Quantum dot room temperature medium wave infrared detector and preparation method thereof

Abstract

According to the quantum dot room-temperature medium-wave infrared detector and the preparation method thereof, while normal transmission of light current is allowed, dark current can be effectively blocked, possibility is provided for the infrared detector to work at room temperature or higher temperature, wider application of the infrared detector in various fields is expected to be promoted, cost is reduced, and miniaturization and integration of a system are achieved. The solar cell comprises a substrate (1), a bottom electrode (2), an electron transport layer (3), a quantum dot layer (4), an organic polymer passivation layer (5), a hole transport layer (6) and a top electrode (7), the bottom electrode is arranged on one side of the substrate, the electron transport layer is arranged on the side, away from the substrate, of the bottom electrode, the quantum dot layer is arranged on the side, away from the bottom electrode, of the electron transport layer, the passivation layer is arranged on the side, away from the electron transport layer, of the quantum dot layer, and the hole transport layer is arranged on the side, away from the quantum dot layer, of the passivation layer. The top electrode is arranged on the side, away from the passivation layer, of the hole transport layer, and bias voltage is applied between the top electrode and the bottom electrode to form an electric field.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectric detectors, and in particular to a quantum dot room temperature medium wave infrared detector and a method for preparing the quantum dot room temperature medium wave infrared detector. Background Art

[0002] In the field of infrared detection, medium-wave infrared (3-5 microns) radiation has good transmission characteristics in the atmosphere and is an important research object for infrared detection. With the development of science and technology, the application demand for medium-wave infrared detection technology in military reconnaissance, target identification, environmental monitoring, medical diagnosis and other fields is increasing.

[0003] At present, medium-wave infrared detectors are mainly based on epitaxial semiconductor growth materials, and the flip-chip bonding process of coupling with the readout circuit is very complicated. At the same time, high-performance detectors require refrigeration equipment to maintain a low operating temperature, which increases the volume and weight of the detectors, and also increases the cost and maintenance difficulty. Detectors operating at room temperature can simplify the system structure, reduce costs, and improve the reliability and stability of the system. Therefore, it is of great significance to study medium-wave infrared detectors operating at room temperature. Summary of the invention

[0004] In order to overcome the defects of the prior art, the technical problem to be solved by the present invention is to provide a quantum dot room-temperature medium-wave infrared detector, which can effectively block dark current while allowing normal transmission of photocurrent, thereby making it possible for the infrared detector to operate at room temperature or higher temperatures. It is expected to promote the wider application of infrared detectors in various fields, reduce costs, and realize miniaturization and integration of the system.

[0005] The technical solution of the present invention is: the quantum dot room temperature medium wave infrared detector comprises: a substrate (1), a bottom electrode (2), an electron transport layer (3), a quantum dot layer (4), an organic polymer passivation layer (5), a hole transport layer (6) and a top electrode (7);

[0006] The bottom electrode is arranged on one side of the substrate, the electron transport layer is arranged on the side of the bottom electrode away from the substrate, the quantum dot layer is arranged on the side of the electron transport layer away from the bottom electrode, the passivation layer is arranged on the side of the quantum dot layer away from the electron transport layer, the hole transport layer is arranged on the side of the passivation layer away from the quantum dot layer, and the top electrode is arranged on the side of the hole transport layer away from the passivation layer, and a bias voltage is applied between the top electrode and the bottom electrode to form an electric field.

[0007] A method for preparing a quantum dot room temperature medium-wave infrared detector is also provided, which comprises the following steps:

[0008] (1) Synthesis of medium-wave responsive mercury telluride quantum dot materials by hot injection method;

[0009] (2) providing a substrate, and preparing a bottom electrode on the substrate by magnetron sputtering technology;

[0010] (3) Spin coating a ZnO solution on the side of the bottom electrode facing away from the substrate to form a film, and annealing by high temperature heating to obtain an electron transport layer;

[0011] (4) depositing mercury telluride quantum dots with an absorption band of 3 to 5 μm onto the electron transport layer by spin coating, and treating with an ethanedithiol solution to obtain a mid-wave infrared quantum dot layer;

[0012] (5) depositing the organic polymer solution onto the quantum dot layer by spin coating to obtain a passivation layer;

[0013] (6) depositing molybdenum trioxide onto the passivation layer to obtain a hole transport layer;

[0014] (7) patterning gold, silver, copper, aluminum or indium tin oxide by electron beam evaporation or magnetron sputtering to form a top electrode;

[0015] Wherein, step (1) comprises the following sub-steps:

[0016] (1.1) Preparation of mercury precursor solution: Under an inert gas atmosphere, oleylamine was selected as the ligand solvent, and the solvent was heated to 150°C and maintained at this temperature for 2 hours to completely remove the moisture in the ligand and the solvent. Subsequently, the system temperature was adjusted to stabilize at

[0017] 110°C, at this time, add mercuric chloride as a mercury source, stir to fully dissolve and disperse it evenly, and obtain the desired mercury precursor solution;

[0018] (1.2) preparing a tellurium precursor solution: in an inert gas atmosphere, dispersing tellurium powder as a tellurium source in a trioctylphosphine ligand solvent, heating the solvent to 120° C., and stirring to ensure that the tellurium source is completely dissolved and evenly dispersed in the solvent, thereby preparing a tellurium precursor solution;

[0019] (1.3) Synthesis reaction and post-treatment: Under the continuous protection of inert gas, the prepared tellurium precursor solution is injected into the mercury precursor solution. The temperature of this injection process is controlled at

[0020] 95℃ to 110℃ to ensure that the size of the product obtained by the reaction is controlled to 8-10 nanometers

[0021] After the reaction has been going on for a while, tetrachloroethylene is used as a quencher to terminate the reaction;

[0022] (1.4) Using at least one of methanol, ethanol or isopropanol as an anti-solvent, the reaction system is centrifuged to remove unreacted substances and impurities; after centrifugation, the obtained product is dispersed in at least one dispersing solvent of chlorobenzene, toluene or n-hexane to obtain a final product dispersion.

[0023] The present invention has the following beneficial effects:

[0024] 1. The present invention adopts the hot injection method to synthesize medium-wavelength quantum dots, which has mild reaction conditions, low cost, easy operation, high success rate, and can realize large-scale production;

[0025] 2. The present invention uses a spin coating method to couple the quantum dot layer and the organic polymer passivation layer, which is simple;

[0026] 3. The detector prepared by the present invention can realize medium-wave infrared detection under room temperature conditions, reduce the dark current of the device, and improve the signal-to-noise ratio;

[0027] 4. The device preparation method provided by the present invention can be extended to the arrayed focal plane to improve the response uniformity between pixels.

[0028] 5. The present invention can effectively block dark current while allowing normal transmission of photocurrent, making it possible for infrared detectors to operate at room temperature or higher temperatures. It is expected to promote the wider application of infrared detectors in various fields and realize the miniaturization and integration of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the structure of the quantum dot room temperature medium wave infrared detector according to the present invention.

[0030] Figure 2 The present invention is a flow chart of a method for preparing a quantum dot room temperature medium wave infrared detector. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0032] It should be noted that the term "comprises" and any variations in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, apparatus, product or equipment that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products or equipment.

[0033] like Figure 1 As shown, the quantum dot room temperature medium wave infrared detector comprises: a substrate 1, a bottom electrode 2, an electron transport layer 3, a quantum dot layer 4, an organic polymer passivation layer 5, a hole transport layer 6 and a top electrode 7;

[0034] The bottom electrode is arranged on one side of the substrate, the electron transport layer is arranged on the side of the bottom electrode away from the substrate, the quantum dot layer is arranged on the side of the electron transport layer away from the bottom electrode, the passivation layer is arranged on the side of the quantum dot layer away from the electron transport layer, the hole transport layer is arranged on the side of the passivation layer away from the quantum dot layer, and the top electrode is arranged on the side of the hole transport layer away from the passivation layer, and a bias voltage is applied between the top electrode and the bottom electrode to form an electric field.

[0035] Preferably, the substrate is made of silicon, sapphire or flexible resin.

[0036] Preferably, the bottom electrode is made of indium tin oxide and has a thickness of 150 to 200 micrometers.

[0037] Preferably, the electron transport layer is made of zinc oxide and has a thickness of 30 nanometers.

[0038] Preferably, the medium-wave infrared quantum dot layer is a mercury telluride quantum dot layer with a thickness of 400 nanometers.

[0039] Preferably, the passivation layer is prepared from a material selected from PCDTPT (poly[4,8-di(2,2-octylcarbonyl)thiophene-2,6-di(3,7-dinitrobenzothiadiazine] copolymer), P3HT (poly(3 hexylthiophene-2,5-diyl)), PM6 (poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophene-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alternate-(5,5-(1',3'-dithiophene-2-yl-5',7'-bis ... dithiophene)]) or D18 (poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-5,5'-(5,8-bis(4-(2-butyloctyl)thiophen-2-yl)dithiophene[3',2':3,4;2",3":5,6]benzo[1,2-c][1,2,5]thiadiazole)]) with a thickness of 30 nm.

[0040] Preferably, the hole transport layer is made of molybdenum trioxide and has a thickness of 3 nanometers.

[0041] Preferably, the top electrode is made of gold, silver, copper, aluminum and indium tin oxide, and has a thickness of 50 to 100 nanometers.

[0042] like Figure 2 As shown, a method for preparing a quantum dot room temperature medium-wave infrared detector is also provided, which comprises the following steps:

[0043] (1) Synthesis of medium-wave responsive mercury telluride quantum dot materials by hot injection method;

[0044] (2) providing a substrate, and preparing a bottom electrode on the substrate by magnetron sputtering technology;

[0045] (3) Spin coating a ZnO solution on the side of the bottom electrode facing away from the substrate to form a film, and annealing by high temperature heating to obtain an electron transport layer;

[0046] (4) depositing mercury telluride quantum dots with an absorption band of 3 to 5 μm onto the electron transport layer by spin coating, and treating with an ethanedithiol solution to obtain a mid-wave infrared quantum dot layer;

[0047] (5) depositing the organic polymer solution onto the quantum dot layer by spin coating to obtain a passivation layer;

[0048] (6) depositing molybdenum trioxide onto the passivation layer to obtain a hole transport layer;

[0049] (7) patterning gold, silver, copper, aluminum or indium tin oxide by electron beam evaporation or magnetron sputtering to form a top electrode;

[0050] Wherein, step (1) comprises the following sub-steps:

[0051] (1.1) Preparation of mercury precursor solution: Under an inert gas atmosphere, oleylamine was selected as the ligand solvent, and the solvent was heated to 150°C and maintained at this temperature for 2 hours to completely remove the moisture in the ligand and the solvent. Subsequently, the system temperature was adjusted to stabilize at

[0052] 110°C, at this time, add mercuric chloride as a mercury source, stir to fully dissolve and disperse it evenly, and obtain the desired mercury precursor solution;

[0053] (1.2) preparing a tellurium precursor solution: in an inert gas atmosphere, dispersing tellurium powder as a tellurium source in a trioctylphosphine ligand solvent, heating the solvent to 120° C., and stirring to ensure that the tellurium source is completely dissolved and evenly dispersed in the solvent, thereby preparing a tellurium precursor solution;

[0054] (1.3) Synthesis reaction and post-treatment: Under the continuous protection of inert gas, the prepared tellurium precursor solution is injected into the mercury precursor solution. The temperature of this injection process is controlled at

[0055] 95℃ to 110℃ to ensure that the size of the product obtained by the reaction is controlled to 8-10 nanometers

[0056] After the reaction has been going on for a while, tetrachloroethylene is used as a quencher to terminate the reaction;

[0057] (1.4) Using at least one of methanol, ethanol or isopropanol as an anti-solvent, the reaction system is centrifuged to remove unreacted substances and impurities; after centrifugation, the obtained product is dispersed in at least one dispersing solvent of chlorobenzene, toluene or n-hexane to obtain a final product dispersion.

[0058] The present invention has the following beneficial effects:

[0059] 1. The present invention adopts the hot injection method to synthesize medium-wavelength quantum dots, which has mild reaction conditions, low cost, easy operation, high success rate, and can realize large-scale production;

[0060] 2. The present invention uses a spin coating method to couple the quantum dot layer and the organic polymer passivation layer, which is simple;

[0061] 3. The detector prepared by the present invention can realize medium-wave infrared detection under room temperature conditions, reduce the dark current of the device, and improve the signal-to-noise ratio;

[0062] 4. The device preparation method provided by the present invention can be extended to the arrayed focal plane to improve the response uniformity between pixels.

[0063] 5. The present invention can effectively block dark current while allowing normal transmission of photocurrent, making it possible for infrared detectors to operate at room temperature or higher temperatures. It is expected to promote the wider application of infrared detectors in various fields and realize the miniaturization and integration of the system.

[0064] Preferably, in the step (2), a substrate is prepared, and a silicon wafer with a size of 1 cm×1 cm is selected as the substrate. The surface of the silicon wafer is processed by a standard cleaning process to ensure that no impurities remain; a layer of indium tin oxide film is sputtered on one side of the silicon wafer as a bottom electrode by magnetron sputtering technology to ensure good conductivity and light transmittance, and the ITO is processed by wet etching to obtain a patterned base electrode; in the step (3), a zinc oxide solution with a concentration of 25 mg / ml is dripped onto the bottom electrode, and a film is formed by spin coating at a speed of 3000 rpm using a coating machine. After the spin coating is completed, the sample is placed in an oven at 150 degrees Celsius for heating and annealing for 30 minutes to remove the solvent and promote the formation of ZnO crystals to obtain an electron transport layer; in the step (4), an appropriate amount of mercury telluride quantum dots with an absorption band of 3 to 5 microns are taken. The solution is uniformly deposited on the electron transport layer by spin coating, the spin coating parameters are set to 2000 rpm, and after spin coating, the quantum dot layer is treated with an ethanedithiol solution to optimize its photoelectric performance and form a medium-wave infrared quantum dot layer; in the step (5), a poly (3-hexylthiophene-2,5-diyl) solution with a concentration of 10 mg / mL is added dropwise to the quantum dot layer, and a film is formed by spin coating at a speed of 3000 rpm to obtain a passivation layer; in the step (6), a molybdenum trioxide film with a thickness of 3 nanometers is deposited on the passivation layer by vacuum thermal evaporation as a hole transport layer; in the step (7), an electron beam evaporation technique is used to evaporate a gold film with a thickness of 80 nanometers on the hole transport layer as a top electrode, and during the evaporation process, patterning is achieved through a mask plate to form a desired electrode shape.

[0065] The present invention effectively passivates the surface defects of the mercury telluride film by introducing a passivation layer on the surface of the quantum dots, significantly reduces the thermally activated carriers in the intermediate gap impurity state, fully utilizes the energy quantization of the quantum dots, and realizes medium-wave infrared detection under room temperature conditions. The structure is designed to form a band engineering interface barrier to form a heterojunction, which prevents the transmission of dark current without affecting the efficiency of photocarrier transmission and shows a more uniform photocurrent mapping.

[0066] The present invention is a vertical photovoltaic device structure. An electric field is formed by applying a bias voltage between a top electrode and a bottom electrode. Incident infrared light is incident from the bottom electrode and absorbed by medium-wave infrared quantum dots. A passivation layer is introduced on the surface of the quantum dots to effectively passivate the surface defects of the mercury telluride film, significantly reduce the thermally activated carriers in the intermediate gap impurity state, make full use of the energy quantization of the quantum dots, and realize medium-wave infrared detection under room temperature conditions.

[0067] The current solution has achieved the purpose of mid-wave infrared detection under room temperature conditions through specific design and material selection, but there are other alternatives that may also achieve this invention purpose. The following are some possible alternatives:

[0068] 1. Replacement of quantum dot materials: In addition to mercury telluride quantum dots, other quantum dot materials with mid-wave infrared absorption capabilities can be considered, such as lead selenide. These materials can also optimize their optoelectronic properties through energy band engineering to achieve detection effects similar to the current solution.

[0069] 2. Change the heterojunction material: The scheme of the present invention uses zinc oxide and poly (3 hexylthiophene-2,5-diyl) / molybdenum trioxide as the band engineering interface barrier. It is possible to consider using other materials with similar energy bands and structures to form a heterojunction to form a heterojunction with a similar energy band structure. It can also prevent the transmission of dark current without affecting the efficiency of photocarrier transmission.

[0070] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. Quantum dot room temperature medium wave infrared detector, characterized by: It comprises: a substrate (1), a bottom electrode (2), an electron transport layer (3), a quantum dot layer (4), an organic polymer passivation layer (5), a hole transport layer (6) and a top electrode (7); The bottom electrode is arranged on one side of the substrate, the electron transport layer is arranged on the side of the bottom electrode away from the substrate, the quantum dot layer is arranged on the side of the electron transport layer away from the bottom electrode, the passivation layer is arranged on the side of the quantum dot layer away from the electron transport layer, the hole transport layer is arranged on the side of the passivation layer away from the quantum dot layer, and the top electrode is arranged on the side of the hole transport layer away from the passivation layer, and a bias voltage is applied between the top electrode and the bottom electrode to form an electric field.

2. The quantum dot room temperature medium wave infrared detector according to claim 1, characterized in that: The substrate is made of silicon, sapphire or flexible resin.

3. The quantum dot room temperature medium wave infrared detector according to claim 2, characterized in that: The bottom electrode is made of indium tin oxide and has a thickness of 150 to 200 microns.

4. The quantum dot room temperature medium wave infrared detector according to claim 3, characterized in that: The electron transport layer is made of zinc oxide and has a thickness of 30 nanometers.

5. The quantum dot room temperature medium wave infrared detector according to claim 4, characterized in that: The medium-wave infrared quantum dot layer is a mercury telluride quantum dot layer with a thickness of 400 nanometers.

6. The quantum dot room temperature medium wave infrared detector according to claim 5, characterized in that: The passivation layer is made of PCDTPT, P3HT, PM6 or D18, and has a thickness of 30 nanometers.

7. The quantum dot room temperature medium wave infrared detector according to claim 6, characterized in that: The hole transport layer is made of molybdenum trioxide and has a thickness of 3 nanometers.

8. The quantum dot room temperature medium wave infrared detector according to claim 7, characterized in that: The top electrode is made of gold, silver, copper, aluminum and indium tin oxide, and has a thickness of 50 to 100 nanometers.

9. The method for preparing a quantum dot room temperature medium wave infrared detector according to claim 8, characterized in that: It includes the following steps: (1) Synthesis of medium-wave responsive mercury telluride quantum dot materials by hot injection method; (2) providing a substrate, and preparing a bottom electrode on the substrate by magnetron sputtering technology; (3) Spin coating a ZnO solution on the side of the bottom electrode facing away from the substrate to form a film, and annealing by high temperature heating to obtain an electron transport layer; (4) depositing mercury telluride quantum dots with an absorption band of 3 to 5 μm onto the electron transport layer by spin coating, and treating with an ethanedithiol solution to obtain a mid-wave infrared quantum dot layer; (5) depositing the organic polymer solution onto the quantum dot layer by spin coating to obtain a passivation layer; (6) depositing molybdenum trioxide onto the passivation layer to obtain a hole transport layer; (7) patterning gold, silver, copper, aluminum or indium tin oxide by electron beam evaporation or magnetron sputtering to form a top electrode; Wherein, step (1) comprises the following sub-steps: (1.1) Preparation of mercury precursor solution: Under an inert gas atmosphere, oleylamine was selected as the ligand solvent, and the solvent was heated to 150°C and maintained at this temperature for 2 hours to completely remove the moisture in the ligand and the solvent. Subsequently, the system temperature was adjusted to stabilize at 110°C, at this time, add mercuric chloride as a mercury source, stir to fully dissolve and disperse it evenly, and obtain the desired mercury precursor solution; (1.2) preparing a tellurium precursor solution: in an inert gas atmosphere, dispersing tellurium powder as a tellurium source in a trioctylphosphine ligand solvent, heating the solvent to 120° C., and stirring to ensure that the tellurium source is completely dissolved and evenly dispersed in the solvent, thereby preparing a tellurium precursor solution; (1.3) Synthesis reaction and post-treatment: Under the continuous protection of inert gas, the prepared tellurium precursor solution is injected into the mercury precursor solution. The temperature of the injection process is controlled between 95°C and 110°C to ensure that the size of the reaction product is controlled within 8 to 10 nanometers. After the reaction is carried out for a period of time, tetrachloroethylene is used as a quencher to terminate the reaction; (1.4) Using at least one of methanol, ethanol or isopropanol as an anti-solvent, the reaction system is centrifuged to remove unreacted substances and impurities; after centrifugation, the obtained product is dispersed in at least one dispersing solvent of chlorobenzene, toluene or n-hexane to obtain a final product dispersion.

10. The method for preparing a quantum dot room temperature medium wave infrared detector according to claim 9, characterized in that: In the step (2), a substrate is prepared, and a piece of A 1cm×1cm silicon wafer is used as the substrate, and the surface of the silicon wafer is processed through a standard cleaning process to ensure that no impurities remain; A layer of indium tin oxide film is sputtered on one side of a silicon wafer as a bottom electrode by magnetron sputtering technology to ensure good conductivity and light transmittance, and the ITO is processed by wet etching to obtain a patterned base electrode; in the step (3), a zinc oxide solution with a concentration of 25 mg / ml is dripped onto the bottom electrode, and a film is formed by spin coating at a speed of 3000 rpm using a coating machine. After the spin coating is completed, the sample is placed in an oven at 150 degrees Celsius for heating and annealing for 30 minutes to remove the solvent and promote the formation of ZnO crystals to obtain an electron transport layer; in the step (4), an appropriate amount of mercury telluride quantum dot solution with an absorption band of 3 to 5 microns is taken and uniformly deposited on the electron transport layer by spin coating, and the spin coating parameters are set to 20 00 rpm, after spin coating, the quantum dot layer is treated with an ethanedithiol solution to optimize its photoelectric performance and form a medium-wave infrared quantum dot layer; in the step (5), a poly (3-hexylthiophene-2,5-diyl) solution with a concentration of 10 mg / mL is added dropwise to the quantum dot layer, and a film is formed by spin coating at a speed of 3000 rpm to obtain a passivation layer; in the step (6), a vacuum thermal evaporation method is used to deposit a layer of molybdenum trioxide film with a thickness of 3 nanometers on the passivation layer as a hole transport layer; in the step (7), an electron beam evaporation technique is used to evaporate a layer of gold film with a thickness of 80 nanometers on the hole transport layer as a top electrode, and during the evaporation process, patterning is achieved through a mask plate to form a desired electrode shape.

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