PbS quantum dot detector and preparation process thereof

Abstract

The invention discloses a PbS quantum dot detector and a preparation method thereof. The preparation method comprises the following steps: preparing a NiO film on a bottom electrode layer by using a sol-gel method; the surface of NiO is coated with an EDT solution, and an EDT film is formed; (S)-(-)-1-(2-naphthyl) ethyl ammonium lead bromide (S (1-2) NPB) is dissolved in the first solution and then added into the PbS solution, and a first mixed solution is formed; spin-coating the EDT film with the first mixed solution to form an initial film; performing ligand exchange on the initial film by using an IBr solution to form a PbS film; c60 is evaporated on the PbS quantum dot film in vacuum to serve as an electron transport layer; depositing SnO2 nanoparticles on the electron transport layer by using a spin-coating method to form a strong n-type layer; and depositing an Au electrode on the strong n-type layer by using a thermal evaporation method to form a top electrode layer. According to the PbS quantum dot detector provided by the embodiment of the invention, dark current can be remarkably reduced, and the photoelectric response performance and the signal-to-noise ratio of a device are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoelectric detectors, and in particular relates to a PbS quantum dot detector and a preparation process thereof. Background Art

[0002] As an excellent semiconductor material, PbS quantum dots are widely used in short-wave infrared (SWIR) detectors due to their tunable bandgap, low preparation cost and wide photoelectric response band. However, the performance of existing PbS quantum dot detectors still faces the following challenges: first, the dark current is high, which limits its sensitivity under weak light conditions; second, the surface defects of quantum dots lead to a high carrier recombination rate, which affects the photoelectric conversion efficiency of the device; third, the interface charge separation efficiency is low, which further restricts its response performance and signal-to-noise ratio.

[0003] To overcome the above problems, current research focuses on the surface passivation and interface engineering of quantum dots. For example, modifying the surface of quantum dots with long-chain ligands can effectively reduce the defect density, but long-chain ligands usually reduce the carrier transport capacity; regulating the interface charge distribution through inorganic interface layers or adding other organic molecules is a complex process and cannot fundamentally improve the dark current problem. In addition, these modification methods often sacrifice the stability and consistency of the device while improving performance, making it difficult to meet the needs of practical applications. Summary of the invention

[0004] The technical problem to be solved by the present invention is that, since the existing PbS quantum dot detectors have various deficiencies, the present invention provides a PbS quantum dot detector and a preparation process thereof.

[0005] In order to solve the above technical problems, an embodiment of the present invention provides a PbS quantum dot detector preparation process, comprising the following steps:

[0006] S1: preparing a NiO thin film on the bottom electrode layer by using a sol-gel method; and coating a 1,3-ethanedithiol (EDT) solution on the NiO surface to form an EDT thin film;

[0007] S2: dissolving (S)-(-)-1-(2-naphthyl)ethylammonium lead bromide (S(1-2)NPB) in the first solution, and then adding it to the PbS solution to form a first mixed solution; spin coating the first mixed solution on the EDT film to form an initial film; and performing ligand exchange on the initial film using an IBr solution to form a PbS film;

[0008] S3: Vacuum evaporation of C on PbS quantum dot film 60 As an electron transport layer;

[0009] S4: Depositing SnO2 nanoparticles on the electron transport layer using spin coating to form a strong n-type layer;

[0010] S5: Depositing an Au electrode on the strong n-type layer using a thermal evaporation method to form a top electrode layer.

[0011] Preferably, in step S2, the first solution comprises: dimethyl sulfoxide; and the doping ratio of S(1-2)NPB is: 4-6wt%.

[0012] Preferably, in step S2, the concentration of the S(1-2)NPB dissolved in the first solution is 8-12 mg / mL; and the concentration of the PbS solution is 50 mg / mL.

[0013] Preferably, step S1 comprises the following steps:

[0014] S11: dissolving Ni(NO3)2 in 2-methoxyethanol and adding a stabilizer to form a second mixed solution;

[0015] S12: Spin-coating the second mixed solution on the bottom electrode layer, drying, and sintering at 250° C.-350° C. for 25-35 minutes to form a NiO film;

[0016] S13: The NiO surface is coated with the EDT solution dissolved in the second solution, immersed for 12 hours, and then rinsed with the second solution and dried.

[0017] Preferably, in step S1, the stabilizer includes ethanolamine; and the second solution includes acetonitrile.

[0018] Preferably, in step S3, the thickness of the electron transport layer is 35-45 nm.

[0019] Preferably, in step S4, the thickness of the strong n-type layer is 25-35 nm.

[0020] Preferably, before step S1, the bottom electrode layer needs to be ultrasonically cleaned with deionized water, ethanol and isopropanol in sequence for 8-12 minutes, and then treated in a plasma cleaner for 3-6 minutes after drying.

[0021] An embodiment of the present invention also provides a PbS quantum dot detector, which is prepared by the above-mentioned PbS quantum dot detector preparation process; the PbS quantum dot detector includes: a bottom electrode layer, a NiO thin film layer, an EDT thin film layer, a PbS thin film layer, an electron transport layer, a strong n-type layer and a top electrode layer in sequence.

[0022] Preferably, the thickness of the electron transport layer is 35-45 nm; the thickness of the strong n-type layer is 25-35 nm.

[0023] Implementing the embodiments of the present invention has the following beneficial effects:

[0024] (1) The embodiment of the present invention introduces (S)-(-)-1-(2-naphthyl)ethylammonium lead bromide (S(1-2)NPB) to coordinate with the surface of PbS quantum dots to construct a highly ordered bulk heterojunction structure. This heterojunction structure forms a built-in electric field between the quantum dots and the interface, which effectively promotes the separation and transmission of photogenerated carriers, thereby significantly reducing the dark current and improving the photoelectric response performance and signal-to-noise ratio of the PbS quantum dot detector. In addition, the lead bromide part of S(1-2)NPB can further reduce the density of recombination centers and improve the stability of the PbS quantum dot film by passivating with surface defects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative work.

[0026] Figure 1 A process flow chart of preparing a PbS quantum dot detector provided for the implementation of the present invention;

[0027] Figure 2 A light absorption spectrum of a PbS quantum dot detector provided for the implementation of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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 making creative work are within the scope of protection of the present invention.

[0029] like Figure 1 As shown, this embodiment discloses a PbS quantum dot detector preparation process, and the PbS quantum dot detector preparation process includes the following steps:

[0030] S1: preparing a NiO thin film on the bottom electrode layer by using a sol-gel method; and coating a 1,3-ethanedithiol (EDT) solution on the NiO surface to form an EDT thin film;

[0031] S2: dissolving (S)-(-)-1-(2-naphthyl)ethylammonium lead bromide (S(1-2)NPB) in the first solution, and then adding it to the PbS solution to form a first mixed solution; spin coating the first mixed solution on the EDT film to form an initial film; and performing ligand exchange on the initial film using an IBr solution to form a PbS film;

[0032] S3: Vacuum evaporation of C on PbS quantum dot film 60 As an electron transport layer;

[0033] S4: Depositing SnO2 nanoparticles on the electron transport layer using spin coating to form a strong n-type layer;

[0034] S5: Depositing an Au electrode on the strong n-type layer using a thermal evaporation method to form a top electrode layer.

[0035] Before step S1, the bottom electrode layer needs to be cleaned. The cleaning of the bottom electrode layer specifically includes: ultrasonic cleaning with deionized water, ethanol and isopropanol for 8-12 minutes in sequence, and then treating in a plasma cleaner for 3-6 minutes after drying. The cleaning time is preferably 10 minutes, and the treatment time is preferably 5 minutes.

[0036] Wherein, the step S1 comprises the following steps:

[0037] S11: dissolving Ni(NO3)2 in 2-methoxyethanol and adding a stabilizer to form a second mixed solution;

[0038] S12: Spin-coating the second mixed solution on the bottom electrode layer, drying, and sintering at 250° C.-350° C. for 25-35 minutes to form a NiO film;

[0039] S13: The NiO surface is coated with the EDT solution dissolved in the second solution, immersed for 12 hours, and then rinsed with the second solution and dried.

[0040] Preferably, in step S1, the stabilizer comprises ethanolamine, and the second solution comprises acetonitrile. The sintering temperature is preferably 300° C. and the sintering time is 30 minutes.

[0041] In step S2, the first solution includes dimethyl sulfoxide, the doping ratio of S(1-2)NPB is 4-6wt%, the concentration of S(1-2)NPB dissolved in the first solution is 8-12mg / mL, and the concentration of PbS solution is 50mg / mL.

[0042] In the step S2, the spin-coated PbS film is annealed at a temperature of 60-100°C to enhance the stability and photoelectric performance of the film.

[0043] In the step S3, the thickness of the electron transport layer is 35-45 nm, preferably 40 nm.

[0044] In the step S4, the thickness of the strong n-type layer is 25-35 nm, preferably 30 nm.

[0045] In the step S5, the thickness of the top electrode layer is 40-60 nm, preferably 50 nm.

[0046] The embodiment of the present invention forms a stable composite halide system by introducing S(1-2)NPB into the iodine-bromine ligand exchange process of the PbS quantum dot film, which effectively inhibits the migration of iodine ions. As an organic-inorganic hybrid ligand with a unique three-dimensional structure, S(1-2)NPB can coordinate with the surface of PbS quantum dots. The reaction is uniformly stirred under weakly acidic conditions to ensure that S(1-2)NPB is fully combined with PbS quantum dots to construct a highly ordered bulk heterojunction structure. This heterojunction structure forms a built-in electric field between the quantum dots and the interface, which effectively promotes the separation and transmission of photogenerated carriers, thereby significantly reducing dark current and improving the photoelectric response performance and signal-to-noise ratio of the device. In addition, the lead bromide portion of S(1-2)NPB can be passivated with surface defects to further reduce the density of composite centers and improve the stability of the quantum dot film.

[0047] Embodiment 1

[0048] Specifically, an embodiment of the present invention provides a process flow for preparing a PbS quantum dot detector.

[0049] (1) ITO glass cleaning and surface modification:

[0050] The ITO glass was ultrasonically cleaned with deionized water, ethanol and isopropanol for 10 min in sequence, and then treated in a plasma cleaner for 5 min after drying.

[0051] (2) Preparation of NiO thin film:

[0052] The NiO thin film was prepared using a sol-gel method. 0.5 M nickel nitrate was dissolved in 2-methoxyethanol and ethanolamine was added as a stabilizer.

[0053] The solution was spin-coated on the modified ITO glass surface at a speed of 2500 rpm, dried and sintered at 300° C. for 30 minutes.

[0054] The NiO surface was coated with EDT solution (0.5 mmol / L, dissolved in acetonitrile) and immersed for 12 h, then rinsed with acetonitrile and dried.

[0055] (3) Preparation of S(1-2)NPB doped PbS quantum dot film:

[0056] PbS quantum dots were dispersed in n-octane solution with a concentration of 50 mg / mL.

[0057] An appropriate amount of S(1-2)NPB was dissolved in dimethyl sulfoxide (DMSO) (concentration of 10 mg / mL) and then added to the PbS solution to make the doping ratio 5 wt%.

[0058] The mixed solution was stirred at room temperature for 30 min to ensure doping uniformity.

[0059] The mixed solution was spin-coated on the EDT film at a speed of 2000 rpm to form an initial film.

[0060] The film was ligand exchanged using IBr solution (0.01 M in pyridine) for 2 minutes, then rinsed with pyridine and dried.

[0061] (4) Electron transport layer and electrode deposition:

[0062] On the optimized PbS quantum dot film, 40 nm of C 60 As electron transport layer.

[0063] Use spin coating method to 60 SnO2 nanoparticles (concentration of 10 mg / mL, solvent is ethanol) are deposited on the layer with a thickness of 30 nm.

[0064] Finally, Au electrode (thickness 50 nm) was deposited by thermal evaporation equipment.

[0065] See also Figure 2 , by using a light source with a wavelength of 1650nm (light intensity 10mW / cm 2 ) The embodiment of the present invention and the PbS quantum dot detector in the prior art were illuminated to test the light responsivity (Responsivity, R) and detectivity (Detectivity, D*) of both. It can be seen that the light responsivity (Responsivity, R) and detectivity (Detectivity, D*) of the embodiment of the present invention are better than those of the control group.

[0066] The PbS quantum dot detectors of the present invention and the prior art were stored for 30 days at a temperature of 25°C and a humidity of 40% to determine the performance difference between the two after 30 days. After 30 days of storage, the performance of the present invention embodiment decayed by less than 3%; the performance of the undoped control device decayed by more than 15% under the same conditions.

[0067]

[0068]

[0069] The device performance was evaluated by accelerated aging tests under electric fields and thermal field environment experiments. The results showed that no obvious iodine ion migration was observed in the PbS quantum dot film with the addition of S(1-2)NPB under reverse voltages of -10 to +10V, and the migration activation energy was increased to above 0.7eV. In chip imaging applications, the modified quantum dot film showed lower noise levels and higher signal-to-noise ratios.

[0070] The embodiment of the present invention further provides a PbS quantum dot detector, which is prepared by the above-mentioned PbS quantum dot detector preparation process. The PbS quantum dot detector comprises: a bottom electrode layer, a NiO thin film layer, an EDT thin film layer, a PbS thin film layer, an electron transport layer, a strong n-type layer and a top electrode layer.

[0071] The thickness of the electron transport layer is 35-45 nm. The thickness of the strong n-type layer is 25-35 nm. The thickness of the top electrode layer is 40-60 nm.

[0072] In summary, the embodiment of the present invention provides a new method for modifying PbS quantum dot film using S(1-2)NPB. Through S(1-2)NPB doping optimization, the charge transfer performance and stability of the PbS quantum dot film are significantly improved, and the migration of iodine ions is effectively suppressed. At the same time, the photoresponsivity and detection rate of the detector are significantly improved, demonstrating the broad application prospects of the present invention in the field of short-wave infrared imaging.

[0073] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A PbS quantum dot detector preparation process, characterized in that: The following steps are involved: S1: preparing a NiO thin film on the bottom electrode layer by using a sol-gel method; and coating a 1,3-ethanedithiol (EDT) solution on the NiO surface to form an EDT thin film; S2: dissolving (S)-(-)-1-(2-naphthyl)ethylammonium lead bromide (S(1-2)NPB) in the first solution, and then adding it to the PbS solution to form a first mixed solution; spin coating the first mixed solution on the EDT film to form an initial film; The initial film was ligand exchanged using IBr solution to form a PbS film; S3: Vacuum evaporation of C on PbS quantum dot film 60 As an electron transport layer; S4: Depositing SnO2 nanoparticles on the electron transport layer using spin coating to form a strong n-type layer; S5: Depositing an Au electrode on the strong n-type layer using a thermal evaporation method to form a top electrode layer.

2. The PbS quantum dot detector preparation process according to claim 1, characterized in that: In step S2, the first solution includes dimethyl sulfoxide; the doping ratio of S(1-2)NPB is 4-6wt%.

3. The PbS quantum dot detector preparation process according to claim 2, characterized in that: In the step S2, the concentration of the S(1-2)NPB dissolved in the first solution is 8-12 mg / mL; the concentration of the PbS solution is 50 mg / mL.

4. The process for preparing a PbS quantum dot detector according to claim 1, characterized in that: The step S1 comprises the following steps: S11: dissolving Ni(NO3)2 in 2-methoxyethanol and adding a stabilizer to form a second mixed solution; S12: Spin-coating the second mixed solution on the bottom electrode layer, drying, and sintering at 250° C.-350° C. for 25-35 minutes to form a NiO film; S13: The NiO surface is coated with the EDT solution dissolved in the second solution, immersed for 12 hours, and then rinsed with the second solution and dried.

5. The process for preparing a PbS quantum dot detector according to claim 4, characterized in that: In the step S1, the stabilizer includes ethanolamine; and the second solution includes acetonitrile.

6. The method for preparing a PbS quantum dot detector according to claim 1, characterized in that: In the step S3, the thickness of the electron transport layer is 35-45 nm.

7. The method for preparing a PbS quantum dot detector according to claim 1, characterized in that: In the step S4, the thickness of the strong n-type layer is 25-35 nm.

8. The method for preparing a PbS quantum dot detector according to claim 1, characterized in that: Before step S1, the bottom electrode layer needs to be ultrasonically cleaned with deionized water, ethanol and isopropanol for 8-12 minutes in sequence, and then treated in a plasma cleaner for 3-6 minutes after drying.

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 processes in claims 1-8; the PbS quantum dot detector comprises in sequence: a bottom electrode layer, a NiO thin film layer, an EDT thin film layer, a PbS thin film layer, an electron transport layer, a strong n-type layer and a top electrode layer.

10. The PbS quantum dot detector according to claim 9, characterized in that: The thickness of the electron transport layer is 35-45 nm; the thickness of the strong n-type layer is 25-35 nm.

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