A Bi2Te3 / PbS quantum dot hybrid photodetector and its preparation method

Abstract

A Bi2Te3 / PbS quantum dot hybrid photodetector and its fabrication method. The detector comprises a substrate, an ITO transparent electrode layer formed on the substrate; a PCBM functional layer formed on the ITO transparent electrode layer; PbS colloidal quantum dots formed on the PCBM functional layer; a bismuth telluride (Bi2Te3) charge transport layer formed on the PbS colloidal quantum dots; and an Al electrode formed on the Bi2Te3 charge transport layer. In the detector fabrication method, the PCBM functional layer is formed by spin coating, the PbS colloidal quantum dot thin film is formed by multiple spin coatings and ligand exchange, the bismuth telluride (Bi2Te3) is grown by magnetron sputtering, and the Al electrode layer is formed by vacuum evaporation. The disclosed device structure is a vertical type. The invention utilizes the high absorption of the PbS colloidal quantum dot thin film layer and the high carrier mobility of the Bi2Te3 thin film. The combination of the two facilitates the collection of photogenerated carriers and the rapid transport of carriers, thereby effectively improving the device's response time and performance.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectric detectors, in particular to the preparation technology of quantum dot hybrid photoelectric detectors. Background Art

[0002] Currently, the most widely used materials for photodetector technology include silicon (Si), mercury cadmium telluride (HgCdTe), indium antimonide (InSb), and indium gallium arsenide (InGaAs). However, due to silicon's band gap of 1.12 eV, its detection limit is 1.1 μm. Meanwhile, HgCdTe, InSb, and InGaAs are unsuitable for low-cost applications due to their high production costs, complex manufacturing processes, and poor compatibility with standard silicon processes. Finding low-cost, high-performance semiconductor materials has become a top priority for developing low-cost detectors, and the emergence of colloidal quantum dots offers a new approach to addressing this challenge.

[0003] However, due to the low carrier mobility of colloidal quantum dots (10 -5 ~10 -2 cm / (V·s)). Photodetectors made solely from quantum dot materials often suffer from slow response speeds and low responsivity. One effective approach to improving the performance of quantum dot photodetectors is to hybridize quantum dots with high-mobility materials. Effective hybridization generates a strong built-in potential, which effectively improves carrier transport and increases both the photoresponse time and speed. Summary of the Invention

[0004] To address the problems of simple quantum dot photodetectors, the present invention provides a Bi2Te3 / PbS quantum dot hybrid photodetector. This detector utilizes the advantages of the carrier mobility of the Bi2Te3 material and the strong absorption rate of the quantum dots themselves. After hybridizing the two, the transmission characteristics of the device are improved to prepare a photodetector with superior performance.

[0005] A Bi2Te3 / PbS quantum dot hybrid photodetector has a vertical multilayer structure, characterized by, from bottom to top, a quartz substrate, an ITO transparent bottom electrode, a PCBM functional layer, a PbS quantum dot photosensitive layer, a Bi2Te3 charge transport layer, and an Al electrode.

[0006] A method for preparing a Bi2Te3 / PbS quantum dot hybrid photodetector comprises the following steps:

[0007] Step 1, cleaning the quartz substrate on which the ITO transparent electrode has been prepared;

[0008] Step 2: Dissolve PCBM in chloroform at a concentration of 100 mg / ml, and spin-coat a layer of PCBM solution on the cleaned ITO substrate;

[0009] The spin coating speed is 2000-2500 rpm, and the spin coating time is 25-35 s.

[0010] Step 3: Spin-coat PbS quantum dots on the substrate after spin-coating PCBM. The solvent for the PbS quantum dots is n-octane with a concentration of 30 mg / mL. Spin-coat 8-10 layers of PbS quantum dots. After each layer of quantum dots is spin-coated, perform TBAI ligand exchange for 60 seconds. After the exchange, wash with methanol.

[0011] The spin coating speed of each layer is 2000-2500rpm, and the spin coating time is 25-35s;

[0012] Step 4: magnetron sputtering a Bi2Te3 film on the PbS quantum dot film. The sputtering is performed at room temperature with a sputtering power of 150-200 W, an Ar flow rate of 60-100 sccm, a sputtering pressure of 3-10 Pa, and a sputtering time of 1-5 s.

[0013] Step 5: A layer of Al electrode is grown on the Bi2Te3 film.

[0014] The functional layer and PbS quantum dot photosensitive layer of the present invention are both prepared by spin coating, which is low-cost. The charge transport layer is prepared by magnetron sputtering, which is highly reliable. After light passes through the ITO transparent electrode and irradiates the photosensitive layer to generate electron-hole pairs, the electrons are transported to the ITO electrode through the PCBM layer, while the holes are transported to the Al electrode through the Bi2Te3 layer. Due to the high carrier mobility of Bi2Te3, the generated holes are rapidly transferred away. The energy band design of the functional layer, photosensitive layer, and charge transport layer can effectively reduce the carrier loss caused by recombination, improving the response time and performance of the device.

[0015] In this context, PbS quantum dots have low carrier mobility, and photogenerated carriers easily recombine before being collected. This severely impacts the response rate and performance of photodetectors fabricated solely using quantum dots. Therefore, hybridization with quantum dots using other high-mobility materials (such as two-dimensional materials) is often used to improve performance. However, the low optical absorption of two-dimensional materials leads to other issues in photodetectors hybridized with quantum dots, such as lower responsivity over a wider wavelength range.

[0016] The present invention leverages the strong optical absorption of the Bi2Te3 material's bandgap and high surface carrier mobility to effectively combine Bi2Te3 with quantum dots, addressing the issues of slow response speed in quantum dot photodetectors and the low responsivity of two-dimensional materials across a wide spectrum. Table 1 compares the performance of several hybrid materials. As can be seen, the present invention achieves the fastest response time and a detection rate that is comparable to or greater than that reported in the literature. Detection was achieved at a bias voltage of 2V.

[0017] Table 1

[0018] Hybrid type Response time (rise / fall) Detection rate (Jones) References <![CDATA[PbS / MoS2]]> - / 0.3(s) <![CDATA[5×10 11 ]]> <![CDATA[ [1] ]]> PbS / SiNx / Si 160 / 320(μs) <![CDATA[7.74×10 10 / 3.32×10 10 ]]> [2] <![CDATA[PbS / Bi2Te3]]> 120 / (μs) <![CDATA[2.1×10 11 ]]> The present invention

[0019] Among them, the references are:

[0020] [1]Kufer D,Nikitskiy I,Lasanta T,et al.Hybrid 2D-0D MoS2-PbS quantumdot photodetectors[J].Adv Mater,2015,27(1):176-180..

[0021] [2]Wang J, Chen J. High-sensitivity silicon: PbS quantum dotheterojunction near-infrared photodetector[J]. Surfaces and Interfaces, 2022,30:101945.

[0022] In the present invention, 8-10 layers of PbS photosensitive layer are spin-coated to ensure sufficient thickness for incident light absorption. However, if the thickness is too thick, the transport efficiency of photogenerated carriers will decrease, and the device detection rate will also decrease. During spin coating, the optimal spin coating thickness is 8-10 layers at a speed of 2000-2500 rpm and a spin coating time of 25-35 seconds. TBAI ligand exchange can replace long-chain ligands in quantum dots with short-chain ligands, effectively improving the transport efficiency of carriers in quantum dots.

[0023] The Bi2Te3 film is prepared with a sputtering power of 150W-200W, an Ar flow rate of 60-100sccm, a sputtering pressure of 3-10Pa, and a sputtering time of 1-5s, which can make the surface metallic state of the Bi2Te3 film dominant, which is most conducive to the transport of carriers during hybridization with quantum dots. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the structure of the detector in Example 1.

[0025] Figure 2 TEM image of quantum dots;

[0026] The figure shows that the quantum dots have good dispersion and particle size consistency, and the average particle size of the quantum dots is 4.01nm.

[0027] Figure 3 HRTEM image of Bi2Te3;

[0028] The analysis of interplanar spacing shows that the prepared film is a Bi2Te polycrystalline film.

[0029] In the figure, 1 is a quartz substrate, 2 is an ITO transparent bottom electrode, 3 is a PCBM functional layer, 4 is a PbS quantum dot photosensitive layer, 5 is a Bi2Te3 charge transport layer, and 6 is an Al electrode.

[0030] Figure 4 This is a graph of the detector response rate in Example 1;

[0031] In the figure, under 660nm light, 2.1×10 11 Jones's response rate. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the embodiments.

[0033] Example 1: The Bi2Te3 / PbS quantum dot hybrid photodetector is a vertical multilayer structure, which includes, from bottom to top, a quartz substrate 1, an ITO transparent bottom electrode 2, a PCBM functional layer 3, a PbS quantum dot photosensitive layer 4, a Bi2Te3 charge transport layer 5, and an Al electrode 6.

[0034] The method for preparing a Bi2Te3 / PbS quantum dot hybrid photoelectric detector comprises the following steps:

[0035] Step 1: The quartz substrate on which the ITO transparent electrode was prepared was immersed at 80° C. for 30 min, then rinsed with deionized water and dried;

[0036] The thickness of the ITO transparent electrode bottom electrode is 270nm;

[0037] The cleaning solution is prepared by mixing hydrogen peroxide: ammonia water: deionized water in a ratio of 1:1:3 by volume.

[0038] Step 2: Dissolve PCBM in chloroform at a concentration of 100 mg / ml, and spin-coat a layer of PCBM solution on the cleaned ITO substrate;

[0039] The PCBM film layer is a functional layer with a thickness of 77 nm;

[0040] The spin coating speed was 2500 rpm and the spin coating time was 30 s.

[0041] Step 3: PbS quantum dots were spin-coated on the substrate after spin-coating PCBM. The solvent for the PbS quantum dots was n-octane with a concentration of 30 mg / mL. Ten layers of PbS quantum dots were spin-coated. After each layer of quantum dots was spin-coated, TBAI ligand exchange was performed for 60 seconds. After the exchange, the substrate was washed with methanol.

[0042] PbS quantum dots are the photosensitive layer;

[0043] The spin coating speed for each layer was 2500 rpm and the spin coating time was 30 s.

[0044] Step 4: magnetron sputtering a Bi2Te3 film on the PbS quantum dot film. The sputtering is performed at room temperature with a sputtering power of 200 W, an Ar flow rate of 60 sccm, a sputtering pressure of 5 Pa, and a sputtering time of 1 s.

[0045] The Bi2Te3 film is a charge transport layer with a thickness of 7nm.

[0046] Step 5, vacuum evaporation grows a layer of Al electrode on the Bi2Te3 film;

[0047] Al is the top electrode with a thickness of 95 nm.

[0048] Step 6: Lead out electrode wires from the ITO electrode and the Al electrode.

[0049] The raw materials involved in the aforementioned Bi2Te3 / PbS quantum dot hybrid photodetector can be obtained through common methods. The one or more steps mentioned in this invention do not exclude the possibility of other methods and processes for combining the steps. It should also be noted that this example is intended only to illustrate the feasibility of the invention and does not limit its scope. Furthermore, any method without substantial changes to the preparation techniques should be considered within the scope of the present invention.

Claims

1. A method for preparing a Bi2Te3 / PbS quantum dot hybrid photodetector, comprising the following steps: Step 1, cleaning the quartz substrate on which the ITO transparent electrode has been prepared; Step 2: Dissolve PCBM in chloroform at a concentration of 100 mg / ml, and spin-coat a layer of PCBM solution on the cleaned ITO substrate; The spin coating speed is 2000-2500 rpm and the spin coating time is 25-35s; Step 3: Spin-coat PbS quantum dots on the substrate after spin-coating PCBM. The solvent for the PbS quantum dots is n-octane with a concentration of 30 mg / mL. Spin-coat 8-10 layers of PbS quantum dots. After each layer of quantum dots is spin-coated, perform TBAI ligand exchange for 60 seconds. After the exchange, wash with methanol. The spin coating speed of each layer is 2000-2500 rpm, and the spin coating time is 25-35s; Step 4: magnetron sputtering a Bi2Te3 film on the PbS quantum dot film. The sputtering is performed at room temperature with a sputtering power of 150-200 W, an Ar flow rate of 60-100 sccm, a sputtering pressure of 3-10 Pa, and a sputtering time of 1-5 s. Step 5: A layer of Al electrode is grown on the Bi2Te3 film.

2. A Bi2Te3 / PbS quantum dot hybrid photodetector with a vertical multilayer structure, characterized by The detector is prepared by the method described in claim 1, and from bottom to top, it comprises a quartz substrate, an ITO transparent bottom electrode, a PCBM functional layer, a PbS quantum dot photosensitive layer, a Bi2Te3 charge transport layer, and an Al electrode.

3. A Bi2Te3 / PbS quantum dot hybrid photodetector according to claim 2, characterized in that The thickness of the ITO transparent bottom electrode is 270 nm.

4. A Bi2Te3 / PbS quantum dot hybrid photodetector according to claim 2, characterized in that The thickness of the PCBM film layer is 77 nm.

5. The Bi2Te3 / PbS quantum dot hybrid photodetector according to claim 2, characterized in that In the PbS quantum dot photosensitive layer, the average particle size of the quantum dots is 4.01 nm.

6. The Bi2Te3 / PbS quantum dot hybrid photodetector according to claim 2, characterized in that The charge transport layer is a Bi2Te3 film with a thickness of 7 nm.

7. The Bi2Te3 / PbS quantum dot hybrid photodetector according to claim 2, characterized in that The thickness of the Al electrode is 95 nm.

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