Dark current suppression method of gold-doped lead sulfide colloid quantum dot photoelectric detector
Through gold doping and repeated spin coating, the thickness of the PbS CQDs photosensitive layer is increased, solving the problem of increasing dark current, and improving the photoelectric properties and simplifying the process.
Patent Information
- Application Number
- CN202411622028.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-14
- Publication Date
- 2025-03-11
AI Technical Summary
In the preparation of PbS CQDs photodetectors, the use of oleic acid ligands can impair the photoelectric properties and lead to an increase in dark currents. Existing methods require multiple coatings to cover the defects, but increase process complexity and time.
The thickness of the QDs photosensitive layer is increased by gold doping and repeated spin coating, the photoelectric properties are enhanced by gold nanoparticles, and dark current is reduced by ligand exchange treatment.
It realizes the reduction of the dark current of the PbS CQDs photodetector, improves the photoelectric properties, and simplifies the process flow, suitable for batch preparation.
Smart Images
Figure CN119604169A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a quantum dot technology, in particular to a dark current suppression method of a quantum dot photoelectric detector. Background Art
[0002] Colloidal quantum dots (CQDs) are semiconductor nanocrystals with a size of less than 20nm and smaller than the Bohr radius of their excitons, and are coated with long-chain organic ligands (such as oleylamine, oleic acid and octadecene). They are "quasi-zero-dimensional" nanomaterials that contain thousands of atoms and have a certain charge on the surface. One or several long-chain organic ligands coated on the surface can protect the quantum dots and improve the stability of the quantum dots dispersed in the solution.
[0003] The preparation of semiconductors by solution method has attracted much attention in the semiconductor industry due to its low cost and easy large-scale production. Among the various CQDs, PbS quantum dots have provided a very promising platform for studying various devices based on photoelectric conversion in the past few decades, especially in the fields of photodetectors, solar cells and light-emitting devices in recent years. In addition to the simple solution process, PbS CQDs are also regarded as highly promising photovoltaic materials due to their high extinction coefficient, good stability, MEG effect and adjustable size.
[0004] In the process of preparing PbS CQDs, oleic acid ligands are usually introduced to cover the surface of CQDs to prevent them from being corroded by water and oxygen. However, this step will also damage the optoelectronic properties of PbS CQDs. This is because the long chain of oleic acid ligands will reduce the carrier transmission speed between QDs. To solve this problem, a common method is to use short-chain ligand ethanedithiol to perform ligand exchange treatment on the synthesized PbS CQDs, replacing the long-chain ligands on its surface with short-chain ligands. Due to the layer-by-layer spin coating method, replacing long-chain ligands with short-chain ligands on the already spin-coated QDs film layer may cause cracks and void defects in the film layer. These defects can cause photogenerated carriers to recombine at defective locations during transmission. In order to cover these defects and reduce dark current, multiple coatings are required during the device manufacturing process, and repeated spin coating can also increase the thickness of the QDs photosensitive layer, absorbing more photons to generate more photogenerated carriers. Summary of the invention
[0005] The purpose of the present invention is to provide a method for reducing the dark current of a PbS CQDs photodetector, by increasing the thickness of the QDs photosensitive layer through gold doping and repeated spin coating, absorbing more photons to generate more photogenerated carriers.
[0006] A method for suppressing dark current of a gold-doped lead sulfide colloidal quantum dot photodetector, characterized in that the method comprises the following steps:
[0007] S1, cleaning quartz substrate;
[0008] S2, drying the quartz substrate after cleaning in step S1 using high-purity nitrogen gas;
[0009] S3, magnetron sputtering a gold electrode with a thickness of 40-100 nm on the quartz substrate cleaned in step S2 as the bottom electrode of the device;
[0010] S4, dissolving the lead sulfide quantum dot powder in n-octane or n-hexane to prepare a 10-50 mg / ml quantum dot solution;
[0011] S5, mixing Au NP with a particle size of 10 nm with the quantum dot solution obtained in step S4 to prepare a mixed solution of Au NP and PbS CQDs with a volume ratio of gold nanoparticle aqueous solution: PbS solution = 1:50-200;
[0012] S6, spin coating the mixed solution of step S5 to form a film covering the gold electrode prepared in step S3;
[0013] S7, using a 1,2-ethanedithiol solution with a concentration of 1 part per ten thousand to cover the quantum dot film spin-coated in step S6 to perform ligand exchange;
[0014] S8, after the ligand exchange in step S7 is completed, the excess ligand is removed by centrifugation and the residual EDT ligand is washed away with methanol solution;
[0015] S9, repeating steps S6, S7, and S8 at least twice to stack and obtain a dense and uniform quantum dot film layer;
[0016] S10, growing a zinc oxide film as an electron transport layer on the quantum dot film obtained in step S9 by magnetron sputtering;
[0017] S11, growing a transparent electrode indium tin oxide (ITO) on top of the zinc oxide film grown in S10 as the top electrode of the device.
[0018] The zinc oxide film has a thickness of at least 100 nm.
[0019] The method of the invention synthesizes small-sized PbS CQDs with a gap of 1.3-1.4 eV, and uses a PbS CQDs solution doped with gold nanoparticles as an improved photosensitive layer to reduce the dark current of the device, thereby preparing an Au / Au NP&PbS-EDT / ZnO / ITO photovoltaic device.
[0020] The technical effects and advantages of the present invention are that the device photosensitive layer can be processed by low-cost solution and can be prepared in batches; the PbSCQDs film layer improves the photoelectric properties by doping with gold nanocrystals; and the Au / Au NP&PbS-EDT / ZnO / ITO photovoltaic photoelectric device reduces the dark current. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 This is a physical picture of the 2cm×2cm Au / Au NP&PbS-EDT / ZnO / ITO device of Example 1.
[0022] Figure 2 TEM image of PbS CQDs of Example 1;
[0023] It can be seen from the figure that PbS CQDs have good dispersion and the size of the quantum dots is about 4nm.
[0024] Figure 3 The UV-visible-infrared absorption spectrum of the mixed solution of PbS CQDs, Au NPs and PbS CQDs in Example 1;
[0025] It can be seen from the figure that the exciton absorption peak of PbS CQDs is at 940nm, and the absorption peak will be enhanced after ligand exchange.
[0026] Figure 4 is a current-voltage curve diagram of the device of Example 1;
[0027] It can be seen from the figure that the dark current of the device is reduced after doping with gold nanocrystals.
[0028] Figure 5 This is a transient photocurrent response curve of the device of Example 1. DETAILED DESCRIPTION
[0029] The present invention is further described in detail below through specific implementation modes, but it should not be understood that the scope of the present invention is limited to the following examples.
[0030] Example 1: A method for suppressing dark current of a gold-doped lead sulfide colloidal quantum dot photodetector, characterized in that the preparation steps are as follows:
[0031] S1, the quartz substrate is immersed in a solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 2:1:10 at 80°C for 0.5h to wash away impurities on the substrate surface and improve the adhesion of the substrate surface.
[0032] S2, the quartz substrate cleaned in step S1 is rinsed with deionized water and then blown dry with high-purity nitrogen gas.
[0033] S3, placing the quartz substrate cleaned in step S2 on the sample stage of a magnetron sputtering device, and magnetron sputtering growing a 50 nm thick gold electrode on the quartz substrate as the bottom electrode of the device.
[0034] S4, dissolving the lead sulfide quantum dot powder in n-octane or n-hexane to prepare a 30 mg / ml lead sulfide quantum dot solution, and then filtering with a 0.22 μm filter and mixing as needed.
[0035] S5, mixing Au NP with a particle size of 10 nm with the quantum dot solution obtained in step S4 according to different volume ratios to prepare a mixed solution of Au NP and PbS CQDs, wherein the ratio of gold nanoparticle aqueous solution to PbS solution is 1:100.
[0036] S6, spin coating the mixed solution obtained in step S5 to form a film covering the gold electrode in step S3.
[0037] S7, using a 1,2-ethylenedithiol (EDT) solution with a concentration of 1 part per ten thousand to cover the quantum dot film spin-coated in step S6 for ligand exchange; the spin coating speed is 1500 revolutions per minute, and the spin coating time is 45 seconds.
[0038] S8, after the ligand exchange in step S7 is completed, the excess ligand is removed by centrifugation and then rinsed again with methanol solution until the residual EDT ligand is washed away.
[0039] S9, repeat steps S6, S7, and S8 for five layers to obtain a dense and uniform quantum dot thin film layer.
[0040] S10, growing a 100 nm zinc oxide film as an electron transport layer on top of the quantum dot film in step S9 by magnetron sputtering.
[0041] S11, magnetron sputtering is used to grow a transparent electrode indium tin oxide (ITO) with a thickness of 80 nm on the zinc oxide film prepared in step S10 as the top electrode of the device.
Claims
1. A method for suppressing dark current of a gold-doped lead sulfide colloidal quantum dot photodetector, characterized in that The method comprises the following steps: S1, cleaning quartz substrate; S2, drying the quartz substrate after cleaning in step S1 using high-purity nitrogen gas; S3, magnetron sputtering a gold electrode with a thickness of 40-100 nm on the quartz substrate cleaned in step S2 as the bottom electrode of the device; S4, dissolving the lead sulfide quantum dot powder in n-octane or n-hexane to prepare a 10-50 mg / ml quantum dot solution; S5, mixing Au NPs with a particle size of 10 nm with the quantum dot solution obtained in step S4 to prepare a mixed solution of Au NPs and PbS CQDs with a volume ratio of gold nanoparticle aqueous solution: PbS solution = 1:50-200; S6, spin coating the mixed solution of step S5 to form a film covering the gold electrode prepared in step S3; S7, using a 1,2-ethanedithiol solution with a concentration of 1 part per ten thousand to cover the quantum dot film spin-coated in step S6 for ligand exchange; S8, after the ligand exchange in step S7 is completed, the excess ligand is removed by centrifugation and the residual EDT ligand is washed away with methanol solution; S9, repeating steps S6, S7, and S8 at least twice to stack and obtain a dense and uniform quantum dot film layer; S10, growing a zinc oxide film as an electron transport layer on the quantum dot film obtained in step S9 by magnetron sputtering; S11, a transparent electrode indium tin oxide (ITO) is grown on top of the zinc oxide film grown in S10 as the top electrode of the device.
2. The dark current suppression method of the gold-doped lead sulfide colloidal quantum dot photodetector according to claim 1, characterized in that The zinc oxide film has a thickness of at least 100 nm.