A PbS quantum dot detector and a preparation method thereof

Abstract

The application discloses a PbS quantum dot detector and a preparation method thereof, and comprises the following steps: dissolving PbS quantum dots in a first solution to prepare a PbS quantum dot solution; dissolving BMIM-BF4 in a second solution to prepare a first ionic liquid solution; adding a third solution into the first ionic liquid solution, stirring until uniform and transparent to form a mixed solution; adding the mixed solution into the PbS quantum dot solution and stirring to form a turbid solution; centrifugal precipitation separation is performed on the turbid solution, and a detergent is added to wash, so that PbS quantum dots with a surface modified by BMIM-BF4 are obtained; the PbS quantum dots with the surface modified by BMIM-BF4 are prepared into a PbS quantum dot film modified by BMIM-BF4; ITO is used as a bottom electrode, and ZnO, the PbS quantum dot film modified by BMIM-BF4, MoO3 and Ag are sequentially deposited on the surface of the bottom electrode to form a p-n heterojunction photoelectric detector. The PbS quantum dot detector disclosed by the embodiment of the application can effectively solve the ion migration problem and significantly improve the photoelectric performance and long-term stability of the film.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photoelectric detectors, and particularly relates to a PbS quantum dot detector and a preparation method thereof. BACKGROUND

[0002] As an important infrared detection technology, the PbS quantum dot detector has attracted much attention in many fields due to its excellent photoelectric performance and flexible adjustability. However, the performance and stability of the PbS quantum dot detector are significantly affected by the ion migration on the surface of the quantum dot. Iodine ions (I-) in the PbS quantum dot are prone to migrate from the quantum dot to other layers (such as the SnO2 layer) of the device under the action of an electric field and temperature, which can cause a series of adverse consequences, such as a decrease in the long-term stability of the device, deterioration of the photoelectric performance, and even formation of crystals due to ion accumulation, resulting in irreversible damage to the device. The traditional interface modification and passivation means have limited effect and cannot fundamentally solve the problem of ion migration. Therefore, how to fundamentally solve the problem of ion migration is an important problem that needs to be solved at present. SUMMARY

[0003] The technical problem to be solved by the application is that the iodine ions in the existing PbS quantum dot detector are prone to migrate during work, and the application provides a PbS quantum dot detector and a preparation method thereof.

[0004] To solve the above technical problem, the application provides a PbS quantum dot detector preparation method, which comprises the following steps:

[0005] S1: dissolving PbS quantum dots in a first solution to prepare a PbS quantum dot solution;

[0006] S2: dissolving 1-butyl-2,3-dimethylimidazolium tetrafluoroborate (BMIM-BF4) in a second solution to prepare a first ionic liquid solution;

[0007] S3: adding a third solution to the first ionic liquid solution, stirring until uniform and transparent to form a mixed solution; and adding the mixed solution to the PbS quantum dot solution and performing secondary stirring to form a turbid solution;

[0008] S4: performing centrifugal sedimentation separation on the turbid solution and adding a detergent for washing to obtain PbS quantum dots with a surface modified by BMIM-BF4;

[0009] S5: preparing the PbS quantum dots with the surface modified by BMIM-BF4 into a PbS quantum dot film modified by BMIM-BF4;

[0010] S6: depositing ZnO, BMIM-BF4 modified PbS quantum dot film, MoO3 and Ag on the surface of ITO as bottom electrode in sequence to form a p-n heterojunction photodetector.

[0011] Preferably, in the step S1, the first solution comprises one or more combinations of n-hexane and n-octane; and the concentration of the PbS quantum dot solution is 8 mg / mL-12 mg / mL.

[0012] Preferably, in the step S2, the second solution comprises ethanol; and the concentration of the first ionic liquid solution is 0.01 mol / L-0.02 mol / L.

[0013] Preferably, in the step S3, the third solution comprises isopropyl alcohol; and the time of the secondary stirring is 20 minutes-40 minutes.

[0014] Preferably, in the step S4, the washing agent comprises n-octane; and the washing times are greater than or equal to 2 times.

[0015] Preferably, the step S5 specifically comprises:

[0016] S51: dissolving the PbS quantum dots with the surface modified by BMIM-BF4 in a fourth solution to form a film-forming solution;

[0017] S52: dropping the film-forming solution on the surface of the ITO substrate, spin coating for 30 seconds at 2000 rpm to prepare a uniform quantum dot film; and dropping the BMIM-BF4 solution on the surface of the spin-coated film, spin coating again to enhance the compactness and interface quality of the film.

[0018] Preferably, the step S5 further comprises:

[0019] S53: annealing the prepared film at 80℃ for 10 minutes under nitrogen protection to improve the crystallization quality and interface stability of the quantum dot film.

[0020] Preferably, in the step S51, the fourth solution comprises toluene; and the concentration of the film-forming solution is 350 mg / mL-450 mg / mL.

[0021] The embodiment of the application further provides a PbS quantum dot detector prepared by the PbS quantum dot detector preparation method.

[0022] The embodiment of the application has the following beneficial effects:

[0023] (1) The present invention introduces the ionic liquid BMIM-BF4 as a surface ligand regulator and ion migration inhibitor for PbS quantum dots. During the preparation process, BMIM-BF4 coordinates with iodine ions on the surface of the PbS quantum dots, significantly enhancing the ionic stability of the PbS quantum dots and optimizing the film quality, thereby improving the photoelectric performance and long-term reliability of the PbS quantum dot detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 A flow chart of a method for preparing a PbS quantum dot detector provided for the implementation of the present invention;

[0026] Figure 2 A graph showing the IV characteristics of a PbS quantum dot detector provided for the implementation of the present invention;

[0027] Figure 3 A comparison light absorption spectrum of a PbS quantum dot detector provided for the implementation of the present invention;

[0028] Figure 4 A light absorption spectrum of a PbS quantum dot detector provided for the implementation of the present invention. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0030] like Figure 1 As shown, this embodiment discloses a method for preparing a PbS quantum dot detector, which includes the following steps:

[0031] S1: dissolving PbS quantum dots in the first solution to prepare a PbS quantum dot solution;

[0032] S2: dissolving 1-butyl-2,3-dimethylimidazolium tetrafluoroborate (BMIM-BF4) in the second solution to prepare a first ionic liquid solution;

[0033] S3: adding the third solution into the first ionic liquid solution, stirring until uniform and transparent to form a mixed solution; and adding the mixed solution into the PbS quantum dot solution and stirring for a second time to form a turbid solution;

[0034] S4: centrifugally precipitating and separating the turbid solution, and washing with a detergent to obtain PbS quantum dots modified by BMIM-BF4 on the surface;

[0035] S5: preparing the PbS quantum dots modified by BMIM-BF4 on the surface into a BMIM-BF4-modified PbS quantum dot film;

[0036] S6: taking ITO as a bottom electrode, sequentially depositing ZnO, the BMIM-BF4-modified PbS quantum dot film, MoO3 and Ag on the surface of the bottom electrode to form a p-n heterojunction photodetector.

[0037] Specifically, in the step S1, the first solution comprises one or more combinations of n-hexane and n-octane. The concentration of the PbS quantum dot solution is 8 mg / mL-12 mg / mL, preferably 10 mg / mL. In the step S2, the second solution comprises ethanol. The concentration of the first ionic liquid solution is 0.01 mol / L-0.02 mol / L, preferably 0.01 mol / L. In the step S3, the third solution comprises isopropyl alcohol. The time for the second stirring is 20 minutes-40 minutes, preferably 30 minutes. The second stirring is used to make the PbS quantum dots and the first ionic liquid solution fully exchange ligands. In the step S4, the detergent comprises n-octane; and the number of washing times is greater than or equal to 2.

[0038] The embodiment of the present application introduces the ionic liquid BMIM-BF4 as a surface modifier of PbS quantum dots, uses the BMIM-BF4 to stably coordinate with the surface ions of the PbS quantum dots through the imidazole cation, and simultaneously uses the tetrafluoroborate to passivate the surface defects of the PbS quantum dots. This method can effectively solve the problem of ion migration, significantly improve the photoelectric performance and long-term stability of the film, and does not need a complex preparation process, and is suitable for large-scale production.

[0039] Specifically, the step S5 is:

[0040] S51: dissolving the PbS quantum dots modified by BMIM-BF4 on the surface into a fourth solution to form a film-forming solution;

[0041] S52: drop the film-forming solution to the surface of ITO substrate, spin-coat at 2000 rpm for 30 seconds to prepare a uniform quantum dot film; and drop the BMIM-BF4 solution on the surface of the spin-coated film, spin-coat again to enhance the compactness and interface quality of the film.

[0042] S53: anneal the prepared film at 80℃ for 10 minutes under nitrogen protection to improve the crystallization quality and interface stability of the quantum dot film.

[0043] Specifically, in the step S51, the fourth solution comprises toluene. The concentration of the film-forming solution is 350 mg / mL-450 mg / mL, preferably 400 mg / mL.

[0044] The embodiment of the present application can significantly enhance the compactness and interface quality of the film by introducing the ionic liquid BMIM-BF4 as a film modifier, thereby preventing the PbS quantum dot film formation process from being affected by the solvent evaporation rate and surface ligand force, resulting in rough film surface, particle aggregation, and further affecting the photoelectric performance of the film and the consistency of the device.

[0045] Example One

[0046] Specifically, the embodiment of the present application provides a preparation of BMIM-BF4 modified PbS quantum dots.

[0047] Experimental steps:

[0048] S1: dissolve PbS quantum dots in n-octane to prepare a 10 mg / mL PbS quantum dot solution;

[0049] S2: dissolve BMIM-BF4 in ethanol to prepare a 0.01 mol / L first ionic liquid solution;

[0050] S3: add a small amount of isopropyl alcohol to the first ionic liquid solution, stir until uniform and transparent to form a mixed solution; and add the mixed solution to the PbS quantum dot solution and stir at 120℃ for 30 minutes to form a turbid solution;

[0051] S4: centrifugal sedimentation separation is performed on the turbid solution, and n-octane is added for washing to obtain PbS quantum dots with a surface modified by BMIM-BF4.

[0052] Example Two

[0053] Specifically, the embodiment of the present application provides a preparation of PbS quantum dot film and device testing.

[0054] S51: dissolve the PbS quantum dots with a surface modified by BMIM-BF4 in toluene to form a 400 mg / mL film-forming solution;

[0055] S52: The film-forming solution is added dropwise to the surface of the SnO2 / ITO substrate, spin-coated at 2000 rpm for 30 seconds, annealed at 100℃ for 15 minutes, to prepare a uniform PbS quantum dot film; and the BMIM-BF4 solution is added dropwise to the surface of the spin-coated film, spin-coated again to enhance the compactness and interface quality of the film.

[0056] S53: The prepared film is annealed at 80℃ for 10 minutes under nitrogen protection, to improve the crystallization quality and interface stability of the quantum dot film.

[0057] See Figures 2-4 . The ion migration inhibition performance and photoelectric response performance of the PbS quantum dot film in the second embodiment are tested respectively. The ion migration inhibition performance of the PbS quantum dot film is determined by testing the I-V characteristic curve of the PbS quantum dot film and observing the current hysteresis behavior under positive and negative voltages. The photoelectric conversion efficiency and detection sensitivity of the PbS quantum dot film are evaluated by measuring the photocurrent response spectrum of the PbS quantum dot film in the short-wave infrared (900-1600 nm) band.

[0058] As shown in Figure 1 and Figure 2 , the unmodified PbS quantum dot film has large hysteresis and large dark current. As shown in Figure 1 and Figure 3 , the BMIM-BF4 modified film has small hysteresis and small dark current. Therefore, it can be known that, by introducing the ionic liquid BMIM-BF4 as a surface ligand regulator and ion migration inhibitor of the PbS quantum dots, the photoelectric performance and long-term reliability of the PbS quantum dot detector are improved in the preparation process. The BMIM-BF4 coordinates with the iodine ions on the surface of the PbS quantum dots, significantly enhancing the ion stability of the surface of the PbS quantum dots, and optimizing the film formation quality of the film, thereby improving the photoelectric performance and long-term reliability of the PbS quantum dot detector.

[0059] The present embodiment also provides a PbS quantum dot detector prepared by the above-mentioned PbS quantum dot detector preparation method. The PbS quantum dot detector comprises, in sequence, an ITO, ZnO, BMIM-BF4 modified PbS quantum dot film, MoO3 and Ag.

[0060] In summary, the present embodiment provides a new method for modifying the PbS quantum dot film with BMIM-BF4, successfully solving the performance degradation problem of the PbS quantum dot detector caused by ion migration, and realizing the preparation of a high-performance and high-stability photoelectric detector. This technology not only provides a new idea for the development of quantum dot infrared detectors, but also opens up a new research direction for the interface optimization and performance improvement of quantum dot photoelectric materials in the future.

[0061] The above-described is only a preferred embodiment of the present application, of course, cannot be limited by this to the scope of the present application, the person skilled in the art can understand that the implementation of all or part of the above-mentioned embodiment process, and according to the equivalent changes made by the claims of the present application, still belong to the scope covered by the present application.

Claims

1. A method for preparing a PbS quantum dot detector, characterized in that, The method comprises the following steps: S1: dissolving PbS quantum dots in a first solution to prepare a PbS quantum dot solution; S2: dissolving 1-butyl-2, 3-dimethyl imidazole tetrafluoroborate (BMIM-BF4) in a second solution to prepare a first ionic liquid solution; S3: adding a third solution to the first ionic liquid solution and stirring until uniform and transparent to form a mixed solution; and adding the mixed solution to the PbS quantum dot solution and stirring again to form a turbid solution; The third solution comprises isopropyl alcohol; S4: centrifugal precipitation separation of the turbid solution and washing with a detergent to obtain PbS quantum dots modified by 1-butyl-2, 3-dimethyl imidazole tetrafluoroborate on the surface; S5: preparing the PbS quantum dots modified by 1-butyl-2, 3-dimethyl imidazole tetrafluoroborate on the surface into a PbS quantum dot film modified by 1-butyl-2, 3-dimethyl imidazole tetrafluoroborate; S6: taking ITO as a bottom electrode, depositing ZnO, the PbS quantum dot film modified by 1-butyl-2, 3-dimethyl imidazole tetrafluoroborate, MoO3 and Ag on the surface of the electrode in sequence to form a p-n heterojunction photodetector.

2. The method of claim 1, wherein the PbS quantum dot detector is prepared by the steps of: In the step S1, the first solution comprises one or more combinations of n-hexane and n-octane; and the concentration of the PbS quantum dot solution is 8 mg / mL-12 mg / mL.

3. The method for preparing a PbS quantum dot detector according to claim 1, wherein: In the step S2, the second solution comprises ethanol; and the concentration of the first ionic liquid solution is 0.01 mol / L-0.02 mol / L.

4. The method of claim 1, wherein the PbS quantum dot detector is prepared by a process comprising: In the step S3, the stirring time is 20 minutes-40 minutes.

5. The method of claim 1, wherein the PbS quantum dot detector is prepared by the steps of: In the step S4, the detergent comprises n-octane; and the washing frequency is greater than or equal to 2 times.

6. The method of claim 1, wherein the PbS quantum dot detector is prepared by a process comprising: The step S5 specifically comprises: S51: dissolving the PbS quantum dots modified by 1-butyl-2, 3-dimethyl imidazole tetrafluoroborate on the surface into a fourth solution to form a film-forming solution; S52: dropping the film-forming solution onto the surface of an ITO substrate and spin coating at 2000 rpm for 30 seconds to prepare a uniform quantum dot film; and dropping a 1-butyl-2, 3-dimethyl imidazole tetrafluoroborate solution onto the surface of the spin-coated film and spin coating again to enhance the compactness and interface quality of the film.

7. The method for preparing a PbS quantum dot detector according to claim 6, wherein: The step S5 further comprises: S53: annealing the prepared film at 80°C for 10 minutes under nitrogen protection to improve the crystallization quality and interface stability of the quantum dot film.

8. The method of claim 6, wherein the PbS quantum dot detector is prepared by the steps of: In the step S51, the fourth solution comprises toluene; and the concentration of the film-forming solution is 350 mg / mL-450 mg / mL.

9. A PbS quantum dot detector, characterized in that, The PbS quantum dot detector is prepared by any one of the PbS quantum dot detector preparation methods in claims 1-8.

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