Energy level regulated PbS quantum dot photodetector and preparation method thereof

Abstract

The application discloses an energy level regulated PbS quantum dot photoelectric detector and a preparation method thereof, and belongs to the technical field of photoelectricity. The detector comprises a substrate, an ITO transparent electrode layer formed on the substrate, an AZO functional layer formed on the ITO transparent electrode layer, PbS colloidal quantum dots formed on the AZO functional layer, a bismuth telluride (Bi2Te3) charge transport layer formed on the PbS colloidal quantum dots, and an Al electrode layer formed on the Bi2Te3 charge transport layer. In the preparation method of the detector, the AZO functional layer is realized by a magnetron method, the PbS quantum dot film is realized by multiple spin coating and ligand exchange, the bismuth telluride (Bi2Te3) is grown by a magnetron sputtering method, and the Al electrode layer is realized by a vacuum evaporation method. The detector is combined with the small-size PbS quantum dots and the wide-response-waveband and high-absorption-rate Bi2Te3 material, and the designed energy band arrangement structure of ITO / AZO / PbS CQDs / Bi2Te3 / Al not only provides convenience for charge separation / transmission, thereby improving the device performance.

Description

Technical Field

[0001] This invention relates to the field of photodetector technology, and in particular to PbS quantum dot photodetectors and their fabrication techniques. Background Technology

[0002] Due to the quantum confinement effect of quantum dots, the band gap of quantum dots can be tuned by adjusting their size, structure, and shape. Increased size leads to a weakening of the confinement of electron and hole wave functions, resulting in a redshift in the absorption spectrum of quantum dots; the larger the size, the more pronounced the redshift. To synthesize large-sized colloidal quantum dots, high growth temperatures and long growth times are typically used. Uncontrollable nucleation processes and Ostwald ripening during growth lead to high defect densities and large size differences between different nanocrystals, degrading the optical properties of the synthesized quantum dots. Therefore, it is difficult to achieve a region of 2.5-3 μm using PbS colloidal quantum dots.

[0003] Large-sized quantum dots are more easily oxidized and more difficult to synthesize. Expanding the response band by increasing the size of quantum dots presents a challenge to quantum dot synthesis technology, as well as the stability of quantum dots and devices. Currently, improving the performance of colloidal quantum dot photovoltaic photodetectors mainly focuses on increasing the mobility of quantum dot thin films and hybridization techniques, but significant performance improvements are difficult to achieve, with responsivity less than 1 AW. -1 . Summary of the Invention

[0004] This invention uses small-sized quantum dots with good stability to fabricate devices, which makes the devices exhibit excellent stability. Even without being packaged and stored for six months after fabrication, the device performance still shows excellent stability and repeatability.

[0005] The energy level modulated PbS quantum dot photodetector is a vertical multilayer structure, characterized by, from bottom to top, a substrate, an ITO or FTO electrode, an AZO functional layer, a PbS quantum dot photosensitive layer, a Bi2Te3 thin film, and an Al electrode.

[0006] A method for fabricating a PbS quantum dot photodetector with energy level modulation includes the following steps:

[0007] Step 1: Clean the transparent substrate on which ITO or FTO transparent electrodes have been prepared;

[0008] Step 2: Magnetron sputter a thin film of AZO on a transparent substrate on which ITO or FTO transparent electrodes have been prepared. Sputtering is performed at room temperature with a sputtering power of 140-220W, an Ar flow rate of 60-100sccm, a sputtering pressure of 3-10Pa, and a sputtering time of 20-100min.

[0009] Step 3: Spin-coat PbS quantum dots on the substrate after sputtering AZO at a spin speed of 2000-2500 rpm for 20-40 s; spin-coat 5-10 layers of PbS quantum dots.

[0010] The solvent for PbS quantum dots is n-octane or n-hexane, with a concentration of 10-50 mg / mL. After each spin-coating of a layer of quantum dots, TBAI ligand exchange is performed for 30-60 seconds. After the exchange, the dots are washed with methanol.

[0011] Step 4: A Bi2Te3 thin film is magnetron sputtered on the PbS quantum dot film. The sputtering is performed at room temperature with a sputtering power of 150-200W, an Ar flow rate of 60-100sccm, a sputtering pressure of 3-10Pa, and a sputtering time of 1-5s.

[0012] Step 5: An Al electrode is deposited on the Bi2Te3 thin film. The Al electrode is deposited using physical vapor deposition for 2-10 minutes, thus completing the detector construction.

[0013] The substrate is diamond, sapphire, or quartz.

[0014] The size of the PbS quantum dots is 3 nm.

[0015] This invention utilizes spin coating and magnetron sputtering techniques to fabricate a novel photodetector based on small-sized PbS colloidal quantum dots. The detector, with an AZO / Bi₂Te₃ / PbS CQDs hybrid structure, exhibits excellent performance and wavelength extension capabilities. Compared to PbS CQDs photodetectors, the synergistic effect of PbS CQDs and Bi₂Te₃ materials extends the response wavelength beyond the absorption range of the quantum dots used, reaching 1050 nm. Furthermore, the AZO / Bi₂Te₃ / PbS CQDs hybrid structure, through bandgap modulation, accelerates carrier transport, thereby improving device performance. This results in excellent performance from the visible to near-infrared range, and under 1050 nm incident light, it exhibits an extremely high responsivity (161 A / W) and detectivity (3.2 × 10⁻⁶). 13 Jones).

[0016] First, both the AZO functional layer and the Bi2Te3 thin film were prepared by magnetron sputtering, which is inexpensive, produces good uniformity, and has high reliability. The PbS quantum dot layer was prepared by spin coating, which is simple to operate, low in cost, and conducive to large-scale preparation.

[0017] Second, AZO has a lower conduction band than PbS CQDs, while ITO has a lower work function than AZO, thus there is no potential barrier hindering electron transport. Conversely, Bi₂Te₃ has a higher valence band than PbS CQDs, while Al has a higher work function than Bi₂Te₃, which facilitates rapid hole transport. When the photosensitive layer absorbs photons and generates excitons (electron-hole pairs), holes are rapidly transferred from Bi₂Te₃ to the Al electrode, while electrons are transferred from AZO to the ITO electrode. This rapid separation and extraction of charge carriers leads to an efficient conversion of incident light into photocurrent, thereby improving device performance.

[0018] Third, the device has two active components: PbS colloidal quantum dots and Bi₂Te₃ material. For incident light within the absorption range of PbS colloidal quantum dots, such as 927 nm, the greater thickness of PbS results in stronger absorption, thus PbS CQDs play a dominant role. For incident light outside the absorption range of PbS CQDs but within the absorption range of Bi₂Te₃, such as 1050 nm, Bi₂Te₃ plays a dominant role. Bi₂Te₃ not only acts as a hole transport functional layer but also broadens the absorption spectrum of the Bi₂Te₃ / PbS quantum dot active layer to 1050 nm by adding an additional absorption peak in the near-infrared region (1050 nm) through strong absorption and a wide response band.

[0019] Fourth, the Bi2Te3 thin film grown by magnetron sputtering has good crystallinity, and no annealing treatment is required for the Bi2Te3 thin film, which greatly simplifies the device fabrication process. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the detector structure in Example 1.

[0021] Figure 2 This is a response rate curve of the detector in Example 1.

[0022] Figure 3 This is the spectral response curve of the detector.

[0023] Wherein: 1 is the substrate; 2 is the ITO or FTO electrode; 3 is the AZO functional layer; 4 is the PbS quantum dot photosensitive layer; 5 is the Bi2Te3 thin film; and 6 is the Al electrode. Detailed Implementation

[0024] The present invention will be further described below with reference to the embodiments.

[0025] Example 1: A PbS quantum dot photodetector with energy level modulation, which is a vertical multilayer structure, characterized in that from bottom to top, it consists of a substrate 1, an ITO or FTO electrode 2, an AZO functional layer 3, a PbS quantum dot photosensitive layer 4, a Bi2Te3 thin film 5, and an Al electrode 6.

[0026] A method for fabricating a PbS quantum dot photodetector with energy level modulation includes the following steps:

[0027] Step 1: Clean the transparent substrate on which ITO transparent electrodes have been fabricated;

[0028] Step 2: A thin film of AZO is magnetron sputtered on the transparent substrate on which the ITO or FTO transparent electrode has been prepared. The sputtering is performed at room temperature with a sputtering power of 200W, an Ar flow rate of 60sccm, a sputtering pressure of 5Pa, and a sputtering time of 60min.

[0029] Step 3: On the AZO sputtered substrate, spin-coat PbS quantum dots. The solvent for PbS quantum dots is n-octane or n-hexane, with a concentration of 30 mg / mL. Spin-coat 10 layers of PbS quantum dots. After each layer of quantum dots is spin-coated, perform TBAI ligand exchange for 60 s. After the exchange, clean with methanol. The spin-coating speed is 2500 rpm and the spin-coating time is 30 s.

[0030] Step 4: A Bi2Te3 thin film is magnetron sputtered on the PbS quantum dot film. The sputtering is performed at room temperature with a sputtering power of 200W, an Ar flow rate of 60sccm, a sputtering pressure of 5Pa, and a sputtering time of 1s.

[0031] Step 5: An Al electrode is grown on the Bi2Te3 thin film. The Al electrode is deposited using physical vapor deposition (PVD) for 5 minutes, thus constructing an energy-level modulated PbS quantum dot photodetector.

[0032] The detector obtained in this embodiment was tested for responsivity and spectral response, and the results are as follows: Figure 2 , 3 As shown. Figure 2 In the study, the device achieved a responsivity of 3.2 × 10⁻⁶ at 1050 nm. 13 Jones, Figure 3 In this study, the device exhibits excellent performance outside the response band of PbS quantum dots (e.g., 1050 nm), thus extending the wavelength of small-sized PbS quantum dot photodetectors. Compared with the photodetector fabricated by PbS CQDs in reference [1], the device achieves superior performance at 1050 nm.

[0033] Table 1 lists the performance of photodetectors fabricated with PbS CQDs. As can be seen from Table 1, the responsivity of this invention is superior.

[0034] Table 1

[0035] Device Structure Excitation wavelength (nm) Detectability (Jones) References <![CDATA[PbS / WS2]]> 808 <![CDATA[3.9×10 8 ]]> [2] <![CDATA[PbS / MoS2]]> 1800 <![CDATA[2.8×10 11 ]]> [3] <![CDATA[PbS / SnS2]]> 970 <![CDATA[2.2×10 12 ]]> [4] <![CDATA[AZO / PbS / Bi2Te3]]> 1050 <![CDATA[3.2×10 13 ]]> This invention

[0036] The references are as follows:

[0037] [1] Qiao, K.; Deng, H.; Yang,

[0038] [2] Yu, Y.; Zhang, Y.; Song, X.; Zhang, H.; Cao, M.; Che, Y.; Dai, H.; Yang, J.; Zhang, H.;

[0039] [3] O.; Ramiro, I.; Gupta, S.; Konstantatos, G. High sensitivity hybrid PbS CQD-TMDC photodetectors up to 2μm[J]. ACS Photonics 2019, 6, 2381–2386.

[0040] [4] Gao, L.; Chen, C.; Zeng, K.; Ge, C.; Yang, D.; Song, H.; Tang, J.Broadband, sensitive and spectrally distinctive SnS2 nanosheet / PbS colloidal quantum dothybrid photodetector[J].Light Sci.Appl.2016,5,e16126.

[0041] The raw materials involved in the aforementioned energy-level modulated PbS quantum dot photodetector can all be obtained through general means. The one or more steps mentioned in this invention do not preclude the existence of other methods and procedures for combining these steps. It should also be noted that this example is only used to illustrate the feasibility of the invention and not to limit its scope. Furthermore, any work that does not substantially change the preparation technique should also be considered within the scope of this invention.

Claims

1. A method for preparing a level-regulated PbS quantum dot photodetector, characterized in that The preparation method includes the following steps: Step 1: Clean the transparent substrate on which ITO or FTO transparent electrodes have been prepared; Step 2: Magnetron sputter a thin film of AZO on a transparent substrate on which ITO or FTO transparent electrodes have been prepared. Sputtering is performed at room temperature with a sputtering power of 140-220W, an Ar flow rate of 60-100sccm, a sputtering pressure of 3-10Pa, and a sputtering time of 20-100min. Step 3: On the substrate sputtered with AZO, spin-coat PbS quantum dots at a spin speed of 2000-2500 rpm for 20-40 s; spin-coat 5-10 layers of PbS quantum dots. The solvent for PbS quantum dots is n-octane or n-hexane, with a concentration of 10-50 mg / mL. After each spin-coating of a layer of quantum dots, TBAI ligand exchange is performed for 30-60 seconds. After the exchange, the dots are washed with methanol. Step 4: A Bi2Te3 thin film is magnetron sputtered on the PbS quantum dot film. The sputtering is performed at room temperature with a sputtering power of 150-200W, an Ar flow rate of 60-100sccm, a sputtering pressure of 3-10Pa, and a sputtering time of 1-5s. Step 5: An Al electrode is deposited and grown on the Bi2Te3 thin film using physical vapor deposition (PVD) with a deposition time of 2-10 min, thus completing the detector construction. The size of the PbS quantum dots is 3 nm.

2. The energy level regulated PbS quantum dot photodetector prepared by the preparation method of claim 1, wherein The detector is a vertical multilayer structure, characterized by, from bottom to top, a substrate, an ITO or FTO electrode, an AZO functional layer, a PbS quantum dot photosensitive layer, a Bi2Te3 thin film, and an Al electrode.

3. The energy level regulated PbS quantum dot photodetector of claim 2, wherein The substrate is diamond, sapphire, or quartz.

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