Photoelectric detector and manufacturing method thereof

Abstract

This application provides a photodetector and a method for fabricating the same, comprising: preparing a colloidal quantum dot film on an indium tin oxide (ITO) glass substrate; placing the prepared colloidal quantum dot film upside down on a substrate; then applying a predetermined pressure to the ITO glass substrate facing away from the colloidal quantum dot film; and uniformly heating the colloidal quantum dot film for a predetermined period of time using a heating device to reduce the spacing between the colloidal quantum dots. In this application, reducing the spacing between lead sulfide colloidal quantum dots through hot pressing can improve mobility, thereby reducing response time, increasing response rate, and enhancing the performance of the photodetector.

Description

Technical Field

[0001] The present application relates to the field of semiconductors, and in particular to a photodetector and a method for manufacturing the same. Background Art

[0002] The response time reflects the speed at which a photodetector responds to transient signals and is an important indicator for evaluating the performance of a photodetector. In applications such as lidar, time-of-flight sensors (TOF), and optical communications, the response time requirements for photodetectors are extremely high, generally in nanoseconds or less. The faster the response time, the smaller the crosstalk between pulse signals, and the higher the final imaging frame rate. Lead sulfide colloidal quantum dots are a new type of short-wave infrared photosensitive material with the following unique advantages: (1) Due to the quantum confinement effect, the absorption peak of lead sulfide colloidal quantum dots redshifts with the increase of quantum dot size, and can cover the entire short-wave infrared band (2500nm); (2) Lead sulfide colloidal quantum dot films can be directly spin-coated or printed on CMOS at low temperature without the need for lattice matching with the substrate, avoiding complex flip-chip or bonding processes; (3) The reported lead sulfide colloidal quantum dot device has a specific detectivity (D * ) has exceeded 10 13 Jones, showing excellent infrared light detection performance; (4) The carrier diffusion distance in the lead sulfide colloidal quantum dot film is short, the lateral crosstalk between pixels is small, and it is easy to achieve large array and high-resolution imaging. In summary, the CMOS short-wave infrared imaging chip based on lead sulfide colloidal quantum dots has the advantages of low-cost preparation, integrated integration, high resolution and low detection limit, and has great application potential.

[0003] However, current PbS CQD photodetectors generally suffer from slow response times, limiting their further development. Reducing response time and increasing response rate could broaden the application range of PbS CQD photodetectors and further lower the average price of related products in the market.

[0004] In view of this, overcoming the shortcomings of the prior art products is an urgent problem to be solved in this technical field. Summary of the Invention

[0005] The main technical problem solved by this application is to provide a photoelectric detector and a method for manufacturing the same. By using a hot pressing method, the spacing between lead sulfide colloidal quantum dots is reduced, which can increase the mobility, thereby reducing the response time, increasing the response rate, and improving the performance of the photoelectric detector.

[0006] To solve the aforementioned problem, this embodiment provides a method for manufacturing a photodetector, comprising:

[0007] Colloidal quantum dot films were prepared on indium tin oxide (ITO) glass substrates;

[0008] The prepared colloidal quantum dot film is placed upside down on the substrate, and then a set pressure is applied to the ITO glass substrate facing away from the colloidal quantum dot film;

[0009] The colloidal quantum dot film is uniformly heated for a preset time by a heating device to reduce the distance between the colloidal quantum dots.

[0010] Furthermore, the set pressure is 30000Pa~35000Pa.

[0011] Furthermore, the preset time length is 1.5h to 2.5h; and the uniform heating temperature of the heating device is 110°C to 130°C.

[0012] Furthermore, the preparation of the colloidal quantum dot film on the ITO glass substrate includes:

[0013] preparing a mixed halogen ligand solution;

[0014] mixing the halogen ligand solution and the initial quantum dot solution to perform liquid-phase ligand exchange to obtain a ligand exchange solution;

[0015] The ligand exchange solution was washed with n-octane;

[0016] The washed ligand exchange solution is centrifuged to obtain a precipitate;

[0017] mixing the precipitate with an n-butylamine solution to obtain a target quantum dot solution;

[0018] The target quantum dot solution was spin-coated onto an ITO glass substrate to form a colloidal quantum dot film.

[0019] Furthermore, the preparation of the mixed halogen ligand solution includes:

[0020] A mixed powder of iodide ion:bromide ion = 5:1 was dissolved in nitrogen-nitrogen dimethylformamide to obtain a mixed halogen ligand solution.

[0021] Furthermore, the colloidal quantum dot film includes first colloidal quantum dots and second colloidal quantum dots, and the first colloidal quantum dots and the second colloidal quantum dots have different absorption peaks.

[0022] Furthermore, the absorption peak of the first colloidal quantum dots is 1300 nm, and the absorption peak of the second colloidal quantum dots is 1150 nm.

[0023] Furthermore, the production method further comprises:

[0024] forming an electron transport layer on an ITO glass substrate;

[0025] A quantum dot solution is spin-coated on the electron transport layer and then cured to prepare a colloidal quantum dot film.

[0026] Furthermore, the production method further comprises:

[0027] The hole transport layer was obtained by spin coating PbS-EDT on the pressure- and temperature-treated colloidal quantum dot film;

[0028] An electrode is evaporated on the hole transport layer.

[0029] To solve the aforementioned problem, this embodiment provides a photodetector, which is manufactured using the manufacturing method described in this application.

[0030] The beneficial effects of the present application are as follows: The present application provides a photodetector and a method for manufacturing the same, comprising: preparing a colloidal quantum dot film on an ITO glass substrate; placing the prepared colloidal quantum dot film upside down on a substrate; and then applying a predetermined pressure to the ITO glass substrate facing away from the colloidal quantum dot film; and uniformly heating the colloidal quantum dot film for a predetermined period of time using a heating device to reduce the spacing between the colloidal quantum dots. In the present application, reducing the spacing between lead sulfide colloidal quantum dots through hot pressing can improve mobility, thereby reducing response time, increasing response rate, and improving the performance of the photodetector. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] To more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0032] Figure 1 This is a schematic diagram of the extraction process of photogenerated carriers in a photodetector provided by an embodiment of the present application;

[0033] Figure 2 1 is a flow chart of a method for manufacturing a photoelectric detector provided in an embodiment of the present application;

[0034] Figure 3 Schematic diagram of the process of the pressurization method provided in the embodiment of the present application;

[0035] Figure 4 This is an actual test chart of the response time of the photodetector prepared as provided in the examples of the present application. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0037] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more features. In the description of the present application, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0038] In this application, the word "exemplary" is used to mean "serving as an example, illustration, or illustration." Any embodiment described in this application as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. The following description is given to enable any person skilled in the art to implement and use the present application. In the following description, details are listed for the purpose of explanation. It should be understood that one of ordinary skill in the art can recognize that the present application can be implemented without using these specific details. In other instances, well-known structures and processes are not elaborated in detail to avoid obscuring the description of the present application with unnecessary details. Therefore, the present application is not intended to be limited to the embodiments shown, but is consistent with the widest scope consistent with the principles and features disclosed in this application.

[0039] It should be noted that since the method of the embodiment of the present application is executed in an electronic device, the processing objects of each electronic device exist in the form of data or information. For example, time is actually time information. It can be understood that if size, quantity, position, etc. are mentioned in subsequent embodiments, the corresponding data exist for the electronic device to process. The details will not be repeated here.

[0040] Example 1:

[0041] At present, the response time of diode-type photodetectors is mainly determined by the extraction rate of photogenerated carriers. Figure 1 As shown in Figure 1, the extraction of photogenerated carriers primarily involves two processes: drift motion driven by the built-in electric field within the depletion region, and diffusion motion from the depletion region boundary through the diffusion region to the electrode for collection. Therefore, the total time it takes for a photogenerated carrier to be collected by the detector is the sum of these two processes. Furthermore, due to the capacitance effect of the diode, the response time of the photodetector is also affected by the RC time constant of the entire detection system. Therefore, the total time constant for a photodetector can be expressed as:

[0042]

[0043] Among them, τ drift is the time constant of the drift motion, which can be expressed as:

[0044]

[0045] And τ diff is the time constant of diffusion motion, which can be expressed as:

[0046]

[0047] τ RC is the RC time constant of the entire detector circuit and can be expressed as:

[0048]

[0049] According to calculations, in lead sulfide colloidal quantum dot photodetectors, its τ drift , τ diff and τ RC The values ​​of are approximately 5.5μs, 30ns, and 400ns, respectively. The large drift time constant results in a slow overall response time for the lead sulfide colloidal quantum dot photodetector. Improving mobility is the key to reducing the drift time constant and, therefore, the response time.

[0050] In order to improve mobility and reduce response time, this embodiment provides a method for manufacturing a photodetector, which specifically includes the following steps:

[0051] S1: Preparation of colloidal quantum dot thin films on ITO glass substrates;

[0052] Wherein, the colloidal quantum dot film is a lead sulfide colloidal quantum dot film.

[0053] S2: Place the prepared colloidal quantum dot film upside down on the substrate, and then apply a set pressure on the ITO glass substrate facing away from the colloidal quantum dot film;

[0054] The set pressure is 30000 Pa to 35000 Pa. In a preferred embodiment, the set pressure is 32000 Pa.

[0055] S3: uniformly heating the colloidal quantum dot film for a preset time by a heating device to reduce the distance between the colloidal quantum dots.

[0056] like Figure 4 As shown, the measured response time of the photodetector prepared by the above method is reduced to 2.1μs.

[0057] The preset time is 1.5 hours to 2.5 hours, and the uniform heating temperature of the heating device is 110° C. to 130° C. In a preferred embodiment, the preset time is 2 hours, and the uniform heating temperature of the heating device is 120° C.

[0058] In S1, the step of preparing a colloidal quantum dot film on an ITO glass substrate includes: preparing a mixed halogen ligand solution, specifically, dissolving a mixed powder of iodide ions and bromide ions in a ratio of 5:1 in nitrogen-nitrogen dimethylformamide to obtain a mixed halogen ligand solution; mixing the halogen ligand solution with an initial quantum dot solution to perform liquid-phase ligand exchange to obtain a ligand exchange solution; washing the ligand exchange solution with n-octane; centrifuging the washed ligand exchange solution to obtain a precipitate; mixing the precipitate with an n-butylamine solution to obtain a target quantum dot solution; and spin-coating the target quantum dot solution onto the ITO glass substrate to form a colloidal quantum dot film.

[0059] In a preferred embodiment, the colloidal quantum dot film includes first and second colloidal quantum dots, wherein the first and second colloidal quantum dots have different absorption peaks. The absorption peak of the first and second colloidal quantum dots is 1300 nm, and the absorption peak of the first and second colloidal quantum dots is 1150 nm. In this embodiment, the different absorption peaks of the first and second colloidal quantum dots enable flat-band processing of the active layer of the photodetector, resulting in a wide-spectrum response detector with a spectral range from visible light to near-infrared light at 1700 nm and an adjustable cutoff wavelength. In addition, quantum dot photodetector devices that have undergone flat-band processing have lower dark current than larger-scale quantum dot devices.

[0060] In a specific application scenario, an electron transport layer is formed on an ITO glass substrate. A quantum dot solution is spin-coated on the electron transport layer and cured to produce a colloidal quantum dot film. Then, PbS-EDT is spin-coated on the pressure- and temperature-treated colloidal quantum dot film to form a hole transport layer. An electrode is then evaporated on the hole transport layer.

[0061] In other embodiments, colloidal quantum dots may be incorporated into a matrix such as perovskite, which may also serve to reduce the detector response time.

[0062] Example 2:

[0063] This embodiment also provides another method for manufacturing a photodetector. The colloidal quantum dot film includes first colloidal quantum dots and second colloidal quantum dots. The colloidal quantum dot film can be prepared on an ITO glass substrate in the following manner.

[0064] In this embodiment, PbI2, PbBr2 and DMF are mixed and dissolved in a glass bottle to prepare a ligand solution; PbI2:PbBr2=2.458g:0.848g are weighed in a glove box, 20ml of DMF is measured, and the mixture is mixed and dissolved in a glass bottle to prepare a ligand solution.

[0065] The first colloidal quantum dots and the second colloidal quantum dots are respectively dissolved in n-octane to obtain solution I and solution II; solution I and solution II are respectively mixed with a ligand solution, and after the mixed solution I and the mixed solution II are separated, a first supernatant liquid is sucked out from the mixed solution I with a dropper, and a second supernatant liquid is sucked out from the mixed solution II with a dropper; a first solid quantum dot and a second solid quantum dot are obtained based on the first supernatant liquid and the second supernatant liquid; DMF and n-butylamine are mixed and shaken evenly to obtain an amine solution; the first solid quantum dot and the second solid quantum dot are respectively mixed with the amine solution to obtain a first quantum dot solution and a second quantum dot solution.

[0066] The method of obtaining the first solid-state quantum dots and the second solid-state quantum dots based on the first supernatant and the second supernatant specifically includes: adding n-octane to the first supernatant and the second supernatant respectively with a pipette and shaking; after the mixed first supernatant and the mixed second supernatant are separated into layers, sucking out the mixed supernatant and the gray matter floating between the two layers from the mixed first supernatant and the mixed second supernatant respectively with a dropper; packaging the mixed supernatant and the gray matter floating between the two layers into different centrifuge tubes, discarding the supernatant, wiping off the residual liquid on the tube mouth and tube wall with a cotton swab, and draining the solvent in the centrifuge tube to obtain the first solid-state quantum dots and the second solid-state quantum dots.

[0067] Specifically, an amine solution at a concentration of 200-400 mg / ml was added to a centrifuge tube containing solid quantum dots at the bottom. The solution was then slowly shaken for 1-2 minutes using a small oscillator to completely dissolve the quantum dots, thereby obtaining the first and second quantum dot solutions. The amine solutions containing quantum dots of different sizes were then mixed in a 1:1 volume ratio and shaken evenly to obtain a mixed quantum dot solution.

[0068] Next, turn on the spin coater and vacuum pump, set the speed to 2500 rpm, the duration to 40 seconds, and the acceleration to 500. Place the device on a tray and use an ear bulb to remove any dust. Spin-coat the quantum dot mixture. Adjust the hot plate temperature to 60-100°C, anneal for 7-10 minutes, and remove the amine solution to prepare a colloidal quantum dot film.

[0069] In this embodiment, the colloidal quantum dot film includes first and second colloidal quantum dots. The first and second colloidal quantum dots have different absorption peaks. This allows the colloidal quantum dot film to be flat-banded, resulting in a detector with a broad spectral response, ranging from visible light to near-infrared light at 1700 nm, and with an adjustable cutoff wavelength. Furthermore, compared to larger quantum dot devices, quantum dot photodetectors that have undergone flat-banding have lower dark current.

[0070] Example 3:

[0071] Based on the aforementioned embodiment 1, this embodiment provides another method for manufacturing a photodetector, which specifically includes the following steps:

[0072] To reduce the presence of halogen ions bridging between quantum dots, a lower concentration of iodine-bromide ligands was used to passivate the quantum dots. A mixed powder of iodide ions and bromide ions (5:1) was dissolved in 10 ml of N,N-dimethylformamide to produce a mixed halogen ligand solution. 10 ml of the ligand solution was then mixed with 10 ml of a lead sulfide quantum dot solution for liquid-phase ligand exchange. After ligand exchange, the lead sulfide quantum dot N,N-dimethylformamide solution was repeatedly washed with 10 ml of n-octane. After washing, the quantum dot DMF solution was centrifuged at 5000 rpm for 5 minutes. The precipitate was then dissolved uniformly in a mixture of N,N-dimethylformamide and n-butylamine and spin-coated onto a substrate at 2500 rpm to complete the preparation of the quantum dot film.

[0073] In order to reduce the distance between lead sulfide colloidal quantum dots and thus increase the mobility of lead sulfide colloidal quantum dot films, the operation process is as follows: Figure 2 As shown in the figure, the prepared PbS CQD film is placed upside down on a clean, flat substrate (silicon wafer). A pressure of 32,000 Pa is then applied to the ITO glass substrate on the back, while the entire film is maintained at a uniform temperature of 120°C. The entire process lasts for two hours. Under the action of temperature and pressure, the spacing between the PbS CQDs gradually decreases, making the entire film denser and smoother. This also promotes coupling between the quantum dots, thereby increasing the film's mobility and reducing the photodetector's response time.

[0074] The above description is only an implementation method of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the description and drawings of this application, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for manufacturing a photodetector, characterized in that: include: forming an electron transport layer on an ITO glass substrate; Spin coating a PbS quantum dot solution on the electron transport layer and performing a curing treatment to prepare a PbS colloidal quantum dot film; The prepared PbS colloidal quantum dot film is placed upside down on a substrate, and then a set pressure is applied to the ITO glass substrate facing away from the PbS colloidal quantum dot film. At the same time, the PbS colloidal quantum dot film is uniformly heated for a preset time using a heating device to reduce the spacing between the PbS colloidal quantum dots. The hole transport layer was obtained by spin coating PbS-EDT on the PbS colloidal quantum dot film that had been subjected to pressure and temperature treatment. An electrode is evaporated on the hole transport layer.

2. The production method according to claim 1, wherein: The set pressure is 30000Pa~35000Pa.

3. The production method according to claim 1, wherein: The preset time length is 1.5h to 2.5h; and the uniform heating temperature of the heating device is 110°C to 130°C.

4. The production method according to claim 1, wherein: The method of preparing a PbS colloidal quantum dot film on an ITO glass substrate comprises: preparing a mixed halogen ligand solution; mixing the halogen ligand solution and the initial quantum dot solution to perform liquid-phase ligand exchange to obtain a ligand exchange solution; The ligand exchange solution was washed with n-octane; The washed ligand exchange solution is centrifuged to obtain a precipitate; mixing the precipitate with an n-butylamine solution to obtain a target quantum dot solution; The target quantum dot solution was spin-coated onto an ITO glass substrate to form a PbS colloidal quantum dot film.

5. The production method according to claim 4, characterized in that: The configuration of the mixed halogen ligand solution comprises: A mixed powder of iodide ion:bromide ion = 5:1 was dissolved in nitrogen-nitrogen dimethylformamide to obtain a mixed halogen ligand solution.

6. The production method according to claim 1, wherein: The PbS colloidal quantum dot film includes first colloidal quantum dots and second colloidal quantum dots, and the first colloidal quantum dots and the second colloidal quantum dots have different absorption peaks.

7. The production method according to claim 6, characterized in that: The absorption peak of the first colloidal quantum dots is 1300 nm, and the absorption peak of the second colloidal quantum dots is 1150 nm.

8. A photoelectric detector, characterized in that: The photodetector is manufactured by the manufacturing method according to claims 1 to 7.

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