A PbS quantum dot detector and a preparation process thereof

Abstract

The application discloses a PbS quantum dot detector and a preparation method thereof, and comprises the following steps: preparing a NiO film on a bottom electrode layer by using a sol-gel method; coating EDT solution on the surface of the NiO to form an EDT film; dissolving (S)-(-)-1-(2-naphthyl)ethyl lead bromide ammonium (S(1-2)NPB) in a first solution, and then adding into a PbS solution to form a first mixed solution; spin-coating the first mixed solution on the EDT film to form an initial film; performing ligand exchange on the initial film by using an IBr solution to form a PbS film; evaporating C 60 As an electron transport layer; using a spin-coating method to deposit SnO2 nanoparticles on the electron transport layer to form a strong n-type layer; using a thermal evaporation method to deposit an Au electrode on the strong n-type layer to form a top electrode layer. The PbS quantum dot detector provided by the embodiment of the application can significantly reduce dark current, and improve photoelectric response performance and a signal-to-noise ratio of the device.

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 process thereof. BACKGROUND

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

[0003] To overcome the above problems, current researches mainly focus 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 the long-chain ligands usually reduce the transport ability of carriers; and using inorganic interface layers or adding other organic molecules to regulate the interface charge distribution is complex and cannot fundamentally improve the dark current problem. In addition, these modification methods often sacrifice the stability and consistency of the device while improving the performance, which is difficult to meet the needs of practical applications. SUMMARY

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

[0005] To solve the above technical problems, the application provides a preparation process of a PbS quantum dot detector, which comprises the following steps:

[0006] S1: preparing a NiO thin film on a bottom electrode layer using a sol-gel method; and coating an EDT solution on the surface of the NiO to form an EDT thin film;

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

[0008] S3: vacuum evaporating C 60 as an electron transport layer;

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

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

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

[0012] Preferably, in the 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, the 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 then sintering at 250-350°C for 25-35 minutes to form a NiO film;

[0016] S13: coating the surface of the NiO with EDT solution dissolved in a second solution, soaking for 12 hours, and then rinsing with the second solution and drying.

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

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

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

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

[0021] The embodiment of the present application also provides a PbS quantum dot detector prepared by the PbS quantum dot detector preparation process.

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

[0023] The embodiments of the present application have the following beneficial effects:

[0024] (1) The embodiments of the present application construct a highly ordered bulk heterojunction structure by introducing (S)-(-)-1-(2-naphthyl)ethyl ammonium lead bromide (S(1-2)NPB) to coordinate with the surface of PbS quantum dots. This heterojunction structure forms a built-in electric field between the quantum dots and the interface, effectively promoting the separation and transport of photo-generated 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 passivate surface defects, further reducing the density of recombination centers and improving the stability of the PbS quantum dot film. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0026] Figure 1 A PbS quantum dot detector preparation process flow chart is provided for the embodiments of the present application.

[0027] Figure 2 A PbS quantum dot detector optical absorption spectrum is provided for the embodiments of the present application. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0029] As shown in Figure 1 The PbS quantum dot detector preparation process disclosed by the present embodiment includes the following steps:

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

[0031] S2: Dissolve (S)-(-)-1-(2-naphthyl)ethyl ammonium lead bromide (S(1-2)NPB) in a first solution, then add to the PbS solution to form a first mixed solution; spin coat the first mixed solution on the EDT film to form an initial film; perform ligand exchange on the initial film using an IBr solution to form a PbS film;

[0032] S3: Vacuum evaporate C 60 as an electron transport layer;

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

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

[0035] Before the step S1, the bottom electrode layer also needs to be cleaned, and 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 drying and processing in a plasma cleaner for 3-6 minutes. The cleaning time is preferably 10 minutes, and the processing time is preferably 5 minutes.

[0036] The step S1 includes the following steps:

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

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

[0039] S13: Coating the surface of the NiO with EDT solution dissolved in a second solution, soaking for 12 hours, and then rinsing with the second solution and drying.

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

[0041] In the step S2, the first solution includes dimethyl sulfoxide; and the S(1-2)NPB doping ratio is 4-6wt%. 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.

[0042] In the step S2, the PbS film after spin coating is subjected to annealing treatment, and the temperature is controlled at 60-100°C to enhance the stability and photoelectric performance of the film.

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

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

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

[0046] In the embodiment of the present application, S(1-2)NPB is introduced into the iodine bromide ligand exchange process of the PbS quantum dot film, forming a stable composite halide system, which effectively inhibits the migration of iodine ions. S(1-2)NPB, as an organic-inorganic mixed ligand with a unique spatial structure, can coordinate with the surface of PbS quantum dots. Uniform stirring reaction is carried out under weak acid conditions to ensure the sufficient combination of S(1-2)NPB and PbS quantum dots, and a highly ordered bulk heterojunction structure is constructed. This heterojunction structure forms an internal electric field between the quantum dots and the interface, effectively promoting the separation and transport of photo-generated carriers, thereby significantly reducing the dark current and improving the photoelectric response performance and signal-to-noise ratio of the device. In addition, the lead bromide part of S(1-2)NPB can be passivated by surface defects, further reducing the density of recombination centers and improving the stability of the quantum dot film.

[0047] Embodiment one

[0048] Specifically, the embodiment of the present application provides a PbS quantum dot detector preparation process.

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

[0050] The ITO glass is ultrasonically cleaned with deionized water, ethanol and isopropanol for 10 minutes, and then dried and treated in a plasma cleaner for 5 minutes.

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

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

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

[0054] The NiO surface is coated with EDT solution (0.5mmol / L, dissolved in acetonitrile), soaked for 12 hours, then washed 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 5wt%.

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

[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 subjected to ligand exchange using an IBr solution (0.01M, dissolved in pyridine) for 2 minutes, and then the film was washed with pyridine and dried.

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

[0062] On the doped and optimized PbS quantum dot film, 40nm of C 60 was vacuum evaporated as an electron transport layer.

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

[0064] Finally, an Au electrode (thickness of 50nm) was deposited by a thermal evaporation device.

[0065] Referring to Figure 2 , the Responsivity (R) and Detectivity (D*) of the PbS quantum dot detector of the present application and the prior art were tested by irradiating them with a light source at a wavelength of 1650nm (light intensity of 10mW / cm 2 ). It was found that the Responsivity (R) and Detectivity (D*) of the PbS quantum dot detector of the present application were superior to those of the control group.

[0066] The PbS quantum dot detector of the present application and the prior art were stored for 30 days in an environment with a temperature of 25℃ 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 PbS quantum dot detector of the present application 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 is evaluated by accelerated aging test under electric field and thermal field environment experiment. The results show that the PbS quantum dot film added with S(1-2) NPB does not observe obvious iodine ion migration under the reverse voltage of-10 to +10 V, and the migration activation energy is increased to more than 0.7 eV. In the chip imaging application, the modified quantum dot film shows lower noise level and higher signal-to-noise ratio.

[0070] The application also provides a PbS quantum dot detector prepared by the PbS quantum dot detector preparation process.

[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 application provides a new method for modifying the PbS quantum dot film by S(1-2) NPB. The charge transport performance and stability of the PbS quantum dot film are significantly improved by S(1-2) NPB doping optimization, and the migration of iodine ions is effectively inhibited. At the same time, the light responsivity and detection rate of the detector are significantly improved, which shows the broad application prospect of the application in the field of short-wave infrared imaging.

[0073] The above only discloses a preferred embodiment of the application, and of course cannot limit the scope of the application. Those skilled in the art can understand that all or part of the above-mentioned processes are implemented, and equivalent changes made according to the claims of the application still belong to the scope covered by the application.

Claims

1. A process for preparing a PbS quantum dot detector, characterized in that, The method comprises the following steps: S1: preparing a NiO film on a bottom electrode layer by using a sol-gel method; and coating EDT solution on the surface of the NiO to form an EDT film; S2: dissolving (S)-(-)-1-(2-naphthyl)ethyl ammonium lead bromide (S(1-2)NPB) in a first solution, and then adding to a PbS solution to form a first mixed solution; and spin-coating the first mixed solution on the EDT film to form an initial film; S3: performing ligand exchange on the initial film by using IBr solution to form a PbS film; S3: Vacuum evaporation of C on the PbS quantum dot film 60 as an electron transport layer; S4: depositing SnO2 nanoparticles on the electron transport layer by using a spin-coating method to form a strong n-type layer; S5: depositing an Au electrode on the strong n-type layer by using a thermal evaporation method to form a top electrode layer.

2. The PbS quantum dot detector fabrication process of claim 1, wherein, In the step S2, the first solution comprises dimethyl sulfoxide; and the doping ratio of the (S)-(-)-1-(2-naphthyl)ethyl ammonium lead bromide is 4-6 wt%.

3. The PbS quantum dot detector fabrication process of claim 2, wherein, In the step S2, the concentration of the (S)-(-)-1-(2-naphthyl)ethyl ammonium lead bromide dissolved in the first solution is 8-12 mg / mL; and the concentration of the PbS solution is 50 mg / mL.

4. The PbS quantum dot detector fabrication process of claim 1, wherein, 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 then sintering at 250-350 °C for 25-35 minutes to form a NiO film; S13: coating EDT solution dissolved in a second solution on the surface of the NiO, soaking for 12 hours, and then rinsing with the second solution and drying.

5. The PbS quantum dot detector fabrication process of claim 4, wherein, In the step S1, the stabilizer comprises ethanolamine; and the second solution comprises acetonitrile.

6. The PbS quantum dot detector fabrication process of claim 1, wherein, In the step S3, the thickness of the electron transport layer is 35-45 nm.

7. The PbS quantum dot detector fabrication process of claim 1, wherein, In the step S4, the thickness of the strong n-type layer is 25-35 nm.

8. The PbS quantum dot detector fabrication process of claim 1, wherein, Before the step S1, the bottom electrode layer also needs to be ultrasonically cleaned with deionized water, ethanol and isopropanol for 8-12 minutes in sequence, and then dried and treated in a plasma cleaner for 3-6 minutes.

9. A PbS quantum dot detector, characterized in that, The PbS quantum dot detector is prepared by using any one of the PbS quantum dot detector preparation processes in the above claims 1-8; and the PbS quantum dot detector comprises, in sequence, a bottom electrode layer, a NiO film layer, an EDT film layer, a PbS film layer, an electron transport layer, a strong n-type layer and a top electrode layer.

10. The PbS quantum dot detector of claim 9, wherein, The thickness of the electron transport layer is 35-45 nm; and the thickness of the strong n-type layer is 25-35 nm.

Images