacked structures, the second electrode layer 4 in the upper stacked structure and the first electrode layer 2 in the lower stacked structure work together to guide out the photoelectrons formed by the first quantum dot infrared absorption layer 3 due to the absorption of infrared photons to form a photocurrent under a certain bias voltage. Based on the strength of the photocurrent, the infrared radiation intensity at the corresponding pixel can be judged.

[0049] In this embodiment, the electrode layers in each stacked structure are transparent to the infrared radiation absorbed by all the quantum dot infrared absorption layers (for example Figure 1 as shown, the material of the second electrode layer 4 is transparent to the infrared radiation absorbed by the first quantum dot infrared absorption layer 3, and again, the material of the top electrode layer b is transparent to the infrared radiation absorbed by the first quantum dot infrared absorption layer 3 and the second quantum dot infrared absorption layer 5).

[0050] In this embodiment, it should be noted that the quantum dot infrared absorption layer in each stacked structure is composed of a certain number of colloidal quantum dots. The energy spacing between the ground state and the first excited state of the sub-energy levels inside the conduction band or valence band formed by multiple colloidal quantum dots corresponds to the infrared radiation band, and the colloidal quantum dots are heavily doped through ligand exchange. The doping can be either N-type doping or P-type doping, so that the Fermi level of the colloidal quantum dots is located between the ground state energy level and the first excited state energy level. The quantum dot infrared absorption layer in each stacked structure uses the principle of intra-band transition between different sub-energy levels inside the same conduction band or the same valence band to detect the infrared radiation in the preset infrared radiation band.

[0051] It can be understood that ligand exchange refers to the ligand exchange reaction: the ligand in a coordination compound can be replaced by other ligands, which is called the ligand exchange reaction. Generally, the reaction mechanism is a nucleophilic substitution reaction.

[0052] Among them, for the mid-short wavelength infrared band, the quantum dots absorb infrared photons through inter-band transition (conduction band electrons and valence band holes). For the mid-long wavelength infrared band, the quantum dots absorb photons through intra-band sub-band transition. Taking the conduction band as an example, the specific principle is described as follows: The quantum dot infrared absorption layer composed of multiple colloidal quantum dots essentially becomes a semiconductor. A conduction band and a valence band are formed inside this semiconductor, and different sub-energy levels are respectively formed inside the conduction band and the valence band. For different sub-energy levels inside the same conduction band, the sub-energy level with the lowest energy is the ground state, and the sub-energy level with higher energy is the excited state. The energy spacing between the low-energy sub-energy level and the high-energy sub-energy level corresponds to the preset infrared radiation band, and the Fermi level of each colloidal quantum dot is located between the ground state energy level and the first excited state energy level. Under infrared radiation, the ground state electrons of the low-energy sub-energy level will absorb the energy of infrared photons, and thus cross the energy spacing and enter the sub-energy level with higher energy, that is, transition to the first excited state, completing the intra-band transition process (which can be simply called intra-band transition), and realizing the detection of the infrared radiation in the preset infrared radiation band. The principle of intra-band transition in the valence band is the same as the above-mentioned intra-band transition principle in the conduction band, so it will not be elaborated here.

[0053] In this embodiment, the thickness of the first quantum dot infrared absorption layer 3 can be 0.1 - 10 μm, and the thickness of the second quantum dot infrared absorption layer 5 can also be 0.1 - 10 μm.

[0054] In this embodiment, it should be noted that the thickness of the first quantum dot infrared absorption layer 3 ranges from [0.1, 10], that is, it includes both the values of 0.1 and 10 at the two endpoints, and also includes the values between the two endpoints. For example, the thickness is 5 μm; the thickness of the second quantum dot infrared absorption layer 5 ranges from [0.1, 10], that is, it includes both the values of 0.1 and 10 at the two endpoints, and also includes the values between the two endpoints. For example, the thickness is 2 μm.

[0055] It can be understood that the infrared detector provided in this embodiment may include one pixel, as Figure 3 shown, or may include multiple pixels, as Figure 4 shown.

[0056] As can be seen from the above technical solutions, the infrared detector provided by the embodiment of the present invention, by setting at least one stacked structure including an electrode layer and a quantum dot infrared absorption layer, disposes the colloidal quantum dots for detecting infrared radiation in the infrared absorption layer in the stacked structure. When a voltage is applied to the two electrode layers above and below the quantum dot infrared absorption layer, the photoelectrons formed by the quantum dot infrared absorption layer due to the absorption of infrared radiation can be guided out to form a photocurrent. Thus, the intensity of the infrared radiation at the corresponding pixel can be judged by the strength of the photocurrent. It can be seen that the embodiment of the present invention uses the easier-to-prepare colloidal quantum dots to achieve direct detection of infrared radiation. Therefore, it is convenient to manufacture and has a low cost. Compared with the solid semiconductor quantum well and quantum dot infrared detectors that need complex epitaxial techniques to be prepared in the prior art, the embodiment of the present invention can greatly reduce the preparation cost and preparation complexity. In addition, since the wavelengths of the infrared radiation detected by the quantum dot infrared absorption layers in different stacked structures are different, integrating infrared detection materials with different detection wavelengths on the same substrate structure can better expand the detection range of the infrared detector and improve the system performance.

[0057] Based on the content of the above embodiment, in this embodiment, for each stacked structure, the size of the quantum dot infrared absorption layer is smaller than that of the electrode layer. For two adjacent stacked structures, the size of the electrode layer of the upper stacked structure is the same as that of the quantum dot infrared absorption layer of the lower stacked structure, and the size of the electrode layer of the upper stacked structure is smaller than that of the electrode layer of the lower stacked structure.

[0058] As Figure 1As shown, for each stacked structure, the size of the quantum dot infrared absorption layer is smaller than that of the electrode layer (for example, the size of the first quantum dot infrared absorption layer 3 is smaller than that of the first electrode layer 2, and the size of the second quantum dot infrared absorption layer 5 is smaller than that of the second electrode layer 4). For two adjacent stacked structures, the size of the electrode layer of the upper stacked structure is the same as that of the quantum dot infrared absorption layer of the lower stacked structure (for example, the size of the first quantum dot infrared absorption layer 3 is the same as that of the second electrode layer 4, and the size of the second quantum dot infrared absorption layer 5 is the same as that of the top electrode layer b). The size of the electrode layer of the upper stacked structure is smaller than that of the electrode layer of the lower stacked structure (for example, the size of the second electrode layer 4 is smaller than that of the first electrode layer 2, and the size of the top electrode layer b is smaller than that of the second electrode layer 4).

[0059] Figure 2 The perspective view of an infrared detector provided by an embodiment of the present invention is shown. It can be understood that in two adjacent stacked structures, the size of the quantum dot infrared absorption layer in the upper stacked structure is smaller than that in the lower stacked structure, so that the electrode layer between two adjacent infrared absorption layers can be exposed. And the electrode layer in the upper stacked structure needs to guide out the photoelectrons formed by the quantum dot infrared absorption layer in the lower stacked structure absorbing infrared radiation to form a photocurrent. Therefore, for two adjacent stacked structures, the size of the electrode layer of the upper stacked structure should be the same as that of the quantum dot infrared absorption layer of the lower stacked structure, so that in the same stacked structure, the size of the electrode layer should be larger than that of the infrared absorption layer to expose the electrode layer for connecting the conductive lead, that is, as Figure 2 shown, the size of the second quantum dot infrared absorption layer 5 is smaller than that of the first quantum dot infrared absorption layer 3, and the size of the second electrode layer 4 is the same as that of the first quantum dot infrared absorption layer 3. Therefore, the size of the second quantum dot infrared absorption layer 5 is also smaller than that of the second electrode layer 4. At the same time, the quantum dot infrared absorption layer in each stacked structure needs to expose the first electrode layer. Therefore, the size of the quantum dot infrared absorption layer in each stacked structure should be smaller than that of the electrode layer. And because the size of the electrode layer in the upper stacked structure is the same as that of the quantum dot infrared absorption layer in the lower stacked structure, therefore, the size of the electrode layer in the upper stacked structure is smaller than that of the electrode layer in the lower stacked structure.

[0060] Based on the content of the above embodiments, in this embodiment, when the infrared detector includes multiple pixels, the multiple pixels are arranged in an array. As Figure 3 shown in the case of including one pixel, Figure 4 shown in the case of including multiple pixels.

[0061] In this embodiment, it should be noted that the quantum dot infrared absorption layer in each stacked structure is fabricated into an array-type multi-pixel structure. After the pixel processing is completed, the electrode layer in the adjacent stacked structure below will be exposed. Among them, the one-dimensional line arrangement or two-dimensional array arrangement of each single-pixel structure inside the multi-pixel structure, and the separation between each single-pixel structure is as Figure 4 shown by each dashed line separation in Figure 4 . The specific arrangement method can be set according to actual requirements. Adopting a regular one-dimensional line arrangement or two-dimensional array arrangement method can simplify and speed up the production process flow, effectively improve the efficiency of batch standardized production of infrared detectors, and reduce production costs.

[0062] In this embodiment, the distance between two adjacent pixels is 10 - 50 μm. It should be noted that the value range of the distance between two adjacent pixels is [10, 50], that is: it includes both the values of 10 and 50 at both ends, and also the values between the two ends. For example, the distance between two adjacent pixels is 30 μm.

[0063] It should be noted that in the infrared detector provided in this embodiment, multiple pixels are arranged at a predetermined distance. The multiple units in the infrared detector are arranged at a certain rule and at a preset predetermined distance interval, so that multiple pixels can work synchronously respectively, improving the overall working efficiency. It should be noted that the working state of the infrared detector can be comprehensively determined and adjusted by combining the distance between two pixels and the specific shapes and sizes of each unit.

[0064] Based on the content of the above embodiment, in this embodiment, an infrared radiation absorption enhancement layer is provided between the substrate layer 1 and the stacked structure a. The infrared radiation absorption enhancement layer includes: a preset specific optical structure or a preset optical film to enhance the absorption of infrared radiation.

[0065] It can be understood that all optical structures or optical coatings that can enhance the light field distribution of infrared radiation inside the detector belong to the scope protected by the present invention, and this embodiment does not limit this. For example, the optical structure can be a triangular optical structure.

[0066] It should be noted that the substrate layer of the infrared detector provided in this embodiment can enhance the infrared radiation absorption ability of the infrared detector by processing various optical structures or coating specific optical films, thereby improving the device performance.

[0067] In this embodiment, the thickness of the electrode layer in each stacked structure is preferably 50 - 500 nm. It should be noted that the value range of the thickness of the electrode layer in each stacked structure is [50, 500], that is: it includes both the values of 50 and 500 at both ends, and also the values between the two ends.

[0068] For example, the thicknesses of the first electrode layer 2 and the second electrode layer 4 are 300 nm.

[0069] In this embodiment, the electrode layers in each stacked structure can be any electrode material that is transparent to infrared radiation, such as ITO (Indium tin oxide), AZO (aluminum-doped zinc oxide (ZnO transparent conductive glass AZO GmbH+Co.KG), etc. This embodiment does not limit this.

[0070] The infrared detector provided in this embodiment further includes: a photocurrent receiver and a current detector. The photocurrent receiver is connected to the quantum dot infrared absorption layer in the stacked structure and is used to receive the photocurrent formed by the quantum dot infrared absorption layer due to absorbing infrared radiation under the bias voltage of the upper and lower electrode layers. The current detector is used to detect the magnitude of the photocurrent received by the photocurrent receiver.

[0071] It should be noted that for two adjacent stacked structures, the electrode layer in the upper stacked structure and the electrode layer in the lower stacked structure together form a bias voltage, which can guide the photoelectrons formed by the quantum dot infrared absorption layer in the lower stacked structure due to absorbing infrared photons to form a photocurrent. Thus, the intensity of the infrared radiation at the corresponding pixel can be judged by the strength of the photocurrent. For example, still referring to Figure 1 the infrared detector shown in the figure that includes two stacked structures, the second electrode layer 4 in the upper stacked structure and the first electrode layer 2 in the lower stacked structure work together to guide the photoelectrons formed by the first quantum dot infrared absorption layer 3 due to absorbing infrared photons to form a photocurrent under a certain bias voltage. The intensity of the infrared radiation at the corresponding pixel can be judged by the strength of the photocurrent. It can be seen that the structural design idea of the infrared detector provided by the present invention is: a substrate and N (N≥2) layer quantum dot detection structures. Among them, an electrode contact layer is immediately followed on the substrate layer, which is the lower electrode of the entire stacked structure. There is an electrode layer on the top layer of the stacked structure, which is the upper electrode of the entire stacked structure. When N≥2, this infrared detector can detect multiple different infrared radiation bands. At this time, the upper and lower connected two-layer structures share a common contact electrode layer. Inside each layer are colloidal quantum dots of different sizes and doping concentrations, which are used to absorb infrared radiation of different wavelengths. Among them, for the short and medium wavelength infrared bands, the quantum dots absorb infrared photons through interband transitions (conduction band electrons and valence band holes), and for the medium and long wavelength infrared bands, the quantum dots absorb photons through intraband subband transitions.

[0072] It should be noted that when N = 1, the infrared detector provided by the present invention is a single-wavelength design. When N ≥ 2, for each increase of an integer in N, one more electrode layer and one more quantum dot infrared absorption layer are repeatedly added. It is only necessary to distinguish the detection wavelengths by adjusting the sizes and material components of the quantum dots in each layer of the quantum dot infrared absorption layer, that is, the working bands of each layer of the quantum dot infrared absorption layer are different from each other. Its working principle is that through the design of appropriate sizes and material combinations, the energy band gap between the conduction band and valence band (ground state) of the quantum dots, and the energy band gap between the sub-bands within the band (ground state and first excited state) are adjusted. Each quantum dot infrared absorption layer can absorb infrared radiation through the inter-band transition between the conduction band ground state and the valence band ground state; it can also be through the transition between the ground state and the first excited state within the same energy band, such as the conduction band. Among them, for the transition absorption between the sub-energy levels within the same energy band, appropriate heavy doping is required so that the Fermi level in the quantum dots is exactly between the ground state energy level and the first excited state. Thus, under infrared irradiation, the ground state electrons can absorb infrared photons and transition to the first excited state, and the readout circuit can read the corresponding infrared radiation information.

[0073] It can be seen that through the stacked multi-layer structure design in the embodiments of the present invention, infrared detection materials with different detection wavelengths are integrated on the same substrate structure, which can expand the detection range of the device and improve the system performance. The ways for the detection materials of different layers to absorb infrared radiation can be inter-band transition or the transition between the sub-energy levels within the band. Through flexible combination methods, the simultaneous detection of infrared radiation with different wavelengths is realized. For example, in the embodiments of the present invention, by changing the sizes and material combinations of the colloidal quantum dots and stacking different numbers of layers of quantum dot materials, the detection of multiple wavelengths can be achieved simultaneously.

[0074] Based on the same inventive concept, another embodiment of the present invention further provides an infrared imager, including the infrared detector described in any one of the above embodiments. Since the infrared imager in this embodiment includes the infrared detector described in the above embodiments, therefore, this embodiment has similar technical effects to the above embodiments, which will not be elaborated here. In addition, for the description of the specific principle, reference can also be made to the introduction of the above embodiments, which will not be elaborated here.

[0075] Based on the same inventive concept, another embodiment of the present invention further provides a method for preparing an infrared detector, Figure 7 which is a flowchart of a method for preparing an infrared detector provided by an embodiment of the present invention, as Figure 7 shown. The preparation method includes:

[0076] Step S701: Prepare a substrate layer;

[0077] In this step, the material piece of the substrate layer can be cleaned by wet cleaning followed by drying or plasma cleaning for cleaning treatment, and an optical structure is processed or an optical thin film is coated on the material piece of the substrate layer to enhance the infrared radiation absorption ability of the infrared detector, thereby forming a substrate layer, and the substrate layer can transmit infrared radiation in a preset infrared radiation band.

[0078] Step S702: Prepare at least one stacked structure from bottom to top above the substrate layer, and prepare a top electrode layer on the surface of the topmost stacked structure; wherein, each stacked structure includes an electrode layer and a quantum dot infrared absorption layer arranged in sequence from bottom to top. For each stacked structure, the size of the quantum dot infrared absorption layer is smaller than that of the electrode layer. For two adjacent stacked structures, the electrode layer of the upper stacked structure has the same size as the quantum dot infrared absorption layer of the lower stacked structure, and the size of the electrode layer of the upper stacked structure is smaller than that of the electrode layer of the lower stacked structure.

[0079] Wherein, the quantum dot infrared absorption layer contains a preset number of colloidal quantum dots for detecting infrared radiation; wherein, the wavelengths of the infrared radiation detected by the quantum dot infrared absorption layers in different stacked structures are different.

[0080] The substrate layer and the electrode layers in each stacked structure are transparent to the infrared radiation absorbed by each quantum dot infrared absorption layer.

[0081] Wherein, the quantum dot infrared absorption layer is prepared by configuring a pre-driving liquid and obtaining it through ligand exchange.

[0082] Step S703: The steps of preparing the stacked structure include:

[0083] Prepare the electrode layer by deposition or sputtering;

[0084] Prepare a quantum dot infrared absorption layer on the electrode layer, specifically including: configuring through a pre-driving liquid and obtaining a preset concentration of doping through ligand exchange.

[0085] Wherein, for different stacked structures, by changing the size and material of the quantum dots, a quantum dot infrared absorption layer capable of absorbing infrared radiation of different wavelengths is obtained.

[0086] In this embodiment, it should be noted that the preparation of the infrared absorption layer containing colloidal quantum dots in this embodiment is relatively simple and only requires chemical preparation without expensive MBE or MOCVD equipment.

[0087] In the above steps, a multi-pixel array structure as shown is formed through spin coating, exposure, and development. Figure 4 The electrode layer in each stacked structure forms a stepped structure after etching treatment.

[0088] It should be noted that when forming the first quantum dot infrared absorption layer on the first electrode layer, first, the material of the colloidal quantum dots is selected, such as PbS quantum dots or PbSe quantum dots. Then, a precursor solution is prepared, and heavily doped colloidal quantum dots are obtained through ligand exchange. The doping can be either N-type doping or P-type doping. For example, iodine molecules can be used to heavily dope PbS quantum dots through ligand exchange, so that the Fermi level in each colloidal quantum dot is above the ground state energy level and below the first excited state energy level. Also, by setting the size of the infrared absorption layer material, the energy spacing between the ground state and the first excited state of the sub-energy levels of the colloidal quantum dots corresponds to the infrared radiation band.

[0089] It should be noted that the first electrode layer is formed on the substrate layer by deposition or sputtering. The first electrode layer is used to connect to an external bias voltage to conduct current, and the first electrode layer also serves as a contact layer to connect the substrate layer and the infrared absorption layer.

[0090] The second electrode layer is formed on the infrared absorption layer by deposition. The second electrode layer can transmit infrared radiation in a preset infrared radiation band.

[0091] The correspondence between the energy spacing between the ground state and the first excited state of the sub-energy levels inside the conduction band or valence band formed by the above-mentioned multiple colloidal quantum dots and the preset infrared radiation band is achieved by reasonably setting the structures and sizes of each component in the infrared detector: When the infrared detector is a single pixel structure or only includes one pixel, it is necessary to reasonably set the structures, the sizes of each side, and the thicknesses of each layer of the substrate layer 1, the first electrode layer 2, the first quantum dot infrared absorption layer 3, and the second electrode layer 4. When the infrared detector is a multi-pixel structure or includes multiple pixels, it is also necessary to consider the arrangement method of each single pixel structure and the spacing distance between each pixel (between the infrared absorption layers 3 of each pixel or between each second electrode layer 4). The above parameters can be specifically designed according to actual needs and are not limited here.

[0092] Step S704: After the substrate layer is prepared, an infrared radiation absorption enhancement layer is prepared on the substrate layer. The infrared radiation absorption enhancement layer includes: a preset specific optical structure or a preset optical film.

[0093] Among them, when the infrared radiation absorption enhancement layer includes a preset optical structure, the optical structure is prepared on the substrate layer; when the infrared radiation absorption enhancement layer includes a preset optical film, the preset optical film is coated on the substrate layer.

[0094] It can be understood that the substrate layer of the infrared detector provided in this embodiment can enhance the infrared radiation absorption ability of the infrared detector by processing various optical structures or coating specific optical films.

[0095] In addition, the preparation method of the infrared detector may further include an annealing step to ensure good contact between components.

[0096] The following combines Figure 1 and Figure 4 to further illustrate the above embodiments:

[0097] In this embodiment, first, the substrate layer needs to be cleaned, including steps such as wet cleaning, drying, and plasma cleaning; then, the substrate layer is appropriately processed, such as by processing various optical structures or coating specific optical films to enhance the absorption of infrared radiation by each quantum dot infrared absorption layer. Next, the first electrode layer is prepared, which can be prepared by methods such as deposition and sputtering; then, the first quantum dot infrared absorption layer is prepared, which is configured from a precursor solution and obtains a specific concentration of doping through ligand exchange. Then, the second electrode layer is prepared, which is fabricated on the first quantum dot infrared absorption layer and is transparent to the infrared radiation absorbed by the first quantum dot absorption layer. This layer works together with the first electrode layer to guide the photoelectrons formed by the first quantum dot infrared absorption layer due to the absorption of infrared radiation to form a photocurrent under a certain bias voltage, thereby imaging the detection object. Then, continue to prepare the second quantum dot infrared absorption layer and repeat the steps of preparing the electrode layer and the quantum dot infrared absorption layer. During this period, quantum dot infrared absorption layers with different absorption wavelengths are obtained by changing conditions, and finally, a stacked multi-(N)-band infrared detector based on colloidal quantum dots is obtained. In this embodiment, it should be noted that during the preparation process of the stacked multi-band infrared detector based on colloidal quantum dots, a good electrode contact effect can be obtained through appropriate annealing and other treatment methods, so that the photo-generated carriers can be better led out to the signal readout circuit. In addition, it should be noted that during the preparation process of the stacked multi-band infrared detector based on colloidal quantum dots, an arrayed planar array structure can be finally formed by methods such as photolithography and etching. The lateral size of each pixel is 1 - 100 μm (including the values of both endpoints, that is, including the values of both endpoints 1 and 100, and also including the values between 1 and 100), and the pixel pitch is 1 - 100 μm (including the values of both endpoints, that is, including the values of both endpoints 1 and 100, and also including the values between 1 and 100). When N ≥ 2, the pixels formed by the upper quantum dot layer infrared absorption layer and the electrode contact layer are smaller than those of the lower layer.

[0098] Step 1): Clean the material, including steps such as wet cleaning and drying;

[0099] Step 2): Form an arrayed thin film (pixel) structure as shown in Figure 4 through spin coating, exposure, development, etc., and the size of each small piece of thin film is the same ( Figure 4as indicated by arrow d). After the etching process, the first electrode layer (indicated by arrow c) is exposed to form a stepped structure, as Figure 1 indicated by arrow c.

[0100] Step 3): Clean the residual glue in Step 2 to form a clean surface;

[0101] Step 4): Spin coat, expose, develop, etc. here to form a thin film array-type thin film (pixel) structure on the sample. The size of each small piece of thin film is the same, but 5 - 20 μm smaller than the side length of the thin film formed in Step 2 (including the values at both endpoints, that is, including the values of both endpoints 5 and 20, and also including the values between 5 and 20). Each thin film (arrow e) is centered with the stepped structure (arrow d) below it; after the etching process, the second electrode contact layer ( Figure 4 arrow d) is exposed to form a stepped structure, as Figure 1 indicated by arrow d.

[0102] Step 4): Clean the residual glue in Step 4 to form a clean surface;

[0103] Step 5): Interconnect the formed array-type pixel structure with the readout circuit through bonding or other interconnection methods. Apply a bias voltage to the upper and lower electrodes of each layer of quantum dot infrared radiation absorption layer in each pixel to read the photocurrent signal formed under infrared irradiation.

[0104] Taking PbS colloidal quantum dots as an example, the preparation and doping process of the infrared absorption layer containing colloidal quantum dots is described as follows: Specifically, PbS quantum dots can be prepared by chemical synthesis. For example, 5 grams of high-purity lead monoxide (PbO), 500 milliliters of 90% pure 1-octadecene (ODE), and 38 milliliters of 90% pure oleic acid (OA) can be placed in a three-neck round-bottom flask and degassed in a vacuum environment at 90 degrees Celsius. Then, under argon, the reaction temperature is raised to 95 - 100 degrees Celsius, and 600 microliters of hexamethyldisilathiane ((TMS)2S) diluted in 30 milliliters of 1-octadecene is rapidly injected. After several minutes, a solution of 750 microliters of hexamethyldisilathiane in 90 milliliters of 1-octadecene is dropped in at a rate of 7.5 milliliters per minute. Thereafter, the reaction is checked in aliquots until quantum dots of the required size are obtained, and then the reaction can be stopped and gradually cooled. Subsequently, the quantum dots need to be precipitated and purified several times with anhydrous acetone and ethanol, and then dispersed in anhydrous toluene. Finally, the concentration is adjusted to 300 milligrams per milliliter, and nitrogen is introduced into the solution to minimize the oxidation of the quantum dots.

[0105] The prepared quantum dots mentioned above also need to be doped. First, the quantum dot solution is spin-coated on a soda-lime glass substrate at a speed of 2000-3000 revolutions per minute to form a thin film. Then, the thin film is treated with a 3-mercaptopropionic acid solution containing zinc iodide for several seconds, and the spin coater is started again for drying treatment, while methanol is dropped in to remove the excess ligands. The above process is repeated until a thin film with the desired thickness is obtained.

[0106] It should be noted that the above method is only a specific embodiment for preparing doped colloidal quantum dots. The device working principle and device structure claimed in the present invention are also applicable to colloidal quantum dots prepared by other types and other methods.

[0107] The embodiment of the present invention reduces the manufacturing cost of multi-band infrared photodetectors. The method described in the embodiment of the present invention is applicable to the preparation of various types of colloidal quantum dot infrared detectors.

[0108] Compared with previous inventions, the present invention has the following significances:

[0109] (1) Compared with the single-layer infrared radiation absorption layer structure, the stacked structure greatly expands the detection band range;

[0110] (2) Compared with the infrared detectors prepared by the epitaxial method, the material preparation cost is reduced.

[0111] It should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the scope. The doping in this type of device is applicable to both n-type doping and p-type doping. Although only an example of a two-layer quantum dot infrared absorption layer is given, it is also applicable to the manufacture of devices with more layers of quantum dot infrared absorption layers. The working mode of each quantum dot absorption layer can be either the interband transition between the conduction band and the valence band or the intraband (intersublevel) transition within the same energy band. In the above schematic diagram, the shape of each pixel is square, but in necessary cases, other shapes can also be used.

[0112] In addition, it should be noted that since the preparation method provided in this embodiment is the preparation method of the infrared detector in the above embodiment, therefore, for the detailed content of some principles and structures, etc., reference can be made to the introduction of the above embodiment, and this embodiment will not be elaborated herein.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An infrared detector, characterized in that, Comprising at least one pixel, the pixel including: a substrate layer, at least one stacked structure, and a top electrode layer arranged in sequence from bottom to top; The stacked structure includes an electrode layer and a quantum dot infrared absorption layer arranged in sequence from bottom to top; for two adjacent stacked structures, the electrode layer in the upper stacked structure and the electrode layer in the lower stacked structure together form a bias voltage, which can guide the photoelectrons formed by the quantum dot infrared absorption layer in the lower stacked structure due to the absorption of infrared photons to form a photocurrent, and thus, the infrared radiation intensity at the corresponding pixel can be judged according to the strength of the photocurrent; Wherein, the quantum dot infrared absorption layer contains a preset number of colloidal quantum dots for detecting infrared radiation; wherein, the wavelengths of the infrared radiation detected by the quantum dot infrared absorption layers in different stacked structures are different; The energy spacing between the ground state and the first excited state of the sub-energy levels inside the conduction band or valence band formed by multiple colloidal quantum dots corresponds to the infrared radiation band, and the colloidal quantum dots are heavily doped through ligand exchange; for the short and medium wavelength infrared bands, the quantum dots absorb infrared photons through interband transitions, and for the medium and long wavelength infrared bands, the quantum dots absorb photons through intraband sub-band transitions; An infrared radiation absorption enhancement layer is arranged between the substrate layer and the stacked structure, and the infrared radiation absorption enhancement layer includes: a preset specific optical structure or a preset optical film to enhance the absorption of infrared radiation, and the optical structure is a triangular optical structure.

2. The infrared detector according to claim 1, characterized in that, For each stacked structure, the size of the quantum dot infrared absorption layer is smaller than that of the electrode layer. For two adjacent stacked structures, the size of the electrode layer in the upper stacked structure is the same as that of the quantum dot infrared absorption layer in the lower stacked structure, and the size of the electrode layer in the upper stacked structure is smaller than that of the electrode layer in the lower stacked structure.

3. The infrared detector according to claim 1 or 2, characterized in that, When the infrared detector includes multiple pixels, the multiple pixels are arranged in an array.

4. The infrared detector according to claim 3, characterized in that, The spacing between two adjacent pixels is 10-50 μm.

5. The infrared detector according to claim 1 or 4, characterized in that, The thickness of the electrode layer in each stacked structure is 50-500 nm.

6. An infrared imager, characterized in that, Including: The infrared detector according to any one of claims 1-5.

7. A method for preparing an infrared detector, characterized in that, Including: Preparing a substrate layer; Preparing at least one stacked structure from bottom to top above the substrate layer, and preparing a top electrode layer on the surface of the topmost stacked structure; wherein, each stacked structure includes an electrode layer and a quantum dot infrared absorption layer arranged in sequence from bottom to top; for two adjacent stacked structures, the electrode layer in the upper stacked structure and the electrode layer in the lower stacked structure together form a bias voltage, which can guide the photoelectrons formed by the quantum dot infrared absorption layer in the lower stacked structure due to the absorption of infrared photons to form a photocurrent, and thus, the infrared radiation intensity at the corresponding pixel can be judged according to the strength of the photocurrent; Wherein, the quantum dot infrared absorption layer contains a preset number of colloidal quantum dots for detecting infrared radiation; wherein, the wavelengths of the infrared radiation detected by the quantum dot infrared absorption layers in different stacked structures are different; Wherein, the quantum dot infrared absorption layer is configured by a pre-driving liquid and obtained through ligand exchange; The energy spacing between the ground state and the first excited state of the sub-levels inside the conduction band or valence band formed by multiple colloidal quantum dots corresponds to the infrared radiation band, and the colloidal quantum dots are heavily doped through ligand exchange; for the short and medium wavelength infrared bands, the quantum dots absorb infrared photons through interband transitions, and for the long and medium wavelength infrared bands, the quantum dots absorb photons through inter-subband transitions within the band; After the substrate layer is prepared, an infrared radiation absorption enhancement layer is prepared on the substrate layer, and the infrared radiation absorption enhancement layer includes: a preset specific optical structure or a preset optical film; Among them, when the infrared radiation absorption enhancement layer includes a preset optical structure, the preset optical structure is prepared on the substrate layer, and the optical structure is a triangular optical structure; when the infrared radiation absorption enhancement layer includes a preset optical film, the preset optical film is coated on the substrate layer.

8. The preparation method according to claim 7, characterized in that, The steps of preparing the stacked structure include: Preparing an electrode layer by deposition or sputtering; Preparing a quantum dot infrared absorption layer on the electrode layer, specifically including: configuring through a pre-driving liquid and obtaining a preset concentration of doping through ligand exchange; Among them, for different stacked structures, by changing the size and material of the quantum dots, a quantum dot infrared absorption layer capable of absorbing infrared radiation of different wavelengths is obtained.

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